Wave Propagation and Mode Localization in Simply Supported Multispan Beams with Couplers on Supports

The influences of couplers on wave propagation and mode localization in simply supported multispan beams with couplers consisting of lumped rotational stiffness and mass on supports are studied. A transfer matrix equation governing the vibrational wave propagation in the simply supported multispan beams with couplers is newly derived and simplified. The eigenvalue of the simplified transfer matrix shows that the larger stiffness or the larger mass of the coupler makes the internal coupling between spans weaker and so it makes the system more sensitive to mode localization. As the wave frequency or the eigenvalues of the system increases, the mass effect is increased while the stiffness effect is decreased. In a case considering the large stiffness and mass at the same time, there is a region with relatively wider passbands and narrower stop bands having small attenuation rates and the normal modes in it become delocalized ones. As an example structure, a simply supported two span beam with a coupler at the midspan is considered.     

误差反向传播算法的数学推导及实现步骤

提供了人工神经网络的一种算法-误差反向传播算法的数学推导方法及上机实现步骤.     

油纸屏障对变压器局部放电超高频检测信号的影响

受变压器内部复杂结构的影响,局部放电超高频信号在变压器内部的传播特性非常复杂。笔者通过变压器局部放电超高频实验研究,分析了油纸屏障对变压器局部放电被测超高频信号的影响。设计了油中气隙放电、油中沿面放电和油中电晕放电3种局部放电模型,在实验油箱中进行局部放电实验,采用超高频小环天线进行放电信号检测,在有无油纸屏障情况下获得了局部放电超高频信号实测数据,对所测局部放电超高频信号在时域和频域上进行了对比分析。结果表明,油纸屏障对超高频信号幅值衰减及信号功率谱有一定影响。     

Impacts of Vegetation on the Intraseasonal Oscillation Simulated by the Community Atmosphere Model (CAM3)

The influences of vegetation on intraseasonal oscillation (ISO) were examined using the Community Atmosphere Model version 3 (CAM3). Two 15-year numerical experiments were completed: the first was performed with a realistic vegetation distribution (VEG run),and the second was identical to the VEG run except without land vegetation (NOVEG run). Generally speaking, CAM3 was able to reproduce the spatial distribution of the ISO, but the ISO intensity in the simulation was much weaker than that observed in nature: the ISO has a relatively much stronger signal. A comparison of the VEG run with the NOVEG run revealed that the presence of vegetation usually produces a weak ISO. The vegetation effects on ISO intensity were significant over West Africa and South Asia, especially in the summer half-year.Vegetation also plays an important role in modulating ISO propagation. The eastward propagation of the ISO in the VEG run was clearer than that in the NOVEG run over the West African and Maritime Continent regions. The northward propagation of the ISO in the VEG run was more consistent with observation than that in the NOVEG run.     

遗传神经网络在滑坡灾害预报中的应用研究

针对传统BP算法易收敛于局部最优以及网络结构难以确定等问题,引进遗传算法进行混合建模.采用遗传学习算法和误差反向传播算法相结合的混合算法来训练前馈人工神经网络,即先用遗传学习算法进行全局训练,再用BP算法进行精确训练,使网络收敛速度加快并避免陷入局部极小.文中结合实例,对BP神经网络,遗传算法改进的神经网络进行了比较分析.实验表明,利用改进的混合模型可以提高预测精度,缩短收敛时间.     

超声纵波换能器用于平测时的测距修正方法研究

研究了超声纵波换能器用于平测时的测距修正方法.首先,根据弹性波理论分析了利用平测布置代替对测布置测量波速时的实际物理意义;然后,分析了两种换能器布置方式的真实传播距离并通过设计混凝土试件切割-测量实验进行了两种布置方式的声时对比;最后,根据实验数据在对测回归直线方程的基础上提出了计算换能器平测布置修正测距的最小二乘法....     

基于波传播方法的边界条件对圆柱壳振动特性的影响分析

在波传播分析方法基础上,采用一种改进傅立叶级数的方法建立了弹性约束边界条件下圆柱壳结构模态分析模型,结合模态叠加理论,给出了圆柱壳结构在任意径向点力激励下的振动响应.通过与商业分析软件ANSYS的结果比较验证了本文方法的高效性与精确性,随后详细分析了边界约束刚度对圆柱壳结构自由振动特性和结构振动响应的影响,并给出了刚度影响的一般性规律.     

提高传感器输出特性线性化的神经网络方法

采用BP神经网络结构和LM网络学习规则对传感器系统的非线性误差进行线性校正和补偿,并对网络结构进行了适当的改进.用Matlab语言实现,计算比较了使用两种不同初始化规则和网络结构时对网络性能的影响.计算机仿真实验表明使用NW初始化规则并改进网络结构后,网络的收敛速度更快,拟合精度也有所改善.     

基于BP神经网络的车牌自动定位方法

提出了基于BP神经网络的车牌自动定位方法。实验表明，由此建立的车牌自动定位模型适角于各类机动车辆，总定位率为99．5%，达到了业务使用的要求。     

Neuronal ApoE Regulates the Cell-to-Cell Transmission of α-Synuclein

The presence of protein inclusions, called Lewy bodies (LBs) and Lewy neurites (LNs), in the brain is the main feature of Parkinson’s disease (PD). Recent evidence that the prion-like propagation of α-synuclein (α-syn), as a major component of LBs and LNs, plays an important role in the progression of PD has gained much attention, although the molecular mechanism remains unclear. In this study, we evaluated whether neuronal ApoE regulates the cell-to-cell transmission of α-syn and explored its molecular mechanism using in vitro and in vivo model systems. We demonstrate that neuronal ApoE deficiency attenuates both α-syn uptake and release by downregulating LRP-1 and LDLR expression and enhancing chaperone-mediated autophagy activity, respectively, thereby contributing to α-syn propagation. In addition, we observed that α-syn propagation was attenuated in ApoE knockout mice injected with pre-formed mouse α-syn fibrils. This study will help our understanding of the molecular mechanisms underlying α-syn propagation.