Temperature Sensors Manufactured from Edible Materials Intended for Oral Cavity Operation

Goran M. Stojanović,Milan Radovanović,Sanja Kojić,Lazar Milić,Mitar Simić,Naturality Company,Raphael Georges Duval,Jelena Vukmirović,Bojan Petrović 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.1

Following the circular economy concept, all areas of science, including electronics, require individual approach. The green electronics approach implies processing natural based materials for development of electronic components even for single use, so that waste does not exist. This paper describes the production of thermistors from 3 different types of edible materials, their testing in laboratory conditions, as well as the application for measuring the temperature in the human oral cavity. To make the thermistor, three types of natural materials were used (carrageenan, polyvinyl alcohol and apple pomace-based). After fabrication, materials were poured into molds. Aluminium foil contacts were placed so that the electrical characterization of the materials could be performed. Several parameters were measured: resistance (R), impedance (Z) and the phase angle (θ) as a function of frequency. In order to determine whether the thermistors have a positive or negative temperature coefficient and to determine their sensitivity, measurements were conducted at three different temperatures: 25 ℃ (room temperature), 37 ℃ (human body temperature), and 50 ℃. The thermistors demonstrated negative temperature coefficient behaviour. Additionally, it was demonstrated that the apple pomace-based thermistor can successfully measure healthy volunteer's temperature.

A simplified matrix stiffness method for analysis of composite and prestressed beams

Biljana Deretić-Stojanović,Svetlana M. Kostić 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.24 No.1

The paper presents the simplified matrix stiffness method for analysis of composite and prestressed beams. The method is based on the previously developed "exact" analysis method that uses the mathematical theory of linear integral operators to derive all relations without any mathematical simplifications besides inevitable idealizations related to the material rheological properties. However, the method is limited since the closed-form solution can be found only for specific forms of the concrete creep function. In this paper, the authors proposed the simplified analysis method by introducing the assumption that the unknown deformations change linearly with the concrete creep function. Adopting this assumption, the nonhomogeneous integral system of equations of the "exact" method simplifies to the system of algebraic equations that can be easily solved. Therefore, the proposed method is more suitable for practical applications. Its high level of accuracy in comparison to the "exact" method is preserved, which is illustrated on the numerical example. Also, it is more accurate than the well-known EM method.

Processing and Characterisation of Hybrid Aramid Fabrics Reinforced with Cross-linked Electrospun PVB Composite Nanofibres

Vera Obradović,Dušica B. Stojanović,Ivona Janković Častvan,Vesna Radojević,Petar S. Uskoković 한국섬유공학회 2018 Fibers and polymers Vol.19 No.9

The aim of this study was to fabricate a new kind of hybrid fabric composites with the cross-linked electrospun poly(vinyl butyral) (PVB) composite nanofibres. The experiments were performed with the 10 wt.% PVB/ethanol solution for electrospinning where the modified silica nanoparticles (mSiO2), the oxidised single-walled carbon nanotubes (o- SWCNT) and the o-SWCNT/mSiO2 hybrid nanoparticles were added to the solution. The electrospun fibres were crosslinked with glutaraldehyde (GA) afterwards in order to reinforce the composite structure by bonding to the p-aramid fabrics. The chemical and thermo-mechanical properties of the hybrid fabric composites were evaluated. The greatest improvement in thermo-mechanical properties was achieved by the sample which contained the cross-linked PVB fibres with the o- SWCNT/mSiO2 hybrid nanoparticles.

Analysis of Surface Potential and Electric Field for Fully Depleted Graded Channel Dual-Material-Double-Gate MOSFET through Modeling and Simulation

Himeli Chakrabarti,Reshmi Maity,Tijana Kevkić,Vladica Stojanović,N. P. Maity 한국전기전자재료학회 2021 Transactions on Electrical and Electronic Material Vol.22 No.4

This article is about an elaborative description of two dimensional investigative mathematical structure of fully depleted graded channel (GC) dual-material-double-gate (DMDG) silicon-on-insulator metal–oxide–semiconductor-fi eld-eff ecttransistor (SOI MOSFET). The surface potential contours in addition with electric field variation throughout the channel establish reduction of short-channel-effects (SCEs). To get better operational analysis, some new characteristics such as temperature effect and interface charge eff ects have been incorporated in the model. In this representation we also incorporate the consequences of high-k dielectric medium HfO2 instead of SiO2 and have made a comparison with the effect in various frameworks. In the GC DMDG composition, the surface potential as well as electric field throughout the channel shows close to step function variations which help to defeat the hot carrier along with drain-induced-barrier-lowering (DIBL) effects. As an outcome, the structure shows that the surface potential profi le increases by using GC DMDG structure over DMDG. All these outcomes of the proposed analytical representation have been compared by TCAD simulation consequence. Very good conformity is observed between them.

Accuracy of incidental dynamic analysis of mobile elevating work platforms

Miomir LJ. Jovanović,Goran N. Radoičić,Vladimir S. Stojanović 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.71 No.5

This paper presents the results of a study into the dynamic behaviour of a support structure of a mobile elevating work platform. The vibrations of the mechanical system of the observed structure are examined analytically, numerically, and experimentally. Within the analytical examination, a simple mathematical model is developed to describe free and forced vibrations. The dynamic analysis of the mechanical system is conducted using a discrete dynamic model with a reduced number of vibrational degrees of freedom. On the basis of the expression for the system energy, and by applying Lagrange's equations of the second kind, differential equations are derived for system vibrations, frequencies are determined, and the laws of forced platform vibration are established. At the same time, a nonlinear FEM model is developed and the laws of free and forced vibration are determined. The experimental and numerical part of the study deal with the examination of the real structure in extreme conditions, taking into account: the lowest eigenfrequency, forced actions that could endanger the general stability, the maximal amplitudes, and the acceleration of the work platform. The obtained analytical and numerical results are compared with the experiments. The experimental verification points to the adverse behaviour of the platform in excitation cases – swaying. In such a situation, even a relatively small physical force can lead to unacceptably high amplitudes of displacement and acceleration – exceeding the usual work values.

Effects of L-NAME, a non-specific nitric oxide synthase inhibitor, on AlCl3-induced toxicity in the rat forebrain cortex

Ivana D. Stevanović,Marina D. Jovanović,Ankica Jelenković,Miodrag Čolić,Ivana Stojanović,Milica Ninković 대한수의학회 2009 Journal of Veterinary Science Vol.10 No.1

The present experiments were done to determine the effectiveness of a non-specific nitric oxide synthase inhibitor, N-nitro-L-arginine methyl ester (L-NAME), on oxidative stress parameters induced by aluminium chloride (AlCl3) intrahippocampal injections in Wistar rats. Animals were sacrificed 3 h and 30 d after treatments, heads were immediately frozen in liquid nitrogen and forebrain cortices were removed. Crude mitochondrial fraction preparations of forebrain cortices were used for the biochemical analyses: nitrite levels, superoxide production, malondialdehyde concentrations, superoxide dismutase (SOD) activities and reduced glutathione contents. AlCl3 injection resulted in increased nitrite concentrations, superoxide anion production, malondialdehyde concentrations and reduced glutathione contents in the forebrain cortex, suggesting that AlCl3 exposure promoted oxidative stress in this brain structure. The biochemical changes observed in neuronal tissues showed that aluminium acted as a pro-oxidant. However, the nonspecific nitric oxide synthase (NOS) inhibitor, L- NAME, exerted anti-oxidant actions in AlCl3-treated animals. These results revealed that NO-mediated neurotoxicity due to intrahippocampal AlCl3 injection spread temporally and spatially to the forebrain cortex, and suggested a potentially neuroprotective effect for L-NAME.

Novel Hybrid Nanostructures of Carbon Nanotube/Fullerene-like Tungsten Disulfide as Reinforcement for Aramid Fabric Composites

Vera Obradović,Danica Simić,Milorad Zrilić,Dušica B. Stojanović,Petar S. Uskoković 한국섬유공학회 2021 Fibers and polymers Vol.22 No.2

Multilayered composites based on aramid fabrics are widely used in impact protection. The objective of this studyis creating a new kind of multiaxial aramid fabric composites with inorganic fullerene-like tungsten disulfide nanoparticles(IF-WS2) and single walled carbon nanotubes (SWCNT) used as nanoreinforcement to enhance the dynamic mechanical andanti-stabbing properties of the composites. The four composites of the Kolon fabric forms were impregnated with 10 wt.%poly(vinyl butyral) (PVB)/ethanol solution which contained different forms of IF-WS2 nanoparticles. The surfaces of IF-WS2were coated with silane coupling agent (m-IF) and the SWCNT were oxidized (o-SWCNT) for the fabrication of the o-SWCNT/m-IF hybrid nanoparticles. The mechanical testing showed that the Kolon/PVB/o-SWCNT/m-IF sample producednearly 62 % of improvement in the tensile strength and 51 % of improvement in the tensile energy absorption compared tothe Kolon/PVB sample. Furthermore, the sample with the o-SWCNT/m-IF hybrid nanoparticles demonstrated 24 % ofenhancement in the impact toughness and 48 % of improvement in the absorbed energy after knife penetration in comparisonwith the Kolon/PVB sample.

Precise Manufacturing and Performance Validation of Paper-Based Passive Microfluidic Micromixers

Mahdee Samae,Pawarit Ritmetee,Somyot Chirasatitsin,Sanja Kojić,Tijana Kojić,Jovana Jevremov,Goran Stojanović,Hani Al Salami 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.3

Micromixers are one of the most frequently used components in microfluidics. Passive micromixers are an emerging type with unique features in terms of reliability, robustness and efficiency. Hence, this study aimed to design, fabricate and test new multilayered passive micromixers consisting of three ad hoc layers, by means of a precise and cost-effective xurography manufacturing technique. The first and third layers are PVC foils, whereas the second layer is paper, incorporating microchannels of straight line or zig-zag configuration. Three different types of papers were analyzed as materials for the middle layer. Results demonstrated that immersing the papers into paraffin wax resulted in significantly improved physical characteristics, including solidification and intactness that reduced leakage of fluids into inside channels, thereby enhancing internal efficacy and delivery mechanisms. Subsequent assessments were carried out on mixing performance at various flow rates, pattern-related flow rates at various pressures and paper types, and results showed the impact of a zig-zag versus straight line configuration, demonstrating the importance of flow patterns on features of micromixers and their applications in microfluidic devices. Furthermore, image analysis was conducted to determine mixing efficiency of the proposed microfluidic micromixers.

In vitro investigation of electrophoretically deposited bioactive hydroxyapatite/chitosan coatings reinforced by graphene

Đ,oš,ić,, Marija,Eraković,, Sanja,Janković,, Ana,Vukaš,inović,-Sekulić,, Maja,Matić,, Ivana Z.,Stojanović,, Jovica,Rhee, Kyong Yop,Miš,ković Elsevier 2017 Journal of industrial and engineering chemistry Vol.47 No.-

<P><B>Abstract</B></P> <P>Graphene (Gr) and natural polymer chitosan (CS) were introduced to hydroxyapatite (HAP) to produce a three-component composite coating, which was fabricated by cathodic electrophoretic deposition on Ti substrates in an ethanol suspension. These HAP/CS/Gr coatings were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements and found that the graphene into HAP/CS composites significantly improves their morphology, thermal stability, and bioactivity. Both HAP/CS and HAP/CS/Gr composite coatings are classified as non-cytotoxic when tested against healthy peripheral blood mononuclear cells (PBMC), while antibacterial activity against <I>Staphylococcus aureus</I> and <I>Escherichia coli</I> could not be verified.</P>