• 한국수정란이식학회지
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• 제29권3호
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• pp.221-228
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• 2014

Despite that porcine spermatogonial stem cells (pSSCs) have been regarded as a practical tool for preserving eternally genetic backgrounds derived from pigs with high performance in the economic traits or phenotypes of specific human diseases, there were no reports about precise definition of niche conditions promoting proliferation and maintenance of pSSCs. Accordingly, we tried to determine niche conditions supporting proliferation and maintenance of undifferentiated pSSCs for short-term. For these, undifferentiated pSSCs were progressively cultured in different composition of culture medium, seeding density of pSSCs, type of feeder cells and concentration of growth factors, and then total number of and alkaline phosphatase (AP) activity of pSSCs were investigated at post-6 day culture. As the results, the culture of $4{\times}10^5$ pSSCs on mitotically in activated $2{\times}10^5$ STO cells in the mouse embryonic stem cell culture medium (mESCCM) supplemented with 30 ng/ml glial cell line-derived neurotrophic factor (GDNF) was identified as the best niche condition supporting effectively the short-term maintenance of undifferentiated pSSCs. Moreover, the optimized short-term culture system will be a basis for developing long-term culture system of pSSCs in the following researches.

• Nuclear Engineering and Technology
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• 제35권6호
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• pp.547-555
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• 2003

Fire hazard and risk analysis at Nuclear Power Plants is implemented on the basis of the normal operational configuration. This steady configuration, however, can be changed due to the temporary displacement of equipment, electric cable and irregular movement of workers through the fire compartments when the on-line maintenance is processed during the power operation mode or the scheduled outage mode for the refueling. With the consequence of this configuration change, the fire analysis condition and the evaluation result will be different from those that were analyzed based on the steady configuration. In this context, at this paper, the general items for the reassessment are categorized when the configuration has changed. The contemporary zone models for the detail fire analysis are also illustrated for their application for each classified condition.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.1115-1120
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• 2005

characteristic of wear between wheel and rail is important factor of judgement to maintenance. KHST is optimized on an exclusive rail, UIC60. but also KHST is running on the variety existing line as well as KS50N, KS60 et,c. Hail profile of KS50N is dissimilar to DIC60. So we can predict that characteristic of wear is embodied also different. In this paper. we deduced the force and point of contact position between wheel and rail through multi-dynamics analysis and predicted wear of wheel and rail through contact problem analysis. we used simplified theory of kallker on contact problem, and Predicted the wear phenomenon of wheel using archard wear equation about each condition.

• 한국ITS학회 논문지
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• 제19권4호
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• pp.1-12
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• 2020

본 연구에서는 COVID-19 대유행에 따른 다중밀집시설 중 하나인 서울역 역사를 대상으로 사회적 거리(Social Distance) 유지 및 보행동선체계 구축에 따른 효과분석을 진행하였다. 분석을 위해 서울역 CAD 및 철도역사 이용객 수 조사를 통하여 서울역 보행 Network를 구축하였으며, Social Force Model을 활용하여 사회적 거리(Social Distance)를 유지하는 보행자를 구현하였다. 이를 바탕으로 시나리오 분석을 수행하였다. 분석결과, 보행동선체계 도입 시 현황과 비교하여 평균보행속도가 감소하였으나 평균보행밀도의 경우 보행 서비스수준(LOS) 'C'를 유지하는 것으로 분석되어 보행동선체계의 효과가 입증되었으며, 향후 보행계획 시 보행 시뮬레이션 모델로서 활용이 가능할 것으로 기대된다.

• 아시안잔디학회지
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• 제16권1호
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• pp.31-40
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• 2002

본 연구는 Olympic 주경기장 그라운드의 잔디 관리와 지반 구조 조사 및 잔디의 시각적 품질과 지반 경도와의 상관관계를 분석하였다. 또한 지반의 이.화학성 분석을 하여 잔디 구장의 조성과 관리 방향을 제시하는 것이 목적이다. Olympic 주경기장의 토양경도 분포는 답압이 집중되는 goal line 지역과 center circle 지역에서 높은 경도를 나타내었으며, 답압이 상대적으로 적은 end line 부근지역에서 낮은 경도를 나타내었다. 또한 토양 경도와 잔디 quality는 음의 상관관계를 나타내었고 토양의 경도가 높을수록 잔디의 quality에 악영향 미치는 것으로 분석되었다. 깊이별 토양 경도는 상토층 하부로 갈수록 높아졌으며 답압 정도는 지표면의 토양 경도를 변화시키고, 하부 6cm까지도 영향을 미치는 것으로 나타났다. 상토층 토양의 화학성은 인산이 2,000ppm 내외(기군치 100~300ppm)의 과대치를 제외하고 는 일반적 기준치에 부합되었다. 토양의 입도분포는 silt와 clay 함량이 USGA 잔디 상토층 토양 기준치(silt 5% 이하, clay 3% 이하)보다 높아 토양 경직을 가속화시키는 요인으로 작용하였다. Olympic 주경기장 잔디 그라운드는 초기 지반 공사시 정확한 시공이 되지 않은 점과 기술적 문제로 인한 하부 지반공사의 미비 등의 결점을 지니고 있다. 지반 경도는 잔디 생육에 밀접한 관계를 가지고 있으며 정상적 잔디생육을 위하여 재시공에 의한 근본적인 토양 경화의 문제점을 해결해야 할 것이다. 이러한 연구를 토대로 향후 건설될 잔디 경기장은 표준 시방에 맞게 설계, 시공되어 토양경직을 유발시키지 않아야 국제 규격에 맞는 잔디 그라운드를 건설할 수 있을 것이다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.82-92
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• 2011

This paper presents a PFC(Power Factor Correction) system to control the power factor of input current of the converter system which is working in the propulsion system of KTX high speed train. In the KTX train system, initially introduced from ALSTOM, the thyristor converter with phase controlling technique is adopted in the current fed type powering system. The input current induces harmonic losses highly because the waveform becomes rectangular shapes according to the filter inductor current increased as the train speed increasing gradually. Especially the interference with the signalling systems is severe concerned due to high current harmonics on the catenary line. To protect this problem, a frequency trap filter(notch filter) is operating with the input converter system. In this paper, an analysis work and PC simulation have been done on the PFC system to upgrade its performance and maintenance efficiency.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1269-1274
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• 2011

To cut down the maintenance expenses at branch lines, the foreign developed countries have developed the low-cost signalling on low-density lines. These examples are FFB(FunkFahrBetrieb) Radio based train operation by German railways(Deutsche Bahn AG), ERTMS REGIONAL by Europe and LOCOPROL system using a GPS. Also, Korea is developing Information and Communication Technology based low-cost signalling on low-density lines. The characteristics of this system are directly controled switch and crossing by driver. For the purpose of this paper, we reviewed the business process for switch and crossing control. Specially, we compared and analysed both methods whether the driver takes control over the operation procedures of switch or the control message is carried by the command of the controller. And by utilizing the instrument of UML, I planned the switch according to the control authority and the operation procedures needed for the control of crossing.

• 설비공학논문집
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• 제24권1호
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• pp.85-89
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• 2012

This study has been conducted to compare two cargo handling systems on MR tanker and Panamax tanker. Submerged hydraulic cargo pumps with hydraulic power packs and frequency converter controlled electric deepwell pumps will be investigated and compared on all aspects of initial cost, installation, operation and maintenance. The result of investigation shows Electric Systems have less manufacturing costs, higher environmental friendliness and reliable operation compare to Hydraulic Systems. Furthermore, the present experimental data will provide important database for Electric Systems onboard new ships and practical and empirical guidelines are constructed for further determine the design of the Electric Systems.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.739-744
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• 2000

Concrete structures generally have cracks, so for the safety and durability of structures, studies to detect cracks using nondestructive tests have been treated in great deal. In order to assure the reliability of concrete structure, microscopic fracture behavior and internal damage progress of concrete under the loading should be fully understood. The purpose of this study predicts location of initial crack and measures direction of crack propagation for on-line monitoring before the crack really grows in structures by using two-dimensional Acoustic Emission(AE) source location based on rectangular method with three-point bending test. This will allow efficient maintenance of concrete structure through monitoring of internal cracking based on AE method.

• Journal of Positioning, Navigation, and Timing
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• 제9권2호
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• pp.125-129
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• 2020

In this paper, Zero velocity UPdaTe (ZUPT) is implemented on the navigation system of Remotely Piloted Aircraft for GNSS denied environment. RPA's navigation system suffers from lack or loss of satellite signal while maintenance or ground test inside a hangar. Although some of the hangars install GPS repeaters for indoor tests, the anti-jamming equipment with array antenna blocks the repeater signal regarding them as hostile jamming signal. With ZUPT, an aircraft navigation system can be tested free from the divergence of navigation solution without line-of-sight satellites. The designed ZUPT aided centralized Kalman Filter is implemented on the Embedded GPS&INS and simulated with Captive Flight Test data. The simulation result shows stable navigation solution without GNSS updates.