• ETRI Journal
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• 제42권5호
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• pp.712-720
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• 2020

Recently, to make the best use of limited and precious spectrum resources, spectrum sharing between satellite and cellular networks has received much interest. In this study, we mathematically analyze the success probability of a fixed (satellite) earth station (FES) based on a stochastic geometry framework. Both the FES and base stations (BSs) are assumed to be equipped with a directional antenna, and the location and the number of BSs are modeled based on the Poisson point process. Furthermore, an exclusion zone is considered, in which the BSs are prohibited from locating in a circular zone with a certain radius around the FES to protect it from severe interference from the cellular BSs. We validate the analytical results on the success probability of the cognitive satellite-terrestrial network with directional antennas by comparing it using extensive computer simulations and show the effect of the exclusion zone on the success probability at the FES. It is shown that the exclusion zone-based interference mitigation technique significantly improves the success probability as the exclusion zone increases.

• 한국군사과학기술학회지
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• 제14권5호
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• pp.850-858
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• 2011

The risk analysis plays an important role in weapon system acquisition project due to uncertainties in the acquisition process. But in domestic, studies on risk analysis are insufficient and risk cost is not included in acquisition budget in policy. Therefore, in this study, we suggest a method that measures risk or success probability of project using the stochastic model. In particular, in order to calculate the success probability, we apply the joint probability distribution model of cost and schedule that are critical factors influencing the project risk. And also we verify the applicability of this model in Korean defence industry environment through case studies.

• 한국항공우주학회지
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• 제48권7호
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• pp.537-546
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• 2020

우주발사체 개발과정에서 설계와 프로세스의 성능지표로 활용되는 신뢰도는 발사 성공률로 유효성이 확인되고, 반복된 발사를 통해 수집된 데이터는 신뢰도 관리를 위하여 피드백 되어야 한다. 본 논문에서는 전 세계 우주발사체의 발사 이력을 조사하여 발사체 모델이나 발사 운용을 통한 기술 성숙도에 따른 발사 성공률을 비교 분석하였고, 사전정보를 반영한 사전확률분포에 발사를 통해 관측된 데이터를 업데이트하는 베이지안 기법을 적용하여 다음 발사에서 예상되는 성공률을 추정하였다. 여러 유형의 사전확률분포를 사용하여 추정한 발사 성공률과 전통적인 통계 기법을 통해 산출한 성공률을 비교 분석하여 적절한 사전분포를 설정하는 방안을 검토하였고, 베이지안 기법을 적용하여 미래의 발사 성공률을 예측하기 위해 고려할 사항들을 제시하였다.

• 유통과학연구
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• 제18권9호
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• pp.31-43
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• 2020

Purpose: This study examined a comprehensive model for assessing the success probability of electric vehicle (EV) commercialization in the Korean market. The study identified three risks associated with successful commercialization which were technology, social, policy, environmental, and consumer risk. Research design, methodology: The assessment of the riskiness was represented by a Bayes belief network, where the probability of success at each stage is conditioned on the outcome of the preceding stage. Probability of success in each stage is either dependent on input (i.e., investment) or external factors (i.e., air quality). Initial input stages were defined as the levels of investment in product R&D, battery technology, production facilities and battery charging facilities. Results: Reasonable levels of investment were obtained by expert opinion from industry experts. Also, a survey was carried out with 78 experts consisting of automaker engineers, managers working at EV parts manufacturers, and automobile industry researchers in government think tanks to obtain the conditional probability distributions. Conclusion: The output of the model was the likelihood of success - expressed as the probability of market acceptance - that depended on the various input values. A model is a useful tool for understanding the EV industry as a whole and explaining the likely ramifications of different investment levels.

• 한국인터넷방송통신학회논문지
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• 제18권5호
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• pp.55-62
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• 2018

MTD(Moving Target Defense)는 자가 복원력이 있는 무선 통신 시스템을 구축할 수 있도록 대상 시스템의 다양한 구조 및 운영 관련 파라미터들을 동적으로 변경시키도록 설계함으로써 공격자의 악의적 공격으로부터 시스템의 취약점을 보호하는 기술이다. 본 논문에서는 MTD-SDR 기술을 기반으로 하는 통신 시스템에서 랜덤/순서적 스캐닝/재밍 공격 성공 확률에 대한 식을 유도하고 시뮬레이션을 통해 그 결과를 검증하였다. 결과적으로 랜덤 스캐닝 공격의 경우에는 전송채널 변화주기 값이 증가할수록 공격성공률이 증가하는 반면, 랜덤 재밍 공격의 경우에는 변화가 없다. 순서적 공격의 경우에는 랜덤 공격과 유사한 경향의 성공률 패턴을 보이지만 전송채널 변화주기가 커져서 전체 전송채널 수에 접근할수록 재밍 공격의 경우에는 최대 2배, 스캐닝 공격의 경우에는 최대 36% 정도 랜덤 공격에 비해 공격 성공률이 높은 것으로 나타났다.

• International Journal of Reliability and Applications
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• 제2권1호
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• pp.27-36
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• 2001

This Paper proposes a new methodology for assessing the reliability of an accident management, which Is based on the reliability physics and the scheme to generate dynamic event tree. The methodology consists of 3 main steps: screening; uncertainty propagation; and probability estimation. Sensitivity analysis is used for screening the variables of significance. Latin Hypercube sampling technique and MAAP code are used for uncertainty propagation, and the dynamic event tree generation method is used for the estimation of non-success probability of implementing an accident management strategy. This approach is applied in assessing the non-success probability of implementing a cavity flooding strategy, which is to supply water into the reactor cavity using emergency fire systems during the sequence of station blackout at the reference plant.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 추계학술대회 논문집
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• pp.331-332
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• 2007

• 한국군사과학기술학회지
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• 제11권3호
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• pp.67-75
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• 2008

In this paper, we analyze the performance of Follower Noise Jamming(FNJ) considering three practical tracking parameters such as tracking bandwidth, tracking time and tracking success probability. The performance of FNJ is compared with that of Partial-Band Noise Jamming(PBNJ) in terms of Symbol Error Rate(SER) at the communication receiver under the assumed typical operation model. It is observed that the performance of FNJ is non-linearly dependent on the tracking bandwidth, the tracking time and the tracking success probability. As we can easily expect, it is also observed that the performance of FNJ is better than that of the PBNJ. Finally, it is shown that, for a fixed tracking bandwidth, the combinations of the required tracking time and the tracking success probability which satisfy a certain required SER.

• 한국기계가공학회지
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• 제7권3호
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• pp.3-11
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• 2008

Robust design pioneered by Dr. G. Taguchi has been applied to versatile engineering problems for improving quality. Since 1980s, the Taguchi method has been introduced to numerical optimization, complementing the deficiencies of deterministic optimization, which is often called the robust optimization. In this study, the robust optimization strategy is proposed by considering the robustness of objective and constraint functions. The statistics of responses in the functions are surrogated by kriging models. In addition, objective and/or constraint function is represented by the probability of success, thus facilitating robust optimization. The mathematical problem and the two-bar design problem are investigated to show the validity of the proposed method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.237-239
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• 2007

In the paper, we analyze the performances of random access channels in multi-service multi-user OFDMA systems. The resource of the random access channels in OFDMA systems is the nubmer of available sub-channels and PN-codes. For given available sub-channels and PN-codes. we analyze the performances of the random access channels of OFDMA systems according to three resource allocation methods (resource full sharing, resource partial sharing, resource partition) in tenus of the access success probability, the blocking probability, the access delay and the throughput of each service class. Further, we find the feasible region of the access probability of each service class in which the allowable minimum access success probability, the allowable maximum blocking probability and the allowable maximum access delay are satisfied. The results also can be utilized to find proper region of the access probabilities of each service class for differentiated quality of service(QoS)s, and for the system operations.