• The Journal of the Acoustical Society of Korea
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• v.23 no.1E
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• pp.3-9
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• 2004

An important inverse problem in the field of acoustics is that of reconstructing the strengths of a number of sources given a model of transmission paths from the sources to a number of sensors at which measurements are made. In dealing with this kind of the acoustical inverse problem, strengths of the discretised source distribution can be simply deduced from the measured pressure field data and the inversion of corresponding matrix of frequency response functions. However, deducing :he solution of such problems is not straightforward due to the practical difficulty caused by their inherent ill-conditioned behaviour. Therefore, in order to overcome this difficulty associated with the ill-conditioning, the problem is replaced by a nearby well-conditioned problem whose solution approximates the required solution. In this paper a microphone array are identified for which the inverse problem is optimally conditioned, which can be robust to contaminating errors. This involves sampling both source and field in a manner which results in the discrete pressures and source strengths constituting a discrete Fourier transform pair.

• Korean Journal of Computational Design and Engineering
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• v.4 no.3
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• pp.259-268
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• 1999

In order to reduce the cost of product and save the processing time, optimal nesting of two-dimensional part is an important application in number of industries like shipbuilding and garment making. There have been many studies on finding the optimal solution of two-dimensional nesting. The problem of two-dimensional nesting has a non-deterministic characteristic and there have been various attempts to solve the problem by reducing the size of problem rather than solving the problem as a whole. Heuristic method and linearlization are often used to find an optimal solution of the problem. In this paper, theoretical and practical nesting algorithm for rectangular, circular and irregular shape of two-dimensional parts is proposed. Both No-Fit-Polygon and Minkowski-Sum are used for solving the overlapping problem of two parts and the dynamic programming technique is used for reducing the number search spae in order to find an optimal solution. Also, nesting designer's expertise is complied into the proposed algorithm to supplement the heuristic method.

• Journal of the Korean Operations Research and Management Science Society
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• v.17 no.3
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• pp.137-158
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• 1992

We study the Multiple Product Single Facility Stockout Avoidance Problem (SAP). That is the problem of determining, given initial inventories, whether there is a multiple product single facility production schedule that avoids stockouts over a given time horizon. The optimization version of the SAP where stockouts are pnelized linearly is also studied. We call this problem the Weighted Stockout Problem (WSP). Both problems are NP-hard in the strong sense. We develop Mixed Integer Linear Programming (MIP) formulations for both the SAP and the WSP. In addition, several heuristic algorithms are presented and performances are tested using computational experiments. We show that there exist polynomial algorithms for some special cases of the SAP and the WSP. We also present a method to phase into a target cyclic schedule for infinite horizon problems. These can be used as a practical scheduling tool for temporarily overloaded facilities or to reschedule production after a disruption.

• IE interfaces
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• v.12 no.1
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• pp.94-101
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• 1999

The set covering(SC) problem is the problem of covering all the rows of an $m{\times}n$ matrix of ones and zeros by a subset of columns with a minimal cost. It has many practical applications of modeling of real world problems. The SC problem has been proven to be NP-complete and many algorithms have been presented to solve the SC problem. In this paper we present hybrid simulated annealing(HSA) algorithm based on the Simulated Annealing(SA) for the SC problem. The HSA is an algorithm which combines SA with a crossover operation in a genetic algorithm and a local search method. Our experimental results show that the HSA obtains better results than SA does.

• Journal of Applied Reliability
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• v.13 no.3
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• pp.153-163
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• 2013

QFD(Quality Function Deployment) is a very important tool to improve market share by reducing the gap between the voice of customer and the product's performance. But QFD is not a problem solving tool, although it is very useful in identifying what has to be solved or improved in order to meet the customer's desires. TRIZ has proved to be a very strong tool to solve the difficult problems that requires inventive thinking. QFD integrated with TRIZ becomes hot research recently. But merely linking between HOQ(House of Quality) in QFD and the contradiction matrix in TRIZ can not provide designers with a concrete method to solve the technical problem in the design process. Practically, the contradiction matrix and 40 inventive principles are not helpful for solving the technical problem. To solve the technical problem using TRIZ, a search for the tool and the object involved in the problem is made, from which the wanted result should be derived. A practical method to integrate QFD and TRIZ is proposed in this paper.

• Korean Journal of Occupational Health Nursing
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• v.10 no.1
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• pp.24-40
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• 2001

This study is to observe the effectiveness of the applied model and to present the improvement plan and directions for development for the case management practical model suitable for the actual condition of Korea Labor Welfare Co. and needs of the industrial injury patients. The concrete purpose of this study is: First, observe the difference of stressor experience and experience degree between the experimental group and the comparative group. Second, observe the difference of stress of the experimental group and the comparative group. Third, find out how the stress affects the support degree and satisfaction degree. Fourth, present the improvement plan of case management model, which can promote the psychosocial rehabilitation of the industrial injury patient based on the research results. The outline of the main research results identified in this study is as follows. The stressors the industrial injury patients perceived are health problems, family matters, the problems concerning hospital recuperation (hospital staff and environmental problems), economical problems, problems of coming back to society, problems with companies, problems with Korea labour Welfare Co. and other problems. And the experience of stressor was prominently lower in experimental group than comparative group in the whole problem, health problem, problems with Korea Labour-Welfare Co. and other problems. The stressor experience degree was conspicuously lower in experimental group in the whole problem experience degree, health problem experience degree, problem with Korea Labour Co. experience degree and other problem experience degree. Besides whether or not the case management is applied is having a prominent affect on the primary factor affecting the stressor experience degree, therefore the patients applied with case management has less stressor than the patient who didn't. The difference of degree of tension experienced by the stressor in both groups, the degree of stress, was not conspicuous in statistics so it shows that the application of case management in this research has not affected the degree of tension. The field which had been the most help was emotional support in help level the experimental group perceived through applying case management about industrial accident patients and recuperation, compensation problem, medical treatment problem, family matters has been helpful in this order. The help level of the whole problem was in higher level than the middle value. The stress factor which affects the case management problem settlement is the whole body of stress. The satisfaction level of help through applying case management was highest in emotional support and family matters, recuperation problem, company problem, compensation problem, and medical treatment problem was the next highest. The satisfaction level of the whole problem was higher than the middle value. The stress factor affecting the satisfaction level of help is the whole body of stress. Therefore to reduce the stress level of industrial accident patients and for them to come back to local societies, we need to reinforce the continuance and responsibility of case management model, increase staff, reinforce the role of counsel and medical treatment, intervene in the patient's plan of leaving the hospital, develop social support system and the need to establish After Care Center.

• Journal of Environmental Health Sciences
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• v.31 no.3
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• pp.207-214
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• 2005

Many Japanese today are suffering from health disorders related to their living environment, such as allergies and hypersensitivity to chemical substances. The Sick House/Building Syndrome has been a serious problem since 1996, due to low level exposure to hazardous chemicals such as formaldehyde and volatile organic compounds (VOCs) emitted in airtight houses. This paper aims to show current status of the syndrome in Japan and practical researches to promote prevention of, and improvement to indoor air pollution due to chemicals.

• Proceedings of the Korean Environmental Health Society Conference
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• 2005.06a
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• pp.143-167
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• 2005

Many Japanese today are suffering from health disorders related to their living environment, such as allergies and hypersensitivity to chemical substances. The Sick House/Building Syndrome has been a serious problem since 1996, due to low level exposure to hazardous chemicals such as formaldehyde and volatile organic compounds (VOCs) emitted in airtight houses. This paper aims to show current status of the syndrome in Japan and practical researches to promote prevention of, and improvement to indoor air pollution due to chemicals.

• Journal of Communications and Networks
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• v.16 no.1
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• pp.36-44
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• 2014

Exploiting the energy-delay tradeoff for energy saving is critical for developing green wireless communication systems. In this paper, we investigate the delay-constrained energy-efficient packet transmission. We aim to minimize the energy consumption of multiple randomly arrived packets in an additive white Gaussian noise channel subject to individual packet delay constraints, by taking into account the practical on-off circuit power consumption at the transmitter. First, we consider the offline case, by assuming that the full packet arrival information is known a priori at the transmitter, and formulate the energy minimization problem as a non-convex optimization problem. By exploiting the specific problem structure, we propose an efficient scheduling algorithm to obtain the globally optimal solution. It is shown that the optimal solution consists of two types of scheduling intervals, namely "selected-off" and "always-on" intervals, which correspond to bits-per-joule energy efficiency maximization and "lazy scheduling" rate allocation, respectively. Next, we consider the practical online case where only causal packet arrival information is available. Inspired by the optimal offline solution, we propose a new online scheme. It is shown by simulations that the proposed online scheme has a comparable performance with the optimal offline one and outperforms the design without considering on-off circuit power as well as the other heuristically designed online schemes.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.3
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• pp.317-328
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• 2000

This paper presents an effective approach to collision-free motion planning of a robot in the work-space including time-varying obstacles. The free arc is defined as a set composed of the configuration points of the robot satisfying collision-free motion constraint at each sampling time. We represent this free arc with respect to the new coordinate frame centered at the goal configuration and there for the collision-free path satisfying motion constraint is obtained by connecting the configuration points of the free arc at each sampling mined from the sequence of free arcs the optimality is determined by the performance index. Therefore the complicated collision-free motion planning problem of a robot is transformed to a simplified SUB_Optimal Collision Avoidance Problem(SOCAP). We analyze the completeness of the proposed approach and show that it is partly guaranteed using the backward motion. Computational complexity of our approach is analyzed theoretically and practical computation time is compared with that of the other method. Simulation results for two cally and practical computation time is compared with that of the other method. Simulation results for two SCARA robot manipulators are presented to verify the efficacy of the proposed method.