Relação entre lacunaridade e largura de banda de uma antena de arame koch-type

A dipole wire antenna of the Koch type is considered. The antenna represents a wire dipole symmetrical with respect to the point of feeding. Arms of the dipole have a geometry similar to Koch's pre-fractal. The curves forming the arms differ from the classical Koch fractal only by the position of the central vertex. A family of antennas is singled out, in which the antennas differ from each other by coordinates of the central vertices. An algorithm for calculating lacunarity is described. A correlation analysis is provided with a correlation of bandwidth as well as relative bandwidth with lacunarity. Antennas having the geometry of the first three iterations of a Koch-type curve are chosen for the analysis. The calculated correlation coefficients are given in the tables. It is shown that increasing the iteration leads to a decrease in the correlation between the selected parameters. It is obtained that the correlation coefficients for the relative bandwidth are smaller than those for the bandwidth. Single-parameter regression models for the bandwidth and the relative bandwidth are constructed. The root-mean-square errors for the models are calculated. The proposed regression formulas can be used to design broadband wire antennas.Se considera una antena de cable dipolo del tipo Koch. La antena representa un dipolo de alambre simétrico con respecto al punto de alimentación. Los brazos del dipolo tienen una geometría similar al prefractal de Koch. Las curvas que forman los brazos difieren del fractal clásico de Koch solo por la posición del vértice central. Se selecciona una familia de antenas, en la que las antenas difieren entre sí por las coordenadas de los vértices centrales. Se describe un algoritmo para calcular la lagunaridad. Se proporciona un análisis de correlación para la correlación del ancho de banda, así como el ancho de banda relativo con lagunaridad. Las antenas que tienen la geometría de las tres primeras iteraciones de una curva de tipo Koch se eligen para el análisis. Los coeficientes de correlación calculados se dan en las tablas. Se muestra que aumentar la iteración conduce a una disminución en la correlación entre los parámetros seleccionados. Se obtiene que los coeficientes de correlación para el ancho de banda relativo son más pequeños que los del ancho de banda. Se construyen modelos de regresión de un solo parámetro para el ancho de banda y el ancho de banda relativo. Se calculan los errores de raíz cuadrada-media para los modelos. Las fórmulas de regresión propuestas pueden usarse para diseñar antenas de cable de banda ancha.É considerada uma antena de cabo dipolo do tipo Koch. A antena representa um dipolo de arame simétrico em relação ao ponto de alimentação. Os braços do dipolo têm uma geometria similar à prefractal de Koch. As curvas que formam os braços diferem do fractal clássico de Koch apenas devido à posição do vértice central. Uma família de antenas é selecionada, na qual as antenas diferem umas das outras pelas coordenadas dos vértices centrais. Um algoritmo é descrito para calcular a lacunaridade. Uma análise de correlação é fornecida para a correlação da largura de banda, bem como a largura de banda relativa com a lagunaridade. As antenas que possuem a geometria das três primeiras iterações de uma curva do tipo Koch são escolhidas para a análise. Os coeficientes de correlação calculados são fornecidos nas tabelas. É mostrado que o aumento da iteração leva a uma diminuição na correlação entre os parâmetros selecionados. Obtém-se que os coeficientes de correlação para a largura de banda relativa são menores que os da largura de banda. Modelos de regressão de um único parâmetro são construídos para a largura de banda e a largura de banda relativa. Os erros médios de raiz quadrada para os modelos são calculados. As fórmulas de regressão propostas podem ser usadas para projetar antenas de cabo de banda larga

On Optimal Frequencies for Reconstruction of a One-Dimensional Profile of Gradient Layer’s Refractive Index

The problem of reconstruction of a one-dimensional profile of gradient layer’s refractive index is investigated. An algorithm for choosing a right frequency, at which a scattered field is measured, is proposed. It is concluded that at the correct choice of frequency one measurement must be sufficient. Moreover, in this case, regularization parameters of the residual functional are chosen as zero. It is shown that in case of measurements being carried out with errors, residual terms must be added to the functional

ON BASE FREQUENCY OF THE SYMMETRICAL SIX-TOOTH-SHAPED MICROSTRIP ANTENNA

Abstract. A symmetrical microstrip six-tooth-shaped antenna is considered. The influence of the maingeometric parameters of the antenna on the base frequency is investigated. The main geometric parameters of the antenna include length and width of the radiator, depth of the rectangular cutouts on its radiator, thickness of the substrate, length of the ground and width of the feedline. Regression analysis is carried out and several mathematical models are constructed. The first model describes a relationship of the base frequency with depth of the rectangular cutouts, the radiator length and width. The second model describes a relationship between the wavelength at the base frequency and the geometry of the radiator. The root-mean-square error and the relative error of these models are calculated. For the base frequency and wavelength, graphs of dependencies on the geometric parameters of the antenna are plotted. We establish that a decrease in values of the base frequency and an increase in the wavelength is associated with an increase in the depth of cutouts and the radiator length. We show that a slight influence on the base frequency is caused by changes in width of the feedline, thickness of the substrate and length of the ground. The proposed formulas, describing relationships of the base frequency as well as the wavelength at this frequency with the geometric parameters of the antenna, can be used to design a six-tooth-shaped antenna in a wide frequency range.Keywords: base frequency, wavelength, six-tooth-shaped microstrip antenna, regression analysis, antennaparameters

On Waveguide Excitation By Source Placed On The Lateral Cross-Section

The problem of excitation of electromagnetic oscillations in a waveguide with metal walls, which has an arbitrary cross-section, is reduced to an infinite set of boundary-value problems for telegraph equations in a quarter of the plane. The values of the longitudinal components of the field or of the lateral components of the magnetic vector (surface currents) on the cross-section of the waveguide can be chosen as the wave sources.It is preliminary shown that the components of the non-harmonic electromagnetic field in the waveguide are expanded into series by two sets of eigen functions of the two-dimensional Laplacian that satisfy the Neumann or Dirichlet boundary conditions. The coefficients of these expansions are the solutions of telegraph equations or derivatives of these solutions. The boundary-value problem for the telegraph equation in a quarter of the plane is considered. It has been established which boundary conditions are sufficient for determining its unique solution. The solvability conditions of the auxiliary over-determined boundary-value problem have been written down. The formulas that give an explicit solution of the telegraph equation in a quarter of the plane in the case of different boundary conditions have been obtained. It is shown how to determine the boundary values of the solutions of the telegraph equations for various types of sources of the electromagnetic field.As an example, the longitudinal components of the field for the high mode of a rectangular waveguide for given pulse sources are determined numerically.

Physical education classes with distance learning as a catalyst for adaptation potential increase of students during the COVID-19 pandemic

Physical education classes at all Russian universities are mandatory and held during the first, second and third years of studying for a bachelor’s degree. In connection with switching to distance learning during the COVID-19 pandemic, the investigated students of Kazan Federal University were engaged in both online physical education classes and self-study physical education classes with the obligatory keeping of a self-monitoring diary, which allowed tracking the dynamics of changes in psycho-emotional, functional states as well as physical fitness. As part of the educational process, teachers and students contacted through the Microsoft Teams platform, where classes and consultations were held; information and control materials were exchanged. A control group and an experimental group were formed with 90 students in each of the groups totalling 180 students. Each of the groups included 30 students of the main subgroup (healthy), 30 students of the preparatory subgroup (with minor deviations in health), and 30 students of the special medical subgroup with confirmed diseases of various nosology. In the control group, the students were engaged in physical education classes, fulfilling the general requirements: they filled out a self-monitoring diary, carried out the recommended tests to assess functional and physical fitness. Calculation of “working pulse rate” according to Karvonen’s formula gave students the opportunity to determine and select the amount and intensity of physical activity in the process of self-study. According to the self-monitoring diaries, the students showed positive dynamics in the psycho-emotional state. Students also noted the interdependence of their mood, well-being, desire to learn and be active on the quantity and quality of physical education classes. Exercises of sufficient intensity improved mood, relieved feelings of anxiety, and increased the positivity of perception of the surrounding environment. For ten weeks of distance learning, the students of the experimental group, whose physical activity was regulated individually, and the intensity of the load was selected with account of peculiarities of the work of their functional systems, showed a value of adaptation potential higher than that of students of the control group

Effect of Blurring of Images on Their First Order Radiomic Features

The effect of uniform blurring of images on their (statistical) radiomic features of the first order is studied. Two sets each consisting of 100 images with sizes of 100 by 100 and 700 by 700 are chosen as a dataset. Tables showing the effect of blurs on seventeen selected radiomic properties are given. The mean, variation and coefficient of variation of changes in the considered properties for various degrees of blurring are estimated. It is concluded that the most representative radiomic properties characterizing blurs are the mean, RMS and energy

Miniaturization of a Koch-Type Fractal Antenna for Wi-Fi Applications

Koch-type wire dipole antennas are considered herein. In the case of a first-order prefractal, such antennas differ from a Koch-type dipole by the position of the central vertex of the dipole arm. Earlier, we investigated the dependence of the base frequency for different antenna scales for an arm in the form of a first-order prefractal. In this paper, dipoles for second-order prefractals are considered. The dependence of the base frequency and the reflection coefficient on the dipole wire length and scale is analyzed. It is shown that it is possible to distinguish a family of antennas operating at a given (identical) base frequency. The same length of a Koch-type curve can be obtained with different coordinates of the central vertex. This allows for obtaining numerous antennas with various scales and geometries of the arm. An algorithm for obtaining small antennas for Wi-Fi applications is proposed. Two antennas were obtained: an antenna with the smallest linear dimensions and a minimum antenna for a given reflection coefficient

Mathematical model of thyroid gland functioning as a follicles system

The thyroid gland represents one of the endocrine glands. Despite the relatively small size of the gland, it plays an essential role in controlling the regulation of metabolism and individual cells' growth using hormones. The main component of the hormones is iodine. The gland consists of follicles that are the organ's structural elements, in which the synthesized thyroid hormone accumulates in a state associated with protein. To construct a model in which the rate of iodine metabolism is set in dependence on the concentration of substances in the colloid. To investigate the change in the size of the follicle and the entire thyroid gland from the concentration of iodine using a mathematical model. The entire thyroid glands work is considered a mega-system, consisting of individual follicles having different volumes. The mathematical model represents a boundary value problem for a system of nonlinear differential equations for concentrations of substances in the follicle. The dynamics of changes in the size of both an individual follicle and the system as a whole is considered under various initial and external conditions. The degree of influence of follicle volume on the level of iodine in the follicle as well as on the production of the thyroid hormone is assessed. The thyroid gland's work is studied, and a mathematical model of the thyroid gland is constructed, which considers the thyroid gland as a mega-system consisting of a certain number of follicles. According to the results of studies, this approach allows more accurate tracking of changes occurring with a single follicle and, consequently, the work of the entire organ. If the thyroid gland is healthy, the follicle size distribution is lognormal

Adaptation to physical activities by international students at a Russian University

The problem of adaptation by international students to studying at a Russian university was addressed. The conditions under which the physical education and physical activity classes at the University exert influence on adaptation of first-year international students were examined. The dynamics of the adaptation potential of first-year international students experiencing different types of motor activity while studying at a Russian university was investigated. The initial psycho-emotional state, physical and functional fitness of the international students before Semester 1 were measured and compared to those of first-year Russian students. It was concluded that initial adaptation reserves of the first-year international students were lower than those of the first-year Russian students. The international students were divided into four groups based on the level of their physical activity. It was found that the international students attending only mandatory physical education classes could adapt to a new cultural environment within one academic year, whereas the international students attending additional non-mandatory classes or sports clubs could accelerate their adaptation by half.Keywords: Physical Education; Sport; International students; Adaptation

Reducing the problem of waveguide excitation by currents in crosssection to a system of integral volterra equations

The problem of excitation of a cylindrical metal waveguide by a source located in the cross section is considered. We assume that the source is surface currents on a flat, infinitely thin metal plate with a smooth boundary. The plate is connected to the generator of non-harmonic oscillations. The boundary of the cross section of a waveguide filled with a homogeneous dielectric is a closed piecewise-smooth contour. The initial physical problem is formulated as a mixed boundary problem for the system of the Maxwell equations. Components of the desired solution for the problem is presented in the form of a series in two sets of two-dimensional eigenfunctions of the Laplace operator. The first set of the eigenfunctions corresponds to the operator with Dirichlet boundary conditions, the second set to the operator with Neumann boundary conditions. We show that the expansion coefficients of the longitudinal components (components directed along the waveguide axis) of the electric and magnetic intensity vectors must be solutions to the jump problem for a system of telegraph equations. The problem of finding the unknown coefficients of the expansion of the longitudinal component of the vector of electric intensity is reduced to solving a system of the Volterra integral equations of the first kind with respect to the derivatives of the desired coefficients. The unknown coefficients of the expansion of the longitudinal component of the vector of magnetic intensity are found by solving a system of the Volterra integral equations of the second kind