• 연구논문집
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• s.23
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• pp.5-13
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• 1993

The present work deals with the theoretical prediction of static & dynamic characteristic of annular type externally pressurized thrust air bearings with metal-sintered porous media. For the evaluation of surface loading effect by machining, it is assumed that the flow at the porous surface is dominant and which is equivalent to the flow through orifice. Finite different method with over-relaxation method is used to solve the numerical problems. The influences of radius ratio, supply pressure and squeeze number on performances are investigated, as the results. The results of this study can be used to predict the optimal running condition and stable realm of porous bearings.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.11
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• pp.898-908
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• 1990

This paper applies the moment method to analyze the transverse electromagnetic(TEM) cell with an inner conductor (septum) of arbitrary rectangular shape and location by employing quast static approximation. The EM field and the characteristic impedance so obtained are shown to be in good agreement with the available data from the previously published papers about the typical TEM cell structure with center septum of zero thickness.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.10
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• pp.139-143
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• 1996

We report on the static and dynamic characteristics of optically modulated resonant tunneling diode oscillator (RTDO) formed in double-barrier quantum-well structure. Under the illumination of Ti:Sapphire laser, the dc current-voltage (I-V) curves of RTDO shifted towared lower voltages. This characteristic was found to odify the series resistance, negtive differential resistance, capacitance, and the inductance of the RTDO. As a result, the resonant frequency of TRDO centered at 5.302 GHz was found to decrease about 20 MHz under the laser illumination. At a constnat bias voltage, the oscillation frequency decreased linearly as the laser power was increased.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.485-488
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• 2000

In this study, the fatigue characteristic of spot weld specimen was studied by using the various specimen. The specimen types were tensile shear specimen welded one spot and two spot, and cross tension. The tensile tests and fatigue tests were executed to know the mechanical properties under static and fatigue load condition. In addition, the relationship was illustrated by finite element method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.117-124
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• 1998

New Thrie-Beam guardrail section has been developed. The Characteristic of its geometry, energy absorbing capability and response to impact has been studied and compared with those of conventional W-Beam guardrail system. To compare the response to impact computer simulation using Barrier Ⅶ program was made. Stretch tests and static loading tests were conducted for the performance verifications.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.6
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• pp.128-133
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• 1994

This paper proposes a new TTL-to-CMOS converter which has low power dissipation. This converter has no static power dissipation for typical TTL output voltage levels. The simulatio result shows that the power dissipation is reduced to about 1/20 of conventional level converter using CMOS inverters. It also has hysteresis due to the positive feedback which makes the converter noise immune. The logic threshold voltages in the hysteresis characteristic can be optimized by changing the size ratios of the transistors.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.353-360
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• 1998

Dynamic measurements are used rather sparingly to determine the elastic moduli of rock cores and modulus values are not much utilized in design practice. The reason seems to result from the general perception that values obtained by dynamic measurement are much higher (about 10 times) than those determined statically. This paper presents results from dynamic and static tests on rock cores. The findings are : 1) elastic moduli can be consistently determined by laboratory seismic testing. 2) nonlear deformation characteristic of rock cores was tentatively proposed with variation in elastic modulus with strain.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.288-291
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• 2004

The characteristics of the buckling analysis module for stiffened composite structures were studied in this paper. Composite stiffened structures have geometrical asymmetry and material properties asymmetry. Due to these reason, postbuckling analysis was essential and the characteristics of postbuckling analysis modules for ABAQUS were researched. Static analysis module was considered. By considering the material nonlinearity, progressive failure mechanism was applied and buckling strength was estimated

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.3
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• pp.229-237
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• 2000

본 논문에서는 멀티브리지 인버터로 구성된 SSSC를 제안하였다. SSSC의 동적특성을 분석하기 위해서 1기 무한모선 전력계통에 SSSC를 연결한 것을 가정하고 EMTP 시뮬레이션을 수행하였고, 축소모형 실험으로 그 특성을 확인하였다. 다중브리지 SSSC는 한 상당 6개의 단상 풀브리지 인버터로 구성되었고, 13-레벨 출력전압을 얻을 수 있다. 다중브리지 SSSC는 전압 주입을 위한 연계 변압기가 필요하기 않고, 전력계통에서 요구되는 동작전압에 따라 브리지 수를 가감하여 용이하게 구성할 수 있다.

• Structural Engineering and Mechanics
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• v.63 no.4
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• pp.509-519
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• 2017

Wind field in mountainous regions demonstrates unique distribution characteristic as compared with the wind field of the flat area, wind load and wind effect are the key considerations in structural design of television towers situated in mountainous regions. The television tower to be constructed is located at the top of Xiushan Mountain in Nanjing, China. In order to investigate the impact of terrain factors of hilltops on wind loads, firstly a wind tunnel test was performed for the mountainous area within 800m from the television tower. Then the tower basal forces such as bending moments and shear strength were obtained based on high frequency force balance (HFFB) test. Based on the experiments, the improved method for determining the load combinations was applied to extract the response distribution patterns of foundation internal force and peak acceleration of the tower top, then the equivalent static wind loads were computed under different wind angles, load conditions and equivalent goals. The impact of terrain factors, damping ratio and equivalent goals on the wind load distribution of a television tower was discussed. Finally the equivalent static wind loads of the television tower under the 5 most adverse wind angles and 5 most adverse load conditions were computed. The experimental method, computations and research findings provide important references for the anti-wind design of high-rise structure built on hilltops.