• Economic and Environmental Geology
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• v.38 no.6 s.175
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• pp.717-729
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• 2005

Peak cooling load of large buildings is generally greater than their peak heating load. Internal and solar heat gains are used fur selection of adquate equipment in large building in cold winter climate like Canada and even Korea. The cost of geothermal heat exchanger to meet the cooling loads can increase the initial cost of ground source heat pump system to the extend less costly conventional system often chosen. Thermal ice storage system has been used for many years in Korea to reduce chiller capacity and shift Peak electrical time and demand. A distribution system designed to take advantage of heat extracted from the ice, and use of geothermal loop (geothermal heat exchanger) to heat as an alternate heat source and sink is well known to provide many benifits. The use of thermal energy storage (TES) reduces the heat pump capacity and peak cooling load needed in large building by as much as 40 to $60\%$ with less mechanical equipment and less space for mechanical room. Additionally TES can reduce the size and cost of the geothermal loop by 1/3 to 1/4 compared to ground coupled heat pump system that is designed to meet the peak heating and cooling load and also can eliminate difficuties of geothermal loop installation such as space requirements and thermal conditions of soil and rock at the urban area.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.10
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• pp.1050-1060
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• 2009

In this paper, a X-Band T/R-module for SAR(Synthetic Aperture Radar) systems based on active phased array antennas is designed and fabricated. The T/R modules have a and width of more than 800 MHz centered at X-Band and support dual, switched polarizations. The output power of the module is 7 watts over a wide bandwidth. The noise figure is as low as 3.9 dB. Phase and amplitude are controlled by a 6-bit phase shifter and a 6-bit digital attenuator, respectively. Further the fabricated T/R module has est and calibration port with directional coupler and power divider. Highly integrated T/R module is achieved by using LTCC(Low Temperature Co-fired Ceramic) multiple layer substrate. RMS gain error is less than 0.8 dB max. in Rx mode, and RMS phase error is less than $4^{\circ}$ max. in Rx/Tx phase under all operating frequency band, or the T/R module meet the required electrical performance m test. This structure an be applied to active phase array SAR Antennas.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.746-752
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• 2020

As environmental issues have been taken seriously, the number of solar power generation facilities has rapidly increased in Korea. The voltage at the output stage of an inverter increases in a system that connects a small-capacity photovoltaic power generation to low-voltage power distribution. This degrades the quality of the low-voltage distribution system and adversely affects the load facility. In this study, a solution was obtained to increase the voltage at the output stage of the solar inverter according to the connection of the low-voltage distribution system. The voltage can be controlled by using reactive power factor control inverters. If the secondary tap is adjusted, the voltage can be adjusted to about 15 V, but there is a problem in that the tap is not adjusted unless the KEPCO distribution regulation voltage is out of the range of 220±13V. If the number of inverters is limited, the inverter can be started within the inverter overvoltage range. If it is connected to three phases, the voltage is distributed. The results indicated that power factor control and active voltage control inverters were easy to apply in the field.