步进电机细分驱动技术的软件实施

步进电机是采用脉冲信号作为驱动信号源的电动机,在微量进给及准确定位等数控领域有着广泛的应用。为使步进电机能更好地满足控制要求,需要采用细分驱动技术。本文论述的是利用软件编程、通过设定循环控制字来分配驱动脉冲信号源,并利用升／降速技术来提高步进电机的控制精度。     

对"承压设备焊接工艺评定标准"的思考(一)

对正在制订的《承压设备焊接工艺评定》标准中各重要观点与主要技术内容进行思考，所总结的心得体会。主要内容有各类焊接工艺评定标准的目的、两个类型的焊接工艺评定，以及两类评定之间的区别与联系。本文还首次提出一些新思路、新观点，如母材、焊材分类细则以及标准以外材料分类要有分类报告佐证；通用的焊接工艺评定规定及使用方法；换热管与管板的焊接工艺评定是评定角焊缝厚度；气瓶焊接工艺评定是两个类型评定的结合，也可以分别评定。《承压设备焊接工艺评定》标准不仅适用于锅炉、压力容器（含气瓶），也适用于包括长输管道在内的压力管道。     

催化重整加热炉炉管焊接工艺试验研究

结合某炼油工程催化重整装置四合一炉炉管焊接施工要求，对炉管用钢的焊接性进行了试验研究，并进行了TIG焊和手工电弧焊的工艺评定。试验结果表明，STF A26耐热钢有较高的淬硬倾向和冷裂敏感性，采取焊前预热和焊后热处理措施，有利于改善焊接接头的力学性能。     

Physical programming for preference driven evolutionary multi-objective optimization

Preference articulation in multi-objective optimization could be used to improve the pertinency of solutions in an approximated Pareto front. That is, computing the most interesting solutions from the designer's point of view in order to facilitate the Pareto front analysis and the selection of a design alternative. This articulation can be achieved in an a priori, progressive, or a posteriori manner. If it is used within an a priori frame, it could focus the optimization process toward the most promising areas of the Pareto front, saving computational resources and assuring a useful Pareto front approximation for the designer. In this work, a physical programming approach embedded in an evolutionary multi-objective optimization is presented as a tool for preference inclusion. The results presented and the algorithm developed validate the proposal as a potential tool for engineering design by means of evolutionary multi-objective optimization.     

Noise measurement of a preamplifier with high input impedance using an NMR console

This article describes the noise measurement of a preamplifier with high input impedance designed for experiments with receive coils in nuclear magnetic resonance (NMR). The noise of the preamplifier was determined in two ways. A circuital analysis of the preamplifier provided an equation for the preamplifier noise calculation and the noise voltage was measured with an NMR console and in accordance with known theory the measured analogue noise signal was modified to a discrete noise signal. An objective function with noise parameters of the preamplifier as variables was created. The noise parameters of the preamplifier were calculated with an optimization procedure and the results of the calculation and of the measurement compared. Qualitative and quantitative agreement was good. It was proved that the noise parameters of a preamplifier for NMR experiments can be measured with an NMR console and derived theory.     

Anomalous creep behaviour of 316 stainless steel at 550°C

The results offifteen constant-load creep tests at 550°C, with nominal stresses in the range 200 to 360 MPa and with test durations ofup to 14 000 h, are presented. The usual primary, secondary and tertiary creep behaviour was exhibited for nominal stresses greater than about 330 MPa. At lower stresses, ‘renewed’ primary and secondary creep regions were observed. The renewed secondary creep strain rates were found to be about an order of magnitude greater than the initial secondary creep strain rates. The results indicate that the occurrence ofthe renewed primary and secondary creep regions is associated with time-dependent exposure to a temperature of 550°C. The presence or magnitude of the prior stress level does not appear to have any significant effect.

The results are relevant to design procedures because extrapolation of short duration or high stress data to long-term design lifetimes is often required. Unless the possibility ofthe occurrence ofrenewed primary and secondary creep is taken into account, gross errors in strain predictions could occur.     

ISTA 3A：2008标准解读

ISTA（国际安全运输协会）是一个致力于包装测试技术研究及相关标准制订的组织。ISTA目前已颁布ISTA 1系至7系的标准，在业界得到广泛应用，其中ISTA 3A：2008是应用最多的标准之一。ISTA标准的设计，基于丰富的经验和大量的测试数据，具有很强的实用性和针对性，并且根据实际情况的变化而不断完善。本文根据实际应用中的一些体会和ISTA组织的解释，对该标准进行了较详细的解读。文章概述了现行国家包装类标准和ISTA标准的区别，分析了ISTA 3A标准的试验应力和试验装置，阐述了各类型包装件角、棱、面的标识方法，并将各试验项目模块化，再以模块组合的形式，归纳出各类型包装件的测试程式。     

A multiobjective GRASP–VND algorithm to solve the waste collection problem

In this paper, the waste collection problem (WCP) of a city in the south of Spain is addressed as a multiobjective routing problem that considers three objectives. From the company's perspective, the minimization of the travel cost is desired as well as that of the total number of vehicles. Additionally, from the employee's point of view, a set of balanced routes is also sought. Four variants of a multiobjective hybrid algorithm are proposed. Specifically, a GRASP (greedy randomized adaptive search procedure) with a VND (variable neighborhood descent) is combined. The best GRASP–VND algorithm found is applied in order to solve the real‐world WCP of a city in the south of Spain.     

Improving the yield of Jatropha curcas's FAME through sol–gel derived meso-porous hydrotalcites

The conversion of fatty acid methyl ester (FAME) from triglycerides using heterogeneous catalysis has gained increasing interest due to the prospect of increased yield at reduced operating costs and reaction conditions. In this paper, meso-porous hydrotalcite was used to catalyze jatropha oil into FAME with relatively higher yield at atmospheric pressure and relatively low reaction temperature. The molar ratio of methanol to oil required was relatively low and the conversion was completed within few hours of reaction time. The reaction was promoted when moderate calcination temperature was applied, the disordered structure of the catalyst was maintained, counterbalance anions was removed, and phase transitions within the oxide lattice was induced. Despite the observed deactivation during successive reaction cycles due to adsorption of residual triglycerides, the catalyst performance was restored effectively by air-re-calcination.