爆炸法修复变形石油套管的研究

针对油田生产中大量石油套管发生变形的现状，提出用爆炸胀形法来修复变形的石油套管，建立了该方法的理论计算模型，推导了炸药量的计算公式，并用工程实例验证了公式的正确性。     

机采油井井口温度的影响因素分析

基于传热学理论,建立了机采油井井简及其周围地层温度场的数学模型,对不同参数下的井口温度进行了模拟,分析了油井产量、含水率、井深、油管半径、环境温度及地温梯度等参数的影响.     

确定地基固结过程中材料参数的反分析法

结合有限单元法和数学规划法提出一确定地基固结过程中材料参数的反分析法。该法可以根据固结过程中的位移值和孔隙水压力值反算地基土的弹性系数、泊松比以及渗透系数。文中通过一些算例对该法进行了验证。     

Theoretical analysis of transient waves in a simply-supported Timoshenko beam by ray and normal mode methods

The dynamic transient responses of a simply-supported Timoshenko beam subjected to an impact force are investigated by two theoretical approaches – ray and normal mode methods. The mathematical methodology proposed in this study for the ray method enable us to construct the solution for the interior source problem and to extend to solve the complicated problem for the multi span of the Timoshenko beam. Numerical results based on these two approaches are compared. The comparison in this study indicates that the normal mode method is more computationally efficient than the ray method except for very short time after the impact. The long-time transient responses are easily calculated using the normal mode method. It is shown that the average long-time transient response converges to the corresponding static value. The Timoshenko beam theory is more accurate than the Bernoulli–Euler beam theory because it includes shear and rotary inertia. This study also provides the slender ratio for which the Bernoulli–Euler beam can be used for the transient-response analysis of the displacement. Moreover, the resonant frequencies obtained from finite element calculation based on the three-dimensional model are compared with the results calculated using the Timoshenko beam and Bernoulli–Euler beam theories. It is noted in this study that the resonant frequency can be accurately determined by the Timoshenko beam theory if the slender ratio is larger than 100, and by the Bernoulli–Euler beam theory if the slender ratio is larger than 400.     

Numerical simulation of solidification processes in enclosures

The present work deals with the development and application of numerical models for the simulation of solidification problems liquid/solid taking diffusion and convection into account. For the calculation of the thermal coupled flow process the finite element method is applied. In order to improve the numerical stability of the free convection problems, the streamline-upwind/Petrov–Galerkin method is used. Solidification processes are moving boundary problems. Three different models are set up which consider latent heat at the solidification front respectively in the mixed zone during the phase transition. Moreover, numerical methods are investigated in order to describe the behaviour of the flow at the boundary of the moving phase. Three examples serve illustrations; the technical example – casting of a transport and storage container – was provided by the company Siempelkamp Gießerei GmbH.     

基于多变量小样本的渗流代理模型及产量预测方法

多孔介质渗流过程中存在的多尺度、多变量、多物理场耦合的非线性渗流问题给复杂渗流机理的表征及数学模型求解提出了巨大的挑战, 综合考虑地下多孔介质耦合渗流过程中关键力学问题的渗流模型往往需要在计算效率和计算精度之间权衡. 近年来, 基于油田多数据的渗流代理模型为高效求解多变量非线性渗流问题提供了思路, 而渗流代理模型在实际油田中的应用往往由于记录不全, 操作不当等因素受到小样本数据的限制. 针对这一问题, 本文提出了一种基于地质?油藏?工艺的多数据小样本渗流代理模型的产量预测方法. 通过填补缺失值, 独热编码分类数据, 数据对数化及标准化等一系列数据预处理方法, 形成了油田产量预测数据库; 经过随机劈分数据集、十折交叉验证, 测试了三种渗流代理模型的预测效果. 结果表明, 三种代理模型的决定系数均超过0.8, 模型预测结果与实际数据较为吻合; 对于小样本多变量的油田数据, 合适的数据预处理方法对模型预测效果影响显著; 经过数据标准化后, 随机森林算法表现最好, 能快速准确预测石油产量(均方误差0.12, 决定系数0.87).      

Free vibration analysis of the axially moving Levy-type viscoelastic plate

In this paper, the viscoelastic theory is applied to the axially moving Levy-type plate with two simply supported and two free edges. On the basis of the elastic – viscoelastic equivalence, a linear mathematical model in the form of the equilibrium state equation of the moving plate is derived in the complex frequency domain. Numerical calculations of dynamic stability were conducted for a steel plate. The effects of transport speed and relaxation times modeled with two-parameter Kelvin–Voigt and three-parameter Zener rheological models on the dynamic behavior of the axially moving viscoelastic plate are analyzed.     

Numerical solution of the problem of motion of a load on a cracked ice sheet

A mathematical model is constructed for the motion of a load on a cracked ice sheet. Examples of calculation of ice deflections are given, and the calculation results are analyzed. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 3, pp. 151–156, May–June, 2008.     

Kinematic limit analysis of frictional materials using nonlinear programming

In this paper, a nonlinear numerical technique is developed to calculate the plastic limit loads and failure modes of frictional materials by means of mathematical programming, limit analysis and the conventional displacement-based finite element method. The analysis is based on a general yield function which can take the form of the Mohr–Coulomb or Drucker–Prager criterion. By using an associated flow rule, a general nonlinear yield criterion can be directly introduced into the kinematic theorem of limit analysis without linearization. The plastic dissipation power can then be expressed in terms of kinematically admissible velocity fields and a nonlinear optimization formulation is obtained. The nonlinear formulation only has one constraint and requires considerably less computational effort than a linear programming formulation. The calculation is based entirely on kinematically admissible velocities without calculation of the stress field. The finite element formulation of kinematic limit analysis is developed and solved as a nonlinear mathematical programming problem subject to a single equality constraint. The objective function corresponds to the plastic dissipation power which is then minimized to give an upper bound to the true limit load. An effective, direct iterative algorithm for kinematic limit analysis is proposed in this paper to solve the resulting nonlinear mathematical programming problem. The effectiveness and efficiency of the proposed method have been illustrated through a number of numerical examples.     

测量两相流中颗粒特性的相位多普勒方法理论模型

本文在几何光学近似Ｍｉｅ散射理论的基础上建立了一种计算激光多普勒信号中相左与粒径关系的数学模型。对几种常用的相对折射率情况下的相差一粒径特性进行了计算,分析并给出了光学系统的最佳配置。计算结果与Ｍｉｅ散射理论的计算结果进行了对比,有限好的一致性。     

一种基于P-S-N的可靠性高精确度数值求解方法

根据应力-强度干涉分布理论和可靠性设计方法,建立基于P-S-N(可靠性-应力-寿命)的可靠度计算数学模型,并利用概率分布密度曲线干涉区间积分、复合梯形法则和辛普生法则来实现可靠度的高精确度数值化求解,通过编写计算机程序算法得以实现。算例表明,与传统的可靠性计算方法相比,系统可靠性的计算精确度得到显著提高,研究成果具有工程应用背景。     

粘弹性固体的精细积分有限元算法

粘弹性固体本构方程的数学表达式分为微分型和积分型两种，其数值求解主要是时域上离散计算。文中从微分型表达式出发导出其状态空间方程的数学表达式，通过严格推导论证了它与微、积分型表达式的等价性；引入状态空间方程，从而利用精细积分格式来求解粘弹性固体本构方程；给出了粘弹性固体本构方程的精细积分有限元算法，为求解粘弹性固体本构方程的数值解提供了一个新的途径，具有计算简便，求解精度高等优点。     

Mathematical modeling of methane flow in a borehole coal mining system

Safety in coal mining is greatly increased by the drainage of the methane content of coal seams through boreholes, simultaneously producing significant energy. The design of suitable drainage technology is based on the mathematical modeling of methane flow in coal seams. In the calculation of the methane pressure, the new mathematical model presented in this paper considers both the sorption phenomenon of methane depending upon the methane pressure and the fact that the variation in methane pressure can create a change in the stress condition of the rock and, as a consequence of this, a change in the permeability of the coal. The new mathematical model can be used for the numerical simulation of the flow processes in coal seams and methane drainage technology can be designed more accurately.     

The mathematical model of bubble group noise

In this paper the mathematical model of bubble group noise are introduced underthe arbitrary conditions by using the method of Euler.The calculation indicates thatthe simulation results consist with the measured value.     

有效集法在数学规划加权残值法中的应用

本文研究有效集法在数学规划加权残值法求解微分方程问题中的应用。从理论上和实际应用方面 阐明，对于数学规划加权残值法和线性规划问题，有效集法比常用的单纯形法更简便、易程序化、计算速度更快，因此更适用于数学规划加权残值法求解微分方程问题。     

Asynchronous free oscillations of linear mechanical systems: A general appraisal and a digression on a column with a follower force

The concept of asynchronous oscillatory response of mechanical systems in free vibrations is addressed as an introduction to a definition of asynchronous modes of vibration. Connection of the asynchronous modes with the localization and other dynamical phenomena is discussed. Then, conditions for the occurrence of asynchronous modes are investigated in depth. It is seen that a non-conservative system, with an asymmetric stiffness matrix – caused, for instance, by circulatory loads, may have an asynchronous mode. Yet, it is also seen that non-conservativeness is not actually mandatory. Two- to four-degree-of-freedom models of a column with a follower force are addressed, allowing for a mathematical modelling and phenomenological discussion.     

分形煤层气藏数值模拟研究——Douglas-Jones预估-校正法的应用

传统的煤层气动力学模型多建立在欧几里得基础上,难以描述煤层气孔隙结构的复杂性和形状的不规则性。为此,以分形理论为基础,通过引入煤层基质和裂缝的分形维数来刻画煤层气孔隙结构的复杂性和吸附特性,建立了双重分形介质渗流模型,采用Douglas-Jones预估-校正法对非线性方程组进行离散,获得了无限大地层和有限地层定产量生产时拟稳态吸附模型的差分方程,求得数值解。结果表明,Douglas-Jones预估-校正法可以有效解决这类非线性模型的求解问题,获得无限大地层定产量生产时变形双重分形介质模型的数值解;分析各种分形参数下的煤层压力动态,做出了典型压力曲线图。对无限大地层,初期分形维数对压力影响不大,后期分形维数越小,压力越高。对有限地层,初期分形维数的影响明显,且分形维数越大,压力越低。压力随分形指数的减小量呈现先增大后减小的趋势,在末期压力平稳趋向同一值。     

Scalable gas-phase processes to create nanostructured particles

The properties of nanoparticles are often different from those of larger grains of the same solid material because of their very large specific surface area. This enables many novel applications, but properties such as agglomeration can also hinder their potential use. By creating nanostructured particles one can take optimum benefit from the desired properties while minimizing the adverse effects. We aim at developing high-precision routes for scalable production of nanostructured particles. Two gas-phase synthesis routes are explored. The first one - covering nanoparticles with a continuous layer - is carried out using atomic layer deposition in a fluidized bed. Through fluidization, the full surface area of the nanoparticles becomes available. With this process, particles can be coated with an ultra-thin film of constant and well-tunable thickness. For the second route - attaching nanoparticles to larger particles - a novel approach using electrostatic forces is demonstrated. The micron-sized particles are charged with one polarity using tribocharging. Using electrospraying, a spray of charged nanoparticles with opposite polarity is generated. Their charge prevents agglomeration, while it enhances efficient deposition at the surface of the host particle. While the proposed processes offer good potential for scale-up, further work is needed to realize large-scale processes.     

State Equations of Unsteady Creep under Complex Loading

A mathematical model describing the unsteady creep of metals under complex loading is proposed. The results of numerical simulation of creep of St.304 steel in complex regimes of block multiaxial cyclic deformation are given. The numerical calculation results obtained are compared with the data of full-scale experiments. Creep is simulated in complex deformation processes accompanied by the rotation of main regions of stress, strain, and creep strain tensors.     

Stationary production rate of a well draining two gas-bearing formations

A mathematical model of the high-pressure gas flow in a gas-dynamic system consisting of a vertical well and two horizontal gas-saturated porous formations is considered. The supercompressibility coefficient is assumed to be a known function of the pressure. The total well production rate and the production rates of the formations opened are found as functions of the wellhead pressure.