关于两端固定轴向运动梁的横向振动

研究两端固定轴向运动梁的横向振动。导出了系统的频率方程，提出了求解该非显式表达的非线性超越方程的数值算法，得到了固有频率和模态函数。     

非线性分数阶微分振子的动力学研究

本文结合Zhang—Shimizu法与Newmark法，解决了二次非线性的Riemann—Liouville分数导数中奇异性问题，从而得到了非线性分数微积分求解的单步数值积分算法。在此基础上对某型非线性分数阶微分振子的动力学行为进行研究，分别讨论了振子自由振动及强迫振动下参数变化对振子非线性特性的影响。数值计算结果表明，该数值方法具有较好的稳定好，收敛速度快，精度较高，编程简单容易等优点。     

基于FFT多谐波平衡法的金属橡胶隔振系统振动特性分析

基于FFT多谐波平衡法,对金属橡胶隔振系统响应特性做了深入研究,并引入"平均功率比"对这类非线性隔振系统的振动传递率进行了新的定义。通过分析金属橡胶非线性隔振系统的本构关系,推导了用FFT多谐波平衡法求解系统响应及振动传递率的公式,并通过按数值方法、单一谐波法及多谐波法对给定算例的计算结果对比,说明了FFT多谐波平衡法在求解金属橡胶隔振系统响应及振动传递率时具有较高的精度。理论和分析表明,FFT多谐波平衡法可求解金属橡胶非线性系统响应及振动特性的精确解析解,具有重要的工程应用价值。     

扬声器低频强非线性振动的周期解

通过能量法求解扬声器低频强非线性振动系统的非线性微分方程，得到幅频关系方程、相频关系方程和强非线性振动的周期解的近似解析式。     

考虑损伤双层扁球面网壳的非线性动力学特性

基于Lematire等效应变损伤理论,计及扁球面网壳各个杆件的损伤影响,应用拟壳法导出了具有损伤的扁球面网壳的动力学非线性控制方程。提出了以中心最大振幅为摄动参数的摄动-变分法的求解方法,对动力非线性控制方程进行了求解,得出了相应的物理量的解析式。据此进行数值分析,得出了相应的特征关系。并用Galerkin方法导出了一个含二次和三次非线性振动微分方程并求解了具有损伤扁球面网壳的的非线性动力学的自由振动方程,给出了准确解。而后利用Melnikov函数法,从理论上给出了考虑损伤的系统发生混沌运动的临界条件,并通过计算机数字仿真证实了考虑损伤的扁球面网壳在非线性强迫振动时存在混沌运动,同时发现损伤使得系统更易发生混沌运动。     

IHB法在多自由度Bouc-Wen滞回非线性系统响应特性研究中的应用

工程中常用Bouc-Wen模型来描述具有滞回特性的振动系统,此类系统是一种多值性的非解析系统,其动力学理论分析比较困难。由于Bouc-Wen滞回模型的微分形式,一般采用数值方法进行积分求解,但对于多自由度系统来说求解速度非常慢,且难以求得不稳定解。故提出将滞回力引入为一个增加的自由度,重新建立振动系统的微分方程,将增量谐波平衡(IHB)法推广至求解该类含Bouc-Wen模型的多自由度滞回非线性系统,并引入弧长法解决由迟滞非线性引起的跳跃和多映射现象。利用该法分析了一些滞回系统的响应特性,通过与数值方法进行精度和效率对比,体现了该方法的优越性。     

三维柔性多体梁系统非线性动力响应分析

研究了三维柔性多体梁系统的非线性动力响应问题。将空间柔性梁的变形分解为轴向变形以及在x-y平面的弯曲变形和在x-z平面的弯曲变形，引用各自的精确振动模态描述变形场，利用拉格朗日乘子法建立起柔性多体梁系统约束非线性动力学方程。结合Newmark直接积分法和Newton-Raphson迭代法，导出了求解该非线性代数一微分方程组的数值方法。仿真算例证明了该方法的正确性和有效性。     

一类非线性振动系统的响应计算方法

研究了一类具有弹性非线性及阻尼非线性的振动系统在简谐激励下的响应计算方法.将等效线性化法与谐波平衡法相结合,求出了系统的近似解析响应.通过与采用数值积分求解结果进行对比分析,表明该方法编程简单、精度高,具有较好的工程实用性.     

单辊驱动轧机水平非线性参激振动机理研究

在考虑轧辊和轧件间摩擦力和水平方向非线性刚度和阻尼的基础上,建立了单辊驱动轧机水平非线性参激振动模型,用多尺度法求解了振动系统在主参数共振情况下的一阶近似解,给出了振动系统的频率响应方程,用数值方法研究了定常解的稳定性,并用分岔图、Poincare映射和Lyapunov指数方法分析了刚度波动对轧机水平非线性参激共振的影响。     

具有非线性运动约束输液曲管振动的分岔

研究了具何非线性运动约束输液曲管在系统参数区域内振动的分岔现象。基于牛顿法推导出了输液曲管模型面内振动的非线性控制方程，利用微分求积法将系统的偏微分方程转化为关于时间域的上阶常微分方程组；在此基础之上，采用数值迭代技术求解了输液曲管的非线性动力学方程。数值模拟表明，输液曲管在系统多种参数区域内俘有复杂的分岔现象；在这些参数区域内，系统将以静态变形、周期运动和混沌等形式作复杂的振动。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.