This paper presents the method of homogenization of several different biological tissues in order to simplify the numerical calculation of the electric field distribution in certain biological ...structures of interest. For this purpose, a 3D model was used with blocks that have the same electromagnetic characteristics as their corresponding biological tissues of the human head. The results obtained in the case of homogenized block model were compared with the ones obtained by using the original heterogeneous model containing the following tissues: skin, fat, muscle, bone, and brain. Homogenization of the model has been caried out only for the layers that precede the layer in which the analysis of electric field distribution was performed. A smart phone was used as the source of electromagnetic radiation at a frequency of 0,9 GHz. A comparative analysis of the electric field intensity in the layer of interest indicates good matches for the heterogeneous and homogenized models. Based on the obtained results, deviations in the electric field intensity can be observed for both models. These deviations range from 3,7% to 5,2% for different layer thicknesses.The proposed homogenization method significantly simplifies the modelling and also reduces the simulation time required to obtain appropriate results.
The objectives of the study are twofold. First, we aim to examine the most influential socio-economic indicators to explain energy consumption in Republic of Serbia. The second objective is to ...develop models that are able to predict the future energy consumption in the Republic of Serbia. This could be the first important step towards proper energy management in the country. Several potential socio-economic indicators are selected to be the independent variables. Regression analysis is conducted to select the most relevant independent variables as well as building the multiple linear regression (MLR) models. In addition, an artificial neural networks (ANN) model is developed as a comparison. Finally, the energy demand is projected to the year 2022. It is found that both models show the declining trend with respect to the current level of energy consumption.
Environmental noise indicator values that are completely accurate and precise can only be obtained through continuous noise monitoring, which is a highly complex and multifaceted task. In case heavy ...road traffic is the dominant noise source, accurate and precise data on annual noise indicator values are also obtainable through semicontinuous monitoring. Such a procedure is a rational approach to the given task, as it requires considerably shorter utilization of resources, whereby the primary issue is how to choose the measurement time interval. To help determine the optimal measurement time interval, this paper uses the results of continuous noise monitoring at a selected measurement location as an attempt to minimize the measurement time interval. The choice of the optimal measuring strategy of the problem defined by multiple criteria has been made using the PROMETHEE method, as the most acceptable method for comparing the different alternatives.
Annual environmental noise monitoring is a legal requirement for local self-governments in the Republic of Serbia. However, Serbian legislation does not stipulate specific monitoring procedures, so ...each local self-government unit has to create its own environmental monitoring program within its jurisdiction. This paper analyzes the reliability of noise monitoring programs in local self-government units, based on short-term measurements. The reliability of applicable environmental noise monitoring programs in Serbia was examined by simulating the program imlementation to the results of noise monitoring obtained through continuous measurement over a period of one year. The above mentioned simulation showed that the monitoring programs based on short-term monthly measurements and a measurement time interval over 24 hours have the best repeatability and reliability result, especially at locations with the same daily noise profile and the occasional occurrence of unexpected short-term noise events. The results obtained in this study indicated that, either with higher or lower degrees of reliability, other programs can be used to monitor noise at measurement points near major urban roads with heavy and relatively constant vehicle flow throughout the day.
The determination of the amount of residual carbon in biomass ash is important not only for the assessment of the efficiency of biomass fuel combustion but also as one of the criteria for the ...estimation of biomass ash potential use. In this paper carbon content in biomass ash was analysed by applying two methods: total organic carbon analysis (TOC) and thermogravimetric analysis (TGA) in an inert (N.sub.2) and oxidizing (O.sub.2) atmosphere. The amount of inorganic (carbonate) carbon can be directly calculated from the TGA curve and the obtained results are in a good agreement with the ones obtained using TOC analyser. On the other hand, the quantitative determination of organic and elemental carbon by TGA is not straight-forward since the temperature range of their oxidation overlaps with dehydration temperature of portlandite that is a constituent of biomass ash. It can be concluded that a basic version of the thermogravimetric analyzer can be used for the determination of inorganic carbon in ash samples, but for total organic carbon determination, it is recommended to use hyphenated techniques, for example, TGA-MS or TGA-FTIR that allows quantitation of evolved gases (CO.sub.2 and H.sub.2O).
Determination of optimal safe distance between buildings is a task of many safety and economic analyses. Generally, it is known that increasing separation distance increases fire protection of an ...adjacent building, but decreases the cost effectiveness of urban solutions. For this reason, CFD Large Eddy Simulation method of Fire Dynamics Simulator software package has been used in this paper to determine optimal separation distance required for preventing fire spread between two residential buildings facing each other. The minimum conditions necessary for ignition of the window curtains in the fire-exposed building located at different building distances (3,5 m, 4,0 m and 4,5 m) were analysed. The obtained results show that the fire does not spread at the distance of 4,5 m, and that the incident heat flux at the curtain surface is higher than the critical heat flux value of 12,6 kW/m2 adopted in many building codes.
For an interdisciplinary approach on different topics of medicinal and analytical chemistry, we applied a known experimental pKa value determination method on the field of the bench top nuclear ...magnetic resonance (NMR) spectrometry of some known biologically active pyridine-based drugs, i.e., pyridoxine hydrochloride, isoniazid, and nicotine amide. The chemical shifts of the aromatic ring protons in the 1H NMR spectrum change depending on the protonation status. The data were analyzed on dependence of the chemical shifts by different pH (pD) environments and then the pKa values were calculated. The pKa values obtained were in agreement with the literature data for the compounds, searched by the students on web programs available at our university. The importance of the pKa values in protein-ligand interactions and distribution etc. of drugs was brought up to the students’ attention. In addition, by the use of a free web application for pKa values prediction, students calculated the predicted modeled pKa value. The experimental and in-silico approaches enhance the tool box for undergraduate students in medicinal chemistry.
District heating systems are important utility systems. If these systems are properly managed, they can ensure economic and environmentally friendly provision of heat to connected customers. ...Potentials for further improvement of district heating systems' operation lie in the improvement of current control strategies. One of the options is the introduction of model predictive control. Multi-step ahead predictive models of consumers’ heat load are a starting point for creating a successful model predictive strategy. For the purpose of this article, short-term multi-step ahead predictive models of heat load of consumers connected to a district heating system were created. The models were developed using the novel method based on SVM (Support Vector Machines) coupled with a discrete wavelet transform. Nine different SVM-WAVELET predictive models for a time horizon from 1 to 24 h ahead were developed. Estimation and prediction results of the SVM-WAVELET models were compared with GP (genetic programming) and ANN (artificial neural network) models. The experimental results show that an improvement in predictive accuracy and capability of generalization can be achieved by the SVM-WAVELET approach in comparison with GP and ANN.
•District heating systems application for increasing in fuel efficiency.•Control and prediction of heat load for individual consumers in district heating systems.•Support vector machine application for district heating system control algorithm.
The monitoring and the control of air pollution which is a consequence of the activities of district heating plants in the area of Niš have indicated that there is a cause and effect relationship ...between the emitted pollutants and air quality on one hand, and health risk on the other hand. The aim of this paper is to determine the correlation between district heating plants, air quality and health risk. The evidence of this connection is the hazardous health quotient and the level of total carcinogenic risk in comparison to measured immission concentration and expected immission concentrations of pollutants from district heating plants in the city.
With climate change and the ever-drier climate, the issue of wildfires is becoming increasingly prominent, generating growing interest in the study of wildfires. The majority of the ongoing research ...is focused on surface wildland fuels with particular emphasis on dead and usually dry fuel. These insights are difficult to transpose to live fuels, particularly to crown fires. The flammability properties of dead and dry forest fuels are of little significance for understanding the onset and spread of crown fires. Hence, research regarding the flammability properties of fresh forest vegetation is very sparse. The same observation applies to crown fires, despite the fact that this type of wildfires is devastating, difficult to suppress, and usually having dramatic consequences. The aim of this paper is to determine how moisture dynamics of live crown samples (terminal parts of basal branches) of two coniferous species,
Abies alba
and
Picea abies
, influence their flammability properties. Experiments were performed in an adapted mass loss calorimeter with a custom-made sample holder in order to mimic the scenario of initiation of crown fires (surface to crown fire interface). Tests were performed with heat flux values of 50, 60, and 70 kW/m
2
and with different moisture levels. At all heat flux values, the results show an increasing trend for the peak heat release rate when moisture content is reduced.
A. alba
samples reach higher peak release rates in comparison with
P. abies
samples. At heat fluxes of 50 kW/m
2
and 60 kW/m
2
, fresh
A. alba
samples take longer to ignite than the
P. abies
samples. At the heat flux of 70 kW/m
2
, for the set of analyzed moisture contents, the ignition time interval for the
A. alba
samples is shorter than for the
P. abies
samples. The results of the principal component analysis (PCA) show that variables such as time to ignition (TTI), peak heat release rate (PHRR), and mean heat release rate (mean HRR) best describe the ignitability of the analyzed conifer samples.
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