铁路客运专线制梁场取证对设备管理的要求

结合工作实践,探讨了铁路客运专线制梁场取证对设备管理的要求,指出制梁场设备必须满足最大生产能力、生产精度需要,以强化设备管理工作,提高工作效率。     

Windows系统中特殊文件的提取与分析

在Windows系统中存在着一些隐藏的特殊系统文件,这些文件中实际上记录了大量的有取证价值的信息。通过运用一些取证分析工具来查看这些文件内容,并对其结构进行分析。     

云计算环境下电子取证研究

云计算是当前信息技术领域的热门话题之一,随着云计算的不断普及,利用云平台的犯罪也呈现上升趋势。由于虚拟化、分布式等技术的引入,使得云环境下的电子取证变得更加困难。文中从云环境中电子取证的挑战、相关工作流程,以及电子取证的建立方面,从技术、法律法规角度进行了探讨,分析了在相关关键技术和法律法规约束条件下如何有效地应对云环境中的犯罪,对中国未来云计算安全做出了有益的探索。     

基于Windows日志的电子证据获取与分析方法研究

为解决Windows日志的实时获取问题,针对2种日志文件格式,分别提出了相应的日志实时获取方法。在实时获取日志的基础上,提出了将日志文件与原子攻击功能关联的方法,将对日志文件的分析转换成对原子攻击功能的分析,大大减少了日志文件分析的时间。提出了一种基于时间的日志关联分析和事件重构方法,实现对计算机犯罪场景的还原。实验结果表明,提出的方法可以有效获取日志证据,重构犯罪过程。     

The structured heat integrated distillation column

This paper describes a unique, proof of the principle test facility and the results of a study carried out to provide experimental evidence needed to properly asses the techno-economic feasibility of heat integrated distillation column (HIDiC) utilizing structured internals to enhance both heat and mass transfer. The plate-packing configuration using structured packing exhibited a superior performance in comparison with the HIDIC based on the plate-fin heat exchanger. Experimental evidence shows that the mass transfer and heat transfer efficiency increase pronouncedly with increasing throughput, which however is accompanied by an increasing pressure drop per stage. Simulation of an industrial scale plate-packing unit revealed that an even better performance can be obtained by increasing the volumetric thermal load via further optimization of internals.     

Reducing total annualized cost and CO2 emissions in batch distillation: Dynamics and control

In this contribution, the direct vapor recompression approach is introduced in a batch distillation operated at an unsteady state condition. This vapor recompressed batch distillation (VRBD) accompanies an isentropic compressor that runs at a fixed as well as variable speed. Aiming to ensure the optimal use of internal heat source, an open‐loop control policy is proposed for the VRBD that adjusts either the overhead vapor splitting or the external heat supply to the reboiler. Again, the variable speed VRBD additionally involves the manipulation of compression ratio. Developing two alternative configurations of VRBD column, the best heat integrated scheme is attempted to identify in the aspects of energy efficiency and total annualized cost for further advancement. A closed‐loop control algorithm for the best performing variable speed VRBD aiming to meet the end objective of relatively high‐purity product discharged at a constant composition is developed. The separation of a reactive system is considered to illustrate these results and demonstrate the effectiveness of the novel VRBD scheme. Performing simulation tests, it is investigated that the closed‐loop control operation substantially improves not only the distillate purity but also the total amount of product. Achieving significant improvement in thermodynamic efficiency and cost by the controlled heat integrated scheme over its conventional counterpart, finally the attractiveness of the VRBD column by investigating its potential to reduce the greenhouse gas (i.e., CO₂) emissions is shown. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2821–2832, 2013     

基于再采样的图像重采样伪作检测

重采样是图像篡改中的一种典型操作,针对现有重采样伪作检测算法对于JPEG压缩格式的图像检测效果不理想,也无法准确估计其中的缩放因子的问题,提出了基于再采样的图像重采样检测算法。该算法先将待检验的JPEG图像以缩放因子小于1进行再次重采样,以削弱JPEG压缩对算法的影响,再利用重采样信号二阶导数具有的周期性来进行重采样操作检测。实验结果表明,该算法具有很强的抗JPEG压缩能力,同时能够准确估计真实的缩放因子。另外,该算法对于经过不同缩放因子而得到的图像进行合成时的重采样操作,也有明显的检测效果。     

基于Markov过程和伪极坐标快速傅里叶变换的重采样篡改检测

针对图像中的重采样篡改操作导致的离散余弦变换(DCT)系数之间相关性的变化,提出了一种新的图像重采样篡改检测方法。首先,提取Markov特征,利用高阶统计量分析重采样图像中离散余弦变换系数之间的关系;然后,将图像所在的笛卡儿坐标映射到伪极坐标(Pseudo-Polar)轴上提取图像的光滑度作为纹理特征,利用纹理特征检测图像的重采样操作;最后,将提取的两类特征输入到支持向量机(SVM)中训练和分类,从而检测出图像中的重采样篡改操作。实验结果表明:所提方法可以检测出图像中的重采样篡改操作,并具有较好的检测率,且对于一定范围内的加噪处理也具有鲁棒性。     

基于后验概率的图像模糊检测方法

数字图像被动盲取证是指在不依赖任何预签名提取或预嵌入信息的前提下,对图像的真伪和来源进行鉴别和取证。图像在经篡改操作时,为了消除图像在拼接边缘产生的畸变,篡改者通常会采用后处理消除伪造痕迹,其中,模糊操作是最常用的手法之一。提出一种人工模糊痕迹检测方法。将经过模糊操作后图像像素之间存在的高度相关性进行模型化表示;采用EM算法估算出图像中每个像素属于上述模型的后验概率;根据所得后验概率的大小进行模糊操作检测。实验结果表明,该算法能够有效地检测出篡改图像中的人工模糊痕迹,并对不同模糊类型、有损JPEG压缩以及全局缩放操作均具有较好的鲁棒性。     

Photographic composite detection using circles

In this work, we propose several new methods for detecting photographic composites using circles. In particular, we focus on three kinds of scenes: (1) two coplanar circles with the same radius; (2) a single circle with its discriminable center; (3) a single circle with geometric constraints for camera calibration. For two circles’ situation, we first estimate the focal length based on the equality of the sizes of two coplanar circles, and then estimate the normal vector of the world circle plane. Inconsistencies in the angles among the normal vectors (Each circle determines a normal vector) are used as evidence of tampering. On the other hand, for the single circle case, we warp the circle to make metric measurement. To demonstrate the effectiveness of the approach, we present results for synthetic and visually plausible composite images.