Littérature scientifique sur le sujet « Fast dynamic interactions »
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Articles de revues sur le sujet "Fast dynamic interactions"
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Wang, Yang, Shih-to Fei, Young-Moo Byun, Paul E. Lammert, Vincent H. Crespi, Ayusman Sen et Thomas E. Mallouk. « Dynamic Interactions between Fast Microscale Rotors ». Journal of the American Chemical Society 131, no 29 (29 juillet 2009) : 9926–27. http://dx.doi.org/10.1021/ja904827j.
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Mowbray, D. J., Sangwoo Chung, Z. L. Mišković, F. O. Goodman et You-Nian Wang. « Dynamic interactions of fast ions with carbon nanotubes ». Nuclear Instruments and Methods in Physics Research Section B : Beam Interactions with Materials and Atoms 230, no 1-4 (avril 2005) : 142–47. http://dx.doi.org/10.1016/j.nimb.2004.12.032.
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Chawla, D., E. D. Lumer et K. J. Friston. « Relating Macroscopic Measures of Brain Activity to Fast, Dynamic Neuronal Interactions ». Neural Computation 12, no 12 (1 décembre 2000) : 2805–21. http://dx.doi.org/10.1162/089976600300014737.
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In this article we used biologically plausible simulations of coupled neuronal populations to address the relationship between phasic and fast coherent neuronal interactions and macroscopic measures of activity that are integrated over time, such as the BOLD response in functional magnetic resonance imaging. Event-related, dynamic correlations were assessed using joint peristimulus time histograms and, in particular, the mutual information between stimulus-induced transients in two populations. This mutual information can be considered as an index of functional connectivity. Our simulations showed that functional connectivity or dynamic integration between two populations increases with mean background activity and stimulus-related rate modulation. Furthermore, as the background activity increases, the populations become increasingly sensitive to the intensity of the stimulus in terms of a predisposition to transient phase locking. This reflects an interaction between background activity and stimulus intensity in producing dynamic correlations, in that background activity augments stimulus-induced coherence modulation. This is interesting from a computational perspective because background activity establishes a context that may have a profound effect on event-related interactions or functional connectivity between neuronal populations. Finally, total firing rates, which subsume both background activity and stimulus-related rate modulation, were almost linearly related to the expression of dynamic correlations over large ranges of activities. These observations show that under the assumptions implicit in our model, rate-specific metrics based on rate or coherence modulation may be different perspectives on the same underlying dynamics. This suggests that activity (averaged over all peristimulus times), as measured in neuroimaging, may be tightly coupled to the expression of dynamic correlations.
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Chung, Sangwoo, D. J. Mowbray, Z. L. Mišković, F. O. Goodman et You-Nian Wang. « Dynamic interactions of fast ions with multiwalled carbon nanotubes ». Radiation Physics and Chemistry 76, no 3 (mars 2007) : 524–28. http://dx.doi.org/10.1016/j.radphyschem.2005.09.020.
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Fiore, Andrew M., et James W. Swan. « Fast Stokesian dynamics ». Journal of Fluid Mechanics 878 (17 septembre 2019) : 544–97. http://dx.doi.org/10.1017/jfm.2019.640.
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We present a new method for large scale dynamic simulation of colloidal particles with hydrodynamic interactions and Brownian forces, which we call fast Stokesian dynamics (FSD). The approach for modelling the hydrodynamic interactions between particles is based on the Stokesian dynamics (SD) algorithm (J. Fluid Mech., vol. 448, 2001, pp. 115–146), which decomposes the interactions into near-field (short-ranged, pairwise additive and diverging) and far-field (long-ranged many-body) contributions. In FSD, the standard system of linear equations for SD is reformulated using a single saddle point matrix. We show that this reformulation is generalizable to a host of particular simulation methods enabling the self-consistent inclusion of a wide range of constraints, geometries and physics in the SD simulation scheme. Importantly for fast, large scale simulations, we show that the saddle point equation is solved very efficiently by iterative methods for which novel preconditioners are derived. In contrast to existing approaches to accelerating SD algorithms, the FSD algorithm avoids explicit inversion of ill-conditioned hydrodynamic operators without adequate preconditioning, which drastically reduces computation time. Furthermore, the FSD formulation is combined with advanced sampling techniques in order to rapidly generate the stochastic forces required for Brownian motion. Specifically, we adopt the standard approach of decomposing the stochastic forces into near-field and far-field parts. The near-field Brownian force is readily computed using an iterative Krylov subspace method, for which a novel preconditioner is developed, while the far-field Brownian force is efficiently computed by linearly transforming those forces into a fluctuating velocity field, computed easily using the positively split Ewald approach (J. Chem. Phys., vol. 146, 2017, 124116). The resultant effect of this field on the particle motion is determined through solution of a system of linear equations using the same saddle point matrix used for deterministic calculations. Thus, this calculation is also very efficient. Additionally, application of the saddle point formulation to develop high-resolution hydrodynamic models from constrained collections of particles (similar to the immersed boundary method) is demonstrated and the convergence of such models is discussed in detail. Finally, an optimized graphics processing unit implementation of FSD for mono-disperse spherical particles is used to demonstrated performance and accuracy of dynamic simulations of $O(10^{5})$ particles, and an open source plugin for the HOOMD-blue suite of molecular dynamics software is included in the supplementary material.
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Ashwin, S. S., Tadasu Nozaki, Kazuhiro Maeshima et Masaki Sasai. « Organization of fast and slow chromatin revealed by single-nucleosome dynamics ». Proceedings of the National Academy of Sciences 116, no 40 (16 septembre 2019) : 19939–44. http://dx.doi.org/10.1073/pnas.1907342116.
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Understanding chromatin organization and dynamics is important, since they crucially affect DNA functions. In this study, we investigate chromatin dynamics by statistically analyzing single-nucleosome movement in living human cells. Bimodal nature of the mean square displacement distribution of nucleosomes allows for a natural categorization of the nucleosomes as fast and slow. Analyses of the nucleosome–nucleosome correlation functions within these categories along with the density of vibrational modes show that the nucleosomes form dynamically correlated fluid regions (i.e., dynamic domains of fast and slow nucleosomes). Perturbed nucleosome dynamics by global histone acetylation or cohesin inactivation indicate that nucleosome–nucleosome interactions along with tethering of chromatin chains organize nucleosomes into fast and slow dynamic domains. A simple polymer model is introduced, which shows the consistency of this dynamic domain picture. Statistical analyses of single-nucleosome movement provide rich information on how chromatin is dynamically organized in a fluid manner in living cells.
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Li, Zhenhua, et Chao Wang. « Suspension Parameters Optimization of Fast Freight Wagon Based on Low Wheel-Rail Dynamic Interactions ». Journal of Physics : Conference Series 2381, no 1 (1 décembre 2022) : 012116. http://dx.doi.org/10.1088/1742-6596/2381/1/012116.
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Abstract The dynamic model of fast freight wagon is established to study the effect of key parameters of the freight wagon on dynamic performance. In order to reduce the wheel-rail dynamic interactions, the parameters such as primary suspension stiffness, arm joint stiffness, and joint stiffness of the anti-yaw damper are optimized. The results indicate that the above suspension parameters have an influence on the fast freight wagon’s dynamic performance. Compared with the simulation results of the original parameters, the wheel-rail vertical force is reduced by 10%, and the wheel-rail lateral force is reduced by 42% and 38% respectively under the straight and curve conditions of the empty vehicle. The wheel-rail vertical force is reduced by 10% and 6%, and the wheel-rail lateral force is reduced by 10% and 16% respectively under the straight and curve conditions of the loaded fast freight wagon. The running stability and safety of the fast freight wagon have been improved.
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Aebischer, Kathrin, Lea Marie Becker, Paul Schanda et Matthias Ernst. « Evaluating the motional timescales contributing to averaged anisotropic interactions in MAS solid-state NMR ». Magnetic Resonance 5, no 1 (11 juin 2024) : 69–86. http://dx.doi.org/10.5194/mr-5-69-2024.
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Abstract. Dynamic processes in molecules can occur on a wide range of timescales, and it is important to understand which timescales of motion contribute to different parameters used in dynamics measurements. For spin relaxation, this can easily be understood from the sampling frequencies of the spectral-density function by different relaxation-rate constants. In addition to data from relaxation measurements, determining dynamically averaged anisotropic interactions in magic-angle spinning (MAS) solid-state NMR allows for better quantification of the amplitude of molecular motion. For partially averaged anisotropic interactions, the relevant timescales of motion are not so clearly defined. Whether the averaging depends on the experimental methods (e.g., pulse sequences) or conditions (e.g., MAS frequency, magnitude of anisotropic interaction, radio-frequency field amplitudes) is not fully understood. To investigate these questions, we performed numerical simulations of dynamic systems based on the stochastic Liouville equation using several experiments for recoupling the dipolar coupling, chemical-shift anisotropy or quadrupolar coupling. As described in the literature, the transition between slow motion, where parameters characterizing the anisotropic interaction are not averaged, and fast motion, where the tensors are averaged leading to a scaled anisotropic quantity, occurs over a window of motional rate constants that depends mainly on the strength of the interaction. This transition region can span 2 orders of magnitude in exchange-rate constants (typically in the microsecond range) but depends only marginally on the employed recoupling scheme or sample spinning frequency. The transition region often coincides with a fast relaxation of coherences, making precise quantitative measurements difficult. Residual couplings in off-magic-angle experiments, however, average over longer timescales of motion. While in principle one may gain information on the timescales of motion from the transition area, extracting such information is hampered by low signal-to-noise ratio in experimental spectra due to fast relaxation that occurs in the same region.
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Sluysmans, Damien, Floriane Devaux, Carson J. Bruns, J. Fraser Stoddart et Anne-Sophie Duwez. « Dynamic force spectroscopy of synthetic oligorotaxane foldamers ». Proceedings of the National Academy of Sciences 115, no 38 (26 décembre 2017) : 9362–66. http://dx.doi.org/10.1073/pnas.1712790115.
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Wholly synthetic molecules involving both mechanical bonds and a folded secondary structure are one of the most promising architectures for the design of functional molecular machines with unprecedented properties. Here, we report dynamic single-molecule force spectroscopy experiments that explore the energetic details of donor–acceptor oligorotaxane foldamers, a class of molecular switches. The mechanical breaking of the donor–acceptor interactions responsible for the folded structure shows a high constant rupture force over a broad range of loading rates, covering three orders of magnitude. In comparison with dynamic force spectroscopy performed during the past 20 y on various (bio)molecules, the near-equilibrium regime of oligorotaxanes persists at much higher loading rates, at which biomolecules have reached their kinetic regime, illustrating the very fast dynamics and remarkable rebinding capabilities of the intramolecular donor–acceptor interactions. We focused on one single interaction at a time and probed the stochastic rupture and rebinding paths. Using the Crooks fluctuation theorem, we measured the mechanical work produced during the breaking and rebinding to determine a free-energy difference, ΔG, of 6 kcal·mol−1 between the two local conformations around a single bond.
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Zhu, Junyao, Mingming Chen, Junfeng Lu, Kun Zhao, Enze Cui, Zhiheng Zhang et Hong Wan. « A Fast and Efficient Ensemble Transfer Entropy and Applications in Neural Signals ». Entropy 24, no 8 (13 août 2022) : 1118. http://dx.doi.org/10.3390/e24081118.
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The ensemble transfer entropy (TEensemble) refers to the transfer entropy estimated from an ensemble of realizations. Due to its time-resolved analysis, it is adapted to analyze the dynamic interaction between brain regions. However, in the traditional TEensemble, multiple sets of surrogate data should be used to construct the null hypothesis distribution, which dramatically increases the computational complexity. To reduce the computational cost, a fast, efficient TEensemble with a simple statistical test method is proposed here, in which just one set of surrogate data is involved. To validate the improved efficiency, the simulated neural signals are used to compare the characteristics of the novel TEensemble with those of the traditional TEensemble. The results show that the time consumption is reduced by two or three magnitudes in the novel TEensemble. Importantly, the proposed TEensemble could accurately track the dynamic interaction process and detect the strength and the direction of interaction robustly even in the presence of moderate noises. The novel TEensemble reaches its steady state with the increased samples, which is slower than the traditional method. Furthermore, the effectiveness of the novel TEensemble was verified in the actual neural signals. Accordingly, the TEensemble proposed in this work may provide a suitable way to investigate the dynamic interactions between brain regions.
Thèses sur le sujet "Fast dynamic interactions"
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Chawla, Dave. « Relating macroscopic measures of brain activity to fast dynamic neuronal interactions ». Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397179.
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Kelada, Fadi Sameh Aziz. « Étude des dynamiques et de la stabilité des réseaux électriques faible inertie avec une forte pénétration de ressources renouvelables ». Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALT065.
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Les systèmes électriques évoluent de manière significative en raison de facteurs économiques, géopolitiques et environnementaux, notamment l'intégration croissante de sources d'énergie renouvelable (RES) interfacées par des convertisseurs électroniques de puissance, connus sous le nom de ressources basées sur des onduleurs (IBR). Ce passage de systèmes dominés par des machines synchrones (SM) à des systèmes dominés par des IBR introduit des défis tels que la réduction de l'inertie, l'intermittence et les problèmes de stabilité. Les techniques traditionnelles d'analyse et de modélisation de la stabilité, qui supposent des dynamiques plus lentes inhérentes aux SM, sont inadéquates pour les dynamiques rapides des IBR. La dominance émergente des IBR nécessite le développement de modèles détaillés de transitoires électromagnétiques (EMT), qui sont intensifs en calcul mais essentiels pour capturer les dynamiques rapides des systèmes électriques modernes. Les cadres de classification de la stabilité existants, historiquement basés sur des systèmes dominés par les SM, sont en cours de révision pour incorporer les influences des IBR, introduisant de nouvelles catégories de stabilité comme la stabilité pilotée par convertisseur (CDS). Ce travail explore de nouvelles perspectives sur les interactions entre les SM, les dynamiques des unités IBR et les dynamiques des réseaux, qui ont été négligées dans la littérature. Il fournit un cadre complet qui est open-source et adaptable pour des topologies de systèmes électriques génériques, permettant des résultats et des analyses évolutifs. De plus, le cadre proposé est utilisé pour déterminer les allocations optimales d'inertie virtuelle et d'amortissement dans les systèmes électriques à faible inertie afin d'améliorer les métriques de stabilité de la fréquencePower systems are evolving significantly due to economic, geopolitical, and environmental factors, notably the increasing integration of Renewable Energy Sources (RES) interfaced through power electronic converters, known as Inverter-Based Resources (IBR). This shift from synchronous machine (SM)-dominated systems to IBR-dominated systems introduces challenges such as reduced inertia, intermittency, and stability issues. Traditional stability analysis and modeling techniques, which assume slower dynamics inherent in SMs, are inadequate for the fast dynamics of IBRs. The emerging dominance of IBRs necessitates the development of detailed Electromagnetic Transient (EMT) models, which are computationally intensive but essential for capturing the fast dynamics of modern power systems. Existing stability classification frameworks, historically based on SM-dominated systems, are being revised to incorporate IBR influences, introducing new stability categories like Converter-Driven Stability (CDS). This work investigates novel insights into the interactions between SMs, IBR unit dynamics, and network dynamics that have been overlooked in the literature. It provides a comprehensive framework that is open-source and adaptable for generic power system topologies, allowing for scalable results and analyses. Furthermore, the proposed framework is utilized to determine optimal allocations of virtual inertia and damping in low inertia power systems to enhance frequency stability metrics
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Boyd, Alistair Richard. « Fluid-structure interaction under fast transient dynamic events ». Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/10835.
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Underwater explosive loading resulting from rapid phase transitions (RPT's) is one example of a fast transient dynamic event. The leakage of substances such as LPG or LNG when stored underwater can cause an RPT. These substances are often stored in a combination of very low temperatures and high pressures with respect to the surrounding fluid (seawater) and their leakage can cause the equivalent of an underwater explosion. Such containers are usually found to be part of a much larger 'storage field' of containers. An RPT occurring in one container will cause underwater explosive loading on neighbouring containers. By simulating an RPT using explosive charges experiments were initially designed using theoretical and empirical techniques. The fluid and structural response of a prototype container subject to symmetric and axisymmetric underwater explosive (UNDEX) loading was then examined experimentally. Theoretical predictions using the finite element hydrocode LS-DYNA and boundary element code USA-DYNA3D were undertaken and compared with experimental observations. Several non-destructive techniques were employed to estimate dynamic collapse buckling criteria from both experimental and theoretical results. The experimental work concluded that the critical regions of the prototype container were the apex and the base under both forms of loading. The quality of the numerical predictions varied dependent on the form of the loading. In some cases the fluid and structural responses were overpredicted, and in others underpredicted. Within the limitations of these numerical procedures it was possible to predict a conservative estimate of a critical charge size under axisymmetric UNDEX loading using LS-DYNA. The critical stand off distance was also estimated from experimental results under symmetric UNDEX loading. The use of numerical approaches to predict fluid-structure interaction as successful for the shock phase of an underwater loading and both LS-DYNA and USA-DYnA3D have been validated for shock loading. Bubble loading simulations proved unsuccessful. Suggested improvements are proposed to increase the application of, and enhance the reliability of, the techniques used in this work.
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France, Lydéric [Verfasser]. « Magmatic/ hydrothermal interactions at fast spreading mid-ocean ridges : implications on the dynamics of the axial melt lens / Lydéric France ». Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover, 2010. http://d-nb.info/1010987348/34.
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Urvoy, Alban [Verfasser], et Tilman [Akademischer Betreuer] Pfau. « Large bandwidth excitation of Rydberg atoms in thermal vapor : fast dynamics and strong interaction effects / Alban Urvoy ; Betreuer : Tilman Pfau ». Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2016. http://d-nb.info/111836922X/34.
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Hedman, Fredrik. « Algorithms for Molecular Dynamics Simulations ». Doctoral thesis, Stockholm University, Department of Physical, Inorganic and Structural Chemistry, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-1008.
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Methods for performing large-scale parallel Molecular Dynamics(MD) simulations are investigated. A perspective on the field of parallel MD simulations is given. Hardware and software aspects are characterized and the interplay between the two is briefly discussed.
A method for performing ab initio MD is described; the method essentially recomputes the interaction potential at each time-step. It has been tested on a system of liquid water by comparing results with other simulation methods and experimental results. Different strategies for parallelization are explored.
Furthermore, data-parallel methods for short-range and long-range interactions on massively parallel platforms are described and compared.
Next, a method for treating electrostatic interactions in MD simulations is developed. It combines the traditional Ewald summation technique with the nonuniform Fast Fourier transform---ENUF for short. The method scales as N log N, where N is the number of charges in the system. ENUF has a behavior very similar to Ewald summation and can be easily and efficiently implemented in existing simulation programs.
Finally, an outlook is given and some directions for further developments are suggested.
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Kaltenbrunner, Andreas. « Dynamics of message Interchange between stochastic Units in the contexts of human communication behaviour and spiking neurons ». Doctoral thesis, Universitat Pompeu Fabra, 2008. http://hdl.handle.net/10803/7549.
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Esta tesis estudia dos diferentes dinámicas de intercambio de mensajes entre unidades estocásticas.Primero, analizamos un conjunto de neuronas estocásticas tipo integración - y - disparo con integración sin pérdidas, un pequeño periodo refractario, y con acoplamiento global y retardado. Se observa una transición de fase acompañada por una histéresis alrededor de un acoplamiento crítico. Para acoplamiento subcrítico el conjunto es gobernado por la dinámica estocástica, mientras que para acoplamiento supracrítico las unidades se organizan en varios subgrupos con actividad auto - sostenida. Un análisis teórico permite caracterizar la transición de fase analíticamente.
La segunda parte se centra en la comunicación humana. Examinamos la comunicación entre comunidades de usuarios en Slashdot, u n popular sitio web. Se encuentran patrones regulares en el tiempo de reacción a una nueva noticia tanto para la comunidad como para usuarios individuales. La estadística de estas actividades sigue distribuciones lognormales con leves variaciones causadas por ciclos diarios y semanales.
This thesis studies two different dynamics of message interchange between stochastic u nits.
First, we analyze an ensemble of stochastic non - leaky integrate - and - fire neurons with global, delayed and excitatory coupling and a small refractory period. We observe a phase transition accompanied by a hysteresis around a critical coupling strength. For subcritical coupling the ensemble is governed by the stochastic dynamics whereas for supracritical coupling the units organize into several phase - locked clusters with self - sustained activity. Theoretical analysis allows to characterize the phase transition analytically.
The second part is focused on human communication behavior. We examine the many - to -many communication activity on the popular website Slashdot. Regular temporal patterns are found in the reaction times of the community and single users to a news - post. The statistics of these activities follow lognormal distributions. Daily and weekly oscillatory cycles cause slight variations of this simple behavior.
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Teles, Tarcisio Nunes. « Mecânica estatística em sistemas com interações de longo alcance : estados estacionários e equilíbrio ». reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/55450.
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Desde os trabalhos de Clausius, Boltzmann e Gibbs, sabe-se que partículas que interagem através de potenciais de curto alcance alcançam, após um processo de relaxação, o estado final estacionário que corresponde ao equilíbrio termodinâmico [I]. Embora nenhuma prova exata exista para isso, na prática, verifica-se que os sistemas não-integráveis com uma energia fixa e um número finito de partículas (ensemble microcanônico, por exemplo) sempre relaxam para um estado estacionário que só depende de quantidades globais conservadas pela dinâmica: energia, momentum e momentum angular. Este estado estacionário corresponde ao estado de equilíbrio termodinâmico e não depende das especificidades da distribuição inicial de partículas. Este cenário muda drasticamente quando a interação entre as partículas passa a ser de longo alcance [2]. A descrição estatística e termodinâmica desses sistemas ainda é objeto de estudo. Contudo, o que se sabe é que esses sistemas têm como propriedade fundamental o fato de que, no limite termodinâmico o tempo de colisão diverge e o equilíbrio termodinâmico nunca é atingido [3]. Nesse trabalho analisamos do ponto de vista teórico e por simulação de dinâmica molecular o estado estacionário atingido por sistemas auto-gravitantes em uma, duas e três dimensões e plasmas não-neutros na dinâmica de um feixe de partículas carregadas. Analisamos ainda um modelo com transição de fases para o estado fora do equilíbrio (HMF). Em todos os casos a teoria proposta na tese mostrou-se consistente com os simulações numéricas empregadas.Since the work of Clausius, Boltzmann and Gibbs, it is known that particles interacting by a short-range potential, after a relaxation process, reach a final stationary state that corresponds to thermodynamic equilibrium. Although no exact proof exists, in practice non-integrable systems with fixed energy and a finite number of particles (i.e., microcanonical ensemble) always relax to a stationary state that depends only on global quantities conserved by the dynamics: energy, momentum and angular momentum. This stationary state corresponds to the state of thermodynamic equilibrium and does not depend on the specifics of the initial particle distribution. This scenario changes drastically when the interaction between particles is longranged [2] The statistical and thermodynamic description of these systems is still an object of study. However, a fundamental property of these systems is the fact that, in the thermodynamic limit, the collision time diverges and thermodynamic equilibrium is never achieved [3].. In this thesis we analyse, from a theoretical point of view and using molecular dynamics simulations, the stationary state achieved by self-gravitating systems in one, two and three dimensions and non-neutral plasmas in the dynamics of charged particle beams. We also analyse a model with out-of-equilibrium phase transitions (HMF). In all these cases, the theory proposed in this thesis is shown to be consistent with the numerical simulations applied.
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Costa, David José Rodrigues dos Santos. « Dynamic stiffness of the piled foundation of a onshore wind turbine ». Master's thesis, 2014. http://hdl.handle.net/10362/14037.
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One of today's biggest concerns is the increase of energetic needs, especially in the developed countries. Among various clean energies, wind energy is one of the technologies that assume greater importance on the sustainable development of humanity. Despite wind turbines had been developed and studied over the years, there are phenomena that haven't been yet fully understood. This work studies the soil-structure interaction that occurs on a wind turbine's foundation composed by a group of piles that is under dynamic loads caused by wind. This problem assumes special importance when the foundation is implemented on locations where safety criteria are very demanding, like the case of a foundation mounted on a dike.
To the phenomenon of interaction between two piles and the soil between them it's given
the name of pile-soil-pile interaction. It is known that such behavior is frequency dependent, and therefore, on this work evaluation of relevant frequencies for the intended analysis is held. During the development of this thesis, two methods were selected in order to assess pile-soil-pile interaction, being one of analytical nature and the other of numerical origin. The analytical solution was recently developed and its called Generalized pile-soil-pile theory, while for the numerical method the commercial nite element software PLAXIS 3D was used. A study of applicability of the numerical method is also done comparing the given solution by the nite element methods with a rigorous solution widely accepted by the majority of the authors.
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Liang, Yi-Cyuan, et 梁益詮. « Fast Urban Flood Inundation Model for Simulating Dynamic Interaction between Street Networks and Storm Sewer Systems ». Thesis, 2016. http://ndltd.ncl.edu.tw/handle/22086613990275607206.
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碩士國立臺灣大學
生物環境系統工程學研究所
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In recent years, flooding in urban areas have been occurring more frequently due to the increasing of extreme rainfall events. Therefore, assessment of high inundation potential areas in metropolises becomes very important. In the past, 2D flood inundation models are often used to simulate flooding areas owing to its accuracy. However, with their time-consuming property, they are usually used in advance to idetify high potential zones of flooding during non-disaster time and then the results are provided to disaster prevention works for reference. Urban flooding surveys often use streets as division criteria. Therefore, this study attempts to develope a street flood inundation model for fast evaluation of street flooding. This model consists of three modules: (1) rainfall-runoff transformation, (2) 1D street flow routing, (3) 1D sewer flow routing. By changing the routing order of these three modules, two different rainfall collection methods including Method A: rainwater into storm sewers first and Method B: rainwater into street first, are proposed to evaluate potential flooding streets right after rainfall events occured. In this study, Mucha drainage basin in Wenshan Distrinct, Taipei, is selected as the study area. Two short duration and one long duration rainfall events are used for simulation and analysis. Due to the closeness to real rainfall collection phenomena, the simulated results from Method B has a better agreement with the measured data of street inundation areas and sewer water levels whether the duration of rainfall event is short or long. Thus, we take method B as a representation of street flood inundation model. Compared to 2D flood inundation models, street flood inundation model has a better performance on computation time and may be used to evaluate the flooding disaster immediately.
Livres sur le sujet "Fast dynamic interactions"
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W, Kreutz E., Quenzer Alain, Schuöcker Dieter, Comité belge d'optique et Conference on High Power Lasers : Sources, Laser-Material Interactions, High Excitations, and Fast Dynamics in Laser Processing and Industrial Applications (1987 : Hague, Netherlands), dir. High power lasers : Sources, laser-material interactions, high excitations, and fast dynamics in laser processing and industrial applications : 31 March-3 April 1987, The Hague, The Netherlands. Bellingham, Wash., USA : The Society, 1987.
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Zeitlin, Vladimir. Geostrophic Adjustment and Wave–Vortex (Non)Interaction. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198804338.003.0008.
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The fundamental process of geostrophic adjustment is treated by the method of multi-scale asymptotic expansions in Rossby number and fast-time averaging (which is explained), first in the barotropic one-layer case, and then in the baroclinic two-layer case. Together with the standard quasi-geostrophic regime of parameters, the frontal (or semi-) geostrophic regime is considered. Dynamical separation of slow and fast motions is demonstrated in both regimes. The former obey quasi-geostrophic or frontal-geostrophic equations, thus providing formal justification of the heuristic derivation of Chapter 5. Fast motions are inertia-gravity waves in quasi-geostrophic case, and inertial oscillations in the frontal-geostrophic case. Geostrophic adjustment is also considered in the presence of coastal, topographic, and equatorial wave-guides, and, again, separation of fast and slow motions is demonstrated, the latter now including long Kelvin waves in the first case, long topographic waves in the second case, and long Kelvin and Rossby waves in the third case.
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Schmid, Hans-Jörg. The Dynamics of the Linguistic System. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198814771.001.0001.
Texte intégralRésumé :
This book develops a model of language which can be characterized as functionalist, usage-based, dynamic, and complex-adaptive. Its core idea is that linguistic structure is not stable and uniform, but continually refreshed and in fact reconstituted by the feedback-loop interaction of three components: usage, i.e. the interpersonal and cognitive activities of speakers in concrete communication; conventionalization, i.e. the social processes taking place in speech communities; and entrenchment, i.e. the cognitive processes taking place in the minds of individual speakers. Extending the so-called Entrenchment-and-Conventionalization Model, the book shows that what we call the Linguistic System is created, sustained, and continually adapted by the ongoing interaction between usage, conventionalization, and entrenchment. The model contributes to closing the gap in usage-based models concerning how exactly usage is transformed into collective and individual grammar and how these two grammars in turn feed back into usage. The book exploits and extends insights from an exceptionally wide range of fields, including usage-based cognitive linguistics, psycholinguistics, interactional linguistics and pragmatics, historical linguistics, sociolinguistics and the sociology and philosophy of language, as well as quantitative corpus linguistics. It makes numerous original suggestions about, among other things, how cognitive processing and representation are related and about the manifold ways in which individuals and communities contribute to shaping language and bringing about language variation and change. It presents a coherent account of the role of forces that are known to affect language structure, variation, and change, e.g. economy, efficiency, extravagance, embodiment, identity, social order, prestige, mobility, multilingualism, and language contact.
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Kreutz. High Power Lasers : Sources, Laser-Material Interactions, High Excitations, and Fast Dynamics in Laser Processing and Industrial Applicati (Proceedings / SPIE). Society of Photo Optical, 1987.
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Finney, Mark, Sara McAllister, Torben Grumstrup et Jason Forthofer. Wildland Fire Behaviour. CSIRO Publishing, 2021. http://dx.doi.org/10.1071/9781486309092.
Texte intégralRésumé :
Wildland fires have an irreplaceable role in sustaining many of our forests, shrublands and grasslands. They can be used as controlled burns or occur as free-burning wildfires, and can sometimes be dangerous and destructive to fauna, human communities and natural resources. Through scientific understanding of their behaviour, we can develop the tools to reliably use and manage fires across landscapes in ways that are compatible with the constraints of modern society while benefiting the ecosystems.
The science of wildland fire is incomplete, however. Even the simplest fire behaviours – how fast they spread, how long they burn and how large they get – arise from a dynamical system of physical processes interacting in unexplored ways with heterogeneous biological, ecological and meteorological factors across many scales of time and space. The physics of heat transfer, combustion and ignition, for example, operate in all fires at millimetre and millisecond scales but wildfires can become conflagrations that burn for months and exceed millions of hectares.
Wildland Fire Behaviour: Dynamics, Principles and Processes examines what is known and unknown about wildfire behaviours. The authors introduce fire as a dynamical system along with traditional steady-state concepts. They then break down the system into its primary physical components, describe how they depend upon environmental factors, and explore system dynamics by constructing and exercising a nonlinear model. The limits of modelling and knowledge are discussed throughout but emphasised by review of large fire behaviours. Advancing knowledge of fire behaviours will require a multidisciplinary approach and rely on quality measurements from experimental research, as covered in the final chapters.
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Romagnoli, Stefano, et Giovanni Zagli. Blood pressure monitoring in the ICU. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199600830.003.0131.
Texte intégralRésumé :
Two major systems are available for measuring blood pressure (BP)—the indirect cuff method and direct arterial cannulation. In critically-ill patients admitted to the intensive care unit, the invasive blood pressure is the ‘gold standard’ as a tight control of BP values, and its change over time is important for choosing therapies and drugs titration. Since artefacts due to the inappropriate dynamic responses of the fluid-filled monitoring systems may lead to clinically relevant differences between actual and displayed pressure values, before considering the BP value shown as reliable, the critical care giver should carefully evaluate the presence/absence of artefacts (over- or under-damping/resonance). After the arterial pressure waveform quality has been verified, the observation of each component of the arterial wave (systolic upstroke, peak, systolic decline, small pulse of reflected pressure waves, dicrotic notch) may provide a number of useful haemodynamic information. In fact, changes in the arterial pulse contour are due the interaction between the heart beat and the whole vascular properties. Vasoconstriction, vasodilatation, shock states (cardiogenic, hypovolaemic, distributive, obstructive), valve diseases (aortic stenosis, aortic regurgitation), ventricular dysfunction, cardiac tamponade are associated with particular arterial waveform characteristics that may suggest to the physician underlying condition that could be necessary to investigate properly. Finally, the effects of positive-pressure mechanical ventilation on heart–lung interaction, may suggest the existence of an absolute or relative hypovolaemia by means of the so-called dynamic indices of fluid responsiveness.
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Kennel, Charles F. Convection and Substorms. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195085297.001.0001.
Texte intégralRésumé :
The magnetosphere is the region where cosmic rays and the solar wind interact with the Earth's magnetic field, creating such phenomena as the northern lights and other aurorae. The configuration and dynamics of the magnetosphere are of interest to planetary physicists, geophysicists, plasma astrophysicists, and to scientists planning space missions. The circulation of solar wind plasma in the magnetosphere and substorms have long been used as the principle paradigms for studying this vital region. Charles F. Kennel, a leading scientist in the field, here presents a synthesis of the convection and substorm literatures, and an analysis of convection and substorm interactions; he also suggests that the currently accepted steady reconnection model may be advantageously replaced by a model of multiple tail reconnection events, in which many mutually interdependent reconnections occur. Written in an accessible, non-mathematical style, this book introduces the reader to the exciting discoveries in this fast-growing field.
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Appasani, Krishnarao, et Raghu Kiran Appasani, dir. Single-Molecule Science. Cambridge University Press, 2022. http://dx.doi.org/10.1017/9781108525909.
Texte intégralRésumé :
Single Molecule Science (SMS) has emerged from developing, using and combining technologies such as super-resolution microscopy, atomic force microscopy, and optical and magnetic tweezers, alongside sophisticated computational and modelling techniques. This comprehensive, edited volume brings together authoritative overviews of these methods from a biological perspective, and highlights how they can be used to observe and track individual molecules and monitor molecular interactions in living cells. Pioneers in this fast-moving field cover topics such as single molecule optical maps, nanomachines, and protein folding and dynamics. A particular emphasis is also given to mapping DNA molecules for diagnostic purposes, and the study of gene expression. With numerous illustrations, this book reveals how SMS has presented us with a new way of understanding life processes. A must-have for researchers and graduate students, as well as those working in industry, primarily in the areas of biophysics, biological imaging, genomics and structural biology.
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Bolens, Guillemette. Kinesic Humor. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780190930066.001.0001.
Texte intégralRésumé :
Literature is one of the richest sources of information concerning the ways in which human beings are able to play with cognition. According to the theory of embodied cognition, human cognition is grounded in sensorimotricity, i.e., the ability to feel, perceive, and move. The pervading cognitive process called perceptual simulation, which is activated when we cognitively process a gesture in a real-life situation, is also recruited when we read about actions, movements, and gestures in texts. Kinesic Humor examines literary works written by major authors—including Chrétien de Troyes, Cervantes, Milton, Saint-Simon, Rousseau, Sterne, and Stendhal—in which perceptual simulations of complex sensorimotor events and kinesic interactions trigger humorous effects. Such works create anticipations regarding movements and sensations, which are unexpectedly thwarted, thus producing cognitive shifts typical of humor. By bringing together literary studies, cognitive studies, gesture studies, and humor studies, this book offers original perspectives on such important artworks as Paradise Lost, Don Quixote, and Le Rouge et le Noir. In it, the importance of rhythm and tonicity in the perception of movements and gestures is a focus of attention. The interactional significance of gestures often lies in their dynamics, and this fact also applies to the cognitive retrieval of narrated gestures during the act of reading. The method of kinesic analysis practiced in this book takes into account such cognitive features in correlation with the historical and cultural contexts in which the literary works were written.
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Beauchamps, Marie, Marijn Hoijtink, Matthias Leese, Bruno Magalhães, Sharon Weinblum et Stef Wittendorp. Introduction : Security/Mobility and the politics of movement. Manchester University Press, 2017. http://dx.doi.org/10.7228/manchester/9781526107459.003.0001.
Texte intégralRésumé :
This chapter introduces the space of inquiry that opens up at the intersection of security and mobility. It begins with briefly setting the stage of the security/mobility dynamic, after which a conceptual exploration follows. Security is regarded as a discourse revolving around threat. Distinct about security today is it being premised on openness which encourages intervention upon and thus regulation of mobility. Mobility is regarded as socially produced motion and concerns the ways in which the fact of displacement is made possible. Attention is then directed at the productive effects of both concepts and their interaction: they bring about particular relations of power, thereby privileging certain forms of security and mobility. The introductory chapter ends with an overview of the structure of the book and the individual chapters.
Chapitres de livres sur le sujet "Fast dynamic interactions"
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Nazarczuk, K. « Design of the Fast Manipulator with Eliminated Joint Limits and Reduced Dynamic Interactions ». Dans Theory and Practice of Robots and Manipulators, 281–86. Vienna : Springer Vienna, 1995. http://dx.doi.org/10.1007/978-3-7091-2698-1_35.
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Li, Haidong, Hai-Lin Liu et Xueyi Liang. « Fast Dynamic Channel Allocation Algorithm for TD-HSPA System ». Dans Human-Computer Interaction. Towards Intelligent and Implicit Interaction, 82–91. Berlin, Heidelberg : Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-39342-6_10.
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Baroni, Fabiano, Joaquin J. Torres et Pablo Varona. « Interacting Slow and Fast Dynamics in Precise Spiking-Bursting Neurons ». Dans Lecture Notes in Computer Science, 106–15. Berlin, Heidelberg : Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/11499220_11.
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Wang, Zifan, Nivin Mothi et Victor Muñoz. « Single-Molecule Fluorescence Spectroscopy Approaches for Probing Fast Biomolecular Dynamics and Interactions ». Dans Protein Folding, 235–46. New York, NY : Springer US, 2021. http://dx.doi.org/10.1007/978-1-0716-1716-8_13.
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Mørch, Alexander M., et Falk Schneider. « Investigating Diffusion Dynamics and Interactions with Scanning Fluorescence Correlation Spectroscopy (sFCS) ». Dans The Immune Synapse, 61–89. New York, NY : Springer US, 2023. http://dx.doi.org/10.1007/978-1-0716-3135-5_5.
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AbstractActivation of immune cells and formation of immunological synapses (IS) rely critically on the reorganization of the plasma membrane. These highly orchestrated processes are driven by diffusion and oligomerization dynamics, as well as by single molecule interactions. While slow macro- and meso-scale changes in organization can be observed with conventional imaging, fast nano-scale dynamics are often missed with traditional approaches, but resolving them is, nonetheless, essential to understand the underlying biological mechanisms at play. Here, we describe the use of scanning fluorescence correlation spectroscopy (sFCS) and scanning fluorescence cross-correlation spectroscopy (sFCCS) to study reorganization and changes in molecular diffusion dynamics and interactions during IS formation and in other biological settings. We focus on the practical aspects of the measurements including calibration and alignment of the optical setup, present a comprehensive protocol to perform the measurements, and provide data analysis pipelines and strategies. Finally, we show an exemplary application of the technology to studying Lck diffusion during T-cell signaling.
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Sun, Fuqiang, Menghua Zhang, Weijie Huang, Yongfeng Zhang, Bo Shi, Peiran Li, Ruikang Zhang et Fei Zheng. « A Fast Human–Computer Interaction Dynamic Modeling Method for Transmission Tower in Power Systems ». Dans Lecture Notes in Electrical Engineering, 1145–55. Singapore : Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-5912-6_85.
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Mulyana, Wahyu, Eko Prasojo, Emirhadi Suganda et Setyo Sarwanto Moersidik. « The Conceptual Models of Dynamic Governance Toward Sustainable Urban Water Management in Metropolitan Area ». Dans Environment & ; Policy, 243–71. Cham : Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-15904-6_14.
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AbstractWater is a key resource needed for human life. Urban water supply has not met the target of fulfilling water rights in terms of quantity, quality, continuity, and affordability. Urban water management system still traditionally emphasizes the physical construction of infrastructure and are still managed fragmented. This research aims to develop the conceptual models of dynamic governance model in urban water governance. The research approach uses a qualitative method by using soft system methodology (SSM) to develop the conceptual model. Research results are the conceptual models of dynamic governance in urban water governance at the policy hierarchy process starting from policy, organizational and operational levels to achieve the goals of sustainable urban water management. The conceptual models are described through the pathways of activities based on the interaction between dynamic capabilities and organizational culture. The dynamic governance model is adapted in Bandung Metropolitan Area as an implementation strategy in the fast-growing urban area.
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Calvaresi, Davide, Ahmed Ibrahim, Jean-Paul Calbimonte, Roland Schegg, Emmanuel Fragniere et Michael Schumacher. « The Evolution of Chatbots in Tourism : A Systematic Literature Review ». Dans Information and Communication Technologies in Tourism 2021, 3–16. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-65785-7_1.
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AbstractIn the last decade, Information and Communication Technologies have revolutionized the tourism and hospitality sector. One of the latest innovations shaping new dynamics and fostering a remarkable behavioral change in the interaction between the service provider and the tourist is the employment of increasingly sophisticated chatbots. This work analyzes the most recent systems presented in the literature (since 2016) investigated via 12 research questions. The often appreciated quick evolution of such solutions is the primary outcome. However, such technological and financial fast-pace requires continuous investments, upskilling, and system innovation to tackle the eTourism challenges, which are shifting towards new dimensions.
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McCauley, Micah J., Joha Joshi, Nicole Becker, Qi Hu, Maria Victoria Botuyan, Ioulia Rouzina, Georges Mer, L. James Maher et Mark C. Williams. « Quantifying ATP-Independent Nucleosome Chaperone Activity with Single-Molecule Methods ». Dans Single Molecule Analysis, 29–55. New York, NY : Springer US, 2023. http://dx.doi.org/10.1007/978-1-0716-3377-9_2.
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AbstractThe dynamics of histone-DNA interactions govern chromosome organization and regulates the processes of transcription, replication, and repair. Accurate measurements of the energies and the kinetics of DNA binding to component histones of the nucleosome under a variety of conditions are essential to understand these processes at the molecular level. To accomplish this, we employ three specific single-molecule techniques: force disruption (FD) with optical tweezers, confocal imaging (CI) in a combined fluorescence plus optical trap, and survival probability (SP) measurements of disrupted and reformed nucleosomes. Short arrays of positioned nucleosomes serve as a template for study, facilitating rapid quantification of kinetic parameters. These arrays are then exposed to FACT (FAcilitates Chromatin Transcription), a non-ATP-driven heterodimeric nuclear chaperone known to both disrupt and tether histones during transcription. FACT binding drives off the outer wrap of DNA and destabilizes the histone-DNA interactions of the inner wrap as well. This reorganization is driven by two key domains with distinct function. FD experiments show the SPT16 MD domain stabilizes DNA-histone contacts, while the HMGB box of SSRP1 binds DNA, destabilizing the nucleosome. Surprisingly, CI experiments do not show tethering of disrupted histones, but increased rates of histone release from the DNA. SI experiments resolve this, showing that the two active domains of FACT combine to chaperone nucleosome reassembly after the timely release of force. These combinations of single-molecule approaches show FACT is a true nucleosome catalyst, lowering the barrier to both disruption and reformation.
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Edelstein-Keshet, Leah. « Pattern Formation Inside Living Cells ». Dans SEMA SIMAI Springer Series, 79–95. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-86236-7_5.
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AbstractWhile most of our tissues appear static, in fact, cell motion comprises an important facet of all life forms, whether in single or multicellular organisms. Amoeboid cells navigate their environment seeking nutrients, whereas collectively, streams of cells move past and through evolving tissue in the development of complex organisms. Cell motion is powered by dynamic changes in the structural proteins (actin) that make up the cytoskeleton, and regulated by a circuit of signaling proteins (GTPases) that control the cytoskeleton growth, disassembly, and active contraction. Interesting mathematical questions we have explored include (1) How do GTPases spontaneously redistribute inside a cell? How does this determine the emergent polarization and directed motion of a cell? (2) How does feedback between actin and these regulatory proteins create dynamic spatial patterns (such as waves) in the cell? (3) How do properties of single cells scale up to cell populations and multicellular tissues given interactions (adhesive, mechanical) between cells? Here I survey mathematical models studied in my group to address such questions. We use reaction-diffusion systems to model GTPase spatiotemporal phenomena in both detailed and toy models (for analytic clarity). We simulate single and multiple cells to visualize model predictions and study emergent patterns of behavior. Finally, we work with experimental biologists to address data-driven questions about specific cell types and conditions.
Actes de conférences sur le sujet "Fast dynamic interactions"
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Zhang, Hao, Paul Ukrainetz, Peter Nikiforuk et Rich Burton. « Neural Adaptive Control of a MIMO Electrohydraulic Servosystem ». Dans ASME 1997 International Mechanical Engineering Congress and Exposition, 7–12. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-1275.
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Abstract Electrohydraulic servomechanisms are well known for their fast dynamic response, high power to inertia ratio, and control accuracy. If the system dynamics can be precisely described and the plant dynamics vary in the vicinity of the designed operation point, a fixed parameter controller may be designed using conventional control theory to acquire the desired output. However, for most industrial systems, it is very difficult to describe the system precisely. In addition, due to disturbances, variations of loads, and changing process dynamics, the system parameters may vary. A neural network approach, using the parallel distributed processing concept with the capability of an ever-improving performance through a dynamic learning process, provides a powerful adaptation ability; its implementation is thus quite feasible for the control of electrohydraulic servosystems. The objective of this research was to apply the neural network control architecture to a nonlinear multiple input-multiple output (MIMO) electrohydraulic servosystem to improve its position and force output performance. This objective was achieved through the use of a neural adaptive control scheme. A neuro-controller was implemented as a subsystem to control the real-time electrohydraulic system so as to track the desired signals defined by a reference model when subjected to system internal interactions and load variations. Experiments were conducted to illustrate the feasibility and benefits of the neural network approach in comparison with the traditional PID control strategies. The position and force outputs of the plant followed the reference model outputs successfully. The proposed control scheme forced the plant outputs to track those of the reference model simultaneously under changes of the load disturbances.
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Liao, G. « Terahertz diagnosis of fast-electron dynamics in ultraintense laser-solid interactions ». Dans 2024 IEEE International Conference on Plasma Science (ICOPS), 1. IEEE, 2024. http://dx.doi.org/10.1109/icops58192.2024.10625863.
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Chandre Vila, Oriol, Yann Nivet, Joseph Morlier et Nicolas Gourdain. « Fast Method For Dynamic Fluid-Structure Interactions Considering Unsteady Aerodynamics ». Dans AIAA SCITECH 2022 Forum. Reston, Virginia : American Institute of Aeronautics and Astronautics, 2022. http://dx.doi.org/10.2514/6.2022-2538.
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Chandre Vila, Oriol, Yann Nivet, Joseph Morlier et Nicolas Gourdain. « Correction : Fast Method For Dynamic Fluid-Structure Interactions Considering Unsteady Aerodynamics ». Dans AIAA SCITECH 2022 Forum. Reston, Virginia : American Institute of Aeronautics and Astronautics, 2022. http://dx.doi.org/10.2514/6.2022-2538.c1.
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Wang, Yu, Aniket Chakrabarti, David Sivakoff et Srinivasan Parthasarathy. « Fast Change Point Detection on Dynamic Social Networks ». Dans Twenty-Sixth International Joint Conference on Artificial Intelligence. California : International Joint Conferences on Artificial Intelligence Organization, 2017. http://dx.doi.org/10.24963/ijcai.2017/417.
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A number of real world problems in many domains (e.g. sociology, biology, political science and communication networks) can be modeled as dynamic networks with nodes representing entities of interest and edges representing interactions among the entities at different points in time. A common representation for such models is the snapshot model - where a network is defined at logical time-stamps. An important problem under this model is change point detection. In this work we devise an effective and efficient three-step-approach for detecting change points in dynamic networks under the snapshot model. Our algorithm achieves up to 9X speedup over the state-of-the-art while improving quality on both synthetic and real world networks.
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Broc, Daniel, Jérome Cardolaccia et Laurent Martin. « Physical and Numerical Methods for the Dynamic Behavior of the Fast Reactor Cores ». Dans ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28918.
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In the frame of the GEN IV Forum and of the ASTRID Project, a program is in progress in the CEA (France) for the development and the validation of numerical tools for the simulation of the dynamic mechanical behavior of the Fast Reactor cores, with both experimental and numerical parts. The cores are constituted of Fuel Assemblies (of FA) and Neutronic Shields (or NS) immersed in the primary coolant (sodium), which circulates inside the Fluid Assemblies. The FA and the NS are slender structures, which may be considered as beams, form a mechanical point of view. The dynamic behavior of this system has to be understood, for design and safety studies. Two main movements have to be considered: global horizontal movements under a seismic excitation, and opening of the core. The dynamic behavior of the core is strongly influenced by contacts between the beams and by the sodium. The contacts between the beams limit the relative displacements. The fluid leads to complex interactions between the structures in the whole core. The paper presents the physical and numerical methods and tools used to describe and simulate the phenomena. A key point is the Fluid Structure Interaction (or FSI): the interactions between the beams and the liquid sodium. The fluid movement is assumed to be described by the equations of a perfect fluid. Simple and efficient homogenization methods may be used to reduce the size of the problem. These methods are integrated in a general computer code, CAST3M developed at the CEA Saclay. This computer code allows to take into account the impacts between the beams. Some applications are presented.
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Peng, Cheng, Fasuo Yan et Jun Zhang. « Coupled Dynamic Response of a Spar Type Floating Offshore Wind Turbine ». Dans ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-23560.
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FOWTs (Floating Offshore Wind Turbine) are feasible renewable devices to harness the wind energy in the near future. However, because of the complicated interactions among wind turbine, mooring system and the hull, the motion of a FOWT under the impact of severe wind, wave and current has not been well studied yet. This research focuses on the coupled numerical analysis of a FOWT. A numerical code COUPLE-FAST is developed by integrating two existing codes, namely, COUPLE and FAST, to carry out the task. In this study, a particular FOWT model is chosen for the numerical simulation, which consists of a NREL 5-MW baseline wind turbine and OC3-Hywind Spar. Although the numerical simulation is limited to this particular type of FOWTs, the results and related code (COUPLE-FAST) may be helpful to the design of FOWTs in the future.
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Oh, Sanghoon, Linjun Zhang, Eric Tseng, Wayne Williams, Helen Kourous et Gabor Orosz. « Safe Decision and Control of Connected Automated Vehicles for an Unprotected Left Turn ». Dans ASME 2020 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/dscc2020-3335.
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Abstract The unprotected left turn of a connected automated vehicle (CAV) is investigated when it has a potential conflict with a connected human-driven vehicle (CHV) approaching in the opposite lane. A control architecture is proposed that includes interactions between the decision making, motion planning, and control levels. By utilizing the road context and information received via vehicle-to-everything (V2X) communication, a reduced state space representation is determined which allows the CAV to evaluate safety in a fast and efficient manner Using a temporal metric, a safety evaluation algorithm is developed which determines the safety of the decision making at controller level. To evaluate the algorithms, data collected with real vehicles is utilized.
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Kataoka, Shunji, Satsuki Minami, Hiroshi Kawai et Shinobu Yoshimura. « Large Scale Dynamic Response Analysis of Rod Bundles in Fluid Using Partitioned Coupling Technique ». Dans ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57710.
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Dynamic responses considering fluid structure interaction (FSI) is important in many engineering fields and some of the FSI phenomena are treated as an acoustic fluid and structure interaction (AFSI) problem. The dynamic interactions between the fluid and structure can change dynamic characteristics of structures and their responses to external excitation such as seismic loading. The authors have developed a coupled simulation system for the large scale AFSI problems using an iterative partitioned coupling technique. In the system, the authors employed ADVENTURE system which adopted an efficient preconditioned iterative linear algebraic solver, and ADVENTURE Coupler is used to handle interface variable efficiently on various parallel computational environments. The authors employ Broyden method for updating interface accelerations to obtain the robust and fast convergence property of fixed point iterations. This paper presents the overview of the coupled analysis system and the results of its application to several AFSI problems are shown. The system runs efficiently in a parallel environment and it is capable for analyses of complex shaped three dimensional structures with more than 20 million degrees of freedom model.
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Broc, Daniel, Gianluca Artini, Jérome Cardolaccia et Laurent Martin. « Fast Reactor Cores : Seismic Excitation in the Vertical Direction — Numerical Methods ». Dans ASME 2018 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/pvp2018-84098.
Texte intégralRésumé :
In the frame of the GEN IV Forum and of the ASTRID Project, a program is in progress in the CEA (France) for the development and the validation of numerical tools for the simulation of the dynamic mechanical behavior of the Fast Reactor cores, with both experimental and numerical parts. The cores are constituted of Fuel Assemblies (or FA) and Neutronic Shields (or NS) immersed in the primary coolant (sodium), which circulates inside the Fuel Assemblies. The FA and the NS are slender structures, inserted in a grid plate, which may be considered as beams form a mechanical point of view. The dynamic behavior of this system has to be understood, for design and safety studies. This dynamic behavior of the core is strongly influenced by the sodium and by contacts between the beams at the pads level and at the top. The fluid leads to complex interactions between the structures in the whole core. The contacts between the beams limit the relative displacements. Two main movements have been considered so far: global horizontal movements under a seismic excitation, and opening of the core. Physical and numerical methods and tools have been developed to describe and simulate the dynamic behavior. These methods are integrated in CAST3M, general computer code developed at the CEA Saclay. The assemblies are modeled as beams. The impacts at the pads between the assemblies are taken into account by using a nonlinear model. The Fluid Structure Interaction is taken into account by using homogenization methods. This paper is devoted to the improvement of these methods to take into account the vertical component of a seismic excitation. The key points are: - the fluid structure coupling in the vertical direction, - the modification of the description of the impacts to take into account the vertical displacements of the assemblies, - the modification of the boundary condition at the foot of the assembly, in order to take into account the uplift with a nonlinear model.
Rapports d'organisations sur le sujet "Fast dynamic interactions"
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Tan, Peng, et Nicholas Sitar. Parallel Level-Set DEM (LS-DEM) Development and Application to the Study of Deformation and Flow of Granular Media. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, mars 2023. http://dx.doi.org/10.55461/kmiz5819.
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We present a systematic investigation of computational approaches to the modeling of granular materials. Granular materials are ubiquitous in everyday life and in a variety of engineering and industrial applications. Despite the apparent simplicity of the laws governing particle-scale interactions, predicting the continuum mechanical response of granular materials still poses extraordinary challenges. This is largely due to the complex history dependence resulting from continuous rearrangement of the microstructure of granular material, as well as the mechanical interlocking due to grain morphology and surface roughness. X-Ray Computed Tomography (XRCT) is used to characterize the grain morphology and the fabric of the granular media, naturally deposited sand in this study. The Level-Set based Discrete Element Method (LS-DEM) is then used to bridge the granular behavior gap between the micro and macro scale. The LS-DEM establishes a one-to-one correspondence between granular objects and numerical avatars and captures the details of grain morphology and surface roughness. However, the high-fidelity representation significantly increases the demands on computational resources. To this end a parallel version of LS-DEM is introduced to significantly decrease the computational demands. The code employs a binning algorithm, which reduces the search complexity of contact detection from O(n2) to O(n), and a domain decomposition strategy is used to elicit parallel computing in a memory- and communication-efficient manner. The parallel implementation shows good scalability and efficiency. High fidelity LS avatars obtained from XRCT images of naturally deposited sand are then used to replicate the results of triaxial tests using the new, parallel LS-DEM code. The result show that both micro- and macro-mechanical behavior of natural material is well captured and is consistent with experimental data, confirming experimental observation that the primary source of peak strength of sand is the mechanical interlocking between irregularly shaped grains. Specifically, triaxial test simulations with a flexible membrane produce a very good match to experimentally observed relationships between deviatoric stress and mobilized friction angle for naturally deposited sand. We then explore the viability of modeling dynamic problems with a new formulation of an impulse based LS-DEM. The new formulation is stable, fast, and energy conservative. However, it can be numerically stiff when the assembly has substantial mass differences between particles. We also demonstrate the feasibility of modeling deformable structures in the rigid body framework and propose several enhancements to improve the convergence of collision resolution, including a hybrid time integration scheme to separately handle at rest contacts and dynamic collisions. Finally, we extend the impulse-based LS-DEM to include arbitrarily shaped topographic surfaces and exploit its algorithmic advantages to demonstrate the feasibility of modeling realistic behavior of granular flows. The novel formulation significantly improves performance of dynamic simulations by allowing larger time steps, which is advantageous for observing the full development of physical phenomena such as rock avalanches, which we present as an illustrative example.
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Karr, Dale G., Bingbin Yu et Senu Sirnivas. Bottom Fixed Platform Dynamics Models Assessing Surface Ice Interactions for Transitional Depth Structures in the Great Lakes : FAST8 – IceDyn. Office of Scientific and Technical Information (OSTI), avril 2015. http://dx.doi.org/10.2172/1325200.
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Wideman, Jr., Robert F., Nicholas B. Anthony, Avigdor Cahaner, Alan Shlosberg, Michel Bellaiche et William B. Roush. Integrated Approach to Evaluating Inherited Predictors of Resistance to Pulmonary Hypertension Syndrome (Ascites) in Fast Growing Broiler Chickens. United States Department of Agriculture, décembre 2000. http://dx.doi.org/10.32747/2000.7575287.bard.
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Background PHS (pulmonary hypertension syndrome, ascites syndrome) is a serious cause of loss in the broiler industry, and is a prime example of an undesirable side effect of successful genetic development that may be deleteriously manifested by factors in the environment of growing broilers. Basically, continuous and pinpointed selection for rapid growth in broilers has led to higher oxygen demand and consequently to more frequent manifestation of an inherent potential cardiopulmonary incapability to sufficiently oxygenate the arterial blood. The multifaceted causes and modifiers of PHS make research into finding solutions to the syndrome a complex and multi threaded challenge. This research used several directions to better understand the development of PHS and to probe possible means of achieving a goal of monitoring and increasing resistance to the syndrome. Research Objectives (1) To evaluate the growth dynamics of individuals within breeding stocks and their correlation with individual susceptibility or resistance to PHS; (2) To compile data on diagnostic indices found in this work to be predictive for PHS, during exposure to experimental protocols known to trigger PHS; (3) To conduct detailed physiological evaluations of cardiopulmonary function in broilers; (4) To compile data on growth dynamics and other diagnostic indices in existing lines selected for susceptibility or resistance to PHS; (5) To integrate growth dynamics and other diagnostic data within appropriate statistical procedures to provide geneticists with predictive indices that characterize resistance or susceptibility to PHS. Revisions In the first year, the US team acquired the costly Peckode weigh platform / individual bird I.D. system that was to provide the continuous (several times each day), automated weighing of birds, for a comprehensive monitoring of growth dynamics. However, data generated were found to be inaccurate and irreproducible, so making its use implausible. Henceforth, weighing was manual, this highly labor intensive work precluding some of the original objectives of using such a strategy of growth dynamics in selection procedures involving thousands of birds. Major conclusions, solutions, achievements 1. Healthy broilers were found to have greater oscillations in growth velocity and acceleration than PHS susceptible birds. This proved the scientific validity of our original hypothesis that such differences occur. 2. Growth rate in the first week is higher in PHS-susceptible than in PHS-resistant chicks. Artificial neural network accurately distinguished differences between the two groups based on growth patterns in this period. 3. In the US, the unilateral pulmonary occlusion technique was used in collaboration with a major broiler breeding company to create a commercial broiler line that is highly resistant to PHS induced by fast growth and low ambient temperatures. 4. In Israel, lines were obtained by genetic selection on PHS mortality after cold exposure in a dam-line population comprising of 85 sire families. The wide range of PHS incidence per family (0-50%), high heritability (about 0.6), and the results in cold challenged progeny, suggested a highly effective and relatively easy means for selection for PHS resistance 5. The best minimally-invasive diagnostic indices for prediction of PHS resistance were found to be oximetry, hematocrit values, heart rate and electrocardiographic (ECG) lead II waves. Some differences in results were found between the US and Israeli teams, probably reflecting genetic differences in the broiler strains used in the two countries. For instance the US team found the S wave amplitude to predict PHS susceptibility well, whereas the Israeli team found the P wave amplitude to be a better valid predictor. 6. Comprehensive physiological studies further increased knowledge on the development of PHS cardiopulmonary characteristics of pre-ascitic birds, pulmonary arterial wedge pressures, hypotension/kidney response, pulmonary hemodynamic responses to vasoactive mediators were all examined in depth. Implications, scientific and agricultural Substantial progress has been made in understanding the genetic and environmental factors involved in PHS, and their interaction. The two teams each successfully developed different selection programs, by surgical means and by divergent selection under cold challenge. Monitoring of the progress and success of the programs was done be using the in-depth estimations that this research engendered on the reliability and value of non-invasive predictive parameters. These findings helped corroborate the validity of practical means to improve PHT resistance by research-based programs of selection.
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Idrissa, Rahmane, et Bethany McGann. Mistrust and Imbalance : The Collapse of Intercommunal Relations and the Rise of Armed Community Mobilization on the Niger-Mali Border. RESOLVE Network, avril 2021. http://dx.doi.org/10.37805/cbags2021.2.
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The border area of Mali, Niger, and Burkina Faso is a site of endemic violence. The area is punctuated by anti-state attacks, the targeted killing of traditional chiefs, and attacks on markets and other socioeconomic convening locales that otherwise serve as central mechanisms for the preservation of normalized intercommunal interactions. In addition, foreign military interventions and asymmetric insurgent warfare pit multiple state and non-state actors equipped with heavy weaponry against one another, adding another level of insecurity and threat to local communities. Community-based armed groups (CBAGs) of Fulani and Tuareg ethnicity have aligned themselves with outside actors carrying out operations in the region out of choice, coercion, or in some cases both. Building on other research reports in RESOLVE’s Community-Based Armed Groups Series, this report explores local perceptions regarding the nature and impact of the violence in southwestern Niger. The report provides a summary of understanding of ongoing conflict dynamics from the most impacted communities and an insight on the knowledge and attitudes around actors participating in the violence. It hopes to inform efforts to bring an end to the violence and increase understanding of participating actors.
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Lokke, Arnkjell, et Anil Chopra. Direct-Finite-Element Method for Nonlinear Earthquake Analysis of Concrete Dams Including Dam–Water–Foundation Rock Interaction. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, mars 2019. http://dx.doi.org/10.55461/crjy2161.
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Evaluating the seismic performance of concrete dams requires nonlinear dynamic analysis of two- or three-dimensional dam–water–foundation rock systems that include all the factors known to be significant in the earthquake response of dams. Such analyses are greatly complicated by interaction between the structure, the impounded reservoir and the deformable foundation rock that supports it, and the fact that the fluid and foundation domains extend to large distances. Presented in this report is the development of a direct finite-element (FE) method for nonlinear earthquake analysis of two- and three-dimensional dam–water–foundation rock systems. The analysis procedure applies standard viscous-damper absorbing boundaries to model the semi-unbounded fluid and foundation domains, and specifies at these boundaries effective earthquake forces determined from a ground motion defined at a control point on the ground surface. This report is organized in three parts, with a common notation list, references, and appendices at the end of the report. Part I develops the direct FE method for 2D dam–water–foundation rock systems. The underlying analytical framework of treating dam–water–foundation rock interaction as a scattering problem, wherein the dam perturbs an assumed "free-field" state of the system, is presented, and by applying these concepts to a bounded FE model with viscous-damper boundaries to truncate the semi-unbounded domains, the analysis procedure is derived. Step-by-step procedures for computing effective earthquake forces from analysis of two 1D free-field systems are presented, and the procedure is validated by computing frequency response functions and transient response of an idealized dam–water–foundation rock system and comparing against independent benchmark results. This direct FE method is generalized to 3D systems in Part II of this report. While the fundamental concepts of treating interaction as a scattering problem are similar for 2D and 3D systems, the derivation and implementation of the method for 3D systems is much more involved. Effective earthquake forces must now be computed by analyzing a set of 1D and 2D systems derived from the boundaries of the free-field systems, which requires extensive book-keeping and data transfer for large 3D models. To reduce these requirements and facilitate implementation of the direct FE method for 3D systems, convenient simplifications of the procedure are proposed and their effectiveness demonstrated. Part III of the report proposes to use the direct FE method for conducting the large number of nonlinear response history analyses (RHAs) required for performance-based earthquake engineering (PBEE) of concrete dams, and discusses practical modeling considerations for two of the most influential aspects of these analyses: nonlinear mechanisms and energy dissipation (damping). The findings have broad implications for modeling of energy dissipation and calibration of damping values for concrete dam analyses. At the end of Part III, the direct FE method is implemented with a commercial FE program and used to compute the nonlinear response of an actual arch dam. These nonlinear results, although limited in their scope, demonstrate the capabilities and effectiveness of the direct FE method to compute the types of nonlinear engineering response quantities required for PBEE of concrete dams.
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Weinberg, Zwi G., Adegbola Adesogan, Itzhak Mizrahi, Shlomo Sela, Kwnag Jeong et Diwakar Vyas. effect of selected lactic acid bacteria on the microbial composition and on the survival of pathogens in the rumen in context with their probiotic effects on ruminants. United States Department of Agriculture, janvier 2014. http://dx.doi.org/10.32747/2014.7598162.bard.
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This research project was performed in context of the apparent probiotic effect of selected lactic acid bacteria (LAB) silage inoculants on the performance of ruminants (improved feed intake, faster live-weight gain, higher milk yields and improved feed efficiency). The overall objective was to find out how LAB affect ruminant performance. The project included several “chapters” as follows: 1. The effect of LAB silage inoculants on the survival of detrimental bacteria in rumen fluid, in vitro study (Weinberg et al., The Volcani Center). An in vitro model was developed to study the interaction between selected LAB and an E. coli strain tagged with green fluorescence protein (GFP) in buffered RF. Results indicated that both LAB inoculants and E. coli survived in the RF for several days; both LAB inoculants and LAB-treated silages did not affect survival of E. coli in rumen fluid in vitro. The effect of feeding baled wheat silages treated with or without three selected LAB silage inoculants on the performance of high-lactating cows (Weinberg et al., The Volcani Center). Treatments included control (no additive), Lacobacillusbuchneri40788 (LB), Lactobacillus plantarumMTD1 40027 (LP) and Pediococcuspentosaceus30168 (PP), each applied at 10⁶ cfu/g FM. The silages were included in the TMR of 32 high milking Holstein cows in a controlled feeding experiment. All baled silages were of good quality. The LB silage had the numerically highest acetic acid and were the most stable upon aerobic exposure. The cows fed the LB silages had the highest daily milk yields, percent milk fat and protein. The microbiome of baled wheat silages and changes during ensiling of wheat and corn (Sela et al., The Volcani Center). Bacterial community of the baled silages was dominated mainly of two genera in total, dominated by Lactobacillus and Clostridium_sensu_stricto_12 with 300 other genera at very low abundance. Fungal community was composed mainly of two genera in total, dominated by Candida and Monascuswith 20 other genera at very low abundance. In addition, changes in the microbiome during ensiling of wheat and corn with and without addition of L. plantarumMTD1 was studied in mini-silos. Overall 236 bacterial genera were identified in the fresh corn but after 3 months Lactobacillus outnumbered all other species by acquiring 95% of relative abundance. The wheat silage samples are still under analysis. The effect of applying LAB inoculants at ensiling on survival of E. coli O157:H7 in alfalfa and corn silages(Adesogan et al., University of Florida). E. coli (10⁵ cfu/g) was applied to fresh alfalfa and corn at ensiling with or without L. plantarumor L. buchneri. The pathogen was added again after about 3 moths at the beginning of an aerobic exposure period. The inoculants resulted in faster decrease in pH as compared with the control (no additives) or E. coli alone and therefore, the pathogen was eliminated faster from these silages. After aerobic exposure the pathogen was not detected in the LAB treated silages, whereas it was still present in the E. coli alone samples. 5. The effect of feeding corn silage treated with or without L. buchnerion shedding of E. coli O157:H7 by dairy cows (Adesogan et al., UFL). BARD Report - Project 4704 Page 2 of 12 Five hundred cows from the dairy herd of the University of Florida were screened for E. coli shedding, out of which 14 low and 13 high shedders were selected. These cows were fed a total mixed ration (TMR) which was inoculated with E. coli O157:H7 for 21 days. The TMR included corn silage treated with or without L. buchneri. The inoculated silages were more stable upon aerobic exposure than the control silages; the silage inoculant had no significant effect on any milk or cow blood parameters. However, the silage inoculant tended to reduce shedding of E. coli regardless of high or low shedders (p = 0.06). 6. The effect of feeding baled wheat silages treated with or without three selected LAB silage inoculants on the rumen microbiome (Mizrahi et al., BGU). Rumen fluid was sampled throughout the feeding experiment in which inoculated wheat silages were included in the rations. Microbial DNA was subsequently purified from each sample and the 16S rRNA was sequenced, thus obtaining an overview of the microbiome and its dynamic changes for each experimental treatment. We observed an increase in OTU richness in the group which received the baled silage inoculated with Lactobacillus Plantarum(LP). In contrast the group fed Lactobacillus buchneri(LB) inoculated silage resulted in a significant decrease in richness. Lower OTU richness was recently associated in lactating cows with higher performance (Ben Shabatet al., 2016). No significant clustering could be observed between the different inoculation treatments and the control in non metric multi-dimentional scaling, suggesting that the effect of the treatments is not the result of an overall modulation of the microbiome composition but possibly the result of more discrete interactions. Significant phylum level changes in composition also indicates that no broad changes in taxa identity and composition occurred under any treatment A more discrete modulation could be observed in the fold change of several taxonomic groups (genus level analysis), unique to each treatment, before and after the treatment. Of particular interest is the LB treated group, in which several taxa significantly decreased in abundance. BARD Report - Project 4704 Page 3 of 12