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51.
We show that the recent tunneling formulas for black hole radiation in static, spherically symmetric spacetimes follow as a consequence of the first law of black hole thermodynamics and the area-entropy relation based on the radiation temperature. A tunneling formula results even if the radiation temperature is different from the one originally derived by Hawking and this is discussed in the context of the recent factor of 2 problem. In particular, it is shown that if the radiation temperature is higher than the Hawking temperature by a factor of two, thermodynamics then leads to a tunneling formula which is exactly the one recently found to be canonically invariant. 相似文献
52.
Using the null-geodesic tunneling method of Parikh and Wilczek, we derive the Hawking temperature of a general four-dimensional rotating black hole. In order to eliminate the motion of ? degree of freedom of a tunneling particle, we have chosen a reference system that is co-rotating with the black hole horizon. Then we give the explicit result for the Hawking temperature of the Kerr–Newman–AdS black hole from the tunneling approach. 相似文献
53.
Optical emission of the plasma generated on SiC samples by pulsed laser beam from an Nd:YAG laser was used to investigate the spatial evolution of the electron temperature (Te) and density (Ne) of the plasma. The range and the profile of the plasma were characterized by the electron temperature Te and the electron density Ne, as functions of the distance from the SiC surface. It was found that the characterized spatial distribution closely coincided with the spatial images of the plasma recorded by a digital camera. The results obtained from the two different experimental measurements are consistent with other data from the literature, obtained either by models or experiments. The present result may give the insight to the complex physical phenomena in the thin film preparations using the pulsed laser deposition (PLD). 相似文献
54.
T. Kato M. Kurata-Nishimura T. Kobayashi Y. Okamura-Oho T. Sano Y. Hayashizaki Y. Matsuo J. Kawai 《Applied Physics A: Materials Science & Processing》2008,92(4):809-812
In order to develop a femtosecond laser ablation (fsLA) ion source for TOF mass spectrometry, we have analyzed time-resolved
images of laser-induced fluorescence from Sm+ ions produced by fsLA of a solid samarium in electric fields. The polarity and the strength of electric fields had a remarkable
effect on the expansion of Sm+ ions. Moreover, accelerating electric fields elongated the duration of the ion emission from the samarium surface in fsLA,
which degraded time-focusing of the ions. We have found that suppression the continuous ion emission caused by fsLA in electric
fields is most important in TOF measurements. 相似文献
55.
以N,N′-二(4-甲氧基水杨基)邻苯二胺(H2L)为配体合成了2个新的稀土配合物[M_2L_3(H_2O)](M=Tb (1),Dy (2)),并对它们进行了红外分析、元素分析和单晶结构分析。单晶衍射结果表明,配合物1和2均为三明治型双核配合物。此外还研究了配合物1和2的磁学性质,结果表明配合物1和2都表现出反铁磁性作用和场诱导效应引起的慢弛豫行为。配合物2的有效能垒和驰豫时间分别为35.45 cm-1和2.7×10~(-10) s。 相似文献
56.
采用高温固相法制备了白蓝光双发射为一体的Cd0.5Zn0.5B4O7∶Ce/Dy系列发光材料. 由XRD测得Cd0.41Zn0.5B4O7∶Ce0.04/Dy0.02的晶胞参数: a=1.3885 nm, b=0.8020 nm, c=0.8670 nm, 属于正交晶系, Pbca空间群. 在Ce/Dy双掺的体系中存在Ce3+和Dy3+两种发光中心, 254~350 nm激发主要是Dy3+的 4F9/2→6H15/2和4F9/2→6H13/2跃迁发射, 而355—390 nm激发主要为Ce3+的5d→4f跃迁发射. 340 nm激发Ce/Dy双掺发光体的发射强度是同浓度Dy3+单掺的31倍, Ce3+是Dy3+的高效敏化剂, 而355—390 nm激发Dy3+是Ce3+的敏化剂. 体系中存在少见的Ce3+→Dy3+与Dy3+→Ce3+的能量双向传递. 相似文献
57.
为了得到最长有效余辉时间的Sr_2MgSi_2O_7:Eu~(2+),Dy~(3+)荧光粉,应用二次通用旋转组合设计对实验进行全程优化,建立了稀土离子掺杂浓度Eu~(2+),Dy~(3+)和有效余辉时间的二元二次回归方程模型,应用遗传算法计算得到有效余辉时间的理论最大值.采用高温固相法合成了最优掺杂浓度Sr_2MgSi_2O_7:0.5mol%Eu~(2+),1.0mol%Dy~(3+)的荧光粉,在370nm激发下观察到了465nm的特征发射,这归因于Eu~(2+)的4f65d1—4f7跃迁.测量了最优荧光粉的热释发光特性,计算得到了陷阱深度为0.688eV,讨论了长余辉发光的特性. 相似文献
58.
Transparent GdTaO4:Eu3+ thick films were prepared from the inorganic salt and 2-methoxyethanol solution containing polyvinylpyrrolidone (PVP) via sol-gel technique. The critical thickness of the film, i.e. the maximum thickness achievable without crack formation via non-repetitive deposition, was 0.8 μm. The effect of PVP on the morphology, crystallization behavior and optical property of the GdTaO4:Eu3+ thick film was investigated. The results indicated that PVP could play an important role in the formation of transparent GdTaO4:Eu3+ thick films, suppressing the stress evolution, adjusting the sol viscosity, ameliorating the crystallinity, and strengthening the covalency of Eu-O bonds. The GdTaO4:Eu3+ thick films prepared with PVP exhibited a superior photoluminescence and X-ray exited luminescence, which implies that it will have promising applications in high-spatial-resolution X-ray imaging and flat panel display devices. 相似文献
59.
Lead-free (Bi0.98−x
La0.02Na1−x
)0.5Ba
x
TiO3 ceramics have been prepared by an ordinary sintering technique and their structure, ferroelectric and piezoelectric properties
have been studied. The results of X-ray diffraction show that La2+ and Ba2+ diffuse into the Bi0.5Na0.5TiO3 lattices to form a new solid solution with a pure perovskite structure, and a morphotropic phase boundary (MPB) exists at
0.04<x<0.10. Compared with pure Bi0.5Na0.5TiO3 ceramics, the (Bi0.98−x
La0.02Na1−x
)0.5Ba
x
TiO3 ceramics possess much smaller coercive field E
c and larger remanent polarization P
r. Because of the low E
c (3.38 kV/mm), large P
r (46.2 μC/cm2) and the formation of the MPB of rhombohedral and tetragonal phases, the piezoelectric properties of the ceramics are significantly
enhanced at x=0.06: d
33=181 pC/N and k
p=36.3%. The depolarization temperature T
d reaches a minimum value near the MPB. The ceramics exhibit relaxor characteristic, which is probably a result from the cation
disordering in the 12-fold coordination sites. The temperature dependences of the ferroelectric and dielectric properties
suggest that the ceramics may contain both polar and non-polar regions at the temperatures above T
d. 相似文献
60.
Y. J. Wang C. M. Leung S. W. Or X. Y. Zhao H. S. Luo X. K. Lv Z. D. Zhang 《Applied Physics A: Materials Science & Processing》2009,97(1):201-204
We report an extrinsic magnetoelectric effect in composite laminates made by sandwiching one thickness-polarized 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (PMN–PT) piezoelectric single crystal plate between two length-magnetized, polymer-based pseudo-1–3 (Tb0.3Dy0.7)0.5Pr0.5Fe1.55 magnetostrictive composite plates. The laminates exhibit large magnetoelectric voltage coefficients (α
V
) of ∼0.17 V/Oe with a flat response for frequencies in excess of 40 kHz and of ∼2.97 V/Oe at the natural resonance frequency
of ∼65 kHz. The distinct advantages of the laminates include high magnetic field sensitivity, low Joule heating loss, wide
operating bandwidth, and low cost. 相似文献