Soil Mechanics (Geotechnics Essay Example | Topics and Well Written Essays - 1000 words

Soil Mechanics (Geotechnics - Essay Example Soil is composed of particles such as silt, clay, gravel and sand and they can also contain other gases that exist in between these particles. The study of soil is very important because this is what makes the study of geotechnical engineering possible. This is a subtopic in civil engineering and it is a very complex topic. Soil mechanics is applicable in many ways as far as building and construction is concerned and some of the best examples are such as building foundations of bridges, dams and sustaining systems of buried pipelines. This is very important because it ensures that buildings do not fall apart easily in the modern world and this contributes a lot to the development of different cities world wide. The study of soils is also very important because it contributes a lot to good agricultural products. Many areas of engineering depend on soil mechanics and some of these areas are such as coastal engineering, geophysical engineering and hydrology among other areas. One of the best ways of approaching the topic on geotechnics and drainage is through understanding the composition and genesis of soils. This is one of the best examples of a diagram that clearly defines the formation of soils as far as volumes of water, air and solid is concerned. The V?, V?, and Vs represent the amount of solids, air and water present in a specific mixture of soil. W?, W?, and Ws in the diagram above stand for the weights of solids, air and water within a soil mixture and M?, M?, and Ms stand for the masses of water, solids and air found in a mixture of soil. The formulae for calculating the weights of all the named particles present is Mass multiplied by the acceleration of gravity which is; Ws=Mg. Types of Triaxial Tests There are several types of triaxial tests but the most common ones are; Consolidated Drained also known a CD, Consolidated Undrained tests which is also referred to as UD and Unconsolidated Undrained. In the consolidated drained or CD, the test is done th rough consolidating and shearing while compressing it with the drainage. In the second type of test, the sample is not drained and in the third type of test, the sample is constantly compressed. This is an example of soil horizons from www.wikipedia.com . A; can be referred to as the colluviums or top soil, B; is the Residual soil that is mature and C; is weathered rock. In most cases, soil deposits become affected by how they are transported to the specific location where they can be found. Understanding the formation and deposition of soils makes it quite easier and understandable especially when it comes to dealing with geotechnics calculations. Clay is composed of several minerals that form structures that look like a sheet which have a length range of 10 x 10 ?7 and 4 x 10?5 and its thickness ranges from 9 x 10?9 and 2x 10?6 and their surface area is large. Through understanding the formation of soils, one can easily understand how different stresses and shears are formed in di fferent phases on a normal circumstance and all this is part of the study of geotechnics (Chen 2010). Stress strain curve diagram. Looking at the curve above, one can easily predict the stability of the soil by measuring the shear strain against its shear strength Cell pressure kN/m2 Deviator stress kN/m2 kN/m2 2 (a). Normal and Over- Consolidated Stratum Normally consolidated stratum is one which is very dense and packed tightly as one goes deep the strata. An over-consolidated clay stratum is one which occurs when water is squeezed out of the ground with

Management Overview Essay Example | Topics and Well Written Essays - 4000 words

Management Overview - Essay Example These approaches are preferred because companies have little control over external factors in their environment, including their competition, but have a great deal of control over internal factors within the firm. This is especially true with PLCs seeming to shorten over time, most notably in technology fields. With all this taken into account, it makes sense for organizations to focus internally to attempt to gain a competitive advantage, rather than being reactionary and responding to external factors consistently (Teece, 1997), which should help them not only get a competitive advantage in the first place but also sustain it over the long term. In this paper, the writer will attempt to analyze changes that have occurred in the field of strategic management. Dell Corporation will serve as the model for this analysis, as its business model has been praised recently due to its unique approach to markets. 1.2 Dell Computers Product Lie Spans have been shortening from some time in Dell ’s sector (computing), which obviously can create problems for a corporation in terms of creating a long term sustained advantage. This is because any advantage gained from innovation is unlikely to last more than one product life cycle, after which competitors will adapt or copy such innovations, meaning that without constant innovation, a company will quickly lag behind. This also means that a company must display excellent flexibility, and be able to change their strategic focus quickly: in Dell’s case, for instance, a weakening desktop market might be inevitable, so they would need to be able to quickly capitalize on other business such as laptops or accessories. Competition in this sector changes frequently, as new firms enter, and new technologies redefine the expectations of the consumer base. While this leads many firms to jump head first into this sector, it has also led to some existing it, when they cannot compete with their competitors, cope with external d ynamics, or maintain enough innovation to keep them competitive with their competitors in the long term. Failed companies within such organizations also frequently do not possess the necessary resources to create or maintain competitive posture: thus the problem can be viewed as both resource based and externally driven. HP, for instance, could not maintain competitive advantage in the tablet market or the PC business because of competition from firms like Apple and Google (Cellan-Jones, 2011), making the company rely solely on its printer/scanner division to stay afloat. Lawson and Samson (2011) show that competitive advantage in this field depends on organizational asset positions as well as strategic flexibility and strategic decisions; there are distinctive flavors of strategic paths that seem to lead to success in this field. This flavor touches on the way the firm is put together and operated, and has a lot to do with organizational culture including working conditions, expect ation, management systems and so on. Samson and Lawson create a definition of the dynamic corporation – which will maintain competitive advantage, which includes things like cross-functional resources and management fascilities, which spans research

Assignment 5 Essay Example | Topics and Well Written Essays - 1500 words - 2

Assignment 5 - Essay Example More generally, we can see that cross-cultural encounters do not always end well for everybody involved. Before understanding what a cross-cultural encounter can do, it is important to understand what one is. In the broadest meaning, such an encounter could be described as any in which two different cultures meet. More specifically, it is one in which ideas that are different between cultures are exchanged, with varying results. In the case of Benin, one of the exchanges was â€Å"the discovery of Benin art by Europeans†. (Mackie 16) This can be seen in the last paragraph of the passage from Bacon, which states that some of the things found in the houses were â€Å"castings of wonderful delicacy of detail, and some magnificently carved tusks†. In the background, we can see that the Benin were perhaps initially pleased by contact with the West. Presumably, they happily traded for the â€Å"glass walking sticks, old uniforms, absurd umbrellas† and so on that Bacon describes as being in most of the warehouses. However, the exchange obviously did not go well for the Benin. In the context Mackie gives us, we know that Bacon is an invader trying to bring Benin â€Å"firmly under British control†. (Mackie 17) Although it is not explicitly mentioned in the passage, some sense of this chilling reason behind the cross-cultural encounter can be seen in the way Bacon describes the Benin people. Bacon was largely unimpressed with what he found, and so the cultural exchange which could have taken place was limited by the Europeans existing prejudices about the Benin people. The way the passage describes the Benin as â€Å"natives† who were tricked by â€Å"the usual cheap finery† reinforces the idea that the Europeans only wanted to manipulate this different culture for their own ends. The fact that the passage describes the Benin in very negative tones elsewhere, such as explaining the â€Å"ruined and uninhabited houses† as being

Nicomachean Ethics Essay Example for Free

Nicomachean Ethics Essay Ancient Greek philosopher Aristotle wrote the Nicomachean Ethics, portraying the significance of studying the realms of ethics and political science. In his work, Aristotle focuses on the theme of how human beings can attain the chief human good—happiness—at which everything aims. Aristotle argues that ethics, the study of moral character, and political science, the branch of knowledge and analysis of political activity and behavior, must be closely studied together in order to fully grasp the meaning of and obtain the good way of life. Aristotle believes that there is only one goal, one ultimate end for every individual—that is eudaimonia, translated as happiness, not as a feeling but happiness as the highest human good or a life full of activity. He claims that a person should live a way of life distinct from the lives of animals, where they only live for the sake of living or pleasure. 1 As human beings, people should use their power of speech to communicate and make rational decisions within a polity, striving to live their lives up to their full potential and to their full capacity for a happy life. 2 The life of politics, the via activa, is thus the key to the chief good or the best life for humans; however, the life of action must be of certain type of quality, in accordance with reason, since different actions may lead to the good or the bad life. In other words, a person’s actions must be in line with arete, with virtue or excellence. 3 Possessing virtue is having the ability to realize the good things, and doing them at the right time and the right way to get things done. Virtues can result to two different ways: a good or bad life. For example, President Lincoln versus Adolph Hitler—both of these men possess the virtue of wisdom, although they have used them disparately, one ending a Civil War in peace and the other manipulating others to killing millions of innocent people. To make it to the good end, Aristotle claims that we must practice virtue by, giving it a certain type of character or ethical quality to our actions. 4 Although human cannot acquire virtue by nature alone, nature allows and gives us the capacity to acquire virtue by learning and through exercising them in our lives. 5 By constantly acting with virtue, we cultivate habituation and ultimately we do not need to be self-controlled to do what is just. Instead, we become accustomed to do what is right willingly and naturally. Activities of good ethics or good moral character are virtues. And so, to best learn and exercise these virtues is by incorporating political science in connection to ethics. Aristotle asserts that the science of politics, the highest master of science combined with many other sciences, must be very well studied, for it is where moral laws are examined and its end, including the ends of other sciences associated with political science, will be the chief human good of all society. 6 Therefore, Aristotle presents the idea that the state must play an important role to aim and shape a society of good citizens, incorporating what the good life is: the life of virtue. 7 The state must look after its citizens morally, creating a type of society that will allow people to have a political life together; consequently, this political life will give them the opportunity and the ability to realize their wide range of capacities and their ideal life. Without the state, humans will not be able to experience the good life, the life of action. They are not self-sufficient enough to work alone, for they need others to be self-sufficient and happy. 8 Having a community will give every individual a chance to experience the struggle within the polity, in which he or she can exercise his or her many virtues, whether it be the ability to be courageous in the face of danger, the ability to make better judgements, or the ability to resist pain in the midst of hard criticism. Consequently, they build up their ethos or character, cultivating them to eventually living a happy life. The life of struggle, of politics, is the life where humans can have the chance to develop their full capacities, abilities, and strengths to overcome many hardships and difficulties. 9 Having a strong state does not achieve full satisfaction; hence, the state must know what eudaimonia is in order to direct and guide its citizens. It is necessary for the state to study and establish what is just and what is ethics. In this way, the state could inculcate what is moral through laws and education. Acquiring the chief good starts at home. Aristotle argues that a good state support an educational system, for a society that promotes morality is the best way of cultivating habituation in young children. 10 Having this strong educational system in the state will successfully encourage parents of each household to train their young children in good principles, abiding by the set of moral laws established in the community; as a result, they will naturally apply their good habits in their daily lives and ultimately gain the perfect virtuous life. Connecting the study of ethics and political science together can bring the whole society into a healthy life of virtue. Ethics is the key in which politics can utilize and produce a good society. By knowing what is righteous and what is ethics, the state can make the ultimate life of happiness possible for its citizens. Political science plays the role of establishing and enforcing good and moral character through an effective system that can guide and habituate every part and class of society. Ultimately, having access to a superfluous life of activity in a way that is in line with reason will let individuals life life to the fullest, of virtue and of happiness.

Polyester: History, Development and Applications

Polyester: History, Development and Applications ABSTRACT:Â   Polyester is a synthetic fiber derived from coal, air, water, and petroleum. Polyester fibers are formed from a chemical reaction between an acid and alcohol, and is developed in a 20th-century laboratory. In the formation of polyester reaction, two or more molecules combine to make a large molecule whose structure repeats throughout its length. Polyester fibers can form very long molecules that are very stable and strong. Polyester has been considered to have several advantages over traditional fabrics such as cotton. One of its most important quality is that it does not absorb moisture, but does absorb oil; this quality makes polyester the perfect fabric for the application of water-, soil-, and fire-resistant finishes. Its another quality, that is, low absorbency also makes it naturally resistant to stains. Polyester is used in the manufacture of many products, including clothing, home furnishings, industrial fabrics, computer and recording tapes, and electrical insulation. As we go along further, we would see the various uses of polyester in all the several fields such as clothing, furnishing, etc. Fabrics woven from polyester thread or yarn are used extensively in apparel and home furnishings, from shirts and pants to jackets and hats, bed sheets, blankets and upholstered furniture. Industrial polyester fibers, yarns and ropes are used in tire reinforcements, fabrics for conveyor belts, safety belts, coated fabrics and plastic reinforcements with high-energy absorption. Polyester fiber is used as cushioning and insulating material in pillows, comforters and upholstery padding. We would discuss in detail the history of polyester, the method of manufacturing of polyester, its various uses, and its importance in our day to day life, how much we use polyester in our life without really noticing that it is polyester we are using. INTRODUCTION: In short we can say that polyester is a category of polymers which contain the ester functional group in their main chain. Even though there are many types of polyester, the term polyester as a specific material most commonly refers to polyethylene terephthalate (PET). Polyesters include naturally-occurring chemicals. Naturally occurring chemicals include that are found in nature and are not man-made such as in the cut in of plant cuticles. An example of synthetic fiber is synthetics through step-growth polymerization such as polycarbonate and polybutyrate. Generally natural polyesters and even a few synthetic ones are biodegradable, that is, they can break down or decay naturally without any special treatment, and can therefore be thrown away without causing pollution. Whereas on the other hand, most synthetic polyesters, which are more commonly used, are not biodegradable. Polyester is a term often defined as long-chain polymers chemically composed of at least 85% by weight of an ester and a dihydric alcohol and a terephthalic acid. In simpler terms, it means that polyester is the linking of several esters within the fibers. Reaction of alcohol with carboxylic acid results in the formation of esters. Polyester also refers to the various polymers in which the backbones are formed by the esterification condensation of polyfunctional alcohols and acids. Polyester can also be classified as saturated and unsaturated polyesters. Saturated polyesters refer to that family of polyesters in which the polyester backbones are saturated. They are thus not as reactive as unsaturated polyesters. The saturated polyesters consist of low molecular weight liquids used as plasticizers and as reactants in forming urethane polymers, and linear, high molecular weight thermoplastics such as polyethylene terephthalate (Dacron and Mylar). Usual reactants for the saturated polyesters are a glycol and an acid or anhydride. Unsaturated polyesters refer to that family of polyesters in which the backbone consists of alkyl thermosetting resins characterized by vinyl unsaturation. They are mostly used in reinforced plastics. These are the most widely used and economical family of resins. Characteristics of polyester Polyester fabrics and fibers are extremely strong and thus durable. Polyester is very durable: it is resistant to most chemicals, stretching and shrinking, wrinkle resistant, mildew and abrasion resistant. Polyester is hydrophobic in nature, that is, these molecules and quick drying. It can be used for insulation by manufacturing hollow fibers. Polyesters quality to retain its shape is good for making outdoor clothing for harsh climates. Polyester can be easily washed and dried, without the added tension of ironing and all because it does not form wrinkles. HISTORY OF POLYESTER: Polyester became famous for Scrunch it, pull it, and wash it without any wear and wrinkles. Polyester was the fabric of choice in an economy that was changing in terms of speed, efficiency and convenience. The textile industrys answer to food industry producing fries and coke was the production of Polyester quick, cheap and easy. Carothers Work It was W.H.Carothers who discovered that alcohols and carboxyl acids could be successfully mixed to create fibers. Carothers was working for DuPont at the time and unfortunately when he discovered Nylon, polyester took a back seat. PET Terylene The incomplete research of Carothers had not advanced to investigating the polyester formed from mixing ethylene glycol and terephthalic acid. Whinfield and Dickson 2 British scientists are the ones who patented PET or PETE in 1941. Polyethylene terephthalate (PET) forms the basis for synthetic fibers like Dacron, Terylene and polyester. Later that year, the first polyester fiber Terylene was created by Whinfield and Dickson along with Birtwhistle and Ritchiethey. Terylene was first manufactured by Imperial Chemical Industries or ICI. DuPonts Role It was in 1946 that DuPont bought all legal rights from ICI, that is, Imperial Chemical Industries. In 1950, the Dealware property of DuPont manufactured another polyester fiber, which they named Dacron. Mylar was introduced in 1952. Polyester was first introduced to the American public in 1951 as the magical fabric that needed no ironing! PET and PEN are DuPont trademarks that have turned the use and consumption of Polyester around. Polyester Becomes Popular Subsequent to the development of Terylene and Dacron, Kodel was developed by Eastman Chemical Products, Inc in 1958. The polyester market underwent rapid expansion and textile mills emerged everywhere. Many of the mills were located at small gas stations and produced cheap polyester apparel. The inexpensive and durable fiber became very popular and the industry expanded rapidly till the 1970s. Unfortunately, the infamous double-knit polyester image hit the industry and polyester soon came to be known as the uncomfortable fabric. The Phoenix Rises Today, polyester is largely regarded as a cheap fabric that is rather uncomfortable for sensitive human skin to wear. It is also not preferred because of its highly inflammable properties. However, the emergence of luxury fibers like polyester microfiber and various polyester blends, the polyester industry is once again on its way to a grand come back. The Tennessee Eastman Company and the Man-Made Fiber Producers Associations (MMFPA) Polyester Fashion Council played a significant role in the revival of polyester. The Tennessee Eastman Company started a YES campaign for polYESter and popularized it via radio and television. The main idea was to focus on the wash and go properties of polyester rather than sell it as a cheap fabric. Hoechst Fibers Industries also played a part in the history of polyester. They conducted various studies from 1981 to 1983 and found that 89% of people could not distinguish between polyester and other natural fibers like cotton, wool and silk. Also, it was found that people were more interested in the appearance of the apparel than the fabric it was made of. Today, the biggest contributor to the appeal of polyester is the discovery of microfibers. Microfibers give polyester the feel of silk and are rapidly becoming the choice of fabric. With an expensive tag to match, the cheap image of polyester seems to be on its way out. Heres to heralding a new era in the history of polyester! MANUFACTURING OF POLYESTER: Polyester Manufacturing Polyester fibers or the synthetic fibers are long chain polymers which are derived from coal, air, water, and petroleum. They are formed through chemical reaction between an acid and alcohol, which forms ester. In this reaction, two or more molecules combine to make a large molecule whose structure repeats throughout its length. These molecules are very stable and strong. There are variations in the compositions and therefore in the properties of polyester fibers. Types of Polyester PHYPERLINK http://www.teonline.com/fibers-yarns-threads/polyester-fiber.htmlolyester fibers are generally available in two varieties- PET (polyethylene terephthalate) and PCDT (poly-1, 4-cyclohexylene-dimethylene terephthalate). PET is the most common production of polyester. It is stronger than PCDT, while PCDT has more elasticity and resilience. Another advantage of PET is that it can be used alone or blended with other fabrics for making wrinkle free and stain resistant clothing that can retain its shape. PCDT is more suitable for heavier applications. These heavier applications include draperies and furniture coverings. Modifications can be introduced in each of these varieties for obtaining specific properties. Raw Materials Polyester is a chemical term which can be broken into poly, meaning many, and ester, a basic organic chemical compound. The principle ingredient used in the manufacture of polyester is ethylene, which is derived from petroleum. In this process, ethylene is the polymer, the chemical building block of polyester, and the chemical process that produces the finished polyester is called polymerization. PET Polyester For manufacturing PET Polyester, the main raw material is ethylene derived from petroleum. This ethylene is oxidized to produce a glycol monomer dihydric alcohol which is further combined with another monomer, terephthalic acid at a high temperature in a vacuum. Polymerization, the chemical process that produces the finished polyester, is done with the help of catalysts. Catalysts are used to speed up the rate of a reaction. Then a colorless molten polyester is formed which then flows from a slot in a vessel on to a casting wheel and takes shape of a ribbon as it cools to hardness. The polymer thus produced by this process is then cut into very small chips, dried to remove all moisture and blended to make it uniform for getting it ready for spinning into yarn. PCDT Polyester This variation of polyester is made by condensing terephthalic acid with 1, 4-cyclohexane-dimethanol to form poly-1, 4-cyclohexylene-dimethylene terephthalate or the PCDT Polyester. As for PET Polyester, PCDT is processed for melt spinning. Spinning Polymer chips are melted at 500-518ÂÂ °F (260-270ÂÂ °C) to form a syrup-like solution. The polymer, which is now in a molten form, is then extruded through a spinneret and the filaments are subsequently drawn into the desired polyester fiber. Variations are introduced to obtain desired end results. Spinnerets having hole of different shapes such as round, trilobal, pentalobal, hexalobal or octalobal can be used for special effects like opacity, luster or its suppression, wicking, comfort or feel. Hollow fibers may be produced to make it lightweight and for providing greater cushioning or insulative properties. Crepe effect can be obtained through crimps. Certain additives may also be combined with the spinning solutions for specific properties. Delusterant can be added to make the fiber dull, a flame retardant may be added or certain other antistatic substance may also be included. The product stream divides into two different application areas which are mainly textile applications and packaging applications, after the first stage of polymer production in the melt phase. In the table shown below, the main applications of textile and packaging polyester are listed. Textile Packaging Staple fiber (PSF) Bottles for CSD, Water, Beer, Juice, Detergents Filaments POY, DTY, FDY A-PET Film Technical yarn and tire cord Thermoforming Non-woven and spun bond BO-PET Biaxial oriented Film Mono-filament Strapping Abbreviations: PSF = Polyester Staple Fiber; POY = Partially Oriented Yarn; DTY = Draw Textured Yarn; FDY = Fully Drawn Yarn; CSD = Carbonated Soft Drink; A-PET = Amorphous Polyester Film; BO-PET = Biaxial Oriented Polyester Film; Drawing After extrusion from the spinneret, the fibers are drawn or elongated, with the help of godet wheels. The polyester fibers are usually drawn up to five times its original length, depending upon the desired properties. The filaments are drawn to a greater extent, for higher tenacity. When the fibers come in contact with the air, they solidify. Generally, the PET fibers are drawn hot as it produces more uniform fibers. PCDT fibers are drawn at higher temperature because of their higher melting point. During the drawing process itself, fibers may be textured which saves time, efforts and production cost and also gives greater quality control over the finished fibers. After the polyester yarn is drawn, it is wound on large bobbins or flat-wound packages, ready to be woven into material. Types of Polyester Yarns Polyester yarns have a wide range of diameters and staple lengths. The yarns are made basically as monofilament yarns, multifilament yarns and spun yarns. Filament Yarns PET Polyester is used to make filament yarns either in monofilament or multifilament forms. The direction and amount of twists are decided by the desired end use. The properties are also pre-determined. There are various types of such yarns. There is the bright, regular tenacity polyester yarn having light, stretch and sag resistance, used for sheer lightweight fabrics like tulle, voile and organdy. The regular tenacity semi dull yarn used for various apparels including lingerie. Its duller version is used for shirts and blouses. Polyester yarns resistant to various chemicals, and micro organisms are produced from high tenacity fibers for such industrial uses as conveyor belts, ropes and nets etc. Textured Yarns These yarns are made of PET multifilaments. Texturizing is either done along with the drawing process or afterwards during throwing or texturizing process. Spun Yarns Spun yarns are made of staple or cut PET or PCDT polyester fibers. The staple may be bright, semi dull or dull and tenacity may be regular, mid or high. It may be polished to reduce crimp and increase luster. It may either be spun alone or blended with other staple such as cotton, wool or rayon and then spun into yarn. Manufacturing Staple Fiber In making polyester staple fiber, polymerization, drying, and melt spinning are much the same as in the manufacture of filament yarn. However, in the melt spinning process, the spinneret has many more holes when the product is staple fiber. The rope-like bundles of polyester that emerge are called tow. Drawing tow * 1: Newly-formed tow is quickly cooled in cans that gather the thick fibers. Several lengths of tow are gathered and then drawn on heated rollers to three or four times their original length. Crimping * 2: Drawn tow is then fed into compression boxes, which force the fibers to fold like an accordion, at a rate of 9-15 crimps per inch (3-6 per cm). This process helps the fiber hold together during the later manufacturing stages. Setting *3: After the tow is crimped, it is heated at 212-302ÂÂ °F (100-150ÂÂ °C) to completely dry the fibers and set the crimp. Some of the crimp will unavoidably be pulled out of the fibers during the following processes. Cutting * 4: Following heat setting, tow is cut into shorter lengths. Polyester that will be blended with cotton is cut in 1.25-1.50 inch (3.2-3.8 cm) pieces; for rayon blends, 2 inch (5 cm) lengths are cut. For heavier fabrics, such as carpet, polyester filaments are cut into 6 inch (15 cm) lengths. Synthesis Synthesis of polyesters is generally achieved by a polycondensation reaction. See condensation reactions in polymer chemistry. The General equation for the reaction of a diol with a diacid is: (n+1) R (OH) 2 + n RÂÂ ´ (COOH) 2 > HO [ROOCRÂÂ ´COO] n ROH + 2n H2O Azeotrope esterification In this classical method, an alcohol and a carboxylic acid react to form a carboxylic ester. To assemble a polymer, the water formed by the reaction must be continually removed by azeotrope distillation. Acylation (HCl method) The acid begins as an acid chloride, and thus the polycondensation proceeds with emission of hydrochloric acid (HCl) instead of water. This method can be carried out in solution or as an enamel. Silyl method In this variant of the HCl method, the carboxylic acid chloride is converted with the trimethyl silyl ether of the alcohol component and production of trimethyl silyl chloride is obtained Acetate method (esterification) Silyl acetate method Ring-opening polymerization Aliphatic polyesters can be assembled from lactones under very mild conditions, catalyzed anionically, cationically or metallorganically. Cross-linking Unsaturated polyesters are thermosetting resins. They are generally copolymers prepared by polymerizing one or more diol with saturated and unsaturated dicarboxylic acids (maleic acid, fumaric acid) or their anhydrides. The double bond of unsaturated polyesters reacts with a vinyl monomer mainly the styrene, resulting in a 3-D cross-linked structure. This structure acts as a thermoset. The cross-linking is initiated through an exothermic reaction involving an organic peroxide, such as methyl ethyl ketone peroxide or benzoyl peroxide. APPLICATION OF POLYESTER: Polyester is used in manufacturing of many products, such as clothing, home furnishings, industrial fabrics, computer, recording tapes, and electrical insulation. It has several advantages over traditional fabrics as it does not absorb moisture. Its low absorbency also makes it naturally resistant to stains. Polyester clothing can be preshrunk in the finishing process. This makes it resist shrinking and it doesnt stretch out of shape. The fabric can be dyed easily, and is mildew resistant too. Textured polyester fibers are an effective, nonallergenic insulator, thus it is used for filling pillows, quilting, outerwear, and sleeping bags. Because of their many desirable qualities, polyester fibers and fabrics have many uses. Polyester is often used in outerwear because of its high tenacity and durability. It is a strong fiber and consequently can withstand strong and repetitive movements. Its hydrophobic property makes it ideal for garments and jackets that are to be used in wet or damp environmentscoating the fabric with a water-resistant finish intensifies this effect. Many jackets and quilted garments are made of polyester. Since polyester can be molded into almost any shape, certain insulating properties can be built-in to the fiber. One method is to create hollow fibers: This process traps air inside the fiber which is then heated by the body. The warm air stays inside and helps warm the body in cool weather. A second method is to use crimped polyester in a fiberfill. The crimp helps keep in warm air. Polyester is an ideal fiber to use for this since it will retain its shape, unlike its cotton and wool counterparts that tend to flatten out over time, significantly reducing their ability to trap warm air. Polyester is often used in pants, shirts, suits, and bed sheets either by itself or as a blend, because of its wrinkle-resistant property and its ability to retain its shape. Since these garments are frequently worn and washed, its stain-resistancy and durability are also desirable. Polyester also has industrial uses as well, such as carpets, filters, synthetic artery replacements, ropes, and films. The pie chart below, taken from Fiber Science by Kathryn L. Hatch, summarizes many of polyesters uses: When the world thinks of plastic films, it thinks of PET. Packaging Applications Polyester film is used in many types of packaging applications ranging from food and drugs to industrial and consumer goods. As plain or metalized, formable, heat-shrinkable and/or coated for barrier, metal adhesion, laminating adhesion, extrusion coating adhesion, printing or sealing, PET film offers excellent characteristics for the packaging market easy machinability, strength, high- and low-temperature resistance, crystal clarity, and printability. The properties that make PET film ideal for packaging applications include: High strength for high speed processes, higher tensions, and higher temperatures Chemical surface treatment during manufacturing or post-manufacturing to enhance characteristics, such as barrier, adhesion, printability, metal adhesion, and release High clarity Strength and resistance to tear Dimensional stability over a very wide range of temperatures and humidity Resistance to attack by moisture and most common solvents Excellent barrier to both oxygen and water vapor to extend shelf- life. Applications Flexible packaging PET film is an excellent laminating substrate for flexible packaging structures, i.e. stand-up pouches, offering excellent flex and puncture resistance. Lidding PET film maintains its strength at both, freezer and oven temperatures, for leak-resistant wraps, lidding, and peelable seals in a wide range of food and nonfood applications. Can laminations Co polyester film is laminated to metal for can applications. Metallized packaging Metallized PET film is used for high barrier, decoration, and embossed holographic applications. Susceptors lightly Metallized PET film is used in microwave Susceptors constructions for browning and cooking food in microwave ovens. Imaging The unique combination of optical, physical, thermal, and chemical properties of polyester film has made it the film of choice for many imaging applications. Some of the major applications include x-ray, photographic, printing, microfilm, photoresist/phototool, overhead projection transparencies, and drafting/reprographics. Currently, these applications account for about 30% of the total PET film consumption. Recent developments in electronic imaging may cause some decline in the use of PET film in some of these applications, but the impact is not expected to be very significant in the near future. The properties that make PET film ideal are its: Brilliantly clear nature Very smooth and glossy surface Ability to: be translucent, opaque, or colored (with suitable additives) have a desired rough or matt finish (with filler additives or coatings) be chemically surface treated during manufacture to enhance adhesion to subsequent coatings Strength and resistance to tear Excellent flatness (freedom from curl and cannot be creased easily) Dimensional stability over a very wide range of temperatures and humidity Resistance to attack by moisture (or most of the common solvents) Non-aging characteristics Shelf life (can be stored for a long time) Applications X-Ray Out of the total PET film usage for imaging applications, more than 30% goes into x-ray base. Typically, a blue-tinted 175 micron PET film is coated with a gelatin-based photosensitive coating and is used as medical x-ray film. Photographic Generally, 100 micron and 175 micron PET film is coated with silver-sensitized layers for photographic applications mainly in professional photographic films and instant photographic applications. Printing PET film is used for printing applications such as in layout, masking, pre-press proofing, plate mounting, and photopolymer plates. PET film is also widely used as a base to print on for displays, signage, posters, labels, etc. Microfilm Originals and duplicates of micro-images of documents, records, drawings, etc., are produced on suitably coated PET film for easy storage, space saving, and retrieval. Photoresist Phototool PET film is used in the plating or etching processes for production of rigid and flexible printed circuits. Overhead Projection Transparencies Coated PET film is used for making overhead projection transparencies in plain paper copying machines. Overhead projection transparencies can be printed by other techniques and written on, as well. Drafting Reprographic PET base film is coated with matt or diazo-sensitized or silver-sensitized lacquers, and is widely used for drafting and in the duplication of engineering drawings. This drawing office film is considered to be more convenient for making subsequent changes in designs, and it can also be used for storage. Industrial Specialty Applications Polyester films thermal, chemical, and dimensional stability coupled with its high tensile strength, durability, flex resistance, and clarity promote broad utilization in Industrial and Specialty applications. Polyester film can be produced in a wide range of thickness (from one to several hundred microns) and visible light transmission from essentially 0% to 99+%. Polyester films ability to be customized through both polymer and surface modification to fit the specific application adds to its versatility and value as a film of choice. Key properties of PET: Dimensional stability, both thermal and moisture Chemical and solvent resistant Strength, tear, and flexual resistance Broad light transmission: optically clear to opaque Surface treatable for adhesion to a variety of materials Broad thickness availability Printable surfaces Few, if any, flexible films available today provide the broad array of performance properties for use in the Industrial and Specialty application market. PET film provides exceptional value in a wide variety of applications. Electrical Applications Polyester film itself is used as electrical insulation. It is also used as a laminate with other substrates, such as non-woven polyester matt (DMD), and organic and inorganic papers, such as aramid paper, silica paper, and mica paper. Polyester film can be used in UL registered electrical systems rated as high as Class F (155ÂÂ °C). Laminates can be used in systems rated as high as Class R (220ÂÂ °C). In motor applications, polyester film is used for ground insulation as slot liners and wedges, as well as phase insulation. The high electrical breakdown voltage, coupled with polyester films high resistance to degradation, makes it ideal for mechanical barriers in wire and cable applications. In transformer and high-voltage distribution equipment applications, polyester film is used to wrap the conductors. Polyester film, with lower extractable content, is effective for use in hermetic applications, such as refrigerator and air conditioner motor/compressor assemblies. PEN polyester film is used where higher temperature performance is required, either in the fabrication stage or in the end-use operating conditions. Thin polyester films (two micron and below) are an integral component of capacitors, where polyesters high dielectric constant and its physical properties enable the component design to be optimized and miniaturized. The physical properties of polyester film (such as dimensional stability, thermal stability at elevated temperatures, and coefficient of friction) combined with its mechanical properties (such as tensile break strength, tensile yield strength, and elongation at break) and its chemical and electrical resistance; make it the preferred material for a wide variety of electrical insulation applications. Magnetics Polyester film is used in a variety of magnetic media, including video, camcorder and audio tapes, and data storage applications such as floppy disks and computer tapes. For all magnetics applications, the base film is further coated with a magnetically receptive coating layer. Polyester film has the excellent dimensional stability required to ensure that the heavy coating layer does not distort and faithfully records the images, sound, or data. The largest volumes of PET film for the magnetic market sector are consumed at present in conventional video and audio tapes. Once again, the dimensional stability of polyester, plus the ability to have a magnetic coating layer adhere to the film, are key to these new applications, which are reaching exceptionally high information densities with corresponding reductions in size and faster data access times. The dynamic nature of this market segment, with new applications growing as others mature, is typical of the innovation that exists in the polyester film industry. Use of polyester in garments Polyester is used in the manufacturing of all kinds of clothes and home furnishings like bedspreads, sheets, pillows, furniture, carpets and even curtains. The disco clothing of the 70s with all its jazz and flash was made of polyester. Hydrophobic nature: High tenacity and good durability makes polyester the choice of fabric for high stress outdoors use. Polyester is also a strong fiber that is hydrophobic in nature. It is thus ideal for clothing to be used in wet and damp environments. The fabric is also coated with a water-resistant finish and further intensifies the hydrophobic nature. Being the most heavily recycled polymer worldwide, it is also used by climbers. Climbing suits, parkas, sleeping bags and other outdoor gear are using the new insulating polyester fiberfill products. One can also do winter windsurfing wearing dry suits lined with polyester fleece. Creating insulation: By creating hollow fibers it is also possible to build insulation into the polyester fiber. Air is trapped inside the fiber, which is then warmed by the heat of the body. This keeps the body warm in cold weather. Another method to build insulation is to use crimped polyester in a fiberfill. The crimp helps keep the warm air in. Polyester is an ideal fabric for this kind of insulation because it retains its shape. Cotton and wool tend to flatten over a period of time and loose the warming effect. Wrinkle resistant: Polyester is also wrinkle resistant and is used very often in everyday clothing like pants, shirts, tops, skirts and suits. Used either by itself or as a blend, it is also stain resistant and hence very popular. Polyester care tips Taking care of polyester clothing is really easy and very time efficient. Polyester clothing can be machine washed and dried. Adding a fabric softener generally helps Dry the fabric at low temperatures to get maximum usage from the clothing. Though polyester does not require much ironing, if

Streetcar Named Desire :: A Streetcar Named Desire Essays

Streetcar Named Desire Tennessee Williams's play A Streetcar Named Desire contains more within it's characters, situations, and story than appears on its surface. Joseph Krutch, author of Twentieth Century Interpretations of A Streetcar Named Desire wrote, â€Å"The authors perceptions remain subtle and delicate†¦ The final impression left is, surprisingly enough not of sensationalism but of subtlety† (38.) As in many of Williams's plays deeper meanings are understood only through close examination of each scene. The reader must ask him or herself as they go whether or not something might lend more than what lies on the surface. The tone is set immediately in scene one when Blanche begins by telling Eunice, â€Å"They told me to take a street-car named Desire, and then transfer to one called Cemeteries and ride six blocks and get off at—Elysian Fields!† (15) Here you can clearly see that Tennessee is not meaning these places literally, rather they are symbolic of the stages Blanche will follow throughout the play. She first takes, â€Å"a street-car named desire† when she falls for her lost love -----, and afterwards, plagued by her own inadequacies Blanche escapes her harsh world by giving herself freely to other men; strangers. Even her behavior toward Stanley is littered with telltale slips, â€Å"—the part blanche talks in French to Stanley saying that she wants him or something.† After desire Blanche transfers â€Å"to (a streetcar) called Cemeteries.† One can see where the â€Å"Cemeteries† might lie in Blanches life. It seems that every time desi re fails Blanche is somehow left unprotected, cold and alone. In scene five Blanches drink, â€Å"foams over and spills on her pretty white skirt,† (80) warning the reader of what lies ahead. Finally Blanche is to get off at â€Å"Elysian Fields,† which makes it very clear that an eventual loss on Blanches part is inevitable. Joseph Krutch writes, â€Å"Though there is in the play a certain haunting dream-like or rather nightmarish quality, the break with reality is never quite made, and nothing happens which might not be an actual event.† How true on not only Blanches part, but each of the characters. The play is so raw and in-your-face that it almost takes on qualities of a fantasy, especially at the time of its debut. But Tennessee was able to create a play that rather expertly walked the fine line between illusion and reality; a task not easily accomplished.

Childhood Sexual Abuse and Eating Disorders Essay -- Psychology Health

Childhood Sexual Abuse and Eating Disorders Recently, a great amount of psychological literature has focused on finding biological and genetic causes of mental illnesses and disorders, including eating disorders. However, according to recent twin studies, the heritability component of eating disorders may only account for 0% to 70% of the variance (Fairburn, Cowen, & Harrison, 1999). The leaves an ample amount of room for speculation of possible environmental risk factors for eating disorders. In this paper, I wish to examine one possible environmental risk that has received attention since the mid-80’s. Since that time, researchers have searched to determine the relationship between childhood sexual abuse, or trauma in general, and the development of eating disorders. It seems somewhat logical to assume that a person who has experienced sexual trauma might develop feelings of dissatisfaction as well as disgust with their own body—the medium of abuse. Also, one might even attribute the anti-pubertal effects achieved through self-starvation as a suppression of sexuality that may be desired by a survivor of sexual abuse. These hypotheses, as well as connections observed between sexual abuse and PTSD and also between anxiety disorders (of which PTSD is one) and eating disorders led many researchers to study this relationship. However, the large body of the studies contradict each other’s findings. Many studies have found no evidence of a relationship between sexual abuse and eating disorders and others have found evidence. In this paper, I would like to examine the results of studies that have been aimed at answering the question, â€Å"Is childhood sexual abuse a risk factor for eating disorders?† Literature Re... ... of Childhood Sexual or Physical Abuse in Japanese Patients with Eating Disorders: Relationship with Dissociation and Impulsive Behaviors. Psychological Medicine, 29(4), 935-942. Pope HG, & Hudson JI (1992). Is childhood sexual abuse a risk factor for bulimia nervosa? American Journal of Psychiatry, 149, 455-463. Pope HG, Mangweith B, Negrao AB, Hudson JI, & Cordas TA (1994). Childhood sexual abuse and bulimia nervosa: A comparison of American, Austrian, and Brazilian women. American Journal of Psychiatry, 151, 732-737. Rorty M, Yager J, & Rossotto E (1994). Childhood sexual, physical, and psychological abuse in bulimia nervosa. American Journal of Psychiatry, 151, 1122-1126. Wonderlich SA, Donaldson MA, Carson DK, Staton D, Gertz L, Leach L, & Johnson M (1996). Eating Disturbance and Incest. Journal of Interpersonal Violence, 11, 195-207. Childhood Sexual Abuse and Eating Disorders Essay -- Psychology Health Childhood Sexual Abuse and Eating Disorders Recently, a great amount of psychological literature has focused on finding biological and genetic causes of mental illnesses and disorders, including eating disorders. However, according to recent twin studies, the heritability component of eating disorders may only account for 0% to 70% of the variance (Fairburn, Cowen, & Harrison, 1999). The leaves an ample amount of room for speculation of possible environmental risk factors for eating disorders. In this paper, I wish to examine one possible environmental risk that has received attention since the mid-80’s. Since that time, researchers have searched to determine the relationship between childhood sexual abuse, or trauma in general, and the development of eating disorders. It seems somewhat logical to assume that a person who has experienced sexual trauma might develop feelings of dissatisfaction as well as disgust with their own body—the medium of abuse. Also, one might even attribute the anti-pubertal effects achieved through self-starvation as a suppression of sexuality that may be desired by a survivor of sexual abuse. These hypotheses, as well as connections observed between sexual abuse and PTSD and also between anxiety disorders (of which PTSD is one) and eating disorders led many researchers to study this relationship. However, the large body of the studies contradict each other’s findings. Many studies have found no evidence of a relationship between sexual abuse and eating disorders and others have found evidence. In this paper, I would like to examine the results of studies that have been aimed at answering the question, â€Å"Is childhood sexual abuse a risk factor for eating disorders?† Literature Re... ... of Childhood Sexual or Physical Abuse in Japanese Patients with Eating Disorders: Relationship with Dissociation and Impulsive Behaviors. Psychological Medicine, 29(4), 935-942. Pope HG, & Hudson JI (1992). Is childhood sexual abuse a risk factor for bulimia nervosa? American Journal of Psychiatry, 149, 455-463. Pope HG, Mangweith B, Negrao AB, Hudson JI, & Cordas TA (1994). Childhood sexual abuse and bulimia nervosa: A comparison of American, Austrian, and Brazilian women. American Journal of Psychiatry, 151, 732-737. Rorty M, Yager J, & Rossotto E (1994). Childhood sexual, physical, and psychological abuse in bulimia nervosa. American Journal of Psychiatry, 151, 1122-1126. Wonderlich SA, Donaldson MA, Carson DK, Staton D, Gertz L, Leach L, & Johnson M (1996). Eating Disturbance and Incest. Journal of Interpersonal Violence, 11, 195-207.