A study on the aromaticity and kinetic stability of fullerene C38 isomers and their molecular ions

The aromaticity of the fullerene C₃₈ isomers and their molecular ions is examined by the topological resonance energy (TRE) method. The aromaticity order obtained by the TRE method is compared with relative energies found in DFT calculation results reported in literature. It is found that all C₃₈ isomers exhibit antiaromaticity when in the neutral state. However, they are highly aromatic in the hexaanionic states. The minimum bond resonance energy (min BRE) method is utilized to estimate the kinetically stability of the C₃₈ isomers and their molecular ions. According to the min BRE method, C₃₈ isomers are only have kinetic stability in penta- and hexavalent molecular anionic states.     

C40H2各种可能异构体芳香性的研究

用键共振能(BRE)和拓扑共振能(TRE)方法,对由从富勒烯C_(40)(D_(5d))产生的富勒烯氢化物C_(40)H_2H所有可能异构体的芳香性进行了研究。研究了氢原子加成位置和芳香性之间的关系。计算结果表明,氢原子的加成位置与C_(40)(D_(5d))中各键的键共振能直接有关。在C_(40)(D_(5d))中C3类碳原子具有最大的反应活性。大部分C_(40)H_2异构体的芳香性高于C_(40)。用拓扑共振能方法得到的C_(40)H_2异构体的稳定性顺序与AM1和PM3半经验方法得到的稳定性顺序是一致的,用键共振能和拓扑共振能方法同样地能预测富勒烯氢化物的稳定性。     

渗流对地下埋管换热器传热管问距的影响

为确定地下水渗流对土壤蓄冷与土壤耦合热泵集成系统中竖直地下管群换热器管间距的影响,本文基于热渗耦合作用下的数学模型,采用整体求解方法模拟了冬、夏季工况下管内流体、地下埋管换热器及周围土壤的温度场,分析了地下水渗流对其传热过程的影响.结果表明在冬夏工况下管间距宜不同,地下水运动对温度场的影响明显,而且地下水流速越高影响越大.     

Raman scattering study on ferroelectric (Ba0.32Sr0.68)2Nb2O7 ceramics

Raman scattering technique was applied to examine the Ba-doping effect to the two low temperature phase transitions of Sr₂Nb₂O₇ (SN) in the temperature range from −190 to 600 °C. The line shape of Raman spectra can be well fitted by multidamped harmonic oscillator model. We did not observe any soft mode related to the two low temperature phase transitions corresponding to those of the pure SN. It is correlated to the disappearance of the incommensurate phase in (Ba_0.32Sr_0.68)₂Nb₂O₇ ceramics. However, the temperature dependence behavior of the three low frequency modes indicates another new structural phase transition around 270 °C. It is considered that the reduction of the interlayer interaction caused by partial replacement of Sr-site by Ba-site, whose ionic radius is larger than that of Sr, may be the reason for the disappearance of the incommensurate phase transition in (Ba_0.32Sr_0.68)₂Nb₂O₇ ceramics.     

室内低温热水地板辐射供暖系统的节能分析

本文阐述了低温热水地板辐射采暖分户热计量系统是一种易控、易调、节能的采暖系统,讨论了地板辐射供暖方式与其他方式在房间内人体热舒适方面的差异,并通过对其综合节能效果的考察,分析了地板辐射供暖系统不稳定供暖过程的数学模型,用数值计算的方法分析了间歇供暖条件下,达到室内要求温度所需的预热量与预热时间的关系。