基于单视角图像处理的刀具磨损检测研究北大核心

针对现有刀具磨损检测存在检测速度慢、人工工作量大、经济效益低等问题,提出一种基于单视角图像处理的刀具磨损检测算法。使用CCD相机对刀具磨损前和磨损后的图像进行单视角提取,通过图像融合变换得到磨损前和磨损后的全景深刀具图像;将刀具磨损前后的全景深图像进行配准,得到磨损区域图像后,将磨损区域图像的像素转化成实际长度值,计算出实际磨损量。实验结果表明:该方案检测速度快,测量误差范围满足检测精度要求,可应用于实际加工。     

面向电子战射频光传输的宽带射频信号杂散产生机理及优化方法

针对电子战系统的宽带射频信号波分复用传输,通过理论分析给出了微波光子链路中各关键参量对杂散信号的影响规律,提出了非均匀信道间隔分配的除杂优化方法。该方法通过微调各通道的波长,使四波混频产生的杂散频率超过电子战接收机带宽,从而降低杂散对系统的影响。该方案实现简单,且无需改变现有电子战系统架构,具有较好的工程实现性。实验结果表明:与等波长间隔相比,5通道非均匀波分复用信号传输1 km时,在接收机带宽内四波混频引起的杂散得到了显著优化,动态范围提升了26 dB以上。     

Promotional effect for SCR of NO with CO over MnOx-doped Fe3O4 nanoparticles derived from metal-organic frameworks

MnO_x-Fe₃O₄ nanomaterials were fabricated by using the innovative scheme of pyrolyzing manganese-doped iron-based metal organic framework in inert atmosphere and exhibited extraordinary performance of NO reduction by CO (CO-SCR). Multi-technology characterizations were conducted to ascertain the properties of fabricated materials (e.g., TGA, XRD, SEM, FT-IR, XPS, BET, H₂-TPR and O₂-TPD). Moreover, the interaction between reactants and catalysts was ascertained by in situ FT-IR. Experimental results demonstrated that Mn was an ideal promoter for iron oxides, resulting in decrease of crystallite size, improve reducibility property, enhance the mobility and the amount of lattice O^2- species, as well as strength the adsorption ability of active NO and CO to form multiple species (e.g., nitrate and carbonate). The unprecedented enhancement of CO-SCR activity over Mn-Fe nanomaterials follows the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) reaction pathway.     

川南地区阳新统气藏异常高压形成转化和预测

本文基于自然流体压裂成藏机理和岩体力学,紧密结合川南阳新统气藏基本特征,探讨异常高压形成和转化机理,进而建立定量预测气层异常高压物理-数学模型。经矿场实际资料验证,气层压力预测值绝对误差一般小于2.0Mpa,相对误差一般小于5.0%。     

逻辑语言中启发式控制

本文论述从逻辑程序本身提取启发式控制信息,以克服由于逻辑语言系统中控制策略的机械性所带来的不完备性和低效性。具体地给出若干启发式控制规则,并证明了这些规则的正确性。运用这些控制规则可以大大地提高系统的运行效率或改善逻辑程序的语义性质。文章最后给出启发式WAM(记作HWAM),并且用实例说明HWAM比WAM更有效,更完善。     

储层毛细管应变对地震纵波速度的影响

本文提出的储层毛细管应变地震波速衰减机理，是指地震波在多孔双相介质传播过程中，使固结很差的储层毛细管（孔隙喉道）优先闭合性应变，其应变量主要控制被压缩气体的体积和波动能量耗散及波束衰减量，据此，建立纵波速度与毛细管压力，孔隙结构，含水饱和度和岩石闭合弹性模量间的数学关系；较好地解释了Ｄｏｍｅｎｉｃｏ效应；初步定量性评价孔隙结构和含气饱和度对地震波速的影响，这对拓宽毛细管压力资料在地震资料解释中的应     

Hydrogen-bonding assembly of heteropolyacid and poly(vinyl alcohol) for strong,flexible, and transparent UV-protective films

Although many preparation approaches have been developed, it remains a huge challenge to achieve ultraviolet (UV)-protection films that combine high transparency, excellent UV-shielding, and mechanical properties. Herein, we demonstrate a facile and eco-friendly process for fabricating strong, flexible, and transparent UV-protective poly(vinyl alcohol) (PVA) films by exploiting silicomolybdic acid (SiMoA) as UV absorber and reinforcing phase. Fourier-transform infrared analysis confirms the formation of strong hydrogen-bonding interactions between PVA and SiMoA. The glass-transition temperature, mechanical properties, and UV-shielding stability of the UV-protective PVA composite films obviously increase with increasing the content of SiMoA. By incorporation of only 2 wt % SiMoA, the UV-protective PVA composite film can block more than 90% of UV light in the entire UV regions and retain high visible light transparency (up to 95%). Simultaneously, the UV-protective PVA composite film presents excellent mechanical properties with a tensile strength of 65.2 MPa and an elongation at break of 172.6%, which are 72.0 and 69.5% higher than that of pristine PVA films. This work provides a simple but effective approach for creating strong, flexible, and transparent UV-blocking polymeric materials via hydrogen-bonding assembly, which are expected to have wide application prospects in UV-protection field. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48813.     

基于信息熵与形态学的鸟鸣数据处理

为了探索一种减少训练量并提高精度,且适应于卷积神经网络的预处理方法,以识别鸟鸣为例,基于信息熵以及形态学在图像处理上的应用,根据鸟鸣的间隔性特点,提出新的处理方案。利用形态学将音频片段归类为有效和噪声信号两类;使用加权的方法利用信息熵预测有效数据的分布。仿真结果表明,形态学使数据量减少且信息熵处理使单个数据稀疏化并起到滤波作用,在保持精度甚至精度提高的情况下缩短了训练时间,为卷积神经网络的数据预处理的简化提供了方向。