大型移动复杂装备状态监测系统研究

实现对大型移动复杂装备的完整实时在线状态监测是一个非常有意义的研究课题。对用于大型装备局部状态监测的系统特点进行了描述，指出了其局限性；将传统的完整状态监测系统归纳为集中式完整状态监测系统，并依据装备端检测装置功能结构的不同，将集中式完整状态监测系统分为三类，指出了灰匣子系统的优势，以及在现有大型移动复杂装备上应用的难点。在对各类系统进行分析比较的基础上，提出了适用于现有复杂装备的分散式完整状态监测系统，对系统的基本思想进行了阐述。实例说明，该系统适于对现有复杂装备的完整状态监测。     

基于VMD和卷积神经网络的变工况轴承故障诊断方法

针对变工况条件下轴承故障数据无法大量获取以及诊断困难的问题,提出了基于变分模态分解和卷积神经网络的轴承故障诊断方法,使用稳态工况获取的数据训练,能对变工况下的数据实现有效诊断.首先对轴承振动信号进行变分模态分解,以获得有限带宽的固有模态函数;然后构建卷积神经网络模型,采用优化技术提高模型适应性,实现对固有模态函数的自适...     

砂土强度和剪胀性的颗粒力学分析

基于广义塑性理论与临界状态概念,研究提出了一个统一三维砂土本构模型,通过一组参数实现了砂土由压缩至剪切过程中状态参量的统一表述。基于ABAQUS提供的用户自定义材料子程序UMAT接口,利用Fortran语言编程实现了该三维弹塑性本构关系模型在软件中的二次开发。分别利用Toyoura砂、Fuji River砂以及Tokachi砂的剪切试验数据与数值模拟结果进行对比,结果表明：提出的有限元计算模型可以有效反映加载过程中不同围压和砂土初始密度对应力-应变曲线的影响,能够准确描述密砂的剪胀特性与应变软化特性以及松砂的剪缩特性与应变硬化特性,从而更加真实地反映三维应力状态下土的变形和强度特性。研究成果进一步扩展了ABAQUS在岩土工程中的应用范围,能够为岩土工程领域的数值分析计算提供更加快捷的解决方案。     

中热固相法制备掺杂钛的钒酸锂正极材料

以Li2CO3和V2O5为原料,用中热固相法制备了掺杂Ti4+的锂离子电池正极材料Li1.1V3―yTiyO8(y=0.05、0.1、0.2),并对其电化学性能进行了研究。研究表明,掺杂Ti能够很好地改善中热固相法产品的电化学性能,且当y=0.1时,Li1.1V3―yTiyO8循环性能最好,首次放电比容量高达250.9 mAh/g。     

基于文本规则的电网融冰决策技术

通过分析文本知识表达技术,重点介绍状态空间法、二值法和产生式系统。根据文本相关规定,对电网冰情制定了分级标准,对冰情的严重程度有了定量的衡量。通过提取文本元规则,选择控制策略,经过规则消除冲突,规则融合,得到1组新的规则集。在状态空间法的基础上,利用分级标准,结合二值法对规则集进行处理,得到1组能用数字和符号描述的规则集。在VFP软件平台上,根据规则集通过编程实现了不同类型电网融冰、除冰措施实施条件的决策。     

Structural, magnetic and dielectric properties of La2−xCaxNiO4+δ (x = 0, 0.1, 0.2, 0.3)

The synthesis, structural, magnetic and dielectric properties of a new type of high permittivity materials La_2−xCa_xNiO_4+δ (x = 0, 0.1, 0.2, 0.3) (abbreviated as LCNs) were reported. The samples were prepared through conventional solid state reaction route. Detailed structural information was retrieved by Rietveld refinement; normalized bond length and bond valence was calculated to investigate the compression/dilation effect of bonds and atoms in unit cell. It can be found all samples belong to K₂NiF₄ structure with space group I4/mmm. Doping of Ca in La₂NiO_4+δ shrinks the unit cell and makes the structure tend to become instable. Three types of (La, Ca)-O bonds, and two kinds of Ni-O bonds exist in LCNs. Along c axis there are alternately compressed (La,Ca)O₉ dodecahedra and lengthened NiO₆ octahedra. Room temperature magnetic measurements show that the materials are paramagnetic and Ca doping can improve the spontaneous magnetization. Furthermore, all samples have colossal values of the dielectric constant (?) at frequencies lower than 1 kHz. Interestingly, La_1.8Ca_0.2NiO_4+δ maintains its high permittivity at frequencies up to 1 MHz while La_1.7Ca_0.3NiO_4+δ has the lowest dielectric loss (tan δ). Calcium doping can effectively enhance ? and inhibit tan δ. The distortion of (La,Ca)O₉ dodecahedra can well explain their dielectric properties.     

Evaluating expectations about negative emotional states of aggressive boys using Bayesian model selection.

Researchers often have expectations about the research outcomes in regard to inequality constraints between, e.g., group means. Consider the example of researchers who investigated the effects of inducing a negative emotional state in aggressive boys. It was expected that highly aggressive boys would, on average, score higher on aggressive responses toward other peers than moderately aggressive boys, who would in turn score higher than nonaggressive boys. In most cases, null hypothesis testing is used to evaluate such hypotheses. We show, however, that hypotheses formulated using inequality constraints between the group means are generally not evaluated properly. The wrong hypotheses are tested, i.e.. the null hypothesis that group means are equal. In this article, we propose an innovative solution to these above-mentioned issues using Bayesian model selection, which we illustrate using a case study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

New optical material europium EDTA complex in polyvinyl pyrrolidone films with fluorescence enhanced by silver plasmons

In our search for efficient Luminescent Solar Concentrators (LSC) we have prepared polyvinyl pyrrolidone (PVP) films incorporated by ethylenediamine tetraacetic acid (EDTA) complex of europium and co-doped with silver nanoparticles (NPs). Steady state fluorescence was studied under weak and strong excitation. Dynamical study was performed by second harmonic of Nd laser. Under weak excitation the fluorescence of europium co-doped with silver plasmons increased by a factor of three and excited by continuous laser by a factor of 50. The lifetimes of films doped by the complex were 755 μs and co-doped with silver nanoparticles 946 μs. This is the first finding that the photon density accumulates the number of plasmons interacting with electronic states of europium increasing its transition probability resulting in the strong intensification of fluorescence. In dynamical measurements of lifetimes a single pulse does not provide enough energy to create such number of plasmons.     

隧道及地下工程岩体模型材料研究现状分析

归纳了当今国内外地质力学模型相似材料的研究现状,指出了常用相似材料的优缺点,并对测试相似材料力学特性的方法作了介绍,最终选取相似程度最好的模型材料,以更好的模拟实际条件。     

架空线路覆冰闪络跳闸特性分析与风险建模

极端冰灾天气下线路覆冰闪络跳闸是激发大电网脆弱性、导致大面积停电的重要因素。覆冰闪络跳闸等现象的风险评估是建立冰灾防御体系的基础。基于电网层面,进行了冰灾天气下线路覆冰闪络跳闸的风险状态识别与风险建模。根据覆冰闪络跳闸特性分析,界定了输电网绝缘系统的脆弱点,即覆冰期绝缘系统冰凌桥接、融冰期冰凌断流等临界点。进一步建立了覆冰闪络状态的划分原则与风险等级,并对预测冰况进行了模糊模式识别和风险评级,为运行人员提供了动态风险信息。针对数据的小样本、多输入等特点,采用统计学习理论结构风险最小化方法,构建了最小二乘支持向量机（least squares support vector machine,LSSVM）冰闪跳闸风险评估模型,依据贝叶斯（Bayesian）证据推理优化模型参数。通过与误差反向传播人工神经网络（artificial neural networkwith error back propagation,BP-ANN）算法对比,验证了该模型的有效性。最后通过脆弱性指标分析了网架结构破坏的严重性与电网绝缘系统的脆弱性。