• Title/Summary/Keyword: Sinusoidal Function

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Bending response of functionally graded piezoelectric plates using a two-variable shear deformation theory

  • Zenkour, Ashraf M.;Hafed, Zahra S.
    • Advances in aircraft and spacecraft science
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    • v.7 no.2
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    • pp.115-134
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    • 2020
  • This paper proposes a bending analysis for a functionally graded piezoelectric (FGP) plate through utilizing a two-variable shear deformation plate theory under simply-supported edge conditions. The number of unknown functions used in this theory is only four. The electric potential distribution is assumed to be a combination of a cosine function along the cartesian coordinate. Applying the analytical solutions of FGP plate by using Navier's approach and the principle of virtual work, the equilibrium equations are derived. The paper also discusses thoroughly the impact of applied electric voltage, plate's aspect ratio, thickness ratio and inhomogeneity parameter. Results are compared with the analytical solution obtained by classical plate theory, first-order-shear deformation theory, higher-order shear deformation plate theories and quasi-three-dimensional sinusoidal shear deformation plate theory.

MTF comparision of CCD camera measured by two methods: Twyman-Green interferometer method and zoom lens method with three sinusoidal gratings (트와이만-그린 간섭계를 이용한 CCD의 MTF 값과 줌 렌즈를 이용한 CCD의 MTF 값 측정 비교.)

  • 홍성목;조재흥;임천석;이윤우;이회윤
    • Proceedings of the Optical Society of Korea Conference
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    • 2003.07a
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    • pp.28-29
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    • 2003
  • 각종 렌즈 및 카메라, 망원경, 현미경 등 다양한 광학계들이 설계 및 개발 되고 있는 시점에서 그 성능을 정확하게 평가하는 것이 매우 중요하다. 광학계의 성능 평가를 위해서는 크게 정성적인 방법과 정량적인 방법으로 나눌 수 있는데, 정성적인 방법에 의한 평가는 분해능 표판이나 주기적인 격자의 상을 스크린 등에 결상시킨 후 사람의 눈을 통해서 한계 분해능을 평가하는 방법이다. 정량적인 방법에 의한 평가는 OTF(Optical Transfer Function)를 측정하거나 설계 자료를 통해 계산해 내는 것이다. (중략)

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Dynamic analysis of a porous microbeam model based on refined beam strain gradient theory via differential quadrature hierarchical finite element method

  • Ahmed Saimi;Ismail Bensaid;Ihab Eddine Houalef
    • Advances in materials Research
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    • v.12 no.2
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    • pp.133-159
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    • 2023
  • In this paper, a size-dependent dynamic investigation of a porous metal foams microbeamsis presented. The novelty of this study is to use a metal foam microbeam that contain porosities based on the refined high order shear deformation beam model, with sinusoidal shear strain function, and the modified strain gradient theory (MSGT) for the first time. The Lagrange's principle combined with differential quadrature hierarchicalfinite element method (DQHFEM) are used to obtain the porous microbeam governing equations. The solutions are presented for the natural frequencies of the porous and homogeneoustype microbeam. The obtained results are validated with the analytical methods found in the literature, in order to confirm the accuracy of the presented resolution method. The influences of the shape of porosity distribution, slenderness ratio, microbeam thickness, and porosity coefficient on the free vibration of the porous microbeams are explored in detail. The results of this paper can be used in various design formetallic foammicro-structuresin engineering.

Analysis of Albedo by Level-2 Land Use Using VIIRS and MODIS Data (VIIRS와 MODIS 자료를 활용한 중분류 토지이용별 알베도 분석)

  • Lee, Yonggwan;Chung, Jeehun;Jang, Wonjin;Kim, Jinuk;Kim, Seongjoon
    • Korean Journal of Remote Sensing
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    • v.38 no.6_1
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    • pp.1385-1394
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    • 2022
  • This study was to analyze the change in albedo by level-2 land cover map for 20 years(2002-2021) using MODerate resolution Imaging Spectroradiometer (MODIS) data. Also, the difference from the MODIS data was analyzed using the 10-year (2012-2021) data of Visible Infrared Imaging Radiometer Suite (VIIRS). For the albedo data of MODIS and VIIRS, daily albedo data, MCD43A3 and VNP43IA, of 500 m spatial resolution of sinusoidal tile grid produced by Bidirectional Reflectance Distribution Function (BRDF) model were prepared for the South Korea range. Reprojection was performed using the code written based on Python 3.9, and the nearest neighbor was applied as the resampling method. White sky albedo and black sky albedo of shortwave were used for analysis. As a result of 20-year albedo analysis using MODIS data, the albedo tends to rise in all land use. Compared to the 2000s (2002-2011), the average albedo of the 2010s (2012-2021) showed the most significant increase of 0.0027 in the forest area, followed by the grass increase of 0.0024. As a result of comparing the albedo of VIIRS and MODIS, it was found that the albedo of VIIRS was larger from 0.001 to 0.1, which was considered to be due to differences in the surface reflectivity according to the time of image capture and sensor characteristics.

Improved instantaneous Following Control Function for High Power Factor PWM Matrix Converter (고역율 PWM 매트릭스 컨버터의 개선된 순시추종 제어함수)

  • Kim, Kwang-Tae
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.19 no.3
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    • pp.35-43
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    • 2005
  • Matrix converters have been studied for eliminating dc link of conventional converter-inverter system, and various undulation strategy have been proposed. Therefore, matrix converter have no energy storage component except for small ac later for the elimination of switching ripple, and can be made compact and highly reliable compare with the do link inverter system. Matrix converter, however, directly connected the input and the output terminals by bidirectional static switch. As a result if the input voltage are asymmetrical, and contain harmonics, the influence of the distortions directly appear on the output terminal. This problem is a major obstacle to the matrix converter. A new control method using average comparison strategy have been proposed in this paper. This control method realizes sinusoidal input and output current unity input displacement factor regardless of load power factor. Moreover, compensation of the asymmetrical and/or harmonic containing input voltage is automatically realized, and calculation time of control function is reduced.

The Design and Simulation of a Fuzzy Logic Sliding Mode Controller (FLSMC) and Application to an Uninterruptible Power System Control

  • Phakamach, Phongsak;Akkaraphong, Chumphol
    • 제어로봇시스템학회:학술대회논문집
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    • 2004.08a
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    • pp.389-394
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    • 2004
  • A Fuzzy Logic Sliding Mode Control or FLSMC for the uninterruptible power system (UPS) is presented, which is tracking a sinusoidal ac voltage with specified frequency and amplitude. The FLSMC algorithm combines feedforward strategy with the Variable Structure Control (VSC) or Sliding Mode Control (SMC) and fuzzy logic control. The control function is derived to guarantee the existence of a sliding mode. FLSMC has an advantage that the stability of FLSMC can be proved easily in terms of VSC. Furthermore, the rules of the proposed FLSMC are independent of the number of system state variables because the input of the suggested controller is fuzzy quantity sliding surface value. Hence the rules of the proposed FLSMC can be reduced. The simulation results illustrate that the purposed approach gives a significant improvement on the tracking performances. It has the small overshoot in the transient and the smaller chattering in the steady state than the conventional VSC. Moreover, its can achieve the requirements of robustness and can supply a high-quality voltage power source in the presence of plant parameter variations, external load disturbances and nonlinear dynamic interactions.

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Effect of Sound Field on the Forced Convection Heat Transfer from an Isothermal Cylinder (음장이 등온원통으로부터의 강제대류 열전달에 미치는 영향)

  • 권영필
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.2
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    • pp.373-380
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    • 1988
  • The effect of sound on the heat transfer from an isothermal cylinder in cross flow is investigated by numerical analysis. The modeling is made for the laminar incompressible flow fluctuating in the range of the Reynolds number, 5.leq.Re.leq.35, by the sinusoidal acoustic field. The instantaneous response of the flow and heat transfer is simulated for various frequencies. It is shown that the heat transfer amplitude decreases and the phase lags behind the flow velocity with increase in the frequency. The time-mean effects of the acoustic field on the flow field and heat transfer, known as the acoustic and thermoacoustic streaming, are analyzed. The time-mean heat transfer coefficients are decreased around the forward stagnation point but increased in the wake region. Such a local difference in heat transfer coefficients is a function of the frequency and becomes greatest at some frequency. However, with balance between the local increase and decrease, the overall heat transfer coefficient is almost unaffected by sound.

A Study on the Periodic Transient Response Characteristics in Annular Fin with Uniform Thickness (均一두께의 環狀흰에서 週期的 過渡應答 特性에 관한 硏究)

  • 김광수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.2
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    • pp.338-348
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    • 1988
  • This study presents an analysis of periodic heat diffusion in an annular fin with uniform thickness. When the temperature of the fin base is changed in the form of a sinusoidal function, the exact temperature solution can be obtained by Laplace transformation in terms of the dimensionless parameters in the infinite series. Local heat flux and average heat flux, local fin efficiency and average fin efficiency were obtained. Particularly, the table of eigenvalues that are the indispensable condition in solving the heat transfer problem of annular fin in a transient state with convection phenomena at the fin edge is provided. The tables of heat fluxes and average heat fluxes, fin efficiencies and average fin efficiencies are also provided from the computed results. Also, substituting the variations of dimensionless parameters into the these exact solutions, the characteristics of these response are investigated.

Utility-Interactive Modulated Sinewave Inverter with a High Frequency Flyback Transformer Link for Small-Scale Solar Photovoltaic Generator

  • Konishi Y.;Chandhaket S.;Ogura K.;Nakaoka M.
    • Proceedings of the KIPE Conference
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    • 2001.10a
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    • pp.683-686
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    • 2001
  • This paper presents a novel prototype of the utility­interactive voltage source type sinewave pulse modulated power inverter using a high-frequency flyback transformer link. The proposed power conditioner circuit for the solar photovoltaic generation and small scale fuel cell has an isolation function due to the safety of the power processing system, which is more cost effective and acceptable for the small-scale distributed renewal energy conditioning and processing systems. The discontinuous current mode(DCM) of this power processing conversion circuit is applied to implement a simple circuit topology and pulse modulated control scheme. Its operation principle is described on the basis of simulation evaluations and theoretical considerations. The simulation results obtained herein prove that the proposed inverter outputs with sinusoidal waveforms and unity power factor currents are synchronized to the main voltage in utility power source grid. In this paper, the soft switching topology of high­frequency linked sinewave pulse modulation inverter is proposed and discussed.

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Numerical Analysis on Flow Phenomena of the Wake behind the Rectangular Obstacle in the Channel (관내 사각지주 후류의 유동현상에 대한 수치해석)

  • Min Yeong-Ui;Kim Yeon-Soo;Kim You-Gon
    • Journal of computational fluids engineering
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    • v.6 no.2
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    • pp.22-31
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    • 2001
  • The two-dimensional unsteady incompressible viscous flow behind rectangular bluff bodies between two parallel plates was analyzed numerically. The steady state flow and the vortex flow behind rectangular bluff bodies in the channel were investigated for two regimes i.e., the laminar(Re = 100, 300, 500) and the turbulent flows(Re = 10⁴∼10/sup 6/). The vortex shedding was generated by a physical disturbance(6%) numerically imposed at the rear of the bluff bodies for a short time. It was observed that the perturbed flow became periodic after a transient period. And in the case of unsteady inflow, the sinusoidal pulsatile flow was applied as the inlet condition in the turbulent flow of Reynolds number of 1.0×10/sup 5/. FLUENT code was employed to solve the problems. The power-law scheme was used to get stable linearized equations and the PISO algorithm was applied to finding the solution of them.

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