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Nomenclatura Unesco > (22) Física > (2203) Electrónica
(2203.01) Circuitos (2203.02) Elementos de circuitos
(2203.03) Válvulas electrónicas (2203.04) Microscopía electrónica
(2203.05) Estados electrónicos (2203.06) Transporte de electrones
(2203.07) Circuitos integrados (2203.08) Fotoelectricidad
(2203.09) Piezoelectricidad (2203.99) Otras (especificar)

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(3307) Tecnología electrónica

Mostrando recursos 1 - 20 de 180,455

1. The Formal Verification of a Payment System - Ross Anderson
. We describe what we believe was the first use of formal methods to verify a bank payment system. This was an electronic purse for offline small-to-medium value payments, and has since developed into the VISA COPAC product. We verified it using a variant of the BAN logic. 1 Introduction UEPS, the Universal Electronic Payment System, was an electronic funds transfer product designed for use in developing countries, where poor telecommunications make offline operation necessary. It was built around smartcard based electronic wallet functions: money is loaded from the bank, via bank cards, to customer cards, to merchant cards, and...

2. Code Generation for Embedded Processors: An Introduction - P. Marwedel
Introduction P. Marwedel 1 New, flexible target technologies As the tendency towards more complex electronic systems continues, many of these systems are equipped with embedded processors. For example, such processors can be found in cars, and in audio-, video-, and telecommunication-equipment. Essential advantages of these processors include their high flexibility, short design time and (in the case of off-the-shelf processors) full-custom layout quality. Furthermore, they allow an easy implementation of optional product features as well as easy design correction and upgrading. Furthermore, processors are frequently used in cases where the systems must be extremely dependable 1 [32]. In such cases,...

3. Memory Organization for Improved Data Cache Performance in Embedded Processors - Preeti Ranjan Panda; Nikil D. Dutt; Alexandru Nicolau; Ru Nicolau
Code generation for embedded processors creates opportunities for several performance optimizations not applicable for traditional compilers. We present techniques for improving data cache performance by organizing variables declared in embedded code into memory, using specific parameters of the data cache. Our approach clusters variables to minimize compulsory cache misses, and solves the memory assignment problem to minimize conflict cache misses. Our experiments demonstrate significant improvement in data cache performance (average 46% in hit ratios) by the application of our memory organization technique using code kernels from DSP and other domains on the LSI Logic CW4001 embedded processor. 1. Introduction Embedded...

4. Transport properties near the Anderson transition - C. Villagonzalo; R.A. Römer; M. Schreiber
. The electronic transport properties in the presence of a temperature gradient rT in disordered systems near the metal-insulator transition (MIT) are considered. The d.c. conductivity oe, the thermoelectric power S, the thermal conductivity K and the Lorenz number L0 are calculated for the three-dimensional (3D) Anderson model of localization using the Chester-Thellung-Kubo-Greenwood formulation of linear response. We show that oe, S, K and L0 can be scaled to one-parameter scaling curves with a single scaling parameter kBT=j(¯ \Gamma Ec)=Ec j. Keywords: disordered solids, metal-insulator transitions, thermoelectric conduction PACS: 61.43.--j, 71.30.+h, 72.15.Cz 1 Introduction In this paper we shall demonstrate...

5. Preconditioning Techniques for Constrained Vector Potential Integral Equations, with Application to 3-D Magnetoquasistatic Analysis of Electronic Packages - M. Kamon; J. R. Phillips
. In this paper techniques are presented for preconditioning equations generated by discretizing constrained vector integral equations associated with magnetoquasistatic analysis. Standard preconditioning approaches often fail on these problems. We present a specialized preconditioning technique and prove convergence bounds independent of the constraint equations and electromagnetic excitation frequency. Computational results from analyzing several electronic packaging examples are given to demonstrate that the new preconditioning approach can sometimes reduce the number of GMRES iterations by more than an order of magnitude. 1. Introduction. The recently developed multipole-accelerated iterative methods for solving potential integral equations have renewed interest in using discretized integral...

6. Middle-Agents for the Internet - Keith Decker; Katia Sycara; Mike Williamson
Like middle-men in physical commerce, middleagents support the flow of information in electronic commerce, assisting in locating and connecting the ultimate information provider with the ultimate information requester. Many different types of middleagents will be useful in realistic, large, distributed, open multi-agent problem solving systems. These include matchmakers or yellow page agents that process advertisements, blackboard agents that collect requests, and brokers that process both. The behaviors of each type of middle-agent have certain performance characteristics---privacy, robustness, and adaptiveness qualities---that are related to characteristics of the external environment and of the agents themselves. For example, while brokered systems are more...

7. A Study of User Participation in Standards Setting - Kai Jakobs; Rob Procter; Robin Williams
This paper explores the views of members of standards setting organisations in the field of electronic communications. It focuses in particular on their experiences of, and attitudes towards, user participation in standards setting. KEYWORDS: standardisation, e-mail, user requirements INTRODUCTION AND MOTIVATION Conventional approaches to the usability of IT privilege the role of design. Elsewhere we have argued for a broader perspective that addresses the whole of the technology life cycle [3]. For example, many important decisions have already been made before designers begin their task. As a result, IT design work increasingly incorporates, and is structured around, standard components which...

8. Visualizing Electronic Document Repositories: Drawing Books And Papers In A Digital Library - Andreas Rauber; Harald Bina
While methods for retrieving documents from large information repositories have improved a lot, presentation of the retrieved documents still leaves a lot to be desired. Important information on documents is usually presented as a textual listing of available metadata attributes such as document size, author information, date of creation, and so on. This requires the user to read and abstract from the presented metainformation. In this paper we present our libViewer system, a Java-Applet interfacing with a number of servers to provide an intuitive metaphor-graphics based representation of document repositories. Contrary to most other multidimensional data visualization approaches we rely...

9. Issues in Automated Negotiation and Electronic Commerce: Extending the Contract Net Framework - Tuomas Sandholm; Tuomas S; Victor Lesser
In this paper we discuss a number of previously unaddressed issues that arise in automated negotiation among self-interested agents whose rationality is bounded by computational complexity. These issues are presented in the context of iterative task allocation negotiations. First, the reasons why such agents need to be able to choose the stage and level of commitment dynamically are identified. A protocol that allows such choices through conditional commitment breaking penalties is presented. Next, the implications of bounded rationality are analyzed. Several tradeoffs between allocated computation and negotiation benefits and risk are enumerated, and the necessity of explicit local deliberation control...

10. Compliance Checking in the PolicyMaker Trust Management System - Matt Blaze; Joan Feigenbaum; Martin Strauss
. Emerging electronic commerce services that use public-key cryptography on a mass-market scale require sophisticated mechanisms for managing trust. For example, any service that receives a signed request for action is forced to answer the central question "Is the key used to sign this request authorized to take this action?" In some services, this question reduces to "Does this key belong to this person?" In others, the authorization question is more complicated, and resolving it requires techniques for formulating security policies and security credentials, determining whether particular sets of credentials satisfy the relevant policies, and deferring trust to third parties....

11. Users And Standardisation -- Worlds Apart? The Example Of Electronic Mail - Kai Jakobs; Rob Procter; Robin Williams
This paper reports and analyses the views of long-standing active members of standards setting working groups in the field of electronic communications. We focus in particular on their experiences of, and attitudes towards, user participation in standardisation. The results reveal attitudes that differ considerably from the official statements.To complement the views of standards professionals, we then explore the attitude of large corporate e-mail users towards standardisation in general, the impact standards have on their decisions regarding choice of corporate systems, and their apparent reluctance to play an active role in standardisation. This includes a closer look at the ways in...

12. Simulation of the Shielding Effectiveness of Cabinets Used in Communications Equipment - Vladica Trenkic; Christos Christopoulos; Trevor M. Benson
The basic formulations used in the description of thin walls and small apertures in simulations based on the Transmission-Line Modelling (TLM) method are described. It is shown that efficient and accurate methods are available which exhibit a reasonable balance between accuracy and computational efficiency. Results of simulations are presented showing the shielding effectiveness of cabinets. I Introduction Of all aspects of design influencing the electromagnetic compatibility (EMC) of equipment, electromagnetic shielding is the one in which the EMC designer has the maximum degree of control. EMC problems occur because a source of electromagnetic interference (EMI) affects, through coupling paths, the...

13. Fast Electronic Digital Image Stabilization - Carlos Morimoto; Rama Chellappa
We present a fast implementation of an electronic digital image stabilization system that is able to handle large image displacements. The system has been implemented in a parallel pipeline image processing hardware (Datacube Max Video 200) connected to a SUN SPARCstation 20/612. Our technique is based on a 2D feature-based multi-resolution motion estimation algorithm, that tracks a small set of features to estimate the motion of the camera. The combination of the estimates from a reference frame is used to warp the current frame in order to achieve stabilization. Experimental results using video sequences taken from a camera mounted on...

14. HyperAudio: Location-Awareness + Adaptivity - Daniela Petrelli; Elena Not; Marcello Sarini; Oliviero Stock; Massimo Zancanaro
The HyperAudio system aims at better supporting a user while visiting a museum by combining location awareness and information adaptation. This mixing of information delivery and physical space proposes new challenges for an effective human-computer-environment interaction. The HyperAudio solution interprets the visitor's behavior (i.e. physical and interactive) to create on the fly object presentations on the basis of the user model, the physical context and the history of interaction. Keywords Location aware systems, adaptive hypermedia, user modeling, intelligent interfaces, mobile devices. INTRODUCTION Recently, many works investigated location-aware systems for augmenting the environment to support users in their everyday activities or...

15. A Practical Introduction to SGML - Michel Goosens; Janne Saarela
SGML, the Standard Generalized Markup Language, deals with the structural markup of electronic documents. It was made an international standard by ISO in October 1986. SGML soon became very popular thanks in particular to its enthusiastic acceptance in the editing world, by large multi-national companies, governmental organizations, and, more recently, by the ubiquity of HTML, HyperText Markup Language, the source language of structured documents on WWW. This article discusses the basic ideas of SGML and looks at a few interesting tools. It should provide the reader with a better understanding of the latest developments in the field of electronic documents...

16. Evolving Electronic Robot Controllers that Exploit Hardware Resources - Adrian Thompson
. Artificial evolution can operate upon reconfigurable electronic circuits to produce efficient and powerful control systems for autonomous mobile robots. Evolving physical hardware instead of control systems simulated in software results in more than just a raw speed increase: it is possible to exploit the physical properties of the implementation (such as the semiconductor physics of integrated circuits) to obtain control circuits of unprecedented power. The space of these evolvable circuits is far larger than the space of solutions in which a human designer works, because to make design tractable, a more abstract view than that of detailed physics must...

17. The Functional Rent Advisor - Slim Abdennadher; Tim Geisler; Sven Panne
Most cities in Germany regularly publish a booklet called "Mietspiegel" that allows calculating an estimate of the fair rent for a flat. The Functional Rent Advisor (FRA) extends the functionality and applicability of the "Mietspiegel" for the city of Munich so that the user needs not to give all required information. The FRA is implemented using the highlevel purely functional language Haskell. This paper shows that Haskell is appropriate to realize non-trivial Internet applications. Simplicity, flexibility, and rapid prototyping were the advantages of using Haskell. 1 Introduction The Functional Rent Advisor (FRA) is the electronic version of the "Mietspiegel "...

18. The Flood-Gate Principle - a Hybrid Approach to a High Security Solution - Ernst-georg Haffner; Thomas Engel; Christoph Meinel
. The classical role of a firewall consists in protecting a computer network against attacks from the outside world, especially the Internet. Firewalls are often expensive, hard to configure and they are comprehended only by experts. Sometimes the level of security is too high to use a firewall, and information flow has not to be "online". Here we propose to use "floodgates " as described in the following. They provide a modern, simple and easyto -understand method to secure a network on a very high security level. Emails, plain files and all sorts of electronic data can be exchanged over...

19. Experiences from Deploying CBR Applications in Electronic Commerce - Mario Lenz
. Today, Electronic Commerce applications are among the most promising application areas of Case-Based Reasoning. When developing Electronic Commerce applications, very often technical issues are addressed very carefully, such as the particular implementation of the underlying CBR system. On the other hand, problems of system deployment sometimes are not paid suÆcient attention. In this article, we will discuss some of the major problems that occurred in one of our projects, and we will report the decisions taken to overcome these diÆculties. Keywords: Case-Based Reasoning, Electronic Commerce. 1 Introduction Due to the wide spread availability of the World Wide Web, a...

20. Low Power Mapping of Behavioral Arrays to Multiple Memories - Preeti Ranjan Panda; Nikil D. Dutt
Large data arrays in behavioral specifications are usually mapped to off-chip memories during system synthesis. We address the problem of system power reduction through transition count minimization on the address bus during memory accesses, when mapping behavioral arrays to multiple memory modules drawn from a library. We formulate the problem as three logical-tophysical memory mapping subtasks, provide algorithms for each subtask, and present experiments that demonstrate the transition count reductions based on our approach. Our experiments show a transition count reduction by a factor of 1.5--6.7 over a straightforward mapping scheme. 1 Introduction and Related Work The increasing demand for...

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