Wearable Radar System Design on Semi-Flexible PCB for Visually Impaired People

This paper presents a compact and wearable frequency-modulated continuous-wave (FMCW) radar on a semi-flexible printed circuit board (PCB) for an anti-collision system. This can enable visually impaired people to perceive their environment better and more safely in their everyday lives. In the proposed design, a multiple-input multiple-output (MIMO) antenna array with four receivers (RXs) and three transmitters (TXs) has been designed to achieve obstacle-detection ability in both horizontal and vertical planes through a specific geometrical configuration. Operating at 76–81 GHz, an aperture coupled wide-beam patch antenna with two parasitic patches is proposed for each channel of RXs and TXs. The fast Fourier transform (FFT) algorithm has been implemented in the radar chip AWR1843 for intermediate frequency (IF) signals to generate a range-Doppler map and search precise target angles in high sensitivity. The complete system, which includes both the MIMO antenna array and the radar chip circuit, is utilized on a six-layer semi-flexible PCB to ensure compactness and ease in wearability. Field testing of the complete system has been performed, and an obstacle-detection range of 7 m (for humans) and 19 m (for larger objects) has been obtained. A wide angular detection range of 64-degree broadside view (±32°) has also been achieved. A voice module has also been integrated to deliver the obstacle’s range and angle information to visually impaired persons.

Фазовые превращения в однокомпонентных многофазных системах: фазово-полевой подход

The problems of constructing a multiphase model of the phase field for the processes of phase transitions of the first kind are considered. Based on the Gibbs energy of the complete system expressed in terms of antisymmetrized combinations of phase fields, it is shown that the equations of dissipative dynamics of a locally nonequilibrium system follow from the condition of its monotonic decrease, preserving the normalization of the sum of variables by one and the following properties of the previously known two-phase model.

Pilot autonomous hybrid hydrogen refueling station utilizing a metal hydride compressor covering local transportation needs

The need for decreasing carbon emissions in the transportation sector in order to meet the targets of the European Union by 2030, inevitably leads to the large scale adoption of cleaner alternatives. Hydrogen fueled vehicles could possibly provide one such alternative, if we could assume that the necessary infrastructure would be widely available throughout Europe. Already, the European Union has committed to the construction of a significant number of Hydrogen Refueling Stations (HRS) by year 2025 and in view of that, there is a need of developing suitable configurations for the production, compression, storage and dispensing of green hydrogen to hydrogen fueled vehicles. This work presents an autonomous hybrid system which produces green hydrogen by PV- powered water electrolysis (PEM), which is subsequently compressed by a novel metal hydride hydrogen compressor to pressures up to 200 bar. This pilot HRS will meet the daily demand of 2 scooters and a golf cart which have been transformed, in order for their electric motor to be powered by a hydrogen fuel cell instead of a battery. An important element of the work which is presented, revolves around the integration of the metal hydride compressor with the rest of the system, and how this integration won’t hinder its functionality. The complete system design and layout is presented, while the results from the system operation could give a good idea regarding the optimal system sizing for similar large scale applications.

The Evaluation of Electric Power by Separate Analysis of Fourier Transform Components

This paper presents a substantiation of an approach for the evaluation of components of apparent power and intended to simplify the computational procedures which usually should be implemented in order to process the preliminary sampled waveform of instantaneous power. The results of carried out studies have shown that both active and reactive power can be calculated by the analysis of calculated components of sine and cosine Fourier transforms. This paper also presents the discussion of restrictions, which should be imposed on the duration of the analyzed signal and on frequencies of the auxiliary trigonometric functions, which are applied in order to calculate components of Fourier transform which are used for the evaluation of active and reactive power. The compliance with these restrictions allows us to eliminate the undesirable bias of active and reactive power estimation caused by the refusal from the decomposition of the analyzed waveform of the instantaneous power by applying the complete system of orthogonal trigonometric functions, as the evaluation of components of the apparent power is attained based on separate analysis of sine and cosine Fourier transforms calculated for the analyzed signal. The results of carried out simulations illustrate the frequency dependencies of sine Fourier transform calculated for the case of compliance with the restrictions, which allow to attain the highest accuracy of estimation and for the case when the duration of analyzed signal does not fit these restrictions.

NUMERICAL STUDY OF THE EFFECT OF MUTUAL ORIENTATION OF OLIGOMER MACROMOLECULES ON THEIR DESTRUCTION UNDER ULTRASONIC CAVITATION

Исследование механизма разрушения макромолекул под действием ультразвуковой кавитации представляет собой важную задачу. На сегодняшний день известен механизм разрушения макромолекул, основанный на том, что в условиях ультразвуковой кавитации создаются микроскопические зоны экстремально высоких давлений, в которых повышается вероятность актов разрыва макромолекулы. Разрыв происходит тогда и только тогда, когда относительная скорость при соударении макромолекул между собой превышает критическое значение. За счёт кавитации доля макромолекул, относительная скорость которых превышает критическое значение, увеличивается. В статье описана предложенная численная модель, которая предназначена для выявления молекулярных весов образуемых фрагментов при соударении. Предложен способ уменьшения количества неизвестных функций в 4 раза по сравнению с полной системой уравнений механики мономерных звеньев, основанный на симметрии в предлагаемой постановке задачи. Численно исследовано влияние взаимной ориентации макромолекул олигомеров на количество образуемых фрагментов. Полученные результаты могут служить ориентиром для развития макроскопической кинетической модели эволюции фракционного состава мономерных звеньев (эволюции концентраций мономерных звеньев различных типовых весов). The study of the mechanism of destruction of macromolecules under the action of ultrasonic cavitation is an important task. To date, the mechanism of destruction of macromolecules is known, based on the fact that microscopic zones of extremely high pressures are created in the conditions of ultrasonic cavitation, in which the probability of acts of rupture of the macromolecule increases. A rupture occurs if and only if the relative velocity when macromolecules collide with each other exceeds a critical value. Due to cavitation, the proportion of macromolecules whose relative velocity exceeds the critical value increases. The article describes the proposed numerical model, which is designed to identify the molecular weights of the fragments formed during collision. A method is proposed to reduce the number of unknown functions by 4 times compared to the complete system of equations of mechanics of monomeric links, based on symmetry in the proposed formulation of the problem. The effect of the mutual orientation of oligomer macromolecules on the number of fragments formed has been numerically investigated. The results obtained can serve as a guideline for the development of a macroscopic kinetic model of the evolution of the fractional composition of monomeric units (the evolution of concentrations of monomeric units of various typical weights).

Evolution of a Polydisperse Ensemble of Ellipsoidal Crystals with Fluctuating Growth Rates in Supercooled Melts

In this paper, an analytical solution to the model of the evolution of ellipsoidal crystals with fluctuating growth rates at the intermediate step of bulk phase transition is presented. A complete system of integrodifferential equations describing the problem was derived and analytically solved using the Laplace integral method. The kinetics of supercooling removal in melts has been found. The particle-volume distribution function represents a pike-shaped curve decreasing its maximum with time. It is demonstrated the differences in the distribution function for ellipsoidal and spherical crystals.

Effect of operation paramaters on the filtration behavior in microfiltratration of TiO2 suspended

The photocatalytic reaction using TiO2 suspended to degrade the residues of toxic organic compounds has been extensively studied, but the ultilization of this process has not been recorded on an industrial scale. One of the primary reasons is the separation of TiO2 catalyst from the treated solution mixture. Conventional mechanical separation methods such as centrifugation, flocculation-deposition do not allow for thorough separation and catalytic reuse, whereas the microfiltration / ultrafiltration membrane process has been demonstrated to be capable of composting isolates very suspended particles. Accordingly, in this study, an experimental system separating TiO2-P25 suspension by microfiltration membrane 0.2 µm on laboratory scale was set up. Effects of operating factors: TiO2 concentration, pH value, transmembrane pressure and crosss flow velocity were investigated. Result shown that TiO2 concentration greater than 1 g / l will fundamentally diminish the permeate flux, futhermore, in the transmembrane pressure differential (∆P) fluctuating from 0.3 to 1.2 bar, the relationship between J and ∆P is a linear relationship. In addition, the study likewise shown that the formation of the cake layer (scale) on the membrane surface is the fundamental driver of the permeate flux degradation over time. These results are the basis for integrating membrane and photocatalytic processes into a complete system for degradation toxic organic compound residues.

Book review: Rabinovich Yа. N. Southern Pskov settlements in the Time of Troubles

The book about the settlements of the south of the Pskov region in the Time of Troubles was written by a well-known specialist in the history of Russia of the XVII century Ya. N. Rabinovich. It will arouse great interest among researchers and a wide range of readers. The book recreates a complete system picture of the events of the Time of Troubles in the south of the Pskov land. This advantage of the book is determined by the involvement of new material from historical sources, new factography and its conceptual understanding. The study of Ya. N. Rabinovich allows us to supplement the history of the Pskov region. The review contains comments on the structuring of the material and wishes in connection with the need to write a generalizing work on the history of Pskov and the Pskov land in the Time of Troubles, as well as biographical texts.