Polarimetric Scattering from Two-Dimensional Dielectric Rough Sea Surface with a Ship-Induced Kelvin Wake

Based on the polarimetric scattering model of second-order small-slope approximation (SSA-II) with tapered wave incidence for reducing the edge effect caused by limited surface size, monostatic and bistatic polarimetric scattering signatures of two-dimensional dielectric rough sea surface with a ship-induced Kelvin wake is investigated in detail by comparison with those of sea surface without ship wake. The emphasis of this paper is on an investigation of depolarized scattering and enhanced backscattering of sea surface with a ship wake that changes the sea surface geometric structure especially for low wind conditions. Numerical simulations show that in the plane of incidence rough sea surface scattering is dominated by copolarized scattering rather than cross-polarized scattering and that under low wind conditions a larger ship speed gives rise to stronger enhanced backscattering and enhanced depolarized scattering. For both monostatic and bistatic configuration, simulation results indicate that electromagnetic scattering signatures in the presence of a ship wake dramatically differ from those without ship wake, which may serve as a basis for the detection of ships in marine environment

Time-Domain Physical Optics Method for the Analysis of Wide-Band EM Scattering from Two-Dimensional Conducting Rough Surface

Time-domain physical optics (TDPO) method is extended to investigate electromagnetic (EM) scattering from two-dimensional (2D) perfectly electrically conducting (PEC) rough surface in both time domain and frequency domain. The scheme requires relatively small amounts of computer memory and CPU time, and has advantage over the Kirchhoff Approximation (KA) method in obtaining transient response of rough surface by a program run. The 2D Gaussian randomly rough surface is generated by Monte Carlo method and then is partitioned into small triangle facets through the meshing preprocess. The accuracy of TDPO is validated by comparing the numerical results with those obtained by the KA method in both backward and specular directions. The transient response and its frequency distribution of radar cross section (RCS) from rough surface is shown, respectively. The scattering results from rough surface with different size in the specular direction are given. The influence of the root mean square height (σ) and correlation length (l) on electromagnetic scattering from PEC rough surface is discussed in detail. Finally, the comparisons of backscattering results at different incident angles are presented and analyzed

Picturing Electron Capture to the Continuum in the Transfer Ionization of Intermediate-Energy He²⁺ Collisions with Argon

Electron emission occurring in transfer ionization for He2+ collisions with argon has been investigated using cold target recoil ion momentum spectroscopy. The double differential cross sections for electron capture to the continuum of the projectile (cusp-shaped electrons) are presented for collision energies from 17.5 to 75 keV/u. For an energy of 30 keV/u, we find a maximum in the experimental ratio of the cusp-shaped electron yield to the total electron yield. This result is explained in terms of the velocity matching between the projectile ion and the electron initially bound to the target. One of the important issues for double electron transitions is the role of electron-electron correlation. If this correlation is weak, then the transfer-ionization process can be viewed as two separate sequential processes. If this correlation is strong, then the transfer-ionization process would happen simultaneously and not sequentially. Our experimental and theoretical results indicate that correlation is weak and that the first step is target ionization followed by charge capture

Sustainable ultra‐strong thermally conductive wood‐based antibacterial structural materials with anti‐corrosion and ultraviolet shielding

In light of the uprising global development on sustainability, an innovative and environmental friendly wood-based material derived from natural pinewood has been developed as a high-performance alternative to petrochemical-based materials. The wood-based functional material, named as BC-CaCl2, is synthesized through the coordination of carboxyl groups (−COOH) present in pinewood with calcium ions (Ca2+), which facilitates the formation of a high-density cross-linking structure through the combined action of intermolecular hydrogen bonds. The as-prepared BC-CaCl2 exhibits excellent tensile strength (470.5 MPa) and flexural strength (539.5 MPa), establishing a robust structural basis for the materials. Meanwhile, BC-CaCl2 shows good water resistance, thermal conductivity, thermal stability, UV resistance, corrosion resistance, and antibacterial properties. BC-CaCl2 represents a viable alternative to petrochemical-based materials. Its potential application areas include waterproof enclosure structure of buildings, indoor underfloor heating, outdoor UV resistant protective cover, and anti-corrosion materials for installation engineering, and so forth

Carbide Nanoparticles Encapsulated in the Caves of Carbon Nanotubes by an In Situ Reduction-Carbonization Route

Carbides (TiC, WC, and NbC) nanoparticles fully encapsulated in the caves of carbon nanotubes (CNTs) were synthesized via an in situ reduction-carbonization route at 600∘C in an autoclave. The structural features and morphologies of as-obtained products were investigated using by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy (HRTEM). HRTEM studies showed that the average diameter of CNTs encapsulated with carbide nanoparticles are in the range of 15–40 nm. The reaction temperature, the reaction time, and the metal catalyst are found to play crucial roles to the product morphology. The growth mechanism of carbide nanoparticles encapsulated in CNTs was discussed in detail

Line Loss Calculation and Optimization in Low Voltage Lines with Photovoltaic Systems Using an Analytical Model and Quantum Genetic Algorithm

With the increasing integration of distributed photovoltaic (PV) generation into distribution networks, challenges such as power reverse flow and high line losses have emerged, leading to greater uncertainty in power systems. To address these issues, this paper presents an analytical model for calculating line losses in low-voltage distribution networks with PV generation, utilizing power flow calculations. A simulation model of a 15 node low-voltage network is developed using SIMULINK to validate the accuracy of the analytical model under the scenario of uniform load distribution (ULD). Additionally, a line loss optimization algorithm based on quantum genetic algorithms (QGA) is proposed for low-voltage distribution networks with distributed PV generation, along with an optimization model. The objective function of the optimization model is based on the reduction in line losses resulting from the integration of the PV system. The example results demonstrate the consistency between the line loss optimization using QGA and the analytical results, highlighting the significant advantages of QGA in terms of speed and accuracy. This research provides valuable insights for line loss optimization in low-voltage distribution networks with distributed PV generation and serves as a theoretical reference for future studies in this field

Identity information based on human magnetocardiography signals

We have developed an individual identification system based on magnetocardiography (MCG) signals captured using optically pumped magnetometers (OPMs). Our system utilizes pattern recognition to analyze the signals obtained at different positions on the body, by scanning the matrices composed of MCG signals with a 2*2 window. In order to make use of the spatial information of MCG signals, we transform the signals from adjacent small areas into four channels of a dataset. We further transform the data into time-frequency matrices using wavelet transforms and employ a convolutional neural network (CNN) for classification. As a result, our system achieves an accuracy rate of 97.04% in identifying individuals. This finding indicates that the MCG signal holds potential for use in individual identification systems, offering a valuable tool for personalized healthcare management

Optimizing Airfoil Aerodynamic Characteristics by Using Proposed CSA-KJ Method

Combined with the cuckoo search algorithm (CSA) and the Kutta–Joukowski (KJ) theorem, a CSA-KJ optimization method was proposed to improve the airfoil aerodynamic characteristics in this work. The fourth-order constant-free polynomial function was employed to describe the airfoil profile. The KJ loop lift of the airfoil was taken as the objective function, and the CSA was applied to iteratively update this method, which was used to optimize the NACA4412 airfoil. The results demonstrate that the optimized effect of the CSA-KJ method on the lift-drag ratio becomes increasingly more significant with the increase of incoming wind speed, and it has the best performance at an angle of attack of 0°. Compared with the NACA4412 airfoil, the average and the maximum lift-drag ratio coefficients of the CSA-KJ4412 airfoil have increased. Meanwhile, the pressure difference distribution is improved, and the aerodynamic characteristic is better. From this, it can be seen that the CSA-KJ method can provide an effective way to optimize the aerodynamic performance of other airfoils