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991.
The all-fiber Tm-doped double-clad laser was reported, incorporating a phase mask scanning technology writing FBG directly into the Tm-doped multi-mode fiber core as cavity mirror, using 800 nm femtosecond laser sources. A fiber grating of 12 mm length was realized with a period of 1.35 μm. Pumped by the 793 nm pigtail fiber output LD, the continuous wave (CW) power could scale to 25.4 W at 1.96 μm with the slope efficiency of 38% respected to the LD output power. The output laser spectrum exhibited multi-peak, due to the multi-mode FBG reflective characteristic. 相似文献
992.
K. Vinay Kumar Reddy B. Sreenivasa Reddy M. Sreenath Reddy Ch. Gopal Reddy P. Yadagiri Reddy K. Rama Reddy 《Radiation measurements》2003,36(1-6):419-423
Studies conducted by Atomic Minerals Directorate of Exploration and Research (AMD) of Hyderabad, India had established the presence of higher concentrations of uranium in Lambapur and Peddagattu areas of Nalgonda district, AP, India and it was estimated that it could be a viable source for commercial extraction. The envisaged extraction process involves dispersion of radioactive particulate matter into atmosphere. Environmental radioactive studies in and around proposed mining areas at this point of time will be extremely useful for establishing base line data before a large scale uranium extraction process comes into existence. To this end, Solid State Nuclear Track Detectors were installed to evaluate indoor radon and thoron concentration levels in the dwellings of the area. The geometric means of radon and thoron concentration levels were found to be (7.1±0.2)×101 and (6.7±0.3)×101 Bq/m3, respectively. Simultaneously, natural background radiation measurements were also made and these levels are found to vary from 770 to 3995 μGy/y in the spatial distribution. 相似文献
993.
A. P. Severyukhin V. V. Voronov Ch. Stoyanov Nguyen Van Giai 《Physics of Atomic Nuclei》2003,66(8):1434-1438
A finite rank separable approximation for the quasiparticle random phase approximation with Skyrme interactions is applied to study the low-lying quadrupole and octupole states in some S isotopes and giant resonances in some spherical nuclei. It is shown that characteristics calculated within the suggested approach are in good agreement with available experimental data. 相似文献
994.
A. Pautrat A. Daignere C. Goupil Ch. Simon B. Andrzejewski A.I. Rykov S. Tajima 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):279-284
We report complex impedance measurements in an untwinned YBaCuO crystal. Our broad frequency range covers both the quasi static
response and the resistive response of the vortex lattice. It allow us to characterize the irreversibility line without the
need of any frequency dependent pinning parameters. We confirm the validity of the two modes model of vortex dynamic, and
extract both the surface critical current and the flux flow resistivity around the first order transition Tm. This latter is identified by the abrupt loss of pinning and by an unexpected step of (T) at Tm.
Received 22 November 2002 / Received in final form 17 February 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: alain.pautrat@ismra.fr
RID="b"
ID="b"UMR 6508 associée au CNRS 相似文献
995.
T. Butz Ch. Meinecke M. Morawski T. Reinert M. Schwertner D. Spemann J. Vogt 《Applied Surface Science》2005,252(1):43-48
This contribution deals with the morphological and elemental characterisation with high-energy (MeV) focused ion beams (in particular protons) with special emphasis on high spatial resolution in the sub-micrometer regime and very low minimum detection limits (sub-ppm) in trace element analysis. The most important methods like particle induced X-ray emission (PIXE), Rutherford backscattering spectrometry (RBS), as well as scanning transmission ion microscopy (STIM) and STIM-tomography will be illustrated by examples from material and life sciences. 相似文献
996.
Ch.?Binek P.?Borisov Xi?Chen A.?Hochstrat S.?Sahoo W.?KleemannEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,45(2):197-201
Perpendicular exchange bias (PEB) involving perpendicular
magnetic anisotropy (PMA) in both the antiferromagnetic (AF) pinning and the
ferromagnetic (FM) sensor layer is expected to become important in future
perpendicular recording and sensing devices. Further, because of the reduced
spin dimensionality, PEB promises to be easier understandable than the
conventional planar exchange bias (EB). In addition to its first realization
using the Ising-type AF compounds FeF2 and FeCl2 we have tested
control strategies of EB being alternative to the conventional magnetic and
thermal ones. Indeed, specific symmetry properties of the pinning layer have
been shown to enable mechanical (viz. piezomagnetic via FeF2) and electric
control (viz. magneto-electric via Cr2O3) of EB, respectively.
Electric control promises to become relevant for TMR devices in MRAM
technology. 相似文献
997.
This paper draws a line from early attempts of modeling stick-slip microdrives to open questions from today’s research. As a basis, it contains a collection of substantial investigations on piezo-actuated stick-slip microdrives for nanomanipulation purposes. Friction models showing special characteristics and their mathematical representations are reviewed. It is found that the working properties of stick-slip drives strongly depend on friction characteristics of the contact points between the guiding elements, which is known for years. However, numerous publications in the field of friction and remaining problems — which cannot be explained by known friction models — indicate that there is a demand for even more friction-related research.Former attempts to model stick-slip drives are based on the so-called LuGre friction model, which is shortly presented. An empirical model called CEIM is also analyzed. It is an adaption of the elastoplastic model. The latter can cover not only the phenomenon “0-amplitude’ (described by the authors in recent publications), but also stick-slip based force generation scenarios. Nevertheless, interesting friction characteristics such as the generation of μN forces with stick-slip drives, which are already proven, cannot be covered by known friction models. It is pointed out which characteristics have to be considered. 相似文献
998.
Morenzoni E. Birke M. Hofer A. Kottmann F. Litterst J. Matthias B. Meyberg M. Niedermayer Ch. Prokscha Th. Schatz G. Wutzke Th. 《Hyperfine Interactions》1996,97(1):395-406
During the last few decades, a variety of methods has been developed which makes use of polarized positive muons as a microscopic probe of the magnetic properties of condensed matter (muon spin rotation, relaxation, resonance,SR). Until now, available beams for SR studies have delivered 100% polarized muons with energies in the MeV range, resulting in a deep penetration of the muons into the sample material under investigation. This presently limits the applications of theSR technique to the study of the bulk characteristics of matter. To be able to control the implantation depth, a very low energy beam of polarized muons is being developed at the Paul Scherrer Institute. Very slow polarized muons (kinetic energy 10 eV, polarization 90%) are obtained from the moderation of a high energy muon beam in a thin film of an appropriate condensed gas. These muons can be used as a source for a beam of tunable energy between a few tens of eV and some tens of keV. Implantation depths in the range of few to a few hundreds of nanometers can thus be achieved by varying the energy. 相似文献
999.
M. Pautrat J.M. Lagrange J.S. Dionisio Ch. Vieu J. Vanhorenbeeck 《Nuclear Physics A》1985,443(1):172-188
The 198Pb and 197Pb isotopes are produced through the 186W(16O, 4n, 5n) reactions. Conversion-electron, γ- and X-ray spectra are measured using the compound-nucleus recoil method. Conversion coefficients and multipolarities are deduced for a large number of transitions. Together with angular distribution measurements and the results of γγt multidimensional coincidences they lead to decay schemes for the two isotopes. Microscopic calculations, performed in the two- or three-quasiparticle approximation with a surface delta interaction, fail to reproduce completely the observed properties, showing similar defects for the odd and even isotope. 相似文献
1000.
Trees, Renormalization and Differential Equations 总被引:1,自引:0,他引:1
Ch. Brouder 《BIT Numerical Mathematics》2004,44(3):425-438
The Butcher group and its underlying Hopf algebra of rooted trees were originally formulated to describe Runge–Kutta methods in numerical analysis. In the past few years, these concepts turned out to have far-reaching applications in several areas of mathematics and physics: they were rediscovered in noncommutative geometry, they describe the combinatorics of renormalization in quantum field theory. The concept of Hopf algebra is introduced using a familiar example and the Hopf algebra of rooted trees is defined. Its role in Runge–Kutta methods, renormalization theory and noncommutative geometry is described. 相似文献