排序方式: 共有17条查询结果,搜索用时 15 毫秒
1.
2.
The bulk crystal of LiSrBO3 (8.39 g) with a size of 21mm×20mm×15mm was grown by high temperature solution growth method. The relationship between growth habit and crystal structure was discussed. The transmission spectrum shows an UV absorption edge at about 300 nm. The melting temperature of this crystal was determined to be 942 ℃ by DTA-TG measurement. The band structure of the LiSrBO3 crystal was studied by means of the first principle method. An indirect band gap was found to be about 4.0 eV,and a low dielectric constant was estimated to be about 1.9 in terms of theoretical results. 相似文献
3.
4.
5.
Varian 2300C 直线加速器6 MV X线的蒙特卡罗模拟 总被引:1,自引:0,他引:1
摘要: 利用先进的蒙特卡罗治疗头模拟程序BEAMnrc, 依据商家提供的详细设计资料, 集成多项优化模拟参数, 对医用直线加速器射线束传输部分进行了模拟, 获得与测量数据一致的模拟结果。 对复杂多叶光栏模型进行了建模, 模拟了非规则野的剂量分布, 以用于后续研究工作。 Based on the detail head structure designing provided by the manufacture, the ray transmission of VARIAN Clinic 2300C 6 MV X beam was simulated by Monte Carlo code, BEAMnrc. To accelerate the simulation efficiency, multiple optimized parameters were optimized. The simulated and the measured data were well coincident. The dose distribution of a complicated irregular field formed by MLC (Multi Leaf Collimators) was simulated, which are the base for further research work. 相似文献
6.
7.
8.
超导微波延迟线及其制冷的研究 总被引:2,自引:2,他引:0
采用 YBCO/ La Al O3薄膜制作出 5ns和 1 0 ns超导微波延迟线 ,并以小型斯特林制冷机作冷源 ,给出了延迟线的延迟和插损特性。在 77K,1 GHz、5GHz、1 0 GHz时 5ns延迟线的插损分别为0 .1 2 d B/ ns、0 .55d B/ ns、1 .2 d B/ ns;1 0 ns超导微波延迟线在 2 GHz、4 GHz、6GHz插损分别为 0 .1 9d B/ ns、0 .4 4d B/ ns、0 .63 d B/ ns。描述了器件与制冷的设计、制作过程 相似文献
9.
模体厚度对MC程序计算速度与效率的影响研究 总被引:1,自引:0,他引:1
基于蒙特卡罗(MC)程序MCNP4c, DOSXYZnrc, DOSRZnrc 和DPM, 考察了模体厚度变化对MC程序计算速度和MC效率的影响, 发现模体的厚度变化对不同MC程序速度提升的影响差异较大, 其中DOSXYZnrc 提升最多, DOSRZnrc提升最小。 从MC效率方面来讲, DPM和DOSRZnrc具有明显的优势。 就4个程序而言, 薄模体均表现出一定的MC 效率优势。 从MC 效率提升角度来看, MCNP4c, DOSXYZnrc和DOSRZnrc表现出一定的相似性, 而DPM相对低些。 也对DOSRZnrc异常的统计不确定性特征、 速度提升进行了研究, 发现其内部植入的光子强迫方差减小技巧在降低体元统计不确定性的同时, 也削弱了薄模体的速度优势。 但是由于显著影响了方差, 所以总体来讲, 仍然提高了DOSRZnrc薄模体的MC 模拟效率。 相似文献
10.
Length dependence of linear and nonlinear optical properties of finite-length BN(5,0) nanotube 下载免费PDF全文
In this paper, we investigate the length dependence of linear and nonlinear optical properties of finite-length BN nanotubes. The recently predicted smallest BN(5,0) nanotube with configuration stabilization is selected as an example. The energy gap and optical gap show the obvious length dependence with the increase of nanotube length. When the length reaches about 24 /~, the energy gap will saturate at about 3.2 eV, which agrees well with the corrected quasi- particle energy gap. The third-order polarizabilities increase with the increase of tube length. Two-photon allowed excited states have significant contributions to the third-order polarizabilities of BN(5,0) nanotube. 相似文献