본 연구는 여섯 개의 서로 다른 쉘로우 딤플(Shallow Dimple)에 의해 나타나는 유동구조 특성에 대한 연구결과을 기술하였다.(쉘로우 딤플(SD), 실린더 딤플(CD), 도우넛 딤플(DD), V자형 딤플(WD), 역방향 실린더 딤플(BCD), 역방향 V자형 딤플(BWD)). 딤플은 복잡하지 않은 제작절차를 비교적 요구하며 압력손실도 상대적으로 적으므로 사각 립(rectangular rib), 실린더와 같은 여러 가지 형상에 비해 열전달 손실을 줄이고 열전달 증대시키는 효과적인 장치이다. 본 연구결과을 통하여 여러 가지 딤플 형상에 따라 서로 다른 와류구조가 딤플의 중앙과 가장자리에서 생성, 발달, 소멸을 주기적으로 반복 발생되고 있음을 파악하였으며, 딤플의 중앙부위에서 와류가 발생할 때에는 서로 다른 딤플형상에서 7-9 Hz의 유사한 발산주기가 발생하였다. 또한, 압력손실정도를 파악하기 위한 마찰계수비는 최대 1.24, 최소 1.13으로 나타났으며 역방향 V자형 딤플이 가장 크고, 도우넛 딤플의 경우가 가장 적었다. 따라서, 서로 다른 딤플형상에서 발생되는 유동구조특성을 비교한 결과 쉘로우 딤플, 역방향 V자형 딤플 및 도우넛 딤플형상이 가장 큰 열전달을 증가시키는 것으로 나타났다.

Our environment is faced with serious problems related to the air pollution from automobiles in these days. In particular, the exhaust emissions of diesel engines are recognized as main causes of the air pollution. DI diesel engine is widely used for the sake of minimization on exhaust emission. Because biodiesel fuel is a renewable and alternative fuel for diesel engine, its usability is expanded. The smoke emission of esterfied rapeseed oil is reduced remarkably in comparison with commercial gas oil, that is, it was reduced approximately 44.5% at 1500rpm. But, brake specific energy consumption showed very slight differences. It was concluded that esterfied rapeseed oil can utilize effectively as an alternative and renew-able fuel for diesel engine.

The potential possibility of oxygenated fuel for di-ether group oxygenated additives such as Methyl tertiary butyl ether(MTBE) and diethylene glycol dimethyl ether(DGM) were investigated for the sake of exhausted smoke reduction from diesel engine. They include oxygen content approximately from 18% to 36%, it is a kind of oxygenated fuel that the smoke emission of them is reduced remarkably compared with commercial diesel fuel. In the experiment by gas chromatography, unburned hydrocarbons of oxygenated fuel were reduced than those of commercial diesel fuel.

From the HCN observations of dense molecular cloud L694-2, Lee et al.(2007) determined internal distributions of density and velocity for the cloud. The density profile collaborates roughly with the Bonnor- Ebert gas sphere, but the velocity field departs significantly from the result of numerical simulations that are started from the BE sphere. Taking L694-2 as an example of collapsing clouds, we have performed a series of collapse simulations and determined initial configurations for the cloud in such a way that the resulting density and velocity profiles both match with the empirically deduced ones. Among many trial configurations the cloud which is initially uniform in density and bound by an expanding envelop depicts most closely the empirically obtained profiles of both density and velocity.