铣制三元流叶轮时产生误差的原因分析及解决方法

对在五坐标数控加工中心上铣制三元流叶轮时出现的叶轮附面尺寸误差问题，进行了详细分析，并提出了问题的解决方法，有效地避免了加工中产生的超差。     

（E）-2-壬烯酸合成方法的改进

(E)-2-壬烯酸是有机合成的一种重要中间体,我们利用Knoevenagel反应机理,改进了(E)-2-壬烯酸的合成工艺,在不使用脱水剂条件下,使用少量吡啶作催化剂,获得了83%的反应收率。     

Experimental Study of Ice Jam Thickening under Dynamic Flow Conditions

River ice jams are a common occurrence on northern rivers, and their formation can present a severe flood risk to nearby communities. As more and more river regulation projects are developed to provide an alternative to fossil fuels for electrical power-generating capacity, our need to understand the mechanisms associated with ice jam formation under variable flow conditions becomes more vital. This is because, at present, hydropeaking operations are often severely curtailed during the ice-affected seasons due to concerns that sudden flow fluctuations might instigate ice jams and associated flooding. Here, an experimental investigation explores the effects of rapid increases in discharge on ice jam formation and evolution. It is found that the thickness of ice jams formed under highly dynamic flow conditions tend to be slightly thinner than those formed during steady carrier flows for comparable discharges. Also, despite the highly dynamic nature of these consolidation events, the resulting ice thicknesses appear reasonably well approximated by steady flow theory.     

Mobile robot path planning based on hierarchical hexagonal decomposition and artificial potential fields

In this article, a new algorithm based on an artificial potential field and hierarchical cell decomposition technique is developed to solve the find-path problem for a mobile robot. The complete map of the workspace including obstacle locations is assumed to be known a priori. The basic cell structure used for decomposition is a hexagon. The artificial potential field is based on an attractive force from the goal position and repelling forces from the obstacles. Computer simulations of the algorithm for various obstacle scenarios are also presented. © 1994 John Wiley & Sons, Inc.     

Chemical mechanical polishing of polymer films

Strategies to reduce capacitance effects associated with shrinking integrated circuit (IC) design rules include incorporating low resistivity metals and insulators with low dielectric values, or “low-κ” materials. Using such materials in current IC fabrication schemes necessitates the development of reliable chemical mechanical polishing (CMP) processes and process consumables tailored for them. Here we present results of CMP experiments performed on FLARE™ 2.0 using a specialized zirconium oxide (ZrO₂) polishing slurry. FLARE™ 2.0 is a poly(arylene) ether from AlliedSignal, Inc. with a nominal dielectric constant of 2.8. In addition, we provide insight into possible removal mechanisms during the CMP of organic polymers by examining the performance of numerous abrasive slurries. Although specific to a limited number of polymers, the authors suggest that the information presented in this paper is relevant to the CMP performance of many polymer dielectric materials.     

Coliphage prevalence in high school septic effluent and associated ground water

At the present time, somatic and male-specific coliphage and human enterovirus groups are being considered as indicators of possible pathogenic human enteric virus contamination from fecal contamination. A primary attribute for any indicator of fecal contamination is its prevalence at the source and in associated ground water. It must be consistently found in the source material at concentrations that are measurable with available techniques. Over a period of ten months, male-specific and somatic coliphage ranged from 7000 to 4,000,000 PFU/L in the effluent from a multi-user septic-tank. Unlike the values determined for septic-tank effluent, coliphage concentrations measured in ground water over this same period only varied by five-fold. Coliphage concentration in ground water under the down-gradient edge of the drainfield contained 1000 PFU/L. This concentration decreased at −1 log₁₀/5 m during 17.4 m of ground-water transport. From these data, coliphage concentrations in septic-tank effluent seem sufficient to allow their use as indicators of fecal contamination in ground water.     

城市加油站的防火与消防管理

介绍汽车加油站在防火设计与消防管理方面需注意的问题，主要包括站址选择、总平面布置、油罐设置、管线布置、卸油方式等方面，同时对加油站的日常操作与防火消防管理提出了要求。     

Reliability and performance analysis of time – space – time switching networks with multiple separated space switches

Since electronic switching systems usually require very strict reliability requirements as well as good performance objectives, we need to jointly analyse the performance and reliability of switching systems. In this paper, we compare conventional time–space–time switches with single space switches with those with multiple separated space switches, from the viewpoints of reliability and performance. We consider time–space–time switching networks which consist of N incoming time switches, i.e. one NxN space switch, two (N/2)x(N/2) space switches, and four (N/4)x(N/4) space switches. We introduce a Markov reliability model to study the effect of failures and analyse the reliability and performance of three different types of switching networks in terms of average blocking probability and the mean time to unreliable operation, as we vary the offered traffic. As a result, T–S–T switching networks with multiple separated space switches exhibit better performance and reliability than those with single space switches.     

基于空间矩的灰度边缘亚像元度量精度分析

灰度图像中边缘定位受采样密度限制，亚像元精度度量方法在需要高精度的应用中受到重视，要想知识到底需要多高的分辨率才能达到定精度指标，就有必要分析特征定位方法的最坏情况的精度，文中用分析和实验的方法给出了基于空间矩的边缘定位方法，对于边缘点，边缘直线以及直边缘区域的最坏情况定位精度分析。分析和讨论的结果不但可以用来确定已知形状位置估计的最大误差，而且还可用于对准的形状几何参数，以获得较高的精度。