• Title/Summary/Keyword: Coaxial structure

Search Result 160, Processing Time 0.03 seconds

Ruthenium Oxide Nanoparticles Electrodeposited on the Arrayed ITO Nanorods and Its Application to Supercapacitor Electrode

  • Ryu, Ilhwan;Lee, Jinho;Park, Dasom;Yim, Sanggyu
    • Proceedings of the Korean Vacuum Society Conference
    • /
    • 2013.02a
    • /
    • pp.296-296
    • /
    • 2013
  • Supercapacitor is a capacitor with extraordinarily high energy density, which basically consists of current collector, active material and electrolyte. Ruthenium oxide ($RuO_2$) is one of the most widely studied active materials due to its high specific capacitance and good electrical conductivity. In general, it is known that the coating of $RuO_2$ on nanoarchitectured current collector shows improved performance of energy storage device compared to the coating on the planar current collector. Especially, the surface structure with standing coaxial nanopillars are most desirable since it can provide direct paths for efficient charge transport along the axial paths of each nanopillars and the inter-nanopillar spacing allows easy access of electrolyte ions. However, well-known fabrication methods for metal or metal oxide nanopillars, such as the process using anodize aluminum oxide (AAO) templates, often require long and complicated nanoprocess.In this work, we developed relatively simple method fabricating indium tin oxide (ITO) nanopillars via sputtering. We also electrodeposited $RuO_2$ nanoparticles onto these ITO nanopillars and investigated its physical and electrochemical properties.

  • PDF

Modeling for gaseous methane/liquid oxygen combustion processes at supercritical pressure (초임계 압력상태의 기체메탄/액체산소 연소과정 해석)

  • Kim, Tae-Hoon;Kim, Yong-Mo;Kim, Seong-Ku
    • Proceedings of the Korean Society of Propulsion Engineers Conference
    • /
    • 2010.11a
    • /
    • pp.85-88
    • /
    • 2010
  • This study has been mainly motivated to numerically model the supercritical mixing and combustion processes encountered in the liquid propellant rocket engines. In the present approach, turbulence is represented by the extended $k-{\varepsilon}$ turbulence model. To account for the real fluid effects, the propellant mixture properties are calculated by using SRK (Souve-Redlich-Kwong) equation of state. In order to realistically represent the turbulence-chemistry interaction in the turbulent nonpremixed flames, the flamelet approach based on the real fluid flamelet library has been adopted. Based on numerical results, the detailed discussions are made for the real fluid effects and the precise structure of gaseous methane/liquid oxygen coaxial jet flame.

  • PDF

An Experimental Study on Flame Structure and Combustion Characteristics of Turbulent Diffusion Flame(II) (난류확산화염의 화염구조와 연소특성에 관한 실험적 연구(2))

  • Choe, Byeong-Ryun;Jang, In-Gap;Choe, Gyeong-Min
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.20 no.3
    • /
    • pp.1050-1060
    • /
    • 1996
  • Recently, attention has been paid to the flame diagnostic by noncontact methods which dose not deform the flame shape. One of them is a method which is using the radical luminous intensity. Generally, this diagnostic method using radical luminous has been investigated its reliability by applying to laminar flame. This study, however, investigated each radical luminous signals through stocastical analysis like auto-correlation, cross-correlation, phase and coherence which were acquired from measuring radical luminous intensity of OH, CH, $O_{2}$, radicals in turbulent diffusion flame. To compare radical luminous intensity in flame with temperature, ion current and concentration , radious distribution of each properties was investigated and considered. In radical luminous intensity, correlation in the reaction zone of flame was higher than in correlation in combusted gas zone. And radious distribution of radical luminous intensity was corresponded with radious distribution of temperature, ion current and concentration. The result of the study confirms that a radical luminous flame diagnosis is possible in the turbulent diffusion flame.

Design and fabrication of Smart Skin Antenna for Phased Array Applications (위상배열 응용을 위한 스마트 스킨 안테나 설계 및 제작)

  • Son, Seong-Ho;Hwang, Woon-Bong
    • Composites Research
    • /
    • v.20 no.3
    • /
    • pp.25-30
    • /
    • 2007
  • This paper describes the basic design and fabrication of smart skin antenna for phased array applications. The smart skin phased array antenna, of which radiation pattern can be electrically steerable without mechanical rotation, has to meet the both mechanical and electrical performance. The smart skin antenna is a honeycomb sandwich structure to enhance the mechanical performance such as strength, weight and so on. The example of smart skin antenna integrated with radome is designed with the resonant frequency of 5 GHz, circular polarization, 2 by 2 subarray, and a coaxial probe-fed excitation. In addition, the performance of raw microstrip patch antenna uncovered radome is investigate. The fabricated smart skin antenna shows a reasonable performance with gain of 12.2 dBi and frequency bandwidth of 6.4 %.

Ka-band Feed Horn Antenna Including Circular-polarizer and Straight Type Mode Converter (Ka-대역 원형편파기와 직선구조 모드변환기를 포함한 급전 혼 안테나)

  • Jung, Young-Bae;Eom, Soon-Young;Jeon, Soon-Ik;Kim, Chang-Joo;Park, Seong-Ook
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
    • /
    • 2007.06a
    • /
    • pp.569-571
    • /
    • 2007
  • In this paper, hem antenna composed of rectangular hern, circular polarizer and straight-type mode convertor is designed and fabricated. The circular polarizer is designed as a dielectric type having broadband characteristic, and it is inserted into the rectangular hem with $45^{\circ}$ inclination. The straight-type mode convertor has a terrace-type structure in order to convert the TEM mode signal of coaxial cable to the TE mode of rectangular waveguide, and this structure minimizes conversion loss. Fabricated hem antenna operates at $30.085\sim30.885GHz$ and has VSWR < 1.5, Axial ratio < 1.0dB and antenna gain of $6.7\sim7.0dBi$ in the band.

  • PDF

Effects of the Recess and Propellants Mass Flow on the Flammability Limit and Structure of Methane-Oxygen Diffusion Flame (인젝터 리세스와 추진제 공급유량이 메탄-산소 확산화염의 가연한계와 구조에 미치는 영향)

  • Hong, Joon Yeol;Bae, Seong Hun;Kim, Jeong Soo
    • Journal of the Korean Society of Propulsion Engineers
    • /
    • v.22 no.1
    • /
    • pp.28-35
    • /
    • 2018
  • In order to analyze the flammability limit and structure of the gaseous methane-gaseous oxygen diffusion flame formed through a shear coaxial injector, combustion experiments were carried out according to the condition of injector recess and propellant mass-flow rate. As a result, it was confirmed that stable anchored flame was observed even at the high oxygen Reynolds number as the propellant momentum flux ratio increased, and that the recess had no significant influence on the flame shape and flammability limit. The anchored flame visualized through a chemiluminescence showed the maximum OH radical emission intensity at a specific position, irrespective of the propellant injection condition, and the radical intensity was greatly reduced by the injector recess.

Microtube Light-Emitting Diode Arrays with Metal Cores

  • Tchoe, Youngbin;Lee, Chul-Ho;Park, Junbeom;Baek, Hyeonjun;Chung, Kunook;Jo, Janghyun;Kim, Miyoung;Yi, Gyu-Chul
    • Proceedings of the Korean Vacuum Society Conference
    • /
    • 2016.02a
    • /
    • pp.287.1-287.1
    • /
    • 2016
  • Three-dimensional (3-D) semiconductor nanoarchitectures, including nano- and micro- rods, pyramids, and disks, are emerging as one of the most promising elements for future optoelectronic devices. Since these 3-D semiconductor nanoarchitectures have many interesting unconventional properties, including the use of large light-emitting surface area and semipolar/nonpolar nano- or micro-facets, numerous studies reported on novel device applications of these 3-D nanoarchitectures. In particular, 3-D nanoarchitecture devices can have noticeably different current spreading characteristics compared with conventional thin film devices, due to their elaborate 3-D geometry. Utilizing this feature in a highly controlled manner, color-tunable light-emitting diodes (LEDs) were demonstrated by controlling the spatial distribution of current density over the multifaceted GaN LEDs. Meanwhile, for the fabrication of high brightness, single color emitting LEDs or laser diodes, uniform and high density of electrical current must be injected into the entire active layers of the nanoarchitecture devices. Here, we report on a new device structure to inject uniform and high density of electrical current through the 3-D semiconductor nanoarchitecture LEDs using metal core inside microtube LEDs. In this work, we report the fabrications and characteristics of metal-cored coaxial $GaN/In_xGa_{1-x}N$ microtube LEDs. For the fabrication of metal-cored microtube LEDs, $GaN/In_xGa_{1-x}N/ZnO$ coaxial microtube LED arrays grown on an n-GaN/c-Al2O3 substrate were lifted-off from the substrate by wet chemical etching of sacrificial ZnO microtubes and $SiO_2$ layer. The chemically lifted-off layer of LEDs were then stamped upside down on another supporting substrates. Subsequently, Ti/Au and indium tin oxide were deposited on the inner shells of microtubes, forming n-type electrodes of the metal-cored LEDs. The device characteristics were investigated measuring electroluminescence and current-voltage characteristic curves and analyzed by computational modeling of current spreading characteristics.

  • PDF

A Study of Dual-Frequency Microstrip Patch Antenna (이중공진 마이크로스트립 패치 안테나에 관한 연구)

  • 장준영;김준모;윤영중;엄순영;전순익
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.9 no.4
    • /
    • pp.515-525
    • /
    • 1998
  • In this paper, for both transmission and reception with single antenna system of satellite communication, dual-frequency antennas which operate simultaneously at 12.5 GHz and at 14.25 GHz are designed, constructed and measured. Also by using dual feeding structure, the problems of single-fed dual-frequency antenna such as the separation of transmitting and receiving signals and single polarization, are solved. Microstrip patch as a radiation element of dual-fed dual-frequency antenna has width and length which are the resonance lengths of the corresponding frequencies for transmission and reception, respectively. The effects of the feed line on the other frequency feeding are minimized with the optimal matching scheme for the feed lines. For solving the space problems of dual-fed two-dimensional array antennas, microstrip-line and coaxial probe feedings are used for each frequency and a two-dimensional $2\times2$ array antenna was designed and measured their characteristics. The experimental results show that errors of resonance frequencies are less than 1.44%, the return losses are less than -21 dB and the isolations between two feeding ports are less than -21 dB. The characteristics of radiation patterns of dual frequency microstrip antenna are measured and evaluated. The directivities, sidelobe levels and cross polarizations are also measured and compared with the simulations. The results show some errors due to the misalignment of coaxial probe feeding.

  • PDF

NO Gas Sensing Properties of ZnO-Carbon Nanotube Composites (산화아연-탄소나노튜브 복합체의 일산화질소 가스 감지 특성)

  • Park, Seong-Yong;Jung, Hoon-Chul;Ahn, Eun-Seong;Nguyen, Le Hung;Kang, Youn-Jin;Kim, Hyo-Jin;Kim, Do-Jin
    • Korean Journal of Materials Research
    • /
    • v.18 no.12
    • /
    • pp.655-659
    • /
    • 2008
  • The NO gas sensing properties of ZnO-carbon nanotube (ZnO-CNT) composites fabricated by the coaxial coating of single-walled CNTs with ZnO were investigated using pulsed laser deposition. Upon examination, the morphology and crystallinity of the ZnO-CNT composites showed that CNTs were uniformly coated with polycrystalline ZnO with a grain size as small as 5-10 nm. Gas sensing measurements clearly indicated a remarkable enhancement of the sensitivity of ZnO-CNT composites for NO gas compared to that of ZnO films while maintaining the strong sensing stability of the composites, properties that CNT-based sensing materials do not have. The enhanced gas sensing properties of the ZnO-CNT composites are attributed to an increase in the surface adsorption area of the ZnO layer via the coating by CNTs of a high surface-to-volume ratio structure. These results suggest that the ZnO-CNT composite is a promising template for novel solid-state semiconducting gas sensors.

A Study on Parabolic Edge Planar Monopole Antenna for UWB Communication (초광대역(UWB) 통신을 위한 포물선 엣지 형태의 평면 모노폴 안테나에 대한 연구)

  • Chang, Tae-Soon;Hur, Jung
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.19 no.6
    • /
    • pp.612-620
    • /
    • 2008
  • In this parer, parabolic edge planar monopole antenna for UWB communication is presented. The antenna have broadband property structurally through planar monopole and ground which have parabolic edge. It is designed close to self-complementary structure as changing curvature of edge of monopole and ground. Monopole and ground of proposed antenna exist on coplanar plane, and excite as coaxial feeding. It used FR4 dielectric substrate of ${\varepsilon}_r=4.4$, and the size is $26{\times}31{\times}1.6mm$. Return loss is more than 10 dB in $3.1{\sim}10.6GHz$. Radiation pattern is about the same that of dipole antenna at all frequency. At measured result, max gain is $1.37{\sim}6.02dBi$ at E-plane.