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1.
The thermoreversible fcc-bcc transition in concentrated block copolymer micellar solutions is shown to be driven by decreases in the aggregation number as the solvent penetrates the core, leading to a softer intermicelle potential. Small-angle neutron scattering measurements in a dilute solution are used to quantify the temperature-dependent micellar characteristics. The observed phase boundary is in excellent agreement with recent simulations of highly branched star polymers. 相似文献
2.
Precipitations that exhibit irrational transformation crystallography can often be explained in terms of the O-lines in the habit plane. The present work developed an analytical O-line method, which is more useful than the numerical O-line method to study the variation in the habit plane and its structure in a systematic manner. This method has an advantage that the orientation relationship (OR) is the output from the calculation, while in many other models interpreting precipitation crystallography the OR is either an input or is constrained by a prerequisite condition. This paper described the derivation of this method and its application to the study of the precipitation crystallography in fcc-bcc systems. Examples were given for three alloy systems, namely Cu-0.33wt%Cr and Ni-45wt%Cr alloys and a duplex-phase a-y stainless steel. The solutions include the OR between the precipitates and their matrix, the habit plane, the invariant line and the dislocation structure in the habit plane. The calculated results are in good agreement with the experimental observations reported in the literatures. Furthermore, the variation in the optimum O-line features with the lattice parameter ratio has also been studied systematically, providing some guidelines for estimating and understanding possible transformation crystallography from different fcc-bcc systems. 相似文献
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The Invar problem 总被引:1,自引:0,他引:1
E. F. Wassermann 《Journal of magnetism and magnetic materials》1991,100(1-3):346-362
After briefly reviewing the history and practical applications of Invar, we present results of recent total energy calculations as a function of the magnetic moment and atomic volume E(M, V). Based on these results, we analyze Invar-relevant physical properties for a broad variety of fcc ferromagnetic and antiferromagnetic 3d-alloy systems as a function of the electron concentration. The observed systematics can principally be understood within the framework of the band calculations mentioned. We also give an answer to the question, why close to the Invar range martensitic fcc-bcc transitions occur. Finally we show that a deeper understanding of all the observed anomalies results from an analysis of available data as a function of the lattice constant. Almost quantitative agreement between experiment and theory allows the conclusion that the moment-volume instabilities are undoubtedly responsible for the magnetic, magnetovolume and structural properties exhibited by 3d-alloy systems. 相似文献
5.
In terms of the concepts of heterogeneous nucleation and the related driving wave process, a version of the dynamic theory
of the formation of martensite crystals is stated in which the wave process initiates the fastest transformation of close-packed
{ie659-01} atomic planes of a parent fcc phase into {ie659-02} planes of a bcc phase. The lattice parameter ratio and the
orientations of habit planes are analytically related with the elastic properties of the γ-phase. Quantitative estimation
performed with the use of elastic moduli for an iron-nickel alloy yields habitus orientations close to {ie659-03}. An experiment
is proposed to verify the theoretical predictions. A new pattern of the short-wave correction that finishes the fcc-bcc rearrangement
is set forth.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 3–7, July, 2008. 相似文献
6.
We describe an analog model for quantum gravity effects in condensed matter physics. The situation discussed is that of phonons propagating in a fluid with a random velocity wave equation. We consider that there are random fluctuations in the reciprocal of the bulk modulus of the system and study free phonons in the presence of Gaussian colored noise with zero mean. We show that, in this model, after performing the random averages over the noise function a free conventional scalar quantum field theory describing free phonons becomes a self-interacting model. 相似文献
7.
The free energy at low temperature in 1D sine-Gordon-Thirring model with impurity coupling is studied by means of functional integrals method. For massive free sine-Gordon-Thirring model, free energy is obtained from perturbation expansion of functional determinant. Moreover, the free energy of massive model is calculated by use of an auxiliary Bose field method. 相似文献
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This paper deals with a model linking bubble dynamics under an acoustic pressure field and production of free radicals in the resulting collapses of this bubble. The bubble dynamics model includes interdiffusion of gas and vapour in the bubble as well as evaporation or condensation at the interface, and it assumes uniformity of the internal pressure and perfect gas law for the gas vapour mixture. At the maximum compression of the bubble, all the reactions of dissociation which can occur are assumed at thermodynamic equilibrium. The local composition (especially in free radicals) in the bubble is then calculated by an algorithm based on free energy minimization using the information concerning the maximum compression provided by the bubble dynamics model resolution. Using this model a comparison of free radicals production has been made for two different driving frequencies (20 kHz and 500 kHz), and at given bubble radius and acoustic pressure, an optimum of liquid bulk temperature has been derived for the production of free radicals very similar to the experimental one concerning oxidation reactions in aqueous phase. 相似文献
10.
在考虑自由体积和局部临界扩散势能的基础上,提出一种新的计算自扩散系数模型,并给出新模型中各个因子物理含义.同时还提出一种计算局部临界扩散势能的新方法,并应用于新模型.另外将衍生van der Waals状态方程应用于求解自由体积,式中所需径向分布函数由Morsali-Goharshadi方程得到.在相同条件下,新模型比原自由体积模型更准确. 相似文献
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Michael Anshelevich 《Communications in Mathematical Physics》2007,276(3):863-899
Free Meixner states are a class of functionals on non-commutative polynomials introduced in [Ans06]. They are characterized
by a resolvent-type form for the generating function of their orthogonal polynomials, by a recursion relation for those polynomials,
or by a second-order non-commutative differential equation satisfied by their free cumulant functional. In this paper, we
construct an operator model for free Meixner states. By combinatorial methods, we also derive an operator model for their
free cumulant functionals. This, in turn, allows us to construct a number of examples. Some of these examples are shown to
be trivial, in the sense of being free products of functionals which depend on only a single variable, or rotations of such
free products. On the other hand, the multinomial distribution is a free Meixner state and is not a product. Neither is a
large class of tracial free Meixner states which are analogous to the simple quadratic exponential families in statistics.
This work was supported in part by NSF grant DMS-0613195. 相似文献
13.
We present a single lane car- following model of traffic flow which is inertial and free of collisions. It demonstrates observed features of traffic flow such as existence of three regimes: free, nonhomogeneous congested (NHC) or synchronized, and homogeneous congested (HC) or jammed flow; bistability of free and NHC flow states in a range of densities, hysteresis in transitions between these states; jumps in the density-flux plane in the NHC regime; gradual spatial transition from synchronized to free flow; long survival time of jams in the HC regime. The model predicts that in the NHC regime there exist many stable states with different wavelengths, and noise can cause transitions between them. 相似文献
14.
We propose a mean-field free energy approach to simulate multi- component fluids. The model has been validated in terms of
the Laplace equation of capillarity and dispersion relation of interfacial waves. Simulations of a ternary system shows that
the total free energy decreases and reaches a minimum after phase separation has occurred. Different drop shapes can be obtained
by adjusting the interaction strengths between individual components. These results demonstrate that both macroscopic free
energy and microscopic fluid-fluid interactions have been well described in our multicomponent model. 相似文献
15.
利用正电子湮没寿命谱实验手段研究了22Na放射源的e+自辐射对三 嵌段共聚物SEBS的正电子湮没参数的影响,而后结合Eldrup的经典模型,研究了SEBS的自由体积孔尺寸和自由体积分数随着温度的变化关系,给出了自由体积分数在Tg以上和在Tg以下各自区域内分别与温度呈线性关系,最后结合Williams-Landel-Ferry(WLF)自由体积理论和Eldrup的经典模型讨论了热膨胀系数和自由体积分数中的A常数.
关键词:
正电子湮没技术
嵌段共聚物
自辐射
热膨胀 相似文献
16.
Using a kinematic approach, we propose a model of arc-like wave segments in which the free ends are stabilized by using a feedback algorithm. The model can demonstrate the experimental results and numerical computations of a reaction-diffusion system. This model also reveals some aspects of spiral wave dynamics with the free ends including not only the stabilization of wave segments using feedback, but also a critical behavior with respect to the initial wave size in media with fixed excitability. 相似文献
17.
The free energies of mixing for molten indium-antimony, cadmium-antimony, indium-bismuth, lead-bismuth and tin-bismuth were calculated from the variation of electrical resistivity with composition employing the model of Takeuchi and Endo. Resistivities measured in this laboratory with an electrodeless technique for In-Sb alloys, together with published values for Cd-Sb, In-Bi, Pb-Bi and Sn-Bi alloys were used in the calculations. Evaluation of the resistivity data gave the composition dependence of the derivatives of the chemical potentials of the constituents and the integral molar free energies of mixing. No assumptions regarding ideal entropy were made to obtain these free energy values although a statistically random mixture of ions is presumed in the scattering model. Conclusions drawn from a comparison between the calculated free energy values and published thermodynamic data for these systems are discussed in terms of departures from regularity and the variations in the effective free electron concentration. 相似文献
18.
The free energy reduction of a dislocation due to a Cottrell atmosphere of solutes is computed using a continuum model. We show that the free energy change is composed of near-core and far-field components. The far-field component can be computed analytically using the linearized theory of solid solutions. Near the core the linearized theory is inaccurate, and the near-core component must be computed numerically. The influence of interactions between solutes in neighbouring lattice sites is also examined using the continuum model. We show that this model is able to reproduce atomistic calculations of the nickel–hydrogen system, predicting hydride formation on dislocations. The formation of these hydrides leads to dramatic reductions in the free energy. Finally, the influence of the free energy change on a dislocation’s line tension is examined by computing the equilibrium shape of a dislocation shear loop and the activation stress for a Frank–Read source using discrete dislocation dynamics. 相似文献
19.
G. Bergmann 《Zeitschrift für Physik A Hadrons and Nuclei》1972,255(1):76-82
The amorphous metals Bi, Ga, Sn and Pb are obtained by quenched condensation. Their Hall effect is measured and compared with the model of free electrons. For Ga and Sn we find a good agreement with the free electron model. However, the Hall coefficient of Bi and Pb is only half as large as the theoretical value. This is particularly surprising because the corresponding liquids agree well with the free electron model and the amorphous state closely resembles the liquid. A trace effect of band structure may be responsible for the deviation. 相似文献
20.
A statistical model for the calculation of inelastic mean free paths and energy losses of electrons in solids is described. Results for the application of the model to the six solid media Al, Au, Ag, Cu, Ni, and Si are presented. Agreement between calculated mean free paths and experimental attenuation lengths indicates that the statistical model provides a useful method in the little-studied electron energy range from a few tens of electron volts to 10 keV. 相似文献