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RESEARCH ARTICLES
OUR TEAM’S CUTTING-EDGE DEVELOPMENTS AND RESEARCH
The influence of carbon nanospheres (CNS) on the electromagnetic proper- ties of composite materials is investigated. CNS are fabricated by high- frequency electrical-discharge treatment of propane–butane mixture in the ratio of 0.5:0.5. The structural characteristics of the synthesized ma- terials are investigated through high-resolution electron microscopy and x-ray diffraction analysis. As revealed, the individual particles measured as of 20–40 nm in size assemble into agglomerates exhibiting a predomi- nantly spherical morphology. Each particle is composed of multilayered, partially closed graphene shells with structural defects. As found, the synthesized material has graphite-like type of short-range atomic order. As shown, the addition of 10–20 wt.% of CNS into epoxy matrix results in increase of dielectric permittivity and shielding properties of compo- sites in frequency range 26–40 GHz.
Key words: carbon nanospheres, permittivity, dielectric loss, electrical conductivity, electromagnetic shielding.
Velocity-Aided Navigation in GNSS-Denied Environments
The Velocity-Aided Navigation (VAN) method for determining latitude, longitude, and altitude is proposed when global navigation satellite system (GNSS) signals are unavailable. Currently, GNSS receivers are the primary navigation systems that meet consumer demand for location accuracy. However, GNSS receivers are not autonomous. Strapdown inertial navigation systems (SINSs), unlike GNSSs, are autonomous. Their operating principle is based on double integration of accelerometer output signals. However, they have a significant drawback: SINS errors increase significantly over time. Two approaches are used to improve accuracy. The first involves using expensive, high-precision gyroscopes and accelerometers. The other involves correcting the SINS by integrating it with navigation systems built on physical principles different from those of the SINS. An alternative method, based on VAN and an inertial measurement unit (IMU), for determining navigation parameters is proposed and does not require double integration of accelerometer output signals. Analytical expressions for the errors of the new method are derived. Calculations showed that the errors of the new method are significantly smaller than those of the autonomous SINS. Experimental testing confirmed the calculation results and demonstrated that the errors of the new method are comparable to those of the SINS integrated with GNSS using a Kalman filter. The proposed alternative VAN method for determining latitude, longitude, and altitude can be used independently, as an alternative to GNSS for integration with the SINS, and can also serve as a backup navigation system.
Keywords: velocity; navigation; latitude; longitude; altitude; gyroscopes; accelerometers; global navigation satellite system; strapdown inertial navigation systems