R. Kadlec

The Response of Layered Materials to EMG Waves from a Pulse Source

The authors present an analysis of conditions on the boundary between layers having varied electromagnetic properties. The research is performed using consistent theoretical derivation of analytical formulas, and the underlying problem is considered also in view of multiple boundaries including the effect of the propagation of electromagnetic waves with different instantaneous speeds. The paper comprises a theoretical analysis and references to the generated algorithms. The algorithms were assembled to enable simple evaluation of all components of the electromagnetic field in relation to the wave propagation speed in a heterogeneous environment. The proposed algorithms are compared by means of different numerical methods for the modelling of electromagnetic waves on the boundary between materials; moreover, the electromagnetic field components in common points of the model were also subject to comparison. When in conjunction with tools facilitating the analysis of material response to the source of a continuous signal, the algorithms constitute a supplementary instrument for the design of a layered material. Such design allows us to realize, for example, a recoilless plane, recoilless transition between different types of environment, and filters for both optical and radio frequencies.

An Experiment to Prove the Effect of Low-Level Magnetic Fields Resulting from Ionospheric Changes on Humans

Abstract The investigation presented in the paper was performed in the laboratories of the Department of Theoretical and Experimental Electrical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, between April 22 and June 26, 2014. We examined a homogeneous sample of male and female participants comprising a total of 49 persons aged 19 to 26. The time required for the measurement of psychophysiological parameters corresponded to 19 minutes, encompassing five stages: Basic (5 mins.), Color (2 mins.), Rest (5 mins.), Math (2 mins.), and Rest (5 mins.). All the measuring cycles were carried out using a BioGraph Infiniti device (Thought Technology, Ltd.). Generally, the impact of the environment upon living organisms constitutes a crucial problem examined by today’s science. In this context, the present article describes the results of an investigation focused on ionosphere parameter variation and its role in the basic function of the nervous system. The discussed research concentrates on the measurement and detection of changes in the region of very low electromagnetic field frequencies; the authors introduce and verify related theoretical and experimental procedures to define the effects that influence brain activity and the cardiovascular system.

Electromagnetic Wave Propagation in Heterogeneous Structures

The paper presents the problem of numerical modelling of high frequency electro- magnetic waves propagation in inhomogeneous materials. For this method, a numerical model was prepared. The model was created in the MatLab and the COMSOL program environment For a layered heterogeneous medium, an algorithm was deduced for the re∞ection on several lay- ers. The layers exist in the form of periodic structures which are composed of a homogeneous material. Re∞ection and refraction on heterogenous material are solved by means of the numerical method. Central in this respect are the refractions and re∞ections on the boundary of materials with difierent properties. This method is suitable for the design application of metamaterials. The deduced algorithm was projected for the visible spectrum.

Passive optical detection of moving targets

The paper discusses the passive optical detection of small-sized targets moving through the air at overhead levels. An experimental module for a standalone locator to operate in real time is presented together with methods usable within the actual implementation of the underlying designer project. Within the supporting tests, an algorithm was developed to detect small particles in a video sequence, and every image of the sequence was properly processed. The applied processing tools or methods included shape detection, filtering, statistic image analysis, and algorithms for the detection of moving objects; the images with recorded movement were stored on an SD card. The resolution of the moving object to be detected can correspond to a value as low as one pixel. Respecting the scope of the analyzed problems, the authors describe in detail not only the entire detection algorithm but also the results obtained from the test algorithm and the actual device.

Comparing the responses of a layered material to EMG waves from a pulse source

The authors report on an analysis of conditions on the boundary between layers having varied electromagnetic properties. The research is performed using consistent theoretical derivation of analytical formulas, and the underlying problem is considered also in view of multiple boundaries.The paper includes a theoretical analysis and references to the generated algorithms. The main algorithm was assembled to enable simple evaluation of all components of the electromagnetic field in relation to the speed of the wave propagation in a heterogeneous environment. The proposed algorithms are compared by means of different numerical methods via the wave equation in the ANSYS; moreover, electromagnetic field components in common points of the model are also subject to comparison. This analytical solution includes the time-dependent propagation of electromagnetic waves in a heterogeneous medium and evaluates the distribution of the electromagnetic field on the surfaces of the boundaries at certain moments of time. When in conjunction with tools facilitating the analysis of material response to the source of a continuous signal, the algorithms constitute a supplementary instrument for the design of a layered material. Advantageously, the presented analysis allows us to acquire an accurate solution of the response of an electromagnetic field to very short pulses and transient or continuous exciting electromagnetic sources.

An investigation of techniques for the infrared-to-visible spectrum transformation

The authors present a survey of methods and physical principles applicable in both harvesting the energy of the infrared spectrum within broadband electromagnetic radiation and ensuring the infrared-to-visible wave conversion. Several transformation procedures are analyzed together with different approaches to fabricating resonant structures at the level of nanoparticles or nanoobjects deposited on resonant or reflecting surfaces. The transformation effect can be utilized as a tool for special setting and changes of the visible spectrum in actual measurement and lighting technology applications.

Numerical analysis of metallic periodic structures in THz region

The article presents results of numerical modelling of planar resonators arrays deigned for THz frequencies. The increase in the resonant frequency of each arrays element is achieved by down-scalling its dimensions. Accompanying effects, as the rise of resistive metal losses are examined also. The presented results have shown the possibilities of down-scalling the geometry of basic planar resonators in order to achieve the resonance phenomena at THz frequencies, eventually in the infrared band.

The Instruments for Noise Spectroscopy

The article describes basic study of broadband noise signal application in the investigation of materials. The aim is flnd a metrology method utilizable for the research on metamaterials in the frequency range of about 100MHz to 10GHz. The instrumental equipment and other requirements are presented. This research report provides an overview of the current potentialities in the described fleld and summarizes the aspects necessary for noise spectroscopy. In the complex investigation of material structures for the micro-wave application (tensor and composite character), the properties of materials are studied by means of the classic single-frequency methods, which bring about certain di-culties in the process (1). In boundary changes with a size close to the wave-length there can occur wrong information concerning the examined objects (2,3). One of the possible ways of suppressing the negative sources of signals consists in the use of wide- band signals like white noise, and in researching into the problem of absorption in the examined material (4). These methods require a source of noise, a receiving and a transmitting antenna, and A/D conversion featuring a large bandwidth; for our purposes, the bandwidth ranged between 0Hz and 10GHz. Until recently it had not been possible to realize an A/D converter of the described speed, or devices with the above-mentioned bandwidth. Currently, high-end oscilloscopes are available with a sampling frequency of tens of Gsa/s. 2. NOISE SOURCE For UWB systems, several methods of the generation of short pulses with large bandwidth have been developed to date (5). However, these singly-iterative processes are not applicable for noise spectroscopy; in this respect, there is a need of a continuous source of noise signal (ideally of white noise) with the given bandwidth. The type of source referred to is currently being produced by certain manufacturers specialized in this fleld. Importantly, for the noise spectroscopy application we require a comparatively large output power of up to 0dB/mW; the assumed bandwidth char- acteristics range up to 10GHz. Nevertheless, at this point it is appropriate to mention the fact that there occurs the fundamental problem of flnding active devices capable of performing signal ampliflcation at this kind of high frequencies. As a matter of fact, our requirements are thus limited by the current status of technology used in the production of commercially available devices; the highest-ranking solution for the bandwidth of up to 10GHz can be found only up to the maximum of 0dB/mW. Our response to the above-discussed problem consisted in an attempt to produce a noise gener- ator in laboratory conditions as, in principle, this type of generator can be considered as su-cient for testing and basic measurement. In view of the price and availability of noise diodes we decided to apply thermal noise on electrical resistance as the basic source of noise. The speciflc connection is shown in Figure 1. The flrst transistor is in the CC conflguration, where we require mainly a high input impedance of the amplifler. The thermal noise at the input is given by its input parameters. The generator could operate even without a resistor at the transistor input, yet the unconnected input would cause a substantial deterioration of the stability. The second and the third transis- tors form a cascade voltage amplifler in the CE conflguration. The output impedance of the third amplifler is 50› for its matching to coaxial line. Figure 2 shows the realization of the tested noise generator; the BFP620 vf transistors were applied. This type of transistor features the characteristic of ft = 65GHz and the maximum stable ampliflcation of 11dB at the frequency of 6GHz. The overall ampliflcation of the two CE ampliflers in cascade for the output power of 0dB/mW would have to approximate the value of 10000, and there is no hf transistor available for this kind of stable ampliflcation. Therefore, for the stable noise generator we have to accept a lower output power.