• 한국초전도ㆍ저온공학회논문지
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• 제6권3호
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• pp.33-37
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• 2004

This paper presents the construction and test results of an HTS induction motor. End rings and short bars were made of HTS tapes, To increase the efficiency and starting torque, HTS tapes can be used as the rotor bars. Because large current is induced in the rotor circuit, HTS tapes quench and high starting torque can be obtained. As the speed of rotor builds up. HTS tapes which are used as short bars become superconducting state again. After the HTS tapes recover from quench, resistance of the rotor circuit is nearly zero. In that case, power loss in rotor circuit is eliminated. Stator of the conventional induction motor was used as the stator of the HTS motor. Rated capacity of the conventional motor was 0.75 kW. Performances of the HTS induction motor were compared with those of the conventional motor with same volume and specification. Test result showed that the speeds of the HTS induction motor were the same with synchronous speed up to 2.6 Nm and 1.788 rpm at 9.7 Nm. It guarantees the high efficiency of the HTS motor. Starting torque of the HTS motor was more than twice of the conventional motor.

• 설비공학논문집
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• 제24권4호
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• pp.306-314
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• 2012

Several numerical or analytical models have been proposed to analyze the thermal response of vertical ground heat exchangers (GHEX). However, most models are valid only after several hours of operation since they neglect the heat capacity of the borehole. Recently, the short time response of the GHEX became important in system simulation to improve efficiency. In this paper, a simple new method to evaluate the short time response of the GHEX by using an analogy model of electric circuit transient analysis was presented. The new transient heat exchanger model adopting the concept of thermal capacitance of the borehole as well as the steady-state thermal resistance showed the transient thermal resistance of the borehole. The model was validated by in-situ thermal response test and then compared with the DST model of the TRNSYS program.

• 대한전자공학회논문지TE
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• 제37권2호
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• pp.6-11
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• 2000

본 논문에서는 단채널 n형 GaAs MESFET 소자의 공핍층의 두께가 선형적으로 변한다는 근사를 적용하여 공핍층내의 2차원 프와송 방정식을 풀어 단채널 GaAs MESFET의 전류-전압 특성을 해석적으로 도출하는 모델을 제안하였다. 이 모델로부터 문턱 전압, 소오스와 드레인의 저항 및 드레인 전류식을 도출하였다 계산 결과로부터 전류-전압 특성 곡선에서 단채널 소자의 특성인 Early 효과를 설명할 수 있었고 소오스 접촉 저항과 드레인 접촉 저항에 의한 전압 강하도 설명할 수 있었다. 더욱이 본 모델은 소자 해석에 있어서 단채널 소자에만 국한되지 않고 장채널 소자의 특성을 해석하는 데에도 적용할 수 있었다.

• 한국수산과학회지
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• 제55권5호
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• pp.495-504
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• 2022

This study examined the antimicrobials properties of bacteria using the minimum inhibitory concentration method. The bacteria were isolated from 30 shellfish (oysters and short neck clams) collected from Jawol-myeon, Ongjin-gun, Incheon and Iwon-myeon, Taean-gun, Chungcheongnam-do, on the west coast of Korea. A total of 528 bacteria were isolated from June to October 2020 and were classified into land-originating (LB; 264 strains) and marine-originating (MB; 264 strains) bacterial groups. Of the LB strains, 10 genera were identified, of which nine were Enterobacteriaceae. All MB strains were identified as species of the genus Vibrio spp.. Antimicrobial resistance to one or more agents was observed in 77.3% of the LB strains, and 90-100% of them were resistant to ampicillin Escherichia spp. were not resistant to ampicillin. The overall multidrug resistance rate of the LB strains was 49.2%, with 85 resistance patterns. Antimicrobial resistance to one or more agents was observed in 98.1% of the MB strains, because most of the V. alginolyticus and V. parahaemolyticus strains were resistant to ampicillin. The overall multidrug resistance rate of the MB strains was 1.9% with 19 resistance patterns.

• Steel and Composite Structures
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• 제36권2호
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• pp.187-196
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• 2020

Double skin composite wall system owns several structural merits in terms of high load-carrying capacity, large axial stiffness, and favorable ductility. A recently proposed form of truss connector was used to bond the steel plates to the concrete core to achieve good composite action. The structural behavior of rectangular high walls under compression and T-shaped high walls under eccentric compression has been investigated by the authors. Furthermore, the influences of the truss spacings, the wall width, and the faceplate thickness have been previously studied by the authors on short walls under uniform compression. This paper experimentally investigated the effect of width-to-thickness ratio on the compressive behavior of short walls. Compressive tests were conducted on three short specimens with different width-to-thickness ratios. Based on the test results, it is found that the composite wall shows high compressive resistance and good ductility. The walls fail by local buckling of steel plates and crushing of concrete core. It is also observed that width-to-thickness ratio has great influence on the compressive resistance, initial stiffness, and strain distribution across the section. Finally, the test results are compared with the predictions by modern codes.

• 한국도로학회논문집
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• 제9권3호
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• pp.123-134
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• 2007

본 연구는 $154^{\circ}C$로 2시간의 단기노화를 거친 혼합물로 제작한 공시체를 $110^{\circ}C$에서 24, 48, 72, 96시간 동안 장기노화를 시켜 아스팔트 혼합물의 노화와 소성변형 저항성을 평가하였다. 혼합물의 노화 시간이 증가함에 따라 강성의 증가로 인한 소성변형 저항성이 증가할 것을 고려하여 변형강도를 이용해 단기노화와 장기노화를 거친 공시체에 대해 소성변형특성을 측정하였다. 또한 노화 시간의 증가에 따른 바인더의 노화 정도를 측정하기 위하여 GPC (Gel-permeation chromatograph) 분석을 통하여 대형분자비율(LMS(%))을 측정하였다. 노화 시간이 길어짐에 따라 LMS(%)가 증가하고 혼합물의 변형강도 값이 커지는 것을 확인하였다. 또한 상관성 분석으로부터 LMS(%)와 변형강도가 상관성이 높은 것으로 나타나 이를 통해 혼합물이 노화되면 소성변형 저항성이 증가됨을 확인하였다. 따라서 LMS(%)의 측정으로 아스팔트 혼합물의 바인더 추출 없이도 소성변형특성을 추정 가능함을 확인하였다.

• 대한토목학회논문집
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• 제29권2A호
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• pp.131-143
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• 2009

지진하중과 같은 횡하중에 대하여 교량구조물의 아칭작용은 교대 사이의 상부구조에 의해 발생하며 이를 상부구조의 저항능력이라고도 한다. 교량구조물의 아칭작용의 크기는 경간의 수에 영향을 받으며 또한 상부구조, 교대와 교각의 연결조건 및 상부구조와 하부구조의 강성비에도 영향을 받는다. 프리캐스트 콘크리트 상자형 교량의 비탄성 지진응답에 대한 아칭작용의 영향을 분석하기 위하여 경간수에 따른 두 가지 종류의 예제교량(교량 SB와 교량 LB), 교각의 높이의 배열에 따른 세가지 종류(대칭, 비대칭)의 교량, 상부구조와 하부구조의 연결조건에 따른 세가지 교량(형식 A, B, C)등에 대한 구분을 조합하여 18가지 종류의 예제구조물을 작성하였으며, 이 예제구조물들에 대하여 역량스펙트럼해석, 비탄성 시간이력해석을 수행하여 지진응답을 비교하여 아칭작용의 영향을 분석하였다. 아칭작용의 영향(최대변위의 감소와 저항능력의 증가)은 교량 SB(short bridge)의 경우가 교량 LB(long bridge) 보다 크게 나타났으며 대칭교량의 경우가 비대칭교량에 비하여 크게 나타남을 알수 있었다.

• Design & Manufacturing
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• 제12권2호
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• pp.16-21
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• 2018

Recently, as the demand for high-precision parts increases due to industrial development, a machine tool system for ultra-precision machining and polishing has been actively developed. As a result, there is an increasing demand for ultra-precision surface roughness along with dimensional processing. However, due to the increase in processing time due to the demand for ultra-precise surfaces and enormous facility investment, it is difficult to secure competitiveness. The polishing process using the abrasive film in super precision machining has been applied to machines, electronic devices, aerospace, and medical fields. Super finishing using the abrasive film which is applied in the industrial field recently can achieve high surface roughness in a short time. Super finishing using the abrasive film which is applied in the industrial field recently can achieve high surface roughness in a short time. Also, application of industrial field is increasing due to advantages such as low noise and low dust. Recently, researches on stainless steel having strong resistance to corrosion, heat resistance, heat resistance, toughness and weldability have been actively conducted with respect to the nuclear energy industry or marine development. Therefore, in this study, surface roughness and residual stress were measured after SUS304 polishing using dynamic analysis of film polishing apparatus and polishing film.

• 유변학
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• 제11권2호
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• pp.153-158
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• 1999

가스사출시 두개이상의 가스흐름가능방향이 존재 할 때 가스는 선택적인 방향으로 흐르게는데 여기에서는 이 가스흐름 방향을 예측하는 방법을 제시하였다. 지금까지는 가스흐름방향은 가스의 하류에 있는 수지의 저항값, 즉 압력손실필요량을 비교하여 예측되어 왔는데 이방법은 대부분의 경우에 정확한 예측력을 가지고 있었다. 그러나 수지의 저항값 또는 압력손실필요량을 비교하는 방법이 실제에는 경우에따라 맞지 아니하였다. 이 연구에서는 수지속도비교가 압력손실필요량비교 보다 한단계위의 판단기준(criterion)이 되는 것을 설명하고 그예를 들어 증명 하고 있다. 압력손실필요량비교 대신 수지속도비교방법을 쓰면 예외없이 모든 경우 정확하게 가스흐름방향을 예측을 할수 있다.

• 한국전기전자재료학회논문지
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• 제21권12호
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• pp.1124-1129
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• 2008

The object of this paper is to acquire the data related to insulation evaluation of hybrid vehicle traction motors. We made a comparative analysis on Insulation Resistance (IR), Dielectric Absorption Ratio (DAR), and Polarization Index (PI) of the motor stators. The experiment was carried out according to IEEE Std. 43 and IEC 60085-1 for insulation resistance test standard of rotating machinery. Test voltage of 500 V was applied between a phase and the enclosure. The IR and the DAR of used motors were lower than those of new ones. The DAR and the PI were $0.92{\sim}1.02$ and $0.74{\sim}1.1$, respectively and the result did not meet the recommendation basis 2 for insulation level H. From the experimental results, we could prepare parameters and basis for insulation evaluation of the traction motor stator by the comparative analysis of short-time insulation resistance changes, DAR and PI.