Improvement of the mechanical properties of 2124 Al/SiCp MMC plate by optimisation of the solution treatment

Static mechanical properties of 2124 Al/SiCp MMC have been measured as a function of solution temperature and time. An optimum solution treatment has been established which produces significant improvements in static mechanical properties and fatigue crack growth resistance over conventional solution treatments. Increasing the solution treatment parameters up to the optimum values improves the mechanical properties because of intermetallic dissolution, improved solute and GPB zone strengthening and increased matrix dislocation density. Increasing the solution treatment parameters beyond the optimum values results in a rapid reduction in mechanical properties due to the formation of gas porosity and surface blisters. The optimum solution treatment improves tensile properties in the transverse orientation to a greater extent than in the longitudinal orientation and this results in reduced anisotropy. © 1996 Elsevier Science Limited.

Comparison of crack growth behaviour between spray-formed and commercial plate Al-Zn-Mg-Cu alloy 7150

This paper compares the crack growth resistance of an experimental spray-formed extrusion with that of a commercial aluminium alloy, the two alloys having similar compositions but markedly different grain structures. Tensile and fracture behaviour is similar in both materials and is influenced by inclusion content. The two materials differ in their crack growth resistance, which is shown to be dependent upon grain size and shape. Environmentally-induced crack growth is favoured by aligned grain boundaries and small grain size.

Manuscript Digitization and Electronic Processing of Manuscripts in the Czech National Library

The paper informs about the history of manuscript digitization in the National Library of the Czech Republic as well as about other issues concerning processing of manuscripts. The main consequence of the massive digitization and record and/or full text processing is a paradigm shift leading to the digital history.

Digitization Projects Carried out by the Mathematical Institute Belgrade

In this paper some current digitization projects carried out by the Mathematical Institute of Serbian Academy of Science and Arts Belgrade and the Faculty of Mathematics Belgrade are described. The projects concern developing of a virtual library of retro-digitized books and an Internet data base and presentation of electronic editions of some leading Serbian journals in science and arts, and the work on the South-Eastern European Digitization Initiative (SEEDI).

Potsdam Library of Astronomical Photographic Plates

ACM Computing Classification System (1998): J.2.

Hough Transform Approach to Identification of Flare Stars in Multi-exposure Plate Images

ACM Computing Classification System (1998): I.2.8 , I.2.10, I.5.1, J.2.

Digitization of Literary Heritage in the Bulgarian Libraries: Facing Problems and Challenges

Paper deals with the current issues and challenges before digitization of literary heritage in the Bulgarian libraries. Main problems are outlined. Socialization of digitized heritage is commented.

Development of New Solutions in the Field of Digitization and Digital Presentation of the National Folklore Heritage

This article briefly reviews the software developments for digital presentation and preservation of Bulgarian folklore treasure created within the project “Knowledge Technologies for Creation of Digital Presentation and Significant Repositories of Folklore Heritage” by teams of the Institute of Mathematics and Informatics.

Digitization of Cultural and Historical Heritage of Armenians in Bulgaria - Priorities and Perspectives

The paper deals with digitization as a method of protecting and preserving cultural and historical heritage of Armenians in Bulgaria. It attempts to establish the level of development of this process in the country, to identify the good examples and information gaps in order to outline the priorities and perspectives.

Discover the Thracians - An Approach for Use of 2D and 3D Technologies for Digitization of Cultural Heritage in the Field of E-learning

Information and communication technologies (ICT) offer an easier access to and a multi-perspective view of cultural heritage artifacts and may also enrich and improve cultural heritage education through the adoption of innovative learning/teaching methods. This paper examines the different practices and opportunities for digitization of cultural artifacts with historical significance and describes the work on a pilot project concerning the development of e-learning materials in the Thracian cultural and historical heritage. The proposed method presents an approach based on a combination of 2D and 3D technologies to facilitate the overall process of digitization of individual objects. This approach not only provides greater opportunities for presenting the Thracian heritage but also new perspectives for studying it - students, scientists, PhD students will have the opportunity to work with the materials without having access to them.

Partner Projects of “Ivan Vazov” Public Library – Plovdiv on Digitization of Cultural and Historical Heritage

Digitization offers excellent opportunities for the preservation and safe-keeping of valuable library collections. The article recounts the first coordinated attempts of “Ivan Vazov” Public Library – Plovdiv at digitizing some of its treasured collections such as manuscripts, early printed books and archives through partner projects and revealing them to the world community.

Digitization of Old Mathematical Periodicals Published by the Institute of Mathematics and Informatics, Bulgarian Academy of Sciences

The digitization practice for retro-converting of the mathematical periodicals, published by the Institute of Mathematics and Informatics, Bulgarian Academy of Sciences (IMI-BAS) and the followed benefits for long-term preserving and assuring open access to these materials is discussed in the article.

Digitization and 3D Scanning of Historical Artifacts

Protection and preservation of our cultural and literary historical and documentary heritage are particularly relevant today. The paper presents methods for creating digital resources of historical artifacts related to the Balkan war. Special attention is paid to the process of 3D scanning of objects. The methodology will be used in building an electronic archive and Virtual Museum.

Digitization and Preservation of City Landmarks Using Limited and Free Web Services

This paper presents a practical approach for digitizing city landmarks based on free and limited Web resources. The digital replicas are then placed on the Web using popular services, like Google earth, and are accessible to a huge user base. The method is easily applicable and quite valuable to organizations with limited funding.

Robust and high current cold electron source based on carbon nanotube field emitters and electron multiplier microchannel plate

The aim of this research was to demonstrate a high current and stable field emission (FE) source based on carbon nanotubes (CNTs) and electron multiplier microchannel plate (MCP) and design efficient field emitters. In recent years various CNT based FE devices have been demonstrated including field emission displays, x-ray source and many more. However to use CNTs as source in high powered microwave (HPM) devices higher and stable current in the range of few milli-amperes to amperes is required. To achieve such high current we developed a novel technique of introducing a MCP between CNT cathode and anode. MCP is an array of electron multipliers; it operates by avalanche multiplication of secondary electrons, which are generated when electrons strike channel walls of MCP. FE current from CNTs is enhanced due to avalanche multiplication of secondary electrons and in addition MCP also protects CNTs from irreversible damage during vacuum arcing. Conventional MCP is not suitable for this purpose due to the lower secondary emission properties of their materials. To achieve higher and stable currents we have designed and fabricated a unique ceramic MCP consisting of high SEY materials. The MCP was fabricated utilizing optimum design parameters, which include channel dimensions and material properties obtained from charged particle optics (CPO) simulation. Child Langmuir law, which gives the optimum current density from an electron source, was taken into account during the system design and experiments. Each MCP channel consisted of MgO coated CNTs which was chosen from various material systems due to its very high SEY. With MCP inserted between CNT cathode and anode stable and higher emission current was achieved. It was ∼25 times higher than without MCP. A brighter emission image was also evidenced due to enhanced emission current. The obtained results are a significant technological advance and this research holds promise for electron source in new generation lightweight, efficient and compact microwave devices for telecommunications in satellites or space applications. As part of this work novel emitters consisting of multistage geometry with improved FE properties were was also developed.