A New Transmit Beamforming Method for Multi-User Communication in Dual-Function Radar-Communication

This paper develops a new transmit beamforming for an integrated mechanical and electrical scanning dual-function radar-communication(DFRC) system. Differing from the related some works using beampattern sidelobe level to communication, we exploit the fact that transmit beamforming weight vector u k in direction θ and weight vector u *k in direction-θ can achieve the same spatial power distribution, and formulate a new transmit beamforming vector design problem accounting for some extra sidelobe level constraints. By doing so, the number of the transmit beamforming weight vectors and the computing demand in the multi-user communication(MUC) scenario can be reduced. Finally, the numerical examples are designed to verify the effectiveness of the proposed design strategy in comparison with the existing method.     

国内轴承钢的生产现状及发展

介绍了2002年国内高碳铬轴承钢的产量及品种结构，评述了国内轴承钢生产工艺装备、质量状况和发展方向。     

Efficient photodegradation of phenol assisted by persulfate under visible light irradiation via a nitrogen-doped titanium-carbon composite

To realize the utilization of visible light and improve the photocatalytic efficiency of organic pollutant degradation in wastewater, a nitrogen-doped titanium-carbon composite (N-TiO₂/AC) prepared by sol-gel methods was applied in the photodegradation of phenol assisted by persulfate under visible light irradiation (named N-TiO₂/AC/PS/VIS). The results show that a synergistic effect exists between visible-light photocatalysis and persulfate activation. Compared with TiO₂/PS/VIS, the phenol degradation rate was found to be observably improved by 65% in the N-TiO₂/AC/PS/VIS system. This significant increase in degradation rate was mainly attributed to the following two factors: 1) The N and C doping can change the crystal structure of TiO₂, which extends the TiO₂ absorption wavelength range to the visible light region. 2) As an electron acceptor, PS can not only prevent electrons and holes from recombining with each other but can also generate strong oxidizing radicals such as ∙SO₄^– and ∙OH to accelerate the reaction dynamics. The process of phenol degradation was found to be consistent with the Langmuir pseudo-first-order kinetic model with an apparent rate constant k of 1.73 min^–1. The N-TiO₂/AC/PS/VIS process was proven to be a facile method for pollutant degradation with high pH adaptability, excellent visible-light utilization and good application prospects.     

PAN/FPU Composite Nanofiber Membrane with Superhydrophobic and Superoleophobic Surface as a Filter Element for High-Efficiency Protective Masks

Recently, because of the outbreak of COVID-19, the demand for various types of filter elements in protective materials has increased globally. Furthermore, new requirements for the filtration performance of PM2.5 liquid (oil) particles have been put forward. In this work, Superhydrophobic and superoleophobic composite nanofibers with excellent filtration capacity for oil and salt particles are developed through the modification of polyacrylonitrile (PAN) by fluoro-polyurethane (FPU) doping. The results show that the PAN/FPU composite nanofibers doped with 9 wt% FPU has a uniform fiber morphology with a diameter of 240 ± 30 nm. Compared to the pure PAN nanofibers, the water-based contact angle of PAN/FPU increases from 90 ± 5° to 151 ± 5°, and the oil-based contact angle increases from 58 ± 2° to 152 ± 3°. Importantly, at a high flow rate of 95 L min⁻¹, the filtration efficiency of the PAN/FPU nanofiber membrane for 0.3 µm oil particles increases from 92 ± 1% to 99.2 ± 0.1%. After cyclic loading, the filtration efficiency of 0.3 µm oil particles remains above 98%. Meanwhile, the filtration efficiency for 0.3 µm salt particles remains at 98.23 ± 0.1%. The PAN/FPU nanofiber membrane developed in this work is effective in applications and has good market prospects as a protective filtration material.     

Preparation and mechanical characteristics of fine-woven cloth and punctured felt preform Cf/C-SiC-ZrC composite

A 3D architecture carbon fiber preform, specifically fine-woven cloth and punctured felt preform, is used to manufacture a novel advanced C_f/C-SiC-ZrC composite. The composite matrix is produced by chemical vapor infiltration (CVI) plus precursor infiltration and pyrolysis (PIP) process and finalized by using a chemical vapor deposition (CVD) of SiC coating to make the final density of the material reach 1.95 g/cm³. The organic precursors of SiC and ZrC have a weight ratio of 4:1 in a xylene solute. The composite mechanical properties, such as tensile, compression, bending, shear, and Z-direction load bearing, are introduced under analysis to find possible applications for the composite. What is more, scanning electron microscope (SEM) images are employed to illustrate the failure behavior of the ceramic composite. The results showed that the punctured filament tows will be beneficial, not only for the composite to withstand compression force up to 308.6 MPa and shear strength to 18.14 MPa but also for the alternatively stacked weave piles and short fiber layers to support the punctured bundles, as well as to hold the composite structure under mechanical forces from different orientations, which is believed to reinforce the ceramic matrix for some high pressure and severe ablation applications.     

Computational modeling of cathodic limitations on localized corrosion of wetted SS 316L at room temperature

The ability of a SS 316L surface wetted with a thin electrolyte layer to serve as an effective cathode for an active localized corrosion site was studied computationally. The dependence of the total net cathodic current, I_net, supplied at the repassivation potential E_rp (of the anodic crevice) on relevant physical parameters including water layer thickness (WL), chloride concentration ([Cl⁻]) and length of cathode (Lc) were investigated using a three-level, full factorial design. The effects of kinetic parameters including the exchange current density (i_o,c) and Tafel slope (β_c) of oxygen reduction, the anodic passive current density (i_p) (on the cathodic surface), and E_rp were studied as well using three-level full factorial designs of [Cl⁻] and Lc with a fixed WL of 25 μm. The study found that all the three parameters WL, [Cl⁻] and Lc as well as the interactions of Lc × WL and Lc × [Cl⁻] had significant impact on I_net. A five-factor regression equation was obtained which fits the computation results reasonably well, but demonstrated that interactions are more complicated than can be explained with a simple linear model. Significant effects on I_net were found upon varying either i_o,c, β_c, or E_rp, whereas i_p in the studied range was found to have little impact. It was observed that I_net asymptotically approached maximum values (I_max) when Lc increased to critical minimum values. I_max can be used to determine the stability of coupled localized corrosion and the critical Lc provides important information for experimental design and corrosion protection.     

含砷氰化尾矿回填利用污染控制技术试验研究

针对某黄金生产企业含砷氰化尾矿污染特征,开展了搅拌洗涤法、臭氧氧化法、酸化溶砷法、铁盐固砷法等多种无害化方法联合处理试验研究,旨在将该含砷氰化尾矿处理至满足氰渣规范回填利用污染控制要求。结果表明：该含砷氰化尾矿回填利用污染控制技术工艺为压滤调浆搅拌洗涤+臭氧氧化+酸化溶砷+铁盐固砷,最佳参数为原矿浆压滤后加水调浆,矿浆浓度40%,臭氧投加量0.66 g/L,酸化溶砷pH值3、曝气量0.1 m³/h、反应时间2 h,铁盐固砷七水合硫酸亚铁投加量20.0 g/L、反应时间1 h。研究结果为该黄金生产企业含砷氰化尾矿回填利用提供了技术支撑。     

Research and Applications of Semi-solid Processing

Since it was pioneered by Flemings and otherresearchers [11, the semi-solid metal processingtechnique has been widely stUdied in the world.Especially in the past decade, SSM as a newproduct forming technique has been rapidly developed and put into commercial applications[2, 31. In recent years, with the development ofthe ado-industry of China, a lot of researchwork on SSM has been done, including the preparation of slumes, reheating and thixoforming[Al6]; moreover, great achievements have …     

多种氧化物改性对BaTiO3介电性能的影响

采用共沉淀BaTiO3为基,适量掺杂Nd2O3稀土氧化物及MgO与ZnO添加剂,获得具有X7R温度特性的低频高压MLC瓷料系统,BaTiO3基瓷的平均晶粒尺寸小于0.8μm,居里点弥散成为居里区.其介电性能为介电系数ε≥3000;容量变化率△C/C≤±15%;介电损耗tgδ≤120×10-4;体积电阻率ρv≥1012Ω·cm;击穿场强Eb≥15 kV/mm.     

Zr对钐铁合金微结构和相组成的影响

研究了添加0．5at％和1．0at％Zr对钐铁合金微结构和相组成的影响。添加和不添加Zr的Sm-Fe合金相比，发现添加1．0at％Zr可以基本消除铸态组织中的α-Fe，并且能同时减少富钐相。多添加18at％Sm的Sm-Fe合金退火后，仍残留少量的α-Fe，而添加1．0at％Zr的Sm-Fe-Zr合金退火后主相Sm2Fe17以及α-Fe的量没有明显的变化，因此有可能避免过长的均匀化退火过程。