On optimal pairwise linear classifiers for normal distributions: the d-dimensional case

We consider the well-studied pattern recognition problem of designing linear classifiers. When dealing with normally distributed classes, it is well known that the optimal Bayes classifier is linear only when the covariance matrices are equal. This was the only known condition for classifier linearity. In a previous work, we presented the theoretical framework for optimal pairwise linear classifiers for two-dimensional normally distributed random vectors. We derived the necessary and sufficient conditions that the distributions have to satisfy so as to yield the optimal linear classifier as a pair of straight lines.In this paper we extend the previous work to d-dimensional normally distributed random vectors. We provide the necessary and sufficient conditions needed so that the optimal Bayes classifier is a pair of hyperplanes. Various scenarios have been considered including one which resolves the multi-dimensional Minsky’s paradox for the perceptron. We have also provided some three-dimensional examples for all the cases, and tested the classification accuracy of the corresponding pairwise-linear classifier. In all the cases, these linear classifiers achieve very good performance. To demonstrate that the current pairwise-linear philosophy yields superior discriminants on real-life data, we have shown how linear classifiers determined using a maximum-likelihood estimate (MLE) applicable for this approach, yield better accuracy than the discriminants obtained by the traditional Fisher's classifier on a real-life data set. The multi-dimensional generalization of the MLE for these classifiers is currently being investigated.     

离子注入聚碳酸酯表面力学性能改变研究

将B^ 和O^ 离子分别注人到高分子化合物聚碳酸酯(PC)中，PC的表面显微硬度和耐磨性能均得到了较大提高。用纳米硬度计测量注人前后PC的显微硬度，硬度提高了7～25倍。用球盘式磨损实验机测量注人前后PC的耐磨性能，磨痕的宽度比未注人的窄，最窄的磨痕(或最窄处)为未注人磨痕宽度的1／3～1／2。傅里叶变换红外光谱(FTIR)测试表明，注人前后高分子的结构发生了变化。     

常温磷化液的研制

常规磷化液中通常含有亚硝酸钠、氟化钠等有害物质.为改善环境,选用污染小的复合促进剂,研制了一种常温锌系磷化液,并应用正交试验法得到了磷化工作液的最佳配比,考察了磷化温度、磷化时间及复合促进剂对磷化质量的影响.磷化工作液的适宜配方为:工业氧化锌5.5g/L,工业氯酸钠2.5g/L,工业硫酸镍2.6g/L,复合促进剂4.0g/L.常温下试件在该磷化液中形成的膜层CuSO4点滴试验时间＞80 s,3%NaCl溶液浸渍时间＞6 h,室内挂片60d无明显锈蚀.     

常温生长类金刚石薄膜的实验研究

利用射频等离子体增强化学气相沉积(RFPECVD)工艺在常温下实现在不锈钢、硅片、玻璃等基底上大面积沉积类金刚石(DLC)膜.薄膜表面光滑致密,与衬底的结合力较高.用Raman,FTIR,SEM,EDX研究了薄膜的形貌、结构与组分.用栓-盘摩擦磨损试验机测试了薄膜的摩擦系数.通过优化沉积参数,所沉积的DLC膜在与100Cr6钢球对磨时摩擦系数低于0.01.在摩擦过程中DLC膜的磨损机制借助SEM进行了研究.     

维氏硬度试验中测量不确定度的评定

介绍了硬度测量不确定度的原理和方法。利用无偏差估计方法和考虑硬度计偏差的方法对维氏硬度试验中的测量不确定度进行了评定。并对两种方法评定的不确定度结果做了比较。     

Research About Microstructure and Wear Resistance of Hardfacing Layer on Cast Iron

It's simple technology to manufacture big trimming die by hardfacing on the base metal of cast iron. The chemical composition, microstructure, hardness, wear resistance and wear mechanism of the hardfacing layer were studied.The experimental results indicate that the hardfacing technology has much more advantages and cheaper than that of traditional process. The chemical composition, microstructure, hardness of the hardfacing metal are all satisfied for manufacturing the big trimming die by welding on cast iron. The wear resistant test of hardfacing layers were carried out by using two different electrodes. The wear resistance of new electrode hardfacing layer is higher than that of normal hardfacing electrode D322. The wear mechanism of hardfacing layer is belongs to abrasive wear model.     

烧结马氏体不锈钢的热处理

本文对烧结 4 10马氏体不锈钢的淬、回火行为进行了研究 ,分析了热处理工艺参数对该种烧结马氏体不锈钢硬度的影响 ,为优化烧结 4 10马氏体不锈钢的热处理工艺提供了技术参考     

The Influence of Rapid Annealing Cycles on the Recrystallisation Behaviour of Cold Rolled Ultra Low Carbon and Low Carbon Steel

For ultra low carbon (ULC) and low carbon steel (LC), the influence of heating rate, annealing temperature, and holding time on the recrystallisation behaviour and the resulting grain size was investigated. For ULC smallest grain sizes of about 9 μm were obtained at the lowest heating rate whereas for LC significant smaller grain sizes of about 5 μm were determined at the highest heating rate. Furthermore, the evolution of the grain size distribution with varying heating rate, annealing temperature, and holding time was studied in dependence of the rolling and normal direction. The state of the as‐hot rolled microstructure as well as the precipitation state exert a strong influence on the development of the recrystallised microstructure along the different directions for both steel grades. The inherent prolonged microstructure due to the cold rolling process is still obvious just after recrystallisation. With ongoing annealing and grain growth, the aspect ratio approaches the equiaxed state. This change proceeds faster for the ULC steel grade. With increasing annealing temperature, the bimodal character of the grain size distribution disappears and the distribution becomes more homogeneous.     

On the orders of transformation matrices (mod n) and two types of generalized Arnold transformation matrices

With the rapid development of information technology, more and more private and public information is distributed through the Internet. The problem of how to distribute information securely through the Internet has arisen. Recently, a lot of technologies have been developed to ensure the security of information. Information hiding[1] is one of these, ranging from digital watermarking, digital fingerprint to steganography. The scrambling transformation is one of the technologies of image infor…