The electrochemical reduction reaction of dissolved oxygen on Q235 carbon steel in alkaline solution containing chloride ions

Cyclic voltammetry, electrochemical impedance spectroscopy, and rotating disk electrode voltammetry have been used to study the effect of chloride ions on the dissolved oxygen reduction reaction (ORR) on Q235 carbon steel electrode in a 0.02 M calcium hydroxide (Ca(OH)(2)) solutions imitating the liquid phase in concrete pores. The results indicate that the cathodic process on Q235 carbon steel electrode in oxygen-saturated 0.02 M Ca(OH)(2) with different concentrations of chloride ions contain three reactions except hydrogen evolution: dissolved oxygen reduction, the reduction of Fe(III) to Fe(II), and then the reduction of Fe(II) to Fe. The peak potential of ORR shifts to the positive direction as the chloride ion concentration increases. The oxygen molecule adsorption can be inhibited by the chloride ion adsorption, and the rate of ORR decreases as the concentration of chloride ions increases. The mechanism of ORR is changed from 2e(-) and 4e(-) reactions, occurring simultaneously, to quietly 4e(-) reaction with the increasing chloride ion concentration.

对螺钉无轴向压力的高精度自动螺丝刀的设计

区别于现有的电动、气动螺丝刀工具,该螺丝刀系统在驱动螺丝时,能对螺钉头实现无轴向压力的调节。刀头在旋转的同时随螺钉轴向进给,转速与进给量匹配,保证刀头与螺钉不脱节。该系统调整精度高,刀头转动精度可达0.72°,其应用于断路器类低压电气产品的自动调试,对确保产品质量、提高生产效率具有积极意义。

旋转机械全息序列相似性匹配故障诊断方法

针对全息诊断分辨率低影响旋转机械故障诊断质量和自动化水平的问题,将时间序列相似性匹配的基本概念和方法引入故障诊断应用中,结合全息诊断信息融合分析旋转机械振动全貌的思想,定义了全息序列及其相似性度量模型,用类时间轴上的多维序列表征转子系统振动全貌,进而利用采用近似三角不等式与B+树结合剪枝策略的全息序列相似性匹配算法实现故障诊断。实验结果表明,该方法能够实现高质量的故障自动分类识别。

基于时间序列数据挖掘的旋转机械预诊断方法研究

基于状态的维护(CBM, Condition Based Maintenance)是近年来新兴的一种设 备维护策略，它的基本理念是在机械设备需要维护的时候才对其进行维护，强调 维护要及时、准确和经济。采用这种维护策略，能够提高工业生产的安全性和可 靠性，系统地降低企业运营成本。 机械设备状态预诊断是实现CBM 的核心支撑技术，对其进行深入研究，对推 动CBM 的发展具有重要意义。但是，由于相关研究起步不久，目前预诊断技术还 未能得到很好的实现，研究人员有必要不断地尝试各种新的有效方法来更好地解 决这一问题，加快其实现方法与技术应用的成熟进程。基于此，本文从数据挖掘 的角度，探索了机械设备预诊断新的解决方法和途径，深入研究和探讨了基于时 间序列数据挖掘的旋转机械预诊断方法。本文的主要工作包括： 1. 结合CBM 的基本理念和应用实际的需求，对机械设备状态预诊断的基本 内涵进行了系统分析。将状态评估、故障预测和剩余有效使用寿命预测三个预诊 断基本功能进一步抽象，提出了包含特征提取、状态预测和模式匹配三个子问题 的预诊断一般流程模式。在详细分析机械设备状态预诊断理论方法和应用技术研 究现状的基础上，提出了预诊断技术研究的发展趋势及各子问题的研究侧重点。 并对利用时间序列数据挖掘这一理论方法解决机械设备状态预诊断问题的可行性 进行了分析。 2. 针对具有波动频繁、噪声干扰严重等特点的原始振动量时间序列无法直接 用于旋转机械性能状态分析的问题，结合全息诊断信息融合分析旋转机械振动全 貌的思想，提出了全息状态矩阵的概念并给出定义，用类时间轴上的多维序列表 征转子系统振动全貌，以实现振动量时间序列的高级表示，为后续预测与匹配分 类工作提供良好的数据源，同时增强全息诊断的信息检索和知识自动获取的能力。 3. 将旋转机械性能状态预测，归结为旋转机械设备维护应用背景下的一维数 值型时间序列预测问题来进行深入研究。针对现有预测方法长期预测能力较弱， 且自动化水平低的不足，提出了用于旋转机械性能状态预测的ARIMA 动态间隔预 测法。该方法以动态间隔获取时间序列样本建模并预测的策略，提高了ARIMA 模 型用于设备状态长期预测的准确性，并且能够实现建模与预测的自动化，满足CBM 系统的实时性要求。 4. 针对全息状态矩阵表示的旋转机械性能状态特征数据，提出了一种全息状 态矩阵相似性匹配方法。结合旋转机械预诊断领域应用的特点定义了全息状态矩 阵的相似性度量模型，基于全息状态矩阵近似距离三角不等式设计了剪枝搜索策 略，并在此基础上设计了全息状态矩阵相似性高效准确匹配算法，不需要借助专家经验和人工识别确认，在一定阈值范围内能够实现高质量的旋转机械性能状态 相似性匹配。 5. 旋转机械基本振动量特征时间序列具有海量、超高维度、短期波动频繁和 大量噪声等特征，与时间序列数据挖掘传统应用的金融商业领域数据不同，直接 采用传统方法会存在搜索速度大幅度降低的问题。针对这一问题，提出了基于随 机投影的时间序列相似性搜索方法。该方法利用近年来新兴的随机投影统计学降 维法，将原始时间序列集映射到低维空间，并利用R*树进行索引，能够在保持高 准确率的同时，实现旋转机械基本振动量特征时间序列相似性快速搜索。 6. 针对现有机械设备性能状态分类方法不考虑误分类代价的问题，提出了一 种代价敏感直推式旋转机械设备性能状态分类法。该方法将代价敏感分类和直推 式学习的基本思想和理论相结合，采用一种代价敏感的直推式分类机制，实现了 机械设备性能状态的代价敏感分类。该方法在保证较高分类准确率的基础上，明 显地降低了误分类总代价。 7. 基于CBM 的基本理念，设计了旋转机械CBM 系统的基本结构，并以本 文理论方法的研究成果为核心，详细设计了各模块的基本功能和处理逻辑，采用 VC#.net 与Matlab 混合编程的方式开发了一个面向大型旋转机械的CBM 系统原 型，以验证本文机械设备预诊断方法研究成果的可操作性和实用性，为CBM 系统 应用技术研究做出了有益的探索。

一种光纤陀螺仪的开发

介绍了应用前苏联Fizoptika公司生产的 94 1 3AM光纤陀螺传感器 ,利用单片机最小系统开发了角速度测量和旋转角度测量仪 ,可测量旋转物体的角度和角速度 .给出了光纤陀螺仪的硬件组成、软件设计思想及标定方法

转子系统油膜振荡的小波包分解与频带能量比例特征分析

在介绍小波包分解原理的基础上 ,对试验测得的单盘单跨转子系统的油膜振荡非平稳信号用小波包分解方法进行了研究。采用db44小波基函数进行 4层小波包分解。给出了各频带内分解信号的特点及频带能量比例 ,其中第 3频带是该转子系统在 960 0r/min时产生油膜振荡的特征频带。得到的试验数据及其分析结果对转子系统油膜振荡研究和旋转机械状态监测等具有重要意义。

像平面与空间平面的变换及其在移动机器人中的应用

说明了像平面与空间平面的变换以及摄像机在固定，旋转和平移时变换矩阵的求解方法．还讨论了该变换在移动机器人定位，障碍物检测，运动参数分析和三维坐标计算上的应用。

计算机辅助机械绘图语言与系统设计

本文针对我国计算机绘制机械图领域内的现状,提出了一种易于掌握的机械图描述语言,以及一个相应的功能较强的绘图系统。该系统便于图形输入,并具有图形的平移、旋转、映射等功能,和较强的剖面域的处理能力。系统带有一个标注专用的笔写式字符库(包括汉字和专用符号)。该系统用 FORTRAN 语言写成,便于向大、中型计算机和存储容量较大的微型机移植。

旋转轴对称弱各向异性介质模型的射线追踪方法

Ray tracing is a rapid and effective method for wave field calculation. Not only in the field of seismic-wave theory, but also in the field of seismic inversion and migration imaging,the seismic ray tracing method has become one of the most important methods. In anisotropic media, group velocity and phase velocity have different propagation directions. The seismic wave propagates along the direction of group velocity , it does not depend on the direction of phase velocity. Ray angle is a complex function with respect to phase angle, it is difficult to measure and calculate. But most rocks are weak anisotropic, so the expression of phase velocity can be simplified greatly. Based on the approximate expression of phase velocity this thesis for rotating axisymmetric weak anisotropic media deduces an expression of the partial derivative of phase velocity and an expression of group velocity with the method of linear approximation. This paper uses the fourth order Runge-Kutta method together with the two-dimensional interpolation and linear interpolation to obtain the parameters of the physical locations. At last the paths of seismic wave in rotating axisymmetric weak anisotropic media are computed. According to the analysis of the computational results, it indicates that the method developed in this paper has strong adaptability, high computational efficiency and high accuracy for rotating axisymmetric weak anisotropic media.

运动与重定向时物-我、物-物空间表征的使用

Eight experiments tested how object array structure and learning location influenced the establishing and utilization of self-to-object and object-to-object spatial representations in locomotion and reorientation. In Experiment 1 to 4, participants learned either at the periphery of or amidst regular or irregular object array, and then pointed to objects while blindfolded in three conditions: before turning (baseline), after rotating 240 degrees (updating), and after disorientation (disorientation). In Experiment 5 to 8, participants received instruction to keep track of self-to-object or object-to-object spatial representations before rotation. In each condition, the configuration error, which means the standard deviation of the means per target object of the signed pointing errors, was calculated as the index of the fidelity of representation used in each condition. Results indicate that participants form both self-to-object and object-to-object spatial representations after learning an object-array. Object-array structure influences the selection of representation during updating. By default, object-to-object spatial representation is updated when people learned the regular object-array structure, and self-to-object spatial representation is updated when people learned the irregular object array. But people could also update the other representation when they are required to do so. The fidelity of representations will confine this kind of “switch”. People could only “switch” from a low fidelity representation to a high fidelity representation or between two representations of similar fidelity. They couldn’t “switch” from a high fidelity representation to a low fidelity representation. Leaning location might influence the fidelity of representations. When people learned at the periphery of object array, they could acquire both self-to-object and object-to-object spatial representations of high fidelity. But when people learned amidst the object array, they could only acquire self-to-object spatial representation of high fidelity, and the fidelity of object-to-object spatial representation was low.

High resolution time-of-flight spectrometer for crossed molecular beam study of elementary chemical reactions

In this article, we describe an apparatus in our laboratory for investigating elementary chemical reactions using the high resolution time-of-flight Rydberg tagging method. In this apparatus, we have adopted a rotating source design so that collision energy can be changed for crossed beam studies of chemical reactions. Preliminary results on the HI photodissociation and the F atom reaction with H-2 are reported here. These results suggest that the experimental apparatus is potentially a powerful tool for investigating state-to-state dynamics of elementary chemical reactions. (c) 2005 American Institute of Physics.

Benzene electro-oxidation in a PEMFC for phenol and electricity cogeneration

In the present investigation, the electrochemically-assisted oxidation of benzene in a H-2-O-2 proton exchange membrane fuel cell (PEMFC) for electricity and phenol cogeneration is studied. Experiments were carried out in a PEMFC electrochemical reactor using Pd black as cathode electrocatalyst at 60 and 80 degrees C, respectively and 1 atm back pressure. Indeed, it was found that the only product detected under the examined experimental conditions was phenol. The online GC product analysis revealed that it is impossible to produce phenol when the fuel cell circuit is open (I = 0) under all the examined experimental conditions. When the fuel cell circuit was closed, however, the phenol yield was found to follow a volcano-type dependence on the cur-rent of the external circuit. It was found that the maximum phenol yield was 0.35% at 100 mA/cm(2) at 80 degrees C. At the same time, the PEMFC performance was also investigated during the phenol generation process. Furthermore, experiments with the rotating ring disc electrode (RRDE) technique showed that the intermediate oxidation product, i.e. H2O2 existed during the oxygen electro-reduction process. The cyclic voltammograms showed that benzene was strongly adsorbed on the Pd surface, leading to a degradation of the PEMFC performance. (c) 2005 Elsevier B.V. All rights reserved.