• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.46-49
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• 2001

An investigation into power conditioners that interface with photovoltaic array and utilities has been completed. The rating for this investigation is residential system(3-5kVA) that interface with a 220V single phase utility connection. As the result of this investigation, a 3kVA high frequency PWM IGBT inverter feeding a high frequency isolation transformer with a sinusoidal current wave was selected. The output of the transformer rectified with a diode bridge rectifier. four IGBT, used as 60Hz switched, reverse the polarity of the rectified current on every other half cycle of the utility voltage. Even though the high frequency link system used more power semiconductors, a net size, weight, and parts cost saving result compared to the other systems due to elimination of 60Hz transformer.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.594-597
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• 1993

With the increase of electric power demand in the downtown area. many problems, such as the difficulty in security of substation site and interference of the electromagnetic wave or damage to person due to outdoor type substation facilities has been occured. Therefore, the compaction of substation facilities is required and the gas insulated switchgear(GIS) has been adopted accordingly. However, much care should be taken of the interface problem between cable and GIS. This paper describes the failure analysis and a countmeasure for prevent ion from failure in the interface.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1300-1305
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• 2001

One of the main noise sources in cabin onboard ships is HVAC system. Up to now, the HVAC system designer manually calculates the HVAC system noise, or uses the program that is generally based on text user interface. In such a case, it is difficult to use the program and also to obtain the flow induced noise. In this study, the HVAC noise analysis program has been developed, which is based on GUI user interface that include 3.D modelling and model modification modules. For calculation of the insertion loss of HVAC system elements, NEBB experimental data and plane wave theory are used. And in order to obtain the flow rate information in each HVAC elements which is used to calculate the flow induced noise calculation, Global Converging Newton-Rapson Method is used.

• Aerospace Engineering and Technology
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• v.7 no.1
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• pp.108-114
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• 2008

The aim of this analysis is to verify the electrical compatibility of the interfaces which exist between TWTA(Travelling Wave Tube Amplifier) which is equipment of the Ka-band payload in COMS (Communication, Ocean and Meteorological Satellite) and external equipments. For each interface, this study checked the compatibility between equipments for the power links, commands, digital telemetry, analog telemetry, and failure condition or AIT(Assembly, Integration and Test) errors. In addition with this interface compatibility verification, this study outputs electrical and manufacturing recommendations to be applied at harness level.

• Earthquakes and Structures
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• v.18 no.6
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• pp.743-752
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• 2020

The phenomenon of reflection and transmission of plane waves at an interface between fluid half space and orthotropic piezothermoelastic solid half-space with two-temperature has been investigated. Energy ratios of various reflected and transmitted waves are computed with the use of amplitude ratios. The law of conservation of energy across the interface has been justified. It is found that the energy ratios are the functions of angle of incidence, frequency of independent wave and depend on the different piezothermoelastic material. A piezothermoelastic material has been considered which is in welded contact with water. Variations of energy ratios corresponding to the reflected waves and transmitted waves are computed and shown graphically for the two different models. A particular reduced case of interest is also discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.60-63
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• 2008

Phase change in combustion of energetic materials happens inevitably. The product gas generated by combustion is at extreme temperature and pressure state. The interaction between a gas and metal generates high strain rate deformation and complex wave phenomena. In order to perform combustion simulation containing phase changes, we develop an elegant model for phase change and provide a proof of performance via vapor explosion example.

• Progress in Superconductivity
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• v.3 no.1
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• pp.70-73
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• 2001

We report the spin injection and transport properties of three terminal devices of Co/Au/$YBa_2$$Cu_3$$O_{y}$(F/N/S) tunnel junctions by injection of spin-polarized quaiparticles using a cobalt ferromagnetic injector. The observed current gain depends on the thickness of Au interlayer and is directly related to the nonequilibrium magnetization due to spin relaxation effects. The tunnel characteristic of a F/N/S tunnel junctions exhibited a zero bias conductance peak (ZBCP). The suppression of the ZBCP was observed due to the suppression of Andreev reflection at the interface, which is due to the spin scattering processes at the interface between a ferromagnetic and a d-wave superconductor.r.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.3
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• pp.210-219
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• 2005

We report on a low-cost V-band wireless transceiver with no use of any local oscillator in the receiver block using a self-heterodyne architecture. V-band millimeter-wave monolithic IC (MMIC) modules were developed to demonstrate the wireless transceiver using coplanar waveguide (CPW) and GaAs PHEMT technologies. The MMIC modules such as the MMIC low noise amplifier (LNA), medium power amplifier (MPA) and the up/down-mixer were installed in the transceiver system. To interface the MMIC chips with the component modules for the transceiver system, CPW-to-waveguide fin-line transition modules of WR-15 type were designed and fabricated. The fabricated LNA modules showed a $S_{21}$ gain of 8.4 dB and a noise figure of 5.6 dB at 58 GHz. The MPA modules exhibited a gain of 6.9 dB and a $P_{1dB}$ of 5.4 dBm at 58 GHz. The conversion losses of the up-mixer and the down-mixer module were 14.3 dB at a LO power of 15 dBm, and 19.7 dB at a LO power of 0 dBm, respectively. From the measurement of V-band wireless transceiver, a conversion gain of 0.2 dB and a $P_{1dB}$ of 5.2 dBm were obtained in the transmitter block. The receiver block showed a conversion gain of 2.1 dB and a $P_{1dB}$ of -18.6 dBm. The wireless transceiver system demonstrated a successful data transfer within a distance of 5 meters.

• The Journal of the Acoustical Society of Korea
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• v.20 no.3E
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• pp.31-37
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• 2001

Finite element model of a cMUT is constructed using the commercial code ANSYS to analyze the cross talk mechanism. Calculation results of the complex load impedance seen by single capacitor cells are presented, and then followed by a calculation of the plane wave real load impedance seen by a parallel combination of many cells that are used to make a transducer. Cross talk between 1-D array elements is found to be due to two main sources: coupling through a Stoneley wave propagating at the transducer-water interface and coupling through Lamb waves propagating in the substrate. To reduce the cross talk level, the effect of various structural variations of the substrate are investigated, which include a change of its thickness and etched trenches or polymer walls between array elements.

• Journal of electromagnetic engineering and science
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• v.10 no.3
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• pp.166-170
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• 2010

To numerically calculate electromagnetic scattering from the electrical-large three-dimensional(3D) objects, the high-frequency approaches have been usually applied, but the accuracy and feasibility of these geometrical and physical optics(GO-PO) approaches, to some extent, are remained to be improved. In this paper, a new framework is developed for calculation of the near-field scattering field of an electrical-large 3D target by using a multilevel fast multipole algorithm(MLFMA) and generation of radar images by using a fast back-projection(FBP) algorithm. The MPI(Message Passing Interface) parallel computing is carried out to multiply the calculation efficiency greatly. Finally, a simple example of perfectly electrical conducting(PEC) patch and a canonical case of Fighting Falcon F-16 are presented.