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Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 59-61). Also available in electronic version. Access restricted to campus users.

This report presents a study of digital predistortion of analog amplifiers and the simulation of a digital predistorter. Predistortion can be of significant benefit in wireless transmitters. As power consumption is becoming a greater concern, digital predistortion helps maximize power efficiency of power amplifiers by allowing them to operate in their most efficient regions while not corrupting data. Many wireless standards use channels with frequency carriers in close proximity to other channels. This leads to the necessity to ensure that spectral regrowth, which adds interference to neighboring frequencies, does not occur. Digital predistortion is a promising method to achieve this. Some major aspects of a predistortion system are discussed. These include the analog or digital predistorter implementation, simulating designs with memory or memoryless power amplifiers, baseband or high frequency predistortion, and training a predistorter. / text

For more than a decade, the separate fields of legislation and cryptography have contributed to the development of electronic signatures from divergent perspectives. Research on legislation establishes the legal requirements for electronic signatures, which have been stipulated in legislative frameworks. Research on cryptography mainly focuses on the development of algorithms to enhance the security and efficiency of the methods adopted to generate electronic signatures, for instance, cryptographic signature schemes. This research draws together the knowledge from both of these fields and takes an integrated approach to assess whether a signature scheme is capable of generating electronic signatures satisfying the legal requirements. This research first identifies and consolidates the legal requirements for electronic signatures in three commonly used legislative frameworks. Based on these requirements, an assessment mechanism called LCD assessment is formalized to evaluate the eligibility of signature schemes in generating legally recognized electronic signatures. Results show that when the LCD assessment is applied to several provably secure signature schemes, one of these schemes does not adequately satisfy the assessment. This significant finding suggests that even a provably secure signature scheme is not necessarily capable of generating legally recognized electronic signatures. Furthermore, electronic signature legislation has been promulgated in many countries. Due to variations in legislation, countries enforce different regulations and divergent standards for electronic signatures. Such enforcement will prevent an electronic signature from being used across the border if the signature cannot simultaneously fulfill multiple regulatory requirements and standards. This issue creates the interoperability problem of public key infrastructure (PKI). Several major countries have attempted to address this problem through adopting different interoperability models. These models are analyzed in this study and the results suggest that the models can only achieve PKI interoperability at a regional level. A new unified PKI framework is proposed with a vision to enhance the PKI interoperability through harmonizing the practices and standards at an international level. Such a framework not only addresses the technical issues for electronic signatures, but also eliminates the legal uncertainties of the use of signature schemes through incorporating the LCD assessment. The outcomes of this research are therefore twofold. First, the LCD assessment provides a mechanism to assess the eligibility of signature schemes from a legal perspective. Second, the new unified PKI framework begins to resolve the issues in cross-border use of electronic signatures through a multi-discipline approach. In addressing the interaction between legislation and technology for electronic signatures, the wider use of electronic signatures in global electronic commerce is envisaged. / published_or_final_version / Computer Science / Doctoral / Doctor of Philosophy

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Even though Latin America is one of the developing regions with excellent regional cooperative bibliographic databases, which is mainly due to the common use of Spanish and Portuguese in countries of the region, access to the printed documents mentioned in the bibliographies is a privilege for a very few. Very slowly Internet is being introduced as a regular service for students, professors and researchers working in Latin American academic institutions, as well as being introduced as a platform for e-publishing and offering digital library services to users. In this context of growing e-publishing and digital libraries initiatives to provide open access to research results, CLACSO (an academic network gathering 173 social science research institutions from 21 countries of Latin America and the Caribbean) decided to build a cooperative digital library with open source Greenstone software to facilitate integrated access to full-text books, articles, papers and working documents of its member institutes.

Digital Library for Earth Science Education, DLESE / The National Science Foundation's (NSF) National Science, Technology, Engineering, and Mathematics Education Digital Library (NSDL) program comprises a set of projects engaged in a collective effort to build a national digital library of high quality science, technology, engineering, and mathematics (STEM) educational materials for students and teachers at all levels, in both formal and informal settings. By providing broad access to a rich, reliable, and authoritative collection of interactive learning and teaching resources and associated services in a digital environment, the NSDL will encourage and sustain continual improvements in the quality of STEM education for all students, and serve as a resource for lifelong learning. Though the program is relatively new, its vision and operational framework have been developed over a number of years through various workshops and planning meetings. The NSDL program held its first formal funding cycle during fiscal year 2000, accepting proposals in four tracks: Core Integration System, Collections, Services, and Targeted Research. Twenty-nine awards were made across these tracks in September 2000.

The US National Science Foundation has established a program to create a National Science, Mathematics, Engineering and Technology Education Digital Library (NSDL). One of the subsidiary NSDL libraries under development is the National Civil Engineering Educational Resources Library (NCERL). The first phase of NCERL is the creation and collection of digital resources in three areas of civil engineeringâ geotechnical (soil), rock, and water engineering (GROW). The concept of interactivities guides the design, development, and evaluation efforts of the GROW digital collection. This article describes the salient features of GROW, defines and discusses interactivities as an emerging, integral part of teaching and learning in civil engineering education. Interactivities take place at three distinct levels: the information resource, the collection, and the context. Very simply, the concept of interactivities can be defined as the emphasis on structured representations of interactive multimedia resources. Additionally, resources are designed with rich learning tasks and organized in pedagogical collections supplemented with contextual information. Preliminary evaluation of GROW-NCERL using interactivities is briefly described.

It has often been said that the library is the heart of the university. As the central repository of recorded knowledge on campus, the library is an essential resource for scholarly activity, and one measure of the greatness of a university is its library's collections. As electronic publishing expands and universities become computer-intensive organizations, what will the academic library's role be in this dynamic, technology-driven environment? Will it still be the heart of the university? This paper examines the medium-term future (10-15 years) of electronic publishing, the emerging "electronic university," and integrated public-access computer systems. Its central theme is that the academic library can synergetically combine traditional collections and services with new computer-based information resources and services to create a unified information system. By employing this strategy, it can continue to be the heart of the evolving electronic university.