Estrogen Signaling Essay Example | Topics and Well Written Essays - 2000 words

Estrogen Signaling - Essay Example Estrogen is one of the important sex hormones. It has definite physiological roles, the most important of which are sexual and reproductive functions. Other biological roles include involvement in various functions attributing to the cardiovascular, immune, central nervous system and musculoskeletal systems (Gustafsson, 2003; cited in Heldring, 2007: 906). The body produces many estrogen types, the most potent of which is 12- beta estradiol or E2. E2, along with its 2 metabolites estriol and estrone exerts various biophysiological effects in the body (Heldring, 2007). These effects are mediated through binding of the molecules of estrogen to specific estrogen receptors. Currently, 2 specific estrogen receptors have been identified and they are ER-alpha and ER-beta. These receptors belong to class-1 nuclear receptors (Petterson and Gustafsson, 2001; cited in Heldring, 2007: 907). Binding of the ligands to these receptors induces certain conformation changes in the receptor which in tu rn leads to a series of changes in the receptors and ultimately ends in the preinitiation complex. The changes which occur in the receptors are migration of ER from cytosol to nucleus, dimerisation of the receptor molecules, binding and interactions between dimerised receptor protein and specific sequences of DNA, recruitment of various coregulator proteins concerned with the biological action and also recruitment of various transcription factors (Paech, Webb, Kuiper, et al,1997; cited in Heldring, 2007: 908).

Students Living at Home and Living Away from Family Essay Example for Free

Students Living at Home and Living Away from Family Essay This Chemistry module is designed for students who wish to study physical sciences or health sciences at tertiary level. | Pre-requisites:| None| ASSESSMENT STRATEGY * The outcomes of this module will be assessed using a variety of assessment strategies including, assignments and reports, in-class tests, laboratory investigations and an examination. * It is proposed that the following approximate weightings be assigned to the various forms of assessment within this module. * There may be significant variation in the assessment methods utilised by trainers in this module. Assignments/reports: 15-25% * Tests: 15-25% * Laboratory Investigations; 10 – 25% * Final Examination: %40 – 60% SUMMARY OF LEARNING OUTCOMES 1. Describe composition of matter and chemical change. 2. Explain trends within the periodic table. 3. Describe Chemical Bonding in its various forms 4. Calculate chemical quantities and stoichiometry 5. Explain Oxidation Reduction reactions 6. Demonstrate a knowledge of Organic Chemistry (Optional Element) LEARNING OUTCOME| ASSESSMENT CRITERIA| 1. Describe composition of matter and chemical change. 1. 1 Describe the nature of matter in terms of atoms and molecules, elements and compounds . 1. 2 Describe atomic structure and electron configuration. 1. 3 Describe chemical change in terms of transfer or sharing of electrons| 2. Explain trends within the periodic table. | 2. 1 Describe chemical periodicity including distinguishing between metals and non-metals2. 2 Relate the electron configuration of elements to their place in the periodic table| 3. Describe Chemical Bonding in its various forms | 3. Recall chemical names and formulae of common ionic and covalent compounds. 3. 2 Describe the nature and theory of chemical bonding for ionic and covalent compounds, metals and network solids3. 3 Describe and explain the shapes and polarity of simple molecules. 3. 4 Describe the states of matter in terms of intermolecular forces. Include the properties of gases. | 4. Calculate chemical quantities and stoichiometry| Students must demons trate that they can complete calculations involving:4. chemical quantities, the mole, percentage composition, and empirical formula. (optional)4. 2 balanced equations, mass-mass stoichiometry, mass-concentration stoichiometry 4. 3 solution stoichiometry, concentrations and volumetric analysis. | 5. Explain Oxidation Reduction reactions| 5. 1 Define Oxidation and reduction and identify oxidised and reduced species in chemical reactions. 5. 2 Determine oxidation number and use it to determine whether oxidation reduction has occurred in particular reactions.

Singapore English

Singapore English Introduction The range of domains and depth of use of English are closely related to the degree and manner of nativization in a non native variety. For the second category of users, however, the use of English is restricted to international purposes and the elite of societies in certain very specific domains like academic discussions and publications. The Singapore award-winning poet, Edwin Thumboo, expresses: We were very conscious of writing in English but not writing in England. We had to domesticate the English Language, give it a local habitation. For instance, I have never published a poem about a nightingale. But, of course, you cannot substitute one bird for another; you have to make the language your own. We were looking for an identity while using English to express it. (The Straits Times, 1989, November 1) Countries are institutionalized varieties, which have developed over an extended period of time and are now used in many domains. In his arguments for recognizing these varieties, Kachru says that non-native users of English have internalizations which are linked to their own multilinguistic, sociolinguistic and sociocultural contexts (B. B. Kachru, 1991, p. 5). The varieties differ from native varieties, in range and depth of their nativized features. The deviations from native norms occur at almost all linguistic levels -phonology, morphology, syntax, semantics, style and discourse, and they are systematic and productive. These latter varieties of non-native English (or new English (for examples of non-native English, see (Moag, 1982), as they have been called recently, have been accorded status by both native and non-native speakers and have received much attention from linguists, educators and writers. Some linguists have gone to the extent of advocating use of the educated nativized variety of English as the standard for teaching (Tay Gupta 1983; Gupta 1986). Historical Background of English in Singapore and Malaysia Any historical discussion on Singapore, especially relating to the period before its independence in 1965, is almost always linked to historical development in Malaysia. This is inevitable as Singapore was one of the Straits Settlements in British Malaya and, in 1963, it became a political component of the independent Malaysia. Therefore, until its separation from Malaysia in 1965, Singapore and Malaysia constituted a single political entity. The establishment of British settlements in Penang (1786) and Singapore (1819) and the British take-over of Malacca in 1824 from the Dutch in Great Britains attempt to control access to the Straits of Malacca, essential to its tea trade with China, mark the beginning of the influx of immigrants and the development of large and diverse speech communities in Malaya. The increasing British influence on the Malay Peninsula coincided with the further influx of large groups of Chinese from the south-eastern provinces of China and the Tamil-speaking Indians from South India. This was a result of increased production of tin and, at the beginning of twentieth century, the establishment of the rubber industry (Platt Weber, 1980). Platt and Weber note that by the twentieth century there had developed in the British Straits Settlements and the Malay States a series of complex communities consisting not only of ethnic subgroups speaking their own native languages and dialects but also belonging to different social classes and backgrounds and engaged in different forms of employment (Platt Weber, 1980, p. 4). At the beginning of nineteenth century, British interests in Malaya and the Straits Settlements expanded, and it was clear to some members of non European ethnic groups that English was an important, powerful language. It was the language of the colonial masters; it was the language of government and administration, and it was used extensively in the judiciary. Thus, a good command of the language was certainly an asset. However, with the rapid expansion of their interests in the region, the British soon saw the need for a group of English-educated non-Europeans who could assist them in their duties. They thus authorized the establishment of private secular mission-supported schools in the Straits Settlements at the beginning of the nineteenth century (for a brief account of the history of English education from 1819 to after 1978, see Chua, 1990). These schools were at first available only to children from the well-to-do families of the different ethnic groups but later medium families were able to use these education. These English-educated school children would use English at home with their neighbors who also attended English-medium schools. Their younger siblings, being impressed by the new language, also acquired some English even before starting school. Thus, the use of English spread from the school domain to the home domain, and later, to the employment and friendship domains (Platt Weber, 1980). It is thus clear that unlike some other varieties of English, Singapore-Malaysian English has developed through education. Some varieties of English like American English, Australian English, Canadian English, New Zealand English, etc. have evolved in a natural way because of mixing of settlers over a period of time, while others like creoles have developed though pidgin English (Platt Weber, 1980). The post-colonial era in the history of Malaysia and Singapore is marked by two major political changes. One was the independence of Malaya in 1957 from British rule, followed by the formation of Malaysia incorporating the Federation of Malaya, the crown states of Sabah and Sarawak and the then self-overned Singapore in 1963. The other was the separation of Singapore from the political union of Malaysia in 1965.These political changes have had an immense influence on the spread and use of English in Malaysia and Singapore. English spread in Singapore Unlike Malaysia, where the use of English is gradually decreasing, Singapore has seen an expansion in its use. This is mainly due to increased enrollments in English-medium schools (Doraisamy ,1969).At the end of 1983, when the Ministry of Education decided that all schools, starting from January 1984, would be gradually converted into National Stream schools and English will be taught as first language. However, as more people are educated in English and with fewer people speaking Malay, English is slowly replacing Malay as the language for inter-ethnic communication, especially among the younger generation (for discussions on interethnic communication, see Platt Weber, 1980, and Tay1982a) . As English is now the common language in all schools we can thus assume that it will play an even more important role in international domains like trade, diplomacy, cultural exchange, conferences and intranational domains such as government administration, law, education, home and friendship communication in the near future. The widespread use of English within the nation itself inevitably means that English has gone through the process called indigenization (Moag Moag, 1977; Moag, 1982; Richards, 1979a) or nativization (B. B. Kachru, 1983a). To use B. B. Kachrus words (B. B. Kachru, 1982b), English has been transplanted from its source country (Britain) and acculturated to the local environment. What this means is that certain features in native British English have been permanently modified in view of the new cultural setting in Singapore which involves the interplay of the distinct ethnic cultures of Malays, Indians, and Chinese. These features manifest themselves in the phonology, lexis, syntax, semantics and styles of discourse in Singapore English. Therefore, when Singaporean English users speak or write English, there are telling signs that distinguish them from native English speakers or writers from Britain, America, Australia or New Zealand, although educated Singaporean speakers or writers have little problem making themselves understood. What are the features that distinguish the English of Singaporeans from that of, for example, the Englishmen or Americans? Characteristics and features of Singapore English The pioneering work done on Singapore and Malaysian English is the book by Tongue entitled The English of Singapore and Malaysia (1974). The book contains useful data on the phonology, syntax and lexis of Singapore English but it lacks theoretical foundation. The data are categorized under the dichotomy of standard and sub-standard forms. Some of the sub-standard forms given are actually not wrong but used in the variety of English. More importantly, Singaporean English is not treated as a system on its own, and the sociolinguistic contexts surrounding the use of sub-standard forms are not considered. Crewes works (1977, 1978a, 1978b, 1979) reflect his purist attitudes towards Singapore English. He regards Singapore English as a foreign language and implies that the English-educated Singaporean is a helpless and pitiable person. Later, Crewe came forward with the book British English and Singapore English.Exercises in Awareness (Crewe, 1979). The book claims to help Singaporeans to get rid of â€Å"Singaporeanisms† with a series of exercises where individual sentences have to be corrected so as to make them look more like British English. A more scholarly and systematic treatment of Singapore and Malaysian English is by Platt and Weber in their book entitled English in Singapore and Malaysia (1980). Using the methods of statistical correlation designed by Labov (1972a, 1972b), they observe that there is a direct correlation between the degree and frequency of divergence from Standard British English and variables such as formality, topic, domain and relationship of interlocutors. They looked at Singapore English as a system. Singapore English have been discussed from different views and therefore variety of characteristics and features have been mentioned and discussed. This study covers parts of these characteristics. Rythem: Deterding (Deterding, 2001; Deterding, Brown, Low, 2005) investigated the contrasting rhythmic properties of two varieties of English: Singapore English, which is often described as syllable-timed, and British English, which is more usually assumed to be stress-timed. Deterings (2001) study showed that there is a significantly greater variability in this measure of syllable-to-syllable duration for British English, which supports previous indications that, by comparison, Singapore English might indeed be regarded as being more syllable-timed. Additionally, it was found that there is little evidence of the influence of speaking rate on the measured differences in rhythm, but there is some evidence that the greater frequency of reduced syllables with a schwa in British English contributes to the difference between the two varieties. Grammar: Difference between Singapore and British English grammar has been discussed by scholars (Deterding, Low, Brown, 2003; Lim, 2004). †¢ Verbs:Verb generally appears in an uninflected form (Wee, 2004).For example, as Wee shows, â€Å"the verb eat is not marked for tense or number. Because the verb are uninflected, time and aspectual information are conveyed via words (using words like yesterday or already). o A.He eat here yesterday o B. He not yet eat lunch o C. They eat already Aspect is marked via forms like always, already or still. Thus, always is used to mark habituality o The bus always late The progressive aspect is marked by still o Late already, you still eat. Be and got: Platt and Weber (1980) noted that Singapore English clauses that are attributive or equative tend not to use the verb be o The house very nice The verb got is used variously in Singapore English as a perfective, a possessive, and an existentional marker o He got go to Japan o You got buy lottery? o You got nice shirt o Here got many people †¢ Nouns: As Wee (2004) mentioned: â€Å"Within the noun phrase, Singaporean tends to make use of articles. It treats non count nouns and its relstive clauses are ordered rather differently than their counterparts in more standard varieties of English†(p. 1058) †¢ Objects: Object preposing is another characteristic of Singapore English. â€Å"The object, (direct or indirect) is commonly preposed, giving rise to example like following†: o To my sister sometimes I speak English o The movie dont know whether good or not †¢ Question forming:† In wh-interrogatives, the interrogative pronoun typically remains in situ†(Wee, 2004, p. 1063) o You buy what? o This bus go where? For yes/no questions, they make use of the invariant tag is it. It also has another tag or not o The food good or not? o You busy or not? †¢ The passive:† Singaporean use kena passive phrase† (Wee, 2004, p. 1064) o The thief kena caught (by the police) †¢ Adjective reduplication: â€Å"Adjective reduplication in Singapore English intensifies the meaning of the base adjective†: o Dont always eat sweet-sweet (very sweet) things. La and Lah: These two Variables perform an important part in Singapore English and are interesting topics for linguistic experts. For instance, findings from Bell and Ser (1983) concluded that: â€Å"The existence of strict rules governing the occurrence of La not only in sentences but also inside the structure of noun phrases and verb phrases. La demonstrates the value of solidarity, friendship, a reduction of social distance between participants, in contrast with Lah dignals hostility and social distancing function†(p.17) References Bell, R. T., Ser, L. P. Q. (1983). To-day la? Tomorrow lah!; the LA Particle in Singapore English. RELC Journal, 14(2), 1-18. Deterding, D. (2001). The measurement of rhythm: a comparison of Singapore and British English. Journal of Phonetics, 29, 217-230. Deterding, D., Brown, A., Low, E. L. (2005). English in Singapore : phonetic research on a corpus. Singapore ; New York: McGraw Hill. Deterding, D., Low, E. L., Brown, A. (2003). English in Singapore : research on grammar. Singapore ; New York: McGraw Hill. Lim, L. (2004). Singapore English : a grammatical description. Amsterdam ; Philadelphia: John Benjamins. Platt, J. T., Weber, H. (1980). English in Singapore and Malaysia : status, features, functions. Kuala Lumpur ; New York: Oxford University Press. Wee, L. (2004). Singapore English: morphology and syntax. In E. W. Schneider B. Kortmann (Eds.), A handbook of varieties of English : a multimedia reference tool. Berlin ; New York: Mouton de Gruyter.

Essay --

​Many youth today are struggling with literacy at many different levels. These gaps in literacy make it hard for many students to further their education. Some students may start out a little behind when it comes to literacy, however, without the proper help from their parents and teachers, these students run a major risk of falling even further behind. Illiteracy is a major issue when it comes to gaining an education. Without knowing how to read, and how to read well and efficiently, it has a major potential of affecting all subjects in school which makes it almost impossible for a student to pass their classes. When students are struggling with literacy, many of them are more than likely afraid to ask for help, they may be embarrassed to admit this fact. This in turn causes them to give up on their education and drop out entirely. ​A tutoring program that students could attend before, during, and after school would be a great place to start in trying to resolve the literacy gaps that students are struggling with. The school could ask teachers to volunteer their time as well as...

Memories are life Essay

â€Å"The only real treasure is in your head. Memories are better than diamonds and nobody can steal them from you† by Rodman Philbrick, The Last Book in the Universe. If we think about what life is made up, we can say that memories build life. We save all the important and happy events that occurred in our lives as well as the most sad and worst moments. It is said that the brain is the most powerful part of humans, but as part of the brain, memory is an essential piece of it. As I mentioned before, memories build life, each day we put on practice what we have learned and live. I believe that in life we don’t have anything secure but our memories, once we die we don’t take anything we have right now. When we remember happy moments we have live, it’s like re-living them again and feeling the joy we felt at the moment. I decided to choose the memory as the topic of my Psychology class essay because from a while ago I started to have issues with my memory. At first I thought it was because of the problems that I was going through at the time, and also preparing for college. Time passed and I still was having trouble with remembering stuff, I came to think it was a hereditary health problem because my dad and grandmother never remember something. I feel frustrated because without a memory is like we never have lived, we constantly live through memories. Remembering what we have gone through and manage to take a positive attitude even if the memory brings us negative feelings. In this essay I will cover specific topics about the memory which is â€Å"the retention of information or experience over time as the result of three key processes: encoding, storage, and retrieval†, according to Laura A. King in  Experience Psychology. Throughout the essay I will discuss the basic memory process, also I will talk about the different stages of memory as well as the different types of memory, along with the explanations of when the memory fails (forgetting). In my opinion these three subjects are very essential part to understand how the memory works and find the explanation of why we forget things, which is my case. But also relate these topics to our daily lives. To begin with, I will explain the process of memory so later on I can discuss the different possibilities of why we forget. The first step in the process of memory is called encoding which is the processing information into memory accordingly to a Sparknotes article, Memory. For instance, we might remember where we ate in the morning even if we didn’t try remembering it but in the contrary it is possible that we are going to be able to remember the material in textbooks we covered during elementary school, high school or even more recent in college. It is stated that in the process of memory encoding, we have to pay attention to the information so we can later recall all the information. In the content of Memory, the second step in memory process is storage, the retention of information over time and how this information is represented in memory (King). In this process is often use the Atkinson-Shiffrin theory that is made up of three separate systems: sensory memory- time frames of a fraction of a second to several seconds, short-term memory- time frames up to 30 seconds and long-term memory- time frames up to life time (King). The third and last step of this course is memory retrieval, the process of information getting out of storage. Likewise, I will explain the first stage of memory called sensory memory or immediate memory. As stated in Experience Psychology, the sensory memory holds information from the world in its original sensory form for only an instant, not much longer that a brief time. In this stage of memory the â€Å"five† senses are used to hold the information accurately. In Sensory Memory by Luke Mastin, the stimulus that is detected by our senses has two options, it can either be ignored meaning it would go away at the instance or it can be perceived staying in our memory. As I mentioned before, our senses are being used in the sensory memory stage and have their specific name for example when we perceived the information through our vision it is called  iconic memory also referred as visual sensory memory. The iconic memory holds an image only for about  ¼ of a second. Not only but also, we also have the echoic memory which refers to auditory sensory memory, this function is in charge to hold part of what we listen/hear. For instance, when the professor is dictating a subject, we are trying to write fast so we can hold on all the information given at the moment and not forget what the professor said. Another stage of memory is called the short-term memory (STM), according to a web article Short-Term Memory, of Luke Bastin, the short-term memory is responsible for storing information temporarily and determining if it will be dismissed or transferred on to our third stage called long-term memory. Short-term memory sometimes is associated with working memory, which is a newer concept that the British psychologist Alan Baddeley came up with. Although working memory emphasizes in the brain’s manipulation and how it collects information so we can easily make decisions as well solve problems and mostly understand the information. It said that the working memory is not as passive as the short-term memory but both have limited capacity to retained information. Additionally to this stage, we have the fi nding of George Miller which wrote in his book called The Magical Number Seven, Plus or Minus Two. In this book Miller talks about two different situations. The first kind of situation is called absolute judgment which states that a person should correctly differentiate between very similar items such as shades of green and high/low-pitched tones. The second situation states that a person must recall items presented in a sequence, meaning that a person must retain certain number of chunks in their short-term memory. King also mentions that to improve short-term memory we consider two ways of doing it, chunking and rehearsal. According to King, chunking involves grouping or packing information that exceeds the 7  ± 2 memory span into higher-order units that can be remembered as single units. For example, when the professor is dictating a list of things like: cold, water, oxygen, air, rain and snow, we are likely able to recall all words or even better all six words instead of having a list like: S IXFL AGSG REATA MERI CA. When we have a list like that it will be harder to remember it because none of the six chunk words make sense, but if we re-chunk the letters we get â€Å"Six Flags Great America†, and that way we have better chance to remember it. The second way to improve our short-term memory is by  rehearsal, ac tually there are two types of rehearsal, maintenance rehearsal and elaborative rehearsal. Maintenance rehearsal is the repeating of things over and over; usually we use this type of rehearsal. In the other hand, we have the elaborative rehearsal which is the organizing, thinking about, and linking new material to existing memories. Continuing with the stages of memory, now I will talk about the third stage which is the long-term memory. In the article, What Is Long-Term Memory? by Kendra Cherry, long-term memory (LTM) refers to the continuing storage of information. In difference of the other two stages of memory, LTM memories can last for a couple of days to as long as many years. LTM is divided into types of memory, declarative (explicit) memory and procedural (implicit) memory. Later on I will explain in detail what are these two types of memory. Now that I have gone through the three stages of memory which are sensory memory, short-term memory and long-term memory, I will discuss the different types of memory. The different types of memory rely on the long-term memory section, the first type of memory that I will talk about is explicit memory also known as declarative memory. This type of memory â€Å"is the conscious recollection of information, such as specific facts and events and, at least in humans, i nformation that can be verbally communicated† (Tulving 1989, 2000). Some examples when we use our explicit memory is when we try to remember our phone number, writing a research paper or recalling what time and date is our appointment with our doctor. It said that this process type of memory is one of the most used in our daily lives, as we constant remember the tasks that we have to do in our day. In another article by Kendra Cherry called Implicit and Explicit Memory, Two Types of Long-Term Memory, informs us about two major subtypes that falls into the explicit memory. One is called episodic memories which are memories of specific episodes of our life such as our high school graduation, our first date, our senior prom and so on. The second subsystem of explicit memory is the semantic memory; this type of memory is in charge to recall specific factual information like names, ideas, seasons, days of the month, dates, etc. I can easily remember my quienceaà ±era party, it was May 24, 2008, at this exact moment I can recall what was the first thing I did when I woke up that and also what I did before sleeping but there are episodes on that day that I’m not able to remember. Moreover, I will discuss the second type of memory which is  implicit memory. Stated by King, implicit memory is the memory which behavior is affected by prior experience without a conscious recollection of that experience, in other words things we remember and do without thinking about them. Some examples of our implicit memories are driving a car, typing on a keyboard, brushing our teeth, and singing a familiar song. Within the implicit memory we have three subtypes; the first one is the procedural memory that according to King is a type of implicit memory process that involves memory for skills. The procedural memory process basically is the main base of the implicit memory, since all of us unconsciously do many things throughout the day, like I mentioned before driving a car or simply dress ourselves to go to school, work or wherever we have to go. The other substype of implicit memory is the classical conditioning which involves learning a new behavior via the process of association, it is said that two stimuli are linked together to produce a new learned response. For instance, phobias are a classical conditioning as the Little Albert Experiment result was. I personally I’m more than afraid to spiders, in other words my phobia is called arachnophobia which can be control and learn to overcome the fear and anxiety it gives me every time I see a spider or even think about a spider. The last subsystem of the implicit memory process is the priming, Kings states that priming is the activation of information that people already have in storage to help them remember new information better and faster. Priming it is sometimes called recognition memory; an example of priming is when little kids are learning colors, they associate two things such as apple and color red. To learn the red color they will remember the apple and it w ould be easier for them. Furthermore, I will talk about what I think is the most important part of my essay that is forgetting. As I said at beginning of my essay I have experienced difficulties with my memory, I forget simple things. For instance, in daily bases my mom gives me a message to give my dad or sisters or just asks me to do something for her, I say yes I will do it but later on I totally forget. Before taking this class, I believe that the reason I forget things, it is because I’m distracted at the time and didn’t paid attention so that’s why later I’m not able to remember it. Now that I have taken the class and researched the topic I found reasons of why we forget things, one reason is the retrieval failure, that is the failure process of  accessing stored memories. It is what we do when we have exams; we try to remember what we have learned/study and we just don’t remember anything. Within the retrieval failure we have what is called interference theory, it is the theory that people forget not because memories are lost from storage but because other informati on gets in the way of what they want to remember (King). There are two kinds of interference that can be a possible reason of forgetting, are is called proactive and retroactive. In the proactive interference occurs when the current information is lost because it is mixed up with previously learned, similar information. This happens to me when I try to study two different subjects right after another, I get confused about both subjects and sometimes I even stop studying because I’m not able to focus and understand the material. The second type of retroactive interference is when the new information interferes with the old information memories, an example of it is when at jobs we learned a new task but forget older tasks. Moving forward, we have another possible cause of forgetting is called decay theory. In another article by Kendra Cherry, Explanations for Forgetting, Reason Why We Forget, decay theory is a memory trace that is created every time a new theory is formed. The only problem is that over time this trace disappears. The failure to store is also a possible reason that causes us to forget, this is because encoding failures sometimes prevent information from entering long-term memory (Cherry). In conclusion, I believe that one of the most essential part of the brain is our memory. We can have billions of dollars and buy anything we want but at the end the only thing we are taking of us is what we have live (memories). We need memories in our life not just to drive from A place to B place or to get the right answer to pass an exam but to remember who we are and what people we have by our side. To revive all the moments we encounter happiness and even sadness, â€Å"memory is a way of holding onto the things you love, the things you are, the things you never want to lose† from the television show The Wonder Year.

Word Choice Past vs. Passed

Word Choice Past vs. Passed Word Choice: Past vs. Passed The words â€Å"past† and â€Å"passed† are surprisingly tricky. As well as sounding similar and starting with the same letters, for example, they can sometimes be used in similar situations. If you want to avoid errors in your written work, though, you may want to check out our guide to how they are used. Past (Noun and Adjective) When used as a noun, â€Å"past† refers to a time before the current moment: History is the formal study of the past. It also refers to a previous point in time when used as an adjective: My past choices were sometimes flawed. Here, â€Å"past† modifies the noun â€Å"choices† to show when they occurred. Past (Adverb and Preposition) Another use of â€Å"past† is as an adverb or preposition, where it means â€Å"beyond a point in time or space.† For instance, we could use it as an adverb like this: They walked past the bridge on the way home. Here, we use the adverb â€Å"past† to modify the verb â€Å"walked.† Passed (Verb) â€Å"Passed† is the simple past tense and past participle form of the verb â€Å"pass.† It is therefore used in a number of situations, which include having: Moved beyond a particular point in time or space Succeeded in a test Handed something to someone Died or departed Changed from one state to another Declined to accept a chance or offer For example, we could use â€Å"passed† in any of the following sentences: They passed the bridge on the way home. She passed her exams with flying colors. He passed me the envelope with a nervous look. She passed away peacefully in her sleep. It passed from a solid to a liquid state. I regret having passed on buying shares in Facebook. This isn’t even a complete list of how â€Å"passed† can be used! The important thing, however, is that â€Å"passed† is always the past tense form of â€Å"pass,† including in the example sentences above. Past or Passed? These terms are most often confused when discussing movement. We can see how similar they are in this case if we repeat two examples from above: They walked past the bridge on the way home. They passed the bridge on the way home. The key here is that â€Å"passed† is a verb, while â€Å"past† in this case is an adverb. To make sure you get this right in your writing, remember that: As a noun and an adjective, â€Å"past† refers to a previous point in time. As an adverb, â€Å"past† should always modify another verb in a sentence. â€Å"Passed† and â€Å"pass† are both verbs spelled with a double â€Å"s.† Furthermore, while â€Å"passed† is the past tense of â€Å"pass,† the word â€Å"past† is never a verb. Consequently, if you need an action word, â€Å"passed† will always be correct. If you need a noun, adverb, adjective, or preposition, on the other hand, the term you need will always be â€Å"past.† Past (noun) = A time before the current moment Past (adjective) = From an earlier time Past (adverb/preposition) = Beyond a point in time or space Passed (verb) = Past tense of â€Å"pass†

Careful with Technical Terms

Careful with Technical Terms Careful with Technical Terms Careful with Technical Terms By Mary One of the most important things to keep in mind is that your writing must be appropriate for your audience. You have to use terminology that makes sense to your readers. When you become a professional in a particular field, you learn the language of that field. As a professional, people hire you to work on their behalf because you have knowledge and skills that they don’t possess. Therefore, you will often find yourself communicating in writing with people who don’t know the language of your field. Your writing has to make sense to the people who read it. If you are a medical billing professional, you know what ICD9, HCFA, and CPT mean. If you are an accountant, you know the difference between a 1099, W-2, W-4, W-9, and K-2 form. If you are an IT professional, you speak in terms of servers, routers, and hubs. If you are a web developer, your language includes terms like .net, PHP, PPC, monetizing, and URL. If you work in a hospital setting, your vocabulary includes terms like DNR, PRN, and QID. If you are a statistician, such terms as chi-square, mutually exclusive, regression analysis, and standard deviation are parts of your every day vocabulary. Chances are that several of the terms you just read don’t make any sense at all to you. When you write, you need to look closely at your messages, to make sure that you aren’t using terms that your readers aren’t likely to understand. You know what you mean. Make sure your writing stands on its own, so that your readers will also know what you mean. That’s what good writing is all about. Want to improve your English in five minutes a day? Get a subscription and start receiving our writing tips and exercises daily! Keep learning! Browse the Business Writing category, check our popular posts, or choose a related post below:20 Types and Forms of HumorTop 11 Writing Apps for iOS (iPhone and iPad)Titled versus Entitled

Iago in Othello essays

Iago in Othello essays An education is the most important thing that every country has to focus on and support. In Laos, it is the small country and lacks high technology, especially about educational systems because Laos is a developing country. For all levels of education, it is facing many challenges and has also a limited budget. And, it isnt easy to resolve the problems of illiteracy, particularly people in rural areas. Even in the city, schools are not enough for the increasing number of students. On the other hand, the United State, which has educational institutions that are opened to all qualified students from around the world. So, in Laos, there are many challenges that are so different from the U.S concerning education systems. Grade schools and colleges in the U.S have both positive as well as negative aspects. Children can enter school when they are 5 years old. At the same time, the children have to start studying from kinder-garden through 12 th grade. Every school does not have rules to control what the students should wear when they go to school. The students have independently to choose their cloths depending on which season or fashion such as short pants, jeans, any kinds of dresses and shirts, and other things. Ladies allow putting on makeup as much as they want to. Also, they can choose any hair styles and colors their hair, and their nails can be allowed to grow and be painted. In addition, all students do not know how to respect their teachers; for instance, during the class, they chew gum and put on a hat. When they want to so out the class, they just walk out without their teachers permissions. Also, every school has transportation to take the students to school. That is the school-bus. It is comfortable for parents who do not have time for their children. The schools have students service; for example, the health care programs to cover their medical when they get an ill or an injury for ...

Description of the Film Separation by Asghar Farhadi Assignment - 1

Description of the Film Separation by Asghar Farhadi - Assignment Example This provides the basis for the conflict within the movie. The characters in the movie are believable and have been developed effectively to depict the setting and themes of the story. The producer manages to use a mix of innocence, temperament, wisdom, and naivety among the characters to bring out the story. Within the conflict between Nader and Simin, the director manages to bring in a different perspective by introducing the innocence of their daughter Termeh. The judges of the family court are presented through the story as wise and prudent. This is evident from both cases involving the divorce filed by the warring family. In the first instance, they rebuffed the claims of Simin by insisting that the complications were insufficient. However, they finally warrant the divorce after analyzing the situation and the irreconcilable differences. The producer holds off Nader’s temper until the point where he boiled over. Symbolism has been used in the movies to great effect. The title of the movies, A Separation, is the main symbol used throughout the movie. The separation that was intended to be away from Tehran eventually turns into one between Simin and Nader as the story concludes. Other instances of separation within the movie include Razieh separating from the traditions in order to be able to provide for her family. Terhem is initially separated from her mother then later by her father. The other elements of separation within the story include Nader father’s death and the miscarriage. The separation, which was disclosed at the beginning of the story in the divorce case, was also a consequence of another attempt to separate from the environment in Teheran. There is an array of thought provoking themes that are presented in the movie A Separation. Social division is the major theme that is explored in the movie. The divisions within the movie have been perpetrated using perceptions around religion, occupation, gender, and age.  Ã‚  

Technical and communication failures that caused disasters Assignment

Technical and communication failures that caused disasters - Assignment Example The technical failure that caused the disaster was the release of methyl isocyanate (MIC) which was due to water that leaked into one of the storage tanks of Union Carbide pesticide factory (Long, 2008). The problem was aggravated by another technical failure when the main warning siren did not go off for another two hours. Apparently, the tank alarms have not functioned for almost four years already. Other technical problems were revealed upon investigation. These include failure to address safety violations, backup system were either not functioning or inexistent, plant was equipped with only one backup system, which was not the norm, over capacity of the tank which held the MIC, water sprays were ineffective and the pipes and valves have not been repaired or replaced (Long, 2008). The technical failure that caused this disaster was the flawed Soviet reactor design which was operated by plant operators who were not properly trained. According to the World Nuclear Association, there was over pressure which was caused by the interaction of very hot fuel with the cooling water (2011). They went on further to say that the over pressure then resulted in the partial detachment of the cover plate of the reactor. The fuel channels were then ruptured and the control rods jammed (World Nuclear Association, 2011). At least 5% of the radioactive reactor core was released through steam and fires, into the atmosphere and downwind (World Nuclear Association, 2011). The reason for the earthquake is due to the abrupt slipping of the crystal rocks comprising the Pacific and North American Plates by as much as 2 meters (7 ft) along their common boundary-the San Andreas fault system (Nakata & Meyer, 2009). There was technical failure in terms of the construction of the buildings. Most of them were extensively damaged because it was built with unreinforced masonry and they were erected on flood plain sediments

Organisational behaviour Essay Example | Topics and Well Written Essays - 3000 words - 2

Organisational behaviour - Essay Example The major purpose of this essay is to highlight the importance of social psychology with reference to organizational behaviour. The organizational behaviour is concerned with the evaluating the impact of individuals and structure on organizational performance whereas organizational social psychology states that relaxed work environment and strengthening social relations among employees and management are going to further enhance the organizational performance in all regards(Heine, Lehman, Markus, & Kitayama, 1999). In the most practical sense an organization is basically a social entity because employees and management work through different social phenomena in order to accomplish organizational goals. According to recent studies organizational development and progress occur in real sense when a sense of family and belonging significantly prevails amongst the ranks of a particular organization. This essay will also highlight application of various facets of social psychology at Vodaf one that include advanced training of top management in counselling techniques, power to initiate innovative projects, cross cultural teamwork and reward for performance system. Finally Vodafone is used to hire tolerant and flexible individuals in order to apply melting pot technique for managing cultural and gender diversity in employees (Eisenberger, Stinglhamber, Vandenberghe, Sucharski, & Rhoades, 2002). The operational concepts of organizational social psychology are decentralized authority, participative management and flexible timing and they mainly spread from Japanese organizations to those that are operating in other regions of the world (Heine, Lehman, Markus, & Kitayama, 1999). Furthermore it is imperative to note that Australian continent is the second most efficient geographical region in terms of adopting modern management concepts. However the American companies are rather slow regarding implementing the contemporary managerial concepts of the 21st century. But the b asic purpose of this part is to evaluate the involvement of social psychological concepts and practices in a management framework for Vodafone’s unit of New Zealand. Additionally, the application of modern management is relatively easy in the featured culture due to its individualistic and professional nature. The fundamental reason for development and increased application of social psychology in organizations is the need to retain employees for longer periods of time while enhancing their organizational commitment (Eisenberger, Stinglhamber, Vandenberghe, Sucharski, & Rhoades, 2002). The social psychology stated that humans have a psychological need of receiving a reward after every six to twelve months and if companies fail to do so then they risk job turnover from core employees (Chryssochoou, 2004). Mutual respect and trust among employees and management is also a vital factor in predicting productivity of the staff. Nevertheless, according to recent research employees l ike to be governed by those individuals who have similar personality dimensions. Employees on the other hand spend more time in organizations that offer them reward for performance, paid and emergency leave and divert resources towards employee training and development (Crisp &Tumer, 2007). The nature of the job should also be sufficiently challenging in order to keep things interesting for the

Digital Media Platforms and Education Research Paper

Digital Media Platforms and Education - Research Paper Example The current developments an advancements in technology have greatly shaped the forms of communications used in education today. Unlike the traditional systems where the instructors had to be physically present in a class room in order to facilitate a lesson, the paradigm shift to the use of digital media have made this element redundant. The application and implementation of digital media in the learning process has offered a wide range of methods by which instructors and students can relay information (Mateer, 2013). For example, the internet and features such as teleconferencing can enable teachers to interact with their students at without necessarily meeting at a central place. This feature allows for all features of a normal classroom situation such as active student participation and the ability to ask immediate questions where a student may need further clarification. It only eliminates the aspect of physical presence. In addition, the technological improvements of digital med ia have also enhanced the speed at which information is passed on from the participants in any learning activity at an institution. This aspect subsequently improves the speed at which students learn and also the depth of knowledge covered. Digital media has also been proven to aid in the forms of communications used by the facilitators during their lessons in the classroom. Audio-visual communication is a key feature that has been brought about by digital media. Learning in the classroom has evolved from the chalk to board communication to audio-visual forms such as videos and computer slides (Belinha, 2010). A commonly used tool is the projector where instructors project their notes on a clear white surface as they explain... This paper approves that from the students’ perspective, potential disadvantages can arise while making the decision between the classroom education and digital learning. For digital learning, students need a lot of discipline and dedication in order for them to sit at a computer screen to listen to lectures, doing and completing any given assignments with respect to deadlines and more so assigning time and a proper schedule to study and conduct research. Since immediate feedback is one of the pros of classroom education, when it comes to digital learning, the process of clarification of any unclear information will take a longer time. Many scholars have also argued that the introduction of digital learning has slowly eradicated the traditional ‘feel’ of having a teacher stand in front of a class to give a lecture. This has a potential detrimental effect on students as it denies an immediate and natural interactivity with the facilitator that could actually enhance their learning capability and understanding. This essay makes a conclusion that even though there are a variety of opinions on the impact of digital media in education, studies conducted and personal experiences have shown a general improvement in the education system that has been brought about by the use of digital media. Despite the glitches that it may have on the learning process, the use of digital media has made great advancements in the classroom and is a clear improvement from the traditional learning process.

Competitive Advantage Assignment Example | Topics and Well Written Essays - 2000 words

Competitive Advantage - Assignment Example It encompasses several aspects of a company's marketing tactics and strategies in building a strong competitive advantage that can secure the company's future. A competitive advantage is plainly a facet or capability of the organisation that it occupies or extends to the customers. For an organisational facet to form a 'competitive advantage', it needs to be unequalled in the market and not acquired by any other existing or upcoming competition in the market. This notion can also be translated in the words of Barney (2002, p9) as, "a firm experiences competitive advantages when its actions in an industry or market create economic value and when few competing firms are engaging in similar actions". Porter (1985, p3) explores the concept of competitive advantage as the capability of an organisation to create value for its customers in a way that procures more value to the customers than the competitors, he says, "Competitive advantage grows out of value a firm is able to create for its buyers that exceeds the firm's cost of creating it. Value is what buyers are willing to pay, and superior value stems from offering lower prices than competitors for equivalent benefits or providing unique benefits that more than offset a higher price. There are two basic types of competitive advantage: cost leadership and differentiation". Hence, a firm's competitive advantage has to be unique among all the other companies in the market. This implies that whatever company owns and provides to customers should have one or more differential aspect that can distinguish it form its competitors. Today, many organisations engage in providing almost same kind of products to a specific range of products. Consequently, the customers need to choose between a lot of options with slight distinction to satisfy their needs and problems. For a firm to win more customers than its competitors and sustain them in the long run, it needs to offer its customers something that is not being currently offered in the market. For instance, a different product with enhanced value, a courteous and friendly workforce, a well-known company image, and a breakthrough in technology helpful in satisfying customers in a much better way than the competitors. The customers would only be willing to buy the company's product or even pay a higher price for it if there's something in the product or service being by the company that the customers perceive to be valuable or different in satisfying their needs than other products in the market. The more the customers perceive the product to be valuable, the more the opportunity for the company to remain successful in the long run. The upcoming section of the paper investigates into some of the aspects of a company's marketing tactics and manoeuvres that could be utilised towards the achievement of a competitive advantage. Winning Customer Satisfaction, Loyalty And Trust Firms consistently endeavour to attain the mellowest possible levels of customer satisfaction and retention to survive in the modern competitive business arena. It is a factor that rightfully approximates a company's emplacement in the competitive market. If the customers are satisfied, the company is likely to be successful; otherwise it is doomed to be obscure in the future

Nitrous Oxide Essay Example | Topics and Well Written Essays - 1000 words

Nitrous Oxide - Essay Example Nitrous oxide (N2O) is an atmospheric trace gas that contributes to the greenhouse effect. It is also involved in the catalytic destruction of ozone in the stratosphere and is increasing in concentration by about 0.25% per year. The increase is believed to result from fertilizer use, emissions from internal combustion engines, biomass burning, and industrial processes (Khalil 1995). It is naturally produced by nitrification and denitrification in soils and in the oceans, and is destroyed in the stratosphere via photolysis (90%) and reaction with excited atomic oxygen [O(1D)] (10%). Its atmospheric lifetime is between 100 and 150 years. Although the major sources and sinks of N2O are known, they are poorly quantified and inadequately balanced, both in terms of mass exchange and in their N and O isotopic composition. Stable isotopes have been used in the past to constrain sources and sinks of other atmospheric trace gases but have yet to be successfully applied to N2O. The isotopic approach to a global N2O budget is hindered by the wide range of observed isotopic values for each of the major natural sources, making it difficult to assign a unique value to each of the source terms. Soil flux samples have been shown to be variable but consistently depleted in both 15N and 18O relative to atmospheric N2O. Oceanic samples have exhibited a trend similar to typical nutrient profiles, with slightly depleted surface waters becoming progressively enriched along the nutricline and stabilizing with depth. Early analytical methods employed infrared absorption techniques (Wahlen 1985) or required decomposition of N2O with subsequent analyses of N2 and CO2. The use of direct injection techniques was introduced in 1993 when Kim and Craig reported heavy enrichment in both the N and O isotopes in two samples of stratospheric air. They proposed that a stratosphere to troposphere return flux of heavy N2O could balance the observed isotopically light source terms, although a simple mass-balance model showed that this led to a considerable overcorrection. Direct injection of N2O was subsequently shown to result in erroneous enrichment of 15N and Delta18O when contaminated by trace amounts of CO2. We present results for 15N and 18O of N2O obtained from samples collected in the lower stratosphere. Five samples were collected at midnorthern latitudes on board NASA's WB-57 aircraft, and two samples were collected at high northern latitude during the 1988 Juelich balloon campaign. We also measured, for comparison, the isotopic composition of tropospheric N2O sampled in La Jolla, California, under clean air conditions. Nitrous oxide mixing ratios decreased with height above the tropopause, whereas the heavy-isotope composition of the remnant N2O was found to be increasingly enriched. If the process responsible for this enrichment is an irreversible sink and if the fractionation factor remains constant, the data should obey what is known as a Rayleigh distillation, in which the resulting isotopic enrichment is related to the fraction remaining by the equation (1) R = R0 x fAlpha-1 where R and Ro are the residual (stratospheric) and initial (tropospheric) heavy-to-light isotope ratios, respectively; f is the fraction of N2O remaining (residual concentration divided by the initial concentration); and is the ratio of the heavy-to-light reaction or photolysis rates. This relationship

Digital Media Platforms and Education Research Paper

Digital Media Platforms and Education - Research Paper Example The current developments an advancements in technology have greatly shaped the forms of communications used in education today. Unlike the traditional systems where the instructors had to be physically present in a class room in order to facilitate a lesson, the paradigm shift to the use of digital media have made this element redundant. The application and implementation of digital media in the learning process has offered a wide range of methods by which instructors and students can relay information (Mateer, 2013). For example, the internet and features such as teleconferencing can enable teachers to interact with their students at without necessarily meeting at a central place. This feature allows for all features of a normal classroom situation such as active student participation and the ability to ask immediate questions where a student may need further clarification. It only eliminates the aspect of physical presence. In addition, the technological improvements of digital med ia have also enhanced the speed at which information is passed on from the participants in any learning activity at an institution. This aspect subsequently improves the speed at which students learn and also the depth of knowledge covered. Digital media has also been proven to aid in the forms of communications used by the facilitators during their lessons in the classroom. Audio-visual communication is a key feature that has been brought about by digital media. Learning in the classroom has evolved from the chalk to board communication to audio-visual forms such as videos and computer slides (Belinha, 2010). A commonly used tool is the projector where instructors project their notes on a clear white surface as they explain... This paper approves that from the students’ perspective, potential disadvantages can arise while making the decision between the classroom education and digital learning. For digital learning, students need a lot of discipline and dedication in order for them to sit at a computer screen to listen to lectures, doing and completing any given assignments with respect to deadlines and more so assigning time and a proper schedule to study and conduct research. Since immediate feedback is one of the pros of classroom education, when it comes to digital learning, the process of clarification of any unclear information will take a longer time. Many scholars have also argued that the introduction of digital learning has slowly eradicated the traditional ‘feel’ of having a teacher stand in front of a class to give a lecture. This has a potential detrimental effect on students as it denies an immediate and natural interactivity with the facilitator that could actually enhance their learning capability and understanding. This essay makes a conclusion that even though there are a variety of opinions on the impact of digital media in education, studies conducted and personal experiences have shown a general improvement in the education system that has been brought about by the use of digital media. Despite the glitches that it may have on the learning process, the use of digital media has made great advancements in the classroom and is a clear improvement from the traditional learning process.

Nitrous Oxide Essay Example | Topics and Well Written Essays - 1000 words

Nitrous Oxide - Essay Example Nitrous oxide (N2O) is an atmospheric trace gas that contributes to the greenhouse effect. It is also involved in the catalytic destruction of ozone in the stratosphere and is increasing in concentration by about 0.25% per year. The increase is believed to result from fertilizer use, emissions from internal combustion engines, biomass burning, and industrial processes (Khalil 1995). It is naturally produced by nitrification and denitrification in soils and in the oceans, and is destroyed in the stratosphere via photolysis (90%) and reaction with excited atomic oxygen [O(1D)] (10%). Its atmospheric lifetime is between 100 and 150 years. Although the major sources and sinks of N2O are known, they are poorly quantified and inadequately balanced, both in terms of mass exchange and in their N and O isotopic composition. Stable isotopes have been used in the past to constrain sources and sinks of other atmospheric trace gases but have yet to be successfully applied to N2O. The isotopic approach to a global N2O budget is hindered by the wide range of observed isotopic values for each of the major natural sources, making it difficult to assign a unique value to each of the source terms. Soil flux samples have been shown to be variable but consistently depleted in both 15N and 18O relative to atmospheric N2O. Oceanic samples have exhibited a trend similar to typical nutrient profiles, with slightly depleted surface waters becoming progressively enriched along the nutricline and stabilizing with depth. Early analytical methods employed infrared absorption techniques (Wahlen 1985) or required decomposition of N2O with subsequent analyses of N2 and CO2. The use of direct injection techniques was introduced in 1993 when Kim and Craig reported heavy enrichment in both the N and O isotopes in two samples of stratospheric air. They proposed that a stratosphere to troposphere return flux of heavy N2O could balance the observed isotopically light source terms, although a simple mass-balance model showed that this led to a considerable overcorrection. Direct injection of N2O was subsequently shown to result in erroneous enrichment of 15N and Delta18O when contaminated by trace amounts of CO2. We present results for 15N and 18O of N2O obtained from samples collected in the lower stratosphere. Five samples were collected at midnorthern latitudes on board NASA's WB-57 aircraft, and two samples were collected at high northern latitude during the 1988 Juelich balloon campaign. We also measured, for comparison, the isotopic composition of tropospheric N2O sampled in La Jolla, California, under clean air conditions. Nitrous oxide mixing ratios decreased with height above the tropopause, whereas the heavy-isotope composition of the remnant N2O was found to be increasingly enriched. If the process responsible for this enrichment is an irreversible sink and if the fractionation factor remains constant, the data should obey what is known as a Rayleigh distillation, in which the resulting isotopic enrichment is related to the fraction remaining by the equation (1) R = R0 x fAlpha-1 where R and Ro are the residual (stratospheric) and initial (tropospheric) heavy-to-light isotope ratios, respectively; f is the fraction of N2O remaining (residual concentration divided by the initial concentration); and is the ratio of the heavy-to-light reaction or photolysis rates. This relationship

The impact of the First World War Essay Example for Free

The impact of the First World War Essay Using the four passages and your own knowledge, assess the view that the impact of the First World War was the main reason for the booming economy in the USA in the 1920’s (40 Marks) I believe that the First World War did not have as much of a significant impact on the American economy as mass production, infact i however see that instead of benefiting the economy the War in fact had the reverse effect to that of which interpretation A and C suggest that the war was the most important factor of the 1920’s American economic boom. Firstly, the biggest reason as to why mass production was the main reason for the economic boom was that the American GNP soaring from $72.4 billion in 1919 to $104 billion 1929 only 15 years after mass production was first implemented in America, the figures show the huge impact that mass production had upon the American economy, this is direct evidence of the huge impact mass production had as opposed to the 3 other interpretations which do not have any direct evidence of the impact they had upon the American economy, this is supporting that mass production had the most important impact on the American economy and shows evidence of why mass production was the main reason for the 1920’s boom. This leads to a criticism of source A as the interpretation does not refer to The First Wold War costing America over $32 Billion, instead of injecting growth into the economy the war in fact had the reverse effect as less money was available in America leading to slow growth in the economy. Mass production had a positive effect upon economy, boosting its GNP through stimulation of the American retail market. This supports why the War was not beneficial to the economic boom of the 20’s compared to mass production. Interpretation B states that ‘the key to the boom was a tremendous increase in productivity resulting from technological innovation and the application of scientific management’ this goes against the point that interpretation D suggests that Andrew Mellon was the key figure of the 1920’s boom in America. The reason why scientific management had a bigger impact than Andrew Mellon’s  reforms is because the implementation of mass production saw workers’ pay increased from $710 to $857, whereas Mellons reforms were based upon the banking in America which had little effect upon all classes whereas mass production benefited all classes of society. Also the scientific changes to production and the national scale it happened saw upon America begin to prosper and boom far before Andrew Mellons policies were implemented, after which there was little impact by Mellons policies as opposed to mass production which propelled the boom this supports the fact that mass production was the key reason for the booming economy in America. Mass production was the main reason for the economic boom is because once it was introduced in 1914 just a few years later there became a clear direct change to Americas economy as interpretation B states ‘Although the population grew by only 16% during the decade, industrial production almost doubled’ The increase in production saw the American economy begin to produce more and more goods, leading to a sharp increase in jobs, sales and profits. This supports my point that mass production was the most important factor to the American economic boom. Further support for mass production being the catalyst for the economic boom is because once production in mass was introduced in 1914 just a few years later there became a clear direct change to Americas economy as interpretation B supports ‘Although the population grew by only 16% during the decade, industrial production almost doubled’ The increase in production saw the American economy begin to produce more and more goods, leading to a sharp increase in jobs, sales and profits. This backs up the point that mass production was the most important factor to the American economic boom. Another point why mass production was the most important reason for the economic boom was the impact on electricity demand. Electricity demand shot up due to businesses needing electricity to power the machinery to mass produce products, interpretation B supports this as it says ‘Electricity consumption more than doubled during the decade mainly because of industrial demand’ the increase propelled a whole new area of business in America  creating thousands of jobs and further  strengthened the American economy showing further evidence that mass production was important to the boom. Mass production also effected domestic consumption of electricity. The increase of electricity usage further developed the economy of America. Interpretation B mentions the increase of power usage: ‘in 1912 only 16% of the population lived in electricity lit dwellings, the proportion had grown to 63% by 1927’ it also states ‘electrical household appliances came into general use. This can be used to criticize Interpretation C as it quotes ‘If every American could own a car and a house, buy quality clothes, own stock, take vacations and go to the movies then clearly there was no longer any significant inequality in society’ This quote is inaccurate as many across America did not see the benefits of the boom as interpretation C suggested. Much of the wealth was split between the North of America and the south. The north saw boomed while in the South the more agricultural based economy began to suffer, farmers where particularly affected by the boom new te chnologies and farming equipment left American farmers with a huge surplus of food. In order to sell the food farmers would drop and drop their prices until it soon became unprofitable and many became bankrupt and fell into poverty, hundreds of thousands of farmers land and homes were repossessed leaving them homeless. this is a criticism of interpretation C as it stated everybody had benefited from the war in America however it is untrue, whereas interpretation B states 63% lived in electricity lit dwellings not over exaggerating the impact it had and so making B more of a valid source. More evidence why mass production was the most important reason for the economic boom was the impact on electricity demand. Electricity demand shot up due to businesses needing electricity to power the machinery to mass produce products, interpretation B supports this as it says ‘Electricity consumption more than doubled during the decade mainly because of industrial demand’ the increase propelled a whole new area of business in America creating thousands of jobs and further strengthened the American economy showing further evidence that mass production was on necessities and not  luxuries while the male was away at war. This created a big stunt in the countries in economic growth. I also believe that passage C is not as important to boom in America, the passage asserts that America had the upper hand compared to its European rivals as WWII had devastated much of the European countries building factories and infrastructure. However this infact had the reverse effect that the passage expected, newly built factories in European countries had the latest technologies installed with modern planning and architecture compared to the previous buildings destroyed in the war. The rebuilding would have also increased productivity and kick-started economies as each country needed to develop and progress after the war. These countries needed lots of workers and so work was easy to find. People could earn wages and rebuild their lives by purchasing new houses. Consumer and governmental spending in the allied and Axis countries stimulated the countries’ economies leading to rapid economic growth. England and France quickly re-established their economies into even stron ger economic powers than before. Furthermore there was a huge amount of inequality in America, Racist inequality was at its highest during the 20’s with extremist groups such as the KKK gaining huge following from American people, and over 5 million people were members of the KKK in the 20’s. With 100’s of blacks being attacked and killed passage C is shown as a further inaccurate and invalid passage as it is contracted by evidence against it showing that America was not equal as Passage C suggest. A big criticism of interpretation D is that the piece is taken from an autobiography published almost 90 years after they had taken place, therefore the passage will not be as valid as a piece from the same time period. Also being an autobiography the piece will always have a bias towards Andrew Mellon and will possibly over play the role he had and will not mention any bad things about him. The passage is not as important as mass production impacted the whole of America on a national scale this showing that the innovation of businesses were more important than the  reforms he implemented. In conclusion I believe that mass production was the fundamental reason for the boom in the 1920’s. Their war was not important and did not have such an impact on American society as it was only a short term temporary effect on the economy, whereas mass production propelled all levels of society and business into economic growth and expansion. Interpretations a D are not as beneficial to the economy as they did not have such a major impact and interpretation D only made a small contribution to the economy unlike mass production which completely overhauled the whole American infrastructure permanently. Source C is also not a fully valid and reliable source, the passage has multiple criticisms due to the war being a very controversial point; however the war was a negative as it stifled the American economy and did not bring any long term positives to America. I believe that mass production was a much more significant reason for the boom in America as opposed to the war and Andrew Mellon’s policies as it had vast evidence of creating one of the most prosperous boom periods any economy has ever witnessed, this period saw America become the most affluent and powerful nations on earth from the 1920’s.

Antilock Brake System Abs Model Based Design Computer Science Essay

Antilock Brake System Abs Model Based Design Computer Science Essay An Antilock Brake System (ABS) is a closed loop control system that modulates the brake torque that is applied to the wheel in order to prevent the controlled wheel from becoming fully locked. ABS is among the most important safety systems in a vehicle. In automatic highway system, automatic brake actuation is a very important part of the overall vehicle control system. It prevents the wheel lock-up under critical braking conditions, such as those encountered with wet or slippery road surfaces and driver panic reaction (Bosch, 1995). By preventing the wheel lock-up, ABS ensures that the vehicle remains responsive to steering wheel inputs. Reduced stopping distance on account of ABS is more evident on wet or slippery road surfaces (Garrick et al., 1998). 1.2 MODEL BASED DESIGN Designers of embedded control system software face difficult challenges. In addition to the need to complete projects at low cost and within tight schedules, embedded control system software designers must provide predictable performance and competitive features for the products they deliver. Traditional methods of designing, testing, and implementing embedded control systems cause designers to wait until late in the design effort, when actual or prototype products and real-time embedded targets become available, to find out if software really works as it was intended to. Only then, as system integration occurs, can the designer uncover the errors that may have found their way into the product during the early design stages. Model-Based Design with MathWorks tools provides a proven technique for creating embedded control systems. It is used today for satellites, aircraft, and many other aerospace applications, in the automotive industry, and for process control, computer peripherals and industrial machinery. Through Model-Based Design, embedded control system design teams can begin evaluating software designs without using prototype products and real-time targets. The MathWorks environment for Model-Based Design allows engineers to mathematically model the behavior of the physical system, design the software and model its behavior, and then simulate the entire system model to accurately predict and optimize performance. The system model becomes a specification from which you can automatically generate real-time software for testing, prototyping, and embedded implementation, thus avoiding manual effort and reducing the potential for errors. Fig 1.1. Model-Based Design for embedded control system software Changes or corrections to the system requirements and specifications are easily incorporated into the model, fully evaluated by simulation, and automatically reflected in the final real-time embedded software. 1.3. MODELING AND SIMULATION To effectively design an embedded control system and accurately predict its performance, designers must understand the behavior of the entire system in which the control system will reside. MATLAB and Simulink form the core environment for Model-Based Design for creating accurate, mathematical models of physical system behavior. The graphical, block-diagram paradigm of the MathWorks environment lets you drag-and-drop predefined modeling elements, connect them together, and create models of dynamic systems. These dynamic systems can be continuous-time, multi-rate discrete-time, or virtually any combination of the three. You can create custom model elements or reuse legacy code-based models by incorporating C, Fortran, or Ada code directly into the modeling environment. The modeling environment is hierarchical and self-documenting. System structure and function can be clearly expressed by grouping model elements in virtually any combination, allowing large teams to work concurrently on the design. Libraries of hierarchical elements can be quickly created, allowing those elements to be reused easily by other members of the design team or on subsequent designs. Fully integrated into the environment is the capability to graphically model event-driven systems using state charts, truth tables, and flow diagrams. Specialized capability for mechanical and electrical power systems allows models of these systems to be constructed using modeling elements that correspond directly to the structure of the physical system, avoiding the need to express them as mathematical equations. If prototype or actual physical systems are available and input/output data can be acquired from them, mathematical models can also be created using system identification techniques. As soon as a hierarchical element of the model is constructed, that element can be simulated. Simulation allows specification, requirements, and modeling errors to be found immediately, rather than waiting until later in the design effort. As the model becomes larger, through the addition of hierarchical elements or by increasing the complexity of existing ones, the designer can continue to find and correct errors during simulation by using the model coverage, performance profiling, and interactive debugging features. When the physical system model is specified to the required level of detail and simulation has shown the model to be accurate, the control system can be designed. 1.4. CONTROL SYSTEM SOFTWARE DESIGN With the behavioral model of the physical system available, the designer can begin the embedded control system software design. The MathWorks environment for Model-Based Design supports many types of control system design techniques and requirements that range from the simple to the most complex and large-scale. For example, some product designs may require using linear control design methods to determine the correct algorithms and parameters for the control system software. Using MATLAB and Simulink, the designer can automatically create the linear physical system models needed by this design technique, calculate the parameters, and then visualize the results using Bode plots and root locus diagrams. Other applications may require less sophisticated techniques to determine the correct control system design. Regardless of the control system design method used, the MathWorks environment for Model-Based Design helps the designer use interactive simulation to quickly evaluate each contr ol system design model in conjunction with the physical system model and avoid the risk, expense, or need for prototypes or actual physical systems. As the control system functional design is completed and the target environment needs to be considered, the designer can specify implementation details for the software directly in the modeling environment. The MathWorks environment supports all aspects of control system software design, including processor, interface, or standards issues. For example, you may need scaled integer or fixed-point data types for target processors that have no floating-point math capability. The effects of fixed-point mathematics can be evaluated by simulation, to see if the proper data sizes and scale factors have been selected. Data structures that are needed to meet software standards or target environment interface requirements can be defined as part of the system model and then realized when the embedded control system software is automatically generated. When the control system software design is complete, you can simulate the entire system model. During simulation, you can automatically collect model profiling and coverage information that will help you assess performance and discover errors. If performance does not meet expectations or errors are found, you can easily change the model to correct the problem and then simulate the model again to confirm the change or correction. Once simulation of the entire system model has shown that the design meets the desired performance requirements, you can automatically generate software for real-time testing and implementation, using the model as a specification. 1.5. EMBEDDED SOFTWARE TESTING AND IMPLEMENTATION Using the system model and Real-Time Workshop, real-time code for testing, validation, and embedded implementation on the production target processor can be automatically generated. As it is created, the code is automatically optimized for fast execution and efficient use of memory. Automatically generating code from the system model avoids errors due to manual translation of the model into code, and saves time, allowing software developers to focus on more demanding tasks. The MathWorks provides a turnkey software environment called xPC Target for real-time prototype testing, calibration, and validation of this automatically generated code using a PC-based hardware target system. xPC Target includes a real-time kernel, device drivers, and all the support software needed to create a rapid control prototyping system for real-time software testing and validation. It can also be used to provide hardware-in-the-loop capability, using code generated automatically from the physical system model. Hardware-in-the-loop testing allows the designer to simulate the real-time behavior and characteristics of their physical system, so that prototype or production control system software can be tested without the need for the actual hardware or operational environment. For embedded system designers who prefer an integrated capability, The MathWorks has a fully tested, custom configured, PC-based target hardware system. Chapter 2 MODELING AND SIMULATION 2.1. MODELING A computer model, as used in modeling and simulation science, is a mathematical representation of something-a person, a building, a vehicle, a tree-any object. A model also can be a representation of a process-a weather pattern, traffic flow, air flowing over a wing. Models are created from a mass of data, equations and computations that mimic the actions of things represented. Models usually include a graphical display that translates all this number crunching into an animation that you can see on a computer screen or by means of some other visual device.   Models can be simple images of things-the outer shell, so to speak-or they can be complex, carrying all the characteristics of the object or process they represent. A complex model will simulate the actions and reactions of the real thing. To make these models behave the way they would in real life, accurate, real-time simulations require fast computers with lots of number crunching power. 2.2. SIMULATION Simulations (and models, too) are abstractions of reality. Often they deliberately emphasize one part of reality at the expense of other parts. Where as models are mathematical, logical, or some other structured representation of reality, simulations are the specific application of models to arrive at some outcome. 2.2.1 Types of simulations Simulations generally come in three styles: live, virtual and constructive. A simulation also may be a combination of two or more styles. Live simulations typically involve humans and/or equipment and activity in a setting where they would operate for real. Think war games with soldiers out in the field or manning command posts. Time is continuous, as in the real world. Another example of live simulation is testing a car battery using an electrical tester. Virtual simulations typically involve humans and/or equipment in a computer-controlled setting. Time is in discrete steps, allowing users to concentrate on the important stuff, so to speak. A flight simulator falls into this category. Constructive simulations typically do not involve humans or equipment as participants. Rather than by time, they are driven more by the proper sequencing of events. A simulator is a device that may use any combination of sound, sight, motion and smell to make you feel that you are experiencing an actual situation. Some video games are good examples of low-end simulators. Simulations are complex, computer-driven re-creations of the real thing. When used for training, they must recreate reality accurately; otherwise you may not learn the right way to do a task. 2.3. MODELING AND SIMULATING ORDINARY SECOND ORDER DIFFERENTIAL EQUATION Consider the second order differential equation (1) This can be written as two first order differential equations if we introduce two new variables, x1(t) and x2(t).   Let x1(t)=y(t).   We can then write two coupled first order equations. (2) (3) The solution can be approximated in Simulink by using two integrators to integrate the first order derivatives. 2.3.1. Building a Simulink Model We start Simulink from the Matlab prompt by typing Simulink.    We will be needing blocks from the Source, Sink, Linear and Non-linear libraries, so double click on them to open them up.   In the window labeled untitled, drag two integrators from the Linear library, connect them, and change their labels. Fig2.1. Building Simulink Model (Step 1) The input to the leftmost integrator is the derivative of x2, and its output is x2.   The input to the rightmost integrator is the derivative of x1 (=x2), and its output is x1.   We can complete the representation of the differential equation except for the input, by adding two gain blocks (and flipping them using the Format option of the Simulink menu. Fig2.2 Building Simulink Model (Step 2) To add the input we will use the clock (from Source), the trigonometric function (from Non-Linear) and another gain block.   The completed diagram should look like the one shown below. Fig2.3. Building Simulink Model (Step 3) 2.3.2. Running Simulation and Viewing Results To view the results of the simulation, add a scope (from Sink).   In this case we only want to view 80 ms of simulation, so go to the Simulation menu and choose Parameters, and set the stop time to 0.08 seconds.   To start the simulation hit the start button, or go to Simulation->Start.   The scope output is shown below (after zooming with the Binocular tool at the top of the scope window. Fig2.4 Simulation Results of the Model It is often desirable to save the data to Matlab.   To save the time variable, the input and the output, we add three To Workspace blocks (from Sink) and give them each a different name (these are the names of the variables that will be in the Matlab workspace). Fig2.5 Building Simulink Model (Step 4) Chapter 3 ANTI-LOCK BRAKING SYSTEM 3.1 INTRODUCTION Antilock Braking Systems (ABS) are closed loop control devices within the braking systems which prevent the wheel lock-up during braking and as a result, retain vehicle steerability and stability. The main ABS components are hydraulic modulators, wheel speed sensors, ECU for signal processing and control and triggering of the signal lamp and of the actuators in the hydraulic modulator. Fig 3.1 Location of the ABS in a vehicle 3.2 DESCRIPTION OF THE SYSTEM The theory behind anti-lock brakes is simple. A skidding wheel (where the tire contact patch is sliding relative to the road) has less traction than a non-skidding wheel. If we have been stuck on ice, for example, we know that if the wheels are spinning we have no traction. This is because the contact patch is sliding relative to the ice. By keeping the wheels from skidding while we slow down, anti-lock brakes benefit in two ways: The vehicle stops faster, and we will be able to steer while we stop. There are four main components to an ABS system: Speed Sensors, Pump, Valve and an ECU. 3.2.1 Speed Sensor The anti-lock braking system needs some way of knowing when a wheel is about to lock up. The speed sensors, which are located at each wheel, or in some cases in the differential, provide this information. 3.2.2 Valves There is a valve in the brake line of each brake controlled by the ABS. On some systems, the valve has three positions: In position one, the valve is open; pressure from the master cylinder is passed right through to the brake. In position two, the valve blocks the line, isolating that brake from the master cylinder. This prevents the pressure from rising further should the driver push the brake pedal harder. In position three, the valve releases some of the pressure from the brake. 3.2.3 Pump Since the valve is able to release pressure from the brakes, there has to be some way to put that pressure back. That is what the pump does; when a valve reduces the pressure in a line, the pump is there to get the pressure back up. 3.2.4 The ECU The ECU receives, filters and amplifies the speed sensor signals and ascertains from them the degree of wheel slip and the acceleration of the individual wheels as well as the reference speed which is the best possible calculation of the vehicle road speed. Most of the systems use vehicle specific LSI circuits for this purpose. Fig 3.2 Anti Lock Brake Pump and Valves 3.3 WORKING OF ABS There are many different variations and control algorithms for ABS systems. We will discuss how one of the simpler systems works. The controller monitors the speed sensors at all times. It is looking for decelerations in the wheel that are out of the ordinary. Right before the wheel locks up, it will experience a rapid deceleration. If left unchecked, the wheel would stop much more quickly than any car could. It might take a car five seconds to stop from 60 mph (96.6 kph) under ideal conditions, but a wheel that locks up could stop spinning in less than a second. The ABS controller knows that such a rapid deceleration is impossible, so it reduces the pressure to that brake until it sees acceleration, then it increases the pressure until it sees the deceleration again. It can do this very quickly, before the tire can actually significantly change speed. The result is that the tire slows down at the same rate as the car, with the brakes keeping the tires very near the point at which they will start to lock up. This gives the system maximum braking power. When the ABS system is in operation we will feel a pulsing in the brake pedal; this comes from the rapid opening and closing of the valves. Some ABS systems can cycle up to 15 times per second. 3.4 TYPES OF ABS: Anti-lock braking systems use different schemes depending on the type of brakes in use. Referring them by the number of channels, that is, how many valves that are individually controlled and the number of speed sensors, we have the following:   i) Four-channel, four-sensor ABS This is the best scheme. There is a speed sensor on all four wheels and a separate valve for all four wheels. With this setup, the controller monitors each wheel individually to make sure it is achieving maximum braking force. ii) Three-channel, three-sensor ABS This scheme, commonly found on pickup trucks with four-wheel ABS, has a speed sensor and a valve for each of the front wheels, with one valve and one sensor for both rear wheels. The speed sensor for the rear wheels is located in the rear axle. This system provides individual control of the front wheels, so they can both achieve maximum braking force. The rear wheels, however, are monitored together; they both have to start to lock up before the ABS will activate on the rear. With this system, it is possible that one of the rear wheels will lock during a stop, reducing brake effectiveness. iii) One-channel, one-sensor ABS This system is commonly found on pickup trucks with rear-wheel ABS. It has one valve, which controls both rear wheels, and one speed sensor, located in the rear axle. This system operates the same as the rear end of a three-channel system. The rear wheels are monitored together and they both have to start to lock up before the ABS kicks in. In this system it is also possible that one of the rear wheels will lock, reducing brake effectiveness. This system is easy to identify. Usually there will be one brake line going through a T-fitting to both rear wheels. We can locate the speed sensor by looking for an electrical connection near the differential on the rear-axle housing. Chapter 4 IMPLEMENTATION OF ANTI-LOCK BRAKING SYSTEM 4.1 BLOCK DIAGRAM OF ABS On initial braking, the brake pressure is increased, the brake slip ÃŽÂ » rises and at the maximum point on the adhesion/slip curve, it reaches the limit between the stable and unstable ranges. From this point on, any further increase in the brake pressure or braking torque does not cause any further increase in braking force FB. In the stable range, the brake slip is largely deformation slip, it increasingly tends towards skidding in the unstable range. Actuator Desired Slip Controller Vehicle Dynamics Actual Slip Fig4.1. Block Diagram of ABS We model the ABS using Matlab/Simulink where in the various mechanical blocks are realized and mathematical models of the same are readily available in the Simulink library. The ABS simulation model follows the below shown control loop. The reference variable is the desired relative slip which is fed as an input to the system. The control system in our case is the wheel whose parameters like wheel speed are measured. The feedback path consists of the user defined equation which measures the relative slip of the wheel and the error is rectified at the initial stage. The model represents a single wheel, which may be replicated a number of times to create a model for a multi-wheel vehicle. Fig 4.2. ABS Control Loop 4.2 ANALYSIS OF ABS: For understanding the concept of ABS, we make use of the free body diagram of a wheel. We make use of the formulae for force and torque acting on the wheel. The below figure gives us a clear understanding about the forces acting on a wheel. The wheel rotates with an initial angular speed that corresponds to the vehicle speed before the brakes are applied. We used separate integrators to compute wheel angular speed and vehicle speed. We use two speeds to calculate slip, which is determined below. Note that we introduce vehicle speed expressed as an angular velocity (see below). . (Equal to wheel angular speed if there is no slip.) (1) Fig 4.3 Free Body Diagram of a single wheel (2) (3) is the wheel speed divided by the wheel radius. is the vehicle linear velocity. is the wheel radius. is the wheel angular velocity. We can also write (3) as (4) Where V is the vehicle speed, à Ã¢â‚¬ ° is the wheel speed and r is the radius of the wheel. From these expressions, we see that slip is zero when wheel speed and vehicle speed are equal, and slip equals one when the wheel is locked. A desirable slip value is 0.2, which means that the number of wheel revolutions equals 0.8 times the number of revolutions under non-braking conditions with the same vehicle velocity. This maximizes the adhesion between the tire and road and minimizes the stopping distance with the available friction. If an excessive brake torque is applied, the wheel will be locked, which means that it slides on the road surface but does not rotate at all. A locked wheel has no lateral stability and less longitudinal friction force, which is the ultimate force to stop the vehicle. Thus, a braking with a locked wheel will cause longer stopping distance and lateral instability. The tire force from the road surface causes the wheel velocity to increase, thus decreases the wheel slip. A high ÃŽÂ ¼ leads to a large tyre force and a low ÃŽÂ ¼ leads to a small tyre force. In the increasing part of the ÃŽÂ ¼-slip curve, an increase of the wheel slip leads to a larger ÃŽÂ ¼ and a larger tyre force, which reverses the wheel slip to a small value. However, in the decreasing part of the ÃŽÂ ¼-slip curve, an increase of the wheel slip leads to a smaller ÃŽÂ ¼ and a smaller tyre force, which causes the wheel slip to increase continuously. So, the peak point of the ÃŽÂ ¼-slip curve is criti cal. When a braking is initiated, the wheel velocity starts to decrease and the wheel slip starts to increase from zero. The wheel slip may stop increasing and start to decrease before the ÃŽÂ ¼ reaches its peak point. But if an excessive brake torque is applied, the wheel slip may go straightly to a large number, which causes the ÃŽÂ ¼ to pass its peak point and reach somewhere in the decreasing part of the ÃŽÂ ¼-slip curve. If the brake torque is not reduced quickly at this point, the reduction of the road friction force will lead to a rapid increase of the wheel slip and eventually to a wheel lockup. ABS tries to detect when this peak point is going to be reached and then reduces the brake torque properly so that a wheel lockup could be avoided. Fig 4.4. ÃŽÂ ¼-slip Friction Curve It appears to be true that maintaining the wheel slip at the peak point of the ÃŽÂ ¼- slip curve is ideal. However, the position of the peak ÃŽÂ ¼ point varies on the different road surfaces. In addition, stay at the peak point of the ÃŽÂ ¼- slip curve sometime may lead to a poor lateral stability. Thus, many control strategies define their performance goal as maintaining the wheel slip near a value of 0.2. This represents a compromise between the lateral stability, which is best at ÃŽÂ »=0 and the maximum deceleration which usually appears when ÃŽÂ » is between 0.1 and 0.3. 4.3 IMPLEMENTATION The friction coefficient between the tire and the road surface,  µ, is an empirical function of slip, known as the  µ-slip curve. We created mu-slip curves by passing MATLAB variables into the block diagram using a Simulink lookup table. The model multiplies the friction coefficient,  µ, by the weight on the wheel, W, to yield the frictional force, Ff, acting on the circumference of the tire. Ff is divided by the vehicle mass to produce the vehicle deceleration, which the model integrates to obtain vehicle velocity. In this model, we used an ideal anti-lock braking controller, that uses bang-bang control based upon the error between actual slip and desired slip. We set the desired slip to the value of slip at which the  µ-slip curve reaches a peak value, this being the optimum value for minimum braking distance (see note below.). Note: In an actual vehicle, the slip cannot be measured directly, so this control algorithm is not practical. It is used here to illustrate the conceptual construction of a simulation model. Fig 4.5. Simulink Model of the ABS In the above figure, the wheel speed, vehicle speed and the stopping distance are measured and the error value is fed back through the feedback path. Also, tire torque and the relative slip are fed as inputs to the wheel speed block. Notice that the model is a reference model which has its own internal block. Double click on the Wheel Speed subsystem in the model window to open it. Given the wheel slip, the desired wheel slip, and the tire torque, this subsystem calculates the wheel angular speed. To control the rate of change of brake pressure, the model subtracts actual slip from the desired slip and feeds this signal into a bang-bang control (+1 or -1, depending on the sign of the error). This on/off rate passes through a first-order lag that represents the delay associated with the hydraulic lines of the brake system. The model then integrates the filtered rate to yield the actual brake pressure. The resulting signal, multiplied by the piston area and radius with respect to the wheel (Kf), is the brake torque applied to the wheel. Fig 4.6. Wheel Speed Model for the ABS The model multiplies the frictional force on the wheel by the wheel radius (Rr) to give the accelerating torque of the road surface on the wheel. The brake torque is subtracted to give the net torque on the wheel. Dividing the net torque by the wheel rotational inertia, I, yields the wheel acceleration, which is then integrated to provide wheel velocity. In order to keep the wheel speed and vehicle speed positive, limited integrators are used in this model. After we build the ABS model in simulink, we have to configure the parameters related to simulation of the model. We need to specify that the signals are exported to the Matlab workspace where they are analyzed and results are viewed. This is done by checking the signal logging field in the configuration parameters option provided in the simulation tab. Fig 4.7. Configuring Parameters for the model We make a Matlab code which makes use of the inputs and outputs used by the simulink model and we plot the waveforms. 4.3.1 ABS Code h = findobj(0, Name, ABS Speeds); if isempty(h), h=figure(Position,[26 239 452 257], Name,ABS Speeds, NumberTitle,off); end figure(h) set(h,DefaultAxesFontSize,8) logsout.unpack(all); plot(Vs.Time, Vs.Data); set(findobj(type,line),color,[0 1 0]); hold on; plot(Ww.Time, Ww.Data); title(Vehicle speed and wheel speed); ylabel(Speed(rad/sec)); xlabel(Time(secs)); set(gca,Position,[0.1300 0.1500 0.7750 0.750]); set(get(gca,xlabel),FontSize,10); set(get(gca,ylabel),FontSize,10); set(get(gca,title),FontSize,10); % Plot arrow with annotation hold on plot([5.958; 4.192],[36.92; 17.29],r-,[5.758; 5.958; 6.029],[36.55; 36.92; 35.86],r- ) text(8.533,54.66,Vehicle speed (omega_v),FontSize,10) plot([7.14; 8.35],[43.1; 56.3],r-,[7.34; 7.14; 7.07],[43.4; 43.1; 44.1],r- ) text(4.342,15.69,Wheel speed (omega_w),FontSize,10) drawnow hold off h = findobj(0, Name, ABS Slip); if isempty(h), h=figure(Position,[486 239 452 257], Name,ABS Slip, NumberTitle,off); end figure(h); set(h,DefaultAxesFontSize,8) slp = logsout.slp.Data; time = logsout.slp.Time; plot(time,slp); title(Slip) xlabel(Time(secs)) ylabel(Normalized Relative Slip) set(gca,Position,[0.1300 0.1500 0.7750 0.750]) set(get(gca,xlabel),FontSize,10) set(get(gca,ylabel),FontSize,10) set(get(gca,title),FontSize,10) Chapter 5 RESULTS AND CONCLUSION After building the model, we simulate it using the options provided in the same Simulink window. 5.1 RUNNING THE SIMULATION 5.1.1 With ABS Press the Play button on the model toolbar to run the simulation. We can also run the simulation by executing the sim(FILE NAME) command in MATLAB. ABS is turned on during this simulation. Fig 5.1 Vehicle Speed and Wheel Speed(with ABS) The model logs relevant data to MATLAB workspace. Logged signals have a blue indicator. In this case yout and slp are logged (see the model).The above figure visualizes the ABS simulation results. The first plot in figure shows the wheel angular velocity and corresponding vehicle angular velocity. This plot shows that the wheel speed stays below vehicle speed without locking up, with vehicle speed going to zero in less than 15 seconds. Fig 5.2 Normalised Relative Slip(with ABS) 5.1.2 Without ABS For more meaningful results, consider the vehicle behavior without ABS. At the MATLAB command line, set the model variable ctrl = 0. This disconnects the slip feedback from the contro