B. Loncar
University of Belgrade
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Featured researches published by B. Loncar.
Plasma Sources Science and Technology | 2007
P. Osmokrovic; Milos Vujisic; Koviljka Stankovic; A. Vasić; B. Loncar
This paper discusses the mechanisms of gas breakdown at low values of pressure and inter-electrode gap, i.e. in the vicinity of the Paschen minimum. In this area of pressure and inter-electrode gap values, breakdown occurs either through gas or vacuum mechanisms, and also the so called anomalous Paschen effect appears. Electrical breakdown of electropositive, electronegative and noble gases has been investigated theoretically, experimentally and numerically. Based on the results obtained, regions in which particular breakdown mechanisms appear have been demarcated. Special attention has been devoted to the anomalous Paschen effect as well as to the avalanche vacuum breakdown mechanism.
international conference on microelectronics | 1997
Z. Stanojevic; D.E. Ioannou; B. Loncar; P. Osmokrovic
In this paper a quantitative analysis has been used for describing and discussing design characterizations of an SOI flash memory cell. Mathematical expressions for the front gate threshold voltage of the SOI memory cell are derived using the equations for a standard SOI MOSFET. Coupling coefficients which exist between the control gate and source and drain regions, are the same as for the silicon body, through stored charge at the floating gate has to be included in these equations and the mathematical expressions for the flash memory cell can be obtained. Implementing this, the voltage of the front gate of a standard SOI MOSFET is equal to the voltage of the floating gate of the memory cell. During analysis, the emphasis is put on the case where the back channel is depleted, because then coupling between the front and back gate can control the threshold voltage of the control gate.
IEEE Transactions on Nuclear Science | 2003
B. Loncar; P. Osmokrovic; Srboljub Stankovic
The goal of this paper is to determine use of gas filled surge arresters (GFSA) with a built-in radioactive sources in radiative environment. Furthermore, a pseudoempiric method has been developed to determine the GFSA pulse shape characteristics. These results are considered relevant for the use of this component in both military applications and space technology.
IEEE Transactions on Plasma Science | 2002
P. Osmokrovic; B. Loncar; Srboljub Stankovic
This paper presents an alternative approach aimed toward improvement of protective characteristics of gas-filled surge arresters (GFSA). Although so far GFSA with built-in radioactive sources proved to have superior protective characteristics, environmental concerns often challenge functional benefits. Experimental results show that a hollow cathode used in GFSA (no radioactive sources), offers significant improvement of protective characteristics as compared to classical designs. A number of theoretical predictions and conclusions are confirmed experimentally.
IEEE Transactions on Plasma Science | 2005
P. Osmokrovic; B. Loncar; Rajko Sasic
The aim of this paper is to present the influence of electrode system parameters on electrical breakdown of gas (electrode effect) with the purpose to improve the gas-filled surge arresters (GFSAs) protective characteristics with the most optimal way. The influence of the electrode parameters on the pulse shape characteristics is examined. As variable parameters, the electrode material and the manner of electrode surface processing are used. The originally developed GFSA model with a composite electrode system enables a high degree of over-voltage protection without environmental contamination.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms | 1998
P. Osmokrovic; Marko Stojanović; B. Loncar; N. Kartalovic; I. Krivokapic
Abstract Aim of this work is to examine the over-voltage protection under the ionizing radiation influence. The use of modern electronic devices (nuclear, military and space technology) in the conditions of ionizing radiation brings up the question of radioactive resistance of electronic components and over-voltage protection components. The question of reliability of these components under the influence of ionizing radiation is also a relevant one. The entire effects of radiation, which cause the irreversible changes of the material characteristics, are defined as the dosage or integral effects. The resistance of the over-voltage material (the Transient Suppresser Diodes (TSD), Metaloxide Varistors, Gas Filled Surge Arresters (GFSA) and Polycarbon Capacitors) subjected to influence of n+γ radiation caused by californium source was examined in order to determine the radiation effects. It was determined that TSD are highly sensitive to the radiation. The radiation effects on Metaloxide Varistors are similar to the effects on the TSD. GFSA showed the temporary characteristics improvement. It was determined that the Polycarbon Capacitor capacity decreases under the influence of radiation. The obtained results are explained theoretically.
Plasma Sources Science and Technology | 2006
P. Osmokrovic; Tamara Živić; B. Loncar; A. Vasić
This paper investigates the validity of the similarity law in cases of dc and pulse breakdown of gases. Geometrically similar systems insulated with SF6 gas were used during experiments. It is shown that the similarity law is valid for dc breakdown voltage if the electron mean free path is included in geometrical parameters of the system, but not for pulse breakdown voltages. The explanation for this is the mechanism of the pulse discharge. The similarity law was expanded to take into account mechanisms of pulse breakdown initiation. Thus, the general similarity law is obtained, the validity of which in case of a pulse breakdown is established experimentally.
IEEE Transactions on Plasma Science | 2007
P. Osmokrovic; Tamara Zivic; B. Loncar; A. Vasić
The aim of this paper is to investigate the justification and the limitation of the geometrical similarity law application on the electrical breakdown of SF6 gas. For this purpose, the measurements of the dielectric breakdown voltage for similar systems insulated with SF6 gas were done. The applied dc voltage source had an 8 V/s rate of rise. Standard double exponential overvoltage pulse (rise time T1=1.2 mus, fall time T2 =50 mus) of the amplitude U1 max=320 V, U 2 max=4.80 kV, and U3 max=640 kV was used. On the basis of the obtained experimental results and theoretical considerations, the conditions under which the geometrical similarity laws are applicable on discharges in gases are determined. It was concluded that there is no correlation between the geometrical similarity of the electrode surface topography and corresponding breakdown voltages. It was shown that the extension of the similarity law, introducing the electron mean free path as a linear dimension of the system, gives a good quantitative agreement. Also, in case of the pulse breakdown voltage, it is necessary to apply the breakdown possibility rise law
IEEE Transactions on Plasma Science | 2006
B. Loncar; P. Osmokrovic; A. Vasić; Srboljub Stankovic
This paper aims to find the possibility of stabilizing the gas-filled surge arresters (GFSA) static working point in gamma- and X-radiation fields by an appropriate choice of constructive parameters. The observed effects on some commercial components have been compared to the originally developed GFSA model with the aim of improving the characteristics of the commercial components. The type of noble gas, the pressure in the gas chamber, the inter-electrode gap value, the electrode material, and the manner of electrode surface processing are used as variable parameters. The obtained results are significant for a better understanding of the prebreakdown effects in gases at low pressures, but also have practical importance for the manufacturer of GFSAs
IEEE Transactions on Plasma Science | 2002
B. Loncar; P. Osmokrovic; Srboljub Stankovic
In this paper, we present temperature stability investigations of different overvoltage protection components employed in low-voltage applications. The following components have been examined: transient suppresser diodes, metal-oxide varistors (MOVs), gas-filled surge arresters (GFSAs), and polycarbonate capacitors. The aim of the research presented here is to identify the effectiveness of the overvoltage protection as a function of temperature. Experimental results show that GFSAs have rather stabile operational characteristics in a wide temperature range (from -90/spl deg/C to +210/spl deg/C). As for MOVs, they exhibit certain improvement of their protective characteristics at higher temperatures. Experimental results are backed up by theoretical explanations.