Diffuse wave density and directionality in anisotropic solids

Several general results are derived for diffuse waves in anisotropic solids, including concise expressions for the modal density per unit volume d(omega), and for the participation factor matrix G. The latter is a second-order tensor which describes the orientational distribution of diffuse wave or reverberant energy, and reduces to the identity I under isotropy. Calculations of G for a variety of example materials show significant deviation from I even under moderate levels of anisotropy.     

Long range density correlations in disordered solids

Although the structure of a glass closely resembles that of a dense liquid over short length scales, its solidity implies that the two-particle distribution function is long range. In this paper the explicit form of this long range behaviour is derived in terms of the elastic constants of the glass and the relationship is shown between density fluctuations and the microscopic form of the displacement vector u(r). With minor modifications these results are valid also for a crystal. Several ramifications of these results are explored.     

非侵入式超声波浆料浓度测量技术研究*

设计了一种基于非侵入式超声波透射衰减法的浆料浓度测量系统,根据超声传播衰减原理,建立超声衰减值与浆料浓度之间的关系。实验中采用生物显微镜和激光粒度仪对颗粒标称粒径进行验证,采用中心频率为200 kHz的超声波换能器,利用一发一收模式对超声波在有机玻璃管内的浆料进行非侵入式测量并分析透射波信号,对体积百分浓度小于25%、不同粒径的石英砂浆料进行测量,通过拟合方法获得浆料温度、体积百分浓度与声衰减对应的关系,并据此构造浓度求解方程,通过现场实时在线测量并与取样结果进行对比验证方程的准确性,结果显示,本方法可有效测量浆料浓度。     

动态冰浆流动的浓度分布及粘性研究

动态冰浆是一种固-液两相流体。文中采用理论模型研究了动态冰浆在非均质流动情况下的冰晶浓度分布,分析了冰晶浓度、冰浆流速、管道直径、冰晶粒径大小对冰浆的动态粘度的影响。分析表明:在高冰晶浓度、低流速情况下,冰浆的平均粘度不仅和冰晶浓度和载流溶液的粘度相关,还受到冰浆流速、管道直径和冰晶颗粒大小的影响。     

固体密度秤

根据杠杆平衡原理,使用杠杆平衡仪设计了固体密度秤.采用与液体密度计读数类似的方法,能够直接读出被测固体的密度.     

测定空气的密度

设计了测量空气密度的简易装置:将塑料桶用带有玻璃管的橡皮塞封上,将直玻璃管和另一个水平放置的内含有一段小水柱的玻璃管用橡皮管相连,上下移动塑料桶,读出直玻璃管中小水柱移动的距离,即可计算出空气密度.     

Time-dependent fluid squeeze-out between solids with rough surfaces

We study the time dependency of the (average) interfacial separation between an elastic solid with a flat surface and a rigid solid with a randomly rough surface, squeezed together in a fluid. As an application we discuss fluid squeeze-out between a tire tread block and a road surface. Some implications for the leakage of seals are discussed, and experimental results are presented to test the theory. The theoretical prediction for the leak rate as a function of the fluid pressure difference is in good agreement with the experimental data for all fluid pressures up to “lift-off”, where the fluid pressure equals the nominal rubber-substrate squeezing pressure.     

Berry phase correction to electron density of states in solids

Liouville's theorem on the conservation of phase-space volume is violated by Berry phase in the semiclassical dynamics of Bloch electrons. This leads to a modification of the phase-space density of states, whose significance is discussed in a number of examples: field modification of the Fermi-sea volume, connection to the anomalous Hall effect, and a general formula for orbital magnetization. The effective quantum mechanics of Bloch electrons is also sketched, where the modified density of states plays an essential role.     

The B3LYP hybrid density functional study on solids

The B3LYP hybrid density functional method, which is very successful in the study of thermochemistry of atoms and molecules, has been applied to some periodic systems recently. The applications to solids and surfaces show that the B3LYP hybrid functional reproduces the experimental energy gaps and magnetic moments for a variety of materials.     

Nonlocal density functional theory of solids: Applications of the weighted density approximation to silicon

Using the density functional formalism together with the weighted density approximation (WDA), we have carried out selfconsistent bandstructure studies of bulk Si in order to identify the influences of different WDA potentials and different pair correlation functions on the electronic spectrum. Improvements of band energies due to consideration of nonlocalities in exchange and correlation energy depend very sensitively on the particular correlation function used. For the prototype semiconductor Si, only one of the six WDA versions tested seems useful.     

The calculation of transport properties and density of states of disordered solids

A computational method is presented for the calculation of the conductivity tensor and the density of states of disordered solids. This is a more general and detailed discussion of an algorithm which has been applied to d.c. and a.c. conductivity, Hall effect and density of states of various systems.     

Method of the spin density functional and the ground state of solids

By using the property of universality of the spin density functional, quasiparticles of the ground state of an electron fluid in a solid are introduced. A model is proposed for the spin density functional of the ground state of a solid.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 76–81, October, 1977.     

Linear-scaling density matrix perturbation treatment of electric fields in solids

We develop a novel linear-scaling [O(N)] algorithm for calculating the optical dielectric constant and Born effective charge. Our method relies on the fact that only the sum of the nondiagonal parts of the electric field perturbation in solids contributes to the first-order derivative density matrix, which can then be obtained through the density-matrix perturbation method. The optical dielectric constant of amorphous SiO(2) is computed using a realistic model for the first time.     

用力敏传感器测量物体的密度

利用力敏传感器测量物体的密度,改进了传统的实验方法和仪器,实现了非电量电测,提高了实验的准确度和稳定性.     

测量可溶性物质的密度

常规方法测量可溶性物质（如食盐）的密度遇到了困难,经过分析研究和实验检测,本文给出的3种实验方法的确可行,实验结果误差较小。     

The method of concentration pulses for studying hydrogen transport in solids

The method of concentration pulses is designed for investigating the kinetics of hydrogen transport in complex diffusion systems and allows one to choose the most probable transport model and determine the rate constants of processes influencing the kinetics, e.g., diffusion, adsorption, and desorption, capture to traps, etc. We describe the idea of the method, its experimental realization, and a procedure for processing the results which allows one to choose the most probable model and determine the desired rate constants. Zh. Tekh. Fiz. 69, 99–103 (January 1999)