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Research

Scientific and Research Interests

At present the scientific and research activity of the department is diverse and abundant. A great part of it is directed to traditional for the Department themes, such as process analysis in electrical circuits and electromagnetic fields. The stedy-state and the transient circuit analysis are made. The electromagnetic fields analysis conducts in non-linear (annisotropic) environments, including in the presence of constant magnets and relative tranlsation, as well UHF fields analysis. Also there is performed an investigation of transformations from continuous to discrete frequency and vise-versa using commutative capacitors and etc. In both of these two main direction of scientific activities solves different tasks for optimisation, tolerance analysis diagnostic and identification. At the same time it develops the relevant programming tools (for diagnostic of analog circuits and circuits with commutative capacitors; identification of unhomogeniousl field structures; optimal syntesis of electromagnetic fields). The using of new high-tech materials and technologies combined with the typical for the contemporary science mathematical approach for research both direct the scientific interests of some professors to a relatively new area of problems, where the Department already acquired a solid research experience and has received significant results. Such are the implementation of RSFQ circuits; application of neural networks; the system described by discrete math structure models (sets theory, proof reasoning theory, functions theory, graph theory, automata models); multi-dimensional systems; the investigation of processes in optical wires, sigma-delta modulators, investigation of quasi-periodical and chaotic modes in non-linear circuits etc.


First steps of the Theoretical Electrical Engineering Department were directed towards creating several analogue and analogue-hybrid computing machines Minichim, a hybrid computing system based on the ISOT 0310 digital computing machine and the analogue-hybrid computing machine ISALTEM-1 using integral circuits. It also developed and implemented a network with local automation, controllers radiosystems for measurement and control. It designed a tool for measurement of the influence of UHF electromagnetic fields, which was manufactured by the experimental plant of TU, Sofia, as well as a cabin for defense of harmful UHF fields, implemented in the laboratory of the State Committee for Standartisation and Metrology.
A part from these activities were stimulated by the creation of four specialised scientific laboratories at the Department: Laboratory of theoretical and experimental modelling, lead initially by Prof. M.P.Zlatev and later by Prof. Vl. Iv. Georguiev; Laboratory on the Problems of transformation of non-electrical quantity, lead by Prof. G. Al. Toshev; Laboratory of electrodynamics, lead by Prof. S. P. Papazov; Laboratory of Forecast, innovations and technology transfer (moved in 1990 to the faculty of Automation), lead by Assoc. Prof. A. T. Moskov. Prof. Moskov also lead the Multimedia Laboratory for Technological Risks at the same Faculty.

 

Members of the Department defended 22 Ph.D. dissertations and 5 D.Sc. dissertations. Under the tutoring of Department professors 12 dissertation more were defended by external scientists, not members of the Department.

Internal and international relations
     
The Department participates intensively in the development of the technical education in our country. Department members took part in the foundation and organisation of several already existing high schools. With their work they contributed to the improvement of the educational process in the area of Theoretical Electrical Engineering.
The Department has long-time contacts with different higher technical institutes and organisations abroad, such as Moscow Energetical Institute, Leningrad Polytechnical Institute and Leningrad Electrotechnical Institute, Higher Technical School in Ilmenau, Wrotzlav Polytechnics, The Centre of Science Management at the Humbolt University – Berlin, the Polytechnics in Burno and Bratislava, the Wien Polytechnic, with which we have co-operation on different contracts for scientific research.
The Department is co-founder of the ISTET (International Symposium on Theoretical Electrical Engineering)(1983-2001). Department representatives are active participants in ISTET workshops and symposiums in 1983, 1985, 1987, 1989, 1995, 2001.
The Deparment created the tradition of organising a biennal summer school in Sozopol, Bulgaria (from 1986 to 2002). The active organisation work of Prof. Vl. I. Georgiev, Assoc. Prof. T. Tzv. Panov, Assoc. Prof. K. P. Ivanov and Assoc. Prof. Dr. K. G. Brandisky, and the forces of the whole Department team contributed to turn the workshop into a centre for international scientific contacts and exchange of ideas and experience in the area of teaching and research in the theory of Electrical Engineering. The workshop provides such contacts no only for the members of the Department, but also for the lecturers and scientists in all similar scientific teams in the country.

International agreements

1. 3468/93 Management of small and middle companies, Assoc. Prof. Dr. Moskov, TU - Sofia.(finished) 
2. NATO Collaborative linkage grant, “Circuit Design and Optimization”, PST.CLG 975709, duration 1999-2001, NATO-country Project Coordinator – Prof. N.G. Maratos, NTUA, Athens, Greece; Partner-country Project Coordinator – Assoc. Prof. V.M. Mladenov, TU-Sofia, Bulgaria.
3. "Academical reconstruction of South Eastern Europe - Theoretical Electrical Engineering", coordinators Assoc. Prof. Dr. K. Brandisky, TU - Sofia and Prof. D. Sc. Ulman, TU - Ilmenau, 2000/2006.

Project sponsored by the World Bank

1. "Modernization of education on Theoretical Electrical Engineering in the Technical University of Sofia", project manager Assoc. Prof. Dr. K. Brandisky, 2003/2004.

Agreements with the National Foundation "Scientific Researchs”

1. TN-554/95 Modern calculating methods for analisys and projects the systems in energetic, coordinator Prof. D. Sc. L. Kolev.
2. TN-568/95 Boundary permissible modes of turbogenerators in Heating Electric Station, coordinator Assoc. Prof. Dr. R. Stancheva.

Dissertations, defended by members of Department Theoretical Electrical Engineering:

 I. Doctor of Sciences Dissertations:

1. Papazov S. P., Electromagnetic systems with optimal structure, 1979.
2. Farhy S. L., Theoretical problems of analysis of lumped parameter complex circuits, 1985.
3. Kolev L. V., Some problems of analysis of linear and nonlinear electrical circuits, 1989.
4. Georgiev Vl. Iv., Some contributions to analysis and synthesis of some SC-circuits, 1995.

II. Thesises of the members of Department Theoretical Electrical Engineering for Ph.D. degree:

1. Farhy S. L., Subharmonic fluctuations in some nonlinear circuits, 1957.
2. Georgiev Vl. Iv., Experimental determinating the transfer function of linear systems with computer technology, 1969, Leningrad.
3. Moskov A. T., Application of the system approach in modelling and testing the stability of the complex electrical charges, 1972.
4. Kolev L. V., Investigation in the extrapolation of the nonstationary  random processes and prediction of the system power, 1972.
5. Hinova I.G., Equivalent schemes and matrix analysis of the nonlinear electromagnetic circuits, 1972.
6. Stancheva R. D., Optimization investigations of the universal collector motors with low power, 1972.
7. Toshev G. Al., Some optimisation developments of radiotechnical devices, 1973.
8. Panov T. Tzv., Optimization developments in the systems for electromagnetic distribution, 1975.
9. Bodurova M. M., Application of the sensitive theory in analysis of the processes in synchronous machines, 1975, Leningrad.
10. Starshimirov T. D., Machine project of the linear electronic schemes – sensitive analysis and tolerance, 1977.
11. Tzochev Hr., Basis of the theory and computation of reliability, 1979.
12. Brandisky K. G., Application of the numerical methods for investigation of the electromagnetic fields in nonhomogeniuos environment, 1983.
13. Georgiev J. D., Using a new possibilities for application of the Grin functions in electromagnetic fields, 1983.
14. Radev N. A., Analysis of the characteristics of the SC-filters with nonideal amplifiers, 1988.
15. Iacheva I. I., Synthesis of the fields in electrotechnical devices, 1989.
16. Stanchev K. P., Module approach in analysis of the nonideal SC-filters, 1990.
17. Vladov S. S., Interval methods for tolerance analysis of the stationary modes in linear electrical circuits, 1990.
18. Mladenov V. M., Some problems in global analysis of the nonlinear circuits, 1993.
19. Valchev D. Z., Analysis of the complex modes in nonlinear circuits from low rank, 1994.
20. Terzieva, S. D., Field problems by the minimization of external losses in one-mode optical fibers, 1999.

Ph.D. thesises, supervised by members of Department Theoretical Electrical Engineering:

Ph.D. thesises, supervised by Prof. D. Sc. M. P. Zlatev

1. Nenov G. A., Investigation in synthesis of the active linear electrical circuits, 1973.
2. Krumov A. V., Statistics probability investigation in the transient processes in electrical systems, 1975.

Ph.D. thesises, supervised by Prof. D. Sc. S. L. Farhy

1. Stavrakieva T. E., Investigation of the differential transformers in impulse power, 1974.
2. Saparev S. S., Investigation of the periodical processes in ferromagnetic static frequency делители на честота, 1975.
3. Kuiumdjiev T. G., Some investigations of the SC-filters, 1987.

Ph.D. thesises, supervised by Prof. D. Sc. V. N. Savov

1. Zlatarsky Iv. V., Contribution to some contemporary problems in electrical dynamics, 1975.
2. Chicharov D. V., Microwave tape lines, 1975.

Ph.D. thesises, supervised by Prof. D. Sc. S. P. Papazov

1. Stanev Il. V., Modelling and optimisation of the electromagnetic  processes in histheresis motors with low power, 1976.

Ph.D. thesises, supervised by Assoc. Prof. Dr. A. T. Moskov

1. Toshev D. A., Prediction of the development of the methods in theoretical electrical engineering, 1980.

Ph.D. thesises, supervised by Prof. D. Sc. Vladimir Georgiev

1. Stoianova Т. М., Methods of synthesis of the SC-circuits, basis on the numerical integration to a high degree, 1988.
2. Gurova E. V., Z-S transformations to a high degree in synthesis of the transfer function, 1996.