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Dynamic Equations (dynamic + equation)
Selected AbstractsVibration of a space arc subject to a critical dynamic loadINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 4 2005Lazarus Teneketzis Tenek Abstract The present study concerns the dynamic behaviour of a space arc subject to a midarc vertical buckling load dynamically applied. The arc is discretized with a set of three-dimensional beam finite elements and the non-linear dynamic equation (large displacements) is solved by means of an unconditionally stable time-dependent scheme over time. The vertical excitation gives rise to a very fast and erratic horizontal wave as the structure begins to vibrate in all directions. This horizontal wave has chaotic characteristics as its attractor indicates. Time,displacement curves are obtained for all components of the midarc point. Although the time algorithm was executed here for 2000 time steps, simulation over longer periods of time can reveal the vibration characteristics and even simulate structural failure under the imposed dynamic buckling load for the space arc structure. Copyright © 2004 John Wiley & Sons, Ltd. [source] Convergence properties of bias-eliminating algorithms for errors-in-variables identificationINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 9 2005Torsten Söderström Abstract This paper considers the problem of dynamic errors-in-variables identification. Convergence properties of the previously proposed bias-eliminating algorithms are investigated. An error dynamic equation for the bias-eliminating parameter estimates is derived. It is shown that the convergence of the bias-eliminating algorithms is basically determined by the eigenvalue of largest magnitude of a system matrix in the estimation error dynamic equation. When this system matrix has all its eigenvalues well inside the unit circle, the bias-eliminating algorithms can converge fast. In order to avoid possible divergence of the iteration-type bias-eliminating algorithms in the case of high noise, the bias-eliminating problem is re-formulated as a minimization problem associated with a concentrated loss function. A variable projection algorithm is proposed to efficiently solve the resulting minimization problem. A numerical simulation study is conducted to demonstrate the theoretical analysis. Copyright © 2005 John Wiley & Sons, Ltd. [source] Spatially varied flow in non-prismatic channels.IRRIGATION AND DRAINAGE, Issue 1 2002I: dynamic equation canal d'irrigation; modélisation; écoulement spatialement varié; équation de transfert; analyse numérique; expérimentation Abstract The bottom width of channels carrying spatially varied flow with increasing discharge is usually flared in the flow direction. This produces a non-prismatic section. This paper, based on the law of linear momentum conservation, presents a new form of the governing dynamic equation for flow in such circumstances. In addition to the computed water surface profile, the proposed equation affects the position of the control section and its flow depth as well. Copyright © 2002 John Wiley & Sons, Ltd. RÉSUMÉ La largeur du lit de cours d'eau, variée spatialement par l'augmentation du débit, influence la direction de l'écoulement. Cette procédure crée une coupe irréguliére de cours d'eau. Cet article présente une nouvelle forme de l'équation dynamique dans cette situation de l'écoulement. La méthodologie est basée sur la loi de conservation linéaire de momentum. L'équation proposée est capable de calculer le profil de niveau de l'eau. Elle affecte aussi sur la situation de coupe de contrôle et la profondeur de l'écoulement. Copyright © 2002 John Wiley & Sons, Ltd. [source] BONDSYM: SIMULINK-based educational software for analysis of dynamic systemCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 2 2010J.A. Calvo Abstract This article presents an educational software called BONDSYM developed to allow engineering students to learn easily and quickly about the analysis of dynamic systems through the Bond Graph method. This software uses the SIMULINK library of MATLAB, which has proven to be an excellent choice in order to implement and solve the dynamic equations involved. The application allows for the representation of the behavior of a dynamic system analyzed through the Bond Graph theory in order to understand the dynamic equations and the physical phenomena involved. Based on block diagram of SIMULINK, the different "bonds" of Bond Graph can be integrated as SIMULINK blocks in order to generate the dynamic model. A few simple models are analyzed through this application. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 18: 238,251, 2010; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20246 [source] Grain transport mechanics in shallow overland flowECOHYDROLOGY, Issue 3 2009S.N. Prasad Abstract A physical model based on continuum multiphase flow is described to represent saltating transport of grains in shallow overland flows. The two-phase continuum flow of water and sediment considers coupled StVenant-type equations. The interactive cumulative effect of grains is incorporated by a dispersive stress term. The mean fluid thrust on the particle in the saltation layer of grains is expressed in terms of a slip velocity. The continuum model leads to the unexpected, but an interesting result is that particle velocity increases with the solid concentration. This increase predicts monotonic behaviour leading to overestimates of particle velocity at higher sediment concentration. To improve the predictions, grain dynamic equations, which incorporate bed collision, are analysed. The analysis leads to an improved model for predicting saltation height. Incorporation of the results in the continuum model yields a velocity-concentration relationship that is consistent with experimental observations for increasing concentration. Laboratory flume experiments explore the evaluation of various parameters from the measured particle velocities by photonic probes. Copyright © 2009 John Wiley & Sons, Ltd. [source] The fundamental solution of poroelastic plate saturated by fluid and its applicationsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 7 2010P. H. Wen Abstract In this paper, the numerical model of the transverse vibrations of a thin poroelastic plate saturated by a fluid was proposed. Two coupled dynamic equations of equilibrium related to the plate deflection and the equivalent moment were established for an isotropic porous medium with uniform porosity. The fundamental solutions for a porous plate were derived both in the Laplace transform domain and in the time domain. A meshless method was developed and demonstrated in the Laplace transform domain for solving two coupled dynamic equations. Numerical examples demonstrated the accuracy of the method of the fundamental solutions and comparisons were made with analytical solutions. The proposed meshless method was shown to be simple to implement and gave satisfactory results for a poroelastic plate dynamic analysis. Copyright © 2009 John Wiley & Sons, Ltd. [source] Swelling effect on the dynamic behaviour of composite cylindrical shells conveying fluidINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 4 2006M. H. Toorani Abstract This paper presents a semi-analytical investigation of a fluid,structure system. Both isotropic and composite cylindrical shells filled with or subjected to a flowing fluid have been considered in this study. The structure may be uniform or non-uniform in the circumferential direction. The hybrid finite element approach, shearable shell theory and velocity potential flow theory have been combined to establish the dynamic equations of the coupled system. The set of matrices describing their relative contributions to equilibrium is determined by exact analytical integration of the equilibrium equations. The linear potential flow theory is applied to describe the fluid effects that lead to the inertial, centrifugal and Coriolis forces. The axisymmetric, beam-like and shell modes of vibrations in both cases of uniform and non-uniform cylindrical shells are investigated. Fluid elastic stability of a structure subjected to a flowing fluid is also studied. This theory yields the high and the low eigenvalues and eigenmodes with comparably high accuracy. Reasonable agreement is found with other theories and experiments. Copyright © 2005 John Wiley & Sons, Ltd. [source] Dynamic Analysis of Tendon Driven Robotic MechanismsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 5 2003Jyh-Jone Lee In this paper, a systematic methodology for the dynamic analysis of tendon-driven robotic mechanisms is presented. The approach utilizes the recursive Newton-Euler equations to compute the kinematic and dynamic equations of all links that locate on the transmission line of a tendon-driven robotic mechanism. The inertias of the intermediate links in the mechanism are taken into account. It is shown that the dynamic equations can be established in a recursive manner from the end-effector links toward the proximal links and can be solved at the proximal end without the need of solving the simultaneous system equations. The joint reaction forces and the tension in each segment of tendon can be also obtained. The methodology can be applied to both endless and open-ended tendon drives. © 2003 Wiley Periodicals, Inc. [source] Robust force control of a flexible arm with a nonsymmetric rigid tip bodyJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 5 2001Yoshifumi Morita In this article, we discuss modeling and robust control of bending and torsional vibrations and contact force of a flexible arm with a nonsymmetric rigid tip body. By using Hamilton's principle and the Lagrange multiplier method, dynamic equations of the constrained flexible arm are derived. Since the flexible arm has the nonsymmetric tip body, the bending and torsional vibrations are coupled. As the obtained boundary conditions of the distributed parameter system are nonhomogeneous, we introduce a change of variables to derive homogeneous boundary conditions. By using the eigenvalues and the correpsonding eigenfunctions related to the distributed parameter system, we derive a finite-dimensional modal model. To compensate for the spillover instability, we construct robust controllers of an optimal controller with a low-pass property and an H, controller. Some experiments have been carried out to show the effectiveness of the proposed robust controllers. © 2001 John Wiley & Sons, Inc. [source] Local Banks Efficiency and EmploymentLABOUR, Issue 3 2008Patrizia Ordine We argue that if banks are not efficient in monitoring the borrowers in the presence of asymmetric information, credit market imperfections have real effects. We estimate dynamic equations using system generalized method of moments (GMM) for bank loans and employment on panel data for Italian firms. The system GMM estimates indicate that the impact of credit market on employment is higher where the local financial market is less developed, asymmetric information is widespread, bank managers are less efficient in assessing the firms' solvency and do not use appropriate methods to evaluate the borrowers' payback capacity. [source] A Discrete, Space Variation Model for Studying the Kinetics of Shape Deformation of Vesicles Coupled with Phase SeparationMACROMOLECULAR THEORY AND SIMULATIONS, Issue 5 2006Jianfeng Li Abstract Summary: The evolution dynamics of phase separation, coupled with shape deformation of vesicles is described by using dissipative dynamic equations, specifically the time-dependent Ginzburg-Landau (TDGL) equations. In order to improve the numerical stability and thus to efficiently deal with a large deformation of vesicles, a new algorithm, namely the discrete space variation model (DSVM) has been developed for the first time. The algorithm is based on the variation of the discretized free-energy functional, which is constructed in discrete membrane space, in contrast to the commonly used continuous free-energy functional. For the sake of numerical tractability, only the cylindrical vesicles (2D), with two components, are taken into consideration to illustrate the efficiency and validity of new algorithm. The simulation results, based on the DSVM algorithm have been compared with those from both linear analysis and strong segregation theory using the continuous space free-energy functional. It is found that the DSVM algorithm can correctly describe the coupling between the lateral phase-separation on the vesicle membrane and the vesicle shape deformation, both for early and late stages. A flower-like vesicle obtained by DSVM simulation. [source] Modelling and identification of rigid-body dynamics of parallel kinematic structuresPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003Martin Grotjahn Dipl.-Ing.Article first published online: 25 MAR 200 A new approach for modelling the dynamics of parallel kinematic (PKM) structures is presented in this paper. It leads to a formulation of the dynamic equations which is linear with respect to a dynamic parameter vector of minimal dimension. Thus, the equations can be directly used for parameter identi.cation by linear estimation techniques. The algorithm utilises Jourdain's principle of virtual power which leads to very efficient resulting code. The parameter reduction is based on opening the kinematic loops so that analytic rules known from serial robots can be implemented. Additionally, a new approach for dynamic parameter identification is suggested. The application to modelling the PKM PaLiDa and identifying its gravitational parameters proves the capacity of the presented approaches. [source] Physical Model-Based Indirect Measurements of Blood Pressure and Flow Using a Centrifugal PumpARTIFICIAL ORGANS, Issue 8 2000Tadashi Kitamura Abstract: This article describes a technique offering indirect measurements of pump pressure differential and flow with certain accuracy independent of changes in blood viscosity. This technique is based on noninvasive measurements of the motor current and rotation speed using the physical model equations of the centrifugal pump system. Blood viscosity included in the coefficients of the dynamic equations is first estimated, and then substitution of the estimated viscosity into the steady equations of the model provides pump flow and pressure differential. In vitro tests using a Capiox pump showed a sufficient linear correlation between actual values and their estimates for pressure differential and pump flow. An in vivo test using a 45 kg sheep showed that the proposed algorithm needs robustness for the convergence of estimates of viscosity. An overall evaluation, however, of the developed algorithm/model showed indications of success in terms of efficient computation and modeling. [source] Dynamisch-thermisches CFD-Verfahren mit angepaßter RegelungsmethodeBAUPHYSIK, Issue 1 2007Tobias Zitzmann Dipl.-Ing. (FH) Zur Reduktion des Zeitaufwands von dynamisch-thermischen Langzeitsimulationen mit CFD-Programmen wurde in kürzlich veröffentlichten Studien eine neuartige Freeze-Flow Methode vorgestellt. Diese basiert auf der periodischen Umschaltung zwischen der volldynamischen Lösung aller Gleichungen und der ausschließlichen Lösung der Enthalpie-Gleichungen (eingefrorene Luftströmung). Dieser Artikel beschreibt eine neue, angepaßte Regelung für diese Umschaltung, wodurch eine zusätzliche Reduzierung der Simulationszeit erzielt wird. In Tests an Modellen für die mechanische und freie Lüftung sowie der freien Konvektion im geschlossenen Raum für feste und zeitveränderliche thermische Randbedingungen wurde im Vergleich zur ununterbrochenen volldynamischen Simulation eine Simulationszeiteinsparung von bis zu 93% erreicht. Dynamic thermal CFD approach using an adaptive control method. Previously published studies have presented a novel freeze-flow method for reducing CPU requirements of long-term dynamic thermal simulations using CFD programs. This works by intermittently switching between solution of the full dynamic equations and solution of the enthalpy equation only (frozen flow). This paper describes a new automated control method for this switching strategy and shows an additional decrease in simulation time. In tests with models for mechanical and natural ventilation and for free convection in a sealed room with constant and time varying thermal boundary conditions, a simulation time reduction of up to 93% was achieved when compared to a continuous fully dynamic simulation. [source] C. botulinum inactivation kinetics implemented in a computational model of a high-pressure sterilization processBIOTECHNOLOGY PROGRESS, Issue 1 2009Pablo Juliano Abstract High-pressure, high-temperature (HPHT) processing is effective for microbial spore inactivation using mild preheating, followed by rapid volumetric compression heating and cooling on pressure release, enabling much shorter processing times than conventional thermal processing for many food products. A computational thermal fluid dynamic (CTFD) model has been developed to model all processing steps, including the vertical pressure vessel, an internal polymeric carrier, and food packages in an axis-symmetric geometry. Heat transfer and fluid dynamic equations were coupled to four selected kinetic models for the inactivation of C. botulinum; the traditional first-order kinetic model, the Weibull model, an nth-order model, and a combined discrete log-linear nth-order model. The models were solved to compare the resulting microbial inactivation distributions. The initial temperature of the system was set to 90°C and pressure was selected at 600 MPa, holding for 220 s, with a target temperature of 121°C. A representation of the extent of microbial inactivation throughout all processing steps was obtained for each microbial model. Comparison of the models showed that the conventional thermal processing kinetics (not accounting for pressure) required shorter holding times to achieve a 12D reduction of C. botulinum spores than the other models. The temperature distribution inside the vessel resulted in a more uniform inactivation distribution when using a Weibull or an nth-order kinetics model than when using log-linear kinetics. The CTFD platform could illustrate the inactivation extent and uniformity provided by the microbial models. The platform is expected to be useful to evaluate models fitted into new C. botulinum inactivation data at varying conditions of pressure and temperature, as an aid for regulatory filing of the technology as well as in process and equipment design. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] | ||||||||||