C语言中常见错误分析

C语言是许多高校开设的第一门程序设计语言,使用方便灵活。根据C语言的特点,并结合实际教学,对在编程中经常遇到的错误进行分析、总结,为初学者尽快掌握C语言,提高程序设计水平提供借鉴。     

基于PCA变换扩散投影的人眼轮廓提取

提出一种PCA变换扩散投影的人眼轮廓提取方法(PCA transform scattering projection,PCATSP),即采用PCA投影对人眼的虹膜进行定位,经在人眼区域内对形状点进行变换后对所得参数进行扩散投影,并结合霍夫变换进行整体处理,从而实现更为鲁棒地提取人眼轮廓.实验中通过与可变形模板法相比较,结果表明PCATSP在平均形状参数误差及整体优化时间上更能精确地提取人眼轮廓,并取得令人满意的效果.     

基于三角带模板的大规模地形实时绘制方法

大规模地形的绘制技术一直是国内外虚拟现实领域的研究热点。为快速实时绘制,又保持真实性,提出一种基于三角带模板的大规模地形实时仿真方法。可用在战场环境仿真、飞行仿真、3D游戏等仿真系统中。先进行地形数据预处理,将地形分成若干相等的小块,并且计算每个小块的包围盒,然后根据地形块的大小确定一族三角带模板。实时绘制时,根据包围盒的屏幕投影误差因子选择合适的三角带模板,用三角带模板快速绘制地形块。采用扫描视锥体投影三角形裁剪方法剔除不需要绘制的地形块,并且采用添加阴影平面的方法消除地形裂缝。最后,在Puget Sound地形数据上进行了实验并进行了分析。实验证明,方法是可行和有效的。     

A post quantum secure construction of an authentication protocol for satellite communication

Satellite's communication system is used to communicate under significant distance and circumstances where the other communication systems are not comfortable. Since all the data are exchanged over a public channel, so the security of the data is an essential component for the communicating parties. Both key exchange and authentication are two cryptographic tools to establish a secure communication between two parties. Currently, various kinds of authentication protocols are available to establish a secure network, but all of them depend on number–theoretical (discrete logarithm problem/factorization assumption) hard assumptions. Due to Shor's and Grover's computing algorithm number theoretic assumptions are breakable by quantum computers. Although Kumar and Garg have proposed a quantum attack-resistant protocol for satellite communication, it cannot resist stolen smart card attack. We have analyzed that how Kumar and Garg is vulnerable to the stolen smart card attack using differential power analysis attack described in He et al and Chen and Chen. We have also analyzed the modified version of signal leakage attack and sometimes called improved signal leakage attack on Kumar and Garg's protocol. We have tried to construct a secure and efficient authentication protocol for satellites communication that is secure against quantum computing. This is more efficient as it requires only three messages of exchange. This paper includes security proof and performance of the proposed authentication and key agreement protocol.     

Structural damage diagnosis using incomplete static responses and LS-SVM

This paper presents novel approach to structural damage detection and estimation using incomplete static responses of a damaged structure and least squares support vector machine (LS-SVM). The presented method is based on the reduced stiffness matrix to formulate incomplete static responses as input parameters to the LS-SVM. The presented method is applied to a plane steel bridge, a four-span continuous beam and four-storey plane frame containing several damages. Also, the effect of the discrepancy in stiffness between the finite element model and the actual tested system has been investigated. The results show that the presented method is sensitive to the location and severity of the structural damage in spite of the incomplete noisy data and modelling errors.     

Quantification of statistical type i and ii errors in correlation analysis of simulated functional magnetic resonance imaging data

The potential of statistical analyses of functional magnetic resonance images using various threshold strategies in combination with correlation analysis was studied by simulating brain activation. Differences in statistical Type I () and II () errors are substantial for the various thresholds. Absolute thresholds and individualized thresholds based on the assumption of a gaussian noise distribution are producing constant -errors and thus do not sufficiently improve discrimination of truly activated pixels even for very high contrast-to-noise ratios (CNR). Only relative threshold strategies related to the maximum correlation coefficient and thus the individual data quality and activation level, i.e., a data-driven approach, can perfectly discriminate true positives, at least for CNR>2.5. To further improve discrimination of activated and non-activated pixel in studies with lower CNR, additional prior knowledge would be necessary. From the data presented, one would also expect that the best performing threshold strategy in this simulation study would perform best underin vivo conditions.Preliminary results presented in abstract form at the 13th Annual ESMRMB Meeting, Prague, Czech Republic, September 12–15, 1996.     

无边界效应D小波软阈值法去除肉品图像斑点噪声

肉品图像中的斑点噪声与肌内脂肪的颜色特征相似,要准确提取肌内脂肪,就必须先对斑点噪声进行滤除。在小波软阈值法滤除SAR图像中的斑点噪声算法基础上,结合肉品图像的特点进行了改进。首先,使用由耿则勋提出的算法,在小波分解时对左右边界进行处理,重构时外推值为0,对离散小波变换的边界效应进行处理,精确重建图像,消除小波变换的边界效应。选择了D8小波,3级分解后,在不同的阈值下进行了实验。结果表明:阈值的选取影响去噪效果,但在所有参数都相同时,改进算法消除边界效应的同时,在斑点指数和方法噪声两个客观评价指标均优于其他几种边界延拓方式,图像失真最小。     

Helicopter maintenance error analysis: Beyond the third order of the HFACS-ME

In this paper a statistical analysis of a sample of 58 helicopter maintenance-induced safety occurrences is conducted to study helicopter accidents and incidents’ survivability and the severity distribution of such occurrences. Analysis is also carried out to identify helicopter main and sub-systems mostly exposed to maintenance errors and to determine various types of such errors. Expected inherent relations between rotorcraft components affected and types of associated maintenance errors are investigated. Human factors-based triggers of these accidents and severe incidents are explored. The concept of Specific Failures (SFs) that immediately precede each of such occurrences is introduced for more detailed representation of the last breached individual and organizational safety barriers. Root causes of these safety occurrences were then sought utilizing the Human Factors Analysis and Classification System-Maintenance Extension (HFACS-ME) taxonomy with a refined focus on its third order categories’ list. The rotorcraft characteristics influencing individuals and organizational behaviours within Maintenance, Repair and Overhaul organizations (MROs) are discussed in the light of the root cause investigation results.

Relevance to industry

The study of human reliability within helicopter maintenance industry is waited to emphasise the understanding of causes and propagation mechanisms of maintainers' errors and their consequences on the overall aviation safety. Previous works often investigated maintenance errors and their roles in promoting aviation accidents of fixed-wing aircraft; this research is investigating the case of rotorcraft.