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The injection valve that we developed is to apply to the natural gas direct injection glow plug ignition engine. In the test to promote the injection valve, the injection performance was recorded good. The injection quantity of high pressure gas is controlled by rack and the spill hole diameter pertinent to the velocity of a needle valve is 0.4111111. When the injection gas is supplied by 8MPa, the proper opening pressure due to the liquid activating jerk pump was 10MPa and the quantity of needle lift that retains stable properties is between 0.1~0.2mm
매실의 낙과 피해를 일으키는 복숭아씨살이좀벌은 땅에 떨어진 핵과류 속에서 유충상태로 월동하고, 노숙유충은 이듬해 봄에 번데기를 거쳐 성충으로 우화하며, 이 성충은 매실나무의 매실핵이 경화되기 전에 산란관을 통해 산란을 함으로서 매실이 낙과하여 그 피해가 상당하다. 이 피해를 줄이고자 낙과된 매실을 수집하여 파괴하는 기계를 개발하여 사용하게 함으로서 씨살이좀벌의 성충을 줄이고, 그 피해를 저감하고자 낙과매실수집파쇄기를 개발하였다. 연구 개발된 낙과매실수집파쇄기의 결론을 요약하면 다음과 같다. 1. 충 구제약제를 살포하지 않은 유기농 매실을 생산하는 농가는 가장 큰 피해를 주는 씨살이좀벌에 의한 낙과 손실을 줄일 수 있을 것으로 사료된다. 2. 매실 과수원에서 어린잡초 위에 낙과 매실을 수집한 결과 평균 수집률이 1차 69.2%와 2차 10.5% 내외를 수집할 수 있어서 개발된 수집파쇄기를 활용하면 씨살이좀벌의 기주를 퇴치하는 기계로 그 효과가 클 것으로 사료된다. 3. 수집파쇄기의 동력원으로 소형 2행정기관을 탑재하고, 일정한 기어 감속비에 의해 축출한 동력을 V 벨트풀리를 통해 감속하여 롤 파쇄기를 회전시켜 수집된 매실 핵을 파괴하는 실험은 비교적 우수한 것으로 나타났다.
This paper deals with a study on combustion and emission characteristics of a direct injection diesel engine dual fueled with natural gas. Dual Fuelling systems tend to emit high unburned fuel especially at low load resulting in a decreased thermal efficiency. This is because natural gas-air mixtures are too lean for flame to propagate under low load conditions. Suction air quantity and injection timing controls are very useful to improve emission and thermal efficiency at low load.
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시식성 곤충상에 대한 정보의 제공과 사후경과시간(PMI) 추정 방법의 연구를 위하여 2010년 6월 2일부터 6월 30일까지 전주시 효자동 부근의 야산(음지)에서 돼지 부패실험을 실시하였다. 그 결과, 채집된 곤충상은 파리목, 딱정벌레목, 집게벌레목, 노린재목, 벌목의 총 5목 19과 33종 135개체였다. 또한 현장의 온도 변화와 6월 9일 채집하여 사육한 3령의 구더기가 6월 12일 번데기로 용화한 시간을 기준으로 PMI를 추정한 결과, 매일의 ADH(accumulated degree of hour) 값을 역산하는 방법으로는 3일 오후 8시에서 9시 사이, 성장에 사용된 시간 당 평균온도를 이용한 방법으로는 3일 오전 0시에서 오전 1시 사이로 사망시간이 추정되었으며, 실제 사망시간과는 각각 14시간과 10시간의 오차가 발생하였다. 추후 사체가 발견된 환경에 따른 적절한 추정 방법 및 오차를 줄이기 위한 추가적인 연구가 필요할 것이다. Researchers of the study initiated the experiment by burying a dead pig in the ground and then observing the decaying process for approximately a month (from June 2, 2010 to June 30, 2010) in an attempt to survey features of forensic entomology as well as Postmortem of Interval(PMI) measurement methodology. The insects collected, in terms of taxonomy, included 19 families, 33 species, 135 kingdoms and 5 orders. Participants of the study calculated PMI statistics on the basis of temperature changes collected by a movable meteorological observatory and a probe-mounted temperature recorder. Based on the hourly rate of maggot accumulation researchers concluded that the pig died between 8 and 9 p.m. of June 3’rd, but the measurement of mean temperature suggested that it took place between midnight of June 2’nd and 1 a.m. of June 3’rd. The former calculation was off by fourteen hours and the latter by ten hours. Additional study is required to reduce experimental error and to enhance methods of locating where pig carcasses are buried.
In general. FDM(finite difference method) and FVM(finite volume method) are used for analyzing the fluid flow numerically. However it is difficult to apply them to problems involving complex geometries. multi-connected domains. and complex boundary conditions. On the contrary. FEM(finite element method) with coordinates transformation for the unstructured grid is effective for the complex geometries. Most of previous studies have used commercial codes such as KIVA or STAR-CD for the flow analyses in the engine cylinder. and these codes are mostly based on the FVM. In the present study. using the FEM for three- dimensional. unsteady and incompressible Navier-Stokes equation. the velocity and pressure fields in the engine cylinder have been numerically analyzed. As a numerical algorithm. fractional step method is used and ALE (arbitrary Lagrangian Eulerian) method is adopted for moving grids
A design method of kinematic Stirling engine with rhombic-drive was proposed. The design method using a mathematical model was for determination of dimensions of important engine elements to results high performance of the engine in terms of thermal efficiency at given design conditions. The proposed design method was used to design an engine 1kW power output, and performances of the designed engine at various operating conditions were predicted by second order mathematical model to give suggestion to improve the performance of the engine. Heat transfer areas of heater, regenerator and cooler were found out as important design parameters of the engine. The design method proposed in this study was considered as desirable because magnitude of the parameters were optimized by the method with consideration of the complex interlocked effects of the parameters on the thermal efficiency of the engine. The designed engine was expected to have 0.93kW and 28.2% of brake power output and overall thermal efficiency respectively, at the design conditions of the 30% of coolant temperature, 700˚C of heater heating temperature, 3.0MPa of engine mean pressure and 2000rpm of engine speed. Performance of the designed engine in terms of thermal efficiency and power output could be improved by increasing heater heating temperature and engine mean pressure, however, it would have limits because materials of the engine was limits of resistance to high temperature and stress. Thermal efficiency of the engine could be increased by speed up the engine up to the design speed of 2000rpm.
The fields of turbomachinery and electrical generators provide many examples of flow through internal passages, at the range of Reynolds Numbers occuring in practice. The flow motion is three dimensional and highly turbulent in most of cases. An adequate understanding. for the characteristic of these turbulent flow is needed for the design of thermo-fluid machinary with a good efficiency. The effect of the curvature on th structure of turbulence in the curved passage have been extensively by many workers, but the effects of curvature have not been well understood inspite of the impotance of the phenomena in the practical design process. In this study, the characteristics of the three-dimensional turbulence flow in a square sectioned 90o bend were investigated by numerical simulation and experiment, and the results were compared with the results obtained by simulation with four near wall turbulence models and experiments.
The transfer function technique is one of the tools that have been used to analyze the noise characteristics of the exhaust muffler. In this paper we obtained a transfer function was obtained using the forward-going and backward-going component of sound pressure in the exhaust muffler, which is compatible with lattice filter algorithm. This form of transfer function to produce the transfer junction of expansion-type and insertion-type mufflers. The transfer function was used to calculate the transmission and insertion showed a good agreement, and it may be concluded that the transfer function of lattice form cam be sued to analyze the noise characteristics of the exhaust mufflers. The transfer function was also used to analyze the effects of the design parameters on the transmission loss.