Ivan Gospodinov, Ventzislav Nikolov, Stephan Filipov
Abstract: Constrained similarity between surfaces can be defined via minimizing the L2 norm of the gradient of the difference between the surfaces. Based on this definition, a definition of constrained similarity between parametrically defined mesh-surfaces is presented. An exact general solution is obtained for the case wherein the imposed constraints are linear. Various examples are presented as well as a MATLAB code for the solution of one of the examples. The code could be adjusted to other cases.
Key words: similarity of parametrical mesh-surfaces, Constrained optimization
Evgeniy Markov, Marin Nedelchev
Abstract: This paper proposes two novel EBG structures with enhanced bandstop capabilities, based on the modified Jerusalem Cross. They are initiated with physical alterations of the initial JC unit cell dividing the cross lines into coupled lines and addition of an electrically small patch presenting a capacitance in the center of the unit cell. Full wave FDTD analysis of infinite 2D periodic structures is performed and their bandgap characteristics are shown. It is shown that the stopband of the proposed structures is wider that the original Jerusalem Cross.
Key words: EBG design, bandstop, bandpass, periodic structures, transmission line analysis, full wave analysis, FDTD, surface waves
Zlatka Valkova-Jarvis, Viktor Stoynov, Kiril Kassev
Abstract: Great expectations and hopes repose in future 5G telecommunications networks for the long-term solution to the shortcomings and limitations of current LTE networks. The concept of next-generation networks is still in the process of development, clarification and elaboration. Will there be dramatic differences between LTE and 5G? In what main ways will the two generations of networks differ and why? Which will be the most important technological developments and what new challenges and problems will these lead to? These and other similar issues have become the focus of attention for the telecommunications scientific community recently. This publication presents some of the main network concepts of upcoming 5G telecommunications networks, the reasons for their development and the scientific issues arising.
Key words: Cloud-based networking, Device-to-device (D2D) communication, LTE networks, Heterogeneous Networks (HetNets), Ultra-Reliable Communication (URC), 5G networks
Todor Tsvetkov, Ilia Iliev
Abstract: In this paper the various direction of arrival (DOA) algorithms precision and computational complexity are analyzed, based on number of snapshots in cognitive radio detection process. The studied algorithms are MUSIC, Capon (MVDR), ROOT MUSIC, ESPRIT-LS and ESPRIT-TLS. The goal of the proposed analysis is to achieve better quality performance with adaptive antenna array processing in cognitive radio systems. Wide and narrow angular separation modes are used for estimation the performance of DOA algorithms in different detection and environment conditions. The simulation results show that ROOT MUSIC, ESPRIT-LS and ESPRIT-TLS are most suitable for use in cognitive radio systems for DOA estimation.
Key words: cognitive radio, direction of arrival, MUSIC, ROOT MUSIC, CAPON, MVDR, ESPRIT
Svetoslav Tashev, Marina Marinova, Vladimir Lazarov
Abstract: This article presents and describes the design and simulation of new multiprocessor computer architectures with supplemental computing elements in the main memory. We study the overall improvement of existing architectures vs the new designed architecture, using simulation models. The simulating models are developed based on existing data comparing time markers, measuring the output performance. Using additional computing elements in the memory allows us to improve the current limitations of the conventional architectures.
Key Words: Processor in memory; cache miss; branch prediction; high performance computer architecture; performance evaluation.
Ventzislav Nikolov, Stefan Panov, Dimitar Pilev
Abstract: This paper presents software supporting the activities of managers of condominium. Addressed are the problems posed by the formalization of that subject area and it is given their decision, taking into account the requirements of the Condominium Act approved in recent years. Considered is the possibility of joint management of several properties from one manager.
Keywords: Databases, SQL, DML, Condominium Law.
Gergana Kaipachka, Nina Sinyagina
Abstract: In the article is being presented the developed version of the approach for fault-tolerant calculations using t-fault diagnostics. The attention is directed to the finding of faults and the conditions for release at block and system level. An algorithm for partially distributed diagnostics of fault-tolerant computer systems is proposed.
Key words: computer security, fault-tolerant computer systems, t-fault diagnostics.
Ventzislav Nikolov, Stefan Panov, Dimitar Pilev
Abstract: The article dealt with the principles laid down in the supporting software for small and middle enterprises activities. Discussed are the principles of construction and interaction of key system modules for financial services, technology, material and warehousing, as well as a module to handle requests for materials and placed orders. Analyzed is the relationship between objects in the three areas subject to formalization followed by their presentation in the proposed system.
Keywords: Relational Databases, financial systems.
Efrem Dubrovin, Maria Marinova, Vladimir Lazarov
Abstract: The performance of a program execution strong depends on the numbers of branch instructions. One of the groups of intruction dependencies is procedural dependencies. There are different techniques which are trying to find and execute branch instructions before they are occurred. With Advanced Branch Prediction Simulator(ABPS) in this paper simulates branch predictors with perceptron and how this increasing the program performance.
Key words: branch prediction technique; simulator for branch prediction with perceptron; instruction dependencies;
Vasil Milovanski, Gergana Kalpachka
Abstract: The current paper represents two ways of studying the current resonance: through a numerical analysis and through the simulation software CircuitMaker. The results yielded by the two methodologies are compared and conclusions are drawn.
Key words: resonance, quality factor, frequency range.