• International Journal of Fluid Machinery and Systems
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• v.7 no.3
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• pp.86-93
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• 2014

This paper describes performance enhancement of a regenerative blower used for a 20 kW fuel cell system. Two design variables, bending angle of an impeller and blade thickness of an impeller tip, which are used to define an impeller shape, are introduced to enhance the blower performance. Internal flow of the regenerative blower has been analyzed with three-dimensional Navier-Stokes equations to obtain the blower performance. General analysis code, CFX, is introduced in the present work. SST turbulence model is employed to estimate the eddy viscosity. Throughout the numerical analysis, it is found that the thickness of impeller tip is effective to increase the blower efficiency in the present blower. Pressure is successfully increased up to 2.8% compared to the reference blower at the design flow condition. And efficiency is also enhanced up to 2.98 % compared to the reference one. It is noted that low velocity region disturbs to make strong recirculation flow inside the blade passages, thus increases local pressure loss. Detailed flow field inside the regenerative blower is also analyzed and compared.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.994-995
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• 2014

Supporting stiffness of seats is an important component affecting dynamic characteristics cognized by a passenger. To analyze dynamic characteristic of a seat for vehicles operating on various road conditions, the seat vibration from road irregularity should be understood and compared. In this study, the seat is analyzed as distributed supporting system. The dynamic stiffness is measured using masses. The characteristic of the seats is analyzed by measuring distributed dynamic stiffness. The distributed dynamic stiffness of the seat is estimated on various locations and the effects of each component such as spatial distribution, compression level and vibration amplitude are analyzed. The influence of seat cover, elastic support and flexible polyurethane foam on the measured stiffness was analyzed.

• Journal of the Korean Operations Research and Management Science Society
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• v.19 no.3
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• pp.169-186
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• 1994

This paper presents three mathematical programming approaches to solving transshipment problems with interval supply and demand requirements. A linear goal programming model was developed based on the data obtained from a nationwide retail firm. Three mathematical programming model results were compared and analyzed, and three separate hypotheses were examined by using the Wilcoxon signed-ranked test for the model applicability. The test results were analyzed and interpreted for decision making.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.213-217
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• 1997

In this study, three-dimensional inite element model was developed and analyzed or DAI using ABAQUS. To verify the developed FE model, simulated results were compared to experimental results of human cadaver by Nahum et. al. (1977). The effect of acceleration pattern and accelerating duration time or DAI was analyzed by means of maximum shear stress and pressure distribution. DAI was favored or angular acceleration rather than linear acceleration, and occured in brain stem, pons and midbrain easily as accelerating duration time was increased.

• Speech Sciences
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• v.4 no.2
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• pp.17-24
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• 1998

In this paper a method to diagnose pathological voices using wavelet transform is sug gested. Pathological voices are collected from hospital and analyzed by the suggested method. Normal voices are collected separately and analyzed. Then the results are compared to find the differences in their characteristics. Three level wavelet transform is used. Normalized energy ratios between the levels and normalized peak-to-peak values are used as parameters. As a result, it was possible to distinguish between normal and pathological voices.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.573-578
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• 2004

Rotem has chosen ADAMS/Rail as the next generation analysis tool, to improve the capability and accuracy of the analysis ability. The dynamic performances of the railway vehicle, which is designed and manufactured by Rotem, have been analyzed and simulated using ADAMS/Rail. In this paper, Dynamic stress of bogie frame on running track is analyzed and compared with the data of real vehicle test. It is performed using ADAMS/AutoFlex and ADAMS/Durability.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.12
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• pp.36-42
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• 1993

By the variational method, the coplanar waveguide(C.P.W) shielded by two conducting plates has been analyzed. The particular potential solution has been obtained for the boundary conditions in C.P.W. The characteristic impedance and the effective dielectric constant in C.P.W. have been obtained by the variational method using the potential function and the assumed basis function for charge distributions. To consider the effect of the conducting plate in C.P.W. two cases, with and without the top plate, have been analyzed and compared respectively.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.333-340
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• 2003

In Korea, drilled shaft are generally socketed into rock. Driven pile has environmental problems such as vibration and noise. Therefore, applications of the drilled shaft are increasing in Korea. In this paper, static load test data of the rock socketed drilled shaft at Gwangandaero and Suyeong 3hogyo are analyzed. The bearing capacities from field test data and theoretical formula are compared and analyzed. From this study, design approaches for drilled shafts in Korea are examined and several suggestions are proposed.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.78-89
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• 2008

In this study the frost penetration depth along national roads in Korea were measured and analyzed over several years. The frost penetration depth was analyzed with respect to the Provinces of Korea and sunny/shaded areas. Additionally, the measurement results were compared to the formular of the US Army Corps of Engineers and Terada in Japan.

• Structural Engineering and Mechanics
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• v.73 no.1
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• pp.75-82
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• 2020

In this study, the problem of torsion of bars with open cross section surrounded by corrugated boundaries is analyzed. An approximate analytical solution is given using perturbation technique. First, the stress analysis for circular open cross-section for arbitrary opening angle is formulated and the problem is analytically solved. Second, the open cross-section with corrugated cross section is analyzed using perturbation method. First order contributions to the stresses and the torques have been added. The results have been exemplified and compared by considering special examples.