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41.
We have synthesized cone-like GeO2 structures via thermal heating of Ge powders. We have investigated the effects of substrate temperature on the sample morphology, revealing that cone-shaped structures are preferentially obtained at higher temperature. The cone-shaped structures, which gradually become thinner to form a sharp tip, appear to be a single-crystalline, hexagonal structure of GeO2. Room-temperature photoluminescence measurement revealed two emission peaks, at about 2.78 and 3.04 eV. 相似文献
42.
We look for a Brans-Dicke type generalization of Horava-Lifshitz gravity. It is shown that such a generalization is possible within the detailed balance condition. Classically, the resulting theory reduces in the low energy limit to the usual Brans-Dicke theory with a negative cosmological constant for certain values of parameters. We then consider homogeneous, isotropic cosmology and study the effects of the new terms appearing in the model. 相似文献
43.
Price D. Fittinghoff D. Benford J. Sze H. Woo W. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1988,16(2):177-184
The Vircator II oscillating virtual-cathode microwave source operates with diode voltages between 600 and 800 kV and diode current between 50 and 120 kA. Maximal microwave output power between 200 and 500 MW is achieved when the diode aspect ratio, cathode surface, charge voltage, and extraction coupling are arranged to simultaneously (1) maximize diode voltage, (2) satisfy magnetic insulation criteria, (3) avoid nonuniform or unstable electron emission, and (4) optimize microwave transmission from the virtual cathode to the launching antenna. Broadband radiation between 0.4 and 5.5 GHz is generated. The central frequency follows the beam plasma frequency. It is tuned by varying the current density with anode-cathode gap adjustments 相似文献
44.
The charged-particle multiplicity distribution and forward-backward correlation ofe + e ? annihilation at 29 GeV are discussed on the basis of a mixed two-component model. 相似文献
45.
The purpose of this paper is to describe the structures of the Möbius semigroup induced by the Möbius transformation group (?, SL(2,?)). In particular, we study stabilizer subsemigoups of Möbius semigroup via the triangle semigroup. In this work, we obtained a geometric interpretation of the least contraction coefficient function of the Möbius semigroup via the triangle semigroup and investigated an extension of stabilizer subsemigoups of the Möbius semigroup. Finally, we obtained a factorization of our stabilizer subsemigoups of the Möbius semigroup. 相似文献
46.
Teik-Cheng Lim 《Czechoslovak Journal of Physics》2004,54(9):947-963
Relationship among interatomic potential functions can be useful in shedding insight on the extent of similarity, and in obtaining
a potential function from parameters of another potential function. The 2-body portion of the Biswas-Hamann (BH) and the Kaxiras-Pandey
(KP) potential functions are related by equating both functions, as well as their corresponding derivatives up to the third
order at the equilibrium bond length. Validity of the parametric relationship is verified by plotting the loose form of the
2-body BH potential in terms of KP parameters and comparing it with the KP potential function. The parametric relationships
developed herein are then compared with those that concern other potential functions, with particular emphasis on the scaling
factors. 相似文献
47.
Investigations were carried out for laser-effected darkening and damage-free laser marking on thermoplastic elastomers (TPEs). Titanium dioxide (TiO2) was studied as the laser-sensitive additive to the TPEs for its role in enhancing laser marking contrast and its effect on the TPE properties. Laser beam characteristics, processing variables and percentage loading of TiO2 in the TPEs were found to have significant effect on the marking contrast. Surface damage-free and high contrast marking have been achieved with short pulse UV lasers. The laser-effected darkening was found to penetrate into the material in the order of a few tens of microns. XPS analysis was carried out to understand the laser-effected darkening mechanism. Potential applications of the technique are highlighted. 相似文献
48.
Jongho Shin Kyungsik Jang Ki-Soo Lim Ik-Bu Sohn Young-Chul Noh Jongmin Lee 《Applied Physics A: Materials Science & Processing》2008,93(4):1015-927
We report the spectroscopic properties of femtosecond laser-irradiated sodium-alumino-borate glass doped with silver and gold
ions. We precipitated gold and silver nanoparticles by laser irradiation and annealing at 400°C for 30 min. The irradiation
and annealing treatment produced different absorption and emission characteristics in Au3+ doped and Au3+, Ag+ codoped glasses, and the possible mechanisms of the observed results are discussed. The size of the nanoparticles was estimated
by TEM and absorption band analysis. 相似文献
49.
Kellie R. England Dr. Sang Ho Lim Lucy M. C. Luong Prof. Marilyn M. Olmstead Prof. Alan L. Balch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(3):874-878
The mono- and di-chloroform solvates of [Au2(μ-1,2-bis(diphenylarsino)ethane)2](AsF6)2 undergo single-crystal-to-single-crystal transformations that result in gain (over 12 hours) or slow loss (over five years) of only one chloroform molecule. The change in solvation results in changes in the structure and luminescence of the digold cation. The cation consists of a pair of slightly bent As-Au-As units that are connected through the two bridging dpae ligands and by aurophilic interactions with Au⋅⋅⋅Au contacts of 3.05152(15) Å in the disolvate or 2.9570(5) Å in the monosolvate. 相似文献
50.
Justin Mark Michael P. Hanrahan Dr. Katherine E. Woo Shannon Lee Prof. Dr. Aaron J. Rossini Prof. Dr. Kirill Kovnir 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(25):6392-6401
Lithiation of van der Waals tetrel-arsenides, GeAs and SiAs, has been investigated. Electrochemical lithiation demonstrated large initial capacities of over 950 mAh g−1 accompanied by rapid fading over successive cycling in the voltage range 0.01–2 V. Limiting the voltage range to 0.5–2 V achieved more stable cycling, which was attributed to the intercalation process with lower capacities. Ex situ powder X-ray diffraction confirmed complete amorphization of the samples after lithiation, as well as recrystallization of the binary tetrel-arsenide phases after full delithiation in the voltage range 0.5–2 V. Solid-state synthetic methods produce layered phases, in which Si-As or Ge-As layers are separated by Li cations. The first layered compounds in the corresponding ternary systems were discovered, Li0.9Ge2.9As3.1 and Li3Si7As8, which crystallize in the Pbam (No. 55) and P2/m (No. 10) space groups, respectively. Semiconducting layered GeAs and SiAs accommodate the extra charge from Li cations through structural rearrangement in the Si-As or Ge-As layers and eventually by replacement of the tetrel dumbbells with sets of Li atoms. Ge and Si monoarsenides demonstrated high structural flexibility and a mild ability for reversible lithiation. 相似文献