• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.07a
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• pp.254-255
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• 2015

지금까지 해양사고 예방을 위해 선박설비 개선, 운항요건 강화 등 하드웨어적인 측면 개선에 주력하였지만, 선박을 운항하는 인적요인에 의해 발생하는 문제점을 최소화하는 것이 필수적이다. 선박조종시뮬레이션은 수행 횟수가 많을수록 조종성능에 익숙해짐에 따라 통계적 유의성의 문제가 발생한다. 본 연구는 인지 시뮬레이터의 개념도에 대해 소개하고자 한다. 고정된 항로가 아닌 랜덤하게 변하는 항로 조건에서 해기사가 어떻게 대응하는지 상황인식에 대한 여러 요소들은 항해 수행에 근저하는 인간 요인의 규명에 중요한 기초자료를 제공할 것으로 판단된다.

• 한국데이터정보과학회:학술대회논문집
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• 2006.04a
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• pp.17-24
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• 2006

오늘날 과학 및 공학연구를 위하여 복잡한 컴퓨터 시뮬레이션을 자주 사용하고 있다. 전통적 물리적 실험이 입력수의 한계와 출력의 측정오차를 가지는 반면 시뮬레이션 실험 또는 전산실험은 입력수에 제한이 거의 없고 대부분 출력 또한 측정오차가 없거나 매우 작다. 이러한 전산 실험의 분석을 위해 비교적 새롭게 등장한 통계적 방법이 DACE(Design and Analysis of Computer Experiments)이나. 본 발표에서는 이 DACE의 기본 개념과 원리를 간단히 소개하고, 실제로 기계설계에 효과적으로 적용된 사례를 보이고, 향후 연구방향 등을 논의하겠다. 특히 시뮬레이션 코드에 존재하는 절대상수의 추정문제(calibration)와 공간선형 모형의 최적선택을 위한 알고리즘을 소개한다.

• Aerospace Engineering and Technology
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• v.4 no.1
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• pp.95-102
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• 2005

This paper introduces the LAE(Liquid Apogee Engine) and station acquisition fuel budget estimation method for the COMS(Communication, Ocean and Meteorological Satellite) of Korea which is planned to be launched in 2008. And the estimation results are also presented. A statistical approach, more specifically, the Monte-Carlo method was employed to have the estimation include the effect of the launch vehicle GTO injection accuracies. A case study was conducted for several potential launch vehicles to compare the fuel requirements.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.1105-1108
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• 2003

통신망을 효율적으로 설계하고 운영하기 위하여 통신망에 대한 구체적인 시뮬레이션이 필요하며 이에 관한 연구가 현재 활발히 이루어지고 있다. 본 논문에서는 통신망 성능 분석을 위한 시뮬레이션 시 필요한 트래픽 생성기의 설계를 위해 실제 트래픽 자료를 수집, 분석하여 HTTP 요구 수준에서 통계적 방법을 통해 확률 분포로 모델링하였다. 기존 연구에서는 응답 크기에 대하여 파레토 분포만을 사용하여 그 특성을 모델링하였지만, 본 연구에서는 지수 분포와 파레토 분포의 혼합으로 모델링할 수 있음을 확인하였다. 또한 응답 크기의 특성은 서버 내 파일 크기의 특성을 그대로 반영하는 것이 아니라 사용자의 웹 문서 요청의 편중화 현상에 영향을 받아 그 특성이 달라질 수 있다는 것을 분석을 통해 확인하였다.

• Proceedings of the Korea Society for Simulation Conference
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• 1999.10a
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• pp.12-17
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• 1999

WATM(Wireless ATM)에서의 매체접근제어(Medium Access Control)는 QoS를 보장하기 위해 다양한 방식들이 제안되어 왔다. 현재까지 제안되어 온 매체접근제어 방식들은 시분할 다중화 방식 (TDMA)과 예약경쟁방식을 주로 사용하고 있다. 이때 활용되는 기능에는 QoS를 보장하기 위해 통계적 다중화, 스케쥴링 또는 예약 방식 등이 있는데 경쟁 방식은 아직까지 slotted-ALOHA를 그대로 사용하고 있다. Slotted-ALOHA방식의 단점을 개선하기 위하여 통계적 방식으로 경쟁을 제어하거나 물리적 방식으로 경쟁을 분리시켜 그 효율을 향상 시켜왔으나 우선 순위가 같은 이동국들이 많을 경우에는 해결할 방법이 없었다. 이러한 문제점들은 기지국 중심의 경쟁방식이라는 점이 그 문제를 해결하는데 있어서의 걸림돌이다. 본 논문에서는 이미 슬롯을 할당받은 동료 이동국에게 예약요청을 피기백킹(piggybacking)함으로써 신속하게 슬롯을 할당을 받을 수 있는 분산 경쟁방식을 제안한다.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.1
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• pp.102-110
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• 1994

The roll response of ships to the narrow band random exciting moment is investigated based on the multiple time scale technique. The results are compared with those calculated from statistical equivalent linearization method. The calculation results have shown that the results calculated from multiple time scale technique eve wider range of multiple values. Numerical simulations of rolling motion of ship are performed to confirm the results.

• Journal of the Korea Society for Simulation
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• v.28 no.4
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• pp.21-32
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• 2019

Inspired by the social behavior models of a bird flock or fish school, particle swarm optimization (PSO) is a popular metaheuristic optimization algorithm and has been widely used from solving a complex optimization problem to learning a artificial neural network. However, PSO is difficult to apply to many real-life optimization problems involving stochastic noise, since it is originated in a deterministic environment. To resolve this problem, this paper incorporates a resampling method called the uncertainty evaluation (UE) method into PSO. The UE method allows the particles to converge on the accurate optimal solution quickly in a noisy environment by selecting the particles' global best position correctly, one of the significant factors in the performance of PSO. The results of comparative experiments on several benchmark problems demonstrated the improved performance of the propose algorithm compared to the existing studies. In addition, the results of the case study emphasize the necessity of this work. The proposed algorithm is expected to be effectively applied to optimize complex systems through digital twins in the fourth industrial revolution.

• School Mathematics
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• v.12 no.3
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• pp.273-299
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• 2010

The purpose of the study is designing and implementing 'Sampling Distributions Simulation' to help students to understand concepts of sampling distributions. This computer simulation is developed to help students understand sampling distributions more easily. 'Sampling Distributions Simulation' consists of 4 sessions. 'The first session - Confidence level and confidence intervals - includes checking if the intended confidence level is actually achieved by the real relative frequency for the obtained sample confidence intervals containing population mean. This will give the students clearer idea about confidence level and confidence intervals in addition to the role of sampling distribution of the sample means among those. 'The second session - Sampling Distributions - helps understand sampling distribution of the sample means, through the simulation method to make comparison between the histogram of sampling distributions and that of the population. The third session - The Central Limit Theorem - includes calculating the means of the samples taken from a population which follows a uniform distribution or follows a Bernoulli distribution and then making the histograms of those means. This will provides comprehension of the central limit theorem, which mentions about the sampling distribution of the sample means when the sample size is very large. The forth session - the normal approximation to the binomial distribution - helps understand the normal approximation to the binomial distribution as an alternative version of central limit theorem. With the practical usage of the shareware 'Sampling Distributions Simulation', we expect students to have a new vision on the sampling distribution and to get more emphasis on it. With the sound understandings on the sampling distributions, more accurate and profound statistical inferences are expected. And the role of the sampling distribution in the inferences should be more deeply appreciated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4A
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• pp.323-329
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• 2011

Most current design codes of concrete structures adopt the partial safety factor format to assure the proper safety margin or reliability against various limit states as a practical design tool. The safety factors, load and resistance factors and so on, are determined based on the theory of structural reliability, which takes into account the statistical uncertainties of both loads and resistances. The establishment of statistical models for load and resistance should be preceded the application of reliability theory. In this paper, especially the influence of the statistical variations of resistance models, which are described in terms of strength of concrete, strength of reinforcements and sectional dimensions and so on, are examined and the probabilistic models for resistance of reinforced concrete members were developed. The statistical data were collected on local tests and experiments in Korea and the Monte Carlo simulation (MCS) technique was used. The results of this paper may be useful and valuable in calibration of design code in this country.

• Journal of the Korea Society for Simulation
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• v.20 no.4
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• pp.21-29
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• 2011

Wireless sensor nodes operate in open environments. The deployed sensor nodes are very vulnerable to physical attacks from outside. Attackers compromise some sensor nodes. The compromised nodes by attackers can lead to false data injection into sensor networks. These attacks deplete the limited energy of sensor nodes. Ye et al. proposed the Statistical En-Route Filtering (SEF) as a countermeasure of the attacks. The sensor node in SEF examines the event reports based on certain uniform probability. Thus, the same energies are consumed in both legitimate reports and false reports. In this paper, we propose a method that each node controls the probability of attempts to verify a report to reduce energy consumption of sensor nodes. The probability is determined in consideration of the remaining energy of the node, the number of hops from the node to SINK node, the ratio of false reports. the proposed method can have security which is similar with SEF and consumes lower energy than SEF.