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This paper proposes a multifunction radar that can not only measure sea currents but also perform sea-surface imaging. The fundamental aspect of the proposed radar comprises transmitting time-shifted up-and-down continuous wave linear frequency modulated signals that allow for the offset of two one-dimensional range images of the sea surface that respectively correspond to the upward linear frequency modulated (LFM) signal and the downward LFM signal. Owing to the Doppler frequency shift from the sea surface, a range offset, which is proportional to the radial velocity of the sea surface, occurs between the upward and downward LFM signals. By using the least-squares linear fitting method in the transformed domain, the range offset can be measured and the current velocity can be retrieved. Finally, we verify the accuracy of current measurement with simulation results. [ABSTRACT FROM AUTHOR]

Boron carbide (B4C) coating on diamond particle is synthesized by heating diamond particles in a powder mix of H3BO3 and B in Ar atmosphere. The composition, bond state and coverage fraction of boron carbide coating on diamond particles are investigated. The boron carbide coating favors to grow on diamond (100) surface rather than on diamond (111) surface. Cu matrix composites reinforced with B4C-coated diamond particles were made by powder metallurgy. The addition of B4C coating gave rise to a dense composite. The influence of B4C coating on both tensile strength and thermal conductivity of the composite were investigated. When the B4C fully covered on diamond particles, the composite exhibited a greatly increase in tensile strength (115 MPa) which was much higher than that for uncoated-diamond/Cu (60 MPa) composites. Meanwhile, a high thermal conductivity of 687 W/mK was achieved in the B4C-coated-diamond/Cu composites. [ABSTRACT FROM AUTHOR]

In this paper, the nonlinear static responses of curled cantilever micro-/nanobeams are investigated. The beams are subjected to a one-sided electrostatic actuation, and the effects of both fringing field and van der Waals force are also included. Based on the combination of the Galerkin method and the choice of the shape function of the beam deformation, the analytical approximate solutions are established. The Pull-In voltages which determine the stability of the curled beam actuators are also obtained. When van der Waals force is neglected, the Pull-In parameters are explicitly presented. These approximate solutions show excellent agreements with numerical solutions obtained by the shooting method and the experimental data for a wide range of beam length. Expressions of these analytical approximate solutions are brief and could easily be used to derive the effects of various factors, such as fringing field, van der Waals force, the width of the beam and the gap, on micro-/nanobeams. [ABSTRACT FROM AUTHOR]

A boron carbide coating was applied to diamond particles by heating the particles in a powder mixture consisting of H3BO3, B and Mg. The composition, bond state and coverage fraction of the boron carbide coating on the diamond particles were investigated. The boron carbide coating prefers to grow on the diamond (100) surface than on the diamond (111) surface. A stoichiometric B4C coating completely covered the diamond particle after maintaining the raw mixture at 1200 °C for 2 h. The contribution of the boron carbide coating to the oxidation resistance enhancement of the diamond particles was investigated. During annealing of the coated diamond in air, the priory formed B2O3, which exhibits a self-healing property, as an oxygen barrier layer, which protected the diamond from oxidation. The formation temperature of B2O3 is dependent on the amorphous boron carbide content. The coating on the diamond provided effective protection of the diamond against oxidation by heating in air at 1000 °C for 1 h. Furthermore, the presence of the boron carbide coating also contributed to the maintenance of the static compressive strength during the annealing of diamond in air. [ABSTRACT FROM AUTHOR]

Specifically, data for sample D3 in Figure 1 in this Article is the same as data in Figure 2 in[1]; data in Figure 2a in this Article appears identical to data in Figure 4a in[1] with the exception that data in this Article contains additional C-C peaks that seem to have been removed in[1]; data in Figure 7a in this Article appears to be identical to data in Figure 4b in[1] with the exception of being shifted by approximately 6eV. The Editors were not able to obtain current contact details for Youhong Sun, Ming Qian, Baochang Liu, Ke Gao, Yinlong Ma, Mao Wen & Weitao Zheng. The Editors no longer have confidence in the data reported in this Article. [Extracted from the article]

Editor's Note: this Article has been retracted; the Retraction Note is available at https://www.nature.com/articles/10.1038/s41598-022-25431-8 [ABSTRACT FROM AUTHOR]

In the synthetic aperture radar (SAR) system with low pulse repetition frequency (PRF) sampling, it is difficult for the motion parameters estimation of the moving targets, because of the Doppler spectrum ambiguity and Doppler centroid frequency ambiguity of the echo signals. Considering that moving targets are sparsely distributed in the observed scene, their positions and velocities can be reconstructed by using the compressed sensing (CS) technique. In this paper, the range-walk correction are implemented by the Keystone transform and the sparse range-walk correction (SRWC), then the CS technique is proposed to reconstruct motion parameters by processing the azimuth signals of the moving targets. Experiments using the simulated and real data are performed, and the results confirm the validity of the proposed method. [ABSTRACT FROM AUTHOR]