基于 Spin/Promela 的 Woo-Lam 协议安全性质高效验证磁

形式化方法是分析验证安全协议的重要技术之一。模型检测是用在形式化方法中实现形式化自动验证的重要手段。基于 Promela 语言,将 P ．Maggi 和 R ．Sisto 提出的建模方法扩展到建立包含三个合法主体和一个攻击者的复杂模型,枚举法和打表法同时被运用在求解攻击者模型需要表示的知识项过程中,提高了协议建模效率,保证了建模准确性。以Woo-Lam 协议为例,运用 Spin 工具成功发现一个已知著名攻击。此通用方法适用于类似复杂协议形式化分析与验证。     

计算机视觉原理分析及其应用

介绍了计算机视觉的原理,分析解释了实现原理的步骤以及发展现状,并且举例说明了计算机视觉的应用,解决了在人脸检测和识别、机器人目标定位、导航等领域的应用问题,并简单论述了计算机视觉技术的发展方向.     

反渗透阻垢剂的合成、应用及机理研究进展

投加阻垢剂是解决反渗透(Reverse osmosis,RO)膜结垢问题简单有效的方法。综述了RO系统中阻垢剂的合成应用、阻垢特征、机理及存在问题。含磷类阻垢剂因导致水体磷污染已经基本被其它几类阻垢剂替代,绿色环保类阻垢剂在阻垢效果和可降解性方面均比聚合物类好。但任何阻垢剂单独使用都难于满足(RO)系统阻垢的实际需求,阻垢剂的复配可相互弥补单一阻垢剂的缺陷,同时发挥其协同效应,而阻垢剂的特征改性具有更强的针对性和适用性。因此,阻垢剂的复配和改性是其研究的趋势和重点。     

Formation and Height of the Interconnected Fractures Zone after Extraction of Thick Coal Seams with Weak Overburden in Western China

Formation of a zone of interconnected fractures during coal mining is a key factor in mine flooding. Coal mines in western China are characterized by thick coal seams with mechanically weak overburden. In situ studies including drill core analysis, drilling fluid loss measurement, and borehole video monitoring were used at the working face 101 in Shaanxi Jinjitan coal mine to explore the maximum height of the interconnected fractures zone (IFZ). Also, tests on a scaled physical model and numerical simulation based on the drilling data were used to study the formation of the fractured zone. By considering data from other mines with similar mining conditions, a logarithmic relationship was found between the maximum height of the IFZ and the thickness of coal excavation. The maximum height of the IFZ was found to be 27 times the thickness of the excavated coal seam, which is far more than in coal mining areas in eastern China. Also, the IFZ in overlying strata of the study area was arch-shaped, not saddle-shaped, as had been observed in previous studies.     

基于深度学习的立体影像视差估计方法综述

三维重建技术常用于自动驾驶、机器人、无人机和增强现实等领域。视差估计是三维重建的关键步骤,随着数据集的增加、硬件和网络模型的发展,深度学习视差估计模型被广泛使用并取得良好效果。然而,这些方法常用室外场景的物体,很少使用在室内场景的数据集中。回顾了双目视差估计的深度学习方法,选用5种深度学习网络：PSMNet(pyramid stereo matching network)、GA-Net(guided aggregation network)、LEAStereo(hierarchical neural architecture search for deep stereo matching)、DeepPruner(learning efficient stereo matching via differentiable patchmatch)、BGNet(bilateral grid learning for stereo matching networks),将其运用在一套真实世界的街景数据集（KITTI2015）和两套室内场景数据集（Middlebury2014、Instereo2K...     

Numerical Simulation of Water Flow from the Coal Seam Floor in a Deep Longwall Mine in China

The study of groundwater flow from the coal seam floor is critical to safe mining operations in China. We developed a numerical simulation model to describe flood water pathways during mining, using the field conditions present at the no. 4196 west work face in the Panxi longwall coal mine, Shandong Province, China, Groundwater flow analysis revealed unusual values for the failure depth of the coal seam floor. The high ground stress and underground pressure, excavation length, width of working face, poor mechanical properties of aquitards, and expansion of fractures by groundwater infiltration all contribute to groundwater flow into the mine. The modeling results predict the time and longwall locations associated with the maximum likelihood of flood occurrence. Such results can be used by decision makers to improve mine design and safety.     

Effects of pre-imidization on rheological behaviors of polyamic acid solution and thermal mechanical properties of polyimide film: an experiment and molecular dynamics simulation

A series of polyamic acid (PAA) solutions and corresponding polyimide (PI) films with different chemical structures were prepared through a partial pre-imidization process, and the rheological behavior of PAA solutions and thermal mechanical properties of PI films were investigated in detail. The FT-IR spectra indicate that the pre-imidization degree (pre-ID) of PI could be accurately controlled by adjusting the amount of dehydration reagents. The PI films with a certain pre-ID exhibit better mechanical properties and lower coefficient of thermal expansion. The viscosity curves of PAA solution with varying shear rate show that the PAA solutions with high pre-ID have low shear sensitivity, which exhibits a lower viscosity at the low shear rate, but retains almost the same viscosity at high shear rate. Chain conformation variations with pre-IDs and solvent content were investigated by molecular dynamic (MD) simulation. The MD results indicate that a sudden increase in cohesive energy density leads to gel at a certain pre-ID and the mobility of molecular chain decreases greatly with solvent volatilization. It is supposed that the molecular chain orientation induced by the pre-imidization will be preserved in the subsequent thermal imidization process. Therefore, the PI films with a certain pre-IDs exhibit more excellent thermal mechanical properties, especially for the PI with rigid-rod segments.

     

Virtual camera calibration and stereo correspondence of single-lens bi-prism stereovision system using geometrical approach

This paper proposes a simple geometrical ray approach to calibrate the extrinsic parameters of the virtual cameras and solve the stereo correspondence problem of the single-lens bi-prism stereovision system. Each images captured using this system can be divided into two sub-images which are generated by two virtual cameras due to the refraction through the bi-prism. This stereovision system is equivalent to the conventional two camera system and the two captured sub-images provide disparity which can be used for depth recovery. The virtual cameras will be calibrated geometrically and the correspondence problem of this system will be solved by applying epipolar geometry constraint on the generated virtual cameras instead of the real CCD camera. Experiments are conducted to validate the proposed method and the results are compared to the conventional approach to confirm its accuracy and effectiveness.     

氮掺杂碳纤维催化剂在二氧化碳电解处理中的研究进展

作为新型催化剂的代表,氮掺杂碳纤维催化剂由于拥有良好的吸附性能、催化活性而被广泛应用于二氧化碳电解处理等领域。综述了目前氮掺杂碳纤维催化剂的研究进展,重点阐述了此种催化剂的合成原理、常用制备方法以及亟待解决的问题,并对其进一步研究和应用进行了展望。     

摄像机标定方法的比较分析

简要介绍了摄像机的标定原理。分析和比较了传统摄像机标定方法、基于主动视觉的标定方法和自标定方法的优缺点及其应用场合,以期为摄像机标定方法的进一步研究提供参考。