Use of vibratory polishing for the location of ion-bombardment induced voids in metal foils

The technique of vibratory polishing has been successfully applied to the controlled removal of surfaces for examination of ion-irradiation damage structure in nickel, a nickel-based alloy, and stainless steel. The application of this technique to the study of voids formed in localized layers in nickel and stainless steel during high dose 20 MeV carbon ion irradiation is described. Transmission electron microscopy observations of the vibratory polished surfaces reveal mechanical damage in the form of linear tracks (～ 100 nm wide) which are produced by the abrasive Al₂O₃ particles used for polishing. These tracks do not prevent observation of irradiation damage structure. An example is shown of a thin (～ 100 nm edge thickness) foil produced entirely by this mechanical polishing process. It is proposed that this technique will be equally applicable to the preparation of transmission electron microscope specimens from a wide range of metals, from alloys containing second-phase particles and from ceramics, glasses and oxides which are not amenable to preparation by chemical or electro-polishing.     

Computer-aided procedures for subdivision design and evaluation

Design and management of residential subdivisions are described using a case study in Regina, Saskatchewan. Capital, operation and maintenance costs of physical services and fuel costs for intra-subdivision trips are compared for four subdivision layouts using the procedures. The solar superblock layout is the lowest subdivision layout. Future procedures to assist subdivision design engineers and planners are summarized.     

The electronic spreadsheet as a didactic learning enhancement

A variety of quantitative techniques (such as capital budgeting or linear programming) may be understood more fully by students when they are able to work through relatively simple applications of the techniques by hand. Unfortunately, such manual computations are inherently susceptible to arithmetic errors. The authors propose that students use the electronic spreadsheet to work out these types of problems during their initial learning stage. An advantage of the electronic spreadsheet for this purpose is the automatic calculation of data by the program thereby eliminating the usual arithmetic errors. As long as appropriate formulas are correctly entered into the spreadsheet, the results should be correct.The method presented by the authors does not yield general solutions to capital budgeting or to linear programming problems. Rather, the methodology requires the student to think through the solution process while removing some of the usual drudgery and potential inaccuracies of manual solutions.     

家庭中的无线安全

现在,在看过论坛的大量文章之后,相信您已经对无线LAN(无线局域网,WLAN)采取了敬而远之的态度。至少,您已经对WLAN产生了怀疑——这并不是一件坏事情。Rik描述了Wep的缺陷,Corey描述了如何将无线访问点转移到DMZ中,而Dave指出应该将它们彻底地放到外面。不过,还没有人说应该完全舍弃WLAN,这是出于两个非常有说服力的理由。首先,WLAN在某些场合非常有用;其次,您完全可以不必听我们的。您已经知道WLAN在办公室的用处。但是,它在家里有什么用呢?正如许多人所指出的,“无线”的价格很便宜,而且确实行之有效(我在撰写本文时,就是通过…     

IPv4/IPv6的共存、过渡与寻址

本文从技术人员的角度对有关IP技术和IP网络的发展前景进行展望.当前的互联网正面临着从传统IPv4协议向IPv6协议的过渡,作者将着重分析过渡需求和主要的技术问题及其当前进展,以及遗留的其他课题.为了实现这一目标,还需要对互联网协议的历史、现状以及未解决的问题进行说明.     

改进缺陷,套刻和聚焦性能的第五世代浸没式曝光系统

论述了第五世代双扫描平台浸液式扫描曝光机的性能和进展。表明了在高速扫描状态下有生产价值的套刻和聚焦性能的实现。浸液式设备更多的关键部分与缺陷有关,而且该机的改进是通过有生产价值的缺陷水平方面来体现的。为了保持这种缺陷水平的改进效果,需要在圆片应用中进行专门稳定的测量。特加是边缘空泡除去(EBR)设计和圆片斜面良流线性是很重要的。     

Understanding Viruses Bio-logically

Networks dominate today’s computing landscape and commercial, technical protection is lagging behind attack technology. As a result, protection program success depends more on prudent management decisions than on the selection of technical safeguards. Managing Network Security takes a management view of protection and seeks to reconcile the need for security with the limitations of technology.     

Accelerated image reconstruction using ordered subsets of projection data

The authors define ordered subset processing for standard algorithms (such as expectation maximization, EM) for image restoration from projections. Ordered subsets methods group projection data into an ordered sequence of subsets (or blocks). An iteration of ordered subsets EM is defined as a single pass through all the subsets, in each subset using the current estimate to initialize application of EM with that data subset. This approach is similar in concept to block-Kaczmarz methods introduced by Eggermont et al. (1981) for iterative reconstruction. Simultaneous iterative reconstruction (SIRT) and multiplicative algebraic reconstruction (MART) techniques are well known special cases. Ordered subsets EM (OS-EM) provides a restoration imposing a natural positivity condition and with close links to the EM algorithm. OS-EM is applicable in both single photon (SPECT) and positron emission tomography (PET). In simulation studies in SPECT, the OS-EM algorithm provides an order-of-magnitude acceleration over EM, with restoration quality maintained.     

Facile Synthesis and Proposed Mechanism of α,ω‐Oxetanyl-Telechelic Poly(3-nitratomethyl-3-methyl oxetane) by an SN2(i) Nitrato Displacement Method in Basic Media

The synthesis of a novel heterocyclic–telechelic polymer, α,ω-oxetanyl-telechelic poly(3-nitratomethyl-3-methyl oxetane), is described. Infrared spectroscopy (IR), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR) spectroscopy have been used to confirm the successful synthesis, demonstrating the presence of the telechelic-oxetanyl moieties. Synthesis of the terminal functionalities has been achieved via displacement of nitrato groups, in a manner similar to that employed with other leaving groups such as azido, bromo, and nitro, initiated by nucleophiles. In the present case, displacement occurs on the ends of a nitrato-functionalized polymer driven by the formation of sodium nitrate, which is supported by the polar aprotic solvent N,N-dimethyl formamide. The formation of an alkoxide at the polymer chain ends is favored and allows internal back-biting to the nearest carbon bearing the nitrato group, intrinsically in an S_N2(i) reaction, leading to α,ω-oxetanyl functionalization. The telechelic-oxetanyl moieties have the potential to be cross-linked by chemical (e.g., acidic) or radiative (e.g., ultraviolet) curing methods without the use of high temperatures, usually below 100°C. This type of material was designed for future use as a contraband simulant, whereby it would form the predominant constituent of elastomeric composites comprising rubbery polymer with small quantities of solids, typically crystals of contraband substances, such as explosives or narcotics. This method also provides an alternative approach to ring closure and synthesis of heterocycles.     

Statistical modeling of dissimilarity increments for d-dimensional data: Application in partitional clustering

This paper addresses the use of high order dissimilarity models in data mining problems. We explore dissimilarities between triplets of nearest neighbors, called dissimilarity increments (DIs). We derive a statistical model of DIs for d-dimensional data (d-DID) assuming that the objects follow a multivariate Gaussian distribution. Empirical evidence shows that the d-DID is well approximated by the particular case d=2. We propose the application of this model in clustering, with a partitional algorithm that uses a merge strategy on Gaussian components. Experimental results, in synthetic and real datasets, show that clustering algorithms using DID usually outperform well known clustering algorithms.