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71.
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Ohne Zusammenfassung 相似文献
74.
Vafek O 《Physical review letters》2007,98(21):216401
It is argued that the specific heat of N massless Dirac fermions in two spatial dimensions interacting with 1/r Coulomb interactions is suppressed logarithmically relative to its noninteracting counterpart. The (dimensionless) coefficient of the logarithm is calculated in a closed form in the leading order in large N expansion, but to all orders in the effective fine structure constant, alpha(F), a procedure which takes into account finite temperature screening. This effect is expected to occur in a single-layer graphene embedded in a dielectric medium. Its dependence on the dielectric constant is calculated analytically. 相似文献
75.
A. Frei Yu. Sobolev I. Altarev K. Eberhardt A. Gschrey E. Gutsmiedl R. Hackl G. Hampel F. J. Hartmann W. Heil J. V. Kratz Th. Lauer A. Liźon Aguilar A. R. Müller S. Paul Yu. Pokotilovski W. Schmid L. Tassini D. Tortorella N. Trautmann U. Trinks N. Wiehl 《The European Physical Journal A - Hadrons and Nuclei》2007,34(2):119-127
The production rates of ultracold neutrons (UCN) with a solid deuterium converter have been measured at the pulsed reactor
TRIGA Mainz. Exposed to a thermal neutron fluence of
n·cm^-2·pulse^-1, the number of detected very cold and ultracold neutrons ranges up to 200 000 at 7mol of solid deuterium
(sD2) in combination with a pre-moderator (mesitylene). About 50% of the measured neutrons can be assigned to UCN with energies
E of
where V
F(sD
2) = 105 neV and V
F(guide) = 190 neV are the Fermi potentials of the sD2 converter and our stainless steel neutron guides, respectively. Thermal cycling of solid deuterium, which was frozen out
from the gas phase, considerably improved the UCN yield, in particular at higher amounts of sD2. 相似文献
76.
77.
Shape memory alloys show a very complex material behavior associated with a diffusionless solid/solid phase transformation between austenite and martensite. Due to the resulting (thermo-)mechanical properties – namely the effect of pseudoelasticity and pseudoplasticity – they are very promising materials for the current and future technical developments. However, the martensitic phase transformation comes along with a simultaneous plastic deformation and thus, the effect of functional fatigue. We present a variational material model that simulates this effect based on the principle of the minimum of the dissipation potential. We use a combined Voigt/Reuss bound and a coupled dissipation potential to predict the microstructural developments in the polycrystalline material. We present the governing evolution equations for the internal variables and yield functions. In addition, we show some numerical results to prove our model's ability to predict the shape memory alloys' complex inner processes. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
78.
Milena Špírková Jelena Pavli?evi? Adam Strachota Rafa? Poreba Oskar Bera Ludmila Kaprálková Josef Baldrian Miroslav Šlouf Nada Lazi? Jaroslava Budinski-Simendi? 《European Polymer Journal》2011,47(5):959-972
Novel all-aliphatic polycarbonate-based polyurethane (PC-PU) elastomers, as well as PC-PU nanocomposites filled with organic-modified clays were synthesized, characterized and studied. It was found that they have very attractive mechanical properties (e.g., elongation at break between 600% and 800%). The prepared PC-PUs possess a distinctly segmented structure, which is the key prerequisite for their behavior as strong physical rubbery networks. All synthesized materials melt at elevated temperatures (between 110 and 200 °C) and hence can be processed like normal thermoplastics. The dispersion of the clay nanofiller was achieved by its one day swelling in the alcohol and a brief successive stirring. This procedure is very successful and leads to a partial exfoliation of the clay (documented by X-ray diffraction and TEM). The best nanocomposites with very good tensile properties, particularly with significantly increased moduli were obtained using the bentonite nanofiller. The study shows that the nanofiller interacts strongly with the hard domains and influences their melting temperature (DMTA and DSC), but it does not affect the glass transition temperature of soft domains. While Cloisite 15A was found to interact preferentially with the hard domains, the organic modified bentonite shows a strong interaction with both soft and hard segments, behaving as a blending agent. Hard domains in neat matrices, formed by hydrogen bonding of hard segments, were practically invisible by X-ray or TEM, but were successfully detected by AFM. Besides excellent mechanical properties, the prepared elastomers and their nanocomposites showed an interesting phase behavior (which was studied by combining DMTA and modulated DSC). 相似文献
79.
80.
Univ. Doz. Dr. P. Bauer Univ. Prof. Dr. P. Hackl 《Mathematical Methods of Operations Research》1982,26(1):B47-B54
Summary The control chart techniques usually applied for continuous inspection are surveyed. A new technique using a parabolic mask is investigated which, in terms of the average run length is superior to other techniques in the case of small trends. Monte Carlo estimates of the average run length are given.
Zusammenfassung Ein neues Verfahren in der statistischen Qualitätskontrolle (die Verwendung einer parabolischen Maske) wird diskutiert, mit bekannten Kontrollkarten- und Maskentechniken verglichen sowie die mittlere Dauer bis zu einer Warnmeldung mittels Monte Carlo Methoden bestimmt.相似文献