南水北调东线第一期工程江苏段低扬程泵站的机组选型研究

针对南水北调东线工程淮安四站、淮阴三站泵型比选,对低扬程泵站选用立式轴流泵和灯泡贯流泵进行了选型对比研究。提出了在目前条件下,立式轴流泵和灯泡贯流泵的选用范围。     

软贴面聚氨酯板材连续生产线简述

介绍了软贴面聚氨酯夹芯板材连续生产线设备的主要组成部分,对生产工艺、发泡液面的控制、理论密度的算法等做了详细介绍,并对在生产过程中,工艺参数对产品质量的影响做了深入分析,以助国内同行参考。     

基于压缩采样匹配追踪的稀疏度和稀疏信道联合估计

原始的压缩采样匹配追踪算法依赖于已知稀疏度,因此本文研究了一种稀疏度和稀疏信道联合估计算法。首先提出了一种新的稀疏向量的替代,能够在有限长度的训练序列下,达到较好的稀疏度和信道估计效果。然后通过对稀疏信道估计中的噪声分量的分析,提出了一种稀疏度估计算法,结合信道估计最终给出了一种稀疏度和稀疏信道联合估计算法。仿真结果表明：新的稀疏向量的替代在稀疏度和信道估计方面都有明显的优势,并且提出的稀疏度和稀疏信道联合估计算法在性能上好于mCoSaMP算法。     

一种基于提升格式的双正交小波设计方法及应用

提升格式是一种新的小波构造方法，它是因构造紧支的第二代小波之需而产生的。Sweldens等人提出的提升格式设计方法只能设计基于Lazy小波的插值小波，为了满足各种应用需要，提出了一种基于任意双正交小波，而非仅针对Lazy小波的增加小波消失矩的新算法。利用小波消失矩和与其对应滤波器在z=1处零点阶数之间的关系，通过求解一组简单的线性方程组来设计基于任意双正交小波的提升系数；根据最佳提升格式的唯一性，给出了求最佳提升系数的迭代算法。     

板材多点成形时柔性压边与刚性压边方式的比较

为了研究不同的压边方式对多点成形结果的影响,采用动力学显式有限元软件对大变形量三维曲面多点成形过程中刚性压边与柔性压边方式进行了数值模拟,对比了二者的成形结果,并且对不同压边力时的柔性压边成形进行了探讨,研究了柔性压边方式的成形规律。结果表明,对于大变形量的三维曲面多点成形,柔性压边方式可以成功避免拉裂和起皱成形缺陷的发生,成形质量良好。这个结果可以作为开发大变形量的多点成形压力机的理论依据。     

基于ComGIS海量影像的存储与快速显示

在地理信息系统中,矢量地图数据更新速度慢、现势性不强.而随着航空航天技术的发展遥感影像的采集更加方便、更新速度快,影像的数据量在不断地增大.如何利用现有的计算机硬件资源对海量影像数据进行高效存储和快速显示?为此,在借助ArcGIS中的组件之一,即ArcSDE(空间数据引擎)的基础上提出了利用数据分块、建立影像金字塔来提高海量影像的显示速度.     

概念车身的T型接头模型拓扑优化设计

通过静态刚度对比,验证了概念车身模型的正确性及可行性。考虑到接头刚度对车身刚度的重要影响,将接头模型加入到概念模型中,建立了T型接头与梁结构的混合模型(TJB模型)。通过权衡扭转工况下各接头部位对开口刚度的实际贡献,选择了车顶部位的关键接头作为修改区域。应用变密度法进行了拓扑优化,并根据优化结果及车身结构特点布置了加强板,取得了良好的修改效果。在车身的概念设计阶段采用拓扑优化方法,不仅可以加快设计进程,而且能够得到性能更优、结构更合理的产品。     

等离子体涂层椭球目标的电磁散射

采用椭球坐标系下的分离变量法,结合介质和目标的边界条件导出了涂层导体椭球的电磁散射场计算公式,将入射场、散射场和内场分为轴对称和非轴对称两部分,数值计算了涂敷椭球粒子的单、双站散射截面的角分布,讨论了散射截面随入射波频率、等离子体碰撞频率、电子浓度和涂层厚度的变化规律,对等离子涂层目标的隐身技术研究有一定意义．     

Online dynamic cardiac imaging based on the elastic-net model

Purpose: The purpose of this work was to develop an online dynamic cardiac MRI model to reconstruct image frames from partial acquisition of the Cartesian k-space data, which utilizes structural knowledge of consecutive image frames. Materials and methods: Using an elastic-net model, the proposed algorithm reconstructs dynamic images using both L₁ and L₂ norm operations. The L₁ norm enforces the sparsity of the frame difference, while the L₂ norm with motion-adaptive weights catches the internal structure of frame differences. Unlike other online methods such as the Kalman filter (KF) technique, the new model requires no assumption of Gaussian noise, and can faithfully reconstruct the dynamic images within a compressive sensing framework. Results: The proposed method was evaluated using simulated dynamic phantoms with 40 frames of images (128?×?128) and a cardiac MRI cine of 25 frames (256?×?256). Both results showed that the new model offered a better performance than the online KF method in depicting simulated phantom and cardiac dynamics. Conclusion: It is concluded that the proposed imaging model can be used to capture a large variety of objects in motion from highly under-sampled k-space data, and being particularly useful for improving temporal resolution of cardiac MRI.     

Defect‐Laden MoSe2 Quantum Dots Made by Turbulent Shear Mixing as Enhanced Electrocatalysts

A high density of edge sites and other defects can significantly improve the catalytic activity of layered 2D materials. Herein, this study demonstrates a novel top‐down strategy to maximize catalytic edge sites of MoSe₂ by breaking up bulk MoSe₂ into quantum dots (QDs) via “turbulent shear mixing” (TSM). The ultrasmall size of the MoSe₂ QDs provides a high fraction of atoms in reactive edge sites, thus significantly improving the catalytic activities. The violent TSM further introduces abundant defects as additional active sites for electrocatalytic reactions. These edge‐proliferated and defect‐laden MoSe₂ QDs are found to be efficient electrocatalysts for the hydrogen evolution reaction, and useful as counter electrodes in dye‐sensitized solar cells. The work provides a new paradigm for creating edge‐proliferated and defect‐rich QDs from bulk layered materials.