LA MAPOTECA VIRTUAL: UN EJEMPLO DE COLABORACIÓN BAJO UNA PLATAFORMA DE SOFTWARE LIBRE

La Mapoteca Virtual es un sitio web construido sobre la plataforma Joomla, auspiciado por la Escuela de Ciencias Geográfica de la Universidad Nacional, en colaboración con UNA VIRTUAL.Este sitio pretende apoyar la labor docente al permitirle cargar y difundir cartografía digital para los estudiantes, y a los investigadores les facilita la localización de cartografía en línea, necesaria para la realización de sus trabajos en diferentes áreas del conocimiento. Adicionalmente, es un espacio para presentar documentos actuales en relación a la práctica de la cartografía y ciencias conexas, a la vez que fomenta la colaboración y el acceso libre a cartografía digital.Palabras clave: Cartografía, Joomla, Mapas digitales, Herramientas didácticas en líneaAbstractThe Virtual Map Library, www.mapoteca.geo.una.ac.cr, is a website constructed on the Joomla platform and supported by the School of Geographic Sciences at National University, Costa Rica, in collaboration with UNAVIRTUAL. The site intends to support the work of education by allowing the teacher to load and disseminate digital cartography for the students and helping geographic investigators locate cartography needed to accomplish their works in different areas of knowledge.In addition, Mapoteca offers a space to present current  documents relating to the practice of cartography and related sciences that at the same time promotes the contribution and free access to digital cartography.Key Words: Cartography, Mapoteca Virtual, Virtual Map Library, Joomla, digital maps, online teaching tools, School of Geographic Sciences, National University, Costa Rica.

L'adeguamento di tradizionali laboratori europei di restauro fotochimico alle tecniche digitali

La presente ricerca ha avuto come obbietivo studiare come stia avvenendo l'adattamento dei tradizionali laboratori fotochimici di film alle tecniche digitali attraverso l'analisi delle politiche di preservazione, del restauro, dei costi relativi all’acquisto di nuove apparecchiature e della migrazione ai nuovi media presso il British Film Institute (BFI), lo Svenska Filminstitutet (SFI), l’Eye Filmmuseum, L'Immagine Ritrovata e ANIM - Cinemateca Portuguesa. A questo scopo è stato utilizzato il metodo dello studio di caso, in cui sono state effettuate interviste con gestori e tecnici delle istituzioni citate al fine di rispondere al quesito della presente ricerca: quali sono l’impatto e le implicazioni di questo adattamento? Quali sono i risultati raggiunti con le nuove attrezzature e metodi di restauro e preservazione? Per arrivare a rispondere a queste domande lo studio è stato diviso in due sezioni. Nella prima parte, sono riportate le interviste svolte presso SFI, BFI, Eye e L'Immagine Ritrovata, realizzate al fine di ottenere dati che permettessero di formulare un'intervista più completa e approfondita. Successivamente, questa intervista più dettagliata è stata condotta con una sola istituzione, la Cinemateca Portuguesa. Pertanto, nella seconda parte dello studio di caso, sono state realizzate interviste a tecnici e dirigenti di ANIM - Cinemateca Portuguesa e dei suoi laboratori partner. L'analisi dei risultati comprende tutte le informazioni provenienti dalle cinque istituzioni intervistate. È stato notato che l'adattamento al digitale ha effettivamente apportato miglioramenti nella preservazione e nel recupero del materiale fotochimico, ma ciò ha anche fatto sorgere alcuni dilemmi nei laboratori. C'è apprensione per la scarsità di materiale della filiera fotochimica e per una sua ipotetica fine nel prossimo futuro, poiché non ci sono ancora sufficienti conoscenze sulla filiera digitale e sul comportamento di questi media con il passare del tempo. Gli intervistati hanno altresì dimostrato positività riguardo alle tecnologie digitali.

Analisi dell'elettromigrazione in circuiti avanzati e possibili strategie per prevederne la comparsa

Il lavoro di tesi si è concentrato sull'applicazione di un innovativo modello per descrivere l'effetto a livello elettrico dell'elettromigrazione nelle linee di interconnessione. Sono stati analizzati gli effetti del guasto in alcuni blocchi circuitali analogici critici per sistemi elettronici ad alta affidabilità. Sono state quindi suggerite alcune soluzioni architetturali che consentano la rilevazione del guasto in tempo reale.

SI SC MDAC switched current-capacitor multiplying digital-to-analog converter

Dissertação apresentada para a obtenção do grau de Mestre em Engenharia Electrotécnica e de Computadores

Parametric analog signal amplification applied to nanoscale cmos wireless digital transceivers

Thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the subject of Electrical and Computer Engineering by the Universidade Nova de Lisboa,Faculdade de Ciências e Tecnologia

Digital Control Implementation to Reduce the Cost and Improve the Performance of the Control Stage of an Industrial Switched-Mode Power Supply

The main objective of this work is the design and implementation of the digital control stage of a 280W AC/DC industrial power supply in a single low-cost microcontroller to replace the analog control stage. The switch-mode power supply (SMPS) consists of a PFC boost converter with fixed frequency operation and a variable frequency LLC series resonant DC/DC converter. Input voltage range is 85VRMS-550VRMS and the output voltage range is 24V-28V. A digital controller is especially suitable for this kind of SMPS to implement its multiple functionalities and to keep the efficiency and the performance high over the wide range of input voltages. Additional advantages of the digital control are reliability and size. The optimized design and implementation of the digital control stage it is presented. Experimental results show the stable operation of the controlled system and an estimation of the cost reduction achieved with the digital control stage.

Digitally-implemented naturally sampled PWM suitable for multilevel converter control

For dynamic closed loop control of a multilevel converter with a low pulse number (ratio of switching frequency to synthesized fundamental), natural sampled pulse-width modulation (PWM) is the best form of modulation. Natural sampling does not introduce distortion or a delayed response to the modulating signal. However previous natural sampled PWM implementations have generally been analog. For a modular multilevel converter, a digital implementation has advantages of accuracy and flexibility. Re-sampled uniform PWM is a novel digital modulation technique which approaches the performance of natural PWM. Both hardware and software implementations for a five level multilevel converter phase are presented, demonstrating the improvement over uniform PWM.

Análise e implementação digital de uma malha de captura de fase para sincronização de conversores à rede elétrica

Dissertação para a obtenção do grau de Mestre em Engenharia Electrotécnica Ramo de Automação e Eletrónica Industrial

Projecto e implementação de osciloscópio digital baseado na norma IEEE1451.0

Os osciloscópios digitais são utilizados em diversas áreas do conhecimento, assumindo-se no âmbito da engenharia electrónica, como instrumentos indispensáveis. Graças ao advento das Field Programmable Gate Arrays (FPGAs), os instrumentos de medição reconfiguráveis, dadas as suas vantagens, i.e., altos desempenhos, baixos custos e elevada flexibilidade, são cada vez mais uma alternativa aos instrumentos tradicionalmente usados nos laboratórios. Tendo como objectivo a normalização no acesso e no controlo deste tipo de instrumentos, esta tese descreve o projecto e implementação de um osciloscópio digital reconfigurável baseado na norma IEEE 1451.0. Definido de acordo com uma arquitectura baseada nesta norma, as características do osciloscópio são descritas numa estrutura de dados denominada Transducer Electronic Data Sheet (TEDS), e o seu controlo é efectuado utilizando um conjunto de comandos normalizados. O osciloscópio implementa um conjunto de características e funcionalidades básicas, todas verificadas experimentalmente. Destas, destaca-se uma largura de banda de 575kHz, um intervalo de medição de 0.4V a 2.9V, a possibilidade de se definir um conjunto de escalas horizontais, o nível e declive de sincronismo e o modo de acoplamento com o circuito sob análise. Arquitecturalmente, o osciloscópio é constituído por um módulo especificado com a linguagem de descrição de hardware (HDL, Hardware Description Language) Verilog e por uma interface desenvolvida na linguagem de programação Java®. O módulo é embutido numa FPGA, definindo todo o processamento do osciloscópio. A interface permite o seu controlo e a representação do sinal medido. Durante o projecto foi utilizado um conversor Analógico/Digital (A/D) com uma frequência máxima de amostragem de 1.5MHz e 14 bits de resolução que, devido às suas limitações, obrigaram à implementação de um sistema de interpolação multi-estágio com filtros digitais.

Decay of unstable states in the presence of colored noise and random initial conditions. II. Analog experiments and digital simulations

The decay of an unstable state under the influence of external colored noise has been studied by means of analog experiments and digital simulations. For both fixed and random initial conditions, the time evolution of the second moment ¿x2(t)¿ of the system variable was determined and then used to evaluate the nonlinear relaxation time. The results obtained are found to be in excellent agreement with the theoretical predictions of the immediately preceding paper [Casademunt, Jiménez-Aquino, and Sancho, Phys. Rev. A 40, 5905 (1989)].

Low cost BIST techniques for linear and non-linear analog circuits

With the ever increasing demands for high complexity consumer electronic products, market pressures demand faster product development and lower cost. SoCbased design can provide the required design flexibility and speed by allowing the use of IP cores. However, testing costs in the SoC environment can reach a substantial percent of the total production cost. Analog testing costs may dominate the total test cost, as testing of analog circuits usually require functional verification of the circuit and special testing procedures. For RF analog circuits commonly used in wireless applications, testing is further complicated because of the high frequencies involved. In summary, reducing analog test cost is of major importance in the electronic industry today. BIST techniques for analog circuits, though potentially able to solve the analog test cost problem, have some limitations. Some techniques are circuit dependent, requiring reconfiguration of the circuit being tested, and are generally not usable in RF circuits. In the SoC environment, as processing and memory resources are available, they could be used in the test. However, the overhead for adding additional AD and DA converters may be too costly for most systems, and analog routing of signals may not be feasible and may introduce signal distortion. In this work a simple and low cost digitizer is used instead of an ADC in order to enable analog testing strategies to be implemented in a SoC environment. Thanks to the low analog area overhead of the converter, multiple analog test points can be observed and specific analog test strategies can be enabled. As the digitizer is always connected to the analog test point, it is not necessary to include muxes and switches that would degrade the signal path. For RF analog circuits, this is specially useful, as the circuit impedance is fixed and the influence of the digitizer can be accounted for in the design phase. Thanks to the simplicity of the converter, it is able to reach higher frequencies, and enables the implementation of low cost RF test strategies. The digitizer has been applied successfully in the testing of both low frequency and RF analog circuits. Also, as testing is based on frequency-domain characteristics, nonlinear characteristics like intermodulation products can also be evaluated. Specifically, practical results were obtained for prototyped base band filters and a 100MHz mixer. The application of the converter for noise figure evaluation was also addressed, and experimental results for low frequency amplifiers using conventional opamps were obtained. The proposed method is able to enhance the testability of current mixed-signal designs, being suitable for the SoC environment used in many industrial products nowadays.

DCM Boost interleaved converter for operation in AC and DC to trolleybus application

This paper is based on the development and experimental analysis of a DCM Boost interleaved converter suitable for application in traction systems of electrical vehicles pulled by electrical motors (Trolleybus), which are powered by urban DC or AC distribution networks. This front-end structure is capable of providing significant improvements in trolleybuses systems and in the urban distribution network costs, and efficiency. The architecture of proposed converter is composed by five boost power cells in interleaving connection, operating in discontinuous conduction mode. Furthermore, the converter can operate as AC-DC converter, or as DC-DC converter providing the proper DC output voltage range required by DC or AC adjustable speed drivers. Therefore, when supplied by single-phase AC distribution networks, and operating as AC-DC converter, it is capable to provide high power factor, reduced harmonic distortion in the input current, complying with the restrictions imposed by the IEC 61000-3-4 standards. The digital controller has been implemented using a low cost FPGA and developed totally using a hardware description language VHDL and fixed point arithmetic. Thus, two control strategies are evaluated considering the compliance with input current restrictions imposed by IEC 61000-3-4 standards, the regular PWM modulation and a current correction PWM modulation. In order to verify the feasibility and performance of the proposed system, experimental results from a 15 kW low power scale prototype are presented, operating in DC and AC conditions.

The ZVS-PWM commutation cell applied to the DC-AC converter

This paper presents the analysis of a dc-ac converter using a zero-voltage-switching (ZVS) commutation cell. First, we show the cell applied to the buck converter. The stages of operation are presented along with the main current and voltage equations. Next, we adapt the converter to the regenerative-operation mode. Hence, the full-bridge converter at low-frequency operation is connected in the dc-dc output stage (at high frequency). The main switches commute at zero voltage. The converter operated at constant frequency with pulse-width modulation (PWM), and neither overvoltage nor additional current stress was observed by digital simulation. A design example and experimental results obtained by prototype, rated at 275 V and 1 kW, are also presented. © 1997 IEEE.

Generating VHDL-AMS models of digital-to-analogue converters from MATLAB®/SIMULINK®

Today, the trend within the electronics industry is for the use of rapid and advanced simulation methodologies in association with synthesis toolsets. This paper presents an approach developed to support mixed-signal circuit design and analysis. The methodology proposed shows a novel approach to the problem of developing behvioural model descriptions of mixed-signal circuit topologies, by construction of a set of subsystems, that supports the automated mapping of MATLAB®/SIMULINK® models to structural VHDL-AMS descriptions. The tool developed, named MS 2SV, reads a SIMULINK® model file and translates it to a structural VHDL-AMS code. It also creates the file structure required to simulate the translated model in the System Vision™. To validate the methodology and the developed program, the DAC08, AD7524 and AD5450 data converters were studied and initially modelled in MATLAB®/ SIMULINK®. The VHDL-AMS code generated automatically by MS 2SV, (MATLAB®/SIMULINK® to System Vision™), was then simulated in the System Vision™. The simulation results show that the proposed approach, which is based on VHDL-AMS descriptions of the original model library elements, allows for the behavioural level simulation of complex mixed-signal circuits.

Computational tool to support design of DAC Converter model AD7528 with the object code in XML

Based on literature review, electronic systems design employ largely top-down methodology. The top-down methodology is vital for success in the synthesis and implementation of electronic systems. In this context, this paper presents a new computational tool, named BD2XML, to support electronic systems design. From a block diagram system of mixed-signal is generated object code in XML markup language. XML language is interesting because it has great flexibility and readability. The BD2XML was developed with object-oriented paradigm. It was used the AD7528 converter modeled in MATLAB / Simulink as a case study. The MATLAB / Simulink was chosen as a target due to its wide dissemination in academia and industry. From this case study it is possible to demonstrate the functionality of the BD2XML and make it a reflection on the design challenges. Therefore, an automatic tool for electronic systems design reduces the time and costs of the design.