Electrostatic theory of rectangular waveguides filled with anisotropic media

The electrostatic (or, in a better word, quasi-electrostatic) theory of waves propagation in a long, rectangular waveguide having perfect electric conductor walls that filled with an anisotropic medium (here, a medium of nanowire-based hyperbolic metamaterials) is presented. Some data on characteristics of these waves are prepared. The presented results include electrostatic field configurations (modes) that can be supported by such structures and their corresponding cutoff frequencies, group velocities, power flows and storage energies.

Effects of fixed cutoff filtering on dark- and light-adapted ERG components and the application of variable cutoff filter

Purpose Human oscillatory potentials (OPs) are derived from dark-adapted (DA) electroretinograms (ERGs) with fixed frequency cutoff filters while light-adapted (LA) OPs are generally not isolated from ERGs. Our purpose was to analyze the effect of cutoff frequencies on DA and LA ERG components using a series of fixed and variable filters. Methods DA and LA ERGs were recorded from 10 healthy eyes of 10 subjects (mean age = 20.5 ± 6.7 years) following ISCEV standards. Each signal was filtered in the Fourier domain to acquire slow (a- and b-waves; below cutoff frequency) and fast (OPs; above cutoff frequency) components. Fixed cutoff frequencies ranged from 60 to 105 Hz and a variable cutoff frequency was calculated. Results were analyzed with statistical tests and specific models. Results DA ERG components were slightly influenced by the filter cutoff frequency. In contrast, fixed and variable filters significantly changed LA components: the lower the cutoff frequency the smaller the b-wave and OP3 and the higher the OP2/OP4 amplitudes. Analyzing the filter frequency limits a transition range between 68.9 Hz and 83.9 Hz was observed where amplitudes vary. Conclusions The present report shows that DA OPs may be isolated from ERGs using filtering procedures with high-pass cutoff frequency at about 75 Hz as recommended by ISCEV. On the other hand, the spectral distribution of low-frequency and high-frequency LA ERG components may overlap. Accordingly, filtering the signal using different cutoff frequencies is not necessarily separating b-wave and OPs.

Evaluation of the Influence of Technological Variation of Parameters of Optical Sensor Elements on the Choice of Optimal Filter Cutoff Frequencies in Systems Based on Light Screens

В измерительных системах на основе световых экранов сигналы оптических датчиков существенно искажены. Это усложняет задачу обнаружения полезных импульсов и увеличивает погрешность системы.В статье исследуется возможность использования одних и тех же частот среза программно реализованного полосового фильтра для всех датчиков измерительной системы на основе световых экранов. Для этого проводится статистическое моделирование на смеси реального шума и эталонного импульса, создаваемого для каждого типа патрона по отдельности. Эталонный импульс – реальный импульс датчика, полученный в момент выстрела и сглаженный при помощи медианного фильтра.Анализ полученных при моделировании данных показал, что для разных датчиков минимальные погрешности наблюдаются на различных рабочих участках, определяемых частотами среза полосового фильтра. Полученные результаты позволяют утверждать, что технологический разброс параметров конструктивных элементов оптического датчика может оказывать существенное влияние на параметры оптимального рабочего участка необходимого полосового фильтра. Это означает, что по возможности необходимо стремиться к созданию оптических датчиков с максимально близкими характеристиками. Если же добиться этого невозможно, то при высоких требованиях к точности измерительной системы целесообразно осуществлять поиск оптимальных частот среза для каждого датчика системы по отдельности, при этом индивидуально для каждого типа патронов. В других случаях возможно использование единого рабочего участка полосового фильтра для различных датчиков и типов патронов. При этом выбор оптимальных частот среза целесообразно осуществлять, исходя из наихудшего случая (патрона, соответствующего импульсу с самой малой амплитудой).Исследование выполнено при финансовой поддержке ИжГТУ имени М. Т. Калашникова в рамках научного проекта № ВАЮ/20-78-23.

Non-Invasive Sheep Biometrics Obtained by Computer Vision Algorithms and Machine Learning Modeling Using Integrated Visible/Infrared Thermal Cameras

Live sheep export has become a public concern. This study aimed to test a non-contact biometric system based on artificial intelligence to assess heat stress of sheep to be potentially used as automated animal welfare assessment in farms and while in transport. Skin temperature (°C) from head features were extracted from infrared thermal videos (IRTV) using automated tracking algorithms. Two parameter engineering procedures from RGB videos were performed to assess Heart Rate (HR) in beats per minute (BPM) and respiration rate (RR) in breaths per minute (BrPM): (i) using changes in luminosity of the green (G) channel and (ii) changes in the green to red (a) from the CIELAB color scale. A supervised machine learning (ML) classification model was developed using raw RR parameters as inputs to classify cutoff frequencies for low, medium, and high respiration rate (Model 1). A supervised ML regression model was developed using raw HR and RR parameters from Model 1 (Model 2). Results showed that Models 1 and 2 were highly accurate in the estimation of RR frequency level with 96% overall accuracy (Model 1), and HR and RR with R = 0.94 and slope = 0.76 (Model 2) without statistical signs of overfitting

Analytical solution of higher order modes of a dielectric-lined eccentric coaxial cable

This study provides an analytic method for the calculation of the cutoff frequencies and waveguide modes of a partially filled eccentric coaxial cable. The method is based on the expressions of the involved electromagnetic fields in bipolar coordinate systems and the validity range of the solution is discussed. It is shown how the waveguide geometry and dielectric parameters may be selected to engineer the lined waveguide's spectral response. Numerical results are included which show good agreement with the corresponding results from full-wave simulations by commercial software.