• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.2
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• pp.157-165
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• 2011

Base isolation system is widely used for reduction of dynamic responses of structures subjected to seismic load. Recently, research on a smart base isolation system that can effectively reduce dynamic responses of the isolated structure without accompanying increases in base drifts has been actively conducted. In this study, a smart base isolation system was applied to an arch structure subjected to seismic excitation and its control performance for reduction of seismic responses was evaluated. In order to make a smart base isolation system, 4kN MR dampers and low damping elastomeric bearings were used. Seismic response control performance of the proposed smart base isolation system was compared to that of the optimally designed lead-rubber bearing(LRB) isolation system. To this end, an artificial ground motion developed based on KBC2009 design response spectrum was used as a seismic excitation. Fuzzy control algorithm was used to control MR damper in the smart base isolation system and multi-objective genetic algorithm was employed to optimize the fuzzy controller. Based on numerical simulation results, it has been shown that the smart base isolation system can drastically reduce base drifts and seismic responses of the example arch structure in comparison with LRB isolation system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.11
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• pp.9-16
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• 2011

We need to establish standard for the ICT based on train control system. In order to solve the ISI problem, this paper evaluate the performance of OFDM and FDE system. We seem that OFDM system is better than FDE system. In order to solve ISI problem, SC System is needed a equalizer. And another method is OFDM System. If system is used SC with a equalizer, It is better than OFDM in terms of PAPR, but this system is not easy to use Multi-Antenna technique, i.e., beam-forming and MIMO-multiplexing. And If system is used high-order modulation, BER performance is worse than OFDM. If we think about in terms of PAPR problem, considerations are considered not significant because the size of relays is not considered in the communication between trains and ground.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.49.2-49.2
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• 2014

The MIRIS (Multi-purpose InfraRed Imaging System) is a compact IR space Telescope, which has been developed by KASI since 2008 as the main payload of Korean STSAT-3. It was launched successfully by a Dnepr Rocket at Yasny Launch site, Russia in November 2013. After the launch, the STSAT-3 successfully settled down at Sun synchronous orbit with altitude of ~ 600km. Communications were regularly made between the ground station and the MIRIS with other secondary payload. We made a series of tests of the MIRIS during the verification period and found that all functions including the passive cooling are working as expected. The MIRIS has a wide-field of view $3.67{\times}3.67$ degrees and wavelength coverage from 0.9 to 2.0 micro-meter with the angular resolution of 51.6 arcsec. The main science missions of the MIRIS are (1) mapping of the Galactic plane with Paschen-alpha line (1.88 micro-meter) for the study of warm interstellar medium and (2) the measurement of large angular fluctuations of cosmic near infrared background radiation with I (1.05 micro meter) and H (1.6 micro meter) bands to identify their origin. We present the results of MIRIS initial operation in this paper.

• 한국지구과학회:학술대회논문집
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• 2010.04a
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• pp.38-39
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• 2010

낙뢰란 뇌운 속에서 분리 축적 된 음 (-)과 양 (+)의 전하 사이 또는 뇌운 속의 전하와 지면에 유도되는 전하 사이에서 발생하는 불꽃 방전을 말한다. 뇌운 안에는 이 불꽃 방전을 반복하기에 충분한 전하의 분리가 계속 일어나고 있는데, 그 결과 양전하 (+)는 구름의 상부에 넓게 분산되어 분포하고, 음전하 (-)는 주로 구름 하부에 분포한다. 이 때 음전하가 대지로 방전되어 발생하는 낙뢰를 부극성 (-)낙뢰, 양전하가 대지로 방전되어 발생하는 낙뢰를 정극성 (+)낙뢰라 한다. 낙뢰의 약 80%는 구름 내부 또는 구름 대 구름 사이에서 발생하고, 약 20%만이 구름과 지면 사이에서 발생하는데, 이러한 구름-지면 낙뢰 (Cloud-to-ground lightning)는 가장 위험하고 그 피해도 크다. 우리나라는 동아시아 몬순 기후의 영향으로 여름철에 대기가 불안정하여 낙뢰가 집중적으로 발생하며, 복잡한 지형과 해양의 영향으로 낙뢰현상의 공간적 변동도 크게 나타난다. 이러한 낙뢰는 최근으로 올수록 강도가 증가하고 있어 그 피해의 증가가 우려되기 때문에 낙뢰 발생 특성에 대한 연구가 필요하다. 본 연구에서는 낙뢰자료와 강수자료, 그리고 시 공간 분해능이 뛰어난 MTSAT-1R (Multi-functional Transport SATellite - 1 Replacement) 정지궤도 위성의 휘도온도를 이용하여 낙뢰 발생 시 강수 및 위성 휘도온도의 특성을 분석하고자 한다. 이러한 연구는 대류활동에 대한 정보 제공 뿐 아니라, 낙뢰 예측성 향상 및 재해 경감에도 활용될 수 있을 것이다. 본 연구에서는 2001년 기상청에 도입되어 운영 중인 신 낙뢰관측 시스템 (Total Lightning Detection System, TLDS)에서 관측된 낙뢰자료와 MTSAT-1R 위성에서 관측된 휘도온도 자료, 그리고 자동기상관측장비 (Automatic Weather System, AWS)에서 관측된 강수자료를 사용하였으며, 세 자료의 출처는 모두 기상청이다. 분석 기간은 2006년부터 2007년까지이며 우리나라에서 낙뢰발생 빈도가 여름철에 집중되어 나타나는 것을 고려하여 여름철 (6~8월) 낙뢰에 대해서만 분석하였다. 또한 낙뢰 발생 사례에 대하여 관측 효율이 90% 이상으로 알려진 위도 $33{\sim}39^{\circ}N$, 경도 $124{\sim}130^{\circ}E$ 영역에서 낙뢰발생시 강수 및 위성 휘도온도의 특성을 분석하였다. 사례는 낙뢰 발생 횟수가 많은 날을 중심으로 먼저 적외영상과 낙뢰영상을 정성적으로 분석한 후 뇌우의 지속시간이 긴 9개 사례를 선정하였다. MTSAT-1R 위성과 낙뢰자료 및 강수자료는 관측주기와 공간규모가 서로 다르기 때문에 세 자료를 함께 사용하기 위해서는 시 공간을 일치시키는 과정이 필요하다. 본 연구에서는 위성자료 관측시간(00분, 33분)과 AWS 지점 위 경도를 시 공간 일치를 위한 기준으로 사용하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.5
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• pp.33-39
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• 2010

This study develops an approximate procedure for incremental dynamic analysis (IDA) using modal pushover analysis (MPA) with empirical equations of the inelastic displacement ratio ($C_R$) and the collapse strength ratio ($R_C$). By using this procedure, it is not required to conduct linear or nonlinear response history analyses of multi- or single- degree of freedom (MDF) systems. Thus, IDA curves can be effortlessly obtained. For verification of the proposed procedure, the 6-, 9- and 20-story steel moment frames are tested under an ensemble of 44 ground motions. The results show that the MPA-based IDA with empirical equations of $C_R$ and $R_C$ produced accurate IDA curves of the MDF systems. The computing time is almost negligible compared to the exact IDA using repeated nonlinear response history analysis (RHA) of a structure and the original MPA-based IDA using repeated nonlinear RHA of modal SDF systems.

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.37-45
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• 2018

A two-axis gimbal-type antenna for a Compact Advanced Satellite (CAS) is used to efficiently transmit high resolution image data to a ground station. In this study, we designed the structure of a two-axis gimbal-type antenna while applying a launch lock device to secure its structural safety under a launch environment. To validate the effectiveness of the structural design, a structural analysis of the antenna was performed. First, a modal analysis was performed to investigate the dynamic responses of the antenna with and without the mechanical constraints of the launch lock device. In addition, a quasi-static analysis was performed to confirm the structural safety of the antenna structure and bolt I/Fs between the antenna base and the satellite. The suitable range of constraint force on the launch lock device was also determined to ensure the structural safety and mechanical gapping of the ball & socket interfaces, which places multi-constraints on the azimuth and elevation stage of the antenna.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.10 s.340
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• pp.1-8
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• 2005

In this paper, a FRAM design style based on PMOS-gating cell structure is described. The memory cell consists of a PMOS access transistor and a ferroelectric capacitor. Its plate is grounded. The proposed scheme employs three novel operating methods: 1) $V_{DD}$ precharged bitline, 2) negative-voltage wordline technique and 3) negative-pulse restore, Because this configuration doesn`t need the on-pitch plate control circuitry, it is effective in realizing cost-effective chip sizes. Implementation for a 2.5-V, 1-Mb FRAM prototype design in a $0.25-{\mu}m$, triple-well technology shows a chip size of $3.22\;mm^{2}$, an access time of 48 ns and an active current of 11 mA. The cell efficiency is 62.52 $\%$. It has gained approximately $20\;\%$ improvement in the cell array efficiency over the conventional plate-driven FRAM scheme.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.2
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• pp.71-81
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• 2007

One of the most important hydrologic components is evapotranspiration. It is a process by which water is evaporated from moist land surfaces and transpired into atmosphere by plants. There are many methods of estimating evapotranspiration rate and its potential such as the methods of soil-moisture sampling, lysimeter measurements, water balance, energy balance, groundwater fluctuations and evapotranspiration. But it is very difficult to estimate evapotranspiration in terms of regional discrete characteristics of topography and/or vegetation. The evapotranspiration is strongly affected by ground covering vegetation, and the degree of vegetation growth. In order to grasp vegetation condition over a vast study area, NDVI (Normalized Difference Vegetation Indices) calculated from the data obtained from NOAA/AVHRR were utilized. Through multi-regression analysis, we developed a model equation to estimate the evapotranspiration using NDVIs and temperature data.

• The Journal of the Acoustical Society of Korea
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• v.31 no.5
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• pp.309-316
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• 2012

This paper suggest configuration method of small-size system and design method of module using multi power. In particular module designed to focus on PDN(Power Distribution Network) and filter configuration method to improve the characteristics of noise sensitive analog IC. For the prevention of high-voltage noise, manufactured module is used the ground-isolated technique and via stitching, and is connected grounds with a series of filters. In this paper, so we analyzed PDN structure through the simulation using lumped modeling and confirmed through measurement. Simulation results, when connecting 4.7uH inductor, we made certain that noise of -7dB decreases much more than when it did not. And it was confirmed 12% less than Background Noise.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.6
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• pp.669-678
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• 2009

Real-time image georeferencing technologies are required to generate spatial information promptly from the image sequences acquired by a multi-sensor system. We thus derive a sequential adjustment algorithm based on the combined adjustment model. By adopting the sequential adjustment model, we develop a sequential AT(Aerial Triangulation) algorithm to georeference image sequences in real-time. The proposed algorithm enables to perform AT rapidly with the minimum computation at the current stage by using the results computed at the previous stage whenever a new image is added. Experiments with simulated data were conducted to verify the effectiveness of the proposed algorithm. The results of the experiments show that the georeferencing of each image took very short time and its accuracy was determined within ${\pm}4cm$ on the ground control points comparing to the results of the existing simultaneous AT.