Acetaldehyde essays

Acetaldehyde essays The chemical compound ethanal more commonly known as acetaldehyde is an organic compound, which is created by the oxidation of ethanol, the loss of two hydrogen atoms to give a product containing a double bond to the oxygen and a single hydrogen bond. Acetaldehyde has many uses in the industrial world including the manufacturing of rubbers, fuels (which was more urgent in the 1970s), and food flavoring and preservative. The general population is exposed to acetaldehyde in many forms and concentrations. For the most part, acetaldehyde is relatively safe, such as in the use of air deodorizers and flavoring agents. However, it can cause some health hazards with increased exposure of high amounts of it, which normally occurs in agricultural industries and fuel stations. Acetaldehyde is a compound that can be found in yeast- fermented products and as a result of forest fires, feces, and insects. Producing acetaldehyde with no contaminates has been successful to date with the bioconversio n method. This enables the use of acetaldehyde in fruits to increase the natural flavoring and to decrease the fruits astringency in order to have an edible fruit in a shorter amount of time. Acetaldehyde has also proven to be a preservative of vitamins in rice, where in, acetaldehyde acts as a cross link to reinforce the grains internal structure. Acetaldehyde has proven its kindness to the environment. It rapidly volatilizes from water or land into the ground where it can biodegrade. Thus, the attributes acetaldehyde possess gives it the ability to have such a wide variety of purposes from developing rubber and substitute fuels to enhancing the flavoring of one of the food groups and preserving the vitamins and minerals in food needed for the nourishment of a healthy body. ...

10 Ways to Blog Your Book to Increase Sales Without Being Pushy or Annoying (Part 2)

10 Ways to Blog Your Book to Increase Sales Without Being Pushy or Annoying (Part 2) Last week I shared the first half of a list devoted to blog post topics that will let your audience know about your work in authentic and engaging ways. I will finish sharing those post ideas with you today in hopes that you’ll be able to spread the good word about your book and increase your sales without making your family and friends and social media followers want to run the other way. (Click here for Part 1) Let’s jump back in! Book Launch Party One of my favorite parts about promoting my books is planning and executing the book launch party. Making my fictional piece of art an experience for others to encounter feels like literally bringing my story to life. After the party, I often write a post sharing the details and a plethora of pictures. Readers who weren’t able to attend due to conflicting schedules or distance can catch up on all the action and of course buy a book through a clearly provided link. Behind the Scenes Facts   Once your readers have had a chance to experience your story world and come to know your characters, give them some bonus material. Creating a list of behind the scenes facts will make your readers feel like they are getting the inside scoop, and therefore special. When others bring up your book in conversation (in the grocery store, at church, in the breakroom) they will be able to say, â€Å"Did you know†¦?† Word of mouth continues to be the greatest form of advertisement, and this type of blog post will keep the conversation going about your book. Interviews When my friend Silvia’s third installment in her YA Mythology trilogy came out, she spread the word through interviews. You can see three great examples of this type of blog post in action here, here and here. Silvia’s posts appear on a writing coach’s blog, a national children’s writing organization website and a fellow author friend’s blog. Search for guest blog post or interview opportunities that will give you and your book lots of (hopefully new!) eyes. Extras If you have created extra materials to go with your books, like discussion guides for book clubs or educational materials for children’s books, let the world know about them through a blog post. Rochelle Groskreutz, author of Easter Elf, and her publisher KWiL, created this adorable activity kit to go with her debut picture book. Not only is this free product value added to her story, but it is also a valuable addition to her website and will likely drive traffic in her direction. Share Some Wisdom Often you learn a thing or two in the process of writing a book. Write a blog post sharing that hard-earned knowledge with others and win yourself some fans and admirers in the process. These types of posts will also assert you as an expert in the field and therefore a credible and reliable source in the field. My friend Blaine did this recently when he learned a few successful tricks in the persnickety process of scanning, resizing and publishing original art when creating a picture book. He explains his process in this blog post about his book, The Leprechaun Who Lost His Luck. And last, but not least, you can write a post like this one, full of links to previously written content, in an effort to both illustrate a point and further spread the word about your work. Best of luck as you share your stories – both the published ones and the ones behind the scenes – with your audience. (Click here for Part 1)

Competitive positioning strategy and generic recommendations for Essay - 1

Competitive positioning strategy and generic recommendations for management 1042 - Essay Example This is because the Bowman’s strategy close helps companies to identify their unique competitive positioning based on their products or service and the pricing model they want to use with these. In a more practice term, companies are found to gain the best form of advantage with their competitive positioning when they are able to have a tangible competitive positioning action plan. This action plan may be composed of several practical tasks to be performed, including market profiling, customer segments, competitive analysis, among others. The world can now be referred to as a global village for several reasons. One of the most reasons is the fact that businesses can now move very easily from one point to another in attempt to expanding their market presence. But as companies move from one point to the other to do business, it is always important that they will appreciate the fact that there is competition within the places they go, a reason of which they must strategically place themselves in a way that makes them take all needed advantage on the market. Brown (2008) indicated that in any competitive market, the only guarantee for individual companies to succeed is for them to have a competitive advantage that is lasting. But for such an enviable competitive advantage to be developed, it is very important that a company will know what it has within its means and how it is positioned in the larger market that serves as an opportunity for improving its value (Porter, 1996). Baumeister and Leary (2005) noted that customers today are highly enlightened about value creation, a reason for which they would select value as the best force factor for doing business with one company and not the other. This is where competitive positioning becomes an important phenomenon for the companies. This is because competitive positioning has been explained to be the process of identifying a company’s value

Environmental Health Essay Example | Topics and Well Written Essays - 2500 words

Environmental Health - Essay Example The venom that gets passed at the time of the bite is the primary reason that causes the disease and subsequently the venom is transmitted into the blood vessels of the patients bringing about maximum detrimental effects. However, with proper treatment an individual can survive the nastiest of the dog bites along with the killer disease i.e. rabies (Willoughby et al. 2508-2514). According to Knobel et al., near about 99% of all individual deaths as a result of rabies occur in the developing nations and even though useful and reasonable control measures are offered, rabies remains a deserted infection throughout most of the developing nations (360-388). A major aspect in the low rate of rabies control is the deficiency in the availability of accurate data in terms of community health impact of the disease. It is widely accepted that the amount of casualties formally reported greatly undervalues the true occurrence of the disease. Patients may not be present for medical treatments of t he clinically acclaimed fatal disease in time wherein only a few cases obtain laboratory affirmation and moreover clinical cases are regularly not reported by the concerned hospital and medical authorities (Knobel et al. 360-388). According to Wells, an extension of protest against rabies—which has been over shadowed in northern Malaya since a very long time—finally occurred in Kuala Lumpur in the year 1952 (731-42). The outbreak was covered up by the necessary mass immunization of dogs, enactment of tough legislations and severe destruction of stray dogs. Similar measures were being engaged in the recent operations with an aim to eradicate the disease completely. From regular annual incidences... The research paper â€Å"Environmental Health† evaluates that three diseases (i.e. Rabies, Avian flu and West Nile Virus) are considered mortal diseases that are responsible for significant occurrences of deaths of human beings in various countries. According to Willoughby et al., rabies in persons is a mortal disease characterized by harsh encephalopathy and widespread paresis. The primary reason for rabies to occur amid individuals is dog bites. Along with this, bite from a dog can deliver excruciating pain that may result in extensive bleeding and may cause death as well if it is not treated appropriately in time. It is a very severe disease and can lead to circumstances in which a victim may suffer from numerous health-related problems such as abnormal vomiting, headache and weakness. These types of physical disorders can lead to extreme downfall in physical along with mental conditions and can have drastic effects that may deteriorate the health in the long-term. Accordin g to the observation of Nerlich and Halliday, a new 21st century virus that might lead to a fresh disease began in the year 1997 when an ailment called ‘bird ï ¬â€šu’ broke out in Hong Kong and killed human beings by way of infection. This was a new twist in avian ï ¬â€šu, the highly infectious disease. According to reports, a total of eighteen people were infected and around six people died from the outbreak of the disease in Hong Kong. The major reason was close contact with chicken. It is a virus for which human beings do not possess any immunity.

Nursing Dissertation to strengthen the Scientific Foundation

Nursing to strengthen the Scientific Foundation - Dissertation Example 4.2.1 Applications of Complexity Theory to Health Care Delivery 76 4.2.2 Advantages of Complexity Theory Conceptualization of Nursing Best Practice 77 4.2.3 Significance of Complexity Theory Conceptualization of Nursing Best Practice 79 4.2.4 Implications of Complexity Theory Conceptualization of Nursing Best Practice 79 4.3 Complexity Science as the Guiding Framework 81 4.4 Descriptive Overview of Conceptual Model of Nursing Best Practice 82 4.5 Proposed Definition of Key Concepts 82 4.6 Summary 88 Chapter V: Conclusion 89 5.1 Introduction 89 5.2 Findings of the Study 89 5.3 Implications for Nursing 92 5.4 Conclusion 92 Chapter I: Introduction to the Study 1.1 Introduction This introductory chapter provides a description of the research problem, as well as the rationale, purpose, framework, and the research questions that guided the study. 1.2 The Problem One of the goals of the discipline of nursing is to increase and strengthen the scientific foundation upon which to base clinical practice. The use of research evidence in practice is an accepted way to achieve this goal and in turn can improve nursing care, optimise patient outcomes, and decrease costs (Higgs, Bum, & Jones, 2001; Titler et al., 1994). However, while the requirement to remain current in knowledge and deliver efficient quality patient care has led to an enthusiastic interest in using research evidence in nursing, as a strategy for the fortification of the basis of the science of nursing, little is known about how evidence is actually translated into nursing practice. One strategy that has been suggested for increasing awareness and the use of evidence in nursing practice is revising and updating organisational policy and procedure manuals based on the... The results of this inquiry provide a new theoretical foundation for nursing practice that is qualitatively different from medicine. This research explains how nurses in practice help patients make transitions and move toward future possibilities by merging the art of nursing with the science of nursing. It further makes visible the experience of nurses and reflects on and claims this work as an essential part of professional practice. The study has the potential to challenge the assumptions that underlie nursing's approach to practice, education, theory and research in its challenge to the dominance of scientific over artistic approaches in the practice of nursing. In particular, this work challenges the analytical, problem focused basis of the nursing process and suggests instead that nurses promote transitions in a process akin to narrative structure in the way that assumes standpoints, makes interpretive leaps, brings events to a climax and recognizes closure. In conclusion, science has approached a better understanding of the universe by reducing phenomena into manageable component parts, and the hallmark of research rigor has been the degree to which confounding influences are isolated or controlled. Management strategies have been focused on finding the best way to achieve desirable performance and then exerting control over process and structure in order to maintain the desired organizational or system performance level. The conceptualization of nursing best practice as an emergent property of a complex adaptive healthcare system.

Competency Based Assessments in Education

Competency Based Assessments in Education Chapter 4 Literature Review on Competence-based Assessment 4.1 Introduction In this chapter, the researcher discusses the literature on competence-based assessment. The first part examines the purposes, the interpretations of competence-based assessment (CBA), the critical attributes of CBA and the issues related to competence. The second part looks into the implementation of CBA around the world and later focuses on the implementation of CBA in Malaysia. 4.2 Competence-based Assessment: An Overview The era of the knowledge -economy and globalisation requires not only individuals who possess a sound understanding of specific subject matter but also those who have relevant industry-related skills and interpersonal skills. These attributes and capabilities are necessary for learners to acquire in order to function well in todays complex and global societies (Baartman et al., 2007). Furthermore, acquisition of complex competences (Baartman et al., 2007) has to be developed in the future human capital through purposeful, effective, learner-centred and competence-based programmes (Baartman et al., 2007) in order to prepare students to meet the needs of tomorrows world. The report of the United States Department of Education Secretarys Commission on Achieving Necessary Skills, the so-called SCANS Report (McNabb, 1997), made clear that students must be ready to function in collaborative settings, interpret complex requirements, and exhibit self-directed, self-assessing behaviour on the job. This means that employers would want more from the graduates than just entry-level job skills which would help develop a nation progressively in accordance to its political and social needs. The relationship between learning and assessment (discussed in Chapters X and Y) means that assessment should take account of political and social purposes (Broadfoot, 1996). Different vocational and educational training programmes from school level to university level have been introduced to prepare and equip individuals to fit into the labour market. One such programme is Competency-Based Education (CBE) with the emphasis on assessment (competency-based assessment) being seen as key to the success of its implementation (Tillema et al, 2000; Frederiksen, 1984; Baartman et al., 2007). 4.2.1 Purposes of Competence-based Assessment Any forms of assessment s including CBA would usually have one or more of three basic purposes to diagnose learning;, to select students for particular provision; to certificate achievements (Carless et. al., 2006; Freeman Lewis, 1997; Ecclestone, 1996; Rowntree, 1987). CBA has been utilised by schools, training colleges and industriy for two main purposes; to measure competencies (McNerney Briggins, 1995) and to certificate (International Labour Organisation, 1996). 4.2.1.1 CBA for Measuring Competence Measuring competence is one of the main purposes of CBA.Generally, the reason for the implementation of CBA is to determine that learners have sufficient knowledge and skills to contribute effectively to the work force(Canning, 2000; Ecclestone, 1997; Kerka, 1998; LPM, 2002; McNabb, 1997). However,according to Hyland (1994), as competence-based education is found to be seriously flawed and ill-equipped to deal with education and training beyond the basic skills., CBA apparently could can be used to measure limited aspects of competence but Hyland (1994). He believes that its influence on training and education for future generations will be actively damaging as it could can only produce individuals who would function without much learning, knowledge and understanding of anything. He attributes this to a This is due to its highly instrumental philosophy thats combined with a narrow and uncritical behaviourist psychology. (Hyland, 1994). Thus, its qualifications resulting from CBA are viewed as basically reliable as indicators of all the most elementary skills and abilities (Armstrong, 1995). The issues of competence in CBA will be further discussed in section 4.4. 4.2.1.2 CBA for Certification It is asserted claimed that CBA provides learners with opportunities to achieve qualifications that relate to required performance in the workplace (Erridge Perry, 1994). Ecclestone (1997) indicates that NVQs, which primarily employ CBA, represent an explicit commitment to creating wider access to accreditation and better levels of achievement. She argues that Tthis could be made possible by severing links between attendance in learning programmes, and the formal assessment and accreditation of outcomes, and by promoting the accreditation of prior learning in which NVQs subsequently serve as serious challenge to traditional assessment approaches (Ecclestone, 1997). For instance, a trainee in a plumbing courseplumber would have the opportunities to acquire the necessary knowledge and skills in plumbing at certain level. He/she would then achieve the qualifications and certification that relate to the required performance of a plumber in the real life workplace once he/she has complet ed the assessment of at the at particular designated level. Nevertheless, CBA is at the same time, argued to be conceptually confusing, empirically flawed and lacking in meeting the needs of a learning society (Chappell, 1996; Ecclestone, 1997; Hyland, 1994;). This may be the results of the use of confusing language or jargons, the decreasing credibility of the competency standards on how they reflect industry standards (Kerka, 1998) and the indifferent implementation of CBA across the industries due to employers ignorance about the its nature and the purpose. of it (Hyland, 1996). 4.2.2 Definitions and Interpretations of CBA There is a wide range of interpretations and definitions given to CBA. In this discussion, CBA the interpretation of- CBA is looked atinterpreted in terms of three different aspects; the assessors roles, the learners responsibilities and the learning outcomes that are based on predetermined criteria. Figure ____tries to reflect the interedependence of these elements.The relationships of the interpretations of these three aspects are as shown in Figure ____. Adapted: Griffin Nix, 1991; Mcnerney Briggins, 1995; Hager, 1994; Elliot, 1994; Cotton, 1995; Ecclestone, 1996) In the assessors perspective, CBA consists of the simple process of seeing, collecting, gathering,and obtaining evidence, and the further process a more complex as well as subjective process of judging and interpreting the evidence of competence demonstrated by learners (Rowe, 1995; Ecclestone, 1996; Mcnerney Briggins, 1995; Hager, 1994; Griffin Nix, 1991). The assessors have to observe gather and judge the evidence of an individuals competence against the specified standards. This means that the assessors have to be very careful in their actions of gathering evidence of competence and they have to decide when it is considered sufficient, based on their expert judgment. For example, when a student successfully builds a drywall framework, the assessor has to gather evidence of competence not only from the product which is the framework but also from the process and the preparations before the student begins to work on it such as work schedule, list of materials and equipment to be u sed, and the like. The assessor then has to use his/her expertise in this area to determine whether or not the evidence of competence gathered is adequate to say that the student has acquired satisfactory competence in building the drywall framework. McNnerney Briggins (1995) state that CBA is the process of identifying the competencies which are the underlying characteristics that lead toof successful performance be this by may it be among a group of employees, typically by department, job category or hierarchical level. CThey say that a list of competencies that is tied to one corporate culture is usually used tobecome associatede with exemplary performance (McNerney Briggins, 1995)ers. They further relate CBA to its training basis where the focus is on who the successful performers are rather than on what people do. This means that it does not just include training in jobs which rely heavily on psychomotor skills, such as manual labour and traditional hourly production work but also involve performing decision-oriented jobs (Mcnerney Briggins, 1995). The Scottish Qualifications Authority (SQA) (2001) stresses the process of seeing whether or not an individual has the necessary skill and knowledge they need to be awarded a Scottish Vocational Qualifications as the key factor in CBA; emphsising the need for assessors to be expert . This undoubtedly requires the assessors to have even thorough knowledge and skills in the fields they are assessing in order to make good and fair judgments. This means is due to the fact that the athat assessors have to assess and collectconsider evidence of competence in terms of knowledge, abilities, skills and attitudes (Rowe, 1995; Ecclestone, 1996; Mcnerney Briggins, 1995) displayed diferentially in authentic contexts by learners in the context of a selected set of real life professional tasks which are of different levels (Hager, 1994). The process of gathering evidence from observable performance is later followed by the more difficult process of making judgment that may be very subjective (Pedd ie Wilmut, Macintosh, 1997). Despite the difficulty in making judgment based on evidence gathered, assessors have to determine whether or not the competency has been achieved by learners (Victoria Curriculum and Assesssment Authority (VCAA), 2001). It is the assessors responsibility, then, to decide if learners performances meet the pre-determined criteria. Thus, assessors have to equip themselves with relevant skills and use appropriate mechanisms in making fair judgments so that the problem of subjectivity among assessors is reduced. Furthermore, assessors have to assess learners ability to apply a particular knowledge, skills, attitudes and values in a specific context according to a required performance standards (New Zealand Qualifications Authority (NZQA), 2002). In other words, assessors themselves have to be extremely knowledgeable and skilful in the art of observing and collecting evidence of competence that come in various tangible and intangible forms. The process of gat hering evidence from observable performance is later followed by the more difficult process of making judgment that is inevitably very subjective (Peddie Wilmut, Macintosh, 1997). Despite the difficulty in making judgment based on evidence gathered, assessors still have to determine whether or not competency has been achieved by learners (Victoria Curriculum and Assesssment Authority (VCAA), 2001). It is the assessors responsibility then, to decide if learners are considered to be competent in a particular context at a particular level based on their performance whether or not it meets the pre-determined criteria. Thus, assessors have to equip themselves with relevant skills and use appropriate mechanisms in making fair judgments so that the problem of subjectivity among assessors is reduced. In addition to assessing and making judgment on students performance based on evidence gathered, assessors would also have to give constructive and supportive feedback to students on their performance and work (Ecclestone, 1996; Sadler, 2009). The assessors would have to point out the strengths and weaknesses as well as the improvements that could be made in the future (Sadler, 2009). Sadler (2009) further proposes that feedback should be given in a manner that would be able toenables educate students to assess and be able to evaluate their own work and give feedback to themselves as well. He suggests that students shcould be taught to monitor the quality of their productions and make adjustments as necessary while they are actually engaged in doing it. In From the learners point of view on the other handperspective, CBA is the platform for them to demonstrate competencies and learning outcomes (Elliot, 1994). These competencies will range from simple constructed responses to comprehensive collections of work over time in very different contexts.Elliot further asserts that CBA requires learners to demonstrate competencies and learning outcomes in performance assessment which vary in terms of simplicity and complexity such as from simple constructed responses to comprehensive collections of work over time, all of which are then judged . Learners are expected to be deeply involved in the assessment process and they areto be aware of the specified criteria that they have to meet as well as the standards of performance that are expected of them right from the beginning even before the assessment is conducted. Theoretically, tThis allows learners to take charge of and control over their own learning outcomes and success by preparing them selves well in advance. In other words, learners would have the autonomy for in their own learning, as CBA canould promote individuality and personal development (Ecclestone, 1996). The learners responsibility includes demostrating the It is also here in CBA that learners have to show their ability to apply theoretical knowledge and procedures, in addition to their understanding ofbeing able to describe the theories or even point to appropriate theoretical knowledge (Cotton, 1995). In demonstrating competence Cotton further elucidates that learners also have to express wise use of common sense in the public by demonstrating good physical, interpersonal and intrapersonal skills with mindful decision- making; that suggests the multiple intelligence described by Gardner (1985). In other words, learners have to demonstrate their abilities in all the three psychological domains of psychomotor, cognitive and affective learning (ANTA, 1998). Similarly, the Australias National Training Auth ority (ANTA) (1998) considers CBA to be a platform for learners to display their skills, knowledge and experience in accomplishing specific tasks as required in the workplace or to obtain a credit towards a qualification in the vocational and education training (VET). A Both the assessors and learners have one thing in common: to focus on and that is the set of learning outcomes that can be derived from an assessment. Learning outcomes cover diverse range of areas including personal qualities, various forms of knowledge and skills (Ecclestone, 1996). In this case it is the evidence of competence that learners have to demonstrate and which the assessors have to observe for and make judgments on, has to meet specified criteria. Thus, CBA consists of specified set of both the general and specific outcomes that assessors, learners and third parties can make reasonably objective judgments with respect to learners achievement or non-achievement of these outcomes (Wolf, 1995). CBA then certifies learners progress based on the demonstrated achievement of these outcomes while the assessments may not be necessarily tied to time served in formal educational settings. The emphasis is on the outcomes specifically, multiple outcomes, each distinctive and separ ately considered which should be specified clearly and as transparent as possible for assessors, assessees and third parties to understand what is being assessed and what should be achieved (Wolf, 1995) . This definition encapsulates the key-features of CBA as it has been developed and promoted for the vocational, technical and professional education and training in the UK while at the same time it signals the American origins of much of the debate (Wolf, 1995). The demonstrated performance that provides evidence of competence has to be at least of the minimum required quality in the real life workplace environment. These are the predetermined criteria set in CBA which are generally based on endorsed industry benchmark or competency standard (ANTA, 1998). The emphasis on outcomes and transparency is not only peculiar to the competence-context but it is also an essential characteristic of criterion-referenced assessment. The emphasis on what learners can actually do and the beneficia l effects of clear criteria on teaching and learning (Glaser, 1963; Popham, 1978) are argued to meet the competence-based literature where in England in the early years of the implementation of CBA, such system was referred to as criterion-referenced approach (Jessup 1991: 167). Jessup (1991) further underlines that what people actually learn from an education and training system and how effectively, as the key factor to measure its success. Thus, CBA is considered a criterion-referenced interpretation of assessment (Nuttall, 1984; Ling, 1999) where individuals are given an award after achieving the pre-determined standards (Cotton, 1995). This critical attribute of CBA will be discussed further in section 4.3.2. 4.3 Critical Attributes of Competence-based Assessment The following section discusses the two learning theories associated with CBA and the nature of its criterion-referenced assessment. 4.3.1 Learning Theories Associated with Competence-based Assessment Learning in the psychology and education contexts is a the process of acquiring knowledge, skills, and values, and world views acquisition and enhancement through ones integrated employment of cognitive, emotional, and experiences (Illeris, 2000; Ormorod, 1995). How this process works is explained variously. Learning as a process focuses on what happens when the learning takes place and the explanations of what happens constitute learning theories. In other words, learning theories are attempts to describe how people and animals learn, and they help uncover the inherently complex process of learning to our understanding. Hill (2002) explains that learning theories have two main values. The first is to provide adequate vocabulary and a conceptual framework in to interpreting examples of observed learning; and the second. Next is to suggest the right directions to look for solutions to practical problem instead of providing the solutions. Learning theories are therefore, the basis for any form of educational assessment (Gipps, 1994) and the theories most commonly associated to with CBA are the behaviourism and, more recently, the constructivism. These two theories will be discussed as CBA essentially involves observable aspects of learning and learning as a process for construction of new knowledge. Although the cognitive theory which looks beyond behaviour to explain brain-based learning is important, the need for it in CBA is not that apparent or crucial. Thus it is not included in the discussion. 4.3.1.1 Behaviourist Learning Theory Behaviourism is a theory of organism (may it be an animal or human) learning that only focuses on objectively observable behaviours and discounts mental activities (Murphy, 1999; Kerka, 1997; Doolittle Camp, 1999) with the assumption that a learner starts off as a clean slate (i.e. tabula rasa) and is essentially passive, responding to environmental stimuli (Murphy, 1999; Kerka, 1997) in the acquisition of new behaviour (Chowdhury, 2006). Learning according to the behaviourists takes place as the result of a response that follows on a specific stimulus and that behaviour is shaped through reinforcement (Kerka, 1997). By repeating the Stimulus-Response (S-R) cycle the learner is conditioned into repeating the response whenever the same stimulus is present and thusbehaviour can be modified and learning is measured by observable change in behaviour (Murphy, 1999; Kerka, 1997; Doolittle Camp, 1999). Theis emphasis on stimulus-response pairing (Murphy, 1999; Chowdhury, 2006) and the rejections to of structuralism (Kerka, 1997) reflected behaviourisms positivistic philosophical base, as the analysis of the human condition relies on only verifiable observations of behaviour and not on untenable mentalistic constructs (Kerka, 1997). Furthermore,Accordingly most human behaviour could can be understood as basic reflexive learning mechanisms or laws that operate on ones experience within the environment (Kerka, 1997). As the approach is seen to be more operational and practical in nature, it has dominated education.n, in which Tthe teacher disseminates selected knowledge, measures learners passive reception of facts, and focuses on behaviour control and task completion (Kerka, 1997). These views of the behaviourists and the learning characteristics that can be found in the education setting are summarised in Table___. Generally, conditioning has been identified in experiments by behaviourists to be a universal learning process. There are two different types of conditioning, each yielding a different behavioural pattern: Classic conditioning occurs when an instinctive reaction responds to a stimulus (Comer, 2004). Essentially, animals and people are biologically wired so that a certain stimulus will produce a specific response. As such, learning process takes place when two events that repeatedly occur close together in time are associated in a persons mind to impulsively produce the same response. The most popular example is Pavlovs observation that dogs salivate when they eat or even see food where food is unconditioned stimulus and the salivation, the unconditioned reflex (Comer, 2004; Chowdhury, 2006). Pavlovs theory of classical conditioning is considered a foundation of learning theories to the behaviourists. According to Pavlovs experiment, when some neutral stimulus, such as the ringing of a bell, is combined with the presentation of food and is repeated for a period of time, the dog salivates with the ringing of the bell, even though food is not given. Hence, the ringing of the bell acts as the conditioned stimulus while salivation is the conditioned response or reflex (Dembo: 1994). The result of this experiment led to the formation of Pavlovs classical conditioning in which an individual responds to some stimulus that would ordinarily produce such a response. Behavioural or operant conditioning occurs when a response to a stimulus is reinforced. Basically, operant conditioning is a simple feedback system: If a response to a stimulus is rewarded or reinforced, then the response is likely to take place in the future. Similarly, when a particular behaviour is rewarded, that behaviour is repeated as shown in the experiment conducted by B.F. Skinner using reinforcement techniques to teach pigeons to dance and bowl a ball. B.F. Skinner based his theory upon the idea that learning is a function of change in overt behaviour where these changes in behaviour are the result of an individuals response to events (stimuli) that occur in the environment (Chowdhury, 2006). According to Skinner, a reward or punishment will either strengthen or weaken a voluntary or automatic behaviour (Skinner: 1968). Ever since its introduction, the reinforced techniques have gone through series of enhancement and have contributed tremendously in training and teaching. The most important aspect of Skinners contribution to training is the significance attached to the desired behaviour to be emitted in certain environment. In order for the trainer to ensure the right behaviour is reinforced in the trainees, the trainer should have the clear idea about the terminal behaviour of the trainees, and should closely follow the trainees to appropriately reinforce correct responses. This is the purpose of programmed instructions including competence-based training in its early years of implementation which was based on this theory of reinforcement (Burns, 1995). . As the emerging learning theory of the early 1900s, behaviourism provided the final found ation for social efficiency as learning which is seen objectively consists of the formation of links between specific stimuli and responses through the application of rewards ( Wirth, 1972 ). The emphasis on the need of objectivity leads to extensive use of statistical and ma thematical analysis. Despite all the remarkable contribution s the learning theory has to offer , the extreme focus on objectivity has totally ignored the significant role the mind play in shaping ones behaviour. Men are treated more like robots or machines than human beings as their thoughts and feelings are not taken into consideration. They are expected to demonstrate desired behaviour through the use of reward and punishment neglecting other factors that may have an influence on the change in behaviour. Thus, the behaviourist theory of learning is lacking in utilizing the full potential of the mind in moulding essential behaviour and in constructing new knowledge . Assessment in Behaviourism Assessment, according to behaviourism, is a test (the stimulus) for which the answer (the response) is conditioned In accordance to the behaviourist learning theory which focuses on the stimulus-response cycle to attain observable conditioned behaviour, assessment in the behaviourism also applies the same concept. Thus, t he test item is the stimulus, the answer is the response and a learner has to be conditioned to produce the appropriate response to any given stimulus ( (Murphy, 1999; Kerka, 1997; Doolittle Camp, 1999). NSince the emphasis is on the response that is observable, no attention is paid to any model of the thinking process of the learner which might intervene between stimulus and response. Consequently, the distinctions between rote learning and learning with understanding is not considered as teaching is a matter deliveringof delivering the appropriate stimuli while learning is a matter of repeating the appropriate response, which will be rewarded. is what matters the most in which teaching is by repetition and then rewarding the appropriate responses. As such, a test composed of many short, atomised, out-of-context questions, and teaching to the test, are both consistent with this approach (Murphy, 1999; Kerka, 1997). Likewise, some forms of CBA which has always been associated to thewith behaviourist theory can be seen to assess, atomistically. applied the atomistic but not out of context approach. The assessor who is an observer ticks off a checklist of predetermined criteria whenever a learner has performed a series of discrete observable tasks. The criteria are the stimuli, the accomplished tasks the responses and learner has to be conditioned to demonstrate the ability to meet the criteria successfully. Although this approach to assessment may developstestify to learners ability to perform observable tasksbehaviours, it does not pay much attention to the theoretical knowledge and understanding (Ashworth, 1992) as the role of the mind is considered insignificant in delivering the required behaviour. While assessing competent observable performance is vital, assessing knowledge and understanding is just as important as it is an essential aspect of competence without which an assessment is lacking in credibility or construct validity (Ashworth, 1992). A valid assessment method should be able to measure what it is supposed to measure which in this case (Watson, 1994). Given the extensive discussion in Chapter ? on the idea of competence, both the observable performance behaviour and underpinning knowledge are aspects of competence that should be assessed and measured. People who understand are those who have clear mental representation of the situation with which they are confronted and are able to deal with it creatively and imaginatively using the acquired knowledge which acts as an interpretive resource for them (Ashworth, 1992). Thus, it is insufficient to assess ones competence just by looking at the performance while ignoring the aspect of knowledge and understanding. It is unfortunate then, if such an assessment method should produce people who are like robots in a factory; they couldwho can perform a job or a task efficiently and effectively but they do not have any understanding of what they were are doing. As the approachCBA also emphasises personal competence within competence concentrates on an individual demonstrating competent performance ((Wolf, 1995), traditional notions of CBA have allowed an and emphasises on personal competences, it leads to one being individualistic perspective whilst lacking ignoring the very necessary in the abability of being able to work as a team player to work as a team whereas team work is essential in performing relevan t aspect of a job in the actual workplace (Ashworth, 1992). As a result, theis behaviourist view of CBA has eventually shifted to the constructivist belief as discussed in the following section.weakened. Despite all the remarkable contributions the learning theory has to offer, the extreme focus on objectivity has totally ignored the significant role that the mind plays in influencing ones behaviour. People are treated more like robots or machines than human beings as their thoughts and feelings are not taken into consideration. They are expected to demonstrate desired behaviour through the use of reward and punishment neglecting other factors that may have an influence on the change in behaviour. 4.3.1.2 Constructivist Learning Theory Constructivism is a theory of learning that has roots in both philosophy and psychology (Doolitle Camp, 1999) founded on the premise that learners actively construct their own knowledge, meaning and understanding of the world they live in by reflecting on their experiences (Doolitle Camp, 1999; Murphy, 1999; Kerka, 1997). Learners learn by doing rather than observing and by bringing prior knowledge into a learning situation (Epstein Ryan, 2002; Carvin, date?) in which they must critique and re-evaluate their understanding of it until they can demonstrate their comprehension of the subject (Carvin). Furthermore, learners need to analyse and transform new information or problems in their minds based on existing knowledge and understanding where these abstract thoughts evolve from concrete action (Murphy, 1999). Learning, therefore, is simply the process of adjusting their mental models to accommodate new experiences. TBasically, the theory of constructivism rests on the notion that there is an innate human drive to make sense of the world by building cognitive structures which include declarative knowledge (know that facts, concepts, propositions) and procedural knowledge (know how techniques, skills, and abilities) (Murphy, 1999). These two components of knowledge have been discussed in depth in Chapter 3. Moreover, learning is a matter of personal and unique interpretation which takes place within the social context and is of useful to the learner as intrinsic motivation emerges from the desire to understand and to construct meaning (Billet, 1996). However, dispositions such as attitudes, values and interests that help learners decide, are often neglected in this theory (Murphy, 1999) making it incomprehensive and insufficient in a way. Philosophically, the essence of constructivism relies on an epistemology that stresses subjectivism and relativism, where personally unique reality resulted from the concept that reality can be known through experience although it may exist separate from experience (Doolitle Camp, 1999). Hence came four essential epistemological tenets of constructivism (Von Glasersfeld ,1984; 1998; Doolitle Camp, 1999); Knowledge is the result of active cognizing by the individual ; Cognition is an adaptive process that functions to make an individuals behaviour more viable given a particular environment; Cognition organizes and makes sense of ones experience, and is not a process to render an accurate representation of reality; and Knowing has roots both in biological/neurological construction, and in social, cultural, and language-based interactions (Dewey, 1916/1980; Garrison, 1997; Larochelle, Bednarz, Garrison, 1998; Gergen, 1995). Thus, constructivism acknowledges the active role learners play in the personal creation of knowledge, the importance of both the individual and social experiences in this knowledge creatio Competency Based Assessments in Education Competency Based Assessments in Education Chapter 4 Literature Review on Competence-based Assessment 4.1 Introduction In this chapter, the researcher discusses the literature on competence-based assessment. The first part examines the purposes, the interpretations of competence-based assessment (CBA), the critical attributes of CBA and the issues related to competence. The second part looks into the implementation of CBA around the world and later focuses on the implementation of CBA in Malaysia. 4.2 Competence-based Assessment: An Overview The era of the knowledge -economy and globalisation requires not only individuals who possess a sound understanding of specific subject matter but also those who have relevant industry-related skills and interpersonal skills. These attributes and capabilities are necessary for learners to acquire in order to function well in todays complex and global societies (Baartman et al., 2007). Furthermore, acquisition of complex competences (Baartman et al., 2007) has to be developed in the future human capital through purposeful, effective, learner-centred and competence-based programmes (Baartman et al., 2007) in order to prepare students to meet the needs of tomorrows world. The report of the United States Department of Education Secretarys Commission on Achieving Necessary Skills, the so-called SCANS Report (McNabb, 1997), made clear that students must be ready to function in collaborative settings, interpret complex requirements, and exhibit self-directed, self-assessing behaviour on the job. This means that employers would want more from the graduates than just entry-level job skills which would help develop a nation progressively in accordance to its political and social needs. The relationship between learning and assessment (discussed in Chapters X and Y) means that assessment should take account of political and social purposes (Broadfoot, 1996). Different vocational and educational training programmes from school level to university level have been introduced to prepare and equip individuals to fit into the labour market. One such programme is Competency-Based Education (CBE) with the emphasis on assessment (competency-based assessment) being seen as key to the success of its implementation (Tillema et al, 2000; Frederiksen, 1984; Baartman et al., 2007). 4.2.1 Purposes of Competence-based Assessment Any forms of assessment s including CBA would usually have one or more of three basic purposes to diagnose learning;, to select students for particular provision; to certificate achievements (Carless et. al., 2006; Freeman Lewis, 1997; Ecclestone, 1996; Rowntree, 1987). CBA has been utilised by schools, training colleges and industriy for two main purposes; to measure competencies (McNerney Briggins, 1995) and to certificate (International Labour Organisation, 1996). 4.2.1.1 CBA for Measuring Competence Measuring competence is one of the main purposes of CBA.Generally, the reason for the implementation of CBA is to determine that learners have sufficient knowledge and skills to contribute effectively to the work force(Canning, 2000; Ecclestone, 1997; Kerka, 1998; LPM, 2002; McNabb, 1997). However,according to Hyland (1994), as competence-based education is found to be seriously flawed and ill-equipped to deal with education and training beyond the basic skills., CBA apparently could can be used to measure limited aspects of competence but Hyland (1994). He believes that its influence on training and education for future generations will be actively damaging as it could can only produce individuals who would function without much learning, knowledge and understanding of anything. He attributes this to a This is due to its highly instrumental philosophy thats combined with a narrow and uncritical behaviourist psychology. (Hyland, 1994). Thus, its qualifications resulting from CBA are viewed as basically reliable as indicators of all the most elementary skills and abilities (Armstrong, 1995). The issues of competence in CBA will be further discussed in section 4.4. 4.2.1.2 CBA for Certification It is asserted claimed that CBA provides learners with opportunities to achieve qualifications that relate to required performance in the workplace (Erridge Perry, 1994). Ecclestone (1997) indicates that NVQs, which primarily employ CBA, represent an explicit commitment to creating wider access to accreditation and better levels of achievement. She argues that Tthis could be made possible by severing links between attendance in learning programmes, and the formal assessment and accreditation of outcomes, and by promoting the accreditation of prior learning in which NVQs subsequently serve as serious challenge to traditional assessment approaches (Ecclestone, 1997). For instance, a trainee in a plumbing courseplumber would have the opportunities to acquire the necessary knowledge and skills in plumbing at certain level. He/she would then achieve the qualifications and certification that relate to the required performance of a plumber in the real life workplace once he/she has complet ed the assessment of at the at particular designated level. Nevertheless, CBA is at the same time, argued to be conceptually confusing, empirically flawed and lacking in meeting the needs of a learning society (Chappell, 1996; Ecclestone, 1997; Hyland, 1994;). This may be the results of the use of confusing language or jargons, the decreasing credibility of the competency standards on how they reflect industry standards (Kerka, 1998) and the indifferent implementation of CBA across the industries due to employers ignorance about the its nature and the purpose. of it (Hyland, 1996). 4.2.2 Definitions and Interpretations of CBA There is a wide range of interpretations and definitions given to CBA. In this discussion, CBA the interpretation of- CBA is looked atinterpreted in terms of three different aspects; the assessors roles, the learners responsibilities and the learning outcomes that are based on predetermined criteria. Figure ____tries to reflect the interedependence of these elements.The relationships of the interpretations of these three aspects are as shown in Figure ____. Adapted: Griffin Nix, 1991; Mcnerney Briggins, 1995; Hager, 1994; Elliot, 1994; Cotton, 1995; Ecclestone, 1996) In the assessors perspective, CBA consists of the simple process of seeing, collecting, gathering,and obtaining evidence, and the further process a more complex as well as subjective process of judging and interpreting the evidence of competence demonstrated by learners (Rowe, 1995; Ecclestone, 1996; Mcnerney Briggins, 1995; Hager, 1994; Griffin Nix, 1991). The assessors have to observe gather and judge the evidence of an individuals competence against the specified standards. This means that the assessors have to be very careful in their actions of gathering evidence of competence and they have to decide when it is considered sufficient, based on their expert judgment. For example, when a student successfully builds a drywall framework, the assessor has to gather evidence of competence not only from the product which is the framework but also from the process and the preparations before the student begins to work on it such as work schedule, list of materials and equipment to be u sed, and the like. The assessor then has to use his/her expertise in this area to determine whether or not the evidence of competence gathered is adequate to say that the student has acquired satisfactory competence in building the drywall framework. McNnerney Briggins (1995) state that CBA is the process of identifying the competencies which are the underlying characteristics that lead toof successful performance be this by may it be among a group of employees, typically by department, job category or hierarchical level. CThey say that a list of competencies that is tied to one corporate culture is usually used tobecome associatede with exemplary performance (McNerney Briggins, 1995)ers. They further relate CBA to its training basis where the focus is on who the successful performers are rather than on what people do. This means that it does not just include training in jobs which rely heavily on psychomotor skills, such as manual labour and traditional hourly production work but also involve performing decision-oriented jobs (Mcnerney Briggins, 1995). The Scottish Qualifications Authority (SQA) (2001) stresses the process of seeing whether or not an individual has the necessary skill and knowledge they need to be awarded a Scottish Vocational Qualifications as the key factor in CBA; emphsising the need for assessors to be expert . This undoubtedly requires the assessors to have even thorough knowledge and skills in the fields they are assessing in order to make good and fair judgments. This means is due to the fact that the athat assessors have to assess and collectconsider evidence of competence in terms of knowledge, abilities, skills and attitudes (Rowe, 1995; Ecclestone, 1996; Mcnerney Briggins, 1995) displayed diferentially in authentic contexts by learners in the context of a selected set of real life professional tasks which are of different levels (Hager, 1994). The process of gathering evidence from observable performance is later followed by the more difficult process of making judgment that may be very subjective (Pedd ie Wilmut, Macintosh, 1997). Despite the difficulty in making judgment based on evidence gathered, assessors have to determine whether or not the competency has been achieved by learners (Victoria Curriculum and Assesssment Authority (VCAA), 2001). It is the assessors responsibility, then, to decide if learners performances meet the pre-determined criteria. Thus, assessors have to equip themselves with relevant skills and use appropriate mechanisms in making fair judgments so that the problem of subjectivity among assessors is reduced. Furthermore, assessors have to assess learners ability to apply a particular knowledge, skills, attitudes and values in a specific context according to a required performance standards (New Zealand Qualifications Authority (NZQA), 2002). In other words, assessors themselves have to be extremely knowledgeable and skilful in the art of observing and collecting evidence of competence that come in various tangible and intangible forms. The process of gat hering evidence from observable performance is later followed by the more difficult process of making judgment that is inevitably very subjective (Peddie Wilmut, Macintosh, 1997). Despite the difficulty in making judgment based on evidence gathered, assessors still have to determine whether or not competency has been achieved by learners (Victoria Curriculum and Assesssment Authority (VCAA), 2001). It is the assessors responsibility then, to decide if learners are considered to be competent in a particular context at a particular level based on their performance whether or not it meets the pre-determined criteria. Thus, assessors have to equip themselves with relevant skills and use appropriate mechanisms in making fair judgments so that the problem of subjectivity among assessors is reduced. In addition to assessing and making judgment on students performance based on evidence gathered, assessors would also have to give constructive and supportive feedback to students on their performance and work (Ecclestone, 1996; Sadler, 2009). The assessors would have to point out the strengths and weaknesses as well as the improvements that could be made in the future (Sadler, 2009). Sadler (2009) further proposes that feedback should be given in a manner that would be able toenables educate students to assess and be able to evaluate their own work and give feedback to themselves as well. He suggests that students shcould be taught to monitor the quality of their productions and make adjustments as necessary while they are actually engaged in doing it. In From the learners point of view on the other handperspective, CBA is the platform for them to demonstrate competencies and learning outcomes (Elliot, 1994). These competencies will range from simple constructed responses to comprehensive collections of work over time in very different contexts.Elliot further asserts that CBA requires learners to demonstrate competencies and learning outcomes in performance assessment which vary in terms of simplicity and complexity such as from simple constructed responses to comprehensive collections of work over time, all of which are then judged . Learners are expected to be deeply involved in the assessment process and they areto be aware of the specified criteria that they have to meet as well as the standards of performance that are expected of them right from the beginning even before the assessment is conducted. Theoretically, tThis allows learners to take charge of and control over their own learning outcomes and success by preparing them selves well in advance. In other words, learners would have the autonomy for in their own learning, as CBA canould promote individuality and personal development (Ecclestone, 1996). The learners responsibility includes demostrating the It is also here in CBA that learners have to show their ability to apply theoretical knowledge and procedures, in addition to their understanding ofbeing able to describe the theories or even point to appropriate theoretical knowledge (Cotton, 1995). In demonstrating competence Cotton further elucidates that learners also have to express wise use of common sense in the public by demonstrating good physical, interpersonal and intrapersonal skills with mindful decision- making; that suggests the multiple intelligence described by Gardner (1985). In other words, learners have to demonstrate their abilities in all the three psychological domains of psychomotor, cognitive and affective learning (ANTA, 1998). Similarly, the Australias National Training Auth ority (ANTA) (1998) considers CBA to be a platform for learners to display their skills, knowledge and experience in accomplishing specific tasks as required in the workplace or to obtain a credit towards a qualification in the vocational and education training (VET). A Both the assessors and learners have one thing in common: to focus on and that is the set of learning outcomes that can be derived from an assessment. Learning outcomes cover diverse range of areas including personal qualities, various forms of knowledge and skills (Ecclestone, 1996). In this case it is the evidence of competence that learners have to demonstrate and which the assessors have to observe for and make judgments on, has to meet specified criteria. Thus, CBA consists of specified set of both the general and specific outcomes that assessors, learners and third parties can make reasonably objective judgments with respect to learners achievement or non-achievement of these outcomes (Wolf, 1995). CBA then certifies learners progress based on the demonstrated achievement of these outcomes while the assessments may not be necessarily tied to time served in formal educational settings. The emphasis is on the outcomes specifically, multiple outcomes, each distinctive and separ ately considered which should be specified clearly and as transparent as possible for assessors, assessees and third parties to understand what is being assessed and what should be achieved (Wolf, 1995) . This definition encapsulates the key-features of CBA as it has been developed and promoted for the vocational, technical and professional education and training in the UK while at the same time it signals the American origins of much of the debate (Wolf, 1995). The demonstrated performance that provides evidence of competence has to be at least of the minimum required quality in the real life workplace environment. These are the predetermined criteria set in CBA which are generally based on endorsed industry benchmark or competency standard (ANTA, 1998). The emphasis on outcomes and transparency is not only peculiar to the competence-context but it is also an essential characteristic of criterion-referenced assessment. The emphasis on what learners can actually do and the beneficia l effects of clear criteria on teaching and learning (Glaser, 1963; Popham, 1978) are argued to meet the competence-based literature where in England in the early years of the implementation of CBA, such system was referred to as criterion-referenced approach (Jessup 1991: 167). Jessup (1991) further underlines that what people actually learn from an education and training system and how effectively, as the key factor to measure its success. Thus, CBA is considered a criterion-referenced interpretation of assessment (Nuttall, 1984; Ling, 1999) where individuals are given an award after achieving the pre-determined standards (Cotton, 1995). This critical attribute of CBA will be discussed further in section 4.3.2. 4.3 Critical Attributes of Competence-based Assessment The following section discusses the two learning theories associated with CBA and the nature of its criterion-referenced assessment. 4.3.1 Learning Theories Associated with Competence-based Assessment Learning in the psychology and education contexts is a the process of acquiring knowledge, skills, and values, and world views acquisition and enhancement through ones integrated employment of cognitive, emotional, and experiences (Illeris, 2000; Ormorod, 1995). How this process works is explained variously. Learning as a process focuses on what happens when the learning takes place and the explanations of what happens constitute learning theories. In other words, learning theories are attempts to describe how people and animals learn, and they help uncover the inherently complex process of learning to our understanding. Hill (2002) explains that learning theories have two main values. The first is to provide adequate vocabulary and a conceptual framework in to interpreting examples of observed learning; and the second. Next is to suggest the right directions to look for solutions to practical problem instead of providing the solutions. Learning theories are therefore, the basis for any form of educational assessment (Gipps, 1994) and the theories most commonly associated to with CBA are the behaviourism and, more recently, the constructivism. These two theories will be discussed as CBA essentially involves observable aspects of learning and learning as a process for construction of new knowledge. Although the cognitive theory which looks beyond behaviour to explain brain-based learning is important, the need for it in CBA is not that apparent or crucial. Thus it is not included in the discussion. 4.3.1.1 Behaviourist Learning Theory Behaviourism is a theory of organism (may it be an animal or human) learning that only focuses on objectively observable behaviours and discounts mental activities (Murphy, 1999; Kerka, 1997; Doolittle Camp, 1999) with the assumption that a learner starts off as a clean slate (i.e. tabula rasa) and is essentially passive, responding to environmental stimuli (Murphy, 1999; Kerka, 1997) in the acquisition of new behaviour (Chowdhury, 2006). Learning according to the behaviourists takes place as the result of a response that follows on a specific stimulus and that behaviour is shaped through reinforcement (Kerka, 1997). By repeating the Stimulus-Response (S-R) cycle the learner is conditioned into repeating the response whenever the same stimulus is present and thusbehaviour can be modified and learning is measured by observable change in behaviour (Murphy, 1999; Kerka, 1997; Doolittle Camp, 1999). Theis emphasis on stimulus-response pairing (Murphy, 1999; Chowdhury, 2006) and the rejections to of structuralism (Kerka, 1997) reflected behaviourisms positivistic philosophical base, as the analysis of the human condition relies on only verifiable observations of behaviour and not on untenable mentalistic constructs (Kerka, 1997). Furthermore,Accordingly most human behaviour could can be understood as basic reflexive learning mechanisms or laws that operate on ones experience within the environment (Kerka, 1997). As the approach is seen to be more operational and practical in nature, it has dominated education.n, in which Tthe teacher disseminates selected knowledge, measures learners passive reception of facts, and focuses on behaviour control and task completion (Kerka, 1997). These views of the behaviourists and the learning characteristics that can be found in the education setting are summarised in Table___. Generally, conditioning has been identified in experiments by behaviourists to be a universal learning process. There are two different types of conditioning, each yielding a different behavioural pattern: Classic conditioning occurs when an instinctive reaction responds to a stimulus (Comer, 2004). Essentially, animals and people are biologically wired so that a certain stimulus will produce a specific response. As such, learning process takes place when two events that repeatedly occur close together in time are associated in a persons mind to impulsively produce the same response. The most popular example is Pavlovs observation that dogs salivate when they eat or even see food where food is unconditioned stimulus and the salivation, the unconditioned reflex (Comer, 2004; Chowdhury, 2006). Pavlovs theory of classical conditioning is considered a foundation of learning theories to the behaviourists. According to Pavlovs experiment, when some neutral stimulus, such as the ringing of a bell, is combined with the presentation of food and is repeated for a period of time, the dog salivates with the ringing of the bell, even though food is not given. Hence, the ringing of the bell acts as the conditioned stimulus while salivation is the conditioned response or reflex (Dembo: 1994). The result of this experiment led to the formation of Pavlovs classical conditioning in which an individual responds to some stimulus that would ordinarily produce such a response. Behavioural or operant conditioning occurs when a response to a stimulus is reinforced. Basically, operant conditioning is a simple feedback system: If a response to a stimulus is rewarded or reinforced, then the response is likely to take place in the future. Similarly, when a particular behaviour is rewarded, that behaviour is repeated as shown in the experiment conducted by B.F. Skinner using reinforcement techniques to teach pigeons to dance and bowl a ball. B.F. Skinner based his theory upon the idea that learning is a function of change in overt behaviour where these changes in behaviour are the result of an individuals response to events (stimuli) that occur in the environment (Chowdhury, 2006). According to Skinner, a reward or punishment will either strengthen or weaken a voluntary or automatic behaviour (Skinner: 1968). Ever since its introduction, the reinforced techniques have gone through series of enhancement and have contributed tremendously in training and teaching. The most important aspect of Skinners contribution to training is the significance attached to the desired behaviour to be emitted in certain environment. In order for the trainer to ensure the right behaviour is reinforced in the trainees, the trainer should have the clear idea about the terminal behaviour of the trainees, and should closely follow the trainees to appropriately reinforce correct responses. This is the purpose of programmed instructions including competence-based training in its early years of implementation which was based on this theory of reinforcement (Burns, 1995). . As the emerging learning theory of the early 1900s, behaviourism provided the final found ation for social efficiency as learning which is seen objectively consists of the formation of links between specific stimuli and responses through the application of rewards ( Wirth, 1972 ). The emphasis on the need of objectivity leads to extensive use of statistical and ma thematical analysis. Despite all the remarkable contribution s the learning theory has to offer , the extreme focus on objectivity has totally ignored the significant role the mind play in shaping ones behaviour. Men are treated more like robots or machines than human beings as their thoughts and feelings are not taken into consideration. They are expected to demonstrate desired behaviour through the use of reward and punishment neglecting other factors that may have an influence on the change in behaviour. Thus, the behaviourist theory of learning is lacking in utilizing the full potential of the mind in moulding essential behaviour and in constructing new knowledge . Assessment in Behaviourism Assessment, according to behaviourism, is a test (the stimulus) for which the answer (the response) is conditioned In accordance to the behaviourist learning theory which focuses on the stimulus-response cycle to attain observable conditioned behaviour, assessment in the behaviourism also applies the same concept. Thus, t he test item is the stimulus, the answer is the response and a learner has to be conditioned to produce the appropriate response to any given stimulus ( (Murphy, 1999; Kerka, 1997; Doolittle Camp, 1999). NSince the emphasis is on the response that is observable, no attention is paid to any model of the thinking process of the learner which might intervene between stimulus and response. Consequently, the distinctions between rote learning and learning with understanding is not considered as teaching is a matter deliveringof delivering the appropriate stimuli while learning is a matter of repeating the appropriate response, which will be rewarded. is what matters the most in which teaching is by repetition and then rewarding the appropriate responses. As such, a test composed of many short, atomised, out-of-context questions, and teaching to the test, are both consistent with this approach (Murphy, 1999; Kerka, 1997). Likewise, some forms of CBA which has always been associated to thewith behaviourist theory can be seen to assess, atomistically. applied the atomistic but not out of context approach. The assessor who is an observer ticks off a checklist of predetermined criteria whenever a learner has performed a series of discrete observable tasks. The criteria are the stimuli, the accomplished tasks the responses and learner has to be conditioned to demonstrate the ability to meet the criteria successfully. Although this approach to assessment may developstestify to learners ability to perform observable tasksbehaviours, it does not pay much attention to the theoretical knowledge and understanding (Ashworth, 1992) as the role of the mind is considered insignificant in delivering the required behaviour. While assessing competent observable performance is vital, assessing knowledge and understanding is just as important as it is an essential aspect of competence without which an assessment is lacking in credibility or construct validity (Ashworth, 1992). A valid assessment method should be able to measure what it is supposed to measure which in this case (Watson, 1994). Given the extensive discussion in Chapter ? on the idea of competence, both the observable performance behaviour and underpinning knowledge are aspects of competence that should be assessed and measured. People who understand are those who have clear mental representation of the situation with which they are confronted and are able to deal with it creatively and imaginatively using the acquired knowledge which acts as an interpretive resource for them (Ashworth, 1992). Thus, it is insufficient to assess ones competence just by looking at the performance while ignoring the aspect of knowledge and understanding. It is unfortunate then, if such an assessment method should produce people who are like robots in a factory; they couldwho can perform a job or a task efficiently and effectively but they do not have any understanding of what they were are doing. As the approachCBA also emphasises personal competence within competence concentrates on an individual demonstrating competent performance ((Wolf, 1995), traditional notions of CBA have allowed an and emphasises on personal competences, it leads to one being individualistic perspective whilst lacking ignoring the very necessary in the abability of being able to work as a team player to work as a team whereas team work is essential in performing relevan t aspect of a job in the actual workplace (Ashworth, 1992). As a result, theis behaviourist view of CBA has eventually shifted to the constructivist belief as discussed in the following section.weakened. Despite all the remarkable contributions the learning theory has to offer, the extreme focus on objectivity has totally ignored the significant role that the mind plays in influencing ones behaviour. People are treated more like robots or machines than human beings as their thoughts and feelings are not taken into consideration. They are expected to demonstrate desired behaviour through the use of reward and punishment neglecting other factors that may have an influence on the change in behaviour. 4.3.1.2 Constructivist Learning Theory Constructivism is a theory of learning that has roots in both philosophy and psychology (Doolitle Camp, 1999) founded on the premise that learners actively construct their own knowledge, meaning and understanding of the world they live in by reflecting on their experiences (Doolitle Camp, 1999; Murphy, 1999; Kerka, 1997). Learners learn by doing rather than observing and by bringing prior knowledge into a learning situation (Epstein Ryan, 2002; Carvin, date?) in which they must critique and re-evaluate their understanding of it until they can demonstrate their comprehension of the subject (Carvin). Furthermore, learners need to analyse and transform new information or problems in their minds based on existing knowledge and understanding where these abstract thoughts evolve from concrete action (Murphy, 1999). Learning, therefore, is simply the process of adjusting their mental models to accommodate new experiences. TBasically, the theory of constructivism rests on the notion that there is an innate human drive to make sense of the world by building cognitive structures which include declarative knowledge (know that facts, concepts, propositions) and procedural knowledge (know how techniques, skills, and abilities) (Murphy, 1999). These two components of knowledge have been discussed in depth in Chapter 3. Moreover, learning is a matter of personal and unique interpretation which takes place within the social context and is of useful to the learner as intrinsic motivation emerges from the desire to understand and to construct meaning (Billet, 1996). However, dispositions such as attitudes, values and interests that help learners decide, are often neglected in this theory (Murphy, 1999) making it incomprehensive and insufficient in a way. Philosophically, the essence of constructivism relies on an epistemology that stresses subjectivism and relativism, where personally unique reality resulted from the concept that reality can be known through experience although it may exist separate from experience (Doolitle Camp, 1999). Hence came four essential epistemological tenets of constructivism (Von Glasersfeld ,1984; 1998; Doolitle Camp, 1999); Knowledge is the result of active cognizing by the individual ; Cognition is an adaptive process that functions to make an individuals behaviour more viable given a particular environment; Cognition organizes and makes sense of ones experience, and is not a process to render an accurate representation of reality; and Knowing has roots both in biological/neurological construction, and in social, cultural, and language-based interactions (Dewey, 1916/1980; Garrison, 1997; Larochelle, Bednarz, Garrison, 1998; Gergen, 1995). Thus, constructivism acknowledges the active role learners play in the personal creation of knowledge, the importance of both the individual and social experiences in this knowledge creatio

separation of powers Essays -- essays research papers

In the United States government there are 3 branches of government, the power given to the central government is divided among these 3 branches. Each of these branches are given powers so that they can check the powers of the other 2 branches ensuring that one branch doesn’t become to powerful One of these branches is the legislative branch this is the branch that includes congress, they are responsible for making laws. The second branch of government is the executive branch this is the branch that includes the president, they are responsible for carrying out laws. The last branch of government is the judicial branch, this branch includes the Supreme Court they are responsible for making sure laws are constitutional. There many different ways at which each of these branches check the powers of the next branch, they include appointing new members to each branch, vetoing laws proposed by a branch, declaring a law unconstitutional and many other different powers.   Ã‚  Ã‚  Ã‚  Ã‚  The legislative branch just like every other branch in the government has the power to check other ones and is checked by the opposing branches. This legislative branch checks the powers of the executive branch in many different ways ensuring that they do not become overpowering. One way in which the legislative branch checks the power of the executive branch is if congress †the legislative branch† decides that the president is not doing his job to the full extent that he should, they have...

Pressure Measurement and Calibration

52 PRESSURE MEASUREMENT AND CALIBRATION (TH2) 53 EQUIPMENT DIAGRAMS 54 55 56 EQUIPMENT DESCRIPTION Refer to the drawing on pages 56, 57 and 58. This equipment is a bench top unit designed to introduce students to pressure, pressure scales and common devices available to measure pressure. The equipment comprises a Dead-weight Pressure Calibrator to generate a number of predetermined pressures, connected to a Bourdon gauge and electronic pressure sensor to allow their characteristics, including accuracy and linearity, to be determined. The Dead-weight Pressure Calibrator, Bourdon gauge and pressure sensor are mounted on a common PVC base plate. The electrical console is free standing. The Dead-weight Pressure Calibrator consists of precision ground piston (10) and matching cylinder (11) with a set of weights (12). In normal use the appropriate combination of weights is applied to the top of the piston, to generate the required predetermined pressure, and then the piston is set spinning, to reduce vertical friction, while the readings from the measuring devices are recorded. The operating range of the Dead-weight Pressure Calibrator and instrumentation is 20 kNm-2 to 200 kNm-2. The Bourdon gauge (5) and pressure sensor (6) are mounted on a manifold block (2) with a priming vessel (4) to contain the hydraulic fluid which is chosen to be water for safety and ease of use. A priming valve (7) between the reservoir and the manifold block allows the cylinder, manifold block and gauge on test to be easily primed with the water ready for use. A damping valve (8) between the cylinder and the manifold block allow the flow f water to be restricted to demonstrate the application of damping. An additional isolating valve (9) on the manifold block allows water to be drained from the manifold block or allows alternative devices to be connected for calibration. Such devices can be tested over the range 20 kNm-2 to 200 kNm-2. The Bourdon gauge (5) supplied is a traditional industrial instrument with rotary scale and mechanical indicator. The gauge has a 6† diameter dial that incorporates an arbitrary scale calibrated in degrees of rotation (independent of unit pressure) in addition to the usual scale calibrated in units of kNm-2. A clear acrylic front face allows observation of the Bourdon tube the mechanism that converts motion of the Bourdon tube to rotation of the indicator needle. The electronic pressure sensor (6) supplied incorporates a semi-conductor diaphragm that deflects when pressure is applied by the working fluid. This deflection generates a voltage output that is proportional to the applied pressure. The pressure sensor should be connected to the socket (20) marked ‘Pressure Sensor’ on the front of the console. The power supply, signal conditioning circuitry etc are contained in a simple electrical console (15) with appropriate current protection devices and an RCD (26) for operator protection. The electrical console is designed to stand alongside the Dead-weight Pressure Calibrator on the bench top. All circuits inside the console are operated by a main on/off switch (16) on the front of the console. 57 The various circuits inside the console are protected against excessive current by miniature circuit breakers, as follows: CONT (27) O/P (28) This breaker protects the power supply and circuits inside the console. This breaker protects the electrical output marked OUTPUT (23) at the rear of the console. The socket is used to power the IFD3 interface used for data logging. The voltage from the pressure sensor is displayed on a digital meter (17) on the electrical console. An additional conditioning circuit incorporates zero and span adjustments and allows the voltage output from the pressure sensor to be converted and displayed as a direct reading pressure meter calibrated in units of pressure. The zero control (21) and span control (22) are mounted on the front of the console for ease of use. A selector switch (18) allows the voltage from the sensor or the direct reading pressure reading to be displayed as required. The voltage from the pressure sensor is simultaneously connected to an I/O Port (19) for the connection to a PC using an optional interface device (TH-IFD) with educational software package (TH2-303). Alternatively, the signal can be connected to a user supplied chart recorder if required. Before use, the priming vessel must be filled with clean water (preferably deionized or demineralised water) and the calibrator, Bourdon gauge and pressure sensor fully primed. 8 OPERATIONAL PROCEDURES This equipment has been designed to operate over a range of pressures from 0 kN/m2 to 200 kN/m2 may damage the pressure sensors. In order to avoid such damage, DO NOT APPLY CONTINUOUS PRESSURE TO THE TOP OF THE PISTON ROD WHEN THE PRIMING VALVE IS CLOSED except by the application of the masses supplied. An impulse may be applied to the piston when operating at a fluid pressure of less than 200 kN/m2. This procedure is described in Experiment P1. The following procedure should be followed to prime the Dead-weight Calibrator and pressure sensors, prior to taking readings: Level the apparatus using the adjustable feet. A circular spirit level has been provided for this purpose, mounted on the base of the dead-weight calibrator. Check that the drain valve (at the back of the Bourdon gauge base) is closed. Fill the priming vessel with water (purified or de-ionized water is preferable). Open the damping valve and the priming valve. With no masses on the piston, slowly draw the piston upwards a distance of approximately 6 cm (i. . a full stroke of the piston). This draws water from the priming vessel into the system. Firmly drive the piston downwards, to expel air from the cylinder back towards the priming vessel. Repeat these two steps until no more bubbles are visible in the system. It may be helpful to raise the central section of the return tube between the manifold block and the priming vessel. This will help to prevent air be ing drawn back into the system as the piston is raised. Raise the piston close to the top of the cylinder, taking care not to lift it high enough to allow ir to enter, and then close the priming valve. The following procedure describes the calibration of the semiconductor pressure sensor. The procedure differs if using the optional TH-303 software, in which case users should instead refer to the Help Text provided with the software. Remove the piston from the cylinder, and switch the selector knob on the console to ‘Pressure’. This the ‘zero’ control on the console until the display reads zero. This sets the first reference point for the sensor calibration. Return the piston to the cylinder, and reprime the system as described above. Place all the supplied masses onto the piston, with the greatest mass (2 ? kg) being added last. This corresponds to an applied pressure of 200 kN/m2. Spin the piston, and adjust the ‘span’ control until the sensor output matches the applied pressure. This sets the second reference point for the calibration. 59 The calibration may be tested by applying a mass to the piston, spinning the piston in the cylinder, and then comparing the applied pressure to the sensor output. Each ? kg of applied mass corresponds to 20 kN/m2 of applied pressure. This piston itself gives an applied pressure of 20 kN/m2. 0 NOMENCLATURE FOR TH2 The following nomenclature has been used for the theory and calculations presented in this manual: Name Piston diameter Cross-sectional area Mass of piston Mass on mass piston Applied mass Acceleration due to gravity Applied force Nom d A Mp Mm Ma g F Units m m? kg kg kg m/s2 kg Type Given Calculated Given Recorded Calculated Given Recorded Definition The diameter of the dead weight calibrator piston. Cross-sectional area of dead weight calibrator cylinder. Mass of the dead-weight calibrator piston. Mass applied to piston. Ma = Mp + Mm g = 9. 1 m/s2 Force applied to fluid in system by piston and masses. F = g x Ma Pressure applied to fluid by dead weight calibrator P = F/A Ambient (atmospheric) pressure of the surroundings. Applied pressure relative to the pressure of total vacuum Needle angle taken from Bourdon gauge scale Semiconductor output taken from console display Gauge pressure taken from Bourdon gauge scale Calibrated semiconductor output taken from console display Applied pressure Barometric pressure Absolute pressure Needle angle Semi-conductor output Indicated Bourdon gauge pressure Indicated semi-conductor pressure Pa Patm Pabs ? e Pb Ps N/m2 N/m2 N/m2 Calculated Recorded Calculated degree Recorded V N/m2 N/m2 Recorded Recorded Recorded 61 NOMENCLATURE FOR ERROR ANALYSIS The following nomenclature has been used for the error analysis presented in this manual: Name Indicated value Actual value Range Definition Gauge reading, i. e. the pressure indicated by sensor used True pressure, pressure applied by dead-weight calibrator Total range of values covered in the results, or total range of values measurable on instrument scale. Calculation Pi = Pb or Ps, depending on the sensor used Actual value = Applied pressure, Pa Range = Largest result – Smallest result = Pi max – Pi min or Range = Maximum possible reading – Minimum possible reading (200 kN/m? for apparatus used) No calculation. Precise data have a small scatter, indicating minimal random error ea = |Pi – Pa | ea max = ? (Pi – Pa)max? e%a = ea max X 100 Pa e%f = ea max X 100 Range Pmin = P1 + P2 + †¦.. + Pn n da = |Pi – Pmin| dm = da1 + da2 + †¦ + dan n ? = da12 + da32 + †¦ + dan2 n-1 ? Precision How closely the results agree with each other. Actual difference Modulus of the difference between indicated value and actual value Accuracy Maximum difference between indicated pressure and actual pressure Percentage accuracy Greatest difference between of actual scale reading indicated pressure and actual pressure, as a percentage of the actual pressure. Percentage accuracy Greatest difference between of full-scale reading indicated pressure and actual pressure, as a percentage of the range. Mean Sum of results divided by number of results. Absolute deviation Difference between a single result and the mean of several results Mean deviation Sum of the absolute deviations divided by the number of absolute deviations Standard deviation Commonly used value in analysis of statistical data 62 DATA SHEET 7 RELATIVE AND ABSOLUTE PRESSURE The measurement of any physical property relies upon comparison with some fixed reference point. Pressure is one such property, and pressure measurement must begin by defining a suitable fixed point. An obvious reference point is that of the ambient pressure of the surroundings. Pressure scales have been based around a zero point of the pressure of the atmosphere at sea level. Pressures lower than atmospheric are assigned negative values; pressures higher than atmospheric have positive values. Gauges for measuring pressure give readings relative to this zero point, by comparing the pressure of interest to the pressure of the surrounding air. Pressure measured with such a gauge is given relative to a fixed value, and is sometimes termed gauge pressure. Gauge measure pressure difference between the pressure to be measured and the barometric (ambient) pressure. This may then need adjusting, to take into account any difference between barometric pressure and the pressure at sea level. Many calculations using equations derived from fundamental physical laws require absolute pressure values. Absolute pressure is the pressure relative to a total absence of pressure (i. e. a total vacuum). On an absolute pressure scale, all pressures have a positive value. The following chart illustrates the difference between gauge pressure, barometric pressure, and absolute pressure. 63 DATA SHEET 8 TECHNICAL DATA The following information may be of use when using this apparatus: Operating range of dead-weight pressure calibrator Diameter of dead-weight calibrator piston Cross-sectional calibrator area of dead-weight 20 kN/m2 – 200 kN/m2 0. 017655 m 0. 000245 m2 20 kN/m2 150 mL Pressure produced in cylinder by mass of piston with no applied masses Approximate capacity of priming vessel 64 EXPERIMENT P1 CONCEPTS OF PRESSURE AND PRESSURE SENSOR BEHAVIOUR OBJECTIVE To gain a basic understanding of the concept of pressure and its measurement. To investigate the behavior of two kinds of pressure sensor, and the effect of damping on pressure measurement. †¢ To gain a basic understanding of the concept of pressure and its measurement. †¢ To investigate the behaviour of two kinds of pressure sensor †¢ To observe the effect of damping on pressure measurement METHOD To investigate the response of two kinds of pressure sensor to a pressure applied by a dead-weight calibrator device. To investigate the response of these sensors to the application of a sudden pressure spike, with varying levels of restriction of the liquid between the pressure application and the sensor. THEORY Pressure is the force exerted by a medium, such as a fluid, on an area. In the TH2 apparatus, pressure is exerted by a piston on a column of water. The pressure applied is then equal to the force exerted by the piston over the cross-sectional area of the fluid. The use of the piston and masses with the cylinder generates a measurable reference pressure, Pa: Pa = Fa A 65 where Fa = gMa, and Fa = force applied to the liquid, Ma = total mass (incl. piston), and A = area of piston. The area of the piston can be expressed in terms of its diameter, d, as: A = ? d2 4 The units of each variable must agree for the equations to be valid. Using SI units, Pa will be in Newtons per square metre (N/m? , also known as Pascals) if Fa is in Newtons, A is in square metres, and d is in metres. The use of specific units of pressure will be covered in exercise B. For this exercise the area of the cylinder is a constant. The pressure can therefore be considered directly proportional to the mass applied to the mass on the piston Pressure measurement is normally concerned with measuring the effects of a pressure differential between two points in a fluid. The simplest form of pressure sensor is a manometer tube, in which a tube of fluid is exposed at one end to the first point in the fluid, and at the other to the second point. Any pressure differential causes a displacement of fluid within the tube, which is proportional to the difference. Manometers (not included with the TH2 apparatus) are cheap, simple, and can be designed to cover a wide range of pressures. However, they are best used for measuring static pressures below about 600 kN/m? , as the required height of the fluid becomes unworkable at greater pressures. Their dynamic response is poor, so they are best suited to measuring static or slowly changing pressures. Some fluids used are toxic (such as mercury), and may be susceptible to temperature change. The Bourdon-type pressure gauge consists of a curved tube of oval cross-section. One end is closed, and is left free to move. The other end is left open to allow fluid to enter, and is fixed. The outside of the tube remains at ambient pressure. When fluid pressure inside the tube exceeds the pressure outside the tube, the section of the tube tends to 66 ecome circular, causing the tube to straighten (internal pressure lower than the ambient pressure conversely causes increased flattening, and the curve of the tube increases). A simple mechanical linkage transmits the movement of the free end of the tube to a pointer moving around dial. This type of gauge is one of the two kinds included in the TH2 apparatus. The second type of pressure gauge included as part of the TH2 is an electromechani cal device. In a basic semiconductor pressure sensor, silicon strain gauges are fixed to one side of a diaphragm. The two sides of the diaphragm are exposed to the two different pressures. Any pressure differential causes the diaphragm to expand towards the lower-pressure side, producing a change in the strain gauge voltage reading. The electronic semiconductor pressure sensor included with the TH2 is a more refined device with improved reliability and sensitivity for pressure measurement. It includes temperature compensation to reduce the effects of temperature variation on the results. The strain gauges used are formed by laying down a protective film of glass onto stainless steel, followed by a thin film of silicon. The silicon is doped to produce semiconductor properties, and a mask is photoprinted onto it. The unmasked silicon is then removed, leaving a pattern of silicon semiconductor strain gauges molecularly bonded onto the surface of the steel. The gauges are connected to an Ohmmeter through a Wheatstone bridge, to amplify the signal produced. 67 In this type of sensor, a diaphragm is still used, but instead of fixing the strain gauges to the surface, the deflection of the diaphragm moves a steel force rod. This transfers the force to one end of the steel strip that the semiconductor resistors are bonded to. The resulting deflection of the strip causes compression in some strain gauges, and tension in others, changing their resistance and producing a measurable output. Both the TH2 pressure sensors are set up to indicate the pressure differential between atmospheric pressure, and fluid pressurized with the use of the dead-weight calibrator. The fluid passes through a damping valve, positioned between the calibrator and the sensors. By partially closing the valve, fluid flow can be restricted. This affects the speed at which pressure is transferred from the point of application to the sensors. EQUIPMENT SET UP Level the apparatus using the adjustable feet. A circular spirit level has been provided for this purpose, mounted on the base of the dead-weight calibrator. Check that the drain valve (at the back of the Bourdon gauge base) is closed. Fill the priming vessel with water (purified or de-ionized water is preferable). Fully open the damping valve and the priming valve With no masses on the piston, slowly draw the piston upwards a distance of approximately 6cm (i. e. a full stroke of the piston). This draws water from the priming vessel into the system. Firmly drive the piston downwards, to expel air from the cylinder back towards the priming vessel. Repeat these two steps until no more bubbles are visible in the system. It may be helpful to raise the central section of the return tube between the manifold block and 68 the priming vessel. This will help to prevent air being drawn back into the system as the piston is raised. Raise the piston close to the top of the cylinder, taking care not to lift it high enough to allow air to enter, and then close the priming valve. PROCEDURE This equipment has been designed to operate over a range of pressure from 0 kN/m2 to 200 kN/m2. Exceeding a pressure of 200 kN/m2 may damage the pressure sensors. In order to avoid such damage, DO NOT APPLY CONTINUOUS PRESSURE TO THE TOP OF THE PISTON ROD WHEN THE PRIMING VALVE IS CLOSED except by application of the mass supplied. An impulse may be applied to the piston when operating at a fluid pressure of less than 200 kN/m2, as is described later in this procedure. Behavior of pressure sensors Spin the piston in the cylinder, to minimize friction effects between the piston and the cylinder wall. While the piston is spinning, record the angle through which the Bourdon gauge needle has moved, and the voltage output of the electronic sensor. Apply a ? kg mass to the piston. Spin the piston and take a second set of readings for the Bourdon gauge needle angle and the electronic sensor. Repeat the procedure in ? kg increments. When using several masses, it will be necessary to place the 2 ? kg mass on top of the other masses. Repeat the procedure while removing the masses again, in ? kg increments. This gives two results for each applied mass, which may be averaged in order to reduce the effects of any error in an individual reading. Effect of damping Apply a single mass to the piston, and spin it. While the piston is spinning, apply an impulse to the top of the piston by striking the top of the rod once, with the flat of the hand. Watch the behavior of the Bourdon gauge needle. Note the final sensor reading after the response settles. Slightly close the damping valve. Change the mass, spin the piston again, and apply an impulse to the rod. Observe any changes in the sensor responses. Repeat the procedure, closing the damping valve a little at a time and noting the response and the final sensor reading each time. RESULTS Tabulate your results under the following headings:- 69 Mass applied to calibrator Mm (kg) Deflection of Bourdon gauge needle (degrees) Output from electrochemical pressure sensor (mV) Notes on sensor behavior (damping) Plot a graph of sensor response against applied mass for each sensor. 70 EXPERIMENT P2 CONCEPTS OF PRESSURE MEASUREMENT AND CALIBRATION OBJECTIVE To convert an arbitrary scale of pressure sensor output into engineering units. To calibrate a semiconductor pressure sensor. METHOD To make use of a dead-weight calibrator in order to produce known forces in a fluid. THEORY It is recommended that students read Data Sheet 1: Relative and Absolute Pressures before proceeding with this exercise. Pressure sensor calibration Variation in a pressure sensor reading may be calibrated, using known pressures, to give a gauge reading in engineering units. From exercise A, the dead-weight calibrator used in the TH2 produces a known reference pressure by applying a mass to a column of fluid. The pressure produced is Pa = F Aa where Fa = gMa, and Fa is the force applied to the liquid in the calibrator cylinder. Ma is the total mass (including that of the piston) 71 g is the acceleration due to gravity, and A is the area of piston. The area of the piston can be expressed in terms of its diameter, d, as: A = ? d2 4 The pressure in the fluid may then be calculated in the relevant engineering units. These known pressures may then be compared to the pressure sensor outputs over a range of pressures. The relationship between sensor output and pressure may be turned into a direct scale, as on the Bourdon gauge scale. Alternatively, a reference graph may be produced. Where the relationship is linear and the sensor output is electrical, the sensor may be calibrated using simple amplifier (a conditioning circuit). When using SI units, the units of pressure are Newtons per square meter (N/m? , also known as Pascals). To calculate the pressure in N/m? , M must be in kg, d in m, and g in m / s?. For the pressure range covered in this exercise, it will be more convenient to use units of kN/m? , where 1 kN/m? = 1000 N/m? (1 N/m? = 0. 001 kN/m? ). Barometric pressure: pressure units and scale conversion Barometric pressures is usually measured in bar. One bar is equal to a force of 105 N applied over an area of 1m?. While bar and N/m? have the same scale interval, pressure in bar often has a more convenient value when measuring barometric pressure. Pressure may also be measured in millimetres of mercury (mmHg). The pressure is given in terms of the height of a column of mercury that would be required to exert an equivalent pressure to that being measured. Another possible unit of measurement is atmospheres (atm). One standard atmosphere was originally defined as being equal to the pressure at sea level at a temperature of 15 °C. A pressure unit still in everyday use is pounds per square inch (psi or lbf / in.? ). One psi is equal to a weight of one pound applied over an area of 1 in.? If a barometer is available to measure the ambient pressure in the room where the equipment is located, the barometer reading should be converted SI units. Pressures may be converted from one scale to another using a conversion factor. A list of conversion factors is provided below. 72 1 atm = = = = = = = = = = = = = = = = = = = = 101. 3 x 103 101. 3 1. 013 760 14. 696 100 x 103 100 0. 987 750. 006 14. 504 133. 3 x 103 133. 3 1. 33 1. 316 19. 337 6. 895 x 106 6. 895 x 103 68. 948 68. 046 51. 715 N/m2 kN/m2 bar mmHg psi N/m2 kN/m2 atm mmHg psi N/m2 kN/m2 bar atm psi N/m2 kN/m2 bar atm mmHg 1 bar 1 mmHg x 103 1 psi x 103 ADDITIONAL EQUIPMENT REQUIRED Values for the piston diameter and weight are provided. These may be replaced by your own measurements if desired. The following equipment will be required to do so: a) Vernier calli pers or a ruler, to measure the piston diameter b) A weigh-balance or similar, to measure the piston weight EQUIPMENT SET UP Carefully remove the piston from the cylinder, weigh it. Take care not to damage the piston, as it is part of a high precision instrument and any damage will affect the accuracy of the experimental results. Level the apparatus using the adjustable feet. A circular spirit level has been mounted on the base of the dead weight calibrator for this purpose. Check that the drain valve (at the back of the Bourdon gauge base) is closed. Fill the priming vessel with water (purified or de-ionized water is preferable). Open the damping valve and the priming valve. 73 With no masses on the piston, slowly draw the piston upwards a distance of approximately 6cm (i. e. full stroke of the piston). This draws water from the priming vessel into the system. Firmly drive the piston downwards, to expel air from the cylinder back towards the priming vessel. Repeat these two steps until no more bubbles are visible in the system. It may be helpful to raise the central section of the return tube between the manifold block and the priming vessel. This will help to prevent air being drawn back into the system as the piston is raised. Raise the piston close to the top of the cylinder, taking care not to lift it high enough to allow air to enter, and then close the priming valve. Set the selector switch on the console to ‘Output’. PROCEDURE This equipment has been designed to operate over a range of pressure from 0 kN/m2 to 200 kN/m2. Exceeding a pressure of 200 kN/m2 may damage the pressure sensors. In order to avoid such damage, DO NOT APPLY CONTINUOUS PRESSURE TO THE TOP OF THE PISTON ROD WHEN THE PRIMING VALVE IS CLOSED except by application of the mass supplied. Conversion of an arbitrary scale into engineering units Spin the piston to reduce the effects of friction in the cylinder. With the needle still spinning, record the angle indicated by the Bourdon gauge needle. Place a ? kg mass on the piston, and spin the piston. Record the value of the applied mass, and the angle indicated by the Bourdon gauge needle. Increase the applied mass in increment of ? kg. Spin the piston and record the needle angle each increment. Repeat the measurements while decreasing the applied mass in steps of ? kg. This gives two readings for each applied mass, which may be averaged to reduce the effect of any error in an individual reading. Calculate the applied pressure at each mass increment. Calculate the average needle angle at each pressure increment. Repeat the experiment, this time recording the applied mass and the indicated pressure on the Bourdon gauge scale. Compare this to the average needle angle recorded previously. 74 Calibration of a semiconductor pressure sensor NOTE: This procedure differs if the TH2-303 software is being used. Please refer to the online product Help Text if using this software. Spin the piston. Record the voltage indicated on the semiconductor output display on the console. Place a ? kg mass on the piston, and spin the piston. Record the applied mass, and the voltage indicated on the semiconductor output display on the console. Increase the applied mass in steps of ? kg, spinning the piston and recording the semiconductor output each time. Repeat the measurement while decreasing the applied mass in steps of ? kg. Calculate the applied pressure at each mass increment. Calculate the average sensor output at each pressure increment. Slowly open the priming valve. Open the valve to its maximum, and check that the damping valve is also fully open. The fluid in the system will now be at approximately atmospheric pressure (it will be slightly higher than atmospheric due to the height of fluid in the reservoir, but this is negligible compared to the range of the sensors). Switch the selector knob on the console to PRESSURE Turn the ZERO control on the console until the display read zero, to set the first reference point for the sensor calibration. Raise the piston close to the top of the cylinder, taking care not to lift it high enough to allow air to enter, and then close the priming valve. Place a large mass on the piston, and calculate the corresponding applied pressure. Spin the piston and adjust the SPAN control until the sensor output matches the applied pressure, to set the second reference point for the calibration. Remove the masses from the piston. Take a set of readings from the calibrated semiconductor sensor, by adding masses to the piston in ? kg increments. Repeat the reading while decreasing the applied mass. This gives two reading for each applied mass, which may be averaged in order to reduce the effect of any error in an individual reading. 75 RESULTS Tabulate your results under the following headings: Barometric pressure Mass of piston Mp Diameter of cylinder, d Cross-sectional area of cylinder, A Mass on piston Mm (kg) Applied mass Ma (kg) Applied force Fa (N) Applied pressure †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦. †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦. †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦.. †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦.. Needle angle N/m2 kg m m2 Indicated Indicated SemiBourdon conductor semiconductor pressure pressure output Pb Ps Pa E ? (mV) (N/m2) (degrees) (N/m2) (N/m2) Plot graphs of average needle angle against applied pressure for the Bourdon gauge, and voltage output against applied pressure for the semiconductor sensor. Plot a graph of indicated pressure against actual pressure for the Bourdon gauge and the calibrated semiconductor pressure sensor. If there is facility for measuring barometric pressure, it is possible to calculate the absolute pressure corresponding to each applied pressure increment. The ambient pressure of the surroundings, Patm should be measured, then converted into N/m2 (if required). An additional column should be added to the results table: Absolute Pressure, Pabs (N/m2). Absolute pressure may then be calculated as Pabs = Pa + Patm 76 EXPERIMENT P3 ERRORS IN PRESSURE MEASUREMENT OBJECTIVE To investigate the sources of error when measuring pressure. METHOD Errors in measuring a quantity, such as pressure, can come from a number of sources. Some can be eliminated by careful choice of equipment and experimental method. Other errors are unavoidable, but can be minimized. In any experiment, it is good practice to note any possible sources of error in the results, and to give an indication of the magnitude of such errors. Errors fall into three general categories: Avoidable errors These are errors that must be eliminated, as any results including such errors will often be meaningless. Such errors include: †¢ †¢ †¢ †¢ Incorrect use of equipment Incorrect recording of results Errors in calculations Chaotic errors, i. e. random disturbances, such as extreme vibration or electrical noise that are sufficient to mask the experimental results. 7 Random errors Random errors should be eliminated if possible, by changing the design of the experiment or waiting until conditions are more favorable. Even if they cannot be eliminated, many random errors may be minimized by making multiple sets of readings, and averaging the results. Random errors include: †¢ †¢ †¢ †¢ Variation of experimental conditions (e. g. changes in ambie nt temperature) Variation in instrumentation performance Variation due to material properties and design (e. g. effect of friction) Errors of judgement (e. g. nconstancy in estimating a sensor reading) Systematic errors Systematic errors produce a constant bias or skew in the results, and should be minimized where possible. They include: †¢ †¢ †¢ †¢ Built-in errors (e. g. zero error, incorrect scale graduation) Experimental errors (due to poor design of the experiment or the apparatus) Systematic human errors (e. g. reading from the wrong side of a liquid meniscus) Loading error (errors introduced as a result of the act of measurement- for example, the temperature of a probe altering the temperature of the body being measured) Errors may also be described in a number of ways: Actual difference – the difference between the indicated value (the value indicated by the gauge or sensor) and the actual scale reading (the true value of the property being measured). The actual value must be known to calculate the actual difference. Accuracy – the maximum amount by which the results vary from the actual value. The actual value must be known. Percentage accuracy of the actual scale reading – the greatest difference between the actual value and the indicated value, expressed as a percentage of the actual value. The actual value must be known. Percentage accuracy of the full-scale reading (total range of the measurement device) – the greatest difference between the actual value and the indicated value, expressed as a percentage of the maximum value of the range being used. The actual value must be known. Mean deviation (or probable error) – The absolute deviation of a single result is the difference between a single result, and the average (mean) of several results. The mean deviation is the sum of the absolute deviations divided by their number. The actual value is not required. The mean deviation is an indication of how closely the results agree with each other. 78 Standard deviation (or mean square error) – the standard deviation is the square root of the mean of the squares of the deviations (‘better’ results are obtained by dividing the sum of the values by the one less than the number of values). This is a common measure of the preciseness of a sample of data- how closely the results agree with each other. The actual value is not required. ADDITIONAL EQUIUPMENT REQUIRED Values for the piston diameter and weight are provided. These may be replaced by your own measurements if desired. The following equipment will be required to do so: †¢ †¢ Vernier callipers or a ruler, to measure the piston diameter A weigh-balance or similar, to measure the piston weight EQUIPMENT SET UP To prime the cylinder, the following procedure should be followed (where this is required in the experiment): Level the apparatus using the adjustable feet. A circular spirit level has been mounted on the base of the dead weight calibrator for this purpose. Check that the drain valve (at the back of the Bourdon gauge base) is closed. Fill the priming vessel with water (purified or de-ionized water is preferable). Fully open the damping valve and the priming valve. With no masses on the piston, slowly draw the piston upwards a distance of approximately 6cm (i. e. a full stroke of the piston). This draws water from the priming vessel into the system. Firmly drive the piston downwards, to expel air from the cylinder back towards the priming vessel. Repeat these two steps until no more bubbles are visible in the system. It may be helpful to raise the central section of the return tube between the manifold block and the priming vessel. This will help to prevent air being drawn back into the system as the piston is raised. Raise the piston close to the top of the cylinder, taking care not to lift it high enough to allow air to enter, then close the priming valve. PROCEDURE This equipment has been designed to operate over a range of pressure from 0 kN/m2 to 200 kN/m2. Exceeding a pressure of 200 kN/m2 may damage the pressure sensors. In order to avoid such damage, DO NOT APPLY CONTINUOUS PRESSURE TO THE 79 TOP OF THE PISTON ROD WHEN THE PRIMING VALVE IS CLOSED except by application of the mass supplied. The following experiments give suggested ways in which particular sources of error may be investigated. It is recommended that only one or two be attempted in a single laboratory session, with each being repeated several times, giving multiple samples for the error analysis. Basic Error Analysis: The accuracy of the semiconductor calibration may be investigated by performing standard error calculations on the calibrated sensor output, using the results obtained in Experiment P2. If results are not available for analysis, the following procedure should be followed: Slowly open the priming valve. Open the valve to its maximum, and check that the damping valve is also fully open. The fluid in the system will now be at approximately atmospheric pressure (it will be slightly higher than atmospheric due to the height of fluid in the reservoir, but this is negligible compared to the range of the sensors). Switch the selector knob on the console to PRESSURE. Turn the ZERO control on the console until the display read zero, to set the first reference point for the sensor calibration. Raise the piston close to the top of the cylinder, taking care not to lift it high enough to allow air to enter, then close the priming valve. Place a large mass on the piston, and calculate the corresponding applied pressure. Spin the piston, and adjust the SPAN control until the sensor output matches the applied pressure, to set the second reference point for the calibration. Remove the masses from the piston. Take a set of readings from the calibrated semiconductor sensor, adding masses to the pan in ? kg increments, and again while decreasing the applied mass. This provides two set of readings for data analysis. The experiment should be repeated to provide further sets of data. Avoidable errors: Incorrect use of equipment Level the apparatus using the adjustable feet. A circular spirit level has been mounted on the base of the dead-weight calibrator for this purpose Check that the drain valve (at the back of the Bourdon gauge base) is closed, and the damping valve is fully open. 80 Remove the piston from the cylinder, then fill the priming vessel with water (purified or de-ionized water is preferable). Close the priming valve, then replace the piston in the cylinder. Take a set of readings without priming the system first. Random errors: Friction effects Prime the system as described in the equipment set up instructions. Tilt the board at an angle of about 5 to 10 degrees. THE EQUIPMENT BASE MUST STILL BE FIRM AND SECURE. Titling the apparatus in this way will exaggerate any friction effects, as the force applied by the piston will no longer be acting straight downwards on the column of fluids, but will have components acting at right-angles to cylinder wall. Spin the piston. Take one reading while the piston is spinning, then observe the behavior of the needle. Continue to watch the needle as the piston stops spinning, then make a note of the new gauge reading. Apply masses to the piston in ? kg increments. At each step, spin the piston, note the sensor output, and then take a second reading after the piston stops spinning. Systematic errors: Zero error Calibrate the semiconductor pressure sensor, but do not include mass of piston in the applied mass when calculating the applied pressure. Take a set of readings from the calibrated semiconductor sensor over a range of applied masses, now including the piston mass in the applied mass calculation. Human error Take a set or readings from the Bourdon gauge pressure scale, but stand at an angle to the dial face when taking each reading. Keep the same viewing angle for each reading. This illustrates the effect of parallax on the readings taken. RESULTS Tabulate your results under the headings on the following page: For each result, calculate the absolute difference, ea between indicated value Pi and the applied pressure Pa. 81 Find the maximum absolute difference, the accuracy ea max and use this value and the corresponding indicated pressure to calculate the % accuracy of actual scale reading and the % accuracy of full-scale reading (use a range of 200 kN/m2). Correlate the data for several test runs, to give a set of indicated pressure readings corresponding to a single applied pressure. Use this correlated data table to calculate the mean of the results, Pmean, the mean deviation, dm, the absolute deviation, da, and the standard deviation, ?. Errors can also be illustrated graphically: 85 Piston diameter, d = †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦. m Piston mass, MP = †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦.. kg Experimental conditions : †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦ Mass Applied Applied Applied Indicated Mean Absolute Standard Actual Accuracy % % Mean on deviation deviation deviation Accuracy Accuracy of mass force pressure pressure difference piston Actual Full result scale scale reading reading Mm dm da PI ea Emax e%a e%f Pmin Ma Fa Pa ? kg) (kg) (kN) (kN/m2) (kN/m2) (kN/m2) (kN/m2) (kN/m2) (kN/m2) 86 Plot a graph of actual pressure against indicated pressure. On the same graph, plot a straight line showing the actual pressure. This will illustrate three characteristics of the results: †¢ †¢ Deviati on of sensor readings from the actual value. Whether any deviation from the true reading is systematic (the graph will be a straight line or a smooth curve) or random (the graph will have no obvious relationship). Precision of the results. Precise results will be close together, not widely scattered. Precise results may still deviate strongly from the actual value. †¢