• Molecules and Cells
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• 제19권1호
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• pp.31-38
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• 2005

Human embryonic stem (hES) cells have unique features including unlimited growth capacity, expression of specific markers, normal karyotypes and an ability to differentiate. Many investigators have tried to use hES cells for cell-based therapy, but there is little information about the properties of available hES cell lines. We compared the characteristics of three hES cell lines. The expression of SSEA-1, -3, -4, and APase, was examined by immunocytochemistry, and Oct-4 expression was analyzed by RT-PCR. Differentiation of the hES cells in vitro and in vivo led to the formation of embryoid bodies (EBs) or teratomas. We examined the expression of tissue-specific markers in the differentiated cells by semiquantitative RT-PCR, and the ability of each hES cell line to proliferate was measured by flow cytometry of DNA content and ELISA. The three hES cell lines were similar in morphology, marker expression, and teratoma formation. However there were significant differences (P < 0.05) between the differentiated cells formed by the different cell lines in levels of expression of tissue-specific markers such as renin, kallikrein, Glut-2, ${\beta}-$ and ${\delta}-globin$, albumin, and ${\alpha}1-antitrypsin$ (${\alpha}1-AT$). The hES cell lines also differed in proliferative activity. Our observations should be useful in basic and clinical hES cell research.

• 고려인삼학회:학술대회논문집
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• 고려인삼학회 1998년도 Advances in Ginseng Research - Proceedings of the 7th International Symposium on Ginseng -
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• pp.224-230
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• 1998

This study showed the anti-invasive activity of ginseng components, panaxadiol (PD) and panamatrlol (PT) on the highly metastatic HT1080 human flbrosarcoma cell line. PD and PT reduced tumor cell invasion through a reconstitute basement membrane in the transwell chamber. A significant down regulation of MMP-9 by PD and PT was detected by northern blot analysis. However, MMP-2 was constantly expressed. Quantitative gelatin based zymography confirmed a marked reduced expression of MMP-9 but not MMP-2 in the treatment of PD and PT. Since the chemical structures of PD and PT are very similar to that of dexamethasone, a synthetic glucocorticoid, it was investigated whether PD and PT act through GR. Western blot analysis and immunocytochemistry showed that PD and PT increased the GR fraction in the nucleus. These results suggest that ursolic acid may induce repression of MMP-9 by stimulating the nuclear translocation of GR and hence inhibiting the activity of AP-1 to TPA-responsible element of MMP-9 promoter region. In conclusion, we suggest that CR-induced down-regulation of MMP-9 by PD and PT contributes to reduce the invasive capacity of HT 1080 cells.

• 전기학회논문지
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• 제62권1호
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• pp.143-148
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• 2013

When the fault occurs in power system, the fault-current exceeds breaking capacity of the circuit breaker. So, reliablity of the power system is decreased sharply. Superconducting fault-current limiter (SFCL) is operated without impedance in normal state. The fault-current is limited by its impedance during the fault condition. However, the SFCL has several weak points such as huge size, high-price, liquid-nitrogen operation for the real power system. In this paper, We suggested the high-speed interrupter to limit the fault-current in case of the single line-to-ground fault. In addition, we compared the high-speed interrupter with the SFCL to ensure the operation reliability. The proposed interrupter detected the fault-current through the CT, and the power was supplied by operation of the SCR control system. In this experiment, the power of high-speed interrupter was applied after the 4.8[msec] from fault instant. The on-off operation of the interrupter was started after half-cycle from the fault. The fault-current was flowed into the impedance element by the switching operation of the high-speed interrupter. So, the fault current was limited within one cycle, and then it didnt exceed the capacity of a circuit breaker. We confirmed that there was slight difference between the SFCL with high-speed interrupter in terms of limiting-time of the fault-current and switching speed of the SCR. The high-speed interrupter was considered to be more efficient than the SFCL in size, cost or reliability.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2008년도 춘계 종합학술대회 논문집
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• pp.38-42
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• 2008

2000년대를 맞이하면서 국내에서는 PC 패키지 게임시장이 쇠퇴하고 유선 인터넷을 기반으로 한 온라인 게임과 무선 인터넷을 기반으로 한 모바일게임, 그리고 가정용 게임기를 중심으로한 고성능 콘솔게임이 새로운 게임 플랫폼의 주류로 자리잡게 되었다. 그중에서도 모바일게임은 시간과 장소의 제약을 극복하는 '이동성'이라는 특징으로 인해 폭발적으로 성장하였다. 그러나, 타 플랫폼과는 달리 모바일게임은 콘텐츠를 사용자의 휴대단말기에 탑재하기 위해서 고가의 무선인터넷 요금을 지불하여야 하고, 휴대단말기의 하드웨어에 장착된 저장 메모리 공간의 부족으로 인해 게임 콘텐츠의 용량 제한이라는 한계를 극복해야하는 문제점이 있다. 모바일게임 콘텐츠의 용량은 주로 이미지 데이터의 용량이 대부분을 차지하므로, 본 논문에서는 이미지 데이터 처리의 최적화를 위한 기술을 압축방식과 이미지 포맷을 유형별로 구분하여 분석함으로써 용량이 제한된 모바일 단말기상에서 최적화된 이미지 데이터들을 포함한 콘텐츠를 제작할 수 있는 방안을 제시한다.

• Journal of Welding and Joining
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• 제28권2호
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• pp.66-73
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• 2010

Conventional fracture test of resistance spot weld had been performed without consideration of paint baking process in automobile manufacturing line. This study was aim to investigate the effect of paint baking on fracture mode and load carrying capacity in fracture test for resistance spot welded 780TRIP steels. With paint baking cycle after resistance spot welds, peel tests and microhardness were conducted on the as-welded and baked samples. Resistance spot welds in AHSS (Advanced High Strength Steels) are prone to display partial interfacial fractures during fracture test or vehicle crash. Baking cycle increased the load-carrying capacity of the resistance spot welded samples and improved the fracture appearance from partial to full button fracture for the L-type peel tests. Specially, the differences in fracture appearance are apparent when the nugget size of spot welds is small enough to produce the partial interfacial fracture. The comparison of macrohardness and microstructure between as-welded and baked samples showed that there are no large difference in change the fracture mode. However, the results of the instrumented indentation test suggested that fusion zone and HAZ of baked sample have less tensile and yield strength and proves that the tempering effects are applied and enhanced the resistance to fracture on welds with application of baking cycle.

• 대한금속재료학회지
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• 제49권12호
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• pp.967-976
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• 2011

Conventional fracture tests of resistance spot welds have been performed without consideration of the paint baking process in the automobile manufacturing line. The aim of this paper is to investigate the effect of the paint baking process on load carrying capacity and fracture mode for resistance spot welded 590 dual phase (DP), 780DP, 980DP, 590 transformation in duced plasticity (TRIP), 780TRIP and 1180 complex phase (CP) steels. With paint baking after resistance spot welding, the l-shape tensile test (LTT) and nano-indentation test were conducted on the as-welded and paint baked samples. Paint baking increased the load-carrying capacity of the resistance spot welded samples and improved the fracture appearance from partial interfacial fracture (PIF) to button fracture (BF). Improvement in fracture appearance after LTT is observed on weldments of 780 MPa grade TRIP steels, especially in the low welding current range with paint baking conditions. The higher carbon contents (or carbon equivalent) are attributed to the low weldability of the resistance spot welding of high strength steels. Improvement of the fracture mode and load carrying ability has been achieved with ferrite hardening and carbide formation during the paint baking process. The average nano-indentation hardness profile for each weld zone shows hardening of the base metal and softening of the heat affected zone (HAZ) and the weld metal, which proves that microstructural changes occur during low temperature heat treatment.

• 한국컴퓨터정보학회논문지
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• 제24권3호
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• pp.201-208
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• 2019

The government has proposed a development model for universities to strengthen the capacity of the College of Humanities as part of the university restructuring policy in line with the trend of the times, and encouraged each university to voluntarily induce the establishment of the humanities development plan through financial support under their own individual conditions. With the decline in the school-age population due to the declining fertility rate, the rapid change in the industrial structure has highlighted the decline in the employment rate of the students of the humanities. Therefore, the government is implementing university grading based on the results of the university structural reform evaluation, and pressing low-grade universities through reduction of capacity and reduction of support. In the course of this change, universities have designated the College of Humanities as the primary target of integration with other majors or and its disintegration. This study examines the direction of the government's attempt to change the humanities in the era of the Fourth Industrial Revolution, and suggests a precedent example during the reform of the humanities college. If the humanities college is integrated with practical studies such as management, design, IT, CT, and engineering, the strengths of the humanities can be highlighted. However, the results of this study suggest that many variables such as consideration of students' aptitudes and interests in the integration process of majors, autonomy in major selection, understanding between departments integrated, and demand for a single major before integration or disintegration should be considered. In addition, an example of a local private university shows that the hasty attempt to integrate or disintegrate the humanities can rather lead to various educational harms.

• 한국산업융합학회 논문집
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• 제25권6_2호
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• pp.1071-1081
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• 2022

As the demand for high-rise buildings increases, the demand for high-speed elevators is also increasing. In order to make a high-speed elevator, a method is needed to reduce the weight of the elevator's components, which is a constraint on the increase in speed. As a measure to reduce the weight, it is possible to remove the traveling cable for power and signal supply. Since the weight of the traveling cable varies depending on the position of the carriage, it is difficult to compensate the weight using the counter weight. The power supply is a structure in which a brush-rail type power input terminal is installed in the elevator hoistway to receive power in a contact-type manner while the carriage is moving. If a small-capacity ESS is installed in a passenger car, power can be supplied uninterruptedly inside the passenger car. A small-capacity ESS charging system to be applied to such an elevator system is required to perform several functions. First, the passenger Car must be able to charge as much as possible even during high-speed operation. A control algorithm with high responsiveness is required because charging starts and ends repeatedly by the partially installed input power stage. In addition, if the input-side line impedance is large due to the structure of the system and the response characteristic is increased, the stability of the system may be lowered. Accordingly, in this paper, we propose a control algorithm that has a stable steady-state output while having a fast response in a transient state. To verify the proposed control algorithm, simulation was conducted using PSIM, and the performance of the controller was verified by manufacturing a prototype buck conveter charger.

• 한국음향학회지
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• 제26권7호
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• pp.366-374
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• 2007

수중에서 무선통신이 기존에는 초음파를 이용한 단거리통신에 국한되었으나 최근 고주파를 이용한 장거리 통신의 필요성이 증가되고 음성뿐만이 아니라 각종 데이터나 고화질 영상자료의 송수신 수요가 늘어나고 있다. 본 연구에서는 수중에서 디지털 변조방식의 차이에 따라 실제 수중통신에 미치는 영향에 대하여 연구하였다. 모의 환경 하에서 PSK기반의 변조방식(BPSK, QPSK, MSK, GMSK)에 대한 시뮬레이션을 통해 실험한 결과 GMSK만이 큰 차이를 보였다. 위 결과를 바탕으로 SNR을 35dB이하로 하고 부산 남방에 위치한 207-선(한국해양자료센타)의 15Km 구간을 모의하여 음성통신과 영상자료를 전송실험한 결과 음성통신시($10^{-2}$BER, 채널용량 1Kbps기준)는 약 8Km의 거리 차이를, 그리고 영상자료($3{\times}10^5$ 화소, 화소 당 정보량 4bit) 전송시는 BPSK, QPSK, MSK 는 60Kbps, GMSK는 45Kbps의 전송율을 확보하여 약 7초의 전송시간 차이가 생김을 확인하였다.

• 한국통신학회논문지
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• 제27권9C호
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• pp.829-835
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• 2002

디지털 가입자 회선(DSL)의 채널 용량에 가장 크게 영향을 미치는 내부 잡음원으로서 근단누화(NEXT) 및 원단누화(FEXT) 잡음을 들 수 있지만, 외부 잡음원인 임펄스 영향에 의해 DSL 성능 열화가 야기되므로 송수신 설계에 있어 이들 잡음원들의 복합적인 성능 분석이 절실히 요구되고 있다. 이에 본 연구에서는 테스트 신호 Cook 펄스를 Middleton의 Class A 임펄스 신호로 모델화 한 후, 가우스 잡음, NEXT 및 FEXT 잡음, 임펄스 잡음의 복합 잡음환경에서 DMT 신호의 SNR 마진을 계산하여 평가를 행하였다. 그 결과 업링크상에서는 루프전송길이에 따른 전송속도의 열화는 크지 않으며, 잡음의 특성에 의해 전송속도가 제한되지만, 다운링크상에서는 루프 전송길이 뿐만 아니라 잡음특성등에 의한 복합적인 열화가 두드러짐을 알 수 있다. 결론적으로 본 연구의 결과는 임펄스 잡음을 포함한 복합환경에서의 ADSL 성능기준을 설정하는데 주요 자료로서 활용될 수 있을 것이다.