• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.253-257
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• 2003

Theoretical-numerical analysis of wave instability is conducted with parametric response function model. Fluctuating instantaneous mass evaporation rate functionally coupled with pressure perturbations with phase lag is assumed to examine the validity of the method. With sufficiently large amplitude and less phase lag to perturbation, combustion response is resonant to pressure waves, unstable waves are amplified, and the system is driven to instability. Magnitude of response is a crucial instability parameter in the determination of a stability margins and makes a critical change of balancing conditions between the amplifying and damping acoustic energies. In the phase regime the unstable waves are amplified, whereas, the acoustic waves are attenuated in the out-of-phase regime. In the intermediate regime, no distinct tendency of unstable waves was determined.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.417-419
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• 1995

Polymer-coated piezoelectric crystals were applied to analyze response characteristic of organic gases. AT-cut quartz crystal with 9 MHz resonant frequency can measure mass of 1 nanogram. Flow type gas-sensing system was used in this experiment. Flow type gas-sensing system has very simple apparatus and shows very fast frequency response for injection of organic gas. We have made parameter using relaxation ratio of frequency response for organic gas. Consequently, we found that the parameter had no relation with quantity of gas injection and dipping.

• Coupled systems mechanics
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• 제1권3호
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• pp.235-245
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• 2012

The nonlinear resonant response of an axially moving beam is investigated in this paper via two different numerical techniques: the pseudo-arclength continuation technique and direct time integration. In particular, the response is examined for the system in the neighborhood of a three-to-one internal resonance between the first two modes as well as for the case where it is not. The equation of motion is reduced into a set of nonlinear ordinary differential equation via the Galerkin technique. This set is solved using the pseudo-arclength continuation technique and the results are confirmed through use of direct time integration. Vibration characteristics of the system are presented in the form of frequency-response curves, time histories, phase-plane diagrams, and fast Fourier transforms (FFTs).

• 한국산학기술학회논문지
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• 제22권6호
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• pp.566-572
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• 2021

본 논문에서는 도시환경과 모래가 많은 토양 아래에 구 형태의 빈 공간이 있을 경우를 가정하고, 해당 목표물의 고유 pole과 고유 공진주파수를 활용하여 목표물을 식별 및 위치를 추정하는 방안을 제시하였으며 가능성을 분석하였다. EM(Electromagnetic) 시뮬레이터를 활용하여 다양한 형태와 크기를 가진 완전도체(PEC: Perfect Electric Conductor)들을 모델링하였고, 이를 통해 획득한 EM 산란응답에 Cauchy 방법을 적용하여 물체의 고유 특성에 해당하는 고유 pole을 축적하여 pole 라이브러리를 생성하였다. 생성된 pole 라이브러리는 목표물에서 추출한 고유 pole과의 비교를 통해 목표물을 식별할 수 있는 가능성을 제공해 준다. 도시환경과 모래가 많은 토양 아래에 구 형태의 빈 공간이 있음을 가정하고 EM 시뮬레이션 모델링을 통해 얻은 전자파 산란 데이터로부터 관심 목표물의 응답을 추출하였으며, 시간영역에서 임펄스 응답의 시간 지연을 이용하여 목표물의 위치를 추정할 수 있었다. 또한 MP(Matrix Pencil) 방법을 적용하여 목표물의 고유 pole을 추출하였다. 최종적으로 계산된 고유 pole과 고유 공진주파수를 pole 라이브러리와 비교하여 탐지된 목표물을 구 형태의 빈 공간(직경 0.2m)으로 추정할 수 있었으며, 계산된 목표물의 위치(깊이)는 약 84 ~ 93%의 정확도를 보였다.

• 조명전기설비학회논문지
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• 제22권11호
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• pp.15-22
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• 2008

This paper presents an innovative prototype of a new conceptual electromagnetic induction heated type far infrared rays radiant heating appliance using the voltage-fed quasi-resonant ZVS-PWM high frequency inverter using IGBTs for food cooking and processing which operates under a constant frequency variable power regulation scheme. This power electronic appliance with soft switching high frequency inverter using IGBTs has attracted special interest from some advantageous view points of safety, cleanliness, compactness and rapid temperature response, which is more suitable for consumer power electronics applications.

• 조명전기설비학회논문지
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• 제14권6호
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• pp.12-17
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• 2000

IN induction heating system the high frequency operation allows a rapid response to current fluctuation in the inverter and result in improved welding quality. To work induction heating of nonferrous metals, a welding power supply is need high working frequency and high power. This paper is shown design technique for increasing working frequency in induction heating for welding coppers. A series-parallel resonate inverter consists of H-type bridges, each of whose arms is composed of a combination of two parallel IGBTs. Inverter operating with the fixed frequency is controlled by pulse width modulation (PWM). As switching adapted the Zero-Voltage Switching technique to reduce switching losses the system is high efficiency. The propose inverter has feature which is high efficiency for very wide load variations with a narrow range of duty cycle ratio control and load short circuit capability. Detailed experimental results obtained from a 48[V] output, 500[W] experimental inverter are presented to verify the concept.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.98.1-98
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• 2002

In principle, a resonance type sensor generally has an oscillation characteristic. Thus, an analysis on transient oscillation response takes a great interest since it is related to the performance of resonant sensor. In particular, system bandwidth has tradeoff with oscillation accuracy, i.e. quality factor. For an efficient analysis of the oscillation characteristic, several analytic methods are introduced and summarized. The results are fundamentally based on the classical describing function method, but can explain the transient oscillation by introducing time varying concept about the predicted limit cycle. After introducing those methods, the application results to the specified system...

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.328.2-328
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• 2002

General modeling of a resonant shunting damper has been made Iron piezoelectric sensor/actuator equation. It is found that an additional damping, which is augmented to a system, is generated by the shunt damping effect The transfer function of the tuned electrical absorber is derived for both series and parallel shunt circuit. The governing equations and associated boundary conditions are derived using Hamilton's Principle. The shunt voltage equation is also derived from the charge generated in PZT due to beam vibration. The frequency response function of the obtained mathematical model is compared with that of the tuned eledtrical absorber and experimental work. The vibration amplitude is reduced about 15 dB at targeted second mode frequency.

• Journal of Power Electronics
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• 제13권1호
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• pp.94-103
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• 2013

A capacitor deterioration of LCL-filter grid-connected PWM converters is progressed by the self-healing mechanism. It leads to the degradation of the filter performance and drop of power factor. Thus, it is required to diagnose fault-point of capacitors and determine the replacement time. Typically, the fault of capacitors is determined when the capacitance is reduced up to 80% from initial value. This paper proposes algorithm to the determine capacitor replacement time of an LCL filter. The algorithm takes the advantage of change of the response on the injected resonant frequency corresponding to 80% value from the initial capacitance. The results of the algorithm are demonstrated through simulations and experiments.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.386-391
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• 2001

In this paper, the vibration characteristics of IHTS(Intermediate Heat Transfer System) piping system of LMR(Liquid Metal Reactor) conveying hot liquid sodium are investigated to eliminate the pipe supports for economic reasons. To do this, a 3-dimensional straight pipe element and a curved pipe element conveying fluid are formulated using the dynamic stiffness method of the wave approach and coded to be applied to any complex piping system. Using this method, the dynamic characteristics including the natural frequency, the frequency response functions, and the dynamic instability due to the pipe internal flow velocity are analyzed. As one of the design parameters, the vibration energy flow is also analyzed to investigate the disturbance transmission paths for the resonant excitation and the non-resonant excitations.