基于宏程序的单线梯形螺纹加工工艺探讨

宏程序是数控系统提供给客户的一种类似于高级语言的编程方式,含有逻辑运算、算术运算和函数等混合功能,通过更改同一程序的参数设置,可实现多种相似工件的精确加工;而梯形螺纹是工程中应用广泛的结合形式,用于传递力和运动。由于螺纹刀牙形角小、刀具强度弱,易引起刀具三刃振动切削而严重影响精度,使得梯形螺纹在传统加工中是一个难点。本文基于FANUC Series Oi mate-TC数控系统,从梯形螺纹加工方法分析、工艺设计和程序编制等方面对梯形螺纹的数控车削方法进行探讨。     

模糊环境下消费类电子产品推荐方法研究

基于消费类电子产品自身的特点,提出一种新型的推荐方法。首先,考虑专家对备选产品进行评分时存在信息共享性,提出处理专家之间相互关联的直觉梯形模糊Shapley加权几何算子,并研究该算子的相关性质。其次,针对专家权重信息部分已知情况,建立规划模型求解专家的Shapley权重值,并运用所提算子对专家意见进行集成以得到各标准下各备选产品的综合评分。在给定顾客目标需求的基础上,基于投影法求出各备选产品在目标产品上的投影值,并将投影值最大的产品推荐给顾客以完成推荐过程。最后,以戴尔中国官网上的笔记本电脑购买为例,阐述该推荐方法的可行性和实用性。     

An experimental comparison of four graph drawing algorithms

In this paper we present an extensive experimental study comparing four general-purpose graph drawing algorithms. The four algorithms take as input general graphs (with no restrictions whatsoever on connectivity, planarity, etc.) and construct orthogonal grid drawings, which are widely used in software and database visualization applications. The test data (available by anonymous ftp) are 11,582 graphs, ranging from 10 to 100 vertices, which have been generated from a core set of 112 graphs used in “real-life” software engineering and database applications. The experiments provide a detailed quantitative evaluation of the performance of the four algorithms, and show that they exhibit trade-offs between “aesthetic” properties (e.g., crossings, bends, edge length) and running time.     

Biospinning: Change of water contents in drawn silk

Changes of the water content in drawn silk during drying were investigated by thermal analysis and ¹H pulse NMR. Water in liquid silk by drawing extruded from the inside of the silk filament into ambient air. The water contents in the drawn silk decreased with drying time. Assuming the nonfreezing water has a concentration of 10 wt % in the liquid silk, the percentage distribution of water in liquid silk is composed of 10 wt % nonfreezing water, 40 wt % freezing water, and 30 wt % free water. This 40 wt % freezing water in the liquid silk may be important for the formation of fine pores on the surface of drawn silk. The apparent pore radius, which was calculated from the results of thermal analysis, on the surface of drawn silk decreased to 5.0 nm and finally to 2.0 nm. The calculated apparent fine pore formed on the surface by drawing was 4.0 nm. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 274–280, 2003     

Birefringence study of drawn Nafion films

Nafion films are birefringent. This optical property has been studied as a function of the draw ratio to obtain insight into the film morphology. At small draw ratios, the structure shows biaxial behavior. At higher draw ratios (>150%), Nafion can be considered to have a uniaxial symmetry. The influence on the birefringence of three different counterions (hydrogen, lithium, and tetramethylammonium) is negligible. Undrawn Nafion shows preorientation, which can be eliminated with drawing in the proper direction. X‐ray experiments suggest that the physical origin of the birefringence in Nafion is mainly due to the orientation of the polymer chains and not due to deformation or form birefringence. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2857–2870, 2004     

二维图形系统的存储与再现技术

地理信息系统（GIS）被广泛应用于科学研究、资源管理、制定规划等。二维图形系统的存储与再生技术则是GIS系统的基础。任意一个图形系统本身由各种图形元素组成，对各种图形元素捕获、储存、加工、传递、转换和显示是获取图形中数据的关键。本文以位图为对象，通过类的建立，继承、绘图系统坐标的建立、位图的绘制、选中、删除、恢复、缩放，以及利用串行化技术实现文档的存储与读取等，阐述二维图形系统的存储和再现基本技术。     

On the manufacture of silver-sheathed Bi-2212 high temperature superconducting wires

High temperature superconductors (HTS) are presently being considered for a variety of defense and commercial applications. However, problems associated with low critical current density (J_c) in long length conductors still need to be addressed. It is realized that success in the fabrication of long lengths of wire and tape (up to 1 km) with optimum superconducting properties relies on improved manufacturing technologies. Unfortunately, there is no systematic study concerning the effect of processing parameters on the green properties of wires and tapes during the deformation processes. The focus of this investigation centered on silver (Ag) sheathed Bi-2212 wire forming processes and use of the two most common techniques, wire drawing and hydrostatic extrusion. Billets of 6.35 mm outside diameter were reduced separately by five different die sequences to a final diameter of 1.63 mm. Wires made by these procedures were characterized for properties such as Bi-2212 relative packing density, sheath material thickness, deformation force, elongation, drawing friction, and microstructural and mechanical properties. These results indicated that the amount of reduction per pass has a significant impact on the characteristics of non-heat treated wires and on the mechanical aspects of the wire drawing operations.     

口模拉伸共聚高密度聚乙烯单丝的取向结构探讨

口模拉伸共聚高密度聚乙烯单丝的取向结构探讨益小苏邹湘坪（浙江大学高分子系杭州３１００２７）谭洪生（齐鲁石化公司树脂所淄博２５５４３６）关键词共聚型聚乙烯，增强型单丝材料，Ｃｏｘ复合材料模型，Ｇｉｂｓｏｎ＆Ｗａｒｄ晶桥模型，口模拉伸工艺高密度聚乙烯（...     

Non-isothermal crystallization kinetics of hot drawn polyester films

The non-isothermal crystallization kinetics of hot drawn poly(ethylene terephthalate) films were studied using the Kissinger and Ozawa equations. The influence of the initial drawing on the crystallization kinetics was investigated. The values of the apparent activation energy and of the Avrami exponent indicates that the nucleation and growth of crystallites depend greatly on the stress submitted to the samples.     

RECOVERY OF AMORPHOUS POLY(ETHYLENE TEREPHTHALATE)FILM UNIAXIALLY DRAWN JUST BELOW THE GLASS TRANSITION TEMPERATURE*

Isothermal recovery in the macroscopic length of homogeneously deformed specimens of amorphous poly(ethyleneterephthalate) (PET) film sample uniaxially drawn at 69℃ to the draw ratios λ_0=1.26～2.20 were studied at temperaturesaround the glass transition temperature (T_g = 73℃). Experimental results indicate that the length recovery took place in twodistinct steps: a fast first step (fast relaxation) followed by a slow second step (slow relaxation). The relaxation processeswere accompanied by the reversion of trans-conformers (1340 cm~(-1)) to gauche, and the dichroic function of the 1340 cm~(-1)band characterizing the segmental orientation along the chain direction decreased to a very low value at the end of the fastrelaxation. This fact led us to assign the fast relaxation as the segmental orientation while the slow relaxation as relaxation ofthe global chain orientation. It was found that the slow relaxation follows a single exponential function, with relaxation timesstrongly dependent on the temperature resembling the glass transition process. The fast relaxation does not follow a singleexponential decay, presumably a distribution of relaxation times is involved.