Sampling and Probe Methods – An Algorithmical View

Inverse scattering problems are concerned with the reconstruction of objects and parameter functions from the knowledge of scattered waves. Today, basically three different categories of methods for the treatment of the full nonlinear scattering problem are known: iterative methods, decomposition methods and sampling/probe methods. Sampling and probe methods have been proposed to detect the unknown scatterer for example in cases when the physical properties are not known or not given in a parametrized modell. A number of different approaches have been suggested over the last years. We will give a survey about these methods and explain the main ideas from an algorithmical point of view. We will group and describe the methods and discuss some relations to ideas which have been developed in the framework of impedance tomography. First, we will study the probe method of Ikehata and the singular sources method of Potthast. We show that these methods are closely related and basically form one unit with two different realizations. The second part is concerned with the range test of Potthast, Sylvester and Kusiak, the linear sampling method of Colton and Kirsch and the factorization method of Kirsch. These methods are founded on similar ideas testing the range of operators for reconstruction. In the final part we study the no response test of Luke and Potthast and the enclosure method of Ikehata. We will see that the enclosure method can be considered as a particular choice of the probing function for the no response test. These two methods are closely related and form two extremes for probing a scatterer with specially constructed waves.     

Preface to a special section on verification,model checking,and abstract interpretation

This special section features six papers concerned with state-of-the-art research in verification, model checking, and abstract interpretation; three research areas that share the goal to provide mathematically well-founded techniques for sound semantic analysis of computer systems. While each area takes a particular view on this problem, there is a growing awareness that a closer collaboration is fruitful and in the last decade methods that combine ideas from different areas have been developed. The papers in this special section are carefully revised and extended versions of articles that have first been presented at the VMCAI 2009 conference.     

Authority and convergence in collaborative learning

Teachers and students have established social roles, norms and conventions when they encounter Computer-Supported Collaborative Learning (CSCL) systems in the classroom. Authority, a major force in the classroom, gives certain people, objects, representations or ideas the power to affect thought and behavior and influences communication and interaction. Effective computer-supported collaborative learning requires students and teachers to change how they understand and assign authority. This paper describes two studies in which students' ideas about authority led them to converge on what they viewed as authoritative representations and styles of representation too early, and the early convergence then hindered their learning. It also describes a third study that illustrates how changes to the CSCL system CAROUSEL (Collaborative Algorithm Representations Of Undergraduates for Self-Enhanced Learning) improved this situation, encouraging students to create representations that were unique, had different styles and emphasized different aspects of algorithms. Based on this research, methods to help students avoid premature convergence during collaborative learning are suggested.     

Special section on testing and security of Web systems

This special section is devoted to a selection of papers that have been originally published in the Proceedings of the International Workshop on Web Quality, Verification and Validation (WQVV) held in Como, Italy, in July 2007. The workshop was part of the Seventh International Conference on Web Engineering (ICWE 2007). These papers investigate different issues of two fundamental “aspects” of quality and dependability of modern Web systems: testing and security. The main contribution of this special section consists in trying to bring the gap between research and “industrial” practice in Web systems. The use of new technologies, tools and methodologies is increasing in the Web and it makes the systems more and more interactive and responsive than in the past. Therefore, limits and problems related to specific aspects of systems quality and dependability are investigated, and new approaches and ideas are proposed to overcome such limitations.     

The distributed data-base for the CERN SPS control system

The present paper describes how some generally accepted ideas on distributed computing systems and data bases have been implemented at the CERN SPS accelerator.     

Effective Memory' and Turing's model of mind

In the first section of his celebrated 1936 paper A. Turing says of the machines he defines that at each stage of their operation they can ‘effectively remember’ some of the symbols they have scanned before. In this paper I explicate the motivation and content of this remark of Turing's, and argue that it reveals what could be labeled as a connectionist conception of the human mind.     

Geometric analysis of nondeterminacy in dynamical systems

This article intends to provide some new insights into concurrency using ideas from the theory of dynamical systems. Inherently discrete concurrency corresponds to a parallel continuous concept: a discrete state space corresponds to a differential manifold, an execution path corresponds to a flow line of a dynamical system. To model non-determinacy within dynamical systems, we introduce a new geometrical object, a section cone. A section cone is a convex set in the space of vector fields, all elements having the same singular points. We show that it is enough to consider flow lines of a single vector field in order to capture the behavior of all flow lines in the section cone up to homotopy (corresponding to equivalence of executions).     

IP报文分类算法综述与评价

本文主要从各算法所依赖的主要数据结构及核心思想的角度将现有的一些有效算法进行分类说明，提出对算法进行分析评价的体系和方法，从理论上比较了各算法的性能优势、适用情况和存在问题，并介绍相关的TCAM技术在分类算法中的应用。最后，本文分析并总结了今后设计高效分类算法较为有效的研究思路。     

A Library Hierarchy for Implementing Scalable Parallel Search Algorithms

This paper describes the design of the Abstract Library for Parallel Search (ALPS), a framework for implementing scalable, parallel algorithms based on tree search. ALPS is specifically designed to support data-intensive algorithms, in which large amounts of data are required to describe each node in the search tree. Implementing such algorithms in a scalable manner is challenging both because of data storage requirements and communication overhead. ALPS incorporates a number of new ideas to address this challenge. The paper also describes the design of two other libraries forming a hierarchy built on top of ALPS. The first is the Branch, Constrain, and Price Software (BiCePS) library, a framework that supports the implementation of parallel branch and bound algorithms in which the bounds are obtained by solving some sort of relaxation, usually Lagrangian. In this layer, the notion of global data objects associated with the variables and constraints is introduced. These global objects provide a connection between the various subproblems in the search tree, but they pose further difficulties for designing scalable algorithms. The other library is the BiCePS linear integer solver (BLIS), a concretization of BiCePS, in which linear programming is used to obtain bounds in each search tree node.     

A CLP framework in Java

This paper discusses some basic ideas about the implementation of GC, a constraint propagation system, with three different implementations of finite variables domains. As it has been our wish to develop a system that uses the OO approach, it is implemented in Java, although other application frameworks are also available for C++.The constraint propagation and variables domains are explained at the application and implementation level and some examples from the litterature are presented in order to clarify the construction of applications with GC.     

Matching typed and untyped realizability

Realizability interpretations of logics are given by saying what it means for computational objects of some kind to realize logical formulae. The computational objects in question might be drawn from an untyped universe of computation, such as a partial combinatory algebra, or they might be typed objects such as terms of a PCF-style programming language. In some instances, one can show that a particular untyped realizability interpretation matches a particular typed one, in the sense that they give the same set of realizable formulae. In this case, we have a very good fit indeed between the typed language and the untyped realizability model — we refer to this condition as (constructive) logical full abstraction.We give some examples of this situation for a variety of extensions of PCF. Of particular interest are some models that are logically fully abstract for typed languages including non-functional features. Our results establish connections between what is computable in various programming languages and what is true inside various realizability toposes. We consider some examples of logical formulae to illustrate these ideas, in particular their application to exact real-number computability.     

Formula databases for high-performance resolution/paramodulation systems

Over the past 25 years, researchers have written numerous deduction systems based on resolution and paramodulation. Of these systems, very few have been capable of generating and maintaining aformula database containing more than just a few thousand clauses. These few systems were used to explore mechanisms for rapidly extracting limited subsets of relevant clauses. We have developed a simple, powerful deduction system that reflects some of the best of the ideas that have emerged from the research. This paper describes that deduction system and casts the idea in a form that makes them easily accessible to researchers wishing to write their own high-performance systems.This work was partially supported by National Science Foundation grant CCR-8810947 and by the Office of Scientific Computing, U.S. Department of Energy under contract W-31-109-Eng-38.     

John Matthews Manly: The Collier's Articles

Abstract

In the fall of 1927, John Matthews Manly wrote a series of articles on contract for Collier's Magazine about the cryptographic section of the Military Intelligence Division of the U.S. Army during World War I. These articles were never published, and they disappeared until recently, when they were discovered in the William Friedman Collection at the George Marshall Foundation Library in Lexington, Virginia. This article describes how the articles were written, how they ended up in the Friedman Collection, and what they contain.     

Special section on Web Systems Evolution

Evolution of Web applications is high for several reasons. Among the others, the need of being constantly updated with the emerging technologies is maybe the most important. Web Systems Evolution is a multifaceted and broad field studying techniques, approaches and tools able to restructure, re-engineer and in general modify a Web application with the intention of renovating or improving some quality aspects of it. This special section is devoted to a selection of papers that have been originally published in the proceedings of the International Symposium on Web Site Evolution, held in Beijing, China in October 2008. The selected papers investigate different issues concerning the evolution of Web Systems, ranging from migration towards SOA to more classic re-engineering and maintenance tasks (e.g., improving the navigational structure). The main contribution of this special section consist of translating some interesting research ideas about Web systems evolution into solutions and tools able to transfer knowledge to the industry.     

可信计算的迅速发展及启示

首先阐述了当前可信计算技术迅速发展的原因,叙述了国内外可信计算的发展历史和现状;其次,根据其不同的特．最划分了可信计算理论和在技术国内外的发展阶段,并关注了产生这种发展历程差异的原因;最后,指出了目前我国信息产业面临的困境,并根据目前面临的形势和国内信息技术发展态势提出了解决思路。     

Collaborative conversational interfaces

This paper proposes a method of designing human-computer speech interfaces based on principles of human conversation. It argues that conversation is the primary mode of language use and that it is fundamentally collaborative. Speech interfaces should therefore be designed to recreate the collaborative nature of natural conversations. The paper presents five strategies for designingcollaborative conversational interfaces, and it describes the principles of human-language use that underly these strategies. The paper also argues that collaborative conversational interfaces have a crucial advantage over other kinds of interfaces in that they are readily adaptive to different levels of experience and styles of use. The paper gives examples of collaborative conversational interfaces that we have developed, and discusses the ways in which these interfaces have been made adaptive.     

Ground truth requirements for radar observations over land and seat†

Abstract

At a first stage of development, ground truth is gathered in conjunction with radar data in order to establish statistical correlations between observed backscatter and properties of the irradiated surface. Significant correlations have been shown to exist between backscatter and many geophysical quantities; for example scatterometer measurements over the ocean can be used to infer wind speed, synthetic aperture radar (SAR) measurements over woodland can allow the separation of tree species, etc. Once statistical relationships are established, the next stage is to try to understand the physics underlying the relationship, both because of its intrinsic interest and because of the need to optimize system performance for particular applications. This places a second role on ground truth, since it must be used to validate the physical theories stemming from it. Microwave scattering from land surfaces is a topic of growing interest as we look towards land observation missions within the coming decade. Several theories have been proposed to account for scattering from surfaces of a vegetation layer, but none of these has been rigorously tested. If they are to contribute effectively to future land missions, it is essential that such testing be carried out. The first section of this paper describes the requirements such testing will put on ground measurements, and tries to identify whether such measurements are feasible. Microwave scattering mechanisms from the sea surface, and particularly their effects on SAR images of waves, and clutter-statistics in SAR sea-surface images are still a matter of some debate. The second section of this paper outlines the problems inherent in sea imaging with SAR and describes experiments that need to be carried out in order that these questions can be resolved.     

Studying properties of classes of default logics

The study of different variants of default logic reveals not only differences but also properties they share. For example, there seems to be a close relationship between semi-monotonicity and the guaranteed existence of extensions. Likewise, formula-manipulating default logics tend to violate the property of cumulativity. The problem is that currently such properties must be established separately for each approach. This paper describes some steps towards the study of properties of classes of default logics by giving a rather general definition of what a default logic is. Essentially our approach is operational and restricts attention to purely formula-manipulating logics. We motivate our definition and demonstrate that it includes a variety of well-known default logics. Furthermore, we derive general results regarding the concepts of semi-monotonicity and cumulativity. As a benefit of the discussion we uncover that some design decisions of concrete default logics were not accidental as they may seem, but rather they were due to objective necessities.     

基于CPCI总线的异步串行模块设计

介绍了基于CPCI总线的异步串行模块的硬件设计与软件设计,其中,硬件设计部分描述了串行接口模块的硬件组成和寄存器定义;软件设计介绍了底层软件、中间件与应用层软件的设计思路,其中重点就底层软件设计,给出了设计方法与工作流程.经验证,该异步串行模块增加了串行通信的可靠性,满足四串口多线程同步满负荷运行的极端使用需求.目前,该模块已成功应用于工业测控等领域.