Fabrication of porous bioactive structures using the selective laser sintering technique

Hydroxyapatite, a ceramic with which natural bone inherently bonds, has been incorporated into a polymer matrix to enhance the bioactivity of implant materials. In order to manufacture custom-made bioactive implants rapidly, selective laser sintering has been investigated to fabricate hydroxyapatite and polyamide composites and their properties investigated. One objective of this research was to identify the maximum hydroxyapatite content that could be incorporated into the matrix, which was sintered at various parameters. The study focused on investigating the control of porosity and pore size of the matrix by manipulating the selective laser sintering parameters of the laser power and laser scan speed. The interception method was used to analyse the internal porous morphology of the matrices which were cross-sectioned through the vertical plane. Most notably, all structures built demonstrated interconnection and penetration throughout the matrix. Liquid displacement was also used to analyse the porosity of the matrices. The laser power showed a negative relationship between porosity and variation in parameter values until a critical power value was reached. However, the same relationship for laser scan speed matrices was inconsistent. The effects of the laser power and laser scanning speed on the features of porous structures that could influence cell spreading, proliferation, and bone regeneration are presented.     

基于中文分词的文本自动校对算法

中文文本自动校对是自然语言处理领域中有着广阔应用前景的一个研究方向.依据中文分词的结果以及常见错误的特点,结合三元字模型的特点,提出了一种有效的文本校对方法,实验表明,该方法具有较高的准确率和召回率.     

电力企业VPN管控系统体系结构设计

虚拟专用网络不仅具备低成本、良好的网络支持等特点,还具备租用专线的安全性优势,已广泛应用于拥有分支机构的大型企业.虚拟专用网络的管理已成为企业IT管理人员不得不认真面对的问题.文章在基于策略的网络管理、移动Agent等网络管理技术的基础上,提出了VPN管控系统架构.该架构能统一地管理包括VPN设备在内的网络设备,结合设备状态信息和预定义的管理策略,动态地实现全网管控,有效地帮助企业IT管理人员监控和管理企业VPN网络,优化网络资源的使用,减少维护工作的时间.     

短路电流对电网结构的影响

分析了发电机接入不同电压等级提供的短路电流、500 kV变电站之间220 kV侧短路电流的相互影响,并以湖北武汉电网为例,进行了理论分析及潮流仿真计算,在此基础上分析了短路电流对电网结构的影响.     

金属铕制备工艺的研究

本文采用正交实验的方法,研究了金属铕的制备工艺条件。实验结果表明,还原－蒸馏温度１１００℃,还原剂过量系数０．３,保温时间１．５小时,金属铕的纯度大于９９．９％,直收率大于９０％     

Effect of H_2 dilution on the structure and properties of nc-CrC/a-C:H coatings deposited by a hybrid beams system

Nanocomposite Cr C/hydrogenated amorphous carbon(nc-CrC/a-C:H) coatings were deposited by a hybrid beams system comprised of a hollow cathode ion source and a cathodic arc ion-plating unit with varying H_2 flow rates. The influences of H_2 flow rates on the morphologies, microstructures, and properties of the coatings were systematically studied. The morphologies and microstructures of the coatings were characterized by SEM, AFM, XPS, Raman spectroscopy, GIXRD, and HRTEM. The mechanical and tribological properties were measured by a nano-indenter, scratch tester, and ball-ondisk tribometer. The wear tracks were evaluated using 3D profilometer, optical microscope, and EDS analysis. It has been found that a moderate H_2 flow rate can effectively smooth the surface, enlarge the fraction of a sp~3 bond, and improve the properties. The coating exhibits the highest hardness and elastic modulus at the H_2 flow rate of 40 sccm. A superior combination of adhesion strength,friction coefficient, and wear resistance can be achieved at the H_2 flow rate of 80 sccm.     

国产与美国CR－39固体径迹探测器探测中子性能的比较研究

用Ａｍ—Ｂｅ中子源照射国产ＳＹ－２型ＣＲ－３９与美国ＣＲ—３９固体径过探测器，在蚀刻时间较短时，测量它们表面径迹密度与蚀刻时间的变化，求得单位质量ＣＲ－３９中可蚀刻径迹数目，并在蚀刻时间较长时，测量两种ＣＲ－３９表面径迹密度的饱和值，对两种ＣＲ—３９探测器进行对比。测量表明，国产ＳＹ—２型ＣＲ—３９与美国ＣＲ－３９探测快中子的灵敏度在误差范围内符合，它们具有相同的快中子灵敏度。     

安多霖对高功率微波照射大鼠性激素和氧化还原系统的影响

选用SD和Wistar大鼠为研究模型。将SD大鼠分为对照组、模型组、6和12 g/kg给药组,给药组动物安多霖连续灌胃30天,100 mW/cm2微波全身照射10分钟,照后24小时取全血分离血清,放射免疫法检测血清睾酮和卵泡刺激素（FSH）活性。将Wistar大鼠分为模型组、3、6和9 mg/kg给药组,给药组动物安多霖连续给药7天,以100 mW/cm2微波照射15分钟,照后继续给药至照后3、7和10天,取血分离血清,分光光度法检测血清过氧化氢酶（CAT）、谷胱甘肽过氧化物酶（GSH-Px）活性和还原型谷胱甘肽（GSH）含量。结果显示,照后SD雄性大鼠血清睾酮含量较对照组显著降低（p〈0.05）,但给药组降低的幅度低于模型组,如12g/kg组与对照组之间无明显差异。从CAT、GSH-Px和GSH的分析结果看,安多霖可不同程度地提高Wistar大鼠血清CAT、GSH-Px活性和GSH含量,尤其是照后7天,6和9 mg/kg给药组GSH-Px活性较模型组有明显的提升（p〈0.05）。从以上结果可以得出,安多霖对微波辐射损伤的大鼠具有一定的保护作用。     

基于改进2DCNN的高光谱遥感图像处理研究

针对传统遥感图像处理中的时间成本和人工成本高、效率低等问题,以提高遥感高光谱图像分类中的处理速度、精度,降低参数量为目标,提出改进的2DCNN模型En-De-2CP-2DCNN.首先,使用1DCNN、2DCNN与3DCNN在Pavia University HSI数据集上分别进行分类实验,对比分析各自优缺点.其次,在保持较快的处理速度和不增加模型参数量的前提下,选择2DCNN为基础模型,参考SegNet的Encoder-Decoder结构,融入双卷积池化思想进行基础模型改进,同时优化学习策略.结果表明:En-De-2CP-2DCNN模型F1为99.96％,达到3DCNN的同等水平(99.36％),较改进前(97.28％)提高2.68个百分点;处理速度(5 s／epoch)和1DCNN位于同一量级,快于3DCNN(96 s／epoch);参数量(2.01 MB)较改进前降低了1.54 MB,虽高于3DCNN(316 KB),但远低于1DCNN(19.21 MB).En-De-2CP-2DCNN模型在处理速度和参数量方面的改进,有利于进一步实现移动端的轻量化部署.     

循环荷载作用下钢结构滞回性能的数值模型

提出了“塑性铰有限分布”的数值模型用以分析钢结构在循环荷载作用下的滞回性能。经与试验结果比较表明模型简单、易于实施，待进一步完善后，可直接用于对梁及压弯构件的模拟。