• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.106-112
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• 1996

In this paper, the propagation of elastic wave generated by loading impact to plates made of isotropic or anisotropic material was studied. And the influence of boundary conditions(free or clamped edge) upon the reflection of elastic wave of isotropic plate such as aluminum plate showed circular interferometric fringe pattern, whereas that of anisotropic plate such as epoxy composite laminates showed elliptical one. And the transverse displacement curves obtained from experiment and theory for both plates agreed well. Also, the waves reflected from the boundary edges showed much differences according to the boundary condition of edges.

• Journal of the Korean Magnetic Resonance Society
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• v.18 no.2
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• pp.47-51
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• 2014

Larger proteins (above molecular weight 50 kDa) usually show slow motional tumbling in solution, which facilitates the decay of NMR signal, resulting in poor signal-to-noise. In the past twenty years, researchers have tried to overcome this problem with higher molecular weight by improvement of hardware (higher magnetic field and cryoprobe), optimization of pulse sequences for lager molecules, and development of isotope-labeling techniques. Actually, GroEL/ES complex (${\approx}$ 900 kDa) was successfully studied using combination of above techniques. Among the techniques used in large molecular studies, the impact of isotope-labeling for large molecules study is summarized and discussed here.

• Journal of information and communication convergence engineering
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• v.6 no.4
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• pp.417-420
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• 2008

Solar electric systems have very little impact on environment, making them one of the cleanest power-generating technologies available. While they are operating, PV systems produce no air pollution, hazardous waste, or noise, and they require no transportable fuels. In PV system design, the selection and proper installation of appropriately-sized components directly affect system reliability, lifetime, and initial cost. In this research, we have studied the PWM(Pulse Width Modulation) signals. I proposed an efficient photovoltaic power interface circuit incorporated with a DC-DC converter and a sine-pwm control method full-bridge inverter. In grid-connected solar power systems, the DC-DC converter operates at high switching frequency to make the output current a sine wave, whereas the full-bridge inverter operates at low switching frequency which is determined by the ac frequency. Thus, it can reduce the switching losses incurred by the full-bridge inverter. Full-bridge converter is controlled by using microprocessor control method, and its operation is verified through computer aided simulations.

• Advances in Computational Design
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• v.1 no.4
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• pp.357-370
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• 2016

This paper aims to examine the dynamic response of a newly designed ultrasonic motor under half-sine shock impulses. Impact shock was applied to the motor along x, y or z axis respectively with different pulse widths to check the sensitivity of the motor to the shocks in different directions. Finite Element Analysis (FEA) with the ANSYS software was conducted to obtain the relative displacement of a key point of the motor. Numerical results show that the maximum relative displacement is of micro meter level and the maximum stress is five orders smaller than the Young's modulus of the piezo material, which proves the robustness of the motor.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.4
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• pp.47-56
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• 1995

In this paper the model of the MQE-IMD-based neural trigger circuit is improved, where MQW-IMD is a new semiconductor device proposed and experimentally demonstrated by the author for the hardware implementation of the neural networks. The electron energy of AlXGa1-XAsbarrier is calculated by Ensemble Monte Carlo simulation according to the variation of Al mole fraction x and the applied electric field, whtich had been roughly estimated in the previous paper because of the difficulty to get the data. And in the consideration of the tunneling of the confined electrons within the quantum well the accuracy of the impact ionization rate is enhaned. Finally, the dependance of the frequency of pulse-train on the number of quantum wells can be calculated by modelling the effect of the distance of the induced positive charge from the cathode on the electric field at the cathode.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.29-35
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• 2016

This paper deals with a design method and capacity loss of an efficient multi-level modulation scheme for dimmable visible light communications (VLC) systems that use light-emitting diodes (LEDs) with efficiency droop. To this end, the impact of such an impairment on dimmable VLC is addressed with respect to multi-level modulations based on pulse-amplitude modulation (PAM) via data-rate optimization formulation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1992.10a
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• pp.141-146
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• 1992

본 연구에서는 먼저 낙하 충격을 받는 전자 제품을 수학적인 모델링을 행하 므로서 낙하 충격시 제품이 받게되는 충격력을 정량화하였고, 전자 제품내 많은 부품들의 낙하충격에 대한 동특성해석의 일환으로 핵심 부품인 PCB(printed circuit board)를 해석하였다. PCB 해석을 위하여 유한요소법을 사용하였고, PCB에 작용하는 half-sine pulse의 속도 변화에 다른 가속도 응 답 및 최대 충격가속도, 주기의 변화에 다른 PCB의 가속도 응답을 해석하였 다. 제시된 해석 기법은 낙하충격에 대비한 적절한 electric component의 layout및 최적의 PCB 취부조건등의 결정을 가능케 함으로써, 설계단계에서 낙하 충격을 고려한 PCB설계가 될 수 있도록 그 활용 방안을 제시하였고 반복된 낙하충격 실험을 줄일 수 있으므로 경비 절감 및 개발 소요기간도 절감할 수 있다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.9
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• pp.786-790
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• 2000

This paper is concerned on the theoretical and experimental approaches of direct piezoelectric effect in the PVDF film. When a cantilever structure of PVDF film is bended by the external force, electric charges are concentrated on the electrode surface of the film due to the direct piezoelectric effect, and output voltage is induced from the terminals of the film. In this paper, a symbolic equation between the external force and the output voltage was introduced. Moreover, the theoretical output voltages were compared with the experimental results by falling balls, which were agreed well each other. This results can be useful in a warning system of abnormal pulse rate and breathing, and in detecting impact force and/or mechanical energy using bending of PVDF film.

• Journal of Photoscience
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• v.5 no.1
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• pp.33-37
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• 1998

One macroscopic effect in the free-running Er:YAG laser is an accumulation of microscopic effects. Understanding of the exogenous water induced mechanical effect on the dental hard tissue by the Qswitched Er:YAG laser has an important impact on the further understanding of the free-running Er:YAG laser ablation on the dental hard tissue. The Q-switched Er:YAG laser (1-$\mu$s-long pulse width) was used in the recoil pressure measurement with an aid of water-jet system and a pressure transducer. The amplitude of the recoil pressure depends on the tooth surface conditions (dry and wet) and the volume of the water upon it. Wet surfaces yielded higher recoil pressure than that of dry, surface, and as the volume of the exogenous water drop increased, the amplitude of the recoil pressure increased also.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.4
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• pp.548-559
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• 2015

We performed a numerical simulation based on the two-dimensional (2-D) unsteady Euler's equation with a single-step Arrhenius reaction model in order to investigate the detonation wave front propagation of an Argon (Ar) diluted oxy-hydrogen mixture ($2H_2+O_2+12Ar$). This simulation operates in the detonation frame of reference. We examine the effect of grid size and the performance impact of integrated quantities such as mass flow. For a given set of baseline conditions, the minimal and maximum grid resolutions required to simulate the respective detonation waves and the detonation cell structures are determined. Tertiary shock wave behavior for various grids and pre-exponential factors are analyzed. We found that particle fluctuation can be weakened by controlling the mass flow going through the oblique shock waves.