• 한국자동차공학회논문집
• /
• 제6권6호
• /
• pp.202-209
• /
• 1998

For development of SDI(Spark-ignited Direct Injection) engine, stratified mixture formation with adequate strength at spark plug was required in wide range of engine operating conditions. So, spray structure under high ambient pressure and spray distribution after impingement on piston bowl in motoring engine was visualized by using laser equipments. Also, incylinder bulk flow structure was measured by using PIV (Paiticle Image Velocimetry) system. Counter-rotating tumble port and bowl piston was found effective to conserve bulk motion directed to spark plug in compression stroke. In addition, mask attached near valve seat in intake port was proposed to attenuate conventional tumble component and enhance counter-rotating tumble component.

• Membrane and Water Treatment
• /
• 제10권5호
• /
• pp.387-394
• /
• 2019

Membrane distillation (MD) is one of the water treatment processes which involves the momentum, heat and mass transfer through channels and membrane. In this study, CFD modeling has been used to simulate the heat and mass transfer in the direct contact membrane distillation (DCMD). Also, the effect of operating parameters on the water flux is investigated. The result shows a good agreement with the experimental result. Results indicated that, while feed temperature is increasing in the feed side, water flux improves in the permeate side. Since higher velocity leads to the higher mixing and turbulence in the feed channel, water flux rises due to this increase in the feed velocity. Moreover, results revealed that temperature polarization coefficient is rising as flow rate (velocity) increases and it is decreasing while the feed temperature increases. Lastly, the thermal efficiency of direct contact membrane distillation is defined, and results confirm that thermal efficiency improves while feed temperature increases. Also, flow rate increment results in enhancement of thermal efficiency.

• 지구물리와물리탐사
• /
• 제20권4호
• /
• pp.199-206
• /
• 2017

해상탐사에서 얻어지는 현장자료는 바람, 파도, 조류, 배경매질의 유속 등 다양한 환경요소에 영향을 받는다. 배경매질의 유속을 제외한 대부분의 환경요소는 자료처리 단계에서 적절한 보정이 이루어지고 있다. 본 연구에서는 배경매질의 유속정보가 파형역산에 미치는 영향을 분석하기 위해 배경매질의 유속정보를 고려하는 파동 방정식 모델링을 활용하여 관측자료를 생성하고, 생성된 자료를 통해 수치 실험을 진행하였다. 수치예제에는 다소 비현실적인 유속이 적용된 결과도 포함되어 있다. 이와 더불어, 탐사자료의 유속정보를 수치적 기법으로 도출하여 역산을 수행하는 알고리즘을 제안하였다. 제안된 알고리즘은 수정된 Marmousi2 모델에 적용하여 유속에 따른 결과를 얻고자 하였다. 기존의 유속을 고려하지 않은 역산 결과와 제안된 알고리즘으로 수행한 역산 결과 비교를 통해 유속의 세기가 갱신되는 물성정보에 미치는 영향을 확인하였다.

• Korea-Australia Rheology Journal
• /
• 제21권3호
• /
• pp.193-200
• /
• 2009

We present a direct simulation technique for two-dimensional mold-filling simulations of fluids filled with a large number of circular disk-like rigid particles. It is a direct simulation in that the hydrodynamic interaction between particles and fluid is fully considered. We employ a pseudo-concentration method for the evolution of the flow front and the DLM (distributed Lagrangian multipliers)-like fictitious domain method for the implicit treatment of the hydrodynamic interaction. Both methods allow the use of a fixed regular discretization during the entire computation. The discontinuous Galerkin method has been used to solve the concentration evolution equation and the rigid-ring description has been introduced for freely suspended particles. A buffer zone, the gate region of a finite area subject to the uniform velocity profile, has been introduced to put discrete particles into the computational domain avoiding any artificial discontinuity. From example problems of 450 particles, we investigated the particle motion and effects of particles on the flow for both Newtonian and shear-thinning fluid media. We report the prolonged particle movement toward the wall in case of a shear-thinning fluid, which has been interpreted with the shear rate distribution.

• 전기학회논문지
• /
• 제60권11호
• /
• pp.2076-2082
• /
• 2011

The goal of this paper is to find an operating conditions of the single direct ethanol fuel cell such as the cell temperature, and flow rates of ethanol and oxygen. To investigate the output characteristics, the electrical current increased from 0[A] with interval of 0.001[A] every 2[s], and the cell voltage was increased until the voltage became 0.05[V]. Related to the effect of the cell temperature, the output characteristics both voltage and power were increased upto 80[$^{\circ}C$] according to the increase of the current density, but those were decreased over that temperature. In addition, the optimal flow rate of ethanol in anode was identified as of 2[mL/min] due to the dependence of generation rate such as the hydrogen ion and electron. And the flow rate of oxygen in cathode was desirable to about 300[sccm/min], it might be affected by the chemical reaction rate of the water formation among hydrogen ion, electron, and oxygen. Consequently, the fundamental conditions were identified in this work, and it will be carried out to find the best conditions of membrane by the effect of the plasma surface treatment, and the effect of other catalysts except for a platinum.

• 한국전기전자재료학회논문지
• /
• 제36권5호
• /
• pp.474-481
• /
• 2023

This paper is an experimental study on the optimal operating conditions of direct charging type electrospray for particulate matter collection. To perform the research, a direct charging type electrospray visualization system was configured to photograph the spray shape of microdroplets, and experiments were performed with varying electrode distance, flow rate, and applied voltage, which are the main factors affecting the particulate matter collection efficacy. Through image processing, the total number of microdroplets according to each condition was analyzed, and the number of microdroplets with a diameter of 1.5 mm or less was confirmed. In addition, by calculating the number of microdroplets per power consumption according to the applied voltage, the optimal operating conditions were derived in terms of energy consumption efficacy, and the microdroplet size distribution was analyzed under the optimal operating conditions. As a result of the experiment, it was confirmed that the optimal operating condition was at a flow rate of 10 mL/min and a voltage of -20 kV in case of 5 mm electrode distance, and at a flow rate of 15 mL/min and a voltage of -30 kV in case of 100 mm electrode distance.

• 산업경영시스템학회지
• /
• 제41권2호
• /
• pp.47-55
• /
• 2018

The Korean Ministry of Education (MOE) required cash flow statements, instead of fund statements, as a component of the financial statements of the Industry-Academic Cooperation Foundations (IACF) when it revised IACF accounting rules in 2012. While the fund statements were aligned its accounts to the operating statements' accounts level, the newly adopted cash flow statements' accounts retreated to two levels higher than those of the operating statements. It may be resulted from the consideration that IACFs' burden of preparing cash flow statements especially in direct method. To help IACFs prepare the cash flow statements, MOE's guidance on IACF accounting rules introduced cash flow statement preparation method and presented a practical example, but it did not check whether the accounts of the cash flow statement were reconciled to the accounts of corresponding balance sheet and operating statement. That means that the guidance still lacks how to assure it was accurately prepared. Our study proposed cash flow statement preparation using reconciliation method which reconciles cash flow statement accounts' amounts to balance sheet and operating statement accounts' amounts with integrity checking and also provided a practical example by using the same case in MOE's guidance on IACF accounting rules to help IACF accounting personnel to prepare a cash flow statement efficiently.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
• /
• pp.62.1-62.1
• /
• 2005

• 한국인터넷방송통신학회논문지
• /
• 제15권4호
• /
• pp.169-175
• /
• 2015

이 연구의 목적은 모바일 학습환경에서 교수실재감, 인지적 실재감, 사회적 실재감, 서비스 질, 학습몰입과 학습 만족도 간의 구조적인 관계를 규명하는데 있다. 설문조사는 국내 W 디지털대학교에서 모바일서비스를 사용하는 학습자 255명을 대상으로 구조방정식 방법을 사용하여 분석하였다. 연구결과 인지적 실재감, 사회적 실재감, 서비스 질은 학습 몰입에 영향을 미치는 것으로 나타났고 인지적 실재감, 서비스 질, 학습몰입은 학습 만족도에 영향을 미치는 것으로 나타났다. 본 연구에서는 연구결과를 토대로 모바일러닝 환경에서 학습몰입과 학습만족도를 높이기 위한 전략을 제시하였다.

• 대한기계학회논문집B
• /
• 제26권10호
• /
• pp.1406-1418
• /
• 2002

The direct simulation Monte Carlo(DSMC) method is employed to calculate the etch rate on Al wafer. The etchant is assumed to be Cl$_2$. The etching process of an Al wafer in a helicon plasma etcher is examined by simulating molecular collisions of reactant and product. The flow field inside a plasma etch reactor is also simulated by the DSMC method fur a chlorine feed gas flow. The surface reaction on the Al wafer is simply modelled by one-step reaction: 3C1$_2$+2Allongrightarrow1 2AIC1$_3$. The gas flow inside the reactor is compared for six different nozzle locations. It is found that the flow field inside the reactor is affected by the nozzle locations. The Cl$_2$ number density on the wafer decreases as the nozzle location moves toward the side of the reactor. Also, the present numerical results show that the nozzle location 1, which is at the top of the reactor chamber, produces a higher etch rate.