• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.276-277
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• 2005

본 연구에서는 MCP법을 이용하여 Bi2212 초전도 튜브를 제작하고 공정 변수에 따른 초전도 튜브의 전기적 특성을 평가하였다. 초전도 분말은 $1100^{\circ}C$에서 용융하여 $300\sim500^{\circ}C$로 예열된 몰드 내에 주입하였으며 몰드는 1000 RPM으로 회전시켰다 제작된 초전도 튜브는 $840^{\circ}C$ 의 $O_2$ 분위기에서 72시간 열처리 하였다. SEM과 XRD 분석결과 튜브는 약 $40{\mu}m$의 크기를 갖는 Bi2212 초전도 상이 일정한 방향성을 갖으며 XRD 분석 결과 튜브 바깥부문에 Bi2201상이 존재하였다. 전기적 특성은 몰드 회전 속도가 증가할수록, 튜브의 두께가 증가할수록, 길이가 감소할수록 높은 $I_c$ 값을 나타내었으며, 이때 50 mm$\times$70 mm$\times$2.5 mm, 1000 RPM의 튜브에서 전기적 특성은 $I_c$=890 A, $T_c$= 80 K의 값을 나타내었다.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.197-202
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• 2010

Post release mechanism is generally used to reduce the severity of the occupant of an errant vehicle impacting a roadside posts. The 820kg-50km/h head-on impact simulations were made using LS-DYNA program for the posts of 101.6mm Dia(t=4.0mm) with and without clip-type release mechanism. The simulation result was compared with impact test result to enhance the credibility of simulation model. The study shows that the high impact severity (THIV, PHD) and excessive deformation threatens the safety of the occupant when a car impacts a rigidly connected posts, while a post with clip-type slip base reduce the impact severity to a safe level.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.5
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• pp.2061-2066
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• 2011

A cycloid speed reducer is one of the rotational speed regulation devices of the machinery. A cycloid speed reducer has an advantage of transmitting high torque, but is known to be unsuitable for high speed rotation. However, it is almost impossible in an analytical method to find a use limit speed when installing such a speed reducer in a 200ton loading transporter. In this research the cycloid reducer was simulated to get its performance depending on friction energy loss in time domain by using by LS-DYNA. The maximum torque of the cycloid speed reducer is 3.5ton-m, so the comparison of analysis results between a case of 60rpm rotation and a case of 162rpm rotation with such a torque showed the following results. In the case of 60rpm rotation, the maximum stress appearing in the RV gear and the pin gear was 463MPa and 507MPa. Lost power due to friction was 50kW; In the case of 162rpm rotation, the maximum stress appearing in the RV gear and the pin gear was 550MPa and 538MPa. Lost power due to friction was 175kW, which was shown to be almost impossible to use.

• Earthquakes and Structures
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• v.11 no.3
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• pp.483-503
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• 2016

This study aims to evaluate seismic performance of existing low and mid-rise reinforced concrete buildings by comparing their displacement capacities and displacement demands under selected ground motions experienced in Turkey as well as demand spectrum provided in 2007 Turkish Earthquake Code for design earthquake with 10% probability of exceedance in 50 years for soil class Z3. It should be noted that typical residential buildings are designed according to demand spectrum of 10% probability of exceedance in 50 years. Three RC building sets as 2-, 4- and 7-story, are selected to represent reference low-and mid-rise buildings located in the high seismicity region of Turkey. The selected buildings are typical beam-column RC frame buildings with no shear walls. The outcomes of detailed field and archive investigation including approximately 500 real residential RC buildings established building models to reflect existing building stock. Total of 72 3-D building models are constructed from the reference buildings to include the effects of some properties such as structural irregularities, concrete strength, seismic codes, structural deficiencies, transverse reinforcement detailing, and number of story on seismic performance of low and mid-rise RC buildings. Capacity curves of building sets are obtained by nonlinear static analyses conducted in two principal directions, resulting in 144 models. The inelastic dynamic characteristics are represented by "equivalent" Single-Degree-of- Freedom (ESDOF) systems using obtained capacity curves of buildings. Nonlinear time history analysis is used to estimate displacement demands of representative building models idealized with (ESDOF) systems subjected to the selected ground motion records from past earthquakes in Turkey. The results show that the significant number of pre-modern code 4- and 7-story buildings exceeds LS performance level while the modern code 4- and 7-story buildings have better performances. The findings obviously indicate the existence of destructive earthquakes especially for 4- and 7-story buildings. Significant improvements in the performance of the buildings per modern code are also obvious in the study. Almost one third of pre-modern code buildings is exceeding LS level during records in the past earthquakes. This observation also supports the building damages experienced in the past earthquake events in Turkey.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.5
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• pp.322-330
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• 2020

Modeling for outliers in time series was carried out using the MSL and extreme high, low tide levels (EHL, HLL) data set in the Busan and Mokpo stations. The time-series model is seasonal ARIMA model including the components of the AO (additive outliers) and LS (level shift). The optimal model was selected based on the AIC value and the model parameters were estimated using the 'tso' function (in 'tsoutliers' package of R). The main results by the model application, i.e.. outliers and level shift detections, are as follows. (1) The two AO are detected in the Busan monthly EHL data and the AO magnitudes were estimated to 65.5 cm (by typhoon MAEMI) and 29.5 cm (by typhoon SANBA), respectively. (2) The one level shift in 1983 is detected in Mokpo monthly MSL data, and the LS magnitude was estimated to 21.2 cm by the Youngsan River tidal estuary barrier construction. On the other hand, the RMS errors are computed about 1.95 cm (MSL), 5.11 cm (EHL), and 6.50 cm (ELL) in Busan station, and about 2.10 cm (MSL), 11.80 cm (EHL), and 9.14 cm (ELL) in Mokpo station, respectively.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.393-395
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• 2015

Weak gravitational lensing is an efficient technique for detecting galaxy clusters and probing their mass distribution. We present a weak gravitational lensing analysis of a large sample of galaxy clusters. We have built a nearly complete sample of 50 optically rich clusters, located in the redshift range 0.1 < z < 0.6 and observed in the Canada France Hawaii Telescope Legacy Survey (CFHT-LS). We used weak gravitational lensing to measure, for each galaxy cluster, the density radial profile, the total mass and the mass-to-light ratio (by comparing with the total luminosity of the member galaxies). This project is a preliminary step towards the next analysis of the weak lensing galaxy clusters in the surveys KiDS and VOICE, which are currently collecting data with the VLT Survey Telescope, in Chile.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.748-749
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• 2007

HVDC(High Voltage Direct Current) is an underwater cable between Jeju Island and Haenam in main land and supplies approximately 50% of electrical usage in Jeju Island. If there is any power failure due to HVDC, it will cost approximately 50,000 US dollars per day including Thermal Electrical Generation. Therefore it is absolutely necessary to recover the problem in rapid timely basis. In conclusion, jointing methode of HVDC cable is needed urgently to upgrade current HVDC underwater cable repair technique in Korea to minimize the cost and time factors.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.808-809
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• 2008

22.9kV 50MVA HTS power cable has been developed and tested by Korea Electrotechnology Research Institute and LS Cable Company and it was supported by a grant from Center for Applied Superconductivity Technology of the 21st Century Frontier R&D Program. In this paper, DC Ic of 100m HTS cable which is installed at Kochang testing station was measured and analyzed. A measurement technique of DC Ic used by resistance and inductance removal method is established. The HTS power cable is composed of 2 layers for transmission and 1 layer for shield. For the analysis of AC losses in an HTS power cable, 2-dimensional numerical calculation was carried out to define the magnetic field distribution. We calculated the magnetization losses in the HTS core of that cable from these fields. These calculated results are in accordance with those of experiment.

• Journal of the Korean Solar Energy Society
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• v.27 no.2
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• pp.29-35
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• 2007

Monitoring system is constructed for evaluating and analyzing performance of installed 50kW grid-connected PV system and have been monitored since October 2005. As climatic and irradiation conditions have been varied through long-term operation, there is necessity for evaluating numerical values of PV(Photovoltaic) system performance to observe the overall effect of environmental conditions on their operation characteristics. This paper presents performance monitoring results and analysis on component perspective(PV array and power conditioning system) and global perspective(yield, losses) of PV system for one year monitoring periods.

• Progress in Superconductivity and Cryogenics
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• v.11 no.3
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• pp.46-49
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• 2009

A 3-phase 100m long, 22.9kV class HTS power transmission cable system was developed by Korea Electrotechnology Research Institute (KERI) and LS cable Ltd. those are participated in the 21st Century Frontier project R&D Program of Korea. It is important to test the DC critical current related with its power capacity before applying to the real power grid. In 1995, several international standards organizations including International Electrotechnical Commission (IEC), decided to unify the use of statistical terms related with 'accuracy' or 'precision' in their standards. It was decided to use the word 'uncertainty' for all quantitative (associated with a number) statistical expressions. In this paper, we measured DC critical current of 22.9kV/50MVA superconducting power cable with several voltage tap and analyzed the uncertainty with these results.