• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.51-58
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• 2004

Optimization of engine desist and operation parameters using a genetic algorithm was demonstrated for direct injection diesel engine combustion. A micro genetic algorithm and a modified KIVA-3V code were used for the analysis and optimization of the engine combustion. At each generation of the optimization step the micro genetic algorithm generated five groups of parameter sets, and the five cases of KIVA-3V analysis were to be performed either in series or in parallel. The micro genetic algorithm code was also parallelized by using MPI programming, and a multi-CPU parallel supercomputer was used to speed up the optimization process by four times. An example case for a fixed engine speed was performed with six parameters of intake swirl ratio, compression ratio, fuel injection included angle, injector hole number, SOI, and injection duration. A simultaneous optimization technique for the whole range of engine speeds would be suggested for further studies.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.6
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• pp.47-52
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• 2012

DAS(Distribution Automation System) is equipped with several software applications such as service restoration, loss minimization, and protective relay coordination. The software applications of DAS are very sensitive to the amount of section load being carried by a particular section of distribution lines. Moreover, each software application requires a different parameter of the section load according to its purpose. Therefore, This paper proposes a new section load management method using real-time measurement data of the distribution lines. In order to provide accurate data to DAS applications, this method considers section loads in terms of the relationship of power versus time. In order to establish that the proposed method is feasible, a performance-testing simulator was developed, and case studies were conducted for a modified real distribution network.

• Structural Engineering and Mechanics
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• v.53 no.5
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• pp.847-865
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• 2015

This paper presents the application of a recently developed meta-heuristic algorithm, called Colliding Bodies Optimization (CBO), for size and topology optimization of steel trusses. This method is based on the one-dimensional collisions between two bodies, where each agent solution is considered as a body. The performance of the proposed algorithm is investigated through four benchmark trusses for minimum weight with static and dynamic constraints. A comparison of the numerical results of the CBO with those of other available algorithms indicates that the proposed technique is capable of locating promising solutions using lesser or identical computational effort, with no need for internal parameter tuning.

• Steel and Composite Structures
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• v.15 no.2
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• pp.163-173
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• 2013

The thermal creep is one of the major factors causing the buckle of steel columns in the fire events. But, few related studies have been reported to evaluate the factors affecting the thermal creep of steel column experimentally or numerically. In this study a series of Fire-resistant steel columns with three different slenderness ratios under a sustained load are tested under a uniform temperature up to six hours in order to evaluate the creep upon three selected factors, temperature, applied load, and column slenderness. Based on experimental results, a proposed creep strain rate model is established as the function of a single parameter of the load ratio of temperature LR(T) to determine the buckling time of steel column due to creep. Furthermore it is found that the creep can be neglected when LR(T) is smaller than 0.77.

• Microbiology and Biotechnology Letters
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• v.19 no.6
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• pp.624-630
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• 1991

Sixty five phenol degrading bacteria were isolated from soil and identified. Sirnility values calculated on the basis of total 46 morphological, biochemical and physiological characteristics of the isolated strains. 65 isolates were divided into 6 clusters at the 70% simility lavei, The dominant organisms were belonged to Azotobacter, Pseudomonas and Flavobactwium.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.11-15
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• 2002

Experimental studies on effects of the interaction of duplex swirl injector and the liquid temperature on the spray characteristics were conducted. Water and fuel were used as a test fluid for the experiments. The drop size distributions of the liquid spray were measured with Malvern particle sizer. The liquid temperature and distance of injectors were adopted as the operating parameter. The results show that SMD decrease as the increases of fuel temperature and pressure. The spray angle increase as fluid temperature increases. For fuel spray, SMD of impacting surface increase as the distance of injectors is lengthened.

• Wind and Structures
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• v.13 no.2
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• pp.95-108
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• 2010

This review paper discusses research from the last few years relating to windborne debris risk models and the essential elements of engineering damage prediction models. Generic types of windborne debris are discussed. The results of studies of debris trajectories that are relevant to damage models are described - in particular the horizontal component of debris velocity as a function of distance travelled. The merits of impact momentum versus impact kinetic energy as a relevant parameter for predicting damage are considered, and how published data from generic cannon Impact tests can be used in risk models. The quantitative variation of debris impact damage with wind speed is also discussed. Finally the main elements of previously-proposed debris damage models are described.

• Journal of the Korean Graphic Arts Communication Society
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• v.13 no.1
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• pp.1-12
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• 1995

Polymeric mesogens having a regularly alternating rigid-flexible repeating structure in the main-chain polymer exhibit distinct even-odd oscillation in their thermodynamic quantities with respect to the number of methylene units in the spacer. The even-odd oscillation depends on the number of methylene groups in the spacer the entropy change at the NI(nematic-isotropic) phase transition becomes less distinct when the linking group is replaced by the carbonate. In our previous work, we have suggested that the characteristics arise from the geometrical arrangement of the linkage. In this work, we have prepared a series of carbonate-type monomer and dimer liquid crystals. The thermodynamic behaviors at the NI phase transition have been compared with those previous reported for the ether- or ester-type liquid crystals. For the dimer series, the orientational order parameter of the mesogenic core was determined by using H-NMR technique. The origin of the difference observed among linking groups was found to the geometrical characteristics of chemical structure.

• Journal of the Korean Operations Research and Management Science Society
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• v.26 no.1
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• pp.97-108
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• 2001

Design and evaluation of AGV-based material handling systems are very complicated due to the randomness and the large number of variables involved Vehicle travel time is a key parameter for designing and evaluating AGV systems. Although loaded travel time is relatively easy to estimate, determination of empty vehicle travel time is difficult due to the inherent randomness of material handling systems. Most previous studies assume that the empty vehicle travel time is the same as the loaded travel time or assume very specific environments. This paper presents new vehicle travel time models for AGV-based material transport systems. The research effort is focused on the estimation of empty vehicle travel time under various vehicle dispatching policies. Simulation experiments are used to verify the proposed travel time models.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.2
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• pp.173-182
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• 1994

A numerical experiment on the effective discharge of waste materials caused in recirculating aquaculture basins was performed. The numerical model used in this study was a 4-level hydrodynamic and advection-diffusion model. Flow structures and settling processes of ss in the various mathematical model basins are discussed. The calculated flow fields of the numerical basin corresponded well with the measured velocity in field basin. In the cases of steep bottom slopes in 4/30, the non-dimensional tractive force($U{\ast}/U{\ast}_c$) which is all important parameter for the deposition pattern of waste materials was stronger than with the mild slope one. The settling pattern of ss depended considerably on the degree of bottom slope of basin. To concentrate deposited waste materials into the center discharge pipe, it is useful to design a cylindrical basin with a steeply conical bottom. In addition, to prevent movement of the deposit area away from the center, it is necessary to locate the circulating ducts at diametrically opposed points on the basin sides.