• Title, Summary, Keyword: TEM

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Design of a TEM Horn Antenna for Impulse Response Measurement System (임펄스 응답 측정 시스템용 TEM 혼 안테나의 설계)

  • 정경호;편성호;정삼영;최재훈
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.7
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    • pp.669-676
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    • 2003
  • In this paper, a novel design method for an ultra-wide band TEM horn antenna is proposed on the basis of parallel plate waveguide theory. A principle of TEM modes generation is analyzed and the characteristics of this antenna are experimentally investigated. The proposed TEM horn antenna has an exponentially tapered structure to increase matching bandwidth. Also, the designed TEM horn has shortened length but increased aperture so that the bandwidth for cutoff frequency is increased. The measured result show that the proposed TEM hem antenna has the frequency band of 75 MHz to 1200 MHz for VSWR less than 2.0 and the bandwidth of the TEM horn becomes more than twice comparing to that of a linearly tapered TEM hem. It is anticipated that the manufactured antenna is applicable to UWB systems for impulse response measurement.

Solution of higher order mode cutoff frequencies in TEM cells by Galerkin method (Galerkin 법을 적용한 TEM cell들의 고조 모드 차단 주파수 해석)

  • 윤재훈;이혁재;김정기
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.24 no.10B
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    • pp.1885-1894
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    • 1999
  • The higher mode cutoff frequencies in Crawford TEM cells computed by the Galerkin method(GM) describe in this paper. The authors also report the half mode boundaries to solve not only the cut-off frequencies of symmetric TEM cells and those of asymmetric TEM cells. It is shown that the measured resonant frequencies of the present symmetric TEM cells and a designed asymmetric TEM cell are agreed with the calculated results.

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Annealing Experiments of Albite Using Optical Microscope Heating Stage (광학현미경 가열실험대를 이용한 알바이트의 등온가열 실험 연구)

  • Park Byung-Kyu;Kim Yong-Jun;Kim Youn-Joong
    • Journal of the Mineralogical Society of Korea
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    • v.18 no.4
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    • pp.289-299
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    • 2005
  • Annealing experiments on albite powders, thin sections, and TEM specimens have been performed utilizing an optical microscope heating stage. Sample orientations were determined by optical microscope and XRD, and then confirmed by TEM diffraction patterns. Partial melting of samples occurred at $1030^{\circ}C$-l2 hr for powder, but at $1060^{\circ}C$-12 hr for TEM specimen. It is difficult to get TEM images of albite microstructures above this temperature due to thickening and the amorphous phase of the melted part. Correlative studies between optical microscopy and TEM indicated that the $1050^{\circ}C$-12 hr annealing in ambient condition was most adequate to observe tweed microstructures in albite through TEM. In situ TEM heating experiments for direct observation of tweed microstructures in albite may require annealing at slightly higher temperatures than $1050^{\circ}C$ considering the high vacuum condition inside TEM.

Dispersion Analysis for Rectangular Coaxial Line and TEM Cell (네모 동축선과 TEM 셀의 분산관계 해석)

  • Cho, Yong-Heui
    • The Journal of the Korea Contents Association
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    • v.7 no.1
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    • pp.124-130
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    • 2007
  • A rectangular coaxial line is mainly utilized as a transition structure from a coaxial line to a rectangular waveguide. A TEM cell is also widely used to measure the EMC characteristics of a DUT. In order to understand the operations of a rectangular coaxial line and a TEM cell, it is essential to analyze the dispersion relations of a rectangular coaxial line and a TEM cell. In this paper, we present simple yet accurate dispersion relations of the TE and TM higher modes based on the TEM mode. Manipulating a mode-matching technique and a Green's function approach allows us to obtain the analytic dispersion equations of a rectangular coaxial line and a TEM cell. In our approach, a rectangular coaxial line is divided into four L-blocks and its electromagnetic fields representations are easily obtained with a superposition. To verify the convergence of our dispersion relations, we perform numerical computations and compare our results with those of FDTD.

Determination of an Underground Seawater Flow Using a TEM Decay Curve (TEM감쇠곡선을 이용한 해수의 지하 유동현상 파악)

  • 황학수;문창규;이상규;이태섭
    • Economic and Environmental Geology
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    • v.34 no.5
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    • pp.499-506
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    • 2001
  • The geophysical monitoring technique using the high resolution time-domain electromagnetic (TEM) method with a coincident loop away was applied for determination of an underground seawater flow in the coastal areas. In comparison of the TEM monitoring to direct current (DC) resistivity monitoring, the TEM response to the under ground seawater flow is less sensitive than the DC resistivity response. However, the TEM monitoring is more effective in terms of measuring time, survey expense, and real-time data processing than the DC monitoring thor evaluating the spatial distribution of the fresh water-seawater transition zone in a regional area.

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그래핀 합성 및 TEM grid막으로의 응용

  • Lee, Byeong-Ju;Jeong, Gu-Hwan
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.461-461
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    • 2011
  • 최근의 나노기술의 발전과 함께 나노미터크기의 물질들의 물성과 미세구조 등을 분석하기 위한 노력들이 활발히 이루어지고 있다. 투과전자현미경(transmission electron microscope; TEM)은 나노물질의 미세구조 관찰, 화학성분 분석, 전자기적 특성평가가 가능한 초정밀 분석장비이다. TEM 관찰을 위한 시편의 제작방법중 TEM 그리드(grid)를 사용하는 방법은, 분석하고자 하는 물질을 망(mesh) 형태의 그리드에 도포하여 샘플을 준비하는 방법으로 다른 방법에 비해 아주 빠르고 간편한 장점이 있다. 그러나 TEM 그리드에 나노물질을 분산/도포하여 공중에 떠있는 형태로 샘플을 제작하려면, 나노물질이 mesh 사이로 빠져나오지 않도록 그리드 mesh의 간격이 아주 미세하여야 하는데, 일반적으로 mesh의 크기가 미세할수록 그리드의 가격은 높아진다. 또한 기존에 사용되고 있는 비정질 탄소박막으로 덮여진 그리드는 극미세 크기의 나노물질 및 탄소나노물질을 분석할 경우, 고해상도의 TEM상을 얻는데 한계가 있다. 한편 그래핀은 2차원의 육각판상의 구조로 탄소원자가 빼곡히 채워진 흑연 한 층의 나노재료이다. 이는 원자단위 두께로 가장 얇은 물질로서 기계적 강도가 우수하여 지지막으로의 응용이 가능하다고 알려져 있다. 따라서 TEM grid막으로 사용할 경우 기존의 고가의 미세한 mesh가 형성된 그리드를 사용하지 않아도 나노물질을 효과적으로 분석할 수 있을 것으로 예상 된다. 본 연구에서는 열화학증기증착법(thermal chemical vapor deposition; TCVD)을 이용하여 300 nm 두께의 니켈박막이 증착된 기판위에 대면적으로 합성한 그래핀을 TEM 관찰용 그리드 위에 전사(transfer)함으로써 나노물질이 그리드 mesh사이로 빠져나오지 않는 저가의 TEM 그리드 제작 방법 및 응용 가능성에 대하여 보고한다.

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TEM specimen preparation for observation of Cu oxides precipitated in the polyimide film and characterization of Cu oxide particles (폴리이미드박막내에 석출된 구리산화물 관찰을 위한 TEM 시편 제조와 구리산화물 분석)

  • You, Young-Sek;Kim, Young-Ho
    • Applied Microscopy
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    • v.25 no.1
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    • pp.130-138
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    • 1995
  • TEM specimen preparation methods have been examined to characterize Cu oxide particles in the polyimide film. Polyimide films were prepared by coating polyamic acid onto Cu films which had been deposited on TEM-mask and glass substrates and Cu foil, followed by thermal curing. In case of TEM-mask, direct observation was possible without further preparation. In other cases, TEM specimen were made by separating polyimide film from the substrate. Polyimide films were removed from glass and Cu foil by dissolving glass in HF solution and Cu foil in $H_{2}SO_{4}$ solution. TEM-mask observation confirms that fine $Cu_{2}O$ particles precipitate in the polyimide as a result of reaction of polyamic acid with Cu. However $Cu_{2}O$ particle reacts with HF and $H_{2}SO_{4}$ solution during dissolving the substrate and interpretation could be misled. It is concluded characterization of $Cu_{2}O$ particle in polyimide using TEM-mask is better than other methods.

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Analysis of Cutoff Frequencies of TEM Cell using FDTD (FDTD를 이용한 TEM Cell의 차단주파수에 관한 분석)

  • 윤영설;공순철;윤재훈;김정기
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.10 no.1
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    • pp.63-69
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    • 1999
  • In this paper, we analyze the cutoff frequencies of the TEM Cells by the FDTD, and introduce new boundary condition for the FDTD to identify the modes. Then, we confirm efficiency of the FDTD comparing results in previous papers. We also give our opinion from the results by FDTD to the arguments, which is resulted from different results about cutoff frequencies in the TEM Cells, especially the symmetric TEM Cells.

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Analysis of Aircraft Upset through TEM and Improvement of UPRT (항공기 비정상 자세 사고의 TEM 분류 및 UPRT 향상에 관한 연구)

  • Choi, Jin-Kook;Jeon, Seung-Joon
    • The Journal of the Korea Contents Association
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    • v.19 no.11
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    • pp.365-374
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    • 2019
  • Loss of Control in Flight(LOC-I) due to aircraft upset attitude has the highest air accident rate, and International Aviation Institute such as ICAO and FAA recommended flight crew to operate aircraft safely through UPRT(Upset Prevention & Recovery Training) program. ICAO has selected Loss of Control(LOC) as key safety indicator, and recommended to respond using TEM(Threat and Error Management). However there are not much specific treats and errors classified for UPRT programs using real TEM based on evidences. This study intends to consider the importance of UPRT through the introduction of UPRT and accident analysis using TEM. Typical upset accidents were classified to common threats as IFR, inadequate training, Automation surprise, and inexperienced copilots. The common errors were cross-check, speed and altitude deviation, callouts, communication, thrust and stall action fail. The undesired aircraft states were inadequate automation mode, Deviation of speed and vertical, stall, and crash. These suggest areas to improve UPRT.

A study on the electromagnetic field distributions in a W-TEM cell having wire array as an inner conductor (와이어 어레이 형태의 내부 도체를 갖는 W-TEM cell의 전자계 분포 특성에 관한 연구)

  • 김명훈;이중근
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.6
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    • pp.1576-1586
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    • 1996
  • The subject of this paper is the analysis of a Wire-TEM cell(W-TEM cell) which has an inner wire array rather than a metallic septum;its basic structure is similiar to a NBS TEM cell. To verify improved performances of this W-TEM cell as a standard EM field generator, well-known quasi-static approximations are employed and their resultant ingegral equations are numerically analyzed by moment method. Although the electric field strength of a W-TEM cell is 1.4 dB lower than tht of a NBS TEM cell, the uniformity of EM field patterns in a W-TEM cell is improved. It is also shown that the EM field distortions resulting from loading by the conditing objects under test(loading effects), are decreased considerably. This paper also deals with the investigations about relationship between the EM field distributions and the number of wire composing the inner conductor. Finally, the experimental analysis is performed on the practical model which is built on the basis of the design variables brought out by the theoretical andnumerical analysis.

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