Моделирование помехозащищенных речевых каналов для технических систем управления

The paper focuses on the application of digital adaptive filtering to ensure the noise-free speech channels of control systems. Noise is an extraneous signal, which enters the channel device input together with the speech. The article conducts a comparative analysis of the three adaptation algorithms (LMS, NLMS, RLS) to be useful for noise suppression. At the same time, an adaptive suppression mechanism with two microphones on the speech channel is used.The related publications compared the algorithms by one or two criteria. This paper offers three comparison criteria: computational complexity, quality of noise suppression, and rate of convergence to the steady-state condition. The number of vector operations in algorithm procedures estimates temporary computational complexity.To compare algorithms by the other two criteria, their implementation was simulated in MATLAB. As the noise, were used the white and pink noise, a sine wave, and a model of the non-stationary signal as well. The noise suppression coefficient and the number of iterations before transition to the steady-state condition have been obtained. The algorithm RLS showed the best quality of suppression while the NLMS algorithm revealed the highest rate of convergence. Experiments have shown that the white noise is suppressed worse, but faster than the sine one.The paper explores influence of some factors on the process of adaptation. It is shown that increase in filter dimension leads to improving quality of adaptation and its speed-down. From simulation results it follows that the noise suppression coefficient has the highest values when at the filter input there are approximately equal signal and noise powers.The results allow us to make commendation to use the NLMS algorithm for real-time systems, and the RLS one for technical systems aimed at recordings of speech signals. The above algorithms can be successfully implemented on modern technology platforms, comprising high-performance digital signal processors and associated peripherals.Статья посвящена применению цифровой адаптивной фильтрации для обеспечения помехозащищенности речевых каналов систем управления, понимая под помехой посторонний сигнал, попадающий вместе с речью на вход канального устройства. В работе проведен сравнительный анализ трех алгоритмов адаптации (LMS, NLMS, RLS), применимых для подавления помех. При этом использован механизм адаптивного подавления с двумя микрофонами в речевом канале.В близких по теме публикациях сравнение алгоритмов проводилось по одному или двум критериям. В данной работе выбраны три критерия сравнения: вычислительная сложность, качество подавления помехи и скорость сходимости к установившемуся режиму. Временная вычислительная сложность оценена по количеству векторных операций в процедурах алгоритмов.Для сравнения алгоритмов по двум другим критериям было проведено моделирование их работы в среде MATLAB. В качестве помехи использованы белый и розовый шумы, синусоидальный сигнал, а также модель нестационарного сигнала. Получены коэффициент подавления помехи и число итераций алгоритма до перехода в установившийся режим. Наилучшее качество подавления показал алгоритм RLS, наивысшую скорость сходимости – алгоритм NLMS. Опыты показали, что белый шум подавляется хуже, но быстрее, чем синусоидальная помеха.Исследовано влияние ряда факторов на процесс адаптации. Показано, что увеличение размерности фильтра ведет к повышению качества адаптации и снижению ее скорости. Из результатов моделирования следует, что коэффициент подавления помех принимает наибольшие значения, если мощности сигнала и помехи на входе фильтра примерно одинаковы.Результаты позволяют рекомендовать алгоритм NLMS для систем реального времени, а алгоритм RLS – для технических систем, работающих с записями речевых сигналов. Рассмотренные алгоритмы могут быть успешно реализованы на современных технических платформах, содержащих высокопроизводительные цифровые сигнальные процессоры и соответствующую периферию

Technological Basis of the Formation of Micromesh Transparent Electrodes by Means of a Self-Organized Template and the Study of Their Properties

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.This Letter presents the results of a study of the physical properties of micromesh transparent electrodes on a flexible substrate, obtained using a template in the form of silica layers subjected to controlled cracking. For the first time, a combined approach to the control of parameters of a micromesh structure (crack width and cell size) by varying the pH and the thickness of the sol layer is proposed. Using this approach, transparent electrodes with a surface resistance of 4.1 Ω/sq with a transparency of 85.7% were obtained. Micromesh electrodes are characterized by linear optical transmission in the visible and IR ranges, which opens up prospects for their use in optoelectronics

Influence of the Addition of Alumina Nanofibers on the Strength of Epoxy Resins

The paper describes the effect of the addition of alumina nanofibers on the mechanical properties of the epoxy resin. Alumina nanofibers functionalized with epoxypropyl functional groups are used in this work. The dependence of the mechanical characteristics on the amount of the additive, as well as the features of its distribution in the material, is investigated. In the work, nanocomposites were obtained, which are epoxy resin with aluminum oxide nanofibers. The mechanical properties of the samples were studied by bending tests and differential mechanical analysis (DMA). It has been shown that the addition of alumina nanofibers leads to an increase in ultimate flexural strength. The maximum of this increase is near the percolation threshold of alumina nanofibers in epoxy resin. With the addition of 0.2% alumina nanofibers, the ultimate flexural strength increases from 41 to 71 MPa. It is shown that after exceeding the percolation threshold of nanofibers, the ultimate strength decreases. In this case, the elastic modulus increases from 0.643 to 0.862 GPa. DMA is shown that the glass transition temperature decreases with increasing amount of the additive. This indicates a decrease in the molecular weight of the polymer. By implication, this suggests that the hardener connects the epoxypropyl functional groups on the nanofibers and the epoxy groups in the resin, and as a result of this process, the nanofibers become natural polymer chain length limiters. The data obtained from mechanical testing and differential mechanical analysis can be used to strengthen epoxy resins in polymer composite materials and molding compositions

Influence of the Addition of Alumina Nanofibers on the Strength of Epoxy Resins

The paper describes the effect of the addition of alumina nanofibers on the mechanical properties of the epoxy resin. Alumina nanofibers functionalized with epoxypropyl functional groups are used in this work. The dependence of the mechanical characteristics on the amount of the additive, as well as the features of its distribution in the material, is investigated. In the work, nanocomposites were obtained, which are epoxy resin with aluminum oxide nanofibers. The mechanical properties of the samples were studied by bending tests and differential mechanical analysis (DMA). It has been shown that the addition of alumina nanofibers leads to an increase in ultimate flexural strength. The maximum of this increase is near the percolation threshold of alumina nanofibers in epoxy resin. With the addition of 0.2% alumina nanofibers, the ultimate flexural strength increases from 41 to 71 MPa. It is shown that after exceeding the percolation threshold of nanofibers, the ultimate strength decreases. In this case, the elastic modulus increases from 0.643 to 0.862 GPa. DMA is shown that the glass transition temperature decreases with increasing amount of the additive. This indicates a decrease in the molecular weight of the polymer. By implication, this suggests that the hardener connects the epoxypropyl functional groups on the nanofibers and the epoxy groups in the resin, and as a result of this process, the nanofibers become natural polymer chain length limiters. The data obtained from mechanical testing and differential mechanical analysis can be used to strengthen epoxy resins in polymer composite materials and molding compositions

Features of Functionalization of the Surface of Alumina Nanofibers by Hydrolysis of Organosilanes on Surface Hydroxyl Groups

Small additions of nanofiber materials make it possible to change the properties of polymers. However, the uniformity of the additive distribution and the strength of its bond with the polymer matrix are determined by the surface of the nanofibers. Silanes, in particular, allow you to customize the surface for better interaction with the matrix. The aim of our work is to study an approach to silanization of nanofibers of aluminum oxide to obtain a perfect interface between the additive and the matrix. The presence of target silanes on the surface of nanofibers was shown by XPS methods. The presence of functional groups on the surface of nanofibers was also shown by the methods of simultaneous thermal analysis, and the stoichiometry of functional groups with respect to the initial hydroxyl groups was studied. The number of functional groups precipitated from silanes is close to the number of the initial hydroxyl groups, which indicates a high uniformity of the coating in the proposed method of silanization. The presented technology for silanizing alumina nanofibers is an important approach to the subsequent use of this additive in various polymer matrices