• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.177-184
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• 2003

The purposes of this study are to develop the real coding genetic algorithm and to obtain the shape optimization of a cable domes by using this scheme. Generally, the structural performance of the cable dome is influenced very sensitively by prestress, geometry and length of the mast because of flexible structures. So, it is very important to decide the optimum shape to get maximum stiffness of cable domes. We use the two models to verify the usefulness of this algorithm for shape optimization and analyze the roof system of Seoul olympic gymnastic arena as one analytical model of practical structures

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.262-270
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• 2004

Basic experiments were carried out using the THT-IV low-power Hall thruster to examine the influences of magnetic field shape and strength, and acceleration channel length on thruster performance and to establish guidelines for design of high-performance Hall thrusters. Thrusts were measured with varying magnetic field and channel structure. Exhaust plasma diagnostic measurement was also made to evaluate plume divergent angles and voltage utilization efficiencies. Ion current spatial profiles were measured with a Faraday cup, and ion energy distribution functions were estimated from data with a retarding potential analyzer. The thruster was stably operated with a highest performance under an optimum acceleration channel length of 20 mm and an optimum magnetic field with a maximum strength of about 150 Gauss near the channel exit and with some shape considering ion acceleration directions. Accordingly, an optimum magnetic field and channel structure is considered to exist under an operational condition, related to inner physical phenomena of plasma production, ion acceleration and exhaust plasma feature. A new Hall thruster was designed with basic research data of the THT-IV thruster. With the thruster with many considerations, long stable operations were achieved. In all experiments at 200-400 V with 1.5-3 mg/s, the thrust and the specific impulse ranged from 15 to 70 mN and from 1100 to 2300 see, respectively, in a low electric power range of 300~1300 W. The thrust efficiency reached 55 %. Hence, a large map of the thruster performance was successfully made. The thermal characteristics were also examined with data of both measured and calculated temperatures in the thruster body. Thermally safe conditions were achieved with all input powers.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.19
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• pp.39-46
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• 1975

The optimum plot size and shape for soybean yield trials were estimated by using two different soybean varieties, Kumkang-daelip and Clark. Long narrow shape plot was generaIly showed lower C.V. value as compared to the plots consisted of more row number with short row length. The results obtained in this experiment provided the optimum size and shape of plots for Clark as 1. 4m x 6m, and for Kumkang-dailip as 1.4m $\times$ 9m, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.5
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• pp.579-588
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• 2003

Optimum fin effectiveness of geometrically and thermally asymmetric trapezoidal fins is represented as a function of the ratio of the fin bottom to top Biot numbers, the ratio of the fin tip to top Biot numbers and fin shape factor. Optimum fin effectiveness is taken as 98% of the maximum fin effectiveness by comparing the increasing rate of fin effectiveness with that of dimensionless fin length. For this analysis, two dimensional separation of variables method is used. Also, the value of the slope of upper surface of the fin and fin efficiency corresponding to optimum effectiveness are presented.

• Plant Resources
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• v.6 no.2
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• pp.94-97
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• 2003

The objective of this study is to investigate morphological characteristics of seeds and effects of environmental factors such as light and temperature on the germination and seedling growth of Adenophora triphylla var. japonica, Codonopsis lanceolata, Platycodon glandiflorum, Which belongs to Campanulaceae and useful for on oriental medicine materials. Seed shape of Codonopsis lanceolata is Elliptic. Platycodon glandiflorum is Oblong. Color of seed coats varied from yellow to dark brown. Seed size of Adenophora triphylla var. japonica is 1.37mm in length, 0.69mm in width. One thousand-seed weight of Adenophora triphylla var. japonica is 258mg. Seed size of Codonopsis lanceolata is 4.45mm in length, 2.11mm in width. One thousand-seed weight of Codonopsis lanoceolata is 1,278mg. Seed size of Platycodon glandiflorum is 2.31mm in length, 1.10mm in width. One thousand-seed weight of Platycodon glandiflorum is 988mg. Optimum temperatures for seed germination and seedling growth range from 20 to $25^{\circ}C$.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.6
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• pp.177-185
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• 2018

There is a need to study dust separator screens with good drainage efficiency while effectively filtering suspended solids and other contaminants entering the intake pumping station, the drainage pumping station and the mediation pumping station, the cooling water inlet of the power plant, and the like. In this paper, Numerical studies were conducted for the optimal design of the dust separator screen using the Coanda effect. The shape of the dust separator screen is important, such as the right curvature radius $R_1$ at the top of the dust separator screen and the left curvature radius $R_2$ at the top, h is the height difference and shape between the screen and the accelerating plate, and ${\theta}$ is the inclination angle of the screen. A total of 4 shape factors were set and the effects of Coanda and drainage performance of each element were compared and analyzed, the optimum length and size of each shape element were derived by classifying the shape elements into direct and indirect influences. Finally, it was possible to effectively filter foreign matter by narrowing the screen spacing, and the drainage performance was analyzed and optimized through numerical studies of dust separator screen.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.335-338
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• 2010

A recent study for tracing the profiles of supersonic axisymmetric Minimum Length Nozzle with uniform and parallel flow at the exit section, the stagnation temperature is taken into account. The aim of this work is to add optimization algorithm to the supersonic nozzle design in order to get the optimum nozzle shape. The comparisons of the nozzle contours based on the method of characteristics are presented. The specific heats and their ratio vary with the stagnation temperature when this temperature of a perfect gas increases. An application is made for air in a supersonic nozzle.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.361-368
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• 1998

This paper sums up the study of the soundproof facilities to be placed on the test track section within the Seoul-Pusan H.S.T project. The objective of this study is to determine optimum design of soundproof including height, length, location, sound absorbing materials for test track(chonan-taejon). This paper shows the model to design the shape and materials of noise barrier for high speed trains(TGV, ICE, etc). Noise prediction is to be conducted by MITHRA. Various parameters affecting the noise propagation outdoors are surveyed and discussed in relation to H.S.T. noise.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.11
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• pp.848-853
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• 2010

We have grown GaN nanowires by the low pressure MOCVD method on Ni deposited oxidized Si surface and have established optimum conditions by observing surface microstructure and its photoluminescence. Optimum growth temperature of $880^{\circ}C$, growth time of 30 min, TMG source flow rate of 10 sccm have resulted in dense nanowires on the surface, however further increase of growth time or TMG flow rate has not increased the length of nanowire but has formed nanocrystals. On the contrary, the increase of ammonia flow has increased the length of nanowires and the coverage of nanowire over the surface. The shape of nanowire is needle-like with a Ni droplet at its tip; the length is tens of micron with more than 40 nm in diameter. Low temperature photoluminescence obtained from the sample at optimum growth condition has revealed several peaks related to exciton decay near band-edge, but does not show any characteristic originated from one dimensional quantum confinement. Strong and broad luminescence at 2.2 eV is observed from dense nanowire samples and this suggests that the broad band is related to e-h recombination at the surface state in a nanowire. The current result is implemented to the nanowire device fabrication by nanowire bridging between micro-patterned neighboring Ni catalysis islands.

• Journal of Ocean Engineering and Technology
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• v.13 no.2 s.32
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• pp.51-57
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• 1999

In this study, one side fillet welded T-joint, used in box type girder and other welding structure, was investigated by stress analysis and bending fatigue test without edge preparation, with variation of joint shape. The purpose of this study is to give the welding condiltion and design standard on manufacturing one side fillet welded T-joint. As a result, the following conclusions were obtained. 1) In one side fillet welded T-joint, the larger the leg length and the penetration depth, the greater the bending fatigue strength because reduction of stress and strain on toe and root. The increase of the longitudinal leg length rather than vertical leg length contributed to the increase in bending fatigue strength. 2) In one side fillet welded T-joint without edge preparation, both general manual welding and general automatic welding were carried out with same condition. In this case, automatic welding showed deeper penetration and more increased longitudinal leg length than manual welding, so that automatic welding offers greater bending fatigue strength. 3) For one side fillet welded T-joint without edge preparation with automatic welding, the ratio(h/t) of the leg length(h) and the main plate thickness(t) in which toe crake can occur was 1.0 over.