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941.
T. M. Mishonov M. V. Stoev Y. G. Maneva 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):533-536
Absorption of Alfvén waves is considered to be the main mechanism of
heating in the solar corona. It is concluded that the sharp increase
of the plasma temperature by two orders of magnitude is related to a
self-induced opacity with respect to Alfvén waves. The maximal
frequency for propagation of Alfvén waves is determined by the
strongly temperature dependent kinematic viscosity. In such a way
the temperature jump is due to absorption of high frequency Alfvén
waves in a narrow layer above the solar surface. It is calculated
the power per unit area dissipated in this layer due to damping of
Alfvén waves that blows up the plasma and gives birth to the
solar wind. A model short wave-length (WKB) evaluation takes into
account the 1/f2 frequency dependence of the transversal magnetic
field and velocity spectral densities. Such spectral densities agree
with old magnetometric data taken by Voyager 1 and recent
theoretical calculations in the framework of Langevin-Burgers MHD.
The presented theory predicts existence of intensive high frequency
MHD Alfvén waves in the cold layer beneath the corona. It is
briefly discussed how this statement can be checked experimentally.
It is demonstrated that the magnitude of the Alfvén waves
generating random noise and the solar wind velocity can be expressed
only in terms of satellite experimental data. It is advocated that
investigation of properties of the solar surface as a random driver by
optical methods is an important task for future solar physics. 相似文献
942.
X. Sheng Y. Zhao J. Zhai L. Jiang D. Zhu 《Applied Physics A: Materials Science & Processing》2007,87(4):715-719
The electro-hydrodynamic (EHD) technique has been successfully applied for manufacturing ZnO photoanode in dye sensitized
solar cells (DSSCs). Porous structure of ZnO film after calcinations was beneficial to the absorption of dye and infiltration
of electrolyte. By using ionic liquid as an electrolyte, a high short-circuit photocurrent density of 12.1 mA/cm2 was attained and the overall photo-to-electric energy conversion efficiency (η) was 3.4% under an AM-1.5 illumination at
100 mW/cm2. At the same time, the influence factors on the solar cell performance, such as the concentrations of polyvinyl alcohol (PVA)
during EHD process and light intensity were discussed.
PACS 81.07.Bc; 84.60.Jt; 81.15.Rs 相似文献
943.
M.-W. Chu Y. Shingaya T. Nakayama 《Applied Physics A: Materials Science & Processing》2007,86(1):101-106
A combined transmission electron microscopy (TEM) and Raman spectroscopy study has been performed on nanocrystalline Ba0.9Sr0.1TiO3 (BST) crystals and tubes. TEM investigations revealed the existence of 90 deg ferroelastic twins in the materials. Raman spectra showed an obvious shoulder (∼750 cm-1) from the broad band at ∼720 cm-1 that nominally represents the quasimode of E(LO4) and A1(LO3). The intensity of this shoulder increases with the twin population in the nanocrystalline materials, suggesting a correlation between the lattice dynamical characteristics and the long-range ferroelastic strain of the twin wall. The ferroelastic strain is mainly constrained along the c-axis of the BST unit cell, and the effect of this constraint is more pronounced in nanocrystalline materials than in bulks due to a significant wall volume ratio in twinned nano-materials. A1 phonons showing collective ion dynamics along the c-direction could be then hardened by the strain, while E symmetry exhibiting vibrations perpendicular to the c-axis would be less affected. The theoretically predicted giant LO–TO coupling in tetragonal ferroelectric perovskites [18] suggests that the hardening of the softest A1(TO1) mode in A1 symmetry is accompanied by that of the hardest A1(LO3) phonon. Consequently, the shoulder could be ascribed to the ferroelastic strain induced hardening of the quasimode with a considerable contribution from the A1(LO3) phonon. PACS 61.72.Ff; 63.22.+m; 77.80.Bh; 77.80.Dj 相似文献
944.
An analytical formula for the average intensity of cosh-Gaussian (ChG) beams diffracted by an aperture in turbulent atmosphere
is derived and some limiting cases are discussed. By using the average intensity formula, some numerical simulation comparisons
are made and some special cases are studied, especially the influences of the ChG beam parameter (Ω0), the propagation distance, the aperture and its size on the average normalized intensity distribution. It is determined
that the evolution properties of the average normalized intensity profile in turbulent atmosphere with aperture are different
not only from those of free space with aperture but also from those in turbulent atmosphere without aperture.
PACS 42.68.Bz; 42.79.Ag; 42.25.Fx 相似文献
945.
Interplay between out-of-plane magnetic plasmon and lattice resonance for modified resonance lineshape and near-field enhancement in double nanoparticles array 下载免费PDF全文
Two-dimensional double nanoparticle (DNP) arrays are demonstrated theoretically, supporting the interaction between out-of-plane magnetic plasmons and in-plane lattice resonances, which can be achieved by tuning the nanoparticle height or the array period due to the height-dependent magnetic resonance and the periodicity-dependent lattice resonance. The interplay between the two plasmon modes can lead to a remarkable change in resonance lineshape and an improvement on magnetic field enhancement. Simultaneous electric field and magnetic field enhancement can be obtained in the gap region between neighboring particles at two resonance frequencies as the interplay occurs, which presents “open” cavities as electromagnetic field hot spots for potential applications on detection and sensing. The results not only offer an attractive way to tune the optical responses of plasmonic nanostructure, but also provide further insight into the plasmon interactions in periodic nanostructure or metamaterials comprising multiple elements. 相似文献
946.
采用高温固相法合成了Tb3+、Yb3+共掺杂的BaGd2ZnO5荧光粉。XRD测量数据表明合成的样品为纯相。在Tb3+特征激发(297 nm)下得到了Yb3+的特征发射(977 nm),并且对Tb3+与Yb3+能级图进行分析,证明Tb3+到Yb3+为合作能量传递。测量了不同Yb3+浓度下Tb3+的5D4能级(544 nm)的发光寿命曲线,计算得到Tb3+与Yb3+的能量传递效率和量子效率,最高量子效率为125.5%。Yb3+的发射与硅太阳能电池的吸收匹配,该材料有可能应用于硅太阳能电池以提高其转换效率。 相似文献
947.
The interfacial electronic structures of molybdenum oxide (MoOx) deposited on fullerene (C60) which could be used as a hole-injecting layer in inverted top-emitting organic light-emitting diodes (TE-OLEDs) were investigated by photoemission spectroscopy. The hole-injecting barrier height (ΦBh) at each interface investigated by an ultraviolet photoemission spectroscopy was reduced to from 1.4 to 0.1 eV as the thickness of MoOx (ΘMoOx) was increased from 0.1 to 5.0 nm on C60. In these interface system, the sign of vacuum-level shift, highest occupied molecular orbital (HOMO)-level shift, and core-level shifts were all positive indicating that the interface mechanism is attributed to the work-function differences due to a band bending at these interfaces. Moreover, the near-edge X-ray absorption fine structure spectra at carbon K-edge did not show any structural modification as well as any chemical reaction at the MoOx-on-C60 interfaces when ΘMoOx was changed on C60. From these results, the inverted TE-OLED with C60 (5.0 nm)/MoOx (5.0 nm) showed the power efficiency of 1.7 lm/W at a luminance of about 1000 cd/m2 and the maximum luminance of about 76.000 cd/m2 at the bias voltage of 11.0 V. It exhibited the highest performance among the inverted TE-OLEDs fabricated as a function of MoOx thickness from 0 to 5.0 nm. 相似文献
948.
H. Y. PAN D. P. YU G. J. LIAN G. C. XIONG X. P. ZHANG X. C. SUN 《Molecular physics》2013,111(19):3049-3054
A study is reported on the growth mechanism of YBa2Cu3O7 with different growth speeds by high resolution transmission microscopy (HRTEM) and analysis of the interface and thin film microstructure. Two thin films were synthesized by pulse laser deposition on [100], miscut 5°, SrTiO3 substrate at 820 °C, one with a pulse laser frequency of 1 Hz and one with 6 Hz. Cross-sections were studied by an H-9000 NAR HRTEM along the [010] direction. The growth process of the sample made at 1 Hz was as follows. First, distorted step flow growth occurred on a step-mediated substrate surface of 3–4 cells thickness. Second, about a 15 nm thickness of island shape growth becomes superimposed on the area of the step flow layer. Finally, thin film growth occurred but with growth fluctuation. The sample made at 6 Hz showed the characteristics of island growth; the growth area of island or ball shape was of small size and dense distribution, and seemed to be a confused mosaic stack. The influence of growth speed on YBCO epitaxial film microstructure was studied explicitly by HRTEM. 相似文献
949.
F. Honda A.V. Andreev V. Sechovský Y. Homma Y. Shiokawa 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(3):313-318
Single crystals of U(Ni1-xPdx)2Si2 with x = 0.05, 0.09 and 0.135 have been grown. Magnetization and electrical resistivity measurements were performed in a wide range
of temperatures and magnetic fields in order to study stability of magnetic phases in the solid solutions between UNi2Si2 and UPd2Si2 with a special emphasis on the type of ground state. In UPd2Si2 the simple AFI-type antiferromagnetic structure of U moments is observed at low temperatures. UNi2Si2 adopts the uncompensated AF structure (UAF) with the + + - stacking of U moments along the c-axis and consequently this compound exhibits a spontaneous magnetization corresponding to 1/3 of the U moment. The substitution
of Pd for Ni leads to a rapid decay of the spontaneous magnetization. The evolution of magnetization and electrical resistivity
behavior with Pd doping is tentatively attributed to the coexistence of the AF-I and UAF phases in the ground state of U(Ni0.91Pd0.09)2Si2 and U(Ni0.865Pd0.135)2Si2. In this scenario, the volume fraction of the AF-I phase rapidly grows with Pd doping on account of the UAF. At lowest temperatures
an irreversible transition to the UAF phase is observed when a sufficiently high magnetic field is applied along the c-axis.
Received 28 March 2002 / Received in final form 8 August 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: sech@mag.mff.cuni.cz 相似文献
950.
We report a ZGP OPO system capable of producing >6 W at a signal wavelength of 3.80 μm and an idler wavelength of 4.45 μm.
The pumping source is the Tm,Ho:GdVO4 laser operated at 2.049 μm with an M
2 of 1.07. The ZGP OPO generated a total combined output power of 6.1 W at signal wavelength and idler wavelength under pumping
power of 18.3 W, and an M
2 of 1.7 for OPO output was obtained. 相似文献