• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.112-114
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• 1993

This paper presents a partitioning technique for equivalent models to large scale power system. The proposed partitioning technique is utilized by using a heuristic approach based on distributed array processor and the coherent groupings of generator buses. In this paper the reduced Ward-PV method considering the characteristics of buses is used to equivalent models of external system. The technique is demonstrated on New England system with 39 buses, 46 lines and 10 generators.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.99-101
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• 2014

다양한 응용 분야에서 대량의 데이타 저장이 빈번해 짐에 따라 분산 파일 시스템에 대한 효용성이 커지고 있으며, 이로 인해 수많은 분산 파일 시스템이 개발되고 있다. 이러한, 분산 파일 시스템의 효율성을 검증할 수 있는 방법에 대한 필요성이 커지고 있다. 또한, SSD와 같은 우수한 성능을 가지는 장치를 사용하는 분산 파일 시스템에서는 SSD와 같은 장치의 효율성을 보기 위한 복잡한 워크로드를 생성 하여 시험할 수 있어야 한다. 하지만 기존의 입출력 시험 도구에서는 복잡한 상황을 시험하는 것이 매우 어렵다. 따라서, 본 논문에서는 필요에 따라 파일의 분포에 따라 다른 입출력 패턴을 가지는 여러 부하 상황을 생성이 가능하며, 웹을 통해 손쉽게 시험할 수 있는 분산 파일 시스템을 위한 웹기반 워크로드 생성기를 개발하였다.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.446-448
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• 1995

This paper dscribes a detail simulation model with EMTP (Electro-Magnetic Transients Program) which is very effective to analyze the interaction between the ac transmission line and STATCON (static condenser). The SATCON was represented by two voltage-source converters connected in parallel and sharing an energy storage dc capacitor bank. The voltage source converters was modeled with ideal gate turn-off switches. The power system was represented by a detail generator model and a distributed tramnsmission line model for detail performance analyses. Analysis results show that the conceived simulation model is very effective to analyze the interaction between the ac transmission line and STATCON, and to evaluate the performance of STATCON.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.115-117
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• 2019

In this paper, an intelligent control scheme based on Fuzzy PID controller is proposed for accurate power sharing in DC Microgrid. The proposed Fuzzy PID controller is designed with the aid of a closed loop control based on per unit power of each distributed generator (DG), and accurate power sharing is successfully realized in proportional to each DG's power rating regardless of the line resistance difference or the load change. Thanks to Fuzzy PID controller, the dynamic response becomes faster and the stability of the microgrid system are improved in comparison to conventional PID controller. The superiority of the proposed method is analyzed and verified by simulation in Matlab and Simulink.

• Journal of ILASS-Korea
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• v.24 no.3
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• pp.130-136
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• 2019

Spray visualization of a vaporizer fuel injection system of a micro turbo jet engine was experimentally studied. The fuel heating by combustion was simulated by the high pressure steam generator and combustor inlet air from the centrifugal compressor was simulated by compressed air stored in the high pressure air tank. Spray visualization was performed with single vaporizer, and then six vaporizers which are same number of micro turbojet engine were used. As a results, the spray characteristics of the vaporizer were understood with pressure difference of the combustor inlet air and the fuel supply pressure. Spray angles with three types of vaporizer configuration were measured. In the results, guide vane configuration has a wider spray angle than the straight tube and smooth curve tube with a swirler, so it is expected that the fuel will be effectively distributed inside the combustor flame tube.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1305-1317
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• 2015

Distributed generation systems (DGSs) have been getting more and more attention in terms of renewable energy use and new generation technologies in the past decades. The self-excited induction generator (SEIG) occupies an important role in the area of energy conversion due to its low cost, robustness and simple control. Unlike synchronous generators, the SEIG has to absorb capacitive reactive power from the outer device aiming to stabilize the terminal voltage at load changes. This paper presents a novel static VAR compensator (SVC) called a magnetic energy recovery switch (MERS) to serve as a voltage controller in SEIG powered DGSs. In addition, many small scale SEIGs, instead of a single large one, are applied and devoted to promote the generation efficiency. To begin with, an expandable mathematic model based on a d-q equivalent circuit is created for parallel SEIGs. The control method of the MERS is further improved with the objective of broadening its operating range and restraining current harmonics by parameter optimization. A hybrid control strategy is developed by taking both of the stand-alone and grid-connected modes into consideration. Then simulation and experiments are carried out in the case of single and double SEIG(s) generation. Finally, the measurement results verify that the proposed DGS with SVC-MERS achieves a better stability and higher feasibility. The major advantages of the mentioned variable reactive power supplier, when compared to the STATCOM, include the adoption of a small DC capacitor, line frequency switching, simple control and less loss.

• Aerospace Engineering and Technology
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• v.6 no.1
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• pp.128-135
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• 2007

Combustion characteristics of full-scale gas generators were studied experimentally by changing the injector number installed at the injector head. Three full-scale gas generators were utilized; they have same total mass flow rate but mass flow rates per injector are different. Thirteen, nineteen and thirty seven injectors, which have internal-mixing and double-swirl characteristics, are distributed in injector heads, respectively. The results showed that pressure fluctuations in the gas generators with 13 and 19 injectors didn't occur around longitudinal resonant frequency, however longitudinal-mode pressure fluctuation appeared slightly in the gas generator with 37 injectors. As the number of injectors increased, deviations of temperature distribution in the combustion chamber decreased gradually, but the damage of injector LOx posts became a little severe.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.309-315
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• 2006

Effects of injector or design on combustion characteristics of full-scale gas generators were studied. Three full-scale gas generators, which have same total mass flow rate but mass flow rate per injector is different depending on their designs, were manufactured. Thirteen, nineteen and thirty seven injectors, which have internal-mixing and double-swirl characteristics, are distributed in injector heads, respectively. The results showed that special pressure fluctuations in the gas generators with 13 and 19 injectors didn't appear around longitudinal resonant frequency, but small longitudinal-mode instability appeared in the gas generator with 37 injectors. As the number of injectors installed in injector heads increased, temperature distribution in combustion chambers showed small deviations, but the damage of LOx posts increased.

• Journal of the Korea Society of Computer and Information
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• v.25 no.11
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• pp.97-104
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• 2020

In this paper, we propose a random number generator PP(PingPong256) and a shuffle technique to improve the problem that the encrypted image is damaged due to a lot of noise by the channel coding of wireless communication recommended in the special environment of space. The PP can constantly generate random numbers by entering an initial value of 512 bits. Random numbers can be encrypted through images and exclusive logical computations. Random numbers can be encrypted through images and exclusive logical computations. The shuffle technique randomly rearranges the image pixel positions while synchronizing the image pixel position and the random number array position and moving the random number arrangement in ascending order. Therefore, the use of PP and shuffle techniques in channel coding allows all pixels to be finely distributed and transmit high-quality images even in poor transmission environments.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.611-617
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• 2008

Nowadays Plate Heat Exchanger (PHE) is widely used in different industries such as chemical, food and pharmaceutical process and refrigeration due to the efficient heat transfer performance, extreme compact design and efficient use of the construction material. In present study, discussed main conception of plate heat exchanger and applied in vacuum. PHE and aimed apply in the fresh water generator which installed in ship to desalinate seawater to fresh water use heat from engines. The experiment is proceeded to investigate the heat transfer between cold and hot fluid stream at different flow rate and supply temperature of hot fluid. Generated fresh water as outcome of the system. PHE is an important part of a condensing or evaporating system. One of common assumptions in basic heat exchanger design theory is that fluid is to be distributed uniformly at the inlet of each fluid side and throughout the core. However, in practice, flow mal-distribution is more common and can significantly reduce the heat exchanger performance. The flow and heat transfer are simulated by the k-$\varepsilon$ standard turbulence model. Moreover, the simulation contacted flow maldistribution in a PHE with 6 channels.