• 항공우주시스템공학회지
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• 제11권5호
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• pp.6-12
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• 2017

본 논문은 75톤급 개방형(Open-cycle) 액체로켓엔진(Liquid Propellant Rocket Engine, LPRE)의 수학적 모델링 및 정상상태(Steady state)에서의 시뮬레이션을 수행한 내용을 다룬다. 액체로켓엔진의 각 구성품들은 열역학 및 동역학적 특성을 이용하여 크게 7개로 분류할 수 있으나, 본 논문의 액체로켓엔진 시뮬레이션 모델을 간단화하기 위해 열전달 모델링을 생략하여 4개의 지배방정식(Govern equation)을 이용하였다. 정상상태에서의 실험 데이터와 시뮬레이션 데이터의 오차율을 통해 모델링을 확인하였으며 공칭 작동점에서의 선형화 모델을 이용하여 안정성을 판단하였다. 또한, 시뮬레이션 모델링을 검증하기 위해 실험 데이터의 과도응답을 비교하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2000년도 제15회 학술강연회논문초록집
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• pp.16-16
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• 2000

항공기 가스 터어빈 엔진의 공기 열역학적 특성을 분석하고 예측하기 위한 simulation program이 KARI-ONEP (Korea Aerospace Research Institute -ON-design Engine Program)의 이름으로 개발되었다. 이 program은 on-design cycle analysis를 위한 것으로서 program의 수행에 필요한 엔진 구성요소별 특성 치 data인 input data를 생성하는 input data generator인 KARI-ONEPi와 cycle analysis를 수행하는 주 program인 KARI_ONEPe로 구성이 되어있다.(중략)

• 대한전기학회논문지:시스템및제어부문D
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• 제50권1호
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• pp.45-50
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• 2001

With increasing complexity of digital logic circuits, fast and accurate verification of functional behaviour becomes most critical bottleneck in meeting time-to-market requirement. This paper presents several techniques for accelerating a cycle-based logic simulation. The acceleration techniques include parallel pattern logic evaluation, circuit size reduction, and the partition of feedback loops in sequential circuits. Among all, the circuit size reduction plays a critical role in maximizing logic simulation speedup by reducing 50% of entire circuit nodes on the average. These techniques are incorporated into a levelized table-driven logic simulation system rather than a compiled-code simulation algorithm. Finally, experimental results are given to demonstrate the effectiveness of the proposed acceleration techniques. Experimental results show more than 27 times performance improvement over single pattern levelized logic simulation.

• 한국분무공학회지
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• 제21권1호
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• pp.7-12
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• 2016

In this study, to research in-cylinder flow characteristics of spark-ignited engine with intake valve closing timing change for Miller cycle. 3D simulation study were used 6 different intake valve profile with $CAD10^{\circ}$ gap for retard intake valve closing timing. Comparison of In-cylinder flow pattern characteristic were accompanied between Base and LIVC. And the efficiency of volume and the work of compression were analyzed with simulation study. When intake valve closing angle was retarded in $CAD50^{\circ}$, the pressure in cylinder was decreased about 12~13 bar and volume efficiency was reduced about 16%. The efficiency of volume and the work of compression were reduced on LIVC.

• 설비공학논문집
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• 제7권3호
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• pp.488-500
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• 1995

An air-cooled ammonia/water GAX(Generator-Absorber heat eXchange) absorption cooling cycle is proposed and its performance is numerically evaluated. It is shown that the performance of the system is greatly dependent on the quality of the refrigerant leaving the evaporator. For any refrigerant concentration in the investigated range(99.1~99.9% ammonia), the cycle COP(coefficient of performance) reaches the highest value, when some amount(about 7%) of refrigerant evaporates in the refrigerant heat exchanger. Among temperature differences in various heat exchangers, the temperature difference between GAX-absorber and the GAX-generator shows the greatest effect on the system performance, whereas pressure losses cause no significant decrease in COP. The system COP increases almost linearly with increasing evaporator temperature, decreasing absorber temperature or decreasing condenser temperature. If both absorber and condenser temperature increase simultaneously, the decrease in the COP becomes larger.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.835-840
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• 2009

Lately, Building Information Modeling (BIM) emerges as the most promising technology, now is expected to bring a great deal of improvement of productivity in every aspect of the construction industry. One of the BIM based scheduling is to use BIM model as a base for applying to schedule analysis and simulation tools. This type of tools may incorporate a various types of information such as the building model, construction method information, resource information, productivity information, rules and constraints to optimize activity sequencing. This paper proposes a framework of BIM based simulating system which can be used to optimize construction processes, especially for the floor construction cycle. For the purpose, all of the necessary components of the system will be defined and represented, and next an algorithm will be introduced to demonstrate the principle of simulating operation. The benefits of this technique are basically two : to test and optimize construction methods in respect of the construction duration and to reduce the floor construction cycle.

• 대한기계학회논문집B
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• 제26권9호
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• pp.1241-1248
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• 2002

Performance extension of the absorption refrigerator with LiBr solution is often faced to operate very close to the crystallization limit. Especially in the development of an air-cooled cycle, the crystallization of working solution in the system is a very difficult problem to overcome. This paper describes the cycle of hot water driven absorption system using a new working absorption solution instead of LiBr solution to improve the efficiency. In this study, we found out the characteristics of new working absorption solution through the cycle simulation and compared LiBr solution to evaluate. The effect of cooling water temperature, weak solution flow rate, hot water temperature and hot water flow rate were also examined. The COP is increased 22% higher in the case of LiBr＋Li1＋LiC1＋LiNO$_3$＋$H_2O$, 2% LiBr＋HO(CH$_2$)$_3$OH＋$H_2O$ than that of LiBr solution for the same operation condition.

• 한국물환경학회지
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• 제26권4호
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• pp.691-699
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• 2010

In recent years, increases in impervious areas with rapid urbanization and land use changes are causing numerous hydrologic cycle and environmental problems. Impermeable pavement have a various defect such as collection rainwater, decreasing of sliding resistance, and etc. In this study, the hydrologic cycle effect of permeable pavement were analyzed by the experiment and the numerical simulation. The numerical model used was a modified SWMM especially for considering the hydrologic cycle effect of permeable pavement. The parameters of modified SWMM were revised by the experimental results. Also, the effects of runoff quantity reduction are reviewed when permeable pavement is applied to Incheon Cheongna watershed. The hydrologic cycle analysis of Incheon Cheongna watershed, continuous simulations of urban runoff were performed. The analysis results of permeable pavement setup effect on runoff are follows: the surface runoff after permeable pavement setup decreases to 74.35% of the precipitation whereas the surface runoff before permeable pavement setup amounts to 81.38% of the precipitation; the infiltration after permeable pavement setup increases to 15.13% of the precipitation whereas the infiltration before permeable pavement setup amounts to 8.32% of the precipitation.

• 설비공학논문집
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• 제10권6호
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• pp.753-762
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• 1998

A domestic refrigerator is composed of many components such as a compressor, evaporator, capillary tube, and the cabinet which plays a great role on the cycle performance, even if it is not the basic component part in the cycle. Recently, the restriction policy on the energy-saving and environmentally friendly refrigerator is reinforced in our nation as well as developed countries. Therefore, in this paper, cycle simulations and experiments were carried out ito understand the characteristics of the cycle performance using CFC 12, HFC 134a, and HC 600a and to know how changes in UA(overall heat transfer coefficients$\times$ heat transfer area) of evaporator, the position displacement of compressor, and the rpm of fan in the freezing room which has influence on the cycle performance. The result shows that the quantitative values of simulation and experiment are not coincident, but their trend is similar. When HFC 134a and HC 600a were used without the change of design in refrigerator used CFC 12, the performance of system in HC 600a is 30% lower, and the case of HFC 134a is 10% lower than that of CFC 12 on freezing temperature.

• 한국수자원학회논문집
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• 제38권6호
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• pp.449-460
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• 2005

본 연구에서는 전형적인 도시하천으로 왜곡된 물순환을 보이는 도림천 유역에 대해서 WEP(Water and Energy transfer Processes) 모형을 이용하여 물순환 모의를 수행하였다. 과거(l975년)와 현재(2000년)의 토지이용도를 이용한 모의를 통해 도시화에 의한 불투수율 증가가 유출특성에 미치는 영향을 분석하였으며, 모의결과 도시의 개발로 인해 과거보다 첨두 도달시간은 감소하고, 첨두 및 총유출량이 증가한 것으로 나타났으며, 침투량과 기저유출량이 감소한 것을 확인할 수 있었다. 또한 왜곡된 물순환을 회복하기 위한 대안으로 침투트랜치와 투수성 포장재의 설치 효과에 대한 모의를 수행하였으며, 모의결과 두 가지 대안을 함께 적용했을 경우에 도시개발 이전의 유출특성에 근접하는 것을 확인할 수 있었다.