Copper is the first of a series of materials that will be certified as thermal-expansion standards by the National Bureau of Standards. The results of tests on five specimens indicate the stock is of consistent quality so that it may be certified as Standard Reference Material 736. A Fizeau interferometer was used for the expansion measurements. Above room temperature a controlled-atmosphere furnace using a calibrated Pt vs Pt-10% Rh thermocouple was used. Below room temperature a cryostat capable of operation with both liquid nitrogen and helium was used with a calibrated platinum resistance thermometer. Values of expansivity were calculated between equilibrium temperatures. The expansivity was used in the analysis of the data. Third-order polynomials were fitted to the data for each of the five specimens in the overlapping temperature ranges from 0 to 70 K, 50 to 270 K, and 210 to 800 K to test for variations between the specimens. The deviations between the five equations were well within the standard deviations of the data for each of the specimens in the respective temperature intervals. All the expansivity data were then pooled and used to obtain an equation for each of the temperature ranges given above. These equations and their integrals were used to calculate the final values of expansivity and expansion, respectively. The results of the statistical analysis of the expansion and expansivity data are presented. A comparison is made with the data in the literature.
A detailed chronology of the early, pre-Internet years of online information systems and services.
Every field of history has a basic need for a detailed chronology of what happened: who did what when. In the absence of such a resource, fanciful accounts flourish. This book provides a rich narrative of the early development of online information retrieval systems and services, from 1963 to 1976—a period important to anyone who uses a search engine, online catalog, or large database. Drawing on personal experience, extensive research, and interviews with many of the key participants, the book describes the individuals, projects, and institutions of the period. It also corrects many common errors and misconceptions and provides milestones for many of the significant developments in online systems and technology.
We demonstrate the direct heteroepitaxial growth of the chalcopyrite semiconductor CuInS2 on silicon (111) substrates by means of three-source molecular beam epitaxy. The pretreatment of the silicon wafers includes sulphur termination which leads to a new surface structure defining the starting condition for successful epitaxy. All stages of the growth process were controlled in situ using Auger electron spectroscopy and low energy electron diffraction. Furthermore, the epitaxial layers were characterized by means of x-ray diffraction methods and by Rutherford backscattering spectrometry including channeling. X-ray rocking curves showed a typical width of 0.2° while the minimum yield due to the channeling effect was found to be 56%.
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