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Investigations of material parameters within the system Al, Al₂O₃, Ta, Ta₂O₅ and TaO_xN_1‐x are presented. This combination is characteristic when using Al sheet for production of substrates including electronic interconnections, vias and resistive groups. They can serve for MCMs due to the specific features of Al. The technological process includes first electrochemical oxidation of Al‐sheet as base isolation layer Al₂O₃ (50‐70μm). This process is followed by vacuum deposition of relatively thick layers of Al (2‐5μm). Each layer is then processed by lithographic methods followed by selective electro‐chemical oxidation as a help process for structuring. The development of this combined structuring method allows the simultaneous achievement of interconnections (Al) and isolation (Al₂O₃) levels with least size up to 50μm. The importance of the method consists of a vertical combination of several conductive layers of Al structured as described above, “burying” the interconnections in the insulating Al₂O₃ films. All necessary combinations and configurations of different kinds of microstrip lines are possible. The dielectric characteristics of Al₂O₃, achieved through the above mentioned method, can be changed in accordance with the parameters of the technological steps and filling of the porous structure. Thus some interesting high frequency features of microstrips are obtained. Extra advantage is the ability of combination of conductive Al layers with other types of such layers as tantalum (Ta). With Ta can be achieved other permittivity constants of the insulation layers and in combination with TaO_xN_1‐x intermediate planes of resistive groups are developed. The measurement of the stripline parameters is done by microwave technics, because the desired application of the substrates is for high‐speed digital signals in the GHz range.

In this paper we present recent studies on the electrochemical migration processes in Ag thin film parallel microstrip lines in MCM(D) structures. The basic concept is applying accelerated local drop‐test of water solutions onto the surface of two adjacent lines, under a given voltage potential. These operational conditions are often met in the interconnection line buses, placed in the top assembly level of multilayered hybrid structures. The subject of investigations are MCM(D) developed on Al‐sheet carrier with internal conducting and isolating layers, produced through unique selective electrochemical anodization of Al and Ta. This technology process also enables the creation of embedded R and C passive components on the base of TaO_xN_1‐x and Ta₂O₅ (or Al₂O₃) respectively. We propose an electrochemical deposition of Ag/Sb alloys on the surface of Al interconnection lines and contact pads to ease the bondability and solderability in chip mounting procedures. The artificially created silver migrated defects and partial shorts are investigated through the high frequency method of coupled transmission lines in order to eliminate the errors and insufficient validity of DC direct measurements.

Recent progress in the investigation of the material parameters of Al/Al₂O₃systems leads to an increase in the possibilities for using embedded TaO_XN_1‐X layers. The use of Al‐sheets as mechanical strength carriers in combination with vacuum‐deposited Al‐layers and electrochemically anodized Al₂O₃ structure requires study. This was found to create a periodic multilayer Al/Al₂O₃ structure. The material qualities of this system allow optimization in order to achieve high speed data processing and signal propagation. The existing studies using Al and Ta combination as well as the high resistance qualities of the modified TaO_XN_1‐X layers have shown satisfactory results. It can be concluded that the development of this new layer combination is possible in the multilayer carrier structures. Some preliminary research studies show a proper adhesion and satisfactory characteristics of the two integrated resistive planes in the multilayer combination Al/Al₂O₃//TaO_XN_1‐X/Ta₂O₅/Al.

In the late 1990s, the tourism in Serbia had been developing spontaneously, supported by the policy of undifferentiated marketing. That kind of approach to tourism development led to unsatisfying results, which is a notion primarily based on Serbia’s obvious natural and social resources. An alternative to this approach to tourism development is the differentiated marketing strategy focusing on relevant market segments called “targets.” That way, it would be possible to commercially valorize a significant number of resources (natural and social) as well as a large number of touristic products.

Due to current trends in the international tourism market – moving away from the concept of mass tourism (holiday at the seaside and “ski resorts”), i.e., the ongoing diversification of tourism products, there is undoubtedly more potential for new tourism development trends. The increasing investment in tourism development of the Danube basin, with a larger number of potential tourist products, is expected to make it more attractive to the tourist market. This should have positive effects on the overall development of tourism in Serbia.

This chapter focuses primarily on the research of the Upper Danube region. It will show the importance of the natural and social (anthropogenic) resources suitable for the development of tourism in this area. Special attention shall be paid to the concept of sustainable tourism development, which develops tourism in accordance with the interests of all stakeholders. The positive interaction between all interest groups creates the conditions that ensure satisfaction of all stakeholders and general welfare.

Complexity and interconnections of the wicked problems constantly challenge policy-makers and public authorities. The tourism system, with its diverse nature and entangled connections among the stakeholders, provides a favourable ground for the emergence of numerous wicked issues. The Bulgarian tourism policy ecosystem has a well-developed legislative basis, envisaging most of the possible problems among the actors. Still, the decision-makers, service delivery managers, technical experts and social researchers need close coordination and a systematic approach to reach a coherent and acceptable solution. The current chapter reveals the gaps in the work of the tourism policy institutions in Bulgaria, caused mainly by the lack of coordination and limited communication among them.

The purpose of this study is to identify an innovative solution for the power transmission gearbox of concrete mixers, according to the specifications provided by the company.

A tailored systematic design approach (inspired to the German systematic framework) has been adopted to comprehensively gather the company specifications and perform in-depth design space explorations. Subsequently, an iterative embodiment design approach has been followed to identify the size of the components for the preferred concept, by using acknowledged mechanical design procedures and finite element analysis tools.

An innovative cycloidal gearbox has been developed, by merging the kinematics underpinning the classical cycloidal drives and the Wolfrom planetary gearbox. The resulting concept provides high reduction rates with a very high overload capacity.

The main limitation of the studies is the absence of in-depth evaluations usually performed in the detail design phase. However, this limitation is a direct consequence of the company specifications, which only asked to find a preferred concept and to perform preliminary evaluations. Accordingly, the subsequent design optimization are intended to be performed by the company’s staff.

The present paper shows an original design approach, opportunely tailored to the design of innovative gearboxes. It can be conveniently adapted and reused by designers involved in similar tasks. Moreover, the designed cycloidal gearbox paves the way for important innovations in the field of concrete mixers, allowing to design more robust and compact devices.

THE recently founded Bulgarian Bibliographical Institute has produced three publications of great interest. The first of these, by Dr. T. Borov, the Director of the Institute and of the National Library of Sofia, Why do we need a Bulgarian Bibliographical Institute?, was published in 1941, before the foundation of the Institute, and, as its sub‐title indicates, is ‘an address to friends’. In it Dr. Borov reviewed briefly the position of Bulgarian bibliography and set forth what he considered should be the aims of the Institute.

This research explores sustainable competitive advantage (SCA) in heritage tourism, focusing on authenticity, cultural preservation, and visitor experience. It examines the role of data in transforming visitor experiences through personalization, marketing insights, and predictive analytics. This chapter also examines the impact of technology, such as mobile applications, augmented reality (AR), and virtual reality (VR), on heritage tourism experiences. It emphasizes the importance of balancing modernization and cultural preservation, emphasizing ethical considerations and safeguarding heritage site authenticity. This chapter also highlights the significance of sustainability in heritage tourism, including eco-conscious practices, community engagement, and resource allocation. It discusses feedback mechanisms, documentation of cultural and historical assets, and heritage preservation as fundamental elements in SCA. The research encourages collaborative innovation within the heritage tourism domain, encouraging academics and industry professionals to explore emerging research topics. This chapter advocates for a future where heritage tourism offers unparalleled and sustainable experiences while safeguarding and celebrating the enduring treasures of the past.

The history of Bulgarian librarianship comprises a history of survival under change imposed by foreign rule. This chapter traces the historical development of Bulgarian libraries and LIS education through the lens of Bulgarian history. Part I presents an overview of Bulgarian history, focusing on four dramatic epochs. During Ottoman rule (1393–1878), Bulgarian libraries survived by hiding. The second epoch, European intervention, Russian, occurred under the Austro-Hungarian, and German rule (1878–1944). Bulgarian LIS survived by adopting European practices and the German academic model of library education. The third epoch, Soviet rule (1944–1989), saw a massive suppression of information, Bulgarian libraries survived by maintaining an undercurrent of dissent. The fourth epoch began in 1989 with the onset of democratic reforms. Bulgarian librarianship survived the financial crisis and anarchy of that epoch by adopting foreign practices and establishing partnerships with foreign library institutions. Part II describes agents of change acting within the Bulgarian LIS field during the radical change from Soviet to democratic rule. The change agents included the formation of a union, cooperation among Bulgarian libraries, and international cooperation with Western institutions.

Research for this chapter incorporated literature reviews, surveys of accredited Bulgarian LIS programs, interviews with Bulgarian and American LIS professionals, and bibliometric analysis of Bulgarian publications.