双腹板、顶底角钢半刚性连接节点的非线性有限元分析

用ANSYS有限元程序对双腹板、顶底角钢半刚性连接节点的非线性性能进行了理论分析,并将计算结果与试验结果进行了比较,两者吻合较好.通过对7个系列共23个双腹板、顶底角钢连接试件的有限元分析,重点探讨了连接的各类组件对节点力学性能的影响.结果表明:梁截面高度、顶底角钢厚度及与柱翼缘相连的顶底角钢螺栓间距对节点力学性能的影响较大;腹板角钢厚度对节点力学性能有一定的影响;柱腹板水平加劲肋、柱截面高度和螺栓直径对节点力学性能的影响较小.双腹板、顶底角钢连接梁柱节点属于典型的半刚性连接节点,建议在设计中考虑其对结构受力性能的影响.     

国产引进型300MW汽轮机通流部分改造及效果分析

提出了对国产引进型300 MW汽轮机通流部分的改造方案.通过性能考核试验验证,改造后的汽轮机效率得到了提高,热耗降低,达到了预期的节能降耗效果.     

简易数字信号传输性能分析仪的设计

为了更好地分析数字信号在传输过程所受码间干扰和噪音等因素的影响．文中设计了一个以FPGA为核心的简易数字信号传输性能分析仪,完成了数字信号发生器、伪随机信号发生器（模拟噪音源）、低通滤波器、加法器、数字信号分析电路的设计．该系统利用FPGA产生数字信号序列（M序列和曼彻施特编码序列）和模拟噪声序列（伪随机信号）,经过由低通滤波器构成的模拟信道进行传输,再由FPGA对数字信号分析提取出同步信号,最后在示波器上以眼图的形式来分析信号的传输性能．对截止频率与通带增益、数据率误差和眼图进行了实测．结果表明误差值均在允许范围内,系统工作稳定,眼图清晰,达到了设计要求的各项指标．     

基于DTMF技术的无线固定终端设计

介绍了一种以单片机ATmega48、GSM无线通信模块SIM300、双音多频解码芯片MT8870及语音芯片NY3P010A为核心设计的无线通信装置,通过RJll连接按键式电话座机,减小无线通信对大脑的辐射．系统可实现拔打电话、接听电话并具有来电语音提示及语音拔号等功能．文章对该装置的工作原理、硬件配置、软件设计及功能进行了详细论述,经样机实验证明,其各项功能完成良好．     

直方图的脑图像分割策略

为了提高核磁共振分割精度和效率,提出了一种基于直方图核磁共振脑图像分割算法.利用脑提取工具剔除脑核磁共振图像中非脑组织.根据灰度变化的特点,将脑图像直方图的区域峰值组成新的直方图,通过基于直方图阈值选取规则将脑组织分割成白质、灰质、脑脊液.实验结果表明:该算法相对于常见的分割算法,获得了较高的分割精度,同时运算效率高,运算时间降低了1~2个数量级.     

基于M2M的电梯安全运行监控系统设计

基于M2M技术提出一种电梯安全运行监控方案。通过对电梯轿厢安装多种类型的传感器,将分布在各处的电梯运行过程中出现的运行状态信息、故障信息通过电话通信网络或Internet网络及时传输到M2M业务监控平台,实现远程分析电梯故障功能,从而使电梯维护人员到达现场可以快速解决电梯故障。该系统可实现电梯监控实时化、智能化,试用效果良好。     

跳频通信技术研究与仿真

跳频技术具有较强的抗干扰、抗噪声,抗频率选择性衰减的能力和较低的误码率。通过建立跳频通信的仿真模型,实现跳频通信在噪声干扰下的性能分析,用Matlab/Simulink选取不同仿真参数来仿真,对比得出比较好的最佳仿真效果。通过分析跳频通信技术难点,给出相应的最佳方案。     

The effect of partial substitution of Ti with Zr, Cr or V in the Mg35Ti10Ni55 electrode alloy on its electrochemical performance

In this paper, Zr, Cr and V were selected as the partial substitution elements for Ti to form Mg₃₅Ti₅M₅Ni₅₅ quaternary alloys prepared by means of mechanical alloying on the basis of the ternary Mg₃₅Ti₁₀Ni₅₅ electrode alloy previously studied by the authors. It is found that all the three quaternary alloys possess an amorphous main phase and exhibit improved cycling stability than the original ternary Mg₃₅Ti₁₀Ni₅₅. The Zr-substituted alloy has also a higher discharge capacity. X-ray photoelectron spectroscopy (XPS) surface analysis reveals that on the surface of each alloy a multi-component oxide composite film is formed, which is more compact and corrosion resistant than the Mg(OH)₂ film and the (TiO₂)_x(NiO)_y(Mg(OH)₂)_z composite films reported previously. Auger electron spectroscopy (AES) analysis shows that the substituting elements tend to reduce the thickness of the passivation films. The thickness of composite oxide film on the alloys is in the following order: Mg₃₅Ti₁₀Ni₅₅>Mg₃₅Ti₅V₅Ni₅₅>Mg₃₅Ti₅Zr₅Ni₅₅>Mg₃₅Ti₅Cr₅Ni₅₅. The result agrees well with that of the polarization resistances (R_P) values obtained from the electrochemical impedance spectroscopy (EIS) Nyquist diagrams. It demonstrates that the thicker the passivation film is, the higher the R_P is and the more difficultly the charge transfer reaction proceeds. Anodic polarization curves indicate that the addition of Cr and Zr decreases effectively the corrosion current. However, the corrosion of the electrode alloys in the electrolyte is still high and proceeds constantly as the corrosion current remains almost constant during further cycles.     

SEM in-situ investigation on fatigue cracking behavior of P/M Rene95 alloy with surface inclusions

The low-cycle fatigue behavior of powder metallurgy Rene95 alloy containing surface inclusions was investigated by in-situ observation with scanning electron microscopy （SEM）. The process of fatigue crack initiation and early stage of propagation behavior indicates that fatigue crack mainly occurs at the interface between the inclusion and the matrix. The effect of inclusion on the fatigue crack initiation and the early stage of crack growth was very obvious. The fatigue crack growth path in the matrix is similar to the shape of inclusion made on the basis of fatigue fracture image analysis. The empiric relation between the surface and inside crack growth length, near a surface inclusion, can be expressed. Therefore, the fatigue crack growth rate or life of P/M Rene95 alloy including the inclusions can be evaluated on the basis of the measurable surface crack length parameter. In addition, the effect of two inclusions on the fatigue crack initiation behavior was investigated by the in-situ observation with SEM.     

基于GMM的说话人识别系统

实现了一个基于高斯混合模型（GMM）的说话人辨识系统。GMM是用多个高斯分布的概率密度函数的组合来描述特征矢量在概率空间的分布状况，不同的说话人对应了不同的GMM。模型的训练采取了极大似然估计（ML）的EM方法。并在不同的数据集上实验，得到了好的结果。