• Solar Energy
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• v.15 no.3
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• pp.3-14
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• 1995

The Direct Contact heat Exchanger(DCHX) has been widely studied in the chemical industry for many years due to its inherent simplicity as a counter-current divice for heat and mass transfer. In many solar systems, the DCHX unit can be combined with the thermal storage unit, or alternatively, it can be used separately from the storage unit, much like an external(to storage) closed heat exchanger system. In the present work, the spray column type of direct contact heat exchangers are studied extensively to harness the solar energy for hot water and spaced heating. Some of the major considerations that are involved in the design of heat exchangers in this study are that : working fluid is a hydrocaabon(such as Texaterm) or water which is either lighter or heavier than storage medium. The experimental data have revealed some interesting characteristics concerning the application of DCHXs for solar energy utilization. These experiments are carried out in the line of solar heating system, major results are as follows : 1) the flow and aspect of working fluid drop for maxium heat transfer 2) efficiency and volumetric heat transfer coefficient of D.C.H.X with a heavier working fluid are higher than those of D.C.H.X with a lighter working fluid.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.2
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• pp.132-138
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• 2009

The energy efficiency and environment-friendly aspect of the railway system would be superior to other on-land transportation systems. In a preliminary feasibility study stage and selection of optimal railway corridor, the energy efficiency and problems related to environment are usually not considered. For the selection of optimal railway corridor, geographical features and facility of management are generally considered. Environment effect factors for the selection of environment-friendly railway corridor are focused and studied in this paper. In this study, various analysis of opinion of specialists (railway, environment, transport, urban planning, survey) and the guideline for construction of environment-friendly railway were accomplished. From these results of various analysis, 7 major categories (topography/geology, flora and fauna, Nature Property, air quality, water quality, noise/vibration, visual impact/cultural assets) were extracted. To select environment friendly railway corridors, many alternatives should be compared optimal corridor must be selected by a comprehensive assessment considering these 7 categories. The investment for railway systems can be encouraged by the considering of main environmental effect factor evaluated with the modified environmental weight factors for environment-friendly railway construction.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.786-791
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• 2007

Korean high speed train(HSR-350x) has adopted a combined electrical and mechanical(friction) braking system. Brake blending control unit(BBCU) controls each brake system to fulfill the required brake performances such as braking distance, deceleration and jerk. Also the braking system should be designed considering the economical management, such as effective use of generated braking energy and the minimum wear of friction materials(a pad and a brake shoe). In this paper, we establish the disc braking force pattern that reduces the wear of pad in the disc braking system by minimizing the variance of the instantaneous disk baking energy during braking time, and compare the wear mass of pad between the conventional disc braking force pattern and the established results.

• Journal of Korean Association for Spatial Structures
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• v.7 no.2 s.24
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• pp.91-96
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• 2007

To improve the land use of urban, Construction of the circular steel column is required recently. The circular steel columns have a advantage for improving a load carrying capacity as wall as reducing a effective section area. However, the circular steel columns under service load, such as earthquake, shows a tendency to cause local buckling and large deformation. To prevent these phenomena, use of diaphragm is considered. It is reported that longitudinal stiffeners has a effect on improving a buckling and fatigue performance of steel structures. The research of effect on diaphragm is not sufficient. Under monotonic and cyclic loadings diaphragm make a important role to prevent local buckling and deformation of used steel structures. Therefore, influence of diaphragm on performance of used steel structures is investigated. In this study, the influence of diaphragm on seismic and deformation performance of circular steel piers was investigated by using elastic-plastic finite element analysis considered geometrical and material non-linearity. The seismic performance of circular steel columns was evaluated for analytical parameter of manufactured part. The seismic performance of circular steel columns was clarified by comparing an energy dissipation of circular steel piers.

• Journal of IKEEE
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• v.27 no.1
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• pp.103-108
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• 2023

This research was carried out experiments with changing processes and design parameters to optimally design a SiC-based 1200V power MOSFET, and then, essential electrical characteristics were derived. In order to secure the excellence of the trench gate type SiC power MOSFET device to be designed, electrical characteristics were derived by designing it under conditions such as planner gate SiC power MOSFET, and it was compared with the trench gate type SiC power MOSFET device. As a result of the comparative analysis, the on-resistance while maintaining the yield voltage was 1,840mΩ, for planner gate power MOSFET and to 40mΩ for trench gate power MOSFET, respectively, indicating characteristics more than 40 times better. It was judged that excellent results were derived because the temperature resistance directly affects energy efficiency. It is predicted that the devices optimized through this experiment can sufficiently replace the IGBT devices generally used in 1200V class, and that since the SiC devices are wide band gap devices, they will be widely used to apply semiconductors for vehicles using devices with excellent thermal characteristics.

• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.7-15
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• 2023

The electric submersible pump (ESP) has been operating in production wells around the world because of its high applicability and operational efficiency among artificial lift techniques. When operating an ESP in a reservoir, variables such as temperature, pressure, gas/oil ratio, and flow rate are factors that affect ESP performance. In particular, free gas in the production fluid is a major factor that reduces the life and operational efficiency of ESP. This study presents the flow loop system which can implement the performance and damage tests of ESP considering field operating conditions to quantitatively analyze the variables that affect ESP performance. The developed apparatus in an integrated system that can diagnose the failure and causes of ESP, and detect leak of tubing by linking ESP and tubing as one system. In this study, the flow conditions for stable operation of ESP were identified through single phase and two phase flow experiments related to evaluation for the performance of ESP. The results provide the basic data to develop the failure prediction and diagnosis program of ESP, and are expected to be used for real-time monitoring for optimal operating conditions and failure diagnosis for ESP operation.

• Journal of Plant Biotechnology
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• v.42 no.2
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• pp.117-122
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• 2015

Canola is a crop globally used for production of oil and biofuel. Cultivation area and import volume of living modified (LM) canola have been increasing every year. As canola import dependence has reached 100% in Korea, efforts have been made for safety management of LM canola and ecological risk assessment. We developed a set of multiplex PCR method for simultaneous detection of 5 LM canola events (Topas 19/2, Rf3, Ms8, RT73 and T45) approved in Korea. The multiplex PCR assay developed allows amplification of estimated products of 5 LM canolas from event specific primer sets. Primer extension time was skipped for a time-consuming process and two annealing steps (20 cycles at $55^{\circ}C$ and 20 cycles at $60^{\circ}C$) were performed for yielding the best result which was sufficient to distinguish five LM canolas. Our results suggest that multiplex PCR method provides a cost and time-effective approach for LM canola detection.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.495-495
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• 2017

도시화는 불투수면의 증가를 야기 시켜 물순환 왜곡, 다양한 오염 물질의 유입으로 인한 비점오염물질 유출, 인공 배출열의 증가로 인한 도시열섬효과 등 다양한 문제를 유발한다. 이러한 수리수문학적 및 환경생태학적 문제를 저감하기 위하여 도시지역과 같은 개발 사업에서는 수환경을 가능한 자연 상태로 복원하는 저영향개발(Low Impact Development, LID)기법이 중요한 대안으로 제시되고 있다. LID기법 중 하나인 옥상녹화는 에너지 이용을 최소한으로 한 자연 녹음의 효과적인 이용을 도모하여 환경공생도시 조성과 식물을 매개로한 자연 순환 과정을 도시구조에 도입하여 순환 시스템 재생이 가능 하도록한다. 노지녹화는 두꺼운 자연 토양을 이용하는 반면 옥상녹화는 적재하중의 제약(옥상의 적재하중 조건은 $150{\sim}180kgf/m^2$이다. 비중이 1.6~1.8인 토양을 20cm 객토한 경우, 약 $320kgf/m^2 $이상의 적재하중이 되기에 식재기반의 경량화는 중요한 사안이다.)으로 인해 용적밀도가 작은 인공경량토양 또는 개량토양을 이용하며, 토양 두께도 얇게 설정된다. 또한 토양의 두께는 식물의 크기와 종류 및 토양의 조성에 따라 다르기에 적재하중 조건을 고려한 적절한 토양과 식재 식물의 크기와 종류 결정은 중요하다. 이에 본 연구에서는 옥상녹화식생에 대한 평가와 이에 대한 시험 프로세스가 가능한 실험 장치를 개발하였다. 옥상녹화 효율성 검증실험장비는 1m*1m*0.6m 아크릴 재질의 녹화셀로 경사조절이 가능하도록 설계하여 경사변화에 따른 유출, 침투, 증발산량의 탄성도 모의 평가를 할 수 있다. 또한 4점식 형태의 로드셀을 이용하여 녹화셀에서 발생하는 증발산량을 측정하고 관측된 증발산량은 RS-232c 이상의 통신프로토콜을 사용하여 주기적인 관측치의 송수신이 가능하며 주기적 자료송수신 외에도 옥상 녹화셀의 측면에 하중 표시기를 설치하여 관측이 가능하다. 또한 저면에 바퀴설치를 통하여 이동 실험이 용이하며 현재 부산대학교 양산캠퍼스 한국 GI&LID 실증단지 연구센터 내 옥상녹화 실험장에 옥상녹화 효율성 검증 실험 장비를 설치하여 자연 혹은 인공강우를 통한 유출, 침투, 증발산량의 시험계측을 실시중이다. 이러한 옥상녹화 효율성 검증실험장비는 최대 하중 2,000kg, 측정해상도 0.02kg 이상을 허용하는 로드셀과 녹화셀을 이용하여 하중을 고려한 식생의 종류에 따른 평가가 가능하므로 최적 식재기반 단면구조 개발에 이용될 수 있을 것이다. 또한 토양 함수량 변화 측정으로 옥상녹화에 이용되는 다양한 종류의 식물의 염분에 대한 저항성과 식물의 성장능력을 평가하여 녹화공간에 따른 옥상녹화에 사용할 식생을 결정할 수 있다.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.3
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• pp.464-469
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• 2015

Response surface methodology (RSM) was used to monitor extraction characteristics of extracts from Sarcodon aspratus. Based on a central composite design, independent variables were microwave power (30~150 W), ethanol concentration (0~100%), and extraction time (1~9 min). Dependent variables were yield, electron-donating ability, total phenol contents, and SOD-like activity. Coefficients of determination ($R^2$) for dependent variables ranged from 0.80 at 0.97. The maximum extraction yield was 50.28% under conditions of 125.1 W microwave power, 18.67% ethanolic concentration, and 7.06 min extraction time. The maximum extraction electron-donating ability was 22.14% under conditions of 31.09 W, 45.76%, and 4.32 min. The maximum extraction total polyphenol content was 30.54 mg tannic acid equivalent/g at 122.54 W, 48.05%, and 8.36 min. The maximum extraction SOD-like activity was 33.44% at 121.17 W, 47.42%, and 8.41 min. Based on superimposition of four dimensional RSM with respect to extraction yield, electron-donating ability, total polyphenol content, and SOD-like activity obtained under various extraction conditions, optimum ranges of extraction conditions were found to be microwave power of 78~88 W, ethanol concentration of 39~57%, and extraction time of 3.5~9 min.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.10
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• pp.1565-1570
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• 2014

Response surface methodology (RSM) was used to optimize extraction conditions of Pleurotus cornocopiae. Coefficients of determination (R2) for dependent variables ranged from 0.86 at 0.91. Maximum extraction yield was 40.81% under the following conditions: microwave power of 60.08 watts, ethanolic concentration of 12.33%, and extraction time of 6.86 min. Maximum extraction electron donating ability was 35.72% at 44.13 watts, 19.30%, and 4.21 min. Maximum extraction superoxide dismutase (SOD)-like activity was 34.87% at 114.01 watts, 65.88%, and 1.56 min. Maximum extraction total polyphenol content was 31.77 mg/g at 50.52 watts, 23.00% and 2.90 min. Based on the superimposition of four dimensional RSM with respect to extraction yield, electron donating ability, SOD-like activity, and total polyphenol content obtained under various extraction conditions, the optimum ranges of extraction conditions were as follows: microwave power of 71.48~92.84 watts, ethanol concentration of 55.01~71.66%, and extraction time of 3~9 min.