• 한국공작기계학회논문집
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• 제15권1호
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• pp.56-62
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• 2006

An experimental investigation was performed to study the characteristics of ER(Electro-Rheological) fluid flow in a horizontal rectangular tube with or without D.C voltage. To determine some characteristics of the ER flow, 2D PIV(Particle Image Velocimetry) technique is employed for velocity measurement. This research found the mean velocity distribution with 0kV/mm, 1.0kV/mm and 1.5kV/mm for Re = 0, 0.62, 1.29 and 2.26. When the strength of the electric field increased, the cluster of ERF are clearly strong along the test tube and the flow rate decreased. In this study, the rheology of ER fluid stagnating or flowing through a dispersion meter will be investigated by PIV method. And then the ER effect, which appears at the ER valves and their appliance will be visualized.

• Structural Engineering and Mechanics
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• 제62권6호
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• pp.675-693
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• 2017

In this paper, based on the first-order shear deformation plate theory, buckling analysis of piezoelectric coupled transversely isotropic rectangular plates is investigated. By assuming the transverse distribution of electric potential to be a combination of a parabolic and a linear function of thickness coordinate, the equilibrium equations for buckling analysis of plate with surface bonded piezoelectric layers are established. The Maxwell's equation and all boundary conditions including the conditions on the top and bottom surfaces of the plate for closed and open circuited are satisfied. The analytical solution is obtained for Levy type of boundary conditions. The accurate buckling load of laminated plate is presented for both open and closed circuit conditions. From the numerical results it is found that, the critical buckling load for open circuit is more than that of closed circuit in all boundary and loading conditions. Furthermore, the critical buckling loads and the buckling mode number increase by increasing the thickness of piezoelectric layers for both open and closed circuit conditions.

• JSTS:Journal of Semiconductor Technology and Science
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• 제7권1호
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• pp.56-65
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• 2007

This paper describes physical meanings of various influences of cavity (or pillar) shape and filling factor of dielectric material on band structures in two-dimensional photonic crystals. Influences of circular and rectangular cross-sections of cavity (or pillar) arrays on photonic band structures are considered theoretically, and significant aspects of square and triangular lattices are compared. It is shown that both averaged dielectric constant of the photonic crystal and distribution profile of photon energy play important roles in designing optical properties. For the triangular lattice, especially, it is shown that cavity array with a rectangular cross-section breaks the band structure symmetry. So, we discuss this point from the band structure and address optical properties of lattice with a circular cross-section cavity.

• 한국전산유체공학회지
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• 제1권1호
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• pp.55-63
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• 1996

Numerical computations are carried out to analyze the characteristics of flow fields around Air Supported Ships. The computations are performed in a rectangular grid system based on MAC(Marker And Cell) method. The governing equations are represented in finite difference forms by forward differencing in time and centered differencing in space except for its convection terms. For the certification of this numerical analysis method, the computations of flow fields around a Catamaran, an ACV(Air Cushion Vehicle) modeled with pressure distribution on free surface and two SES(Surface Effect Ship)'s are carried out, The results of the present computations are compared with the previously presented computational and experimental results in the same condition.

• Computational Structural Engineering : An International Journal
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• 제1권1호
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• pp.49-57
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• 2001

This paper presents exact solutions for the modal stress-resultant distributions for vibrating rectangular Mindlin plates involving two opposite sides simply supported while the other two sides free. These exact stress-resultants of vibrating plates with free edges, hitherto unavailable, are very important because they serve as benchmark solutions for checking numerical solutions and methods. Using the exact solutions of a square plate, this paper highlights the problem of determining accurate stress-resultants, especially the transverse shear forces and twisting moments in thin plates, when employing the widely used numerical methods such as the Ritz method and the finite element method. Thus, this study shows that there is a need for researchers to develop refinements to the Ritz method and the finite element method for determining very accurate stress-resultants in vibrating plates with free edges.

• Journal of Magnetics
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• 제20권4호
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• pp.405-412
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• 2015

In this study, we describe the effects of changing the magnet shape of permanent magnets (PMs) in a rotor Halbach-array PM generator for reciprocating free piston generator applications. More specifically, the rectangular-shaped magnets were replaced by the trapezoidal-shaped magnets. The initial design, an analytical magnetic field solution of rectangular shaped magnets, is presented and air-gap magnetic flux density and thrust force were estimated. The results were compared to the finite element analysis (FEA) showing excellent agreement. Using FEA, the effect of the shape of the magnets on the flux density and thrust force waveforms is analyzed. Moreover, the proportion of the Halbach array in the machine was optimized by the means of a parametric search. The results obtained from the analytical calculations and FEA were validated by comparing to those of Radial-array PM generator.

• 한국소음진동공학회논문집
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• 제15권4호
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• pp.474-482
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• 2005

A theoretical method is presented to investigate the thermoelastic and dynamic response of functionally graded material (FGM) rectangular plates made up of metal and ceramic. The temperature is assumed to be constant in the plane of the plate and to vary in the thickness direction only. Material properties are assumed to be temperature-dependant, and vary continuously through the thickness according to a power law distribution in terms of the volume fraction of the constituents. The third order shear deformation theory (TSDT) to account for rotary inertia and transverse shear strains is adopted to formulate the theoretical model. The modal analysis technique is used to develop the analytic solutions of the dynamic problem. The effect of material compositions and temperature fields is examined. The present theoretical results are verified by comparing with those from finite element analysis by ANSYS.

• 전자공학회논문지A
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• 제31A권2호
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• pp.18-25
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• 1994

In this papaer, the input impedance of the rectangular microstrip patch antennas with the multilayered structure is analysed by using the moment method technique in the spectral domain. The analysis is carried out for two different feeding structures : directfeeding structure and electromagnetic-feeding structure. In order to obtain the accurate input impedance, the current distribution on the microstrip feed line is modeled by the quasi-TEM travelling wave and the PWS(piecewise sinusoidal) mode. The input impedances of the designed microstrip antennas are measured and compared with the calculation. which shows a good agreement.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.589-593
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• 2003

Narrowband and wideband characterizations of radio propagation channels in tunnel environments are investigated by using ray tracing techniques. For a rectangular straight tunnel and a rectangular curved tunnel, received power is simulated when the receiver moves away from the transmitter. The fast fading statistics of the narrowband propagation are analyzed in terms of cumulative distribution function, level crossing rate and average fade duration. The tunnel wideband radio propagation channel is characterized in terms of mean excess delay and rms delay spread.

• 조명전기설비학회논문지
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• 제17권2호
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• pp.41-48
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• 2003

접지 시설의 효율적인 시설 계획을 위해서는 시공 전에 접지전극에 전류가 유입할 때 접지 전극주변에 발생하는 전위분포 및 전류에 의한 접지저항을 추정하는 것이 접지 설계에 있어서 매우 중요하다. 본 논문에서는 사각판상의 접지전극을 대지에 직접 시공 매설하여 지표면 전위의 분석으로 접지저항을 측정하고, 또한 사각판상 접지 저항 값의 이론적 계산식에서 구한 접지저항값과 축소된 사각판상의 접지전극 모델을 수조에 넣고 모의 실험을 통해 측정된 접지저항값을 비교·분석하였다.