• Title/Summary/Keyword: Poisson's equation

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Creep Behavior of Plastics Used in Automobile Instrument Panels (자동차 인스트루먼트 패널에 사용되는 플라스틱의 크리프 거동)

  • Kim, Young-Sam;Jeon, Chi-Hoon;Tumur-Ochir, Erdenebat;Yum, Young-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.12
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    • pp.1549-1556
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    • 2011
  • Tensile and creep tests were performed at various temperatures to investigate the mechanical properties of plastics used in automotive instrument panels. Mechanical properties such as Young's modulus and Poisson's ratios changed markedly with the test temperature. Three-point bending creep tests were performed for three kinds of plastics under four loading conditions. Coefficients in the time-hardening power law creep equation were obtained from the experiment, and the creep behavior was represented by a simple expression. The results of finite element creep analysis showed good agreement with the experimental results, while the difference between the numerical and experimental results increased with the load.

Determination of Deformation Modulus of Rock Mass with Measured Tunnel Displacement (측정된 터널변위에 의한 암반 변형계수의 결정)

  • Park, Jae-Woo;Park, Eun-Gyu;Kim, Gyo-Won
    • The Journal of Engineering Geology
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    • v.17 no.4
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    • pp.655-664
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    • 2007
  • The major geotechnical parameters employed in tunnel design are deformation modulus, Poisson's ratio, friction angle, cohesion, etc. Among these parameters, the deformation modulus is the most significant parameter in tunnel deformation. However, determination of the modulus for rock mass by means of tests is very difficult due to factors affecting including discontinuities and sample size, etc. Thus input values used in the numerical analysis are generally determined by empirical method. A numerical analysis on tunnel was conducted with geotechnical parameters determined through the geological field mapping, laboratory tests, and evaluation of boring data, and some discrepancy between the computed result and tunnel displacements measured was found. Thus, further analyses by changing the deformation modulus of rock mass were performed to determine a relationship between the modulus and computed displacement. Data from two tunnel sites were used to verify the applicability of the proposed method and a correlative equation between deformation modulus and tunnel displacement is proposed. The deformation modulus of rock mass was around 30-40% of young's modulus of intact rock in these cases.

CdZnTe Detector for Computed Tomography based on Weighting Potential (가중 퍼텐셜에 기초한 CT용 CdZnTe 소자 설계)

  • Lim, Hyunjong;Park, Chansun;Kim, Jungsu;Kim, Jungmin;Choi, Jonghak;Kim, KiHyun
    • Journal of radiological science and technology
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    • v.39 no.1
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    • pp.35-42
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    • 2016
  • Room-temperature operating CdZnTe(CZT) material is an innovative radiation detector which could reduce the patient dose to one-tenth level of conventional CT (Computed Tomography) and mammography system. The pixel and pixel pitch in the imaging device determine the conversion efficiency of incident X-or gamma-ray and the cross-talk of signal, that is, image quality of detector system. The weighting potential is the virtual potential determined by the position and geometry of electrode. The weighting potential obtained by computer-based simulation in solving Poisson equation with proper boundaries condition. The pixel was optimized by considering the CIE (charge induced efficiency) and the signal cross-talk in CT detector system. The pixel pitch was 1-mm and the detector thickness was 2-mm in the simulation. The optimized pixel size and inter-pixel distance for maximizing the CIE and minimizing the signal cross-talk is about $750{\mu}m$ and $125{\mu}m$, respectively.

Analysis of Threshold Voltage Characteristics for Double Gate MOSFET Based on Scaling Theory (스켈링이론에 따른 DGMOSFET의 문턱전압 특성분석)

  • Jung, Hak-Kee;Han, Ji-Hyung;Jeong, Dong-Soo
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2012.05a
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    • pp.683-685
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    • 2012
  • This paper have presented the analysis of the change for threshold voltage and drain induced barrier lowering among short channel effects occurred in subthreshold region for double gate(DG) MOSFET with two gates to be next-generation devices, based on scaling theory. To obtain the analytical solution of Poisson's equation, Gaussian function been used as carrier distribution to analyze closely for experimental results, and the threshold characteristics have been analyzed for device parameters such as channel thickness and doping concentration and projected range and standard projected deviation of Gaussian function. Since this potential model has been verified in the previous papers, we have used this model to analyze the threshold chatacteristics. As a result to apply scaling theory, we know the threshold voltage and drain induced barrier lowering is changed, and the deviation rate is changed for device parameters for DGMOSFET.

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Subthreshold Characteristics of Double Gate MOSFET for Gaussian Function Distribution (가우스함수의 형태에 따른 DGMOSFET의 문턱전압이하특성)

  • Jung, Hak-Kee;Han, Ji-Hyung;Lee, Jong-In;Kwon, Oh-Shin
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2012.05a
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    • pp.716-718
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    • 2012
  • This paper have presented the change for subthreshold characteristics for double gate(DG) MOSFET based on scaling theory and the shape of Gaussian function. To obtain the analytical solution of Poisson's equation, Gaussian function been used as carrier distribution and consequently potential distributions have been analyzed closely for experimental results, and the subthreshold characteristics have been analyzed for the shape parameters of Gaussian function such as projected range and standard projected deviation. Since this potential model has been verified in the previous papers, we have used this model to analyze the subthreshold chatacteristics. The scaling theory is to sustain constant outputs for the change of device parameters. As a result to apply the scaling theory for DGMOSFET, we know the subthreshold characteristics have been greatly changed, and the change of threshold voltage is bigger relatively.

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Dependence of Drain Induced Barrier Lowering for Ratio of Channel Length vs. Thickness of Asymmetric Double Gate MOSFET (비대칭 DGMOSFET에서 채널길이와 두께 비에 따른 DIBL 의존성 분석)

  • Jung, Hakkee
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.19 no.6
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    • pp.1399-1404
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    • 2015
  • This paper analyzed the phenomenon of drain induced barrier lowering(DIBL) for the ratio of channel length vs. thickness of asymmetric double gate(DG) MOSFET. DIBL, the important secondary effect, is occurred for short channel MOSFET in which drain voltage influences on potential barrier height of source, and significantly affects on transistor characteristics such as threshold voltage movement. The series potential distribution is derived from Poisson's equation to analyze DIBL, and threshold voltage is defined by top gate voltage of asymmetric DGMOSFET in case the off current is 10-7 A/m. Since asymmetric DGMOSFET has the advantage that channel length and channel thickness can significantly minimize, and short channel effects reduce, DIBL is investigated for the ratio of channel length vs. thickness in this study. As a results, DIBL is greatly influenced by the ratio of channel length vs. thickness. We also know DIBL is greatly changed for bottom gate voltage, top/bottom gate oxide thickness and channel doping concentration.

Influence of Ratio of Top and Bottom Oxide Thickness on Subthreshold Swing for Asymmetric Double Gate MOSFET (비대칭 이중게이트 MOSFET에서 상단과 하단 산화막 두께비가 문턱전압이하 스윙에 미치는 영향)

  • Jung, Hakkee
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.20 no.3
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    • pp.571-576
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    • 2016
  • Asymmetric double gate(DG) MOSFET has the different top and bottom gate oxides thicknesses. It is analyzed the deviation of subthreshold swing(SS) and conduction path for the ratio of top and bottom gate oxide thickness of asymmetric DGMOSFET. SS varied along with conduction path, and conduction path varied with top and bottom gate oxide thickness. The asymmetric DGMOSFET became valuable device to reduce the short channel effects like degradation of SS. SSs were obtained from analytical potential distribution by Poisson's equation, and it was analyzed how the ratio of top and bottom oxide thickness influenced on conduction path and SS. SSs and conduction path were greatly influenced by the ratio of top and bottom gate oxide thickness. Bottom gate voltage cause significant influence on SS, and SS are changed with a range of 200 mV/dec for $0<t_{ox2}/t_{ox1}<5$ under bottom voltage of 0.7 V.

Analysis of Subthreshold Swing for Ratio of Channel Length and Thickness of Asymmetric Double Gate MOSFET (비대칭 DGMOSFET의 채널길이와 두께 비에 따른 문턱전압이하 스윙 분석)

  • Jung, Hakkee
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.19 no.3
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    • pp.581-586
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    • 2015
  • This paper has analyzed the variation of subthreshold swing for the ratio of channel length and thickness for asymmetric double gate MOSFET. The asymmetric double gate MOSFET has the advantage that the factors to control the short channel effects increase since top and bottom gate structure can be fabricated differently. The degradation of transport property due to rapid increase of subthreshold swing can be specially reduced in the case of reduction of channel length. However, channel thickness has to be reduced for decrease of channel length from scaling theory. The ratio of channel length vs. thickness becomes the most important factor to determine subthreshold swing. To analyze hermeneutically subthreshold swing, the analytical potential distribution is derived from Poisson's equation, and conduction path and subthreshold swing are calculated for various channel length and thickness. As a result, we know conduction path and subthreshold swing are changed for the ratio of channel length vs. thickness.

Subthreshold Current Model for Threshold Voltage Shift Analysis in Junctionless Cylindrical Surrounding Gate(CSG) MOSFET (무접합 원통형 게이트 MOSFET에서 문턱전압이동 분석을 위한 문턱전압이하 전류 모델)

  • Jung, Hakkee
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.21 no.4
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    • pp.789-794
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    • 2017
  • Subthreshold current model is presented using analytical potential distribution of junctionless cylindrical surrounding-gate (CSG) MOSFET and threshold voltage shift is analyzed by this model. Junctionless CSG MOSFET is significantly outstanding for controllability of gate to carrier flow due to channel surrounded by gate. Poisson's equation is solved using parabolic potential distribution, and subthreshold current model is suggested by center potential distribution derived. Threshold voltage is defined as gate voltage corresponding to subthreshold current of $0.1{\mu}A$, and compared with result of two dimensional simulation. Since results between this model and 2D simulation are good agreement, threshold voltage shift is investigated for channel dimension and doping concentration of junctionless CSG MOSFET. As a result, threshold voltage shift increases for large channel radius and oxide thickness. It is resultingly shown that threshold voltage increases for the large difference of doping concentrations between source/drain and channel.

Chromatic Aberration Correction Method by Considering Local Properties of the Image (영상의 국부적 특성을 고려한 색수차 보정 방법)

  • Kang, Hee;Kang, Moon Gi
    • Journal of the Institute of Electronics and Information Engineers
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    • v.50 no.9
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    • pp.119-126
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    • 2013
  • In this paper, we propose a chromatic aberration removal algorithm in image capture devices, which considers local properties of the image. Chromatic aberration is generated by the fact that the refractive index of the lens is different for different wavelengths, which produces color artifacts on strong edge due to misalignment of RGB channels. Under the characteristics of the artifacts, the proposed algorithm first estimates the regions with the apparent color artifacts as the neighborhoods of the strong edge. In the regions, the proposed algorithm removes the color artifacts by matching the edges of RGB channels. The widely used conventional methods based on global image warping could not remove the color artifacts of longitudinal chromatic aberration and purple fringing identified by the image sensor, whereas the matching process of the proposed method could reduce them. Experimental results show that the proposed algorithm outperforms the conventional methods on objective and subjective criteria.