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71.
72.
Shu Fen Wang Wen Guo Zou Su Wen Liu Dong Xu Duo Rong Yuan Guang Jun Zhou 《Journal of Physics and Chemistry of Solids》2004,65(7):1243-1245
The photoluminescence properties of the Bi3+ in sol-gel derived ZnTiO3 nanocrystals have been investigated. An ultra-violet emission at 360 nm and a visible emission band at 506 nm have been observed, originating from two kinds of emission centers. The former is ascribed to the 3P1-1S0 transition of Bi3+ and the latter to the recombination of the electrons with the photo-generated holes trapped in the zinc vacancies. In all cases the latter contribution is predominant. 相似文献
73.
Optimized prefactored compact schemes 总被引:1,自引:0,他引:1
The numerical simulation of aeroacoustic phenomena requires high-order accurate numerical schemes with low dispersion and dissipation errors. In this paper we describe a strategy for developing high-order accurate prefactored compact schemes, requiring very small stencil support. These schemes require fewer boundary stencils and offer simpler boundary condition implementation than existing compact schemes. The prefactorization strategy splits the central implicit schemes into forward and backward biased operators. Using Fourier analysis, we show it is possible to select the coefficients of the biased operators such that their dispersion characteristics match those of the original central compact scheme and their numerical wavenumbers have equal and opposite imaginary components. This ensures that when the forward and backward stencils are added, the original central compact scheme is recovered. To extend the resolution characteristic of the schemes, an optimization strategy is employed in which formal order of accuracy is sacrificed in preference to enhanced resolution characteristics across the range of wavenumbers realizable on a given mesh. The resulting optimized schemes yield improved dispersion characteristics compared to the standard sixth- and eighth-order compact schemes making them more suitable for high-resolution numerical simulations in gas dynamics and computational aeroacoustics. The efficiency, accuracy and convergence characteristics of the new optimized prefactored compact schemes are demonstrated by their application to several test problems. 相似文献
74.
新型微球板电子倍增器和微通道板相比具有高增益、无离子反馈、制备简单、造价低廉等优点。介绍了微球板电子倍增器的工作原理、特点和广阔的应用前景。由于微球板基体的形成技术是微球板制备的关键技术,论文从理论上研究了微球板基体烧结过程中的烧结速率。并采用自行设计组分的高铅玻璃,用立式炉成珠设备进行了玻璃微珠的制备。探索了微球板制备过程中玻璃微珠的分级技术、微球板电子倍增器基体成型工艺和技术。制备出基本满足要求的微球板电子倍增器基体。给出了制造的样品和文献上样品结构的SEM对比照片,最后对实验过程中的一些现象进行了分析,并给出了实验的结论。 相似文献
75.
76.
77.
Andrew Bach Xinglong Jiang Joseph Mckenna Kapa Prasad Oljan Repic Wen‐Chung Shieh 《Journal of heterocyclic chemistry》2004,41(4):637-640
An efficient approach has been developed for the synthesis of an isofervenulin analogue 1 employing a one‐pot condensation‐substitution reaction of a chlorocarboethoxytriazine (electrophile) with a urea (nucleophile). The resulting cyclization reaction resulted in the synthesis of a pyrimido‐heterocycle in good yield in either acidic or basic media. The former was assisted by utilizing trimethylsilyl chloride. 相似文献
78.
LD泵浦固体激光器基模振荡光的场分布噪音 总被引:3,自引:3,他引:0
通过调整泵浦光直径,使得LD端面泵浦固体激光器的振荡光工作于基模.在排除高阶横模的条件下,测量了由于热透镜的不稳定引起的光场场分布的噪音.实验发现,基模振荡光的高斯半径、光束指向角都在波动,而且光斑存在畸变波动.对一个未采取抑制措施的2W连续LD端面泵浦Nd:YAG固体激光器进行了测量.结果表明,在总功率不变的情况下,激光束峰值点附近的光强波动达到6.3%;激光的高斯半径波动达到5.8%;激光的指向角波动达到0.3mrad. 相似文献
79.
Jianhu Yang Shixun Dai Nengli Dai Lei Wen Lili Hu Zhonghong Jiang 《Journal of luminescence》2004,106(1):9-14
Nonradiative decay of 4I13/2→4I15/2 transition of Er3+ has been investigated in a series of oxide glasses. For Er3+-doped glass samples, the Judd-Ofelt analysis on absorption spectra was performed and the fluorescence lifetime was determined by extrapolating to zero Er3+ concentration limit. Infrared spectra were measured in order to investigate the influence of OH− groups in different glasses. The effects of glass matrix on the decay rate were discussed from the viewpoint of phonon energy, variations of effective fields, and OH− groups. Compared to other glasses, phosphate glass presents low quantum efficiency and large nonradiative decay rate due to its high phonon energy and hygroscopic behavior. 相似文献
80.
利用一维拉格朗日流体动力学程序Med103详细研究了产生类镍Ag,Cd,In,Sn, Sb离子和类氖Fe,Co,Ni,Cu,Zn离子的等离子体状态.通过对电子温度、离子丰度、离子数密度等状态参量的分析比较,得到了这两类等离子体状态之间的对应关系.即类镍银的等离子体状态与类氖铁 的相近,类镍镉的与类氖钴的相近,依次类推.利用这一对应关系可以方便地由类氖机理x射线激光的等离子体状态来对相应元素的类镍x射线激光的等离子体状态进行判断.
关键词:
类氖
类镍
等离子体状态
x射线激光 相似文献