• Transactions on Electrical and Electronic Materials
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• v.18 no.1
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• pp.16-20
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• 2017

A RF-MEMS (radio-frequency microelectromechanical-system) based DPDT (double pole double throw) switch for the Ku band has been designed and analyzed for this article. The switch topology is based on the FG-CPW (finite ground-coplanar waveguide) configuration of a microstrip-transmission line. An FEM-based multiphysics solver is used for the evaluation of the spring constant, stress distribution, and pull-in voltage regarding the requirements of the switch-beam unit. The electromagnetic performance of the switch is investigated for a $675{\mu}m$ thick silicon substrate. For the operational frequency of 14.5 GHz, an insertion loss better than -0.3 dB, a return loss better than -40 dB, and input/output- and output-port isolations better than -35 dB are achieved for the switching unit.

• Journal of the Korean Society of Safety
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• v.16 no.3
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• pp.99-105
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• 2001

This paper presents results km a series of model tests oil vertically loaded single piles to compare the behaviors of H and pipe piles under the same ground condition. The aims of this paper were to compare the bearing capacity of H-pile md pipe piles under in the same ground condition and to estimate the effect of gravity acceleration and relative soil density. Relative density of soil were made to be 40%, 80% and embedded length of pile on sand was increased by 10, 12, 14, 16 times of the diameter of pile, respectively. As a results of test series, allowable load of H-pile is from 6.4% to 18.2% larger than allowable load of pipe pile in relative density 80% and from 9.1% to 39.4% larger than allowable load of pipe pile in relative density 40%. As a results of numerical analysis, we were predicted behaviour of stress-displacement of pile with model test. In the case of relative density 80% and 40%, bearing capacity of H pile represent from 17.74% to 18.6% larger than allowable load of pipe pile.

• Journal of Biosystems Engineering
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• v.23 no.3
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• pp.219-228
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• 1998

This study was conducted to develop the mathematical model and computer simulation program(TPPMTV98) for predicting the tractive performance of tracked vehicles. It takes into account major design parameters of the vehicle as well as the pressure-sinkage and shearing characteristics of the soil, and the response of the soil to repetitive loading. Structural analysis and numerical iterative method were used for the derivation of mathematical model. The simulatiom model TPPMTV98 can predict the ground pressure distribution and the shear stress under a track, the motion resistance, the tractive effort and the drawbar pull of the vehicles as functions of slip. Predicted tractive performance results obtained by the simulation model were validated by comparing the results firm the Wong's model, the offectiveness of Wong's model validated by many of the experiment. It was found that there is fairy close agreement between the prediction by TPPMTV98 and the results from Wong's model. The computer simulation model TPPMTV98 can be used for the optimization of tracked vehicle design or for the evaluation of vehicle candidates for a given mission and environment.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.97-104
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• 2001

The magnitude and the orientation of in-situ stresses contribute to ground displacement and stresses in the field of underground space. This paper investigates in-situ stresses at various depth on the basis of 392 data which were determined by over-coring and hydro-fracturing test methods in the Korea peninsula. The result shows that in-situ stress distribution are more or less non-uniform through the Granite and Gneiss sub-area, and that the K-value in the Volcanic sub-area are below 1 at the deep depth. Also, the result of three dimensional numerical analyses of tunnel shows that the direction and magnitude of displacement around tunnel are much effected by the stress difference between the maximum and the minimum horizontal stress.

• Journal of the Korean Geotechnical Society
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• v.34 no.11
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• pp.5-19
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• 2018

The characteristics of the skin shear stress distribution for the fixed length of the ground anchor are extremely nonlinear and the engineering mechanisms are complex relatively. So it is difficult to design the anchors simulating the actual behavior by considering various soil conditions and nonlinear behavior. Due to these limits, constant skin shear stress distributions for the whole fixed length of the ground anchor are usually assumed in the design for the sake of convenience. In this study, to assess the pull-out behavior of the tension-type ground anchors, the in-situ pull-out tests in weathered-soil conditions were carried out. Based on the test results, the skin shear behaviors for the fixed length of tension-type ground anchors were established and the multi-linear slip shear model predicting this behavior and an analytical technique applying this model were proposed. From the similarity between the results of the in-situ pull-out tests and those of the analytical technique, the applicability and availability of the multi-linear slip shear model and the proposed analytical technique were verified. The maximum shear stress was developed at the start point of the fixed length acting with the smaller load than the maximum pull-out load but the minimum shear stress was developed at the start point of the fixed length and the maximum shear stress was developed at the point apart from the start point of the fixed length after the maximum pull-out load.

• Land and Housing Review
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• v.7 no.4
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• pp.261-269
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• 2016

Pipe-roof method is one of the mostly used method to prevent the ground subsidence during the tunnel construction. As pipe-roof method has made technical advancement and performance improvement, it suggested to utilize pipe-roof to a permanent support system rather than a temporal pre-reinforcing method. Therefore, in this study, pipe-roof method is numerically simulated using finite element method to evaluate effects of pipe-roof on behavior of ground and structure. Analyses are performed considering two major conditions that are with and without the application of pipe-roof and the shape of tunnel cross section. The results are presented with respect to variation of settlement and vertical stress distribution. Based on this results, it is found that ground settlement above the shallow tunnel can be considerably reduced by application of pipe-roof system. Also, the shape of tunnel cross section can influence on the mechanical behavior of ground and structure.

• Earthquakes and Structures
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• v.6 no.3
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• pp.251-266
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• 2014

Dynamic analyses for a suite of ground of motions were conducted on concrete gravity dam sections to examine the earthquake induced stresses and effective damping. For this purpose, frequency domain methods that rigorously incorporate dam-reservoir-foundation interaction and time domain methods with approximate hydrodynamic foundation interaction effects were employed. The maximum principal tensile stresses and their distribution at the dam base, which are important parameters for concrete dam design, were obtained using the frequency domain approach. Prediction equations were proposed for these stresses and their distribution at the dam base. Comparisons of the stress results obtained using frequency and time domain methods revealed that the dam height and ratio of modulus of elasticity of foundation rock to concrete are significant parameters that may influence earthquake induced stresses. A new effective damping prediction equation was proposed in order to estimate earthquake stresses accurately with the approximate time domain approach.

• Proceedings of the Korean Geotechical Society Conference
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• 1994.09a
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• pp.169-174
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• 1994

This paper presents the results of a parametric study on the bearing capacity behavior of a footing located above geogrid-reinforced ground using the finite element method of analysis. A wide range of boundary conditions were analyzed, with varing geogrid design parameters such as depth of geogrid layer, length and siffness of geogrid, and number of geogrid layer, were analyzed. Based on the results of analysis, the optimum geogrid design parameters were determined, which maximize the reinforcing effect of geogrid reinforcement for a given conidition. Furthermore, the mechanistic behavior of a geogrid-reinforced ground subjected to a footing load was discussed using the results of analysis such as stress distribution, propagation of plastic yielding, displacement vector among others.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.1
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• pp.141-148
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• 2008

This paper presents experimental results on the safety of persons and protection of low-voltage equipments of the sub-station due to a single-phase ground fault in 22.9 kV-Y distribution system. In order to evaluate the hazard voltages and the stress voltage of the low-voltage(LV) equipment due to faults between high-voltage systems and earth based on the newly prescribed KS C IEC 60364 standard series, the verification tests in a 22.9[kV] neutral multiple grounding system were carried out. From the experimental results, we introduce serious problems causing some discomfort when applying KS C IEC 60364 standard series to the existing domestic distribution system and the effective protective measures against temporary overvoltages due to a ground fault in the common grounding which is combined the 22.9 kV-Y grounding and the customer's installation grounding are proposed. As a consequence, it was found that the equipotential bonding is an important prerequisite for the effectiveness of the protective measures for the safety of persons and LV equipment in the combined 22.9 kV-Y and low-voltage grounding system.

• Journal of the Korean Geotechnical Society
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• v.27 no.2
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• pp.5-15
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• 2011

This research performed the laboratory model tests for Top-Base Foundation developed in Japan and Floating Top-Base Foundation developed in Korea on the typical clayey soft soils, namely, clay, clayey silt and clayey sand. The performances of the two types of top-base foundation were compared with each other and evaluated by measuring load-settlement, heaving of foundation side, ground stress distribution in this model tests. The change of settlement caused by the increase of top base width was also analyzed. As a result of the model tests, Floating Top-Base Foundation showed better performance in bearing capacity improvement, settlement decrease, stress dispersion effect and lateral confinement force. And settlement caused by the increase of top base width converged to a regular value from $5{\times}5$ layout of the width.