• Journal of Navigation and Port Research
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• v.29 no.7
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• pp.603-609
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• 2005

This paper presents the method for developing an optimum hull form with minimum wave resistance using SQP( sequential quadratic programming) as an optimization technique. The wave resistance is evaluated by a Rankine source panel method with non-linear free surface conditions and the ITTC 1957 friction line is used to predict the frictional resistance coefficient. The geometry of the hull surface is represented and modified using NURBS(Non-Uniform Rational B-Spline) surface patches. To verify the validity of the developed program the numerical calculations for Wigley hull and Series 60 Cb=0.6 hull are performed and the results obtained after the numerical calculations are compared with the initial hulls.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.367-368
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• 2002

The design of capsule body for self-propelled endoscope is important from the frictional resistance point of view. The capsule should be able to overcome the frictional resistance in order to move along the intestine. The motivation of this work was to gain a better understanding of the capsule body design on the frictional resistance of the capsule inside an intestine. A special experimental set-up was built to measure the frictional resistance as the capsule was being pulled inside the pig intestine specimen. Tests were performed with open and closed intestine specimens. Experimental data showed that smooth cylindrical capsule geometry resulted in the least frictional resistance. The resistance inside the closed intestine specimen was about four times higher than that of the open specimen. It is expected that the results of this work will be used to design the optimum propulsion system for the microendoscope.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.85-85
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• 2012

For effective light harvesting, a design weighting should be implemented in a front geometry, in which the incident light transmits from a surface into a light-active layer. We designed a three-dimensionally patterned transparent conductor layer for effective light management. A transparent conductive oxide (TCO) film was formed as three-dimensional structures. This efficiently drives the incident light at the front surface into a Si absorber to yield a reduction in reflection and an enhancement of current. This indicates that an optimum architecture for a front TCO surface will provide an effective way for light management in solar cells.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.11
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• pp.17-28
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• 1995

In this paper, we developed a two-dimensional numerical simulator which could analyze the stripe geometry semiconductor laser diodes by modifying the commercial semiconductor device simulator, MEDICI. In order to study the characteristics of semiconductor laser diodes, it is necessary to solve the Helmholtz wave equation and photon rate equation in addition to the basic semiconductor equations. Also the recombination rates due to the spontaneous and the stimulated emissions should be included, which are very important recombination mechanisms in semiconductor laser diodes. Therefore, we included the solution routines which analyzed the Helmholtz wave equation and the photon rate equation and two important recombination rates to simulate the semiconductor laser diodes. Then we simulated the gain-guiding and index-guiding DH(Double Heterostructure) semiconductor laser diodes to verify the validity of the implemented functions. The results obtained from simulation are well consistent with the previously published ones. This allows us to know the operating characteristics of DH laser diodes and is expected to use as a tool for optimum design.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.4
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• pp.398-410
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• 1998

Two-phase flow phenomena are observed in many industrial facilities and make much importance of optimum design for nuclear power plant and the liquid transportation system. The particular flow pattern depends on the conditions of pressure, flow velocity, and channel geometry. However, the research on drag reduction in two-phase flow is not intensively investigated. Therefore, experimental investigations have been carried out to analyze the drag reduction and void fraction by polymer addition in the two-phase flow system. We find that the polymer solution changes the characteristic of two-phase flow. The peak position of local void friction moves from tile wall of the pipe to the center of the pipe when polymer concentration increase. And then we predict that it is closely related with the frau reduction.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.185-192
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• 1999

This paper presents the results of a parametric study on the behavior of tunnel face reinforced with horizontal pipes. A three-dimensional finite element model was adopted in this study to capture the three-dimensional nature of tunnel face behavior under various boundary conditions. A parametric study was peformed on a wide range of boundary conditions with emphasis on the effect of reinforcing layouts on the deformation behavior of tunnel face. The results of analysis such as tunnel face deformation behavior under various conditions were thoroughly analyzed, and a database for the behavior of tunnel face under different reinforcing conditions was established for future development of a semi-empirical design/analysis method for the tunnel face reinforcing technique. The results indicated that there exits an optimum reinforcing layout for a given tunnel condition, which must be selected with due consideration of tunnel geometry and ground condition.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1740-1745
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• 2004

A simplified resistor network model for electrical and mass transport in anode-supported planar solid oxide fuel cell (SOFC) was constructed in order to investigate the effect of interconnect rib geometry on the cell performance. For accurate potential calculation, activation and concentration over-potentials at the electrode/electrolyte interfaces were fully considered in this calculation. When contact resistance was not considered, the optimum interconnect rib length were calculated to be $0.1{\sim}0.2$ mm for 2 mm half unit cell for given operation conditions and properties. However, with realistic contact resistance, the interconnect rib length should be increased to provide larger contact area and thus to obtain better performance.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2000.11a
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• pp.237-242
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• 2000

This study was carried out to optimize burner of the condensing gas boiler which can save energy by utilizing the latent heat of combustion gas and reduce pollutants emission. Three reasonable distances between burner and heat exchanger were decided through the experiments of model flat burner. The optimum burner geometry was determined from flame stability, pollutant emission characteristics and applicability to practical boiler system. The boiler designed by this research reaches turn-down ratio 5:1 in the domain of equivalence ratio 0.68∼0.85 and thermal efficiency of 98%. Emission of NOx and CO concentration was under 35ppm and 104ppm.

• Journal of Welding and Joining
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• v.14 no.6
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• pp.81-92
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• 1996

This study is to compare the weldability of Zircaloy-4 end cap of nuclear fuel pin using by GTA and Nd :YAG LB. The welding parameters which affect bead width and penetration depth have been investigated. The effect of joint geometry of end cap for GTAW and LBW has been studied and optimum conditions of Zircaloy-4 endcap welding have been found. Microstructures and microhardness of GTA and LB welded zones have been also compared.

• Tunnel and Underground Space
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• v.6 no.2
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• pp.166-174
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• 1996

Stability of rock slope is greatly affected by the geometry and strength of discontinuities developed in the rock mass. In this study an analytical method which is capable of analyzing the effect of relative orientation between the discontinuities and the slope face on the safety of slope by assessing their vector components was used to evaluate the stability and the maximum cut-angle for the proposed slope design. The results of computerized vector analysis revealed that slope area under investigation might be divided into 3 sections of different face directions. The safety factors for benches in each 3 sections were calculated using the limit-equilibrium theory. Then, by utilizing the concept of probabilistic risk analysis, the susceptibility of entire slope failure was estimated. Based on the distribution of safety factor in each bench, the maximum cut angle of each section could be selected differently ot achieve the permanent stability of the entire slope.