• Title/Summary/Keyword: Nonlinear equations

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Analysis of trusses by total potential optimization method coupled with harmony search

  • Toklu, Yusuf Cengiz;Bekdas, Gebrail;Temur, Rasim
    • Structural Engineering and Mechanics
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    • v.45 no.2
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    • pp.183-199
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    • 2013
  • Current methods of analysis of trusses depend on matrix formulations based on equilibrium equations which are in fact derived from energy principles, and compatibility conditions. Recently it has been shown that the minimum energy principle, by itself, in its pure and unmodified form, can well be exploited to analyze structures when coupled with an optimization algorithm, specifically with a meta-heuristic algorithm. The resulting technique that can be called Total Potential Optimization using Meta-heuristic Algorithms (TPO/MA) has already been applied to analyses of linear and nonlinear plane trusses successfully as coupled with simulated annealing and local search algorithms. In this study the technique is applied to both 2-dimensional and 3-dimensional trusses emphasizing robustness, reliability and accuracy. The trials have shown that the technique is robust in two senses: all runs result in answers, and all answers are acceptable as to the reliability and accuracy within the prescribed limits. It has also been shown that Harmony Search presents itself as an appropriate algorithm for the purpose.

Battery State Estimation Algorithm for High-Capacity Lithium Secondary Battery for EVs Considering Temperature Change Characteristics

  • Park, Jinho;Lee, Byoungkuk;Jung, Do-Yang;Kim, Dong-Hee
    • Journal of Electrical Engineering and Technology
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    • v.13 no.5
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    • pp.1927-1934
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    • 2018
  • In this paper, we studied the state of charge (SOC) estimation algorithm of a high-capacity lithium secondary battery for electric vehicles (EVs) considering temperature characteristics. Nonlinear characteristics of high-capacity lithium secondary batteries are represented by differential equations in the mathematical form and expressed by the state space equation through battery modeling to extract the characteristic parameters of the lithium secondary battery. Charging and discharging equipment were used to perform characteristic tests for the extraction of parameters of lithium secondary batteries at various temperatures. An extended Kalman filter (EKF) algorithm, a state observer, was used to estimate the state of the battery. The battery capacity and internal resistance of the high-capacity lithium secondary battery were investigated through battery modeling. The proposed modeling was applied to the battery pack for EVs to estimate the state of the battery. We confirmed the feasibility of the proposed study by comparing the estimated SOC values and the SOC values from the experiment. The proposed method using the EKF is expected to be highly applicable in estimating the state of the high-capacity rechargeable lithium battery pack for electric vehicles.

Error Analysis of time-based and angle-based location methods

  • Kim, Dong-Hyouk;Song, Seung-Hun;Sung, Tae-Kyung
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • v.1
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    • pp.479-483
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    • 2006
  • Indoor positioning is recently highlighted and various kinds of indoor positioning systems are under developments. Since positioning systems have their own characteristics, proper positioning scheme should be chosen according to the required specifications. Positioning methods are often classified into time-based and angle-based one, and this paper presents the error analysis of these location methods. Because measurement equations of these methods are nonlinear, linearization is usually needed to get the position estimate. In this paper, Gauss-Newton method is used in the linearization. To analyze the position error, we investigate the error ellipse parameters that include eccentricity, rotation angle, and the size of ellipse. Simulation results show that the major axes of error ellipses of TOA and AOA method lie in different quadrants at most region of workspace, especially where the geometry is poor. When the TOA/AOA hybrid scheme is employed, it is found that the error ellipse is reduced to the intersection of ellipses of TOA and AOA method.

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The Constant Angle Excavation Control of Excavator's Attachment using Fuzzy Logic Controller (퍼지 제어기를 이용한 유압 굴삭기의 일정각 굴삭 제어)

  • Seo, Sam-Joon;Park, Gwi-Tae;Shin, Dong-Mok;Kim, Kwan-Soo;Yim, Jong-Hyung
    • Proceedings of the KIEE Conference
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    • 1996.07b
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    • pp.1079-1082
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    • 1996
  • To automate an excavator the control issues resulting from environmental uncertainties must be solved. In particular the interactions between the excavation tool and the excavation environment are dynamic, unstructured and complex. In addition, operating modes of an excavator depend on working conditions, which makes it difficult to derive the exact mathematical model of excavator. Even after the exact mathematical model is established, it is difficult to design of a controller because the system equations are highly nonlinear and the state variable are coupled. The objective of this study is to design a fuzzy logic controller(FLC) which controls the position of excavator's attachment. This approach enables the transfer of human heuristics and expert knowledge to the controller. Excavation experiments are carried out to check the performance of the FLC.

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Revaluation of Tsunami Risk at the Site of Ulchin Nuclear Power Plant (울진 원자력발전소 부지에 대한 지진해일 위험도 재평가)

  • 이해균;이대수
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.14 no.1
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    • pp.1-7
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    • 2002
  • In the past, safety assessment on the site of Ulchin Nuclear Power Plants against tsunamis was carried out with probable maximum earthquake magnitude and related tsunamigenic fault parameters. Recently, however, based on the seismic gap theory, some seismologists warned about earthquakes of larger magnitudes than had been expected. In this study, we revaluated tsunami risk with a finite difference model based on linear and nonlinear shallow water equations. Firstly, we simulated the\`83 tsunami and compared the calculated water surface profile with the observed wave heights. Secondly, we evaluated the rise and drop of sea water level at the site of Ulchin Nuclear Power Plant with fault parameters of the past '83, '93 tsunamis and some dangerous faults. Finally, we showed that the cooling water intake facility of Ulchin Nuclear Power Plants would be safely operated in disastrous tsunamis.

The Numerical Analysis and Experimental Verification of the Heat Transfer Effect on the Highly Pressurized Gas Spring (고압 밀폐 가스 스프링에서의 열전달 효과 수치해석 및 실험적 검증)

  • Han, Insik;Choi, Kyojun;Kim, Jaeyong;Lee, Yoonbok
    • Transactions of the Korean Society of Automotive Engineers
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    • v.21 no.2
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    • pp.87-97
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    • 2013
  • Recently the use of gas spring in the combat and commercial vehicle's suspension is increasing. Because of its nonlinear characteristics, the gas spring can support wide range of dynamic loads and gives good ride quality. In design of gas spring, isothermal and adiabatic processes are applied generally, but those processes could not produce heat transfer effect in the simulation. So in this study, heat transfer differential equation and BWR/Ideal state equation are used to calculate the pressure of gas spring which is changing with time. The numerical analysis showed that the pressure of gas spring forms a hysteresis loop in the both of the state equations. But the peak pressure value of BWR equation over 0.1Hz frequency are higher than that of adiabatic process. And the test results showed that the differences between test results and ideal gas equation are smaller than those of BWR equation, so the ideal equation is more accurate than BWR equation in this case.

A frame work for heat generation/absorption and modified homogeneous-heterogeneous reaction in flow based on non-Darcy-Forchheimer medium

  • Hayat, Tasawar;Ahmad, Salman;Khan, Muhammad I.;Khan, Muhammad I.;Alsaedi, Ahmed
    • Nuclear Engineering and Technology
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    • v.50 no.3
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    • pp.389-395
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    • 2018
  • The present work aims to report the consequences of Darcy-Forchheimer medium in flow of Cross fluid model toward a stretched surface. Flow in porous space is categorized by Darcy-Forchheimer medium. Further heat transfer characteristics are examined via thermal radiation and heat generation/absorption. Transformation procedure is used. The arising system of nonlinear ordinary differential equations is solved numerically by means of shooting method. The effects of different flow variables on velocity, temperature, concentration, skin friction, and heat transfer rate are discussed. The obtained outcomes show that velocity was enhanced with the increase in the Weissenberg number but decays with increase in the porosity parameter and Hartman number. Temperature field is boosted by thermal radiation and heat generation; however, it decays with the increase in the Prandtl number.

Numerical Modeling of Heat Transfer for Squeeze Casting of MMCs (용탕주조법을 이용한 금속복합재료 제조공정의 열전달 해석)

  • Jung, Chang-Kyu;Jung, Sung-Wook;Nam, Hyun-Wook;Han, Kyung-Seop
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.10
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    • pp.2104-2113
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    • 2002
  • A finite element model is developed for the process of squeeze casting of metal matrix composites (MMCs) in cylindrical molds. The fluid flow and the heat transit. are fundamental phenomena in squeeze casting. To describe heat transfer in the solidification of molten aluminum, the energy equation is written in terms of temperature and enthalpy are applied in an axisymmetric model which is similar to the experimental system. A one dimensional flow model simulates the transient metal flow. A direct iteration technique was used to solve the resulting nonlinear algebraic equations, using a computer program to calculate the enthalpy, temperature and fluid velocity. The cooling curves and temperature distribution during infiltration and solidification were calculated fer pure aluminum. Experimentally, the temperature was measured and recorded using thermocouple wire. The measured time-temperature data were compared with the calculated cooling curves. The resulting agreement shows that the finite element model can accurately estimate the solidification time and predict the cooling process.

Equivalent Damping Ratio Based on Earthquake Characteristics of a SDOF Structure with an MR Damper (지진특성에 따른 MR감쇠기가 설치된 단자유도 구조물의 등가감쇠비)

  • Moon, Byoung-Wook;Park, Ji-Hun;Lee, Sung-Kyung;Min, Kyung-Won
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.1
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    • pp.87-93
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    • 2008
  • Seismic control performance of MR dampers, which have severe nonlinearity, varies with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with the MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with the MR damper is calculated using Newmark and Hall's equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. Frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed. Finally. response reduction factors for equivalent linear systems are proposed in order to improve accuracy in the prediction of the actual nonlinear response.

A FINITE-VISCOELASTIC CONTINUUM MODEL FOR RUBBER AND ITS FINITE ELEMENT ANALYSIS

  • Kim, Seung-Jo;Kim, Kyeong-Su;Cho, Jin-Yeon
    • Journal of Theoretical and Applied Mechanics
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    • v.1 no.1
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    • pp.97-109
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    • 1995
  • In this paper, a finite viscoelastic continuum model for rubber and its finite element analysis are presented. This finite viscoelatic model based on continuum mechanics is an extended model of Johnson and Wuigley's 1-D model. In this extended model, continuum based kinematic measures are rigorously defied and by using this kinematic measures, elastic stage law and flow rule are introduced. In kinematics, three configuration are introduced. In kinematics, three configuration are introduced. They are reference, current and virtual visco configurations. In elastic state law, it is assumed that at a certain time, there exists an elastic potential which describes the recoverable elastic energy. From this elastic potential, elastic state law is derived. The proposed flow rule is based on phenomenological observation. The flow rule gives precise relaxation response. In finite element approximation, mixed Lagrangian description is used, where total and similar method of updated Lagrangian descriptions are used together. This approach reduces the numerical job and gives simple nonlinear syatem of equations. To satisfy the incompressible condition, penalty-type modified Mooney-Rivlin energy function is adopted. By this method nearly incompressible condition is obtain the virtual visco configuration. For verification, uniaxial stretch tests are simulated for various stretch rates. The simulated results show good agreement with experiments. As a practical experiments. As a preactical example, pressurized rubber plate is simulated. The result shows finite viscoelastic effects clearly.