广义二阶流体管内轴向流动

在流体的本构关系中引入分数阶导数运算，对于介于粘性与弹性之间的流体的描述更具有合理性。本文将这种关系引入二阶流体，研究其管内轴向流动。我们先求出了１／２阶导数的解析解，用以验证Ｌａｐｌａｃｅ数值反演的ＣＲＵＭＰ方法的有效性。然后用ＣＲＵＭＰ法分析二阶流体管内轴向流动的特征。分析表明粘弹性特征越明显的流体，其速度与应力对分数导数的阶数越具有敏感性。     

Krein's strings with singular left boundary

M. G. Krein established a one-to-one correspondence between strings with regular left boundary and their spectral measures. In this note we treat strings with a certain class of singular left boundary and obtain a condition that the spectral measure grows polynomially.     

An integer linear programming approach for approximate string comparison

We introduce a problem called maximum common characters in blocks (MCCB), which arises in applications of approximate string comparison, particularly in the unification of possibly erroneous textual data coming from different sources. We show that this problem is NP-complete, but can nevertheless be solved satisfactorily using integer linear programming for instances of practical interest. Two integer linear formulations are proposed and compared in terms of their linear relaxations. We also compare the results of the approximate matching with other known measures such as the Levenshtein (edit) distance.     

Radiation beyond four space-time dimensions

We present a set of formulas describing classical radiation of a rank-s tensor field from an accelerated pointlike source in a flat space-time of an arbitrary even dimension d. These formulas allow straightforwardly and algorithmically evaluating the total intensity and radiated momentum for any s and d by hand or using a computer. The practical application of the obtained results is limited for s > 1 because the energy-momentum tensor for the pointlike source is not conserved. This usually means that contributions to the radiation from tensions of the forces causing the acceleration of the radiation source cannot be neglected. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 156, No. 2, pp. 282–291, August, 2008.     

Vibrations of elastic string with nonhomogeneous material

In this paper we analyze from the mathematical point of view a model for small vertical vibrations of an elastic string with fixed ends and the density of the material being not constant. We employ techniques of functional analysis, mainly a theorem of compactness for the analysis of the approximation of Faedo-Galerkin method. We obtain strong global solutions with restrictions on the initial data u₀ and u₁, uniqueness of solutions and a rate decay estimate for the energy.     

Friction and heat transfer in drag-reducing surfactant solution flow through curved pipes and elbows

A study of drag-reducing flow in curved pipes was conducted. In contrast to earlier studies we show that if we use a modified definition of drag reduction that includes only the turbulence effects, we observe indeed the same level of drag reduction in both coiled and straight pipes. More complex results showing reduced drag reduction compared to curved pipes were achieved with elbows. Two elbows of different size and type were tested in turbulent flow of both water and drag-reducing surfactant solution. A more elaborate analysis was conducted for a half-inch threaded elbow with a ratio of curvature radius to diameter of 1.2. The pressure drop and heat transfer were measured in a section downstream from the elbow over a distance of x/D = 130 in order to investigate the hydrodynamic and thermal developments of the flow. The pressure drop coefficient of the elbow was calculated for water and a surfactant solution, based on the total increase in pressure drop in the system due to the presence of the elbow. For a larger welded elbow of 6″ diameter some drag reduction was measured for the surfactant solution.     

An investigation of pressure transients in pipelines with two-phase bubbly flow

This paper presents a two-dimensional model for the analysis of the pressure transient of a two-phase homogeneous bubbly mixture flowing in a pipeline and the numerical integration using the centre implicit method (CIM). Experiments were conducted to confirm the proposed sonic speed equation of an air–water mixture for an air concentration of less than 1%. The 2D CIM model is compared with the method of characteristics (MoC) for a two-phase bubbly flow in a pipeline. The comparisons show that the proposed 2D CIM model generally gives good agreement with the method of characteristics.     

Generalized conformal invariance conditions on a sigma model of the open bosonic string including the first massive mode

Conformal invariance conditions on a sigma model of the open bosonic string including the tachyon, the abelian gauge field an the first excited massive mode are calculated up to order a′. Inner symmetries are used to compute conformal invariance conditions from renormalization group beta functions.     

相对论性核碰撞中φ介子增强

用强子和弦级联模型LUCIAE系统地研究了相对论性p+p和Pb+Pb碰撞中φ介子产生.在模型框架内实验测得的158AGeV/cPb+Pb碰撞中φ介子产额相对于同能量p+p碰撞的增强现象,依赖于弦发射胶子的集体效应和奇异夸克压低约化两机制,在一定程度内能得到解释.