Aspects of scanning microdensitometry. III. The monochromator system.

Microdensitometric errors can result from various factors associated with the monochromator system, including imperfect monochromaticity of the light, incorrect setting of the wavelength, and non-uniform illumination of either the microscopic field or the objective aperture. Certain types of potential error are characteristic of particular instruments. Thus in the Vickers M85 microdensitometer, where the flying spot is the reduced image of a hole situated at the monochromator exit aperture, the interpretation of results obtained with different spot sizes is complicated by the fact that the hole size affects both the spatial resolution and the spectral bandwidth of the system. Similarly, in instruments in which the monochromator exit slit lies in an aperture plane the numerical aperture of the whole system may be affected by the spectral bandwidth and vice versa. Overall instrumental sensitivity is mainly limited at the blue and red ends of the spectrum respectively by the lamp output and the photomultiplier tube sensitivity. Quartz-iodine lamps are slightly brighter than conventional tungsten sources, especially at short wavelengths, but tend to be less stable photometrically and are more expensive. Simple refracting monochromators and graded-spectrum interference filters in general pass more light, in the visible spectrum, than do grating monochromators of similar bandwidth. Most errors of wavelength setting can be avoided by routinely measuring at that wavelength, lambda(max), found empirically to give the maximum absorbance or integrated absorbance. Off-peak wavelengths can be set reproducibly with the aid of an eyepiece spectroscope, or by adjusting the wavelength so that the absorbance of a given specimen is some precise fraction of that at lambda(max).     

第25卷第1期英文摘要

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Some granular aspects of E.H.L. traction

A phenomenological examination of traction in elastohydrodynamic lubricated contacts shows there is a direct analogy with shear behaviour of beds of granules. The behaviour of a supposed granular lubricant under shear is formulated with regard to packing arrangements and agrees well with experimental results. The possibility of actual granularity in high-pressure lubricants is discussed and suggestions are made for methods of testing the hypothesis and for future work.     

第25卷第2期英文摘要

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IMTS 96美国国际制造技术展览会综述

在1996年芝加哥国际制造技术展览会上打出展示“跨入21世纪机械制造技术”的口号,吸引了来自30多个国家和地区的1300多个参展单位,在10万m~2的展览会场上展示了世界最新的机床制造技术及其设备,参观者创下了超过12万余人的新纪录。本文将从这次展览会上展出的展品来看当前机床制造技术发展中一些值得关注的动向,并作简要介绍。     

Stamping of Nonuniform Channels. 5. Calculation Methods for Channel Extrusion. 5.1. Formulas

Russian Engineering Research - Formulas are derived for the most important parameters of channel extrusion.     

Stamping of Nonuniform Channels. 5. Calculation Methods for Channel Extrusion. 5.3. Extrusion of Hardening Materials

Russian Engineering Research - Channel extrusion is studied experimentally for hardening materials. Comparison of the experimental and theoretical results shows that the formulas are highly accurate.     

Stamping of Nonuniform Channels. 5. Calculation Methods for Channel Extrusion. 5.2. Extrusion of Nonhardening Materials

Russian Engineering Research - Channel extrusion is studied experimentally for nonhardening materials. Comparison of the experimental and theoretical results shows that the formulas are highly...     

Stamping of Nonuniform Channels. 6. Fibrous Structure in Channel Extrusion. 6.1. Basic Principles

Russian Engineering Research - The importance of predicting the fibrous structure of extruded parts is established. Some incorrect statements about channel extrusion in the literature are noted. A...