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Letteratura scientifica selezionata sul tema "Dynamic equivalent method"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 9 febbraio 2022

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Articoli di riviste sul tema "Dynamic equivalent method"

Gonidou, Luc-Olivier, Jean-Louis Nicks e François Dekmeer. "Equivalent F* Method for Dynamic Reanalysis". AIAA Journal 58, n. 4 (aprile 2020): 1891–96. http://dx.doi.org/10.2514/1.j058737.

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FRITTELLI, MARCO, e MARCO MAGGIS. "CONDITIONAL CERTAINTY EQUIVALENT". International Journal of Theoretical and Applied Finance 14, n. 01 (febbraio 2011): 41–59. http://dx.doi.org/10.1142/s0219024911006255.

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In a dynamic framework, we study the conditional version of the classical notion of certainty equivalent when the preferences are described by a stochastic dynamic utility u(x,t,ω). We introduce an appropriate mathematical setting, namely Orlicz spaces determined by the underlying preferences and thus provide a systematic method to go beyond the case of bounded random variables. Finally we prove a conditional version of the dual representation which is a crucial prerequisite for discussing the dynamics of certainty equivalents.

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Zhang, Wei, Chuan Qiong Sun e Huan Wang. "Equivalent Static Loads Method for Flexible Structural Shape Optimization". Advanced Materials Research 308-310 (agosto 2011): 2364–67. http://dx.doi.org/10.4028/www.scientific.net/amr.308-310.2364.

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Study on the flexible structural shape optimization problem under dynamic loading conditions. The dynamic loads are transformed to equivalent static loads (ESLs), and then the static response optimization can be used for dynamic response optimization. A structural shape optimization model, which has been established by ESls method, is utilized to design the flexible components in the multibody dynamic system. A shape optimization for a four-bar linkage had been generated by using the ESLs method, and the results indicate that there are noticeable improvements in the total mass and the maximum stress.

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Martin, K., C. Escudero, A. Erkoreka, I. Flores e J. M. Sala. "Equivalent wall method for dynamic characterisation of thermal bridges". Energy and Buildings 55 (dicembre 2012): 704–14. http://dx.doi.org/10.1016/j.enbuild.2012.08.024.

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Zheng, Wenzhe, Jing Bu, Ningyu Zhang, Qian Zhou e Jiankun Liu. "Dynamic Equivalence of Wind Farms Considering Complex Terrain". MATEC Web of Conferences 260 (2019): 02013. http://dx.doi.org/10.1051/matecconf/201926002013.

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The dynamic equivalence of wind farms is widely used for model simplification. While, the accuracy will be lower without considering the influence of wind speed correlation caused by topography and wake effect. In order to improve the accuracy, this paper proposes a dynamic cluster equivalence method of coherent generators based on hierarchical clustering analysis. Firstly, it analyses the impacts of equivalence’s accuracy such as wind speed distribution, wake effect and control strategy of turbine. Then, it uses hierarchical clustering method to correlate the disturbed trajectory of rotor current of the intra-site turbines and obtains the dynamic clustering results. Finally, it uses power loss method to obtain the equivalent parameters of multi-machine equivalent model. Simulation results verify the effectiveness of this method.

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Cai, Yongyang, Kenneth Judd e Jevgenijs Steinbuks. "A nonlinear certainty equivalent approximation method for dynamic stochastic problems". Quantitative Economics 8, n. 1 (marzo 2017): 117–47. http://dx.doi.org/10.3982/qe533.

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Broccardo, Marco, e Armen Der Kiureghian. "Nonlinear stochastic dynamic analysis by evolutionary tail-equivalent linearization method". Structural Safety 90 (maggio 2021): 102044. http://dx.doi.org/10.1016/j.strusafe.2020.102044.

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Guo, Ning, Hao Chen, Zhong Zhang, Fei Du e Chao Xu. "Comparative study of dynamically equivalent modeling methods for honeycomb sandwich structure: numerical simulations and experiments". Mechanical Sciences 11, n. 2 (11 settembre 2020): 317–28. http://dx.doi.org/10.5194/ms-11-317-2020.

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Abstract. The structure of the lightweight honeycomb sandwich panel is complex. Thus, establishing an equivalent simplified model is indispensable to improve the efficiency of the dynamic analysis of honeycomb sandwich panels. In this paper, three commonly used dynamically equivalent modeling methods for honeycomb sandwich panel are studied: a dynamically equivalent method based on laminated plate theory, a single-layer plate equivalent method based on the theory of Hoff (1948), and an improved equivalent method based on Allen (1969). Using theoretical study, numerical simulations, and experiments, the applicability of these equivalent methods and the effect of design parameters on the dynamic characteristics are studied, and the optimal dynamically equivalent method for honeycomb sandwich panels is obtained.

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Wang, Ran, Hao Tian, Hong Liu Wang, Yang Zhao, Chen Yang e Xin Bin Hou. "SSPS Dynamic Modeling and the Flexible Vibration Suppression". Applied Mechanics and Materials 799-800 (ottobre 2015): 724–27. http://dx.doi.org/10.4028/www.scientific.net/amm.799-800.724.

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Space solar power satellite (SSPS) as a very large flexible spacecraft structure with complex configuration, large size and number of units bring the difficulties to dynamics modeling and analysis. Considering SSPS structure characteristics, equivalent strain and kinetic energy theory is adopted to establish the equivalent beam model of SSPS truss structure. The assumed mode method is adopted to describe the flexible body. The modal truncation method implements the dynamics system order reduction. Mixed coordinates method is adopted to establish the rigid-flexible coupled dynamic model. The established dynamic model can reflect dynamic characteristics of SSPS, achieve control requirements for SSPS and decrease the workload of simulation calculation. The independent modal space control (IMSC) method is proposed to active control research view of the large displacement, nonlinearity, low and dense mode frequency, light damping of flexible structures. Simulation results on flexible solar array show the effectiveness of the control method.

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Wei, Changzhu, Ruiming Wang, Wei Zheng e Jialun Pu. "Equivalent dynamic modeling of flexible morphing aircraft". Science Progress 104, n. 2 (aprile 2021): 003685042110109. http://dx.doi.org/10.1177/00368504211010946.

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A morphing aircraft can maintain optimal flight performance by adaptively changing shape. However, large deformation and fast motion of aircraft modules lead to complicated dynamics during morphing process. This paper proposes a mechanistic equivalent model with parameters identified by optimization method. Based on the dynamics of the aircraft modules with large deformation and fast motion and considering the coupling characteristics of rigid bodies and gimbal joints, an equivalent dynamic model of morphing aircraft is built in this study. Considering the huge amount of highly coupled parameters in the equivalent model, particle swarm optimization algorithm is used to identify the equivalent parameters based on the sample data of flexible model. By comparing the simulation results of proposed model to those of rigid model and flexible model, it can be seen that the accuracy of the proposed equivalent model is comparable to that of the flexible model, but the computational load is only 10% of that of flexible model. Further, based on this high-fidelity model with low computational load, an optimized morphing process is obtained, and the attitude variation during morphing is reduced by 4.23%.

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Più fonti

Tesi sul tema "Dynamic equivalent method"

SANTOS, RODRIGO BIANCHI. "PARAMETRIC OPTIMIZATION OF TRUSS STRUCTURES UNDER DYNAMIC LOADING USING THE EQUIVALENT STATIC LOAD METHOD". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2018. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=35802@1.

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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Otimização estrutural sujeita a carregamentos dinâmicos é um problema desafiador em vários aspectos, a começar pelo grande número de restrições que devem ser atendidas em todos os instantes de tempo. Além disso, o custo computacional para avaliar os gradientes destas restrições é bastante elevado e requer um grande espaço de armazenamento. Na literatura, alguns métodos reduzem o número de restrições avaliando em instantes de tempo selecionados, como o pior caso por exemplo, ou ainda constroem um funcional equivalente, integrando as restrições violadas ao longo do tempo, assim eliminando essa dependência. Nesta dissertação, o método do Carregamento Estático Equivalente (ESL) é utilizado, no qual o problema dinâmico original é transformado em uma sequência de subproblemas de otimização linear estática com múltiplos casos de carga. Um atrativo deste método é a possibilidade da solução de problemas não lineares, evitando o alto custo devido às repetidas análises estruturais e cálculos das restrições. Problemas clássicos de treliças planas submetidas a carregamentos dinâmicos são resolvidos utilizando o método ESL. A função a ser minimizada é a massa da treliça, que está sob restrições de tensão e deslocamento, onde as variáveis de projeto são as áreas da seção transversal dos membros. Além disso, uma interface utilizando ANSYS e MATLAB é desenvolvida para uma abordagem modular, na qual a análise via elementos finitos e a otimização possam ser realizadas separadamente. Este processo viabiliza a otimização de estruturas que apresentam comportamentos não lineares a partir da utilização de diversos softwares comerciais disponíveis no mercado.
Structural optimization subject to dynamic loading is a challenging problem in many aspects, starting with the large number of constraints that must be respected at all instants of time. Furthermore, the computational cost to evaluate the gradients of these constraints is significantly high and requires a large storage space. In the literature, some methods reduce the number of constraints evaluating at selected instants of time, such as the worst case. Alternatively, a single equivalent functional is constructed to eliminate the time dependence by integrating the violated constraints over time. In this work, the Equivalent Static Load (ESL) method is used, in which the original dynamic problem is reduced into a number of static linear optimization problems with multiple load cases. An attractive feature of this method is the possibility of solving non-linear problems, avoiding the high cost due to repeated structural analyzes and constraint calculations. Classical problems of plane trusses subjected to dynamic loads are solved using the ESL method. The function to be minimized is the truss mass, which is subjected to stress and displacement constraints, where the design variables are the cross-sectional areas of the members. In addition, an interface using ANSYS and MATLAB was developed for a modular approach, in which finite element analysis and optimization can be performed separately. This process makes possible the optimization of structures that present non-linear behavior from the use of most structural analysis software packages available on the market.

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Lázaro, Navarro Mario. "The Eigenvalue Problem in Linear Viscoelastic Structures: New Numerical Approaches and the Equivalent Viscous Model". Doctoral thesis, Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/30062.

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El análisis y el control de las vibraciones cobra especial importancia en muchas ramas de la ingeniería, en especial la ingeniería mecánica, civil, aeronáutica y automovilística. Tal es así que prácticamente se identi¿ca como un área independiente dentro del análisis dinámico de estructuras. Desde los comienzos de esta teoría, las fuerzas disipativas o de amortiguamiento han sido uno de los fenómenos más difíciles de modelizar. El modelo viscoso, por su sencillez y versatilidad ha sido y sigue siendo el gran paradigma de los modelos de amortiguamiento. Sin embargo, como consecuencia de la aparición de materiales con memoria se introdujo el fenómeno de la viscoelasticidad; Esta, si bien está también 'íntimamente ligada ' a la velocidad de la respuesta, necesito de la introducción de las denominadas funciones hereditarias, que permiten poner a las fuerzas disipativas como función no solo de la velocidad instantánea sino de la historia de velocidades desde el comienzo del movimiento, de ahí el termino memoria. De forma natural, el avance teórico introducido en el modelo supone también una complicación computacional, pues donde antes teníamos un sistema lineal de ecuaciones diferenciales ahora tenemos un sistema de ecuaciones integro-diferenciales. El análisis de las vibraciones libres de los sistemas con amortiguamiento viscoelástico conduce a un problema nolineal de autovalores donde la característica principal es una matriz de amortiguamiento que depende de la frecuencia de excitación. El estudio de la solución de autovalores y autovectores de este problema es importante si se desean conocer los modos de vibración de la estructura o si se pretende obtener la respuesta en el dominio de la frecuencia del sistema. El objetivo fundamental de esta Tesis Doctoral es doble: Por un lado, profundizar en el conocimiento del problema de autovalores de sistemas viscoelásticos proponiendo para ello nuevos métodos numéricos de resolución. Por otro, desarrollar un nuevo modelo viscoso que, bajo ciertas condiciones, reproduzca la respuesta del modelo viscoelástico con su¿ciente aproximación. La Tesis se divide en ocho capítulos, de ellos el cuerpo principal se encuentra en los seis centrales (Capítulos 2 a 7. Todos ellos son artículos de investigación que, o bien han sido publicados, o bien están en proceso de revisión en revistas contenidas en el Journal Citation Reports (JCR). Por esta razón, todos los capítulos conservan la estructura intrínseca de un artículo, incluidas una introducción y una bibliografía en cada uno. Los cuatro primeros capítulos (Capítulos 2 a 5) se centran en el estudio del problema no lineal de autovalores. Se proponen dos metodologías de resolución: la primera es un procedimiento iterativo basado en el esquema del punto-¿jo y desarrollado para sistemas proporcionales o ligeramente no-proporcionales (aquellos en los que los modos se presentan desacoplados o casi desacoplados). La segunda metodología (presentada en dos capítulos diferentes), denominada paramétrica, permite obtener soluciones casi-analíticas de los autovalores, tanto para sistemas de un grado de libertad como para sistemas de múltiples grados de libertad y dentro de 'estos, para sistemas proporcionales y no proporcionales. El estudio del problema de autovalores se completa con un capítulo dedicado a los autovalores reales, también denominados autovalores no viscosos. En 'él se demuestra una nueva caracterización maten ática que deben cumplir dichos autovalores y que permite proponer un nuevo concepto: el conjunto no-viscoso. Los dos 'últimos capítulos (Capítulos 6 y 7) analizan el Modelo Viscoso Equivalente como propuesta para la modelización de la respuesta de sistemas viscoelásticos. El análisis se realiza desde el dominio de la frecuencia estudiando la función de transferencia. En una primera etapa (pen último capítulo), de naturaleza más maten ática, se demuestra que la función de transferencia exacta de un modelo viscoelástico se puede expresar como suma de una función de transferencia propia de un modelo viscoso más un término denominado residual, directamente dependiente del nivel de amortiguamiento inducido y del acoplamiento modal (noproporcionalidad de la matriz de amortiguamiento). En una segunda etapa ('ultimo capítulo), se desarrolla una aplicación para estructuras reales formadas por entramados planos de elementos 1D amortiguados con capas de material visco elástico. Este tipo de estructuras ha permitido usar una variante mejorada del método paramétrico para la obtención de los autovalores, de forma que en este 'ultimo capítulo ha servido como nexo de unión de las metodologías más importantes desarrolladas en la Tesis.
Lázaro Navarro, M. (2013). The Eigenvalue Problem in Linear Viscoelastic Structures: New Numerical Approaches and the Equivalent Viscous Model [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/30062
TESIS

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Bahcecioglu, Tunc. "Parallel Solution Of Soil-structure Interaction Problems On Pc Clusters". Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612954/index.pdf.

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Numerical assessment of soil structure interaction problems require heavy computational efforts because of the dynamic and iterative (nonlinear) nature of the problems. Furthermore, modeling soil-structure interaction may require

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Thakore, Vaibhav. "Nonlinear dynamic modeling, simulation and characterization of the mesoscale neuron-electrode interface". Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5529.

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Extracellular neuroelectronic interfacing has important applications in the fields of neural prosthetics, biological computation and whole-cell biosensing for drug screening and toxin detection. While the field of neuroelectronic interfacing holds great promise, the recording of high-fidelity signals from extracellular devices has long suffered from the problem of low signal-to-noise ratios and changes in signal shapes due to the presence of highly dispersive dielectric medium in the neuron-microelectrode cleft. This has made it difficult to correlate the extracellularly recorded signals with the intracellular signals recorded using conventional patch-clamp electrophysiology. For bringing about an improvement in the signal-to-noise ratio of the signals recorded on the extracellular microelectrodes and to explore strategies for engineering the neuron-electrode interface there exists a need to model, simulate and characterize the cell-sensor interface to better understand the mechanism of signal transduction across the interface. Efforts to date for modeling the neuron-electrode interface have primarily focused on the use of point or area contact linear equivalent circuit models for a description of the interface with an assumption of passive linearity for the dynamics of the interfacial medium in the cell-electrode cleft. In this dissertation, results are presented from a nonlinear dynamic characterization of the neuroelectronic junction based on Volterra-Wiener modeling which showed that the process of signal transduction at the interface may have nonlinear contributions from the interfacial medium. An optimization based study of linear equivalent circuit models for representing signals recorded at the neuron-electrode interface subsequently proved conclusively that the process of signal transduction across the interface is indeed nonlinear. Following this a theoretical framework for the extraction of the complex nonlinear material parameters of the interfacial medium like the dielectric permittivity, conductivity and diffusivity tensors based on dynamic nonlinear Volterra-Wiener modeling was developed. Within this framework, the use of Gaussian bandlimited white noise for nonlinear impedance spectroscopy was shown to offer considerable advantages over the use of sinusoidal inputs for nonlinear harmonic analysis currently employed in impedance characterization of nonlinear electrochemical systems. Signal transduction at the neuron-microelectrode interface is mediated by the interfacial medium confined to a thin cleft with thickness on the scale of 20-110 nm giving rise to Knudsen numbers (ratio of mean free path to characteristic system length) in the range of 0.015 and 0.003 for ionic electrodiffusion. At these Knudsen numbers, the continuum assumptions made in the use of Poisson-Nernst-Planck system of equations for modeling ionic electrodiffusion are not valid. Therefore, a lattice Boltzmann method (LBM) based multiphysics solver suitable for modeling ionic electrodiffusion at the mesoscale neuron-microelectrode interface was developed. Additionally, a molecular speed dependent relaxation time was proposed for use in the lattice Boltzmann equation. Such a relaxation time holds promise for enhancing the numerical stability of lattice Boltzmann algorithms as it helped recover a physically correct description of microscopic phenomena related to particle collisions governed by their local density on the lattice. Next, using this multiphysics solver simulations were carried out for the charge relaxation dynamics of an electrolytic nanocapacitor with the intention of ultimately employing it for a simulation of the capacitive coupling between the neuron and the planar microelectrode on a microelectrode array (MEA). Simulations of the charge relaxation dynamics for a step potential applied at t = 0 to the capacitor electrodes were carried out for varying conditions of electric double layer (EDL) overlap, solvent viscosity, electrode spacing and ratio of cation to anion diffusivity. For a large EDL overlap, an anomalous plasma-like collective behavior of oscillating ions at a frequency much lower than the plasma frequency of the electrolyte was observed and as such it appears to be purely an effect of nanoscale confinement. Results from these simulations are then discussed in the context of the dynamics of the interfacial medium in the neuron-microelectrode cleft. In conclusion, a synergistic approach to engineering the neuron-microelectrode interface is outlined through a use of the nonlinear dynamic modeling, simulation and characterization tools developed as part of this dissertation research.
Ph.D.
Doctorate
Physics
Sciences
Physics

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Leinonen, M. (Mikko). "Finite element method and equivalent circuit based design of piezoelectric actuators and energy harvester dynamics". Doctoral thesis, Oulun yliopisto, 2015. http://urn.fi/urn:isbn:9789526208374.

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Abstract The main objective of this thesis was to use and combine Finite Element Method (FEM) and small signal equivalent circuit models in actuator and energy harvesting design and to study the dynamics of the said designs. The work is divided into four different sections. In the first section, the small signal parameters are derived for a pre-stressed piezoelectric actuator using a series of measurements. In addition, the tunability of the resonance frequency using mass and series capacitors is investigated. In the second section, a piezoelectric Fabry Perot Interferometer actuator is simulated using FEM and the small signal parameters are derived using FEM simulations. The modelled results are compared with the actual measurements and the resonance frequency is found to differ by only 0.8 percent from the measured values when the mirror is attached to the actuator. In the third section a piezoelectric wide band energy harvester is developed with multiple beam topology. Two different designs are compared, one produced using the conventional PZT-steel structure and one with a PZT-LTCC structure. The final section presents an FEM model for a shoe mounted energy harvester and concentrates on the modelling of walking dynamics in FEM. The simulation results are compared to actual measurements and the simulated power values are found to differ by only 7% when the cymbal stroke is below 1.3 mm. The generated model is also expandable to other types of energy harvesters and the methods developed can be used in a variety of different energy harvesting simulations and harvester development. The results show that the equivalent circuit approach together with FEM modelling is a powerful tool in the dynamics design of piezoelectric actuators and energy harvesters
Tiivistelmä Väitöstyön päätavoitteena oli yhdistää elementtimenetelmät (FEM) ja piensignaalimallit aktuaattorien ja energiankorjuukomponenttien suunnittelussa ja tutkia niiden dynamiikkaa. Työ on jaettu neljään eri osaan. Ensimmäisessä osassa piensignaalimallit johdettiin pietsosähköisestä aktuaattorista mittausten avulla. Lisäksi resonanssitaajuuden muuttamista tutkitaan massan ja sarjaan kytketyn kapasitanssin avulla. Toisessa osassa simuloidaan pietsosähköistä Fabry Perot interferometria käyttäen elementtimenetelmää. Lisäksi komponentin piensignaalimalli luodaan käyttäen simulointimallia. Lopuksi piensignaalimallin ja prototyypin mittaustuloksia verrataan. Mallin resonanssitaajuus poikkeaa mitatusta vain 0.8 %, kun aktuaattoriin on kiinnitetty peili. Kolmannessa osassa kehitetään ja verrataan toisiinsa kahta erilaista laajakaistaista monipalkkista pietsosähköistä energian korjuukomponenttia. Toinen komponenteista on toteutettu perinteisellä PZT-teräs rakenteella ja toinen yhteissintratulla PZT-LTCC rakenteella. Viimeisessä osassa luodaan simulaatio malli kenkään asennetulle cymbal tyyppiselle pietsosähköiselle energian korjuukomponentille ja kävelyn dynamiikkaa tutkitaan. Luotua mallia verrataan prototyypin mittaustuloksiin ja simuloitu energian tuotto poikkeaa vain 7 % alle 1.3 mm puristusliikkeellä. Tulokset osoittivat, että piensignaalimallin ja elementtimenetelmän yhdistäminen on tehokas apu pietsosähköisten aktuaattorien ja energiankorjuukomponenttien dynamiikan suunnittelussa

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Karaagacli, Taylan. "Determination Of Dynamically Equivalent Fe Models Of Aircraft Structures By Using Modal Test Data". Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612522/index.pdf.

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Reliable flutter analysis of aircraft structures is a major requirement to determine safe flight envelops. Dynamically equivalent finite element model of an aircraft structure correlating well with experimental modal is a major requirement for a reliable flutter analysis. Currently available model updating techniques require enormous time and engineering work to achieve appropriate finite element models of aircraft structures. The method developed within the scope of this thesis work aims to remove important disadvantages of common model updating procedures. In doing this, the method starts with a simple finite element mesh obtained by connecting measurement points, used in the Ground Vibration Test of an aircraft structure, with 3 D Euler-Bernoulli beam elements. Initial estimates of the geometric and material properties are determined by solving structural identification equations derived from the mass and stiffness orthogonality of experimental modes. By using those initial estimates, an initial finite element model is constructed. Starting from this initial finite element model, structural identification equations are updated and solved iteratively by using experimental natural frequencies and eigenvectors of the v updated finite element model representing the same mode shapes with measured normal modes. Iterations are continued until eigen solution of the updated finite element model closely correlates with experimental modal data. The applicability of the method is illustrated on a scaled aircraft model and a real aircraft structure. The results are quite satisfactory but the method requires further improvements to achieve a much better correlation level in case of real aircraft structures.

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Genest, Laurent. "Optimisation de forme par gradient en dynamique rapide". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC022/document.

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Afin de faire face aux nouveaux challenges de l’industrie automobile, les ingénieurs souhaitent appliquer des méthodes d’optimisation à chaque étape du processus de conception. En élargissant l’espace de conception aux paramètres de forme, en augmentant leur nombre et en étendant les plages de variation, de nouveaux verrous sont apparus. C’est le cas de la résistance aux chocs. Avec les temps de calcul long, la non-linéarité, l’instabilité et la dispersion numérique de ce problème de dynamique rapide, la méthode usuellement employée, l’optimisation par plan d’expériences et surfaces de réponse, devient trop coûteuse pour être utilisée industriellement. Se pose alors la problématique suivante : Comment faire de l’optimisation de forme en dynamique rapide avec un nombre élevé de paramètres ?. Pour y répondre, les méthodes d’optimisation par gradient s’avèrent être les plus judicieuses. Le nombre de paramètres a une influence réduite sur le coût de l’optimisation. Elles permettent donc l’optimisation de problèmes ayant de nombreux paramètres. Cependant, les méthodes classiques de calcul du gradient sont peu pertinentes en dynamique rapide : le coût en nombre de simulations et le bruit empêchent l’utilisation des différences finies et le calcul du gradient en dérivant les équations de dynamique rapide n’est pas encore disponible et serait très intrusif vis-à-vis des logiciels. Au lieu de déterminer le gradient, au sens classique du terme, des problèmes de crash, nous avons cherché à l’estimer. L’Equivalent Static Loads Method est une méthode permettant l’optimisation à moindre coût basée sur la construction d’un problème statique linéaire équivalent au problème de dynamique rapide. En utilisant la dérivée du problème équivalent comme estimation du gradient, il nous a été possible d’optimiser des problèmes de dynamique rapide ayant des épaisseurs comme variables d’optimisation. De plus, si l’on construit les équations du problème équivalent avec la matrice de rigidité sécante, l’approximation du gradient n’en est que meilleure. De cette manière, il est aussi possible d’estimer le gradient par rapport à la position des nœuds du modèle de calcul. Comme il est plus courant de travailler avec des paramètres CAO, il faut déterminer la dérivée de la position des nœuds par rapport à ces paramètres. Nous pouvons le faire de manière analytique si nous utilisons une surface paramétrique pour définir la forme et ses points de contrôle comme variables d’optimisation. Grâce à l’estimation du gradient et à ce lien entre nœuds et paramètres de forme, l’optimisation de forme avec un nombre important de paramètres est désormais possible à moindre coût. La méthode a été développée pour deux familles de critères issues du crash automobile. La première est liée au déplacement d’un nœud, objectif important lorsqu’il faut préserver l’intégrité de l’habitacle du véhicule. La seconde est liée à l’énergie de déformation. Elle permet d’assurer un bon comportement de la structure lors du choc
In order to face their new industrial challenges, automotive constructors wish to apply optimization methods in every step of the design process. By including shape parameters in the design space, increasing their number and their variation range, new problematics appeared. It is the case of crashworthiness. With the high computational time, the nonlinearity, the instability and the numerical dispersion of this rapid dynamics problem, metamodeling techniques become to heavy for the standardization of those optimization methods. We face this problematic: ”How can we carry out shape optimization in rapid dynamics with a high number of parameters ?”. Gradient methods are the most likely to solve this problematic. Because the number of parameters has a reduced effect on the optimization cost, they allow optimization with a high number of parameters. However, conventional methods used to calculate gradients are ineffective: the computation cost and the numerical noise prevent the use of finite differences and the calculation of a gradient by deriving the rapid dynamics equations is not currently available and would be really intrusive towards the software. Instead of determining the real gradient, we decided to estimate it. The Equivalent Static Loads Method is an optimization method based on the construction of a linear static problem equivalent to the rapid dynamic problem. By using the sensitivity of the equivalent problem as the estimated gradient, we have optimized rapid dynamic problems with thickness parameters. It is also possible to approximate the derivative with respect to the position of the nodes of the CAE model. But it is more common to use CAD parameters in shape optimization studies. So it is needed to have the sensitivity of the nodes position with these CAD parameters. It is possible to obtain it analytically by using parametric surface for the shape and its poles as parameters. With this link between nodes and CAD parameters, we can do shape optimization studies with a large number of parameters and this with a low optimization cost. The method has been developed for two kinds of crashworthiness objective functions. The first family of criterions is linked to a nodal displacement. This category contains objectives like the minimization of the intrusion inside the passenger compartment. The second one is linked to the absorbed energy. It is used to ensure a good behavior of the structure during the crash

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Silva, Clovis Antonio da. "Um novo algoritmo, naturalmente paralelizável, para o cálculo de permeabilidades equivalentes em reservatórios". Universidade do Estado do Rio de Janeiro, 2008. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=1252.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Neste trabalho é apresentado um novo procedimento numérico para o upscaling de permeabilidade utilizando condições de contorno periódicas. Este procedimento combina decomposição de domínio com elementos finitos mistos na discretização do problema local de pressão-velocidade necessário para se encontrar as permeabilidades equivalentes.
A new numerical method is proposed for the permeabilities upscaling take into consideration periodic boundary conditions. This method combines domain decomposition with mixed finite elements in discretization of the local problem of pressure-velocity necessary to meet the equivalent permeabilities.

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Marchetti, Fabien. "Modelling and characterisation of anisotropic multilayered plates on a wide frequency range". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI130.

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Le présent travail de thèse traite de la modélisation vibratoire et de la caractérisation dynamique de matériaux multicouches anisotropes. Dans le premier chapitre, une classification de quelques modèles analytiques de multicouche et techniques de caractérisation expérimentales de structures planes est établie sous la forme d'une synthèse bibliographique. Elle regroupe les récents résultats publiés autour du sujet. Le second chapitre propose une extension d'un modèle équivalent de multicouche au cas des structures anisotropes. Ce modèle décrit les premières courbes de dispersion de la structure et tient compte des phénomènes de cisaillement pouvant agir sur le mode de flexion en hautes fréquences. Le principal avantage du modèle réside dans sa simplicité et sa rapidité grâce à son nombre de variables cinématiques indépendant du nombre de couches. Les caractéristiques du multicouche sont définies par les 5 rigidités de flexion d'une plaque équivalente mince qui est comparée à ce dernier. L'extension de modèle est validée à l'aide d'une étude expérimentale réalisée sur des plaques composites en fibres de carbone. Un intérêt tout particulier est porté sur la modélisation de l'amortissement structurel. Une définition énergétique du facteur de perte, décrite par une formulation spatiale et temporelle de l'atténuation, est comparée à une définition équivalente. Une nouvelle définition de la formulation spatiale est proposée dans le cas de structures très amorties et est comparée aux résultats de la littérature. Dans le troisième chapitre, la technique de caractérisation RIC est étendue au cas des structures anisotropes. Cette méthode inverse s'appuie sur l'analyse du champ de déplacement de la structure et possède, grâce à son aspect local, des atouts non négligeables pour des applications industrielles. La méthodologie est tout d'abord présentée pour l'identification de sources (objectif initial de la méthode) et est ensuite adaptée à la caractérisation. Plusieurs applications numériques et expérimentales sont présentées afin de valider cette extension. Enfin, le quatrième chapitre porte sur la caractérisation expérimentale d'un sandwich en nids d'abeille sur une large bande fréquentielle (1 à 300 kHz). Le comportement dynamique complexe de cette structure épaisse est décrit au travers des résultats prometteurs fournis par les simulations de notre modèle et les estimations de RIC. Ces résultats sont également comparés à ceux d'un modèle de référence et d'autres méthodes de caractérisation
This PhD thesis concerns the modelling and the dynamic characterisation of anisotropic multilayered structures. In the first chapter, a classification of some analytical models and experimental methods of characterisation is presented in the form of a bibliographical synthesis where the main published results are gathered. The second chapter introduces an extension of an equivalent model of multilayered structures to the case of anisotropic materials. This model describes the first dispersion curves of the structure and considers the shear phenomena that can affect the bending mode in high frequencies. The main advantage of the model lies in its simplicity and rapidity thanks to a number of kinematic variables independent of the number of layers. The characteristics of the multilayer are defined by the 5 flexural rigidities of a thin equivalent plate which is compared to the multilayer. The results of the model are validated by means of an experimental study on carbon fiber composite plates. A particular interest is dedicated to the modelling of structural damping. An energetic loss factor, based on a temporal and spatial definition of the attenuation, is compared to an equivalent one. A new definition of the spatial attenuation is suggested for high damped structures and is compared to literature. In the third chapter, the methodology of the characterisation technique CFAT is adapted for anisotropic plates. This inverse method is based on the displacement field analysis of the structure and has, by means of its local aspect, relevant advantages for industrial applications. This adaptation is, as a first step, introduced for the identification of sources (initial objective of the method) and applied, in a second step, for the characterisation. Several numerical and experimental applications are presented to validate the results of the method. Finally, the fourth chapter deals with the experimental characterisation of a honey comb sandwich on a high frequency range (1 to 300 kHz). The complex dynamic behaviour of this thick structure is described through the promissing results given by the simulations of our model and the estimations of RIC. These results are also compared to the ones of a reference model and other characterisation methods

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Uherek, Jan. "Statická a dynamická analýzy ocelové konstrukce". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409745.

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The thesis deals with a description and a static and dynamic analysis for an existing construction of lookout tower. The steel watchtower is located in Město Albrechtice and is made up of two lattice towers connected by a bridge. Main point was to create calculation models for the purpose of dynamic and static analysis, in the software SCIA Engineer 19.1, which is based on the principle of finite element method. Attention was paid to load created by winds according to Eurocode 1 and Eurocode 3, glaze and rime ice load and dynamic coefficient calculation. The thesis also includes an assesment of selected parts of the construction according to Eurocodes.

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Libri sul tema "Dynamic equivalent method"

Huffaker, Ray, Marco Bittelli e Rodolfo Rosa. Linear and Nonlinear Dynamic Behaviour. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198782933.003.0002.

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In this chapter, we describe how highly erratic dynamic behavior can arise from a nonlinear logistic map, and how this apparently random behavior is governed by a surprising order. With this lesson in mind, we should not be overly surprised that highly erratic and random appearing observed data might also be generated by parsimonious deterministic dynamic systems. At a minimum, we contend that researchers should apply NLTS to test for this possibility. We also introduced tools to analyze dynamic behavior that form the foundation for NLTS. In particular, we have stressed the quite unexpected capability to achieve some form of predictability even with only one trajectory at hand. In subsequent chapters, we treat known nonlinear dynamical systems as unknown, and investigate how NLTS methods rely on a single solution (or multiple solutions) generated by them to reconstruct equivalent systems. This is a conventional approach in the literature for seeing how NLTS methods work since we know what needs to be reconstructed.

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Capitoli di libri sul tema "Dynamic equivalent method"

Pradlwarter, H. J., e G. I. Schuëller. "Accuracy and Limitations of the Method of Equivalent Linearization for Hysteretic Multi-Storey Structures". In Nonlinear Stochastic Dynamic Engineering Systems, 3–21. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-83334-2_1.

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Paz, Mario, e William Leigh. "Uniform Building Code 1997: Equivalent Lateral Force Method". In Structural Dynamics, 699–729. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/978-1-4615-0481-8_23.

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Paz, Mario. "Uniform Building Code-1994 Equivalent Static Lateral Force Method". In Structural Dynamics, 707–65. Boston, MA: Springer US, 1997. http://dx.doi.org/10.1007/978-1-4684-0018-2_24.

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Paz, Mario. "Equivalent Static Lateral Force Method: Uniform Building Code—1985". In Structural Dynamics, 511–44. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4615-7918-2_23.

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Paz, Mario. "Equivalent Static Lateral Force Method: Uniform Building Code—1988". In Structural Dynamics, 545–67. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4615-7918-2_24.

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Paz, Mario. "Equivalent Static Lateral Force Method: Uniform Building Code-1985". In Structural Dynamics, 511–44. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4684-9907-0_23.

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Paz, Mario. "Equivalent Static Lateral Force Method: Uniform Building Code-1988". In Structural Dynamics, 545–67. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4684-9907-0_24.

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Vassilopoulou, Isabella, e Charis J. Gantes. "Nonlinear Dynamic Response of MDOF Cable Nets Estimated by Equivalent SDOF Models". In Computational Methods in Applied Sciences, 345–79. Dordrecht: Springer Netherlands, 2013. http://dx.doi.org/10.1007/978-94-007-6573-3_17.

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Guo, Cheng, e Delin Wang. "A Dynamic Equivalence Method Considering the Spatial Effect of Wind Farms". In Lecture Notes in Electrical Engineering, 357–74. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-10-7212-3_23.

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de Jong, Jan, Johannes van Dijk e Just Herder. "On the Dynamic Equivalence of Planar Mechanisms, an Inertia Decomposition Method". In New Trends in Mechanism and Machine Science, 51–59. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-44156-6_6.

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Atti di convegni sul tema "Dynamic equivalent method"

Moller, Jakob Glarbo, Hjortur Johannsson e Jacob Ostergaard. "Thevenin equivalent method for dynamic contingency assessment". In 2015 IEEE Power & Energy Society General Meeting. IEEE, 2015. http://dx.doi.org/10.1109/pesgm.2015.7286120.

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Lee, Se-Jung, Hyun-ah Lee e Gyung-Jin Park. "Nonlinear Dynamic Response Topology Optimization Using the Equivalent Static Loads Method". In 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference
20th AIAA/ASME/AHS Adaptive Structures Conference
14th AIAA. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2012. http://dx.doi.org/10.2514/6.2012-1356.

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Tripathi, Shivam, Mahiraj Singh Rawat e V. G. Durgarao Rayudu. "Dynamic Voltage Instability Identification of Power System using Thévenin Equivalent Method". In 2020 IEEE Students Conference on Engineering & Systems (SCES). IEEE, 2020. http://dx.doi.org/10.1109/sces50439.2020.9236698.

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Li, Wei, e Hui Wang. "An Improved Dynamic Equivalent Method for the DC Offshore Wind Farm". In 2019 IEEE 3rd International Electrical and Energy Conference (CIEEC). IEEE, 2019. http://dx.doi.org/10.1109/cieec47146.2019.cieec-2019475.

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Onori, Simona, Lorenzo Serrao e Giorgio Rizzoni. "Adaptive Equivalent Consumption Minimization Strategy for Hybrid Electric Vehicles". In ASME 2010 Dynamic Systems and Control Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/dscc2010-4211.

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This paper proposes a new method for solving the energy management problem for hybrid electric vehicles (HEVs) based on the equivalent consumption minimization strategy (ECMS). After discussing the main features of ECMS, an adaptation law of the equivalence factor used by ECMS is presented, which, using feedback of state of charge, ensures optimality of the strategy proposed. The performance of the A-ECMS is shown in simulation and compared to the optimal solution obtained with dynamic programming.

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Wang, Peng, Zhenyuan Zhang, Qi Huang, Xiaotian Tang e Wei-Jen Lee. "A Robust-Improved Method for Dynamic Equivalent Modeling of Active Distribution Network". In 2020 IEEE/IAS 56th Industrial and Commercial Power Systems Technical Conference (I&CPS). IEEE, 2020. http://dx.doi.org/10.1109/icps48389.2020.9176767.

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Yang, Zhou, Duan Yao, Zhang Buhan, Li Junfang e Wang Kai. "Study of Coherency-based Dynamic Equivalent Method for Power System with HVDC". In 2010 International Conference on Electrical and Control Engineering (ICECE 2010). IEEE, 2010. http://dx.doi.org/10.1109/icece.2010.495.

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Yang, Linchao, Zheng Xu, Boliang Lou, Hua Zhou e Wen Hua. "A Dynamic Equivalent Method of Three-Sequence Network for Electromagnetic Transient Simulation". In 2019 IEEE Innovative Smart Grid Technologies - Asia (ISGT Asia). IEEE, 2019. http://dx.doi.org/10.1109/isgt-asia.2019.8881239.

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Wang, Peng, Zhenyuan Zhang, Qi Huang e Wei-Jen Lee. "Wind Farm Dynamic Equivalent Modeling Method for Power System Probabilistic Stability Assessment". In 2019 IEEE Industry Applications Society Annual Meeting. IEEE, 2019. http://dx.doi.org/10.1109/ias.2019.8912443.

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Alibrandi, Umberto, e Khalid M. Mosalam. "Tail Probability Equivalent Linearization Method for Stochastic Dynamic Analysis of marine Risers". In Proceedings of the 6th International Symposium on Reliability Engineering and Risk Management. Singapore: Research Publishing Services, 2018. http://dx.doi.org/10.3850/978-981-11-2726-7_cos06.

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Rapporti di organizzazioni sul tema "Dynamic equivalent method"

Cai, Yongyang, Kenneth Judd e Jevgenijs Steinbuks. A Nonlinear Certainty Equivalent Approximation Method for Dynamic Stochastic Problems. Cambridge, MA: National Bureau of Economic Research, settembre 2015. http://dx.doi.org/10.3386/w21590.

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Cai, Yongyang, e Kenneth Judd. A Simple but Powerful Simulated Certainty Equivalent Approximation Method for Dynamic Stochastic Problems. Cambridge, MA: National Bureau of Economic Research, febbraio 2021. http://dx.doi.org/10.3386/w28502.

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