• Title/Summary/Keyword: Electric-field Intensity

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Wind field generation for performance-based structural design of transmission lines in a mountainous area

  • Lou, Wenjuan;Bai, Hang;Huang, Mingfeng;Duan, Zhiyong;Bian, Rong
    • Wind and Structures
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    • v.31 no.2
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    • pp.165-183
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    • 2020
  • The first step of performance-based design for transmission lines is the determination of wind fields as well as wind loads, which are largely depending on local wind climate and the surrounding terrain. Wind fields in a mountainous area are very different with that in a flat terrain. This paper firstly investigated both mean and fluctuating wind characteristics of a typical mountainous wind field by wind tunnel tests and computational fluid dynamics (CFD). The speedup effects of mean wind and specific turbulence properties, i.e., turbulence intensity, power spectral density (PSD) and coherence function, are highlighted. Then a hybrid simulation framework for generating three dimensional (3D) wind velocity field in the mountainous area was proposed by combining the CFD and proper orthogonal decomposition (POD) method given the properties of the target turbulence field. Finally, a practical 220 kV transmission line was employed to demonstrate the effectiveness of the proposed wind field generation framework and its role in the performance-based design. It was found that the terrain-induce turbulence effects dominate the performance-based structural design of transmission lines running through the mountainous area.

Dynamic analysis of a magneto-electro-elastic material with a semi-infinite mode-III crack under point impact loads

  • Feng, Wenjie;Liu, Jinxi
    • Structural Engineering and Mechanics
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    • v.27 no.5
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    • pp.609-623
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    • 2007
  • The problem of a semi-infinite magneto-electro-elastically impermeable mode-III crack in a magneto-electro-elastic material is considered under the action of impact loads. For the case when a pair of concentrated anti-plane shear impacts, electric displacement and magnetic induction impacts are exerted symmetrically on the upper and lower surfaces of the crack, the magneto-electro-elastic field ahead of the crack tip is determined in explicit form. The dynamic intensity factors and dynamic energy density factor are obtained. The method adopted is to reduce the mixed initial-boundary value problem, by using the Laplace and Fourier transforms, into three simultaneous dual integral equations, one of which is converted into an Abel's integral equation and the others into a singular integral equation with Cauchy kernel. Based on the obtained fundamental solutions of point impact loads, the solutions of two kinds of different loading cases are evaluated by integration. For some particular cases, the present results reduce to the previous results.

Dynamic Response of an Anti-plane Shear Crack in a Functionally Graded Piezoelectric Strip

  • Kwon, Soon-Man;Lee, Kang-Yong
    • Journal of Mechanical Science and Technology
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    • v.18 no.3
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    • pp.419-431
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    • 2004
  • The dynamic response of a cracked functionally graded piezoelectric material (FGPM) under transient anti-plane shear mechanical and in-plane electrical loads is investigated in the present paper. It is assumed that the electroelastic material properties of the FGPM vary smoothly in the form of an exponential function along the thickness of the strip. The analysis is conducted on the basis of the unified (or natural) crack boundary condition which is related to the ellipsoidal crack parameters. By using the Laplace and Fourier transforms, the problem is reduced to the solutions of Fredholm integral equations of the second kind. Numerical results for the stress intensity factor and crack sliding displacement are presented to show the influences of the elliptic crack parameters, the electric field, FGPM gradation, crack length, and electromechanical coupling coefficient.

Effect of Secondary Flows on the Particle Collection Efficiency in Single Stage Electrostatic Precipitator (1단 전기 집진기에서 2차 유동이 집진 효율에 미치는 영향)

  • Lee, Jae-Bok;Bae, Gwi-Nam;Hwang, Jung-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.2
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    • pp.251-259
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    • 2000
  • The ionic wind formed in a nonuniform electric field has been recognized to have a significant effect on particle collection in an electrostatic precipitator(ESP). Under normal operating conditions the effect of ionic wind is not pronounced. However, as the flow velocity becomes smaller, the ionic wind becomes pronounced and induces secondary flow, which has a significant influence on the flow field and the particle collecting efficiency. In this paper, experiments for investigating the effect of secondary flow on collection efficiencies were carried out by changing the flow velocities in 0.2-0.7m/s and the applied voltages in 9-11kV/cm. The particle size distributions and concentrations are measured by DMA and CNC. To analyze the experimental results, numerical analysis of electric filed in ESP was carried out. It shows that particle collection is influenced by two independent dimensionless numbers, $Re_{ehd}\;and\;Re_{flow}$ not by $N_{ehd}$ alone. When $Re_{flow}$, decreases for constant $Re_{ehd}$, the secondary flow prohibits the particle collection. But when $Re_{ehd}$ increases for constant $Re_{flow}$, it enhances the particle collection by driving the particles into the collection region.

Design and Fabrication of Electrostatic Inkjet Head using Silicon Micromachining Technology

  • Kim, Young-Min;Son, Sang-Uk;Choi, Jae-Yong;Byun, Do-Young;Lee, Suk-Han
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.8 no.2
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    • pp.121-127
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    • 2008
  • This paper presents design and fabrication of optimized geometry structure of electrostatic inkjet head. In order to verify effect of geometry shape, we simulate electric field intensity according to the head structure. The electric field strength increases linearly with increasing height of the micro nozzle. As the nozzle diameter decreases, the electric field along the periphery of the meniscus can be more concentrated. We design and fabricate the electrostatic inkjet heads, hole type and pole type, with optimized structure. It was fabricated using thick-thermal oxidation and silicon micromachining technique such as the deep reactive ion etching (DRIE) and chemical wet etching process. It is verified experimentally that the use of the MEMS inkjet head allows a stable and sustainable micro-dripping mode of droplet ejection. A stable micro dripping mode of ejection is observed under the voltages 2.5 kV and droplet diameter is $10\;{\mu}m$.

Finer Silver Nano-Particle Producing in Water Utilizing a Dielectric Bed (유전체 층을 이용한 수중 은 나노입자의 소형화 제조)

  • Moon, Jae-Duk
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.12
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    • pp.2250-2255
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    • 2010
  • An fine silver particle has a variety of uses, such as in killing micrograms and as catalysts. Many techniques have been used for the production of the fine particles. Faraday cell, consisting of two silver electrodes in an electrolyte, is unique, but it is hard to get a very fine particle by this method. A finer silver nano-particle producing cell, utilizing a dielectric bed as a lower electric current and higher field controlling means, has been proposed and investigated. The I-V characteristics of the cell and effect of the dielectric bed on the producing finer silver nano-particles have been investigated. The I-V characteristics of the cell with the dielectric bed were different from that of the same system without the bed, due to the increased cell resistance and elevated electric field intensity. It is found that the proposed cell with the dielectric bed can produce finer silver nano-particles effectively, which, however, can be used as one of effective fine silver nano-particle producing means.

Comparing Microscale Behaviors of Block Copolymer with Polymer Blend Thin Films under Electric Fields (전기장 하에서의 블록 공중합체와 고분자 블렌드의 미세 구조 변화 거동 비교)

  • Bae, Joonwon
    • Applied Chemistry for Engineering
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    • v.29 no.4
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    • pp.395-398
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    • 2018
  • In this work, profound microscale behaviors of block copolymer and polymer blend under electric field were investigated using microscopic methods and compared systematically. To this end, both the block copolymer and blend containing polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) were introduced. The two polymers have a similar dielectric constant. Under an identical experimental condition such as temperature, film thickness, field intensity, and exposure time, the polymer blend responded more sensitively than the block copolymer. The presence of covalent bond suppressed the mobility of constituents in block copolymer. This study will be essential for future research activities regarding behaviors of polymeric materials under external fields.

Temperature and DC Electric Field Dependence of Second Harmonic Generation in Mg:$LiNbO_3$ (Mg:$LiNbO_3$ 에서 제2고조파발생의 온도 및 직류전장 의존도)

  • 진용성
    • Korean Journal of Optics and Photonics
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    • v.4 no.1
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    • pp.84-89
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    • 1993
  • Spatial homogenity of Mg (4 mole %):LiNb$O_3$ is investigated by studying the characteristic of Second Harmonic Generation in Mg:LiNb$O_3$ as a function of temperature and DC Electric Field. It is found that the temperaturs at which the intensity of the second harmonic is reduced to the first zero from its maximum for the phase matching condition is shifted linearly to the strength of DC Electric field applied to optic axis of Mg:LiNb$O_3$. From these results, the electro-optic coefficient of Mg:LiNb$O_3$ is estimated to be higher than that of Congruent LiNb$O_3$ by a factor of 1.5.

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A Study on the Integrated-Optical Electric-Field Sensor utilizing Ti:LiNbO3 Y-fed Balanced-Bridge Mach-Zehnder Interferometric Modulators (Ti:LiNbO3 Y-fed Balanced-Bridge 마하젠더 간섭 광변조기를 이용한 집적광학 전계센서에 관한 연구)

  • Jung, Hongsik
    • Journal of the Institute of Electronics and Information Engineers
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    • v.53 no.1
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    • pp.29-35
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    • 2016
  • We have demonstrated a $Ti:LiNbO_3$ electro-optic electric-field sensors utilizing a $1{\times}2$ Y-fed balanced-bridge Mach-Zehnder interferometric (YBB-MZI) modulator which uses a 3-dB directional coupler at the output and dipole patch antenna. The operation and design were proved by the BPM simulation. A dc switching voltage of ~16.6 V and an extinction ratio of ~14.7 dB are observed at a wavelength of $1.3{\mu}m$. For a 20 dBm rf power, the minimum detectable electric-fields are ~1.12 V/m and ~3.3 V/m corresponding to a dynamic range of about ~22 dB and ~18 dB at frequencies 10 MHz and 50 MHz, respectively. The sensors exhibit almost linear response for the applied electric-field intensity from 0.29 V/m to 29.8 V/m.

A Study on the Development of a Lightning Warning System by the Measurement of Electric Field at the Ground (대지전장측정에 의한 뇌경보시스템 개발에 관한 연구)

  • Kil, Gyung-Suk;Lee, Sung-Keun;Song, Jae-Yong;Kim, Jum-Sik;Kwon, Jang-Woo
    • Journal of Sensor Science and Technology
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    • v.10 no.4
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    • pp.250-258
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    • 2001
  • In this study, a lightning warning system (LWS) which can predict a lightning return stroke is developed, and the LWS is based on the measurement of electric field intensity at the ground level. The LWS consist of a rotation-type field mill as an electric field sensor, an impedance changer, a two-stage amplifier, and a microprocessor unit. From the calibration experiment, the frequency bandwidth and the maximum resolution of the LWS are $DC{\sim}200\;[Hz]$ and 73 [V/m], respectively. Also, the LWS can measure the electric field strength caused by a thunderstorm up to 18.7 [kV/m] at the ground. To ensure the sensing ability of the developed LWS in an actual situation, computer simulation using thundercloud models was carried out, and the result showed that the LWS can monitor the movement of thunderclouds within 6 [km] from the observation site.

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