Monthly Archives: November 2011

Optimal Beamforming for MIMO Communication Systems

Georgi Iliev

Abstract: in the presented work some algorithms for optimal beamforming used in MIMO communication systems are considered and investigated. The full dimension algorithm has very high computational complexity and it is hard to be implemented in most network applications. The algorithm with reduced complexity is a good alternative. Extensive simulations investigating both algorithms are implemented. The obtained results prove the advantages of reduced dimension method which considerably reduces the time for finding the optimal solution. Major advantage of the second algorithm is that the requirements for signal to noise ratio at the receiver side are fulfilled for lower level of overall transmission power.

Key words: wireless communication systems, beamforming, algorithms for optimization, algorithms for optimal beamforming

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Analysis of e-Learning Platforms

Daniela Minkovska, Anastasia Vangetova

Abstract: This article presents a brief overview of e-Iearning platforms. Selection criteria are defined, with key selection criteria being described and justified. A comparative analysis of some existing platforms is also made. The most appropriate platforms are selected according to the results of the analysis.

Key words: E-Iearning, E-learning platforms, Course Management System (CMS), Learning
Management System (LMS), education

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System of Heuristic Principles for Modifying Circuit Properties by the Miller Theorem

Cyril Mechkov

Abstract: In this paper the basic idea behind the Miller theorem is enlarged and generalized to a principle for modification of circuit properties (mainly impedances). This principle explains fundamental circuit phenomena (Miller effect, virtual ground, bootstrapping, negative impedance, etc. ); it helps understanding and designing a lot of well-known basic circuits (negative feedback amplifiers, resistive and time-dependent converters, negative impedance converters, etc.) and provokes inventing new electronic circuits. Six modificating principles are proposed in total – the first three of them are intended for virtual impedance increasing and the next three – tor virtual impedance decreasing.

Key words: Miller theorem, Miller effect, virtual element, virtual impedance increasing and
decreasing.

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Increasmg the Performance of Web Applications

Georgi Naydenov

Abstract: The purpose of this investigation is to increase the performance of a conventional Web application, improving some selected functional parameters. The methods and resorts applied for this aim are presented. The results obtained make it possible to evaluate the web application performance before and after the improvement.

Keywords: Web applications, performance

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Organization and Automation of Processes in the Student Distribution

Tasho Tashev, Ognian Nakov,
Adelina Aleksieva-Petrova, Anastasios Profitis

Abstract: The main goal of this paper is to describe and analyze the user requirements and use cases in order to design the architecture for the students’ distribution in elective courses and projects. Within the Technical University – Sofia it facilitates and automates processes defining the procedures for allocating management, student desires and classification of students’ options based on set of criteria and the desired layout. The designed architecture meets all requirements and realizes all processes required by the Technical University – Sofia. The interface is completed and user friendly for management and allocation of student desired arrangement or classification of students’ options.

Key words: education, process, use case, student distribution.

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Experimental Study of the Method “Three Nearest Space Neighbors” for Determining the Structure Similarity of Protein Molecules

Dobrinka Petrova, Stoicho D. Stoichev

Abstract: The method uses two different approaches for comparison of protein molecules that
depend on the number of the secondary structure elements. If this number is greater than 4 then
the basic elements of the graph model are the secondary structure elements. If this number is less
or equal to 4 then the basic elements of the graph model are the amino acids of the protein
molecule. We show the experimental results of both cases for large number of protein molecules.

Key words: amino acids, proteins, primary and secondary structure of protein molecule, structure similarity of protein molecules

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The Challenges of XML Parallel Parsers

Adriana Georgieva

Abstract: The rapid growth of XML presents a fresh set of challenges to established enterprise applications and XML-developers. This article briefly presents the basic concepts of traditional tools for XML parsing as Document Object Model and Simple API for XML. Most XML parsers are still using algorithms that are inherently serial, which show little improvement on newer computing hardware. In this paper, is suggested a different point of view about XML parsers with the creation of advanced algebraic processor. The possibilities of this linear algebraic model, combined with principles of parallel programming allow efficient solutions for parsing, search, extraction and manipulation over semi-structured data with hierarchical structures. Parallelizing input documents into multiple chunks (threads) is the key to performance improvement of XML parsing process.

Key words: Algebraic Processor (AP), DTD (Document Type Definition), Syntax Analyzer (Parser),
Uniform Resource Identifier (URI), well-formed XML.

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Automatic Réseau Grid Lines Removal from Images of Carte du Ciel Plates

Nadezhda Zlateva, Alexander Marinov, Dimo Dimov

Abstract: The réseau grid was originally superimposed over archival Carte du Ciel photo plates to assist photogrammetry of stellar images. But that complicates the computer registration (attachment to contemporarily stellar catalogs) of the digitized plates today. Réseau grid has insufficient accuracy for the modern catalogs and its presence in the scanned images of plates confuses usage of known programs designed for stellar registration. The article proposes an approach to automatically isolate the réseau grid from images of Carte du Ciel plates. The approach needs no preliminary data on celestial reference of the plate. The approach exploits the even placement of the vertical and horizontal grid lines by calculating the corresponding projection profiles to find local maxima corresponding to the lines.

Key words: Astronomy & Informatics, Astroinformatics, Réseau grid, Carte du Ciel plates, Projection profiles, Hough transform.

Multiple Sequence Alignment by Genetic Algorithm

Emilyan Asenov

Abstract: In this paper is proposed a design of genetic algorithm for solving the problem for
multiple sequence alignment. This design targets to be as much as possible reusable and flexible.
It can be used as a foundation for future deveIopment of metaheuristic library as well as it is going
to be reused for the development of multiple sequence alignment applications based on another
metaheuristics. This paper provides detailed explanation how the problem for the multiple
sequence alignment can be adjusted to the abstraction of the Genetic Algorithm.

Key words: Metaheuristics, Multiple Sequence Alignment, Genetic Algorithm

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Introduction in Stream Programming – The OpenCL Platform Layer

Nikolay Landzhev

Abstract: This paper looks into the platform layer of OpenCL, the most widely used standard for
stream programming. The platform layer allows us to query the compute devices, such as CPUs,
GPUs, and other programmable parallel processors. It also provides us with functions to: discover
all OpenCL capable devices in a system, list their capabilities, and create contexts that contain one
or more compute devices. We are also going to look at how to create, compile and run a program
that uses OpenCL on Microsoft Windows. The program will utilize the OpenCL platform layer in
order to get information for the compute devices in our system.

Key words: GPU, GPGPU, Multicore, OpenCL, AMD Stream, Stream Programming

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