新工科背景下基于调查统计的物理与数学相关性研究及启示

本文基于数据统计分析说明数学在物理学习中的重要性.结合研究结果,本文提出新工科专业课程设置应遵循的基本原则,指出课程设置应强化基础课程,尊重认知规律和教育规律,突出专业特色,辐射前沿领域及交叉学科.应用物理学专业改革应满足学生的个体需求.建议将部分传统必修课转为选修课.在物理专业课程教学中,按毕业规划将学生分类;针对不...     

H-ZSM-5分子筛上环己烯芳构化反应历程的理论研究

基于76T簇模型,采用量子力学和分子力学联合的ONIOM2(B3LYP/6-31G(d,p):UFF)方法研究了H-ZSM-5分子筛上环己烯芳构化反应历程.结果表明,环己烯首先吸附在分子筛酸性位上,与酸性质子共同脱除一个H2分子后,在分子筛骨架氧上生成烷氧配合物中间体;然后再脱质子得到环己二烯,同时酸性位复原;再经历脱氢和脱质子历程,最后得到产物苯,并吸附在复原的分子筛酸性位上.计算得到脱氢的活化能依次为279.64和260.21kJ/mol,脱质子的活化能依次为74.64和59.14kJ/mol.所有脱氢反应都是吸热过程,生成表面烷氧活性中间体,随后的脱质子反应能垒较低,而且是放热过程.此外,比较了环己烯在分子筛酸性位上的三个竞争反应,即脱氢、质子化和氢交换反应的活化能垒,证明环己烯优先发生脱氢反应.     

计算材料科学中桥域多尺度方法的若干进展

材料科学中存在固有的多尺度特性,桥域多尺度方法是在宏观尺度(如连续介质力学)中引入不同的细微观尺度的计算区域,乃至纳米尺度的分子动力学、量子力学计算区域,将不同尺度的研究方法通过一定的数学模型耦合在一起。该方法既能节约计算成本,又能保证所研究问题的物理特性。本文对多尺度方法的基本概念、跨尺度桥域多尺度方法的发展、基本原理、耦合方法和离散方程进行了讨论,给出了几个应用算例,并在最后进行了总结,展望了今后的可能发展方向。     

量子体系的相空间规范变换

外尔于1918年引入的规范变换实际上是相位变换而非真正的尺度变换,但规范不变性、规范理论等概念都沿袭了下来.我们发现,针对由量子化条件[x,p]=i(h)而来的量子体系之本征值问题存在规范变换,或者说尺度变换,x→x/α,p→αp,该变换保体系的能量谱不变.量子谐振子、氢原子问题及一类多体问题的精确解析解证实了这一点....     

Theoretical Study on Thermodynamic Properties and Hydrophilicity of Polychorinated Phenothiazines （PCPTZs）

The thermodynamic properties of 135 polychlorinated phenothiazines (PCPTZs) in the standard state are calculated using a combination of quantum mechanical computations performed with the Gaussian 03 program at the B3LYP/6-311G** level, and their octanol-water partition coefficients (logKow) are calculated based on group contributions. The chlorine substitution pattern strongly influenced the thermodynamic properties and hydrophilicity of the compounds. The thermodynamic properties of congeners also depend on the chlorine substitution pattern. The effect of chlorine substitution pattern is quantitatively studied by considering the number and position of Cl atom substitution (NPCS). The results show that the NPCS model may be used to predict the thermodynamic properties and hydrophilicity for all 135 PCPTZ congeners.     

In Situ Tests of Multiwalled Carbon Nanotubes with Strength Close to Theoretical Predictions

Using MEMS technology and transmission electron microscopy we show experimentally multiwalled carbon nanotubes with a mean fracture strength of larger than 100 GPa, which exceeds the earlier observations by a factor of approximately 3. These results are in excellent agreement with quantum-mechanical estimations. This performance is made possible by omitting chemical treatments from the sample preparation process, thus avoiding the formation of defects. High-resolution imaging is used to directly determine the number of fractured shells and the ehirality of the outer shell. Electron irradiation at 200keV for 10, 100 and 1800s lead to improvements of the maximum sustainable loads by factors of 2.4, 7.9 and 11.6 compared with non-irradiated samples of similar diameter. This effect is attributed to crosslinking between the shells. This procedure is a cost effective way of customizing the properties of multiwall nanotubes for many applications of interest ranging from nanocomposites to nanodevices.     

The He--McKellar--Wilkens effect for spin-1 particles on non-commutative space

By using star product method, the He-McKellar-Wilkens （HMW） effect for spin-one neutral particle on noncommutative （NC） space is studied. After solving the Kemmer-like equations on NC space, we obtain the topological HMW phase on NC space where the additional terms related to the space-space non-commutativity are given explicitly.