矩阵特征值和特征向量的计算方法(上)

设 A 是 n×n 正方矩阵,一般而言其元素可以是复的。我们要解的问题就是要求出这样的λ值和这样的 n 维向量 v,使 Av=λv。每一个这样的λ值称为矩阵 A 的一个特征值,固有根或特征根,而对应的向量称为对应于该特征值的特征向量。     

高速寻呼协议—FLEX^TM

本文介绍了Ｍｏｔｏｒｏｌａ的高速寻呼协议－ＴＬＥＸ＾ＴＭ的帧结构、优点及应用。     

电子医疗数据云服务安全

医疗信息技术的重要性最近几年得到了戏剧性的提升。研究者、开发者以及公司已经开始努力发展手机、网络、桌面以及企业E健康应用。这些发展又提升了E健康应用和健康信息系统(HIS)之间的互通和数据交换的重要性,进而导致了对敏感数据和数据交换的安全性的担忧。这篇文章强调了基于云计算服务的HISs和E健康应用之间的标准化数据交换机制和互通性。这项服务在包含有大量的病人记录的HISs上提供一个单一的检索电子医疗记录和搜索此类信息的E健康应用的入口。再者,这项研究提出一个统一的安全平台提供给开发者、安全医疗提供者和组织者一个连接框架的渠道去检索和管理医疗记录,以及提供给大量注册者个人一个连接通道到自己的医疗记录(PHR)。此项服务和平台已经在埃及亚历山大大学医学院示范的医生、病人和医院管理者之间进行了定性的评估。评估结果比较乐观,不过原型的实现还需要更多的研究。     

BCI competition III: dataset II- ensemble of SVMs for BCI P300 speller

Brain-computer interface P300 speller aims at helping patients unable to activate muscles to spell words by means of their brain signal activities. Associated to this BCI paradigm, there is the problem of classifying electroencephalogram signals related to responses to some visual stimuli. This paper addresses the problem of signal responses variability within a single subject in such brain-computer interface. We propose a method that copes with such variabilities through an ensemble of classifiers approach. Each classifier is composed of a linear support vector machine trained on a small part of the available data and for which a channel selection procedure has been performed. Performances of our algorithm have been evaluated on dataset II of the BCI Competition III and has yielded the best performance of the competition.     

Temporal variations in road traffic fatalities in South Africa

The annual road traffic fatality (RTF) burden of 43 deaths per 100 000 inhabitants in South Africa (SA) is disproportionately high in comparison to the world average of 22 per 100 000 population. Recent research revealed strong geographical variations across district councils in the country, as well as a substantial peak in mortality occurring during December. In this study, the factors that explain temporal variations in RTFs in SA are examined. Using weekly data from the period 2002–2006 for the country's nine provinces, non-linear auto-regression exogenous (NARX) regression models were fitted to explain variations in RTFs and to assess the degree to which the variations between the provinces were associated with the temporal variations in risk factors. Results suggest that a proportion of the variations in weekly RTFs could be explained by factors other than the size of the province population, with both temporal and between-province residual variance remaining after accounting for the modelled risks. Policies directed at reducing the effects of the modifiable risks identified in our study will be important in reducing RTFs in SA.     

Probing the electromagnetic field distribution within a metallic nanodisk

A Co nanolayer is used as a local probe to evaluate the vertical inhomogeneous distribution of the electromagnetic (EM) field within a resonant metallic nanodisk. Taking advantage of the direct relation between the magneto-optical activity and the electromagnetic field intensity in the Co layer, it is shown that the nonuniform EM distribution within the nanodisk under plasmon resonant conditions has maximum values close to the upper and lower flat faces, and a minimum value in the middle.     

Pixel selection for near-infrared chemical imaging (NIR-CI) discrimination between fish and terrestrial animal species in animal protein by-product meals

This paper proposes a method based on near-infrared hyperspectral imaging for discriminating between terrestrial and fish species in animal protein by-products used in livestock feed. Four algorithms (Mahalanobis distance, Kennard-Stone, spatial interpolation, and binning) were compared in order to select an appropriate subset of pixels for further partial least squares discriminant analysis (PLS-DA). The method was applied to a set of 50 terrestrial and 40 fish meals analyzed in the 1000-1700 nm range. Models were then tested using an external validation set comprising 45 samples (25 fish and 20 terrestrial). The PLS-DA models obtained using the four subset-selection algorithms yielded a classification accuracy of 99.80%, 99.79%, 99.85%, and 99.61%, respectively. The results represent a first step for the analysis of mixtures of species and suggest that NIR-CI, providing valuable information on the origin of animal components in processed animal proteins, is a promising method that could be used as part of the EU feed control program aimed at eradicating and preventing bovine spongiform encephalopathy (BSE) and related diseases.     

Accurate measurement of magnesium content in alphaolefins by laser induced breakdown spectroscopy （LIBS） technique

In this paper,results are presented on first application of laser-induced breakdown spectroscopy(LIBS) technique for quantitative determination of Mg concentration in alpha-olefins. It is demonstrated that this technique gives accuracies in Mg concentrations which are comparable with those of traditional methods,as ICP-OES,in short times and without need for sample preparation. Limits of detection for Mg of the order of 500 ppb are demonstrated. Moreover,a brief discussion about the realization of proper calibration curves and the definition of the limit of detection(LOD) is reported.