• Journal of Electrical Engineering and Technology
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• v.3 no.1
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• pp.52-59
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• 2008

This paper describes the secant method for solving the economic dispatch (ED) problem with generator constraints and transmission losses. The ED problem is an important optimization problem in the economic operation of a power system. The proposed algorithm involves selection of minimum and maximum incremental costs (lambda values) and then the evaluation of optimal lambda at required power demand is done by secant method. The proposed algorithm has been tested on a power system having 6, 15, and 40 generating units. Studies have been made on the proposed method to solve the ED problem by taking 120 and 200 units with generator constraints. Simulation results of the proposed approach were compared in terms of solution quality, convergence characteristics, and computation efficiency with conventional methods such as lambda iterative method, heuristic methods such as genetic algorithm, and meta-heuristic methods like particle swarm optimization. It is observed from different case studies that the proposed method provides qualitative solutions with less computational time compared to various methods available in the literature.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.96-111
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• 1995

A bellows is a component installed in the automobile exhaust system to reduce the impact from an engine. It's stiffness has a great influence on the natural frequency of the system. Therefore, it must be designed to keep the specified stiffness that requires in the system. This study present the finite element analysis of U-typed bellows using a curved conical frustum element and the shape optimal design with specified stiffness. The finite element analysis is verified by comparing with the experimental results. In the shape optimal design, the weight is considered as the cost function. The specified stiffness from the system design is transformed to equality constraints. The formulation has inequality constraints imposed on the fatigue limit, the natural frequencies, the buckling load and the manufacturing conditions. A procedure for shape optimization adopts a thickness, a corrugation radius, and a length of annular plate as optimal design variables. The external loading conditions include the axial and lateral loads with a boundary condition fixed at an end of the bellows. The recursive quadratic programming algorithm is selected to solve the problem. The result are compared with the existing bellows, and the characteristics of the bellows is investigated through the optimal design process. The optimized shape of the bellows are expected to give quite a good guideline to the practical design.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.50-57
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• 2009

Lane Keeping Assistant Systems (LKAS) require the cooperative operation between drivers and active steering angle/torque controllers. An LKAS is proposed in this study such that the desired reference path generation (DRPG) system generates the desired path to minimize the trajectory overshoot. Based on the reference path from the DRPG system, an optimal controller is designed to minimize the cost function. A HIL (Hardware In the Loop) simulator is constructed to evaluate the proposed LKAS system. The single camera is mounted on the simulator and acquires the monitor images to detect lane markers. The performance of the proposed system is evaluated by HIL system using the Carsim and the Matlab Simulink.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.4
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• pp.388-394
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• 1999

This paper is concerned with an application of Parallel Genetic Algorithms(PGA) to optimal econmic load dispatch(ELD) in power systems. The ELD problem is to minimize the total generation fuel cost of power outputs for all generating units while satisfying load balancing constraints. Genetic Algorithms(GA) is a good candidate for effective parallelization because of their inherent principle of evolving in parallel a population of individuals. Each individual of a population evaluates the fitness function without data exchanges between individuals. In application of the parallel processing to GA, it is possible to use Single Instruction stream, Multiple Data stream(SIMD), a kind of parallel system. The architecture of SIMD system need not data communications between processors assigned. The proposed ELD problem with C code is implemented by SIMSCRIPT language for parallel processing which is a powerfrul, free-from and versatile computer simulation programming language. The proposed algorithms has been tested for 38 units system and has been compared with Sequential Quadratic programming(SQP).

• Structural Engineering and Mechanics
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• v.56 no.5
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• pp.707-726
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• 2015

There is a growing trend of considering uncertainty in optimization process since last few decades. In this regard, Robust Design Optimization (RDO) scheme has gained increasing momentum because of its virtue of improving performance of structure by minimizing the variation of performance and ensuring necessary safety and feasibility of constraint under uncertainty. In the present study, RDO of reinforced concrete folded plate and shell structure has been carried out incorporating uncertainty in the relevant parameters by Monte Carlo Simulation. Folded plate and shell structures are among the new generation popular structures often used in aesthetically appealing constructions. However, RDO study of such important structures is observed to be scarce. The optimization problem is formulated as cost minimization problem subjected to the force and displacements constraints considering dead, live and wind load. Then, the RDO is framed by simultaneously optimizing the expected value and the variation of the performance function using weighted sum approach. The robustness in constraint is ensured by adding suitable penalty term and through a target reliability index. The RDO problem is solved by Sequential Quadratic Programming. Subsequently, the results of the RDO are compared with conventional deterministic design approach. The parametric study implies that robust designs can be achieved by sacrificing only small increment in initial cost, but at the same time, considerable quality and guarantee of the structural behaviour can be ensured by the RDO solutions.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.2
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• pp.270-287
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• 2015

According to the increase of the operating cost and material cost of a ship due to the change of international oil price, a demand for the lightening of the ship weight is being made from various parties such as shipping companies, ship owners, and shipyards. To satisfy such demand, many studies for a light ship are being made. As one of them, an optimal design method of an existing hull structure, that is, a method for lightening the ship weight based on the optimization technique was proposed in this study. For this, we selected a hatch cover of a bulk carrier as an optimization target and formulated an optimization problem in order to determine optimal principal dimensions of the hatch cover for lightening the bulk carrier. Some dimensions representing the shape of the hatch cover were selected as design variables and some design considerations related to the maximum stress, maximum deflection, and geometry of the hatch cover were selected as constraints. In addition, the minimization of the weight of the hatch cover was selected as an objective function. To solve this optimization problem, we developed an optimization program based on the Sequential Quadratic Programming (SQP) using C++ programming language. To evaluate the applicability of the developed program, it was applied to a problem for finding optimal principal dimensions of the hatch cover of a deadweight 180,000 ton bulk carrier. The result shows that the developed program can decrease the hatch cover's weight by about 8.5%. Thus, this study will be able to contribute to make energy saving and environment-friendly ship in shipyard.

• Composites Research
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• v.26 no.4
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• pp.207-212
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• 2013

In this study, the thickness optimization for uni-directional (UD) glass fiber reinforced polymer (GFRP) laminates of the spar cap of composite tidal blades was performed under the tip deflection constrains. The spar cap was composed of GFRP composites and carbon fiber reinforced polymer (CFRP) composites. The stress distributions in the blade as well as its material costs for the optimized results were additionally investigated. The optimized thickness was obtained by interacting a sequential quadratic programming (SQP) algorithm and an ABAQUS software to calculate an objective function. It was confirmed that the thickness of UD GFRP increased with a decrease of the restrained tip deflection when a thickness of UD CFRP laminates was constrained to 9 mm. The weight of the optimized spar-cap increased up to 96.2% while the maximum longitudinal tensile stress decreased up to 24.6%. The thickness of UD GFRP laminates increased with a decrease of the thickness of UD CFRP laminates when the tip deflection was constrained to 126.83 mm. The weight increased up to 40.1%, but the material cost decreased up to 16.97%. Finally, the relationships among the weight, internal tensile stress, and material costs were presented based on the optimized thicknesses of the spar cap.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6630-6638
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• 2014

The concerns for higher returns among investors in Korea are increasing as local interest rates lag behind the global market. The aim of this study was to provide a basis for estimating the precise return on investment to private investors and stakeholders of office buildings by identifying the optimal scale estimation of office building space, derived from managerial expenses. The literature on the economies theories of scales were reviewed, and the average administrative costs on an appropriate scale were assessed by cross-analysis and regression analysis using the U-shaped quadratic and cubic function. The findings suggest that the average office building managerial costs are approximately 6-11% according to the region, 10-13% according to the grade, and 8-9% according to size. Corporate-owned buildings represent the highest in terms of the average managerial costs, and there is an approximately 11.5% difference when it comes to outsourcing. In addition, the elapsed year showed that approximately 5.3 years to meet the lowest U-shaped curve of the average managerial cost. The 'Total floor area' variable shows a ${\bigcap}$-shape as it continue to increase to 72,000-Pyung then decrease gradually. This study presents the fundamental proposition of efficient and practical management of cost, lease and operation for real estate management firms by utilizing LCC.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.1
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• pp.68-78
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• 2012

A layout of an LNG FPSO should be elaborately determined as compared with that of an onshore plant because many topside process systems are installed on the limited area; the deck of the LNG FPSO. Especially, the layout should be made as multi-deck, not single-deck and have a minimum area. In this study, a multi-floor layout for the liquefaction process, the dual mixed refrigerant(DMR) cycle, of LNG FPSO was determined by using the optimization technique. For this, an optimization problem for the multi-floor layout was mathematically formulated. The problem consists of 589 design variables representing the positions of topside process systems, 125 equality constraints and 2,315 inequality constraints representing limitations on the layout of them, and an objective function representing the total layout cost. To solve the problem, a hybrid optimization method that consists of the genetic algorithm(GA) and sequential quadratic programming(SQP) was used in this study. As a result, we can obtain a multi-floor layout for the liquefaction process of the LNG FPSO which satisfies all constraints related to limitations on the layout.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.12
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• pp.865-873
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• 2019

To improve the survivability of a missile, it needs to be lowered that the detection possibility by radars on the ground. The radar exposure of the target is given as a function of relative distance from the radar to the target and RCS (Radar Cross Section). The RCS of the missile is determined by the incidence angle of the target to electromagnetic radiation emitted from the radar. Under the assumption that the missile equips appropriate attitude control system, the attitude of the missile to minimize radar exposure at a high altitude is investigated in this paper. Two different types of performance cost are considered: the total sum of RCS and the total sum of SNR during the flight. Optimal solutions against multiple ground radars are found by using a SQP (Sequential Quadratic Programming)-based optimization technique.