• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.2
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• pp.82-89
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• 2018

This paper presents a novel prototype of dual mode control based phase shift ZVS PWM high frequency load resonant inverter with lossless snubber capacitors in addition to a single active auxiliary resonant snubber for electromagnetic induction heating(IH) foam metal based consumer fluid dual packs(DPA) heater. The operating principle in steady state and unique features of this voltage source soft switching high frequency inverter circuit topology are described in this paper. The lossless snubber and auxiliary active resonant snubber assisted constant frequency phase shift ZVS PWM high frequency load resonant inverter employing IGBT power modules actually is capable of achieving zero voltage soft commutation over a widely specified power regulation range from full power to low power. The steady state operating performances of this dual mode phase shift PWM series load resonant high frequency inverter are evaluated and discussed on the basis of simulation and experimental results for induction heated foam metal heater which is designed for compact and high efficient moving fluid heating appliance in the consumer pipeline systems.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.209-212
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• 2001

수중에서 물과 공기 다공을 갖는 다공성 매질의 주파수 및 다공율 변화에 따른 음향특성을 고찰하였다. 다공성 매질로서 원통형 다공을 인위적으로 균일하게 배열한 판형 루사이트 (Lucite)를 사용하였다. 수중에서 음파를 다공성 매질의 원통형 다공의 축 방향과 평행하게 입사하였을 때, 빠른 파 (fast wave)는 다공 내의 매질에 영향을 받지 않으나, 느린 파 (slow wave) 및 원통형 다공을 전파하는 비평면 고차 정상 모드 파 (nonplanar higher normal mode wave)는 다공 내의 매질에 크게 영향을 받는다. 3MHz부터 4MHz까지의 주파수 영역에서 전체 파 (total wave), 빠른 파 및 느린 파의 음속 및 음압투과계수를 주파수 및 물과 공기 다공율 변화에 따라 측정하였다. 비강체 다공성 매질에서의 음파 전파특성에 대한 MBA (modified Biot-Attenborough) 모델의 이론 결과와 실험결과를 비교, 분석하였다.

• Journal of Korean Society of Steel Construction
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• v.12 no.4 s.47
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• pp.363-374
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• 2000

An accurate method is presented for vibrations of rhombic plates having three different combinations of clamped, simply supported, and free edge conditions. A specific feature here is that the analysis explicitly considers the moment singularities that occur in the two opposite corners having obtuse angles of the rhombic plates. Stationary conditions of single-field Lagrangian functional are derived using the Ritz method. Convergence studies of frequencies show that the corner functions accelerate the convergence rate of solutions. In this paper, accurate frequencies and normalized contours of the vibratory transverse displacement are presented for highly skewed rhombic plates, so that a significant effect of corner stress singularities nay be understood.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.31-38
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• 2002

This paper presents the analysis of the flight test data measured by the sensors installed on a four-seat canard aircraft. The inherent stall proof characteristics of canard aircraft was verified from the stall test. The dihedral effect, adverse yaw and roll control power were examined and the neutral point that determines the longitudinal stability of the aircraft was investigated. The dynamic characteristics such as dutch roll mode were also examined. Without relying on the parameter identification method, the aerodynamic derivatives or the relations between the aerodynamic derivatives were obtained by analyzing the steady state flight data.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.48-54
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• 2015

This study investigates the result of thermal stress analysis on burning plate by classes at outdoor gas boiler. In the analysis results at the steady state, the maximum stress and deformations are 666,8MPa at A type and 0.20476mm at B type respectively. The deformation becomes larger as the field goes on from the center to the outside at burning plate. As there are 8 types in the order of maximum stress and deformation, F and C type have safest among 8 types respectively. Therefore, F type becomes most excellent on strength and safety among 8 types. By using the analysis result of burning plate model at gas boiler, it is possible to design the model applied practically at the safe component parameters of boiler system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.559-567
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• 1999

A piezoelectric flextentional sonar transducer has been simulated using a coupled FE-BEM. The dynamics of the sonar transducer is modelled in three dimensions and is analyzed with external electrical excitation conditions. Different results are available such as steady-state displacement modes, underwater directivity patterns, resonant frequencies, bandwidths, quality factors, output acoustic powers and transmitting voltage responses. It is shown that the present barrel-stave sonar transducer of the piezoelectric material produces flextentional displacements which could be related with higher output power, lower quality factor and more omnidirectional beam pattern than other types of sonar transducers. The results of the present sonar transducer modelling are also compared with those of a commercial package such as ATILA.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.10
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• pp.34-41
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• 1998

In this paper, we evaluate synchronization techniques suitable for high-speed ATM satellite communications with a transmission rate of 155Mbit/s, and propose optimal algorithms that improve the tracking performance, where QPSK is selected for a modulation scheme, and the receiver is operated in burst mode. Based on these asumptions, we proposed modified algorithms and architectures for automatic frequency control(AFC), carrier recovery(CR), and symbol timing recovery(STR) for burst acquisition. Analysis is performed under AWGN environments with respect to the number of required symbol, steady-state stability, and hardware implementation for the proposed algorithms.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.2
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• pp.30-37
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• 2008

An object transport system is driven by a conveyor belt system or a magnetic levitation system. It is an indispensable device in many fields and especially it is very important in the factory automation. However, the conventional transport system can damage precision optical components by the contact force and destroy the inner structure of semiconductor by the magnetic field. The new transport system for transporting without damage is required. The ultrasonic transport system is a device that transports objects on the elastic body using ultrasonic wave. In this paper, an object transport system using the ultrasonic wave is developed for transporting precision elements without damage. Traveling waves are generated by the ultrasonic wave generator fixed in both ends of the beam. The traveling wave of the ultrasonic transport system is theoretically analyzed. Transport direction of the object is examined according to phase difference and frequency. The theoretical results are verified by experiments.

• Journal of the Korean Society for Railway
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• v.14 no.6
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• pp.515-525
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• 2011

In this study, Urban maglev is applied to inductive-loop speed and position detection system for the top-level classification system for the entire system, and performed functional analysis On-board signal equipment, Wayside-signal equipment divided by the reliability, availability, maintainability, and safety through analysis of the proposed formula. RDB and by applying a system service for each device was calculated to availability, safety analysis. The PHA, FMEA, HAZOP over the Top Event of the FTA is performed by presenting the results. This also shows approach methods and relative activities for project to accomplish and ensure the system requirements.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.3
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• pp.32-39
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• 2003

The output voltage of synchronous generator is regulated constantly by field current control in excitation system High frequency PWM converter (current control mode buck converter) type excitation systam fer synchronous generator is able to control exciter current when the load change happened. This paper deals with the design and evaluation of the excitation system for a synchronous generator to improve the steady state and transient stability. The simulation and experimental results show that the proposed excitation system is able to improve the response time by the DVR(digital voltage regulator) of 50[kW] synchronous generator.