共查询到20条相似文献,搜索用时 15 毫秒
1.
SIH G.C. 《中国科学:物理学 力学 天文学(英文版)》2014,57(1):39-50
The formalism of the earlier fatigue crack growth models is retained to account for multiscaling of the fatigue process that involves the creation of macrocracks from the accumulation of micro damage.The effects of at least two scales,say micro to macro,must be accounted for.The same data can thus be reinterpreted by the invariancy of the transitional stress intensity factors such that the microcracking and macrocracking data would lie on a straight line.The threshold associated with the sigmoid curve disappears.Scale segmentation is shown to be a necessity for addressing multiscale energy dissipative processes such as fatigue and creep.Path independency and energy release rate are monoscale criteria that can lead to unphysical results,violating the first principles.Application of monoscale failure or fracture criteria to nanomaterials is taking toll at the expense of manufacturing super strength and light materials and structural components.This brief view is offered in the spirit of much needed additional research for the reinforcement of materials by creating nanoscale interfaces with sustainable time in service.The step by step consideraton at the different scales may offer a better understanding of the test data and their limitations with reference to space and time. 相似文献
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V. S. Kobytev M. I. Slobodskoi T. N. Golosova L. E. Popov 《Russian Physics Journal》1996,39(2):157-159
In this paper, we estimate the volume density of dislocation sources formed as a result of contact interaction between dislocations slipping in an octahedral plane and Lomer-Cottrell dislocation locks. Assuming that during the deformation each dislocation source forms a slip trace, we estimate the average distance between slip traces. This distance turns out to be two to three orders of magnitude less than the experimentally observed value. We draw the conclusion that dislocation lock sources may ensure plastic deformation of fcc crystals.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 62–64, February, 1996. 相似文献
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《Physics letters. [Part B]》2006,638(1):44-49
A (p, t) study of eight nuclei in the rare earth region identified 96 0+ states (67 new). Their density at low energy is used to corroborate a fundamental property of quantum phase transitional behavior and to provide a new signature of nuclei near the critical point. 相似文献
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Mecozzi A 《Optics letters》2004,29(7):673-675
Probability density functions are given for nonlinear phase noise in a photonic communication system in which the information is encoded in the optical phase, both unconditioned and conditioned to the detection of a given amount of pulse energy. It is shown that the reach of a transmission system is increased by approximately 41% by ideal postcompensation of the nonlinear phase noise. 相似文献
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Alexander Pergament 《Phase Transitions》2013,86(3):159-168
On the basis of the Ashcroft empty core model potential, the equation for the constant of Coulomb interaction in the theory of excitonic insulator is modified. It is shown that in this case the dependence of the energy gap width on the charge carrier density obeys the Mott criterion in the limit of low densities. The conformity of the theory with some experimental data concerning metal–insulator phase transitions in doped semiconductors and transition metal compounds is discussed. 相似文献
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We study the uncertainties of quantum mechanical observables, quantified by the standard deviation (square root of variance) in Haar-distributed random pure states. We derive analytically the probability density functions (PDFs) of the uncertainties of arbitrary qubit observables. Based on these PDFs, the uncertainty regions of the observables are characterized by the support of the PDFs. The state-independent uncertainty relations are then transformed into the optimization problems over uncertainty regions, which opens a new vista for studying state-independent uncertainty relations. Our results may be generalized to multiple observable cases in higher dimensional spaces. 相似文献
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M. Kutschera 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(4):263-265
There exists profound discrepancy in the high density behaviour of the nuclear symmetry energy obtained in realistic variational many-body (VMB) calculations and in relativistic mean-field (RMF) calculations. While the symmetry energy decreases to negative values in the former approach it increases monotonically in the latter one. The origin of this discrepancy is discussed and it is argued that VMB prediction is more reliable. It is shown that vanishing of the symmetry energy implies proton-neutron separation instability in dense matter.This work was partially supported by KBN grants 2 0204 91 01 and 2 0054 91 01. 相似文献
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根据陶瓷介质材料具有高介电常数和高工作场强的特性,从理论上分析了陶瓷电容器具有的储能密度高、可工作在数kHz至数MHz的振荡放电回路中和老化缓慢等特性。对试制的1μF/500V的多层陶瓷电容器(MLC)试样品进行了750V 的1min直流耐压和100Hz重复充放电等可靠性试验研究,结果表明:该MLC在500V工作电压下(对应的体积储能密度达到720J/L)重复充放电寿命达107次以上;50kHz振荡放电输出电流峰值达320A;试验前后电气性能保持不变。因此,这种陶瓷电容器适合用作强脉冲大功率电源的储能元件。 相似文献
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N. Kaiser 《The European Physical Journal A - Hadrons and Nuclei》2010,45(1):61-68
We extend a recent calculation of the nuclear energy density functional in the framework of chiral perturbation theory by
computing the isovector surface and spin-orbit terms: ([(?)\vec] rp - [(?)\vec] rn\vec \nabla \rho _p - \vec \nabla \rho _n )2
G
d(r \rho) + ([(?)\vec] rp - [(?)\vec] rn\vec \nabla \rho _p - \vec \nabla \rho _n ·([(J)\vec]p - [(J)\vec]n\vec J_p - \vec J_n )G
so(r \rho) + ([(J)\vec]p - [(J)\vec]n\vec J_p - \vec J_n )2
G
J(r \rho) pertaining to different proton and neutron densities. Our calculation treats systematically the effects from 1p \pi -exchange, iterated 1p \pi -exchange, and irreducible 2p \pi -exchange with intermediate D \Delta -isobar excitations, including Pauli-blocking corrections up to three-loop order. Using an improved density-matrix expansion,
we obtain results for the strength functions G
d(r \rho) , G
so(r \rho) and G
J(r \rho) which are considerably larger than those of phenomenological Skyrme forces. These (parameter-free) predictions for the strength
of the isovector surface and spin-orbit terms as provided by the long-range pion-exchange dynamics in the nuclear medium should
be examined in nuclear structure calculations at large neutron excess. 相似文献
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Shao-Long Chen Xiao-Gang He Xue-Peng Hu Yi Liao 《The European Physical Journal C - Particles and Fields》2009,60(2):317-321
An unparticle
with scaling dimension
has peculiar thermal properties due to its unique phase space structure. We find that the equation of state parameter
, the ratio of pressure to energy density, is given by
providing a new form of energy in our universe. In an expanding universe, the unparticle energy density
evolves dramatically differently from that for photons. For
, even if
at a high decoupling temperature T
D is very small, it is possible to have a large relic density
at present photon temperature T
γ
0, large enough to play the role of dark matter. We calculate T
D and
using photon–unparticle interactions for illustration. 相似文献
15.
H. Hinkelmann 《Solid State Communications》1973,12(3):183-184
We investigate equilibrium correlation functions appearing in the linear response of an arbitrary solid or liquid to an electromagnetic field. The contributions from electrons and nuclei are considered. They are expressed solely by the dynamics of the nuclei. 相似文献
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A. Narayanaswamy G. Chen 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(12-13):1877-1884
A formal proof to relate the concept of electromagnetic local density of states (LDOS) to the electric and magnetic dyadic Green's functions (DGF) is provided. The expression for LDOS is obtained by relating the electromagnetic energy density at any location in a medium at uniform temperature T to the electric and magnetic DGFs. The appropriate boundary conditions governing the DGFs are obtained and it is seen that the two types of DGFs are electromagnetic duals of each other. With this the concept of LDOS is also extended to material media. The LDOS is split into two terms—one that originates from the energy density in an infinite, homogeneous medium and the other that takes into account scattering from inhomogeneities. The second part can always be defined unambiguously, even in lossy materials. For lossy materials, the first part is finite only if spatial dispersion is taken into account. 相似文献
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Various relationships are derived for simulation of random processes with simple or composite probability density functions. Depending on the properties of the corresponding parameters the resulting process is either stationary or non-stationary. Practical digital simulation with the formulas derived is fast enough to be used in real time with computer controlled simulators. 相似文献
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M. B. SWEATMAN 《Molecular physics》2013,111(9):573-581
Density expansion theories are often used, within the density functional formalism, to approximate the Helmholtz free-energy functional of simple classical fluids. An overview of the theoretical framework of density expansion theories is presented. Several density functional theories that employ truncated density expansions are then analysed with attention focused on their thermodynamic properties. It is found that, of these theories, only the commonly used mean-field theory satisfies the Gibbs adsorption equation; the inconsistencies within the other theories arise from truncation of the density expansion without appropriate modification of the expansion coefficients. Other repercussions of truncating the density expansion are discussed. 相似文献
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A systematic derivation of a relativistic inhomogeneity correction to the kinetic energy is given on the basis of the gradient expansion technique and the Foldy-Wouthuysen representation. 相似文献