Lilyana Koleva

20200304-03
A study of the efficiency as a usability characteristic in E-learning environment
Maria Todorova, Lilyana Koleva, Elena Koleva

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The world of technology is changing at an extremely fast pace. Covid-19 has given further impetus to modernization in education, and it seems unlikely that schools and universities will continue to function as they did before ...  read more

20190910-02
Overall robust optimization approach for electron beam induced grafting process
Lilyana Koleva, Elena Koleva, Monica R. Nemtanu, Mirela Braşoveanu

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The article presents a review of how to pick or design the correct most cost-effective BLDC (Brushless Direct Current) motor controller to fit the needs of the project. After a brief overview of the history and presenting ...  read more

20190304-06
Simulation of the temperature distribution and modelling of molten pool parameters at electron beam drip melting of copper
Tsvetomira Tsonevska, Elena Koleva, Lilyana Koleva, Georgi Mladenov

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In this article quasi steady-state two-dimensional heat model is implemented for the simulation of the temperature distribution in the cast copper ingots through electron beam drip melting. Regression models are estimated ...  read more

20180708-13
Modelling of E-beam crosslinking of composite hydrogels
Maria Demeter, Ion Călina, Cătălin Vancea, Toni P. Paneva, Elena G. Koleva, Lilyana St. Koleva

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Response Surface Methodology and robust engineering approach were applied for the investigation of preliminary experimental data related to the synthesis of composite biopolymer-based hydrogels via electron beam (e-beam) radiation ...  read more

20160506-48
Graphical user interface for optimization of starch modified by electron beam irradiation
Elena G. Koleva, Lilyana St. Koleva, Mirela Braşoveanu, Monica R. Nemţanu, Toni P. Paneva, Ventzislav K. Tzotchev

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Experimental investigation of electron beam induced graft copolymerization of starch (corn and potato), using electron beam generated by a linear accelerator with energy of 5.5 MeV and 6.23 MeV is performed. The modification ...  read more

20160506-31
Emittance – quantitative characteristic of welding beam quality
Elena Koleva, Georgi Mladenov, Volodya Dzharov, Dimitar Todotov, Marin Kerdjiev, Lilyana Koleva

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The management of the quality during electron beam welding directed to optimization of the process parameters is an important way to improve the use of the expensive equipment and to make the EBW process more efficient in consuming materials, time and energy.

 ...  read more

20160506-03
State of the arts of additive manufacturing by selective electron beam melting
Georgi Mladenov, Elena Koleva, Lilyana Koleva, Volodya Dzharov

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In this paper the applications of electron beam additive manufacturing systems are reviewed. There by selective electron beam melting of welding wires or of some area of the upper powder layer of a sandwich structure, 2D soldered ...  read more

20170304-04
Model-based optimization of electron beam welding for obtaining defect-free welds
Elena Koleva, Lilyana Koleva, Georgi Mladenov

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The optimization of welds obtained by electron beam welding is a multi-criterial task, involving the requirements for the geometrical characteristics of the welds, together with the fulfilment of the requirements for lack ...  read more

20170506-05
Ergonomic criteria for evaluating the quality of e-learning
Maria Todorova, Dimitrina Karamanska, Elena Koleva, Lilyana Koleva

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The term “quality” is a wide-ranging concept for which each person or professional sector has its own definition. The most progressive quality point of view is that it is entirely determined by the customer or the end ...  read more