球面插值PH曲线

本文讨论球面上PH曲线的C1Hermite插值问题。基于球极投影保持PH性质这一特性,通过球极投影把球面数据投影到平面上,构造一条平面PH曲线。然后,逆投影回球面得到一条球面有理插值PH曲线。球面PH曲线对球面数据达到C1插值,拓宽了PH曲线在机器人路径的设计、数控加工的计算等方面的应用范围。     

基于伸缩矢量函数的平面参数曲线的插值变形

针对平面参数曲线的插值变形问题,构造了伸缩矢量函数,将插值数据点转化为变形主方向矢量,用此伸缩矢量函数去作用待变形曲线,使曲线发生形变且变形后能通过给定的插值点,此方法能够精确控制变形范围,在变形与未变形部分之间具有C2连续性。     

保形几何Hermite插值

本文将保形概念引入到几何:Hermite插值,利用三次Bezier曲线段构造了一条GC2连续的保形参数三次几何:Hermite插值曲线,曲线在相邻两个型值点之间,由两段三次:Bezier曲线组成。该曲线的所有Bezier点由型值点及相应的曲率信息直接计算产生,无需求解矢量方程组,因此该曲线计算简单,局部修改方便。     

自由曲面上曲线物理空间和参数空间互相转换算法

根据曲面曲线上的点与曲面参数域之间的对应关系,提出了一种实用的物理空间与参数空间的转换算法.曲面和曲线离散后,用迭代法求得曲线离散点列对应的曲面参数值,以求得的参数值为型值点在曲面参数平面上构造插值曲线,然后根据插值曲线细分曲面曲线可得到曲面曲线在曲面参数平面上更加精确的投影曲线.计算实例表明投影曲线映射到三维空间与原曲面曲线高度一致.     

一种实用的自由曲面上曲线插值算法

直接在自由曲面上构造曲线是非常实用的造型技术,实现在曲面上曲线插值的主要思路是将其转化为一般的曲线插值问题求解。基于曲面及其参数之间的对应关系,提出了一种实用的算法,即根据给定的曲面上型值点,首先在参数域平面上构造插值曲线,再将该参数域内插值曲线映射到曲面上,获得曲面上曲线,从而实现曲面上曲线插值的目的。给出了具体的算法步骤,并对参数曲线不在参数域内部的特殊情况进行了处理。图例显示该法具有满意的效果。     

用细分螺线插值容许G~2Hermite数据

为使几何细分方法生成的平面螺线段插值平面容许G2Hermite数据,基于平面双圆弧插值理论提出了该方法首末端点处新的细分规则。理论分析表明,修改后的细分方法所得极限曲线是曲率单调、不变号的螺线段,且插值首末端点处的点、切向、曲率。数值算例表明,修改后的细分方法收敛速度较快,极限曲线具有较好的形状。     

以给定的三次Bézier曲线为边界测地线的双三次Bézier曲面构造

曲面上的测地线是曲面上一类重要的曲线.测地线在计算机可视化、图像处理、服装设计等领域均有广泛应用.该文利用一条曲线为所在曲面的测地线当且仅当它的从切面与该曲面在这条曲线上的切平面重合这一论断,做了以下工作：对给定的三次Bézier曲线,构造双三次Bézier曲面,使该曲面以给定的曲线为其边界测地线;讨论了具有给定测地线的组合双三次Bézier曲面的连续性拼接问题;为了说明所给方法的有效性,给出了几个数值实例.     

单位向量的妙用

本文首先利用微分法建立球面上某点处的切平面方程和法线方程,通过对法线方程的研究,发现球面上任何点的法线必过球心,由此启发,可以借助于过球心的单位向量找到切点,进而建立切平面方程和法线方程。     

基于函数值的有理二次插值曲线的区域控制

将插值曲线约束于给定的区域之内是曲线形状控制中的重要问题.构造了一种基于函数值的分母为二次的C1连续有理二次插值函数,该函数中含有参数,因而可以在插值条件不变的情况下通过对参数的选择进行曲线的局部修改,同时可通过对参数的控制实现C2连续的插值.给出了将该种插值曲线约束于给定的折线、二次曲线之上、之下或之间的充分条件及将其约束于给定折线之上、之下或之间的充分必要条件.     

视觉光滑插值样条曲线及保凸插值

给定平面上凸数据,作出保凸插值曲线是工程设计中重要问题之一。普通插值样条曲线没有保凸性。本文给出视觉光滑插值样条曲线可以解决这一问题。     

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.