An H^1-Galerkin Expanded Mixed Element Method for Semi-linear Hyperbolic Wave Equation

An H1-Galerkin expanded mixed finite element method is discussed for a class of second order semi-linear hyperbolic wave equations. By using the mixed formulation, we can get the optimal approximation for three variables: the scalar unknown, its gradient and its flux(coefficient times the gradient), simultaneously. We also prove the existence and uniqueness of semi-discrete solution. Finally, we obtain some numerical results to illustrate the efficiency of the method.

EXPANDABLE PARALLEL FINITE ELEMENT METHODS FOR LINEAR ELLIPTIC PROBLEMS

In this article,two kinds of expandable parallel finite element methods,based on two-grid discretizations,are given to solve the linear elliptic problems.Compared with the classical local and parallel finite element methods,there are two attractive features of the methods shown in this article:1)a partition of unity is used to generate a series of local and independent subproblems to guarantee the final approximation globally continuous;2)the computational domain of each local subproblem is contained in a ball with radius of O(H)(H is the coarse mesh parameter),which means methods in this article are more suitable for parallel computing in a large parallel computer system.Some a priori error estimation are obtained and optimal error bounds in both H^1-normal and L^2-normal are derived.Finally,numerical results are reported to test and verify the feasibility and validity of our methods.

Reduced Expanding Load Method for Simulation-Based Structural System Reliability Analysis

The current situation and difficulties of the structural system reliability analysis are mentioned. Then on the basis of Monte Carlo method and computer simulation, a new analysis method reduced expanding load method (RELM) is presented, which can be used to solve structural reliability problems effectively and conveniently. In this method, the uncertainties of loads, structural material properties and dimensions can be fully considered. If the statistic parameters of stochastic variables are known, by using this method, the probability of failure can be estimated rather accurately. In contrast with traditional approaches,RELM method gives a much better understanding of structural failure frequency and its reliability index β is more meaningful.To illustrate this new idea, a specific example is given.

Application of Homotopy Perturbation Method and Parameter Expanding Method to Fractional Van der Pol Damped Nonlinear Oscillator

In this study, homotopy perturbation method and parameter expanding method are applied to the motion equations of two nonlinear oscillators. Our results show that both the (HPM) and (PEM) yield the same results for the nonlinear problems. In comparison with the exact solution, the results show that these methods are very convenient for solving nonlinear equations and also can be used for strong nonlinear oscillators.

Homotopy analysis solutions for the asymmetric laminar flow in a porous channel with expanding or contracting walls

In this paper, the asymmetric laminar flow in a porous channel with expanding or contracting walls is investigated. The governing equations are reduced to ordinary ones by using suitable similar transformations. Homotopy analysis method （HAM） is employed to obtain the expres- sions for velocity fields. Graphs are sketched for values of parameters and associated dynamic characteristics, especially the expansion ratio, are analyzed in detail.

Development of a Synchronization Method for Fluid-Thermal Study of Hypersonic Flow

A synchronization method is developed for the fluid-thermal study of hypersonic flow.Different from conventional loosely/tightly coupled methods which separately deal with the flow field and the structure temperature field,the presented method expresses the governing equations in a unified framework so that the two fields can be calculated simultaneously.For efficiently solving the unified equations,the finite volume method together with the dual-time stepping approach is employed.Like in the flow field,the local time step is also used in the temperature field,which is determined from thermal conductivity spectral radii.In order to treat the fluid-structure interface more conveniently,an expanded virtual boundary is introduced.For validation,several fluid-thermal hypersonic flow problems are simulated.The computed results are compared with those obtained from the coupled methods and the experiment.In the continuous heating problems,the stagnation temperatures predicted by both the coupled and synchronization methods are in good agreements with the experimental data.In the unsteady flowthermal hypersonic flows,the stagnation heat fluxes predicted by the presented method and tightly coupled method are basically the same,which agree better with the experimental data than those predicted by the loosely coupled method.In terms of prediction of the stagnation temperature,the synchronization method shows better accuracy than the tightly coupled method.

Homotopy analysis solution for micropolar fluid flow through porous channel with expanding or contracting walls of different permeabilities

The flow of a micropolar fluid through a porous channel with expanding or contracting walls of different permeabilities is investigated. Two cases are considered, in which opposing walls undergo either uniform or non-uniform motion. In the first case, the homotopy analysis method （HAM） is used＇to obtain the expressions for the velocity and micro-rotation fields. Graphs are sketched for some parameters. The results show that the expansion ratio and the different permeabilities have important effects on the dynamic characteristics of the fluid. Following Xu＇s model, in the second case which is more general, the wall expansion ratio varies with time. Under this assumption, the governing equations axe transformed into nonlinear partial differential equations that can also be solved analytically by the HAM. In the process, both algebraic and exponential models are considered to describe the evolution of α（t） from the initial state α0 to the final state al. As a result, the time-dependent solutions are found to approach the steady state very rapidly. The results show that the time-dependent variation of the wall expansion ratio can be ignored because of its limited effects.

Analytic solution to the micropolar-fluid flow through a semi-porous channel with an expanding or contracting wall

The flow of a micropolar fluid in a semi-porous channel with an expanding or contracting wall is investigated. The governing equations are reduced to ordinary ones by using similar transformations. To get the analytic solution to the problem, the homotopy analysis method （HAM） is employed to obtain the expressions for velocity fields. Graphs are sketched and discussed for various parameters, especially the effect of the expansion ratio on velocity and micro-rotation fields.

The Design and Analysis of Helium Turbine Expander Impeller with a Given All-Over-Controlled Vortex Distribution

To make the large-scale helium cryogenic system of fusion device EAST （experimen- tal advanced super-conducting tokamak） run stably, as the core part, the helium turbine expander must meet the requirement of refrigeration capacity. However, previous designs were based on one dimension flow to determine the average fluid parameters and geometric parameters of impeller cross-sections, so that it could not describe real physical processes in the internal flow of the tur- bine expander. Therefore, based on the inverse proposition of streamline curvature method in the context of quasi-three-dimensional flows, the all-over-controlled vortex concept was adopted to design the impeller under specified condition. The wrap angle of the impeller blade and the whole flow distribution on the meridian plane were obtained; meanwhile the performance of the designed impeller was analyzed. Thus a new design method is proposed here for the inverse proposition of the helium turbine expander impeller.

Methods to Improve the Long Distance Time-Varying Channel Transmission Performance of Expendable Profiler

To improve the transmission performance of XCTD channel, this paper proposes a method to measure directly and fit the channel transmission characteristics by using frequency sweeping method. Sinusoidal signals with a frequency range of 100 Hz to 10 k Hz and an interval of 100 Hz are used to measure transmission characteristics of channels with lengths of 300 m, 800 m, 1300 m, and 1800 m. The correctness of the fitted channel characteristics by transmitting square wave, composite waves of different frequencies, and ASK modulation are verified. The results show that when the frequency of the signal is below 1500 Hz, the channel has very little effect on the signal. The signal compensated for amplitude and phase at the receiver is not as good as the uncompensated signal.Alternatively, when the signal frequency is above 1500 Hz, the channel distorts the signal. The quality of signal compensated for amplitude and phase at receiver is better than that of the uncompensated signal. Thus, we can select the appropriate frequency for XCTD system and the appropriate way to process the received signals. Signals below1500 Hz can be directly used at the receiving end. Signals above 1500 Hz are used after amplitude and phase compensation at the receiving end.

THE BOUNDARY EXPANDING-CONTRACTING PRINCIPLE

In paper [5], we proposed the boundary expanding-contracting principle and the boundary expanding-contracting method (BECM). In this paper we make some complemental statements and detailed proofs about the principle.

综合教学目标导向的课程教学体系创新——基于BOPPPS方法的探索

立足于人力资源管理课程教学面临的新问题,为实施完成人力资源管理教学的知识、能力与素养培养目标,采用BOPPPS教学方法对人力资源管理课程教学体系创新。以绩效管理章节为例,通过在导言、学习目标/结果、先测、参与式学习、后测、总结和产学研拓展7个阶段针对知识、能力与素养不同教学目标而实施不同的策略,探索人力资源管理课程教学体系创新。期望能够解决人力资源管理教学面临的问题,同时给其他课程改革带来启示。

改进人工势场引导的双向扩展随机树路径规划算法

针对地面移动机器人在复杂环境之下要求规划路径实时性强、路线平滑度高、避障精确完备等需求,在快速扩展随机树算法(RRT)的基础之上,提出一种由改进人工势场法(APF)引导的双向扩展随机树算法(APF-Bi-RRT^(*))。首先,在每次迭代的过程之中两棵随机树同时分别从起始点和目标点进行扩展,以加快算法收敛速度;其次,在算法随机树生长方向上,引入目标偏置策略来优化随机子节点的选取,并在随机树和障碍物中加入人工势场分量,限制路径方向选择的随机性,改进算法克服引力和斥力过大导致陷入局部最优值或目标不可达的问题;最后,在形成锯齿型规划路径之上应用一种采样优化和关键节点平滑策略,进一步缩短和平滑原路径的总距离。对比实验结果证明,该算法既克服了传统随机树算法的节点盲目扩展的问题,又兼顾了生成路径的效率和平滑性,与目标偏置RRT算法相比,在规划路径长度上减少了9.7%左右,在运行时间上缩短了65.3%左右,在算法迭代次数上减少了78.2%左右。

可膨胀微球制备方法和影响因素及应用进展

可膨胀微球是一种典型的单壁单芯的核-壳结构,由高分子聚合物壳和烷烃液体核组成。因其优异的发泡性能和可控的泡孔结构广泛应用于发泡剂等领域。然而,可膨胀微球的制备周期长、影响因素多且相互制约,导致其制备和研究困难。本综述总结了可膨胀微球的5种制备方法,概括了粒径、膨胀温度和膨胀倍率的影响因素,分析了性能调控的手段,分类总结了应用领域,尤其是热-机械转变特性的应用。最后对可膨胀微球的研究方向和发展前景进行了展望,以期望为可膨胀微球的持续研究提供参考。

模拟高原环境下敏化方式对乳化炸药爆轰性能的影响研究

为研究高原环境对不同敏化方式乳化炸药的影响程度,选取3种典型的敏化材料制备乳化炸药样品,模拟并对比分析了高原环境(-20℃、约0.05 MPa)储存后乳化炸药的微观结构和爆轰性能变化。结果表明:低温低压下的高原环境主要从加剧破坏乳化体系稳定性与热点分布两方面影响炸药的性能,在该环境下化学敏化炸药相较于物理敏化炸药的析晶程度较低,但热点变化较大,导致爆轰性能下降;物理敏化中,膨胀珍珠岩炸药晶体的生长方式更加复杂,因此更易破乳析晶,储存稳定性与爆轰性能均有明显降低;相对而言,树脂微球炸药在低温低压下的析晶程度与爆轰性能均较稳定。综合上述结果,树脂微球乳化炸药具有更好的高原适应性。

建筑用膨胀珍珠岩的资源特性及研究现状分析

对国内外建筑用膨胀珍珠岩的相关产品标准进行梳理,对膨胀珍珠岩的化学成分、微观结构及亲水机理进行分析,指出保持膨胀珍珠岩优异绝热性能的关键是改变其表层的亲水官能团及微孔结构,总结有机硅憎水剂喷涂、聚合物包覆、SiO2气凝胶填充等膨胀珍珠岩改性方法的机理及研究现状,为相关技术人员生产或使用膨胀珍珠岩提供参考。

森林抚育间伐的影响、工作原则及技术要点分析

抚育间伐是森林培育过程中的一项重要技术措施,对林分密度和空间布局、林木健康成长等有着十分重要的影响。然而实践中,由于对森林抚育间伐对象确定不合理、技术运用不恰当等原因,导致林木抚育间伐效果不理想。文章介绍了森林抚育间伐的重要影响,然后指出了抚育间伐作业过程中应当遵循的原则,最后重点从合理确定间伐抚育对象、选择适宜的间伐方式、控制间伐强度、加强后期管理等方面提出了提高抚育间伐效果的一些措施建议。

膨胀结晶法裂缝填充技术分析与评价

文中通过面积修复率和超声脉冲速度法评价了西卡膨胀结晶自修复剂的修复效果。试验结果表明,膨胀结晶自修复剂作用下生成的修复产物有效填充了裂缝区,提升了水泥砂浆内部的密实度,该膨胀结晶自修复剂的修复产物主要有Mg(OH)_(2)和CaCO_(3)。

基于扩展不确定度半宽的灌装机修正装置研究

为提升灌装机生产企业全面认识灌装机计量性能和定量包装商品计量指标的关联性,提升灌装机生产研发水平,同时为帮助定量包装生产企业进行科学灌装,实现成本节约、规避风险的目的。通过对定量灌装机测量方法设定,建立其数学模型并计算出灵敏系数,再从定容式灌装机(称重法)的影响量分析和不确定度评定作为切入点,进一步认识测量不确定区并提出扩展不确定度半宽的灌装机修正设想,从而建立定容式灌装机(称重法)的修正公式:V_(修设)=2V_(标注净含量)-V-_(i)+U,最终通过研究开发灌装机修正装置,对罐装时灌装机的稳定性、电子天平、电子密度计、温度计的最大允许误差或扩展不确定度等公式未知数的录入得出体积修正设定值并控制灌装机的灌装量设置量。通过现场测试,修正后的灌装机能以满足企业灌装时大概97.5%的灌装量数值刚好落在大于标注净含量的区间要求。同时,在对灌装机修正值影响量分析中的结论值得部分重质量、轻计量的企业管理者重视,因为高稳定性的灌装机是企业降低罐装成本和罐装风险的关键要素,精准的计量器具是生产质量的保证。

UPLC-MS/MS法测定半夏中根茎膨大剂的残留

目的了解半夏药材种植过程中根茎类膨大剂的使用现状,并筛选出可能会在半夏药材中残留的根茎类膨大剂。方法采用QuEChERS法对不同批次半夏药材及饮片进行提取,采用Phenomenex F5(100 mm×2.1 mm,1.7μm)色谱柱,以甲醇和0.1%甲酸水溶液为流动相,梯度洗脱,流量为0.3 mL·min^(-1),采用分时间窗口多反应监测模式对29种根茎类膨大剂化合物进行定性和定量检测。结果29种植物生长调节剂的质量浓度均在一定范围内与对应峰面积呈线性关系,检测限为0.4~2.0μg·kg^(-1);在所添加的3个水平浓度下,方法回收率在80.2%~114.5%,RSD均在2.3%~8.8%。38批半夏样品的根茎除野外自采批次,其余均检出不同程度的根茎类膨大剂。其中氯化胆碱普遍应用于半夏栽培过程中,半夏人工种植过程中涉及的根茎类膨大剂多达10余种,主要集中在人工合成外源性生长素(吲哚丁酸、2,4-二氯苯氧乙酸),细胞分裂素(玉米素、烯腺嘌呤、6-氨基腺嘌呤),含氮杂环类(多效唑、环丙嘧啶醇、烯效唑),季铵盐类(矮壮素),还有部分其他类的生长调节剂。结论该方法操作方便简易,准确可靠,可同时快速筛查半夏药材中29种根茎类膨大剂的残留。