IRS辅助的SWIPT系统中基于能效优先的波束成形设计与优化

以智能反射面(intelligent reflecting surface,IRS)辅助的无线携能通信(simultaneous wireless information and power transfer,SWIPT)系统为背景,研究了该系统中基于能效优先的多天线发送端有源波束成形与IRS无源波束成形联合设计与优化方法。以最大化接收端的最小能效为优化目标,构造在发送端功率、接收端能量阈值、IRS相移等多约束下的非线性优化问题,用交替方向乘子法(alternating direction method of multipliers,ADMM)求解。采用Dinkelbach算法转化目标函数,通过奇异值分解(singular value decomposition,SVD)和半定松弛(semi-definite relaxation,SDR)得到发送端有源波束成形向量。采用SDR得到IRS相移矩阵与反射波束成形向量。结果表明,该系统显著降低了系统能量收集(energy harvesting,EH)接收端的能量阈值。当系统总电路功耗为?15 dBm时,所提方案的用户能效为300 KB/J。当IRS反射阵源数与发送天线数均为最大值时,系统可达最大能效。     

DCNN深度特征与交替方向乘子的相关滤波跟踪

针对采用相关滤波的判别式目标跟踪遇到的瓶颈问题：由于目标快速移动引起边界效应，使得相关滤波器在学习与更新过程中可能会引入错误，最终错误的累积将导致跟踪失败。在采集深度学习特征与样本相似性度量的基础上，提出一种引入交替方向乘子方法的改进相关滤波目标跟踪算法，选择DCNN深度特征有效地表征待跟踪目标的初始状态，通过在线分类过程中样本相似性比对与半监督学习，辅助解决相关滤波器在学习过程中存在的自学习问题。所提目标跟踪算法特别适合训练样本为持续获得的、同时存储空间较小的机器学习过程，提高目标在快速运动与部分遮挡等复杂情况下的跟踪成功率，针对VOT2016标准测试视频的实验表明：当目标面临快速运动时，对比CN、SAMF、STC算法，所提DA-CFT跟踪算法将跟踪成功率分别由60.4%～73.4%、67.2%～82.9%、80.9%～88.1%提升至85.6%～91.0%。     

基于改进EEMD与混沌振子的配电网故障选线

提出改进的集合经验模态分解(MEEMD)和混沌振子相结合的电网故障微弱信号检测方法。首先,建立神经网络预测模型,通过神经网络对配网各线路零序电流进行短时预测,滤除故障信号中的背景信号;其次,为了检测配网发生单相接地故障后微弱的5次谐波信号,提出结合多尺度排列熵和完备集合经验模态分解(CEEMD)改进的改进的集合经验模态分解算法;处理已经滤除背景信号的故障信号,提取其第一固有模态函数作为混沌振子的输入。混沌振子对和内驱动力信号同频的外策动力信号有较高的敏感性,通过混沌振子输出的相图完成电网故障选线。     

Alternating Multilayer Structural Epoxy Composite Coating for Corrosion Protection of Steel

Epoxy composite coatings filled with fillers have been used extensively as anticorrosion materials. In this study, an alternating multilayer structure is designed to obtain multifunctional epoxy resin composite coating based on stepwise coating method via adding graphene and α‐alumina. Their mechanical properties, thermal conductivity, dielectric and anticorrosion properties are characterized. The toughness and the thermal conductivity clearly increase, while the dielectric properties decrease approximately to zero when the filler mass fraction increases from 0.00% to 0.15%. The whole corrosion process is controlled by electrochemical reaction, and the fillers effectively block the corrosive medium, thus improving the anticorrosion performance of the composite coating.     

等离子弧异质异构增材制造构件的组织与力学性能分析

采用等离子弧增材系统实现了不锈钢/高强钢异质异构增材构件制备，等离子弧增材构件具有良好的沉积形貌及优异的力学性能.为揭示叠合方式对等离子弧异质增材构件的宏微观组织和力学性能特征影响，研究采用了体视显微镜、金相显微镜、拉伸及硬度等测试方法.结果表明，不锈钢/高强钢异质异构增材构件中存在两种过渡形式，即以奥氏体枝晶过渡和马氏体组织过渡.增材构件横截面硬度波动较大，主要是混合过渡区域的高合金元素导致的组织变化引起的.叠合方式的改变能够显著影响材料性能，在强度下降不多的情况下，提高材料的冲击韧性.     

A CCD-ADI method for two-dimensional linear and nonlinear hyperbolic telegraph equations with variable coefficients

In this paper, a combined compact finite difference method (CCD) together with alternating direction implicit (ADI) scheme is developed for two-dimensional linear and nonlinear hyperbolic telegraph equations with variable coefficients. The proposed CCD-ADI method is second-order accurate in time variable and sixth-order accurate in space variable. For the linear hyperbolic equation, the CCD-ADI method is shown to be unconditionally stable by using the Von Neumann stability analysis. Numerical results for both linear and nonlinear hyperbolic equations are presented to illustrate the high accuracy of the proposed method.     

交变拉伸载荷下油管丝扣密封性能研究

针对高压注入井油管在服役环境下长期承受交变拉伸载荷作用存在泄漏风险的问题，通过搭建交变拉伸载荷下油管丝扣密封性能测试试验平台、优选试验设备及制定合理的试验步骤，对平扣、BGT扣、FOX扣油管试样在10~50 t拉伸交变载荷下的密封性能进行了模拟。模拟结果显示:对3种扣型油管试样施加同等拉伸载荷，其密封性能随交变次数增加而降低，降低幅度为平扣>BGT扣>FOX扣；50 t拉伸载荷施加5次后，3种扣型油管试样的密封性能分别为5.67 MPa、32.69 MPa、73.67 MPa。研究表明，平扣无法满足注入井的密封要求，BGT扣及FOX扣具有较好的适用性。研究结果为注入井油管扣型选择提供了依据。     

超临界二氧化碳+水交替驱注入井极限关井时间计算

针对超临界CO₂+水交替驱注入井在关井之后形成水合物冻堵段的问题，采用数值模拟和室内实验方法，计算了注入井的极限关井时间。结果表明：在后注水的情况下，地层内CO₂会向注入井端发生反向扩散，CO₂反向扩散到井底的时间为1.6～32.3d，射孔孔眼内的扩散时间为1.0～4.5d；后注气时，极限关井时间主要受渗透率、累计注气量、地层深度影响，极限关井时间为20.0～30.0d；CO₂水合物生成的诱导时间一般低于30min，远低于后注水和后注气时井筒内CO₂和水进入到冻堵位置的时间。该研究结果对CO₂驱的广泛应用具有重要意义。     

Effects of stray AC on corrosion of 3-layer polyethylene coated X70 pipeline steel and cathodic delamination of coating with defects in 3.5 wt-% NaCl solution

In this work, the effects of stray alternating current (AC) on the corrosion of coated X70 pipeline steel and the delamination of 3-layer polyethylene (3PE) coatings with defects were investigated using COMSOL Multiphysics simulation, electrochemical impedance spectroscopy and three-dimensional (3D) digital microscope techniques. The results showed that under the same level of AC interference, pits with deeper maximum pit depth were observed at the smaller defect areas than those at larger defect areas. It was consistent with the simulation results that a greater corrosion current density was accompanied on samples with smaller defects. According to 3D digital images, the larger delamination of 3PE coatings was found on samples with smaller defects. With the increase of current density, the impedance of samples with small defects decreased, while that of samples with large defects increased. Additionally, with the same defect size, the maximum pit depth became deeper and the corrosion was more severe.     

A facile method for preparation of PGS@ZB‐N and gas‐sol alternating synergistic effect for fire resistance of EVA

Through the simple precipitation of palygorskite (PGS) by zinc borate (ZB) (to make PGS@ZB) and the decoration of PGS@ZB by dodecylamine (N), a novel organic‐inorganic@inorganic hybrid flame retardant of PGS@ZB‐N was prepared and was incorporated with ethylene vinyl acetate copolymer (EVA) to improve its flame retardance. The structure and morphology of PGS@ZB‐N were characterized by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), and scanning electron microscopy (SEM), and it was confirmed that the PGS@ZB‐N hybrid had been successfully prepared. The flame retardancy and burning behavior of EVA/PGS@ZB‐N/EG (EG = expandable graphite) composite were studied through thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 (by the vertical burning test), and cone calorimeter test (CCT) characterizations. The prepared EVA/PGS@ZB‐N/EG composite obtained an LOI value of 41.2% with the addition of 30 wt% PGS@ZB‐N/EG. It was found that EVA/PGS@ZB‐N/EG was protected through a gas phase and condensed phase alternating synergistic effect mechanism.