小子样测定叶片S-N曲线试验方法研究

根据试验要求,对叶片在样本较少情况下测定其疲劳极限σ-1和S-N曲线。通过振动疲劳试验的方法进行研究,试验采用升降法选择所施加振动应力的水平,采用异方差回归分析方法进行疲劳试验数据的分析。最后获得叶片材料的均值S-N曲线和置信度为95%、可靠度为99.9%的P-S-N曲线,并得到各自曲线上的疲劳极限σ-1。此方法保证试验的顺利进行并且具有较高的可靠性,对于小样本测定材料的S-N曲线具有较好的实用价值。     

基于灰色系统理论的小样本动态测量数据处理

小样本动态测量不确定度评定一直是计量领域的热点,有别于传统的统计理论,文中应用灰色系统理论来实现小样本动态测量不确定度评定.首先通过对动态测量在各离散采样点所得小样本测量数据平均运算,再进行多项式高阶拟合,克服最小二乘法在高阶回归分析时的病态缺陷,得到精确的动态测量的期望函数.然后对各离散采样点上的小样本测量数据,按照累加生成原则进行处理,根据灰色系统理论,得到对应的不确定度信息,由此得到小样本动态测量结果.最后通过具体的小样本动态测量实例,验证了灰色方法、贝塞耳方法和蒙特卡罗方法的评定结果,并达到很好的一致性.     

煤矿型水胶炸药存储稳定性能测试

为确定煤矿型水胶炸药在储存过程中受到环境因素影响,是否会对煤矿型水胶炸药的安全稳定性能产生影响,特进行本次试验。试验采用小样本升降法得出半数引火量来确定炸药的可燃气安全值从而得出水胶炸药受到环境影响程度。试验结果表明:煤矿型水胶炸药在煤矿环境存储过程中的安全性可达400g以上,为水胶炸药的储存稳定性提供了理论依据。     

水下探测中继平台系统研究

水下升降中继控制系统能够依照控制策略实现天线仓的升降过程,通过水声通信机、卫星天线实现潜标与远程指挥机的周期性数据上传及指令下载。设计了系统的结构与通信方案,解决了水下小型排缆绞车、深水直流小功率电机、升降控制策略及通信协议等关键技术问题。介绍了锚系系统设计方案、工作流程、每个结构部分的功能需求及系统应用;通过预先设定的中继控制仓时间表,控制天线仓的升降,完善可靠的升降控制过程及通信协议,为系统功能的实现提供了条件。     

MB8镁合金高周疲劳实验研究

采用升降法对MB8镁合金室温高周疲劳行为进行实验研究。结果表明:利用升降法计算出MB8镁合金在应力比R=0.1,循环基数为107条件下的疲劳强度为90.2MPa,相当于其抗拉强度的34%左右;合金的疲劳裂纹萌生于试样表面,裂纹扩展区由小的平面状断面组成,没有明显的疲劳辉纹存在,合金疲劳断口呈现韧性断裂特征。     

基于秩的小样本粗差判别

根据小样本粗差判别的具体情况 ,提出使用新序列秩的最大熵估计法及一阶差分分位数法判别小样本粗差 ,这两种方法简单易行 ,便于实时处理 最后还给出了具体实例进行说明     

基于支持向量机的小样本响应曲面法研究

当影响因素和响应输出的关系较为复杂时,应用传统响应曲面法(RSM)、非参数响应曲面法(NPRSM)和人工神经网络(ANN)难以拟合真实的响应曲面,不仅需要大的样本量,而且泛化风险大,不易达到全局最优.将RSM归结为可有限制地主动获取样本的小样本机器学习问题,提出了一种基于支持向量机(SVM)的RSM.以大间隔网格取样,利用SVM拟合过程,对拟合方程寻优确定极值大致区域,再逐步缩小间隔求精.算例研究表明,该方法的拟合与泛化性能优于NPRSM和基于ANN的RSM,能在小样本条件下建立全局性数值模型,寻优可以得到多个极值.     

顺序统计量在小样本检验中的理论和方法研究

本文研究了均匀分布、指数分布和正态分布的顺序统计量的差商序列概率分布。讨论了它们在小样本检验问题中的应用。该理论和方法对武器装备小样本检验具有一定的意义。     

基于两空间线性鉴别分析的小样本人脸识别

指出了线性鉴别分析及其几种改进方法在处理小样本人脸识别问题时存在的不足,提出了一种基于两空间线性鉴别分析的小样本人脸识别方法.首先将样本投影到总体散布矩阵的非零空间中进行分析;进而将类内散布矩阵分成零空间和非零空间进行鉴别向量确定和鉴别特征提取,最后将得到的两种鉴别特征融合,从而使用最近邻法进行分类.实验结果表明,在进行小样本的人脸识别时,该方法的识别效果优于其他线性方法.     

大型旋转机械升降速过程故障诊断HMM-AR方法研究

由于大型旋转机械升降速过程振动的复杂多样性，对其进行监测能获得较平稳运行更多的机组状态信息。本文通过提取 Ａ Ｒ 系数反映振动特征，并将隐 Ｍ ａｒｋｏｖ 模型引入升降速过程故障诊断研究中，实验证明应用 Ｈ Ｍ Ｍ  Ａ Ｒ 法能较好地达到机组故障诊断目的。     

Subattomole sensitivity in biological accelerator mass spectrometry

The Uppsala University 5 MV Pelletron tandem accelerator has been used to study (14)C-labeled biological samples utilizing accelerator mass spectrometry (AMS) technology. We have adapted a sample preparation method for small biological samples down to a few tens of micrograms of carbon, involving among others, miniaturizing of the graphitization reactor. Standard AMS requires about 1 mg of carbon with a limit of quantitation of about 10 amol. Results are presented for a range of small sample sizes with concentrations down to below 1 pM of a pharmaceutical substance in human blood. It is shown that (14)C-labeled molecular markers can be routinely measured from the femtomole range down to a few hundred zeptomole (10 (-21) mol), without the use of any additional separation methods.     

Diffusion of clusters down (1 1 1) aluminum islands

The key factor determining nucleation processes and faceting in homoepitaxial growth as well as texture competition is the mobility of adatoms and small clusters across step edges and facets. Using a combination of molecular dynamics and ab initio calculations, we investigate the mechanisms of small clusters (dimer and trimer) diffusion down the aluminum (1 1 1) surface. In this paper we report results of molecular dynamics studies. Our study shows that the clusters dissociate at the step-edge of compact islands. As a result, the clusters diffuse down the step by an exchange mechanism with a small or medium Schwoebel barrier. The mechanism of this down-diffusion/dissociation is discussed and the corresponding energetics are calculated using the molecular statics method. We find a large anisotropy between the barriers at the two types of 1 1 0 oriented steps.     

Odor Recorder Capable of Wide Dynamic Recordable Range Based on Higher Order Sensing and Signal Extraction Technique for Small Signal

The odor recording method for extending dynamic recordable range was proposed. In this method, the enriched information obtained from higher order sensing based on preconcentrator with variable temperature was utilized so that the contribution of component with small ratio to sensor response could be separately extracted from that of the main component. Then, the signal extraction technique for small signal was developed using Savitzky-Golay filter for qualitative and quantitative detection of component with small ratio, and then this extracted information was used in recording process. It was found that the target odors including component with small ratio down to 1% were successfully recorded using this proposed method. This method is useful to extend the dynamic recordable range especially in the case that the component with high contribution in impression has low contribution to sensor responses.     

Deformation of varying thickness of conical shells subjected to axisymmetric loading with various end conditions

A conical shell subjected to uniform internal pressure is analysed by the finite element displacement method. The end conditions considered are clamped-clamped (CC), small end clamped-big end free (CF), and small end free-and big end clamped (FC). The semi cone angles considered are (=) 30, 45 and 60°. It is shown that by properly varying the thickness the deflections and stresses can be brought down considerably. The results are presented in the form of graphs and tables.     

基于分位数函数和Bootstrap分布的不确定度评定研究

最大信息熵方法是基于概率分布评定测量不确度的主要方法之一。其所依赖的高阶矩需要较大样本的测量数据,而校准/检测实验室的测量一般为小样本,故用最大熵方法评定小样本测量不确定度缺乏一定的可靠性。提出了基于分位数函数和概率权重矩作为约束条件的最大信息熵不确定度评定法,把矩的计算从高次降为一次,并结合遗传算法求解概率分布,用Bootstrap分布估计扩展不确定度和包含区间,解决了由分位数区间估计分布不对称所致的复杂计算问题。     

Micro‐ and Nanoprinting into Solids Using Reaction‐Diffusion Etching and Hydrogel Stamps

Micropatterned hydrogel stamps soaked in appropriate chemical etchants can imprint various types of micro‐ and nanoarchitectures into metals, conductive oxides, semiconductors, glasses, and crystals. Localized etching is mediated by a reaction‐diffusion process initiated from the stamp microfeatures and gives lateral resolution down to approximately 300 nm. The method is well suited for the rapid prototyping of small‐scale devices including multilevel microfluidic systems and curvilinear optical elements.     

The use of printed circuits in cryogenics as heat sinks for electrical temperature sensor leads

Errors can often occur in low temperature thermometry on account of heat conducted down the electrical leads to the sensors. One method of avoiding this is to fit small heat sinks close to and at the same temperature as the sensor itself. Small printed circuits of thin copper on Mylar prove both convenient and very efficient in this respect, and analysis of their mode of operation enables one to calculate the dimensions of a circuit to meet any specific application.     

Simulation Analysis and Experiment Study of Nanocutting with AFM Probe on the Surface of Sapphire Substrate by Using Three Dimensional Quasi-steady Molecular Statics Nanocutting Model

The three-dimensional quasi-steady molecular statics nanocutting model is used by this paper to carry out simulation analysis of nanocutting of sapphire in order to explore the effects of conical tools with different tip radii of probe and straight-line cutting at different cutting depths, on cutting force. Meanwhile, this paper uses a cutting tool of atomic force microscopy (AFM) with a probe tip similar to a semisphere to conduct nanocutting experiment of sapphire substrate. Furthermore, from the experimental results of nanocutting sapphire substrate, this paper innovatively proposes the theoretical model and equation that the specific down force energy (SDFE) during nanocutting by using AFM probe as the nanocutting tool, is approximately a constant value. This paper uses three-dimensional quasi-steady molecular statics nanocutting model to simulate calculation and obtain nanocutting down force. It is compared with the down force calculated by SDFE theoretical equation proposed for verification. As a result, the down force obtained by the paper's simulation is very close to the down force calculated by SDFE theory. Therefore, it can be verify that the three-dimensional quasi-steady molecular statics nanocutting theoretical model used by this paper is feasible. The SDFE proposed by this paper is defined as equating to down force energy dividing the removed volume of down press of the workpiece by the AFM probe. From the experimental data and the calculation results, it is found that the values of SDFE under different down force actions are almost close to a constant value. The three-dimensional quasi-steady molecular statics nanocutting sapphire workpiece model is to find the trajectory of each atom of the sapphire workpiecs being cut whenever the diamond cutter goes forward one step. It uses the optimization search method to solve the force equilibrium equation of the Morse force in the X, Y and Z directions when each atom moves a small distance, so as to find the new movement position of each atom, and step by step calculates the behavior during cutting.     

铝合金轮毂弯曲疲劳试验的有限元模型

在铝合金轮毂产品开发阶段,针对试压铸小批量样件来进行的弯曲疲劳试验,是必须通过的台架试验之一．为避免试验的盲目性,减少试验次数,从而降低试验成本,提高试验的可靠性,有限元数值分析技术被采用,并已成为铝合金轮毂开发的先进设计技术手段．为正确应用该技术进行虚拟台架试验,必须建立有效的计算模型．基于理论分析与应用实践,考虑螺栓预紧力影响的非线性接触,以及加载杆与轮毂的材料异同,建立了轮毂弯曲疲劳台架试验的3种有限元力学模型：加载杆与轮毂为同种材料的整体线弹性分析模型、加载杆与轮毂为不同材料的线弹性分析模型、考虑各元件间的接触关系及螺栓预紧力影响的非线性分析模型．通过分析与比较,以及典型轮毂的试验验证,研究了以上3种有限元力学模型的优缺点、应用范围及计算的可靠程度,并以典型轮毂为例,用试验验证了模型的准确性．研究表明：加载非线性模型较为准确;线弹性模型可以用于轮辐处易发生疲劳破坏的分析;加载杆与轮毂材料异同对最大等效应力影响不大;对螺栓孔附近易破坏的轮毂,应采用考虑预紧力影响及非线性接触的模型．     

分形方法导出改进的牛顿第二定律及万有引力定律

牛顿第二定律及万有引力定律是根据实验结果总结出来的。为了探讨从理论上导出这两个定律的可能性，根据能量守恒定律，给出用变维分形方法针对一个实例（小球沿长斜面滚下）导出改进的牛顿第二定律及万有引力定律的方法。具体给出了适用于实例的常维分形结果：改进的万有引力定律F=-GMm / r199989和改进的牛顿第二定律F=ma101458。