Исследуется хаотичность передаваемых сигналов защищенных систем связи на основе динамического хаоса с помощью распространенных методов нелинейной динамики (максимальный показатель Ляпунова, показатель Хёрста и рекуррентные графики). В качестве защищенной системы связи на основе динамического хаоса рас-смотрено устройство имитозащиты контролируемых объектов с повышенной структурной скрытностью сигна-лов-переносчиков. С помощью методов нелинейной динамики, проведено исследование временных реализаций передаваемых в канале связи сигналов, полученных в среде ScicosLab с помощью рассматриваемого устройства. Анализ полученных данных показывает, что исследуемые сигналы в целом обладают свойствами хаотичности и потенциально могут обеспечить защищенность передаваемой в беспроводных каналах связи информации от несанкционированного доступа. Описанный в данной работе подход к исследованию хаотичности передавае-мых сигналов, основанный на комплексном применении известного математического аппарата методов нелиней-ной динамики, потенциально можно применять для исследования хаотичности передаваемых сигналов широкого класса систем защищенной связи на основе динамического хаоса.Ключевые слова: нелинейная динамика, хаотические сигналы, устройство имитозащиты контролируемых объ-ектов, радиоканал. ВведениеВ настоящее время идет активное развитие защищенных систем связи в гражданских и военных сферах применения. Одним из самых перспективных направлений в области за-щищенных систем связи является использование хаотических сигналов. Хаотические сигна-лы по сравнению с классическими шумоподобными сигналами обладают следующими пре-имуществами: большое потенциальное число кодовых конструкций, сплошной спектр мощности, непредсказуемость на больших интервалах времени, повышенная защищенность от несанкционированного доступа [1]. В настоящее время интерес представляет исследова-ние защищенных систем связи на основе хаотических сигналов. При этом одним из самых существенных вопросов использования хаотических сигналов в области защищенных систем связи является обеспечение хаотичности передаваемых сигналов как возможного показателя защищенности от несанкционированного доступа [2].Целью данной статьи является исследование хаотичности передаваемых сигналов защи-щенных систем связи на основе динамического хаоса с помощью распространенных методов нелинейной динамики.

Due to the COVID-19 epidemic, the challenge of introducing methods for investigating patients reducing or eliminating the probability of infection of medical staff is currently relevant. This article provides an analytical review of new technological approaches to organizing the work of medical personnel in carrying out auscultation of patients with COVID-19. The development and approval of such technologies is shown to have started around the world. The ubiquitous and large-scale introduction of these methods into medical practice therefore seems expedient.

In this article, based on the mathematical, numerical and computer modeling carried out by the combined application of E&F Chaos, Past, Fractan, Visual Recurrence Analysis, Eviews Student Version Lite programs, some of the well-known 2D models of S-chaos are modeled, the data obtained are studied using nonlinear dynamics methods and the fact of their relation or non-relation to chaotic (quasi-chaotic) processes is established. As a result, it was found that the time diagrams obtained for the studied 2D models of S-chaos have a complex noise-like appearance and are continuous in the time domain. The resulting spectral diagrams have both a complex noise-like and regular appearance and are continuous in the spectral regions. The obtained values of BDS-statistics show that some of the time implementations can be attributed to chaotic (quasi-chaotic) processes. Also, the obtained values of BDS-statistics show that the studied 2D models of S-chaos have a property characteristic of classical chaotic (quasi-chaotic) processes: the slightest change in the initial conditions leads to the generation of a new set of signals. The obtained values of the lower bound of the KS-entropy show that the studied models also have the properties of chaotic (quasi-chaotic). Taking into account the conducted research and data from known works [1–5], it is possible to conclude that 2D models of S-chaos can relate to chaotic (quasi-chaotic) processes.

In this article, the authors evaluated the crest factor of bionic signals used in hydroacoustic communication systems, using the example of the study of signals based on the use of recordings of sounds of various whale species. The calculations and literature analysis show that the sound recordings of the following whale species have an acceptable crest factor value (p ≤ 4): Blue whale, Alaska humpback whale, Atlantic blue whale and Northeast Pacific blue whale. Recordings of the sounds of these types of whales should be used in the appropriate hydroacoustic communication systems. In contrast, recordings of the sounds of such whale species as Atlantic fin whale, Atlantic minke whale, South Pacific blue whale, and Western Pacific blue whale have an increased crest factor value (p > 4) and without adaptation, it is impractical to use them in appropriate hydroacousticcommunication systems. It is established that bionic signals used in hydroacoustic communication systems, based on the example of the study of signals based on the use of recordings of sounds of various species of whales, can have both an acceptable value of the crest factor or an increased one. It is advisable to pay attention of the de-velopers and manufacturers of the corresponding hydroacoustic communication systems to this conclusion during designing, testing and implementation of such systems.

The analysis of the use of chaotic signals filtered through a broadband bandpass filter to ensure stealth and reliability of data transmission operations in radio communication systems is carried out. Time realizations of chaotic signals generated by the well-known Chua and Rikitake generators are obtained. They were filtered using a broadband bandpass filter, and the data obtained was studied using BDS-statistic and crest factor. As a result of the studies, it was found that under certain research conditions, time realizations of Chua generator and Rikitake generator, obtained by broadband filtering, are suitable. Other considered time realizations are not suitable for radio communication systems, since either they have low stealth from the outside observer, or they have an unacceptable crest factor value for radio communication systems. From this we can conclude that filtering chaotic signals using a broadband bandpass filter as a whole is a promising approach to ensure the stealth and reliability of data transmission in radio communication systems. The authors, basing on the conducted research and conclusions from well-known works, consider it appropriate to use broadband filtering to ensure the stealth and reliability of data transmission in radio communication systems when using chaotic signals, along with widely used methods.