• Title/Summary/Keyword: scattering currents

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Y$Ba_2$$Cu_3$$O_7$ 모서리 죠셉슨 접합의 균일성 (Uniformity of $YBa_2$$Cu_3$$O_7$ Step-edge Josephson Junctions)

  • 이순걸;황윤석;김진태
    • Progress in Superconductivity
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    • 제2권2호
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    • pp.81-85
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    • 2001
  • Uniformity of critical currents of YBa$_2$Cu$_3$O$_{7}$ step-edge Josephson junctions on SrTiO$_3$(100) substrates have been studied at various step-line angles. 15 identical junctions were made in series on each substrate that has a long straight step-edge line. Step-line angles studied were 0$^{\circ}$, 15$^{\circ}$, 30$^{\circ}$, and 45$^{\circ}$with respect to the crystal major axes of the substrate. Scattering of junction critical currents among the junctions on the same substrate increased with the step-line angle. Current-voltage curves showed standard resistively-shunted-junction (RSJ) characteristics in most of the 0$^{\circ}$junctions. However, the number of junctions showing RSJ behavior decreased with increasing step-line angle. Variations of detailed microstructure of the step-edge among junctions, which are coupled with the d-wave symmetry of YBa$_2$Cu$_3$O$_{7}$, are believed to be the main cause for the nonuniformity in the critical current.ent.

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원격탐사자료를 이용한 인공구조물 건설에 의한 군산 유부도 조간대의 지형변화 및 표면특성에 관한 연구 (Research of Topography Changes by Artificial Structures and Scattering Mechanism in Yoobu-Do Inter-tidal Flat Using Remote Sensing Data)

  • ;김덕진;김승희
    • 대한원격탐사학회지
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    • 제29권1호
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    • pp.57-68
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    • 2013
  • 20세기 후반부터 유부도 주위에서 하구언 축조 등 비교적 큰 규모의 간척사업들이 진행되었다. 이러한 간척사업의 시작으로 인공구조물들이 연안에 축조됨에 따라 주변 해역의 해류, 조위 및 조류의 변화를 야기하여 퇴적 및 침식으로 인한 연안지형의 변화가 예상된다. 따라서 이 연구에서는 유부도 조간대를 포함하는 Landsat TM/ETM+자료를 1998년부터 2012년까지 획득한 후 waterline 기법을 적용하여 인공구조물 축조에 의한 지형변화를 탐지하였다. 그 결과 유부도의 동쪽, 북동쪽, 서쪽 조간대에서 주로 퇴적이 일어났으며 그 면적이 약 4.5 $km^2$ 이상 되었다. 한편, RADARSAT-2의 완전편파 SAR자료에 Freeman-Durden decomposition을 적용하여 퇴적이 뚜렷이 일어난 지역에 대한 산란특성을 분석하였다. 그 결과 동쪽 퇴적지역은 서쪽 및 북동쪽의 퇴적지역과는 다른 산란특징이 관찰되었으며, 이는 퇴적환경의 차이로 인해 다른 종류의 퇴적물이 퇴적되어 발생한 것으로 여겨진다.

PMCHW 적분식을 이용한 3차원 유전체의 전자파 과도산란 (Transient Electromagnetic Scattering from 3-Dimensional Dielectric Objects by Using PMCHW Integral Equation)

  • 서정훈;한상호;안현수;정백호
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2003년도 추계학술대회 논문집 전기물성,응용부문
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    • pp.78-81
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    • 2003
  • In this paper, we analyze the transient electromagnetic response from three-dimensional dielectric bodies using a time-domain PMCHW (Poggio, Miller, Chang, Harrington, Wu) formulation. The time-domain unknown coefficients of the equivalent currents are approximated by a set of orthonormal basis functions that are derived from the Laguerre polynomials. Numerical results computed by the proposed method are presented.

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ZnO 바리스터 미세조직 균일화와 새지 에너지 내량 향상에 관한 연구 (A Study on the Microstructral Uniformity and Surge Energy Capability of ZnO Varistor)

  • 한세원;조한구;서형권;정세영
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 1999년도 추계학술대회 논문집
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    • pp.637-639
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    • 1999
  • ZnO varistors have been widely used to protect power system and electronic system against overvoltages based on their excellent nonlinearity. In order to increase their protection capability, ZnO varistors are chosen by several electrical parameters according to their applications, namely 1mA DC voltage, 1eakage currents, impulse residual voltages, withstanding capability to impulse surge, and energy absorption capability. But these Parameters have scattering properties due to the nonuniformity of electrical characteristics. In this study, the effect of the microstructrual nonuniformity on the surge absorption capability of ZnO varistors.

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거친 도체 표면 후방 산란 계산을 위한 모서리 효과 저감 기법 (Edge-Effect Reduction Technique to Compute the Backscattering from Randomly Rough Conducting Surfaces)

  • 황지환;권순구;오이석
    • 한국전자파학회논문지
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    • 제25권5호
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    • pp.585-591
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    • 2014
  • 본 연구에서는 roof-top 기저함수와 모서리 효과(edge-effect)를 저감시키기 위해 개선된 윈도우 함수를 적용한 2차원 모멘트법의 수치 해석 기법과 그 결과들을 제시한다. 모멘트법을 이용한 2차원 수치 산란 모델은 roof-top 기저함수를 적용하여 임의 방향 표면 전류 성분 표현과 계산 효율을 높였으며, 수치적으로 생성된 표면 양 끝단의 모서리에서 발생되는 산란 특성을 제거하기 위해 입사각별 가중치를 둔 개선된 윈도우 함수를 제안한다. 또한, 거칠기가 있는 표면의 산란 특성 분석을 위한 개선된 2차원 수치 해석 기법의 정확도를 검증하기 위해서 SPM(Small Perturbation Model)의 계산결과와 비교/분석하였다.

Broadband metamaterial absorber using resistive layers

  • Kim, Y.J.;Yoo, Y.J.;Hwang, J.S.;Son, H.M.;Rhee, J.Y.;Kim, K.W.;Lee, Y. P.
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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    • pp.359.1-359.1
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    • 2016
  • The electromagnetic (EM) properties of media, such as propagation, focusing and scattering, strongly rely on the electric permittivity and the magnetic permeability of media. Recently, artificially-created metamaterials (MMs) composed of periodically-arranged unit cells with tailored electric permittivity and magnetic permeability have drawn wide interest due to their capability of adjusting the EM response. MM absorbers using the conventional sandwich structures usually have very high absorption at a certain frequency, and the absorption properties of MMs can be adjusted simply by changing the geometrical parameters of unit cell. In this work, we suggested an incident-angle-independent broadband perfect absorber based on resistive layers. We analyze the absorption mechanism based on the impedance matching with the free space and the distribution of surface currents at specific frequencies. From the simulation, the absorption was expected to be higher than 96% in 1.4-6.0 GHz. The corresponding experimental absorption was found to be higher than 96% in 1.4-4.0 GHz, and the absorption turned out to be slightly lower than 96% in 4.0-6.0 GHz owing to the irregularity in the thickness of resistive layers.

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RCS Numerical Simulation of Stealth Modified Three-Surface Aircraft

  • Cheng, Liangliang;Yue, Kuizhi;Xing, CuiFang;Yu, Dazhao
    • International Journal of Aeronautical and Space Sciences
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    • 제17권1호
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    • pp.101-108
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    • 2016
  • The RCS characteristics of stealth modified three-surface aircraft are analyzed in this paper. Prototype A is built with CATIA software and the three-dimensional digital models of modified stealth three-surface B and C are also designed based on carrier-based aircraft Su-33; the numerical simulation of RCS characteristics of three-surface aircraft is conducted with RCSAnsys software based on physical optics method and the method of equivalent currents; The following results are obtained by comparative analysis and mathematical statistics: (1) by the use of physical optics method and equivalent electromagnetic current method, the scattering intensity for each part of the model and RCS characteristic of the aircraft can be analyzed efficiently and accurately; (2) compared with model A, the mean RCS value of model B is reduced to 14.1% in forward direction and 48.1% in lateral direction; (3) compared with model A, the mean RCS value of model C decreases to 11.4% in forward direction and 21.6% in lateral direction. The results are expected to provide theoretical basis and technical support to the conceptual design of aircraft and stealth technology research.

Analysis of Flat-Band-Voltage Dependent Breakdown Voltage for 10 nm Double Gate MOSFET

  • Jung, Hakkee;Dimitrijev, Sima
    • Journal of information and communication convergence engineering
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    • 제16권1호
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    • pp.43-47
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    • 2018
  • The existing modeling of avalanche dominated breakdown in double gate MOSFETs (DGMOSFETs) is not relevant for 10 nm gate lengths, because the avalanche mechanism does not occur when the channel length approaches the carrier scattering length. This paper focuses on the punch through mechanism to analyze the breakdown characteristics in 10 nm DGMOSFETs. The analysis is based on an analytical model for the thermionic-emission and tunneling currents, which is based on two-dimensional distributions of the electric potential, obtained from the Poisson equation, and the Wentzel-Kramers-Brillouin (WKB) approximation for the tunneling probability. The analysis shows that corresponding flat-band-voltage for fixed threshold voltage has a significant impact on the breakdown voltage. To investigate ambiguousness of number of dopants in channel, we compared breakdown voltages of high doping and undoped DGMOSFET and show undoped DGMOSFET is more realistic due to simple flat-band-voltage shift. Given that the flat-band-voltage is a process dependent parameter, the new model can be used to quantify the impact of process-parameter fluctuations on the breakdown voltage.

Bi-2223선재의 임계전류 측정기술 비교 (Interlaboratory Comparison of Critical Current Measurements on Ag-sheathed Bi-2223 tapes)

  • Lee, Kyu-Won;Han, Gi-Youl
    • Progress in Superconductivity
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    • 제3권1호
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    • pp.99-103
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    • 2001
  • We have conducted two runs of interlaboratory comparison on Ag-sheathed Bi-2223 tapes to evaluate the level of measurement techniques for the critical current measurement. Two classes of specimens were prepared for parallel and serial routings and sent to four participating laboratories. The critical currents of specimens were measured at 77 K in zero magnetic field. In the first comparison, we used twenty different Bi-2223 tapes as specimens for comparison and participating laboratories measured the specimens using their own instruments and procedures. As a result, the scattering of data on the first comparison showed -3.0% to +l2.2% for the parallel routing and -0.7% to +l5.1% for the serial routing. Major sources of these variations were attributed to different measurement techniques. Thus, the second comparison of measurement was done on the same specimens under specified measurement conditions, particularly in terms of cooling procedure and sweep rate of the test current. The variations for the second comparison were decreased -3.1% to +3.2% far the parallel routing and -1.8% to +7.7% fur the serial routing.

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Fracture characterization with high frequency single-hole EM survey

  • Seo, Soon-Jee;Song, Yoon-Ho;Kim, Hee-Joon;Lee, Ki-Ha;Suh, Jung-Hee
    • 대한자원환경지질학회:학술대회논문집
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    • 대한자원환경지질학회 1999년도 춘계 공동학술발표회
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    • pp.90-93
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    • 1999
  • We present a high frequency electromagnetic (EM) inversion scheme for detecting and characterizing a fracture using single-hole data. At high frequencies, say above tens of mega-hertz, since displacement currents cannot be ignored, electrical permittivity as well as electrical conductivity is to be considered together for analyzing the EM scattering data. In this paper, we have developed a three-step inversion scheme to map the fracture and to evaluate its electrical conductivity and permittivity. We performed EM profiling along the z-axis using three-component receivers for each source. The model was excited by a vertical magnetic dipole and the resistant magnetic fields were inverted using the non-linear least-squares method. Background resistivity and permittivity were easily obtained using vertical magnetic fields below 1 MHz and above 10 MHz, respectively. Both the vertical and dipping sheets were successfully mapped using the phase difference between 40 and 41 MHz. The electrical property of the sheet was well resolved using the information obtained in the previous two steps and secondary magnetic fields. Our study shows the potential of imaging the fracture in single-hole survey environment using the high frequency EM method.

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