The VLISP verified PreScheme compiler

This paper describes a verified compiler for PreScheme, the implementation language for thevlisp run-time system. The compiler and proof were divided into three parts: A transformational front end that translates source text into a core language, a syntax-directed compiler that translates the core language into a combinator-based tree-manipulation language, and a linearizer that translates combinator code into code for an abstract stored-program machine with linear memory for both data and code. This factorization enabled different proof techniques to be used for the different phases of the compiler, and also allowed the generation of good code. Finally, the whole process was made possible by carefully defining the semantics ofvlisp PreScheme rather than just adopting Scheme's. We believe that the architecture of the compiler and its correctness proof can easily be applied to compilers for languages other than PreScheme.This work was supported by Rome Laboratory of the United States Air Force, contract No. F19628-89-C-0001, through the MITRE Corporation, and by NSF and DARPA under NSF grants CCR-9002253 and CCR-9014603. Author's current address: Department of Computer Science and Engineering, Oregon Graduate Institute, P.O. Box 91000, Portland, OR 97291-1000.The work reported here was supported by Rome Laboratory of the United States Air Force, contract No. F19628-89-C-0001. Preparation of this paper was generously supported by The MITRE Corporation.This work was supported by Rome Laboratory of the United States Air Force, contract No. F19628-89-C-0001, through the MITRE Corporation, and by NSF and DARPA under NSF grants CCR-9002253 and CCR-9014603.     

小议JavaScript库——Dojo、jQuery和PrototypeJS的比较

这是一篇小文章,讨论了JavaScript的应用库,JavaScript是最近两年飞速发展的技术领域,希望这篇文章能引发你的兴趣,帮助你进入这个领域。     

理解LINQ-to-SQL

大多数Web应用程序都是以数据驱动的,并且以关系数据库为中心。然而,多年来架构师已经设计了通过对象来建模问题域的应用程序。对象和关系数据库之间的通信一直都不流畅和简单。建立这类通信时遇到的困难通常称为“对象/关系阻抗失配”（O/ RM）。需要一个持久层来保存对象和从关系表载入对象。这些年来,产生了许多设计样式,为从事这项任务的架构师提供指南。现在,开发人员可以自己编写整个持久层,或者借助像NHibernate或Genome等O/RM工具的帮助,进行设计。     

An enhanced Support Vector Machine classification framework by using Euclidean distance function for text document categorization

This paper presents the implementation of a new text document classification framework that uses the Support Vector Machine (SVM) approach in the training phase and the Euclidean distance function in the classification phase, coined as Euclidean-SVM. The SVM constructs a classifier by generating a decision surface, namely the optimal separating hyper-plane, to partition different categories of data points in the vector space. The concept of the optimal separating hyper-plane can be generalized for the non-linearly separable cases by introducing kernel functions to map the data points from the input space into a high dimensional feature space so that they could be separated by a linear hyper-plane. This characteristic causes the implementation of different kernel functions to have a high impact on the classification accuracy of the SVM. Other than the kernel functions, the value of soft margin parameter, C is another critical component in determining the performance of the SVM classifier. Hence, one of the critical problems of the conventional SVM classification framework is the necessity of determining the appropriate kernel function and the appropriate value of parameter C for different datasets of varying characteristics, in order to guarantee high accuracy of the classifier. In this paper, we introduce a distance measurement technique, using the Euclidean distance function to replace the optimal separating hyper-plane as the classification decision making function in the SVM. In our approach, the support vectors for each category are identified from the training data points during training phase using the SVM. In the classification phase, when a new data point is mapped into the original vector space, the average distances between the new data point and the support vectors from different categories are measured using the Euclidean distance function. The classification decision is made based on the category of support vectors which has the lowest average distance with the new data point, and this makes the classification decision irrespective of the efficacy of hyper-plane formed by applying the particular kernel function and soft margin parameter. We tested our proposed framework using several text datasets. The experimental results show that this approach makes the accuracy of the Euclidean-SVM text classifier to have a low impact on the implementation of kernel functions and soft margin parameter C.     

如何在选用数据集与集合之间做出决策

在软件行业中，五年就像是一个地质时代。五年前，Microsoft宣布了自己的Micorsoft．NET Framework计划。从那以后，DataSet（数据集）才开始作为关键对象出现在基于．NET的应用程序中，执行多种数据相关的任务。也是五年前，DataSet被誉为ADO记录集（Recordset）的威力增强版。那么在．NET Framework出现之前，您是如何设计数据访问层（DAL，Data Access Layer）的呢？我想您一定是以ADO和它全能的Recordset对象——断开的、且可进行XML序列化的——为中心构建数据访问层。     

Nano and Microtechnologies for the Study of Magnetotactic Bacteria

Magnetotactic bacteria (MTB) naturally synthesize magnetic nanoparticles that are wrapped in lipid membranes. These membrane‐bound particles, which are known as magnetosomes, are characterized by their narrow size distribution, high colloidal stability, and homogenous magnetic properties. These characteristics of magnetosomes confer them with significant value as materials for biomedical and industrial applications. MTB are also a model system to study key biological questions relating to formation of bacterial organelles, metal homeostasis, biomineralization, and magnetoaerotaxis. The similar size scale of nano and microfluidic systems to MTB and ease of coupling to local magnetic fields make them especially useful to study and analyze MTB. In this Review, a summary of nano‐ and microtechnologies that are developed for purposes such as MTB sorting, genetic engineering, and motility assays is provided. The use of existing platforms that can be adapted for large‐scale MTB processing including microfluidic bioreactors is also described. As this is a relatively new field, future synergistic research directions coupling MTB, and nano‐ and microfluidics are also suggested. It is hoped that this Review could start to bridge scientific communities and jump‐start new ideas in MTB research that can be made possible with nano‐ and microfluidic technologies.     

User Interfaces for Complex Engineering Software: Application of Virtual Reality

IT systems for engineers are becoming more numerous and complex and will further proliferate in the future. It is infeasible to expect users to be trained to work with a plethora of systems, especially as many of them will only see occasional use. Therefore, in the near future, systems will need user interfaces that allow intuitive access and usage. This paper examines a new style of user interface based on virtual reality.     

Kinetic and reaction mechanisms of calcium bisulfite catalytic oxidation

In this paper, the oxidation of calcium bisulfite in the presence of ferrous ions as a catalyst is studied in a laboratory scale apparatus at a fixed oxygen partial pressure (21.3 kPa) and at a temperature of 45 °C. The analysis of the experimental results, carried out by using the theory of mass transfer with chemical reaction, indicates that the slow reaction regime has been explored, and the transition from the kinetic to the diffusional subregime identified. A kinetic analysis allows to develop a reaction rate equation, assuming that the bisulfite oxidation in the presence of ferrous ions follows a parallel reaction mechanism; the resulting overall reaction rate has been found to be of first order with respect to ferrous ion concentration and of three halves with respect to bisulfite concentration. Moreover, the catalytic effect of ferrous ions has been compared with that of manganese ions previously studied, showing that ferrous is a catalyst more active than manganese.