• Journal of Korea Society of Industrial Information Systems
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• v.24 no.1
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• pp.39-44
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• 2019

A high-temperature superconducting(HTS) generators have been actively studied because of its advantages of weight, size, and efficiency. A large-scale superconducting wind power generator becomes a very low-speed high-torque rotating machine. In these machines, high electromagnetic force and torque are important issued. Two generators connected in series on one shaft design are one of the solution to overcome the high torque problem. In this paper, the authors design and analyze a 15 MW class HTS generator. The 15 MW HTS generator is confirmed in terms of magnetic field distribution and torque performance using a 3D finite element method. As a result, the designed generators generates less torque than a conventional generator. The designed 15 MW superconducting generator will be effectively utilized in the construction of the large-scale wind power generation system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.77-83
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• 2020

4WD technology is being actively applied to passenger cars. Therefore, dry multi-plate clutches are used for transfer cases. On the other hand, dry clutches have problems related to large vibrations and poor ride quality. To solve this problem, this paper proposes a multi-plate clutch with an MR fluid. When fastening the multi-plate clutch in the transfer case, the proposed MR clutch was applied to reduce the shock and friction, which is a key component in a four-wheel-drive system. MR multi-plate clutch has a fluid coupling mode and a compression mode. A torque model equation was derived for the optimal design. The analysis was performed using Ansys Maxwell to optimize the design parameters of the multi-plate clutch. Electromagnetic field analysis confirmed the strength of the magnetic field when the number of disks and plates were changed, and the maximum strength of the magnetic field was 0.45 Tesla. By applying this to the torque equation, the spacing between the plates was 2 mm, and the inner and outer diameters of the plates were selected to be 45 mm and 55 mm, respectively. Overall, this paper proposes an optimal design technique to maximize the performance of an MR multi-plate clutch.

• The Korean Journal of Pesticide Science
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• v.2 no.2
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• pp.16-21
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• 1998

Bis-aromatic ${\alpha},{\beta}$-unsaturated ketone derivatives represented as substrate(S) were synthesized and their fungicidal activities in vivo against rice blast(Pyricularia oryzae) and tomato leaf blight(Phytophthora infestans) were examined with the quantitative structure activity relationships(QSAR) using 3D QSAR, comparative molecular field analysis (CoMFA). The 3D CoMFA results and those of 2D QSAR were compared and the results reveal that both results show similar trend. The two important factors, steric and electronic, contribute toward the activity. We assumed that fungicidal activity for rice blast was greatly improved by increasing with positive charge of ${\beta}$-carbon and introduction of bulky derivatives into $R_{2}$ group, while that for tomato leaf blight was improved by decreasing the positive charge of ${\beta}$-carbon and introduction of smaller molecular derivative into $R_{2}$ group. The CoMFA analyses clearly demonstrate its potential in unraveling the steric and electronic features of the molecules through contour maps.

• The Journal of the Acoustical Society of Korea
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• v.43 no.1
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• pp.103-111
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• 2024

Axial-flow fans are used to transport fluids in relatively low-pressure flow regimes, and a variety of design variables are employed. The tip geometry of an axial fan plays a dominant role in its flow and noise performance, and two of the most prominent flow phenomena are the tip vortex and the tip leakage vortex that occur at the tip of the blade. Various studies have been conducted to control these three-dimensional flow structures, and winglet geometries have been developed in the aircraft field to suppress wingtip vortices and increase efficiency. In this study, a numerical and experimental study was conducted to analyze the effect of winglet geometry applied to an axial fan blade for an air conditioner outdoor unit. The unsteady Reynolds-Averaged Navier-Stokes (RANS) equation and the FfocwsWilliams and Hawkings (FW-H) equation were numerically solved based on computational fluid dynamics techniques to analyze the three-dimensional flow structure and flow noise numerically, and the validity of the numerical method was verified by comparison with experimental results. The differences in the formation of tip vortex and tip leakage vortex depending on the winglet geometry were compared through a three-dimensional flow field, and the resulting aerodynamic performance was quantitatively compared. In addition, the effect of winglet geometry on flow noise was evaluated by numerically simulating noise based on the predicted flow field. A prototype of the target fan model was built, and flow and noise experiments were conducted to evaluate the actual performance quantitatively.

• Journal of The Korean Association For Science Education
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• v.37 no.2
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• pp.253-262
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• 2017

This study aims at investigating the perceptions of science teachers about the role of visual representations in the teaching of electromagnetism, and finding out how science teachers use visual representations in their teaching of electromagnetism and the difficulties they experience in dealing with those representations. A total of 121 science teachers responded to the online survey. The results showed that most of the teachers agreed to the significance of using visual representations in the classroom but regarded their role as means of simply delivering science knowledge rather than constructing or generating knowledge. For the three visual representations widely used in teaching of electromagnetism in secondary schools (electrostatic induction on electroscope, magnetic field around current carrying wire, structure and principle of electric motor), the teachers preferred teacher-centered use of visual representations rather than student-centered and teacher's construction of representations were the most frequent among four types of use; interpretation, construction, application, and evaluation. The difficulties of teaching with these three visual representations were categorized into several factors; teachers, students, the characteristics of the representations, and lack of resources and classroom environment. Teachers' limited perceptions about the role of visual representations were associated with the ways of using visual representations in their teaching. Implications for the effective use of visual representations for science learning and teaching were discussed.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.1
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• pp.49-54
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• 2022

The copper plating process used to fabricate the submicron damascene pattern of Cu wiring for Si wafer was applied to the plating of a PCB pattern of several tens of microns in size using the same organic additives and current density conditions. In this case, the non-uniformity of the plating thickness inside the pattern was observed. In order to quantitatively analyze the cause, a numerical calculation considering the solution flow and electric field was carried out. The calculation confirmed that the depletion of Cu²⁺ ions in the solution occurred relatively earlier at the bottom corner than the upper part of the pattern due to the plating of the sidewall and the bottom at the corner of the pattern bottom. The diffusion coefficient of Cu²⁺ ions is 2.65 10^-10 m²/s, which means that Cu²⁺ ions move at 16.3 ㎛ per second on average. In the cases of small damascene patterns, the velocity of Cu²⁺ ions is high enough to supply sufficient ions to the inside of the patterns, while sufficient time is required to replenish the exhausted copper ions in the case of a PCB pattern having a size of several tens of microns. Therefore, it is found that the thickness uniformity can be improved by reducing the current density to supply sufficient copper ions to the target area.

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.13-23
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• 2008

The triaxial compression tests and consolidation tests using NaCl solution and leachates as substitute pore (or saturated) water in samples were carried out to find out the behavior characteristics of strength, deformation and permeability coefficient of contaminated clay. Also, the chemical property analysis on the clay samples using scanning electron microscope and energy dispersive x-ray spectrometer were involved. The magnitudes of composition ratio were shown in the order of O, C, Si, Al, and Fe as a result of chemical composition analysis for clay samples. Besides, as the results of triaxial compression tests and consolidation tests, the shear strength, compression and permeability properties were increased with increasing in the concentration of contaminant (NaCl). It may be considered that these circumstances be caused by the changes of soil structure to flocculent structure due to the decrease in the thickness of diffuse double layer with increasing in the concentration of electrolyte. MT3D model was also using to grasp the procedures that the groundwater may be contaminated by the leachates permeated through the clay liner. The results of contaminant transport analysis showed a tendency that the predicted concentration of groundwater was higher with increasing in the initial concentration of $Cl^-$ ion and increased as a nonlinear curves with time. The transportation distance calculated by the use of regression equation between the distance from contaminant source and the concentration of $Cl^-$ ion was increased with increasing the initial concentration.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.283-283
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• 2010

17~18% 대역의 고효율 결정질실리콘 태양전지를 양산하기 위하여 국내외에서 다양한 연구개발이 수행되고 있으며 국내 다결정실리콘 태양전지 양산에서도 새로운 구조와 개념에 입각한 공정기술과 관련 장비의 국산화에 집중적인 투자를 진행하고 있다. 주지하는 바와 같이, 태양전지의 광전효율은 표면에 입사되는 태양광의 반사를 제외하면 흡수된 광자에 의해 생성되는 전자-정공쌍의 상대적인 비율인 내부양자효율에 의존하게 된다. 실제 생성된 전자-정공쌍은 기판재료의 결정상태와 전기광학적 물성 등에 의해 일부가 재결합되어 2차적인 광자의 생성이나 열로서 작용하고 최종적으로 전자와 정공이 완전히 분리되고 전극에 포집되어 실질적인 유효전류로 작용한다. 16% 이상의 고효율 결정질 실리콘 태양전지 양산이 요구되고 있는 현실에서 광전효율 개선 위해 가장 우선적으로 고려되어야 할 변수는 입력 태양광스펙트럼에 대한 결정질 실리콘 표면반사율을 최소화하여 광흡수를 극대화하는 것이라 할 수 있다. 현재까지 다결정 실리콘 표면을 화학적으로 혹은 플라즈마이온으로 50-100nm 직경의 바늘형 피라미드형상으로 texturing 함으로 단파장대역에서 광반사율의 감소를 기대할 수 있기 때문에 결정질실리콘 태양전지효율 개선에 긍정적인 영향을 미치는 것으로 알려져 있다. 고효율 다결정실리콘 태양전지 양산공정에 적용하기 위해 마스크를 사용하지 않는, RIE기반 건식 저반사율 결정질실리콘 표면 texturing 패턴연구를 수행하였다. 마스크없이 표면 texturing이 완료된 시료들에 대하여 A1.5G 표준태양광스펙트럼의 300-1100nm 파장대역에서 반사율과 minority carrier들의 life time 분포를 측정하고 검토하여 공정조건을 최적화 하였다. 저반사율의 건식 결정질실리콘 표면 texturing에 가장 적합한 플라즈마파워는 100W 내외로 낮았고 $SF_6/O_2$ 혼합비율은 0.8~0.9 범위엿다. 본 연구에서 확인된 최적의 texturing을 위한 플라즈마공정 조건은 이온에 의한 Si표면원자들의 스퍼터링과 화학반응에 의한 증착이 교차하는 상태로서 확인된 최저 평균반사율은 ~14% 내외였고 p-형 결정질실리콘 표면 texturing 패턴과 minority carrier의 life time 상관는 단결정이 16uS대역에서 14uS대역으로 감소하는 반면에서 다결정은 1.6uS대역에서 1.7uS대역으로 오히려 미세한 증가를 보여 다결정 웨이퍼생산과정에서 발생하는 saw-damage 제거의 긍정적 효과와 texturing공정의 표면 결함발생에 의한 부정적 효과가 상쇄되어 큰 변화를 보이지 않는 것으로 해석된다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.67-75
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• 2011

This paper investigates the radiated emission from the enclosure aperture, when the enclosure contains a 4-layer PCB and the PCB is driven by a pulse train additive with the switching noise from an active device. Radiated emission characteristics with and without switch noise cases, respectively, are analyzed by changing the PCB location and the slot direction. The equivalent circuit of a DC-DC converter is used to simulate the switching noise of active device. Also, MWS simulation results are directly connected to the ADS simulator as a 2-port block. The simulated results are compared with the measured ones.

• Journal of the Korean Society of Clothing and Textiles
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• v.20 no.1
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• pp.76-86
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• 1996

복식사 연구의 한 방법으로서, 문헌을 통하여 다량의 정보 수집이 가능할 경우, 사회과학의 분야에서 사용되어 온 내용분석법을 도입하여 정보의 수량화를 꾀할 수 있다. 본 연구에서는 내용분석법을 이용하여 1856년부터 1870년에 이르기까지 미국 여성의 평상복(daydress)중 재킷과 치마의 유행 경향을 당시의 대포적인 패션 잡지인 Godey's Ladies Book과 Perterson's Magazine의 패션 삽화를 토대로 분석하였다. 1856∼1870년은 미국의 남북전쟁 발발 5년 전부터 남북전쟁 직후 5년까지 의 15년간의 기간을 이르며, 해당 15년은 전쟁 전, 전쟁 중, 그리고 전쟁 후의 5년간씩의 3 시기로 나뉘어졌다. 연구의 목적은 여성 평상복의 디자인이 위의 기간 동안 남북전쟁의 한 영향으로서 군복 '라일의 경향을 띄게 되는지의 여부를 조사하는 것이다. 군복 스타일의 경향은 몸에 꼭 맞는 실루엣(fitted silhouette), 에플렛(epaulet), 스텐딩 칼라(standing collar), 더블 여밈 (double-breastedness) 다수의 단추의 사용 및 장식(buttons)으로 정의되었다. 여성스러운 스타일의 경향은 풍성한 실루엣 (full silhouette), 플라운스가 된 치마(flounced skirt), 그리고 러플/fp이 스/리본 (ruffles/lace/ribbons)의 사용 여부로 정의되었다. 연구의 초점은 객관적이고 체계적인 문헌 정보의 수집 방법을 수립하는 데 있었으며, 수집된 자로는 각 변수의 빈도 분포포에 의해 조사되었다. Fitted silhouette, epaulet, 그리고 standing collar는 제 3시기에 가장 많이 나타났고 제 1시기에 가장 적게 나타났다. 여성스러운 스타일에 있어서 full sihouette과 trounced skirt는 제 1시기에 가 장 많이 보였고 전쟁 당시와 전후에 점차적으로 적게 나타났다. Buttons나 double breastedness 등은 제 2시기에 가장 많이 보이고 제 3시기에는 오히려 가장 낮은 빈도수를 보였다. 반면에 ruffles/lace/ribbons는 fitted silhouette 등의 군복 스타일의 변수와 더불어 제 3시기에 가장 많이 보인 것으로 분석되었다. 전반적인 유행의 경향에 있어서, 군복 스타일의 변수와 여성스러운 경향의 변수를 각각 종합하여 분석해 보면, 제 2시기를 중심으로 전자의 유행은 점차적으로 증가하고 후자의 유행은 감소되고 있는 것을 볼 수 있다. 그러나 당시 미국 패션은 유럽 왕실의 유행에 의해 크게 영향을 받은 것을 감안할 때 본 연구의 결괴는 서양 복식의 역사의 선상에서 조심스럽게 해석되어야 할 것 이다.