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Applications of Graph Theory for the Pipe Network Analysis (상수관망해석을 위한 도학의 적용)

  • Park, Jae-Hong;Han, Geon-Yeon
    • Journal of Korea Water Resources Association
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    • v.31 no.4
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    • pp.439-448
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    • 1998
  • There are many methods to calculate steady-state flowrate in a large water distribution system. Linear method which analyzes continuity equations and energy equations simultaneously is most widely used. Though it is theoretically simple, when it is applied to a practical water distribution system, it produces a very sparse coefficient matrix and most of its diagonal elements are to be zero. This sparsity characteristic of coefficient matrix makes it difficult to analyze pipe flow using the linear method. In this study, a graph theory is introduced to water distribution system analysis in order to prevent from producing ill-conditioned coefficient matrix and the technique is developed to produce positive-definite matrix. To test applicability of developed method, this method is applied to 22 pipes and 142 pipes system located nearby Taegu city. The results obtained from these applications show that the method can calculate flowrate effectively without failure in converage. Thus it is expected that the method can analyze steady state flowrate and pressure in pipe network systems efficiently. Keywords : pipe flow analysis, graph theory, linear method.

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Vibration Analysis of a Lathe Performing Non-Circular Cutting (비원형 단면의 선삭 가공시 발생하는 진동해석)

  • 신응수;박정호
    • Journal of KSNVE
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    • v.10 no.2
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    • pp.291-298
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    • 2000
  • This paper intends to provide an analytic vibrational model of non-circular cutting by a lathe and to investigate its stability criteria. A single degree-of-freedon model based on the orthogonal cutting theory has the characteristics of parametric excitation due to the nonlinear cutting force that changes periodically its direction as well as its magnitude. The Floquet theory has been applied to investigate the stability of the linearized system and the stability diagrams have been obtained with respect to the ovality, the cut velocity and the cut depth. Also nonlinear analysis has been performed to verify the linear analysis and compare the results with those from circular cutting. Results show that a critical cut depth is decreased as the ovality is increased while a critical cut velocity is increased as the ovality is increased. Also, a good agreement in critical conditions has been observed between the linear and nonlinear analyses for the ovality less than 2%. Accordingly, the linear analysis can be said to be applicable for most practical oval cuttings whose ovality are much less than 2%.

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Linear Distributed Passive Target Tracking Filter for Cooperative Multiple UAVs (다중 UAV 협업을 위한 선형 분산 피동 표적추적 필터 설계)

  • Lee, Yunha;Kim, Chan-Young;Ra, Won-Sang;Whang, Ick-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.67 no.2
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    • pp.314-324
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    • 2018
  • This paper proposes a linear distributed target tracking filter for multiple unmanned aerial vehicles(UAVs) sharing their passive sensor measurements through communication channels. Different from the conventional nonlinear filtering schemes, the distributed passive target tracking problem is newly formulated within the framework of a linear robust state estimation theory incorporated with a linear uncertain measurement equation including the coordinate transform uncertainty. To effectively cope with the performance degradation due to the coordinate transform uncertainty, a linear consistent robust Kalman filter(CRKF) theory is devised and applied for designing a distributed passive target tracking filter. Through the simulations for typical UAV surveillance mission, the superior performance of the proposed method over the existing schemes of distributed passive target tracking are demonstrated.

Performance Analysis of Multiple Wave Energy Converters due to Rotor Spacing

  • Poguluri, Sunny Kumar;Kim, Dongeun;Ko, Haeng Sik;Bae, Yoon Hyeok
    • Journal of Ocean Engineering and Technology
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    • v.35 no.3
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    • pp.229-237
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    • 2021
  • A numerical hydrodynamic performance analysis of the pitch-type multibody wave energy converter (WEC) is carried out based on both linear potential flow theory and computational fluid dynamics (CFD) in the unidirectional wave condition. In the present study, Salter's duck (rotor) is chosen for the analysis. The basic concept of the WEC rotor, which nods when the pressure-induced motions are in phase, is that it converts the kinetic and potential energies of the wave into rotational mechanical energy with the proper power-take-off system. This energy is converted to useful electric energy. The analysis is carried out using three WEC rotors. A multibody analysis using linear potential flow theory is performed using WAMIT (three-dimensional diffraction/radiation potential analysis program), and a CFD analysis is performed by placing three WEC rotors in a numerical wave tank. In particular, the spacing between the three rotors is set to 0.8, 1, and 1.2 times the rotor width, and the hydrodynamic interaction between adjacent rotors is checked. Finally, it is confirmed that the dynamic performance of the rotors slightly changes, but the difference due to the spacing is not noticeable. In addition, the CFD analysis shows a lateral flow phenomenon that cannot be confirmed by linear potential theory, and it is confirmed that the CFD analysis is necessary for the motion analysis of the rotor.

[ $H_2$ ]-optimal Control with Regional Pole Assignment via State Feedback

  • Wang Guo-Sheng;Liang Bing;Duan Guang-Ren
    • International Journal of Control, Automation, and Systems
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    • v.4 no.5
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    • pp.653-659
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    • 2006
  • The design of $H_2$-optimal control with regional pole assignment via state feedback in linear time-invariant systems is investigated. The aim is to find a state feedback controller such that the closed-loop system has the desired eigenvalues lying in some desired stable regions and attenuates the disturbance between the output vector and the disturbance vector. Based on a proposed result of parametric eigenstructure assignment via state feedback in linear systems, the considered $H_2$-optimal control problem is changed into a minimization problem with certain constraints, and a simple and effective algorithm is proposed for this considered problem. A numerical example and its simulation results show the simplicity and effectiveness of this proposed algorithm.

On a sensitivity of optimal solutions in fuzzy mathematical linear programming problem

  • Munakata, Tsunehiro;Nishiyama, Tadayuki
    • 제어로봇시스템학회:학술대회논문집
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    • 1994.10a
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    • pp.307-312
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    • 1994
  • The authors have been devoted to researches on fuzzy theories and their applications, especially control theory and application problems, for recent years. In this paper, the authors present results on a comparison of optimal solutions between ones of an ordinary-typed mathematical linear programming problem(O.M.I.P. problem) and ones of a Zimmerman-typed fuzzy mathematical linear programming problem (F.M.L.P. problem), and comment about the sensitivity (differences and fuzziness on between O.M.L.P. problem and F.M.L.P. problem) on optimal solutions of these mathematical linear programming problems.

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A 3D RVE model with periodic boundary conditions to estimate mechanical properties of composites

  • Taheri-Behrooz, Fathollah;Pourahmadi, Emad
    • Structural Engineering and Mechanics
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    • v.72 no.6
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    • pp.713-722
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    • 2019
  • Micromechanics is a technique for the analysis of composites or heterogeneous materials which focuses on the components of the intended structure. Each one of the components can exhibit isotropic behavior, but the microstructure characteristics of the heterogeneous material result in the anisotropic behavior of the structure. In this research, the general mechanical properties of a 3D anisotropic and heterogeneous Representative Volume Element (RVE), have been determined by applying periodic boundary conditions (PBCs), using the Asymptotic Homogenization Theory (AHT) and strain energy. In order to use the homogenization theory and apply the periodic boundary conditions, the ABAQUS scripting interface (ASI) has been used along with the Python programming language. The results have been compared with those of the Homogeneous Boundary Conditions method, which leads to an overestimation of the effective mechanical properties. According to the results, applying homogenous boundary conditions results in a 33% and 13% increase in the shear moduli G23 and G12, respectively. In polymeric composites, the fibers have linear and brittle behavior, while the resin exhibits a non-linear behavior. Therefore, the nonlinear effects of resin on the mechanical properties of the composite material is studied using a user-defined subroutine in Fortran (USDFLD). The non-linear shear stress-strain behavior of unidirectional composite laminates has been obtained. Results indicate that at arbitrary constant stress as 80 MPa in-plane shear modulus, G12, experienced a 47%, 41% and 31% reduction at the fiber volume fraction of 30%, 50% and 70%, compared to the linear assumption. The results of this study are in good agreement with the analytical and experimental results available in the literature.

A Numerical Study on One-Dimensional Consolidation of Soft Clay with Finite Strain Consolidation Theory (유한변형율(有限變形率) 압밀이론(壓密理論)에 의한 연약(軟弱) 점토(粘土)의 -차원(次元) 압밀(壓密)에 관한 수치(數値) 해석적(解析的) 연구)

  • Yoo, Nam-Jae;Jung, Yoon-Hwa;Lee, Myung-Woog
    • Journal of Industrial Technology
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    • v.11
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    • pp.85-98
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    • 1991
  • A numerical study was performed to investigate characteristics of one-dimensional consolidation of soft clay. Results of consolidation tests with the remolded normally consolidation clay of having a very high initial void ratio were analyzed by using the numerical technique of finite difference method based on the finite strain consolidation theory, to evaluate consolidational characteristics of soft clay under surcharges on the top of clay. On the other hand, a numerical parametric study on soft clay consolidated due to its self-weight was also carried out to find its effect on one-dimensional consolidation. Terzaghi's conventional consolidation theory, finite strain consolidation theories with linear and non-linear interpolation of effective stress - void ratio - permeability relation were used to analyze the test results and their results were compared to each other to figure out the difference between them. Therefore, the validity of theories was assessed.

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Dynamic Response Characteristics of a Floating Ocean City in Waves (부유식 해양도시의 동적응답특성)

  • 구자삼;홍석원
    • Journal of Ocean Engineering and Technology
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    • v.8 no.2
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    • pp.80-92
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    • 1994
  • The dynamic response characteristics of a floating ocean city are examined for presenting the basic data for the design of huge offshore structures supported by a large number of floating bodies in waves. The numerical approach which is accurate in linear system is based on combination of a three dimensional source distribution method, wave interaction theory and the finite element method of using the space frame element. The hydrodynamic interactions among the floating bodies are taken into account in their exact form within the context of linear potential theory in the motion and structural analysis. The method is applicable to an arbitrary number of three dimensional bodies having any individual body geometries and geometrical arrangement with the restriction that the circumscribed, bottom-mounted. Imaginary vertical cylinder for each body does not contain any part of the other body. The validity of this procedure was verified by comparing with experimental results obtained in the literature.

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Bending analysis of composite skew cylindrical shell panel

  • Haldar, Salil;Majumder, Aditi;Kalita, Kanak
    • Structural Engineering and Mechanics
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    • v.70 no.1
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    • pp.125-131
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    • 2019
  • A nine node isoparametric plate bending element is used for bending analysis of laminated composite skew cylindrical shell panels. Both thick and thin shell panels are solved. Rotary inertia and shear deformation are incorporated by considering first order shear deformation theory. The analysis is performed considering shallow shell theory. Both shallow and moderately deep skew cylindrical shells are investigated. Skew cylindrical shell panels having different thickness ratios (h/a), radius to length ratios (R/a), ply angle orientations, number of layers, aspect ratio (b/a), boundary conditions and various loading (concentrated, uniformly distributed, linear varying and doubly sinusoidal varying) conditions are analysed. Various new results are presented.