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The unknown current distribution (UCD), line leakage current density (LLCD) and other integral characteristics of a linear grounding structure (GS), shaped either as an arbitrary linear star (LS) or polygon (LP), are presented in this paper. The UCD of the GS is determined by numerical solving of system of integral equations of two‐potential (SIE‐TP). The GS is placed in homogeneous and isotropic earth and its integral characteristics are analysed in the power frequency domain.

The purpose of this paper is to estimate influence of the pillar concrete foundation approximated by a semiconducting semi‐sphere on the pillar grounding system.

Unknown current distributions and impedance of pillar grounding system, which consists of a ferro armature modelled as a single electrode inside concrete foundation, ring electrode and two earthing conductors, are determined in this paper. Concrete foundation is approximated by a semi‐spherical semiconducting inhomogeneity. The expressions for electric scalar potential are formed using the quasi‐stationary image theory, including a recently proposed Green's function for the point source in the presence of a semiconducting sphere. Based on the quasi‐stationary antenna model, unknown currents are determined solving the system of integral equations using the moment method and polynomial approximation for current distributions.

The influence of inhomogeneity is not negligible for real values of specific conductivity of the inhomogeneity domain. The same goes for earthing conductor influence, especially the one on electric scalar potential distribution on the ground surface.

Besides the analyzed system, the model is applicable for solving for example a grounding system in the vicinity of large holes in the ground (pond and small lake) filled with water, treated as semi‐sphere or near vertical container (silage and reservoir) having semi‐spherical basis with a lower one buried in the ground.

Obtained results give possibility to analyze influence of semiconducting ground inhomogenities, which can be treated as semi‐spherically shaped ones, on grounding system. It results in better accordance of projected and real grounding system's characteristics.

The purpose of this paper is to present a new function for approximating lightning channel‐base currents which is useful in return stroke modelling and for calculating lightning electromagnetic fields and induced effects in conductive structures, installations and systems.

The derivative and integral of the function are obtained analytically. Function parameters are calculated to approximate theoretically assumed or experimentally measured first stroke channel‐base currents using least‐squares method. The proposed expressions are useful for calculating lightning electromagnetic field using thin wire antenna approximation and lightning stroke models. Analytically obtained Fourier transform of the function is needed in the case of a lossy ground.

The function can approximate both double and one‐rise front waveshapes, so as faster and slower decaying tails. Some important function characteristics can be chosen prior to the approximation procedure, such as the current peak and rise‐time to peak, which is an advantage in comparison to other functions from literature. Parameters can be calculated so to obtain the desired decreasing‐time to half of the peak value; maximum current steepness due to analytically obtained derivative; charge transfer corresponding to the function integral; the specific energy corresponding to integral of the square of the function, etc.

This function can be used also for approximation of other impulse quantities of interest.

The new proposed function for lightning current modelling is suitable for generalization of the procedure for computing electromagnetic fields and induced effects.

This paper aims to present the approximation of lightning currents waveshapes by the multi-peaked analytically extended function (MP-AEF) for the experimentally measured channel-base currents in the artificially triggered lightning discharges. Modified transmission line model of lightning return strokes having the channel current both linearly decaying and sinusoidally changing with height (MTLSIN) is used to calculate the lightning electromagnetic field.

MP-AEF’s parameters for the artificially triggered lightning channel-base currents are calculated by using Marquardt least squares method (MLSM). Lightning electromagnetic fields are calculated based on electromagnetic theory relations, thin-wire antenna model of the vertical lightning channel and the assumption of the perfectly conducting ground. MTLSIN model as an engineering model of lightning strokes is used to obtain the electric field results as these are simultaneously measured in rocket-triggered lightning experiments together with the channel-base currents.

MP-AEF approximates multi-peaked pulse waveshapes. Some important function parameters are chosen prior to the approximation procedure, such as current peaks and the corresponding time moments of those peaks, which presents an advantage in comparison to other functions. The desired accuracy of approximation is obtained by choosing an adequate number of function terms. MLSM is used for the estimation of unknown parameters. Using MTLSIN model, the influence of the channel height and return stroke speed on the lightning electromagnetic field waveshape is analyzed in this paper.

MP-AEF may be used for approximation of various multi-peaked waveshapes. It has no errors in the points of maxima which is important for the lightning protection systems design. MTLSIN model may be validated by using simultaneously measured lightning electromagnetic fields at various distances from the channel and for channel heights estimated in the experiments. It is also possible to approximate measured current derivatives by MP-AEF and use them for further computation.

MTLSIN model is proposed in this paper for the evaluation of lightning electromagnetic fields induced by artificially triggered lightning discharges. The procedure is based on the approximation of lightning channel-base currents by the multi-peaked analytically extended function previously proposed by the authors. This function may be used not only for representing lightning currents but also for other waveshapes as current derivatives, electric and magnetic fields and their derivatives, which are all important for the lightning protection design. MTLSIN gives lightning electromagnetic fields results which are in better agreement with measured fields than those obtained by other models from literature.

This paper aims to deal with the previously unknown prediction accuracy of students’ activity pattern in a blended learning environment.

To extract the most relevant activity feature subset, different feature-selection methods were applied. For different cardinality subsets, classification models were used in the comparison.

Experimental evaluation oppose the hypothesis that feature vector dimensionality reduction leads to prediction accuracy increasing.

Improving prediction accuracy in a described learning environment was based on applying synthetic minority oversampling technique, which had affected results on correlation-based feature-selection method.

The major contribution of the research is the proposed methodology for selecting the optimal low-cardinal subset of students’ activities and significant prediction accuracy improvement in a blended learning environment.

The purpose of this paper is to provide a suggestion for the research framework on tourists as target groups for planning city branding strategies with reference to possible differences for tourists having a different country of origin. This framework was applied to analyze and compare the perception of Banja Luka city brand (Bosnia and Herzegovina) by four main target group by country of origin.

The suggested research framework combines qualitative generation of tourist’s city brand associations and brand personality with quantitative measurements of city brand perception (scale developed following the framework of Anholts’ (2006) City Brand Index adjusted to tourists as target groups).

The developed research framework was demonstrated in the example of Banja Luka main target groups. Three dimensions of city brand which largely coincide Anholt’s (2006) dimensions were extracted: tourist attractiveness, life standard and safe and pleasant atmosphere. Differences between analyzed countries were found in city brand perception, brand associations, brand personality, but also in all other analyzed categories.

Possible limitation of the study is the fact that results were interpreted including both those who have visited Banja Luka and those who are not personally familiar with it.

Practical implications of research findings are demonstrated in form of branding suggestions focused on particular target groups.

The study suggests a research framework on tourists as target groups in the city branding process. Also, it contributes to a very scarce research on differences in city brand perception by target groups by country of origin, but also to the literature related to Banja Luka city brand and tourism development.

The purpose of this paper is the development of an efficient approach for extraction of the microwave FET noise wave temperatures.

The proposed approach is based on an artificial neural network (ANN) trained to determine the noise wave temperatures from the given measured transistor noise parameters.

The presented approach enables not only efficient, but also an accurate direct extraction of the noise wave temperatures. This is confirmed by the validation of the proposed approach that is done by comparison of the transistor noise parameters obtained using the extracted noise wave temperatures with the measured noise parameters.

Application of ANN is a novel approach to extract the noise wave temperatures, which provides more efficient microwave FET noise wave modeling.

This paper aims to show the implementation in the terrestrial trunked radio (TETRA)-based sensor network. The publicly available data show that, in Serbia, the annual damage caused by hailstorms in the past seven years has been estimated almost at an average level of 40m of euros. As the amount of hail was not changed, the hail suppression system of the Republic of Serbia has to be improved, both technically and organizationally, to get better efficiency and protection and to reduce the damage.

In this paper, the authors show the implementation and improvements in the modern terrestrial trunked radio (TETRA)-based sensor network, and they propose the scientific use of sensors for remote control of automatic hail suppression rocket stations.

The authors’ idea is that TETRA should be used as an operational and official telecommunicating system for hail suppression activities units. A number of sensors, connected in a network, are used to maintain a high-quality functioning of this digital radio system, managed remotely and controlled either by operators or automatically.

The presented study with a real example attempts to explain as to how the system functions and how it can improve hail suppression activities.

For more than four decades, persistent economic activities and a focused growth strategy resulted in significant infrastructural and other favorable economic and institutional changes in the world's developing nations. High-quality growth is not just a function of sound economic policies but also implementing a broad range of social policies. The BRICS (Brazil, Russia, India, China and South Africa) nations have proven their testimony on both these factors. Following their path are some other emerging economies like N-11 (or Next Eleven propounded by Goldman Sachs (2005) Report), which this present study tries to examine as successors of BRICS.

Along with panel data regression modelling, the study has applied econometric procedures robust to heterogeneities across various nations and have been able to produce more reliable results that can be generalized for other similar groups of countries. 11 independent variables (both economic and institutional) have been used to meet the study's objective for a period of 34 years (1985–2018).

The findings of the study reveal that the governments of both the group of countries must work toward their macro-economic stability factors (external debt stocks), technological capabilities (mobile and fixed broadband subscriptions), human capital (health expenditure) and political conditions (mainly the rule of law) to enhance their sustainable economic growth.

This study enhances knowledge of the determinants of economic growth in emerging countries. Firms from BRICS and N-11 may better understand the factors influencing their internationalization process (both economic and institutional). The study is significant not just for the researchers but also for the policymakers of the BRICS and N-11 to understand in which areas their country is leading or lagging. The study is useful even for the policymakers of other emerging countries of the world who might take lessons from these nations (especially BRICS) and follow their success path. This study helps the governments of other groups of emerging countries such as PIN (Pakistan, Indonesia and Nigeria); MINT (Mexico, Indonesia, Nigeria and Turkey); CIVETS (Colombia, Indonesia, Vietnam, Egypt, Turkey and South Africa), etc. which can follow the path of BRICS economies in growth and formulate policies to increase their economic growth accordingly. At the enterprise level, it helps MNCs understand BRICS and N-11 markets and formulating entry and growth strategies in these most emerging countries of the world.

The present study is unique. It tries to investigate the projections of the Goldman Sachs report after 15 years of its release. It tries to determine the factors responsible for the economic development in the N-11 countries with advanced econometric techniques. Majorly, the focus is to comparatively analyze the growth trajectory for BRICS and N-11 nations and suggest whether N-11 has the potential to become successors of BRICS. A concentrated effort to examine the most significant drivers (both economic and institutional), which may lead to economic progression, has been made in this study.

The purpose of this paper is to develop a simple and efficient conservative semi-Lagrangian scheme (SL) for solving advection equation in fast fluid dynamics (FFD), so FFD can provide fast indoor airflow simulations while preserving conservation for energy and species transport.

This study thus proposed a mass-fixing type conservative SL that redistributes global surplus/deficit on the advected field after performing the standard semi-Lagrangian advection. The redistribution weights were designed to preserve the properties of conservatives and monotonicity.

The effectiveness of the conservative SL was validated with several test cases, and the results show that the proposed scheme is indeed conservative with negligible impact on the accuracy of the standard solutions. The numerical tests show that the proposed scheme was indeed conservative with negligible impact on the accuracy of the flow prediction.

The FFD with conservative SL can effectively enforce the energy and species conservation for indoor airflow and predict airflow distributions with reasonable accuracy.