一种改进的推广能力衡量准则

通过对支撑向量机推广能力的分析 ,提出了一种构造性的与样本分布有关的推广能力衡量准则 .该准则与统计学习理论中的推广能力准则具有几何上的一致性 ,由样本的二阶统计量构成 ,比已有的完全不依赖于样本分布的推广能力上界更能反映学习过程的收敛性和收敛速率 .较为重要的一点是该准则在学习过程之前是可处理的 ,所以它可以用作所有分类器中数据预处理的准则 ,同时也可以为支撑向量机模型的选择提供依据 .文中最后给出的人工及实际的例子也很好地说明了该准则的合理性 .

以新版《检测和校准实验室能力认可准则》(CNAS-CL01:2018)要求开展检测方法验证的问题及解决方法

检测实验室中检测结果的准确性至关重要,对标准检测方法的验证是获得检测结果准确性的重要前提;对申请CNAS认可的实验室而言,如果方法验证不符合认可准则的要求,将直接造成申请的技术能力不予认可。本文依据《检测和校准实验室能力认可准则》的要求,以实际发生的案例为例,通过分析问题产生原因,从体系文件的控制、方法验证技术操作、记录的规范填写等3个方面,对实验室开展方法验证的方法进行全面细致地讲解,以期用于指导实验室有效地开展方法验证工作。

制定人员能力准则的方法和体会

一、对于94版“培训”这一要素。在提法。

温湿度及纸箱尺寸对堆码强度影响的实验研究

考虑远洋运输及全球气候变化,进行了纸箱堆码强度实验。重点考虑温度、湿度、尺寸对堆码强度的影响。根据国家标准,设计了4种箱型,每种箱型共取33个实验点,每点3个纸箱,环境处理5h。实验结果表明:湿度是强度的最大影响因素,尺寸次之,温度影响不明显。按单位面积的压溃力进行纸箱强度相对比较,比较过程合理。从这个角度讲,小纸箱承载能力要高。将堆码强度作为约束引入到UpSide Up箱型的装填布局,提出了承载能力准则。

Response and energy dissipation of rock under stochastic stress waves

The response and energy dissipation of rock under stochastic stress waves were analyzed based on dynamic fracture criterion of brittle materials integrating with Fourier transform methods of spectral analysis. When the stochastic stress waves transmit through rocks, the frequency and energy ratio of harmonic components were calculated by analytical and discrete analysis methods. The stress waves in shale, malmstone and liparite were taken as examples to illustrate the proposed analysis methods. The results show the harder the rock, the less absorption of energy, the more the useless elastic waves transmitting through rock, and the narrower the cutoff frequency to fracture rock. When the whole stress energy doubles either by doubling the duration time or by increasing the amplitude of stress wave, ratio of the energy of elastic waves transmitting through rock to the whole stress energy (i.e. energy dissipation ratio) is decreased to 10%-15%. When doubling the duration time, the cutoff frequency to fracture rock remains constant. However, with the increase of the amplitude of stress wave, the cutoff frequency increases accordingly.

苦练内功——质检机构生存发展之本

目前，我国一些地区的检测市场竞争日益激烈。如何求生存、谋发展。已成为现阶段质检机构面临的重大课题。

A study of the energy yield criterion of geomaterials

The study results of the internal friction character of geomaterials conclude that the internal friction exists in mechanical elements all the time having a direction opposite to the shear stress,and the deformation failure mechanism of geomaterials greatly differs from that of metals. For metals,the failure results from shear stresses make the crystal structure slip; whereas for geomaterials,owing to its attribute of granular structures,their deformation follows the friction law,it is the co-action of shear stresses and perpendicular stresses that makes grains overcome the frictions between them,thus leading to the final failure of relative sliding.Therefore,on the basis of the cognition above,a triple shear energy criterion is proposed. Its corresponding Drucker-Prager criterion for geomaterials is also given. The new criterion can be rewritten to the Mohr-Coulomb criterion by neglecting the effect of the intermediate principal stress,and to the Mises criterion by not taking the internal friction angle into consideration. Then the studies of yield criteria commonly used are conducted systematically from the points of stress,strain and energy of geomaterials. The results show that no matter which expression form of stress,strain or energy is used for the yield criterion,the essence is the same and the triple shear energy yield criterion is the unified criterion of materials. Finally,the experimental verification is conducted in connection with the practical application of the triple shear energy yield criterion in an engineering project,and the calculation result shows that the Mohr-Coulomb criterion which only takes the single shear surface into account is more conservative than the energy criterion that does consider the effect of triple shear surfaces.

Application of Fuzzy-AHP method in the evaluation of logistics capability in e-commerce environment

In order to solve the complex problem of evaluation of logistics capability in e-commerce environment, an index system model of logistics capability is established based on the method of Fuzzy-AHP in this paper. The results show that the method of Fuzzy-AHP is a powerful and flexible multi-criteria decision-making tool for dealing with complex problems where both qualitative and quantitative aspects need to be considered, and the human preference model is uncertain and decision-makers are reluctant or unable to assign exact numerical values to the comparison judgments. The evaluation model of logistics capability based on method of Fuzzy-AHP can help to make an effective decision in the evaluation of logistics capability. By this way we can effectively deal with the uncertainty and vagueness in the evaluation process of logistics capability. Logistics companies can diagnose their own weaknesses in the area of logistics and enhance their competitiveness.

A NEURAL FUZZY INFERENCE SYSTEM

This paper proposes a new neural fuzzy inference system that mainly consists of four parts. The first part is about how to use neural network to express the relation within a fuzzy rule. The second part is the simplification of the first part, and experiments show that these simplifications work. On the contrary to the second part, the third part is the enhancement of the first part and it can be used when the first part cannot work very well in the fuzzy inference algorithm, which would be introduced in the fourth part. Finally, the fourth part "neural fuzzy inference algorithm" is been introduced. It can inference the new membership function of the output based on previous fuzzy rules. The accuracy of the fuzzy inference algorithm is dependent on neural network generalization ability. Even if the generalization ability of the neural network we used is good, we still get inaccurate results since the new coming rule may not be related to any of the previous rules. Experiments show this algorithm is successful in situations which satisfy these conditions.

Failure behavior and criteria of metallic glasses

Metallic glasses(MGs)constitute an emerging class of advanced structural materials due to their excellent mechanical properties.However,brittle failure at room temperature and the resultant complicated fracture behavior greatly limit their wide engineering applications.Over the past decades,the deformation and fracture in ductile or brittle mode referring to material compositions,load conditions,sample size,etc.,have been widely studied,and significant progress has been made in understanding the failure behavior of MGs.Micromechanisms of fracture have been revealed involving shear banding,cavitation and the nature of the crack tip field.The ductile-to-brittle transition and inherent governing parameters have been found.To well describe and predict the failure behavior of MGs,failure criteria for ductile and brittle MGs have been established empirically or based on atomic interactions.In this paper,we provide a detailed review of the above advances and identify outstanding issues in the failure of MGs that need to be further clarified.