Antibacterial properties and corrosion resistance of AISI 420 stainless steels implanted by silver and copper ions

Silver or copper ions are often chosen as antibacterial agents. But a few reports are concerned with these two antibacterial agents for preparation of antibacterial stainless steel (SS). The antibacterial properties and corrosion resistance of AISI 420 stainless steel implanted by silver and copper ions were investigated. Due to the cooperative antibacterial effect of silver and copper ions, the Ag/Cu implanted SS showed excellent antibacterial activities against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) at a total implantation dose of 2×1017 ions/cm2. Electrochemical polarization curves revealed that the corrosion resistance of Ag/Cu implanted SS was slightly enhanced as compared with that of un-implanted SS. The implanted layer was characterized by X-ray photoelectron spectroscopy (XPS). Core level XPS spectra indicate that the implanted silver and copper ions exist in metallic state in the implanted layer.     

基于动三轴试验的黄土高边坡地震稳定性分析

以山西某机场边坡为例,对其场区的黄土进行了固结不排水的动三轴试验,得到了材料的动力特征和模量衰减曲线。应用有限元软件分析了在地震荷载作用下机场边坡的稳定性,拟合模量衰减曲线作为滞后阻尼参数;并结合数值分析的方法,建立了该边坡的计算模型。为了分析其稳定性,在边坡上设置5个监测点进行模拟。计算结果表明:地震荷载下,水平位移随坡高的增加而增大,坡脚处的竖直位移达到最大值0.88 cm。当地震波加速度达到最大时,位移累计值也相应的达到最大;地震荷载作用下的水平推力对边坡稳定性有较大影响;边坡的塑性区域主要集中在边坡坡面。     

A channel- and QoS-adaptive turbo coded modulation architecture for mobile multimedia communication

This paper proposed a cross-layer dual adaptive coded modulation architecture using turbo codes for mobile multimedia communication, which simultaneously adapted to both the varying channel characteristics and the quality of service (QoS) of various mobile multimedia services to increase the average system throughput substantially. A pragmatic channel-adaptive turbo coded modulation scheme, which comes within 2.5dB of the Shannon limit, was optimally designed, and then a QoS-adaptive scheme was superimposed to build the dual adaptive architecture. Simulation results show that the novel dual adaption reduces the difference with the fading channel capacity to 2dB when assuming different services occur in equal probability and the service duration follows the exponential distribution.     

从高斯光束到帽顶光束Z扫描:分析测量灵敏度和可靠性

利用快速傅里叶变换方法分析了Z扫描归一化透过率曲线.研究了入射光束空间分布对Z扫描测量灵敏度和可靠性的影响.提出了截取高斯光束(即近帽顶光束)Z扫描表征技术,该技术不仅提高了测量灵敏度和可靠性,而且提高了光能量的利用率.     

基于PXI的航空发动机尾气静电监测系统

通过对航空发动机静电监测技术的原理及其现状分析,设计了一套基于PXI总线的航空发动机尾气静电监测系统。详细介绍了系统硬件组成与相关软件功能模块设计。该系统以PXI主控计算机为核心,以LabVIEW软件编程为系统开发工具,有效地提高了系统的自动化程度、灵活性和可靠性,降低了系统组建成本。在实际模拟测试中,能够准确快速地监测到发动机尾气中故障颗粒,取得了应用效果,具备推广与应用前景。     

Effects of low-frequency electromagnetic field on the surface quality of 7050 aluminum alloy ingots during the hot-top casting process

To improve the quality of 7050 aluminum alloy ingots, low-frequency electromagnetic (LFE) field was applied during the conventional hot-top casting process. Macrostructures and microstructures of the ingots by the conventional and LFE hot-top casting processes were studied. The experimental results show that when the LFE field is turn off during the hot-top casting process, cold folding appears, and the as-cast structure becomes very coarse. Additionally, the thickness of the shell zone is much thinner during the low-frequency electromagnetic hot-top casting process than that during the conventional hot-top casting process. Some reasons for low-frequency electromagnetic field improving the surface quality, refining the structure of the ingot, and minimizing the thickness of the shell zone have been studied.     

基于局部离群因子和波动阈值的古籍版面图像分析方法

古籍版面图像结构复杂,对其进行有效、准确的分析是实现古籍汉字识别与检索的前提和基础。对古籍汉字版面分析的关键问题展开研究,在对古籍版面特点进行分析与归纳的基础上,提出基于LOF和波动阈值的古籍版面分析方法。首先,采用基于LOF的分类算法对古籍版面图像投影分割后的区域进行分类,确定存在分割问题的候选混合区域;然后,利用波动阈值对候选混合区域中的文字与框线粘连部分进行分割;最后,确定古籍版面中的文字区域并输出。实验结果表明,该算法能够有效地分离古籍文字区域和框线区域,版面分类和分割准确率分别为87.02%和78.69%。     

基于查询与内容的文档表示模型

在信息检索中,文档表示模型的优劣是影响检索性能的重要因素之一.根据全信息理论,认识论信息是语法信息、语义信息和语用信息的三位一体.当前主流的文档表示模型主要利用语法和语义信息,造成语用信息的缺失,成为改善检索性能的瓶颈.该文提出了一种整合用户查询行为与文档内容的文档表示模型,将用户隐性反馈的语用信息和文档自身的语义、语法信息相结合,动态调整索引库关键词权重,从而提高信息检索的查全率和查准率.     

不同钢丝堆积态下悬索桥主缆除湿性能

主缆除湿系统是悬索桥主缆在设计过程中的重要环节,直接影响主缆在工作中的服役寿命.针对主缆实际形貌特点,基于计算流体动力学(computational fluid dynamics,CFD)数值计算方法,系统研究了主缆内不同钢丝堆积态对主缆内部空气流动特性的影响,并通过南沙大桥(虎门二桥)实桥试验对数值计算结果进行验证.结果表明:通过数值模拟得到均一态的压降和试验实测压降的相对误差低于5％,表明所建立模型的准确性.松散态结构的存在会有效改变缆内横截面上的速度分布,在0.03倍直径处双堆积态下各个孔隙率下的速度增加率达到最大值,相较于单一堆积态缆内速度增加了12.9％;松散态堆积结构的松散程度对缆内的湍动能影响不明显,但是相比均一态堆积结构,双态堆积结构会使缆内的湍流变化更剧烈,湍动能峰值更大;不同孔隙率对于缆内内部的压降分布的影响不明显,相对于均一态在孔隙率为21.5时的双堆积态下最大压降仅减小了26 Pa.     

高速无人飞行器航迹规划算法与仿真

文章根据遍布威胁的战场环境,构造了基于威胁源的Voronoi图,得到规避威胁的航迹路线;综合各种威胁的强度信息,计算出每条航迹路线的代价;最后采用Dijkstra算法,搜索出最优航迹路线,并运用C#编制图形化界面,实现了仿真结果的图形显示。