Todor Kableshkov University of Transport

Sofia, Bulgaria

Todor Kableshkov University of Transport

Sofia, Bulgaria
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Kolesnikov N.,Novgorod State University | Zhiglinsky S.,Novgorod State University | Petrov R.,Novgorod State University | Bichurin M.,Novgorod State University | And 3 more authors.
2017 15th International Conference on Electrical Machines, Drives and Power Systems, ELMA 2017 - Proceedings | Year: 2017

In this paper it is proposed to use magnetoelectric material as the sensing element of position sensors for car. Proposed ME position sensor has several advantages against the traditional one such as smaller size and weight. Magnetostrictive-piezoelectric layered structure based on PZT and Metglas was used as sensor. The designed sensor showed the peak voltage pulse of about 150 mV. Sensors were tested on a real internal combustion engine of a car. © 2017 IEEE.

Rotaru A.,Technical University Gheorghe Asachi | Kolev C.,Todor Kableshkov University of Transport
Environmental Engineering and Management Journal | Year: 2010

Dobruja is a historical region shared by Romania and Bulgaria; it is located on the western Black Sea coast, around the Danube River. The main geological, seismic and geotechnical features, as well as natural hazards are presented in this review. A comparative analysis is made between the northern and southern parts of Dobruja. The region has witnessed various kinds of natural hazard over the past decades, and this paper describes the geotechnical characteristics and chronology of two of the more frequently occurring events, namely earthquakes and soil liquefaction. The structural relationships between the different rock formations in Romania and Bulgaria are analyzed, to show the extent to which they influence the dynamics of these events. The stability of foundations on liquefacted sand, silty clay and karsts on which installations such as wind generators, the nuclear power station and breakwaters are built have been examined in the light of the geoenvironmental risks. The similarity in structural, geotechnical and environmental relationships between Romania and Bulgaria engender common risks that could be properly addressed only through collaboration between scientists from both countries.

Zamfirova G.,Todor Kableshkov University of Transport | Gaydarov V.,Todor Kableshkov University of Transport
Chemistry and Chemical Technology | Year: 2013

Flat plates of poly(allyl(p-allylcarbonate) benzoate) obtained via photopolymerization and thermal polymerization have been studied by means of microindentation. The plates were about 3 mm thick. The values of microhardness (MHV)/total microhardness (MHT) have been determined. Accordingly, structural changes in the plate bulk due to the polymerization method were detected. The plates obtained by photopolymerization possess a superficial layer harder than the inner layers and its thickness is not uniform. Also, microindentention shows that the increase in the polymerization time during thermopolymerization leads to improved elasticity and resistance against plastic deformation. Microindentation data of the plates here studied shows that poor mechanical properties correspond to an unfinished network, while good mechanical properties correspond to a better crosslinked network. © Zamfirova G., Gaydarov V., Lopez-Velazquez D., 2013.

Kassabov O.,Todor Kableshkov University of Transport | Vlachkova K.,Sofia University
AIP Conference Proceedings | Year: 2015

Minimal surfaces with isothermal parameters admitting Bézier representation were studied by Cosín and Monterde. They showed that, up to an affine transformation, the Enneper surface is the only bi-cubic isothermal minimal surface. Here we study bi-quartic isothermal minimal surfaces and establish the general form of their generating functions in the Weierstrass representation formula. We apply an approach proposed by Ganchev to compute the normal curvature and show that, in contrast to the bi-cubic case, there is a variety of bi-quartic isothermal minimal surfaces. Based on the Bézier representation we establish some geometric properties of the bi-quartic harmonic surfaces. Numerical experiments are visualized and presented to illustrate and support our results. © 2015 AIP Publishing LLC.

Niculescu M.,Polytechnic University of Bucharest | Golgojan A.I.,Polytechnic University of Bucharest | Bednarz A.,Silesian University of Technology | Ivanova G.,Todor Kableshkov University of Transport | Maly T.,Brno University of Technology
Transport Problems | Year: 2014

This paper discusses smart railway infrastructure systems. The meaning of "smart" is described followed by a discussion on the benefits of the use of smart infrastructure. Some key components of smart infrastructure, few examples and case studies are presented. Our analysis suggests that the implementation of a smart system may well lead to energy savings of 25%, therefore smart systems should be implemented in larger scale.

Zamfirova G.,Todor Kableshkov University of Transport | Cherneva S.,Bulgarian Academy of Science | Gaydarov V.,Todor Kableshkov University of Transport | Vladkova T.,University of Chemical Technology and Metallurgy of Sofia
Bulgarian Chemical Communications | Year: 2015

Mechanical properties of three samples from liquid silicone rubber were investigated by means of microindentation experiments and finite-element simulations. The experimental and numerical load-displacement curves were compared and showed good coincidence. One of the aims of present work was seeking of correlation between some standard classical mechanical characteristics and parameters obtained by micro- and nanoindentation. The influence of the crosslinking on mechanical properties was investigated as well. Moreover parameters describing plastic behavior of investigated materials (such as yield strength, distribution of equivalent Von Mises stress in investigated materials during the process of microindentation, distribution of the equivalent plastic strain after unloading), which aren't possible to be obtained only by means of microindentaion experiments, were determined by means of numerical simulations. © 2015 Bulgarian Academy of Sciences, Union of Chemists in Bulgaria.

Kolev C.,Todor Kableshkov University of Transport | Maslarski S.,Todor Kableshkov University of Transport | Maslarski S.,Bauer Bulgaria Ltd.
Geotechnical Special Publication | Year: 2016

This paper is dedicated to the study of elastic shortening of the pile body under applied vertical static load. It considers cast-in-place RC piles, executed by using casing pipe. Very often, the importance of the elastic shortening is overlooked in practice. In the cases when designed piles are standing, the elastic shortening can reach the impressive 71% of total vertical deformation. It is impossible to be ignored. The study is based on thirteen in-situ and one laboratory experiments and their comparison with the Theory of elasticity. The in-situ experiments are executed near different major cities in Bulgaria and the laboratory test is hold in "Todor Kableshkov", University of Transport, Sofia, Bulgaria. © ASCE.

Asenova I.,Todor Kableshkov University of Transport | Balik F.,Wroclaw University of Technology
Advances in Electrical and Electronic Engineering | Year: 2013

In symbolic sensitivity analysis very important role plays the number of additionally generated expressions and in consequence additional number of arithmetical operations. The main drawback of some methods based on the adjoint graph or on the twograph technique, i.e. the necessity to multiply analyze the corresponding graph, is avoided. Advantages of the method suggested are that, the matrix inversion is not required and the Coates graph is significantly simplified. Simplifications of the method introduced in this paper lead to the significant reduction of the final symbolic expressions without violation of accuracy. This simplification method can be considered as SBG-type and has an important impact on symbolic analysis. A special software tool called HoneySen has been developed to implement the suggested method. In the paper, it was shown that the presented method is more efiective than the transimpedance method taking the number of arithmetical operations and the circuit insight into consideration. Comparison results for the multiparameter sensitivity calculations of the voltage the transfer function for a fourth-order low pass filter and a secondorder high-pass filter are presented. © 2013 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING.

Hristova M.,Todor Kableshkov University of Transport
Cybernetics and Information Technologies | Year: 2016

The present article models and examines k∨n systems, in particular Triple modular redundancy (2∨3) and 3∨5. The aim of the study is to derive mathematical models, which are used for determining the impact of structural redundancy (the number of channels n and the threshold of the quorum function k) on the reliability of the system. The probability of failure-free operation p and the Mean Time Between Failures (MTBF) are used as reliability indicators.

Katev P.D.,Todor Kableshkov University of Transport
Proceedings of 9th International Conference, ELEKTRO 2012 | Year: 2012

Networks based on WiMAX (Worldwide Interoperability for Microwave Access) provide efficient packet radio interface. These networks enable high data transmission rates. WiMAX is the newest wireless broadband Internet technology based on IEEE 802.16 standard. Based on OFDM (Orthogonal Frequency Division Multiplexing), this system uses radio frequency range from 2 to 11 GHz. Calculation of path loss is very important, because it gives approximate values compared to any, obtained from real measurements. So it is helpful for initial deployment of WiMAX networks, providing an opportunity for cell planning. In this paper I discuss and compare following path loss models - Free Space Path Loss Model (FSPL Model), Hata-Okumura Extended Model (called also ECC-33 Model), Cost 231 Walfish-Ikegami Model and Stanford University Interim Model. In this paper I take the information on the location of buildings, the height of the transmitting antenna, receiving antenna and the others, consistent with conditions in Bulgaria. In each country, there are portions of the spectrum set aside for commercial purposes. In Europe and much of Asia, the 3.5 GHz spectrum range is used for broadband wireless, so I make calculations for 3.5 GHz. From calculations, that I made, can be concluded, that FSPL model, gives the lowest path loss, in all type of terrains - rural, suburban and rural areas. Model ECC-33 can predict path loss in urban and suburban areas, but it is unusable in rural areas. Also I can conclude, that model SUI, has approximately the same values of path loss with those, computed with FSPL model. My research shows that all four models for calculating the path loss are applicable to various areas, and we must compromise between coverage area and low interference of the transmitted signals, when we design WiMAX network. © 2012 IEEE.

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