共查询到20条相似文献,搜索用时 15 毫秒
1.
Based on the observation that Martian magnetic moment is gradually reducing from the ancient to the present, we investigate the O^+ ion flux distribution along magnetic field lines and the ion escaping flux in Martian tail with different assumed Martian magnetic moments. The results show that the O^+ ion flux along magnetic field lines decreases with distance from Mars; the ion flux along the field line decreases more quickly if the magnetic moment is larger; the larger the magnetic moment, the smaller the ion escaping flux in the Martian tail. The ion escaping flux depends on Z-coordinate in the Martian tail. With decrease of the magnetic moment, the ion escaping flux in the Martian tail increases. The results are significant for studying the water loss from Mars S uFface. 相似文献
2.
C. Catalfamo D. Bruno G. Colonna A. Laricchiuta M. Capitelli 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):613-621
Transport coefficients of equilibrium Martian atmosphere have been calculated in the second non-vanishing Chapman-Enskog approximation
and compared with existing literature results. The present work improves previous calculations by considering a very detailed
chemistry model of Martian atmosphere that includes 53 species and by extending the temperature range up to 50 000 K. 相似文献
3.
A. Laricchiuta D. Bruno M. Capitelli C. Catalfamo R. Celiberto G. Colonna P. Diomede D. Giordano C. Gorse S. Longo D. Pagano F. Pirani 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):607-612
In the perspective of higher approximations of the Chapman-Enskog theory for transport property calculations, existing transport
cross sections databases for interactions involving Earth atmosphere species have been updated and extended to Mars atmosphere
components, proposing a phenomenological approach for the derivation of the relevant elastic collision integrals in neutral-neutral
and neutral-ion interactions. Inelastic collision integrals terms, due to resonant charge exchange channels, have been considered
and the asymptotic approach extended to the estimation of charge transfer cross section of multiple resonant processes.
Electronic supplementary material Supplementary Online Material 相似文献
4.
We point out that the time-dependent gauge transformation technique may be effective in investigating the nonadiabatic geometric phase of a subsystem in a composite system. As an example, we consider two uniaxially coupled spin -1/2 particles with one of particles driven by rotating magnetic field. The influences of coupling and precession frequency of the magnetic field on geometric phase are also discussed in detail. 相似文献
5.
S. Momota M. Kanazawa A. Kitagawa S. Sato Y. Nojiri 《The European physical journal. Special topics》2007,150(1):315-316
The longitudinal and transverse momentum (PL and PYenT) distributions of projectile-like fragments, which were produced with an Ar beam and various targets (C, Al, Nb, Tb, Au),
were measured at E=290A MeV. No significant target effects are found in P L distribution. The width of PT distribution increases with target mass. It is plausible that this result is explained by the deflection of orbit arising
from Coulomb repulsion. The nuclear structural effects are observed in isotopic and isotonic distributions of production cross-sections
of fragments, which are derived from observed momentum distributions. 相似文献
6.
To study the effect of opacity on the solar x-ray spectral line, using the method of escape factor, we analyze the effect of opacity on the solar oxygen VIII spectral line, and we estimate the effective emission thickness of the oxygen VIII emitting region in the solar atmosphere. Results show that the opacity has a greater effect on the solar oxygen VIII spectral line, and the effective emission thickness of the oxygen VIII ion is greater than that for some ions in the solar ultraviolet spectral line. This study has important reference significance in solar plasma diagnoses in the x-ray region. 相似文献
7.
V. Palyok I.A. Szabó D.L. Beke A. Kikineshi 《Applied Physics A: Materials Science & Processing》2002,74(5):683-687
Surface relief formation at holographic recording on amorphous selenium films was demonstrated and investigated. The presence
of this optical phase modulation component is essential for ensuring significant, stable and erasable optical recording in
a-Se films at 290–320 K temperatures, where conventional photodarkening was known as insignificant and unstable. Photocrystallization
can only be observed in super-exposed a-Se films at the given experimental conditions of hologram recording. Erasing behavior
of surface relief gratings under heat treatment was also investigated in order to reveal further details of the mechanism.
Photoinduced structural transformations within the amorphous phase, connected to local ordering under the condition of light-induced
fluidity, are proposed as an explanation for the relief formation and erasing. The observed reversible optical recording process
may be useful for the various optoelectronic applications of photoconductive a-Se layers.
Received: 12 June 2000 / Accepted: 6 June 2001 / Published online: 30 August 2001 相似文献
8.
Sundance O Bilson-Thompson Derek B Leinweber Anthony G Williams Gerald V Dunne 《Annals of Physics》2004,311(2):267-287
It is known that exactly self-dual gauge-field configurations with topological charge |Q|=1 cannot exist on the untwisted continuum four-torus. We explore the manifestation of this remarkable fact on the lattice four-torus for SU(3) using advanced techniques for controlling lattice discretization errors, extending earlier work of De Forcrand et al. for SU(2). We identify three distinct signals for the instability of |Q|=1 configurations, and show that these signals manifest themselves early in the cooling process, long before the would-be instanton has shrunk to a size comparable to the lattice discretization threshold. These signals do not appear for the individual instantons which make up our |Q|=2 configurations. This indicates that these signals reflect the truly global nature of the instability, rather than the local discretization effects which cause the eventual disappearance of the would-be single instanton. Monte-Carlo generated SU(3) gauge-field configurations are cooled to the self-dual limit using an -improved gauge action chosen to have small but positive errors. This choice prevents lattice discretization errors from destroying instantons provided their size exceeds the dislocation threshold of the cooling algorithm. Lattice discretization errors are evaluated by comparing the -improved gauge-field action with an -improved action constructed from the square of an -improved lattice field-strength tensor, thus having different discretization errors. The number of action-density peaks, the instanton size, and the topological charge of configurations is monitored. We observe a fluctuation in the total topological charge of |Q|=1 configurations, and demonstrate that the onset of this unusual behavior corresponds with the disappearance of multiple-peaks in the action density. At the same time discretization errors are minimal. 相似文献
9.
Matthew A. C. Lamont 《The European Physical Journal C - Particles and Fields》2009,62(1):203-210
The nuclear wave-function is dominated at low- and medium-x by gluons. As the rapid growth of the gluon distribution towards low x, as derived from current theoretical estimates, would violate unitarity, there must be a mechanism that tames this explosive
growth. This is most efficiently studied in colliders running in e+A mode, as the nucleus is an efficient amplifier of saturation effects occurring with high gluon densities. In fact, large
A can lead to these effects manifesting themselves at energies a few orders of magnitude lower than in e+p collisions. In order to study these effects, there are proposals to build an e+A machine in the USA, operating over a large range of masses and energies. These studies will allow for an in-depth comparison
to A+A collisions where results have given tantalising hints of a new state of matter with partonic degrees of freedom. In
order to explain these results quantitatively, the gluons and their interactions must be understood fully as they are the
dominant source of hard probes at both RHIC and LHC energies. 相似文献
10.
Thin-film transistors were made using 50-nm-thick directly deposited nanocrystalline silicon channel layers. The transistors
have a coplanar top gate structure. The nanocrystalline silicon was deposited from discharges in silane, hydrogen and silicon
tetrafluoride. The transistors combine a high electron field effect mobility of ∼10 cm2 V-1s-1 with a low ‘off’ current of ∼10-14 A per μm of channel length and an ‘on’/‘off’ current ratio of ∼108. This result shows that transistors made from directly deposited silicon can combine high mobility with low ‘off’ currents.
Received: 28 May 2001 / Accepted: 30 May 2001 / Published online: 30 August 2001 相似文献
11.
Response of the Earth's Magnetosphere and Ionosphere to Solar Wind Driver and Ionosphere Load: Results of Global MHD Simulations 下载免费PDF全文
Three-dimensional global magnetohydrodynamic simulations of the solar wind-magnetosphere-ionosphere system are carried out to explore the dependence of the magnetospheric reconnection voltage, the ionospheric transpolar potential, and the field aligned currents (FACs) on the solar wind driver and ionosphere load for the cases with pure southward interplanetary magnetic field (IMF). It is shown that the reconnection voltage and the transpolar potential increase monotonically with decreasing Pedersen conductance (∑ p ), increasing southward IMF strength (Bs) and solar wind speed (Vsw). Moreover, both regions 1 and 2 FACs increase when Bs and vsw increase, whereas the two currents behave differently in response to ∑p. As ∑p increases, the region 1 FAC increases monotonically, but region 2 FAC shows a non-monotonic response to the increase of ∑p : it first increases in the range of (0,5) Siemens and then decreases for ∑p 〉 5 Siemens. 相似文献
12.
A. Schäfer 《The European Physical Journal A - Hadrons and Nuclei》2007,32(4):371-377
Hadron structure physics has in recent years reached a level of precision which allows for a change of perspective. Model-based
arguments are often quite unreliable. However, meanwhile they can be more and more replaced by controlled and systematic QCD
approaches. The story of the strange electric form factor, which provided much of the motivation for the PAVI Conference series
provides a typical example to illustrate this statement. However, high-precision theory is technically very challenging and
progress is, therefore, unpleasantly slow. This fact and the present status in general is illustrated by a few typical examples. 相似文献
13.
K. Hermann M. Witko R. Druzinic R. Tokarz 《Applied Physics A: Materials Science & Processing》2001,72(4):429-442
The local electronic structure at the V2O5 (010) surface is studied by ab initio density functional theory (DFT) methods using gradient-corrected functionals (RPBE)
where embedded clusters as large as V20O62H24, representing one or two crystal layers of the substrate, are used as models. Results of local binding and charging of differently
coordinated surface-oxygen sites as well as densities of states allow a characterization of the detailed electronic structure
of the surface. Electronic and geometric details of surface-oxygen vacancies as well as hydrogen adsorption are studied by
appropriate clusters. A comparison of the data, concerning vacancy energies, charging, geometric relaxation, and diffusion,
shows sizeable variations between different oxygen sites and can give further insight into possible mechanisms of surface
relaxation and reconstruction. Hydrogen is found to stabilize at all surface-oxygen sites forming surface-OH and H2O species. As a result, the binding of surface oxygen with its vanadium neighbors is weakened. Therefore, the presence of
hydrogen at the oxide surface facilitates oxygen removal and can contribute to the enhanced yield of oxygenated products near
vanadia-based surfaces.
Received: 10 April 2000 / Accepted: 25 July 2000 / Published online: 7 March 2001 相似文献
14.
R. Job A.G. Ulyashin W.R. Fahrner A.I. Ivanov L. Palmetshofer 《Applied Physics A: Materials Science & Processing》2001,72(3):325-332
Oxygen and hydrogen accumulations at buried implantation-damage layers were studied after post-implant-ation annealing of
hydrogen- and helium-implanted Czochralski (Cz) silicon. Hydrogen implantation was carried out at energies E=180 keV and doses
D=2.7×1016 cm-2, and helium implantation at E=300 keV and D=1016 cm-2. For comparison hydrogen implantation was also done into float-zone (Fz) silicon wafers. Post-implantation annealing at 1000 °C
was done either in H2 or N2 atmosphere. Hydrogen and oxygen concentration profiles were measured by secondary ion mass spectroscopy (SIMS). It is shown
that the ambient during annealing plays a significant role for the gettering of oxygen at buried implantation-damage layers
in Cz Si. For both hydrogen and helium implantations, the buried defect layers act as rather effective getter centers for
oxygen and hydrogen at appropriate conditions. The more efficient gettering of oxygen during post-implantation annealing in
a hydrogen ambient can be attributed to a hydrogen-enhanced diffusion of oxygen towards the buried implantation-damage layers,
where a fast oxygen accumulation occurs. Oxygen concentrations well above 1019 cm-3 can be obtained. From the comparison of measurements on hydrogen-implanted Cz Si and Fz Si one can conclude that at the buried
defect layers hydrogen is most probably trapped by voids and/or may be stable as immobile molecular hydrogen species. Therefore
hydrogen accumulated at the defect layers, and is preserved even after high-temperature annealing at 1000 °C.
Received: 3 July 2000 / Accepted: 11 July 2000 / Published online: 22 November 2000 相似文献
15.
Barrier Enhancement Effect of Postannealing in Oxygen Ambient on Ni/AIGaN Schottky Contacts 下载免费PDF全文
Al0.2 Ga0.8N/GaN samples are grown by metalorganic chemical vapour deposition (MOCVD) method on (0001) sapphire substrates. A 10nm-thick Ni layer is deposited on AlGaN as the transparent Schottky contact. The effect of postannealing in oxygen ambient on the electrical properties of Ni/AlGaN is studied by current-voltage- temperature (I-V-T) measurement. The annealing at a relatively low temperature of 300℃ for 90 s results in a decrease of the ideality factor from 2.03 to 1.30 and an increase of the Schottky barrier height from 0.77eV to 0.954 e V. The I-V-T analysis confirms the improvement originated from the formation of NiO, a layer with higher resistance, which could passivate the surface states of AlGaN and suppress the tunnelling current. Furthermore, the annealing also leads to an increase of the transmittance of the contacts from 57.5% to 78.2%, which would be favourable for A1GaN-based photodetectors. 相似文献
16.
17.
V. Hnatowicz J. Kvítek V. Švorčík V. Rybka 《Applied Physics A: Materials Science & Processing》1994,58(4):349-352
Samples of PolyPropylene (PP) and PolyEthylene (PE) implanted with 150 keV F+, As+ and I+ ions with a dose of 1×1015 cm–2 were studied using standard Rutherford Back Scattering (RBS) technique. No fluorine atoms above the present RBS detection limit were observed in the ion-implanted polymers. The measured depth profiles of As and I atoms are significantly broader than those predicted by the TRIM code for pristine polymers. The differences can be explained by stepwise polymer degradation due to ion bombardment. Massive oxidation of the ion-implanted polymers is observed. The oxidation rate and the resulting oxygen depth profile depend strongly on the polymer type and implanted ion mass. In the samples implanted with F+ ions, an uniformly oxidized layer is built up with a mean oxygen concentration of 15 at.%. In the samples implanted with As+ and I+ ions, a non-uniform oxygen depth distribution is observed with two concentration maxima on the sample surface and in a depth correlated with implanted ion range. 相似文献
18.
Numerical Investigation and Wind Tunnel Validation on Near-Wake Vortical Structures of Wind Turbine Blades 下载免费PDF全文
Zhenyu Zhang Li Chen & Tongguang Wang 《advances in applied mathematics and mechanics.》2016,8(4):556-572
Computational fluid dynamics (CFD) has been used by numerous researchers
for the simulation of flows around wind turbines. Since the 2000s, the experiments
of NREL phase VI blades for blind comparison have been a de-facto standard
for numerical software on the prediction of full scale horizontal axis wind turbines
(HAWT) performance. However, the characteristics of vortex structures in the wake,
whether for modeling the wake or for understanding the aerodynamic mechanisms
inside, are still not thoroughly investigated. In the present study, the flow around NREL
phase VI blades was numerically simulated, and the results of the wake field were
compared with the experimental ones of a one-to-eight scaled model in a low-speed
wind tunnel. A good agreement between simulation and experimental results was
achieved for the evaluation of overall performances. The simulation captured the complete
formation procedure of tip vortex structure from the blade. Quantitative analysis
showed the streamwise translation movement of vortex cores. Both the initial formation
and the damping of vorticity in near wake field were predicted. These numerical
results showed good agreements with the measurements. Moreover, wind tunnel wall
effects were also investigated on these vortex structures, and it revealed further radial
expansion of the helical vortical structures in comparison with the free-stream case. 相似文献
19.
丹参酮I的光谱特性及pH对其分子结构的影响 总被引:1,自引:0,他引:1
本文对丹参酮I(TanI)分子的紫外吸收、荧光光谱,液氮低温下的荧光、磷光光谱等光谱行为进行了详细的对比研究,考察了酸度对各种光谱的发光强度及波长位置影响的规律,计算了磷光寿命、荧光量子产率、偏振等重要参数。pH对TanI的荧光光谱特性有影响。在强酸或强碱介质中TanI的荧光被显著狞灭,发射光谱蓝移,并有分子结构的变化,在强碱性介质中TanI发生了不可逆的开环反应。 相似文献
20.
Silicon Dioxide Coating Deposited by PDPs on PET Films and Influence on Oxygen Transmission Rate 下载免费PDF全文
A silicon dioxide film is deposited on the polyethyleneterephtMate (PET) by a penning discharge plasma source at ambient temperature in a high vacuum chamber. Hexamethyldisiloxane and oxygen are adopted as precursor and reactive reagent to grow a nano-scale silicon dioxide layer on polymer surfaces. For the chemical structure analysis X-ray photoelectron spectroscopy is performed to demonstrate the content of Si, 0 and C elements. It is noticed that a higher silicon concentration is contained if Ar plasma is used for pretreatment. X-ray diffraction analysis shows that a micro-crystal silicon dioxide is formed by peak patterns at 25,84° and 21.8°. The barrier properties examined by oxygen transmission rate show that the permeation parameter of the 12-μm-thick PET film drastically decreases from 135 cc/m^2 per day for the control one to O. 713 cc/m^2 per day for the as-deposited one after Ar plasma treatment. The surface morphology related to the barrier properties of SiOx-coated polymers os also investigated by scanning electron microscopy and atomic force microscopy. 相似文献