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Publikacije (45904)

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Damir Suljevic, Anida Čorbić, Erna Islamagić, M. Fočak, Filip Filipić, Andi Alijagic

Cadmium is a heavy metal classified as an environmental hazard, and its toxicity is subject to extensive research. Japanese quails were exposed to cadmium chloride (CdCl2) ad libitum for 20 days. Bone marrow, peripheral blood and liver were analyzed following the exposure. Moreover, we have provided the very first explanation of hematopoietic lines in Japanese quail. Following CdCl2 exposure, changes in the number, size and morphology of blood cells were observed in both peripheral blood and bone marrow. Alterations included severe erythrocyte damage, monocytosis and lymphopenia. In the liver of Cd-exposed animals we observed necrotic cells, absence of hematopoietic regions and cytogenetic changes of hepatocytes. Alterations in the bone marrow were also noted, as well as giant phagocytic cells, most likely macrophages. In vivo, CdCl2 exposure caused swift and destructive changes in the hematopoietic niche, liver and other tissues responsible for the detoxification cycle of cadmium and its compounds.

E. Husak, A. Kovacevic, I. Karabegović

Clearances between rotating and stationary parts in a screw compressor are set to ensure the efficient operation and allow for thermal deformation without unwanted contacts. The change in clearances is caused by both pressure and temperature changes within the machine. If clearances are too large, the increased leakage flows will reduce efficiency. However, if the nominal clearances are too small, contacts between the rotating and stationary parts can occur as a consequence of rotor and casing deformations. In order to determine the operational clearances, a numerical analysis of deformation of screw compressor rotors and casing has to be performed. This paper discusses how the temperature of rotor and casing surfaces calculated from the one-dimensional chamber model in the SCORG could be used as a boundary conditions for a steady state thermal and structural analysis of a screw compressor solid parts. Deformations of rotors and casing under temperature load were calculated using a commercial Finite Element Analysis code ANSYS. Operational clearance are estimated from these deformations and some recommendations for further work are proposed.

Yoga and mindfulness improve the blood circulation and thereby reduces the causes of hypertension hearth attack or stroke. Complete yoga breathing has the role in oxygenating the blood and therefore assists fresh nutrients to reach all peripheral vessels and capillaries. Yoga helps to prevent various circulatory ailments and illnesses such as high blood pressure, shallow breathing, muscle tension and coronary heart disease. During moderate to intense yoga exercise hearth rate increases and as a result hearth pumps more blood, systolic blood pressure rise and blood volume increases. It provides better circulation and formation of new capillaries. The purpose of this review is to investigate the efficacy of yoga exercise on circulatory system, pulse and hearth rate, systolic and diastolic blood pressure and cardiovascular function. A review of literature was conducted from Pubmed, Research Gate, Medline and Google Scholar.

V. Stefanović, S. Urošević, Željko Stević, I. Mladenović-Ranisavljević

The research in this article aimed at determining the importance of occupational safety and health (OSH) factors at work as criteria for development of the OSH climate. Based on the views of 28 responsible persons of the OSH management system, the significance of the criteria was determined using the rough step-wise weight assessment ratio analysis method. The obtained results show that development of the OSH climate in organizations primarily depends on the factors of the work environment and the commitment of the management to the OSH system. The results also point out that education of employees in the field of safety at work has a significant impact. A comparison of the obtained results was made in the sensitivity analysis using the full consistency method. The specific dimensions of the safety climate at work were determined and ranking of the OSH factors was performed.

Ervin Karić, I. Petric, V. Mićić

The aims of this study were to determine improved kineticparameters in five kinetic models for oxidation of n-butane intomaleic anhydride in an industrial fixed-bed reactor, and tosimulate the reactor performance. On the basis of the measuredprocess parameters, inlet and outlet concentrations of n-butanewere calculated and then used to fit the kinetic models. Theindustrial fixed-bed reactor was approximated by 10 continuousstirred tank reactors (CSTR) connected in series. Based on thecalculated outlet concentration of n-butane from the industrialreactor, the outlet concentration of n-butane from thepenultimate reactor was calculated. Then the concentrations ofn-butane were calculated until the inlet concentration of nbutanein the first reactor was obtained. Kinetic parameterswere determined by comparing the inlet concentrations of nbutanein the first reactor with the inlet concentration of nbutaneobtained on the basis of the measured processparameters in the industrial fixed-bed reactor. Kinetic modelswith improved kinetic parameters showed better simulationresults compared to kinetic models with the existing kineticparameters. The best agreement of simulation results andmeasured values was achieved with application of the kineticmodel 2 (Equations (2a-c)). The smallest deviations ofnumerical simulation in comparison with measured values of theoutlet pressure of reaction mixture were 0.45, 0.75 and 0.75%for application of the kinetic model 3 (Equations (3a-c)). Thepercentage deviations of numerical simulation with improvedkinetic parameters and the existing kinetic parameters incomparison with measured values of inside reactor temperaturewere in the range 0.90-5.36% and in the range 4.17-9.78%(kinetic model 2, Equations (2a-c)), respectively.

Ana Maravić, T. Rončević, Lucija Krce, Nada Ilić, B. Galić, Vedrana Čulić Čikeš, Ivana Carev

Abstract Halogenated boroxine dipotassium trioxohydroxytetrafluorotriborate, K2[B3O3F4OH] (boroxine) was previously shown to be very effective in inhibition of several carcinoma cell lines, including the skin cancer. Here, we investigated its antimicrobial potential by targeting the multidrug-resistant opportunistic pathogens associated with skin and wound infections. The antimicrobial testing against eleven bacterial and four fungal species revealed good activity of boroxine against pathogenic filamentous fungi Penicillium funiculosum and Aspergillus niger (MIC50 64 and 128 µg/ml), and a moderate bioactivity against the yeast Candida albicans (MIC50 512 µg/ml). Among the tested multidrug-resistant bacteria, the best antibacterial effect, stable over a 24-h period, was observed against the methicillin-resistant Staphylococcus aureus strain (MRSA) at MIC of 1024 µg/ml. The atomic force microscopy (AFM) used to investigate the morphology of S. aureus cells revealed indentations on its cell envelope after the boroxine exposure. These results show that in addition to the antitumor effect, boroxine exerts wide spectrum antimicrobial activity, thus may help preventing the development of skin and wound-related opportunistic infections.

S. Gutić, Herzegovina

Graphene-based materials and their role in electrocatalysis related to hydrogen production have been intensively investigated by many authors, often justified through a low price of such materials. In this study we used single-step electrodeposition/graphene oxide reduction route to prepare Ni@reduced-graphene-oxide composites for electrochemical hydrogen evolution reaction (HER). As the precursors for reduced graphene oxide, two different home-made graphene oxides were used. When compared to pure electrodeposited Ni, composite catalysts show improved catalytic activity which depends on Ni electrodeposition time in a volcano-type fashion. Using electrochemically prepared graphene oxide, HER overvoltage needed to reach 10 mA cm −2 was reduced to only −97 mV, showing the improvement by roughly 200 mV when compared to pure electrodeposited Ni. It was concluded that structural disorder and surface oxidation of graphene-based materials are the key properties for reaching high HER activities of such prepared catalysts. Based on this observation, it was discussed whether it is economically justified to use high quality graphene oxide for the preparation of HER catalysts, as the price (production and commercial) of this material can be extremely high, often exceeding the price of platinum.

O. Muta, Kouki Matsuzaki, H. Gačanin

In this paper, we propose a two-dimensional pilot allocation scheme over frequency- and delay-time domains (2D-PFD) for channel estimation in massive multiple-input multiple-output (MIMO)/time division duplex (TDD) system, where two- dimensional pilot resources are simultaneously allocated to each user for their uplink channel estimation. We evaluate bit error rate (BER) performance of massive MIMO/TDD system using the 2D-PFD scheme by computer simulation in order to clarify the effectiveness of the proposed pilot allocation compared with single dimensional pilot allocation over either delay-time domain or frequency domain, respectively.

Admira Beha, Husnija Hasanbegović

The aim of this paper is to determine the opinions of deaf workers on their labor capacity and the opinions of their hearing co-workers about the labor capacities of the deaf. The sample consisted of 247 respondents, of whom 127 were deaf and 120 were hearing workers. Qualitative and quantitative analysis were used in processing the results. Testing was performed by Wilks' Lambda, tested significance in discriminant analysis was done by F test, at the statistical significance of 0.01. It was found that the sub-sample of respondents had a statistically significant difference in views on claims regarding the exploitation of deaf workers by employers, the employment of deaf people in low-paid simple occupations, and the equally successful but insignificant productivity of deaf workers. The statistical differences found indicate that there are differences in the assessment of the labor capacity of deaf workers in the hearing work environment. Qualitative analysis found that hearing impairment and the subjective attitudes of colleagues without hearing impairment have the greatest impact on the assessment of the labor capacity of deaf workers.

Internet of Things (IoT) devices such as Samsung Gear S3 Frontier smartwatch are great sources of potential digital evidence, due to their constant daily use. The main aim of this paper is to analyze the capabilities and limitations of IoT forensics of a Samsung Gear S3 Frontier smartwatch. Main concepts of IoT forensics, a summary of the current and future research progress and challenges, is given. A scenario of watch events during 3 hours of usage was recorded, which forensic analysis had to restore. Manual extraction and analysis of data, along with the detailed look at the discovered relevant files, and achieved results are presented. The primary contribution of this paper consists of a detailed approach to a particular smartwatch forensic, which supports future forensic investigations.

A. Mujcinagić, M. Kusljugic, J. Osmic

In this paper, the frequency response metrics of interconnected electric power systems (EPS) of Slovenia, Croatia and Bosnia and Herzegovina (ENTSO-E SCB control block) is presented. In the upcoming period in this region significant integration of wind energy is expected. Increased wind integration has great impacts on EPS frequency response due to decreasing total system inertia. A frequency response metrics calculation in a short period after a disturbance occurred is essential for design of any further frequency control action. Comparison of local bus frequency and frequency of centers of inertia is in the focus of this work. The regional EPS of South East Europe (SEE) is modeled using PSS/E. Frequency response metrics calculations and plots are performed using Python simulation language.

E. Omerdic, J. Osmic, D. Toal, Cathal W. O’Donnell

A new control algorithm for Directly Interconnected offshore Wind Turbines with permanent magnet synchronous Generators (DIWTG) is presented. In the DΓWTG offshore wind park configuration, Wind Turbines with Permanent Magnet Synchronous Generators (WTPMSG) are directly connected to the offshore AC collection grid without using a power converter. The offshore AC collection grid is then connected, via a transformer, to the offshore AC transmission grid. In order to achieve maximum power point tracking, the (collective) speed of DΓWTGs is controlled by an onshore back to back converter. By measuring the active power and speed of the permanent magnet generators, wind speed at each turbine is estimated and used for calculation of the reference speed of WTPMSGs. Voltage control at the power converter side is performed in a way which allow the DΓWTGs to be operated at a constant V/f where the maximum resultant frequency at nominal wind speed is 16.67 Hz.

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