The Computer Industry: Growth and Evolution with Special Emphasis on Government Regulation and Antitrust, Selected References, 1974

This report provides bibliography of resources related to the growth of the computer industry that were published in 1974

Computed tomography for dimensional metrology

The paper gives a survey of the upcoming use of X-ray computed tomography (CT) for dimensional quality control purposes: i.e. for traceable measurement of dimensions of technical (mechanical) components and for tolerance verification of such components. It describes the basic principles of CT metrology, putting emphasis on issues as accuracy, traceability to the unit of length (the meter) and measurement uncertainty. It provides a state of the art (anno 2011) and application examples, showing the aptitude of CT metrology to: (i) check internal dimensions that cannot be measured using traditional coordinate measuring machines and (ii) combine dimensional quality control with material quality control in one single quality inspection run

Koordinatenmessung mit industrieller Röntgen-Computertomografie

Industrial computed tomography (CT) has lately experienced a distinct development with respect to the coordinate measuring technique. Numerous measuring tasks can already be solved reasonably and in competition with other measuring techniques. This article describes - by means of a special test body and selected measurands and characteristics - the dimensional measuring properties of industrial CT systems. The possible influence of different physical effects on these dimensional measurands is demonstrated. In addition, a correction method to improve the accuracy of the geometric data determined by CT is presented

A new method of performance verification for x-ray computed tomography measurements

Through its ability to measure otherwise inaccessible internal structures, x-ray computed tomography (CT) has become a useful tool in the field of dimensional metrology. However, the lack of international standards for performance verification and the determination of metrological characteristics has so far prevented it from becoming a standardized measurement technology. This paper considers how a test object comprising a dismantleable tetrahedral assembly of four calibrated alumina spheres can be employed to assess the metrological performance of an industrial-type CT system. The measurement accuracy was characterized in terms of sphere size, separation and form errors. In all cases, sub-voxel accuracy was achieved, with errors as small as 1/10 of a voxel being obtained. Good measurement repeatability was demonstrated even upon dismantling and reconstructing the reference object. The tetrahedral test object offers a simple robust solution for the verification of metrological performance with great versatility and adaptability. © 2014 IOP Publishing Ltd

Three-Dimensional Imaging of Nerve Tissue by X-Ray Phase-Contrast Microtomography

AbstractWe show that promising information about the three-dimensional (3D) structure of a peripheral nerve can be obtained by x-ray phase-contrast microtomography (p-μCT; Beckmann, F., U. Bonse, F. Busch, and O. Günnewig, 1997. J. Comp. Assist. Tomogr. 21:539–553). P-μCT measures electronic charge density, which for most substances is proportional to mass density in fairly good approximation. The true point-by-point variation of density is thus determined in 3D at presently 1 mg/cm3 standard error (SE). The intracranial part of the rat trigeminal nerve analyzed for the presence of early schwannoma “microtumors” displayed a detailed density structure on p-μCT density maps. The average density of brain and nerve tissue was measured to range from 0.990 to 0.994g/cm3 and from 1.020 to 1.035g/cm3, respectively. The brain-nerve interface was well delineated. Within the nerve tissue, a pattern of nerve fibers could be seen that followed the nerve axis and contrasted against the bulk by 7 to 10mg/cm3 density modulation. Based on the fact that regions of tumor growth have an increased number density of cell nuclei, and hence of the higher z element phosphorus, it may become possible to detect very early neural “microtumors” through increases of average density on the order of 10 to 15mg/cm3 by using this method