Periodica Polytechnica (Budapest University of Technology and Economics)
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Evaluation of Viscoelastic Performance and Molecular Structures of Natural Rubber/NBR Blends Reinforced by Carbon Black and Nano-Silica
Get PDFThis study focuses on the evaluation of the dynamic mechanical properties, molecular structure, density, hardness, swelling behavior of natural rubber blends (NR) and nitrile rubber (NBR) reinforced with carbon black and/or nano-silica. An experimental work has been conducted to study of the effects of increasing NR content and incorporating nano-silica on the mechanical properties and molecular structure were studied using dynamic mechanical analysis (DMA) and Fourier transform infrared (FTIR) spectroscopy. The results show that increasing the NR content and/or incorporating nano-silica into the elastomer leads to a higher storage modulus with no significant change in the glass transition temperature. FTIR analysis indicates the compatibility of the polyblends and the presence of oxidation of the main polymer chain generated during the grinding of the rubber. Additionally, the results of the swelling study demonstrate that stronger molecular interactions occur on the surface of the nano-silica between the nitrile radicals in the NBR and the silanol (Si-OH) radicals. These findings suggest that blending NR and NBR with carbon black and/or nano-silica can improve the mechanical properties and compatibility of the resulting polyblends, with potential applications in the development of advanced elastomeric materials
Assessment of Simultaneous Heating Demands for Consumer Groups
Get PDFThe paper presents the determination of the simultaneity factor in district heating systems based on the simultaneous heat demand level of a group of consumers. The simultaneity factor is formed on a probability theory basis, involving a prescribed risk. The simultaneity factor is a ratio that indicates the proportion of the aggregated nominal heat demand of consumers that occurs at a specific time. As known, the simultaneity factor is less than one. Knowledge of the simultaneity factor allows us to uncover performance reserve capacity in a district heating system. This way, there are often opportunities for expanding district heating systems, connecting new consumers, and improving the economic efficiency of operation.
Measurement of Accident Risk and a Case Study from Hungary
Get PDFFor the cost-benefit analysis of road safety measures, it is essential to estimate the national value of statistical life. By calculating the updated values, it is possible to assess the aggregate national value of statistical life for road traffic crashes, thereby also characterizing the road safety situation in the country. It is important that the values set and the methods used are compatible with the practices of the European Member States. It must be stressed that updating the values is of major importance both for the cost-benefit analysis of the various road safety measures and for raising public and decision-makers' awareness of the huge losses. The full identification and use of loss figures is an important element of road safety. In this article we present possible methods for estimating the value of statistical life
Analysis of Constraints against Efficiency of Seaport-hinterland Logistics in Nigeria
Get PDFHaving realized that most Nigerian seaports are congested and the problem of moving goods have been difficult, the Federal Government through Bureau of Public Enterprises and Nigerian Shippers’ Council were mandated to identify Inland Container Depots (ICDs) and Container Freight Stations (CFSs) across the country with connectivity to rail transport. Since 2004 to date, these have mostly not been functioning. This paper therefore examined the constraints and possible factors responsible. The Nigerian Ports Authority, Road Haulage Association, Terminal Operators, selected Shipping companies were used as respondents. 34.1% (253) from the population of 743 respondents were sampled with the use of Cochran formula and stratified random sampling technique. Shaphiro Test and multiple regression were used to analyze the constraints against the use of ICDs and CFSs. Principal Component Analysis was used to extract the major factors hindering port-hinterland logistics in Nigeria. It was observed that 50% of general logistics constraints emanated from lack of efficient rail system, enforcement and finance combined. Extracted causative factors against port-hinterland movements of goods are: inadequate terminal capacity, parking and inadequacy of cargo handling facilities. The research concluded that both general constraints and causative factors are to be looked into with stringent policy enforcement
Optimization of Breakpoint Chlorination Technologies for Drinking Water Treatment: a Hungarian Case Study
Get PDFAmmonium ion is one of the major pollutants found in drinking water sources in Hungary, especially in deep aquifers. under oxidative conditions, ammonium can transform into nitrite ions in the water system, posing potential health risks. In Hungary mostly biological process or breakpoint chlorination are used to eliminate ammonium ion from raw water during the drinking water treatment process. When breakpoint chlorination is applied, harmful by-products are formed. Trihalomethanes concentrations have long been regulated in Hungary, therefore during the design and optimization of the breakpoint technologies trihalomethane concentrations have been considered. However, haloacetic acids (HAA5) and chlorate ion have been recently regulated in accordance with EU Directive 2020/2184. Chlorate is a by-product that appears in treated water when sodium hypochlorite is used in breakpoint chlorination.Experiments were carried out at four Hungarian case study areas to determine the optimal strategy for breakpoint chlorination: applying higher chlorine dosages with lower contact times, or lower chlorine dosages with higher contact times. The investigations concluded that the preferable dosing strategy is to use lower chlorine concentrations and longer contact times. This approach reduces chemical demand (cost-effective) and has a neutral effect on THMs formation. it can be concluded that when the raw water contains ammonium ion concentrations above 0.5 mg/l, the use of sodium hypochlorite may raise concerns due to elevated chlorate ion levels in the treated water, particularly during summer. Further research is required to expand the optimization strategy, considering not only ammonium and trihalomethane concentrations but also chlorate concentrations
Improved Droop Controller for Distributed Generation Inverters in Islanded AC Microgrids
Get PDFStability in island microgrids is crucial for efficient power distribution among distributed generation (DG) inverters. Conventional droop control, while effective in power sharing, poses challenges with voltage stability due to frequency and voltage deviations resulting from changing load power. Such deviations can lead to system instability, impacting power flows within each inverter. Therefore, this paper introduces a proposed droop control approach that effectively tackles the issues of frequency and voltage deviation, aiming to restore them to their rated values and significantly enhance transient response in power flows among inverters. The novel method incorporates integrating controllers for frequency and voltage, coupled with the utilization of virtual impedances. These virtual impedances, comprising virtual positive/negative-sequence impedance (VPI/VNI) loops at the fundamental frequency and a virtual harmonic impedance (VHI) loop at harmonic frequencies, play a crucial role in overcoming mismatched line impedance conditions, ultimately improving overall system performance. Simulation results demonstrate the effectiveness and outstanding performance of inverters operating in parallel within an island AC microgrid. The proposed approach ensures stable voltage and frequency levels in all operational states, regardless of varying load conditions