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Search Results: 1 - 10 of 8526 matches for " Vladimir Vuki? "
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Minimum dropout voltage on a serial pnp transistor of a moderately loaded voltage regulator in a gamma radiation field
VukiVladimir ?.
Nuclear Technology and Radiation Protection , 2012, DOI: 10.2298/ntrp1204333v
Abstract: The main examined value in an experiment performed on moderately loaded voltage regulators was the serial pnp transistor’s minimum dropout voltage, followed by the data on the base current and forward emitter current gain. Minimum dropout voltage decreased by up to 12%, while the measured values of the forward emitter current gain decreased by 20-40% after the absorption of a total ionizing dose of 500 Gy. The oxide trapped charge increased the radiation tolerance of the serial lateral pnp transistor owing to the suppression of interface trap formation above the base area. Current flow through the serial transistor of the voltage regulator had an influence on the decrease in the power pnp transistor’s forward emitter current gain. Due to the operation with a moderate load of 100 mA, loss of emitter injection efficiency was not as important as during the operation with high current density, thus eliminating the negative influence of emitter crowding on the radiation hardness of the voltage regulator. For a moderate load, gain in the negative feedback reaction was enough to keep output voltage in the anticipated range. Only information procured from tests of the minimum dropout voltage on the moderately loaded voltage regulators were not sufficient for unequivocal determination of the examined integrated circuit’s radiation hardness. [Projekat Ministarstva nauke Republike Srbije, br. 171007: Physical and functional effects of the interaction of radiation with electrical and biological systems]
On-line monitoring of base current and forward emitter current gain of the voltage regulator's serial pnp transistor in a radiation environment
VukiVladimir ?.,Osmokrovi? Predrag V.
Nuclear Technology and Radiation Protection , 2012, DOI: 10.2298/ntrp1202152v
Abstract: A method of on-line monitoring of the low-dropout voltage regulator's operation in a radiation environment is developed in this paper. The method had to enable detection of the circuit's degradation during exploitation, without terminating its operation in an ionizing radiation field. Moreover, it had to enable automatic measurement and data collection, as well as the detection of any considerable degradation, well before the monitored voltage regulator's malfunction. The principal parameters of the voltage regulator's operation that were monitored were the serial pnp transistor's base current and the forward emitter current gain. These parameters were procured indirectly, from the data on the voltage regulator's load and quiescent currents. Since the internal consumption current in moderately and heavily loaded devices was used, the quiescent current of a negligibly loaded voltage regulator of the same type served as a reference. Results acquired by on-line monitoring demonstrated marked agreement with the results acquired from examinations of the voltage regulator's maximum output current and minimum dropout voltage in a radiation environment. The results were particularly consistent in tests with heavily loaded devices. Results obtained for moderately loaded voltage regulators and the risks accompanying the application of the presented method, were also analyzed.
Impact of forward emitter current gain and geometry of pnp power transistors on radiation tolerance of voltage regulators
VukiVladimir,Osmokrovi? Predrag V.
Nuclear Technology and Radiation Protection , 2010, DOI: 10.2298/ntrp1003179v
Abstract: Low-dropout voltage regulators with various geometries and technological realisations of serial pnp power transistors were exposed to ionizing radiation. Although devices with vertical emitters were considered much less susceptible to the influence of radiation on forward emitter current gain than circuits with round emitters, the experiment showed a similar degradation of current gain in both cases. The main reason of high radiation susceptibility of the examined vertical serial pnp transistor is the implementation of an interdigitated emitter, with high perimeter-to-area ratio, causing the great increase of serial transistor’s base current, but a minor influence on the maximum output current. Transistors with round emitters with small perimeter-to-area ratio expressed a moderate current gain degradation, but a rapid fall of the emitter injection efficiency, causing a significant decrease of the maximum output current. Regardless of the similar forward emitter current gain degradation, reliability and operational characteristics of two types of low-dropout voltage regulators were completely different.
The cycle index of the automorphism group of $\mathbb{Z}_n$
Vladimir Bo?ovi?,?ana Kovijani? Vuki?evi?
Mathematics , 2015,
Abstract: We consider the group action of the automorphism group $\I_n=\aut(\Zz_n)$ on the set $\Zz_n$, that is the set of residue classes modulo $n$. Clearly, this group action provides a representation of $\I_n$ as a permutation group acting on $n$ points. One problem to be solved regarding this group action is to find its cycle index. Once it is found, there appears a vast class of related enumerative and computational problems with interesting applications. We provided the cycle index of specified group action in two ways. One of them is more abstract and hence compact, while another one is basically procedure of composing the cycle index from some \textit{building blocks}. However, those \textit{building blocks} are also well explained and finally presented in very detailed fashion.
Effects of selected factors on rheological and textural properties of probiotic yoghurt
Milka Stijepi?,Spasenija Milanovi?,Jovana Glu?ac,Vladimir Vuki
Mljekarstvo , 2011,
Abstract: The aim of this work was to study the influence of inulin (1 %), combination of inulin (1 %) and acacia honey (4 %), heat treatment of milk, and storage time on the rheological and textural properties of probiotic yoghurt. Rheological properties were assessed trough viscosity, syneresis and texture (firmness, consistency, cohesiveness and index of viscosity). Yoghurt was prepared from milk (1,5 % fat) with added inulin (1%) before heat treatment at 85 °C for 20 min or 95 °C for 10 min. After cooling to 55 °C honey (4 %) was added. Samples were inoculated using probiotic starter culture (70 % w/w Streptococcus thermophilus, 10 % w/w Lactobacillus bulgaricus, 10 % w/w Lactobacillus acidophilus, 10 % w/w Bifidobacterium ssp.). Yoghurt samples were held on +5 °C during 21 days. Measurements of pH value, lactic acid, viscosity, syneresis, and textural properties were done after 1, 7, 14 and 21 days of storage. The results of this study show that honey addition significantly decreased fermentation time compared to fermentation time of control samples or samples containing inulin. Furthermore, addition of honey and inulin to milk caused significant lower syneresis (p<0,05) during storage time, while there was no significant influence on viscosity and texture of final product. The applied heat treatment of milk had no significant influence on rheological properties of probiotic yoghurt.
Modeling key interactions between dopamine D2 receptor second extracellular loop and arylpiperazine ligands
?ukalovi? Vladimir,?o?ki? Vuki,Andri? Deana,Rogli? Goran
Journal of the Serbian Chemical Society , 2012, DOI: 10.2298/jsc111028212s
Abstract: Second extracellular loop (ecl2) of dopamine (DA) D2 receptor is an essential part of dopaminergic ligands binding pocket. To form a part of the ligand binding surface it has to fold down into the transmembrane domain of the DA receptor. The current study describes the modeling of the D2 DA receptor ecl2 and its interactions with arylpiperazine ligands. In order to model D2 DA receptor ecl2, the number of arylpiperazine ligands was used to propose pharmacophore model. D2 DA receptor ecl2 model was built using Accelrys Discovery Studio. To test the proposed model, docking analysis was performed and key amino acid residues were determined. Proposed receptor-ligand iteractions were rationalized and compared with measured binding affinity. It is shown that D2 DA receptor ecl2 significantly participates in receptor-ligand complex formation through aromatic, hydrophobic and polar interaction. Taking them in account would benefit GPCR molecular modeling and facilitate the design of novel active compounds.
New therapy strategies for treatment of severe sepsis and septic shock in Intensive care unit of Clinical centre in Kragujevac
Jev?i? Jasna,?urbatovi? Maja,Drakuli?-Mileti? Svetlana,Vuki?evi? Vladimir
Srpski Arhiv za Celokupno Lekarstvo , 2008, DOI: 10.2298/sarh0806248j
Abstract: INTRODUCTION Despite numerous advances in medicine, the mortality rate of severe sepsis and septic shock remains high, 30-50%. New therapy strategies include: early goaldirected therapy, fluid replacement, early and appropriate antimicrobials, source of infection control, use of corticosteroids, vasopressors and inotropic therapy, use of recombinant activated protein C, tight glucose control, low-tidal-volume mechanical ventilation. They have been shown to improve the outcomes. The adequacy and speed of treatment influence the outcome, too. OBJECTIVE The objective was to evaluate if new therapy strategies had been integrated in our routine practice. METOD Patients with severe sepsis or septic shock, who were treated in the Intensive Care Unit (ICU) over a ten-month period, were analyzed retrospectively. The descriptive epidemiological method was applied. Central venous catheterization, central venous pressure, antibiotics, fluid resuscitation, mechanical ventilation, vasopressors, corticosteroids, blood administration, deep vein thrombosis prophylaxis, stress ulcer prophylaxis, glucose control, were evaluated. RESULTS 27 patients were analyzed. Patient characteristics were: age, 49.9 years (18-77) with 30-day in-hospital mortality rate of 48.1%. All patients received broad-spectrum antibiotics. Blood cultures were obtained in 85.2% patients. Adequate antimicrobial treatment was applied to 59.3% and 74.1% patients had central venous pressure monitoring. Average central venous pressure was 8.47±5.6 mm Hg (-2- 20). Aggressive fluid therapy was given to 33.3% of the cases and 66.7% of the patients with septic shock received vasoactive drugs while 29.6% received corticosteroids. Red blood cell transfusions were applied in 59.3% of patients. All patients received stress ulcer prophylaxis, and 37% of them deep vein thrombosis prophylaxis. The average value of morning glucose was 9.11±5.03 mmol/l (3.7-22.0). 63% of patients were mechanically ventilated. Blood lactate was not determined. CONCLUSION Evidence-based clinical guidelines for management of severe sepsis and septic shock have not been implemented in a widespread, systematic way in the ICU of the Clinical Centre, Kragujevac. Institutional acceptance of this protocol, and education of clinicians may improve survivability for patients with sepsis.
Textural characteristics of fermented milk beverages produced by kombucha
Milanovi? Spasenija D.,Ili?i? Mirela D.,Durakovi? Katarina G.,VukiVladimir R.
Acta Periodica Technologica , 2009, DOI: 10.2298/apt0940063m
Abstract: Rheological properties of fermented dairy products are very important parameters of the product quality. The behaviour of gel formed during fermentation of milk is influenced by a great number of factors, such as: milk composition, starter culture, flavourings addition, etc. The aim of this research was to examine the influence of fat content, and kombucha inoculum concentration on textural characteristics of fermented milk beverages: firmness, consistency, cohesiveness and viscosity index after production and during 10 days of storage. Higher fat content of beverage affects the firmness, consistency, cohesiveness and viscosity index, while higher amount of inoculum in beverages has an opposite effect on textural characteristics of samples during storage.
Bo?idar V Krsti?,Milun Babi?,Vuki? N Lazi?,Vladimir N Rai?evi?
Thermal Science , 2010, DOI: tsci100412019k
Abstract: Analysis of output quality of power transmitters is possible in position when characteristics are determined earlier. This is the reason why we focused on determination of these characteristics for a concrete power hydro-transmitter. This means that the investigation task primarily consisted of determination of functional characteristics, defining of the sliding curves and temperature regimes of a concrete hydrodynamic clutch. Results of velocity and pressure field investigations in the working space of this clutch, obtained by use of the same test setup, are the basis for determination and analysis of the functional characteristics, sliding curves and temperature regimes. In this work we also analyzed function of the hydrodynamic transmitter in assembly with an internal combustion engine, as well as a process of acceleration and deceleration of a vehicle with this assembly in it.
Contribution to the development of the method of forecasting the frequency and duration of "failure" of technical systems
Vuki?evi? Milan
Glasnik ?umarskog Fakulteta , 2007, DOI: 10.2298/gsf0795049v
Abstract: An active approach to the market means the full adaptation of the production system to the demands of the consumers, and the high profitability. To realize the above, production system should create the conditions for the simulation of the behavior of the system in real conditions. In the opposite the behavior of the system will be highly uncertain because of the disturbance in the system. The simulation of the behavior of the system in real conditions includes the existence of reliable information, obtained based on previous research. A series of such information also includes the information on the production cycle of a series of products. The components of the production cycle are also different disturbances. This paper analyses the failures of the technical system. This fact points to the significance of creating the conditions for forecasting the frequency and duration of the "failure". This paper, based on research of two formatisers, presents the methodology of carrying out the forecasting in real conditions.
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