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131.
132.
Michael Meyberg Elvezio Morenzoni Thomas Wutzke Uwe Zimmermann Franz Kottmann Klaus Jungmann Björn Matthias Thomas Prokscha 《Hyperfine Interactions》1994,87(1):1075-1081
At PSI we are investigating the technique of decelerating an existing very intense secondary beam of surface
+ (4 MeV) to an energy of 10 eV using appropriate moderators. These
+ can then be used as a source of a tertiary beam of low energy muons with tunable kinetic energy between 10 eV and 10 keV.With a 1000 A layer of solid Argon deposited on an Al substrate we obtain a moderation efficiency (with respect to the number of incoming surface
+) of the order of 10–4.Results of our investigations and the present status of the project are presented together with future plans and possibilities. 相似文献
133.
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135.
Volkmar Nejedl Michael Panzner Stefan Baunack Ulrich Franz Arnold Luft Klaus Wetzig 《Mikrochimica acta》1998,130(1-2):89-95
The laser induced modification of iron surfaces with atmospheric species was investigated by means of Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). Different laser systems were used for irradiating iron samples in a wide range of the laser processing parameters up to small foci and ultra short pulses.A nitriding of iron connected with an oxidation of the near surface region was observed in the wavelength range between 193 nm and 10.6 m using large foci (0.1 cm2) and short pulses (10...1400ns). In case of small foci (7·10–6cm2) with ns-pulses (50 ns) an enrichment of the iron melt with nitrogen and an advanced oxidation of the surrounding area of the laser spot were detected. When using shorter pulses (200 fs, 40 ps) no indications for a nitriding were found. 相似文献
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137.
P. Brüesch F. Stucki Th. Baumann P. Kluge-Weiss B. Brühl L. Niemeyer R. Strümpler B. Ziegler M. Mielke 《Applied Physics A: Materials Science & Processing》1993,57(4):329-337
In this contribution we have studied the key electrical parameters of silica aerogels and of silica-aerogel-based composites, namely the dielectric constants , the dielectric losses tan (at 1 kHz), and the breakdown fields E
b (at 50 Hz). For low-density bulk silica aerogels we find =1.25 and tan =0.0005. E
b is about 500 kV/cm in quasi-homogeneous fields, and of the order of MV/cm in strongly inhomogeneous fields. The dielectric constants of partially densified aerogels increase linearly with density; their dielectric losses are relatively large and their breakdown fields are comparativiely low. The same results are found for aerogels in the form of settled materials, i.e. aerogel granules and powders in air. Acrylate-based aerogel composites with volume fractions larger than 70% have low dielectric constants but their losses are at least 10 times higher than those of low-density aerogels. These materials sustain high local fields in the MV/cm region, while in quasihomogeneous fields, breakdown occurs at about 100 kV/cm. Based on the present results and the interplay with other physical properties (low mechanical resistance, low thermal conductivity, adsorption of water, etc.), silica aerogels and silica aerogel-acrylate-based composites are predicted to have a low potential for electrical insulation. 相似文献
138.
Summary We prove that every mixing
d
by automorphisms of a compact, connected, abelian group is mixing of all orders.Oblatum 5-II-1992The second author gratefully acknowledges support from NSF grant DMS-91-03056 at the Ohio State University 相似文献
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140.
We show that a maximal partial spread inPG(3,q) is either a spread or has at most
lines. This implies that it is not possible to cover all points but the points of a Baer-subspace by lines. 相似文献