A Single-phase of Supercritical CO_2/Polystyrene Solution in Foam Extrusion

The high quality single-phase solution of CO2/ Polystyrene was achieved,by analyzing the influential factors for polymer microcellular foaming extrusion.The curve of pressure distribution along the barrel was determined.The axial position of gas-injecting port on the barrel was chosen form the results of stable foaming,and the number of gas-injecting ports in the circumference of the barrel was determined from the CO2 solubility in polymer.The effect of the screw rotation speed on CO2 solubility was studied,and the effects of pressure difference between the gas and the polymer melt on gas-injecting process and on the foaming stability were investigated.The influence of the gas temperature before injection on the single-phase of CO2/Polystyrene solution also was studied.

Five-dimensional teleparallel theory equivalent to general relativity,the axially symmetric solution,energy and spatial momentum

A theory of （4＋1）-dimensional gravity is developed on the basis of the teleparallel theory equivalent to general relativity. The fundamental gravitational field variables are the five-dimensional vector fields （pentad）, defined globally on a manifold M, and gravity is attributed to the torsion. The Lagrangian density is quadratic in the torsion tensor. We then give the exact five-dimensional solution. The solution is a generalization of the familiar Schwarzschild and Kerr solutions of the four-dimensional teleparallel equivalent of general relativity. We also use the definition of the gravitational energy to calculate the energy and the spatial momentum.

Spherically symmetric solution in higher-dimensional teleparallel equivalent of general relativity

A theory of（N＋1）-dimensional gravity is developed on the basis of the teleparallel equivalent of general relativity（TEGR）.The fundamental gravitational field variables are the（N＋1）-dimensional vector fields,defined globally on a manifold M,and the gravitational field is attributed to the torsion.The form of Lagrangian density is quadratic in torsion tensor.We then give an exact five-dimensional spherically symmetric solution（Schwarzschild（4＋1）-dimensions）.Finally,we calculate energy and spatial momentum using gravitational energy-momentum tensor and superpotential 2-form.

AN EQUIVALENT PROPOSITION TO THE CONJECTURE OF GOLDBACH

In this paper,a formula is given. The formula gives the number of prime number solutions of the indefinite equation p 1+p 2=2n , and based on it, an equivalent proposition to the conjecture of Goldbach is obtained.

3D elastic waveform modeling with an optimized equivalent staggered-grid finite-difference method

Equivalent staggered-grid(ESG) as a new family of schemes has been utilized in seismic modeling,imaging,and inversion.Traditionally,the Taylor series expansion is often applied to calculate finite-difference(FD) coefficients on spatial derivatives,but the simulation results suffer serious numerical dispersion on a large frequency zone.We develop an optimized equivalent staggered-grid(OESG) FD method that can simultaneously suppress temporal and spatial dispersion for solving the second-order system of the 3 D elastic wave equation.On the one hand,we consider the coupling relations between wave speeds and spatial derivatives in the elastic wave equation and give three sets of FD coefficients with respect to the P-wave,S-wave,and converted-wave(C-wave) terms.On the other hand,a novel plane wave solution for the 3 D elastic wave equation is derived from the matrix decomposition method to construct the time-space dispersion relations.FD coefficients of the OESG method can be acquired by solving the new dispersion equations based on the Newton iteration method.Finally,we construct a new objective function to analyze P-wave,S-wave,and C-wave dispersion concerning frequencies.The dispersion analyses show that the presented method produces less modeling errors than the traditional ESG method.The synthetic examples demonstrate the effectiveness and superiority of the presented method.

Cosmological application on five-dimensional teleparallel theory equivalent to general relativity

A theory of（4＋1）-dimensional gravity has been developed on the basis of which equivalent to the theory of general relativity by teleparallel.The fundamental gravitational field variables are the 5-dimensional（5D） vector fields（pentad）,defined globally on a manifold M,and gravity is attributed to the torsion.The Lagrangian density is quadratic in the torsion tensor.We then apply the field equations to two different homogenous and isotropic geometric structures which give the same line element,i.e.,FRW in five dimensions.The cosmological parameters are calculated and some cosmological problems are discussed.

Exact Solutions for a Class of Nonlinear PDE with Variable Coefficients Using ET and ETEM

In this article, by using the modified CK direct method, we give a relationship between the generalized fifth-order KDV equations with variable coefficients and the corresponding constant coefficients ones. Then, we construct the abundant travelling solutions by the extended trial equation method (ETEM) in terms of different functions, such as the elliptic functions, rational functions, hyperbolic functions and trigonometric functions. The extended trial equation method is powerful and can be used to other partial differential equations and more research can be done by this method.

Improvement of the Corrosion Resistance of High Alloyed Austenitic Cr-Ni-Mo Stainless Steels by Solution Nitriding

Characteristic features of austenitic steel grades combine a good corrosion resistance with a low hardness, wear resistance and scratch resistance. An interesting possibility for improving the wear behaviour of these steels without loss of their corrosion resistance lies in enriching the near surface region with nitrogen. The process of a solution nitriding allows the rise of the solution of nitrogen in the solid phase. On this state nitrogen increases the corrosion resistance and the tribilogical load-bearing capacity. The aim of the study was, to investigate the improvement of the pitting corrosion behaviour by solution nitriding. A special topic was to observe the effect of nitrogen by different molybdenum content. So austenitic stainless steels (18% Cr, 12% Ni, Mo gradation between 0.06 to 3.6%) had been solution nitrided. The samples could be prepared with various surface content of nitrogen from 0.04 to 0.45% with a step-by-step grinding. The susceptibility against pitting corrosion of these samples had been tested by determination of the stable pitting potential in 0.5M and 1M NaCl at 25°C. For the investigated steel composition and the used corrosion system there is no influence of molybdenum on the effectiveness of nitrogen. The influence of nitrogen to all of the determined parameters can be described well by PRE = Cr + 3,3 * Mo + 25 *N. XPS analysis of the sample surfaces support the results of the pitting corrosion tests.Additionally surface investigations with an acid elektolyte (0,1M HC1 + 0,4M NaCl) were performed. In this case the passivation effective nitrogen content increases markedly with rising molybdenum concentration of the steel. Obviously an interaction of Mo and N is connected with a strongly acid electrolyte.

纵向槽钢和轴力共同作用的盾构隧道等效刚度解析解

为准确快速地预测纵向槽钢加固技术对盾构隧道等效刚度的影响,开展了纵向槽钢加固技术的理论研究。解析地提出了纵向槽钢和纵向轴力耦合作用的盾构隧道等效刚度理论解,并与经典理论、模型试验和数值模拟对比验证了本方法的可靠性。结果表明盾构隧道的中性轴φ随槽钢、纵向轴压力的增加而减小,其大小直接改变了隧道管片间的接触状态,从而影响了隧道的等效刚度;盾构隧道的等效刚度与纵向轴压力呈S曲线正相关,与弯矩呈非线性反相关,与隧道管片宽度、槽钢截面面积、数量、弹性模量呈线性正比关系;盾构隧道的等效刚度贡献大小顺序依次为纵向槽钢数量、截面面积、弹性模量。从理论上诠释了纵向槽钢等敏感性参数对隧道等效刚度的影响机理,可准确快速地预测纵向槽钢加固效果。

考虑损伤效应的隧道二维渗流场解析及涌水量预测

隧道圆周面涌水量是隧道工程的重要参数,以往研究未考虑隧道开挖损伤因素对渗流场的影响,而隧道施工会对围岩造成一定程度的损伤。考虑隧道开挖损伤的影响,推导了径向未注浆、径向欠注浆及径向完全注浆3种不同径向注浆型式下的隧道二维渗流场理论解析解,而后对隧道渗流场理论解析研究中常用的两种等代圆方法在矩形隧道中的适用性展开了探讨,并对隧道圆周面涌水量及衬砌外水压力的径向注浆参数展开敏感性分析,最后将隧道二维渗流场理论解析解与数值解对比。结果表明:隧道二维渗流计算模型能较好地反映隧道圆周面的涌水量;开挖损伤对隧道圆周面涌水量有着较为显著的影响,对初支施作前的影响最大,对二衬施作后的影响程度最小;当径向注浆相对渗透系数k m/k g达到100,径向注浆相对厚度d g达到1.0倍的隧道内径r 0时,继续增大k m/k g或d g/r 0对降低隧道圆周面涌水量Q和拱顶衬砌外水压力p的效益将不再明显。研究成果可为不良地质岩层隧道的径向注浆设计提供一定的理论指导。

基于荷载等效理论的柱体结构剪切变形解析

为了提高具有铁木辛科梁性质的柱体结构剪切变形的计算效率和精度,基于荷载等效分布理论、节点解析法以及具有正交内插特性的铁木辛柯梁理论,提出了一种高效求解梁柱节点剪切变形位移的等效分布荷载-有限元算法,并通过研究2种工况算例验证了算法的可靠性。结果表明:该算法利用非常少的单元(1个或2个单元)便可以获得位移、旋转角、剪切力和弯矩的高精度近似解;其他基于位移的方法,如简化积分法,大约需要40个单元才能获得类似的结果。所提方法可以在不同的连接条件下直接获得铁木辛柯梁柱的稳定函数和弯曲荷载,有效提高了柱体结构剪切变形有限元分析解的精确性。

强夯加固粉土地基的竖向附加动应力传递特性

强夯法在各类地基处理项目中得到了广泛应用,但其加固机理仍落后于实践,特别是强夯引起的地基内部竖向附加动应力传递特性。鉴于此,先基于Boussinesq应力解和动量定理推导强夯竖向附加动应力和附加剪应力拟静力解。然后,以新疆维吾尔自治区乌鲁木齐市机场北区扩建项目为工程背景,运用夯锤速度法,模拟1000~4000 kN·m能级间强夯引起的动力波传播过程、竖向附加动应力传递特性和夯后土体位移场。最后,将拟静力解与动力数值解的计算结果进行对比分析。研究结果表明:强夯引起的动力波传播呈半圆弧形,竖向附加动应力传递呈半椭圆形。动力波的传播距离决定了强夯影响范围,竖向附加动应力显著区边界决定了强夯有效加固区。由拟静力解得到的竖向附加动应力相比数值解沿深度方向的衰减更快。该研究结果可为强夯法地基处理工程提供重要参考。

氯化钾溶液电化学阻抗测量过程中的等效电路模型研究

等效电路模型是溶液电化学阻抗测量过程中研究其复杂物理化学过程的重要手段,在溶液电导率测量仪等设备的工程技术研发中具有重要的应用。本文选取氯化钾溶液为研究对象,使用电化学工作站和铂黑平行双电极测量0.01 mol/L至1 mol/L氯化钾溶液的阻抗谱,采用Lima和Randles两种等效电路模型对测量结果进行拟合并对比两个模型的精度。基于测量过程中不同频段下溶液的导电物理化学机制不同的事实,对测量结果进行分频段模拟以进一步提高模拟精度,并在Lima和Randles等效电路模型的基础上简化出高频等效电路模型。采用高频等效电路模型对在高频下不同浓度溶液的电导率测量结果进行模拟,对比并分析了浓度不同所引起的溶液内物理化学过程的差异。

生物阻抗谱参数提取算法研究

生物阻抗测量技术起源于生物电理论,其利用生物组织的电特性对人体信号提取和分析,用以进行一些生理、病理研究。根据生物细胞等效电路模型建立以各元件参数为求解变量的复阻抗-频率响应函数模型,通过对函数曲线回归求解实现等效电路拟合,采用非线性最小二乘法(NLS)思想,并引入遗传算法(GA)提供初始值估计减小拟合误差。

Impact of stress on solute transport in a fracture network: A comparison study

This paper compares numerical modeling of the effect of stress on solute transport （advection and matrix diffusion） in fractured rocks in which fracture apertures are correlated with fracture lengths. It is mainly motivated by the performance and safety assessments of underground radioactive waste repositories. Five research teams used different approaches to model stress/deformation, flow and transport pro- cesses, based on either discrete fracture network or equivalent continuum models. The simulation results derived by various teams generally demonstrated that rock stresses could significantly influence solute transport processes through stress-induced changes in fracture apertures and associated changes in per- meability. Reasonably good agreement was achieved regarding advection and matrix diffusion given the same fracture network, while some observed discrepancies could be explained by different mechanical or transport modeling approaches.

Applying Functional Equivalence Theory in Translating the Introduction to Scenic Spots

Since we have entered in the 21 st century, the economy of the whole world has experienced a process of transformation and upgrading, the outstanding performance is the proportion of the third industry in the national economy, and the third industry's contribution to the national economy is growing. Since our government has taken the reform and opening up policy,they attach great importance to the development of the third industry in our country. After more than 30 years of reform and opening- up,the development of tourism industry, also be called the"Smokeless Industry", has been given priority within the booming third industry. There is no doubt that tourism has a bright development prospect. With the rapid development of economy and the deepening of the opening degree, there will be more and more foreigners coming to China for sightseeing. Under this big background, the high quality English introduction of tourist attractions is in great demand. This article is aimed at exploring the practical value of functional equivalence applying to the translation of scenic spots introduction, and provides some feasible solution for tourism translation.

分数阶Cuk变换器的瞬态和稳态特性分析

文中建立了电感电流连续模式(CCM)运行的分数阶Cuk变换器的非线性等效电路模型和非线性数学模型,利用等效小参量(ESP)符号分析法得到了其等效数学模型;然后基于谐波平衡原理,迭代求解获得了变换器状态变量瞬态和稳态近似周期解;进而分析了电感和电容分数阶次对状态变量直流工作点和周期解闭合轨道以及纹波分量的影响,并通过仿真验证了文中方法所得状态变量瞬态解和稳态解的准确性;最后,以电感和电容阶次均为0.9的分数阶Cuk变换器为例进行了实验验证。实验和文中方法所得状态变量(输出电压与电感电流)的稳定时间分别为1.56 ms和1.52 ms,输出电压平均值分别为2.110 V和2.959 V,纹波电压峰值分别为96 mV和109 mV,电感电流平均值分别为0.112 A和0.148 A,纹波电流峰值分别为52 mA和59 mA。可见,对于状态变量的瞬态和稳态特性,文中方法和实验所得结果均比较接近。文中还进一步验证了该方法的有效性以及所得状态变量瞬态和稳态解的准确性。文中方法所得分数阶变换器的稳态解同储能元件的阶次相关,可用于分析分数阶阶次对电路特性的影响;此外,也可根据所得到的稳态解的解析表达式,对变换器系统的稳定性进行分析。

层状异性蠕变地层桩基沉降位移的理论解

考虑软土地层层状异性及流变特性,采用虚拟柱状结构等效流变模型,建立了桩基不同荷载条件和承载模式下沉降位移的理论解。研究了不同荷载等级条件下桩基沉降位移的空间分布特征及其时效特性。结果显示,软土地层中桩基承载模式随荷载增大呈动态演化。当桩基处于摩擦承载模式时,桩基沉降位移为桩体压缩瞬态弹性变形;当桩侧阻抗无法平衡桩顶荷载时,桩基承载模式转化为摩擦与桩端共同承载模式,桩基总位移为桩体变形和桩底土体沉降位移的叠加。同时,对于桩端承载状态,由于土体的流变特性,桩基总位移呈现显著的时效特性。随荷载增大,桩端位移的时效性更趋显著。

基于二阶ETP解析解的空调-建筑电热耦合系统辨识方法

对空调-建筑电热耦合系统进行建模是挖掘空调调节潜力的基础。为解决当前基于二阶等效热参数(ETP)建模研究中存在的拟合精度有限、电热耦合特性考虑不足等问题,文中首先推导了二阶ETP模型解析递推形式,具有高拟合精度、递推值有界、步长灵活可调的优势,可提高模型的准确性、可靠性以及对多样化数据采集技术的适应性。然后,采用平均能效比刻画空调电热转化过程,提出考虑平均能效比的空调-建筑电热耦合解析化模型参数辨识方法,综合利用室内气温拟合机制和制热量拟合机制进行参数寻优。最后,搭建实际测试环境对所提方法性能进行验证。结果表明,该方法能在现有基础上显著提升参数辨识的准确率,从而为能源系统仿真、空调负荷调控等应用提供更加准确可靠的模型基础。

双圆盾构隧道结构纵向等效抗弯刚度解析解

在邻近施工的作用下,双圆盾构隧道会发生纵向不均匀位移;而双圆盾构隧道的纵向等效抗弯刚度是表征其纵向抗弯性能的重要力学参数,也是预测外部荷载作用下双圆盾构隧道纵向变形的关键参数。为保障双圆盾构隧道结构安全,对双圆盾构隧道的纵向受力变形进行预测。基于纵向等效连续化模型,考虑螺栓预紧力的作用和环缝影响范围的影响,推导得到双圆盾构隧道的纵向等效抗弯刚度解析解。结合双圆盾构隧道截面的特点,分别考虑中性轴位于上部边缘、上部双拱、腰部和下部双拱的4种情况,并给出界限弯矩表达式。以国内首条双圆盾构隧道为例,分析弯矩、螺栓预紧力和环缝影响范围对双圆盾构隧道纵向抗弯性能的影响。研究表明:1)当存在螺栓预紧力时,纵向等效抗弯刚度随着外部弯矩增加而呈现“反S”形态下降,并最终趋于无预紧力条件下的隧道纵向等效抗弯刚度值。2)中性轴位置亦非固定位置,随着外部弯矩增加,中性轴逐渐下移;且当外部弯矩小于环缝启动弯矩时,隧道的纵向抗弯刚度与均质隧道抗弯刚度一致。3)当环缝长度影响系数小于1时,中性轴位置始终保持不变,但纵向等效抗弯刚度有效率随着环缝作用区系数增大而迅速下降;当环缝长度影响系数大于1时,中性轴上移,管片受压范围增大,随着环缝作用区系数增大,纵向等效抗弯刚度有效率值缓慢减小并趋于一个定值。4)增大螺栓预紧力,环缝张开启动弯矩随之增大,隧道的抗弯刚度衰减更慢,同时中性轴位置上移,管片受压范围扩大。