Engineer do to improve environment Free Essays

It is estimated that the world oil reserves will last for 30 to 40 years. On the other hand, solar energy is infinite 4. Example: Changing Airport and KALI designed to fully used the solar energy Main point 2 : Reduce the uses of chlorofluorocarbons (CUFF) and reduce the energy consumption. We will write a custom essay sample on Engineer do to improve environment or any similar topic only for you Order Now 1. Past: most cooling device like refrigerator and air conditioner using CUFF 2. Effect : destroy the Ozone layer in the atmosphere 3. Now: upgrade of the air conditioner and refrigerator without using CUFF and less energy consumption. 4. Main point 3: The uses of biodegradable item 1 . More technologically advanced 2. Produce materials ; withstand extreme temperatures, durable and easy to use 3. Biodegradable products are those that can be decomposed by microbes and other natural biological processes 4. 80% vegetable starch and 20% of vegetable oil 5. Biodegradable items are useful in reducing the amount of waste in landfills Plastic bags 10-20 years Soft plastic (bottle). How to cite Engineer do to improve environment, Papers

Romance free essay sample

Who would think that listening to hip hop music one would be influenced to live, think, and act a certain way? Joan Moorings Fly Girls, blotches, and hoes: Notes of a Hip Hop feminist, argues that the rampant sexism and machismo in hip hop music Is the fault of both African American men and women and damages the larger African community. She compares hip hop music to an abusive relationship. She states that hip hop music is the only way in which young black men are allowed to hide and express their pain. She believes that black men are engaged in war and, racism and white power structure have conditioned black men to believe the enemy is brown. She states that for most black men there is no trust, no community, and no family. She believes that hip hop is the mirror in which brothers see themselves. She states that black women are hurt when they hear black men calling them pitches and hoes. We will write a custom essay sample on Romance or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page She states that in the last thirty years the number of two-parent household has decreased from 70 to 38 percent. She says that the cause of death among black men ages fifteen to twenty-four Is homicide.The hip hop community creates sexism and schisms In the African American community because of the way hip hop artist dress, what they say and how they behave. Most hip hop performers dress In a very provocative way. Rap artist ill Kim want to the Grammar award wearing a purple sequence dress with one of her breast out covering the nipple with a piece of fabric. The men wear pants that expose their underwear and private area. The women wear short skirt and tight pants. They also wear half shirts with their bra showing and, cleavage hanging out. By dressing in a sexual way it makes the black community think that it is okay.In some of the hip hop songs the artist talks about expensive clothes. In the videos they show woman wearing tight clothes. The woman in these videos encourages young girls to dress like them. When these girls dress like the woman In the video they become poplar. While becoming poplar they gain friends and dress In style. Joan Morgan says weve all been recipients of the competitive way when Lung for male attention (5). This shows that woman dont have self-love for who they are. Most of hip hop songs encourage the use of improper English. Salt Shaker by Ill Jon amp: Stateside Boys states, Shasta crank on the floor wide openOcean Skeet so much they call her Billy Roll like an eighteen wheeler That hoe fine but this hoe a killer Shake it like a salt shaker She leaked, shes soaking wet In hip hop music slang are used. Some of the slang used are disks, hood rat, billing, blitz, silent, and grind. The slang that rappers use has become a language In the African American community. They use this slang because they dont want other races to know what they are talking about. Using slang make the black community more acceptable among there pears. With slang makes It easy for them to communicate with each other without sounding nerdy.By using improper English it Not only does improper English affect their ability to communicate but it will also affect the young children in school. Joan Morgan says, my feminism places the black community on its list of priorities (2). This shows that as a community things need to change. Hip hop music encourages deviant behavior. A deviant person behaves in a way that is not acceptable. Hip hop music encourages sex. In most hip hop music men talk about how big women breast and butt are. They also talk about going to bed with them. In the music videos there are scenes where there are men and women in bed half naked.

Chimpanzee Politics Essay Example

Chimpanzee Politics Essay Chimpanzee Politics by Frans de Waal chronicles a colony of 23 chimpanzees who live in an outdoor, open-air space at the Arnhem Zoo in the Netherlands. Of these 23 chimpanzees there are four males: Yeroen, Luit, Nikkie and Dandy. The colony also consists of three female subgroups, the largest made up of Mama, Gorilla, Franje, Amber and three children, Moniek, Roosje and Fons. The second largest subgroup includes Krom, Spin, Jimmie and her two sons Jakie and Jonas. And the third female subgroup consists of Tepel, and her two children Tarzan and Wouter. Puist is also considered part of Tepel’s subgroup. Even though she usually associates more with the males than with the females and children, there is an exception when it comes to Tarzan and Wouter, to whom Puist plays an aunt-like role. There are three remaining females, Oor, Zwart and Henny, but they play a rather small role in this particular book. Throughout Chimpanzee Politics, de Waal attempts to explain the social organization of chimpanzees. A benefit of being able to observe these primates in such a facility is that fieldworkers are able to see the animals on a regular basis, witnessing the countless social interactions that take place. De Waal notes that much of the research on chimpanzees has been done through observations in their wild habitat, and although â€Å"these observations are extremely important it is impossible to follow social processes in every detail in the jungle [Researchers] will not fail to note the results of social changes, but they will often be ignorant of the causes† (p. 4). Thus, with a space in which researchers can watch the animals daily, the more we are able to understand the social dynamics of the chimpanzees. Frans de Waal conducted his research by means of observations. He monitored the chimpanzees’ behavior, their relationships, their habits. He divided his studies into categories to emphasize main themes and key components within this culture: personalities, power takeovers, restless stability, sexual privileges and social mechanisms. The social relationships between chimpanzees are constantly changing, and are mostly categorized within and across genders (i. e. , male/male, male/female, female/female). As to be expected, interactions between males are far different than those between females. We will write a custom essay sample on Chimpanzee Politics specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Chimpanzee Politics specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Chimpanzee Politics specifically for you FOR ONLY $16.38 $13.9/page Hire Writer Relationships between males seem to center around the ideas of sex and power. De Waal frequently discusses the role of intimidation and submission with males. Males commonly use intimidation as a means to dominate, such as with bluff displays. During a bluff display a chimpanzee’s hair will stand on end while they stomp and grunt. These displays serve to create a sort of superiority over another male, and sometimes result in conflict, yet it is rare that chimpanzees actually fight. The author describes the males’ quarrels as â€Å"controlled fighting. † They only bite extremities, usually a finger or a foot, and less frequently a shoulder or the head Since this is virtually the only way the males fight each other, they cannot be out to prove their respective physical strengths. The crucial factor is their capacity to fight effectively within the rules. A male must be able to get his hands and feet quickly out of the way, and he must equally quickly be able to sei ze hold of his opponent’s hand or foot† (p. 104) In times of tension grooming is a common practice, and differences are often pacified by kissing or even licking each other’s wounds. Males also practice submission to dominance with â€Å"greetings† (and females also practice this, as well), which de Waal describes as â€Å"no more than a sequence of short, panting grunts known as pant-grunting,† which is commonly accompanied by a series of bows (p. 78). These greetings may be taken even further by the dominant male by performing a bluff-over, in which â€Å"the dominant ape steps or leaps over the ‘greeter’ [while] the submissive ape ducks and puts his arms up to protect his head† (p. 78). These displays are commonly performed by lower-ranking males or females as a show of compliance to a high-ranking male, more specifically the alpha male. Furthermore, it emphasizes the hierarchy between males. In Chimpanzee Politics we learn of the power struggle surrounding Yeroen, Luit and Nikkie. At the start of de Waal’s research, Mama actually held the leadership position, until her and Gorilla were removed from the colony for three months, at which point Yeroen became the alpha male. However, with time Luit slowly started to take over the leadership role. It began when Luit openly mated with Spin in close proximity to Yeroen, something that is usually not tolerated by the alpha male. Then Luit and Nikkie formed a coalition. Nikkie supported Luit and they worked together to dethrone Yeroen. As a result of separating interventions, Yeroen’s ties with the females slowly deteriorated and he became isolated, ultimately losing his power. Yeroen reacted with tantrums, screaming and kicking, an apparent sign of desperation. As time passed, power shifted once again. After Luit attacked Nikkie on a few occasions, their collaboration ultimately ended, and both Nikkie and Yeroen became less submissive toward Luit. Tensions between Nikkie and Luit increased, and therefore resulted in frequent grooming sessions. Eventually, Nikkie and Yeroen displayed a bold gesture of unity. â€Å"When Nikkie began to display Yeroen usually went and stood close behind him, wrapped his arms around his waist, pressed his lower belly against Nikkie’s bottom and hooted gently. This gesture is called ‘mounting,’ and it certainly originates from a sexual act ut has no sexual significance Nikkie and Yeroen literally formed a closed front. † (p. 126) In time, Nikkie became the new alpha male, but it was rather short-lived. Based on his actions, the keeper decided Nikkie was not prepared to fill such a role, and he was removed from the colony for the rest of the season. While Nikkie was gone, Luit regained his dominance, but only to be broken upon Nikkie’s arrival when once again he formed a coalition with Yeroen. Power continued to shift through the years, but in the end, Nikkie takes on the leadership position. However, unlike Luit and Yeroen who had been lone leaders, Nikkie shared his role with Yeroen, whose duty was to keep order and peace. The female chimpanzees also play a highly influential role when it comes to the success of a dominant male. As with Yeroen, without the support of the females, a male risks isolation and loss of power. In a population such as this, the females have more political influence. They will defend certain males, aiding in the rise to power, or simply to protect. For example, consider this situation when Luit is trapped in a tree, cornered by Nikkie and Yeroen: Nikkie and Yeroen climb up toward where Luit is sitting. Luit has no option but to fight back, because he cannot escape. Nikkie and Yeroen grab hold of him and bite him, but this unequal struggle does not last long, because the highest-ranking females band together and quickly follow Luit’s attackers up into the tree. Yeroen is bitten by both Mama and Puist. Mama then drags Yeroen out of the tre e and chases him Puist stays in the tree and, together with Gorilla, launches an attack on Nikkie† (p. 129) As highlighted by this passage, females can provide critical conflict support. Shortly after this episode Nikkie was removed, but this example shows how females interact with the males. Males often run to females for comfort, reassurance, and protection, because often females will band together to defend against a male, as we see in the above situation. Females also serve to as mediators between male conflict. De Waal provides one example by discussing how one female chimpanzee presented herself to a male, and as he followed her she slowly approached his opponent. Both males began to groom her and eventually she left, leaving the males to groom each other and therefore mollified tension (p. 07). Male and female relationships also have a sense of reciprocity. Females want a safe environment to raise their offspring, and males offer protection mothers and their children, and in exchange females offer support or grant sexual privileges. Relationships between females are generally less confrontational, conflicts are far more rare. Although they do have a hierarchy, it differs from that of the males in that it stays stable for years, and rather than being determined by physical superiority, female’s are ranked by personality and age (p. 178). In this colony, Mama is at the top of the female hierarchy, followed by Puist and Gorilla. Females often form strong bonds together, and therefore help each other against male aggression. The females in a particular subgroup watch over each other’s children and support one another. For example, Amber has a special attachment to Mama’s daughter, Moniek, and helps care for Mama care for her. Unlike males, who use interventions as a way to gain power, females carry out sympathy-biased interventions in which they defend family and close friends (p. 191). One of the most fascinating observations that Frans de Waal made is the chimpanzees’ ability to strategize. As the alpha male, Nikkie utilized the strategy of divide and rule. He kept interactions between Yeroen and Luit limited, and frequently intervened in order to prevent them from forming a coalition that could threaten Nikkie’s leadership. This proves that chimpanzees are aware of not only their own relationships, but of the relationships of others, as well. The same strategic intelligence can be noted with Yeroen, who seemed to demonstrate the ability to rationalize. Yeroen deliberately formed a coalition with Nikkie instead of Luit, Yeroen was aware the Luit had no use for him, but Nikkie however would grow to depend on Yeroen, and together they would dethrone Luit and Yeroen would still maintain a high-ranking role in the colony. This shows the chimpanzees’ future-oriented behavior, â€Å"this ability to consider a remote goal and weight the consequences of a choice that could explain why a male, such as Yeroen, formed the alliance that ultimately offered the best prospects† (p. 186). Strategizing is of course not limited to just males, the females strategize as well, but use it for different purposes. The females strategize to create a secure environment, the often partake in sexual bargaining with males as a way to get what they want, such as protection of their children. Despite the many conflicts discussed in Chimpanzee Politics, chimpanzees also work together, collaborating to achieve a goal. One chimpanzee will hold a branch steady while another gathers branches, and males often let females to take things right from their hands. â€Å"Chimpanzee males are surprisingly generous when it comes to material things Their control rests on giving. They give protection to anyone who is threatened and receive respect and support in return† (p. 99). This book is filled with implications of human behavior, the most notable being the ability to strategize, their capacity to weigh options, predict future outcomes and apply a plan to reach a goal. The whole concept of reciprocity within this colony of apes also hints at human behavior, the idea of doing something to gain something, w hether it be through coalitions, nonintervention alliances, sexual bargaining or reconciliation blackmail (p. 200). Although humans may not use these exact tactics, we do apply the same notions of reciprocity. This exhibits the acute awareness the chimpanzees have of their own surroundings and relationships. One example in particular emphasizes the way a male chimp will shift his attitude with the intention of reaching a certain goal. Luit, for example, upon the dethronement of Yeroen, Luit changed his aim to stabilizing his new role (p. 117). During conflicts, Luit would support the more disadvantaged individual, and commonly intervened in quarrels so as to preserve tranquility and safety among the group. De Waal astutely pointed out that the chimpanzees’ â€Å"interest in power is not greaer than that of humanity; it is just more obvious† (p. 08). By writing this book, Frans de Waal aimed to create a connection between apes and humans. His explanation of the complex social patterns that exist amongst a colony of apes in a zoo showed that chimpanzees possess a keen thought process that grants them the ability to carry out certain tasks that were previously believed to be uni que to humans. This research provides insight into the reasoning behind the chimpanzees’ actions, their motives. The rationale behind such behavior emphasize that it is not just instinct that drives them, but intelligence.

Shelley essays

Shelley essays The Romantic Period, which lasted about 45 years, gave birth to a new genre of literature, political thought, and it began a new era of history. Many authors contributed to the new ideals that characterize The Romantic Period. One author in particular was Percy Shelley who had written during The Romantic Period. The romantic ideals and characteristics can be found in the writings of Shelley. One of the ideologies of The Romantic Period was the creativity of the imagination, and Shelleys writings are littered with examples of this ideology. One example of this is in Shelleys poem To Sidmouth and Castlereagh, in this poem Shelley refers to these men as Two vipers tangled into one (20). Through this description Shelley indicates what he thinks of these two men by attributing non-human characteristics to them, and thus gives an example of the use of Shelleys imagination. Another example of Shelley giving humans non-human characteristics is in the poem Ode to the West Wind in which Shelley gives himself these characteristics as What if my leaves are falling like its own! (58) Also in the poem The flower that smiles today, Shelley gives a flower positive human characteristic, The flower that smiles today. (1) Even in the poem O World, O Life, O Time, Shelley imagines that he must deal with the challenges that each brings to him, O World, O Life, O Time, On whose last ste ps I climb. (1-2) It can be seen that Shelleys imagination provided him with a strong basis for his writings. Another characteristic of The Romantic Period that is seen in Shelleys writings is the theme of the supernatural. The mention of gods, death, or characters of myth are present throughout Shelleys works. An example of the supernatural in Shelleys poems is in the poem Alastor ...

Challenges and complexities faced by the expatriate manager when Essay

Challenges and complexities faced by the expatriate manager when managing across cultures - Essay Example Here it is time to mention that globalization brought a lot of difficulties together with opportunities, as diversity at the workplace demands new approaches to be used in human resource management. Nowadays much attention is paid to challenges and complexities faced by the expatriate manager when managing across culture. The issue is worth-discussing, thus the given paper is devoted to discussion of the main problems the manager may face and the strategies, which can be used to help him. The paper will prove that correct management and the awareness about the cultural peculiarities can help managing across culture. The movie â€Å"Outsourced† will be used as a case study to analyze the issue. It is not an easy task to manage across cultures. However, proper human resource management can help (Spataro, 2005). Correct management can help the company define beneficial approaches and find its place at the market. It is necessary each member of the company should understand his/he r functions and significance. In the modern world the organizations are anxious about the diversity issue at the workplace. The main task of the managers is to create the best environment for work, which should be based on the confidence and respect. The organization should not only take care about the working environment but also value workers’ rights. ... Global companies are beneficial for workers, as they can communicate with the representatives of other cultures; it is favorable for them in terms of developing their communicative skills and broadening the outlook. â€Å"When an organization acknowledges differences among its workforce, it can manage its employees in such a way as to create harmony in work practices and higher standards of cooperation. First, it is about understanding differences in these characteristics within an organization, and second it is about acknowledging these differences. And last, it is about developing work practices to create an inclusive environment† (McLauren). Undoubtedly, many problems can arise. One of such problem is cultural shock and difficulties in communication (Rowden, 2000). In the movie â€Å"Outsourced† Todd faced a problem of diversity. Diversity is the synonym to the word â€Å"difference†. In the modern world this term acquires much wider meaning as it is commonly used to define the workers of the company, who are different and possess unique qualities (Spreitzer, 2007). Such differences demand corresponding changes the way the company is managed. These changes are essential as the diversity creates many problems, which need to be resolved by the manager in to work successfully. In the movie â€Å"Outsourced† Todd has to manage people with quite different cultural views and first of all he has to tolerate the differences that is not an easy task. Here it is essential to mention the world â€Å"tolerance†. This term is applied to multinational companies and as a rule it has a negative meaning. The trouble is that in such staffs the employees tend not to respect each other, but rather to tolerate, because of

Putnam Essay Example | Topics and Well Written Essays - 500 words

Putnam - Essay Example I do believe that people still talk of divorce "in an almost pious reverence", but this I believe is bound to change since divorce is continuously becoming so common. The time will come when divorce will be talked about openly and sadly will be seen as a normal day-to-day happening in society. Putnam based his claims on the fact that he feels he still can depend on his parents although he gets to spend time with them separately. He has found resolution in his family's situation of which he has quaintly expressed when he wrote that "The safest environment for me was to be with one happy parent at a time, instead of two miserable ones all the time." I find the discussions in his essay convincing and supportive on his claim on what the divorce of his parents has done for him. He was able to present negative implications of the divorce and at the same time presented a clear understanding and acceptance of his living situation "with two houses to call home." 4.) Putnam has several warrants, some of them stated explicitly and some implied.

Factors Affecting Contrast In An Xray Image Health Essay

Factors Affecting Contrast In An Xray Image Health Essay To test resolution, a line pair guage is used. To measure MTF in an x-ray system, the sine wave equivalent of a line pair gauge is used. The closest distinguishable pair of cycles determines the best MTF, it is quoted in cycles per mm [2]. A common way to express the system resolution is to quote the frequency where the MTF is reduced to either 3%, 5% or 10% of the original height [3]. MTF and spatial frequency are related by MTF curves. Examples of MTF curves are given below; Mammography System: Fig 2: MTF curve for a mammography system [4]. Chest Radiography System: Fig 3: MTF curve for a typical chest X-ray. Three different detector types are indicated on the plot [5]. Fluoroscopy System: Fig 4: MTF curve for a Fluoroscopy system with plots shown for individual components of the imaging process. The film and the optics have excellent resolution. The MTF of the imge intensifier is shown to have a limiting resolution of approximately 4.8 cycles/mm. The TV camera is the worst in the series, it limits the MTF of the overall image during live fluoroscopy and videotaped imaging. [6] Question 2: Contrast is the variation in brightness or optical density across an image. Factors affecting contrast in an x-ray image include the tube output, or the kVp. This is a measure of the energy of the x-ray beam leaving the x-ray tube and passing through the patient to form an image. X-rays with higher kVp can penetrate deeper into materials. In an image with the correct kVp bone is white and soft tissues and air are gray/black. If the kVp is too high, the x-rays will pass through even dense bone, creating an image that is mostly black with indistinguishable features [7]. The opposite occurs when a kVp which is too low is used. The most suitable kVp depends on the feature under investigation. Also among the factors affecting the image contrast is the patient. The density, the atomic number Z and the thickness of the part of the patient being imaged. Denser tissue, tissue with higher Z or tissue of a greater thickness results in lighter areas on the image because they have blocked the x-r ay from exposing the image receptor. Variation in contrast occurs because tissues in the body attenuate x-rays differently. The human eye can percieve a difference of approximately 2% in contrast between adjacent areas [8]. The final influence on image contrast to be discussed here is the image receptor. In film imaging, the contrast of the resultant image depends on the sensitivity of the film used. To produce an image with the correct contrast, a film with corrresponding sensitivity must be chosen before imaging. In digital imaging, there is no fixed sensitivity. It has the advantage of being able to record the full range of exposures and digital processing after imaging can be used to improve the contrast in the image. Image contrast can be evaluated using a densiometer. This device emits light of a known energy. The light is reflected back from the image and detected by the densitometer. The difference in energy between emitted and detected light is used to compute the optical density (blackness) in that area. Since contrast is the variation in optical density, this method can be used to survey the contrast in the image. Question 3: The following description is based on an article from the NDT database [9]. Spatial resolution of an x-ray system is limitied by the size of the focal spot. Fourier analysis can be used to calculate the focal spot size. X-rays are passed through a test object with a known pattern. This test object is placed between the x-ray source and detector, the arrangement is shown in the figure below. The focal spot of the x-ray is not assumed to be point-like, as the detector is moved away from the source, the detected focal spot appears larger. Blurring of the image by the detector is included, this blurring is related to the point spread funtion (psf) of the detector. Otherwise, an ideal detector is assumed. Image deterioration due to noise is also factored into the description. Fig 5: Setup for determing the focal spot size. The X-ray source, the flat object, and the intensity distribution measured at the detector system lie in different planes for which different coordinate systems with the variables (x, y), (x, y) and (x, y) respectively, are used. This is done in order to include magnification effects in the calculations. The measurement of the x-ray transmission, t, is derived mathematically. This is done by convolving the intensity distribution of the focal spot f with the transmission profile of the flat object g and the detector point spread function d. Also, t is deteriorated by noise, which is taken into consideration by addition of a noise term n to the result of the convolution. In order to take into account the geometrical magnification, V, of the setup, these functions are represented in one of these planes (here the plane of the detector), whereby the physical magnification effects of the setup were observed before the convolution is accomplished, this is shown in the second part of the equation below. The magnification is the distance between the source and the detector system divided by the distance between the source and the object. The Convolution Theorem states that the Fourier transform of a convolution is the product of the Fourier transforms. Conversely, the Fourier transform of a product is the convolution of the Fourier transforms. Using the above equation, a deconvolution of t with gâ‚ ¬Ã‚  (â‚ ¬Ã‚  d yields an estimate of f. In a technique like this, a suitable test object is measured. The resulting image corresponds to a convolution of the test object with the intensity distribution of the focal spot and other factors. Information on the focal spot is derived from this measurement using knowledge on the test object and other influencing values which means that the convolution process is undone to a certain extent. Also, with the presented method an arbitrary two dimensional intensity distribution can be measured, regardless of shape. According to the convolution theorem, a convolution in the spatial domain corresponds to a point-by-point multiplication in the corresponding Fourier domain. Furthermore, according to the addition theorem, an addition in the spatial domain corresponds to an addition in the corresponding Fourier domain. (Note: lower case letters represent functions and upper case letters represent the Fourier transforms of the equivalent functions.) The initial equation now becomes; At certain spatial frequencies | N | can be significantly higher than| F Æ’-â‚ ¬Ã‚  P |. At these spatial frequencies division of T by P mainly increases noise and deteriorates the image quality. This is due to the fact, that information on F is lost at these spatial frequencies. For that reason, independently of the deconvolution method applied, all spatial frequencies which are contained with high intensity in | F | should be contained with high intensity in |P| in order that | FÆ’- P | is significantly larger than | N |. This means that the test object (in combination with the detector imaging properties) should contain the major spatial frequencies which are required to describe the focal spot with sufficient intensity. In this case F can be restored well at these spatial frequencies, which yields a good estimate of f. Question 4: Using a bar phantom similar to that used for determining resolution can lead to an error determining the focal spot size. This is because the line pairs are aligned in one direction only. For accurate measurement of the focal spot size, many images with the bar phantom at different angles would be necessary [10]. To overcome this problem, a star phantom is used. This is a disc of alternating Lead spokes and x-ray transparent material. At a particular diameter of the focal spot the image of the spokes blurs, i.e., adjacent spokes cannot be distinguished from each other. The diameter of the blur is an indication of the focal spot size [11]. Fig 6: Star pattern for testing focal spot size [12] Question 5: 5a. The most obvious parts of a CT scanner are the moving patient table and the gantry or tube. Conventional projection radiography is limited because it collapses 3D objects onto 2D images. CT has a rotating system of emission and detection and so it can give accurate 3D diagnostic information about the distribution of structures inside the body. Inside the gantry there is the X-ray tube, x-ray detectors and slip-rings. The X-ray beam is collimated and radiates in a fan-beam shape. The x-ray emitter and detectors rotate in the gantry to measure projections that form an image that is a slice though the body. There are brushes around the rotating slip-rings to transmit signals. In CT, the linear attenuation coefficient, ÃŽÂ ¼ is measured. This tells how much intensity is lost as the beam travels through the medium. This distribution of ÃŽÂ ¼ is the basis of image formation. There are two distinct motions of the x-ray beam relative to the patients body during CT imaging. One motion i s the scanning of the beam around the body. The other motion is the movement of the beam along the length of the body.   This is achieved by moving the body through the beam as it is rotating around Fig 7: External appearance of a CT scanner. [13] Fig 8: Basic schematic of the construction of a CT scanner. Fig 9: CT image quality and electromechanical acceptance tests. The Priority column indicates which of the tests are the most important. [14] 5b. CT images are formed by multiple intersecting projections. This is illustrated in the figure on the left. In the bottom right section, it is seen that the combination of the projections causes blurring in the final image. The blurring goes as 1/r, i.e., it is proportional to the distance from the centre point. The 2D Fourier transform of 1/r is 1/à Ã‚ . Since the inverse of 1/à Ã‚  is |à Ã‚ |, it is possible to compute the 2D Fourier Transform of the blurred image, multiply the Fourier transform of the resultant image by |à Ã‚ | and the calculate the inverse Fourier transform to obtain a sharper image [15]. Fig 10: On the left, unfiltered back projections and on the right, filtered back projections. The conversion is done in the spatial domain by convolving the projection with the IFT of |à Ã‚ |. Fig 11: The mathematics of the image reconstruction process, can be expressed compactly in the above equation, where the terms have been grouped to reflect the filtered-back-projection approach [15]. 5c. The fundamental system performance indicators are CT number, resolution, noise, and patient dose.26 The accuracy of CT numbers is measured by scanning a water-filled phantom at least monthly. The CT number for water should be zero over a 20-cm-diameter phantom, with a variation of less than 1 CT number. Deviation from the expected CT number of 0 for water at any energy is adjusted by applying a correction factor for the pixel value. Constancy of the value should be monitored with a daily scan. An overall check of system performance is obtained from semiannual measurements of CT image noise, defined as the standard deviation of CT numbers in a region of interest. Constancy of performance is checked by evaluation of the standard deviation in the daily water scan mentioned previously. Resolution is measured by scanning phantoms on a monthly basis. Of particular importance is low contrast resolution, which is a sensitive indicator of changes in component performance as they affect noise. Patient dose is evaluated semiannually. Specially designed ionization chambers provide measurements from which the dose may be calculated for the exposure conditions (narrow beam, variable slice thickness) used in CT. The values should agree with manufacturers specifications to within 20%. [hendee]