分形图像分析及其在纳米ZnO中的应用

研究了分形图像的分析过程,利用MATLAB软件完成了分形维数计算程序的设计.并提取了纳米ZnO透射电镜像的分形图像,利用分形维数计算程序计算其分形维数,证明这种图像数字化方法能对纳米ZnO的形态进行评判,从而实现了定量描述纳米ZnO的形态.     

爆破振动信号时频特征的三维分形特性研究

为进一步研究爆破振动信号能量特征,基于小波包变换方法对爆破振动信号时频能量特征进行分析。在二维矩形盒维数模型的基础上建立了计算三维曲面分形盒维数模型,并计算得到实测爆破振动信号时频能量谱的三维分形盒维数D3d=2.148 8。该分形维数满足空间分形条件2D3d3,验证了爆破振动信号时频能量谱具有三维分形特征。经研究三维分形曲面盒维数D3d与其剖面二维分形盒维数D2d之间的数值关系,表明计算空间分形曲面分维数的常规假设D3d=D2d+1并非严格成立。研究表明,所提出的长方体覆盖空间曲面的分形维数计算方法可行、有效,为进一步研究爆破振动信号特征、控制爆破地震效应提供了新的研究思路。     

纳米3Y-TZP陶瓷粉体形貌的分形分析

为了应用分形理论确定纳米3Y－TZP粉体制备方法的优劣，采用共沸蒸馏法和醇水溶液加热法制备了纳米3Y－TZP粉体，利用TEM观察确定了粉体粒径尺寸和团聚体形貌，并运用分形理论分析了分形维数和粉体烧结性能的关系。结果表明：纳米粉体在颗粒尺寸相同的情况下，粉体分形维数越低，团聚体半径越小，烧结性能越好；对粉体TEM图像进行分形维数计算并与粉体红外光谱分析和烧结结果进行了比较，确定醇水溶液加热法制备纳米3Y－TZP粉体效果较好。     

基于数学形态学分段分形维数的电机滚动轴承故障模式识别

电机轴承是旋转机械中应用最广且最易损坏的机械零件之一,分形维数可以有效地描述滚动轴承振动信号的复杂性和不规则性。基于数学形态学的分形维数具有计算速度快,估计准确的特点,可以正确地区分滚动轴承系统的状态和判断轴承系统的故障行为。本文阐述了基于数学形态学的分形维数计算方法,,针对扁平结构元素长度的选取缺乏指导性的问题,提出一种基于数学形态学的分段分形维数计算方法,运用该方法对电机轴承实测信号进行分析,结果表明,该方法在一定程度上提高了分形维数计算的科学性和精确性,在电机轴承故障模式识别领域是行之有效的。     

水泥砂浆断面形貌像素点法与投影法分形的计算对比研究

为对比分析像素点覆盖法和投影覆盖法计算水泥砂浆断口分形维数的优缺点,采用这2种方法分别计算水泥砂浆在3种不同养护龄期下的断面分形维数,探索分形维数与抗压强度之间的关系。结果表明,像素点覆盖法计算得到的断口分形维数为2.258 0～2.265 6,相关系数为0.988 6～0.989 3,计算精确度高,数值变化区间小;投影覆盖法计算得到的断口分形维数为2.856 0～2.918 9,相关系数为0.921 4～0.935 2,计算精度较差,但数值变化区间大,有利于实际应用,与抗压强度呈良好相关性。     

异步轧制Pb-Ca-Sn-Al合金晶界节点分形分析

为了确定晶界节点分形维数是否存在,以低碳钢冷轧薄板标样为研究对象,在MATLAB软件平台上自行开发了晶界分形维数计算程序,采用标准分形图形-koch曲线检验了自开发分形程序的准确性,利用该程序计算了3种标准下(不同晶粒延伸度)不同晶粒度级别的金相图片晶界节点分形维数,并研究了不同工艺条件下Pb-Ca-Sn-Al合金晶界节点的分形维数.结果表明:自开发的分形计算程序准确;晶界节点的分形维数存在;不同工艺条件Pb-Ca-Sn-Al合金晶界节点的分形维数与工艺参数之间存在定量联系.在一定范围内,随着压下率、异速比、退火温度的增加,晶界节点的分形维数随之增加;随退火时间的增加,Pb-Ca-Sn-Al合金晶界节点分形维数先上升后下降;退火张力增加,晶界节点分形维数下降.     

形态学广义分形维数在发动机故障诊断中的应用

发动机故障信号是一种典型的非线性信号,分形几何理论为描述非线性故障信号的特性提供了一个有力的分析工具。广义分形维数能够很好的描述信号的几何特征和局部尺度行为,所蕴含的信息比单一的分形维数要深刻而全面。针对传统的广义分形维数计算方法的缺陷,本文提出基于数学形态学操作的广义分形维数计算方法,并对发动机正常、失火和气门间隙过大故障信号进行了分析,结果表明,与传统的盒计数法计算的广义分形维数相比,形态学广义分形维数能够更加有效地区分发动机在不同状态下的信号,并且数学形态学只涉及简单的加减和取大、取小运算,因此计算简单快速,为准确判断发动机故障状态提供了一种快速有效的新方法。     

高速铁路无砟轨道不平顺分形特征分析EI北大核心CSCD

无砟轨道不平顺作为线路服役状态的直接表征,一直是高速铁路检查与维修作业的核心。为了深刻而有效地掌握无砟轨道不平顺的时空分布特征,从分形几何的基础物理含义出发,确定轨道不平顺的分形特征,比选轨道不平顺分形维数的计算方法,通过分析典型高速铁路无砟轨道不平顺的累计检测数据,讨论分形维数进行轨道区段质量管理的可行性与合理性。结果表明:轨道不平顺具有典型自相似性和标度不变性的分形特征,各种分形维数方法进行轨道不平顺计算的结果具有显著差异性,变差法计算的精度、鲁棒性好,适合进行轨道不平顺分形维数计算;分形维数可以有效地表征线路轨道服役状态逐渐恶化的趋势,受线路作业维修干扰较少。建议结合线路具体养修条件,进一步对不同线路条件下轨道不平顺分形维数特征进行深入研究。     

一类递归集的Hausdorff维数

对由自相似压缩映射生成的递归集，引入了一种网测度α（Ｅ），证明了它与Ｈａｕｓｄｏｒｆｆ测度最多在一点上不相等．由此给出了这类递归集的Ｈａｕｓｄｏｒｆｆ维数。简化了部分分形集维数的计算，并以例子说明．     

分形理论在定向凝固固—液界面中的应用

本文叙述了分形理论中镍基高温合金定向凝固固－液界面研究中的应用。从分形的基本理论出发，论证了定向凝固固－液界面是一种不规则的分形结构，并用分形维数的新方法定量地描述了固－液界面和生长形态，给出了界面分形维数与凝固速率之间的关系。发现随着凝固速率的增加，固－液界面的分形维数呈指数规律增加，而且，从热力学角度对分形维数不仅仅是单纯描述不规则图形的几何参量，而是对一个依赖于凝固参数而变化的态函数做了较为     

LRZ-4型微机自控连续乳化炸药生产线技术的研究及应用

文章介绍了LRZ－4型微机自控连续乳化炸药生产线的工艺,自控系统的设计,关键设备的研制及生产线的应用,并在此基础上详细阐述了该生产线所具备的安全,质量保障体系及独特的工艺技术。     

金属材料试样制备与力学性能试验结果的相关性 第一讲 试样的取样部位及机加工与力学性能试验结果的相关性

介绍了金属材料试样制备与力学性能试验结果的相关性。对国家标准中关于力学性能试验试样取样和机加工的要求、力学试验取样和制样过程中需要注意的问题、机加工质量的检验等问题进行了讨论。结果表明金属材料试验试样的制备与力学性能试验的结果有着非常密切的相关性,由于这个原因,力学试验试样的取样和机加工必须严格按照国家标准的要求进行,机加工后必须检验加工质量,以保证力学试验结果的正确性。     

Tuning Optimization for Second-Order Dynamic Filters for Random Signal Spectral Analysis

Initial formulas are derived for the spectral window of a narrow-band second-order dynamic filter and for the relative dispersion of the estimator for the spectral power density as measured by the correlation filter method, together with the general expression for the optimum tuning law for the filter damping coefficient for linear variation in the central frequency within the analysis band.     

A hybrid finite difference/helmholtz integral scheme for ultrasonic scattering

Two techniques for analyzing the scattering of elastic waves by flaws are combined in a hybrid model. One is a finite difference scheme for handling the details of the interaction with the flaw, the other is a Helmholtz integral scheme for extending the results into the far field. Results are given for the diffraction coefficients for a semi-infinite thin crack, and for a 270° corner.     

Kriterien des Betriebsfestigkeitsnachweises für die Festlegung der Versuchslaufzeit bei der Substitution von Stahl- durch Aluminiumbauteile am Beispiel von Nutzfahrzeugrädern

The experimental structural durability proof bases on a damage equivalent shortening of the design spectrum into a test spectrum with reduced length taking statistics founded safety factors into account. Historically, test spectra were first derived for steel parts using Woehler-lines for steel; the damage equivalence was calculated by applying the Palmgren-Miner rule with the modification according to Haibach. When aluminium parts were introduced later, the question arose, whether test spectra developed for steel parts could be applied without modifications for their durability proof. Caused by different slopes of aluminium before and after the knee-point, the test spectra derived for steel wheels result for aluminium components a lower cumulated damage in comparison to the design spectra. This fact requires a longer test duration for aluminium components when test spectra or proving grounds developed for steel components are used. By the example of steel and aluminium wheels for commercial vehicles with comparable fatigue critical areas, the material dependent features regarding the required test life for the structural durability proof of aluminium parts are demonstrated.     

A Rational Fundamental Equation of State for Pentafluoroethane with Theoretical and Experimental Bases

A fundamental equation of state for pentafluoroethane was established on the basis of not only assessment of the experimental data but also by introducing parameters for virial coefficients having a theoretical background in statistical thermodynamics. The equation of state has a range of validity for temperatures from the triple point up to 500 K and pressures up to 70 MPa. The estimated uncertainties of the equation are 0.1% for the vapor pressure, 0.15% in density for the saturated-liquid phase, 0.5% in density for the saturated-vapor phase, 0.1% in density for the liquid phase, 0.1% in pressure for the gaseous phase, 0.5% in density for the supercritical region, 0.01% in speed of sound for the gaseous phase, 0.9% in speed of sound for the liquid phase, 0.5% in isobaric specific heat for the liquid phase, and 1.2% in isochoric specific heat for the liquid phase. The derived specific heats in the gaseous phase are close to the values from the virial equation of state with the second and third virial coefficients derived from intermolecular potential models and precise speed-of-sound measurements.     

Foreign Subsidiaries and Technology Sourcing in Spain

Firms acquire external technological knowledge via different channels. In this paper, we compare the technology sourcing of foreign subsidiaries and domestic firms looking at domestic R&D outsourcing, international R&D outsourcing, domestic cooperation for innovation and international cooperation for innovation. We use data from the Spanish Technological Innovation Panel for the years 2005–2009 for 10,206 innovative firms operating in Spain. We apply a multivariate probit specification which allows for systematic correlations among the different choices. The results show that the different technology sourcing choices are interdependent and that foreign subsidiaries show a different pattern of external technology sourcing. Compared to affiliated domestic companies, foreign subsidiaries show a smaller propensity for external technology sourcing via R&D outsourcing from independent firms in the host country, for international R&D outsourcing and for international cooperation for innovation. In contrast, foreign subsidiaries show a greater propensity for domestic cooperation for innovation. However, foreign subsidiaries are not a homogenous group in this respect.     

Treasure of the Past IX: Exposure Standardization of Iodine-125 Seeds Used for Brachytherapy

A method for calibrating iodine-125 seeds in terms of exposure has been established. The standard free-air ionization chamber, used for measuring soft x rays, was chosen for the measurements. Arrays of four to six seeds were used to enhance the ionization-current-to-background-current ratio. Seeds from an array were measured individually in a re-entrant chamber. The quotient of the exposure rate for the array by the sum of the ionization currents in the re-entrant chamber is the calibration factor for the re-entrant chamber. Calibration factors were established for three types of iodine-125 seeds. The overall uncertainty for the seed exposure calibrations is less than 6%.     

Approximating the risk for time-to-failure models through using statistics of extremes

This paper studies the approximation of the partitioned multiobjective risk method's (PMRM) extreme event risk function for time-to-failure models. The analytic expression of the approximation for the extreme event risk function is derived through the use of the statistics of extremes for the case where the underlying distribution is of an extreme-value type III for minima. This analytic expression provides an effective theoretical tool for understanding the behavior of conditional expected values for time-to-failure models for a large class of distribution functions used in reliability. The results are confirmed for example problems of exponential and uniform distributions.     

Viscosity and Thermal Conductivity Equations for Nitrogen, Oxygen, Argon, and Air

New formulations for the viscosity and thermal conductivity for nitrogen, oxygen, argon, and air are given. Air is treated as a pseudo-pure fluid using an approach adopted from previous research on the equation of state for air. The equations are valid over all liquid and vapor states, and a simplified cross-over equation was used to model the behavior of the critical enhancement for thermal conductivity. The extrapolation behavior of the equations for nitrogen and argon well below their triple points was monitored so that both could be used as reference equations for extended corresponding states applications. The uncertainties of calculated values from the equations are generally within 2% for nitrogen and argon and within 5% for oxygen and air, except in the critical region where the uncertainties are higher. Comparisons with the available experimental data are given.