• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권5호
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• pp.1618-1637
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• 2014

Clustering wireless sensor network is an efficient way to reduce the energy consumption of individual nodes in a cluster. In clustering, multihop routing techniques increase the load of the Cluster head near the sink. This unbalanced load on the Cluster head increases its energy consumption, thereby Cluster heads die faster and create an energy hole problem. In this paper, we propose an Energy Balancing Cluster Head (EBCH) in wireless sensor network. At First, we balance the intra cluster load among the cluster heads, which results in nonuniform distribution of nodes over an unequal cluster size. The load received by the Cluster head in the cluster distributes their traffic towards direct and multihop transmission based on the load distribution ratio. Also, we balance the energy consumption among the cluster heads to design an optimum load distribution ratio. Simulation result shows that this approach guarantees to increase the network lifetime, thereby balancing cluster head energy.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2002년도 춘계공동학술대회
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• pp.378-384
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• 2002

In this paper, we propose a mixed integer optimization approach for solving the inventory problem with variable lead time, reorder point, crashing cost and price -quantity discount. Chang and Chang[15] study a continuous review inventory model in which lead time is a decision variable under price-quantity discount. However, their study cannot find the optimal solution due to the flaws in the modeling and the solution procedure. We present a complete procedure to find the optimal solution for the model. In addition to the above contribution, we also apply the minimax distribution free approach to the model to devise a practical procedure which can be used without specific information on demand distribution.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2004년도 추계학술대회 및 정기총회
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• pp.250-278
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• 2004

The product rate variation problem, to be called the PRVP, is to sequence different type units that minimizes the maximum value of a deviation function between ideal and actual rates. The PRVP is an important scheduling problem that arises on mixed-model assembly lines. A surge of research has examined very interesting methods for the PRVP. We believe, however, that several issues are still open with respect to this problem. In this study, we consider convex bipartite graphs, perfect matchings, permanents and balanced sequences. The ultimate objective of this study is to show that we can provide a more efficient and in-depth procedure with a graph theoretic approach in order to solve the PRVP. To achieve this goal, we propose formal alternative proofs for some of the results stated in the previous studies, and establish several new results.

• 한국경영과학회지
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• 제24권1호
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• pp.49-58
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• 1999

A new channel access function is proposed to enhance the performance of the Joint CDMA/PRMA. It is obtained in consideration of the number of terminals in reservation mode and the number of terminals in contention mode whose probability distribution is estimated by applying pseudo Bayesian approach. Simulation results show that the performance of the Joint CDMA/PRMA can be improved by applying new channel access function under voice-only traffic and mixed voice/random-data traffic.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.828-833
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• 2004

The performance of a mixed $H_{\infty}/H_2$ design with pole placement constraints based on robust vibration control for a piezo/beam system is investigated. The governing equation of motion for the piezo/beam system is derived by Hamilton's principle. The assumed mode method is used to discretize the governing equation into a set of ordinary differential equation. A robust controller is designed by $H_{\infty}/H_2$ feedback control law that satisfies additional constraints on the closed-loop pole location in the face of model uncertainties, which are derived for a general class of convex regions of the complex plane. These constraints are expressed in terms of linear matrix inequalities (LMIs) approach for the multiobjective synthesis. The validity and applicability of this approach for vibration suppressions of SMART structural systems are discussed by damping out the multiple vibrational modes of the piezo/beam system.

• 산업경영시스템학회지
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• 제32권4호
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• pp.93-100
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• 2009

This paper addresses the facility layout problem in multi-bay environments, where the bays are connected at one or both ends by an inter-bay material handling system. In most previous studies, the main concern is to allocate facilities or departments to the bays whose widths are fixed. In this research, we suggest the efficient models that provide the optimal layout solution under flexible bay width environments. We also suggest a mathematical model that provides the optimal solution using two-way facility allocation approach instead of one-way allocation technique. This paper also shows the approach of TABU search to the assignment and layout design of the departments. The results generated from TABU search are compared to the result from the mathematical model. Models are developed using mixed integer programming for various test problems and solved by CPLEX.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.161-167
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• 2009

This paper offers a competitor analysis model for use by contractors as parts of more informed approach in identifying key competitors, and as a basis for formulating bidding strategies. Linear mixed model approach is used in measuring competitiveness between bids (by using bid competitiveness percentage) according to: (i) project size, (ii) work sector; (iii) work nature; and (iv) number of bidders. The model was tested empirically by application to a bidding dataset obtained from a large Hong Kong contractor. Allowing for heterogeneity across competing contractors (i.e. with the model parameters that varied across contractors), the results indicate that competitiveness in bidding of this contractor is generally greater than the majority of his competitors.

• Steel and Composite Structures
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• 제48권5호
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• pp.583-597
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• 2023

This paper introduces a novel approach to multi-material topology optimization (MTO) targeting in-plane bi-directional functionally graded (IBFG) non-uniform thickness Reissner-Mindlin plates, employing an alternative active phase approach. The mathematical formulation integrates a first shear deformation theory (FSDT) to address compliance minimization as the objective function. Through an alternating active-phase algorithm in conjunction with the block Gauss-Seidel method, the study transforms a multi-phase topology optimization challenge with multi-volume fraction constraints into multiple binary phase sub-problems, each with a single volume fraction constraint. The investigation focuses on IBFG materials that incorporate adequate local bulk and shear moduli to enhance the precision of material interactions. Furthermore, the well-established mixed interpolation of tensorial components 4-node elements (MITC4) is harnessed to tackle shear-locking issues inherent in thin plate models. The study meticulously presents detailed mathematical formulations for IBFG plates in the MTO framework, underscored by numerous numerical examples demonstrating the method's efficiency and reliability.

• Computers and Concrete
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• 제12권6호
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• pp.785-802
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• 2013

Ready-mixed soil material, known as a kind of controlled low-strength material, is a new way of soil cement combination. It can be used as backfill materials. In this paper, artificial neural network and nonlinear regression approach were applied to predict the compressive strength of ready-mixed soil material containing Portland cement, slag, sand, and soil in mixture. The data used for analyzing were obtained from our testing program. In the experiment, we carried out a mix design with three proportions of sand to soil (e.g., 6:4, 5:5, and 4:6). In addition, blast furnace slag partially replaced cement to improve workability, whereas the water-to-binder ratio was fixed. Testing was conducted on samples to estimate its engineering properties as per ASTM such as flowability, strength, and pulse velocity. Based on testing data, the empirical pulse velocity-strength correlation was established by regression method. Next, three topologies of neural network were developed to predict the strength, namely ANN-I, ANN-II, and ANN-III. The first two models are back-propagation feed-forward networks, and the other one is radial basis neural network. The results show that the compressive strength of ready-mixed soil material can be well-predicted from neural networks. Among all currently proposed neural network models, the ANN-I gives the best prediction because it is closest to the actual strength. Moreover, considering combination of pulse velocity and other factors, viz. curing time, and material contents in mixture, the proposed neural networks offer better evaluation than interpolated from pulse velocity only.

• 한방재활의학과학회지
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• 제18권4호
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• pp.217-230
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• 2008

Objectives : The purpose of this study was to investigate the type, sites and period of injuries in Mixed Martial Arts. Methods : The questionnaire composed of 26 items was used as the research tool for this study. The respondents were 84 athletes of Mixed Martial Arts who participated in Spirit MC Amateur League in September, 2007. Data analysis use chi-square examination by SPSS$^{(R)}$ 12.0 program. Results : 1. Frequently, strikers are damaged at face and waist, grapplers are damaged at knee and waist. 2. Frequently, beginers are damaged at muscle and tendon, experts are damaged at bone and joint. 3. Age, career, specialty and injured type have significant correlations. 4. Age, career, training time and concern response have significant correlations. 5. Oriental medical treatment are friendly but not well-known to the athletes. Conclusions : Injuries of Mixed Martial Arts is multifactorial, so approach of athlete's individuality is important.