ISSN 2738-0971 | eISSN 2738-1013
Bulletin of Natural Sciences Research
Open access journal | Double-blind peer review

Tijana Kevkić

Faculty of Sciences and Mathematics, University of Priština in Kosovska Mitrovica, Kosovska Mitrovica, Serbia

Articles

Open Access Original Scientific Paper

ANALYSIS OF STATIC BEHAVIOR OF ION SENSITIVE FIELD EFFECT TRANSISTOR FOR PH MEASUREMENTS

by Tijana Kevkić, Reshmi Maity, Dragana Todorović, Biljana Vučković, N. P. Maity

The Ion-Sensitive Field-Effect Transistor (ISFET) is one of the most popular pH sensors traditionally using to measure hydrogen ion concentration (pH) of the electrolytic solutions. It is developed from Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) by replacing gate electrode with an electrolytic solution to be tested, and a reference metal electrode immersed in that solution. Basic principle of ISFET operation is based on that of standard NMOS structure in conjunction with the insulator-electrolyte capacitor as described in this paper. The site-binding theory (generalized to two kinds of binding sites), together with the Gouy - Chapman- Stern model for the potential profile in the electrolyte, is coupled to the MOS physics. As a result, an approximate analytical model which completely describes static behavior of the ISFET is obtained. The developed description can serve as useful tool for understanding many contemporary biosensors based on original ISFET structure which has broad application in biomedicine, biological, chemistry and environmental areas.

View Full-Text DOI 10.5937/bnsr12-37850 Published: 15 Jul 2022
Open Access Original Scientific Paper

INTERPOLATION LOGISTIC FUNCTION IN THE SURFACE POTENTIAL BASED MOSFET MODELING

by Tijana Kevkić, Vladica Stojanović

Introduction of the Interpolation Logistic (IL) function in an approximate Surface-Potential-Based MOSFET model has been proposed in this paper. This function can be precisely determined in accordance with different MOSFET device characteristics. The IL function also provides continual behavior of the surface potential in entire useful region of MOSFET operation. Unlike the approximate analytical models which can meet in literature, continual and smooth transition of the surface potential between weak and strong inversion region here is achieved without using of any empirical parameter. Furthermore, thanks to the IL function, speed and manner of that transition are controlled. The values obtained for the surface potential are verified extensively with the numerical data, and a great agreement is found for the MOSFET devices from different technology generations.

View Full-Text DOI 10.5937/univtho8-17067 Published: 08 Dec 2018
Open Access Original Scientific Paper

HOMOTOPY PERTURBATIONS METHOD: THEORETICAL ASPECTS & APPLICATIONS

by Vladica Stojanović, Tijana Kevkić

The application of the homotopy perturbation method (HPM) in two different research's area has been proposed in this paper. First, the HPM has been used for approximate solving of the well-known implicit equation for electrostatic surface potential of MOSFET transistor. The approximate analytical solution obtained in this case has relative simple mathematical form, and simultaneously high degree of accuracy. Next, HPM has been applied in determination of the invariant measures (IMs) of the non-linear dynamical systems with chaotic behavior. The convergence and efficiency of this method have been confirmed and illustrated in some characteristic examples of chaotic mappings.

View Full-Text DOI 10.5937/univtho8-17290 Published: 30 Jun 2018
Open Access Original Scientific Paper

MODIFICATION OF TRANSITION'S FACTOR IN THE COMPACT SURFACE-POTENTIAL- BASED MOSFET MODEL

by Tijana Kevkić, Vladica Stojanović, Dragan Petković

The modification of an important transition’s factor which enables continual behavior of the surface potential in entire useful range of MOSFET operation is presented. The various modifications have been made in order to obtain an accurate and computationally efficient compact MOSFET model. The best results have been achieved by introducing of the generalized logistic function (GL) in fitting of considered factor. The smoothness and speed of the transition of the surface potential from the depletion to the strong inversion region can be controlled in this way. The results of the explicit model with this GL functional form for transition's factor have been verified extensively with the numerical data. A great agreement was found for a wide range of substrate doping and oxide thickness. Moreover, the proposed approach can be also applied on the case where quantum mechanical effects play important role in inversion mode.

View Full-Text DOI 10.5937/univtho6-11360 Published: 25 Dec 2016
Open Access

ASSESSMENT OF RADIATION RISK FROM DRINKING WATER AT PUBLIC FOUNTAINS ON THE WIDER TERRITORY OF KRUŠEVAC

by Biljana Vučković, Nataša Todorović, Jovana Nikolov, Dragan Radovanović, Tijana Kevkić

Measurements of radon concentrations in drinking waters conducted on wider territory of the town of Kruševac included 16 public fountains, of which 4 are in the city itself and 12 in the surrounding area. Measurements of radon concentrations in water were carried out using radon detector RAD7 (DURRIDGE Co.). The values ​​of radon concentrations in water are in the range of (5.3 ± 0.8) Bq l-1 to (71.0 ± 7.2) Bq l-1 and are below the reference level of 100 Bq l-1, recommended by the European Commission. Since radon represents one of the most important causes of malignant diseases, annual effective doses of ingestion and inhalation are determined, whose mean values ​​are in the range of 0.04 mSv y-1 to 0.52 mSv y-1, and from 14.84 μSv y-1 to 198.8 μSv y-1, respectively. During sampling, water temperatures and their pH values were measured. These results are the first results of measuring radon in water in this area by this method. The aim of this paper is to evaluate whether there is, or not, a radiological risk to people's health due to the use of water primarily for drinking, but also for other purposes.

View Full-Text DOI 10.5937/univtho9-18421