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УДК 533.915, 621.396.67 Предмет и цель работы: В настоящее время наиболее острой проблемой в развитии и создании новых образцов военной техники является усовершенствование защиты объектов в радиоэлектронной борьбе. Перспективное направление создания малозаметных антенн – использование низкотемпературной плазмы. Кроме того, плазменными антеннами можно быстро управлять, перестраивая рабочую частоту и диаграмму направленности. В плазменных антеннах роль токопроводящего элемента играет газовый разряд в ограниченном объеме. Целью работы является исследование эффективности преобразования энергии поверхностной волны, распространяющейся в продольно неоднородном цилиндрическом плазменном столбе, в излучение. Плазменный столб ограничен диэлектрической оболочкой. В середине столба коаксиально расположен узкий металлический цилиндрический стержень. Методы и методология: Анализ выполнен методом спектрального разложения электромагнитного поля рассматриваемой волноведущей системы по полному набору функций, описывающих поверхностную и пространственные волны плазменной антенны. Результаты: Получена система интегро-дифференциальных уравнений для нахождения коэффициентов этого разложения. Эти коэффициенты определяют амплитуды отраженной и рассеянной на неоднородности плазмы волн и волны, прошедшей через неоднородность, а также диаграммы направленности излучения. Система уравнений справедлива для произвольного продольного изменения плотности плазмы. Определены зависимости коэффициентов трансформации энергии поверхностной волны от градиента плотности плазмы для некоторых значений электрического радиуса плазменного столба, диэлектрической проницаемости диэлектрика и его толщины. Продемонстрировано, что часть энергии поверхностной волны, которая трансформируется в излучение под острыми углами, может составлять 25÷30 %. Диаграммы направленности являются остронаправленными и имеют один лепесток. Максимум излучения расположен под углом в несколько градусов к направлению распространения поверхностной волны. Ширина лепестка уменьшается, а его положение сдвигается к 0° при увеличении градиента плотности плазмы. Исследовано влияние диэлектрика и радиуса металлического стержня на характеристики излучения. Заключение: Волноведущая система, рассмотренная в работе, является достаточно адекватной моделью плазменной антенны. Энергия, вводимая в такую антенну, с высокой эффективностью преобразуется в излучение под малыми углами к оси. Ключевые слова: цилиндрическая плазменная антенна, метод спектрального разложения, излучение, поверхностные волны, диаграмма направленности, низкотемпературная плазма Статья поступила в редакцию 12.02.2020 Radio phys. radio astron. 2020, 25(2): 158-167 СПИСОК ЛИТЕРАТУРЫ 1. Rayner J. P., Whichello A. P., and Cheetham A. D. Physical characteristics of plasma antennas. IEEE Trans . Plasma Sci . 2004. Vol. 32 , Is. 1. P. 269–281. DOI: 10.1109/TPS.2004.826019 2. Истомин Е. Н., Карфидов Д. М., Минаев И. М., Рухадзе А. А., Тараканов В. П., Сергейчев К. Ф., Трефилов А. Ю. Плазменный несимметричный вибратор с возбуждением поверхностной волной. Физика плазмы. 2006. Т. 32, № 5. С. 423–435. 3. Шевченко В. В. Плавные пе реходы в открытых волноводах. Введение в теорию. Москва: Наука, 1969. 192 с. 4. Kirichenko Yu. V. Study of a Longitudinally Nonuniform Plasma Layer. J. Commun. Technol. Electron. 2017. Vol. 62 , Is. 2. P. 166–174. DOI: 10.1134/S106422691702005X 5. Kirichenko Yu. V. Cylindrical Plasma Antenna with Large Longitudinal Density Irregularity. J. Commun. Technol. Electron. 2018. Vol. 63, Is. 5. P. 438–445. DOI: 10.1134/S1064226918050042 6. Артеменко А. Н., Карлов В. Д., Кириченко Ю. В. Теоретические основы плазменных антенн бегущей волны . Монография. Харьков: ООО ”ДИСА ПЛЮС“, 2018. 194 с. 7. Уолтер К. Антенны бегущей волны. Москва: Энергия, 1970. 449 с.

—An analysis is performed for the characteristics of an interference microwave switch with distributed switched wave power as a device for outputting energy from an active resonant microwave compressor. The proposed device is a cascade of conventional microwave switches based on H-tees connected in series with straight arms. It is shown that such a switch can multiply reduce the switched wave power by uniformly distributing it across the switches of the tees, which is done by adjusting the lengths of the tee arms. It was also established that between the lengths there is a functional relationship in which uniform distribution is achieved. The results of an experimental study of the microwave switch of two and/or three tees at low and high power are presented.

The rate of the feed velocity and specific load in the air separator are interrelated and require a rational approach to their choice, because reducing the rate of velocity increases grain flow thickness, which adversely affects the efficiency of grain separation in the separation zone, but limits separator performance. Based on the research of many authors, it was concluded that the feed velocity of grain material into the pneumatic separation channel should be in the range of 0.4… 0.6 m/s. Taking into account that using a feeder unit for multilevel grain input, the total thickness of grain flow is divided by the number of the involved levels of input. The main condition is to ensure a single layer of grain feed at the velocity at which the most intense release of light impurities. Therefore, the purpose of the study is to identify rational parameters of the guide gravitational surface of the feeder unit with the provision of appropriate performance characteristics of the grain flow during its multilevel feeding into the pneumatic separating channel. As a result of experimental research, the dependences of the modes of movement of grain material on the gravitational guide curve on its main parameters, namely, the length of the acceleration section Lp, its angle α and the radius of the arcuate section r. On the basis of the carried-out research parameters of a gravitational guide surface at which a single-layer mode of movement of grain material for a range of specific loadings is reached are established qB = 250 – 500 kg/hour. Accordingly, for the conditions of movement of grain material with a thickness of one grain with the velocity of feeding into the pneumatic separation channel vв = 0.5…0.6 m/s, the rational parameters of the guide gravity curve for cereals with the internal friction coefficient φтер = 0.47…0.73 there are: the length of the acceleration section Lp = 0.2 m, the angle of its inclination α = 33° and the radius of the arcuate section r = 0.15 m.

The purpose of the article.Consider method by which calculated required detection range helicopter that can provide guidance for fighter destroyed helicopter. It is believed that ensured detection helicopter radio equipment, which provide the work of the command post. Results. The article analyzed the trend of improving helicopters in recent years.The noted a growing possibility of using the helicopter to meet the challenges on the battlefield, putting helicopters in a row with means of attack, using airborne equipment.The conclusion that the fight against helicopters important issue is the calculation time required for adecision on their application at the command post defense. In the article, the example of an automated system of decision-making at the command post Brigade tactical aviation airfields considered the possibility of using the proposed method and the calculations detection range, providing decision by the person who decides brigade of tactical aviation. Conclusions. It is shown that one of the key conditions for the organization and the successful interception of enemy helicopters are grounded and timely decisions on management of fighter aircraft on the remote control of Air Force tactical level.Uncertainty and dynamism of the airspace, time constraints, significant amounts of information and uncertainty that characterize the actions of enemy helicopters that are clearly uncertain and contradictory, causing growth requirements for the feasibility and the efficiency of decision-making on the Air Force control panel of the tactical level. One of the directions of fulfilling such requirements is automation of the processes of management of fighter aviation at the stage of combat operations. Мета статті. Розглянути метод, за допомогою якого розраховується необхідна дальність виявлення вертольота, яка може служити орієнтиром для винищувача знищеного гелікоптера. Вважається, що забезпечено виявлення вертолітної радіотехніки, що забезпечує роботу командного пункту. Результати. У статті проаналізована тенденція вдосконалення вертолітної техніки за останні роки. Відмічена зростаюча можливість використання вертольота, для вирішення завдань на полі бою, що ставить вертолітну техніку в один ряд разом із засобами нападу, з використанням літакової техніки. Зроблений висновок про те, що при боротьбі з вертольотами важливим питанням є розрахунок необхідного часу на прийняття рішення по їх застосуванню на командному пункті протиповітряної оборони. У статті, на прикладі роботи автоматизованої системи прийняття рішення на командному пункти аеродромів бригади тактичної авіації розглянута можливість використання запропонованої методики та проведені розрахунки виявлення дальності, що забезпечує прийняття рішення особою, яка приймає рішення, бригади тактичної авіації. Показано, що одним з ключових умов організації та успішного перехоплення вертольотів противника є обґрунтовані і своєчасні рішення по управлінню винищувачами на дистанційному управлінні тактичного рівня ВВС. Невизначеність і динамічність повітряного простору, часові обмеження, значний обсяг інформації і невизначеність, щохарактеризують дії вертольотів противника, які явно невизначені і суперечливі, що обумовлює зростання вимог до здійсненності та ефективності прийняття рішень на панелі управління ВПС. Одним з напрямків виконання таких вимог є автоматизація процесів управління винищувальної авіації на етапі бойових дій.

У статті розглянуто питання аналізу можливостей забезпечення заданої дальності дії РЛС, здатної здійснювати радіолокаційне спостереження малопомітних, малорозмірних та маневруючих цілей. Обгрунтована доцільність використання когерентної пачки радіоімпульсів для забезпечення необхідної дальності виявлення із заданими показниками якості. Надано порівняльний аналіз можливостей використання поодинокого і пачкового радіосигналів. Доведена необхідність врахування корельованих фазових флуктуацій радіоімпульсів прийнятої пачки при вимірюванні дальності до цілі. Вважається, що фазові флуктуації розподілені за нормальним законом с нульовим середнім, а їх кореляція убуває зі збільшенням інтервалу між радіоімпульсами пачки за експоненціальним або знакозмінним законами. На вхід приймального пристрою РЛС надходять відбиті від цілей сигнали на фоні некорельованого гаусівського шуму. Розгляд проводиться для моделі сигналу з випадковою амплітудою та початковою фазою. Оцінювання часу запізнення радіолокаційного сигналу здійснюється за критерієм максимуму натурального логарифма відношення правдоподібності, усередненого по усім можливим значенням випадкових неінформативних параметрів. В явному вигляді отримано вираз нормованої функції розузгодження когерентної пачки за наявністю фазових флуктуацій її радіоімпульсів. Врахування фазових флуктуацій радіоімпульсів прийнятої пачки при вимірюванні дальності до цілі дозволить покращити ефективність вирішення когерентно-імпульсними РЛС завдань за призначенням.

Planets are thought to form at the early stage of stellar evolution when the mass accretion is still ongoing. RY Tau is a T Tauri type star at the age of a few Myr, with accretion disc seen at high inclination, so that line of sight crosses both the wind and the accretion gas flows. In a long series of spectroscopic monitoring of the star in 2013-2020, we detected variations in H-alpha and NaI D absorptions at radial velocities of infall (accretion) and outflow (wind) with a period of about 22 days. The absorptions in the infalling and the outflowing gas streams vary in anti-phase: an increase of infall is accompanied by a decrease of outflow, and vice versa. These flip-flop oscillations retain phase over several years of observations. We suggest that this may result from the MHD processes at the disk-magnetosphere boundary in the propeller mode. Another possibility is that a massive planet modulates some processes in the disc and provides the observed effects. The period, if Keplerian, corresponds to a distance of 0.2 AU, which is close to the dust sublimation radius in this star. The presence of the putative planet may be confirmed by radial velocity measurements: expected amplitude is > 90 m/s if a planet mass is > 2 Mj., 7 pages, 12 figures, accepted for publication in MNRAS

The subject of the study is the methodology for calculating the radar detection zones of the meter range, the formation of which is significantly influenced by the Earth. The aim of the work is the development and analysis of the mathematical model of the detection zone, which generalizes the known model to the case when the radar antenna does not have a phase center or it does not coincide with the beginning of the chosen coordinate system for calculating the antenna pattern. The model is based on the method of reflective interpretation and takes into account the features of antenna construction. The radiating elements of the antenna in the form of wave channels are located on two floors, which makes it possible to select the heights of floors and their excitation with signals with certain amplitudes and initial phases to reduce the depth of the dip in the radiation pattern in certain angular sectors. In such antennas there is usually no phase center, therefore, in the mathematical model of the detection zone, not only the amplitude, but also the phase characteristics of the antenna are taken into account. This made it possible to take into account the differences in the phases of the fields in the directions to the target and the reflection point and to clarify the result of the interference of the direct and reflected waves. The calculations of the detection zones illustrating the effect on their parameters of the electric properties of the ground, elevations of the antenna and its inclination with respect to the horizon are carried out. The mathematical model is realized with the help of an accessible and simple computer mathematical package Mathcad. The computer model allows, with changes in the design of the antenna or electrical parameters of the Earth, to promptly estimate the detection zones and their control capabilities to improve the conditions for detecting targets at certain elevation angles.

We present the results of studying a cascade microwave switch capable of stable operation at the power level of a regular waveguide. The cascade stage is formed by connecting several identical H-joints in the side branch of the tee of a conventional microwave interference switch. The connection distributes the power of the switched wave between the joints and varies the level of the switched power. The method of the scattering matrix is used to analyze the properties of such a switch based on H-joints with different matching levels of the side branch. It is shown that the cascade of sufficiently well-matched joints can decrease the level of the switched power by several times and ensure a higher operating power and a better stability of the switching, while the cascade with coupling worse than a certain boundary value can increase the power of the switched mode by several times and ensure switching of a lower-power mode. The numerical criterion of the coupling quality is found, which divides operation of the switch with increased and decreased switched powers. It is also found that in the switch under consideration, the microwave energy is distributed between the cascade elements in the process of the switching, which can affect greatly both the switching process and the characteristics of the switched mode during the process. The results of the analysis are compared with the experimental data at high and low power levels.

We propose a superconducting interference switch of a resonance microwave compressor on the basis of a waveguide H-plane tee, whose lateral arm contains a switching cavity having controllable parameters and based on another H-plane tee. The transmission coefficient of the switch is evaluated for the case of controlling the Q-factor and/or resonance frequency of the switching cavity externally. It is shown that the proposed switch can ensure high-efficiency transmission of the stored energy to the load at a minimal value of the controlling parameter (compared with the known solutions).

В статті піднімається питання проектування костюму регіону в тісному взаємозв’язку з оточуючим його предметно-просторовим середовищем, зокрема в аспекті колірної єдності, задля підвищення рівня презентації культурної спадщини регіону як туристичного ресурсу. Визначено колористику природнього середовища Херсонщини в контексті проектування костюму регіону як засобу атракції в туризмі, для чого: зібрано та систематизовано базу фотоілюстративного матеріалу з зображеннями пейзажів Херсонської області; відповідно до розробленого алгоритму зонального розподілення регіону визначено відсоткове співвідношення характерних кольорів для кожної зони природного середовища Херсонщини; визначено палітри характерних кольорів регіону для кожної з виділених зон за всіма порами року, якими доцільно оперувати в ході проектування костюму різного призначення, що заплановано експлуатувати на заданій території.

Studies of phenomena accompanying the interaction of superstrong electromagnetic fields with matter, in particular, the generation of an electron–positron plasma, acceleration of electrons and ions, and the generation of hard electromagnetic radiation are briefly reviewed. The possibility of using thin films to initiate quantum electrodynamics cascades in the field of converging laser pulses is analyzed. A model is developed to describe the formation of a plasma cavity behind a laser pulse in the transversely inhomogeneous plasma and the generation of betatron radiation by electrons accelerated in this cavity. Features of the generation of gamma radiation, as well as the effect of quantum electrodynamics effects on the acceleration of ions, at the interaction of intense laser pulses with solid targets are studied.

We study the processes of radiation output from a microwave storage cavity through a superconducting interference switch, which is based on a H-junction with a superconducting switching cavity connected to the side branch of the junction for various ways of controlling the parameters of the switching cavity. It is shown that efficient control over radiation output in such a switch can be achieved by varying the resonance frequency or Q-factor of the switching cavity, as well as by varying these parameters simultaneously. It is found that in the case of controlling the resonance frequency of the switching cavity, there exists an optimal interval of the frequency variation, within which the total efficiency and extraction efficiency are maximum. When the Q-factor of the switching cavity changes, the dependence of the total efficiency and extraction efficiency on the Q-factor has the monotonic character. The mixed regime of radiation output control is also studied. The envelopes of the output compressor pulses are plotted on the basis of recurrent relationships between the amplitudes of the waves in the system for three regimes of switch operation. It is shown that pulses with an almost rectangular shape of the envelope can be formed in the regime of controlling the switching cavity by varying the Q-factor. An example of possible realization of the switching cavity is considered.

The microwave pulse compression procedure consists of excitation of a working mode in a resonant cavity and transforming the mode into an auxiliary one that is coupled to an output line. Both transforming and coupling involve switching. Transients were calculated by recursion relations giving higher accuracy at short time constants. Demonstration experiments were run in the X-band. The compressor prototype showed power amplification of 15 dB at an output pulse width of 2.7 ns and a peak power of 1.5 MW. Mode transformation efficiency approached 0.7. A sequence of nanosecond and sub-nanosecond microwave pulses within the length of an input feeding pulse can be, in principle, obtained.

The article deals with the estimation of the radial velocity when using a coherent burst of radio pulses as applied to the presence of correlated fluctuations of the initial phases in the radio pulses reflected from the target. The accuracy of the measurement of the burst frequency is evaluated for case of coordinated processing without taking intoaccount the phase fluctuations. The signals at the input of the radar’s receiver is an additive mixture of signals reflected from the targets, and uncorrelated Gaussian noise, that is the assumption of investigating. It is assumed, that the phasefluctuations of the received radio pulses bursts are distributed according to normal probability laws with zero mean, and correlations of phase fluctuations decrease with exponential or alternating, sign-variable laws by increasing interval between radio pulses within the bursts. This analysis makes it possible to determine the conditions under which the complication of the processing algorithm for this radar signal is considered justified. Удосконалення та розвиток сучасних аеродинамічних об'єктів радіолокаційного спостереження викликає збільшення вимог до їх засобів виявлення та відстеження. Збільшення маневруючих можливостей мішеней і здатність їх виконувати поставлені завдання на малих висотах з округленням місцевості обумовлює необхідність оцінки отриманої відстані до мети з різними радарами з максимально високою точністю. Визначення радіальної швидкості мішені при первинній обробці радіолокаційної інформації здійснюється в когерентно-імпульсному радіолокаторі, який використовує когерентний викид радіоімпульсів в якості звукового сигналу. Ступінь когерентності цього вибуху визначає тривалість його фазової структури і, як наслідок, міру дозволу радіальної швидкості і точність вимірювання радіальної швидкості повітряного об'єкта. Метою статті є аналіз впливу статистичних характеристик флуктуацій початкових фаз радіальних імпульсів отриманого когерентного вибуху на зниження точності вимірювання радіальної швидкості мішені. Результати. У статті розглядаються питання оцінювання радіальної швидкості при використанні когерентної пачки радіоімпульсів стосовно випадку наявності у відбитих від цілі радіоімпульсах корельованих флуктуацій початкових фаз. Оцінюється точність вимірювання частоти пачки для випадку узгодженої обробки без врахування фазових флуктуацій її радіоімпульсів. Розгляд проводиться у припущенні, що на вхід приймального пристрою РЛС надходить адитивна суміш відбитих від цілей сигналів й некорельованого гаусівського шуму. Вважається, що фазові флуктуації радіоімпульсів прийнятої пачки розподілені за нормальним законом знульовим середнім, а кореляція фазових флуктуацій зі збільшенням інтервалу між радіоімпульсами пачки убуває за експоненціальним або знакозмінним законами. Наведений аналіз дозволяє визначити умови, при яких ускладнення алгоритму обробки даного радіолокаційного сигналу вважається виправданим. Висновки. В результаті досліджень визначено, що вплив реальних умов радіолокаційного спостереження призводить до появи флуктуацій початкових фаз радіоімпульсів повторного спалаху. Точність вимірювання радіальної швидкості мішені значно залежить від статистичних характеристик фазових коливань, значення яких визначають умови оптимізації частотно-часової обробки радіолокаційного сигналу.

Classical T Tauri stars with ages of less than 10 Myr possess accretion discs. Magnetohydro-dynamic processes at the boundary between the disc and the stellar magnetosphere control the accretion and ejections gas flows. We carried out a long series of simultaneous spectroscopic and photometric observations of the classical T Tauri stars, RY Tauri and SU Aurigae, with the aim to quantify the accretion and outflow dynamics at time-scales from days to years. It is shown that dust in the disc wind is the main source of photometric variability of these stars. In RY Tau, we observed a new effect: during events of enhanced outflow, the circumstellar extinction becomes lower. The characteristic time of changes in outflow velocity and stellar brightness indicates that the obscuring dust is near the star. The outflow activity in both stars is changing on a time-scale of years. Periods of quiescence in the variability of the Hα profile were observed during the 2015-2016 period in RY Tau and during the 2016-2017 period in SU Aur. We interpret these findings in the framework of the magnetospheric accretion model, and we discuss how the global stellar magnetic field can influence the long-term variations of the outflow activity.© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society, This research was supported by the RFBR grant 16-02-00140. It was based partly on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias, using ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOTSA. We acknowledge support from a Visitors Programme at the Department of Astronomy at Stockholm University. JFG and RMGA were supported by Fundacao para a Ciencia e a Tecnologia (FCT) through national funds (UID/FIS/04434/2013) and by FEDER through COMPETE2020 (POCI-01-0145-FEDER-007672). RMGA is supported by the fellowship PD/BD/113745/2015, under the FCT PD Program PhD::SPACE, funded by FCT (Portugal) and POPH/FSE (EC) and by CRUP through a cooperation programme (PAULIF: TC-16/17). DEM acknowledges his work as part of the research activity supported by the National Astronomical Research Institute of Thailand (NARIT), Ministry of Science and Technology of Thailand. SYuG was supported in part by the Ministry of Education and Science of Russia (the basic part of the Stateassignment, RK no. AAAA-A17-117030310283-7) and by the Act no. 211 of the Government of the Russian Federation, agreement No 02.A03.21.0006.

In the laser --- electron beam head-on interaction electron energy can decrease due to radiation reaction, i.e. emission of photons. For 10--100~fs laser pulses and for the laser field strength up to the pair photoproduction threshold, it is shown that one can calculate the resulting electron and photon spectra as if the electron beam travels through a constant magnetic field. The strength of this constant field and the interaction time are found as functions of the laser field amplitude and duration. Using of constant field approximation can make a theoretical analysis of stochasticity of the radiation reaction much simpler in comparison with the case of alternating laser field, also, it allows one to get electron and photon spectra much cheaper numerically than by particle-in-cell simulations., Comment: I I Artemenko et al 2019 Plasma Phys. Control. Fusion 61 074003

The principles of current filtering in three-phase three-wire power supply system at an asymmetric sinusoidal source that correspond to the actual European standard are considered. The advantages of forming a sinusoidal symmetrical input current by parallel connection of the active filter and the reactive compensator are shown. The feasibility to compensate the inactive sinusoidal Fryze's current by reactive elements under arbitrary combination of load and source parameters is proved and formula for direct calculation of the reactive compensator parameters for generation of inactive Fryze's current in the source unbalanced mode is obtained. Results of numeric modelling are given.

В результате петролого-минералогических и микрозондовых исследований установлено, что сульфидная минерализация в андезитах и дацитах верхнеюрской вулканической группы, изученных на о. Иризар, Скуа и Винтер, является сингенетической и относится к вкрапленному типу. В брекчиях метадацитов о. Иризар содержание сульфидов достигает 20—25% объема породы. В пиритах из брекчии дацитов о. Иризар присутствуют примеси Au (0,08 %), Ag (0,04 %), Со (0,17 %) и Си (0,12 %). В пирите из дацитов о. Скуа опре­делены содержания Au (0,06 %) и Со (0,11 %), а в пиритах из андезитов о. Винтер обнаружены Au 10.18 %), Ag (0,05 %) и Со (0,10 %). В результате проведенных работ определена перспективность исследований андезитов и дацитов верхнеюрской вулканической группы на благороднометальную минерализацию.

We develop a combined method for calculating the characteristics of the integrated lens antennas for millimeter-wave wireless local radio-communication systems on the basis of the geometrical and physical optics approximations. The method is based on the concepts of geometrical optics for calculating the electromagnetic-field distribution on the lens surface (with allowance for multiple internal re-reflections) and physical optics for determining the antenna-radiated fields in the Fraunhofer zone. Using the developed combined method, we study various integrated lens antennas on the basis of the data on the used-lens shape and material and the primary-feed radiation model, which is specified analytically or by computer simulation. Optimal values of the cylindrical-extension length, which ensure the maximum antenna directivity equal to 19.1 and 23.8 dBi for the greater and smaller lenses, respectively, are obtained for the hemispherical quartz-glass lenses having the cylindrical extensions with radii of 7.5 and 12.5 mm. In this case, the scanning-angle range of the considered antennas is greater than ±20° for an admissible 2-dB decrease in the directivity of the deflected beam. The calculation results obtained using the developed method are confirmed by the experimental studies performed for the prototypes of the integrated quartz-glass lens antennas within the framework of this research.

We study theoretically helical edge and surface states of 2D and 3D topological insulators (TI) tunnel-coupled to metal leads and show that their transport properties are strongly affected by contacts as the latter play a role of a heat bath and induce damping and relaxation of electrons in the helical states of TI. A simple structure that produces a pure spin current in the external circuit is proposed. The current and the spin current delivered to the external circuit depend on the relation between characteristic lengths: decay length due to tunneling, contact length and, in case of 3D TI, mean free path and spin relaxation length caused by momentum scattering. If the decay length due to tunneling is the smallest one, then the electric and spin currents are of order of the conductance quantum in 2D TI, and of order of the conductance quantum multiplied by the ratio of the contact width to the Fermi wavelength in 3D TI. A role of electron–electron interaction is discussed in case of 2D TI, and it is shown that in contrast to the conventional Luttinger liquid picture the interaction can be treated perturbatively. The presence of interaction results in suppression of density of states at the Fermi level and hence in decrease of the electric and spin currents.

We are considering a problem of the measurement of the dispersion of the random pulse signal with unknown time of arrival against the white noise and the correlated Gaussian interference. By applying a maximum likelihood method, we synthesize quasi-optimal, quasi-likelihood and adaptive estimation algorithms. We also find out the theoretical and experimental dependences for the characteristics of the obtained dispersion estimates that are then used in the study of the efficiency of the introduced algorithms and in the further investigation revea

A formula for the ionization rate in extremely intense electromagnetic field is proposed and used for numerical study of QED (quantum-electrodynamical) cascades in noble gases in the field of two counter-propagating laser pulses. It is shown that the number of the electron-positron pairs produced in the cascade increases with the atomic number of the gas where the gas density is taken to be reversely proportional to the atomic number. While the most electrons produced in the laser pulse front are expelled by the ponderomotive force from region occupied by the strong laser field there is a small portion of the electrons staying in the laser field for a long time until the instance when the laser field is strong enough for cascading. This mechanism is relevant for all gases. For high-$Z$ gases there is an additional mechanism associated with the ionization of inner shells at the the instance when the laser field is strong enough for cascading. The role of both mechanisms for cascade initiation is revealed.

UDC 621.37 We propose a commutator for the interference switch of microwave electromagnetic radiation on the basis of a waveguide H-junction made as a cavity with tunable parameters, which is connected to one arm of this junction. The superconducting version of a microwave compressor with such a switch is analyzed. The conditions of effective switch operation in the mode of electromagnetic energy storage and its fast output in the case of controllable manipulation of the Q-factor and resonant frequency of the switching cavity are determined. Estimates of the output parameters of the superconducting compression system are presented for storing- and switching-cavity Q-factors of about 5 · 10 8 . The possibility of increasing the radiated power in such a compression system by 40–60 dB for output microwave pulses with durations of about 5–10 ns is demonstrated. Variants of practical implementation of the system are considered.

The new electronic database developed by the authors and titled “Astronomers of Ukraine” is described as a source of the main biographical data on astronomers of Ukraine from the 15th century until the beginning of the 21st century. The database is an upgrading component of the Ukrainian Virtual Observatory portal and contains the main biobibliographical data and papers concerning astronomers of Ukraine, as well as links to their publications. The existing biographical sources about astronomers in the world are discussed briefly. A list of the principal publications about astronomers of Ukraine is given.

Quasi-likelihood and maximum likelihood estimate algorithms of the amplitude of a radio signal with free-form envelope and unknown duration and initial phase are synthesized. Characteristics of the synthesized algorithms are found. The comparison of the accuracy of amplitude estimates is carried out.

Results of observations of short-term wind variability in the classical T Tauri stars RW Aur and DR Tau are presented. Since the H CaII emission is absorbed by the absorption component of the H∈ line, which arises in the wind at a radial velocity of about −120 km/s, the ratio of equivalent widths of the H and K emission lines of ionized calcium is used as an indicator of the line-of-sight wind density. Observations showed that the wind densities of RW Aur and DR Tau vary with a characteristic time of 4 to 5 days, i.e., with a period that is somewhat shorter than the period of the axial rotation of these stars. These results are interpreted in the framework of the conical wind model, which predicts cyclic repetitions of accretion and ejection events caused by the interaction of the star’s magnetosphere with the ionized gas at the inner boundary of the accretion disc.

This paper presents design and experimental verification of electronically steerable integrated lens antennas (ILAs) for WLAN/WPAN communication systems operating in the 60-GHz frequency band. The antenna is comprised of a quartz extended hemispherical lens, four switched aperture coupled microstrip antenna (ACMA) elements, and a distribution circuit based on SPDT MMIC switches. The designed ILAs are capable of electronic steering between four different antenna main beam directions in one plane. Fixed beam and electronically steerable ILA prototypes are fabricated and tested. The results are given for two quartz dielectric lenses with the radii of 7.5 and 12.5 mm in order to meet a wide range of WLAN/WPAN requirements. The measured maximum gains of the designed ILAs are 18.4 and 23.2 dBi. The experimental results of the fabricated electronically steerable quartz ILA prototypes prove the simulation results and show $\pm {\hbox{35}}^{\circ}$ and $\pm {\hbox{22}}^{\circ}$ angle sector coverage for the lenses with the 7.5 and 12.5 mm radii, respectively. The bandwidth of the ILAs exceeds the frequency band of 57–66 GHz allocated for WLAN/WPAN applications. The designed ILAs meet all the requirements for steerable directional antennas of 60-GHz WLAN/WPAN systems.

We consider the development of an integrated lens antenna for LAN radio communication systems operated in the 60 GHz frequency band. The antenna is an extended hemispherical silicon lens. On its flat surface, a microstrip antenna element is located. The use of silicon, which has a dielectric permittivity e = 11.7, as the lens material ensures the maximum range of scanning angles for the minimum axial size of the lens. The approximate analytical formulas, which are used for initial calculations of the lens parameters, allow one to evaluate the basic parameters of the lens antenna integrated with the microstrip antenna element. For further optimizing the parameters of the lens and the antenna element, 3D simulation of the electromagnetic-field distribution was performed. Based on its results, we have developed and manufactured extended hemispherical silicon lenses, which had radii of 6 and 12 mm. The planar microstrip antenna element was manufactured by the low temperature co-fired ceramics (LTCC) technology. The results of simulation and experimental studies of the manufactured prototypes demonstrate that the developed lens antennas has directivities of 17.6 and 23.1 dBi for lenses with radii of 6 and 12 mm, respectively. In this case, the maximum beam deflection angle is achieved, which is equal to 55°, while the permissible decrease in the directivity is no more than 6 dBi compared with the case of a non-deflected beam. The obtained results show that the developed integrated lens antennas can find applications in high-speed radio communication systems operated in the millimeter-wave range.

We intended to compile the most complete catalog of bona fide members and candidate members of the beta Pictoris association, and to measure their rotation periods and basic properties from our own observations, public archives, and exploring the literature. We carried out a multi-observatories campaign to get our own photometric time series and collected all archived public photometric data time series for the stars in our catalog. Each time series was analyzed with the Lomb-Scargle and CLEAN periodograms to search for the stellar rotation periods. We complemented the measured rotational properties with detailed information on multiplicity, membership, and projected rotational velocity available in the literature and discussed star by star. We measured the rotation periods of 112 out of 117 among bona fide members and candidate members of the beta Pictoris association and, whenever possible, we also measured the luminosity, radius, and inclination of the stellar rotation axis. This represents to date the largest catalog of rotation periods of any young loose stellar association. We provided an extensive catalog of rotation periods together with other relevant basic properties useful to explore a number of open issues, such as the causes of spread of rotation periods among coeval stars, evolution of angular momentum, and lithium-rotation connection., Forthcoming article, Received: 20 June 2016 / Accepted: 09 September 2016; 40 pages, 2 figures. The online figures A1-A73 are available at CDS

Surface temperature inhomogeneities in classical T Tauri stars (CTTS) induced by magnetic activity and mass accretion lead to rotational modulation of both photometric and spectroscopic parameters of these stars. Using the extended photometric catalogue by Grankin et al. (2007), we have derived the periods and amplitudes of the rotational modulation of brightness and color for 31 CTTS; for six of them, the periods have been revealed for the first time. The inclinations of the rotation axis and equatorial rotational velocities of CTTS have been determined. We show that the known periods of brightness variations for some of the CTTS are not the axial rotation periods but are the Keplerian periods near the inner boundary of the dusty disk. We have found that the angular velocity of CTTS with a mass of 0.3 - 3 M_sun in the Taurus-Auriga complex remains constant in the age range 1 - 10 Myr. CTTS on radiative evolutionary tracks rotate faster than completely convective CTTS. The specific angular momentum of CTTS depends on the absolute luminosity in the H\alpha- line., Comment: 12 pages, 4 figures

The problem of how to rotate a mirror system of a space telescope (reflector) by means of a parallel-structure mechanisms has been solved. Schemes of such mechanisms are presented. Mechanisms with three degrees of freedom, which are the simplest in terms of structure, are of the utmost interest.

We study theoretically transport properties of one-dimensional system of interacting electrons pinned by an impurity. Long-range Coulomb interaction in such a system is known to induce a 4 k F electron density modulation characterized by extremely slow, slower than any power law, decay of the density correlations which can be described as a one-dimensional Wigner crystal. We study non-stationary regime of conduction corresponding to sliding of the 1D Wigner crystal depinned by the applied voltage. In this regime the dc current is accompanied by current oscillations with frequency f = I ¯ / e . We calculate I–V curves and ac current generated by sliding. Our approach is based on the ideas of Luttinger liquid. We study also the case of magnetic impurity and show that applied voltage induces not only the electrical current, but also the spin current as well, in other words, the current becomes spin polarized. We find that a spin bias applied to the system contributes to electric current both in case of magnetic and non-magnetic impurity, and this is related to violation of the spin–charge separation at the impurity site.

The spin transport as the current flows through an impurity in a one-dimensional conductor is analyzed. The interacting electrons are described in terms of the Luttinger liquid theory. Both the Coulomb and short-range interactions are considered; the latter appears when the gate screens the long-range part of the Coulomb potential. The cases of magnetic and nonmagnetic impurities are considered. It has been revealed that, for a magnetic impurity, the electric current flow induces the generation of the spin current, which has direct and alternating components. At low temperatures and voltages, the current can be completely spin-polarized. For a nonmagnetic impurity, the spin current generation is absent. The spin current flowing though the wire affects the current-voltage characteristic for both magnetic and nonmagnetic impurities. The results have been obtained for a rather strong electron-electron interaction.

A new regime of electron transport through an impurity in 1D conductors, which resembles the Josephson effect in its manifestations, is predicted. Passage of current through the impurity under voltages above the threshold value is accompanied with generation of ac current oscillations. The temperature below which the effect can be observed, the threshold voltage, and the frequency range are determined by the impurity potential and the strength of electron-electron interaction. The generation line width and the current-voltage characteristics are determined.

The low-temperature heat capacity of a quasi-one-dimensional conductor in the Luttinger liquid state is studied for conductors with a charge density wave and without it. It is shown that pinning of the Luttinger liquid leads to localization of spins and a strong effect of the magnetic field on the thermodynamics of samples resembling the effect observed in recent experiments. We believe that this indicates the possibility of the formation of a Luttinger liquid in quasi-one-dimensional crystals.

We study theoretically electronic transport through a contact of a quantum wire with 2D or 3D leads and find that if the contact is not smooth and adiabatic then the conduction is strongly suppressed below a threshold voltage $V_T$, while above $V_T$ the dc current $\bar I$ is accompanied by coherent oscillations of frequency $f=\bar I / e$. The effect is related to interelectronic repulsion and interaction of dc current with the Friedel oscillations near a sharp contact. In short conducting channels of length $L < L_0 \simeq \hbar v_F/eV_T$ and at high temperatures $T > T_0 \simeq eV_T/k_B$ the effect is destroyed by fluctuations., 10 pages, to be published in JETP Letters, vol. 91

We report the first results of experiments that demonstrate the amplification of megawatt nanosecond microwave pulses in a Cherenkov maser with a dielectric rod and moderately relativistic annular electric beam generated in a compact linear induction accelerator module. The input signal was generated by a resonant microwave compressor operating in a 3-cm wavelength range. A maximum gain of ∼12.5 dB and a maximum output power of ∼16 MW for a pulse duration of ∼4 ns at a frequency of 9.388 GHz were obtained with a quartz rod. The dependence of the gain on the compressor power was determined for various values of the accelerating voltage and beam current.

Long-term, uniform series of U BV R observations of T Tauri and Ae Herbig stars obtained over 20 yr at the Maidanak Observatory as part of the ROTOR program are analyzed. We find a linear relationship between the characteristic variability time scale and the bolometric luminosity of the star+disk system: the higher the luminosity, the slower the brightness variations. This dependence is valid over a wide range of masses and luminosities, from T Tauri stars to Ae Herbig stars. On average, the variability time scale is one-quarter the Keplerian period at the dust-sublimation radius, which is known from interferometric observations. Some T Tauri stars have periods from 25 to 120 days, which are preserved over several observing seasons. These periods correspond to Keplerian orbits with semi-major axes from 0.14 to 0.52 AU. The results obtained provide indirect evidence for the existence of protoplanets in the gas-dust disks of stars in early stages of their evolution toward the main sequence.

The impact of the Struve astronomical dynasty on the development of astronomy in Ukraine in the 19th–20th centuries is studied. First of all, the role of F.G.W. Struve and O.V. Struve in the formation of astronomical research programs at the observatories at the Kharkiv, Kyiv, Odesa, and Mykolayiv, in equipping the observatories with instruments, in practical training of astronomers as well as in the organization of astronomy-geodetic expeditions (19th century). Particular attention is paid to the activity of L.O. Struve as a director of the Astronomical observatory of Kharkiv University and his works conducted together with G.A. Shajn and B.P. Gerasimovich (20th century) as well as to the impact of his scientific and public activity, including one he made as a President of IAC, on the development of astronomy in the Soviet Union and Ukraine. A range of important documents from the archives of Russian Academy of Sciences, Institute of astronomy and State Archive of Ukraine are cited.

We study theoretically two effects related to impurity depinning that are common for 1D Luttinger liquid (LL) and linear-chain CDW conductors. First, we consider the electron transport through a single impurity in a 1D conducting channel and study a new regime of conduction related to LL sliding at voltage above a threshold one. The DC current in this regime is accompanied by oscillations with frequency $f =I/e$. This resembles the CDW depinning in linear-chain conductors, the Josephson effect, and the Coulomb blockade. Second, we found that strong pinning of the LL by impurities leads to a magnetic field dependence of the low-temperature specific heat similar to that observed experimentally in CDW compounds. We interpret this in favor of possibility of formation of the LL in linear-chain compounds., 6 pages, paper presented at the ECRYS-2008 conference (Aug. 2008), accepted for publication in Physica B: Physics of Condensed Matter

The microwave transmission system of an X-band antenna-amplifier (a relativistic traveling-wave tube intended for operation in the fundamental nonaxisymmetric HE11 mode of a dielectric rod) has been investigated. A specially designed two-frequency tunable resonance microwave pulse compressor is used as an RF drive source. The microwave transmission system is incorporated into a hollow high-voltage electrode of a linear induction accelerator. It is shown that this transmission system can be reasonably matched in a frequency band of about 700 MHz, and microwave pulses with a duration of ∼4 ns and a peak power of at least up to 1.6 MW can be transmitted via it without substantial losses and envelope distortions. It is also shown that the actual configuration of the device virtually does not affect the angular distribution of the far-field radiation pattern of the rod antenna, which is an extension of the slow-wave structure of the amplifier.

We present the results of theoretical analysis of the operation of a waveguide bridge as a device for microwave-energy extraction and the data of experimental studies of 3-cm compressors with energy extraction through the bridge. We determine conditions under which the bridge can be used as an efficient output device capable of doubling the output pulsed power of the compressor.

The wind interaction with the dusty environment of the classical T Tauri star RY Tau has been investigated. During two seasons of 2013-2015 we carried out a spectroscopic and photometric (BVR) monitoring of the star. A correlation between the stellar brightness and the radial velocity of the wind determined from the H-alpha and Na D line profiles has been found for the first time. The irregular stellar brightness variations are shown to be caused by extinction in a dusty disk wind at a distance of about 0.2 AU from the star. We suppose, that variations of the circumstellar extinction results from cyclic rearrangements of the stellar magnetosphere and coronal mass ejections, which affect the dusty disk wind near the inner boundary of the circumstellar disk., Comment: 13 pages, 1 table, 8 figures. Accepted for publication in Astronomy Letters, 2016

We consider the problem of the determination of the radio wave attenuation factor. We show that the attenuation factor can be used for the information leakage detecting due to the side electromagnetic radiation of information facilities. We illustrate the thematic examples of the experimental determination of the attenuation factor for decimetric waves propagating through the paths leaving buildings. We give references for obtaining of the correct results during simulation of radio wave attenuation processes for the paths leaving buildings.