面向航天器测试的时序数据模式表示方法研究*

通过计算某一点与其左右两相邻点斜率的比值确定出变化点,连接这些变化点,就得到一种基于斜率变化阈值的时间序列分段线性STC表示算法。来自航天器不同分系统的真实数据集实验表明,使用STC算法作为航天器测试时间序列的模式表示方法,与其他分段线性表示算法相比,该方法具有算法简单、拟合程度高和适应能力强的特点。     

航空器地面畅通滑出时间研究

对航空器在机场地面畅通滑出时间进行精确预测,是开展机场地面拥堵疏导和降低航空器地面滑行冲突风险研究的前提.目前国内外学者在建立航空器地面畅通滑出时间预测模型时,在机型分类、样本数据区间选择、自变量选取、定义或计算方法等方面存在不合理问题.首次从跑道资源占用角度选取数学模型的自变量,并提出了改进的畅通滑出时间算法.先对样本数据进行整体拟合(拟合度为0.93),然后使用拟合斜率法查找拟合曲线的分段点,对样本数据区间进行分割和选取,针对不同机型的畅通滑出时间分别建立了对数正态分布模型,最后用首都国际机场实际运行数据进行检验,结果显示重型机和中型机畅通滑出时间误差范围在±3分钟内的预测准确率分别为94.12％和100％,表明该预测方法是可行的,且具有较高的准确性.     

截面轮廓曲线分段约束拟合

本文以线段和圆弧为逼近基元对封闭的截面曲线进行分段拟合,给出了曲线的拟合算法和逼近误差的分析表达式。在对截面曲线分界点进行迭代寻优后,得到了综合累积误差最小的分界点,并以此进行截面曲线的分段拟合;针对拟合所得的曲线,提出了具体的约束修正方法。通过实例分析表明,该算法简单有效,能较好地解决以线段和圆弧为基元的截面曲线拟合问题。     

基于惯导角度量测的轨道平面最佳线形参数估计算法

轨道线形分段及线形参数优化是铁路轨道既有线复测工作的核心。基于惯导角度量测数据,提出了一种轨道平面线形分段及最佳线形参数估计算法。所提算法根据轨道线形变化规律,利用组合迭代的方法计算轨道的最佳线形参数。该算法将轨道平面线形确定建模成优化问题：首先根据定长曲率曲线最小二乘拟合斜率变化对轨道进行概略分段;然后基于量测数据拟合轨道线形;最后使用组合迭代算法进行精确分段并确定最佳线形参数。仿真算例结果表明,所提算法结果优于现有人工判定算法——基于两组不同分段点的线形参数拟合结果,与穷举法结果更为接近,所提算法均方根误差（RMSE）仅比穷举法高4.93%,但计算量仅为穷举法的0.02%。西安地铁三号线的实测结果也验证了所提算法的有效性。     

时序模式发现算法研究

针对时序数据 ,提出一种新的时序模式的逻辑表示法 ,通过分段线性表示法 ,将时序曲线拟合为线段序列 ,从而以相对应的线段的斜率反正切值序列作为模式的逻辑表示 .在此基础上 ,设计出时序模式发现算法 ,此算法能够自动地发现所有 (子 )模式 .有关实验结果证明算法是行之有效的 .     

基于视频分割的关键帧选取

综合考虑了基于帧分块的局部似然比特征和基于小波变换的全局的边缘信息,利用这两者进行镜头边界检测,从视频镜头重构度 (SRD) 角度出发,针对线性拟合方法,采用了最小二乘法曲线拟合优化方法,分段重构出视频曲线,求出曲线的极值点,并以极值点代表关键帧.通过实验数据比较表明,该方法与实际的情况相符并取得明显的数值效果.     

基于Gocator视觉传感器的轨头参数计算

轮轨间紧密接触使轨头轮廓产生不规则变化,传统钢轨检测方法主要测量钢轨的垂直磨耗和水平磨耗,不能全面反映钢轨横截面的轮廓信息。基于Gocator视觉传感器采集、拼接得到的完整轨头轮廓数据及标准钢轨轨头轮廓曲线解析式,提出计算轨头剩余面积、轨头45°角磨耗和轨头角度参数的计算方法。该方法通过传感器拼接得到的离散点数据,采用优化分段三次的拟合方法进行多项式拟合,依次对多项式积分得到整个轨头剩余面积;通过轨头45°角所在直线与测量轮廓的交点计算其磨耗;通过计算轨头圆弧相交点处切线斜率得到轨头角度。实验数据表明,在钢轨同一截面计算得到的参数误差小,精度高,计算速度快,这些参数的有效测量值为钢轨自动化打磨维护提供指导意义。     

确定时间序列分段点的方法研究

现有的时间序列分段线性表示一般把局部极值点作为分段点,但是局部极值点并不能完全刻画时间序列的状态变化,根据时间序列线性分段的基本思想,提出在确定局部极值点的基础上引入斜率差值大的分段点,以便得到较高的拟合精度。新的分段点通过比较相邻序列段的斜率实现,斜率差值越大,该点的状态改变越明显。实验证明该方法拟合误差小,有很好的实用性。     

基于分段Bezier曲线的手绘雕刻图案矢量化

针对手绘复杂雕刻图案的特点,利用分段三次Bezier曲线实现手绘复杂雕刻图案的矢量化。提出一种自适应区分线条图案和区域块图案及提取区域块图案边界的解决方案。依据检测的角点信息将得到的轮廓边界分解成若干条独立的线段。曲线拟合时,为提高拟合精度,根据线段数据点到曲线的偏移量对线段进一步细分,提出一种实现分段曲线光滑连接的新方法。实验结果表明,该方法对手绘复杂雕刻图案的矢量化具有算法复杂度低、矢量化效果较好的优势,有广泛的实用性。     

基于斜率提取边缘点的时间序列分段线性表示方法

本文引入解析几何中的斜率,提出了一种新颖的基于斜率提取边缘点的时间序列分段线性表示方法SEEP。对于斜率变化范围比较集中的时间序列,SEEP表示方法有着非常好的效果,与以往的分段线性表示方法相比,SEEP表示方法与原始时间序列之间的拟合误差更小,而且要小很多;对于斜率变化范围比较大的时间序列,SEEP表示方法与原始时间序列之间的拟合误差,和以往的分段线性表示方法相比,也相差不大,并且SEEP表示方法计算简单,易于实现。算法的时间复杂度仅为O（n）,     

Fast and precise points-to analysis

Many software engineering applications require points-to analysis. These client applications range from optimizing compilers to integrated program development environments (IDEs) and from testing environments to reverse-engineering tools. Moreover, software engineering applications used in an edit-compile cycle need points-to analysis to be fast and precise.In this article, we present a new context- and flow-sensitive approach to points-to analysis where calling contexts are distinguished by the points-to sets analyzed for their call target expressions. Compared to other well-known context-sensitive techniques it is faster in practice, on average, twice as fast as the call string approach and by an order of magnitude faster than the object-sensitive technique. In fact, it shows to be only marginally slower than a context-insensitive baseline analysis. At the same time, it provides higher precision than the call string technique and is similar in precision to the object-sensitive technique. We confirm these statements with experiments using a number of abstract precision metrics and a concrete client application: escape analysis.     

源代码分析技术的理论与实践发展

源代码分析技术对于软件安全缺陷分析是一项非常重要的手段.分析了软件源代码分析工具的技术手段和发展过程,最后对源代码分析的理论和实践进行了分析总结.     

C语言的别名分析方法研究

别名分析对于数据流分析、程序优化和分析工具的实现非常重要.文章提出了一种需求驱动,流非敏感的分析算法来解决指针别名问题.通过构造程序表达式图(PEG)把指针别名问题转化成判断两个指针节点是否是联通的问题,它不同于传统的别名分析方法,它不需要构造别名集合和对其求交集,所以提高了分析指针别名的效率.     

The use of protocol analysis for determining ability requirements for personnel selection on a computer-based task

Abstract

The role of cognitively oriented tasks in the workplace continues to increase as automation of physical task components advances. Difficulties in automating the operator's cognitive processes have placed a renewed emphasis on the human component in advanced manufacturing systems. While traditional task analysis techniques have made significant contributions to improving productivity when important task elements are visually observable, their focus on manual task procedures make them less effective for cognitively oriented activities. This research has made a first attempt at integrating techniques from several disciplines to develop a cognitive task analysis methodology. The utility of this combined approach is examined for a new system being tested in the United States Postal Service. This task requires operators to encode, via a keyboard, addresses presented on a video display terminal. Results support the hypothesis that, for cognitively oriented tasks, a consensus based analysis technique (the Position Analysis Questionnaire) can be significantly improved by including data from task analysis provided the methodology is suitable for identifying non-physical task components.     

A system to assist survey analysts

The researcher who knows little about computers but wants to conduct a survey and analyse the results by computer can land himself in some difficulty if he does not appreciate some of the problems of computerization. This paper describes a system which is designed to aid such a person by providing assistance with the design of the questionnaire, the capturing of the data and the final analyses.     

A novel analysis space for pointer analysis and its application for bug finding

The size of today’s programs continues to grow, as does the number of bugs they contain. Testing alone is rarely able to flush out all bugs, and many lurk in difficult-to-test corner cases. An important alternative is static analysis, in which correctness properties of a program are checked without running it. While it cannot catch all errors, static analysis can catch many subtle problems that testing would miss.We propose a new space of abstractions for pointer analysis—an important component of static analysis for C and similar languages. We identify two main components of any abstraction—how to model statement order and how to model conditionals, then present a new model of programs that enables us to explore different abstractions in this space. Our assign-fetch graph represents reads and writes to memory instead of traditional points-to relations and leads to concise function summaries that can be used in any context. Its flexibility supports many new analysis techniques with different trade-offs between precision and speed.We present the details of our abstraction space, explain where existing algorithms fit, describe a variety of new analysis algorithms based on our assign-fetch graphs, and finally present experimental results that show our flow-aware abstraction for statement ordering both runs faster and produces more precise results than traditional flow-insensitive analysis.     

基于因子分析法和聚类分析法的副省级城市宜居情况聚类评价

重点选取了15个副省级城市的第一产业比重、人口密度、人均绿地、园林面积、医院数目,市政建设面积、地方财政税收等42个指标,使用SPSS作为计算工具,使用因子分析方法简化评价指标,计算相关系数矩阵,判别因子分析可行性,利用主成分分析法求因子载荷,将因子进行旋转得出更有实际意义的因子解释,并计算因子得分,利用该结果计算Mi...     

Cost analysis of object-oriented bytecode programs

Cost analysis statically approximates the cost of programs in terms of their input data size. This paper presents, to the best of our knowledge, the first approach to the automatic cost analysis of object-oriented bytecode programs. In languages such as Java and C#, analyzing bytecode has a much wider application area than analyzing source code since the latter is often not available. Cost analysis in this context has to consider, among others, dynamic dispatch, jumps, the operand stack, and the heap. Our method takes a bytecode program and a cost model specifying the resource of interest, and generates cost relations which approximate the execution cost of the program with respect to such resource. We report on COSTA, an implementation for Java bytecode which can obtain upper bounds on cost for a large class of programs and complexity classes. Our basic techniques can be directly applied to infer cost relations for other object-oriented imperative languages, not necessarily in bytecode form.     

数据分析需求与实现

数据分析是从海量数据中发现隐含信息或知识的过程。基于一个公安破案辅助数据分析系统,深入研究数据分析任务的需求与实现,提出首先规划分析思路、细化分析功能,然后用多视角数据透视和智能分析两种手段,从微观与宏观、定量与定性等不同角度互为补充地使系统具有完备的分析功能。该研究对如何开发具有实用价值的数据分析系统有普遍的指导意义。