• Journal of the Korea Institute of Building Construction
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• v.14 no.6
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• pp.591-596
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• 2014

This study investigates the perception of the sunken costs of an urban development project, which is currently a social problem through a questionnaire survey. The results indicate that local and federal governments, political authorities, association members, landowners, etc. partially recognize their responsibility in bearing the sunken cost. It is also found that all stakeholders who participated in the maintenance project felt shared responsibility of bearing the sunken costs and exchanging solutions to mitigate the same, rather than making one party deal with the same. This study also suggests that with regard to reducing these sunken costs, the public sector should offer indirect support (by bearing the cost of infrastructure, tax benefits, regulation relaxation, etc.) rather than direct support so that the association members can make a reasonable choice on the project execution.

• Journal of the Korean Operations Research and Management Science Society
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• v.31 no.1
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• pp.91-103
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• 2006

Given a bill of materials (BOM) tree T labeled by the breadth first search (BFS) order from node 0 to node n and a general network ${\Im}=(V,A)$, where V={1,2,...,m} is the set of production facilities and A is the set of arcs representing transportation links between any of two facilities, we assume that each node of T stands for not only a component. but also a production stage which is a possible stocking point and operates under a periodic review base-stock policy, We also assume that the random demand which can be achieved by a suitable service level only occurs at the root node 0 of T and has a normal distribution $N({\mu},{\sigma}^2)$. Then our integrated model of facility location problems and safety stock optimization problem (FLP&SSOP) is to identify both the facility locations at which partitioned subtrees of T are produced and the optimal assignment of safety stocks so that the sum of production cost, inventory holding cost, and transportation cost is minimized while meeting the pre-specified service level for the final product. In this paper, we first formulate (FLP&SSOP) as a nonlinear integer programming model and show that it can be reformulated as a 0-1 linear integer programming model with an exponential number of decision variables. We then show that the linear programming relaxation of the reformulated model has an integrality property which guarantees that it can be optimally solved by a column generation method.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.83-86
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• 1996

In this paper we study the problem of augmenting a physical network to improve the topology for new survivable network architectures. We are given a graph G=(V,E,F), where V is a set of nodes that represents transmission systems which be interconnected by physical links, and E is a collection of edges that represent the possible pairs of nodes between which a direct transmission link can be placed. F, a subset of E is defined as a set of the existing direct links, and E/F is defined as a set of edges for the possible new connection. The cost of establishing network $N_{H}$=(V,H,F) is defined by the sum of the costs of the individual links contained in new link set H. We call that $N_{H}$=(V,H,F) is feasible if certain connectivity constrints can be satisfied in $N_{H}$=(V,H,F). The computational goal for the suggested model is to find a minimum cost network among the feasible solutions. For a k edge (node) connected component S .subeq. F, we charactrize some optimality conditions with respect to S. By this characterization we can find part of the network that formed by only F-edges. We do not need to augment E/F edges for these components in an optimal solution. Hence we shrink the related component into a node. We study some good primal heuristics by considering construction and exchange ideas. For the construction heuristics, we use some greedy methods and relaxation methods. For the improvement heuristics we generalize known exchange heuristics such as two-optimal cycle, three-optimal cycle, pretzel, quezel and one-optimal heuristics. Some computational experiments show that our heuristic is more efficient than some well known heuristics.stics.

• Transactions on Electrical and Electronic Materials
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• v.15 no.6
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• pp.291-296
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• 2014

In recent years, researchers have extensively investigated polymers filled with inorganic nanoparticles because these materials present improved physical properties relative to those of conventional unfilled polymers. Oxides, silica in particular, are the most commonly used inorganic particles because they possess good properties and can be fabricated at a low cost. However, oxides are hydrophilic in nature, and this leads to the presence of water at the interface between the nanoparticles and the polymer matrix. Due to the predominance of particle-matrix interfaces in nanocomposites, the presence of water at the interlayer region can be problematic. Moreover, the hydrophobic nature of most polymers, particularly for polyolefins such as polyethylene, may make it difficult to remove this interfacial water. In this paper, as-received and moistened samples of agglomerated nanosilica/polyethylene were dried using an isothermal treatment at $60^{\circ}C$, and the efficacy of this treatment was studied using dielectric spectroscopy. The Maxwell-Wagner-Sillars relaxation peaks were observed to shift to lower frequencies by three decades, and this was linked to a modification of the water content, due to drying, at the interfaces between silica and polyethylene and at the interfaces within the nanosilica agglomerates. The evolution of the extracted retardation time is explained by the nanosilica hydrophily and the free volume introduced by the nanoparticles.

• Journal of the Korean Operations Research and Management Science Society
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• v.23 no.2
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• pp.29-46
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• 1998

In this paper, we develop detailed algorithms for implementing the so-called Limited Column Generation procedure for Local Access Telecommunication Network(LATN) design problem. We formulate the problem into a tree-partitioning problem with an exponential number of variables. Its linear programming relaxation has all integral vertices, and can be solved by the Limited Column Generation procedure in just n pivots, where n is the number of nodes in the network. Prior to each pivot. an entering variable is selected by detecting the Locally Most Violated(LMV) reduced cost, which can be obtained by solving a subproblem in pseudo-polynomial time. A critical step in the Limited Column Generation is to find all the LMV reduced costs. As dual variables are updated at each pivot, the reduced costs have to be computed in an on-line fashion. An efficient implementation is developed to execute such a task so that the LATN design problem can be solved in O(n$^2$H), where H is the maximum concentrator capacity. Our computational experiments indicate that our algorithm delivers an outstanding performance. For instance, the LATN design problem with n＝150 and H＝1000 can be solved in approximately 67 seconds on a SUN SPARC 1000 workstation.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1882-1890
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• 2014

This paper proposes an augmented Lagrange Hopfield network (ALHN) based method for solving multi-objective short term fixed head hydrothermal scheduling problem. The main objective of the problem is to minimize both total power generation cost and emissions of $NO_x$, $SO_2$, and $CO_2$ over a scheduling period of one day while satisfying power balance, hydraulic, and generator operating limits constraints. The ALHN method is a combination of augmented Lagrange relaxation and continuous Hopfield neural network where the augmented Lagrange function is directly used as the energy function of the network. For implementation of the ALHN based method for solving the problem, ALHN is implemented for obtaining non-dominated solutions and fuzzy set theory is applied for obtaining the best compromise solution. The proposed method has been tested on different systems with different analyses and the obtained results have been compared to those from other methods available in the literature. The result comparisons have indicated that the proposed method is very efficient for solving the problem with good optimal solution and fast computational time. Therefore, the proposed ALHN can be a very favorable method for solving the multi-objective short term fixed head hydrothermal scheduling problems.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.54-68
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• 1995

In this paper, we develop detailed algorithms for implementing the so-called Limited Column Generation procedure for Local Access Telecommunication Network (LATN) Design problem. We formulate the problem into a tree-partitioning problem with an exponential number of variables. Its linear programming relaxation has all integral vertices, and can be solved by the Limited Column. Generation procedure in just n pivots, where n is the number of nodes in the network. Prior to each pivot, an entering variable is selected by detecting the Locally Most Violated (LMV) reduced cost, which can be obtained by solving a subproblem in pseudo-polynomial time. A critical step in the Limited Column Generation is to find all the LMV reduced costs. As dual variables are updated at each pivot, the reduced costs have to be computed in an on-line fashion. An efficient implementation is developed to execute such a task so that the LATN Design problem can be solved in O(n$^{2}$H), where H is the maximum concentrator capacity. Our computational experiments indicate that our algorithm delivers an outstanding performance. For instance, the LATN Design problem with n = 150 and H = 1000 can be solved in approximately 67 seconds on a SUN SPARC 1000 workstation.

• Journal of Information Processing Systems
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• v.5 no.2
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• pp.105-116
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• 2009

To solve the general problems surrounding the application of genetic algorithms in stereo matching, two measures are proposed. Firstly, the strategy of simplified population-based incremental learning (PBIL) is adopted to reduce the problems with memory consumption and search inefficiency, and a scheme for controlling the distance of neighbors for disparity smoothness is inserted to obtain a wide-area consistency of disparities. In addition, an alternative version of the proposed algorithm, without the use of a probability vector, is also presented for simpler set-ups. Secondly, programmable graphics-hardware (GPU) consists of multiple multi-processors and has a powerful parallelism which can perform operations in parallel at low cost. Therefore, in order to decrease the running time further, a model of the proposed algorithm, which can be run on programmable graphics-hardware (GPU), is presented for the first time. The algorithms are implemented on the CPU as well as on the GPU and are evaluated by experiments. The experimental results show that the proposed algorithm offers better performance than traditional BMA methods with a deliberate relaxation and its modified version in terms of both running speed and stability. The comparison of computation times for the algorithm both on the GPU and the CPU shows that the former has more speed-up than the latter, the bigger the image size is.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.127-136
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• 2004

This paper is the first of two companion papers concerning the analysis and design of a pneumatic vibration isolation system. The design optimization of the pneumatic vibration isolation system is required for the reduction of cost, endeavor and time, and it needs modeling and calculation algorithm. The nonlinear models are devised from the fluid mechanical expression for components of the system and the calculation algorithm is derived from the mathematical relationship between the models. It is shown that the orifice makes the nonlinear property of the transmissibility curve that the resonant frequency changes by the amplitude of excited vibration. Linearization of the nonlinear models is tried to reduce elapsed time and truncation error accumulation and to enable the transmissibility calculation of the system with multi damping chambers. The equivalent mechanical models generated by linearization clarify the function of each component of the system and lead to the linearized transfer function that can give forth to the transmissibility exactly close to that of nonlinear models. The modified successive under-relaxation method is developed to calculate the linearized transfer function.

• 전기의세계
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• v.14 no.3
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• pp.10-17
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• 1965

This paper presents a method of the voltage-reactive power control in the long and short range operations and introduces a conception, "optimum control pattern." The optimum control pattern, aiming at the over-all system control, is defined as the optimum voltage distribution which minimizes the system operating cost under the conditions that the specified power be supplied and the system voltage be kept within the specified bounds. The following procedure was adopted to obtain this optimum pattern. In the first place, a power system was divided into three blocks, namely, load, substation and generator. Lagrange's, multiplier method is applied to each block in turn, paying attention only at the operating voltage distribution. Phase angles at each bus are then modified so that the continuity of active power is maintained. This procedure may be called "block relaxation method with Lagrange's multipliers." In a long range operation, this control pattern determines the optimum installation capacity of reactive power sources. In a short range operation, it also gives the reference state of real time control and the optimum switching capacity of reactive power souces. The real time control problem is also studied from the standpoint of cooperation of control devices such as generators, shunt capacitors, shunt reactors and ratio load controllers. A proposal for the real time control will contribute to the automation of power system operation in the near future. in the near future.