• Title/Summary/Keyword: second-order system

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THE SENSITIVITY OF STRUCTURAL RESPONSE USING FINITE ELEMENTS IN TIME

  • Park, Sungho;Kim, Seung-Jo
    • Journal of Theoretical and Applied Mechanics
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    • v.3 no.1
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    • pp.66-80
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    • 2002
  • The bilinear formulation proposed earlier by Peters and Izadpanah to develop finite elements in time to solve undamped linear systems, Is extended (and found to be readily amenable) to develop time finite elements to obtain transient responses of both linear and nonlinear, and damped and undamped systems. The formulation Is used in the h-, p- and hp-versions. The resulting linear and nonlinear algebraic equations are differentiated to obtain the first- and second-order sensitivities of the transient response with respect to various system parameters. The present developments were tested on a series of linear and nonlinear examples and were found to yield, when compared with results obtained using other methods, excellent results for both the transient response and Its sensitivity to system parameters. Mostly. the results were obtained using the Legendre polynomials as basis functions, though. in some cases other orthogonal polynomials namely. the Hermite. the Chebyshev, and integrated Legendre polynomials were also employed (but to no great advantage). A key advantage of the time finite element method, and the one often overlooked in its past applications, is the ease In which the sensitivity of the transient response with respect to various system parameters can be obtained. The results of sensitivity analysis can be used for approximate schemes for efficient solution of design optimization problems. Also. the results can be applied to gradient-based parameter identification schemes.

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Development of 3-D Flow Analysis Code Using Unstructured Grid System (I) - Numerical Method - (비정렬격자계를 사용하는 3차원 유동해석코드 개발 (I) - 수치해석방법 -)

  • Kim, Jong-Tae;Myong, Hyon-Kook
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.9 s.240
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    • pp.1049-1056
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    • 2005
  • A conservative pressure-based finite-volume numerical method has been developed for computing flow and heat transfer by using an unstructured grid system. The method admits arbitrary convex polyhedra. Care is taken in the discretization and solution procedures to avoid formulations that are cell-shape-specific. A collocated variable arrangement formulation is developed, i.e. all dependent variables such as pressure and velocity are stored at cell centers. Gradients required for the evaluation of diffusion fluxes and for second-order-accurate convective operators are found by a novel second-order accurate spatial discretization. Momentum interpolation is used to prevent pressure checkerboarding and the SIMPLE algorithm is used for pressure-velocity coupling. The resulting set of coupled nonlinear algebraic equations is solved by employing a segregated approach, leading to a decoupled set of linear algebraic equations fer each dependent variable, with a sparse diagonally dominant coefficient matrix. These equations are solved by an iterative preconditioned conjugate gradient solver which retains the sparsity of the coefficient matrix, thus achieving a very efficient use of computer resources.

Case Study for Buckling Design of Temporary Bridges using System Buckling Analysis (시스템좌굴 해석법을 이용한 라멘형가교 주요부재의 좌굴설계에 관한 사례 연구)

  • Kyung, Yong Soo;So, Byoung Hoon;Bang, Jin Hwan;Kim, Moon Young
    • Journal of Korean Society of Steel Construction
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    • v.19 no.1
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    • pp.87-98
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    • 2007
  • Generally, main girders and steel piers of temporary bridges form the steel rahmen structure. In this study, the rational stability design procedure for main members of temporary bridges was presented using a 3D system buckling analysis and second-order elastic analysis. Six types of temporary bridges, which can be designed and fabricated in reality, were chosen and the buckling design for them was performed in consideration ofload combinations of dead and live loads, thermal load, and wind load. Effective buckling length of steel piers, transition of 3D buckling modes, and effects of second-order analysis were investigated through a case study involving six temporary bridges.

Internal Model Control of UPS Inverter with Robustness of Calculation Time Delay and Parameter Variation (연산지연시간과 파라미터 변동에 강인한 UPS 인버터의 내부모델제어)

  • Park, Jee-Ho;Keh, Joong-Eup;Kim, Dong-Wan;An, Young-Joo;Park, Han-Seok;Woo, Jung-In
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.51 no.4
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    • pp.175-185
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    • 2002
  • In this paper, a new fully digital current control method of UPS inverter, which is based on an internal model control, is proposed. In the proposed control system, overshoots and oscillations due to the computation time-delay are compensated by explicit incorporation of the time-delay in the current control loop transfer function. The internal model controller is adopted to a second order deadbeat reference-to-output response which means that its response reaches the reference in two sampling time including computational time-delays. That is, the average current of filter capacitor is been exactly equal to the reference current with a time lag of two sampling intervals. Therefore, this method has an essentially overshoot free reference-to-output response with a minimum possible rise time. The effectiveness of the proposed control system has been verified by the simulation and experimental respectively. From the simulation and experimental results, the proposed system is achieved the robust characteristics to the calculation time delay and parameter variation as well as very fast dynamic performance, thus it can be effectively applied to the power supply for the critical load.

A Study on the Institutional Aspects of Rural Spatial Planning System (농촌지역 공간계획체계의 특성에 관한 연구)

  • 이상문
    • Journal of Korean Society of Rural Planning
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    • v.1 no.1
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    • pp.35-48
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    • 1995
  • The drastic change of spatial structure in rural area and the recent rural development policies(related to settlement reorganization and plot rearrangement) make the rural space planning more important than ever. So this paper tries to evaluate the institutional aspects of rural spatial planning system focused on planning area. land use classification and hierachical order between existing plans. The results of this study can be summarized as follows. First, the rural planning areas are classified into 4-tiers(e.g., Gun, Myon, District, Village). Second, the rural land use planning has 3-tiers(e.g., macro, mediate and micro zoning) from the viewpoint of land use classification system, but it doesn't have mediate-micro zoning system. Third, the spatial plans in rural area, positioned in local planning, were categorized into regional planning system and land use planning system. However there's no linkage between both sides of each hierachial planning order.

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Image Data Classification using a Similarity Function based on Second Order Tensor (2차 텐서 기반 유사도 함수를 이용한 영상 데이터 분류)

  • Yoon, Dong-Woo;Lee, Kwan-Yong;Park, Hye-Young
    • Journal of KIISE:Software and Applications
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    • v.36 no.8
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    • pp.664-672
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    • 2009
  • Recently, studies on utilizing tensor expression on image data analysis and processing have been attracting much interest. The purpose of this study is to develop an efficient system for classifying image patterns by using second order tensor expression. To achieve the goal, we propose a data generation model expressed by class factors and environment factors with second order tensor representation. Based on the data generation model, we define a function for measuring similarities between two images. The similarity function is obtained by estimating the probability density of environment factors using a matrix normal distribution. Through computational experiments on a number of benchmark data sets, we confirm that we can make improvement in classification rates by using second order tensor, and that the proposed similarity function is more appropriate for image data compared to conventional similarity measures.

Limitation of effective length method and codified second-order analysis and design

  • Chan, S.L.;Liu, Y.P.;Zhou, Z.H.
    • Steel and Composite Structures
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    • v.5 no.2_3
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    • pp.181-192
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    • 2005
  • The effective length method for flexural (column) buckling has been used for many decades but its use is somewhat limited in various contemporary design codes to moderately slender structures with elastic critical load factor (${\lambda}_{cr}$) less than 3 to 5. In pace with the use of higher grade steel in recent years, the influence of buckling in axial buckling resistance of a column becomes more important and the over-simplified assumption of effective length factor can lead to an unsafe, an uneconomical or a both unsafe and uneconomical solution when some members are over-designed while key elements are under-designed. Effective length should not normally be taken as the distance between nodes multiplied by an arbitrary factor like 0.85, 1.0, 2.0 etc. Further, the classification of non-sway and sway-sensitive frames makes the conventional design procedure tedious to use and, more importantly, limited to simple regular frames. This paper describes the practical use of second-order analysis with section capacity check allowing for $P-{\delta}$ and $P-{\Delta}$ effects together with member and system imperfections. Most commercial software considers only the $P-{\Delta}$ effect, but not member and frame imperfections nor $P-{\delta}$ effect, and engineers must be very careful in their uses. A verification problem is also given for validation of software for this type of powerful second-order analysis and design. It is a trend for popular and advanced national design codes in using the second-order analysis as a norm for analysis and design of steel structures while linear analysis may only be used in very simple structures.

Generalization of Recurrent Cascade Correlation Algorithm and Morse Signal Experiments using new Activation Functions (순환 케스케이드 코릴레이션 알고리즘의 일반화와 새로운 활성화함수를 사용한 모스 신호 실험)

  • Song Hae-Sang;Lee Sang-Wha
    • Journal of Intelligence and Information Systems
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    • v.10 no.2
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    • pp.53-63
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    • 2004
  • Recurrent-Cascade-Correlation(RCC) is a supervised teaming algorithm that automatically determines the size and topology of the network. RCC adds new hidden neurons one by one and creates a multi-layer structure in which each hidden layer has only one neuron. By second order RCC, new hidden neurons are added to only one hidden layer. These created neurons are not connected to each other. We present a generalization of the RCC Architecture by combining the standard RCC Architecture and the second order RCC Architecture. Whenever a hidden neuron has to be added, the new RCC teaming algorithm automatically determines whether the network topology grows vertically or horizontally. This new algorithm using sigmoid, tanh and new activation functions was tested with the morse-benchmark-problem. Therefore we recognized that the number of hidden neurons was decreased by the experiments of the RCC network generalization which used the activation functions.

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Urgent problems and solution strategies in 2nd cycle of long-term care hospital accreditation (요양병원 인증 2주기 당면과제 및 해결방안)

  • Kim, Kyung Sook
    • Korea Journal of Hospital Management
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    • v.21 no.3
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    • pp.65-70
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    • 2016
  • The Long-Term Care Hospital (LTCH) accreditation system was initiated in 2013 in the form of mandatory accreditation system in order to improve patient safety and the quality of medical service at LTCHs. By June 2016, the accredited LTCHs were 76.2%. This research was conducted to review the implementation process in the first cycle and to promote development of the second cycle of LTCH accreditation system. There are some changes which reinforced the accreditation standards, accreditation survey, and public access to accreditation results in order to strengthen patient safety in the first cycle LTCH accreditation system. LTCHs which participated in the accreditation system achieved certain outcomes in respect to patient safety and employee satisfaction. However, there are several urgent problems in placement criteria of night duty health care providers, reinforcement plans in the accreditation system, and incentives for accredited hospitals. In order to solve these problems, the most important thing is to clearly recognize the fact that the healthcare accreditation system is not the means for control and regulate hospitals but a system to induce hospitals to continue to strive for improvements in patient safety and medical service quality. In addition, it is required that LTCHs, accrediting agency and the Ministry of Health and Welfare compromise and cooperate to seek solutions every time issues related to the accreditation system arise.

Analysis on a saturating system with an intelligent limiter

  • Yang, Sang-Sik
    • 제어로봇시스템학회:학술대회논문집
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    • 1989.10a
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    • pp.1091-1096
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    • 1989
  • All mechanical systems have saturation nonlinearity in actuators or in final control elements. When controllers have integral action, reset windup can cause instability as well as make the system performance unsatisfactory. In this study, an intelligent limiter which needs no tuning of parameters is tested with the PDF controller used for control of a second order plant. This paper presents analysis of the stability of the system using the describing function method and the Nyquist stability theorem. The improvement of the system performance by the limiter is illustrated by computer simulations.

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