• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2001년도 ICCAS
• /
• pp.71.1-71
• /
• 2001

In this paper, an improved method of environment map building and a region search algorithm for mobile robot are presented. For the environment map building of mobile robot, measurement data of ultrasonic sensors and certainty grid representation is usually used. In this case, inaccuracies due to the uncertainty of ultrasonic data are included in the map. In order to solve this problem, an environment map building method using a Bayesian model was proposed previously[5]. In this study, we present an improved method of probability map building that uses infrared sensors and shift division Gaussian probability distribution with the existing Bayesian update method using ultrasonic sensors. Also, a region search algorithm for ...

• Smart Structures and Systems
• /
• 제11권1호
• /
• pp.103-122
• /
• 2013

It is essential to update the model with reflecting observation or inspection data for reliability estimation of existing structures. Authors proposed updated reliability analysis by using Particle Filter. We discuss how to apply the proposed method through numerical examples on reinforced concrete structures after verification of the method with hypothetical linear Gaussian problem. Reinforced concrete structures in a marine environment deteriorate with time due to chloride-induced corrosion of reinforcing bars. In the case of existing structures, it is essential to monitor the current condition such as chloride-induced corrosion and to reflect it to rational maintenance with consideration of the uncertainty. In this context, updated reliability estimation of a structure provides useful information for the rational decision. Accuracy estimation is also one of the important issues when Monte Carlo approach such as Particle Filter is adopted. Especially Particle Filter approach has a problem known as degeneracy. Effective sample size is introduced to predict the covariance of variance of limit state exceeding probabilities calculated by Particle Filter. Its validity is shown by the numerical experiments.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2007년도 정기 학술대회 논문집
• /
• pp.645-650
• /
• 2007

According to most studies, assessment of aging structure is trend to detect flaw size by sensor than using existing subjective evaluation by expert for objective evaluation. But Uncertainties existing in the sensor make difference between measured flaw size and actual flaw size, In this paper, Probability of Detection(POD) have been used to quantify the uncertainties and POD is updated by relationship measured flaw size and actual flaw size (Heasler, 1990), also we proposed probabilistic updating approach method to improve measurement accuracy(the difference of measured PDF and actual PDF) by using updated POD.

• Advances in concrete construction
• /
• 제1권1호
• /
• pp.85-102
• /
• 2013

Prior concrete strength distributions can be updated by using direct information from test results as well as by taking into account indirect information due to conformity control. Due to the filtering effect of conformity control, the distribution of the material property in the accepted inspected lots will have lower fraction defectives in comparison to the distribution of the entire production (before or without inspection). A methodology is presented to quantify this influence in a Bayesian framework based on prior knowledge with respect to the hyperparameters of concrete strength distributions. An algorithm is presented in order to update prior distributions through numerical integration, taking into account the operating characteristic of the applied conformity criteria, calculated based on Monte Carlo simulations. Different examples are given to derive suitable hyperparameters for incoming strength distributions of concrete offered for conformity assessment, using updated available prior information, maximum-likelihood estimators or a bootstrap procedure. Furthermore, the updating procedure based on direct as well as indirect information obtained by conformity assessment is illustrated and used to quantify the filtering effect of conformity criteria on concrete strength distributions in case of a specific set of conformity criteria.

• 산업경영시스템학회지
• /
• 제29권1호
• /
• pp.72-75
• /
• 2006

Event trees are widely used graphical tool to denote the accident inintiation and escalation to more severe accident. But they have some drawbacks in that they do not have efficient way of updating model parameters and also they can not contain the information about dependency or independency among model parameters. A tool that can cure such drawbacks is an influence diagram. We introduce influence diagrams and explain how to update model parameters and obtain predictive distributions. We show that an event tree can be converted to a statistically equivalent influence diagram, and bayesian prediction can be made more effectively through the use of influence diagrams.

• 대한전자공학회논문지SP
• /
• 제45권3호
• /
• pp.11-19
• /
• 2008

영상 내에서 이동하는 객체를 추출하는 전경 분리 방법은 객체의 일치 추적 및 인식에 있어서 필수적인 기술이다. 하지만 이동하는 객체 주변에 그림자가 발생하는 경우 이러한 전경 분리 방법에서는 그림자도 전경 영역으로 잘못 판단하여 분리하게 되어 이동 객체의 정확한 형태를 파악하거나 위치를 추정하기 어려운 문제가 있다. 본 논문에서는 이러한 문제를 해결하기 위하여 색상 정보를 이용하여 그림자를 모델링하고 이를 통해 전경 영역 내의 그림자 화소를 Bayesian 분류법에 따라 제거하는 방법을 제안하였다. 특히 제안하는 방법은 매개변수 갱신 과정을 통해 그림자의 특성이 동적으로 모델링되기 때문에 주변 조명의 지속적인 변화에 적응적으로 대응할 수 있다. 실험 결과 제안하는 방법은 다양한 환경에서 그림자를 효과적으로 제거하는 것을 확인하였다.

• Journal of Communications and Networks
• /
• 제17권1호
• /
• pp.75-83
• /
• 2015

In mobile ad-hoc networks (MANETs), nodes are mobile in nature. Collaboration between mobile nodes is more significant in MANETs, which have as their greatest challenges vulnerabilities to various security attacks and an inability to operate securely while preserving its resources and performing secure routing among nodes. Therefore, it is essential to develop an effective secure routing protocol to protect the nodes from anonymous behaviors. Currently, game theory is a tool that analyzes, formulates and solves selfishness issues. It is seldom applied to detect malicious behavior in networks. It deals, instead, with the strategic and rational behavior of each node. In our study,we used the dynamic Bayesian signaling game to analyze the strategy profile for regular and malicious nodes. This game also revealed the best actions of individual strategies for each node. Perfect Bayesian equilibrium (PBE) provides a prominent solution for signaling games to solve incomplete information by combining strategies and payoff of players that constitute equilibrium. Using PBE strategies of nodes are private information of regular and malicious nodes. Regular nodes should be cooperative during routing and update their payoff, while malicious nodes take sophisticated risks by evaluating their risk of being identified to decide when to decline. This approach minimizes the utility of malicious nodes and it motivates better cooperation between nodes by using the reputation system. Regular nodes monitor continuously to evaluate their neighbors using belief updating systems of the Bayes rule.

• 대한토목학회논문집
• /
• 제38권4호
• /
• pp.505-516
• /
• 2018

교량 유지관리 전략 수립 시 현재 상태를 기반으로 미래 상태를 예측할 수 있어야 하며, 상태예측모델의 신뢰도가 높아질수록 효과적인 유지관리 의사결정이 가능하다. 그러나 인력기반 반복 주기적인 현행유지관리는 관리자가 목표하는 관리(등급)수준의 교량 상태를 정확히 예측하지 못해서 막대한 보수 보강비용이 발생될 가능성이 있고, 합리적인 유지관리 의사결정을 도모하는데 어려움을 겪는다. 이에 따라 본 논문에서는 국내 교량 점검 이력 데이터를 이용하여 불확실성을 고려한 교량 부재별 대표 상태예측모델을 개발하고, 개발된 상태예측모델을 실제 유지관리 대상 교량에 보다 높은 정확도로 적용 가능한 베이지안 업데이트 기법을 제안하였다. 또한, 모니터링 업데이트 상태예측모델 기반 예방적 유지관리가 기존 현행유지관리 대비 비용 효율성 측면에서 유리함을 제안하기 위해 각각의 유지관리비용 산출에 따른 교량 점검 타당성 분석을 수행하였다.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제18권3호
• /
• pp.271-279
• /
• 2018

Purpose: Probabilistic safety analysis was performed to enhance the safety and reliability of nuclear power plants because traditional deterministic approach has limitations in predicting the risk of failure by crack growth. The study introduces a probabilistic approach to establish a basis for probabilistic safety assessment of passive components. Methods: For probabilistic modeling of fatigue crack growth rate (FCGR), various FCGR tests were performed either under constant load amplitude or constant ${\Delta}K$ conditions by using heat treated X-750 at low temperature with adequate cathodic polarization. Bayesian inference was employed to update uncertainties of the FCGR model using additional information obtained from constant ${\Delta}K$ tests. Results: Four steps of Bayesian parameter updating were performed using constant ${\Delta}K$ test results. The standard deviation of the final posterior distribution was decreased by a factor of 10 comparing with that of the prior distribution. Conclusion: The method for developing a probabilistic crack growth model has been designed and demonstrated, in the paper. Alloy X-750 has been used for corrosion fatigue crack growth experiments and modeling. The uncertainties of parameters in the FCGR model were successfully reduced using the Bayesian inference whenever the updating was performed.

• Steel and Composite Structures
• /
• 제20권6호
• /
• pp.1345-1368
• /
• 2016

This paper presents the probabilistic-based assessment of composite steel-concrete structures through an innovative framework. This framework combines model identification and reliability assessment procedures. The paper starts by describing current structural assessment algorithms and the most relevant uncertainty sources. The developed model identification algorithm is then presented. During this procedure, the model parameters are automatically adjusted, so that the numerical results best fit the experimental data. Modelling and measurement errors are respectively incorporated in this algorithm. The reliability assessment procedure aims to assess the structure performance, considering randomness in model parameters. Since monitoring and characterization tests are common measures to control and acquire information about those parameters, a Bayesian inference procedure is incorporated to update the reliability assessment. The framework is then tested with a set of composite steel-concrete beams, which behavior is complex. The experimental tests, as well as the developed numerical model and the obtained results from the proposed framework, are respectively present.