• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.720-723
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• 2004

This study is intended to propose a systematic approach for determining optimum Life-Cycle Cost (LCC)-effective seismic design for continuous PSC bridges considering lifetime expected seismic risks. In the paper, a set of cost function for LCC analysis of bridges is proposed. The total LCC functions consist of initial cost and direct/indirect damage costs considering repair/replacement costs, human losses and property damage costs, road user costs, and indirect socio-economic losses. The damage costs are expressed in terms of Park-Ang median global damage indices (Park and Ang, 1985) and lifetime damage probabilities. The proposed approach is applied to model bridges of both moderate seismicity regions like Korea and high seismicity regions like Japan. Since, in case of bridges, a number of parameters may have an influence on optimal target reliability, various sensitivity analyses are performed in this study. It may be expected that the proposed approach can be effectively utilized for the development of cost-effective performance criteria for design and upgrading of various types of bridges as well as continuous PC bridges.

• Journal of Energy Engineering
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• v.18 no.4
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• pp.258-263
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• 2009

Jet Loop Reactor(JLR), in which a two-phase nozzle is installed, is the new design technique for the treatment of high concentration wastewater by accelerating of oxygen contacting between substrate and surrounding bacteria. This numerical study of the two phase jet flow was conducted to find the optimum design of JLR. It was shown that there was a minimum velocity in the nozzle for continuous circulation of wastewater. The optimum location and the size of the draft tube for continuous circulation were examined. It was certain that the smaller the air size is, the more the effect of the mixing increases. The relation between the mixing effect and the turbulence was confirmed.

• Magazine of the Korea Concrete Institute
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• v.5 no.4
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• pp.167-178
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• 1993

The objective of this paper is to look into the possibility of the detailed and practical optimum design of rt:inforced concrete beam using methods oi discrete mathematical programming. In this discrete optimum formulation, the design variables are the overall depth, width and effective depth of members, and area of longitudinal reinforcement. In addition, the details such as the amount of web reinforcement and cutoff points of longitudinal reinforcement are also considered as variables. Total cost has been used as the objective function. The constraints include the code requirments such as flexural strength, shear strength, ductility, serviceability, concrete cover. spacing, web reinforcement, and development length and cutoff points of longitudinal renforcement. An optimization algorithm is presented for effective optimum design of R.C. beam with discrete de sign variables. First, the continuous variable optimization can be achieved by Feasible Direction Method. Using the results obtained from the continuous variable optimization, a branch and bound method is used to obtained the discrete design values. The proposed algorithm is applied to test problem for reliability, and the results are compared with those of graphical method and rounded-up method. And a simply supported R.C. beam and a two-span continuous R.C. beam are presented as numerical examples for effectiveness and applicability. It is considered that the presented algorithm can be effectively applied to the discrete optimum design of R.C. beams.

• ETRI Journal
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• v.30 no.4
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• pp.535-545
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• 2008

This paper introduces a systematic top-down and bottom-up design methodology to assist the designer in the implementation of continuous-time (CT) cascade sigma-delta (${\Sigma}{\Delta}$) modulators. The salient features of this methodology are (a) flexible behavioral modeling for optimum accuracy-efficiency trade-offs at different stages of the top-down synthesis process, (b) direct synthesis in the continuous-time domain for minimum circuit complexity and sensitivity, (c) mixed knowledge-based and optimization-based architectural exploration and specification transmission for enhanced circuit performance, and (d) use of Pareto-optimal fronts of building blocks to reduce re-design iterations. The applicability of this methodology will be illustrated via the design of a 12-bit 20 MHz CT ${\Sigma}{\Delta}$ modulator in a 1.2 V 130 nm CMOS technology.

• Journal of Ocean Engineering and Technology
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• v.17 no.6
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• pp.53-57
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• 2003

Optimum design of most structural system requires that design variables are regarded as discrete quantities. This paper presents the use of Genetic Algorithm for determining the optimum design for truss with discrete variables. Genetic Algorithm are know as heuristic search algorithms, and are effective global search methods for discrete optimization. In this paper, Elitism and the method of conferring penalty parameters in the design variables, in order to achieve improved fitness in the reproduction process, is used in the Genetic Algorithm. A 10-Bar plane truss and a 25-Bar space truss are used for discrete optimization. These structures are designed for stress and displacement constraints, but buckling is not considered. In particular, we obtain continuous solution using Genetic Algorithms for a 10-bar truss, compared with other results. The effectiveness of Genetic Algorithms for global optimization is demonstrated through two truss examples.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.111-119
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• 2005

This study presents continuous and discrete optimum design algorithm and computer programs for unbraced and braced steel frame structures under earthquake loads. The program, which is avaliable to perform structural analysis and optimum design, continuous and discrete, simultaneously is developed. And the program adopts various braced types, Untraced, Z-braced(V), Z-braced(inverse-V), X-braced(A), X-braced(B), X-braced(C) and K-braced, in steel structures with static loads and seismic effects. The objectives in this optimization are to minimize the total weight of steel, and design variables, based on the ultimate strength requirements of AISC-ASD specifications, the serviceability requirements and allowable story drift requirements of ATC-3-06, and various constraints. The purpose is to present proper braced type for seismic effects by comparing and analysing results of various cases.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.62-65
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• 1989

Optimizing transient response for both tracking reference signals and disturbance rejection is determined by the poles and zeros of the transfer function. Thus, optimal pole assignment and how should weighting matrix for the performance index be chosen is very important to achieve optimum transient response. This paper focus its attention on the choosing and analysis of weighting matrix for optimum pole assignment. Optimum pole assignment is defined for linear time-invariant continuous systems.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.11
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• pp.116-121
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• 1999

Since the material flow near the die part in CONFORM (Continuous Extrusion Forming) process is similar to that of side-extrusion, the side-extrusion model of tube shaped aluminum profiles was studied for the die design in CONFORM process. In this paper, the effects of process parameters in the side -extrusion through a two-hole die face, such as material flow, height and thickness of the tube, velocities of punch and lengths of bearing land were investigated using UBET program and DEFORM commercial FEM code. The optimum lengths of the bearing lands and punch velocities for obtaining the straight shape products required were determined.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.201-208
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• 2003

Since the real steel box girder bridges have a large number of design variables and show complex structural behavior, it would be impractical to directly use the algorithm for its optimum design. Thus, in this study, for optimum design of real steel box girder bridge, approximated reanalysis using an higher-order Improved self-adjusted Convex Approximation (ISACA) which was newly proposed on a previous study by the author is applied for the numerical efficiency. To demonstrate the efficiency, robustness, and convergence of the approximated reanalysis technique using the ISACA, a real bridge having two continuous spans is used as an illustrative example. From the results of the numerical investigation, it may be positively stated that the efficiency, robustness, and convergence of the approximated reanalysis using an ISACA is superior compared with the previous approximated reanalysis techniques.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.327-334
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• 2003

Thermal Prestressing Method for continuous composite girder bridges is a new design and construction method developed to induce initial composite stresses in the concrete slab at negative bending regions. Due to the induced initial stresses, prevention of tensile cracks at concrete slab, reduction of steel girder section, and reduction of reinforcing bars are possible. Thus, economical and construction efficiency can be improved. Method for determining optimum heating region of Thermal Prestressing Method, has not been established although such method is essential for increasing efficiency of the designing process. Trial-and-error method used in previous studies is far from efficient and more rational method for computing optimal heating region is required. In this study, efficient method for determining optimum heating region in the use of Thermal Prestressing Method is developed based on artificial neural network algorithm, which is widely adopted to pattern recognition, optimization, diagnosis, and estimation problems in various fields. Back-propagation algorithm, which is commonly used as a learning algorithm in neural network problems, is used for training of the neural network. Through case studies of 2-span continuous and 3-span continuous composite girder bridges using the developed process, the optimal heating regions are obtained.