Mechanism of Mitochondrial Connexin43′s Protection of the Neurovascular Unit under Acute Cerebral Ischemia-Reperfusion Injury

We observed mitochondrial connexin43 (mtCx43) expression under cerebral ischemia-reperfusion (I/R) injury, analyzed its regulation, and explored its protective mechanisms. Wistar rats were divided into groups based on injections received before middle cerebral artery occlusion (MCAO). Cerebral infarction volume was detected by 2,3,5-triphenyltetrazolim chloride staining, and cell apoptosis was observed by transferase dUTP nick end labeling. We used transmission electron microscopy to observe mitochondrial morphology and determined superoxide dismutase (SOD) activity and malondialdehyde (MDA) content. MtCx43, p-mtCx43, protein kinase C (PKC), and p-PKC expression were detected by Western blot. Compared with those in the IR group, cerebral infarction volumes in the carbenoxolone (CBX) and diazoxide (DZX) groups were obviously smaller, and the apoptosis indices were down-regulated. Mitochondrial morphology was damaged after I/R, especially in the IR and 5-hydroxydecanoic acid (5-HD) groups. Similarly, decreased SOD activity and increased MDA were observed after MCAO; CBX, DZX, and phorbol-12-myristate-13-acetate (PMA) reduced mitochondrial functional injury. Expression of mtCx43 and p-mtCx43 and the p-Cx43/Cx43 ratio were significantly lower in the IR group than in the sham group. These abnormalities were ameliorated by CBX, DZX, and PMA. MtCx43 may protect the neurovascular unit from acute cerebral IR injury via PKC activation induced by mitoKATP channel agonists.     

基于非负矩阵分解的单通道故障特征分离方法

针对单通道振动信号的多特征分离问题,提出了一种基于正交非负矩阵分解的故障特征提取方法。首先,采用短时傅里叶变换,利用时频分布来描述信号中的局部故障特征,通过核心一致性指标评估子空间维数;然后,在幅值谱矩阵分解的基础上,通过正交性约束实现低维嵌入分量信息的分离,获取局部特征的准确描述;最后,采用相位恢复理论重构出特征波形,对仿真信号和滚动轴承故障数据进行了测试。结果表明,所提出的方法能利用单通道信号有效地分离出微弱的局部故障特征,为机械状态的早期故障诊断识别提供了一种有效手段。     

微细电火花放电通道自身磁场仿真研究

针对微细电火花加工中放电通道等离子体电流沿电极轴向产生较强的环向磁场问题,以放电等离子体理论和麦克斯韦方程为基础,基于假设,建立了放电通道自身磁场的物理模型。结合放电通道自身磁场形式和磁场分布的特点,从静磁场微分方程出发,给出了该物理模型的理论求解方法,并应用Ansoft Maxwell有限元分析软件,对微细电火花放电通道的磁场分布和磁场强度进行了仿真分析,得到了放电通道自身磁场特性的变化规律,以及微细电火花加工工艺参数对放电通道等离子体自身磁场强度的影响规律。     

无线信道测量设备系统响应消除问题研究

信道测量是获取信道特性最有效最直接的方式之一。随着测量带宽的增加,测量精度的提升以及测量指标的丰富,在无线信道测量过程中消除测量设备系统响应成为不可忽视的重要步骤。研究了测量设备系统响应对客观物理信道的影响,并提出了一种消除测量设备系统响应的理论方法。通过实验室模拟测试与实地场景测量的实测数据,验证了所提出方法的可行性,同时分析了影响测量设备系统响应的客观因素以及采样色散对信道冲击响应的影响。     

短电弧机床加工电源的反馈环路设计

为使短电弧加工过程中电弧放电通道更容易、有效地建立,使其电源电气特性满足试验要求,通过分析短电弧加工脉冲电源系统的增益特性,设计出满足短电弧加工试验所需的电源反馈环路,并建立基于Matlab的电源反馈环路仿真模型,通过仿真验证了设计的电源反馈环路具有输出电压平稳,受外界干扰小,响应速度快等优点,具有良好的可行性及稳定性. 最后通过电源空载及短电弧切削加工试验,验证了设计的电源反馈环路能够满足短电弧加工试验所需要求,为短电弧加工机理研究提供了重要的技术支持.     

Al-Zn-Mg-Cu合金新型等通道转角双向镦挤变形行为分析

以超高强度Al-Zn-Mg-Cu合金为研究对象,采用数值模拟和实验相结合的方法对其等通道转角双向镦挤过程进行分析。结果发现,变形过程可以分为近局部镦粗、剪切变形、最后填充三个阶段,变形结束后试样根据金属流动和网格畸变程度划分为小变形区、不变形区、剪切变形区、剧烈变形区。不同加载方式使变形区域发生不同程度偏移,上下冲头速度差越大,变形均匀性越差,速度比为1时可获得最大的应变量为3.97,且变形均匀性系数最低为1.89。同时,对不同路径下的多道次变形行为进行研究,发现4道次结束后,B路径比A路径变形更加均匀充分,其变形均匀性系数降低了29 %,剪切变形区占比提升了14 %。     

Trees and wood: working with natural river processes

A history of land clearance and riparian tree and wood management has resulted in limited riparian woodland and wood along British rivers. However, river management approaches are now being promoted that ‘work with natural processes’ to reduce flood risk through measures intended to restore, protect and emulate the natural function of catchments, rivers, estuaries and coasts. Wood has started to be reintroduced into river channels during river restoration and natural flood management activities, but this needs to be undertaken using appropriate quantities, locations and designs that mimic natural tree‐wood features. This paper reviews the knowledge that is needed to support wood reintroduction activities including (i) the characteristics of the riparian tree species and wood that are present; (ii) the importance of river size relative to that of trees and wood pieces; and (iii) the way trees, wood and geomorphic processes interact across rivers and floodplains of different energy and style.     

深井综放工作面沿空顺槽超前支架应用及效果

为了解决深井综放工作面沿空顺槽超前支护难题,分析沿空面侧向岩层结构及综放面沿空顺槽支架–围岩关系,建立确定沿空顺槽超前支护强度的力学模型,针对ZQ5200/21.5/45型超前液压支架的特征、工作阻力变化情况、沿空顺槽表面位移观测结果,验证了支架选型的合理性,可以有效控制沿空顺槽巷道围岩变形。     

基于通道参数估计的多输入多输出雷达定位

针对统计MIMO雷达定位精度和目标分辨力不高的现状,提出基于收发通道参数估计的高精度MI-MO雷达定位方法。与传统做法不同,该方法采用共轭信号延迟发射模式,处理回波数据时首先估计MIMO雷达虚拟通道的系数,再利用估计结果修正目标参数估计模型,对目标实施定位。理论分析和仿真结果均表明:该方法极大地提高了统计MIMO雷达的定位精度和目标分辨能力,充分开发了大间距配置MIMO雷达参数估计的潜能。