• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.10
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• pp.1040-1047
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• 2002

In this paper, we investigated noise decoupling on the power bus by the screw connection, used to the mechanical join and grounding of the PCB ground to chassis. The screw connection penetrates the power bus and then it affects noise propagation on the power bus. To verify effect of the screw connection, we compare bare board with board having screws connection with 0.5 mm separation between power bus and chassis. From these results, we observed that the power bus noise was decreased about 5 dB at the frequency range from 0.1 GHz to 1 GHz. Also, we verified that a 4-layer PCB with signal trace had the better signal quality up to 600 MHz by the screw connection. Therefore, these results will be useful in designing to the high speed circuit and chassis.

• Journal of the Korean GEO-environmental Society
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• v.23 no.8
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• pp.17-22
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• 2022

To reduce the bump of bridge/earthwork transition area caused by the settlement of the soft ground during public use, the road agencies have been continuously overlay or repavement at those areas. In this study, the vehicle-mounted ground penetrating radar with 1GHz air-coupled antenna was used to estimate the settlement amount of those areas for nine bridges built in the soft ground. Results shows that it is possible to effectively measure the thickness of pavement up to a depth of 1 m on an asphalt road with ground penetrating radar technology that can inspect under the road surface. Distinctively deformation of the road surface, the variation in the thickness of the pavement measured at bridge/earth transition areas is equivalent to a minimum of 50 mm and a maximum of 600 mm, and there is a risk of cavity in the ground. The difference in the increased pavement thickness is 50~250 mm for each bridge connection, which may cause the differential settlement. In this study, by using the result of the ground penetration radar, a plan for improving drivability and maintenance of the settlement is suggested and applied to the field.

• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.313-324
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• 2010

In this study, an unbraced five-story steel-framed structure was designed in accordance with KBC2005 to understand the features of structural behavior for the arrangement of semi-rigid connections. An inelastic time history analysis of structural models was performed, wherein all the connections were idealized as fully rigid and semi-rigid. Additionally, horizontal and vertical arrangements of semi-rigid connections were used for the models. A fiber model was utilized for the moment-curvature relationship of a steel beam and a column, a three-parameter power model for the moment-rotation angle of the semi-rigid connection, and a three-parameter model for the hysteretic behavior of a steel beam, column, and connection. The base-shear force, top displacement, story drift, required ductility for the connection, maximum bending moment of the column, beam, and connection, and distribution of the plastic hinge were investigated using four earthquake excitations with peak ground acceleration for a mean return period of 2,400 years and for the maximum base-shear force in the pushover analysis of a 5% story drift. The maximum base-shear force and story drift decreased with the outer vertical distribution of the semi-rigid connection, and the required ductility for the connection decreased with the higher horizontal distribution of the semi-rigid connection. The location of the maximum story drift differed in the pushover analysis and the time history analysis, and the magnitude was overestimated in the pushover analysis. The outer vertical distribution of the semi-rigid connection was recommended for the base-shear force, story drift, and required ductility for the connection.

• Korean Journal of Applied Biomechanics
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• v.26 no.1
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• pp.83-92
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• 2016

Objective: This study aimed to compare differences in biomechanical factors according to distance changes in relation to approaches during a round of golf to obtain basic data on golf swings. Methods: The research subjects were 8 KPGA-affiliated professional golfers who performed approach shots that put a ball into a circle of 8 feet in diameter from distances of 30, 50, and 70 m. Data were collected by using six infrared cameras and a ground reaction force device, which were applied to calculate biomechanical factors by using Kwon3D XP. The calculated data were subjected to one-way ANOVA by using SPSS 20.0, with the significance level set at p value of 0.05. Results: Elapsed time, stance width, clubhead position variation, clubhead synthesis speed, and cocking angle significantly differed according to distance change during the approach swing. Clubhead speed was positively related with stance width and clubhead displacement. Ground reaction force significantly differed according to distance change during the approach swing. Factors before and after showed differences in other states, except in the impact state. Conclusion: In the present study, we drew several conclusions regarding biomechanical factors and ground reaction forces according to distance change in the approach swing of professional golfers. According to these conclusions, we suggest that distance control with swing range is more important than power control in maintaining the accuracy and consistency of golf swing and is the most important mechanism of golf swing.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.151-156
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• 2007

Topology optimization has been widely used in many research areas due to its ability in providing intial designs for the problems with complex boundary conditions. This also has been useful in compliant mechanisms, but resulting layouts may not be immediately manufacturable because they usually consist of members with varying widths and shapes. Also, there occurs some numerical difficulties such as checkerboards or hinge patterns which result from 1-node connection, and intermediate values which make the manufacturing of the designed structure difficult. Though there are many remedies given to avoid this problems, they cannot be prevented. One may avoid this difficulty by employing uniform ground beams and explicit hinge joints. The proposed method is to connect uniform ground beams with elastic short-beam hinge joints. By choosing the widths of short beams as design variables, dominant deformations can occur mainly by flexible joints having intermediate widths. Unlike the conventional methods used for compliance minimization, intermediate widths must appear in compliant mechanism design problems. Also, the present approach does not encounter the problem of one-point hinges.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.4
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• pp.55-61
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• 1998

Generally, in the calculation of ground resistance in the grounding system, the method measuring ground potential rise which is caused by low frequency source injection is used. But both lightning and surge impulse re very harmful to electric equipment. In this connection, this paper presents the results of an experimental investigation of transient behavior of ground impedances when lightening current is injected to the electric rod the experimental results are agreement with the theoretical analysis. In addition, the states on the behavior of ground electrodes under impulse currents due to lighting strokes are presented. And the impulse impedance reductions caused by discharge in the soils are presented.

• Journal of Korean Society of Steel Construction
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• v.22 no.3
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• pp.281-291
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• 2010

In this study, a five-story steel frame was designed in accordance with KBC2005 to evaluate the effects of the beam-column connection on the structural behavior. The connections were designed as fully rigid and semi-rigid. The fiber model was used to describe the moment-curvature relationship of the steel beam and the column, the power model for the moment-rotation angle of the semi-rigid connection and the three-parameter model for the hysteretic behavior of the steel beam, column, and connection. The structure was idealized as separate 2-D frames and as connected 2-D frames. The peak ground accelerations of four earthquake records were modified in a time-history analysis for the levels of the mean return period and for the maximum base-shear force in a pushover analysis. The top story displacement, base-shear force, story drift, demanded ductility ratio for the semi-rigid connection, maximum bending moment of the column, beam, and connection, and distribution of the plastic hinge were examined in the time-history analysis. The frame with the semi-rigid connection yielded a lower base-shear force, less magnitude, and increasing ratio in the bending moment of the column, beam, and connection than the frame with a fully rigid connection. The TSD connection was deemed to have secured the economy and safety of the sample structure that was subjected to seismic excitation for the Korean design level.

• Journal of the Korean Geotechnical Society
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• v.29 no.10
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• pp.5-18
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• 2013

The differential settlement between the foundations causes the critical damage on the transmission tower constructed in soft ground. Connected-pile foundation for transmission tower structures is an option to prevent the differential settlement. It consists of main foundations and connection beams that are placed between the individual foundations at each corner of tower. In this study, 24 model pile load tests were conducted at a construction site in jeonlabuk-do to investigate the effects of the connection beams on transmission tower foundation. In model tests, various load conditions and connection beam conditions were considered. As the test results, the displacements of connected-pile foundation differed in accordance with load directions. The settlements of connected-pile foundation decreased with the increased stiffness of connection beams, lateral load capacity decreased in accordance with load height, and the lateral load capacity on the failure criteria was similar regardless of load direction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.713-719
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• 2015

The change in induced voltage according to the relationship of ground connection between the aluminum sheath layer and a conductor pair in a general telecommunication cable is analyzed. When a measurement is practiced under the condition of separated sheath grounds with an averaged ground resistance of $42.6{\Omega}$, the induced voltage decreases 10 % to the induced voltage without sheath grounds. The induced voltage decreases approximately 50 % in the case of a one-sided common ground and decreases by more than 90 % in the case of a both-sided common ground. This experimental result is similar to the values calculated using the methods of the ITU Directives. In addition, according to a comparison analysis utilizing this ITU method, the measurement error range will be below 10 % in the state of ground resistance of central office less than $10{\Omega}$ and for the terminal side with $100{\Omega}$ less or more.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.3
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• pp.431-436
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• 2009

As the telecommunication lines bring into widespread use, one of the most important aspects related to power distribution systems is effectively to evaluate the effect on the telecommunication lines from power lines. One of the efficient methods to evaluate the effect is to measure the induced voltage of a telecommunication line as a result of a ground-loop. If the power lines cause high induced voltage, the ground reference in the telecommunication lines is no longer a stable potential, so signals may ride on the noise. A ground loop is common wiring conditions where a ground current may take more than one path to return to the grounding electrode at the arrangement between the power lines and telecommunication lines. When a multi-path connection between the power lines and telecommunication line circuits exists, the resulting arrangement is known as a ground loop. Whenever a ground loop exists, there are potential for damages or abnormal operations of the telecommunication lines. The power lines can induce the voltage on the communication line. The effects can be calculated by considering the inductances and capacitances. However, if we assume that there are only power lines, it doesn't have a practical meaning because there are conductors with other purpose in the neighborhood of the lines. If we consider that case, we need more complex system. Therefore we suggest more complex system considering the conductors with other purpose in the neighborhood of the lines. The neutral wires and the overhead ground wires are considered for calculating the induced voltage. We assume that there are the messenger wires beside the power line as a result of increased use of them. The main purpose of this paper is a study on a shielding effect of messenger wires in the distribution lines. EMTP(Electro-Magnetic Transients Program) program is used for the induced voltage calculation.