• Journal of Bio-Environment Control
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• v.27 no.1
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• pp.7-12
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• 2018

This study was conducted to determine effects of precooling and storage methods on asparagus spears' quality such as changes of fresh weight and color during simulated export distribution. Two types of precooling methods, air cooling and hydrocooling, were applied prior to packaging by comparing with no precooling as a control. Asparagus spears were packed with oxygen transmission rate (OTR) film for modified atmosphere packaging (MAP) and perforated (PF) film for a conventional packaging. All treatments were stored at $8^{\circ}C$ for 20 hours, and subsequently at $4^{\circ}C$ by final storage day, which is simulated distribution temperature condition from Yanggu, Korea to Shimonoseki, Japan. The half cooling time was 12 minutes for air cooling and 15 seconds for the hydrocooling, indicating precooling process of asparagus spears faster with the hydrocooling. Rates of respiration and ethylene production were lowest with hydrocooling. Fresh weight loss was higher, approximately 11%, at the control condition in conventional storage, compared with the MAP, less than 0.5%. Carbon dioxide and oxygen content in the MAP was in the permissible ranges for asparagus spears under recommended CA/MA conditions under both the air cooling and hydrocooling. Ethylene content in the film package was lower with the precooling treatment. Firmness of stems was lowest with the hydrocooling prior to the MAP. Visual quality, off-odor, and hue angle value were best with hydrocooling prior to the MAP. In conclusion, the combination of hydrocooling with the MAP is effective in preserving quality during the export distribution process.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.435-436
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• 2014

최근 대용량 PCS(Power Conditioning System)는 신재생에너지, 에너지저장장치 등의 다양한 산업 분야에서 수요가 증가하고 있다. 본 논문에서는 신재생에너지 분야에서 대용량 시스템으로 발전용 에너지원으로 사용되는 2.8MW 연료전지 시스템의 수랭형 PCS 개발을 위하여 수랭식 IGBT Stack 및 냉각 장치를 설계, 제작하여 열적 안정성을 실험을 통하여 검증하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.4
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• pp.282-287
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• 2016

Recently in order to protect the ocean environment and to reduce energy consumption, shipbuilders have been developing highly economized ships. This research analyzed the possibility of adopting the onshore absorption refrigerator to offshore ships having a cooling system with refrigerant by using the waiste heat of the engine jacket cooling water instead of compression refrigerators. The results showed that R236fa could be a suitable medium for absorbing the heat of the absorber and condenser in an absorption refrigerator. The cooling system using R236fa achieved a high COP of 0.798, which is 15% and 5% higher than an air cooling system with a cooling tower and a water cooling system with a heat exchanger, respectively. The cooling system with R236fa achieved high efficiency with a 25% reduction in flow rate of LiBr solution and only 15.7% flow rate of cooling medium as compared to the water cooling system. The heating of sea water by the engine jacket water flowing out from the generator can prevent the crystallization of LiBr solution due to the low temperature of sea water.

• Journal of the Korea Society of Computer and Information
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• v.16 no.7
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• pp.1-11
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• 2011

Many researchers have studied on the methods to improve the processor performance. However, high integrated semiconductor technology for improving the processor performance causes many problems such as battery life, high power density, hotspot, etc. Especially, as hotspot has critical impact on the reliability of chip, thermal problems should be considered together with performance and power consumption when designing high-performance processors. To alleviate the thermal problems of processors, there have been various researches. In the past, mechanical cooling methods have been used to control the temperature of processors. However, up-to-date microprocessors causes severe thermal problems, resulting in increased cooling cost. Therefore, recent studies have focused on architecture-level thermal-aware design techniques than mechanical cooling methods. Even though architecture-level thermal-aware design techniques are efficient for reducing the temperature of processors, they cause performance degradation inevitably. Therefore, if the mechanical cooling methods can manage the thermal problems of processors efficiently, the performance can be improved by reducing the performance degradation due to architecture-level thermal-aware design techniques such as dynamic thermal management. In this paper, we analyze the cooling efficiency of high-performance multicore processors according to mechanical cooling methods. According to our experiments using air cooler and liquid cooler, the liquid cooler consumes more power than the air cooler whereas it reduces the temperature more efficiently. Especially, the cost for reducing $1^{\circ}C$ is varied by the environments. Therefore, if the mechanical cooling methods can be used appropriately, the temperature of high-performance processors can be managed more efficiently.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.432-433
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• 2010

본 논문에서는 직렬형 디젤 하이브리드 전기 트럭 구동을 위한 견인 전동기 제어 시스템 개발에 대해 소개한다. 높은 출력 밀도를 요구하는 복합형 전기 차량의 특성을 고려하여 매입형 영구자석 동기전동기를 선정하고, 대전류 고효율 시스템 구성을 위해 수랭식 MCU(Motor Control Unit)를 개발 하였다. 또한 빠른 토크 응답 특성과 넓은 영역의 속도 운전을 위한 약자속 제어 기법을 적용하였으며, 전체 시스템 효율을 향상시키기 위해 단위 전류당 최대 토크 제어 기법(MTPA)이 사용 되었다. 개발 된 제어 시스템 및 제어 기법을 실험을 통해 검증 하였다.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.13 no.3
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• pp.1-8
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• 2017

Variable refrigerant flow (VRF) systems have recently attracted attention in many countries due to a variety of advantages over conventional system. Especially, the water-cooled VRF heat pump, including geothermal heat pump, is a system that accurately controls the flow rate of refrigerant for the improved efficiency under part load operation. This paper describe the process of generating the cooling and heating energy performance curve coefficients and performance expressions for modeling water cooled VRF system using EnergyPlus. Through this study, the process for generating performance curves can be implemented into EnergyPlus or other comparable building energy analysis tools for the long-term evaluation of heat pump under dynamic conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.179-185
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• 2014

Average temperature and temperature uniformity in a battery cell are the important criteria of the thermal management of the battery pack for hybrid electric vehicles and electric vehicles (HEVs and EVs) because high power with large size cell is used for the battery pack. Thus, liquid cooling system is generally applied for the HEV/EV battery pack. The liquid cooling system is made of multiple cooling plates with coolant flow paths. The cooling plates are inserted between the battery cells to reject the heat from batteries to coolant. In this study, the cooling plate with U-shaped coolant flow paths is considered to evaluate the effects of coolant flow condition on the cooling performance of the system. The counter flow and parallel flow set up is compared and the effect of flow rate is evaluated using CFD tool (FLUENT). The number of counter-flows and flow rate are changed and the effect on the cooling performance including average temperature, differential temperature, and standard deviation of temperature are investigated. The results show that the parallel flow has better cooling performance compared with counter flow and it is also found that the coolant flow rate should be chosen with the consideration of trade-off between the cooling performance and pressure drop.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.2545-2552
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• 2014

This study is aiming to suggest the effective thermal management system design technologies for the high voltage and capacity battery system of the electricity driven vehicles and introduce the theoretical designing methods. In order to investigate the effective operation of the battery system for the electricity driven vehicles, the heat generation model for Li-ion battery system using the chemical reaction while charging and discharging was suggested and the thermal loads of the heat sources (air or liquid) for cooling and heating were calculated using energy balance. Especially, the design methods for the cooling and heating of the battery system for maintaining the optimum operation temperature were investigated under heating, cooling and generated heat (during charging and discharging) conditions. The battery thermal management system for the effective battery operation of the electricity driven vehicles was suggested reasonably depending on the variation of the season and operation conditions. In addition, at the same conditions under summer season, the cooling method using the liquid and active cooling technique showed a relatively high capacity, while cooling method using the passive cooling technique showed a relatively low capacity.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.1
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• pp.43-50
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• 2024

Large planar military antenna boasts a range of electrical components, including TRA(Transmit-Receive Assembly), signal processors, etc. which engage in computations and calculations. These processes generate a significant amount of heat, leading to unforeseen consequences for the equipment. To mitigate these adverse effects, it's imperative to implement a cooling system that can effectively reduce heat-related issues. Given the antenna's intricate nature and the multitude of components it houses, a two-step estimation process is necessary. The first step involves a comprehensive model calculation to determine the total flow characteristics, while the second step entails a thermal analysis of individual TRA set. In this study, we depicted an antenna set using simplified 3D models of its components, considering their material and thermal properties. The sequential analysis process facilitated the calculation of branched flow rates, providing insights into the individual TRA. This approach also allowed us to design a cooling system for the TRA set, assessing its thermal stability in high-temperature environments. To ensure the optimal performance of TRA, breaking down the analysis into stages based on the cooling system's structure can assist operators in predicting numerical results more effectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.2
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• pp.79-87
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• 2011

A fishing lamp is fishing gear to gather fish in the night. But the cost of oil which is used to a light fishing lamp, goes significantly up to almost one hundred million won for 50 tonnage vessels and forty million won in case of vessels less than 10 tonnages. This cost has almost taken 30.40% of total fishing costs. As oil price increases, the business condition of the fishery gets worse and worse. Therefore, it is very urgent to develop an economical fishing lamp, to solve the problem of fishery's business difficulty. This research aims at developing a fishing lamp for squid jigging fishery and hairtail angling fishery using the LED, which has excellent efficiency and durability. One fishing lamp has about 160Watt capacity and five fishing lamps are installed one aluminium panel in which sea water flows to emit generated heat from LED to outside. Developed fishing lamp lights to an effective direction of jigging and angling operation. This fishing lamp can be controlled to light the direction of fish shoal because the aluminium panel can be controlled to up and down direction. The wave length of fishing lamp has white and blue color. White color light is to gather fish shoal of horizontal direction and blue color light is to gather fish shoal of vertical direction. After development of this fishing lamp, 60.110 units are established on the boat, and operated fishing. Consequently, in the case of squid jigging, spent energy was reduced to 39%, in the case of hairtail angling, 68% of spent energy was reduced. And the catch was more than another boat.