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Article

Vesna Javor, Karl Lundengård, Milica Rančić and Sergei Silvestrov

This paper aims to present the approximation of lightning currents waveshapes by the multi-peaked analytically extended function (MP-AEF) for the experimentally measured…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Research limitations/implications

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.

Originality/value

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.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Sanja Kovačić, Nemanja Milenković, Iva Slivar and Milica Rancic

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…

Abstract

Purpose

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.

Design/methodology/approach

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).

Findings

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.

Research limitations/implications

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

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

Originality/value

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.

Details

International Journal of Tourism Cities, vol. 6 no. 2
Type: Research Article
ISSN: 2056-5607

Keywords

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