• 터널과지하공간
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• 제14권4호
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• pp.275-286
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• 2004

본 논문에서는 신규 터널노선과 교차하는 폐터널의 보강방식을 결정하기 위하여 의사결정기법을 검토하였고, 여러 가지 의사결정기법들 중에서 설문조사의 과정을 최소화 하고, 조사항목 별 정성적ㆍ정량적 특성을 모두 반영할 수 있도록 쌍대비교와 퍼지근사추론을 이용하여 폐터널의 보강방식에 대한 적정성을 평가하여 보았다. 페터널 보강방식을 선정하기 위하여 4개의 주 요인들 즉, 시공성, 경제성, 안전성, 유지관리성을 평가의 수단으로 사용하였고, 간단한 설문조사와 쌍대비교행렬을 이용하여 4가지 주 요인들의 가중치를 결정하였다. 퍼지근사추론은 4개의 주 요인별 평가점수를 산정 하는데 사용되어졌고, 이 결과들에 가중치를 반영하여 최종적인 폐터널의 보강방식을 선정할 수 있었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1278-1282
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• 2005

Air mattress is now used widely to prevent the pressure ulcer by reducing the localized pressure peaks. In this paper an air-cell mattress and its pressure control method based on an approximate anthropometric model are presented. The air-cell mattress has eighteen cylindrical air cells made of porous material allowing air leakage to contribute in reducing the development of pressure ulcer by lowering the pressure peak, temperature and humidity. To determine an optimal air-cell pressure appropriate for each user, we divide the parts of the body into four sections such as head, trunk, hip, and leg. Then, the pressure of each section is independently calculated from the weight of each part based on the individual body height and weight and the approximate anthropometric model. Air supply system for the air-cell mattress is implemented by using four electronic solenoid valves and an air compressor, and it is driven by a real-time micro-controller. The experimental results with seven subjects shows that the proposed air-cell mattress is effective for the prevention of the pressure ulcer.

• 한국해양공학회지
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• 제24권1호
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• pp.20-33
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• 2010

The paper deals with strength design of a riser support installed on floating production storage and offloading (FPSO) vessel under various loading conditions - operation, extreme, damaged, one line failure case (OLFC) and installation. The design problem is formulated such that thickness sizing variables are determined by minimizing the weight of a riser support structure subject to stresses constraints. The initial design model is generated based on an actual FPSO riser support specification. The finite element analysis (FEA) is conducted using MSC/NASTRAN, and optimal solutions are obtained via moving least squares method (MLSM) in the context of response surface based approximate optimization. For the meta-modeling of inequality constraint functions of stresses, a constraint-feasible moving least squares method (CF-MLSM) is used in the present study. The method of CF-MLSM, compared to a conventional MLSM, has been shown to ensure the constraint feasibility in a case where the approximate optimization process is employed. The optimization results present improved design performances under various riser operating conditions.

• Journal of the Korean Data and Information Science Society
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• 제7권2호
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• pp.235-245
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• 1996

확률변수 (X,Y)가 이변량 정규분포를 따르는 경우, 모상관계수 ${\rho}$에 관한 여러 가설들 중에서 $H_{0}:{\rho}={\rho}_{0}$인 경우에는 알려진 분포를 이용한 통계적 추론을 하기가 어렵다. 이러한 경우 Fisher에 의해 제안된 Z-변환을 이용한 근사적 검정법이 사용되어 오고 있으나 근사적인 방법이기 때문에 주어진 표본의 크기가 충분히 많지 않은 경우에는 적용에 무리가 있을 수 있다. 그래서 본 논문에서는 먼저 표본 상관계수 R의 분포를 모의실험을 통하여 직접 구하여 검정한 정확 검정법과, 붙스트랩(bootstrap) 방법을 이용하여 구한 붙스트랩 검정법을 제시하고, Fisher의 방법의 효율성과 실제성을 검토하고 제시된 방법들과 서로 비교하고자 한다.

• 한국통신학회논문지
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• 제38C권11호
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• pp.1029-1043
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• 2013

CS(Compressed Sensing)는 오늘날 신호 처리 영역에서 많은 주목을 받고 있는 이론 중의 하나이다. 이 CS 분야에서 효과적인 복구 알고리즘을 설계하는 것은 가장 큰 도전적 연구 중의 하나로 인식되고 있다. 이에 따라 다양한 복구 알고리즘이 많은 문헌을 통해서 제안 되었으며 최근에 Maleki와 Donoho에 의해 제안된 AMP(Approximation Message Passing) 알고리즘은 기존에 제시된 알고리즘에 비해 간단한 구조를 가지고 있지만 좋은 성능을 보여줌으로써 상당한 주목을 받고 있다. 기존의 (BP) Belief Propagation 알고리즘은 오직 희소(Sparse) 센싱 행렬에서만 좋은 성능을 보여 준 것에 반해, AMP 알고리즘은 밀집(Dense) 센싱 행렬에 기초를 둔 Belief Propagation 알고리즘임에도 불구하고 이와 비슷한 성능을 보여준다. 본 논문은 다양한 영역에서 AMP 알고리즘이 적용되기 위하여 이에 대한 지침 및 기존의 고전적 Message Passing 알고리즘과의 관계에 대해 분석하였다. 또한 기존의 알고리즘과의 비교 분석을 통해 AMP 알고리즘의 우수성을 제시하였다.

• IEIE Transactions on Smart Processing and Computing
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• 제6권4호
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• pp.299-304
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• 2017

A wireless passive sensor network is a network consisting of sink nodes, sensor nodes, and radio frequency (RF) sources, where an RF source transfers energy to sensor nodes by radiating RF waves, and a sensor node transmits data by consuming the received energy. Against theoretical expectations, a wireless passive sensor network suffers from many practical difficulties: scarcity of energy, non-simultaneity of energy reception and data transmission, and inefficiency in allocating time resources. Perceiving such difficulties, we propose a simple contending-type medium access control (MAC) scheme for many sensor nodes to deliver packets to a sink node. Then, we derive an approximate expression for the network-wide throughput attained by the proposed MAC scheme. Also, we present an approximate expression for the optimal partition, which maximizes the saturated network-wide throughput. Numerical examples confirm that each of the approximate expressions yields a highly precise value for network-wide throughput and finds an exactly optimal partition.

• Journal of Mechanical Science and Technology
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• 제16권2호
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• pp.203-210
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• 2002

For effective response surface modeling during sequential approximate optimization (SAO), the normalized and the augmented D-optimality criteria are presented. The normalized D-optimality criterion uses the normalized Fisher information matrix by its diagonal terms in order to obtain a balance among the linear-order and higher-order terms. Then, it is augmented to directly include other experimental designs or the pre-sampled designs. This augmentation enables the trust region managed sequential approximate optimization to directly use the pre-sampled designs in the overlapped trust regions in constructing the new response surface models. In order to show the effectiveness of the normalized and the augmented D-optimality criteria, following two comparisons are performed. First, the information surface of the normalized D-optimal design is compared with those of the original D-optimal design. Second, a trust-region managed sequential approximate optimizer having three D-optimal designs is developed and three design problems are solved. These comparisons show that the normalized D-optimal design gives more rotatable designs than the original D-optimal design, and the augmented D-optimal design can reduce the number of analyses by 30% - 40% than the original D-optimal design.

• Journal of Mechanical Science and Technology
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• 제17권12호
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• pp.1969-1976
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• 2003

In the early phases of the product life cycle, Life Cycle Assessment (LCA) is recently used to support the decision-making for the product concepts, and the best alternative can be selected based on its estimated LCA and benefits. Both the lack of detailed information and time for a full LCA for a various range of design concepts need a new approach for the environmental analysis. This paper explores a new approximate LCA methodology for the product concepts by grouping products according to their environmental characteristics and by mapping product attributes into environmental impact driver (EID) index. The relationship is statistically verified by exploring the correlation between total impact indicator and energy impact category. Then, a neural network approach is developed to predict an approximate LCA of grouping products in conceptual design. Trained learning algorithms for the known characteristics of existing products will quickly give the result of LCA for newly designed products. The training is generalized by using product attributes for an EID in a group as well as another product attributes for the other EIDs in other groups. The neural network model with back propagation algorithm is used, and the results are compared with those of multiple regression analysis. The proposed approach does not replace the full LCA but it would give some useful guidelines for the design of environmentally conscious products in conceptual design phase.

• 한국통신학회논문지
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• 제27권1C호
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• pp.78-83
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• 2002

유한 상태 기계(finite state machine)의 도달성 분석(reachability analysis)은 통신 프로토콜이나 마이크로 프로세서 설계 등의 다양한 컴퓨터 원용설계응용(computer-aided design applications)에 매우 유용하다. 도달성 분석은 정확한 도달가능상태를 계산하는 정해분석(exact analysis)과 도달 불가능상태의 일부만을 계산하는 근사분석(approximate analysis)으로 나뉘는데, 본 논문은 기존의 방법보다 크게 정확도를 향상시킨 근사 도달분석 기법을 소개하며, 그 기본적인 원리는 근사분석 알고리즘을 반복 적용하되 이전 근사분석 결과를 이후의 근사분석에 활용하는 반복적 근사 도달성 분석 (iterative reachability analysis)을 통해 근사분석의 정확도를 향상시킬 수 있도록 하는 것이다. 반복적 근사 도달성 방식을 이용하여 기존의 근사분석보다 크게 향상된 근사도달상태를 계산할 수 있음을 실험적으로 증명하였다.

• 한국정밀공학회지
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• 제18권10호
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• pp.45-52
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• 2001

This paper presents a study on the position tracking control of a robot system on the uncertain elastic base. The elastic bathe is a nonholonomic system but it can be changed into holonomic system, which is much easier to analyze, by modeling an elastic base as a virtual robot that has passive joints. Also, Jacobian operators, which represent the overall robot system including base movement, are defined and applied to the changed model. However, because base movements are not known, the exact Jacobian operators can＇t be estimated. The control algorithm proposed is that uses only Jacobians of a real robot as approximate Jacobian operators. Therefore the approximate Jacobian operators compensate the measured errors from external sensors. The proposed control strategy is evaluated by the simulation and experiment of a single-axis robot system on the elastic base.