• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.5-13
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• 2017

To lunch the Korea Space Launch Vehicle-II(KSLV-II), the second launch complex will be constructed on the Naro Space Center and Kerosene Filling System (KFS) will be also installed newly. KFS of KSLV-II launch complex system is being designed based on Naro Launch Complex. But this must supply fuel to fuel tanks of the vehicle with only a supply pump because KSLV-II is a 3-stage launch vehicle unlike Naro Launch Vehicle or Test Launch Vehicle (TLV). A sudden rise of pump output pressure is recognized during fuel filling scenario selection process. This occurs because return flow can not actively deal with a lot of flow change using flow control method of orifice type. To solve this problem, it is verified that fuel can be stably supplied by installation of accumulator and an appropriate adjustment of filling mode change sequence through flow analysis of various cases.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.5
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• pp.132-140
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• 2018

To lunch the Korea Space Launch Vehicle-II(KSLV-II), a second launch complex will be built at the Naro Space Center, and a Kerosene Filling System (KFS) will be installed. KFS of KSLV-II launch complex system is being designed based on Naro Launch Complex. But this must supply fuel to fuel tanks of the vehicle with only a supply pump because KSLV-II is a 3-stage launch vehicle unlike Naro Launch Vehicle or Test Launch Vehicle (TLV). A sudden rise of pump output pressure is recognized during fuel filling scenario selection process. This occurs because return flow can not actively deal with much flow change using the orifice-type flow-control method. To solve this problem, it is verified that fuel can be stably supplied by installing an accumulator, designed for appropriate adjustment of filling-mode change sequence via flow analysis of various cases.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.6
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• pp.666-671
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• 2023

As international environmental regulations on ship emissions are gradually strengthened, interest in electric propulsion and hybrid propulsion ships is increasing, and various solutions are being developed and applied to these ships, especially stabilization of the power system and system efficiency. The direct current distribution system is being applied as a way to increase the power. In addition, verification and testing of safety and performance of marine DC distribution systems is required. As a result of establishing a DC distribution test bed, verifying the performance of the DC distribution (variable speed power generation) system, and analyzing fuel consumption, this study applied a variable speed power generation system that is applied to DC power distribution for ships, and converted the power output from the generator into a rectifier. A system was developed to convert direct current power to connect to the system and monitor and control these devices. Through tests using this DC distribution system, the maximum voltage was 751.5V and the minimum voltage was 731.4V, and the voltage fluctuation rate was 2.7%, confirming that the voltage is stably supplied within 3%, and a variable speed power generation system was installed according to load fluctuations. When applied, it was confirmed through testing that fuel consumption could be reduced by more than 20% depending on the section compared to the existing constant speed power generation system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.794-801
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• 2017

When a radial wheel is placed so as to partially overlap a conductive plate and rotated, a lift force is generated on the wheel, a thrust force along the edge, and a lateral force which tends to reduce the overlap region. When several of these wheels are combined, it is possible to realize a system in which the stability of the remaining axes is ensured, except in the traveling direction. To validate the overall characteristics of the multi-wheel system, we propose a transfer system levitated magnetically using radial electrodynamic wheels. The proposed system is floated and propelled by four wheels and arranged in a structure that allows the thrusts generated by the front and rear wheels to offset each other. The dynamic stability of the wheel and the effect of the pole number on the three-axial forces are analyzed by the finite element method. At this time, the thrust and levitation force are strongly coupled, and the only factor affecting them is the wheel rotation speed. Therefore, in order to control these two forces independently, we make use of the fact that the ratio of the thrust to the levitation force is proportional to the velocity and is independent of the size of the gap. The in-plane and out-of-plane motion control of the system is achieved by this control method and compared with the simulation results. The experimental results show that the coupled degrees of freedom can be effectively controlled by the wheel speed alone.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.9
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• pp.795-801
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• 2014

STEP Cube Lab. classified as a pico-satellite has been being developed by SSTL(Space Technology Synthesis Laboratory) in Chosun University. Its main mission objective is to perform the on-orbit verification of core space technologies, which will be the potential candidates for future space missions. In this paper, to guarantee successful mission operation of the cube satellite under extremely severe space thermal environment condition, the system level thermal design and analysis has been performed. The effectiveness of the design has been verified through on-orbit thermal analysis of cube satellite.

• Journal of Korean Society of Transportation
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• v.22 no.3 s.74
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• pp.145-157
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• 2004

The cycle length design model of the Korean traffic responsive signal control systems is devised to vary a cycle length as a response to changes in traffic demand in real time by utilizing parameters specified by a system operator and such field information as degrees of saturation of through phases. Since no explicit guideline is provided to a system operator, the system tends to include ambiguity in terms of the system optimization. In addition, the cycle lengths produced by the existing model have yet been verified if they are comparable to the ones minimizing delay. This paper presents the studies conducted (1) to find shortcomings embedded in the existing model by comparing the cycle lengths produced by the model against the ones minimizing delay and (2) to propose a new direction to design a cycle length minimizing delay and excluding such operator oriented parameters. It was found from the study that the cycle lengths from the existing model fail to minimize delay and promote intersection operational conditions to be unsatisfied when traffic volume is low, due to the feature of the changed target operational volume-to-capacity ratio embedded in the model. The 64 different neural network based cycle length design models were developed based on simulation data surrogating field data. The CORSIM optimal cycle lengths minimizing delay were found through the COST software developed for the study. COST searches for the CORSIM optimal cycle length minimizing delay with a heuristic searching method, a hybrid genetic algorithm. Among 64 models, the best one producing cycle lengths close enough to the optimal was selected through statistical tests. It was found from the verification test that the best model designs a cycle length as similar pattern to the ones minimizing delay. The cycle lengths from the proposed model are comparable to the ones from TRANSYT-7F.

• Journal of KSNVE
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• v.5 no.3
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• pp.275-283
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• 1995

본 글에서는 지능구조물의 개념설명과 더불어 ERF의 특성, ERF를 함유란 함유 한 지능구조물 시스템의 구성, 동적 모델링과 진동제어 그리고 그 응용성에 관한 연구 현황과 방향에 대해 살펴보았다. 설명한 바와 같이 지능구조물은 새로운 차원의 신생 하는 첨단분야로서, 소음 및 진동에 관련된 무한한 잠재력과 다양한 응용성으로 미루 어 볼때 아주 매력적인 연구 분야이다. 그러나, 여러 응용 시스템의 상품화 단계로의 도약에 있어서 각 시스템 구성 요소 분야별 해결해야할 연구 사항들이 있다. 먼저, 액추에이팅을 수행하는 ERF 자체의 내구성 문제로서 고온에서 ERF의 효과 하락과 장시간 사용시 ERF에 의한 마멸, 고체 입자의 침전에 의한 초기 상태 불안정 등이 있다. 아울러 기존의 장치의 성능을 능가하기 위해 보다 큰 효과를 나타내는 새로운 차원의 ERF개발이 요구된다. 그리고 센서기술 분야에서는 호스트 재료에 보다 쉽게 결합이 되고 여러가지 형태의 요구조건을 만족시킬 수 있으며 외부 환경조건에 강건 하고 다양한 센서 개발이 요구된다. 또한, 보다 일번적인 동적 모델링을 통해 적용 시스템에 적합하고 강건한 제어기에 대한 연구가 진행되어야 한다. 마지막으로 능동 제어기를 실제로 구현하기 위한 호스트 재료 각 요소마다 센서의 설치, 페회로 피드백 시스템 장착, 상호간의 인터페이스 등의 기술 발전이 요구되며, 아울러 보다 효율적 인 시스템의 성능 특성을 실현할 수 있는 호스트 재료와 기계 메카니즘이 필요로 된다. 이상의 설명에서 알 수 있듯이 지능구조물에 대한 연구는 어느 한 분야에서만 아니라 기계, 전기전자, 토목, 물리, 재료과학 등 통합형식에 의한 접근 방향으로 추진되어야 할 것이다.서 세탁기의 진동 소음을 저감시키기 위해 진동 소음원에 대해 논술하고, 진동해석을 위해 컴퓨터 시뮬레이션 결과를 이용한 저진동 기술 개발에 대하여 기술하고자 한다.rotary piston)식 압축기는 약 20여년 전 부터 냉방용 압축기에서부터 널리 쓰이게 되었다. 약 10여년전부터 상용화 된 스크롤(scroll) 형 압축기도 현재 상대적으로 용량이 큰 가정용 냉방기를 중심으로 많이 쓰이고 있다. 스크류형 압축기는 보통 중대형 상업용에 주로 쓰인다. 해결하려 하였고, 수치해석은 피스톤의 운동을 배제한 단순화한 흡배기계의 정상상태 유동해석이 주를 이루어왔다. Taghaui and Dupont 등[5]은 KIVA코드를 사용하여 흡기포트와 연소실 그리고 밸브의 움직임을 동시에 고려한 수치해석을 도입하였다. 하지만 이들이 밸브의 운동을 고려하기 위해 사용한 이동격자는 격자점은 시간에 따라 변화하지만 그 격자의 수가 일정하게 유지되어 있어서 밸브의 완전개폐를 해석할 수가 없다. 강희정[6]은 단일 실린더와 단일 배기밸브를 갖는 문제로 단순화하여 피스톤과 밸브의 움직임을 고려하므로써 배기행정 후 소음이 어떻게 전파해 나가는가를 연구하였다. 본 연구에서도 최소밸브간격과 최대밸브간격 사이에서만 계산이 가능하나 흡기의 경우는 밸브가 닫힐 때 생기는 압력파가 중요하므로 실린더와 밸브사이에 벽면조건을 주어 밸브의 개폐를 모사하였다.술을 보유하고자 한다. 이용한 해마의 부피측정은 해마경화증 환자의 진단에 있어 육안적인 MR 진단이 어려운 제한된 경우에만 실제적 도움을 줄 수 있는 보조적인 방법으로 생각된다.ofile whereas relaxivity at high field is not affected by τS.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.849-860
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• 2019

This paper is a study on the development of equipment system to obtain data on stability in excavation of sharp curve section of Shield TBM. Shield TBM equipment is being used a lot recently for tunnel excavation. Excavation may result in inevitable detours by buildings above the ground or existing underground structures. Preconstruction simulation is required to verify the stability of the construction in case of this. Therefore, it is necessary to establish an automated control system through the development of this equipment system and conduct simulation through simulation of excavation model in the sharp curve section. A system shall be developed to control the left and right angles and thrust of the equipment, and to view data on the earth pressure and propulsion pressure of the equipment in real time during excavation. With this system, the necessary data can be collected for field testing through excavation method and excavation simulation by angle. It is expected that it will be very useful in assessing the actual Shield TBM by conducting a scale-down model experiment.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1799-1804
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• 2009

Bimodal Tram is spotlighted for alternative public transportation system which have punctualness, efficiency, and convenience running between capacity of bus and light rail transit. It have the advantage of automatic operation system when it runs at exclusive right-of-way as like as railway, runs as same as a bus at road concurrently. However, concrete construction plan is not established since the law as well as government subsidy are not defined. For activating bimodal tram construction, this paper analyzed as below. 1) understanding obstacles of activating construction through current status of local governments' bimodal tram promotion plan, 2) finding essential elements for legislation through transportation mode characteristics comparison and system rules analysis, 3) related foreign law analysis.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.33-45
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• 2019

In this study, numerical simulations were performed to investigate the steady-state characteristics of a symmetric pintle nozzle by varying the position of the pintle and the altitude. The pintle nozzle shape was used in a linear pintle nozzle that had been analyzed prior to the study, and the boundary conditions of the chamber were considered to be according to the propellant burn-back characteristics. A software was used to perform a verification analysis of the square nozzle, pintle nozzle, and high-altitude conditions with an appropriate analytical technique. The pintle position had three different nozzle throat area conditions-: fully closed, half open, and fully open, and the altitude was set at 0, 5, and 20 km. The study compared the thrust, pintle drive load, and static stability at each condition.