• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.71-74
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• 2007

The objective of this presentation is to introduce a recent development of a magnetostrictive grating technique using an optimal yoke to efficiently generate and measure SH (Shear-Horizontal) waves in a plate. Gratings are effective means to generate frequency-tuned waves, but the gap between magnetostrictive gratings inevitably obstructs magnetic flow. Because magnetic field is the main physical quantity to actuate and sense ultrasonic waves, the transducer performance is most significantly influenced by the magnetic field distribution in the strips. Thus, wave transduction efficiency can be substantially improved if better magnetic flow is formed in the strips. To improve the efficiency, the topology optimization method was used to determine an optimal yoke configuration. A series of experiments on an aluminum plate were conducted using a grating with and without the designed yoke; when the yoke was used, the signal outputs increased up to 60 %.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.681-688
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• 2011

Structural model of laminated composite plates based on the first order shear deformable plate theory and subjected to a combination of magnetic and thermal fields is developed. Coupled equations of motion are derived via Hamilton's principle on the basis of electromagnetic equations (Faraday, Ampere, Ohm, and Lorenz equations) and thermal equations which are involved in constitutive equations. In order to obtain the implications of a number of geometrical and physical features of the model, one special case is investigated, that is, free vibration of a composite plate immersed in a transversal magnetic field. Special coupling effects between the magnetic and elastic fields are revealed in this paper.

• 한국자동차공학회논문집
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• 제5권3호
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• pp.171-171
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• 1997

Sound intensity distributions and energy flow in the near field of dipole source system and flat plate were investigated. First, the effectiveness of complex acoustic intensity was proved by using mathmatical and experimental methods in order to indentify noise sources and transmission paths of dipole field which is effected by the presence of neighbouring coherent sources. Next, analytical complex acoustic intensity method was discussed and the characteristics and energy flow of sound induced from the plate are clarified. The velocity of plate obtained from Finite Element Method was used for calculation of complex acoustic intensity in the near field. Finally experimental complex acoustic intensity method was applied to a passenger car. It can be seen that complex acoustic intensity method using both of active and reactive intensity is vital in devising a strategy for the identification and the reduction of vibration and noise.

• 한국자동차공학회논문집
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• 제5권3호
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• pp.159-171
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• 1997

Sound intensity distributions and energy flow in the near field of dipole source system and flat plate were investigated. First, the effectiveness of complex acoustic intensity was proved by using mathmatical and experimental methods in order to inden- tify noise sources and transmission paths of dipole field which is effected by the presence of neighbouring coherent sources. Next, analytical complex acoustic intensity method was discussed and the characteristics and energy flow of sound induced from the plate are clarified. The velocity of plate obtained from Finite Element Method was used for calculation of complex acoustic intensity in the near field. Finally experimental complex acoustic intensity method using both of active and reactive intensity is vital in devising a strategy for the identification and the reduction of vibration and noise.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1283-1285
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• 1993

A new simulation method for a device including the Floated Field Plate(FFP) is proposed. The external resistance is connected with FFP in order to simulate FFP as a electrode. The numerical I-V characteristic obtained from MEDICI simulation shows fairly good results such as low leakage current and abrupt breakdown voltage curve. The convergence is improved conveniently compared with conventional method which utilize heavily-doped poly silicon as a electrode.

• 설비공학논문집
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• 제18권4호
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• pp.359-369
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• 2006

This study aims deriving analysis the flow characteristic of kitchen hood system with using 3-D numerical analysis method and improving the system to expel pollutes more efficiently. This system is applied with $k-{\varepsilon}$ turbulent model and using incompressibility viscosity flow range and boundary condition which are related to Bossinesq approximation following density variation in control volume. To understand the flow characteristics of four models, this study only focuses on velocity field, temperature field, and concentration field varying with followings whether separation plate is set or not and the shapes of separation plates. The quantity of air, speed of exhaust fan and temperature and concentration of heating source are concerned as constant values.

• Steel and Composite Structures
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• 제32권2호
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• pp.173-187
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• 2019

This study is concerned with the stability of laminated composite plates modelled using Eringen's nonlocal differential model (ENDM) and a novel refined-hyperbolic-shear-deformable plate theory. The plate is assumed to be lying on the Pasternak elastic foundation and is under the influence of an in-plane magnetic field. The governing equations and boundary conditions are obtained through Hamilton's principle. An analytical approach considering Navier series is used to fine the critical bucking load. After verifying with existing results for the reduced cases, the present model is then used to study buckling of the laminated composite plate. Numerical results demonstrate clearly for the first time the roles of size effects, magnetic field, foundation parameters, moduli ratio, geometry, lay-up numbers and sequences, fiber orientations, and boundary conditions. These results could be useful for designing better composites and can further serve as benchmarks for future studies on the laminated composite plates.

• Coupled systems mechanics
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• 제6권3호
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• pp.287-316
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• 2017

This paper studies the particularities of the forced vibration of the hydro-elastic system consisting of a moving elastic plate, compressible viscous fluid and rigid wall. This study is made by employing the discrete-analytical solution method proposed in the paper by the authors (Akbarov and Panakhli (2015)). It is assumed that in the initial state the fluid flow is caused by the axial movement of the plate and the additional lineally-located time-harmonic forces act on the plate and these forces cause additional flow field in the fluid and a stress-strain state in the plate. The stress-strain state in the plate is described by utilizing the exact equations and relations of the linear elastodynamics. However, the additional fluid flow field is described with linearized Navier-Stokes equations for a compressible viscous fluid. Numerical results related to the influence of the problem parameters on the frequency response of the normal stress acting on the plate fluid interface plane and fluid flow velocity on this plane are presented and discussed. In this discussion, attention is focused on the influence of the initial plate axial moving velocity on these responses. At the same, it is established that as a result of the plate moving a resonance type of phenomenon can take place under forced vibration of the system. Moreover, numerical results regarding the influence of the fluid compressibility on these responses are also presented and discussed.

• Transactions on Electrical and Electronic Materials
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• 제18권4호
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• pp.199-202
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• 2017

Silicon carbide (SiC) is being spotlighted as a next-generation power semiconductor material owing to the characteristic limitations of the existing silicon materials. SiC has a wider band gap, higher breakdown voltage, higher thermal conductivity, and higher saturation electron mobility than those of Si. When using this material to implement Schottky barrier diode (SBD) devices, SBD-state operation loss and switching loss can be greatly reduced as compared to that of traditional Si. However, actual SiC SBDs exhibit a lower dielectric breakdown voltage than the theoretical breakdown voltage that causes the electric field concentration, a phenomenon that occurs on the edge of the contact surface as in conventional power semiconductor devices. Therefore in order to obtain a high breakdown voltage, it is necessary to distribute the electric field concentration using the edge termination structure. In this paper, we designed an edge termination structure using a field plate structure through oxide etch angle control, and optimized the structure to obtain a high breakdown voltage. We designed the edge termination structure for a 650 V breakdown voltage using Sentaurus Workbench provided by IDEC. We conducted field plate experiments. under the following conditions: $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $75^{\circ}$. The experimental results indicated that the oxide etch angle was $45^{\circ}$ when the breakdown voltage characteristics of the SiC SBD were optimized and a breakdown voltage of 681 V was obtained.

• Journal of Platform Technology
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• 제11권3호
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• pp.68-75
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• 2023

본 논문은 110V 이하의 낮은 직류 및 교류전원을 이용하여 보리종자의 발아율을 높이는 방법에 관한 것이다. 여기서 사용된 실험장치는 평행평판이며, 정전기장의 크기를 키우기 위하여 평판의 밑면을 위면 크기보다 더 넓도록 설계하였다. 결과적으로 평판에 공급된 정전기장의 크기는 3종류로 첫 번째 400V/cm에서 600V/cm까지, 두 번째 600V/cm에서 900V/cm까지, 그리고 세 번째 2200V/cm에서 2400V/cm까지 만들었다. 평행평판의 내부에서 정전기장을 해석하기 위한 방법으로 유한차분법을 적용하였다. 본 논문에서 실험에 사용된 식물종자는 국내에서 생산된 보리종자를 사용하였다. 본 논문에서 제시된 정전기장을 이용한 보리종자의 평균 발아율은 57%이고, 2.45GHz의 마이크로파를 이용한 경우는 65%이며, 대조군의 경우는 31%의 결과가 나왔다. 정전기장을 이용한 경우와 2.45GHz의 마이크로파를 이용한 경우의 중요한 차이점은 건식방법과 습식방법이다. 이 두 방법을 실질적인 종자발아에 적용할 경우는 각각 실험방법의 장단점을 고려하여 적합한 방식을 선택해야 한다.