共查询到20条相似文献,搜索用时 15 毫秒
1.
We measured the out-of-plane elastic constants C(33) of a Co/Pt superlattice by picosecond ultrasound, and found that they were closely related to the thickness ratio of Co and Pt layers; C(33) was smaller than the prediction from the bulk values except for a specific thickness ratio. This behavior can be explained by the weak bonding at the interfaces that occurs to reduce the elastic strain energy, not by the interfacial strain. This view explained the relationship among C(33), the elastic strain energy, and perpendicular magnetic anisotropy. 相似文献
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《Journal of Physics and Chemistry of Solids》1996,57(11):1709-1711
It is shown that the non-linear variation with temperature of the single crystal elastic constants of sodium is not related to the effects of lattice defects, but to non-classical behavior at low temperatures. 相似文献
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In a soft elastic film compressed on a stiff substrate, creases nucleate at preexisting defects and grow across the surface of the film like channels. Both nucleation and growth are resisted by the surface energy, which we demonstrate by studying creases for elastomers immersed in several environments-air, water, and an aqueous surfactant solution. Measurement of the position where crease channeling is arrested on a gradient thickness film provides a uniquely characterized strain that quantitatively reveals the influence of surface energy, unlike the strain for nucleation, which is highly variable due to the sensitivity to defects. We find that these experimental data agree well with the prediction of a scaling analysis. 相似文献
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An alternative floor field (FF) model is proposed by incorporating the agitated behavior and elastic characteristics of pedestrians. The agitated behavior which is regarded as an important factor to pedestrian dynamics is depicted by introducing a parameter to revise the transition probability of pedestrians to move to the neighboring cells. To characterize elasticity of pedestrians, it is assumed that a cell can hold more than one pedestrians in crowd condition, while it can hold only one pedestrian in normal condition. In addition, a method to deal with conflicts is employed by considering the effects of agitated behavior and desired velocity. Numerical simulations are carried out to investigate pedestrian evacuation from a room. The results show, that as the value of agitated parameter increases, the evacuation time decreases to the minimum value and then increases gradually. Also, the faster-is-slower effect which is obtained by some other simulation models can be reproduced by the proposed model. Finally, the influence of exit width and the corresponding mechanism on evacuation process is investigated which is expected to be helpful to the exit design of public rooms. 相似文献
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We propose and study the collective behavior of a model of networked signaling objects that incorporates several ingredients of real-life systems. These ingredients include spatial inhomogeneity with grouping of signaling objects, signal attenuation with distance, and delayed and impulsive coupling between non-identical signaling objects. Depending on the coupling strength and/or time-delay effect, the model exhibits completely, partially, and locally collective signaling behavior. In particular, a correlated signaling (CS) behavior is observed in which there exist time durations when nearly a constant fraction of oscillators in the system are in the signaling state. These time durations are much longer than the duration of a spike when a single oscillator signals, and they are separated by regular intervals in which nearly all oscillators are silent. Such CS behavior is similar to that observed in biological systems such as fireflies, cicadas, crickets, and frogs. The robustness of the CS behavior against noise is also studied. It is found that properly adjusting the coupling strength and noise level could enhance the correlated behavior. 相似文献
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《Physics letters. A》1988,134(2):131-133
We study a quenched random mixture of Blume-Capel and Ising spins at low temperature. If the Blume-Capel concentrations is sufficiently small, the model behaves like an Ising model at low temperature. 相似文献
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The buckling of a folded membrane submitted to a bi-axial compression is studied in the framework of the continuum non-linear
elasticity theory. We show that the formation of the fold patterning can be quantitatively well described with a simple non-linear
model.
As a matter of fact, with this model, we recover the experimental phase diagram of a secondary buckling instability with a
very good precision. In addition, depending on the anisotropy of the applied compressive stress, we find that the buckling
coarsening dynamics can be described as a 1D spinodal decomposition (for a uni-axial stress) or as a 2D XY model (for an isotropic
bi-axial stress) with an irrotational non-scalar order parameter. For an isotropic bi-axial stress, we indeed recover the
famous coarsening exponent: n=1/4. This exponent has to be confirmed
experimentally. 相似文献
12.
Kuppalapalle Vajravelu Sreedharamalle Sreenadh Palluru Devaki Kerehalli V. Prasad 《Central European Journal of Physics》2011,9(5):1357-1365
The constitution of blood demands a yield stress fluid model, and among the available yield stress fluid models for blood
flow, the Herschel-Bulkley model is preferred (because Bingham, Power-law and Newtonian models are its special cases). The
Herschel-Bulkley fluid model has two parameters, namely the yield stress and the power law index. The expressions for velocity,
plug flow velocity, wall shear stress, and the flux flow rate are derived. The flux is determined as a function of inlet,
outlet and external pressures, yield stress, and the elastic property of the tube. Further when the power-law index n = 1 and the yield stress τ
0 → 0, our results agree well with those of Rubinow and Keller [J. Theor. Biol. 35, 299 (1972)]. Furthermore, it is observed that, the yield stress and the elastic parameters (t
1 and t
2) have strong effects on the flux of the non-Newtonian fluid flow in the elastic tube. The results obtained for the flow characteristics
reveal many interesting behaviors that warrant further study on the non-Newtonian fluid flow phenomena, especially the shear-thinning
phenomena. Shear thinning reduces the wall shear stress. 相似文献
13.
This paper investigates the dynamical behaviour of network traffic
flow. Assume that trip rates may be influenced by the level of
service on the network and travellers are willing to take a faster
route. A discrete dynamical model for the day-to-day adjustment
process of route choice is presented. The model is then applied to a
simple network for analysing the day-to-day behaviours of network
flow. It finds that equilibrium is arrived if network flow consists
of travellers not very sensitive to the differences of travel cost.
Oscillations and chaos of network traffic flow are also found when
travellers are sensitive to the travel cost and travel demand in a
simple network. 相似文献
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Universal behavior in a generalized model of contagion 总被引:1,自引:0,他引:1
Models of contagion arise broadly in both the biological and the social sciences, with applications ranging from the transmission of infectious diseases to the spread of cultural fads. In this Letter, we introduce a general model of contagion which, by explicitly incorporating memory of past exposures to, for example, an infectious agent, rumor, or new product, includes the main features of existing contagion models and interpolates between them. We obtain exact solutions for a simple version of the model, finding that under general conditions only three classes of collective dynamics exist. Furthermore, we find that, for a given length of memory, the class into which a particular system falls is determined by only two parameters. Our model suggests novel measures for assessing the susceptibility of a population to large contagion events, and also a possible strategy for inhibiting or facilitating them. 相似文献
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In this paper, we have studied the night driving behaviors in the car-following model in periodic boundary conditions. The evolution of uniform traffic under both small and large perturbations is investigated. The simulations show that the traffic is always unstable when V′<0 with V the optimal velocity. The traffic clusters, the kink–antikink waves, and the unstable clusters are observed under different sensitivity parameters. Even more interesting phenomenon is observed when the randomness effect is considered. Under large perturbations, it is shown that the traffic will be unstable if its density is smaller than a threshold. The density corresponding to the threshold increases with the decrease of the sensitivity parameter values. 相似文献
17.
We study the critical behavior of certain two-parameter families of correlated percolation models related to the Ising model on the triangular and square lattices, respectively. These percolation models can be considered as interpolating between the percolation model given by the + and – clusters and the Fortuin-Kasteleyn correlated percolation model associated to the Ising model. We find numerically on both lattices a two-dimensional critical region in which the expected cluster size diverges, yet there is no percolation. 相似文献
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《Physica A》2006,368(1):294-304
The collective dynamics of large-scale computer networks remains elusive due to not only the internal adaptive behaviors of network-wide flows, but also the spatial–temporal changes in the external environment. In this paper, we investigate the time-dependent collective behavior by using a computer network model, recently developed to study space–time characteristics of congestion in large networks. We use the evolving correlation pattern, the largest eigenvalue, and the information entropy to analyze the macroscopic pattern of changing network congestion. We find the collective behavior becomes more pronounced during transient periods of pattern shifting, and the macroscopic pattern becomes gradually indistinct as the observed timescale increases to some extent. We also find that the evolving pattern of spatial–temporal correlation is more useful to reveal the time-dependent collective behavior of our model at different forcing levels. 相似文献
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M. Baudequin G. Ryschenkow S. Roux 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(1):157-162
Light fibrous materials composed of elastic fibers display a non-linear elastic behavior, where the non-linearity is due to
the increase in the number of contacts between fibers under compression. Testing glass wool under compression up to 95% shows
such a strongly non-linear behavior. A model is proposed to account for the divergence of the compressive stress as the strain approaches a threshold compression , with . Quantitative analysis of the experimental data on glass wool is fully consistent with this result.
Received 2 February 1999 相似文献
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AbstractThis paper examines the thermoelectric behaviour of a thermoelectric thin film bonded to an elastic substrate. A calculation model for thermoelectric thin films is developed based on the singular integral equation method. The interface shear stress is found to exhibit singular behaviour at the ends of the films. Numerical results for the thermal stress distribution in the film and the film/substrate interface are obtained. Effects of film thickness and the substrate to film stiffness ratio on the stress of the film and the stress intensity factor of the interface are identified. The effects of interface electricity conductivity and the elastic–plastic deformation of the film are discussed. 相似文献