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931.
G. Amato G. Benedetto L. Boarino M. Maringelli R. Spagnolo 《Applied Physics A: Materials Science & Processing》1991,52(4):280-284
In photothermal measurements of low optical absorption coefficients, as in the case of thin films of amorphous semiconductors, the substrate absorption can play a non-negligible role. In this paper, the substrate influence is discussed and generalized on the basis of a theoretical model of a two-layer absorbing sample, and the interaction of the thermal and optical parameters which control the photothermal process in the sample is shown. Some experimental results obtained on thin films of amorphous silicon carbide deposited on different substrates are presented and discussed. 相似文献
932.
P. J. Ouseph 《Applied Physics A: Materials Science & Processing》1990,50(4):361-364
With the help of an external force the stable levitation range of a magnet over a superconductor can be increased. In the experiments discussed here the external force is supplied by a bar magnet kept 4.5 cm above the superconductor sample. 相似文献
933.
We study wave equations with energy-dependent potentials. Simple analytical models are found useful to illustrate difficulties
encountered with the calculation and interpretation of observables. A formal analysis shows under which conditions such equations
can be handled as evolution equation of quantum theory with an energy-dependent potential. Once these conditions are met,
such theory can be transformed into ordinary quantum theory.
This work was supported by the agreement between IN2P3 and ASCR (collaboration no. 97-13) and by the Grant Agency of ASCR
(J.M., grant No.A1048305). 相似文献
934.
A. Andrighetto O. Bajeat A. E. Barzakh S. Essabaa D. V. Fedorov A. M. Ionan V. S. Ivanov R. Leroy G. Lhersonneau K. A. Mezilev F. V. Moroz S. Yu. Orlov V. N. Panteleev L. Stroe L. B. Tecchio A. Villari Yu. M. Volkov X. F. Wang 《The European Physical Journal A - Hadrons and Nuclei》2005,23(2):257-264
A series of on-line mass separation experiments have been performed at the IRIS facility to measure the yield and release of Rb and Cs neutron-rich isotopes produced by fission reaction of 238U. A 1 GeV proton beam was used to bombard uranium carbide targets with the densities of 11 g/cm3 and 1.5 g/cm3 held at temperatures in the range (2000-2230) °C. The release curves of Rb and Cs long-lived isotopes were measured from both kinds of targets. The overall production efficiency was determined making use of experimentally measured cross-sections of that isotope production. Comparison of the experimental yields of Rb and Cs isotopes with the calculated ones after corrections for losses due to finite release times suggests that the diffusion is the dominating process reducing the efficiency for short-lived isotopes. When normalized to the same thickness, an enhancement for the high-density rod target of the measured isotope yields is observed when going far from stability. This is possibly explained by the reactions induced by secondary neutrons. A significant odd-even effect with higher yields of Cs even neutron isotopes has been observed, confirming a similar effect obtained in earlier experiments. 相似文献
935.
E-L. Hellqvist V. Nagesh H. G. Grimmeiss M. Kleverman 《Applied Physics A: Materials Science & Processing》1991,53(1):43-46
High-resolution studies of a deep impurity in Si/Ge alloys are presented. It is shown that gold forms at least two different centers, a single substitutional defect and a gold pair. The energy structure and internal transitions of these defects were studied for different alloy compositions and implications of possible strain and alloying effects are briefly discussed.Dedicated to H.-J. Queisser on the occasion of his 60th birthday 相似文献
936.
H. Baba N. Takahashi A. Yokoyama T. Saito 《The European Physical Journal A - Hadrons and Nuclei》1998,3(3):281-292
The reaction of 238U with 12C was studied radiochemically with the purpose of elucidating fast fission characteristics. From the difference in the mass
distribution below and above the critical energy where fast fission is predicted to set in, fast fission component was extracted
in far-asymmetric mass region and interpreted as the mass diffusion following the Fokker-Planck equation. Anomalous charge
dispersion widths in the corresponding mass region and a sudden increase of the whole mass distribution width at the critical
energy were also observed to support the above result. The reaction time of fast fission deduced from the width and position
of the mass distribution was 5×10−21s as well by taking into account the effect of neutron emission during the diffusion process, which turned out to be more
than one order of magnitude longer than the corresponding life time of typical deep inelastic scattering but substantially
short compared to ordinary fusion-fission life time. Evaluation of the driving potential for mass drift required dinuclear
configuration be of an elongated or deformed form for fast fission in contrast to a more compact form for the deep-inelastic
process.
Received: 11 November 1997 相似文献
937.
GaAs/Ge的MOCVD生长研究 总被引:3,自引:3,他引:0
用常压MOCVD在Ge衬底上外延生长了GaAs单晶层,研究了GaAs和6e的极性与非极性材料异质外延生长,获得了质量优良的GaAs/Ge外延片,GaAs外延层X射线双晶衍射回摆曲线半高宽达16弧秒.10K下PL谱半峰宽为7meV.讨论了极性与非极性外延的界面反相畴问题和GaAs-Ge界面的Ga、Ge原子互扩散问题. 相似文献
938.
P. P. Li P. M. Hui 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(3):371-376
The dynamics of opinion formation based on a majority
rule model is studied in a network with the social hierarchical
structure as one of its limits. The exit probability is found to
change sensitively with the number of nodes in the system, but not
with the parameter of homophyly characterizing the network
structure. The consensus time is found to be a result of
non-trivial interplay between the network structure characterized
by the parameter of homophyly and the initial bias in opinion. For
unbiased initial opinion, a common consensus is easier to be
reached in a random network than a highly structured hierarchical
network and it follows the behavior of the length of shortest
paths. For biased initial opinion, a common consensus is easier
to be reached in a hierarchical network, as the local majority
opinion of the groups may take on the biased opinions and hence be
the same. 相似文献
939.
Fountain codes provide an efficient way to transfer information over erasure channels like the Internet. LT codes are the first codes fully realizing the digital fountain concept. They are asymptotically optimal rateless erasure codes with highly efficient encoding and decoding algorithms. In theory, for each encoding symbol of LT codes, its degree is randomly chosen according to a predetermined degree distribution, and its neighbours used to generate that encoding symbol are chosen uniformly at random. Practical implementation of LT codes usually realizes the randomness through pseudo-randomness number generator like linear congruential method. This paper applies the pseudo-randomness of chaotic sequence in the implementation of LT codes. Two Kent chaotic maps are used to determine the degree and neighbour(s) of each encoding symbol. It is shown that the implemented LT codes based on chaos perform better than the LT codes implemented by the traditional pseudo-randomness number generator. 相似文献
940.
STM study of In nanostructures formation on Ge(001) surface at different coverages and temperatures 下载免费PDF全文
Different In/Ge(001) nanostructures have been obtained by annealing the samples at 320℃ with different coverages of In. Annealing a sample with a critical coverage of 2.1 monolayer of In, different In/Ge(001) nanostructures can be obtained at different temperatures. It is found that thermal annealing treatments first make In atoms form elongated Ge{103}-faceted In-clusters, which will grow wider and longer with increasing temperature, and finally cover the surface completely. 相似文献