• Journal of the Microelectronics and Packaging Society
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• v.12 no.3 s.36
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• pp.219-226
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• 2005

When a ferroelectric film has an inhomogeneous distribution of charged defects, a voltage shift in the polarization curve is induced by the internal field generated in the film. The direction and the magnitude of voltage shift in the P-V hysteresis curves obtained by the Sawyer-Tower method are different from those obtained by the virtual ground method. In this study, the asymmetric behavior in the P-V hysteresis curves of inhomogeneous ferroelectric films was investigated with a physical model and the polarization curves obtained by the Sawyer-Tower and the virtual ground methods are compared.

• Journal of KSNVE
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• v.8 no.5
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• pp.799-806
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• 1998

Noise and vibration due to railway traffic are major causes of environmental pollution in the city. In course of judging, assessing and coping with the problem, it becomes imperative to predict the vibration level induced by railway traffic passing through downtown in the city. The vibration due to railway traffic is transferred to the neighbouring buildings through the ground. In this study, as a method predicting vibration level of the buildings near railway, a vibration transfer formula is suggested. This formula is used to calculate vibration level occuring at the bottom of the neighbouring buildings, which are located at a certain distance from railway.

• Geomechanics and Engineering
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• v.15 no.3
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• pp.861-868
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• 2018

Recent occurrences of earthquakes in Korea have increased the importance of considering how horizontal loads affect foundation structures as a result of wind and dynamic impact. However, to date, there are few studies on tunnelling-induced behaviour of ground and pile structures simultaneously subjected to horizontal and vertical loads. In this research, therefore, the behaviour of ground and single piles due to tunnelling were investigated through a laboratory model test. Three cases of horizontal loads were applied to the top of the pile. In addition, a numerical analysis was carried out to analyse and compare with the results from the laboratory model test.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.3
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• pp.35-39
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• 2001

The precision grinding process is carried out with fine-cutting operation after coarse-cutting operation. So, the laminated grinding wheel has been developed to reduce the ineffectiveness induced by changing the operations. In this study, to investigate the possibility of the practical use of the laminated grinding wheel, the surface residual stress of the workpiece ground by the laminated grinding wheels was compared with that ground by the general grinding wheel, and the influence of the difference in grain sizes, between the coarse grit and fine grit of the laminated grinding wheel, on the surface roughness of the workpiece was investigated.

• Journal of the Korean GEO-environmental Society
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• v.17 no.7
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• pp.27-33
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• 2016

This study expanded Terzaghi arching formula, which assumed a vertical surface as a sliding surface, to consider an arbitrarily inclined surface as a sliding surface and examined the effect of a sliding surface. This study firstly developed a formula to expand the existing Terzaghi arching formula to consider an inclined surface as well as a vertical surface as a sliding surface under the downward movement of a trap door. Using the expanded formula, the effect of excavation, ground, and surcharge conditions on a vertical stress was examined and the results were compared with them from Terzaghi arching formula. The comparison indicated that the induced vertical stress was highly affected by the angle of an inclined sliding surface and the degree of influence depended on the excavation, ground, and surcharge conditions. It is expected that the results from this study would provide a better understanding of various arching phenomenon in the future.

• Proceedings of the KIEE Conference
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• 2008.10c
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• pp.215-217
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• 2008

DC fraction system can damage human and other facilities due to the rising of rail potential. Therefore the earth fault detection relay protects system using rail potential induced in train operation and ground fault. However the conventional protection system cannot operate due to the fault resistance and might operate unwanted voltage rising due to the other substation ground fault. So this paper models DC traction system using PSCAD/EMTDC and simulates the rail potential rising. We can estimate the rail potential rising in DC traction system through the various simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.11
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• pp.5497-5512
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• 2016

An improved optimal weights based on parallel interference cancellation algorithm has been proposed to cancel for interference induced by multi-user access satellite to ground uplink system. Due to differences in elevation relative motion between the user and the satellite, as well as access between users, resulting in multi-user access interference (Multi-user Access Interference, MUI), which significantly degrade system performance when multi-user access. By steepest gradient method, it obtained based on the MMSE criterion, parallel interference cancellation adjust optimal weights to obtain the maximum SINR. Compared to traditional parallel interference cancellation (Parallel Interference Cancellation, PIC) algorithm or serial interference cancellation ( Successive interference Cancellation, SIC), the accuracy of which is not high and too many complex iterations, we establish the multi-user access to the satellite to ground up link system to demonstrate that the improved WPIC algorithm could be provided with high accuracy and relatively low number of iterations.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.146-153
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• 2009

One dimensional site response analysis is widely used in prediction of the ground motion that is induced by earthquake. Equivalent linear analysis is the most widely used method due to its simplicity and ease of use. However, the equivalent linear method has been known to be unreliable since it approximates the nonlinear soil behavior within the linear framework. To consider the nonlinearity of the ground at frequency domain, frequency dependent algorithms that can simulate shear strain - frequency dependency have been proposed. In this study, the results of the modified equivalent linear analysis are compared to evaluate the degree of improvement and the applicability of the modified algorithms. Results show the novel smoothed curve that is proposed by this study indicates the most stable prediction and can enhance the accuracy of the prediction.

• Proceedings of the KSR Conference
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• 2001.05a
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• pp.375-380
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• 2001

Generally, countermeasures for the train-induced vibration are divided into the measures at the source, propagation path and receiving object. Among these measures the countermeasure at the source location is the most active and effective one in the field of railroad. In this study, the effectiveness of each anti-vibration measures at the track(source location) such as elastic rail fastener, ballast mat were evaluated through the comparison of acceleration level, insertion loss at the installed locations of each measures. As result of field measurement of vibration at the railroad track supporting structures and on the ground nearby the structures, elastic rail fastener showed vibration reduction effect of 4.5 ∼7.3㏈ on the concrete slab, 1.6∼3.7㏈ on the ground with the train operation speed of 80km/hr. In the case of ballast mat, the vibration reduction effect at the concrete slab and on the ground were 11.9∼13.3㏈ and 6.1∼7.6㏈, respectively.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.86-92
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• 2000

Recently, the Korea National Railways (KNR) is undertaking a program of electrification of the existing railway routes. In order to implement the ongoing plan, KNR authorized a preliminary engineering study of its electrical systems. This effort included a comprehensive analysis of new grounding networks. The new grounding system runs in parallel with the rails and is connected to all metal structures such as rails, overhead protection wires and substation grounding grids etc., creating an equipotential ground network. This paper presents a study on coupling levels that can disturb signaling and telecommunications in adoption of the new grounding network The simulation for the study is carried out using Matlab software, Several different scenarios are analyzed, including the load condition and a few fault conditions with different fault locations. The induced potentials on the communication cables are computed. The effect of the buried ground wires is also analyzed by comparing the results with and without the presence of the ground wires, The results presented in the paper can be used as a reference for estimating coupling levels in similar rail systems.