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1
ČULÍK, J., V. KELLNER, F. FRANTÍK und M. JURKOVÁ. „Determination of lower aliphatic halogen hydrocarbons in beer by using a statistical and dynamical headspace analysis.“ Kvasny Prumysl 41, Nr. 4 (01.04.1995): 105–10. http://dx.doi.org/10.18832/kp1995007.
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Ovcharenko, V. N. „Adaptive parameter identification in dynamical and static systems“. Automation and Remote Control 72, Nr. 3 (März 2011): 570–79. http://dx.doi.org/10.1134/s0005117911030088.
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3
Wicke, Jason, und Robert Jensen. „A Pilot Study of a Dynamical Systems Approach to Examining Changes in Static Balance of Adolescents“. Perceptual and Motor Skills 95, Nr. 1 (August 2002): 267–78. http://dx.doi.org/10.2466/pms.2002.95.1.267.
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In a dynamical systems model, movement patterns are dictated by several variables, called control parameters. The goal of this pilot study was to assess whether changes on a static balance task can be described by a dynamical systems model with body inertial properties as one of the potential control parameters. Three aspects of a dynamic system were examined in relation to a 2-ft. static balance task: a relation between the changes in the balance pattern and the control parameter, a relation between the stability of the balance pattern and the stability under perturbed conditions (1-ft. balance task), and during the perturbation lack of relation between the balance pattern and the control parameters. Nine adolescent boys, 15.3 ± 1.0 yr. old were examined twice over a 14-wk. period. During each testing session, participants' body mass, moments of inertia, and radius from the ankle to the center of mass were calculated, after which 1- and 2-ft. balance tasks were performed. Center of pressure coordinates were recorded using a Kistler force plate. The body parameters were used to calculate the natural frequency of the body to represent the control parameter. Significant relations among all three aspects of a dynamic system examined in both the lateral and anterior-posterior axes were found. This investigation was designed for exploratory purposes and limited to correlational analysis; therefore, no concrete conclusions could be drawn. The results, however, suggest a dynamical systems approach to the study of static balance patterns may be possible.
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Sheng, Dong Fa. „Dynamical Behaviors of Nonlinear Viscoelastic Piles with Damage“. Advanced Materials Research 479-481 (Februar 2012): 234–39. http://dx.doi.org/10.4028/www.scientific.net/amr.479-481.234.
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Base on the constitutive model expressed by convolution method for viscoelastic materials with damage, the initial-boundary-value problem analyzing static-dynamic behaviors of homogeneous, isotropic viscoelastic. Tiimoshenko beams with damage, placed on a viscoelastic foundation, is formulated under the case of finite deflections. And we adopt the model to simulate the dynamical behaviors of viscoelastic piles with damage placed on a viscoelastic foundation. The numerical methods in nonlinear dynamics are used to solve the simplified systems. The phase-trajectory diagrams, Poincare sections and bifurcation diagrams are all obtained. The influences of the material parameters of pile and foundation and load parameter on the dynamic behavior of the nonlinear system are investigated in detail.
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Nareddy, Vahini Reddy, Jonathan Machta, Karen C. Abbott, Shadisadat Esmaeili und Alan Hastings. „Dynamical Ising model of spatially coupled ecological oscillators“. Journal of The Royal Society Interface 17, Nr. 171 (Oktober 2020): 20200571. http://dx.doi.org/10.1098/rsif.2020.0571.
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Long-range synchrony from short-range interactions is a familiar pattern in biological and physical systems, many of which share a common set of ‘universal’ properties at the point of synchronization. Common biological systems of coupled oscillators have been shown to be members of the Ising universality class, meaning that the very simple Ising model replicates certain spatial statistics of these systems at stationarity. This observation is useful because it reveals which aspects of spatial pattern arise independently of the details governing local dynamics, resulting in both deeper understanding of and a simpler baseline model for biological synchrony. However, in many situations a system’s dynamics are of greater interest than their static spatial properties. Here, we ask whether a dynamical Ising model can replicate universal and non-universal features of ecological systems, using noisy coupled metapopulation models with two-cycle dynamics as a case study. The standard Ising model makes unrealistic dynamical predictions, but the Ising model with memory corrects this by using an additional parameter to reflect the tendency for local dynamics to maintain their phase of oscillation. By fitting the two parameters of the Ising model with memory to simulated ecological dynamics, we assess the correspondence between the Ising and ecological models in several of their features (location of the critical boundary in parameter space between synchronous and asynchronous dynamics, probability of local phase changes and ability to predict future dynamics). We find that the Ising model with memory is reasonably good at representing these properties of ecological metapopulations. The correspondence between these models creates the potential for the simple and well-known Ising class of models to become a valuable tool for understanding complex biological systems.
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El-Nabulsi, Rami Ahmad. „Asymptotically Static Universe Dominated by Phantom Energy“. Zeitschrift für Naturforschung A 70, Nr. 2 (01.02.2015): 101–8. http://dx.doi.org/10.1515/zna-2014-0242.
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AbstractIn this article, we investigated a generalised scalar field cosmology characterised by a time-dependent coupling function, a time-dependent cosmological constant, a chameleonic field, and a time-dependent equation of state parameter. Based on a particular choice of the Hubble parameter as function of the scalar field and its time derivative, we have investigated the dynamics of the Friedmann–Robertson–Walker flat universe. We have observed that for a particular choice of the free parameters in the theory, the universe accelerates with time and asymptotically tends toward a static universe. For specific values of the free parameters, the asymptotically static universe may be dominated by phantom energy or a cosmological constant without the need to implement in the theory multiple scalar fields or additional interactions. It is also pointed out that an asymptotically static universe is as well one special class of solutions for Horndeski and generalised galileons cosmologies. Special properties and features are discussed accordingly.
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Novosyadlyj, B. „Dark Sector in Cosmology: Dark Energy on Cosmological and Astrophysical Scales“. Ukrainian Journal of Physics 64, Nr. 11 (25.11.2019): 998. http://dx.doi.org/10.15407/ujpe64.11.998.
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The properties and observational manifestations of the dynamical dark energy on the cosmological and astrophysical scales are discussed. We consider the dynamical dark energy in the form of quintessential and phantom scalar fields with different parameters of the equation of state and the effective sound speed. The evolution of the dynamical dark energy and its impact on the dynamics of expansion of the Universe, halos, and voids, and its behavior in the static gravitational fields of astrophysical objects are analyzed. The current state and possible tests designed to establish the nature of dark energy are highlighted.
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Radosz, Wojciech, Grzegorz Pawlik und Antoni C. Mituś. „Characterization of Monte Carlo Dynamic/Kinetic Properties of Local Structure in Bond Fluctuation Model of Polymer System“. Materials 14, Nr. 17 (31.08.2021): 4962. http://dx.doi.org/10.3390/ma14174962.
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We report the results of the characterization of local Monte Carlo (MC) dynamics of an equilibrium bond fluctuation model polymer matrix (BFM), in time interval typical for MC simulations of non-linear optical phenomena in host-guest systems. The study contributes to the physical picture of the dynamical aspects of quasi-binary mosaic states characterized previously in the static regime. The polymer dynamics was studied at three temperatures (below, above and close to the glass transition), using time-dependent generalization of the static parameters which characterize local free volume and local mobility of the matrix. Those parameters play the central role in the kinetic MC model of host-guest systems. The analysis was done in terms of the probability distributions of instantaneous and time-averaged local parameters. The main result is the characterization of time scales characteristic of various local structural processes. Slowing down effects close to the glass transition are clearly marked. The approach yields an elegant geometric criterion for the glass transition temperature. A simplified quantitative physical picture of the dynamics of guest molecules dispersed in BFM matrix at low temperatures offers a starting point for stochastic modeling of host-guest systems.
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Pilati, T., F. Demartin und C. M. Gramaccioli. „Atomic displacement parameters for garnets: a lattice-dynamical evaluation“. Acta Crystallographica Section B Structural Science 52, Nr. 2 (01.04.1996): 239–50. http://dx.doi.org/10.1107/s0108768195010925.
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Atomic displacement parameters (a.d.p.'s), together with vibrational spectra (Raman and IR) and thermodynamic functions, have been calculated for some minerals of the garnet group, such as pyrope (Mg3Al2Si3O12), grossular (Ca3Al2Si3O12), andradite (Ca3Fe2Si3O12) and almandine (Fe3A12Si3O12). For this purpose, a rigid-ion Born–von Karman model has been applied, using empirical atomic charges and valence force fields derived from a best fit to the vibrational spectra of a group of orthosilicates and oxides. Agreement with the experimental data is good, with the only exception of pyrope and almandine: for these minerals the calculated a.d.p.'s of the Mg2+ atom in the former and of the corresponding Fe2+ atom in the latter are too low. This result confirms the unusual behaviour of these atoms, for which dynamic disorder has been claimed. However, if the values of the specific heat and entropy are considered and compared with our calculations, this situation can be best explained assuming the transition to static disorder of the Mg2+ and Fe2+ atoms to occur at low temperature.
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Dogaru, Radu, und Leon O. Chua. „Edge of Chaos and Local Activity Domain of FitzHugh-Nagumo Equation“. International Journal of Bifurcation and Chaos 08, Nr. 02 (Februar 1998): 211–57. http://dx.doi.org/10.1142/s0218127498000152.
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The local activity theory [Chua, 97] offers a constructive analytical tool for predicting whether a nonlinear system composed of coupled cells, such as reaction-diffusion and lattice dynamical systems, can exhibit complexity. The fundamental result of the local activity theory asserts that a system cannot exhibit emergence and complexity unless its cells are locally active. This paper gives the first in-depth application of this new theory to a specific Cellular Nonlinear Network (CNN) with cells described by the FitzHugh–Nagumo Equation. Explicit inequalities which define uniquely the local activity parameter domain for the FitzHugh–Nagumo Equation are presented. It is shown that when the cell parameters are chosen within a subset of the local activity parameter domain, where at least one of the equilibrium state of the decoupled cells is stable, the probability of the emergence of complex nonhomogenous static as well as dynamic patterns is greatly enhanced regardless of the coupling parameters. This precisely-defined parameter domain is called the "edge of chaos", a terminology previously used loosely in the literature to define a related but much more ambiguous concept. Numerical simulations of the CNN dynamics corresponding to a large variety of cell parameters chosen on, or nearby, the "edge of chaos" confirmed the existence of a wide spectrum of complex behaviors, many of them with computational potentials in image processing and other applications. Several examples are presented to demonstrate the potential of the local activity theory as a novel tool in nonlinear dynamics not only from the perspective of understanding the genesis and emergence of complexity, but also as an efficient tool for choosing cell parameters in such a way that the resulting CNN is endowed with a brain-like information processing capability.
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GOLDSTEIN, R. S., M. F. ZIMMER und Y. OONO. „MODELING MESOSCALE DYNAMICS OF FORMATION OF δ′-PHASE IN Al-Li ALLOYS“. Modern Physics Letters B 07, Nr. 16 (10.07.1993): 1083–94. http://dx.doi.org/10.1142/s0217984993001077.
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A mesoscale minimal model study of the α−δ′ two-phase system is presented. A minimal model free energy is introduced which reveals universal features of the ordering dynamics of the disordered into the L1 2 ordered state. Static phenomenological parameters of the minimal model are chosen to reproduce the equilibrium phase diagram, and dynamical ones are chosen to reproduce recent experimental scattering results by H. Chen’s group.
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Ghafoori, Mohammad, Ahmad Rastegarnia und Gholam Reza Lashkaripour. „Estimation of static parameters based on dynamical and physical properties in limestone rocks“. Journal of African Earth Sciences 137 (Januar 2018): 22–31. http://dx.doi.org/10.1016/j.jafrearsci.2017.09.008.
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Choi, Yuncherl, Jongmin Han und Jungho Park. „Dynamical Bifurcation of the Generalized Swift–Hohenberg Equation“. International Journal of Bifurcation and Chaos 25, Nr. 08 (Juli 2015): 1550095. http://dx.doi.org/10.1142/s0218127415500959.
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In this paper, we prove that the generalized Swift–Hohenberg equation bifurcates from the trivial states to an attractor as the control parameter α passes through critical points. The bifurcation is divided into two groups according to the dimension of the center manifolds. We show that the bifurcated attractor is homeomorphic to S1 or S3 and it contains invariant circles of static solutions. We provide a criterion on the quadratic instability parameter μ which determines the bifurcation to be supercritical or subcritical.
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KRAWIECKI, A. „DYNAMICAL PHASE TRANSITION IN THE ISING MODEL ON A SCALE-FREE NETWORK“. International Journal of Modern Physics B 19, Nr. 32 (30.12.2005): 4769–76. http://dx.doi.org/10.1142/s0217979205033017.
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Dynamical phase transition in the Ising model on a Barabási–Albert network under the influence of periodic magnetic field is studied using Monte-Carlo simulations. For a wide range of the system sizes N and the field frequencies, approximate phase borders between dynamically ordered and disordered phases are obtained on a plane h (field amplitude) versus T/Tc (temperature normalized to the static critical temperature without external field, Tc∝ ln N). On these borders, second- or first-order transitions occur, for parameter ranges separated by a tricritical point. For all frequencies of the magnetic field, position of the tricritical point is shifted toward higher values of T/Tc and lower values of h with increasing system size, i.e. the range of critical parameters corresponding to the first-order transition is broadened.
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MEHTA, ANITA, und JEAN-MARC LUCK. „HEARINGS AND MISHEARINGS: DECRYPTING THE SPOKEN WORD“. Advances in Complex Systems 23, Nr. 03 (Mai 2020): 2050008. http://dx.doi.org/10.1142/s0219525920500083.
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We propose a model of the speech perception of individual words in the presence of mishearings. This phenomenological approach is based on concepts used in linguistics, and provides a formalism that is universal across languages. We put forward an efficient two-parameter form for the word length distribution, and introduce a simple representation of mishearings, which we use in our subsequent modeling of word recognition. In a context-free scenario, word recognition often occurs via anticipation when, part-way into a word, we can correctly guess its full form. We give a quantitative estimate of this anticipation threshold when no mishearings occur, in terms of model parameters. As might be expected, the whole anticipation effect disappears when there are sufficiently many mishearings. Our global approach to the problem of speech perception is in the spirit of an optimization problem. We show for instance that speech perception is easy when the word length is less than a threshold, to be identified with a static transition, and hard otherwise. We extend this to the dynamics of word recognition, proposing an intuitive approach highlighting the distinction between individual, isolated mishearings and clusters of contiguous mishearings. At least in some parameter range, a dynamical transition is manifest well before the static transition is reached, as is the case for many other examples of complex systems.
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Lindsten, Fredrik, Thomas B. Schön und Lennart Svensson. „A non-degenerate Rao-Blackwellised particle filter for estimating static parameters in dynamical models*“. IFAC Proceedings Volumes 45, Nr. 16 (Juli 2012): 1149–54. http://dx.doi.org/10.3182/20120711-3-be-2027.00184.
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Dew, Ryan, Asim Ansari und Yang Li. „Modeling Dynamic Heterogeneity Using Gaussian Processes“. Journal of Marketing Research 57, Nr. 1 (14.10.2019): 55–77. http://dx.doi.org/10.1177/0022243719874047.
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Marketing research relies on individual-level estimates to understand the rich heterogeneity of consumers, firms, and products. While much of the literature focuses on capturing static cross-sectional heterogeneity, little research has been done on modeling dynamic heterogeneity, or the heterogeneous evolution of individual-level model parameters. In this work, the authors propose a novel framework for capturing the dynamics of heterogeneity, using individual-level, latent, Bayesian nonparametric Gaussian processes. Similar to standard heterogeneity specifications, this Gaussian process dynamic heterogeneity (GPDH) specification models individual-level parameters as flexible variations around population-level trends, allowing for sharing of statistical information both across individuals and within individuals over time. This hierarchical structure provides precise individual-level insights regarding parameter dynamics. The authors show that GPDH nests existing heterogeneity specifications and that not flexibly capturing individual-level dynamics may result in biased parameter estimates. Substantively, they apply GPDH to understand preference dynamics and to model the evolution of online reviews. Across both applications, they find robust evidence of dynamic heterogeneity and illustrate GPDH’s rich managerial insights, with implications for targeting, pricing, and market structure analysis.
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Li, L., Y. Z. Chen, D. G. Zhang und W. H. Liao. „Large Deformation and Vibration Analysis of Microbeams by Absolute Nodal Coordinate Formulation“. International Journal of Structural Stability and Dynamics 19, Nr. 04 (April 2019): 1950049. http://dx.doi.org/10.1142/s0219455419500494.
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This investigation uses the absolute nodal coordinate formulation (ANCF) method to solve statics and dynamics of microbeams for the first time. A comprehensive model for the investigation of statics and dynamics of microbeams by using gradient deficient elements of the ANCF and modified couple stress theory (MCST) is developed. The vibration equations of a planar hub-microbeam system with constant angular rotations are derived considering the static equilibrium. Accuracy of the ANCF method for microbeams is demonstrated. Large deformation problems of cantilever microbeams are solved and the influences of material length scale on beam deformation are studied. When the beam thickness becomes smaller, the deflection of the microbeam calculated by the current model is smaller, and the size effect becomes more significant. The size effect only has influence on the bending vibration of the microbeam. The variations of the angular speed as well as the scale parameter can trigger frequency veering phenomena. The present work could be used in dynamic or vibration predictions for microelectromechanical systems (MEMS) with both large displacements and large deformations.
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Smolar, V. A., T. I. Karyakina und I. I. Maglevanny. „Effects of a Perpendicularly Applied Magnetic Field on Harmonically Driven Quasi-two-dimensional Electron Gas: the Static Macrostates Symmetry Breaking and Generation of Even Harmonics in System Output“. Nelineinaya Dinamika 17, Nr. 2 (2021): 141–56. http://dx.doi.org/10.20537/nd210201.
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In this paper, we consider activation processes in a nonlinear metastable system based on a quasi-two-dimensional superlattice and study the dynamics of such a system, which is externally driven by a harmonic force in regimes of controlled instabilities. The spontaneous transverse electric field is considered as an order parameter and the forced violations of the order parameter are considered as a response of a system to periodic driving. The internal control parameters are the longitudinal applied electric field, the sample temperature and the magnetic field which is orthogonal to the superlattice plane. We investigate the cooperative effects of self-organization and high harmonic forcing in such a system from the viewpoint of catastrophe theory It is shown through numerical simulations that the additional magnetic field breaks the static macrostates symmetry and leads to generation of even harmonics; it also allows the control of the intensity of particular harmonics. The intensity of even harmonics demonstrates resonant-type nonmonotonic dependence on control parameters with the maxima at points close to critical points of the synergetic potential.
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O’Gorman, Paul A. „The Effective Static Stability Experienced by Eddies in a Moist Atmosphere“. Journal of the Atmospheric Sciences 68, Nr. 1 (01.01.2011): 75–90. http://dx.doi.org/10.1175/2010jas3537.1.
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Abstract Water vapor directly affects the dynamics of atmospheric eddy circulations through the release of latent heat. But it is difficult to include latent heat release in dynamical theories because of the associated nonlinearity (precipitation generally occurs where there is upward motion). A new effective static stability is derived that fundamentally captures the effect of latent heat release on moist eddy circulations. It differs from the usual dry static stability by an additive term that depends on temperature and a parameter measuring the up–down asymmetry of vertical velocity statistics. Latent heat release reduces the effective static stability experienced by eddies but cannot reduce it to zero so long as there are nonprecipitating regions of the eddies. Evaluation based on reanalysis data indicates that the effective static stability in the lower troposphere ranges from ∼80% of the dry static stability at high latitudes to ∼25% in the tropics. The effective static stability provides a solution to the longstanding problem of how to adapt dry dynamical theories to the moist circulations in the atmosphere. Its utility for climate change problems is illustrated based on simulations with an idealized general circulation model. It is shown to help account for changes in the thermal stratification of the extratropical troposphere, the extent of the Hadley cells, the intensity of extratropical transient eddies, and the extratropical eddy length.
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Pierrot, F., C. Reynaud und A. Fournier. „DELTA: a simple and efficient parallel robot“. Robotica 8, Nr. 2 (April 1990): 105–9. http://dx.doi.org/10.1017/s0263574700007669.
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SummaryThe DELTA parallel robot, designed by an EPFL (Ecole Polytechnique Fédérale de Lausanne) research team, is a mechanical structure which has the advantage of parallel robots and ease of serial robots modeling. This paper presents solutions for a complete modeling of the DELTA parallel robot (direct and inverse kinematics, inverse statics, inverse dynamics), with few arithmetic and trigonometric operations. Our method is based on a satisfactory choice of kinematic parameters and on a few restricting hypotheses for the static and dynamic models. We give some details of each model, we present some computation results and we put the emphasis on some particular points, showing the capabilities of this mechanical structure.
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Guo, Feng, Hong Zhang, Chao-Yang Zhang, Xin-Lu Cheng und Hai-Quan Hu. „Effect of electronic excitation to intermolecular proton transfer in bulk nitromethane: Tuned parameter SCC-DFTB and first principles study“. Journal of Theoretical and Computational Chemistry 14, Nr. 02 (März 2015): 1550013. http://dx.doi.org/10.1142/s0219633615500133.
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To understand the reaction mechanism involving hydrogen transfers through hydrogen-bond bridge, we carried out both Self-Consistent Charge Density Functional Tight-Binding (SCC-DFTB) calculations of bulk nitromethane and Density Functional Theory (DFT) calculations of singlet ground state/triplet excited state molecular nitromethane using B3LYP functional. Firstly, we tuned the repulsive parameters of the SCC-DFTB method for nitromethane with dataset calculated from DFT at B3LYP/6-311g level. The molecular dynamics simulations are carried out with tuned parameters to get the dynamical properties of the bulk nitromethane, and the static calculations are intended to give energy profile of the reaction process. These calculations indicate the excitation of nitromethane molecule making the proton transfer reactions possible, and lowering the reaction barrier.
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Belardinelli, M. E., und E. Belardinelli. „The quasi-static approximation of the spring-slider motion“. Nonlinear Processes in Geophysics 3, Nr. 3 (30.09.1996): 143–49. http://dx.doi.org/10.5194/npg-3-143-1996.
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Abstract. The spring-slider is a simple dynamical system consisting in a massive block sliding with friction and pulled through a spring at a given velocity. Understanding the block motion is fundamental for studying more complex phenomena of frictional sliding, such as the seismogenic fault motion. We analyze the dynamical properties of the system, subject to rate- and state-dependent friction laws and forced at a constant load velocity. In particular we study the limits within which the quasi-static model can be used. The latter model approximates the complete model of the system without taking into account the inertia effects. The system parameters are here found to be grouped into three characteristic times of the three dynamics present in the complete model. A necessary condition for the quasi-static approximation to hold is that the characteristic time of the inertial equation is much smaller than the other two characteristic times. We have studied a modification of one of the classical forms of the rate- and state-dependent friction laws. Subsequently we have developed a linear analysis in the neighbourhood of the equilibrium point of the system. For the quasi-static model we rigorously found, by means of a nonlinear analysis, a supercritical Hopf bifurcation, a dynamical property of the complete model. The classical form of the friction laws can be obtained as a particular case of the one we considered, but fails to preserve the Hopf bifurcation in the quasi-static approximation. We conclude that to have a good quasi-static approximation of the system, even in nonlinear conditions, the form of the friction laws considered is a critical factor.
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Li, Zhuo, Meng Yang Zhao und Liang Zhou. „Research on Driving Comfort Evaluation of Lower Limb Based on Muscular Forces“. Applied Mechanics and Materials 602-605 (August 2014): 416–19. http://dx.doi.org/10.4028/www.scientific.net/amm.602-605.416.
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Driving comfort is one of the most important indexes for automobile comfort evaluation. The joint torque calculation model of the lower limb in driving posture is established in the presented work firstly. The relationship between cab layout parameters and the joint torque can be obtained through dynamical simulation in the MATLAB by employing Kane method. A new method based on muscular forces is proposed to evaluate the automobile comfortableness. The force of each muscle can be obtained by employing static optimization algorithm of inverse dynamics. The impact of cab layout parameters , joint torque and the muscular forces on driving comfort and the relationship between them can be found through the analysis. As an reference, these parameters can be used to optimize the cab and offer an important support for its optimization.
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NANDGAONKAR, AJAY, P. DURGANANDINI, MIHIR ARJUNWADKAR und D. G. KANHERE. „STATIC AND DYNAMICAL PROPERTIES OF A SINGLE IMPURITY IN A STRONGLY CORRELATED HOST“. International Journal of Modern Physics B 13, Nr. 07 (20.03.1999): 807–18. http://dx.doi.org/10.1142/s0217979299000679.
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We study, using numerical exact diagonalisation, some static and dynamical properties of a single impurity substituted into a one-dimensional repulsive Hubbard chain. A systematic scan of the parameter-space reveals a rich magnetic phase diagram. Interactions on the lattice stabilize the local moment phase of the impurity. A scalar impurity is seen to induce local moments on the neighbouring sites near Half Filling. Static spin and charge correlation functions reflect a non-Fermi liquid character of the ground state in the presence of a scalar impurity.
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Li, Haifeng, Qing Chen, Chang Fu, Zhe Yu, Di Shi und Zhiwei Wang. „Bayesian Estimation on Load Model Coefficients of ZIP and Induction Motor Model“. Energies 12, Nr. 3 (11.02.2019): 547. http://dx.doi.org/10.3390/en12030547.
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Parameter identification in load models is a critical factor for power system computation, simulation, and prediction, as well as stability and reliability analysis. Conventional point estimation based composite load modeling approaches suffer from disturbances and noises, and provide limited information of the system dynamics. In this work, a statistics (Bayesian Estimation) based distribution estimation approach is proposed for both static and dynamic load models. When dealing with multiple parameters, Gibbs sampling method is employed. The proposed method samples all parameters in each iteration and updates one parameter while others remain fixed. The proposed method provides a distribution estimation for load model coefficients and is robust for measuring errors. The proposed parameter identification approach is generic and can be applied to both transmission and distribution networks. Simulations using a 33-feeder system illustrated the efficiency and robustness of the proposal.
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Tamang, Jharna, und Asit Saha. „Dynamical Behavior of Supernonlinear Positron-Acoustic Periodic Waves and Chaos in Nonextensive Electron-Positron-Ion Plasmas“. Zeitschrift für Naturforschung A 74, Nr. 6 (26.06.2019): 499–511. http://dx.doi.org/10.1515/zna-2018-0476.
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AbstractPropagation of nonlinear and supernonlinear positron-acoustic periodic waves is examined in an electron-positron-ion plasma composed of static positive ions, mobile cold positrons, and q-nonextensive electrons and hot positrons. Employing the phase plane theory of planar dynamical systems, all qualitatively different phase portraits that include nonlinear positron-acoustic homoclinic orbit, nonlinear positron-acoustic periodic orbit, supernonlinear positron-acoustic homoclinic orbit, and supernonlinear positron-acoustic periodic orbit are demonstrated subjected to the parameters $q,{\mu_{1}},{\mu_{2}},{\sigma_{1}},{\sigma_{2}}$, and V. The nonlinear and supernonlinear positron-acoustic periodic wave solutions are reported for different situations through numerical computations. It is observed that the nonextensive parameter (q) acts as a controlling parameter in the dynamic motion of nonlinear and supernonlinear positron-acoustic periodic waves. The dynamic motions for the positron-acoustic traveling waves with the influence of an extrinsic periodic force are investigated through distinct qualitative approaches, such as phase portrait analysis, sensitivity analysis, time series analysis, and Poincaré section. The results of this paper may be applicable in understanding nonlinear, supernonlinear positron-acoustic periodic waves, and their chaotic motion in space plasma environments.
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Herrera-Aguilar, A., A. M. Kuerten und Roldão da Rocha. „Regular Bulk Solutions in Brane-Worlds with Inhomogeneous Dust and Generalized Dark Radiation“. Advances in High Energy Physics 2015 (2015): 1–15. http://dx.doi.org/10.1155/2015/359268.
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From the dynamics of a brane-world with matter fields present in the bulk, the bulk metric and the black string solution near the brane are generalized, when both the dynamics of inhomogeneous dust/generalized dark radiation on the brane-world and inhomogeneous dark radiation in the bulk as well are considered as exact dynamical collapse solutions. Based on the analysis on the inhomogeneous static exterior of a collapsing sphere of homogeneous dark radiation on the brane, the associated black string warped horizon is studied, as well as the 5D bulk metric near the brane. Moreover, the black string and the bulk are shown to be more regular upon time evolution, for suitable values for the dark radiation parameter in the model, by analyzing the soft physical singularities.
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Vitková, Zuzana, Marián Tárník, Jarmila Pavlovičová, Anton Vitko, Jarmila Oremusová, Ján Murgaš und Andrej Babinec. „From Static to Dynamic Modeling of Surfactants Micellization“. Tenside Surfactants Detergents 58, Nr. 1 (01.01.2021): 4–12. http://dx.doi.org/10.1515/tsd-2020-2296.
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Abstract Micelles and micellization appeal long lasting interest as promising drug carriers. A conventional parameter providing information about formation of micelles is critical micelle concentration (cmc). Its value roughly separates two states of the surfactant solution – namely states with and without presence of micelles. If concentration of surfactants in water solution approaches cmc some physical quantities abruptly change, and this phenomenon is a key to determine value of the cmc. From numerous approaches for determination of the cmc the paper considers the conductivity-based method. But rather than studying the mechanism of micellization that is primarily carried out by the colloid chemists, the paper is focused on the development of an information rich and optimal dynamical model of the conductivity vs. concentration dependence. The model is derived from the solutions of the 1st order differential equation. The optimal model parameters are determined by the downhill simplex algorithm and the cmc is computed on the basis of the curvature of the concentration dependence of the conductivity.
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Dobrosavljević, V. „TYPICAL-MEDIUM THEORY OF MOTT–ANDERSON LOCALIZATION“. International Journal of Modern Physics B 24, Nr. 12n13 (20.05.2010): 1680–726. http://dx.doi.org/10.1142/s0217979210064563.
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The Mott and the Anderson routes to localization have long been recognized as the two basic processes that can drive the metal–insulator transition (MIT). Theories separately describing each of these mechanisms were discussed long ago, but an accepted approach that can include both has remained elusive. The lack of any obvious static symmetry distinguishing the metal from the insulator poses another fundamental problem, since an appropriate static order parameter cannot be easily found. More recent work, however, has revisited the original arguments of Anderson and Mott, which stressed that the key diference between the metal end the insulator lies in the dynamics of the electron. This physical picture has suggested that the "typical" (geometrically averaged) escape rate [Formula: see text] from a given lattice site should be regarded as the proper dynamical order parameter for the MIT, one that can naturally describe both the Anderson and the Mott mechanism for localization. This article provides an overview of the recent results obtained from the corresponding Typical-Medium Theory, which provided new insight into the the two-fluid character of the Mott–Anderson transition.
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Han, Jianxin, Lei Li, Gang Jin, Wenkui Ma, Jingjing Feng, Haili Jia und Dongmei Chang. „Qualitative Identification of the Static Pull-In and Fundamental Frequency of One-Electrode MEMS Resonators“. Micromachines 9, Nr. 12 (22.11.2018): 614. http://dx.doi.org/10.3390/mi9120614.
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This paper attempts to qualitatively identify the static pull-in position, pull-in voltage, and fundamental frequency of one-electrode microresonators from a physical perspective. During theoretical derivation, a generalized one-degree-of-freedom (1-DOF) model in nondimensional form derived using the differential quadrature method (DQM) is first introduced and then transformed for frequency normalization. Based on the deduced formulas, the upper and lower bounds of the static pull-in position and pull-in voltage are both deduced through mathematical proof. To distinguish the monotonic and nonmonotonic behavior of the fundamental frequency versus direct current (DC) voltage, a critical condition decided only by cubic stiffness is then determined. For the first time, two extreme static positions, as well as the corresponding fundamental frequencies and DC voltages to identify different frequency behaviors are derived, and their variations versus cubic stiffness are then discussed and verified. During the simulation process, a high-order DQM and COMSOL 2D model are both applied for numerical analyses. Guided by nondimensional results, typical behaviors with specific physical parameters are examined in detail. Results demonstrate that the curve tendencies between all the qualitative results and quantitative numerical simulations in dimensional form agree well with each other, implying the possibility of using 1-DOF model to qualitatively discuss physical parameters effects on the system statics and dynamics.
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Chang, De Gong, S. M. Li und Cong Feng An. „The Influence Analysis of Globular Indexing Cam Mechanism Size Parameters on Transmission Performance“. Advanced Materials Research 426 (Januar 2012): 163–67. http://dx.doi.org/10.4028/www.scientific.net/amr.426.163.
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The globular indexing cam mechanism is a kind of high-speed and high-precision indexing mechanism, widely used in the field of mechanical transmission, which has the character of smooth transmission, high-precision indexing, large transfer torque, wider choice of dynamic and static ratio, simple structure and low cost, etc. In this paper, the working principle and the main movement parameters of globular indexing cam mechanism are analyzed, and the dynamics simulation of this mechanism is done by using ADAMS dynamic simulation software to analyze the influence of size parameters on the transmission performance, which provides reliable theoretical basis for understanding the property and designing the parameter of globular indexing mechanism.
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Narzilloev, Bakhtiyor, Javlon Rayimbaev, Ahmadjon Abdujabbarov und Bobomurat Ahmedov. „Regular Bardeen Black Holes in Anti-de Sitter Spacetime versus Kerr Black Holes through Particle Dynamics“. Galaxies 9, Nr. 3 (06.09.2021): 63. http://dx.doi.org/10.3390/galaxies9030063.
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In this work, test particle dynamics around a static regular Bardeen black hole (BH) in Anti-de Sitter spacetime has been studied. It has been shown for neutral test particles that parameters of a regular Bardeen black hole in Anti-de Sitter spacetime can mimic the rotation parameter of the Kerr metric up to the value a≈0.9 providing the same innermost stable circular orbit (ISCO) radius. We have also explored the dynamics of magnetized particles with a magnetic dipole moment around a magnetically charged regular Bardeen black hole in Anti-de Sitter spacetime. As a realistic astrophysical scenario of the study, we have treated neutron stars orbiting a supermassive black hole (SMBH), in particular, the magnetar PSR J1745-2900 orbiting Sgr A* with the parameter β=10.2, as magnetized test particles. The magnetized particles dynamics shows that the parameter β, negative values of cosmological constant and magnetic charge parameter of the central BH cause a decrease in the ISCO radius. We have compared the effects of the magnetic charge of the Bardeen BH with the spin of rotating Kerr BH and shown that magnetic charge parameter can mimic the spin in the range a/M≃(0,0.7896) when Λ=0 at the range of its values g/M≃(0,0.648).
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CAO, GUO-YUN, und CHEN CHEN. „LOCAL REDUCTION OF FOLD BIFURCATION RELEVANT TO VOLTAGE COLLAPSE IN AN ELECTRIC POWER SYSTEM“. International Journal of Bifurcation and Chaos 12, Nr. 05 (Mai 2002): 1039–46. http://dx.doi.org/10.1142/s0218127402004875.
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In this paper, the reduction approach based on the center manifold theory for parameter-dependent nonlinear dynamical systems is applied to simplify the analysis of the fold bifurcation relevant to voltage collapse in a simple electric power system. This technique enables us to obtain a lower-dimensional and topologically equivalent system in the neighborhood of the bifurcation value, which is a subset in the state-parameter space. Explicit formulas are presented for the computation of quadratic coefficients of the Taylor approximations to the center manifold for the fold bifurcation in parameter-dependent dynamical systems. It is demonstrated that it is the fold bifurcation but not other static bifurcations that occurs in the reduced power system, via validating the nondegenerate conditions for the fold bifurcation. The dynamics of the reduced system are visualized by two- and three-dimensional plots, which show that the reduction method is applicable and accurate to analyze local bifurcations in the power system. Furthermore, time domain simulation and modal analysis technique for linear systems are applied to distinguish the voltage stability from the rotor (angle) stability in the electric power system.
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Zeng, Fan, Jing Jun Lou und Shi Jian Zhu. „Study on Giant Magnetostrictive Material with Design and Simulation of Displacement Magnifying Mechanism“. Advanced Materials Research 675 (März 2013): 219–26. http://dx.doi.org/10.4028/www.scientific.net/amr.675.219.
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In order to make full use of advantages of giant magnetostrictive material and to improve output characteristics of giant magnetostrictive actuator, displacement magnifying mechanism is designed based on flexible hinges. The design parameter of the flexible hinges and strength of material of flexible hinges are calculated. Based on the analysis and comparison, the statics and dynamics analysis was carried on by analytic method and ANSYS12.1 software,the input stiffness, magnifying multiple and the relationship between output displacement and load are calculated,and the stress analysis shows that the maximum stress of magnifying mechanism is less than the maximum allowable stress of materials. The resonance frequency,vibration modes and harmonic response of the mechanism were resulted by Finite element method, and the dynamics parameters of system are get.
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Šnīders, A. „Transient Process Modelling in Waste Water Aeration Unit“. Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference 1 (26.06.2006): 269. http://dx.doi.org/10.17770/etr2003vol1.2017.
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To minimize the expenditure of electrical energy for communal waste water biological treatment the simulation and investigation of oxygen transfer efficiency in aeration tank have been made. Soluted oxygen transfer efficiency ? 0 (Fig.1.) is one of the main important factor directly estimating the expenditure of electrical power for waste water aeration. The research object is an aeration tank (Fig.2.) with one input impact -–the air blower’s capacity Lg (m3/h), one output controlled parameter – dissoved oxygen concentration C (g/m3) and several perturbances such as waste water temperature T (oC), waste water afflux Q (m3/h) and biological oxygen need La (g/m3) for complete purification. Oxygen’s transfer efficiency depends on the waste water temperature, the depth of aerator immersion h (m), air flow intensity ? d (m3/disc.h) and the air diffusor’s density ? s. For simulation and practical design of the air blower control system the equations of statics C=f(Lg, Q, La, T, h, ? d , ? s) and dynamics C=f(t) have been compiled. That made possible to estimate the static gains for control channel Ka and for perturbances Kq, KT as well as the time constant of the aeration tank Ta. The analysis prove that the aeration tank is a non-stationary control object with the variable static and dynamic parameters and needs adaptive controller with predication of oxygen consumption. The block diagram for transient process simulation of the oxygen concentration control system have been compiled using model of the actual PID controller and the “Matlab” subprogram “Simulink”.
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Zhu, Qidan, Peng Lu, Zhibo Yang, Xun Ji und Yu Han. „Multi-Parameter Optimization for the Wet Steam Accumulator of a Steam-Powered Catapult“. Energies 12, Nr. 2 (13.01.2019): 234. http://dx.doi.org/10.3390/en12020234.
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Selecting the optimal parameters for wet steam accumulator of steam-powered catapult is an important task, due to launching safety. There is no literature on the topic of the parameters optimization for wet steam accumulator of steam-powered catapult. The genetic algorithm (GA) was used to determine the optimal wet steam accumulator in this article. The sink-off-the-bow (SOB), angle of attack and rate of climb were used to create the objective function. The multi-objective optimization can be converted to single-objective optimization, which is subject to angle of attack and rate of climb. Moreover, the simulation model of the steam catapult system was built by creating a thermodynamics model of steam-powered catapult, a mathematical model of traction release device, a statics model of tensioning, a statics model of full takeoff power, a mathematical model of catapult force build-up with holdback, a model of release, a dynamics model of power stroke, a dynamics model of free deck run and a dynamics model of fly away. Finally, the optimal combination of the wet steam accumulator was obtained via numerical simulation. The GA method can effectively find the optimal parameters of wet steam accumulator, and its optimized parameters can increase the safety of catapult launch process.
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Ayub, Syahrial, Muhammad Zuhdi und Muhammad Taufik. „PARAMETER-PARAMETER FISIKA UNTUK MENGUNGKAP STRUKTUR STATIS BAWAH PERMUKAAN GUNUNGAPI“. ORBITA: Jurnal Kajian, Inovasi dan Aplikasi Pendidikan Fisika 7, Nr. 1 (09.05.2021): 181. http://dx.doi.org/10.31764/orbita.v7i1.4358.
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ABSTRAKParameter-parameter fisika gunungapi diungkap dengan metode geofisika. Survei kakas gravitasi dan magnetik yang menghasilkan anomali positive bagi medan gravitasi dan magnetiknya, mengungkap struktur statis bawah permukaannya. Analisis tremor volkanik mengungkap dinamika internalnya. Gerakan-gerakan (aliran) fluida magma di dalam gunungapi menjadi sumber getar yang memancarkan gelombang seismik yang di sebut tremor volkanik. Lokasi, migrasi, daya pancar, bentuk geometri sistem pipa-kantong magma, periodisasi, model matematis dan sebagainya. Gempa volkanik yang disebabkan aktivitas magma dapat dijadikan indikator. Hasil pengeplotan posisi hiposenter dan episenter terhadap gempa volkanik yang terjadi, juga dapat mengungkap struktur statis bawah permukaan gunungapi. Kata Kunci : parameter-parameter fisika gunungapi; struktur statis bawah permukaanbawah permukaan ABSTRACTUsing methods of geophysics, physical parameters of volcano are described. Gravity and magnetic surveys yield positive anomaly on their fields, which can be interpreted as an accumulated material beneath the surface with certain values of its mass density and magnetic susceptibility. Analysis of volcanic tremor at the volcano to the knowledge of its internal dynamics. Fluid magma movements inside a volcano acts as source of vibrations which radiate sesmic wave called volcanic tremor. Location, migration, radiation power, geometry of magma chamber-pipe system, periodicities, mathematical models, etc. Volcanic earthquakes caused by magma activity can also be used as indicators. The results of the hypocenter and epicenter position of the volcanic earthquake that occurred, can also reveal the subsurface static structure of the volcano. Keywords : physical parameters;subsurface static structure
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Zafirovski, Zlatko, und Nikolay Vatin. „Empirical-Statical-Dynamical (ESD) Methodology for Extrapolation of Rock Mass Properties for Construction of Tunnels“. Applied Mechanics and Materials 725-726 (Januar 2015): 349–54. http://dx.doi.org/10.4028/www.scientific.net/amm.725-726.349.
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The investigation in rock masses in interaction with engineering structures is extremely important in a process of design of tunnels. The main problem is how to extrapolate the parameter from the zone of testing to the whole volume that is of interes for interaction analyses of the system rock mass-structure. In this article Empirical-Statical-Dynamical (ESD) methodology of extrapolation is presented. The basis of the methodology lies in combination of the results from geotechnical and geophysical testings and rock mass classification, connected with definition of adequate regressive models.
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Hwang, Yunn Lin, und Van Thuan Truong. „A Synchronous Approach for Numerical Simulation of Machine Tools“. Key Engineering Materials 642 (April 2015): 317–22. http://dx.doi.org/10.4028/www.scientific.net/kem.642.317.
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In this paper, a synchronous approach for dynamic simulation of machine tools is described. Computer Aided Engineering (CAE) method models and analyzes a dynamical parameter prototype of machine tools. In which, the flexible structure, interactive movement, non-linear factor effects as well as characteristics of resonance frequencies and mechanical transfer function are considered. The integrating Finite Element Method (FEM), Multi-Body Dynamics (MBD) and control carries out a solution of machine tools simulation for predicting dynamic machine behaviors. The static analysis and modal analysis of components are presented with sample examples. Cybernetic characteristics like Bode diagram and such a controller are implemented for movement tailors. The synchronous approach deduces a practically technical method for machines tools.
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Shah, Yash, Andrea Vacca und Sadegh Dabiri. „Air Release and Cavitation Modeling with a Lumped Parameter Approach Based on the Rayleigh–Plesset Equation: The Case of an External Gear Pump“. Energies 11, Nr. 12 (12.12.2018): 3472. http://dx.doi.org/10.3390/en11123472.
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In this paper, a novel approach for the simulation of cavitation and aeration in hydraulic systems using the lumped parameter method is presented. The presented approach called the Hybrid Rayleigh–Plesset Equation model is derived from the Rayleigh–Plesset Equation representative of bubble dynamics and overcomes several shortcomings present in existing lumped parameter based cavitation modeling approaches. Models based on static approximations do not consider the non-equilibrium effects of phase change on the system and incorrectly predict the system dynamics. On the other hand, the existing dynamic cavitation modeling strategies account for the non-equilibrium effects of phase change but express the evolution of phases through approximations of the Rayleigh–Plesset Equation (such as exclusion of nonlinear interactions in bubble dynamics), which often lead to physically unrealistic time-scales of bubble growth or dissolution. This paper presents a dynamic model for cavitation which is capable of predicting cavitation in hydraulic systems while preserving the nonlinear dynamics arising from the Rayleigh–Plesset Equation. The derived model determines the evolution of phases in terms of physically realizable parameters such as the bubble radius and the nuclei density, which can be estimated or determined experimentally. The paper demonstrates the effectiveness of the derived modeling approach with the help of numerical simulations of an External Gear Machine. Results from the simulations employing the proposed model are compared with an existing dynamic cavitation modeling approach and validated with experimental results over a range of dynamic parameters.
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Ferreira, J. A., F. Gomes de Almeida und M. R. Quintas. „Semi-empirical model for a hydraulic servo-solenoid valve“. Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 216, Nr. 3 (01.05.2002): 237–48. http://dx.doi.org/10.1177/095965180221600303.
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High-performance proportional valves, also called servo-solenoid valves, can be used today in closed-loop applications that previously were only possible with servo-valves. The valve spool motion is controlled in a closed loop with a dedicated hardware controller that enhances the valve frequency response and minimizes some non-linear effects. Owing to their lower cost and maintenance requirements as well as increasing performance they can compete with servo-valves in a large number of applications. This paper describes a new semi-empirical modelling approach for hydraulic proportional spool valves to be used in hardware-in-the-loop simulation experiments. The developed models use either data sheet or experimental values to fit the model parameters in order to reproduce both static (pressure gain, leakage flowrate and flow gain) and dynamic (frequency response) valve characteristics. Valve behaviour is divided into two parts: the static behaviour and the dynamic behaviour. A parameter decoupled model, with a variable equation structure, and a flexible model, with a fixed equation structure, are proposed for the static part. Spool dynamics are modelled by a non-linear second-order system, with limited velocity and acceleration, the parameters being adjusted using optimization techniques.
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Soldatenko. „Estimated Impacts of Climate Change on Eddy Meridional Moisture Transport in the Atmosphere“. Applied Sciences 9, Nr. 23 (20.11.2019): 4992. http://dx.doi.org/10.3390/app9234992.
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Research findings suggest that water (hydrological) cycle of the earth intensifies in response to climate change, since the amount of water that evaporates from the ocean and land to the atmosphere and the total water content in the air will increase with temperature. In addition, climate change affects the large-scale atmospheric circulation by, for example, altering the characteristics of extratropical transient eddies (cyclones), which play a dominant role in the meridional transport of heat, moisture, and momentum from tropical to polar latitudes. Thus, climate change also affects the planetary hydrological cycle by redistributing atmospheric moisture around the globe. Baroclinic instability, a specific type of dynamical instability of the zonal atmospheric flow, is the principal mechanism by which extratropical cyclones form and evolve. It is expected that, due to global warming, the two most fundamental dynamical quantities that control the development of baroclinic instability and the overall global atmospheric dynamics—the parameter of static stability and the meridional temperature gradient (MTG)—will undergo certain changes. As a result, climate change can affect the formation and evolution of transient extratropical eddies and, therefore, macro-exchange of heat and moisture between low and high latitudes and the global water cycle as a whole. In this paper, we explore the effect of changes in the static stability parameter and MTG caused by climate change on the annual-mean eddy meridional moisture flux (AMEMF), using the two classical atmospheric models: the mid-latitude f-plane model and the two-layer β-plane model. These models are represented in two versions: “dry,” which considers the static stability of dry air alone, and “moist,” in which effective static stability is considered as a combination of stability of dry and moist air together. Sensitivity functions were derived for these models that enable estimating the influence of infinitesimal perturbations in the parameter of static stability and MTG on the AMEMF and on large-scale eddy dynamics characterized by the growth rate of unstable baroclinic waves of various wavelengths. For the base climate change scenario, in which the surface temperature increases by 1 °C and warming of the upper troposphere outpaces warming of the lower troposphere by 2 °C (this scenario corresponds to the observed warming trend), the response of the mass-weighted vertically averaged annual mean MTG is -0.2 ℃ per 1000 km. The dry static stability increases insignificantly relative to the reference climate state, while on the other hand, the effective static stability decreases by more than 5.4%. Assuming that static stability of the atmosphere and the MTG are independent of each other (using One-factor-at-a-time approach), we estimate that the increase in AMEMF caused by change in MTG is about 4%. Change in dry static stability has little effect on AMEMF, while change in effective static stability leads to an increase in AMEMF of about 5%. Thus, neglecting atmospheric moisture in calculations of the atmospheric static stability leads to tangible differences between the results obtained using the dry and moist models. Moist models predict ~9% increase in AMEMF due to global warming. Dry models predict ~4% increase in AMEMF solely because of the change in MTG. For the base climate change scenario, the average temperature of the lower troposphere (up to ~4 km), in which the atmospheric moisture is concentrated, increases by ~1.5 ℃. This leads to an increase in specific humidity of about 10.5%. Thus, since both AMEMF and atmospheric water vapor content increase due to the influence of climate change, a rather noticeable restructuring of the global water cycle is expected.
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Saint-Paul, M., C. Opagiste und C. Guttin. „Static and dynamical elastic behavior of Lu5Ir4Si10 around its first-order structural phase transition“. International Journal of Modern Physics B 34, Nr. 12 (10.05.2020): 2050116. http://dx.doi.org/10.1142/s0217979220501167.
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Ultrasonic velocity measurements could be performed on a good quality single crystal of [Formula: see text] around its transition around 80 K. The behavior of the stiffness components demonstrates a first-order transition. The temperature dependence of the longitudinal elastic stiffness components [Formula: see text] and [Formula: see text] can be analyzed by the classical Landau theory and assuming a stricter coupling between the strain and the order parameter. A theoretical approach and experimental results are discussed.
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Soon, W., E. Posmentier und S. Baliunas. „Climate hypersensitivity to solar forcing?“ Annales Geophysicae 18, Nr. 5 (31.05.2000): 583–88. http://dx.doi.org/10.1007/s00585-000-0583-z.
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Abstract. We compare the equilibrium climate responses of a quasi-dynamical energy balance model to radiative forcing by equivalent changes in CO2, solar total irradiance (Stot) and solar UV (SUV). The response is largest in the SUV case, in which the imposed UV radiative forcing is preferentially absorbed in the layer above 250 mb, in contrast to the weak response from global-columnar radiative loading by increases in CO2 or Stot. The hypersensitive response of the climate system to solar UV forcing is caused by strongly coupled feedback involving vertical static stability, tropical thick cirrus ice clouds and stratospheric ozone. This mechanism offers a plausible explanation of the apparent hypersensitivity of climate to solar forcing, as suggested by analyses of recent climatic records. The model hypersensitivity strongly depends on climate parameters, especially cloud radiative properties, but is effective for arguably realistic values of these parameters. The proposed solar forcing mechanism should be further confirmed using other models (e.g., general circulation models) that may better capture radiative and dynamical couplings of the troposphere and stratosphere.Key words: Meteorology and atmospheric dynamics (climatology · general or miscellaneous) · Solar physics · astrophysics · and astronomy (ultraviolet emissions)
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Cantrell, Robert Stephen, Chris Cosners und Vivian Hutson. „Permanence in ecological systems with spatial heterogeneity“. Proceedings of the Royal Society of Edinburgh: Section A Mathematics 123, Nr. 3 (1993): 533–59. http://dx.doi.org/10.1017/s0308210500025877.
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SynopsisA basic problem in population dynamics is that of finding criteria for the long-term coexistence of interacting species. An important aspect of the problem is determining how coexistence is affected by spatial dispersal and environmental heterogeneity. The object of this paper is to study the problem of coexistence for two interacting species dispersing through a spatially heterogeneous region. We model the population dynamics of the species with a system of two reaction–diffusion equations which we interpret as a semi-dynamical system. We say that the system is permanent if any state with all components positive initially must ultimately enter and remain within a fixed set of positive states that are strictly bounded away from zero in each component. Our analysis produces conditions that can be interpreted in a natural way in terms of environmental conditions and parameters, by combining the dynamic idea of permanence with the static idea of studying geometric problems via eigenvalue estimation.
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Klauer, Christian, Maximilian Irmer und Thomas Schauer. „A muscle model for hybrid muscle activation“. Current Directions in Biomedical Engineering 1, Nr. 1 (01.09.2015): 386–89. http://dx.doi.org/10.1515/cdbme-2015-0094.
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AbstractTo develop model-based control strategies for Functional Electrical Stimulation (FES) in order to support weak voluntary muscle contractions, a hybrid model for describing joint motions induced by concurrent voluntary-and FES induced muscle activation is proposed. It is based on a Hammerstein model – as commonly used in feedback controlled FES – and exemplarily applied to describe the shoulder abduction joint angle. Main component of a Hammerstein muscle model is usually a static input nonlinearity depending on the stimulation intensity. To additionally incorporate voluntary contributions, we extended the static non-linearity by a second input describing the intensity of the voluntary contribution that is estimated by electromyography (EMG) measurements – even during active FES. An Artificial Neural Network (ANN) is used to describe the static input non-linearity. The output of the ANN drives a second-order linear dynamical system that describes the combined muscle activation and joint angle dynamics. The tunable parameters are adapted to the individual subject by a system identification approach using previously recorded I/O-data. The model has been validated in two healthy subjects yielding RMS values for the joint angle error of 3.56° and 3.44°, respectively.
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Zhao, Long, Yifei Yan, Xiangzhen Yan und Lei Zhao. „Structural Parameters Optimization of Elastic Cell in a Near-Bit Drilling Engineering Parameters Measurement Sub“. Sensors 19, Nr. 15 (30.07.2019): 3343. http://dx.doi.org/10.3390/s19153343.
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The downhole engineering parameters measurement sub is a key component of the rotary steerable drilling system. To enable a measurement sub to serve reliably under downhole complex conditions, the structural parameters optimization of its key but weak elastic cell is systematically studied. First, the multiple relations among measurement sensitivities, structural stiffnesses, and strength during structural parameters design are summarized. Second, the selection of the structural parameters of the elastic cell is characterized as a multi-objective optimization model, which is solved using the non-dominated sorting genetic algorithm II (NSGA-II). Furthermore, the finite element method (FEM) is used to verify the measurement performance and static strength of the proposed structure. Finally, transient dynamics analysis is applied to investigate the dynamic strength of the designed structure. The results show that the proposed parameters optimization strategy can quickly obtain the database for the structural parameters design of an elastic cell. The static analysis results based on the FEM further verify the effectiveness of the proposed method. Transient dynamic analysis also reveals the relative rigor of the proposed methodology framework to some extent. This work has practical significance for improving the drilling efficiency and reducing drilling risks. In addition, this proposed methodology has good extensibility.
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Arnold, Lutz G., und Wolfgang Kornprobst. „COMPARATIVE STATICS AND DYNAMICS OF THE ROMER R&D GROWTH MODEL WITH QUALITY UPGRADING“. Macroeconomic Dynamics 12, Nr. 5 (November 2008): 702–16. http://dx.doi.org/10.1017/s1365100508070375.
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This paper replaces increasing product variety with quality upgrading in the Romer model [Romer, Paul M., Journal of Political Economy 98 (1990), S71–S102]. We show that the range of parameters for which a steady state exists can be divided into two subspaces with well-behaved comparative statics and saddle-point dynamics in one subspace, but with “perverse” comparative-statics properties and either equilibrium indeterminacy or instability in the other subspace. These results for the closed economy can also be used to characterize the dynamics of the M-country open-economy version of the model.
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Marten, H., K. Gesicki und R. Szczerba. „Dynamical Structures of Planetary Nebulae — Models Against Observations“. Symposium - International Astronomical Union 155 (1993): 315–18. http://dx.doi.org/10.1017/s0074180900171062.
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Hydrodynamical calculations of Planetary Nebulae (PNe) over 25000 yrs of evolution which include timedependent effects of ionization as well as variable central stars winds and parameters consistent with stellar model calculations show a great variety of velocity and density structures which strongly deviate from the often assumed “homogeneous shells, expanding with constant velocities” (Marten & Schönberner, 1991, hereafter MS). By means of a static photoionization code we calculate the surface brightness in the 10 most prominent nebular emission lines for density structures of the model sequence “VS” as given by MS. The obtained radial emissivities are used together with the velocity and temperature structure of the ionized gas to calculate (thermally broadened) line profiles in order to derive “measured” expansion velocities. We compare the theoretical surface brightnesses with observations and demonstrate some difficulties in the interpretation of nebular expansion velocities, expansion distances and ages.