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991.
Zs. Kajcsos Ch. Sauer W. Zinn W. Meisel H. Spiering M. Alflen P. Gütlich 《Hyperfine Interactions》1992,71(1-4):1469-1477
Increasing attention is being paid to non-conventional Mössbauer methods in view of the extension of Mössbauer Spectroscopy (MS) to a broadening field of applications. With such long-lasting experiments the shortening of the measuring time required for a given statistical significance is of major practical importance. It is shown that the statistical utility rateu allows one to determine which experimental parameters have a primary role, and it also enables sucessive optimization. It is pointed out for various MS measurements that the strategy for improving the experimental performance is strongly dependent on the given problem. As examples, time-differential Mössbauer measurements and conversion electron Mössbauer spectroscopy are discussed. 相似文献
992.
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
993.
H. Backe P. Graffé D. Habs M. Hies Ch. Illgner H. Kunz W. Lauth H. Schöpe P. Schwamb W. Theobald P. Thörle N. Trautmann R. Zahn 《Hyperfine Interactions》1993,78(1-4):35-45
An ultra-sensitive laser spectroscopic method has been developed for the hyperfine spectroscopy of short-lived isotopes far off stability produced by heavy ion induced nuclear reactions at very weak intensity (> 1/s). It is based on resonance ionization spectroscopy in a buffer gas cell with radiation detection of the ionization process (RADRIS). As a first on-line application of RADRIS optical spectroscopy at242fAm fission isomers is in progress at the low target production rate of 10/s. The resonance ionization has been performed in two steps utilizing an excimer dye laser combination with a repetition rate of 300 Hz. The first resonant step proceeds through terms which correspond to wavelengths of 466.28, 468.17 or 426.56 nm; the second non-resonant step is achieved with the 351 nm radiation of the excimer laser itself, running with XeF. The frequency scans of the tuneable dye laser at 466.28 and 468.17 nm exhibit broad resonance ionization signals, the latter with a large isotope shift between242fAm and243Am which is in accordance with the large quadrupole moment of the242fAm fission isomer.Work supported by the Bundesministerium für Forschung und Technologie under contract 06 MZ 188 I. 相似文献
994.
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
995.
S. F. Biagi M. Bourquin A. J. Britten R. M. Brown H. J. Burckhart A. A. Carter Ch. Doré P. Extermann M. Gailloud C. N. P. Gee W. M. Gibson J. C. Gordon R. J. Gray P. Igo-Kemenes P. Jacot-Guillarmod W. C. Louis T. Modis Ph. Rosselet B. J. Saunders P. Schirato H. W. Siebert V. J. Smith K. -P. Streit J. J. Thresher S. N. Tovey R. Weill 《Zeitschrift fur Physik C Particles and Fields》1985,28(2):175-185
996.
A high pressure-high temperature cell which permitsin-situ pressure and temperature calibration is described. The cell is in an opposed anvil configuaration, and houses two samples
with four probes each along with a miniature furnace and a thermocouple. The pressure and temperature capability of the cell
are 100 kbar and 1000°C respectively. This cell was developed to study the electrical resistivity of metals and alloys at
high pressure and high temperature. Bismuth was used to calibrate the cell. We report in this paper the design details and
the performance of this cell. Ni has been chosen as a test problem and the observed behaviour is indicated to show the quality
of data. 相似文献
997.
Timothy Ch. U. Kalu 《European Journal of Operational Research》1998,110(3):2268
Despite Nigeria's current economic crisis and the need to remove control structures which were originally designed to protect national interest so as to attract foreign investment in upstream activities of its oil sector, the notion of an indigenously controlled oil sector is still alive in the country. The current paper utilizes a multiperiod goal programming model to examine the effect the enforcement of Nigeria's Petroleum Decree on the utilization of domestic petroleum-related expertise would have on the survival of the multinational oil companies and, therefore, of the oil industry. The results indicate that there are some benefits to the nation in enforcing the Decree, but that to do so now will trigger a chain of events that will culminate in the demise of the oil industry. The results also highlight the danger in using legislation to regulate strategic industries and the role operational researchers can play in public policy design and decisions in the future. 相似文献
998.
Let G be a finitely generated torsion-free group, which is a metabelian product of Abelian groups. We establish a criterion for endomorphisms satisfying some extra restriction to be invertible in G. Test sets for IA-endomorphisms of G are described and its test rank computed. 相似文献
999.
In digital and analog simulations of the RCSJ-model of a Josephson junction we find both Pomeau-Manneville type I and type III intermittency; they are related to a square root and to a linear voltage onset, respectively. 相似文献
1000.
M. Ausloos F. Gillet Ch. Laurent P. Clippe 《Zeitschrift für Physik B Condensed Matter》1991,84(1):13-16
We have examined the deviation from linearity of the temperature dependence of the electrical resistivity of a YBaCuO ceramics. We have observed at high temprature a crossover behavior toward a logarithmic temperature dependence at lower temperature. It seems relevant to attribute the origin of such a term to a pair breaking mechanism contribution, thus to give a lower bound to the existence of superconductivity fluctuations onset temperature. Our findings also implies that carriers are bosons aboveT
c
. 相似文献