МОДЕЛЬ МАТРИЧНОЙ ВЗАИМНОКОРРЕЛЯЦИОННОЙ ФУНКЦИИ ЗОНДИРУЮЩЕГО И ОТРАЖЕННОГО ВЕКТОРНЫХ СИГНАЛОВ ДЛЯ КОНЦЕПТУАЛЬНОГО ПРОЕКТИРОВАНИЯ РАДИОЛОКАТОРА С СИНТЕЗИРОВАННОЙ АПЕРТУРОЙ НА ВОЗДУШНОМ НОСИТЕЛЕ

In order to simulate the process of design development in full on computer models, including virtual tests of the synthetic aperture radar on an air carrier in model media, the study develops a structural scheme of the conceptual design of the synthetic aperture radar on an air carrier. The scheme is invariant with respect to the type of an air carrier with a synthetic aperture radar: an aircraft, a helicopter, an unmanned aerial vehicle and similar ones: an air carrier "enters" it by only an automatic control system, a model of trajectory instabilities and a spectrum of frequencies of elastic oscillations of its design. To perform a computer simulation of radar systems with full polarization sensing, a model of a matrix cross-correlation function of probing and reflected vector signals is proposed. As a model of the scattering object, a set of independent point reflectors distributed over space and generally having different rates of motion is accepted. The reflected signal is a sum of elementary signals, their form completely repeats the shape of the emitted signal, and the amplitude, the phase and polarization are respectively determined by the coordinate, velocity and polarization parameters of elementary reflectors forming a spatially extended object. Taking into account the developed models for the formation of the vector sounding signal and the matrix response function of the distributed radar object, a block-diagram of the model of the matrix cross-correlation function of the emitted and reflected vector signals is proposed. A block-diagram is the basis for the development of an algorithm and a program for computer modeling of the primary signal processing in a radar station with full polarization sensing.Для имитации на компьютерных моделях процесса проектной разработки в полном объеме, включая виртуальные испытания радиолокатора с синтезированной апертурой на воздушном носителе, в модельных средах разработана структурная схема концептуального проектирования радиолокатора с синтезированной апертурой на воздушном носителе. Схема инвариантна относительно типа воздушного носителя с радиолокатором с синтезированной апертурой – самолета, вертолета, беспилотного летательного аппарата и подобных: воздушный носитель «входит» в нее только системой автоматического управления, моделью траекторных нестабильностей и спектром частот упругих колебаний своей конструкции. Для выполнения компьютерного моделирования радиолокационных систем с полным поляризационным зондированием предложена модель матричной взаимнокорреляционной функции зондирующего и отраженного векторных сигналов. В качестве модели рассеивающего объекта принята совокупность независимых точечных отражателей, распределенных по пространству и имеющих в общем случае разные скорости движения. Отраженный сигнал представляет собой сумму элементарных сигналов, форма которых полностью повторяет форму излученного сигнала, а амплитуда, фаза и поляризация определяются соответственно координатными, скоростными и поляризационными параметрами элементарных отражателей, образующих пространственно-протяженный объект. С учетом разработанных моделей формирования векторного зондирующего сигнала и матричной функции отклика распределенного радиолокационного объекта, предложена блок-схема модели матричной взаимнокорреляционной функции излученного и отраженного векторных сигналов. Блок-схема является основой для разработки алгоритма и программы компьютерного моделирования процесса первичной обработки сигналов в радиолокационной станции с полным поляризационным зондированием

MODEL OF A MATRIX CROSSCORRELATION FUNCTION OF THE PROBING AND REFLECTED VECTOR SIGNALS FOR A CONCEPTUAL DESIGN OF A SYNTHETIC APERTURE RADAR ON AN AERIAL CARRIER

In order to simulate the process of design development in full on computer models, including virtual tests of the synthetic aperture radar on an air carrier in model media, the study develops a structural scheme of the conceptual design of the synthetic aperture radar on an air carrier. The scheme is invariant with respect to the type of an air carrier with a synthetic aperture radar: an aircraft, a helicopter, an unmanned aerial vehicle and similar ones: an air carrier "enters" it by only an automatic control system, a model of trajectory instabilities and a spectrum of frequencies of elastic oscillations of its design. To perform a computer simulation of radar systems with full polarization sensing, a model of a matrix cross-correlation function of probing and reflected vector signals is proposed. As a model of the scattering object, a set of independent point reflectors distributed over space and generally having different rates of motion is accepted. The reflected signal is a sum of elementary signals, their form completely repeats the shape of the emitted signal, and the amplitude, the phase and polarization are respectively determined by the coordinate, velocity and polarization parameters of elementary reflectors forming a spatially extended object. Taking into account the developed models for the formation of the vector sounding signal and the matrix response function of the distributed radar object, a block-diagram of the model of the matrix cross-correlation function of the emitted and reflected vector signals is proposed. A block-diagram is the basis for the development of an algorithm and a program for computer modeling of the primary signal processing in a radar station with full polarization sensing

Effect of preliminary treatment on microstructure, mechanical properties and fracture of Ni3Al samples synthesized by spark plasma sintering

A comparative study of microstructure parameters and mechanical property characteristics of consolidated Ni3Al samples formed by spark plasma sintering after a preliminary short-term mechanical activation and mixing in a mortar is carried out. It is found out that the grain size of the mechanically pre-activated material is several times smaller than that of the material sintered after mixing in a mortar. This feature is manifested in the differences in the values of microhardness and short-term strength. The annealing temperature effect on the structure parameters and mechanical properties of Ni3Al samples is revealed depending on the pretreatment. It is assumed that the formation of a high-defect structural state, characterized by fine grains combined with an increased level of microdistortions, during mechanical activation predetermines the strength properties of the material both after spark plasma sintering and after deformation and heat treatment

Ti-Al3_3Ti metal-intermetallic laminate (MIL) composite with a cubic titanium trialuminide stabilized with silver: Selection of fabrication regimes, structure, and properties

Ti-Al$_3$Ti metal-intermetallic laminate (MIL) composites are known as promising structural materials due to the unique combination of their specific properties. However, their application is still limited due to the extremely high brittleness of the Al3Ti phase. In this study, we attempt to address this issue by changing the D0$_{22}$ crystal structure of Al$_3$Ti to the more ductile L1$_2$ structure by alloying it with silver. To select the best fabrication regimes of Ti-Ti(Al$_{1−x}$Ag$_x$)$_3$ composites, in situ synchrotron X-ray diffraction analysis was performed to reveal the chemical reactions occurring upon heating the Ti-Al-Ag sample. The analysis showed that the highest amount of Ti(Al$_{1−x}$Ag$_x$)$_3$ phase with the L1$_2$ structure appears at 930 °C. This temperature was chosen for subsequent spark plasma sintering experiments. Scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction analysis revealed that the sintered sample consisted mainly of Ti, Ti(Al$_{1−x}$Ag$_x$)$_3$, and a minor fraction of the Ag-Al compound distributed in the central parts of the intermetallic layers and at the grain boundaries. Modification of the titanium trialuminide crystal structure positively affected the properties of the composite, providing a 60% increase in fracture toughness. The Ag-Al phase also contributed to toughening, causing an additional crack deflection effect

The influence of duration of preliminary mechanical activation on microhardness of specimens of Ni3Al intermetallide synthesized under conditions of spark plasma sintering

In this work we perform an investigation of the influence of duration of preliminary mechanical activation in high energy ball mills on the microhardness of Ni3A intermetallide specimens synthesized under conditions of spark plasma sintering