• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.943-946
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• 2007

In-plane piezoelectric charge constant of Electro-Active paper (EAPap) was investigated based on direct and converse piezoelectric effects. EAPap samples were made with cellulose film with very thin gold electrode coated on both sides of the film. To characterize direct piezoelectricity of EAPap, induced charge was measured when mechanical stress was applied to EAPap. In-plane piezoelectric charge constant was extracted from the relation between induced charge and applied in-plane normal stress. To investigate converse piezoelectricity, induced in-plane strain was measured when electric field was applied to EAPap. Piezoelectric charge constant was also extracted from the relation of induced in-plane strain and applied electric field. Piezoelectric charge constants obtained from direct and converse piezoelectricity are 31 pC/N and 178 x 10-12m/V for 45 degree sample, respectively. Measured piezoelectric charge constants of EAPap provide promising potential as a piezoelectric material.

• Structural Engineering and Mechanics
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• 제43권6호
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• pp.835-845
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• 2012

This paper focuses on the stochastic response analysis of industrial masonry chimneys to surface blast-induced random ground motions by using a three dimensional finite element model. Underground blasts induce ground shocks on nearby structures. Depending on the distance between the explosion centre and the structure, masonry structures will be subjected to ground motions due to the surface explosions. Blast-induced random ground motions can be defined in terms of the power spectral density function and applied to each support point of the 3D finite element model of the industrial masonry system. In this paper, mainly a parametric study is conducted to estimate the effect of the blast-induced ground motions on the stochastic response of a chimney type masonry structure. With this purpose, different values of charge weight and distance from the charge centre are considered for the analyses of the chimney. The results of the study underline the remarkable effect of the surface blast-induced ground motions on the stochastic behaviour of industrial masonry type chimneys.

• Structural Engineering and Mechanics
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• 제53권5호
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• pp.897-919
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• 2015

In this study, the effects of ground shocks due to explosive loads on the dynamic response of historical masonry bridges are investigated by using the multi-point shock response spectrum method. With this purpose, different charge weights and distances from the charge center are considered for the analyses of a masonry bridge and depending on these parameters frequency-varying shock spectra are determined and applied to each support of the two-span masonry bridge. The net blast induced ground motion consists of air-induced and direct-induced ground motions. Acceleration time histories of blast induced ground motions are obtained depending on a deterministic shape function and a stationary process. Shock response spectrums determined from the ground shock time histories are simulated using BlastGM software. The results obtained from uniform and multi-point response spectrum analyses cases show that significant differences take place between the uniform and multi-point blast-induced ground motions.

• 한국세라믹학회지
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• 제36권9호
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• pp.923-929
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• 1999

The cause of optical nonlinearity induced in thermally poled silica glass is believed to be the space charge polarization. Since the second order optical nonlinearity (electro-optic effect) can be used in optical switches the optical nonlinearity in silica glass has drawn a large attention. Space charge polarization occurs when an ionic conducting material is subjected to dc electric field by the blocking electrode. Thermal poling performed to induce the optical nonlinearity in silica glass is basically identical to the process generating space charge polarization. As a first step to understand the mechanism of space charge polarization in silica glass hence the induced optical nonlinearity the absorption currents as functions of time were measured for various types of silica glasses and analyzed by the theory of space charge polarization. It was found that the electrical relaxation exhibited a step by the space charge polarization in the relatively long time range and dielectric loss peak showed a maximum at a specific temperature which is depending on type of silica glass. It was turned out that this relaxation might be a cause of nonlinearity in electrical conductivity of silica glass.

• Nuclear Engineering and Technology
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• 제29권6호
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• pp.451-458
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• 1997

Signal shapes from a closed-ended coaxial HPGe detector are investigated by numerical methods. The detector used in this study has a volume of 72 ㎤ with relative efficiency of 15%. The electric field and potential distributions in the detector are determined by solving the Poisson equation at the depletion and operating bias. Hence the time dependent signal shapes induced on the electrode are obtained from the energy balance consideration and tv solving the equation of motion for the charge carriers. For various initial positions of a charge carrier pair, the collection times of induced charge vary in the range of 70 - 404 nsec.

• 대한전기학회논문지
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• 제45권2호
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• pp.301-309
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• 1996

This paper estimates the electric field effect near 765[kV] AC double transmission line with numerical data. The induced voltage and current of a human and car under who kinds of phase arrangement are calculated when each of two objects is insulated or grounded. When the calculated results of the low-reactance and superposition phase arrangement are compared, it is proved that the induced voltage and current of the former are about 30 [%] smaller than that of the latter. The induced current of a human and car are less than 0.5[mA] which is about 10[%] less than that of the American National Standard Code. Also the induced voltage and current of dead lines by other live lines are calculated. Finally the effective number and position of shield wires to reduce the field in ground level are considered. charge simulation method and surface charge method are used to simulate the 2 or 3 dimensional transmission line model respectively.

• 동력기계공학회지
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• 제12권6호
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• pp.64-69
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• 2008

The spatial fuel distribution of the stratified charge of a high pressure 6-hole injector was examined in a single cylinder optical direct injection spark ignition(DISI) engine. The effects of in-cylinder charge motion, and fuel injection pressure, and coolant temperature were investigated using a planar LIF(Laser Induced Fluorescence) technique. It was confirmed that the in-cylinder tumble flow played more effective role in the spatial fuel distribution of the stratified charge than the swirl flow during the compression stroke and the fuel distribution area increased due to the activation of the fuel vaporization by the increase of the coolant temperature. But, the increase of the fuel supplying pressure could not change the pattern of the fuel vapor distribution against the expectation.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2007년도 추계학술대회
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• pp.51-54
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• 2007

The induced-charge electroosmosis (ICEO) is a kind of electroosmotic flow which is generated by the electrical charge induced by an externally-applied electric field. That kind of electrokinetic phenomenon provides a nonmechanical technique to handle microscale flows and particles. In this work, we report that the ICEO-like flow is observed around two kinds of circular-cylindrical rod submerged in a dielectric liquid. The conductivity of the solution is varied by adding a surfactant. The flow field is visualized by the PIV method, and average flow speed shows a remarkable dependence on electrical input frequency. Interestingly, the characteristics of the flow are quite different from the conventional ICEO with respect to the flow direction and the locations of center of vortices.

• 한국전산구조공학회논문집
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• 제34권4호
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• pp.191-197
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• 2021

분자동역학에서의 원자들의 유도전하를 계산하기 위해서는 유도전하를 미지수로 하는 선형방정식을 풀어야 하는데 원자들의 위치가 변화할 때마다 필요한 계산이므로 상당한 계산비용이 요구된다. 따라서 효율적인 유도전하 계산 방법은 다양한 시스템을 해석하기 위해서 필수적이다. 본 연구에서는 constraints가 존재하는 Lagrange 방정식의 해에 대한 선형 시스템, 즉 saddle point를 가지는 문제를 해결하기 위해서 Uzawa method를 도입하였다. Uzawa 매개변수가 수렴 속도에 영향을 미치는 단점을 극복하고 행렬 연산의 효율성을 위해서 Schur complement와 preconditioned conjugate gradient (PCG) 방법을 통해 계산의 효율성을 극대화하는 가속 Uzawa algorithm을 적용한다. 두 금속 나노입자가 전기장에 놓여진 분자동역학 수치모델을 통해서 제시된 방법이 유도전하계산의 수렴성, 효율성 측면에서 모두 향상된 결과를 도출함을 확인하였다. 특히 기존의 가우스 소거법에 의한 계산보다 약 1/10으로 계산비용이 절감되었고, 기본 Uzawa method에 비하여 conjugate gradient (CG)의 높은 수렴성이 입증되었다.

• 소성∙가공
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• 제32권4호
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• pp.191-198
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• 2023

We examined the martensitic transformation kinetics for metastable stainless steel during electrochemical polishing (EP) using different types of electrolytes. Martensite fraction measured with EBSD showed that the electrolyte with high relative permittivity exhibited comparably higher levels of martensitic transformation. The amount of charge build-up on the specimen surface during EP with different types of electrolytes was calculated using COMSOL multiphysics simulations to understand these phase transformation characteristics. The effect of charge build-up-induced stress was analyzed using previously published first-principles calculations. We discovered that the electrolyte with high relative permittivity accumulated a greater amount of charge build-up, resulting in a stronger driving force for stress-induced martensitic transformation.