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911.
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用火花预电离辅助介质阻挡放电装置在大气压空气中实现了均匀的类辉光放电。通过用光谱模拟法和波尔兹曼图解法对N 2 第一负带系B2Σ→X 2Σ(0,0)带发射谱线的分析,对放电过程中N 2 的转动温度进行了诊断。研究了不同频率和放电模式下转动温度的变化规律,对由两种方法计算所得的温度进行了对比。实验结果表明,转动温度会随着外加频率的增加而缓慢的增加;当放电从类辉光模式变到丝状放电模式时,转动温度会有70K左右的升高。 相似文献
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915.
A sequential decay model is used to study isoscaling, i.e. the factorization of the isotope ratios from sources of different isospins and sizes over a broad range of excitation energies, into fugacity terms of proton and neutron number, R21(N, Z) = Y2( N, Z)/Y1( N, Z) = Cexp(αN -βZ). It is found that the isoscaling parameters α and β have a strong dependence on the isospin difference of equilibrated source and excitation energy, no significant influence of the source size on α andβ has been observed. It is found that α and β decrease with the excitation energy and are linear functions of 1/T and △(Z/A)2 or△(N/A)2 of the sources. Symmetry energy coefticient Gsym is constrained from the relationship of a and source △(Z/A)2, /3 and source △(N/A)2. 相似文献
916.
With all driving fields on Raman resonance, a tripod-type atomic system quickly evolves into a dark state decoupled from the lossy excited level. The dark state depends strongly on field Rabi frequencies, spontaneous decay rates, and the initial atomic population in a complicated way. Analytical results reveal that it is a sixfold degenerate dark state with its three components superposed both coherently and incoherently due to population redistribution from spontaneous emission. 相似文献
917.
An Experimental Study of Mg Aggregation in AA5754 Alloys by Positron Annihilation Spectroscopy
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Defects in an AA5754 (Al-3.0%Mg) alloy are investigated by coincidence Doppler broadening spectroscopy and positron lifetime spectroscopy. The results indicate enhancement of positron trapping by Mg atoms in this Al-Mg alloy after quenching treatment at 623K, which may be due to the formation of vacancy-Mg complexes or the aggregation of Mg near the vacancy sites. It is speculated that the aggregation of Mg atoms in the moderate temperature range is responsible for cracking in spot welding of AA5754 alloys. 相似文献
918.
A single-photon detector based on an InGaAs avalanche photodiode has been developed for use at telecom wavelengths. A suitable delay and sampling gate modulation circuit are used to prevent positive and negative transient pulses from influencing the detection of true photon induced avalanches. A monostable trigger circuit eliminates the influence of avalanche peak jitter, and a dead time modulation feedback control circuit decreases the afterpulsing. From performance tests we lind that at the optimum operation point, the quantum efficiency is 12% and the dark count rate 1.5 × 10^-6 ns^-1, with a detection rate of 500 kHz. 相似文献
919.
Raman and X-Ray Investigation of Pyrope Garnet (Mg0.76Fe0.14Ca0.10)3Al2Si3O12 under High Pressure
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The compressional behavlour of natural pyrope garnet is investigated by using angle-dlspersive synchrotron radiation x-ray diffraction and Raman spectroscopy in a diamond anvil cell at room temperature. The pressureinduced phase transition does not occur under given pressure. The equation of state of pyrope garnet is determined under pressure up to 25.3 GPa. The bulk modulus KTO is 199 GPa, with its first pressure derivative K′TO fixed to 4. The Raman spectra of pyrope garnet are studied. A new Raman peak nearly at 743 cm^-1 is observed in a bending vibration of the SiO4 tetrahedra frequency range at pressure of about 28 GPa. We suggest that the new Raman peak results from the lattice distortion of the SiO4 tetrahedra. All the Raman frequencies continuously increase with the increasing pressure. The average pressure derivative of the high frequency modes (650-1000 cm^-1) is larger than that of the low frequency (smaller than 650 cm^-1). Based on these data, the mode Grǖneisen parameters for pyrope are obtained. 相似文献
920.
The lattice dynamics of rhombohedral GaG6 is studied as a function orpressure to probe Its high pressure phase with low superconducting transition temperature using the density functional liner-response theory. The pressureinduced phase transition in CaC6 is attributable to the softening transverse acoustic (TA) phonon mode at the zone boundary X (0.5, 0.0, 0.5) point. The high pressure phase is then explored by performing fully structural optimization in the supercell which accommodates the atomic displacements corresponding to the eigenvectors of the unstable mode of TA(X). The high-pressure phase is predicted to be a monoclinic unit cell with space group P21/m. 相似文献