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241.
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243.
F. Strieder L. Gialanella U. Greife C. Rolfs S. Schmidt W. H. Schulte H. P. Trautvetter D. Zahnow F. Terrasi L. Campajola A. D’Onofrio V. Roca M. Romano M. Romoli 《Zeitschrift für Physik A Hadrons and Nuclei》1996,355(1):209-218
The absolute cross sectionσ of thed(7Li,p)8Li reaction near theE cm=0.61 MeV resonance has been measured using a7Li ion beam and a windowless gas target system filled with D2 gas. The proton yield of the reaction and theβ-delayedα-activity of the residual nuclides8Li were observed both concurrently with the elastic scattering yield, relatingσ to the Rutherford scattering cross sectionσ R. The resulting values,σ (fromp)=143.6±8.9 mb andσ (from8Li)=151±20 mb, lead to a weighted mean value ofσ=153±6 mb (x 2=2.26) including all available values andσ=146±5 mb (x 2=0.05) removing some values from the data set. The consequences for the expected flux of high-energy solar neutrinos are discussed. 相似文献
244.
The electric field gradients at27Al and63Cu nuclei which are nearest neighbors to the muon in the face-centered cubic metals aluminum and copper, with muon at an octahedral
interstitial site, are studied. The electron density fluctuations needed for the evaluation of the electronic, or valence,
contributions to field gradients are taken from earlier investigations involving the spherical solid approximation. The enhancement
factors a that have to be applied to the electric field-gradients obtained from these approximations, due to the departures
of the electronic wave-functions from plane-wave character, and the incorporation of antishielding effects, have been obtained
for both APW and OPW approaches to the conduction electron wave-functions and good agreement is found between the results
by the two approaches. Size effects due to the lattice distortion associated with the presence of the muon are included through
actual point ion summations using available calculated displacements of the ions surrounding the muon. The valence contributions
are the dominant ones but the size effect contributions are also significant. The net field-gradient obtained for the27Al site is significantly smaller than experiment while that for63Cu is substantially larger than experiment. Possible sources that could lead to better agreement with experiment are discussed
and it is concluded that major improvement is needed in the valence effect contributions in both metals. 相似文献
245.
Jochen Kripfganz Andreas Laser Michael G. Schmidt 《Zeitschrift fur Physik C Particles and Fields》1997,73(2):353-362
The main perturbative contribution to the free energy of an electroweak interface is due to the effective potential and the tree level kinetic term. The derivative corrections are investigated with one-loop perturbation theory. The action is treated in derivative, in heat kernel, and in a multi local expansion. The massive contributions turn out to be well described by the Z-factor. The massless mode, plagued by infrared problems, is numerically less important. Its perturbatively reliable part can by calculated in derivative expansion as well. A self consistent way to include the Z-factor in the formula for the interface tension is presented. 相似文献
246.
247.
R. Khattree D. P. Schmidt I. E. Schochetman 《Journal of Optimization Theory and Applications》1999,103(2):359-384
We consider an infinite-dimensional isotonic regression problem which is an extension of the suitably revised classical isotonic regression problem. Given p-summable data, for p finite and at least one, there exists an optimal estimator to our problem. For p greater than one, this estimator is unique and is the limit in the p-norm of the sequence of unique estimators in canonical finite-dimensional truncations of our problem. However, for p equal to one, our problem, as well as the finite-dimensional truncations, admit multiple optimal estimators in general. In this case, the sequence of optimal estimator sets to the truncations converges to the optimal estimator set of the infinite problem in the sense of Kuratowski. Moreover, the selection of natural best optimal estimators to the truncations converges in the 1-norm to an optimal estimator of the infinite problem. 相似文献
248.
During stress-induced transformation NiTi shows a distinct generation of transformation bands. A simple one-dimensional model for superelastic NiTi wires has been developed to show exemplarily methods to account for these bands in plasticitybased models. To clarify the dependence of the transformation bands on the distribution of latent heat and therefore on the mechanical behaviour, optical and thermographical experiments have been performed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
249.
Schmidt WG Hahn PH Bechstedt F Esser N Vogt P Wange A Richter W 《Physical review letters》2003,90(12):126101
The InP(001)(2 x 1) surface has been reported to consist of a semiconducting monolayer of buckled phosphorus dimers. This apparent violation of the electron counting principle was explained by effects of strong electron correlation. Combining first-principles calculations with reflectance anisotropy spectroscopy and LEED experiments, we find that the (2 x 1) reconstruction is not at all a clean surface: it is induced by hydrogen adsorbed in an alternating sequence on the buckled P dimers. Thus, the microscopic structure of the InP growth plane relevant to standard gas phase epitaxy conditions is resolved and shown to obey the electron counting rule. 相似文献
250.
A. Schmidt F. Garwe U. Hübner T. May W. Paa M. Zeisberger G. Zieger H. Stafast 《Applied physics. B, Lasers and optics》2012,109(4):631-642
The THz radiation emission of Au-coated nanogratings (fused silica substrate, 30?nm Au layer thickness, 500?nm grating constant) upon fs laser irradiation (785?nm, 150?fs, 1?kHz,???1?mJ/pulse) is observed in both directions along the laser beam axis (forward and backward) and for both, illumination of the Au/air or the Au/silica interface. THz radiation along the laser beam propagation is emitted in a narrow solid angle of about 15°?fwhm independent on the laser pulse fluence, the angle of incidence and the nanograting profile. The bar width and groove depth of the nanograting as well as the angle of laser beam incidence strongly affect the THz radiation yield. The energy of single THz light pulses is measured absolutely (2?fJ in the 0.3?C0.38?THz range) using a highly sensitive and fast superconducting transition edge sensor. The bi-directional emission of THz radiation is in agreement with the model assumption of surface plasmon polaritons propagating simultaneously on both Au layer interfaces (Au/air and Au/silica). 相似文献