Numerical simulation of thermodynamic equilibrium establishment in a cosmological model with arbitrary acceleration

We present the results of a numerical simulation of the previously constructed strict mathematical model of thermodynamic equilibrium establishment in an originally nonequilibrium cosmological ultrarelativistic plasma in a universe with any acceleration, under the assumption of scaling restoration for elementary particle interactions at energies above a unitary limit. The limiting parametres are found for a residual nonequilibrium distribution of nonequilibrium relic ultra-high energy particles.     

三分子自催化反应扩散系统中化学波的二维格子Boltzmann模拟

建立二维区域带平方衰减反应的三分子自催化反应扩散系统的数学模型,利用浓度分布的Chapmann-Enskogz展开及多尺度技术,给出基于格子Boltzmann模型的二维三分子自催化反应扩散系统的数值求解法,得到半开放自催化反应扩散系统在反应与扩散机制同时作用所产生化学波的过程和浓度空间分布值.数值结果表明本文提供的求解化学波现象的方法是有效的.     

基于用户交互模型的会员网站每日活跃用户量分析

现有的网站往往向注册用户提供服务,而网站中的每日活跃用户量往往决定着网站建设的成败。为了描述网站中每日活跃用户的动态变化,本文将用户在网站上的交互行为分为响应、扩散和衰落三种类型,并提出了一种基于用户交互模型的每日活跃用户量模型。通过响应、扩散和衰落三种交互行为的定义,进一步推导出每日活跃用户随着时间的变化率。通过对每日活跃用户随着时间的变化率进行分析得到如下结论,当网站中用户的响应概率小于衰落概率时网站的活跃用户将趋向于0,反之活跃用户趋于某个固定的常数。大量的真实数据实验表明,不论网站自身的运营是否成功,本文提出的方法都可以很好的描述网站的每日活跃用户数量及其发展趋势,这对于网站的建设和维护具有重要的指导意义。     

化学振荡反应的频域特征

本文应用自行研制的化学振荡反应计算机数据采集与处理系统，收集了苯胺－溴酸钾－硫酸非催化化学振荡反应体系的时间序列信号数据及其功率谱图，探讨了电极信号处于非平衡定态，周期，拟周期等状态时的功率谱特征。     

Convective-dispersive transport of solutes involved in sequential first-order decay reactions

Problems of solute transport involving sequential first-order decay reactions frequently occur in soil systems. Examples are the migration of radionuclides, in which the chain members form a first-order decay reaction, and the simultaneous movement of various interacting nitrogen species. This study presents analytical solutions that describe the simultaneous convective-dispersive transport of up to four species involved in such a consecutive chain reaction. Evaluation of the analytical solutions is not straightforward but requires, among other things, the calculation of complex complementary error functions. A FORTRAN IV computer program (CHAIN) that can be used to evaluate the analytical solutions is described. Application of this program to problems of solute transport is illustrated with two examples, one dealing with radionuclide transport and one with nitrification.     

Technical note The effect of rate of decay of rain path profile on microwave communication

The attenuation of radio waves due to rain can be predicted with a good degree of accuracy, provided the rain rate characteristics over the entire path of propagation are known. The attenuation due to rain is usually deduced on the basis of point rain rate, which can lead to inaccuracy in the estimation of attenuation. We use the concept of rate of decay of rain path profile to estimate the attenuation due to rain. The attenuation has been deduced at 11GHz and 13.4 GHz for 56 elevation angle by using the theory of decay rate of rain path profile, its controlling factor, gamma, and rain rate distribution over Delhi, a tropical station in India. The theoretically-estimated attenuation is compared with observed values, as well as with values obtained using the International Radio Consultative Committee (CCIR) method. The CCIR model is found to overestimate the attenuation.     

Time symmetry and thermodynamics

It is commonly thought that time asymmetry and process irreversibility find their best illustrations in thermodynamics. We argue that neither Fourier's law of heat transfer nor the second law of thermodynamics can indicate such an irreversible arrow of time. Irreversible processes of nonequilibrium systems are out of the scope of thermodynamics and belong in the research field of dynamics. The solution of any differential equation will automatically define the time symmetry or time asymmetry. Reversible processes and extreme irreversible processes are the only two types of process that can be treated in thermodynamics. There is no tight connection between time symmetry and reversibility, nor between time asymmetry and irreversibility. Temporal irreversibility is characterized by dynamic properties such as velocities. An electronic circuit is devised to illustrate that wave form process can be irreversible. The techniques of Fourier spectra and decay frequency spectra may be used to characterized dynamic properties.     

On decay of correlations for an exclusion process with asymmetric boundary conditions

We consider a symmetric exclusion process on a discrete interval of S points with various boundary conditions at the endpoints. We study the asymptotic decay of correlations as S → ∞. The main result is proving asymptotic independence of a stationary distribution at points of the interval that are far enough away. We do not use Derrida’s algebraic technique but develop a new technique, which has a visual probabilistic sense.     

基于查询子主题分类的多样性搜索评价方法

多样化检索结果的评测通常假设一个查询词包含多个权重各不相同的用户子意图,并在此假设的基础上对检索结果进行评测.虽然大多数已经存在的多样化检索评测方法利用了这些特性对检索结果进行评测,但在评测过程中,它们都忽略了查询子意图的类型信息;而不同类型的查询子意图对信息需求具有不同的特点.首先,通过引入衰减函数对这种特点进行描述,进而对用户子意图的分类方法进行抽象;在此基础上,提出了利用查询子意图类型信息进行多样化检索结果评测的框架,该框架定义了利用查询子意图类型信息进行多样化检索评测的方法应该具有的结构;然后,讨论了在用信息类和导航类作为子意图分类方法的前提下,其对应的衰减函数的形式;最后,在TREC与NTCIR测试集上的实验结果表明了所提出方法的有效性.     

基于时间衰减模型的模糊会话关联规则挖掘算法

现有的关联规则挖掘算法没有考虑数据流中会话的非均匀分布特性和历史数据的作用,并且忽略了连续属性处理时的“尖锐边界”问题。针对这些问题,本文提出一种基于时间衰减模型的模糊会话关联规则挖掘算法。首先,针对数据流中会话的非均匀分布特性,基于时间片对会话进行划分,完整的保留了时间片内会话之间的相关性信息;然后,采用模糊集对会话的连续属性进行处理,增加了规则的兴趣度和可理解性;最后,在考虑历史数据作用和允许误差情况的基础上,基于时间衰减模型挖掘数据流中的临界频繁项集和模糊关联规则。实验结果表明,本文方法在提高时间效率、降低冗余率和增加规则兴趣度方面存在明显优势。     

Improved sampling techniques for the direct simulation Monte Carlo method

The direct simulation Monte Carlo (DSMC) method is a widely used approach for flow simulations having rarefied or nonequilibrium effects. It involves heavily to sample instantaneous values from prescribed distributions using random numbers. In this note, we briefly review the sampling techniques typically employed in the DSMC method and present two techniques to speedup related sampling processes. One technique is very efficient for sampling geometric locations of new particles and the other is useful for the Larsen-Borgnakke energy distribution.     

基于残差分析的GM(1,1)模型有效性研究

GM(1,1)模型是处理贫信息数据序列的有效工具,也是灰色理论体系中应用广泛、具有基础性地位的一类重要模型.从一个新的视角-残差的角度,对该模型的有效性和使用范围进行分析.结果表明,GM(1,1)除了对指数衰减趋0的序列实现+∞上的拟合外,对算术级数序列和指数增加的序列拟合效果不佳,残差分布是不均匀的,且有不断扩大的趋势.     

Limit sets, zero dynamics, and internal models in the problem of nonlinear output regulation

In this paper, we lay the foundations for a nonequilibrium theory of nonlinear output regulation, giving a more general (nonequilibrium) definition of the problem, deriving necessary conditions, and, using these necessary conditions, we present a set of sufficient conditions and a design methodology for the solution of the problem in question. Our analysis leads to a nonequilibrium enhancement of the internal model principle.     

A new field of phase diagrams of stationary nonequilibrium states

Diamond is a metastable phase, while graphite is the stable phase in low pressure equilibrium phase diagrams of carbon. There seemed to be no way to get diamond from graphite under low pressures. However, a new activated low pressure diamond deposition process has emerged. A new concept of phase diagrams of stationary nonequilibrium states on the basis of nonequilibrium thermodynamics can be used for explanation of the “thermodynamic paradox” that the diamond growth with graphite etching takes place under activated low pressure. The agreement between CALPHAD prediction and experiments is excellent.     

Molecular dynamics, smoothed-particle applied mechanics, and irreversibility

We explore the relationship of Monaghan's version of “smoothed-particle hydrodynamics,” here called “smoothed-particle applied mechanics,” to nonequilibrium molecular dynamics. We first use smoothed particles to model the simplest possible linear transport problems, as well as a liquid-drop problem. We then consider both gas-phase and dense-fluid versions of Rayleigh-Bénard convection, all in two space dimensions. We also discuss the possibility of combining the microscopic and macroscopic techniques in a hybrid scheme well-suited to the massively-parallel modelling of large-scale nonequilibrium flows.     

Consistent initial conditions for lattice Boltzmann simulations

We propose a simple and effective iterative procedure to generate consistent initial conditions for the lattice Boltzmann equation (LBE) for incompressible flows with a given initial velocity field u₀. Using the Chapman-Enskog analysis we show that not only the proposed procedure effectively solves the Poisson equation for the pressure field p₀ corresponding to u₀, it also generates at the same time the initial values for the nonequilibrium distribution functions {f_α} in a consistent manner. This procedure is validated for the decaying Taylor–Green vortex flow in two dimensions and is shown to be particularly effective when using the generalized LBE with multiple relaxation times.     

The automatic control system of a multi-component nonequilibrium extraction process in the pulse column

The construction of the process dynamic model and the automatic control system of a plant constitute the two major objectives that allow the plant to be controlled in automatic mode. The model selected was the dynamic model of the nonequilibrium extraction process in the pulse column based on the mass transfer diffusion kinetics. The use of the molecular diffusion equation in the calculations is conditioned by the fact that diffusion limits the examined process of mass transfer and allows the kinetic processes of the reaction to be disregarded. For the developed model, spatial-temporal profiles were calculated for the distribution of uranium, nitric acid, plutonium, thorium, and neptunium concentrations throughout the height of the column extractor after a step change in the aqueous phase flow rate. The results of the head column automatic control system (ACS) synthesis are presented for the operation in the first and second cycles of irradiated nuclear fuel extraction purification. Several options for the system were examined, with their structural and parametric syntheses being performed on the basis of the column linear dynamic model. The findings of the research are presented in relation to the ACS with a constant-rate actuating mechanism. Several methods of development of the ACS software and hardware tools were studied for the implementation of the formulated requirements.     

Numerical simulation of turbulent reactive flows

A direct numerical simulation of a turbulent homogeneous field is used study the decay of the concentration of a scalar quantity which is advected, diffused and undergoes the effect of a sink term which models the effect of a chemical reaction. The reaction rate and the one-species formulation used herein are oriented towards the simulation of the combustion of a premixed gas in order to study various quantities useful for turbulent combustion models. Computations yield results depending on the “chemical time” under the form of various probability density functions (PDF) calculated from the realizations of the reactive scalar fields.