2.4 Consumer Behaviour & Holidays Case Study Example | Topics and Well Written Essays - 1000 words

2.4 Consumer Behaviour & Holidays - Case Study Example The regular elements that basically impact the holiday decision-making process are levels of contribution, situational variables, expectation, sentimentality and fantasizing. Then again, this is altogether different from customary decision-making process that is generally sequenced and organized. In this model, the requirement for a particular administration or item is distinguished and data pursuit and different choices are assessed. The consumer is further headed towards acquiring an item and there in the wake of setting a buying decision (Moore & Simmons, 2010). In the conventional consumer decision-making, the technique for hunting down data is generally organized and it is either outer, interior or both of them. Data gathering process in the holiday decision-making is a continuous and nonstop process. The data is gathered throughout and after the holidays experience and it is generally memory based than outer based. Holiday decision creators are low data searchers and data is ac cumulated in a non-reason way. Then again, in conventional consumer decision-making, get-together data is exceptionally vital and the data is seen as the main impetus in the consumer decision-making process. Under this model, the consumers are sharp data searchers and they complete a genuine research before settling down on a specific item (Weiss & Wenger, 2002). The interviews conducted in the case shows the different behaviour of the two persons who were deciding on going for a trip. The first issue talks about a situation where the decision maker is confused about finally going on a holiday or not in spite of the fact that they had already decided on two destinations for their holiday. This clearly shows a confusion in the decision making process. Thus as a holiday service provider it will be very difficult to assess whether or not to consider them as a consumer. The next scenario talked about is a

Summarizing how information security Essay Example | Topics and Well Written Essays - 750 words

Summarizing how information security - Essay Example Information Security System of Citibank With Respect To CIA Triangle CIA Principle The CIA triad namely Confidentiality, Integrity and Availability can be considered as one of the simple and widely applicable security models for an organization which assures to protect all kinds of information from external threats. These three major principles are supposed to be relevant with the entire security analysis of an organization (Imperial College London, 2012). Confidentiality: Confidentiality can be acknowledged as the ability to maintain secrecy of information from unauthorized external users. It is possibly the major apparent aspect of the CIA triangle in terms of security assurance for an organization. However, this principle is frequently attacked by the external users through Cryptography and Encryption techniques in order to transfer files or information from one system to another (Imperial College London, 2012). In the context of Citibank, it has been found that the organization s eeks to implement a well-built security system in order to protect the information related to financial aspects and other banking transactions of its 200 million customers (Citigroup Inc., 2012). Integrity: According to the CIA principle, the aspect of integrity can be stated as the ability to make sure of keeping or storing data or information in an appropriate and unaffected way. It has been learnt that Citibank manages the personal data, records as well as information of each client in an appropriate manner and with the assistance of Citi Records Management Policy as well as Citi Data Management Policy. Furthermore, the organization implements advanced security processing system of each data, record or information that are collected from individual clients in terms of appropriate and secured storage capacity (Citigroup Inc., 2012). Availability: This principle of the CIA triad relates to the accessibility of transaction records or information by an appropriate and authorized user at the right time. However, various security issues with respect to accessing transactional record and information of a client by other external or unauthorized persons have been recorded. The organization is known to adopt an advanced form of process to identify the appropriate and authorized persons (Citigroup Inc., 2012). Security Policies in Citibank Citibank ensures an effective and efficient form of security policy regarding maintaining and protecting data, information or record of its individual client. In the context of information security, it can be stated that the organization strictly maintains laws and regulations in order to increase the level of protecting information from external threats. Citibank significantly pursues a formal set of rules and regulations pertaining to The Gramm-Leach-Bliley Act (GLBA) which is also known as ‘Financial Services Modernization Act of 1999.’ According to this Act, the financial service providers need to possess appropria te information security systems in order to maintain and protect the personal form of information of each client. Moreover, the regulatory Act also focuses on maintaining an effective and appropriate CIA principle with respect to the various transactions made by any financial institution

Contrast Effect Essay Example | Topics and Well Written Essays - 500 words

Contrast Effect - Essay Example According to Six Sigma, quality requires entrepreneurs to look at their own business from the customer's perspective and not be based on their own perspectives. By understanding the transaction from the needs and processes of customers, the company is able to explore on what costumers see and feel. Consequently, marketers can identify areas where significant value or improvement be added. Kotler (2000, p. 36) underscored that customer expectations are relevant key determinants of their satisfaction, consumption experiences, and loyalty. It is wise that marketers need to either meet or exceed such expectations; otherwise, it could lead to customer defection or dissatisfaction. Feldman and Lynch (1988) argued that when customers express their expectations before their consumption experience, it would most likely bring them more convenient during the experience. The same points were emphasized by Morwitz and Fitzsimons (2004); Dholakia and Morwitz (2002); Kardes, Allen, and Pontes (1993 ); and Fitzsimons & Williams (2000) respectively. have less or no knowledge that there will be an upcoming service evaluation process versus those forewarned customers about a service encounter, which later be asked to evaluate the said service; tend to supply higher negative post-experience evaluations (Ofir a

International finance structure and IPE of international Debt Essay

International finance structure and IPE of international Debt - Essay Example The diagram also illustrates the law of demand. Fewer dollars will be demanded when the price of a dollar increases according to the law of demand. The chapter also provides appropriate examples, the Microsoft Vista example is very appropriate to understand how the exchange rate works in different countries. Interest rates also play a pivotal role in determining the value of a dollar. Business expectations also play a crucial role in determining the exchange rate, since Mexican Peso has been taken up as an example it is very important to also consider interest rates in Mexico and business expectations in Mexico. Capital gain is another subject that the chapter highlights. The business expectations in the United States are juxtaposed with the business expectations in Mexico. The demand part is initially presented in the chapter and the second part of the chapter comprehensively explains the supply side of the Dollar and how it relates to the Mexican economy. National income in the Uni ted States also plays a key role in the supply of the Dollar. ... same concept can be applied to different currencies and its exchange rate can easily be found out and in addition to this the factors affecting the exchange rate can also be found out. Foreign exchange rates are comprehensively explained in the following parts of chapter 7. Gold standard, Bretton Woods and floating exchange rate are the three most important exchange rate structures that have been used to determine the exchange rate. The Bretton Woods system of exchange was introduced in the year 1944 and the system was established in the Bretton Woods conference in New Hampshire. There is rapid growth and development taking place all across the globe, to make sure that everything goes on well, a system which should stabilize the growth is a must. This paper will throw light upon the advantages of the Bretton Woods system and it will also provide a comprehensive understanding of the Bretton Woods fixed exchange rate system. The system has very old roots, after the devastating World Wa r one all the countries wanted financial security to make sure that economic growth in the country takes place. The great depression in the 1929 was a result of the failure in the introduction of gold standard. Each and every currency intentionally deflated its currency in order to get high margin of profit from the exports which would decrease the deficit from the country’s economy. The same had an adverse affect on all the countries, it triggered off international deflation, and this majorly impacted many countries, mass unemployment increased, big enterprises were going bankrupt, global economy witnessed hyper inflation. There were talks held among the representatives of various countries to form a system which would bring stability with regard to the financial and economic well being

The Color Purple Essay Example for Free

The Color Purple Essay The novel the color purple by Alice Walker is well known for is revolutionary theme of black lesbianism. Until this novel and other leading writers touched on the subject of black lesbianism, it was viewed as dirty and unspeakable. The protagonist, Celie, brings respect and positive attributes to the idea of black lesbianism. Walker’s depicture of Celie not only relates constructive events towards lesbianism, but also journeys through the rejection of male dominance and how it brings Celie freedom. Most of Celie’s freedom comes in the form of monetary relief and independence. However freedom also comes from Celie’s change of world view; from a repressive patriarchal society and God to a gentle and softer version of religion. Walker emphasizes the oppression black women face in relationships with black men (brothers, fathers, husbands, lovers) and the bond the women must form with each other in order to free themselves. Right from the beginning of the novel, Walker introduces a hard to digest picture of rape, incest, and sexual cruelty. He never had a kine word to say to me†¦ Then he push his thing inside my pussy. When that hurt, I cry. He start to choke me† (Walker 1). This telling of rape by her father is also seen through the eyes of the reader as lacking emotion or at least the emotions such as anger and anguish that come with an event such as rape. Celie’s life begins to form into a picture of a slave’s, with her missing feelings and reactions to the horrible fates that befall her. After this rape, Celie becomes pregnant and is forced to separate with her child straight after. According to Ana Marie Fraile-Marcos who wrote a critical essay on Walker’s â€Å"womanist† representation of lesbianism, Celie’s sexual abuse becomes endemic after her two successive pregnancies and deliveries. Celie seems to accept sexual exploitation and oppression as shaping factors in her life and not only does Celie become a sexual object, her story also echoes the life of a slave. An auction scene is called to mind when Celie is told to walk in front of Albert, while he decides whether or not to take her as his new wife. Along with the physical oppression, Celie also has to endure psychological oppression due to her sexual exploitation. During Celie’s pregnancies, she had to put up with the confusing torment of her mother at the same time as her father blames her for her mother’s slow passing. Finally Celie’s mother passes cursing her, although Celie is at a loss to what she did wrong. Next to her mother’s negative affliction, Celie also curses herself and believes that she is on the road to hell for committing incest imposed on her by her father. In her mind, Celie is living in â€Å"sin without redemption† (Fraile-Marcos). The men were forces of her oppression, which made Celie turn towards women for her liberation. During her childhood, Celie was close with her sister and found a love that she would sincerely protect. â€Å"She scared. But I say I’ll take care of you. † Although Celie’s love for Nettie is a bond that lasts through the whole novel, the most important figure to influence Celie’s change in submissiveness is Shug Avery. Through uncovering the letters Nettie wrote to Celie, forcing Albert to beat Celie less, and just being the woman who did whatever she wanted, Shug was the leading character who taught Celie the beauty of sexuality. After quizzing Celie in Shug’s first stay, Shug deemed Celie a virgin due to her never having sex with someone that she loves. From that point, Shug begins to teach her about the female body, which Celie enjoys because sexuality turns from a negative and repressive force, to one that becomes exciting. Shug’s most important contribution to Celie’s self-realization is love, both sexually and spiritually† (Fraile-Marcos). Through this self-realization, Celie comes to the conclusion that she has a sister who loves her and will always write to her, and has Shug who has the intention of loving her and helping her get on her feet. All of the forces involved in Celie’s positive evolution come from the female gender, which leads Celie to her chang e in religion. Shug’s spiritual contribution to Celie’s self realization is the modification of the picture of God in Celie’s mind. At the start of the novel, Celie’s version of God was one who was a white authority figure, who only gave orders and punished the people who stepped out of line. â€Å"Okay, I say. He big and old and tall and graybearded and white. He wear white robes and go barefooted† (Walker 194). Celie’s version of God did not have time for her and saw her sufferings as something to just move on from. However, Shug soon initiates a spiritual awakening that begins with her description of God, who doesn’t have specific characteristics and instead is more a spiritual presence. God ain’t a he or a she, but an It†¦ Don’t look like nothing, she say. It ain’t a picture show. It ain’t something you can look at apart from anything else, including yourself† (Walker 195). Shug showed that God was found within everyone and everything, instead of a figure impossible to relate to. Celie’s journey dragged her from a hellish, detached exis tence to a life she could feeling pulsing through her body. After her self-revelation and freedom from oppression, Celie supported herself thorough making pants. This created an independent woman out of Celie, and taught her to rely on herself more than the people around her such as her oppressors or even Shug. Believing God was a white, despotic figure lead Celie to her rejection of the world, rejection to male dominance, and her acceptance of an unfair society. However, femininity brought Celie back to the world and showed her the kind, caring, and gentle side of life. Walker took the reader through a journey of finding Celies personal voice and also helped the reader accept and appreciate the rejection of male dominance.

Education + Parents involvement Essay Example for Free

Education + Parents involvement Essay Childhood carries a similar attitude for all the children [boys and girls] unto the age 3 years in respect of play, fun and learning. A careful study of Montessori education reveals that the child develops learning, reading and a domestic-kind of assignment as a workshop, tells a lot about the child within three years. This is irrespective of the gender. Reading skills are picked up by children only in this age. Influence on Early childhood education World Literacy of Canada (WLC) approach to early childhood education programming in recent years has been the Early Years of Study This study of Reversing the Real Brain Drain (published in 1999) by Hon. Margaret Norrie McCain and Dr.J.Fraser Mustard. The findings are: Need for early childhood development programs based on the new understanding of brain development in the early years of and its effect on subsequent learning, behavior and health for individuals. First three years of a child, sets the stage for competence and coping skills for the later stages of life. Need for more integrated framework for early child development and parenting support. Recommendations for parental guidance: Parents must be provided with awareness, support and skills for the early development of their children. Build relation with children. Undertake programs to parents and educators to learn new ways to nurture children and develop responsive relationships between adults and children. Participation of parents in children’s programs. ï‚ § Interactive and supportive learning system with children along with parents. ï‚ § Active role with children in play and reading at home. ï‚ § Create a safe and friendly environment for children. ï‚ § Create programs where children of all backgrounds and abilities will feel loved and valued – this will stimulate brain development, learning and self-confidence. ï‚ § Play-based learning, and problem solving for young children under the guidance of educators and parents. Resources of early childhood development ï  ¶ Toy and resource libraries ï  ¶ Nutrition programs ï  ¶ Cultural events for children .e.g mobile toy book lending libraries ï  ¶ Theme-based learning ï  ¶ Play-kits. Special efforts and care for parents who are isolated to participate and benefit from the program. Create an awareness that children are part of social structure and emphasis on early childhood development. Parents involvement and its influence on achievement of Reading by students. The approach of the parent towards children is of similar kind with regard to education. Parents who stay-at-home moms can dedicate more time for motivating children in their reading habits especially to boys, by studying their interests and by discussing the topics which will detail about their approach to reading habits. Compelling boys to read for a certain hours of a day, forcibly, would not derive maximum results, as some parents believe. Instead motivation and allowing the boys to think and re-think about themselves, is certainly an achievement for the parents in the long run for developing reading habits. Today’s tech-savvy days also stand as a hindrance to the attainment of reading habits to children. The reason being, an easy access to television, computer, internet, video games, cartoon movies has enabled the children to move away from books, which is not at all a good ground for school education. Parental guidance with teacher’s support is the only solution for imbibing reading habits to children. For instance, the recent ‘Harry Potter’ novels have created a large amount of selling of books around the world. Harry Potter, movies as well as books have been sold by publishers. This includes readers of all ages, including adolescents. †¢ Sorcerer’s Stone †¢ Chamber of Secrets †¢ Prisoner of Ascaban †¢ Goblet of fire This is a relevant example, that children do read books, based on fiction, magic and fun. When it comes to the reading of curriculum, children may not feel as interesting as the fiction is. There is still scope for creating energy and interest among the students, and it mostly rests on the shoulders of parents and teachers. The precious hours of study of students are in the environment of school. The core area for their their learning activity and personality development. Students depict 60 percent effect of their school, while the parental guidance is only 40 percent. Most of the part what they are is shaped only in school. It is a well-known fact that parents and teachers work together to bring the best out of the students. How can parents tell if teachers are doing a good job?   Ed World’s â€Å"Principal Files† team members offer their perspective. Included: Look at the work students bring home and â€Å"the hard sell†. Parents communication with teachers is the key ingredient to the parents to know how their children are studying in the school. Term Grade papers, newsletters give a correct picture of students performance. According to Principal Nina Newlin â€Å"A teacher who has a good relationship with students is likely to be a regular parent informant†. nformation can be through email, telephone but there is a genuine concern about events in classroom to inform to the parents.. Mostly students evaluate a good’ teacher. Parents are also are guided by students in getting answers for their questions.   Students are always honest in answering to the questions of parents about the events in the classroom. Conversation at dinner table, a look at home work or a independent activity given, suggest to the parents, the performance of their children. A prompt check over the assignments is very important duty on the part of parents for the overall efficiency of the student. It also discloses a fact to the student that he/she is being monitored closely and there’s no opportunity to haywire. Many schools follow the procedure of being fair in classroom rules and procedures, tough in standards of performance, and fun in learning and classroom lessonsâ€Å"follow them home† wherever it is required.   Visiting school premises and watching students in the classroom also gives a true picture and to the satisfaction of the parents.   Volunteering also helps parent-teacher community to train the students for maximum achievements in their academic pursuit. Ultimately, if the student is happy and active in and out of learning area, it is learnt by the parent that the student is learning and happy in school area. What are effective steps for boys literacy with the involvement of parents Many child psychologists agree that adaptation of psychological methods to motivate children in inculcating reading habits, would certainly bring about a change in the development of boys. A thorough, methodical and continuous assistance of the parents is required, without imposing any punishments but rewards for one-to-one achievements that a child is prompted to do. In other words, ‘if you read this particular book and tell me’ ‘a reward would be a candy or a snack of your choice’. To this many child psychologists agree. Children are more smarter than parents. Therefore, parents must never let the children know that they are indirectly pursuing the children towards the concept of ‘sit with books for hours and read’, instead an idea of ‘helping hand’ or an atmosphere of an activity should be created. Parents can also prepare a long-term plan for improving the reading habits, by maintaining a statistical record of hours of reading spent by the child. This will also give a clear picture to the parent, whether the goal is being attained. A good amount patience, having a great understanding about the child, likes and dislikes, dos and don’ts, individual perception of the child towards the environment, study of personality will truly help the parent to remove the lacunae in the child. Particularly in the case of boys, in their adolescence they are action oriented. In other words, play indoor games, outdoor games, video games, watch movies, ride bikes, are some of the areas of interest for a large number of boys. A good and plain discussion with boys, about their activities outdoor, at school or college, a bit of guidance, without involving any argumentative statements, will direct the boys to ‘the thinking area’ of their own attainments and to reach set goals. A good friend for a boy should be made available ‘at home itself’ and that is none other than the ‘parent’. Many experts on education made the research study on boys reading habits. They formed an opinion that, boys mostly feel reading is an activity done by girls. Thus, boys are trailing behind the girls. A recent study in Canada, published in ‘Reading Manitoba’ found that 76% of the boys interviewed did not see reading as a feminine activity, and 73% enjoyed reading. Experts opine that offering the choice of material according to the boys interest, would be a good solution in achieving reading habits to the boys. Conclusion Education for children all over the world carries a great importance. Nations which are developed have more advanced sources for imparting education viz., Australia, Newzealand, U.S., Britain.   An analysis of education states that, many parents opt education overseas instead of domestic education. The reason being, parents believe, that the overseas curriculum is extensive, focusing the student to many aspects of education. Although this is partly true, the domestic education shapes the students [K-12] and effective methods of imparting education and touching the interests areas of students must be developed. For instance., domestic projects, like ‘how to do laundry’ ‘how to be a good host’ ‘attend a super market’, these will outline the interests of a students and reveal so much of personality from the students. Based on the results, parents and teachers can study their interests, and accordingly encourage them reading habits in those areas, thereby students also begin to learn to be active.   Modern day system of education, is such as mushroom of notes and homework, internals, exams, to some extent children also feel agitated over the system of education and lose the interest in studies. Adding to this, if parents emphasise more on reading, they catch the boredom and flee to find fund moments elsewhere, which is a common factor among students.   Finally to conclude, a change in system of education, close monitoring by parents and teachers will only lead the children back to the good old days of reading comics, enid blytons, phantom or sherlock holmes. www.worldlit.ca http://www.liamodonnell.com/. Article by Gary Hopkins,Education World ® Copyright  © 2004 Education World

Radial Ball Bearing Material

Radial Ball Bearing Material You are tasked with selecting a material that is suitable for the balls in a radial ball bearing such as the one shown in Fig. 1. Radial ball bearings although intended primarily for radial loads, will also carry a certain amount of thrust.    Ball Figure 1 Ball bearing The following details are known in relation to radial ball bearing design: Youngs modulus should have a minimum of 200 GPa. The compressive strength should have a value à ¯Ã¢â‚¬Å¡Ã‚ ³ 300 MPa. The balls must not fail under load. It can be assumed that the contact stress can be modelled for a sphere on a flat (see Fig. 1). An assumption should be made that the material for the ball and the raceway are the same and therefore they have the same moduli and Poissons ratio has a value of 1/3. The balls should be light. Material selection process. This refers to selecting a material that meets all the constraints and objective below. Design requirements: Table 1 Table of design requirements Function   Suitable for balls in a radial ball bearing Constraints Youngs modulus must be greater than 200 Gpa. Compressive strength should not have a value of less than 300Mpa. (Assumption)Moduli and Poissons ratio being the same (ratio of ). Objectives The balls must not fail under load, contact should be modelled for a sphere on a flat. The balls should be light. Free variables Cross sectional area Material choice Mass of ball Below is a figure of all materials with a mechanical property (Youngs modulus greater than 200Gpa and Compressive strength greater than 300Mps) against density: Seen below is a table of the materials and their corresponding Youngs modulus. Table 2 Table of materials Name Youngs modulus (GPa) Tungsten carbides 625 700 Boron carbide 440 472 Silicon carbide 400 460 Alumina 343 390 Tungsten alloys 310 380 Aluminium nitride 302 348 Silicon nitride 290 318 Zirconia 200 250 Nickel-based super alloys 150 245 Nickel-chromium alloys 200 220 Nickel 190 220 Low alloy steel 205 217 Medium carbon steel 200 216 Low carbon steel 200 215 High carbon steel 200 215 Stainless steel 210 Although seen above, 16 values have passed the requirements so far, further analysis will be conducted, and this can be seen below; The below table illustrates the materials that meet the design requirements, the table is ranked based on Youngs modulus, from highest modulus to lowest. The Compressive strength of the material must also be considered, a minimum compressive strength of 300MPa must apply. The table below illustrates each materials Youngs modulus and corresponding compressive strength. Table 3 Materials with Youngs modulus and compressive strengths that meet design requirements (density also noted) Name Youngs modulus (GPa) Compressive strength (MPa) Tungsten carbides 625 700 3.35e3 6.83e3 Boron carbide 440 472 2.58e3 5.69e3 Silicon carbide 400 460 690 5.5e3 Alumina 343 390 690 5.5e3 Tungsten alloys 310 380 555 800 Aluminium nitride 302 348 1.97e3 2.5e3 Silicon nitride 290 318 524 5.5e3 Zirconia 200 250 3.6e3 5.2e3 Nickel-based super alloys 150 245 300 1.9e3 Nickel-chromium alloys 200 220 365 460 Nickel 190 220 70 1e3 Low alloy steel 205 217 400 1.5e3 Medium carbon steel 200 216 305 1.76e3 Low carbon steel 200 215 250 395 High carbon steel 200 215 335 1.16e3 Stainless steel 189 210 170 1e3 Below is a bubble chart of Youngs modulus versus compressive strength: Figure 2 Bubble chart of Youngs modulus of Compressive strength The above figure is on a logarithmic scale. Only materials that have passed the requirements were plotted. When surfaces are placed in contact they touch at one or a few discrete points. If the surfaces are loaded, the contacts flatten elastically and the contact areas grow until failure of some sort occurs. (Duffy, 2010) Compressive stress causes this. As the requirements state; should be modelled as a sphere on a flat, this allows the student to use following formulae (contact stresses); Figure 3 Sphere on a flat (Duffy, 2010) (Yield Stress)   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   The following is subbed in to produce the below: x x x x = = The mass of the sphere must be derived, this is done below; Where is density and is volume Volume of a sphere is denoted as: m= The student knows the objective is to minimise the mass of the ball, the derivation above is done on that basis and results in the equation being flipped above. From the material selection index above, the equation can be related in the logarithmic scale: = This results in: This now means the slope can be known to be = 0.222 The above value is known as an index line; Index lines can be used to compare the performance of different materials, and to find replacement materials. Materials that are on the line will all perform equally well in each design. Materials above the line have a higher performance index and will therefore perform better; those below the line have a lower index value. (Edupack, 2006) The below bubble chart illustrates the material selection process using the slope; Figure 4 Material selection with material index As seen from above, with a material index of 0.222 the following two materials passed (whole record is within the selection was used); Name Index slope =0.2222 Silicon nitride 6.55e101 Zirconia 1.66e100 As seen from above the materials are both ceramic. An additional chart plotting the materials costs can also be seen below; Figure 5 Price of selected material Figure 6 Price of selected material Pass only A table of the materials cost can also be seen below; Table 4 Table of costs Name Price(EUR/kg) Zirconia 17.1-24.7 Silicon nitride 32.3-49.4 (i) It has been identified that both Youngs modulus and compressive strength are important material properties when selectin ball bearings, below is a detailed summary of why each property is important; Youngs modulus refers to a materials elastic modulus. This determines the stiffness of a solid material. This is a proportional (constant) between stress as long as stress is less than the yield point. This results in a smaller strain with the same stress in a stiffer material. In relation to a ball bearing Youngs modulus of Silicon nitride is about 1.5 times that of steel, meaning a smaller contact surface is present when there is a high contact pressure. Hertz theory means the maximum load for combination steel- Silicon nitride reduced with 30%. In relation to the contact of the bearing we know it will be a sphere on a flat. The balls within a bearing are going to experience both an axial and radial force. If the force is too great for the material this may result in deformation (changing of shape). This affects the ball bearings ability to perform, this can be compared to as a wheel on a car, if it is flat may result in a pulling motion. If severe deformation occurred this may result in the bearing not allowing for rotation. This means that Youngs modulus is important when selecting materials for ball bearings. Youngs modulus mathematical representation; It is noted from CES EduPack that silicon nitride is used mostly for ball bearings the Youngs modulus is known to be; 290-318 GPa (Edupack, 2006) Compressive strength refers to a materials resistance to compressive stress. This is when a force is applied in an inwards direction in the material. It is opposite to tensile stress. As a ball bearing is going to have one point of contact, (below) compressive strength is an important element in choosing the material. This is due to the radial forces applied when the ball is in the raceway. Once again, if the radial force is greater than the materials compressive strength abilities this will result in deformation. This will affect the bearings performance. Compressive strength can be up to 10 times greater than tensile stress. Ceramic material has a good compressive strength due to crack propagation, since there are more internal cracks in ceramics (than most materials) if placed under tension cracks will propagate and produce failure where if it is placed under compression it works in the opposite manner. Compressive strength mathematical representation; It is noted from CES EduPack that silicon nitride is used mostly for ball bearings the compressive strength is known to be; 524-5.5e3 MPa   (Edupack, 2006) (ii) The other material properties of Silicon Nitride which lead to superior operating performance can be seen below; General properties Density3.1e3-3.4e3kg/m^3 Price*32.3-49.4EUR/kg Date first used1958 Mechanical properties Youngs modulus290-318GPa Shear modulus*100-128GPa Bulk modulus*210-232GPa Poissons ratio0.26-0.28 Yield strength (elastic limit)*600-720MPa Tensile strength600-720MPa Compressive strength524-5.5e3MPa Elongation0% strain Hardness Vickers1.4e3-1.6e3HV Fatigue strength at 10^7 cycles*300-500MPa Fracture toughness4-6. 7MPa.m^0.5 Mechanical loss coefficient (tan delta)*2e-5-5e-5 Thermal properties Melting point2.39e3-2.5e3 °C Maximum service temperature1e3-1.2e3 °C Minimum service temperature-272271 °C Thermal conductor or insulator?Good conductor Thermal conductivity22-30W/m. °C Specific heat capacity670-800J/kg. °C Thermal expansion coefficient3.2-3.6 µstrain/ °C Electrical properties Electrical conductor or insulator?Good insulator Electrical resistivity1e20-1e21 µohm.cm Dielectric constant (relative permittivity)7.9-8.1 Dissipation factor (dielectric loss tangent)*5e-4-7e-4 Dielectric strength (dielectric breakdown)*11-131000000 V/m Optical properties TransparencyTranslucent Refractive index1.95-2 Processability Moldability2-3 Weldability1-2 Eco properties Embodied energy, primary production116-128MJ/kg CO2 footprint, primary production4.63-5.12kg/kg RecycleRecycle (Edupack, 2006) The above characteristics result ceramic materials being the optimum material for ball bearings; High speed, faster acceleration this is because ceramics are only 40% as dense as steel. However, the material can deliver 30-50% higher running speeds with reduced skidding and less lubrication needed. Lighter in weight ceramic ball bearings are more rigid to that of steel ball bearings and lighter in weight.   This allows for lower coefficients and a higher overall RPM (rotation per minute) Greater accuracy since ceramics has 50% higher modulus of elasticity than steel. This means less of a deformation which leads to vibration and spindle deflection, this increases components productivity and quality. Reduced friction: benefits of this include: longer life, energy efficiency reduced noise levels, less heat and less lubrication needed. Non-conductive materials like Silicon nitride eliminate the pitting and fluting of raceways which ic common in electrical motor applications. If steel is used in bearings the electricity could cause magnetic field (EMF) and this could act as a conducted damaging the bearings over time. Ceramic materials are immune to EMF, which mean they perform well even when electricity is present. Corrosion resistance Silicon nitride; more effective than steel balls in the presence of liquids such as water or corrosive materials. Corrosion resistance can be enhanced when ceramic balls are used with dry fil, lubricant on the ring and retainer components. Longer operating life Up to 5 to 10 times longer than standard metal bearings. Higher temperature operation ceramic ball bearings can operate in high temperatures (up to 1,800  °F) Less noise and vibration due to a lower coefficient of friction (Ibsco, 2011) The two materials chose were Silicon Nitride and Zirconia. A brief description can be seen below outlining why the individual ceramic is the optimum choice; Silicon Nitride: This material contains high temperature capabilities, meaning it has a low thermal expansion coefficient which gives good thermal shock resistance compared to other ceramic materials. The material is up to 58% lighter than steel silicon (Carter, 2009). As the material is lighter it means a smaller force is needed to roll the element. The main advantage to this is that silicon nitride can carry similar loads to that of silicon steel with less force needed. Zirconia: Zirconia was made for high performance duties such as (atmospheric journeys). This means the material has the highest temperature ability. However, this material has a high thermal expansion (almost like steel) but weighs less so it does not have the same weight saving and thermal shock resistance found in other ceramic materials. (Carter, 2009) Zirconia is used when low loads are applied or when high temperature capabilities are needed (corrosive too). (iii) Porosity refers to a measure of void (empty spaces in a material) and is a fraction of the volume of voids over the total volume between 0% and 100% (Quora, 2003) Technical ceramics do not have open porosity. To achieve porosity manufacturing process must be done (use of additives). This then allows closed and open pores to be created, ranging from nm to  µm. Porosity can have various effects on the mechanical properties of ceramics (as chosen). The following properties are effected: Compressive strength Density Fatigue Youngs modulus Fracture toughness Shear modulus Tensile strength Any residual porosity will influence elastic properties and strength. For some materials, the magnitude of the modulus of elasticity E decreases with volume fraction per; It is known that porosity affects flexural strength as it reduces cross-sectional area. It also results in pores acting as stress concentrates. (Duffy, 2010) (iv) Below is a completed table for ceramic materials having 20vol% porosity. This is done by using the following; The below calculation for silicon nitride is done for clarity; ) = 199.424 GPa Where is the modulus of elasticity and is the porosity volume. Table 5 Ceramic materials with 20vol% Material Modulus of Elasticity GPa Porosity at 20vol% E(20%) Porosity GPa Silicon nitirde 304 0.2 199.424 Zirconia 205 0.2 134.48 Silicon carbide 345 0.2 226.32 Aluminum oxide 393 0.2 257.808 Glass-ceramic 120 0.2 78.72 Mullite 145 0.2 95.12 Spinel 260 0.2 170.56 Magnesium oxide 225 0.2 147.6 Fused silica 73 0.2 47.888 Soda-lime glass 69 0.2 45.264 As seen from the above, silicon nitride is the ceramic material resulting in a modulus of elasticity when having a porosity volume of 20%. References Carter, 2009. Carter. [Online] Available at: http://www.carterbearings.co.uk/unasis/hybrid-and-ceramic-bearings/ceramic-matericals-and-their-properties-part-2/[Accessed Saturday Feburary 2017]. Duffy, J., 2010. Moodle. [Online] Available at: http://moodle.itb.ie/pluginfile.php/115304/mod_resource/content/0/CES%20EduPack%20-%20USEFUL%20SOLUTIONS%20to%20COMMON%20PROBLEMS%202008%20-%2001Jan13.pdf[Accessed Wednesday Feburary 2017]. Edupack, C., 2006. s.l.: s.n. Ibsco, 2011. Ibsco. [Online] Available at: http://www.ibsco.com/ceramic-ball-bearings.php[Accessed Saturday Feburary 2017]. Quora, 2003. Quora. [Online] Available at: 2017[Accessed Wednesday Feburary 2017].