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Silicon alkoxides(TEOS:tetraethylorthosilicate and TMOS:tetramethylorthosilicate) were synthesized from silicon tetrachloride and ethanol or methanol with the variation of the mole ratio (alcohol/SiCl_4) and the water contents in the alcohol. The optimum mole ratios of alcohol/SiCl_4 were measured to be betweem 4 and 5 and the reactions completed within one hour. The yield of TEOS decreased from 70% to 48% as the water contents increased from 0.1% to 1.0% in ethanol.
컴포넌트 기술은 소프트웨어를 신속하고, 효과적으로 개발할 수 있는 대안으로 90년대 초반부터 각광을 받기 시작하였다. 이러한 컴포넌트 기술을 활용하는 컴포넌트 기반 개발 방법론이 현재까지 소프트웨어 산업에서의 새로운 대안으로 인식되고 있다. 현재 산업계에서는 컴포넌트 기반 개발 프레임워크 중의 하나인 J2EE를 적용한 개발이 많아지고 있다. 이는 J2EE가 단순히 컴포넌트 기반의 어플리케이션을 구현할 수 있는 수단이 될 뿐만 아니라 어플리케이션 개발 시 제공해야 하는 많은 서비스들을 J2EE 플랫폼을 통해 제공하기 때문이다. 그러나 J2EE 컴포넌트를 테스트하는 것은 기존의 자바 클래스의 테스트보다 더 많은 노력이 필요하고, 어려운 작업이기 때문에 많은 경우에 충분한 테스트를 수행하지 않는다. 많은 개발자들이 J2EE/EJB 컴포넌트를 개발할 때 고려해야 할 사항과 채택해야 하는 테스트 전략에 관해서 알지 못하기 때문이다. 이에 본 논문에서는 기존의 J2EE/EJB 컴포넌트 개발 시 고려해야 할 사항과 테스트 전략에 대해 살펴본다. Component technologies which enable quickly and effectively to develop softwares have begun to come into the spotlight since early 1990s. Nowadays a component-based development methodology using the component technologies is recognized as a new alternative to improve productivity in the software industries. Currently, a number of software development works are performed on a J2EE environment, one of component-based development frameworks. This phenomena arises from J2EE's versatility. A J2EE framework provides plentiful services required to develop component-based softwares. Thus the developers only concentrate on the implementations of business logics. But component testing is a very difficult task since it requires more efforts than the previous Java class testing. So many developers do not perform enough testing works. In fact, many developers do not know about considerations needed to implement EJB components and testing strategies used to verify the components. This paper introduces systematically testing strategies for EJB component test.
The non-manifold geometric modeling technique enables designers to handle wireframe models, surface models and solid models in a single data structure. The Euler operation is making and deleting topological entities according to the Euler-Poincare formula, so, we can make valid models. In this study, we compose a non-manifold modeling data structure and implementation the Euler operators using the composed data structure. Data structure is based on Weiler's radial-edge data structure and Euler operation is based on Euler formuler suggested by Yamaguchi. For application, we implemented the data strucrue and the Model Editor which is composed of Euler operators by using the SGI workstation, C++ language and Open Inventor.
As the use of hot water in multifamily housing in Korea increases, it is desirable to apply solar hot water(SHW) system into apartments to save energy used for hot water. The study aims to evaluate the energy saving sffect of the solar hot water collectors in multifamily housing. First, the energy costs for hot water in selected 31 pyung apartment were surveyed. Actual SHW system were installed and then the their performance in terms of water temperature and flow rate was monitored. Form the survey and the experiment it found that the use of the solar hot water system applied in the apartments contributes to the enegy saving ofabout over 10%
The objective of this study is to develop a PC level freeform surface modeling system which explicitly represents information of part geometry. In this study, freeform surface modeling system consist of three modules; freeform surface modeler, input/output modules and interface with Database. Surface modeler uses nonuniform rational B-spline(NURBS) function with nonuniform knot vector for the flexible modeling work. This presentation scheme is extended easily to represent other attributes such as machining and surface modification. In addition, interface with database is achieved, which provides a natural and efficient method for manipulating a part and improves the design environment.
The performance of moisture removal system is investigated analytically and experimentally. The program for the moist air calculation and for the condensing tube design are developed to examine the factors which affect moisture removal rate. Experimental apparatus comprises condensing tube, cooling system, vacuum pump, measurement and control devices. Thermoelectric cooling system and vapor compression refrigeration system are used to cool the air, and the performance of two systems are compared each other. Thermoelectric cooling system is compact and free from noise and vibration, but cooling rate of it is relatively slow compared to that of vapor compression refrigeration system. Air velocity, indoor temperature and humidity, temperature of coolant, size and material of condensing tube are found to affect the performance of moisture removal.
Burning velocities of propane-air mixtures were experimentally investigated in a constant-volume combustion chamber. The propane-air mixture was prepared by controlling partial pressures. Flame propagation process was observed as a function of mixture strength. A spherical combustion chamber contains a pair of parallel windows through which optical access into the chamber can be provided. Laser two beam deflection method was adopted to measure the local flame propagation, which gave information on the flame size and flame propagation speed. Pressure development was also measured by a piezoelectric pressure transducer to characterize combustion in quiescent mixtures. Burning velocity was calculated from flame propagation speed and pressure measurements. In this experiment, the values of flame speed are within totally 1.1% error range including 0.5% location error and 1% visual error. Laser two beam method was found to be feasible in measuring flame propagation in that the measured values are comparable to the available data in literatures.
Polypropylene(PP)에 대한 maleic anhydried(MAH)의 그래프트 반응에서 그래프트율을 향상시킬 수 있는 조건으로 괴상중합과 용액중합형태를 비교하여 반응특성을 조사하였다. 비슷한 양의 자유라디칼 개시종을 형성하는 조건에서 괴상중합이 용액중합보다 높은 그래프트율을 나타내었다. 괴상중합조건에서는 반응온도와 반응시간이 최적조건과 관련이 있음을 확인할 수 있었다. 그래프트 반응에 사용되지 못한 MAH의 형태를 여과액으로부터 분리하여 열중량분석한 결과 괴상중합의 경우 미반응 MAH보다는 단일중합체상태의 poly(maleic anhydride)(MAH)로 주로 존재하였다. 따라서 더 높은 그래프트율을 얻기 위해서는 PMAH의 생성반응을 억제하는 조건의 모색이 필요할 것으로 판단되었다. The grafting reaction characteristics was investigated for the bulk and solution-type grafting of maleic anhydride(MAH) to polypropylene(PP) in order to find the optimum condition of the enhanced graft yield. Bulk-type grafting showed the higher graft yield under the condition of almost similar amount of free radical active sites formed. Reaction temperature and time were believed to have a close relation with the optimum condition of bulk-type grafting. MAH which was not grafted was separated from the filtrate and was analysed by thermogravimetry. Poly(meleic anhydride) (PMAH), the homopolymer of MAH, was the main component of the non-grafted MAH for the bulk-type grafting. Therefore the enhanced graft yield seems to be obtained possibly by suppressing the homopolymerization of MAH for the bulk-type grafting.