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61.
Non-Markovian Brownian motion in a periodic potential is studied by means of an electronic analogue simulator. Velocity spectra, the Fourier transforms of velocity autocorrelation functions, are obtained for three types of random force, that is, a white noise, an Ornstein—Uhlenbeck process, and a quasimonochromatic noise. The analogue results are in good agreement both with theoretical ones calculated with the use of a matrix-continued-fraction method, and with the results of digital simulations. An unexpected extra peak in the velocity spectrum is observed for Ornstein-Uhlenbeck noise with large correlation time. The peak is attributed to a slow oscillatory motion of the Brownian particle as it moves back and forth over several lattice spaces. Its relationship to an approximate Langevin equation is discussed. 相似文献
62.
G. A. Stergioudis 《Zeitschrift für Physik B Condensed Matter》1993,93(1):1-4
The tendency of boron-containing, iron-based glasses to show non monotonic changes of Curie Temperature (T
c
) and room temperature saturation magnetization (SM) was examined by magnetic measurements and Mossbauer spectroscopy. Depending on B/Fe ratio theT
c
and SM first increased up to a maximum value and then steadily decreased, probably because of a shortrange ordering, due to the strong chemical interaction between iron and boron atoms, leading iron atoms in vicinity with Fe-atoms rather than another TM-atom. Finally, the phenomenon becomes analogous to the order-disorder phenomenon in crystalline alloys. An observed unusual crystallization behaviour, consisting of heterogeneous nucleation, was also ascribed to this ordering, which leads to the formation of associations, acting as the first nuclei of crystallization. 相似文献
63.
Patterned uniformly (100)-orientated silicon nanocrystallite (SiNC) films were fabricated based on hydrogen ion implantation technique and typical electrochemical anodic etching method. The surface morphology and microstructure characteristics of the films were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and atomic force microscopy. The efficient field emission with low turn-on field of about 3.2 V/μm at current density of 0.1 μA/cm2 was obtained. The emission current density from the SiNC films reached 1 mA/cm2 under a bias field of about 11 V/μm. The experimental results demonstrate that the SiNC films have great potential applications for flat panel displays. 相似文献
64.
《Journal of Crystal Growth》2006,286(2):424-430
Control over the morphology of calcium carbonate (CaCO3) crystals has been achieved through the use of anionic, amphiphilic block copolypeptides during crystallization. Microspheres of CaCO3 can be synthesized by the introduction of preformed organic, amphiphilic block copolypeptide templates, poly(l-aspartate sodium salt)100-block-[poly(l-phenylalanine)25-random-(l-leucine)25] (1) and poly(l-glutamate sodium salt)100-block-[poly(l-phenylalanine)25-random-(l-leucine)25] (2). When cationic amphiphiles are used in lieu of the anionic amphiphiles, only CaCO3 rhombohedra are produced. The self-assembling amphiphile controls the precipitation of the microspheres by acting as a template to form giant CaCO3 microspheres. These microspheres are composed of nanocrystals ranging in size from 10 to 60 nm using 1 and 20 to 100 nm using 2. 相似文献
65.
66.
The tunneling of single electrons in small capacitance tunnel junctions is influenced by charging effects and by the fluctuations of the elecromagnetic environment. We study the effect of an external circuit with arbitrary impedance on the tunneling of quasiparticles and Cooper pairs in voltage driven Josephson junctions. We present results at finite temperatures and also consider an acdriven system. 相似文献
67.
P. Dawson J. W. Haas III K. B. Alexander J. Thompson T. L. Ferrell 《Surface science》1991,250(1-3):L383-L388
The intensity of surface enhanced Raman scattering from benzoic acid derivatives on mildly roughened, thermally evaporated Ag films shows a remarkably strong dependence on metal grain size. Large grained (slowly deposited) films give a superior response, by up to a factor of 10, to small grained (quickly deposited) films, with films of intermediate grain size yielding intermediate results. The optical field amplification underlying the enhancement mechanism is due to the excitation of surface plasmon polaritons (SPPs). Since surface roughness characteristics, as determined by STM, remain relatively constant as a function of deposition rate, it is argued that the contrast in Raman scattering is due to differences in elastic grain boundary scattering of SPPs (leading to different degrees of internal SPP damping), rather than differences in the interaction of SPPs with surface inhomogeneities. 相似文献
68.
《Journal of Crystal Growth》2006,286(1):152-155
A relatively simple method was described for coating and modifying iron nanoparticles with a hexagonal close-packed (hcp) cobalt layer. It was realized by depositing cobalt onto the poly(N-vinyl-2-pyrrolidone) (PVP) modified iron particles in ethanol solution. XRD, XPS and HRTEM were used to characterize the product. The Co layers, grown as the exclusive hcp phase, were ascribed to the inducement of the body-centered cubic (bcc) iron cores. Thus-prepared hcp Co-coated Fe particles displayed a much enhanced coercivity and decreased saturation magnetization (MS) compared with that of the uncoated sample. 相似文献
69.
M. I. Oshtrakh O. B. Milder V. A. Semionkin L. I. Malakheeva P. G. Prokopenko 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(3):671-677
Summary Characterization of iron storage proteins in liver and spleen from normal chicken and chicken with lymphoid leukemia in comparison
with human liver ferritin were considered by M?ssbauer spectroscopy (preliminary results). Small differences in M?ssbauer
hyperfine parameters for both normal and lymphoid leukemia chicken liver and spleen were observed. The value of quadrupole
splitting for human liver ferritin was higher than those for chicken tissues. A decrease of iron content in lymphoid leukemia
chicken tissues was also found, however, the reason of this fact (pathology or feeding) was not clear yet. 相似文献
70.
Summary The interceluster organization of a two-dimensional colloidal system undergoing diffusion-limited cluster-cluster aggregation
is considered. During this process the system evolves into a stationary, scaling state. In this state the organization arises
from effective intercluster repulsion due to the mutually exclusive depletion zones surrounding each cluster. It is shown
that in the scaling regime the relevant size of the depletion zones is determined by the separation between clusters, rather
than the cluster size.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献