 Wysłany: Śro 17:33, 19 Cze 2013 Temat postu: |
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| Unlike most other technological factors, CT scanner x-ray tubes on multislice CT scanners positively benefit, since the load to the tube is reduced by the use of a multislice detector. In this aspect, the CT scanner x-ray tube for multislice CT does not necessarily have to be a larger one. However, the situation may be totally different when faster rotation is used in combination with a multislice detector system. Because of these challenging specifications,hollister, entirely new tube designs are required for the purposes of precision,abercrombie france, safety and product life.
The heat capacity of the CT scanner x-ray tube is more or less proportional to its size or mass and a characteristic of the material known as the specific heat. As heat is added to an object, the temperature increases in proportion to the amount of heat added. When a given amount of heat is added, the temperature increase is inversely proportional to the anode of the CT scanner x-ray tube heat capacity. In an anode with a large heat capacity, the temperature rise is smaller than in one with a small heat capacity. In other words, the temperature of the anode is determined by the relationship between its heat content and its heat capacity. X-Rays and the Relationship to Produced Heat. In order to evaluate the problem of the CT scanner x-ray tube heating, it is necessary to understand the relationship of three physical quantities: heat, temperature and heat capacity. Heat is a form of energy and can be expressed in energy units. The most current CT scanning techniques place a high heat load on the CT scanner x-ray tube, due to the need for high tube current values to provide enough photons in the image, when scanning with fast rotations and fine slices. Increasing rates of patient obesity mean that the size of the average patient is an added burden on the x-ray tube, as higher tube currents need to be used in order to generate enough photons to give reasonable image quality. To scan a sufficiently long length, while avoiding overheating, CT scanner x-ray tubes have generally been developed to have high anode heat capacities and high cooling rates. Some designs have low anode heat capacities, but very high cooling rates to compensate. These two specifications of the CT scanners x-ray tubes: heat capacity and cooling rate need to be jointly considered in order to assess the overall heat load capability. Examples of designs of CT scanner x-ray tubes that improve cooling rates are: spiral-groove bearings with liquid metal lubrication, and anodes with direct oil cooling. The future demands of computed tomography imaging, regarding the x-ray source,louboutin, can be summed as follows: increased scan power, shorter rotation times, shorter cool-down times and smaller focal spots,louboutin, all highly beneficial to the patient and the physician in diagnosis and treatment. X-Ray Tubes in Multislice CT Scanners. Author's Bio: Heat is produced in the focal spot area on the rotating anode of the CT scanner x-ray tubes by the bombarding electrons from the cathode. Since only a small fraction of the electronic energy is converted in x-radiation,louboutin pas cher, it can be ignored in heat calculations. We will assume all of the electron energy is converted into heat. In a single exposure,ralph lauren, the quantity of heat produced in the focal spot area is given by the general expression: Heat = Anode Potential * MAS By scott carlos See all Articles by Thomas CableGet Updates on Medical Advice and ResourcesGet Updates on Thomas Cable Average: 0 Your rating: None Tweet The heat produced during x-ray production can be a limiting factor in CT scanning,abercrombie and fitch, especially with spiral scanning of relatively large anatomical regions. Improved Technologies Lead to Challenging Tasks for CT Scanner X-Ray Tubes. Relationships Between Heat, Temperature and Heat Capacity. Temperature is the physical quantity associated with an object that indicates its relative heat content. Temperature is specified in units of degrees. Physical changes, such as melting, are directly related to an object's temperature rather than its heat content. As for any given object, the relationship between temperature and heat content of the anode of the CT scanner x-ray tube involves a third quantity: heat capacity, which is characteristic of the anode. The range of the heat capacity of modern multislice CT scanner x-ray tubes is from several mega-heat-units up to 8 mega-heat-units,hollister. Heat dissipation rate of the largest CT scanner x-ray tubes peaks at over 2000 kilo-heat-units per minute. The heat is produced in the focal spot on the anode. From this area, the heat moves by conduction throughout the anode body and by radiation to the tube housing; heat is also transferred, by radiation, from the anode body to the tube housing. Heat is removed from the tube housing by transfer to the surrounding cooling medium. When the tube is in operation,hollister uk, heat generally flows into and out of the three areas mentioned above. Damage can occur if the heat content of any area exceeds its maximum heat capacity. To produce x-ray,hogan, relatively large amounts of electrical energy must be transferred to the x-ray tube. Only a small fraction of the energy deposited in the CT scanner x-ray tube is converted into x-rays; most appears in the form of heat. This places a limitation on the use of CT scanner x-ray tubes. If excessive heat is produced in the CT scanner x-ray tube, the temperature will rise above critical values, and the CT scanner x-ray tube can be damaged. This damage can be in the form of a melted anode or ruptured tube housing. In order to prevent this damage,cheap nfl jerseys, the CT scanner operator must be aware of the quantity of heat produced and its relationship to the heat capacity of the CT scanner x-ray tube. The Future of CT Scanner X-Ray Tubes. The general relationship can be expressed as follows: Heat = Heat Capacity * Temperature One of the major challenges in developing CT scanner x-ray tubes for contemporary,louboutin, high-performance CT scanners is to provide design features to accommodate the high levels of heat produced. 相关的主题文章： By John Mepham smart card chips In the 2000 election I also worked summer basketball camps for Jud Heathcote at Michigan State and Bill Foster at Northwestern. I saw Tom Izzo when he was just beginning his coaching career at Michigan State, along with Mike Deane. |
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| Wysłany: Nie 13:06, 16 Cze 2013 Temat postu: |
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| Borrowing costs, comprising of interest charges and loan fees, are significantly higher for poor credit recipient when equivalence to consumer with better and excellent credit .Always being in double digit,ralph lauren, interest charge on private loans for poor credit often exceed 20% mark. Should you consider obtaining a poor credit loan ,do not get amazed by huge monthly payment and inflated cost or lending. To avoid the disappointment,abercrombie, it is recommended to reckon huge lending cost as an investment into better credit ,as a online bad credit loans help you rebuild the history of timely payments ,driving your scores up,hollister,and making it simpler to specify for loans with finer rates and terms in future.
People with online bad credit usually have their hands tied once it comes to obtaining cash in forms of loans and lines of credit. Because recipient with negative payment histories pose a huge risk to investors,air jordan, many banks and borrowing institutions easily ignore to loan cash to individual with online bad credit loan.However,there are growing numbers of investors,hollister, attracted by higher cash making opportunities in online bad credit market,louboutin, that are able to underwrite loans specifically geared towards consumers with derogatory credit record .Higher interest rates and loan fees drive more investor to reckon smaller credit scores for successful loan application,abercrombie france, often making good return on investment and getting a loyal consumer base. Unsecured loans only need a signature of the recipient with security interest requirement waived. That is why they are usually called signature loans. In case of online bad credit,scarpe hogan, a co-signer with a better credit is frequently needed in order to get a signature loan.Cosigner serves as an additional layer of protection to the investor, as consigning a loan comes with responsibility of loan refund should a principal recipient fail to pay. Anybody could be a co-signer, and recipient usually enquires their friends, parents, or relatives to consign on a loan. It is noteworthy that should your credit only have minor blemishes or should the loan sum be low, a co-signer may not be required. Author',louboutin;s Bio: Like loans available to better credit recipient, poor credit personal loans come in secured and unsecured forms. Secured loans, usually backed by the equity in the real estate that you own, are frequently the almost favourable form of lending,louboutin pas cher, as they feature lower interest charge and have lower qualification standards. A lien is located on the property used a security interest in order to get a secured poor credit loan. While such loans provide fine terms, they also pose a venture of losing security interest in case of a default. That is why unsecured private loans for online bad credit are obtaining increasingly popular. By Mark Fulton See all Articles by Mark FultonGet Updates on Financial FreedomGet Updates on Mark Fulton Average: 0 Your rating: None Tweet Typically, private loans for poor credit may be utilized for any intention you desire. Most individual take them out to economic huge purchases, such as furniture, cars, or appliances,louboutin pas cher, consolidate debts, or catch up on overdue bills and patch some holes in the budget. It is not advisable though,abercrombie, to blow the loan proceeds on something you do not require ,as the price sticker you will have to pay is too high ,due to huge loan charges. 相关的主题文章: 0 Your rating How it can be improved 0 Your rating Consider who/what you are working towards very carefully. Sometimes the best way to figure out what we do want is through a serious examination of what it is that we do not want! Write out lists, pros and cons etc. |
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