一种混合模式反相强阳离子交换色谱固定相的制备及其保留机理的考察

采用一种简单的“混合配体”方法将辛基和磺酸基键合到硅胶表面,制备了辛基-磺酸基共同键合硅胶(OSS)材料。通过元素分析和吸附容量检测对OSS材料进行表征,证明辛基和磺酸基已成功键合到硅胶表面上。将该OSS硅胶材料作为混合模式反相强阳离子交换(RP/SCX)色谱固定相,在反相液相色谱(RPLC)流动相条件下,采用几种碱性探针分子定量地考察了该固定相的混合模式RP/SCX保留机理。通过改变流动相中缓冲盐的浓度,考察了溶质保留因子和盐浓度的对数和倒数的关系,得到了几种碱性探针分子在该混合模式OSS固定相上的单点和两点保留机理的数学模型。对两种数学模型的方程进行了线性拟合,结果表明两点保留机理更加符合实验的结果。此外,根据混合模式两点保留机理的数学方程,可以得到单一的疏水或离子交换作用力对总保留的影响,对混合模式色谱的实际分离应用可提供有价值的参考。     

Microstructure and wear resistance of composite layers on a ductile iron with multicarbide by laser surface alloying

Multicarbide reinforced metal matrix composite (MMC) layers on a ductile iron (QT600-3) were fabricated by laser surface alloying (LSA) using two types of laser: a 5 kW continuous wave (CW) CO₂ laser and a 400 W pulsed Nd:YAG laser, respectively. The research indicated that LSA of the ductile iron with multicarbide reinforced MMC layers demonstrates sound alloying layers free of cracks and porosities. The microstructure, phase structure and wear properties of MMC layers were investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), as well as dry sliding wear testing. The microstructure of the alloyed layer is composed of pre-eutectic austenite, ledeburite, spherical TiC, Cr₇C₃ and Cr₂₃C₆ with various morphologies. TiC particles are dispersed uniformly in the upper region of MMC layers. The average hardness of LSA layers by CO₂ laser and pulsed Nd:YAG laser is 859 HV_0.2 and 727 HV_0.2, respectively. The dry sliding wear testing shows the wear resistance of ductile iron is significantly improved after LSA with multicarbide.     

SiCp/6061Al金属基复合材料激光焊接研究

采用高能ＣＯ_２激光束对 ＳｉＣ颗粒增强 ６０６１铝基复合材料 ＳｉＣｐ／６０６１ＡＩＭＭＣ进行激光焊接、研究激光焊接工艺参数及填充材料对焊缝显微组织的影响。结果表明,对 ＳｉＣｐ／６０６１Ａｌ复合材料进行激光焊接,可以获得气孔很少、质量较高的焊接接头,但在激光直接熔化焊接焊缝中形成针状Ａｌ_４Ｃ_３脆性相,脆性相Ａｌ_４Ｃ_３的数量与尺寸随激光束功率密度增加而增大,随焊接速度增大而减少。激光焊接时加入０．３ｍｍ厚的金属钛片作为填充材料,在焊缝中形成ＴｉＣ增强相,从而抑制了脆性相Ａｌ_４Ｃ_３的形成。     

地铁通信系统的集中告警

集中告警设备利用计算机网络技术和计算机本身的高速数据处理能力,对城市轨道交通中地铁通信各系统进行集中监测告警管理。将通信各系统网络及设备的运行状态和告警信息集中反映到告警设备上,可及时、准确、迅速地获取设备的运行状态信息,以便维护人员快速、准确处理各系统设备故障。并可形成统一的综合管理报表,从而提高通信网络的维护质量和管理水平。     

Industrial case study: Evaluation of a mixed-mode resin for selective capture of a human growth factor recombinantly expressed in E. coli

Mixed-mode chromatography resins are gaining popularity as effective purification tools for challenging feedstocks. This study presents the development of an industrial application to selectively capture recombinant human vascular endothelial growth factor (rhVEGF) on Capto MMC from an alkaline feedstock. Capto MMC resin contains a ligand that has the potential to participate in ionic, hydrophobic, and hydrogen boding interactions with proteins and is coupled to a highly cross-linked agarose bead matrix. VEGF is a key growth factor involved in angiogenesis and has therapeutic applications for wound healing. In this process, it is expressed in Escherichia coli as inclusion bodies. Solids are harvested from the cell lysate, and the rhVEGF is solubilized and refolded at pH 9.8 in the presence of urea and redox reagents. The unique mixed-mode characteristics of Capto MMC enabled capture of this basic protein with minimal load conditioning and delivered a concentrated pool for downstream processing with >95% yields while reducing host cell protein content to <1.2%. This study explores the impact of loading conditions and residence time on the dynamic binding capacity as well as the development of elution conditions for optimal purification performance. After evaluating various elution buffers, l-arginine HCl was shown to be an effective eluting agent for rhVEGF desorption from the Capto MMC mixed-mode resin since it successfully disrupted the multiple interactions between the resin and rhVEGF. The lab scale effort produced a robust chromatography step that was successfully implemented at commercial manufacturing scale.     

模块化多电平变换器关键问题研究综述

随着电力电子技术的快速发展,多电平变换器及其相关技术的研究正逐步成为高压大功率运用场合的热点问题.模块化多电平变换器（Modular Multilevel Converter,MMC）因其具有模块化的结构优势,弥补了传统多电平变换器的不足.相对于传统多电平变换器,MMC具有谐波含量少、开关损耗低、故障穿越能力强等特点.本文首先从MMC的拓扑结构和工作原理入手,分析了MMC的技术特点.其次,根据当前国内外的相关理论研究,对MMC主电路建模、参数设计、调制策略以及子模块电容均压策略等关键问题进行了对比分析.最后,本文对MMC的前景进行了展望.     

Polyhydroxyalkanoate granules quantification in mixed microbial cultures using image analysis: Sudan Black B versus Nile Blue A staining

Polyhydroxyalkanoates (PHA) can be produced and intracellularly accumulated as inclusions by mixed microbial cultures (MMC) for bioplastic production and in enhanced biological phosphorus removal (EBPR) systems. Classical methods for PHA quantification use a digestion step prior to chromatography analysis, rendering them labor intensive and time-consuming. The present work investigates the use of two quantitative image analysis (QIA) procedures specifically developed for PHA inclusions identification and quantification. MMC obtained from an EBPR system were visualized by bright-field and fluorescence microscopy for PHA inclusions detection, upon Sudan Black B (SBB) and Nile Blue A (NBA) staining, respectively. The captured color images were processed by QIA techniques and the image analysis data were further treated using multivariate statistical analysis. Partial least squares (PLS) regression coefficients of 0.90 and 0.86 were obtained between QIA parameters and PHA concentrations using SBB and NBA, respectively. It was found that both staining procedures might be seen as alternative methodologies to classical PHA determination.     

WINCE 6.0对大容量、高速MMC卡的支持

在WINCE 6.0平台上实现对大容量、高速MMC卡的支持。     

一种SD/MMC存储器启动方案在SoC中的设计与实现

本文通过分析嵌入式系统的启动过程,设计实现了基于SD/MMC存储卡的直接启动方案.该方案基于AMBA总线,采用硬件描述语言(Verilog HDL)实现SD/MMC启动控制器,利用EDA工具VCS进行仿真,synplify进行综合,采用Altera公司的FPGA进行验证.全文从系统架构设计出发,详细介绍了启动过程的硬件设计和软件流程,最后给出仿真、综合和FPGA验证结果.     

A TiB2 metal matrix composite coating enriched with nitrogen: Microstructure and wear properties

Metal matrix composites containing titanium nitrides or titanium borides raise great interest to researchers due to their high wear resistance and enhanced corrosion properties. In the present investigation composite coatings containing both titanium nitrides/carbonitrides and titanium diborides were produced on plain steel substrates using the plasma transferred arc (PTA) technique with argon-nitrogen mixtures in the plasma and shielding gas. The microstructure of the metal matrix composites (MMC) obtained was thoroughly studied and found to consist of primary titanium diboride particles surrounded by a eutectic matrix containing, apart from ferrite, both titanium diboride and titanium carbonitride particles. The wear behavior of the composite coatings was assessed by pin on disk experiments. The wear rate against both a tool steel counterbody and an alumina counterbody is of the order of 10⁻⁴ mm³/m. The friction coefficient for both the alloyed layer-tool steel system and the alloyed layer-alumina system increases up to sliding speed of 0.30 m/s and then decreases, when the sliding speed increases further. Specifically, the friction coefficients are varied between the values 0.5 and 0.65. The wear mechanism for the tribosystem alloyed layer-tool steel is characterized by plastic deformation and adherence of material coming from the alloyed layer to the surface of the ball, while for the tribosystem alloyed layer-alumina ball, severe plastic deformation and formation of oxide layer are observed.