共查询到20条相似文献,搜索用时 546 毫秒
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三能级原子与辐射场随时间演化的耦合系统的特性 总被引:1,自引:0,他引:1
研究了级联型三能级原子与单模辐射场相互作用时基耦合随时间变化的JC模型。动用密度算符方法,讨论了该模型能级算符光子数分布,平均光子娄等性质,比较了该模型与标准JC模型结果的区别。 相似文献
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基于能量最小的统计三级截值模型 总被引:1,自引:0,他引:1
从能量函数出发,用统计学方法建立了统计三级截值模型,克服了用光学技术实现Hopfield模型时难以表示其高动态范围互连权重的弱点。与光学中通常采用的模型相比,统计三级截值模型提高了网络的存储容量和寻址能力。 相似文献
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用固体的Einstein模型与Debye模型分别导出了相应模型的固气相变的蒸发热和蒸发压公式,并对其做了数值计算,结果表明,蒸发热与温度之间近似呈线性关系,这与工程上经验近似是一致的。 相似文献
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现代植物生命科学研究中的物理模型及其意义 总被引:4,自引:0,他引:4
介绍了现代植物生命学研究中的本质部刚性导管模型,细胞壁圆筒模型,细胞膜双层电模型,植物热机模型以及气孔蒸腾速率振荡的RLC电路模型等物理学模型,指出了这些模型的意义。 相似文献
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A. A. Shatskiy 《Journal of Experimental and Theoretical Physics》2020,130(3):409-417
The equations of motion of a test particle are integrated for the field of a rotating Kerr black hole (BH) (in accordance with [1]). Due to the lack of analytical transformations for the Carter–Penrose diagrams (CPDs) for the Kerr metric, the topology of the Kerr BH is studied by analytical investigation of the equations of motion. Transformations for the CPDs for the Reisner–Nordström metric are analyzed. The problem of boundary conditions for the Reisner–Nordström topology is analyzed. A solution to this problem of boundary conditions is proposed. It is proved that, in the Reisner–Nordström topology, only one way to go to another universe is possible. For the Kerr topology, the possibility of the existence of an alternative transition to another universe that does not coincide with the universe for the ordinary transition is found. This alternative transition is performed through a surface with a zero radial coordinate (zero radius). Initial conditions for the falling particle are found that correspond to an alternative transition to another universe. The tidal forces acting on a falling body in the Kerr metric are estimated, and the possibility of the transition of the body to other universes without being destroyed by tidal forces is proved. 相似文献
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L. E. Zhmur 《Radiophysics and Quantum Electronics》1972,15(4):367-371
One-dimensional nonisothermal diffusion in ionospheric plasma (the F-region) is considered in the stationary case. The analysis is carried out for two species of positive ions with allowance for the ionization and recombination processes and the effect of gravity. A system of two coupled equations is derived for the concentrations of the electrons and ions. A transition is made to the case when the ions which determine dissociative recombination are impurity ions. For this case criteria are presented whose fulfilment causes the distribution that has been found to coincide with that obtained by Mange [9] without allowance for photochemical processes. 相似文献
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R. A. Vadov 《Acoustical Physics》2005,51(3):265-270
The disagreement between the experimental and calculated positions of the first convergence zone are known from many publications. The most probable cause for such a disagreement, namely, the incorrect specification of the input data for the calculations, is considered. The lack of simultaneity between the hydrological surveys of the region and the acoustic experiments is emphasized. The experimental data obtained by the author in five ocean regions are presented. These data characterize the diurnal variability of the distance from the source to the nearest boundary of the convergence zone. The relations proposed by different researchers for calculating the sound speed from the temperature, salinity, and hydrostatic pressure are analyzed. It is shown that these relations lead to a substantial difference in the estimated depth dependence of the hydrostatic gradient of the sound speed. The position of the first convergence zone is calculated for the propagation conditions determined by vertical temperature and salinity profiles with the subsequent recalculation of these profiles into sound speed profiles by using eight different formulas known from the literature. It is shown that different formulas lead to different values of the distance to the first zone; this difference is substantially greater than that between the calculations and experiment. The necessity of improving the recalculation relations in view of the experimental data on sound propagation in natural oceanic waveguides, including the data on the actual positions of the convergence zones, is emphasized. 相似文献
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G. Abbiendi et al. 《The European Physical Journal C - Particles and Fields》1999,11(3):409-425
The structure of both quasi-real and highly virtual photons is investigated using the reaction , proceeding via the exchange of two photons. The results are based on the complete OPAL dataset taken at centre-of-mass energies close to the mass of the Z boson. The QED structure function and the differential cross-section for quasi-real photons are obtained as functions of the fractional momentum x from the muon momentum which is carried by the struck muon in the quasi-real photon for values of ranging from 1.5 to 400 GeV. The differential cross-section for highly virtual photons is measured for GeV and GeV, where and are the negative values of the four-momentum squared of the two photons such that . Based on azimuthal correlations the QED structure functions and for quasi-real photons are determined for an average of 5.4 GeV.
Received: 8 February 1999 / Published online: 28 September 1999 相似文献
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Influence of the random dynamic parameters of the human body on the dynamic characteristics of the coupled system of structure-crowd 总被引:2,自引:0,他引:2
The presence of human occupants may change the dynamic behaviour of structures considerably. While this effect is considered in mechanical engineering (e.g. interaction between driver seat and driver) and biomechanics (potentially damaging effects of vibrations) by using equivalent mass-spring-damper systems for the human body, the design practice in civil engineering still often clings to the so-called mass-only model, i.e. the occupants are considered only as additional masses when analysing the dynamic behaviour of floor slabs and stand structures. Recent research efforts aim to improve this situation by recommending averaged models for the human body. This approach seems to be reasonable for large crowds; however, for smaller groups, the question arises whether the random scatter in the dynamic characteristics of the human body leads to random scatter in the effective natural frequency and the effective damping of the coupled structure-crowd system. Based on a probabilistic model for the dynamic characteristics of the human body, an extensive study is presented in this paper. The key variables are the natural frequency of the bare structure, the ratio of the crowd’s mass to the structure mass and the group size. The scatter in the effective dynamic characteristics of the coupled system is revealed by the 90%-confidence interval. Furthermore, the maximum span of the respective bounds is used to identify cases where the averaged model fails to predict the real behaviour of the coupled system. 相似文献
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An approach is proposed for analyzing the inverse spectral problems for the Schrodinger equation based on writing the equation for the analog of the number-of-quanta operator for a harmonic oscillator. This equation makes it possible to determine not only the one-dimensional mapping of the energy eigenvalues but also the linear equation for the point spectrum shift operator of the Schrodinger problem. The solvability conditions of the latter lead to a nonlinear equation that determines the class of allowable potentials. Two classes of potentials regular in R(1) and symmetrical are isolated on the basis of the proposed approach. The first of these leads to equidistant spectra with a gap of arbitrary size and location. The spectrum of the second potential class is a combination of three rigorously equidistant spectra with ground states that are shifted by an arbitrary amount. Generalizations to the case of essentially nonequidistant spectra are shown to be possible. 相似文献
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In this work we derive lower bounds for the Hausdorff and fractal dimensions of the global attractor of the Sabra shell model
of turbulence in different regimes of parameters. We show that for a particular choice of the forcing term and for sufficiently
small viscosity term ν, the Sabra shell model has a global attractor of large Hausdorff and fractal dimensions proportional
to log ν −1 for all values of the governing parameter ε, except for ε =1. The obtained lower bounds are sharp, matching the upper bounds
for the dimension of the global attractor obtained in our previous work. Moreover, the complexity of the dynamics of the shell
model increases as the viscosity ν tends to zero, and we describe a precise scenario of successive bifurcations for different
parameters regimes. In the “three-dimensional” regime of parameters this scenario changes when the parameter ε becomes sufficiently
close to 0 or to 1. We also show that in the “two-dimensional” regime of parameters, for a certain non-zero forcing term,
the long-term dynamics of the model becomes trivial for every value of the viscosity.
AMS Subject Classifications: 76F20, 76D05, 35Q30 相似文献
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A. Yu. Grosberg 《Journal of statistical physics》1985,38(1-2):149-160
The collapse (globulization) of an ideal heteropolymer chain under the action of an external attractive field is considered. The problem of the collapse of different types of primary structures, including mobile, periodic, large-block, and statistical structures, is formulated. It is shown that for a random heteropolymer, the mathematical image of the globular state is the chain-length independence of the probability distribution of a random thermal distribution function of the end monomer coordinates. The free energy per monomer of a chain in a globular state and local densities of monomers of all types are shown to be a self-averaging quantities. An exactly solvable model is proposed for a globule formed by a statistical heteropolymer chain. In this model, different types of monomers are attracted to different centers by linear elastic forces with identical elastic constants. The modulus of elasticity is obtained for a heteropolymer globule with respect to the attraction of different types of monomers in different directions. It is shown that this modulus is higher for a short-periodic polymer than for a statistical one. 相似文献