Origin of the thermoreversible fcc-bcc transition in block copolymer solutions

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.     

A systematic study of irrational precipitation crystallography in fcc–bcc systems with an analytical O-line method

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.     

第一原理对铝的静态结构和相变的计算

 在密度泛函理论（DFT）和广义梯度近似（GGA）下,用缀加平面波加局域轨道（APW+lo）方法对铝的晶格常数、体弹模量以及在静态高压下的固态相变进行了计算。计算得出面心立方晶格结构（fcc）向六角密堆积结构（hcp）和体心立方结构（bcc）的相变分别发生在220 GPa和330 GPa,hcp向体心结构bcc的相变发生在380 GPa。计算结果和实验数据以及其它理论计算符合较好。     

The Invar problem

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.     

Mechanism of the fcc-bcc martensitic transformation with the fastest transformation of close-packed planes. I. The lattice parameter ratio and habitus planes

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.     

Analog model for quantum gravity effects: phonons in random fluids

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.     

Functional Integrals and Free Energy in sine-Gordon-Thirring Model with Impurity Coupling

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.     

Modelling of free radicals production in a collapsing gas-vapour bubble

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.     

基于扩散势能和自由体积的自扩散系数模型

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．     

Free Meixner States

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.     

Presence of many stable nonhomogeneous states in an inertial car-following model

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.     

A mean-field free energy lattice Boltzmann model for multicomponent fluids

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.     

三嵌段共聚物SEBS中自由体积行为的温度及e+辐照时间依赖性的研究

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T_g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     

Kinematic model of propagating arc-like segments with feedback

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.     

Free energy and electrical resistivity of molten alloys

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.     

Free energy change of a dislocation due to a Cottrell atmosphere

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.     

The hall effect of amorphous-non transition metals

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.     

Electron inelastic mean free paths and energy losses in solids II: Electron gas statistical model

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.