• 제목/요약/키워드: Surface Active Element

검색결과 61건 처리시간 0.026초

아크 용접에서 구동력에 따른 열 및 물질 유동에 관한 연구

  • 김원훈;나석주
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 1996년도 제7회 학술강연회논문집
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    • pp.27-41
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    • 1996
  • In this study the heat transfer and fluid flow of the molten pool in stationary gas tungsten arc welding using argon shielding gas were investigated. Transporting phenomena from the welding arc to the base material surface, such as current density, heat flux, arc pressure and shear stress acting on the weld pool surface, were taken from the simulation results of the corresponding welding arc. Various driving forces for the weld pool convection were considered, self-induced electromagnetic, surface tension, buoyancy, and impinging plasma arc forces. Furthermore, the effect of surface depression due to the arc pressure acting on the molten pool surface was considered. Because fusion boundary has a curved and unknown shape during welding, a boundary-fitted coordinate system was adopted to precisely describe the boundary for the momentum equation. The numerical model was applied to AISI 304 stainless steel and compared with the experimental results.

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Highly Sensitive and Selective Glucose Sensor Realized by Conducting Polymer Modified Nanoporous PtZn Alloy Electrode

  • Jo, Hyejin;Piao, Hushan;Son, Yongkeun
    • Journal of Electrochemical Science and Technology
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    • 제4권1호
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    • pp.41-45
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    • 2013
  • Platinum is a well known element which shows a significant electrocatalytic activity in many important applications. In glucose sensor, because of the poisoning effect of reaction intermediates and the low surface area, the electrocatalytic activity towards the glucose oxidation is low which cause the low sensitivity. So, we fabricate a nanoporous PtZn alloy electrode by deposition-dissolution method. It provides a high active surface and a large enzyme encapsulating space per unit area when it used for an enzymatic glucose sensor. Glucose oxidase was immobilized on the electrode surface by capping with PEDOT composite and PPDA. The composite and PPDA also can exclude the interference ion such as ascorbic acid and uric acid to improve the selectivity. The surface area was determined by cyclic voltametry method and the surface structure and the element were analyzed by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray spectroscopy (EDX), respectively. The sensitivity is $13.5{\mu}A/mM\;cm^2$. It is a remarkable value with such simply prepared senor has high selectivity.

유한한 기판 크기가 2소자 E-평면 선형 배열 안테나의 방사 특성에 미치는 영향 (Effect of a Finite Substrate Size on the Radiation Characteristics of Two-Element Linear E-plane Array Antennas)

  • 윤영민;김부균
    • 전자공학회논문지
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    • 제49권12호
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    • pp.95-110
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    • 2012
  • 유한한 기판 크기가 2 소자 E-평면 마이크로스트립 패치 선형 위상 배열 안테나의 방사 특성에 미치는 영향에 대하여 연구하였다. 서로 다른 유전상수를 가지는 기판을 이용하여 2 소자 E-평면 배열 안테나의 기판 크기에 따른 평균 능동소자패턴 특성을 분석하고 빔 주사각도에 따른 배열 안테나의 방사패턴 특성을 분석하였다. 전산모의 실험 결과 E-평면상에 배열된 2 소자 배열안테나의 방사패턴은 주로 E-평면 기판 가장자리에서 회절되어 방사되는 필드에 의해 결정되며 안테나 소자 간 상호 결합으로 인한 기생 방사가 배열 안테나의 방사패턴에 미치는 영향은 상대적으로 작게 나타났다. 안테나 소자 중심에서 E-평면 방향 기판 가장자리까지의 거리가 $0.35{\lambda}_0$ 일 때 배열 안테나의 방사패턴 특성이 가장 향상되었다.

유한요소법을 통한 판에서 시간반전 램파의 공간집속성능 규명 (Investigating the Spatial Focusing Performance of Time Reversal Lamb Waves on a Plate through the Finite Element Method)

  • 최정희;이해성;박현우
    • 한국소음진동공학회논문집
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    • 제21권12호
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    • pp.1120-1131
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    • 2011
  • Researches using time reversal acoustics(TRA) for impact localization have been paid attention to recently. Dispersion characteristics of Lamb waves, which restrict the utility of classical nondestructive evaluation based on time-of-flight information, can be compensated through the application of TRA to Lamb waves on a plate. This study investigates the spatial focusing performance of time reversal Lamb waves on a plate using finite element analysis. In particular, the virtual sensor effect caused by multiple wave reflections at the boundaries of a plate is shown to enable the spatial focusing of Lamb waves though a very small number of surface-bonded piezoelectric(PZT) sensors are available. The time window size of forward response signals, are normalized with respect to the number of virtual active sensors. Then their effects on the spatial focusing performance of Lamb waves are investigated.

RIS를 활용한 무선 통신 시스템에서 능동 반사 소자를 활성화하는 기법에 관한 연구 (A study on scheme for activating active elements in RIS aided wireless communication system)

  • 배진수;유승근;송형규
    • 전기전자학회논문지
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    • 제27권4호
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    • pp.425-429
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    • 2023
  • 본 논문에서는 reconfigurable intelligent surface(RIS)의 능동소자를 활성화하는 기법을 제안한다. 최근 RIS는 무선 통신 시스템에서 통신 커버리지와 주파수 효율을 향상기키는 기술로 주목받고 있다. RIS는 수신받는 신호의 위상과 진폭을 조절할 수 있는 기술로 도심과 같이 장애물이 많은 지역에 활용하면 더 좋은 통신 성능을 보장할 수 있다. 하지만 RIS에 의해 신호는 두 번의 페이딩을 겪게 되고 이에 따라 통신 성능의 저하가 발생한다. 최근 이러한 문제를 해결하기 위해 능동 반사 소자를 활용한 RIS가 연구되고 있다. 하지만 RIS 전체를 능동 반사 소자로 활용하게 되면 에너지 소비량이 증가하게 된다. 이에 본 논문에서는 RIS 반사 소자 중 일부만 능동 반사 소자로 활용하는 시스템을 제안하고 활성화되는 능동 반사 소자를 선택하는 기법에 대해 제안한다.

Comparisons of smart damping treatments based on FEM modeling of electromechanical impedance

  • Providakis, C.P.;Kontoni, D.P.N.;Voutetaki, M.E.;Stavroulaki, M.E.
    • Smart Structures and Systems
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    • 제4권1호
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    • pp.35-46
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    • 2008
  • In this paper the authors address the problem of comparing two different smart damping techniques using the numerical modelling of the electro-mechanical impedance for plate structures partially treated with active constrained layer damping treatments. The paper summarizes the modelling procedures including a finite element formulation capable of accounting for the observed behaviour. The example used is a smart cantilever plate structure containing a viscoelastic material (VEM) layer sandwiched between a piezoelectric constrained layer and the host vibrating plate. Comparisons are made between active constrained layer and active damping only and based on the resonance frequency amplitudes of the electrical admittance numerically evaluated at the surface of the piezoelectric model of the vibrating structure.

능동회로에서의 노이즈 규명 및 MPM기법을 통한 저감 (Noise identification on active circuits and reduction using MPM technique)

  • 오경석;이종복;고일관;허춘
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2005년도 제36회 하계학술대회 논문집 D
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    • pp.3063-3065
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    • 2005
  • In the raper, the noise involved on the active circuit is identified using correlation function. In order to identify the unknown noise source location, signals from each points on the system are detected and the location is identified by a concept calico Noise Source Surface. The fault diagnosis method is suggested for each element by identifying the noise source in active circuit using SVM. Experiment is conducted to confirm the validity of the proposed method. Also a method to reduce and control the noise in the system signal by using Matrix Pencil Method is introduced.

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MOVPE 단결정층 성장법 III. 원자층 성장법 (Metal-Organic Vapor Phase Epitaxy III. Atomic Layer Epitaxy)

  • 정원국
    • 한국표면공학회지
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    • 제23권4호
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    • pp.197-207
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    • 1990
  • Atomic layer epitaxy is a relatively new epitaxial pprocess chracterized by the alternate and separate exposure of a susbstrate surface to the reactants contaning the constituent element of a compound semicoductror. The ideal ALE is expected to provide sevral advantageous as petcts for growing complicated heterostrutures such as relativly easy controls of the layer thinkness down to a monolayer and in forming abrupt heterointerfaces though monolayer self-saturatio of the growth. In addition, since ALE is stongly dependent on the surface reaction, the growth can also be controlled by photo-excitation which provides activation can be energies for each step of the reaction paths. The local growth acceleration by photo-excitation can be exploited for growing several device strures on the same wafer, which provides another important practical advantage. The ALE growth of GaAs has advanced to the point the laser opertion has been achieved from AlGs/GaAs quantun well structures where thee active layers were grown by thermal and Ar-laser assisted ALE. The status of the ALE growth of GaAs and other III-V compounds will be reviewed with respect to the growth saturation behavior and the electrical properties of the grown crystals.

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코로나방전에 의한 polyethylene terephthalate 필름의 표면처리 (Surface treatment of polyethylene terephthalate films by corona discharge)

  • 김명룡
    • E2M - 전기 전자와 첨단 소재
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    • 제8권3호
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    • pp.316-323
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    • 1995
  • A vital step in magnetic tape manufacturing is the surface modification of polymer substrate prior to ink application. A critical element for good adhesion of magnetic ink on polymeric substrate is the ability to join ink in cost-effective manner. Corona discharging is one of the effective methods of modifying polymer surface to improve adhesion while maintaining the desirable properties of the film itself. Surface treatment by corona which is exposure of film surface to electron or ion bombardment, rather than mere exposure to active species, like atomic oxygen or ozone, can enhance adhesion by removing contaminant, electret, roughening surface, and/or introducing reactive chemical groups. Reactive neutrals, ions, electron and photons generated during the corona treatment interact simultaneously with polymers to alter surface chemical composition, wettability, and thus film adhesion. However, it is highly recommended that extensive chains scission be avoided because it can lead to side-effect by forming sticky matter, resulting in dropouts. This paper reviews principles of surface preparation of polymer substrate by corona discharging. In addition, the experimental section provides a description of parameter optimization on corona discharging treatment and its side-effect. Experimental results are discussed in terms of surface wetting as determined by contact angle measurements.

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판의 충격위치 추정을 위한 시간반전 램파의 공간모임성능 규명 (Investigating the Spatial Focusing Performance of Time Reversal Lamb waves for Impact Localization on a Plate)

  • 박현우
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2011년도 추계학술대회 논문집
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    • pp.418-429
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    • 2011
  • Researches using time reversal acoustics (TRA) for impact localization have been paid attention to recently. Dispersion characteristics of Lamb waves, which restrict the utility of classical nondestructive evaluation based on time-of-flight information, can be compensated through the application of TRA to Lamb waves on a plate. This study investigates the spatial focusing performance of time reversal Lamb waves on a plate using finite element analysis. In particular, the virtual sensor effect caused by multiple wave reflections at the boundaries of the plate is shown to enable the spatial focusing of Lamb waves though a very small number of surface-bonded piezoelectric (PZT) sensors are available. The time window size of forward response signals, are normalized with respect to the number of virtual active sensors. Then their effects on the spatial focusing performance of Lamb waves are investigated.

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