- TITLE:
EVALUATION OF THE INDICATORS PRIORITY IN PREPARING THE TIME-TABLE FOR EDUCATIONAL STUDIES FOR LECTURERS IN UNIVERSITY
- AUTHOR(S):
F. Rashidova
- ABSTRACT:
The most important indicators for preparing the time table for educational study have been selected. The priority of indicators and their weight coefficients have been estimated using the rank correlation methods and subjective statistics, based on the teachers opinion. The concordance coefficient of Kendall is evaluated and the significance is proved by 2χ criteria. The obtained results will be used for creating a computer system for preparing an optimal time – table for higher educational studies.
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EVALUATION OF THE INDICATORS PRIORITY IN PREPARING THE TIME-TABLE FOR EDUCATIONAL STUDIES FOR LECTURERS IN UNIVERSITY
- TITLE:
BRAKING BEHAVIOR INVESTIGATION OF INDUCTION DRIVE BY DIRECT CURRENT INJECTION
- AUTHOR(S):
J. Djagarova, I. Genchev
- ABSTRACT:
The most common breaking method used in variable-frequency drive is by injecting direct current. A mathematical model of induction motor direct torque control is suggested, in which two sources of DC voltage are put into effect. The model is realized in Matlab. Braking modes during different voltage parameters are simulated. The achieved results from the experiment are analyzed - they show the efficiency of the braking method.
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BRAKING BEHAVIOR INVESTIGATION OF INDUCTION DRIVE BY DIRECT CURRENT INJECTION
- TITLE:
APPROACHES FOR SECURING ELECTRONIC AUTOMATION SYSTEMS
- AUTHOR(S):
S. Bobev
- ABSTRACT:
This article discusses the basics associated with securing an automatic electronic system, both software and hardware. Ensuring generally can be classified as such purely control character reference whether a system is functioning properly, but also to reserve its functions. Object of the examination are also areas which are useful in such devices, the need for this type of modules and basic types of structures.
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APPROACHES FOR SECURING ELECTRONIC AUTOMATION SYSTEMS
- TITLE:
MECHANISM OF FORMATION OF BORIDE LAYERS ON POWDER METALLURGY MATERRIALS FROM THE SYSTEM FE-C-CU
- AUTHOR(S):
I. Mitev, I. Vinev
- ABSTRACT:
In this study the mechanism of formation of boride diffusion layers of semi-permeable saturating environments in semi-permeable construction materials from the system Fe-C-Cu is traced. The main iron matrix of iron powders type NC 100.24, to which is added 2,0% Cu and 0,4% C. After sintering at 1150ºС density of the samples vary between 5,80÷7,00g/cm3. In diffusive enrichment was conducted at 950ºС
for 10÷100min. Formation mechanism of the diffusion coatings is studied using X-ray diffraction analysis of resulting diffusion coatings. X- rays from were filmed X-ray diffractometer in unfiltered Kα radiation from iron anode at a critical voltage 7,1kV and Kαav = 1,93728Ǻ. It has been shown that the seeds of low boride phase Fe2B and their growth were fixed after the first 20÷40min saturation at a temperature of 950ºС, regardless of the density of the test samples. The nucleation of high boride phase is formed after the first 20min of saturation at 950ºC on samples having a density of 7,00g/cm3 and 60min at samples having a density of 5,80g/cm3.
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MECHANISM OF FORMATION OF BORIDE LAYERS ON POWDER METALLURGY MATERRIALS FROM THE SYSTEM FE-C-CU
- TITLE:
INFLUENCE OF SINTERING TEMPERATURE ON THE STRENGTH PROPERTIES OF THE POWDER STRUCTURAL MATERIAL FROM THE SYSTEM FE-C-P
- AUTHOR(S):
I. Mitev, I. Todorova
- ABSTRACT:
In the present study the influence of phosphorus over the strength characteristics of the powder construction materials of triple system Fe-С-Р is detected. Research samples are subjected to a base iron powder type - ASC 100.29. To the iron matrix 0,2÷1,0%C and 0,3÷0,45%Р is added. Pressing is carried out with the effort of 600MPa and sintering is conducted at 950÷1250ºС for 30 min at a protective environment
of dissociated ammonia. The density of the samples after sintering is in the range 7,10÷7,12g/cm 3. In tables and graphics are presented experimental results for tensile strength, yield strength and elongation.
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INFLUENCE OF SINTERING TEMPERATURE ON THE STRENGTH PROPERTIES OF THE POWDER STRUCTURAL MATERIAL FROM THE SYSTEM FE-C-P
