• Title/Summary/Keyword: continuity and stability

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On the development of succesive finite element code for semiconductor devices analysis (유한요소법(有限要素法)에 의한 반도체(半導體) 소자(素子) 해석(解析)의 안정화(安定化)에 관한 연구(硏究))

  • Choi, Kyung
    • Journal of Industrial Technology
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    • v.9
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    • pp.109-117
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    • 1989
  • In the finite element analysis of semiconductor devices analysis, the solution often be diverged due to the numerical instability of discretized equations. To overcome this problems, a noble finite element code which guarantees a successful convergence is developed. The factor of divergence in the current continuity equation of semiconductor governing equations is derived using stability test and an adaptive mesh refine scheme is introduced to eliminates the divergence properties. A test calculation of GaAs MESFET model reveals that the proposed scheme has a robust self-convergence property and is suitable for the semiconductor devices analysis.

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A Design Compensation for Stable Flow/Pressure Control of Variable Displacement Type Piston Pump (가변용량형 피스톤 펌프의 안정적인 유량/압력제어를 위한 설계보상)

  • Jung, Dong-Soo;Kim, Hyoung-Eui;Kang, E-Sok
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.2
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    • pp.165-174
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    • 2007
  • Variable displacement type piston pump uses various controllers for controlling more than one state quantity like pressure, flow, power, and so on. These controllers need the mathematical model closely expressing dynamic behavior of pump for analyzing the stability of control systems which usually use various kinds of state variables. This paper derives the nonlinear mathematical model for variable displacement type piston pump. This model consists of two 1st oder differential equations by the continuity equations and one 2nd oder differential equation by the motion equation. To simplify the model we obtain the linear state variable model by differentiating the three nonlinear equations. And we verify this linearized model by comparison of simulation with experimentation and analyze the stability for the flow/pressure control. Finally this paper suggests the design compensation to ensure the stability of the systems.

Finite element method for porous media using equal order element (동차선형요소를 사용한 다공질 매체의 커플링 유한요소해석)

  • Park, Tae-Hyo;Tak, Moon-Ho
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2008.04a
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    • pp.20-25
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    • 2008
  • The finite element analysis for porous media is severe job because constituents have different physical peoperties, and element's continuity and stability should be considered. Thus, we propose the new mixed finite element method in order to overcome the problems. In this method, multi time step, remeshing step, and sub iteration step are introduced. The multi time step and remeshing step make it possible to satisfy a stability and an accuracy during sub iteration in which global time is determined. Finally, the proposed method is compared with the ABAQUS(2007) software and exact solution(Schiffman 1967) through two dimensional consolidation model.

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A Survey on LEO-PNT Systems

  • Hong-Woo Seok;Sangjae Cho;Seung-Hyun Kong;Jung-Min Joo;Jongwon Lim
    • Journal of Positioning, Navigation, and Timing
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    • v.12 no.3
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    • pp.323-332
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    • 2023
  • Today, services using Positioning, Navigation, and Timing (PNT) technology are provided in various fields, such as smartphone Location-Based Service (LBS) and autonomous driving. Generally, outdoor positioning techniques depend on the Global Navigation Satellite System (GNSS), and the need for positioning techniques that guarantee positioning accuracy, availability, and continuity is emerging with advances in service. In particular, continuity is not guaranteed in urban canyons where it is challenging to secure visible satellites with standalone GNSS, and even if more than four satellites are visible, the positioning accuracy and stability are reduced due to multipath channels. Research using Low Earth Orbit (LEO) satellites is already underway to overcome these limitations. In this study, we conducted a trend analysis of LEO-PNT research, an LEO satellite-based navigation and augmentation system. Through comparison with GNSS, the differentiation of LEO-PNT was confirmed, and the system design and receiver processing were analyzed according to LEO-PNT classification. Lastly, the current status of LEO-PNT development by country and institution was confirmed.

Dynamics of Honeymoon and Statics of Structure: Changes and Continuity of Foreign Policy in the Moon Jae-In Administration (하니문의 동학(動學)과 구조의 정학(靜學): 문재인 정부의 외교정책, 변화와 연속성)

  • Choi, Jinwoo
    • Korean Journal of Legislative Studies
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    • v.24 no.2
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    • pp.5-38
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    • 2018
  • A seismic change is under way in diplomatic topography surrounding the Korean Peninsula. A new dynamic is being generated that could lead to a breakthrough in the nuclear stalemate and to an end of hostility between the two Koreas. Moon Administration's bold and creative foreign policy, which is alleged to place South Korea in the "driver's seat", is probably responsible for what is happening on the Korean Peninsula. However, on the other hand, Moon Administration's foreign policy shows a lot of continuity with foreign policy of previous conservative governments. In particular, the Moon government's emphasis on the vitality of the ROK-US alliance and its commitment to close coordination with the US in dealing with nuclear issues of North Korea is the hallmark of the continuity in South Korea's foreign policy. Emphasizing and sharing the notion of the continuities in foreign policy could contribute to social integration by garnering bi-partisan support. It could also spawn sense of stability, predictability, and confidence to diplomatic counterparts in other countries. And it could help avoid the negative effects of expectation-reality gap in the event that the outcome of all the diplomatic endeavor falls short of expectation held by citizens.

Internal Viscous Flow Computation Within the Jet Pump Elements (제트 폄프 요소 내부의 유동 해석)

  • Cho J. K.;Oh S. W.;Park W. G.;Oh S. M.;Lee S. W.
    • 한국전산유체공학회:학술대회논문집
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    • 1996.05a
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    • pp.99-104
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    • 1996
  • The jet pump is being used in many fields for several purposes because of its simple construction and easy operation. The characteristics of the geometrical variables, pressure gradient and velocity distribution of the jet pump are studied using the CFD technique. The flow calculations through a bended nozzle. a mixing chamber and a venturi are presented and phenomenological aspects are discussed. This study solve 3-D steady incompressible Navier-Stokes equations using the Iterative time marching scheme. The governing equations are differenced with 1st-order accurate backward difference scheme for the time derivatives and 3rd-order accurate QUICK scheme for the convective terms. The Mark-and-cell concept was applied efficiently to solve continuity equation, which is differenced 2nd-order accurate central differenced scheme. The 4th-order artificial damping is added to the continuity equation for numerical stability. A O-type of grid system is generated inside a nozzle and venturi of the jet pump. It has concluded that the results of present study properly agree with physical flow phenomena.

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Technique Proposal to Stabilize Lipschitz Continuity of WGAN Based on Regularization Terms (정칙화 항에 기반한 WGAN의 립쉬츠 연속 안정화 기법 제안)

  • Hahn, Hee-Il
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.20 no.1
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    • pp.239-246
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    • 2020
  • The recently proposed Wasserstein generative adversarial network (WGAN) has improved some of the tricky and unstable training processes that are chronic problems of the generative adversarial network(GAN), but there are still cases where it generates poor samples or fails to converge. In order to solve the problems, this paper proposes algorithms to improve the sampling process so that the discriminator can more accurately estimate the data probability distribution to be modeled and to stably maintain the discriminator should be Lipschitz continuous. Through various experiments, we analyze the characteristics of the proposed techniques and verify their performances.

Incompressible Viscous Flow Analysis around a High-Speed Train Including Cross-Wind Effects (측풍영향을 고려한 고속전철 주위의 비압축성 점성 유동 해석)

  • Jung Y. R.;Park W. G.;Kim H. W.;Ha S. D.
    • 한국전산유체공학회:학술대회논문집
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    • 1995.10a
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    • pp.55-63
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    • 1995
  • The flow field around a high-speed train including cross-wind effects has been simulated. This study solves 3-D unsteady incompressible Navier-Stokes equations in the inertial frame using the iterative time marching scheme. The governing equations are differenced with 1st-order accurate backward difference scheme for the time derivatives, 3th-order accurate QUICK scheme for the convective terms and 2nd-order accurate central difference scheme for the viscous terms. The Marker-and-Cell concept was applied to efficiently solve continuity equation, which is differenced with 2nd-order accurate central difference scheme. The 4th-order artificial damping is added to the continuity equation for numerical stability. A C-H type of elliptic grid system is generated around a high-speed train including ground. The Baldwin-Lomax turbulent model was implemented to simulate the turbulent flows. To validate the present procedure, the flow around a high speed train at constant yaw angle of $45^{\circ}\;and\;90^{\circ}$ has been simulated. The simulation shows 3-D vortex generation in the lee corner. The flow separation is also observed around the rear of the train. It has concluded that the results of present study properly agree with physical flow phenomena.

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A Case Study of Extra Reinforcement by Road Extension work on Existing Cut Slope Reinforced with Counterweight Fill and Stabilizing Piles (압성토 및 억지말뚝으로 보강된 도로의 확장공사로 인한 추가 보강사례 연구)

  • Park, Jeong-Yong;Kim, Woo-Seong;Kim, Jae-Kyoung;Yang, Tae-Sun;Na, Kyung-Joon
    • Journal of Korean Society of societal Security
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    • v.1 no.2
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    • pp.67-72
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    • 2008
  • To confirm the stability of a cut slope in the road extension construction site, several investigations were carried out and countermeasures of slope was studied. This paper describes a study of design case of extra reinforcement on existing cut slope reinforced by preloading and piles in roads. To investigate the effect of stabilizing piles installed in a cut slope, an instrumentation system also designed, was. As a result that the stabilizing file and earth anchor are considered as the extra reinforcement, both stabilizing pile and earth anchor guarantee the stability of cut slope. However, stabilizing pile is selected in aspects of economy and continuity to the existing cut slop reinforcement including counterweight fill and stabilizing piles.

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