The nearest neighbor and the bayes error rates

The (k, l) nearest neighbor method of pattern classification is compared to the Bayes method. If the two acceptance rates are equal then the asymptotic error rates satisfy the inequalities Ek,l + 1 ? E*(?) ? Ek,l dE*(?), where d is a function of k, l, and the number of pattern classes, and ? is the reject threshold for the Bayes method. An explicit expression for d is given which is optimal in the sense that for some probability distributions Ek,l and dE* (?) are equal.     

钢复合化学热处理的表层特性及应用

本文通过对比试验研究了20—Cr2Ni4钢经渗碳或氰化处理和渗碳或氰化与低温电解渗硫相结合的复合化学热处理以后的表面层特性和摩擦学行为。结果表明；渗碳或氰化后再进行低温电解渗硫可获得一具有层状结构的硫化物层。它不仅能够降低摩擦系数，而且能起到固体润滑作用。     

AN EXPERIMENTAL-NUMERICAL METHOD FOR MEASURING CRACK PROPAGATING VELOCITIES UNDER STRESS WAVE LOADING

An experimental-numerical method for measuring dynamic crack propagating velocities under stress wave loading is established in this paper. The experiments of the three-point bend specimen are done on the improved Hopkinson bar. Deflection of loading point, dynamic load and instantaneous crack length are measured, then crack propagating velocities are calculated. Experiments on 40Cr steel show that the results given by this method have a good agreement with that obtained by the resistance fracture gage method. Therefore this method is feasible for measuring crack propagating velocities under high loading rate and will have wide application.     

Influence of initial textures on dynamic recrystallization and textures in AZ31 magnesium alloys

1　INTRODUCTIONMagnesiumisthelightestmetallicstructurema terialwithhighspecificstrengthandthereforeiswidelyusedinautomotive ,electronicsandaerospaceindustries[1,2 ] .However ,magnesiumoftenshowsinsufficientplasticityatroomtemperatureduetoitsHCPstructurewithlessindependentsystemsofbasalslip .Toenhanceformabilityofmagnesium ,ahigherdeformingtemperatureisusuallyusedwithtwopur poses .Thefirstistoactivatenewslipsystemsbesidesbasalslip ,sothatmorethanfiveindependentslipsystemscanbeprovided ,be…     

锻钢的热成形性

<正> 锻件在均匀性、不能有孔隙和机械性能方面要满足严格的技术要求。因此,热成形的目的,不仅是锻出预期形状的毛坯,而且要把铸态组织尽可能压实,以消除任何孔隙。但是,如果得到足够成形性的条件已知,这个压实的任务就可以只由热成形来完成。已经有150种以上适合于制造锻件的商业用钢和实验用钢做过热拉伸试验,试验的目的是确定各种影响热     

陶瓷热障涂层技术及其在大功率柴油机上的应用

等离子喷涂陶瓷热障涂层是近年来极为引人注目的研究领域。本文介绍了热障喷涂层的材料、涂层结构和涂层的工艺技术，阐述了涂层的技术性能和损毁机理。本文报告了热障涂层在大功率柴油机上的应用研究进展和经过三千多小时在机车柴油机上运行试验的结果，并就今后进一步的发展提出了意见。     

TZM、TZC钼合金的表面氧化和内氧化

一、引言在钼中添加钛和锫(TZM、TZC)可阻碍1000～1400℃下钼的再结晶,为这些合金提供最佳的高温机械性能。钼合金中一般都含有过剩的碳,过剩的碳除起脱氧剂     

抗营养性植物次级代谢产物的潜在治疗性应用(三)

皂甙是甾醇(C27)的糖苷类化合物或三萜类(C30)皂角苷配基母核与一个或多个碳水化合物侧链相连(图11)。许多生长在温带的豆类植物含有各种皂甙，具有多种正面的和负面的生物学效应。由于皂甙的两面性及其表面活性性质，它是极佳的致泡剂，可形成非常稳定的泡沫。它们的生物学价值与其化学结构密切相关，化学结构决定了极性、疏水性和化合物的酸性。