• Title/Summary/Keyword: Permittivity

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A study on the deformation of a bubble and a drop in a uniform electric field (균일전기장에 의한 기포와 액적의 변형에 관한 연구)

  • Gwon, Yeong-Cheol;Kim, Mu-Hwan;Gang, In-Seok;Cho, Hae-Jung;Kim, Suk-Joon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.6
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    • pp.2023-2035
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    • 1996
  • In the present study, the characteristics of the electrical deformation of a bubble and a drop under a uniform electric field have been investigated to understand EHD heat transfer enhancement by an electric field. The deformation of the bubble and the drop have been studied theoretically using an electric normal stress acting on their interfaces and assured by the numerical analysis and the experiment. From the variation of bubble volume and free energy, it is found that a bubble is compressed in an electric field and free energy had larger value with increasing W and the permittivity of a dielectric fluid. The electric normal stress induced on the interface of the bubble and the drop is different. Because of the surface charge induced at the drop interface, the electric normal stress acting on the drop is much larger than that of the bubble. The drop is, therefore, deformed much more than the bubble. In addition, the experimental and numerical results show that the aspect ratio and the contact angle of the bubble increase with increasing W.

A Directivity Design of Loop Type Dipole Antenna for RFID Tag (RFID 태그용 루프형 다이폴 안테나의 지향성 설계)

  • Kim, Min-Seong;Min, Kyeong-Sik
    • Journal of Navigation and Port Research
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    • v.32 no.10
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    • pp.805-811
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    • 2008
  • This paper presents a design of RFID(Radio Frequency Identification) tag antenna which is available for a vehicle's side mirror and directivity characteristics by mr body. The proposed Tag antenna is designed symmetrical structure to improve the broad bandwidth characteristic and the readable range. A proposed tag antenna($30\;mm{\times}24\;mm{\times}1\;mm$) has resonant frequency at 910 MHz and bandwidth is 780 MHz ($540\;MHz{\sim}1320\;MHz$). The chip impedance is the 16 - $j131\;{\Omega}$ and the complex conjugate impedance of commercial chip has been used for tag antenna design. In order to evaluate effects of tag antenna for side view mirror's permittivity as well as car body(conductor), radiation pattern characteristics and readable range have been calculated and measured. The optimized position for a vehicle's RFID system has been observed in the inside of a side mirror and the calculated results show good agreement with the measured results.

Variation in optical, dielectric and sintering behavior of nanocrystalline NdBa2NbO6

  • Mathai, Kumpamthanath Chacko;Vidya, Sukumariamma;Solomon, Sam;Thomas, Jijimon Kumpukattu
    • Advances in materials Research
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    • v.2 no.2
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    • pp.77-91
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    • 2013
  • High quality nanoparticles of neodymium barium niobium ($NdBa_2NbO_6$) perovskites have been synthesized using an auto ignition combustion technique for the first time. The nanoparticles thus obtained have been characterized by powder X-ray diffraction, thermo gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, Raman spectroscopy and transmission electron microscopy. UV-Visible absorption and photoluminescence spectra of the samples are also recorded. The structural analysis shows that the nano powder is phase pure with the average particle size of 35 nm. The band gap determined for $NdBa_2NbO_6$ is 3.9 eV which corresponds to UV-radiation for optical inter band transition with a wavelength of 370nm. The nanopowder could be sintered to 96% of the theoretical density at $1325^{\circ}C$ for 2h. The ultrafine cuboidal nature of nanopowders with fewer degree of agglomeration improved the sinterability for compactness at relatively lower temperature and time. During the sintering process the wide band gap semiconducting behavior diminishes and the material turns to a high permittivity dielectric. The microstructure of the sintered surface was examined using scanning electron microscopy. The striking value of dielectric constant ${\varepsilon}_r=43$, loss factor tan ${\delta}=1.97{\times}10^{-4}$ and the observed band gap value make it suitable for many dielectric devices.

Fabrication and Time-Dependent Analysis of Micro-Hole in GaAs(100) Single Crystal Wafer Using Wet Chemical Etching Method (습식 화학적 식각 방법에 의한 시간에 따른 GaAs(100) 단결정 웨이퍼에서의 마이크로 구멍의 제작 및 분석)

  • Lee, Ha Young;Kwak, Min Sub;Lim, Kyung-Won;Ahn, Hyung Soo;Yi, Sam Nyung
    • Korean Journal of Materials Research
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    • v.29 no.3
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    • pp.155-159
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    • 2019
  • Surface plasmon resonance is the resonant oscillation of conduction electrons at the interface between negative and positive permittivity material stimulated by incident light. In particular, when light transmits through the metallic microhole structures, it shows an increased intensity of light. Thus, it is used to increase the efficiency of devices such as LEDs, solar cells, and sensors. There are various methods to make micro-hole structures. In this experiment, micro holes are formed using a wet chemical etching method, which is inexpensive and can be mass processed. The shape of the holes depends on crystal facets, temperature, the concentration of the etchant solution, and etching time. We select a GaAs(100) single crystal wafer in this experiment and satisfactory results are obtained under the ratio of etchant solution with $H_2SO_4:H_2O_2:H_2O=1:5:5$. The morphology of micro holes according to the temperature and time is observed using field emission - scanning electron microscopy (FE-SEM). The etching mechanism at the corners and sidewalls is explained through the configuration of atoms.

Design and Manufacture of Triple-Band Antennas with Two Branch Line and a Vertical Line for WLAN/WiMAX system applications (2개 분기선로와 수직 선로를 갖는 WLAN/WiMAX 시스템에 적용 가능한 삼중대역 안테나 설계 및 제작)

  • Choi, Tae-Il;Yoon, Joong-Han
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.23 no.6
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    • pp.740-747
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    • 2019
  • In this paper, an antenna applicable to WLAN and WiMAX frequency bands is designed, fabricated, and measured. The proposed antenna is designed to have two branch strip line in the patch plane and a rectangular slit in the ground plane based on microstrip feeding for triple band characteristics and added a vertical strip in the ground plane to enhance impedance bandwidth characteristics. The proposed antenna is designed on a substrate with a relative permittivity of 4.4, a thickness of 1.0 mm, and has a size of $18.0mm(W1){\times}37.3mm$ (L4+L5+L7). From the fabricated and measured results, impedance bandwidths of 480 MHz (2.32 to 2.80 GHz) for 2.4/2.5 GHz band, 810 MHz (3.22 to 4.03 GHz) for 3.5 GHz band, and 1,820 MHz (5.05 to 6.87 GHz) for 5.0 GHz band were obtained based on the impedance bandwidth. Measured 3D pattern and gains are displayed.

A Sudy on the Underground Condition of Road Using 3D-GPR Exploration (3D-GPR탐사를 이용한 도로하부 지반상태에 대한 연구)

  • Lee, Sung-Ho;Jang, Il-Ho
    • Journal of the Korean GEO-environmental Society
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    • v.20 no.2
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    • pp.49-58
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    • 2019
  • A study on the analysis of underground ground condition using 3D-GPR exploration was carried out in this paper. The test bed was constructed similar to the field, and the detection analysis was carried out for each depth of cavity and underground burial. Through this, we were able to know the permittivity of the ground by inversion, and we could confirm the depth of detection for the joint by accurate calculation. We confirmed the signal waveforms in the cavity under the road through 3D-GPR exploration, analyzed more quantitatively in subjective and empirical analysis. The subsidence and depth of the subsurface settlement can be observed through 3D-GPR survey, and ground condition change after the ground reinforcement can be confirmed through the exploration section.

Dielectrophoresis for Control of Particle Transport: Theory, Electrode Designs and Applications (입자 이동 제어를 위한 유전영동: 이론, 전극 구조 및 응용분야)

  • Lee, Minji;Kim, Ji-Hye;Koo, Hyung-Jun
    • Korean Chemical Engineering Research
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    • v.57 no.2
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    • pp.149-163
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    • 2019
  • Under non-uniform electric field, a directional force along the electric field gradient is applied to matter having permanent or induced dipoles. The transport of particles by the directional force is called dielectrophoresis (DEP). Since the strength and direction of the DEP force depend on parameters, such as permittivity and conductivity of particles and surrounding media, and frequency of the applied AC electric field, particle can be precisely manipulated by controlling the parameters. Moreover, unlike electrophoresis, DEP can be applied to any particles where dipole is effectively induced by electric field. Such a DEP technique has been used in various fields, ranging from microfluidic engineering to biosensor and microchip research. This paper first describes the fundamentals of DEP, and discusses representative microelectrode designs used for DEP study. Then, exemplary applications of DEP, such as separation, capture and self-assembly of particles, are introduced.

Design and Implementation of Triple-band WLAN Antenna with Microstrip Lines (마이크로스트립 선로를 이용한 삼중대역 WLAN 안테나의 설계 및 제작)

  • Yoon, Joong-Han
    • The Journal of the Korea institute of electronic communication sciences
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    • v.14 no.1
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    • pp.33-40
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    • 2019
  • In this paper, a microstrip-fed triple-band antenna for WLAN system with microstrip lines was designed, fabricated and measured. The proposed antenna is composed of two strip lines and slit in the ground plane and then designed in order to get triple band characteristics. We carried out simulation on $L_3$, $L_{10}$, and slit parameters, and adjusted the parameters of the proposed antenna to satisfy the required frequency band and bandwidth. The proposed antenna is made of $32.0{\times}44.0{\times}1.0mm$ and is fabricated on the permittivity 4.4 FR-4 substrate. The experiment results shows that the proposed antenna obtained the -10 dB impedance bandwidth 120 MHz (890 MHz~1.01 MHz), 440 MHz (2.35~2.79 GHz), and 1,280 MHz (5.07~6.35 GHz) covering the triple WLAN bands. Also, the measured gain and radiation patterns characteristics of the proposed antenna are presented at required frequency band, respectively.

A Study on TE Scattering by a Resistive Strip Grating Between a Double Dielectric Layer Using PMM (PMM을 이용한 2중 유전체층 사이의 저항띠 격자구조에 의한 TE 산란에 관한 연구)

  • Yoon, Uei-Joong
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.19 no.4
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    • pp.21-26
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    • 2019
  • In this paper, TE(transverse electric) scattering problems by a resistive strip grating between a double dielectric layer are analyzed by using the PMM(point matching method) known as a numerical method of electromagnetic fileld. The boundary conditions are applied to obtain the unknown field coefficients, the scattered electromagnetic fields are expanded in a series of Floquet mode functions, and the resistive boundary condition is applied to analysis of the resistive strip. The numerical results for the normalized reflected and transmitted power are analyzed by according as the width and spacing of resistive strip, the relative permittivity and thickness of the double dielectric layers, incident angles, and uniform resisitivity. Typically, the reflected power for the conductive strip increased as the value of the relative dielectric constant increased, the reflected power for the resistive strip with uniform resistivity decreased as the value of the resisvivity increased. The numerical results for the presented structure of this paper are shown in good agreement compared to those of the existing papers.

Analysis of TE Scattering by a Conductive Strip Grating Between a Double Dielectric Layer (2중 유전체층 사이의 완전도체띠 격자구조에 의한 TE 산란 해석)

  • Yoon, Uei-Joong
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.19 no.2
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    • pp.47-52
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    • 2019
  • In this paper, TE(transverse electric) scattering problems by a conductive strip grating between a double dielectric layer are analyzed by applying the FGMM(Fourier-Galerkin moment method) known as a numerical method of electromagnetic fileld. The boundary conditions are applied to obtain the unknown field coefficients, and the conductive boundary condition is applied to analysis of the conductive strip. The numerical results for the normalized reflected and transmitted power are analyzed by according as the width and spacing of conductive strip, the relative permittivity and thickness of the double dielectric layers, and incident angles. Generally, as the value of the dielectric constant increases, the reflected power increases and the transmitted power decreases, respectively. As the dielectric constant increases, the current density induced in the strip increases as it goes to both strip ends. The numerical results for the presented structure of this paper are shown in good agreement compared to those of the existing papers.