This article provides an overview of recent developments relating to the application of thesauri in information organisation and retrieval on the World Wide Web. It describes some recent thesaurus projects undertaken to facilitate resource description and discovery and access to wide-ranging information resources on the Internet. Types of thesauri available on the Web, thesauri integrated in databases and information retrieval systems, and multiple-thesaurus systems for cross-database searching are also discussed. Collective efforts and events in addressing the standardisation and novel applications of thesauri are briefly reviewed.

From the early information retrieval systems to recent web search engines, most systems ask user to express their information need in a query. While the online information systems, such as search engines and digital libraries, bring the great opportunity of accessing huge amount of information directly, they also present challenges on users’ competence of formulating good queries. In library, thesauri and classification schemes are not only indexing tools, but also concept consultation tools. Thesauri and classification schemes haven’t fully adapted in to digital library and IR system, because there are not universal concept hierarchies. This essay introduces the ideal of using query-based concept structures to improve subject access to digital libraries. It reports some early work of an ongoing project that explores the usability and effectiveness of query-based concept structures, which naturally connects static knowledge in the information collection and user dynamic information need, as intermediary. Methodologies and experimental designs are laid out. The preliminary results are presented and further research is discussed.

Conference is sponsored by the Library of Congress Cataloging Directorate. / The decade of the 1990s saw the development of a proliferation of metadata element sets for resource description. This paper looks at a subset of these metadata schemes in more detail: the TEI header, EAD, Dublin Core, and VRA Core. It looks at why they developed as they did, major points of difference from traditional (AACR2/MARC) library cataloging, and what advantages they offer to their user communities. It also discusses challenges to implementers of these schemes and possible future developments. It goes on to identify some commonalties among these cases, and to attempt to generalize from these some lessons for developers of metadata element sets. It concludes by suggesting we also look carefully at emerging schemes being developed by publishers in support of electronic commerce and rights management, and think seriously about the implications of commodity metadata upon our traditional bibliographic apparatus.

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There is evidence for the existence of non-classical bonding in several binary antimonides, selenides, and tellurides. Owing to such non-classical bonding, some of these solid materials exhibit exciting semiconducting and thermoelectric properties, which make them attractive from a technological view point. However, lack of efficiency is a serious limitation in most of those thermoelectrics. It is very crucial, hence, to find new materials with superior properties and understand the structure and bonding in such materials, in order to facilitate the fine-tuning of the physical properties. With this expectation, several quaternary barium copper chalcogenides are synthesized and characterized in the present study. The chalcogen elements, selenium tellurium, are used in various ratios, in order to understand and tune the binding interactions. Extensive single crystal x-ray diffraction studies are expected to reveal the minute details of the bonding interactions together with electronic structure calculation and physical property measurements. In addition, characterization techniques such as powder x-ray diffraction, electron microscopy, differential scanning calorimetry, thermopower and conductivity measurements are utilized. The ternary and quaternary chalcogenides, Ba₂Cu₄₋ₓSeyTe₅₋y were synthesized from the elements in stoichiometric ratios at 700°C, followed by annealing at 600°C. The ternary telluride Ba₂Cu₄₋ₓTe₅ crystallizes in a new structure type, space group C2/c, with lattice dimensions of a = 9.4428(6) Å, b = 9.3289(6) Å, c = 13.3028(8) Å, β = 101.635(1)°, V = 1147.8(1) Å3, for x = 0.75(1) (Z = 4). The corresponding selenide-telluride adopts another new, but strongly related, structure type, space group P4₁2₁2, with a = 6.5418(3) Å, c = 25.782(2) Å, V = 1103.3(1) Å3, for Ba₂Cu₃.₂₆₍₂₎Se₀.₇₂₉₍₈₎Te₄.₂₇₁ (Z = 4). Between 0.13 and 1.0 Te per formula unit can be replaced with Se, while the Cu content appears to vary only within 0.67 ≤ x ≤ 0.81 for Ba₂Cu₄₋ₓSeyTe₅₋y. Despite crystallizing in different crystal systems, the telluride and the selenide-telluride exhibit topologically equivalent structure motifs, namely chains of Cu(Se,Te)₄ tetrahedra with a Cu atom cis/trans chain as well as an almost linear Te atom chain. All these chalcogenides - as far as measured - are p-doped semiconductors, as determined by Seebeck coefficient and electrical conductivity measurements. Two new orthorhombic chalcogenides, Ba₂Cu₆₋ₓSeyTe₅₋y and Ba₂Cu₆₋ₓSyTe₅₋y were synthesized at 800°C. They are isostructural and crystallize in a new structure type, with space group Pbam. Ba₂Cu₆₋ₓSyTe₅₋y, with a = 9.6560(6) Å, b = 14.0533(9) Å, c = 4.3524(3) Å and Ba₂Cu₅.₆₄Se₁.₀₉Te₃.₉₁with a = 9.7048(6) Å, b = 14.1853(9) Å, c = 4.3840(3) Å. They have Cu6 units extending along c-axis, and two such units are interconnected by S or Se atoms along a-axis. These compounds are nonmetallic with low Seebeck coefficients. Two more new quaternary chalcogenides were uncovered, BaCu₅.₉₂₆₍₁₅₎SeTe₆ and BaCu₅.₇₂₍₁₆₎Se₀.₄₆₄₍₁₅₎Te₆.₅₃₆ with a = 6.9680(2) Å and a = 6.9888(4) Å, respectively, in space group Pm̅3. These compounds have basic Cu₈Te₁₂ frameworks, which can be an important feature for thermoelectric materials. Ba occupies the void. One Cu atom from each cage cluster of eight such cages forms a Cu₈ cube with Se atom occupying it. BaCu₅.₉SeTe₆ was experimentally determined to be p-type doped semiconductor with moderate Seebeck coefficient value.

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This study was undertaken to investigate the effects of imperfections in the initial geometry of bracing members on the stability of the structural frameworks. The general non-linear behaviour of frameworks, consisting of single columns, or multistorey frames stiffened by curved bracings, were studied under the effects of combined vertical and horizontal load systems. The study was divided into two main parts. In part one, the study examined the structural frameworks in the following situations: i) Influence of initial bowing on the behaviour of individual members subjected to axial or eccentric forces. ii) General static behaviour of a single column restrained by curved member or members. iii) General static behaviour and instability of multistorey frameworks with non-linear cross bracings. It has been the goal of the thesis to reinforce the theory put forward to explain the particular type of instability encountered, therefore a critical state, or transient instability region, has been investigated. The characteristics of individual curved members were determined using the theory of large deformations. The general behaviour and the stability of frameworks restrained by imperfect bracing systems were studied using tangent slope and influence coefficient techniques. The results of this study have shown that the initial imperfections of bracings are very important and have major effects on the overall behaviour of the braced frame structures. The particular type of instability encountered, i. e. the critical state or the transient instability region, may be considerably influenced by the initial geometric imperfections of bracings and the relative magnitude of the ratio between vertical and horizontal applied loads on the frameworks. The critical loads have been presented in a series of curves and tables. In part two of the study, the dynamic behaviour at the critical state, i. e. in the region of transient instability, has been investigated. Numerical methods for the dynamic analysis of structural frameworks have been discussed. A new procedure of numerical differentiation has been presented and its advantage over existing procedures has been shown. The method is convenient for use with a digital computer and can also be used for solving simple problems with a calculator. In general the results of parameters studied were presented in a series of curves and tables to enable the stability and dynamic actions to be readily determined for a wide range of structural configurations. Finally, a test programme was carried out to investigate experimentally the non-linear behaviour of frameworks restrained by these imperfect bracings. Three separate models were used in the experimental programme. The experimental results were used to verify the general accuracy of the theoretical methods of analyses. In general the theoretical results and the experimental ones were in very close agreement.