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Intheapplicationsofindustrialandcommercialrefrig erationsystem ,iftherequiredrefrigerationtemperatureisverylow ,theconventionalvaporcompressionsystemisdiffi culttomeettherequirementbecausewhenthedifferencebe tweentheevaporatingtemperatureandthecondensingtemper atureissohighthatitishardtofindarefrigeranttomeettheneedsasthecondensingpressureisnottoohighandtheevap oratingpressureisnottoolow .Whentherefrigeratingtemper atureisverylow ,thecascaderefrigerationcycleissuitabletobeused .Itcannotonlysat… 相似文献
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The distribution and characteristics of nonmetallic micro-inclusions of GCrI5 bearing steel were explored through metallographic area method in virtue of tracer method and electronic microscope.The results show that the micro-inclusions,of which the average value is 0.032%,are mainly the compounds formed via the adsorption/aggregation of multielement deoxidized compounds and secondarily deoxidized products on tundish liquid level.The micro-inclusions of diameters from 0 to 5 μm are 92.5% in total,which basically determines the characteristics of inclusions distribution in casting slab.The inclusions of diameters more than 10 μm only account for less than 1% in total,which have little influence on steel quality.The relationship between equilibrium compositions of the first deoxidation products and molten steel compositions was also calculated based on thermodynamic theory. 相似文献
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Mechanicalvapourcompressioncyclesaremainlyemployedinmostrefrigerationsystems .Chlorofluoro carbons(CFCs)orhydrochlorofluorocarbons(HCFCs)aregenerallyusedasrefrigerantsinthesesystemsdrivenbyelectricityfromburningfossilfuels ,whichresultsino zonedepletionduetotheleakageandpoorrecoveryofthoseman maderefrigerants,andglobalwarmingowingtoCO2 emissionfrom powerstationsandthereasonisthatCFCsorHCFCsarepowerfulgreenhousegases.Inaddition,otherenvironmentalissuesarealsocausedbytheNOx,SO2 andpartic… 相似文献
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The study on Traditional Chinese Medicine (TCM)by the technology and method of thermal science is a new cut-in point in interdisciplinary science, and its purpose is to study the tongue inspection in TCM from the view of the bio-heat transfer theory. In this paper human tongues were studied with the infrared thermal imaging technology. And the characteristic relationship between temperature distribution and age, tongue color as well as infrared thermal tongue image concerning the characteristic of viscera was analyzed by the experimental data, which confirms that the change in temperature distribution in different positions of the tongue is related to the diseases of different internal organs of the body. From a series of invasive experiments in animals, the blood perfusion rate was measured with the equipment of CBI-8000 Doppler Blood Flow Meter and MP-100 Physiologic Research System for the first time and the characteristic relationship curve between the temperature on the surface of the tongue and the blood perfusion rate was obtained. From the experiments the temperature on the surface of the tongue reflects objectively the tongue color which is influenced by the blood perfusion rate. This will help to develop some new cognition in the theory of TCM. 相似文献
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Configuration Consideration for Expander in Transcritical Carbon Dioxide Two-Stage Compression Cycle
To investigate the configuration consideration of expander in transcritical carbon dioxide two-stage compression cycle, the best place in the cycle should be searched for to reinvest the recovery work so as to improve the system efficiency. The expander and the compressor are connected to the same shaft and integrated into one unit, with the latter being driven by the former,thus the transfer loss and leakage loss can be decreased greatly. In these systems, the expander can be either connected with the first stage compressor ( shortened as DCDL cycle) or the second stage compressor ( shortened as DCDH cycle), but the two configuration ways can get different performances. By setting up theoretical model for two kinds of expander configuration ways in the transcritical carbon dioxide two-stage compression cycle, the first and the second laws of thermodynamics are used to analyze the coefficient of performance, exergy efficiency, inter-stage pressure,discharge temperature and exergy losses of each component for the two cycles. From the model results, the performance of DCDH cycle is better than that of DCDL cycle. The analysis results are indispensable to providing a theoretical basis for practical design and operating. 相似文献
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初论一流大学与研究生院建设的关系 总被引：3，自引：0，他引：3
作者回顾了我国研究生教育２０ 年的发展史,认为研究生院的建立,为培养高层创新型人才、创建一流大学起了奠基石的作用。通过借鉴国外一流大学的办学经验,得出研究生教育的发展是建立一流大学的核心。因此,加强研究生院的建设,完善研究生院的功能对创建一流大学有着不可替代的作用 相似文献
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面向21世纪的研究生培养目标和质量保证 总被引：18，自引：2，他引：18
马一太 《学位与研究生教育》2001,(4):8-11
本文分析了进入21世纪前十年国内外人才需求的变化,提出研究生培养模式和培养目标要国际化的观点.分析了促进我国研究生培养总体水平提高和优秀人才脱颖而出的措施.从几个重要方面提出面向21世纪研究生教育和质量保证体系的构图.解情况 相似文献
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Attheendoftheyear2000,annualglobalfluo rocarbonrefrigerantemissionfrommobileandunitaryairconditioningequipmentsislikelytosurpass100000tons,correspondingtoaglobalwarmingim pactofmorethan150milliontonsofCO2.Evenlar gerindirectCO2emissionresultsfromthegeneration ofpowerconsumedtodrivethesystems[1].Within creasingfocusongreenhousegasemissionreductions,strictregulationsontheuseofsynthesizedrefrigerants suchasHCFCsandHFCsmaybeexpected,possiblyfollowedbyphase outtargetsanddates.Theinterna tionale… 相似文献
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In order to identify the locations of irreversible loss within the transcritical carbon dioxide refrigeration cycle with an expansion turbine, a method with respect to the second law of thermodynamics based on exergy analysis model is applied. The effects of heat rejection pressures, outlet temperatures of gas cooler and evaporating temperatures on the exergy loss, exergy efficiency and the coefficient of performance (COP) of the expansion turbine cycle are analyzed. It is found that the great percentages of exergy losses take place in the gas cooler and compressor. Moreover, heat rejection pressures, outlet temperatures of gas cooler and evaporating temperatures have strong influence on the exergy efficiency, COP and the exergy loss of each component. The analysis shows that there exists an optimal heat rejection pressure corresponding to the maximum exergy efficiency and COP, respectively. The results are of significance in providing theoretical basis for optimal design and the control of the transcritical carbon dioxide system with an expansion turbine. 相似文献
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新世纪高水平大学图书馆的建设 总被引：6，自引：1，他引：5
本文分析国外一流大学及其图书馆的水平，对比我国重点大学图书馆的现状，给出21世纪高水平大学图书馆建设的构图。 相似文献
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