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As the main component of the anchorage system in marine aquaculture facilities, the anchor pile is key to ensuring safety and stability. However, conventional monopiles have limited capacity to withstand uplift forces, thus rendering them susceptible to deviations and potentially causing damage to facility structures. Hence, a new winged monopile is proposed to improve and optimize the anchor pile. In this study, laboratory experiments are conducted to investigate the effect of load inclination angle (θ = 0°, 30°, 45°, and 60°), wing length (L = 30, 50, and 70 mm), and wing width (W = 10, and 20 mm) on the uplift resistance capacity of anchor piles in silty clay. The results show that: the winged monopile exhibits at least a 15% improvement in uplift performance compared with the conventional monopile (without wings) when the smallest wing plate parameters are selected (W = 10 mm, L = 30 mm). Additionally, the effect of the wing width on the uplift resistance under an oblique load is more evident than that of the wing plate length. As the area of the wing plate increases, the range of improved wing plate efficiency first increases, and then gradually decreases. This study can be used as a reference for the design optimization of uplift piles and the construction of marine aquaculture. [ABSTRACT FROM AUTHOR]

With respect to the detection and recognition of an Artificial Modulation Target (AMT) with different modulated types, the state-of-the-art methods generally suffer the deficiencies of overfitting and insufficient generalization of existing neural network solutions. To address these problems, this paper proposes a multi-scale amplitude-phase feature discrimination method for AMTs in SAR images. First, a multi-type modulated AMT Dataset is generated (AMT Detection and Modulation Type Recognition Dataset, ADMTR Dataset), wherein the factors of jamming position, jamming-to-signal ratio (JSR), and the modulated parameter are considered to enhance the generalization. Second, a Multi-Input Multi-Output Fusion Wavelet Neural Network (MIMOFWTNN) is established, which not only uses the amplitude information of the scene but also adequately makes use of the phase and high-frequency information. This empowers us to detect the AMT in a higher dimensional feature space such that the type recognition can be implemented with more certainty. Analysis and discussions conducted on comparison experiments and ablation experiments demonstrate that the proposed network can achieve an average accuracy of 96.96% on the cross-validation set and a correct rate of 99.0% on the completely independent test set, which outperforms the compared methods. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) metasurfaces comprising artificially designed subwavelength unit cells have drawn considerable attention due to the EM properties beyond the limits of natural materials. As one of the representative structures, active polarization conversion metasurface (APCM) is switchable by loading active components. It provides great freedom to manipulate the polarization state of EM waves. However, the current research mainly focused on the application of communication and paid less attention to the radar effect of APCM. APCM redistributes electromagnetic wave energy in multi-polarization channels, so it will have great application potential in polarimetric radar. Herein, based on the fully polarimetric radar one-dimensional high resolution range profile, the radar effect of time-modulated metasurface is studied. For this purpose, a method of target scattering mechanisms manipulation and a polarization-insensitive structure of APCM are proposed. The amplitude-phase joint modulation method is specifically analyzed in detail. The distance transformation and virtual multi-target phenomena are further discovered. Virtual targets along the distance dimension are generated in multi-polarization channels, while the scattering mechanisms of k-order targets are effectively manipulated. The relationship between the target scattering matrix and the modulation parameters is obtained. It may provide an effective method for the application of active metasurface in fully polarimetric radars. [ABSTRACT FROM AUTHOR]

Spectrum conversion involves the movement of a signal from one frequency to another, and it is well-studied in materials interacting with electromagnetic waves from microwave to optical frequencies. In this paper, a time-modulated active frequency selective surface (AFSS) absorber/reflector is proposed to manipulate the spectral distribution of the echo signal. The discrete harmonics based on the period modulation and the continuous spectrum based on the random coding modulation are analyzed in detail. In addition, a simple digital-coding control network based on field programmable gate array (FPGA) in the time-modulated AFSS absorber/reflector (TMAAR) is used to switch between absorbing and reflecting states flexibly. By coding "0" and "1" elements with the controlled sequences, the TMAAR is able to achieve the predefined modulation function for spectrum conversion. On this basis, a prototype of the designed TMAAR is manufactured. The linear frequency modulation radar echo experiments are performed to verify the required function of spectrum conversion. [ABSTRACT FROM AUTHOR]

Due to the effect of range-Doppler coupling between the time delay and shifted frequency of an LFM waveform, LFM radar is particularly susceptible to shift frequency jamming. A new deceptive jamming method, the Preceded Frequency-shift False Target (PFFT), has a similar signature to real radar targets, which indicates that conventional ECCM, such as leading-edge tracking, could be invalid when countering it. In this paper, the basic principle of PFFT is introduced and its signatures analyzed. Then, a new method for discrimination between a preceded false target generated by Digital Radio Frequency Memory (DRFM) and a radar target is proposed. By comparing the echo arrival time at the radar receiver front end with that estimated after a matched filter, the new method can extract the frequency modulation jamming signature and make a correct judgment. Simulation results are presented to verify the validity of the proposed method.

Reconfigurable metasurfaces have shown unprecedented capabilities in controlling electromagnetic (EM) waves in recent years and play an essential role in information manipulation. However, most research on reconfigurable metasurfaces is limited to planar rigid structures, with only one control function and suitable for specific single polarization. Achieving simultaneous control of phase, polarization, and frequency in the conformal structure has significant practical implications in many applications, but remains obviously challenging. In this paper, a flexible multifunctional time‐varying phase‐modulated metasurface (MTPM) with orthogonal polarization control is proposed for conformal applications to manipulate the spectrum distribution. It enables time encoding capability in controlling the phase characteristics of x‐ and y‐polarized EM waves individually by switching the bias voltage of the PIN diode in two directions. Discrete harmonic spectrum and continuous Doppler frequency shifts are implemented separately on two orthogonal polarizations by applying different time coding sequences. As a practical application, a conformal MTPM for radar feature transformation is explored. Multiple discrete false targets and defocusing phenomena can be realized respectively for x‐ and y‐polarized waves. Both simulated and measured results verify the validity of the proposed method and prototype. [ABSTRACT FROM AUTHOR]

Some highrise buildings have elevator rooms or stair houses on the top, which will lead to obvious shadows on the top of the building. When using the deeplearning algorithm to extract the top information of buildings on highresolution remote sensing images, the extracted results have breakage or holes, which leads to the appearance of patches. Based on the Unet and Resnet network, the ResnetUnet considering Patches (RUP) Network is proposed. The improved model not only has high accuracy but also solves the problems of incomplete extraction and patches when there are shadows on the top of the building. [ABSTRACT FROM AUTHOR]

Salisbury screens have a number of unique electromagnetic scattering characteristics. When appropriately designed, the Salisbury screen can reach the radar target signature transform. Based on the electromagnetic scattering characteristics of the Salisbury screen, we designed a novel dihedral corner, and theoretically analyzed and simulated its electromagnetic scattering characteristics in this study. The results reveal the monostatic radar cross section curves of the 90°and 60° Salisbury screen dihedral and metal dihedral, respectively. Taking an orthogonal dihedral corner as an example, we obtained the polarization scattering matrixes for different incident degrees. In addition, we investigated the influence of illumination frequency, target gestures, and other key factors on the polarization characteristics of the Salisbury screen dihedral corner. The theoretical and simulation analysis results show that compared with the conventional metal dihedral corner, the Salisbury screen dihedral corner significantly influences the scattering characteristics and will have potential application in electronic warfare.