Structure and Properties of Polymers Essay

Structure and Properties of Polymers Essay Structure and Properties of Polymers Essay C 10 Lecture Notes Freely jointed chain, a â€Å"phantom† chain n links of same length, ak Joints permit completely free rotation Mean squared end to end length = nkak2 Contour (stretched out) length Lc=nkak Persistence length aq=ak/2 What is the size of the blob? For an ideal Kuhn chain RG2 = RL2/6 (approx.) RG: Characteristic radius of blob 3. Non-crystalline Polymer (Physical States of Matter) 3.1 Glass transition temperature Specific volume a) Tg occur in all materials where crystallinity doesn’t get in the way b) Because it is not an equilibrium phase, glass transition is not a thermodynamic transition Melt/Rubber Glass Equilibrium line T 0 Specific volume Specific volume 1. Cool slowly 2. Heat quickly Tg depends on time scale of observation Slow cool Fast heat Anneal 0 T 0 T 3.2 Polymeric states Molecular weight Increase molecular weight to infinity (chemically linked) → All RUBBER in this region Tg Glass Rubber Viscous melt T 1 GPa Glass log E Rubber 1 MPa ~ 10 MPa Viscous creep Temperature Spring: purely elastic, ÏÆ' = EÃŽ µ Dashpot: purely viscous, ÏÆ' = ÃŽ ·ÃŽ µ stiff spring model elasticity of glass (Eg) dashpot controls short relaxation time processes (frees upon reaching Tg) Eg-Er Er ÃŽ ·1(T) ÃŽ ·2(T) weak spring model elasticity of glass (Er) dashpot for longest relaxation time processes (frees for rubber-melt transition) ÃŽ ·1 and ÃŽ ·2 solid → glass: Eg ÃŽ ·2 solid, ÃŽ ·1 free → rubber: Er viscosity, ÃŽ · = ÏÆ'/ÃŽ µ 4.1 Behavior of spring/dashpot models ÏÆ' ÃŽ µ Maxwell element Time tot = E + − CON. EQN ÏÆ' ÏÆ'0 at time t = Ï„, ÏÆ' = ÏÆ'0/e 0 t ÏÆ' ÃŽ µ = ÏÆ'0/E t Voigt element Add stresses, ÏÆ'tot = EÃŽ µ + ÃŽ ·ÃŽ µ − CON. EQN â‘ ¢ Constant ÃŽ µ, ÃŽ µ = 0 ÏÆ' = EÃŽ µ Constant ÏÆ', ÏÆ' = 0 4.2 How realistic? Assumptions: (i) Viscosity Newtonian ÃŽ · ≠  f (ÃŽ µ) Not very good assumption at high strain rate (ii) Only two relaxation processes Ï„1 Ï„2 LHS controls Tg Relaxation of molecular chain segments RHS longest Ï„ Unraveling of entangled chain N (Ï„) Relaxation Time Spectrum Ï„ Note: N (Ï„): number of elements with Ï„ between Ï„ and Ï„ + d Ï„, like ‘density of state† 5.1 Modulus of glass Eg ~ E of van der Waals solid (held together by VdW forces), approx. 1 GPa Einorganic glass ~ 65 GPa → combinations of ionic bonding and Si – Si Emetal : steel ~ 210 GPa Al ~ 70 GPa Epolymer chain pulled out ~ 250 GPa 5.2 Viscosity of ÃŽ ·1 dashpot In region of Tg, (a) Time-temperature superposition (Fig 5.1) (b) Superimposed curve, made by shifting data by log aT (Fig 5.2 b) (c) Plot of shift factor aT vs. temperature (Fig 5.2 c) Williams-Landel-Ferry (WLF) found empirical equation to describe (c) Ts ~ reference temperature, works well if Ts = Tg With C1 = 17.4 , C2 = 51.6 K Implication: log aT (i.e. ÃŽ ·1) turns to ∞ when T = Tg – C2 → (Tg – 51.6) K ∠´Creep of polymer glass turns to zero at temperature (Tg – 51.6) K or lower Justification of WLF in terms of free volume Specific volume Occupied volume 0 T Second Input: Doolittle Equation 5.3 Elasticity of Rubber Spring 5.4 Viscosity of dashpot Rubber ⇄ viscous melt? Viscous flow ~ relative motion of centers of masses of molecules A. Reptation Model Molecules effectively confined in tube by entangling neighbours Constraints physical cross-linked points Reptation - Molecule can only escape lengthwise Parameters: Need two other equations: B Above critical molecular weight for

Atomic Number 5 Element Facts

Atomic Number 5 Element Facts Boron is the element that is atomic number 5 on the periodic table. It is a metalloid or semimetal that is a lustrous black solid at room temperature and pressure. Here are some interesting facts about boron. Fast Facts: Atomic Number 5 Atomic Number: 5Element Name: BoronElement Symbol: BAtomic Weight: 10.81Category: MetalloidGroup: Group 13 (Boron Group)Period: Period 2 Atomic Number 5 Element Facts Boron compounds form the basis for the classic slime recipe, which polymerizes the compound borax.The element name boron comes from the Arabic word buraq, which means white. The word was used to describe borax, one of the boron compounds known to ancient man.A boron atom has 5 protons and 5 electrons. Its average atomic mass is 10.81. Natural boron consists of a mix of two stable isotopes: boron-10 and boron-11. Eleven isotopes, with masses 7 to 17 are known.Boron exhibits properties of either metals or nonmetals, depending on the conditions.Element number 5 is present in the cell walls of all plants, so plants, as well as any animal that eats plants, contain boron. Elemental boron is non-toxic to mammals.Over a hundred minerals contain boron and it is found in several compounds, including boric acid, borax, borates, kernite, and ulexite. Yet, pure boron is extremely difficult to produce and the element abundance is only  0.001% of the Earths crust. Element atomic number 5 is rare in the solar system. In 1808, boron was partially purified by Sir Humphry Davy and also by  Joseph L. Gay-Lussac and L. J. Thà ©nard. They achieved purity of about 60%. In 1909  Ezekiel Weintraub isolated nearly pure element number 5.Boron has the highest melting point and boiling point of the metalloids.Crystalline boron is the second hardest element, following carbon. Boron is tough and heat resistant.While many elements are produced via nuclear fusion inside stars, boron is not among them. Boron appears to have been formed by nuclear fusion from cosmic ray collisions, before the solar system was formed.The amorphous phase of boron is reactive, while crystalline boron is not reactive.There is a boron-based antibiotic. It is a derivative of streptomycin and is called boromycin.Boron is used in super hard materials, magnets, nuclear reactor shielding, semiconductors, to make borosilicate glassware, in ceramics, insecticides, disinfectants, cleaners, cosmetics, and many other products. Boron is added to steel and other alloys. Because it is an excellent neutron absorber, it is used in nuclear reactor control rods. Element atomic number 5 burns with a green flame. It can be used to produce green fire and is added as a common colorant in fireworks.Boron can transmit part of infrared light.Boron forms stable covalent bonds rather than ionic bonds.At room temperature, boron is a poor electrical conductor. Its conductivity improves as it is heated.Although boron nitride is not quite as hard as diamond, it is preferred for use in high temperature equipment because it has superior thermal and chemical resistance. Boron nitride also forms nanotubes, similar to those formed by carbon. However, unlike carbon nanotubes, boron nitride tubes are electrical insulators.Boron has been identified on the surface of the Moon and Mars. The detection of both water and boron on Mars supports the possibility Mars may have been inhabitable, at least in the Gale Crater, at some point in the distant past.The average cost of pure crystalline boron was about $5 per gram in 2008. Sources Dunitz, J. D.; Hawley, D. M.; Miklos, D.; White, D. N. J.; Berlin, Y.; Marusić, R.; Prelog, V. (1971). Structure of boromycin. Helvetica Chimica Acta. 54 (6): 1709–1713. doi:10.1002/hlca.19710540624Eremets, M. I.; Struzhkin, V. V.; Mao, H.; Hemley, R. J. (2001). Superconductivity in Boron. Science. 293 (5528): 272–4. doi:10.1126/science.1062286Hammond, C. R. (2004). The Elements, in Handbook of Chemistry and Physics (81st ed.). CRC press. ISBN 978-0-8493-0485-9.Laubengayer, A. W.; Hurd, D. T.; Newkirk, A. E.; Hoard, J. L. (1943). Boron. I. Preparation and Properties of Pure Crystalline Boron. Journal of the American Chemical Society. 65 (10): 1924–1931. doi:10.1021/ja01250a036Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.

Think Piece 1 Term Paper Example | Topics and Well Written Essays - 1000 words

Think Piece 1 - Term Paper Example There is also a difference between criminalization and decriminalization; this is due to the fact that criminalization is a form of punishment, while decriminalization is the change of a previously punishable act to a legal one, in order to save vulnerable people, for example abortion. Various acts and behaviors have been criminalized in the United States, while others have been decriminalized. Keywords: Crime, Process of Criminalization, Process of Decriminalization, Criminalization, Decriminalization, Punishment, Violation, Criminal HIV Transmission, Child Abuse, Domestic Violence, Prostitution, Abortion, Homosexuality, Gambling, Marijuana Crime can be defined as an abuse of society rules of behavior as stated and expressed by a criminal legal code (Siegel, 2009). Walston-Dunham on the other hand defined crime as â€Å"conduct in abuse of the criminal laws of a state, the government, or a local jurisdiction, for which there is no legally acceptable justification or excuse† ( 1990, p. 499). Criminalization refers to both the absolute means that place certain conduct under the threat of punishment, and to the legal action of introducing these means. Criminalization can therefore be defined as the â€Å"legally binding decision to put a certain form of conduct under the threat of punishment† (Duff, Farmer, Marshall, Renzo, & Tadros, 2010, p. 239). The difference between crime and the process of criminalization is that crime is a violation of rules that are set to govern a society, while the process of criminalization is a punishment for the law breakers. Decriminalization refers to â€Å"adjustment of moral boundaries to social change or, to retain the vocabulary borrowed from Piaget, as normative accommodation† (Abel, 1995, p. 214). Criminalization takes precedence over its counterpart decriminalization (Spierenburg, 2008). The difference between the process of criminalization and decriminalization is that in criminalization, there is a form of punishment and the acts and behaviors are regarded as illegal, while decriminalization is the change of a previously punishable act to a legal one, in order to save vulnerable people; hence in decriminalization the acts and behaviors that were regarded as illegal are no longer illegal. Examples of acts and behaviors that have been decriminalized in the United States include abortion, homosexuality, marijuana use, and gambling. Examples of acts and behaviors that have been criminalized in the United States include criminal HIV transmission, child abuse, prostitution, and domestic violence. Laws governing abortion have been varied in different states. In 1973 many states criminalized abortion. However, it was permitted when a woman`s life was at risk and many US courts stated that all abortion laws were unconstitutional. The court recognized that a woman`s right to privacy includes a right to determine whether or not to continue her pregnancy, but that right is not absolute (Marsh all Cavendish, 2009). Abortion has been the central platform for the women’s movement. Its decriminalization maintains that abortion can either be a medical or a legal issue, but a woman`s right (Anleu, 2000). Decriminalization doesn’t provide women with an absolute right to abortion, and is to be practiced by medical practitioners under critical circumstances. Homosexuality in the United States is a behavior that has been decriminaliz

Managment in Aviation Case Study Example | Topics and Well Written Essays - 2250 words

Managment in Aviation - Case Study Example But these conventional languages are flattering less common for the theoretical regulation. Every now and then even industrial dealings and employee associations are confusingly scheduled as synonyms, though these normally demote to the relationship between management and workers and the behavior of labours in corporation. The hypothetical regulation is based mostly on the supposition that workers are individuals with altering goals and needs, and as such should not be contemplation of as essential business resources, such as trucks and filing cabinets. The field takes a constructive vision of workers, supercilious that practically all wish to contribute to the enterprise productively, and that the main obstacles to their comings and goings are lack of knowledge, inadequate teaching, and failures of procedure (Armstrong, Michael, Human Resource Management Practice, 10th edition (2006). Practitioners in the field see HRM as a more innovative view of workplace management than the traditional approach. Its practices force the managers of an endeavour to express their goals with specificity so that they can be unspoken and assumed by the workforce, and to make available the resources needed for them to successfully accomplish their assignments. As such, HRM techniques, when properly practiced, are expressive of the goals and operating practices of the enterprise overall. HRM is also seen by many to have a key role in risk reduction within organisations. Synonyms such as personnel management are often used in a more restricted sense to describe activities that are necessary in the recruiting of a workforce, providing its members with payroll and benefits, and administrating their work-life needs. So if we move to actual definitions, Torrington and Hall (1987) define personnel management as being: "Those decisions and actions which concern the management of employees at all levels in the business and which are related to the implementation of strategies directed towards creating and sustaining competitive advantage"( While Miller 1987, p. 352). Academic Theory The goal of human resource management is to help an organization to convene planned goals by drawing, and preserving workers and also to administer them successfully. The keyword here possibly is "fit", i.e. HRM advancement looks for to certify a fit between the management of an organization's employees, and the overall strategic direction of the company (Miller, 1989). The essential principle of the academic theory of HRM is that humans are not equipments; therefore we need to have an interdisciplinary assessment of people in the workplace. Fields such as psychology, industrial engineering, industrial and organizational psychology, industrial relations, sociology, and critical theories: postmodernism, post-structuralism play a chief role. Many colleges and universities tender bachelor and master degrees in Human Resources

Management Planning Paper Essay Example for Free

Management Planning Paper Essay The Boeing Corporation is the world’s leading aerospace company and is the largest manufacturer of commercial jetliners as well as military aircrafts. Boeing has teams that manufacture missiles, satellites, defense systems, and communication systems. NASA turns to Boeing when they need something and Boeing operates the International Space Station. Boeing has a broad range of capabilities and skills, which is probably the reason they are the world’s leading aerospace company. With the Boeing headquarters in Chicago, more than 170,000 people in 70 different countries find themselves employed with the corporation and most of them hold a college degree (Boeing Corporation,  2012). It takes many hard working employees and managers to make Boeing a successful corporation. This paper will discuss the planning function of management, analyze the influence of legal issues, ethics, and corporate social responsibility and their effects on management planning. I will also analyze factors that influence the company’s strategic, tactical, operational, and contingency planning as they relate to the Boeing Corporation. The planning function of management is the process of setting goals within the corporation that are expected to be achieved over a set period. Therefore, Boeing got to be the world’s leading aerospace company by setting such goals. The Boeing Corporation has engineer departments, sales departments, mechanical departments, and product testing departments among a few others. Each individual department will have set goals put in place by corporate and guidelines regarding how they should achieve the desired goal for each project. Each goal is designed for each department to become the most efficient in their levels. There are six steps in management planning. The steps listed in provided course materials are situational analysis, alternative goals and plans, goal and plan evaluation, goal and plan selection, implementation, and monitor and control (Thomas S. Bateman, Scott A. Snell,  2009). Step one gathers and summarizes information that is in question. It examines current conditions with an attempt at forecasting future conditions. Step two generates alternative goals that may be used as an alternate if the first desired plan does not ork. Step three evaluates the potential of the alternative goals and prioritizes/eliminates ones that might or might not work. Step four in management planning is the selecting of goals believed to be most appropriate and feasible by the managers. Step five implements the goals and plans into action by managers. Goal achievement is likely to be linked to the organizationâ₠¬â„¢s reward system to encourage employees to achieve the goals and implement plans properly (Thomas S. Bateman, Scott A. Snell,  2009). Step six is essential in making sure goals and plans are met. If the goals and plans are not monitored and controlled managers would not know if they were ever met successfully. Boeing the huge corporation that it is has had its fair share of legal issues. The corporation has to pay special attention to detail when it concerns obeying the laws and regulations in regard the manufacturing of aircraft. The planes must be tested for safety and flying ability before they ever hit the mainstream public. Notices on the aircraft tell passengers when they should be buckled and when it is considered safe to unbuckle. Engineers have to provide manuals for the aircrafts in case any issues may arise when in use. Ethical issues come into play when Boeing makes bids to other corporations like the military or NASA. They are not allowed to charge prices that people believe to be unfair or make any changes after things have already been agreed upon. This means that the sales department has to plan how much they want to sell their product for. The main corporate social responsibility that Boeing has is safety. They have to engineer items safe for the public to be on/use. With Boeing being the world’s leading Aerospace Corporation, millions of people rely on the use of their products. That means that engineers have to know the latest safety information and managers have to make sure that they put the safety information to use. Strategic planning is used by the Boeing Corporation when making new aircraft and other items. They have to figure out how to market their item just right so that buyers will be interested in it. This planning has led Boeing to make planes more efficient and comfortable for passengers to ride on. Tactical planning is organized for competition, such as Airbus and demand for product. Boeing is a competitor of Airbus, which is another aerospace engineering corporation. Boeing has to be aware of competitor’s new products and when they will be released. This means that they have to formulate and release products either better or more efficient than the competition’s. Operational planning identifies the specific procedures and processes required at the lower-levels within an organization (Thomas S. Bateman, Scott A. Snell,  2009). So within the Boeing Corporation this would be those who deal with the delivery schedules and human resources departments. Every plane that takes off or leaves an airport has to be scheduled and the arrival/departure times displayed so that the public is aware. Human resources is responsible for the hiring/firing of Boeing’s many employees and any issues consumers may have with a product or service. If someone believes that they did not have a good experience in the flight he or she would call the resource department, and the department would most likely do everything in his or her power to make the person feel better. Contingency plans are put in place in case of any challenges that may arise when making their products. A good example of Boeing’s contingency plan is in 2008 they were trying to produce 40 aircraft a year but the United States hit an economic crisis. This meant that Boeing had to cut back their number of aircraft being created so they did not feel the effects of the economic crisis. So Boeing did not become the world’s leading aerospace corporation by doing nothing. It took hard work, planning, and management. There are six steps in management planning that corporations follow to try to ensure their survival in a competitive world. Boeing has had its fair share of legal and ethical issues and tries to abide by the rules and regulations for safety set forth by the goverment. Boeing tries to keep a strategic plan when creating new products and a tactical plan on how to market their items.

René Magritte :: essays research papers

Renà © Magritte   Ã‚  Ã‚  Ã‚  Ã‚  Renà © Magritte was born in Belgium on November 21, 1898. His childhood took place in Charlerloi. He was born to poverty and held left-wing political views. Magritte’s mother killed herself when he was only fourteen. He later joined the Communist Party. However, he preferred not to use his art for political causes.   Ã‚  Ã‚  Ã‚  Ã‚  Magritte started to create successful oil paintings in the 1920s. This is when Magritte started to come into his own. In 1922, Magritte got married to Georgette Berger. Magritte was inspired by Georgette and she became his model. He also became friendly with Victor Servranckx, who had developed a very geometric-abstract style. This was the beginning of a new direction for Magritte. In 1927 Magritte and Georgette moved to Paris to be closer to where it all happens. He started to take part in the activities of the Surrealists, which became his style of choice for the majority of his life. Magritte began combining words and images in his paintings. These word-pictures were not mere illustrations of an object or a concept. Just the opposite, his work was intended to gently destabilize our mental habits of representation. Magritte elaborated a instructive classification of this type of painting, the simplest which consisted of denying an images through words, or vice v ersa. Magritte shared the Surrealist concept of the power of desire and eroticism to change life and wanted to translate this idea through unconventional images. He continued involving metamorphosis in his work. In Black Magic, a naked woman leaning on a rock gradually merges into the blue sky. The painter was, nevertheless, distrustful of the obvious seduction of beautiful colors. In The Rape he even pushed it to the point of obsession with the features of a woman's face replaced by sexual attributes, such as breasts, a belly button and pubic hair.. In 1940, Magritte was going through a crisis resulting from the German occupation in World War II. Also, at this point Magritte’s financial situation became an issue and his dissatisfaction with his own paintings. From then on, he decided that a feeling of pleasure and an atmosphere of happiness had to predominate over the sense of anxiety. Magritte first thought about changing his iconography and began to paint the leaf-birds, which are seen in two works from 1942, Treasure Island and The Companions of Fear.

Examinations. Good or Bad? Essay

Examination is a very wide word, which is used in all spheres of life. It is the most feared word of many students. We have examinations everywhere around the world. In Singapore, students take examinations every few months and major examinations every few years. As a result, many parents often push their children to strive in examinations. This causes them to feel extremely pressured as they have to juggle extra co-curricular activities that are compulsory in Singapore’s education system as well as to ensure that they do not neglect their studies and to meet their parents’ expectations. They often end up burning the midnight oil when there are examinations, leaving them worn out. Hence, the majority of students in Singapore feel that exams should be abolished. However, examinations are also proven to be beneficial. They help observe if we were able to consolidate what we have learnt and it has given students the drive to study. Without examinations, do you think a stud ent will spend time revising? Clearly, examinations should not be abolished. Examinations have given students the drive to study. As many parents expect their children to pass with flying colours during examinations, they usually will push them to study, hoping that by doing so they will get good grades. Sending them to tuition classes or even taking time off work to help them with their studies are ways parents will push them to work hard. As many parents always tell their children, â€Å"getting good grades will get you a good job†. By doing so, students will have to put in effort into their studies and do frequent revision which helps them to understand better. Should examinations be abolished, students will not be motivated to study and do revision. Without revision, there is no point in having classes as one will not learn and remember everything being taught. Students will then laze around and waste unnecessary time which could have been used for revision which will be beneficial to them. Not only do examinations give students the drive to study, they are also used to evaluate students. It is important for schools to evaluate how well students can consolidate the material presented to them, as otherwise the teachers might have explained everything in class in vain. The evaluation based on the grades taken in exams can help the teachers see what the students’ mistakes are and what misconceptions they may have and the teacher can correct them. Moreover, it helps them to see the students’ areas of  strengths and weaknesses and ensure that the teacher is able to maintain their strengths and improve their weaknesses. Hence, students will be able to learn better and it is no doubt that examinations are helping the students. Some people point out that examinations cause a large amount of stress to many students. Admittedly, students tend to feel extremely pressured when they hear the word â€Å"examinations†. This is because they are being pressured to meet their parents’ expectations by studying extremely hard, and sometimes, even burning the midnight oil. While doing so, they also have to attend extra co-curricular activities as well as to attend ballet classes, piano classes, tuition classes, and many more. However, if students learn to manage their time properly, I do not see why they should feel stressed. By completing their homework and revision on time and by drawing out timetables, there should not be a problem when it comes to dealing with examinations. Moreover, instead of doing last-minute revision, they could have done revision every day after school. This way, they will not panic. Furthermore, if students do not waste unnecessary time lazing around and playing video games, ther e should not be a problem with not completing their revision on time. Additionally, stress helps boost brain power as well as create mental toughness, increase clarity, and it helps in greater appreciation for one’s circumstances, and contribute to a sense of confidence built on a history of overcoming of obstacles. Hence, when it comes to examinations as a whole, the good outweighs the bad. All in all, examinations have been beneficial to many people.