NOx/CO2/H2O在BaO(001)表面吸附的理论研究

采用密度泛函理论(DFT)研究了NOx/CO2/H2O在BaO(001)表面不同覆盖度下的吸附情况.计算表明NO以N端吸附在表面氧位,形成NO22-吸附物种;CO2以C端吸附在表面氧位,形成表面CO32-;而H2O在表面发生解离吸附,导致BaO表面的羟基化.NO2有两种主要的吸附模式:以N端吸附在表面氧位,或以O端吸附表面Ba位.各物种在表面的吸附顺序为:NO≈H2O相似文献   

Stochastic Simulation of Turing Patterns

We investigate the effects of intrinsic noise on Turing pattern formation near the onset of bifurcation from the homogeneous state to Turing pattern in the reaction-diffusion Brusselator. By performing stochastic simulations of the master equation and using Gillespie＇s algorithm, we check the spatiotemporal behaviour influenced by internal noises. We demonstrate that the patterns of occurrence frequency for the reaction and diffusion pro- cesses are also spatially ordered and temporally stable. Turing patterns are found to be robust against intrinsic fluctuations. Sfochastic simulations also reveal that under the influence of intrinsic noises, the onset of Turing instability is advanced in comparison to that predicted deterministically.     

锌卟啉轴向配合物的光谱特性及配位二聚体分子内的能量传递

通过轴向配位作用构造了ZnTPP-H₂(m-py)TPP卟啉二元体系,研究了配位二聚体的可见吸收光谱和荧光发射光谱特性,考察了二聚体分子内的能量传递过程,观察到能量从激发态ZnTPP^*流向H₂(m-py)TPP。作为对比,研究了ZnTPP-py体系的可见吸收光谱和荧光发射光谱。轴向配位的吡啶引起了ZnTPP荧光光谱明显红移,没有分子内的能量转移过程发生。用吸收光谱和荧光光谱方法计算了加合反应的平衡常数,得到了基本一致的结果。     

含混合价态钒的晶体[N(CH3)4]4[H5PMo5V9O42]·3.5H2O的合成与结构

含有钒和钼的化合物在催化、抗病毒药物、功能材料等领域具有广阔的应用前景 [1～ 4 ] .近年来 ,钒取代的杂多化合物或金属 -氧簇的合成与表征已引起人们的广泛关注 ,许多新的化合物已被合成 ,如含五价钒的化合物 K7[Mo8V5O4 0 ]· 8H2 O和 Na3[VMo12 O4 0 ]· 1 9H2 O[5,6 ] ,含有混合价态钒的簇阴离子[( V V Mo10 ) VO4 0 ]6 - 和 [Mo8V V4 O4 0 ]8- 的化合物 [7,8] ,含双帽 Keggin 结构的簇阴离子[PMo6 VMo6 O4 0 ( V O) 2 ]5- 和 [PMo8V 4 V 2 O4 2 ]5- 的化合物 [9,10 ] 等 ,但所报道的含混合价态钒的 V- Mo化合物中含…     

广义泊松回归模型的推广及其在医疗保险中应用

计数数据往往存在过离散(over-dispersed)即方差大于均值特征,若利用传统的泊松回归模型拟合数据往往会导致其参数的标准误差被低估,显著性水平被高估的错误结论。负二项回归模型、广义泊松回归模型通常被用来处理过离散特征数据。本文以两类广义泊松回归模型GP-1和GP-2模型为基础,将其推广为更为一般的GP-P形式,其中P为参数。此时,P=1或P=2,GP-P模型就退化为GP-1和GP-2模型。文中最后利用此类推广的GP-P模型处理了一组医疗保险数据,并与泊松回归模型、负二项回归模型拟合结果进行了比较。结果表明,推广后的GP-P模型的拟合效果更优。     

Analysis of dark soliton generation in the microcavity with mode-interaction

Mode-interaction plays an important role in the dark soliton generation in the microcavity. It is beneficial to the excitation of dark solitons, but also facilitates a variety of dark soliton states. Based on the non-normalized Lugiato-Lefever equation, the evolution of dark soliton in the microcavity with mode-interaction is investigated. By means of mode-interaction, the initial continuous wave(CW) field evolves into a dark soliton gradually, and the spectrum expands from a single mode to a broadband comb. After changing the mode-interaction parameters, the original modes which result in dual circular dark solitons inside the microcavity, are separated from the resonant mode by 2 free spectral ranges(FSR). When the initial field is another feasible pattern of weak white Gaussian noise, the large frequency detuning leads to the amplification of the optical power in the microcavity, and the mode-interaction becomes stronger. Then, multiple dark solitons, which correspond to the spectra with multi-FSR, can be excited by selecting appropriate mode-interaction parameters. In addition, by turning the mode-interaction parameters, the dark soliton number can be regulated, and the comb tooth interval in the spectrum also changes accordingly. Theoretical analysis results are significant for studying the dark soliton in the microcavity with mode-interaction.     

六元和五元环芳香化合物在Si(001)-2´1面上的Diels-Alder加成反应—— 结合能与芳香化合物共振能的相关性

建议了一种能量分解方案用于解释苯与Si(001)-2´1面发生[4+2]加成反应时结合能相当低这一有趣现象, 并通过密度泛函簇模型计算证实, 这种能量分解方案可以应用于其他的六元和五元环芳香化合物, 并揭示了这些芳香化合物与Si(001)-2´1面发生[4+2]加成反应时, 其结合能与芳香化合物的共振能有较强的相关性.     

Mg2(BH4)2(NH2)2脱氢机理的理论研究

对Mg₂(BH₄)₂(NH₂)₂的脱氢机理展开系统的理论研究发现相对于分子内的脱氢过程,分子间的脱氢过程在热力学和动力学方面都是比较有利的. Mg₂(BH₄)₂(NH₂)₂脱氢过程的第一步是BH₄^-中的B-H^δ-和NH2-中     

泛Kennard-Stone算法的数据集代表性度量与分块采样策略

在大数据机器学习时代, 选择更具代表性的数据集对于模型的训练和验证尤为重要. Kennard- Stone(KS)算法及其各种变种(泛KS算法)是一大类优异的数据集分割方法, 但其采样比例或采样数的选择仅能依靠经验或根据建模结果事后评判. KS算法依据原始文献的计算复杂度为\mathrm{O}\left(K^{\mathrm{3}}\right), 难以用于超大数据样本量的计算. 本文基于数据集完备性的讨论, 提出泛KS算法的数据集代表性度量, 以简正振动采样的甲烷分子中碳氢键数据特征分布为例展示采样集代表性效果. 简化KS采样过程的筛选算法, 提高算法效率至\mathrm{O}\text{'}\left(K^{\mathrm{2}}\right). 提出将数据集切分成多个子集分别实施KS采样的分块采样策略, 可进一步提高算法效率至\mathrm{O}″\left(K\right). 偏最小二乘回归测试结果表明， 该方法在提高采样效率的同时仍可保障采样集的代表性.