基于OpenFOAM的过冷流动沸腾数值模拟

过冷流动沸腾现象被广泛应用于工业生产和动力系统中,对该现象的准确预测是两相流CFD模拟的重要研究方向。本文详细阐述了该模拟过程中的欧拉两流体模型及相关辅助模型,基于开源CFD平台OpenFOAM,模拟了4.5 MPa下竖直圆管内的过冷流动沸腾,得到了截面空泡份额、液相平均温度及壁面温度沿轴向的分布。计算结果与实验值符合良好,说明了模型的有效性和程序的正确性。本文可为在OpenFOAM中添加新的模型及开发新的求解器以模拟过冷流动沸腾问题提供参考。     

超厚水泥稳定碎石基层室内试验及数值模拟分析

为了研究细观层次下碎石混合料中裂纹的产生发展及应力应变分布情况,以水泥碎石基层为研究对象,依托望谟至贞丰公路超厚宽幅水泥稳定碎石基层施工项目,进行原材料选择与检测。首先利用规划求解法进行混合料配合比设计得出最优配比;然后进行室内击实试验获得最大干密度与最优含水量,并进行无侧限压缩试验获得无侧限抗压强度,再利用灰色关联法获得原材料对混合料7 d无侧限抗压强度的关联度大小;最后利用有限元分析软件ANSYS对水泥碎石试件在单轴受压及抗折情况下碎石混合料中裂纹的产生、扩展及贯通的全过程以及应力分布情况进行模拟,通过与无侧限抗压强度试验结果对比,证明了此数值模拟方法的可靠性和合理性。结果显示:随水泥剂量的增加,水泥稳定级配碎石混合料最佳含水量及最大干密度随之增加;混合料水泥剂量与水泥碎石基层混合料7 d无侧限抗压强度之间的关联度4.75 mm碎石集料筛孔处的通过率混合料含水量;竖向受压过程中随着水泥剂量的增加,混合料试件破坏时的最大位移逐渐增加,且应力集中更加明显,骨料的破坏程度随之增大;混合料抗折破坏过程首先始于大粒径碎石骨料的水泥与碎石骨料界面过渡区,然后逐渐扩展,水泥剂量越大,混合料抗折能力越强,但应力集中越明显。     

特种液芯光纤微弯性能实验研究

采用自研制的液芯光纤,通过其在自由状态下的微弯传光性能的测试,研究液芯光纤的轴向微小弯曲和光强损失之间的关系,给出了实验数据及分析,为液芯光纤的进一步应用提供实验依据。     

PCI总线接口技术在高速数据传输系统中的应用

设计了一种基于PCI总线的高速数据传输系统,讨论了PCI总线控制器9054的性能及三种传输模式,提供了该系统的硬件实现设计和基于VISA库的驱动程序开发过程。经实际测试,该设计可靠性高、实时性好、数据传输通道之间完全独立,能更方便地用于各种标准总线、仪器、仪表之间的集成。对于实现高速、多通道、大数据量吞吐的传输系统,PCI总线有着较高的性价比。     

Usability evaluation of anti-phishing toolbars

Phishing is considered as one of the most serious threats for the Internet and e-commerce. Phishing attacks abuse trust with the help of deceptive e-mails, fraudulent web sites and malware. In order to prevent phishing attacks some organizations have implemented Internet browser toolbars for identifying deceptive activities. However, the levels of usability and user interfaces are varying. Some of the toolbars have obvious usability problems, which can affect the performance of these toolbars ultimately. For the sake of future improvement, usability evaluation is indispensable. We will discuss usability of five typical anti-phishing toolbars: built-in phishing prevention in the Internet Explorer 7.0, Google toolbar, Netcraft Anti-phishing toolbar and SpoofGuard. In addition, we included Internet Explorer plug-in we have developed, Anti-phishing IEPlug. Our hypothesis was that usability of anti-phishing toolbars, and as a consequence also security of the toolbars, could be improved. Indeed, according to the heuristic usability evaluation, a number of usability issues were found. In this article, we will describe the anti-phishing toolbars, we will discuss anti-phishing toolbar usability evaluation approach and we will present our findings. Finally, we will propose advices for improving usability of anti-phishing toolbars, including three key components of anti-phishing client side applications (main user interface, critical warnings and the help system). For example, we found that in the main user interface it is important to keep the user informed and organize settings accordingly to a proper usability design. In addition, all the critical warnings an anti-phishing toolbar shows should be well designed. Furthermore, we found that the help system should be built to assist users to learn about phishing prevention as well as how to identify fraud attempts by themselves. One result of our research is also a classification of anti-phishing toolbar applications. Linfeng Li is a student at the University of Tampere, Finland. Marko Helenius is Assistant Professor at the Department of Computer Sciences, University of Tampere, Finland.     

基于遗传算法的污水输送泵站优化调度

污水输送泵站在城市排水系统中担负着重要的任务。本文在分析泵站运行现状和泵站自身特征的基础上,以泵组总功率最小为目标函数,建立泵站优化调度问题的数学模型。在此基础上提出基于遗传算法的泵站优化调度,并开发了相应的优化调度软件。     

Hydrothermal routes to various controllable morphologies of nanostructural lithium aluminate

The α-LiAlO₂ powders have been successfully prepared by a hydrothermal route based on using the surfactant of heax-adecyltrimethyl ammonium bromide (CTAB) as the template. One-dimensional (1D) nanorods with higher and lower aspect ratio, 2D mesoporous microsheets were respectively observed with different concentration of the surfactants. A high specific surface area up to 151 m²/g was obtained by this method. The formation mechanism of the nanostructural lithium aluminate was proposed.     

结合图像信号显著性的自适应分块压缩采样

均匀分块压缩感知对图像信号进行压缩采样, 无法有效地分离出重要区域和背景区域。为此,本文提出了一种基于显著性的自适应分块压缩采样方法。根据图像信号的显著性,该方法利用四叉树算法进行自适应图像分块,有效分离出重要区域和背景区域。根据区域块的显著度动态设置观测值数量,重要度区域设置高采样率,背景区域设置低采样率,从而提高重要区域的图像重建质量。实验分析表明,在得到更好的视觉效果的同时,本文算法观测值数量较少,且重构图像的PSNR(峰值信噪比)、MSSIM（平均结构相似性）指标,以及运行时间均优于均匀分块压缩采样算法。     

一种控制系统串行口驱动程序的实现

控制系统中的通信是设计人员经常需要面对的问题,本文介绍了一种工业控制系统中串行口驱动程序的设计与实现。     

洪水可控性与水库调洪最高水位分布规律研究

针对水库防洪调洪能力,提出了可控洪水与不可控洪水的概念,研究水库在防洪调度中闸门全开后的调洪最高水位值的分布情况。通过仿真计算,分析在起调水位和洪峰流量不变的情况下,对应不同峰现时间的不同洪水过程所能达到的调洪最高水位。结论表明,在该值与起调水位之间的水位是可控的。基于此,给出用于查询的起调水位-洪峰-峰现时间表格,可在洪水预报的基础上快速判断一场洪水对水库防洪安全的影响程度。