Synthesis of titanium nitride thin films deposited by a new shielded arc ion plating

Thin films of titanium nitride (TiN) were deposited on stainless steel substrates by a modified deposition technique, double-layered shielded arc ion plating with vicarious circular holes (DL-SAIP). The results show that the TiN film with the distance of 10 mm between the double-layered shield plates had the least droplets. The deposition rate of the films prepared with the new technique was more homogeneous than that of all the other shielded arc ion plating. The film/substrate adhesion and microhardness values of the TiN films were higher than 40 N and 18 GPa, respectively. Thus such TiN thin films can be expected in applications.     

Abrasive resistance of arc sprayed carbonitride alloying self-shielded coatings

Wear-resistant coatings were prepared on the surface of the Q235 low-carbon steel plate by HVAS with the carbonitride alloying self-shielded flux-cored wire. Detection and analysis on the microstructure and properties of the coatings were carried out by using scanning electron microscope, microhardness tester and wear tester. The forming, the wear resistance and its mechanism of the coatings were studied. The results show that the coatings have good forming, homogeneous microstructure and compact structure. The coatings have good hardness, the average microhardness value reaches 520 HV_0.1, and the highest value is up to about 560 HV_0.1. As a result, the coatings have good abrasive wear performance and adhesion strength.     

The influence of compressive stress applied by hard coatings on the power loss of grain oriented electrical steel sheet

To reduce the core loss of electrical steel the vacuum arc ion plating technique has been used to deposit titanium nitride (TiN) layers on highly grain oriented electrical steel sheets. The layer thickness, the stresses of layers and coated sheets and the achieved reduction in core losses have been measured as functions of coating duration and applied bias voltage. Well adhered layers with high compressive stress up to 6.8 GPa have been produced. With increasing bias voltage the layer thickness decreases and the intrinsic stress of the layers increase. A further increase of bias voltage leads to a drop in stress due to thermal relaxation. In general, the tensile stress of the coated sheets rises with increasing layer thickness while the core loss of the coated material decreases with increasing tensile stress of the steel sheet and increasing bias voltage. The highest reduction of core loss has been found to be 28% (from P_1.7=0.86 W/kg for commercially coated HGO electrical steel sheet with glass film to 0.62 W/kg for TiN coated material) and is due to the reduction of excess loss only.     

Vertex‐Transitive Cubic Graphs of Square‐Free Order

A classification of connected vertex‐transitive cubic graphs of square‐free order is provided. It is shown that such graphs are well‐characterized metacirculants (including dihedrants, generalized Petersen graphs, Möbius bands), or Tutte's 8‐cage, or graphs arisen from simple groups PSL(2, p).     

Unitary Graphs

Unitary graphs are arc‐transitive graphs with vertices the flags of Hermitian unitals and edges defined by certain elements of the underlying finite fields. They played a significant role in a recent classification of a class of arc‐transitive graphs that admit an automorphism group acting imprimitively on the vertices. In this article, we prove that all unitary graphs are connected of diameter two and girth three. Based on this, we obtain, for any prime power , a lower bound of order on the maximum number of vertices in an arc‐transitive graph of degree and diameter two.     

Asymptotics of Christoffel functions on arcs and curves

For a system of smooth Jordan curves and arcs asymptotics for Christoffel functions is established. A separate new method is developed to handle the upper and lower estimates. In the course to the upper bound a theorem of Widom on the norm of Chebyshev polynomials is generalized.     

Arc Length Estimation and the Convergence of Polynomial Curve Interpolation

When fitting parametric polynomial curves to sequences of points or derivatives we have to choose suitable parameter values at the interpolation points. This paper investigates the effect of the parameterization on the approximation order of the interpolation. We show that chord length parameter values yield full approximation order when the polynomial degree is at most three. We obtain full approximation order for arbitrary degree by developing an algorithm which generates more and more accurate approximations to arc length: the lengths of the segments of an interpolant of one degree provide parameter intervals for interpolants of degree two higher. The algorithm can also be used to estimate the length of a curve and its arc-length derivatives. AMS subject classification (2000) 65D05, 65D10     

Chromatography of glycols. Regularities in the retention of C3−C6 branched glycols in gas-solid and gas-liquid chromatography

Summary Linear correlation between the major physico-chemical properties of glycols and their relative retention volumes measured by gas-solid (GSC) and gas-liquid (GLC) chromatography is shown. The coefficients of the linear regression equations describing the relationship between the relative retention volumes and the physico-chemical parameters (boiling point, density, etc.) are given. The values of the change in the free energy for the stationary phases studied are given as well as the increments of this change per −CH₂- and CH₃-group. The main factors determining the retention of branched glycols on Polysorb, Tween and poly(ethylene glycol) are shown to be the distance between the hydroxyl groups in their molecules, the presence of alkyl substituents and the type and the number of these substituents.     

结构光焊缝检测传感器设计理论的研究

对电弧光的干扰进行了深入的研究，建立了电弧干扰的光照模型，依据透视变换理论，给出了光源倾斜照射和摄像机斜接收情况下，被检测物体与摄像机这间的一般坐标变换数学模型，这两个模型对结构光传感器的设计具有非常重要的指导意义，基于这两个模型设计的结构光传感已在自动焊接实验中获得了成功的应用。     

CO_2焊接短路过渡过程的动态分析─短路液桥的动态变化与力学测算

ＣＯ＿２气体保护焊接是一种高效、节能和低成本的焊接方法，在钢结构焊接生产中得到了广泛的应用。但也存在着诸如：金属飞溅、焊缝成形较差等问题，要解决这些问题，必须首先对ＣＯ＿２焊接过程的电弧形态以及熔滴变化情况从理论上深入分析研究。本文以高速摄影与光线示波器同步进行拍摄，记录了ＣＯ＿２悍接短路过渡中熔滴的长大、缩颈、脱落的全过程以及相对应的电流电压波形。利用影片数据分析处理系统对所得影片及记录波形进行了分析处理，得到了熔滴过渡形成金属液桥爆断瞬间的最大电流值及所受合力的大小。从理论上更进一步研究了短路过渡的机理，建立了短路过渡的模型，这对正确调节焊接工艺规范，保证焊接质量具有重大的指导意义，研究结果表明：在常规短路过渡ＣＯ＿２焊接中，抑制飞溅是提高ＣＯ＿２焊接质量的关键，利用焊接规范来调节短路频率和短路峰值电流是抑制飞溅的主要途径。