• Title/Summary/Keyword: Central difference method

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Interval Scan Inspection Technique for Contact Failure of Advanced DRAM Process using Electron Beam-Inspection System

  • Oh, J.H.;Kwon, G.;Mun, D.Y.;Kim, D.J.;Han, I.K.;Yoo, H.W.;Jo, J.C.;Ominami, Y.;Ninomiya, T.;Nozoe, M.
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.12 no.1
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    • pp.34-40
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    • 2012
  • We have developed a highly sensitive inspection technique based on an electron beam inspection for detecting the contact failure of a poly-Si plugged layer. It was difficult to distinguish the contact failure from normal landing plugs with high impedance. Normally, the thermal annealing method has been used to decrease the impedance of poly-Si plugs and this method increases the difference of charged characteristics and voltage contrast. However, the additional process made the loss of time and broke down the device characteristics. Here, the interval scanning method without thermal annealing was effectively applied to enhance the difference of surface voltage between well-contacted poly-Si plugs and incomplete contact plugs. It is extremely useful to detect the contact failures of non-annealed plug contacts with high impedance.

Dynamic rod worth measurement method based on eqilibrium-kinetics status

  • Lee, Eun-Ki;Jo, YuGwon;Lee, Hwan-Soo
    • Nuclear Engineering and Technology
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    • v.54 no.3
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    • pp.781-789
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    • 2022
  • KHNP had licensed Dynamic Control rod Reactivity Measurement (DCRM) method using detector current signals of PWRs in 2006. The method has been applied to all PWRs in Korea for about 15 years successfully. However, the original method was inapplicable to PWRs using low-sensitivity integral fission chamber as ex-core detectors because of their pulse pile-up and the nonlinearity of the mean-square voltage at low power region. Therefore, to overcome this disadvantage, a modified method, DCRM-EK, was developed using kinetics behavior after equilibrium condition where the pulse counts maintain the maximum value before pulse pile-up. Overall measurement, analysis procedure, and related computer codes were changed slightly to reflect the site test condition. The new method was applied to a total of 15 control rods of 1000 MWe and 1400 MWe PWRs in Korea with worths in the range of 200 pcm -1200 pcm. The results show the average difference of -0.4% and the maximum difference of 7.1% compared to the design values. Therefore, the new DCRM-EK will be applied to PWRs using low sensitivity integral fission chambers, and also can replace the original DCRM when the evaluation fails by big noises present in current or voltage signals of uncompensated/compensated ion chambers.

A Generalized Finite Difference Method for Solving Fokker-Planck-Kolmogorov Equations

  • Zhao, Li;Yun, Gun Jin
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.4
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    • pp.816-826
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    • 2017
  • In this paper, a generalized discretization scheme is proposed that can derive general-order finite difference equations representing the joint probability density function of dynamic response of stochastic systems. The various order of finite difference equations are applied to solutions of the Fokker-Planck-Kolmogorov (FPK) equation. The finite difference equations derived by the proposed method can greatly increase accuracy even at the tail parts of the probability density function, giving accurate reliability estimations. Compared with exact solutions and finite element solutions, the generalized finite difference method showed increasing accuracy as the order increases. With the proposed method, it is allowed to use different orders and types (i.e. forward, central or backward) of discretization in the finite difference method to solve FPK and other partial differential equations in various engineering fields having requirements of accuracy or specific boundary conditions.

A Study on a Signal Processing Method for Detection of the Weld seam by Using Laser Displacement Sensor (레이저 변위센서를 이용한 용접선 검출에서 신호처리에 관한 연구)

  • ;;Kim, J. W.
    • Journal of Welding and Joining
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    • v.13 no.4
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    • pp.65-74
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    • 1995
  • The weld seam tracking sensor is indispensable to improve the flexibility of automatic arc welding systems. Among the position sensing methods available, a laser displacement sensor is one of the most prevailing methods. In this study, a laser displacement sensor was examined on detecting the weld seam of lap joints in sheet metal arc welding. The output signal of the laser displacement sensor may ontain severe fluctuation from the effect of arc light, spatters, fume, etc. So a variety of signal processing methods was applied to smooth the output signal of the sensor. And then the weld joint was determined by using the central difference method. It was revealed that the quadratic mean method plays an important role in detecting the weld seam during welding especially.

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Dynamic Instability Analysis of Euler Column under Impact Loading (충격하중을 받는 Euler기둥의 동적좌굴 해석)

  • 김형열
    • Computational Structural Engineering
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    • v.9 no.3
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    • pp.187-197
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    • 1996
  • An explicit direct time integration method based solution algorithm is presented to predict dynamic buckling response of Euler column. On the basis of large deflection beam theory, a plane frame finite element is formulated and implemented into the solution algorithm. The element formulation takes into account geometrical nonlinearity and overall buckling of steel structural frames. The solution algorithm employs the central difference method. Using the computer program developed by the author, dynamic instability behavior of Euler column under impact loading is investigated by considering the time variation of load, load magnitude, and load duration. The free vibration of Euler column caused by a short duration impact load is also studied. The validity and efficiency of the present formulation and solution algorithm are verified through illustrative numerical examples.

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CFD based simulations of flutter characteristics of ideal thin plates with and without central slot

  • Zhu, Zhi-Wen;Chen, Zheng-Qing;Gu, Ming
    • Wind and Structures
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    • v.12 no.1
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    • pp.1-19
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    • 2009
  • In this paper, the airflow around an ideal thin plate (hereafter referred to as ITP) with various ratios of central slot is simulated by using the finite-difference-method (FDM)-based Arbitrary-Lagrangian-Eulerian descriptions for the rigid oscillating body. The numerical procedure employs the second-order projection scheme to decouple the governing equations, and the multigrid algorithm with three levels to improve the computational efficiency in evaluating of the pressure equation. The present CFD method is validated through comparing the computed flutter derivatives of the ITP without slot to Theodorsen analytical solutions. Then, the unsteady aerodynamics of the ITP with and without central slot is investigated. It is found that even a smaller ratio of central slot of the ITP has notable effects on pressure distributions of the downstream section, and the pressure distributions on the downstream section will further be significantly affected by the slot ratio and the reduced wind speeds. Continuous increase of $A_2^*$ with the increase of central slot may be the key feature of the slotted ITP. Finally, flutter analyses based on the flutter derivatives of the slotted ITP are performed, and moreover, flutter instabilities of a scaled sectional model of a twin-deck bridge with various ratios of deck slot are investigated. The results confirm that the central slot is effective to improve bridge flutter stabilities, and that the flutter critical wind speeds increase with the increase of slot ratio.

Smoke Image Recognition Method Based on the optimization of SVM parameters with Improved Fruit Fly Algorithm

  • Liu, Jingwen;Tan, Junshan;Qin, Jiaohua;Xiang, Xuyu
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.14 no.8
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    • pp.3534-3549
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    • 2020
  • The traditional method of smoke image recognition has low accuracy. For this reason, we proposed an algorithm based on the good group of IMFOA which is GMFOA to optimize the parameters of SVM. Firstly, we divide the motion region by combining the three-frame difference algorithm and the ViBe algorithm. Then, we divide it into several parts and extract the histogram of oriented gradient and volume local binary patterns of each part. Finally, we use the GMFOA to optimize the parameters of SVM and multiple kernel learning algorithms to Classify smoke images. The experimental results show that the classification ability of our method is better than other methods, and it can better adapt to the complex environmental conditions.

Comparison with Threshold Limit Value (TLV) of Menthol Cigarettes between Expert and Consumer Panel

  • Lee Seung-Yong;Lee Whan-Woo;Kim Young-Hoh
    • Journal of the Korean Society of Tobacco Science
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    • v.28 no.1
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    • pp.58-66
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    • 2006
  • Threshold limit value (TLV) test between expert and consumer panel was conducted about absolute, recognition and difference threshold respectively. And we tried to suggest appropriate and minimum acceptable menthol concentration level by consumer panel. Determination of threshold value was based on ASTM E 679-79 method by forced-choice ascending concentration series. In addition, a semi-ascending paired difference method was referred to conduct test. The group threshold value was determined as the value of geometric mean individual threshold. The smokers were dividend by two groups, trained and consumer panel. Trained panel was selected according to sensitivity to menthol discrimination. Consumer panel wasrecruited in proportion as population ratios including female smokers. They were all over twenty years old volunteers and summed up thirty four persons. In terms of sensor evaluation, overall difference test with seven-category scale by both trained and consumer panelists were done. On judging correct or incorrect answer, two by three cut-off levels applied to. Every test was conducted with two sessions, before smoking and during smoking period. And, only two samples served each paneI per test with regard to sensory fatigue and reliable results. All tests were replicated, and in total 32 times per panelist. In conclusion, the recognition threshold about consumer and expert panel was 358 ppm/cig. and 276 ppm/cig. in separately. Besides, absolute and difference thresholds were obtained also. And, we conduct difference threshold test with two different ways, upward and downward. And, The results of each method were 246, 195 ppm/cig., 1414, 1336 ppm/cig. and 1047, 972 ppm/cig.

AN OVERLAPPING SCHWARZ METHOD FOR SINGULARLY PERTURBED THIRD ORDER CONVECTION-DIFFUSION TYPE

  • ROJA, J. CHRISTY;TAMILSELVAN, A.
    • Journal of applied mathematics & informatics
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    • v.36 no.1_2
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    • pp.135-154
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    • 2018
  • In this paper, an almost second order overlapping Schwarz method for singularly perturbed third order convection-diffusion type problem is constructed. The method splits the original domain into two overlapping subdomains. A hybrid difference scheme is proposed in which on the boundary layer region we use the combination of classical finite difference scheme and central finite difference scheme on a uniform mesh while on the non-layer region we use the midpoint difference scheme on a uniform mesh. It is shown that the numerical approximations which converge in the maximum norm to the exact solution. We proved that, when appropriate subdomains are used, the method produces convergence of second order. Furthermore, it is shown that, two iterations are sufficient to achieve the expected accuracy. Numerical examples are presented to support the theoretical results. The main advantages of this method used with the proposed scheme are it reduce iteration counts very much and easily identifies in which iteration the Schwarz iterate terminates.

A Study on a Visual Sensor System for Weld Seam Tracking in Robotic GMA Welding (GMA 용접로봇용 용접선 시각 추적 시스템에 관한 연구)

  • 김동호;김재웅
    • Journal of Welding and Joining
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    • v.19 no.2
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    • pp.208-214
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    • 2001
  • In this study, we constructed a visual sensor system for weld seam tracking in real time in GMA welding. A sensor part consists of a CCD camera, a band-pass filter, a diode laser system with a cylindrical lens, and a vision board for inter frame process. We used a commercialized robot system which includes a GMA welding machine. To extract the weld seam we used a inter frame process in vision board from that we could remove the noise due to the spatters and fume in the image. Since the image was very reasonable by using the inter frame p개cess, we could use the simplest way to extract the weld seam from the image, such as first differential and central difference method. Also we used a moving average method to the successive position data or weld seam for reducing the data fluctuation. In experiment the developed robot system with visual sensor could be able to track a most popular weld seam. such as a fillet-joint, a V-groove, and a lap-joint of which weld seam include planar and height directional variation.

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