眼轴长度测量方法及进展研究

为配合临床实现人工晶体屈光度数计算,以及为日常眼病预防提供依据,眼生物参数测量特别是眼轴长度测量逐渐被人们所重视。以眼轴长度为目标,论述了现有的眼轴长度测量方法,包括超声测量方法和光学测量方法。重点概述了光学部分相干原理,低相干原理和光学相干层析(OCT)技术在眼轴长度测量方面的研究进展,分别介绍了各方法及典型仪器的测量原理、测量精度及范围,论述了眼轴长度测量的发展方向。光学测量方法以其无损伤、快速、高精度等优点逐渐替代了超声测量方法,但对于晶体混浊眼还需依靠超声测量方法。     

光学舱装配中轴向间隙测量的改进

传统的轴向间隙的测量采用塞尺,存在一定的弊端,采用新的在被测部件上施加一定的拉力,同时用百分表测量轴向间隙的办法,可克服传统测量轴向间隙的弊端,而且准确、具体.     

轴向车铣工件表面粗糙度的研究

给出院 轴向车铣工件理论粗糙度的数学模型,分析了主要工艺参数对工件理论粗糙度的影响,并通过实验对工件的表面粗糙度进行了分析,得到用轴向车铣完全可实现零件的精加工。     

Experimental investigation on the effect of axial gap on performance and unsteady pressure pulsations of low head axial flow hydraulic turbine

The stable operation of axial flow turbines (AFTs) in the energy conversion process directly affects their safety and performance. Because of its unstable pressure features, a dynamic analysis of its internal flow characteristics is required. To analyze, evaluate, and compare the pressure variation within the turbine under the base gap (Ƣ = 0.05D) and different axial gaps (Ƣ) of 0.09D, 0.14D, and 0.18D, a reliable measurement approach is required. Pressure sensors were installed on the flow domain of the AFT to measure dynamic pressure pulsation under various Ƣ and running flow conditions. Based on the experimental result, a 28% and 2.8% increase in turbine efficiency was recorded when the Ƣ was increased from 0.05D to 0.09D at 0.8Q_d (design flow rate) and 1.0Q_d, respectively.Further analysis of the frequency spectra reveals different unsteadiness in the flow structures due to changes in Ƣ which resulted in various excitation signals. A decrease in the Ƣ leads to an increase in pressure pulsation intensity. Consequently, AFT with Ƣ of 0.09D was recommended since it provides maximum efficiency with fewer pulses compared with Ƣ = 0.05D, where the vibrations are at peak value. The findings above will aid in the optimum use of energy resources since energy generated from AFT is clean and free of pollution and can lead to a sustainable energy generation process.     

用于工业三维点测量的接触式光学探针

为了快速、准确地获得大尺寸工业产品或带有深槽孔工件的关键点三维坐标,本文基于工业近景摄影测量理论、立体视觉技术等,研究并实现了两种工业便携式、接触式光学探针测量系统。研究了测量系统涉及的探针设计、探针标定以及三维点解算等关键技术,设计了点阵式和手持相机式两种适用于不同工业场合的工业探针。针对点阵式探针的测量,提出了一种用于解算探针坐标系与世界坐标系相对关系的点云匹配方法。此外,采用拟合虚拟球的方法准确标定了两种探针的内部参数。最后,通过对比标准球与三坐标测量机的测量结果,得到系统的测量精度可达0.1 mm/m。该精度满足一般大、中型工件的三维点测量精度标准。     

示波器探头的选择与校准

本文以常用的无源电压探头为例，论述了无源电压探头的工作原理，频率特性，探头的选择以及探头的正确使用方法和探头的校准。     

滚珠丝杠副轴向静刚度立卧检测方案对比分析

在分析了轴向静刚度影响因素的基础上,针对关键影响因素,从简化方案设计的角度出发,提出了卧式和立式两种检测方案并分别进行了试验装置的三维设计.对这两种方案分别进行了原理阐述、关键结构介绍以及优缺点总结,并着重说明了立式检测方案的几点独到之处.综合考虑整体结构、性能、造价以及试验效率等方面,立式检测方案优于卧式检测方案,并据此研制了滚珠丝杠副轴向静刚度立式试验装置.     

深沟球轴承密封槽尺寸测量方法分析

通过对不同尺寸的深沟球轴承密封槽尺寸测量方法的对比分析,阐述了各自的特点,并根据其特点提出了具体的适用范围。     

Observation of lattice fringes of the Si(111)–7×7 structure by reflection electron microscopy*

Lattice fringes of Si(111)–7×7 reconstructed surface structure in reflection electron microscopy (REM) are observed for the first time, and their characteristic features are presented. Due to a glancing reflection condition in REM, the fringes with a spacing of 2.3 nm of the 7×7 surface structure lattice are seen in a region of a certain defocus range (about 6–8 μm) in a foreshortened image. The glancing reflection geometry also results in a complicated dependence of fringe directions on imaging conditions (beam alignment, crystal orientation). A shift of the fringes across the surface atomic steps and out of phase boundaries is observed.     

测量与控制系统精度评价的熵方法

通过对传统测控系统误差的分析,建立测量与控制系统精度评价的熵方法分析通用模型。为消除量纲对熵值计算的影响,并使连续变量离散化,提出以分辨率为单位对量程区间进行刻划(即“刻度概率”),进而推导建立静态和动态熵方法不确定度评价指标体系,为测量与控制系统精度的进一步分析提供了依据。     

亚音速轴流压气机转子子午流面上的流场模拟

以具有试验数据的某亚音速轴流压气机转子为研究对象,建立了子午流面上的流场模型,采用有限差分法求解转子子午流面的控制方程.计算结果与试验数据进行了对比,比较的结果说明模拟的结果能够满足工程应用的需要,并且从气流参数分布规律的角度对转子设计的合理性进行了分析.     

Specimen preparation methods for the examination of surfaces and interfaces in the transmission electron microscope

Various techniques for the preparation of cross-sectional and plan view TEM specimens of surfaces and interfaces are described. Particular emphasis is given to preparative methods which are both generally applicable and which minimize differential thinning of the materials present on either side of the interface of interest, thereby improving the reliability of the approach.     

Application of nanoparticle tracking analysis platform for the measurement of soot-in-oil agglomerates from automotive engines

Nanoparticle Tracking Analysis (NTA) has been applied to characterising soot agglomerates of particles and compared with Transmission Electron Microscoscopy (TEM). Soot nanoparticles were extracted from used oil drawn from the sump of a light duty automotive diesel engine. The samples were prepared for analysis by diluting with heptane. Individual tracking of soot agglomerates allows for size distribution analysis. The size of soot was compared with length measurements of projected two-dimensional TEM images of agglomerates. Both the techniques show that soot-in-oil exists as agglomerates with average size of 120 nm. NTA is able to measure particles in polydisperse solutions and reports the size and volume distribution of soot-in-oil aggregates; it has the advantages of being fast and relatively low cost if compared with TEM.     

多倍捻锭子轴向磁力传动计算及其有限元分析

多倍捻锭子利用磁场作用力传递转矩,它的结构参数、永磁体分布影响磁力的大小变化,因此需要进行轴向磁力计算。针对轴向磁力传动结构,由经验求解法和等效磁荷原理建立磁力计算数学模型,采用有限元分析软件,通过仿真与计算,探讨磁力线、磁感应强度和磁场强度分布,研究不同计算方法时的磁转矩值,为轴向磁力传动结构优化设计和磁路分布提供依据,具有重要的实际应用价值。     

63CY14-1B轴向柱塞泵结构改进设计

针对轴向柱塞泵噪声大,返修率高的情况,进行结构改进,降低了泵的噪声,提高了泵的性能。并进行了新旧泵的噪声对比试验,验证了改进效果。     

Investigation of the analysis parameters and background subtraction for high-k materials with atom probe tomography

In this paper we present depth profiles of a high-k layer consisting of HfO₂ with an embedded sub-nm thick ZrO₂ layer obtained with atom probe tomography (APT). In order to determine suitable measurement parameters for reliable, reproducible, and quantitative analysis, we have investigated the influence of the laser energy and the specimen temperature on the resulting elemental composition. In addition we devise a procedure for local background subtraction both for the composition and the depth scale that is crucial for gaining reproducible results. We find that the composition of the high-k material remains unaffected even for extreme laser energies and base temperatures, while higher laser energies lead to an accumulation of silicon at the upper interface of the high-k layer. Furthermore we show that APT is capable of providing sub-nm depth resolution for high-k materials with high reproducibility, good compositional accuracy, and high measurement yield.     

工程机械轴向柱塞泵车载松靴故障诊断报警装置的研究

通过调查统计,确定以松靴故障作为工程机械轴向柱塞泵车载故障诊断装置的诊断目标．经过分析讨论,将油液的温度信号作为特征信号,以单片机作为工程机械上轴向柱塞泵松靴故障诊断报警装置的控制核心,并对报警装置中软硬件设计作了简要介绍。     

电磁动态挤出机转动与轴向振动之间特性关系研究

简要介绍了电磁动态挤出机的基本特征,通过实际螺杆简化成广义螺杆建立了振动的力学模型.通过实验测定了转速与振幅频率之间的关系,并通过实验验证了理论分析的合理性,并得到结论:在一定范围内,转速越高(低)螺杆轴向振动振幅越大(小),当其他条件确定时,转速随振幅或频率的增大而减小,但降低的幅度不大.     

Comparison of the axial resolution of practical Nipkow-disk confocal fluorescence microscopy with that of multifocal multiphoton microscopy: theory and experiment

We compare the axial sectioning capability of multifocal confocal and multifocal multiphoton microscopy in theory and in experiment, with particular emphasis on the background arising from the cross‐talk between adjacent imaging channels. We demonstrate that a time‐multiplexed non‐linear excitation microscope exhibits significantly less background and therefore a superior axial resolution as compared to a multifocal single‐photon confocal system. The background becomes irrelevant for thin (< 15 µm) and sparse fluorescent samples, in which case the confocal parallelized system exhibits similar or slightly better sectioning behaviour due to its shorter excitation wavelength. Theoretical and experimental axial responses of practically implemented microscopes are given.     

Optimisation of mass ranging for atom probe microanalysis and application to the corrosion processes in Zr alloys

Atom probe tomography uses time-of-flight mass spectrometry to identify the chemical nature of atoms from their mass-to-charge-state ratios. Within a mass spectrum, ranges are defined so as to attribute a chemical identity to each peak. The accuracy of atom probe microanalysis relies on the definition of these ranges. Here we propose and compare several automated ranging techniques, tested against simulated mass spectra. The performance of these metrics compare favourably with a trial of users asked to manually range a simplified simulated dataset. The optimised automated ranging procedure was then used to precisely evaluate the very low iron concentration (0.003-0.018 at%) in a zirconium alloy to reveal its behaviour in the matrix during corrosion; oxygen is injected into solution and has the effect of increasing the local iron concentration near the oxide-metal interface, which in turn affects the corrosion properties of the metal substrate.