• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1997.10a
• /
• pp.126-131
• /
• 1997

Recently, the ground motion occurred by vehicles or trains has been recognized one of the major factors of damage of structures nearly the motion source. To isolate the environments from ground motions, it is necessary to understand the wave propagation in half spaces. Especially, Rayleigh wave is the primary concern because it transmits a major portion of the total source energy and decays the energy more slowly with response to distance than the other waves. In this study, the preliminary data(wave length and damping effect) to design the isolating system are obtained. For this, a field dynamic test is performed, using the exciter which can generate the 100kN vertical cyclic load in the range of 1-60 Hz is used. The fifteen accelerometers to measure the ground response are set up in 3 radial direction at intervals of 10 meters in each row. The wave lengths are calculated using the distance and the phase between the measuring points. The damping effects of the Rayleigh-wave are also observed from the experiments.

• Journal of Electrical Engineering and Technology
• /
• v.7 no.3
• /
• pp.406-410
• /
• 2012

This paper looks into the field inside the wide rectangular box structure that is excited by the High Power Electromagnetic(HPEM) source as a potential threat to electric grid and communication networks causing malfunction or destruction. The rectangular box is assumed power/ground planes and its internal field is calculated by the cavity model with the lightning strike excitation as an HPEM pulse. The accuracy of the calculation method employed here is validated through a $156mm{\times}106mm{\times}508{\mu}m$ parallel metallic plate case which is manufactured and tested, and is applied to the size of a building. With the help of the cavity model that takes into account loading, the level of the electric field is shown to decrease when a metal pillar is loaded between the power and ground planes.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.11 no.2
• /
• pp.7-11
• /
• 2015

Recently, as the demand for sustainable energy sources is increasing, ground-source heat pump (GSHP) systems are receiving growing attention. However, the initial cost of GSHP system is higher than it of the conventional systems, especially, in small-size buildings. Therefore, for the application to the small-size building, it is necessary to develop small-size ground heat exchanger with small-size buildings. In this study, analysis of unit-type heat exchanger due to grouting materials. As a result, 1492.14 W of heat exchange rate was acquired in the condition of cement-silica sand-graphite materials.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2006.05a
• /
• pp.157-159
• /
• 2006

The advantages of LED(Light Emitting Diode) are low electric power consumption, long life time and excellent visibility. And a LED light source does not include the mercury(Hg) and or a filament, it is expected as an environmentally friendly next generation light source with its good reliability. In order to design and develope the flash lantern using LED for aironautical ground lights, technical trends and new standards about the aironautical ground lights were inspected, and power consumption and flash time for effective luminous intensity of aironautical ground lights were analyzed.

• Proceedings of the SAREK Conference
• /
• 2005.11a
• /
• pp.148-154
• /
• 2005

Ground-source (Geothermal) heat pump (GSHP) systems can achieve a higher coefficient of performance than conventional air-source heat pump (ASHP) systems. However, GSHP systems are not widespread in Japan because of their expensive boring costs. The authors have developed a GSHP system that employs the cast-in-place concrete pile foundations of a building as heat exchangers in order to reduce the initial boring cost. In this system, eight U-tubes are arranged around the surface of a cast-in-place concrete pile foundation. The heat exchange capability of this system, subterranean temperature changes and heat pump performance were investigated in a foil-scale experiment. As a result, the average values for heat rejection were 186${\sim}$201 W/m (for pile, 25 W/m per Pair of tubes) while cooling. The average COP of this system was 4.6 while cooling; rendering this system more effective in energy saving terms than the typical ASHP systems. The initial cost of construction per unit for heat extraction and rejection is ${\yen}$72/W for this system, whereas it is f300/W for existing standard borehole systems.

• Proceedings of the KIEE Conference
• /
• 2006.04a
• /
• pp.291-293
• /
• 2006

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.17 no.2
• /
• pp.30-41
• /
• 2021

This paper presents the heating performance analysis results of a heat pump system using a dual heat source. In this paper, a dual heat source refers to the ground-coupled heat exchanger using both a surface water heat exchanger (SWHE) and a vertical ground heat exchanger (VGHE). In order to evaluate the system performance, we installed a monitoring system to measure the temperature and power consumption of a heat pump and then collected operation data with 4 different load burdened ratios of the dual heat source heat exchanger. During the whole measurement period, the average heating capacity of a water-to-water heat pump unit was 37.3 kW. In addition, the compressor of the heat pump consumed 9.4 kW of power, while the circulating pump of the dual heat source heat exchanger used 6.7 kW of power. Therefore the average heating coefficient of performance (COP) for the heat pump unit was 4.0, while the entire system including the circulating pump was 2.7. Finally, the parallel use of SWHE and VGHE was beneficial to the system performance; however, further researches are needed to optimize the design data for various load ratios of the dual heat source heat exchanger.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.34 no.E
• /
• pp.1-11
• /
• 1992

Increasing national concern on nonpoint source pollution of surface and ground water Systems has led researchers and policy makers to develop certain agricultural Best Management Practices. As an initial step of broad study program above mentioned, this study reflected the effects of different tillage practice on bulk density and degree of saturation on two regional soils, namely Tama silt loam and Catlin silt loam. Results may help to clarify some of the conflicting findings on the impact of tillage systems on these parameters and it may also explain some of the reasons for specific role that different tillage systems play regarding nonpoint source pollution from agricultural fields.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.8 s.113
• /
• pp.806-813
• /
• 2006

An important factor of vibration test using MAST(multi axial simulation table) system is the reliance of input excitation source. Generally the generation of input excitation source is obtained by the measured data on special road in proving ground. The measured data on special road have more exciting energy than the data of real fields, therefore the time and expense for test can be reduced. But the magnitude of input excitation source must be defined by comparison with the excited energy on real field. The object of this paper makes the data base of domestic roads for the definition of input excitation source which is obtained by the measured data on special road in proving ground. These real field data on domestic roads are analyzed by the power spectral density and interrelationship index.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.10
• /
• pp.1916-1922
• /
• 2009

Introducing distributed generators(DGs) to utility distribution system can cause malfunction of relay on the grid when ground faults or severe load unbalances are occurred on the system. Because DGs interconnected to the grid can contribute fault currents and make bidirectional power flows on the system, fault currents from DGs can cause an interference of relay operation. A directional over current relay(DOCR) can determine the direction of power flow whether a fault occurs at the source side or load side through detecting the phases of voltage and current simultaneously. However, it is identified in this paper that the contributed fault current(Ifdg) from the ground source when was occurred to contribute single-line-to-ground(SLG) fault current, has various phases according to the distances from the ground source. It means that the directionality of Ifdg may not be determined by simply detecting the phases of voltage and current in some fault conditions. The magnitude of Ifdg can be estimated approximately as high as 3 times of a phase current and its maximum is up to 2,000 A depending on the capacity of generation facilities. In order to prevent malfunction of relay and damage of DG facilities from the contribution of ground fault currents, Ifdg should be limited within a proper range. Installation of neutral ground reactor (NGR) at a primary neutral of interconnection transformer was suggested in the paper. Capacity of the proposed NGR can be adjusted easily by controlling taps of the NGR. An algorithm for unidirectional relay was also proposed to prevent the malfunction of relay due to the fault current, Ifdg. By the algorithm, it is possible to determine the directionality of fault from measuring only the magnitude of fault current. It also implies that the directionality of fault can be detected by unidirectional relay without replacement of relay with the bidirectional relay.