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1.
A set of parallel replicas of a single simulation can be statistically coupled to closely approximate long trajectories. In many cases, this produces nearly linear speedup over a single simulation ( M times faster with M simulations), rendering previously intractable problems within reach of large computer clusters. Interestingly, by varying the coupling of the parallel simulations, it is possible in some systems to obtain greater than linear speedup. The methods are generalizable to any search algorithm with long residence times in intermediate states. 相似文献
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Asymmetric simple exclusion processes are important for understanding low-dimensional multi-particle dynamic phenomena. The effect of irreversible detachments of particles on dynamics of asymmetric simple exclusion processes is studied using analytical and computer simulation techniques. In the simplest model, where particles can only detach from a single site in the bulk of the system, a theory is presented and used to calculate explicitly phase diagrams and particle density profiles. The complexity of the phase behavior is discussed in terms of a recent domain-wall theory for driven lattice systems. The theoretical results qualitatively and quantitatively agree with computer Monte Carlo simulations. 相似文献
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为了研究材料细观尺度的力学性能与失效行为,达到对材料微结构的“性能导向型”设计与性能预测的目的,通过程序设计结合有限元数值模拟的方法实现多元多相异质体材料微观组织结构的计算机仿真、材料微结构的细观力学计算与虚拟失效分析.以材料微观组织结构计算机仿真软件ProDesign构造的多晶体材料与多晶体基复合材料微结构的代表性体积单元为基础,基于对商业有限元软件ABAQUS的二次开发,实现对材料微结构细观力学的数值计算,并根据数值模拟结果预测微结构的材料性能,识别“材料结构弱点”,评估异质体材料微结构内微裂纹的启裂
关键词:
材料微结构
数值模拟
各向异性
虚拟失效 相似文献
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A molecular dynamics computer simulation of a glass-forming Yukawa mixture is used to study the anisotropic dynamics of a single particle pulled by a constant force. Beyond linear response, a scaling regime is found where a force-temperature superposition principle of a Peclet number holds. In the latter regime, the diffusion dynamics perpendicular to the force can be mapped on the equilibrium dynamics in terms of an effective temperature, whereas parallel to the force a superdiffusive behavior is seen in the long-time limit. This behavior is associated with a hopping motion from cage to cage and can be qualitatively understood by a simple trap model. 相似文献
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Takahide Oya Yoshiyuki Takahashi Masayuki Ikebe Tetsuya Asai Yoshihito Amemiya 《Superlattices and Microstructures》2003,34(3-6):253
A single-electron circuit can be operated as a discrete dynamical system because it changes its internal state discontinuously because of electron tunneling. To confirm this idea, we designed a sample circuit for discrete dynamical operation and confirmed by computer simulation that the circuit successfully generated a sequence of discrete-time outputs by following a return map. The concept of discrete dynamical systems will be useful in developing new functional systems that consist of quantum devices and nanostructures. 相似文献
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提出了一种通过相空间压缩实现时空混沌系统广义同步的方法. 以Fitzhugh-Nagumo反应扩散时空混沌系统为例,仿真模拟说明了该方法的有效性与实用性. 通过研究有界噪声作用下该系统的同步效果,表明这种同步方法具有较强的抗干扰能力. 此方法可以实现任意时空混沌系统的广义同步,具有普适性. 同步控制器结构简单、易于应用.
关键词:
时空混沌
广义同步
相空间压缩 相似文献
10.
George Stell 《Journal of statistical physics》1991,63(5-6):1203-1221
Some properties of a system of hard-core particles with attractive wells in the Baxter sticky-sphere limit and a related limit are considered, as is the approach to these limits. A demonstration of the result of Stell and Williams that sticky spheres of equal diameter in the Baxter limit are not thermodynamically stable is given, and the way in which size polydispersity can be expected to restore thermodynamic stability is discussed. The implications of these results for the PY sticky-sphere approximation and recent sticky-sphere computer simulations are then examined. It is concluded that the Baxter PY sticky-sphere approximation for a monodisperse system may well be a reasonable one for a slightly polydisperse system of sticky spheres and that existing simulation results may also be relevant to such a system. How polydisperse a system must be in quantitative terms in order for the PY approximation to be useful remains to be seen, however. The question of whether the PY sticky-sphere approximation may prove to be useful and appropriate in describing monodisperse systems with pair potentials for which the attractive wells arenot extremely narrow is also considered; it is noted that firm evidence concerning this question also appears to be lacking. Implications for systems near, but not in, the limit of zero attractive-well width are also considered, especially in terms of the relative size of the well width and the degree of size polydispersity in the repulsive cores. The possible pertinence of such considerations to colloidal systems is observed. The importance of taking into consideration the extremely long equilibration times that can be expected for systems with very narrow attractive wells is also pointed out, in connection both with real colloidal systems and in computer simulations. It is further observed that in the Baxter limit sticky spheres described quantum mechanically are indistinguishable from hard spheres so described; near the zero-well-width limit, the quantal behavior hinges on the number of bound states and thus the well depth as well as the relative size of the de Broglie thermal wavelength and the well width. Related results and investigations relevant to the issues described above are cited. 相似文献
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M. B. Smirnov S. V. Karpov V. Yu. Davydov A. N. Smirnov E. E. Zavarin V. V. Lundin 《Physics of the Solid State》2005,47(4):742-753
Computer simulation of the dynamics of layered AlN/GaN superlattices is performed to elucidate the microscopic nature of the vibrational states corresponding to the strongest bands in the Raman spectra. Experimental Raman spectra are shown to consist of two groups of lines, one of which exhibits a two-mode behavior and the other shows a one-mode behavior as the relative layer thicknesses are varied. The results of computer simulation and calculations within the dielectric-continuum approximation suggest that the behavior of the observed vibrational modes is dictated by the degree of their localization and that the interlayer coupling is due to long-range dipole-dipole interactions. It is shown that the delocalized modes, which exhibit one-mode behavior, can be used as a sensitive probe of the structure and composition of superlattices. 相似文献
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Coupling theory is employed to analyze coupling gain and a new optical system is proposed for image edge enhancement, in which the ordinarily discarded background light is recycled as a pump source to amplify the signal light. We demonstrate the principle of optical correlation and compare the discrimination capability of two kinds of correlators by computer simulation. The results show that edge enhancement preprocessing can improve discrimination capability effectively. 相似文献
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Improved Computer Program for Magnetron Injection Gun Design 总被引:1,自引:0,他引:1
Yi Sheng Yeh Ming Hsiung Tsao Han Ying Chen Tsun-Hsu Chang 《International Journal of Infrared and Millimeter Waves》2000,21(9):1397-1415
Gyrotron has received extensive attention owing to its high-power capability, especially when the wavelength shrinks below the millimeter-wave range. The electron beam of a gyrotron is typically generated by a magnetron injection gun (MIG). For high cathode current density, the MIG may operate in a region that combines temperature limited and space-charge limited emissions. An improved computer program for electron gun design is appropriate for MIGs that operate between space-charge limited and temperature limited emission. Moreover, the initial input formation of the program resembles that of the EGUN code. Analysis of a Pierce electron gun and MIGs reveals that the stimulated beam current appears consistent with the measured results. However, EGUN simulation results in which the cathode emitters of MIGs are chosen for the temperature limited emission differ from those of our simulation results. This difference is most likely owing to that the initial emitting energy can not be completely described in the EGUN simulation. Finally, the improved computer program is used to design a MIG for a Ka-band, TE01 mode gyro-TWT. 相似文献
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Density Matrix Simulations of the Effects of J Coupling in Spin Echo and Fast Spin Echo Imaging 总被引:1,自引:0,他引:1
L. A. Stables R. P. Kennan A. W. Anderson J. C. Gore 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,140(2):305-314
A computer simulation has been used to calculate the effects of J coupling on the amplitudes of echoes produced by CPMG sequences. The program computes the evolution of the density matrix for different pulse intervals and can predict the signals obtainable from spin systems of any size and complexity. Results from the simulation confirm the prediction that a decrease in the effects of J coupling is largely responsible for the bright fat signal seen in fast spin echo imaging at high pulse rates. The effects of J coupling on CPMG echotrains are examined for A3B2 and A3B2C2 spin systems over a wide range of J coupling and chemical shift values and pulse spacings. The effects of J coupling on the point spread function obtained with fast spin echo imaging are also discussed. 相似文献
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Molecular-Dynamics computer simulations were used to study 2 nm wide polystyrene films confined in slit pores, defined by
inorganic crystalline surfaces. The simulated systems mimic experimentally studied hybrid materials, where polystyrene is
intercalated between mica-type, atomically smooth, crystalline layers. A comparison between the experimental findings and
the simulation results aims at revealing the molecular origins of the macroscopically observed behavior, and thus provide
insight about polymers in severe/nanoscopic confinements, as well as polymers in the immediate vicinity of solid surfaces.
Pronounced dynamic inhomogeneities are found across the 2 nm thin film, with fast relaxing moieties located in low local density
regions throughout the film. The origins of this behavior are traced to the confinement-induced density inhomogeneities, which
are stabilized over extended time scales by the solid surfaces.
Received 9 August 2001 and Received in final form 7 January 2002 相似文献
17.
Efficient quantum simulation of open quantum dynamics at various Hamiltonians and spectral densities
Na-Na Zhang 《Frontiers of Physics》2021,16(5):51501
Simulation of open quantum dynamics for various Hamiltonians and spectral densities are ubiquitous for studying various quantum systems. On a quantum computer, only log2N qubits are required for the simulation of an N-dimensional quantum system, hence simulation in a quantum computer can greatly reduce the computational complexity compared with classical methods. Recently, a quantum simulation approach was proposed for studying photosynthetic light harvesting [npj Quantum Inf. 4, 52 (2018)]. In this paper, we apply the approach to simulate the open quantum dynamics of various photosynthetic systems. We show that for Drude–Lorentz spectral density, the dimerized geometries with strong couplings within the donor and acceptor clusters respectively exhibit significantly improved efficiency. We also demonstrate that the overall energy transfer can be optimized when the energy gap between the donor and acceptor clusters matches the optimum of the spectral density. The effects of different types of baths, e.g., Ohmic, sub-Ohmic, and super-Ohmic spectral densities are also studied. The present investigations demonstrate that the proposed approach is universal for simulating the exact quantum dynamics of photosynthetic systems. 相似文献
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We use the molecular dynamics computer simulation technique to study the behavior of electron plasmas in the presence of highly
charged ions and strong magnetic fields. Such systems are encountered in electron cooler and electron target facilities, where
large recombination rates have been observed. Our simulation results show enhanced electron densities in the vicinity of the
ion, with the enhancement depending only weakly on the bulk density.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
He J. Levi E. Zabar Z. Birenbaum L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1989,17(3):429-438
The authors consider the design of capacitively driven, multisection, electromagnetic coil launchers, or coil guns, taking their transient behavior into account. A lumped-parameter computer simulation is developed to predict the performance of the launcher system. It is shown that a traveling electromagnetic wave can be generated on the barrel by the resonance of drive coils and their capacitors. More than half of the energy initially stored in the capacitor bank can be converted into kinetic energy of the projectile in one shot, and an additional quarter can be utilized in subsequent shots, if the launcher dimensions, resonant frequency, and firing sequence are properly selected. The projectile starts smoothly from zero initial velocity and with zero initial sleeve current. Section-to-section transitions which have significant effects on the launcher performance are also discussed. Experimental results were obtained with a small model and are in good agreement with theoretical predictions 相似文献
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J. M. BESSON 《高压研究》2013,33(1-6):01-11
Abstract Calculations of the properties of condensed matter systems can be crucially tested by comparison with their experimental pressure behavior. When validated by such a comparison theoretical models become reliable computer experiments and can be used to explore properties of the system which are intrinsically unobservable by experiment alone. Three examples are given of such methods: (i) The behavior of wurtzite indium nitride under pressure which is shown to be due to a second-order isostructural phase transition. (ii) The instability of tetrahedrally bonded semiconductors (Ge) under pressure which turns out to be related to a second-order process. (iii) The explanation of the lattice dynamics of a-boron at ambient conditions which can be understood only by comparison of its high pressure behavior with calculations. 相似文献