Implementation of new equipment for the laboratory exercises – Testing of low-voltage electrical installations

This study was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia, and these results are parts of the Grant No. 451-03-68/2022-14/200132 with University of Kragujevac - Faculty of Technical Sciences Čačak.This paper presents the new equipment that is used for laboratory exercises in the subject of Electrical installations and lighting at the undergraduate academic and professional studies in the Faculty of Technical Sciences in Čačak. Multifunctional electrical installation safety testers for testing domestic and industrial electrical installations were presented. A demonstration board that provides simulation of different types of faults in electrical installations is also presented. As an illustrative example, the paper presents the procedure and results obtained during the realization of the exercise - Measurement of ground fault loop impedance in TT and TN earthing systems and checking the conditions for automatic disconnection of supply.Publishe

The determination of the mean value of the non-homogenous background radiation and the measurement uncertainty using Welch-Satterthwaite equation

In this paper, the procedure for determination of the mean value of non-homogenous background radiation and the expression of measurement uncertainty is considered. The background radiation is described using the Student's distribution, and the measurement uncertainty using the Welch-Satterthwaite equation. The proposed algorithm was experimentally verified under well-controlled laboratory conditions and satisfactory results were obtained. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 171007

Influence of gamma radiation on measurement fast pulse voltages by Kerr electro-optic effect

In this paper, the possibility of measuring the electronic pulse from an electronic generator for plasma heating by electro-optical method is considered. The experiments are performed by applying the Kerr effect on an electronic generator model. Kerr effect shows very good characteristics for measuring nanosecond pulse rate. However, the results obtained show that these characteristics are significantly spoiled by gamma radiation in a dynamic state as well as by the absorbed dose of gamma radiation. When the simplicity of measuring with a capacitive probe is added to that, it can be concluded that the Kerr electro-optical effect is not recommended for measurement in fusion experiments

Correlation of Color Doppler with Multidetector CT Angiography Findings in Carotid Artery Stenosis

The aim of this paper was to examine the correlation between the Color Doppler ultrasound (CD-US) and multidetector CT angiography (MDCTA) diagnostic methods, and to define the degree and extent of stenosis in patients with internal carotid artery stenosis. This was a cross-sectional study with a consecutive series of patients. All US examinations were always carried out by the same physician-angiologist, while all CT examinations were always carried out by the same physician-radiologist. Both worked independently from each other. The stenosis area was measured at the narrowest point by NASCET criteria for US/CT. Peak systolic velocity (PSV) over 210 cm/sec and end diastolic velocity (EDV) over 110 cm/sec criteria were applied for stenoses with lumen narrowed over 70%, while PSV under 130 cm/sec and EDV under 100 cm/sec criteria were applied for those with lumen narrowed under 70%. A total of 124 carotid arteries were observed; namely, 89 narrowed and 68 surgically treated. All patients were reviewed by US and then by MDCTA; patients with 70–99% stenosis underwent surgery. The correlation coefficient between stenosis degree measured by US and MDCTA was 0.922; p < 0.01. The average difference between US and MDCTA diagnostic methods was 3% (Z = -1.438, p > 0.05). The US and CT matching level for stenoses from 70 to 99% was very high (κ = 0.778, p < 0.01). In conclusion, there is a highly significant statistical correlation among both diagnostic methods when measuring stenosis degree and extent. US is more dependent on the physician, while MDCTA is more objective and independent from the physician. We think it would be appropriate to undertake an MDCTA exam for those patients who are candidates for carotid endarterectomy

Preparation and characterization of bismuth germanium oxide (BGO) polymer composites

Bismuth germanium oxide Bi12GeO20 (BGO) has very interesting electrical, optical and magnetic properties. In order to make devices based on this material more flexible, its powder was used for preparing polymer composites. This study reports investigation of the effects of using different solvents and polymers in preparation of BGO composite on the microstructural and optical behaviour of the resulting material. Preparation of such composites by a solution casting method is described. Poly (methyl methacrylate) (PMMA) and polystyrene (PS)) were used as matrix materials and acetone and chloroform as solvents. Their microstructure and the quality of BGO dispersion and deaggregation in polymer matrix were analyzed by SEM, Raman, XRD and optical spectroscopy. The influence of particle size distribution, their shapes, and concentration on the optical transmission is calculated based on Mie scattering theory and discussed, too