• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.265-265
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• 2012

한반도 지역의 강설(snowfall)은 전체 연 강수량의 약 10% 이하로 매우 적은 양을 차지하고 있다. 하지만 강설은 대기질(air quality)을 개선하고 산불 발생률을 저감시키며, 특히 봄철 수자원의 제공과 가뭄피해 경감 등 수문학적으로도 중요한 기능을 가진다. 하지만 최근 기후변화로 인해 폭설 현상이 빈번하게 발생하여 사회 경제적 손실을 유발하고 있다. 따라서 강설로 인한 피해를 최소한으로 줄이기 위해서는 정확한 강설탐지 및 강설 추정 방법이 필요하다. 최근 해외의 수많은 연구들을 통하여 수동 마이크로파 센서 자료를 활용한 강설 추정의 가능성이 확인되고 있다. 하지만 수동 마이크로파 센서의 휘도온도를 이용한 추정 방법들은 대기의 연직 구조 파악에 어려움이 있기 때문에 정확한 강설량을 추정하는 데에 한계가 있다. 그러나 2006년 발사된 CloudSat의 Cloud Profiling Radar는 강설의 연직 프로파일에 대한 가치 있는 정보를 제공하기 때문에 수동 마이크로파 센서 자료와의 결합을 통해 보다 정확한 강설 추정 알고리즘을 제시할 수 있을 것으로 판단된다. 따라서 본 연구에서는 CloudSat의 Cloud Profiling Radar (CPR) 자료와 수동 마이크로파 센서인 NOAA의 Microwave Humidity Sounder (MHS) 센서 자료를 결합하여 한반도 강설 추정에 적합한 알고리즘을 개발하고자 한다.

• Journal of Astronomy and Space Sciences
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• v.36 no.3
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• pp.213-223
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• 2019

This paper analyzes delta-Vs to maintain an extremely low altitude on the Moon and investigates the possibilities of performing a CubeSat mission. To formulate the station-keeping (SK) problem at an extremely low altitude, current work has utilized real-flight performance proven software, the Systems Tool Kit Astrogator by Analytical Graphics Inc. With a high-fidelity force model, properties of SK maneuver delta-Vs to maintain an extremely low altitude are successfully derived with respect to different sets of reference orbits; of different altitudes as well as deadband limits. The effect of the degree and order selection of lunar gravitational harmonics on the overall SK maneuver strategy is also analyzed. Based on the derived SK maneuver delta-V costs, the possibilities of performing a CubeSat mission are analyzed with the expected mission lifetime by applying the current flight-proven miniaturized propulsion system performances. Moreover, the lunar surface coverage as well as the orbital characteristics of a candidate reference orbit are discussed. As a result, it is concluded that an approximately 15-kg class CubeSat could maintain an orbit (30-50 km reference altitude having ${\pm}10km$ deadband limits) around the Moon for 1-6 months and provide almost full coverage of the lunar surface.

• International Journal of Internet, Broadcasting and Communication
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• v.14 no.2
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• pp.171-182
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• 2022

In this study, by classifying latent groups for disaster safety awareness focusing on the four sub-factors of the developed disaster awareness scale of high school students, the characteristics of each group were examined, and the differences between latent classes according to inter-individual differences were investigated. As a result of analysis based on the data of a total of 1054 high school students, the disaster safety awareness of high school students was classified into three latent groups. Each latent group was named 'High Safety Awareness Type(SAT)', 'Normal SAT', and 'Low SAT' according to its characteristics. In all four fire safety awareness sub-factors, 'High SAT', which had a high score, accounted for 56.5% of the total, and 'Normal SAT', which had a moderate score in the sub-factors, had the lowest ratio at 20.3%. There were no significant differences by gender, grade, and academic achievement of the latent group. These results are not only meaningful as the first study of the latent profile analysis of high school students on disaster safety awareness, but also help to identify the characteristics of individuals in each latent group with more subdivisions and provide useful data for disaster safety awareness education according to individual differences. The implications of this study and suggestions for follow-up studies were discussed.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.517-519
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• 2003

하드웨어 검증과 모델 체킹 등의 분야에서, SAT(satisfiability problem)나 항진 명제 검사(tautology checking)는 매우 중요한 문제이다. 그러나 이들은 모두 NP-complete 문제이므로 그 복잡도가 매우 크다. 이를 해결하기 위한 여러 연구가 진행되고 있고, 그 결과 성능이 좋은 solver들이 개발되었다. 하지만 문제가 커질수록 solver의 처리 시간이 급격하게 증가한다. 이 논문에서는 solver가 복잡한 문제를 더 효율적으로 풀기 위해 논문“Local search for Boolean relations on the basis of unit propagation”［5］에서 제안된 preprocessor(전처리기), P_EQ의 개념을 설명하고, 실험을 통한 결과를 제시한다.

• ETRI Journal
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• v.24 no.6
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• pp.415-428
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• 2002

This paper presents a new satellite radio interface, satellite code division multiple access (SAT-CDMA), for the satellite component of IMT-2000. The SAT-CDMA was proposed by Korea and was based on wideband CDMA (WCDMA) for a high degree of commonality with the terrestrial component of IMT-2000. Because a satellite link has a longer round trip delay and a higher Doppler shift than a terrestrial link, we developed new technologies that would make the satellite component especially efficient. We present the main features of the SAT-CDMA radio interface by focusing on satellite-specific schemes. We also demonstrate with extensive comparison results the performance of the main technologies in the SAT-CDMA radio interface.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.953-956
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• 2005

The vibroacoustic analysis has been carried out on the RazakSAT qualification model which was developed by SI and ATSB. Statistical energy analysis was used for the analysis and the results was compared with acoustic test results. The equipments of the RazakSAT are simplified as uniformly distributed mass on the panels in the SEA model. According to the comparison of the analysis and test results, SEA is useful estimation of the response in high frequency region and the results are valid when the assumption of equipartition of modal energy is agreed.

• International Journal of Contents
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• v.10 no.3
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• pp.41-46
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• 2014

A cause-effect graph considers only the desired external behavior of a system by identifying input-output parameter relationships in the specification. When testing a software system with cause-effect graphs, it is important to derive a moderate number of tests while avoiding loss in fault detection ability. Pairwise testing is known to be effective in determining errors while considering only a small portion of the input space. In this paper, we present a new testing technique that generates pairwise tests from a cause-effect graph. We use a Boolean Satisbiability (SAT) solver to generate pairwise tests from a cause-effect graph. The Alloy language is used for encoding the cause-effect graphs and its SAT solver is applied to generate the pairwise tests. Using a SAT solver allows us to effectively manage constraints over the input parameters and facilitates the generation of pairwise tests, even in the situations where other techniques fail to satisfy full pairwise coverage.

• Journal of Information Technology Services
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• v.7 no.2
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• pp.127-135
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• 2008

The concept of preprocessing is widely used in various computer science area such as compiler and software engineering for the purpose of macro processing and optimization. In addition, preprocessing is also used in SAT solvers in order to eliminate redundant literals and clauses to speed up its solving time before searching the state space. However, there is an unexpected run-time error such as stack-overflow during this step, in case the size of a given set of clauses is huge which impedes SAT solvers. In this case, the preprocessing should be applied at the encoding time to optimize its size. In this paper this idea is applied to several Sudoku problems. As a result, significant improvements are obtained with respect to the number of variables and clauses as well as the solving time compared to the previous works.

• Magazine of RCR
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• v.9 no.2
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• pp.16-24
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• 2014

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.4
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• pp.377-386
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• 2015

DubaiSat-2 is the first satellite developed in Korea equipped with a hall-effect thruster. In this paper, the performance of the DubaiSat-2 hall-effect thruster is verified by analyzing the orbit information of DubaiSat-2. The preparation and performance of orbit operations during 8 months after launch (2013.11.21., UTC) is emphasized and the effects of solar activity on orbit evolution is analyzed. In particular, the hall-effect thruster's thrust is estimated by analyzing difference between observed orbit evolution and predicted orbit. As a result, the estimated thrust is similar to the ground experiment result of 11 mN. The summarized result in this paper would be important reference to improve the stability and effectiveness of satellite operation during the early operation and normal mission lifetime in case of low Earth orbit satellites.