scholarly journals Using information processing algorithms that factor in the effect of secondary modulation of radar signals

2020 ◽  
Vol 30 (2) ◽  
pp. 42-48
Author(s):  
V. A. Bratkov ◽  
A. A. Sentsov ◽  
V. B. Polyakov
Keyword(s):  
Power Plants ◽  
Spectral Component ◽  
Probability Of Detection ◽  
Radar Signal ◽  
Signal Spectrum ◽  
Spectral Structure ◽  
Detection Range ◽  
Radar Station ◽  
Reflected Signal ◽  
The Impact

The article provides an assessment of the impact the dynamic structures of power systems of aircraft systems have on the spectrum of the reflected radar signal. In the conditions of autonomous actions of the fighter, the tasks of long-range detection of airborne targets are assigned directly to the onboard radar station. It is necessary to resolve the contradictions associated with increasing the detection range without changing the energy indicators of the onboard radar station. This is possible by optimizing the processing of many spectral components of the signal reflected from the propeller and turboprop engine of airborne targets. The location of propeller reflections in the spectrum of the reflected signal is determined by the technical parameters of the power plant and its mode of operation. The percent of the total energy of the reflected signal spectrum outside the main spectral component is comparable with the energy reflected from the airframe of the aviation complex, most of which is the energy reflected from the rotating elements of power plants. Therefore, the development of an algorithm for detecting a signal with a complex spectral structure that maximizes the probability of detection under time and computational resources restrictions is a very relevant scientific task. The scientific novelty lies in the development of an algorithm for detecting a signal with a complex spectral structure and its detection characteristics taking the effect of secondary modulation into account as well as in the development of practical recommendations for optimizing algorithms for detecting airborne targets. Using the developed algorithm in the fighter’s pulse-Doppler radar station will increase the detection range of an air target against the background of interfering reflections from the water surface.

АКУСТИЧНА ПОМІТНІСТЬ БЕЗПІЛОТНИХ ЛІТАЛЬНИХ АПАРАТІВ З СИЛОВИМИ УСТАНОВКАМИ НА БАЗІ ПОРШНЕВИХ ДВИГУНІВ

2020 ◽  
pp. 62-80
Author(s):  
В. В. Руденко ◽  
И. В. Калужинов ◽  
Н. А. Андрущенко
Keyword(s):  
Control System ◽  
Internal Combustion Engine ◽  
Power Plants ◽  
Combustion Engine ◽  
Spectral Characteristics ◽  
Experimental Studies ◽  
Internal Combustion ◽  
Detection Range ◽  
Acoustic Signature ◽  
Static Conditions

The presence in operation of many prototypes of UAVs with propeller propellers, the use of such devices at relatively low altitudes and flight speeds makes the problem of noise reduction from UAVs urgent both from the point of view of acoustic imperceptibility and ecology.The aim of the work is to determine a set of methods that help to reduce the visibility of UAVs in the acoustic range. It is shown that the main source of noise from the UAV on the ground is the power plant, which includes the engine and the propeller. The parameters of the power plants influencing the processes that determine the acoustic signature of the UAV were investigated. A comprehensive analysis of the factors affecting visibility was carried out. The power plants include two-stroke and four-stroke engines, internal combustion and two-blade propellers. The use of silencers on the exhaust of the internal combustion engine was considered. The spectral characteristics of the acoustic fields of the propeller-driven power plants for the operating sample of the UAV "Eco" were obtained. The measurements were carried out in one-third octave and 1/48 octave frequency bands under static conditions. The venue is the KhAI airfield. Note that the propellers that were part of the power plants operated at Reynolds numbers (Re0,75<2*105), which can significantly affect its aerodynamic and acoustic characteristics. It is shown that when choosing a UAV control system, one should take into account the fact that two-stroke piston engines are the dominant source in the noise of propeller-driven control systems in the absence of a hood and mufflers in the intake and exhaust tracts. The use of a four-stroke internal combustion engine significantly reduces the noise of the control system. In the general case, the position of the boundaries of the zone of acoustic visibility of a UAV at the location of the observer is determined by the ratio between the intensity of acoustic radiation perceived by the observer from the UAV and the intensity of sound corresponding to the natural acoustic background and depends on the degree of manifestation of acoustic effects accompanying the propagation of sound in a turbulent atmosphere - the refraction of sound waves. Absorption and dissipation of acoustic energy. The calculation and comparison of the UAV detection range was carried out taking into account the existing natural maskers.The results of experimental studies are presented that allow assessing the degree of acoustic signature of the UAV. A set of measures aimed at reducing the intensity of the acoustic signature of the UAV in various regions of the radiation spectrum has been determined.

scholarly journals Impact of the Wind Turbine on the Parameters of the Electricity Supply to an Agricultural Farm

2021 ◽  
Vol 13 (13) ◽  
pp. 7279
Author(s):  
Zbigniew Skibko ◽  
Magdalena Tymińska ◽  
Wacław Romaniuk ◽  
Andrzej Borusiewicz
Keyword(s):  
Power Plant ◽  
Wind Turbine ◽  
Wind Power ◽  
Rural Areas ◽  
Power Plants ◽  
Reactive Power ◽  
Supply Voltage ◽  
Common Source ◽  
Voltage Fluctuations ◽  
The Impact

Wind power plants are an increasingly common source of electricity located in rural areas. As a result of the high variability of wind power, and thus the generated power, these sources should be classified as unstable sources. In this paper, the authors attempted to determine the impact of wind turbine operation on the parameters of electricity supplied to farms located near the source. As a result of the conducted field tests, variability courses of the basic parameters describing the supply voltage were obtained. The influence of power plant variability on the values of voltage, frequency, and voltage distortion factor was determined. To estimate the capacity of the transmission lines, the reactive power produced in the power plant and its effect on the value of the power factor were determined. The conducted research and analysis showed that the wind power plant significantly influences voltage fluctuations in its immediate vicinity (the maximum value registered was close to 2%, while the value required by law was 2.5%). Although all the recorded values are within limits specified by the current regulations (e.g., the THD value is four times lower than the required value), wind turbines may cause incorrect operation of loads connected nearby. This applies mainly to cases where consumers sensitive to voltage fluctuations are installed in the direct vicinity of the power plant.

scholarly journals Searching for energy-resolved quasi-periodic oscillations in AGN

2021 ◽  
Author(s):  
Dominic I Ashton ◽  
Matthew J Middleton
Keyword(s):  
Power Law ◽  
Spectral Component ◽  
Broad Band ◽  
Initial Study ◽  
Periodic Oscillations ◽  
Single Observation ◽  
Curved Space ◽  
Multiple Observations ◽  
Band Noise ◽  
The Impact

Abstract X-ray quasi-periodic oscillations (QPOs) in AGN allow us to probe and understand the nature of accretion in highly curved space-time, yet the most robust form of detection (i.e. repeat detections over multiple observations) has been limited to a single source to-date, with only tentative claims of single observation detections in several others. The association of those established AGN QPOs with a specific spectral component has motivated us to search the XMM-Newton archive and analyse the energy-resolved lightcurves of 38 bright AGN. We apply a conservative false alarm testing routine folding in the uncertainty and covariance of the underlying broad-band noise. We also explore the impact of red-noise leak and the assumption of various different forms (power-law, broken power-law and lorentzians) for the underlying broad-band noise. In this initial study, we report QPO candidates in 6 AGN (7 including one tentative detection in MRK 766) from our sample of 38, which tend to be found at characteristic energies and, in four cases, at the same frequency across at least two observations, indicating they are highly unlikely to be spurious in nature.

scholarly journals How detection ranges and usage stops impact digital contact tracing effectiveness for COVID-19

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Konstantin D. Pandl ◽  
Scott Thiebes ◽  
Manuel Schmidt-Kraepelin ◽  
Ali Sunyaev
Keyword(s):  
Disease Spread ◽  
Contact Tracing ◽  
Behavioral Characteristics ◽  
Policy Makers ◽  
Detection Range ◽  
Proximity Detection ◽  
Effective Technology ◽  
Different Types ◽  
Effectiveness And Efficiency ◽  
The Impact

AbstractTo combat the COVID-19 pandemic, many countries around the globe have adopted digital contact tracing apps. Various technologies exist to trace contacts that are potentially prone to different types of tracing errors. Here, we study the impact of different proximity detection ranges on the effectiveness and efficiency of digital contact tracing apps. Furthermore, we study a usage stop effect induced by a false positive quarantine. Our results reveal that policy makers should adjust digital contact tracing apps to the behavioral characteristics of a society. Based on this, the proximity detection range should at least cover the range of a disease spread, and be much wider in certain cases. The widely used Bluetooth Low Energy protocol may not necessarily be the most effective technology for contact tracing.

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