多应力条件下可靠性试验数据采集与处理系统的设计

介绍了一种多应力条件下的可靠性试验数据采集与处理系统。系统硬件平台以工控机为基础,从通用雷达板级可靠性试验所涉及测试信号的性质及数据采集的实际要求出发,选用基于PXI总线的数据采集和输出板卡来完成激励信号的加载和响应信号的采集。系统软件采用Labwindow/CVI与VisualC＋＋编程实现,通过调用PXI板卡的驱动函数,实现对板卡的控制以及数据处理;该数据采集系统测试效率、精度高,而且操作简单,具有良好的扩展性。     

GPS／Galileo双模捕获引擎的VLSI实现

随着卫星导航进入多星座时代,兼容GPS和Galileo的双模接收机成为目前卫星导航接收机设计的热点。捕获是卫星导航接收机基带信号处理的关键部分之一。本文通过对两种信号捕获算法的分析,提出了一种可以兼容GPS和Galileo信号的捕获引擎的VLSI结构。该结构兼顾了GPS和Galileo的信号特点,可以对GPS信号进行时域并行搜索和对Galileo信号进行时域部分并行搜索。最后给出了该结构各个组成单元的设计方法,在Altera公司的EP2S180FPGA器件上验证通过,并在0．18μm的CMOS工艺下综合,电路规模是3514231平方微米。     

面向润滑站加注系统的CAN通信接口设计

针对目前油田润滑站系统中加注过程繁琐、实时性差等问题,设计了一套由PC机与多台射频读卡控制器组成的润滑站加注系统。介绍了以通用型单片机AT89C52为核心．通过CAN协议控制器和CAN驱动器实现通信接口的设计,给出了硬件原理图及软件流程图。通过CAN通信模块在射频读卡控制器中的应用,有效保证了加注系统中数据通信的实时性、可靠性和稳定性。     

离心式永磁直流发电机的设计研究

离心式永磁直流发电机把皮带轮与离心式转子设计为一体,磁场得到了充分利用,降低了成本。本文介绍了电子稳压器通过移相、削波输出电压稳定的直流电,解决了小型农用车的低速照明问题和用电设施需用直流电的问题。     

论"以学习者为中心"对外语教学的指导意义

"以学习者为中心"强调了解学习者的实际情况和实际需求,以此为出发点确定教学内容及教学方法.在外语教学过程中,一方面,教师应尊重事实,不摒弃所谓过时的教学方法和教学重点;另一方面,力图改变一些不利于学习者自身发展的事实,变被动地吸收知识为主动地探索知识,让学习者学会自学方法,不断提高自学能力.这就是"以学习者为中心"对外语教学的指导意义.     

A (Triphenylphosphine)Silver (I) Complex as a New Performance Additive in Free‐Radical Photopolymerization under Air

Unusual photochemical properties of an Ag(I)‐derived complex, i.e., bis[(µ‐chloro)bis(triphenylphosphine)silver (I)] ([Ag](PPh₃)) are demonstrated when used in free‐radical photopolymerization reactions: i) [Ag](PPh₃) can act as an innovative photoinitiating system when associated with a commercial type I photoinitiator 2,2‐dimethoxy‐2‐phenylacetophenone to overcome the oxygen inhibition effect during the free‐radical photopolymerization of acrylate monomers, thus accelerating the kinetics of polymerization under air; ii) silver‐based nanoparticles can be in situ generated under air, thus leading to new antibacterial coatings which prevent the growth of Escherichia coli and Staphylococcus aureus after few hours of incubation.     

Preparation and thermal properties of Alkoxy Silane functionalized polyether sulfone/well‐defined poly(trimethoxysilyl) propyl methacrylate‐based hybrid materials

In this study, novel polyethersulfone (PES) and poly(trimethoxysilyl) propyl methacrylate (PMPS) containing hybrid materials were prepared. PES was functionalized with trimethoxysilane groups by UV‐induced grafting reaction. PMPS was synthesized by atom transfer radical polymerization. In the followed process, the functionalized PES mixed with different amount of PMPS, thermally treated to promote sol–gel crosslinking process to prepare the PES‐based hybrid materials. The trimethoxysilane grafted PES chains are covalently bonded with the well‐defined trimethoxysilane groups of PMPS. The chemical structure of the prepared PES and PMPS is confirmed by Fourier transform infrared analysis. The morphology of the hybrids was investigated by scanning electron microscopy. The results of thermogravimetric analysis show that the thermal stability of the hybrid materials was significantly affected with the addition of PMPS. POLYM. ENG. SCI., 58:1346–1352, 2018. © 2017 Society of Plastics Engineers     

Solid solution limit of Fe2O3 in mullite crystals,produced from kaolin by solid state reactions

Porcelain, wall/floor tiles, and roofing tiles are classified as traditional ceramics and are produced from natural raw materials such as clay, quartz, and feldspar. The raw materials are selected by the oxide content which provides the desired properties of the final product. However, impurities such as Fe₂O₃ and TiO₂ may have a significant influence on both physical/mechanical properties and aesthetic appearance. Fe₂O₃, which is of particular importance, causes black maculation formation in tablewares, in which whiteness is essential. The only way to overcome the black maculation is to corrupt the Fe₂O₃ crystal structure and to employ Fe^2+/3+ cation, making a solid solution with a host crystal (i.e. mullite-3Al₂O₃·2SiO₂). The aim of this study is to identify the solubility limit of Fe₂O₃ in mullite crystals. With the scope of the study, an illite/kaolinite was utilized by adding an increasing amount of Fe₂O₃ (e.g. 1–2–4–6–8–10?wt%) into the recipes fired at 1300?°C for 3?h after homogenization. According to the mullite phase content, it is concluded that ~ 5?wt% of Fe₂O₃ could be dissolved in mullite crystal structure on the basis of the Rietveld refinement of the XRD patterns.     

The effect of BMP‐2 and VEGF loading of gelatin‐pectin‐BCP scaffolds to enhance osteoblast proliferation

A composite scaffold of gelatine (Gel)‐pectin (Pec)‐biphasic calcium phosphate (BCP) was successfully fabricated. Growth factors such as bone morphogenetic protein‐2 (BMP‐2) and vascular endothelial growth factor (VEGF) were loaded into the Gel‐Pec‐BCP hydrogel scaffolds by freeze‐drying. The surface morphology was investigated by scanning electron microscopy, and BCP dispersion in the hydrogel scaffolds was measured by energy dispersive and X‐ray diffraction spectroscopy. The results obtained from Fourier transform infrared spectroscopy and quantitative measurements showed successfully loading of BMP‐2 and VEGF into the Gel‐Pec‐BCP hydrogel scaffolds. In addition MC3T3‐E1 preosteoblasts were cultivated on the three types of scaffolds to investigate the effects of BMP‐2 and VEGF on cell viability and proliferation. The Gel‐Pec‐BCP scaffolds loaded with VEGF and BMP‐2 demonstrated more cell spreading and proliferation compared to those of the Gel‐Pec‐BCP scaffolds. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41241.     

A Comparative Study on Changes and Relationships of Kernel Biochemical Components in Different Types of Maize

A great deal of genetic variability and breeding efforts have yielded a number of specialty maize types. Little is known about how the off‐target traits in specialty maize kernel have changed and how they compare to those of standard maize genotypes. In this study, we compared the normal (NORMAL), high‐oil (HOM) and high‐protein maize (HPM) genotypes in terms of oil, protein, fatty acids and some mineral components. We also investigated the relationships among the evaluated traits in different kernel types. We detected a significant variation among the maize types for all of the investigated traits. Specialty maize genotypes had a superior performance for the traits they were specifically bred for, as well as kernel mineral content over the normal genotypes. HOM and HPM had similar values in terms of their fatty acid composition. However, they were different from the standard genotypes, with higher oleic and lower linolenic acid levels, which indicates that the specialty maize genotypes possess a better oil quality. Correlation analysis revealed that only three pairs of correlations out of 46 values had the same sign and a similar level of significance in different types. Such similarities or differences in correlation values for different types should be taken into account in the efforts for developing high quality maize genotypes.