排序方式: 共有21条查询结果,搜索用时 15 毫秒
1.
总结了近年来用于不对称催化羟醛缩合反应的各种有机小分子催化剂, 简要阐述了每种类型的催化剂的催化机理以及它们的优缺点, 同时对有机小分子催化反应的发展进行了展望. 相似文献
2.
Flow Field and Temperature Field in GaN-MOCVD Reactor Based on Computational Fluid Dynamics Modeling
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Metal organic chemical vapor deposition(MOCVD) growth systems are one of the main types of equipment used for growing single crystal materials, such as GaN. To obtain film epitaxial materials with uniform performance,the flow field and temperature field in a GaN-MOCVD reactor are investigated by modeling and simulating. To make the simulation results more consistent with the actual situation, the gases in the reactor are considered to be compressible, making it possible to investigate the distributions of gas density and pressure in the reactor.The computational fluid dynamics method is used to study the effects of inlet gas flow velocity, pressure in the reactor, rotational speed of graphite susceptor, and gases used in the growth, which has great guiding significance for the growth of GaN film materials. 相似文献
3.
4.
5.
6.
The structural and magnetic properties of Sm ion-implanted GaN with different Sm concentrations are investigated. XRD results do not show any peaks associated with second phase formation. Magnetic investigations performed by superconducting quantum interference device reveal ferromagnetic behavior with an ordering tem- perature above room temperature in all the implanted samples, while the effective magnetic moment per Sin obtained from saturation magnetization gives a much higher value than the atomic moment of Sm. These results could be explained by the phenomenological model proposed by Dhar et al. [Phys. Rev. Lett. 94(2005)037205, Phys. Rev. B 72(2005)245203] in terms of a long-range spin polarization of the GaN matrix by the Sm atoms. 相似文献
7.
利用复变函数法和Stroh算法研究了反平面载荷作用下一维六方准晶压电材料中唇口次生裂纹的断裂问题,首次构造了唇口次生两不对称裂纹的缺陷力学模型,推出了含唇口次生两不对称裂纹的无限大区域到单位圆外部区域的保角变换公式,得到了裂尖处的场强度因子和能量释放率的解析表达式.数值算例揭示了缺陷尺寸,特别是唇口高度和裂纹长度对场强度因子和能量释放率的影响.结果表明:增加裂纹两边的长度会促进裂纹的扩展,增加唇口的高度,会抑制裂纹的扩展.最后,在给定条件下,这些解析结果可以简化为其它的缺陷模型的解,比如唇口次生单裂纹和唇口次生两对称裂纹的解,同时还可以退化为经典的Griffith裂纹和唇口无次生裂纹的解,以上结果与理论分析的结论是一致的. 相似文献
8.
光纤F-P传感器偏振互相关解调中光楔参数的影响研究 总被引:3,自引:1,他引:2
对光纤法布里-珀罗(F-P)腔长偏振互相关解调法中的双折射光楔进行了理论和实验研究,建立了双折射光楔对干涉光程差影响的数学模型,并进行了数值仿真。仿真结果表明,当楔角为4°时,要保证楔面内任意点处的光程误差在15nm以内,入射角应小于0.3°,光楔光轴倾斜应小于0.8°,楔面垂直度误差应小于0.15°。采用光楔进行了偏振光干涉实验,实验干涉条纹与理论条纹基本一致,实验干涉条纹的倾斜度与理论倾斜度相差0.02°。 相似文献
9.
10.