平面并联机构刚度与动力学指标分析

针对典型的串联和并联机构，建立了动力学模型。分析了在外力输入时机构的静刚度和动刚度。提出使用冗余驱动方式提高刚度及其一致性。根据运动刚度分析方法，建立了主动力输入时的刚度矩阵。定义了反映加速度性能的动力学指标，用于评价和优化机构的设计。给出了几种典型机构的动力学指标的分布图形，说明冗余并联机构的动力学指标最好。     

振动助渗制备45钢表面铝化物涂层及其抗高温氧化性能

为降低渗铝温度以细化晶粒和提高45钢表面的抗高温氧化性能,采用振动助渗在其表面制备纳米结构铝化物涂层。采用X射线衍射仪分析涂层的相组成,采用扫描电子显微镜和原子力显微镜观察涂层的微观组织结构,采用能量色散光谱仪分析涂层微区化学成分,采用划痕仪检测涂层与基体的结合强度。结果表明:铝化物涂层主要由η-Fe_2Al_5和少量θ-FeAl_3相组成,且其具有单层、致密及均匀特性。120min振动助渗下形成的铝化物涂层表面呈现出凹坑和丘陵状两种典型纳米结构区域,且距表面越远,涂层的纳米晶越粗大;垂直加载载荷68N时出现噪声信号,涂层开始发生破损;涂层抗氧化试验中的氧化增重量和剥落量仅为未表面涂层处理45钢试样的1/60和1/160,说明铝化物涂层显著增强了45钢表面抗高温氧化的能力。     

参比温度曲线法的改进与实验研究

相变蓄热材料应用广泛,其热物性的测量至关重要。本文基于参比温度曲线法的基本思想,从相变蓄热材料的理论步冷曲线特征和实际测量过程出发,针对相变阶段中能量平衡方程的显热因素和相变结束阶段降温过程的温差因素进行分析和改进,得到了改进后的计算方程。并以十二水磷酸氢二钠、月桂酸和硬脂酸三种相变材料为例进行相变材料步冷曲线的实验研究,结合改进后的计算方程进行相变潜热值的计算。结果表明:改进后的方程对潜热的计算值与DSC测量值相比更接近,误差控制在10%以内。参比温度曲线法的改进对于相变蓄热材料的快速开发和调制具有一定的实践指导意义。     

Application of compressed sensing using chirp encoded 3D GRE and MPRAGE sequences

An implementation of Non-Fourier chirp-encoding in 3D Gradient Recalled Echo (GRE), susceptibility-weighted imaging (SWI) and Magnetization Prepared Rapid Gradient Echo (MPRAGE) sequences is presented with compressive sensing reconstruction. 3D GRE and MPRAGE sequences were designed, in which the phase encoding (PE) direction was encoded with spatially selective chirp encoding Radio Frequency (RF) pulses, while the slice and the readout directions were Fourier encoded using gradients. During each excitation along the PE direction, a different spatially-selective RF excitation pulse was used to encode the PE direction with a complete set of unitary chirp encoding basis. Multichannel compressive sensing reconstruction on the undersampled in vivo data demonstrated that images reconstructed from chirp encoded data were able to preserve the spatial resolution better than the Fourier encoding. The mean Structural Similarity (SSIM) across five subjects at the acceleration factor of 6, for chirp encoded MPRAGE was 0.934 compared to 0.912 for Fourier encoded MPRAGE. The implementation of prospective undersampling demonstrated the feasibility of using chirp encoding in clinical practice for accelerated imaging. The minimum intensity projection of the compressive sensing (CS) reconstructed susceptibility weighted images revealed that chirp encoding is able to delineate small vessels better than the Fourier encoding with the SSIM of 0.960 for chirp encoding compared to the SSIM of 0.949 for the Fourier encoding. Improved performance of chirp encoding for CS reconstruction and SWI, along with the feasibility of implementation makes them a practical candidate for clinical MRI scans.     

影响粉末流化的本征作用力及其调节

本文归纳了人们对粒间力的分析和计算，指出了影响颗粒间作用进而影响其流化质量的各种因素，并从改善微细物料流化质量的角度，综述了近年来国内外流化微细物料的诸多措施，将其归结为两大类型：外力场方法与本征途径，以作为进一步探求微细物料流态化的研究基础．     

混合物表面张力的新方程

本文基于Ｈａｎｓｅｎ展开式，采用表面相表面积分率，建立了一个液体混合物表面张力的新方程。对于７１个二元体系，关联和计算的总平均相对误差为０．４８０％；对于６个三元体系，预测的总平均相对误差为２．２８％。新方程形式简单，参数少，精度较高，并且具有预测能力。     

CO低温氧化负载金催化剂研究进展

从合成方法、制备条件和金粒子尺寸、载体效应等方面介绍了影响负载型纳米Au催化剂催化活性的因素、可能的反应机理。评述了选择适当的合成方法可以有效地控制金粒子直径,并使其均匀分散于载体之上,从而得到更好的催化活性。适当的焙烧温度与载体类型也是获得高活性催化剂的必要条件。     

A novel polishing technology for epoxy resin based on 355 nm UV laser

The electromagnetic shielding film has drawn much attention due to its wide applications in the integrated circuit package, which demands a high surface quality of epoxy resin. However, gaseous Cu will splash and adhere to epoxy resin surface when the Cu layer in PCB receives enough energy in the process of laser cutting, which has a negative effect on the quality of the shielding film. Laser polishing technology can solve this problem and it can effectively improve the quality of epoxy resin surface. The paper studies the mechanism of Cu powder spraying on the compound surface by 355 nm ultraviolet (UV) laser, including the parameters of laser polishing process and the remains of Cu content on compound surface. The results show that minimal Cu content can be realized with a scanning speed of 700 mm/s, a laser frequency of 50 kHz and the distance between laser focus and product top surface of -1.3 mm. This result is important to obtain an epoxy resin surface with high quality.     

水样中苯氧羧酸类除草剂固相萃取检测

目的利用计算机分子模拟技术选择合适的功能单体以制备固相萃取柱,用来检测池塘水样中苯氧羧酸泪除草剂。方法利用计算化学方法筛选出最优的功能单体,并用其制柱,并对池塘中水样进行检测。结果顺利制成萃取率较高的萃取柱,测得回收率达到83.9%。结论计算机模拟能够在法庭科学方面成功代替部分常规实验,大大节约了人力物力。     

新型冷库冷风机控制器

介绍一种新型冷风机控制器。该控制器不但能够实现对电子膨胀阀与除霜等主要方面的控制,而且附带各种传感器的接口,能够通过计算机网络实现实时远程监控,在第一时间发现故障,便于维护修理,同时节能效果显著。它的出现在某种程度上实现了机电一体化,并向着整体联合控制的方向发展。