THE INFLUENCE OF CONDUCTIVE PASSIVE PARTS ON THE MAGNETIC FLUX DENSITY PRODUCED BY OVERHEAD POWER LINES

There has been apprehension about the possible adverse health effects resulting from exposure to power frequency magnetic field, especially in the overhead power lines vicinity. Research work on the biological effects of magnetic field has been substantial in recent decades. Various international regulations and safety guidelines, aimed at the protection of human beings, have been issued. Numerous measurements are performed and different numerical algorithms for computation of the magnetic field, based on the Biot-Savart law, are developed. In this paper, a previously developed 3D quasistatic numerical algorithm for computation of the magnetic field (i.e. magnetic flux density) produced by overhead power lines has been improved in such a way that cylindrical segments of passive conductors are also taken into account. These segments of passive conductors form the conductive passive contours, which can be natural or equivalent, and they substitute conductive passive parts of the overhead power lines and towers. Although, their influence on the magnetic flux density distribution and on the total effective values of magnetic flux density is small, it is quantified in a numerical example, based on a theoretical background that was developed and presented in this paper

Computation of Carson formulas using piecewise approximation of kernel function

Novel approach for the high-accurate computation of Carson formulas is presented. Carson formulas are used for computation of per-unit length (pul) self and mutual impedances of infinitely long parallel conductors. Numerical algorithm described in this paper uses a piecewise approximation of the kernel function which appears in the Carson formula corrections. Approximated kernel function is multiplied by the rest of the integrands in the impedance correction expressions and analytically integrated. By using the proposed algorithm, highaccurate results with the desired computed n-digit accuracy can easily be obtained. Results computed by the proposed algorithm are compared with the two most commonly used approximation methods for large frequency range

Magenta and alternative red colour spectroscopy on nautical charts in the visible and near-infrared electromagnetic spectrum

The International Hydrographic Organization (IHO) publishes Regulations and Technical specifications for the official nautical charts in order to standardize the use of colours to all hydrographic offices of IHO Member States. The use of magenta is reserved for highlighting, drawing attention and to distinguish information to elements of a chart of maritime importance and it is necessary to ensure its visibility.So far, there is no information on the spectrographic composition of colours intended to highlight specific content. For the first time, spectroscopy of magenta and alternative red colour is performed on the charts of hydrographic offices that have officially published colour compositions. Spectroscopy extends beyond the visible area to the near-infrared part of the electromagnetic spectrum. The article presents the absorption curves of magenta and red colour that contain information on the spectrographic composition of these colours in the visible and near-infrared spectrum. The purpose of the study is to show what proportion of black colour added to magenta or red can give positive response or positive absorption properties in the near-infrared part of the spectrum. The results are also part of preparatory research aimed at introducing colour twins, a system of hidden graphical elements designed to protect nautical charts from forgery and to expand their information content

SPECTROMETRY OF STANDARD COLOURS ON CROATIAN SEA CHARTS

Standardizacija boja na službenim pomorskim navigacijskim kartama u svijetu obuhvaća preporuke i tehničke specifikacije, kako bi se izbjegle zabune i/ili pogreške zbog primjene različitih kombinacija boja i time negativno utjecalo na sigurnost plovidbe. S obzirom na to da do sada nije bilo podataka o spektrografiji primjenjenih boja, provodi se spektrografsko ispitivanje kao polazište za standardizaciju primjene boja na pomorskim kartama. U radu se daju spektrogrami boja na hrvatskim pomorskim kartama, te se osim vidljivog dijela spektra po prvi put prikazuju i rezultati za dio bliskog infracrvenog dijela spektra. Zaključno se interpretiraju dobiveni rezultati primjene boja na hrvatskim pomorskim kartama te daje preporuka za provedbu spektrografije boja na kartama drugih država članica IHO-a. Dobiveni rezultati bit će osnova za uvođenje blizanaca boja odnosno sustava skrivenih grafičkih elemenata za proširenje informacijskog sadržaja karte, što je krajnji cilj istraživanja.The standardization of colours on the official navigation sea charts worldwide includes recommendations and technical specifications to avoid confusion and/or errors due to the application of different colour combinations and therefore adversely affect navigation safety. Since no data on the spectrography of applied colours have been available so far, spectrographic measurement is conducted as a starting point for standardizing the use of colours on sea charts. This paper presents spectrograms of colours on the Croatian sea charts, and for the first time, apart from the visible part of spectrum, it also shows results for the part of the near-infrared part of electromagnetic spectrum. In conclusion, the results of colour use on the Croatian sea charts are interpreted and a recommendation is made to measure the spectrography of colours on the charts of other IHO member states. The results obtained will be the basis for the introduction of colour-twins or the system of hidden graphic elements to expand the information content of charts, which is the ultimate objective of the researc

Energy Harvesting on AB-Class Power Amplifier Applying Thermoelectric Generators in Push–Pull Mode

Amplifiers are among the most commonly used circuits in electronics, performing a variety of functions in a wide range of electronic systems. Depending on the application and design, each amplifier generates waste heat. For power amplifiers that operate at low efficiency and high output power, the amount of wasted energy can be significant. This paper presents an energy harvesting system based on the application of thermoelectric generators on the output transistors of the AB-Class power amplifier. The converted electrical energy can be used in several ways, feeding the energy back into the power supply (increasing the “efficiency”) or powering surrounding sensors and sub-circuits. In this work, a comparative analysis of the successfully converted energy obtained from different generator models in various thermal configurations was carried out. All measurements are performed on an experimentally established setup. Due to the low thermoelectric efficiency of the generators as well as the realized low temperature gradient, only 0.84% of the waste heat can be converted into electrical energy in the best case scenario. Finally, a new thermal push–pull concept was presented, the main purpose of which is to generate additional energy and protect semiconductor components from overheating

Transient Linear Circuit Analysis Using Finite Element Technique

In this paper, a novel algorithm for a transient linear circuit analysis based on the Finite Element Technique (FET) was established. The FET procedure allows a straightforward solution for complex electric circuits since it is based on the Finite Element Method (FEM) approach. The developed algorithm allows us to select various types of time integration schemes when forming a local system of equations for a coupled circuit finite element. To illustrate the basic principle of the developed FET-based algorithm and to perform transient analysis, a random coupled linear circuit was analyzed. Numerical solutions obtained using Heun’s and the generalized trapezoidal rule (ϑ-method) integration schemes were compared to the solution obtained by Matlab Simulink software. It was shown that the accuracy of results depends on the employed time integration scheme when performing the FET procedure. It was shown that using Heun’s method as the time integration scheme yields more accurate results than using the ϑ-method time integration scheme