Periodic tables of diatomic and triatomic molecules

The Mendeleev periodic table of atoms is one of the most important principles in natural science. However, there is shortage of analog for molecules. Here we propose two periodic tables, one for diatomic molecules and one for triatomic molecules. The form of the molecular periodic tables is analogous to that of Mendeleev periodic table of atoms. In the table, molecules are classified and arranged by their group number G, which is the number of valence electrons, and the periodic number P, which represents the size of the molecules. The basic molecular properties, including bond length, binding energy, force constant, ionization potential, spin multiplicity, chemical reactivity, and bond angle, change periodically within the tables. The periodicities of diatomic and triatomic molecules are thus revealed. We also demonstrate that the periodicity originates from the shell-like electronic configurations of the molecules. The periodic tables not only contain free molecules, but also the "virtual" molecules present in polyatomic molecules. The periodic tables can be used to classify molecules, to predict unknown molecular properties, to understand the role of virtual molecules in polyatomic molecules, and to initiate new research fields, such as the periodicities of aromatic species, clusters, or nanoparticles. The tables should be of interest not only to scientists in a variety of disciplines, but also to undergraduates studying natural sciences.     

煤中微量元素的酸脱除率与元素周期律 |-以渭北晚古生代5号煤层为例

对比了渭北晚古生代5号煤样品酸处理前后微量元素含量的变化。结果表明,按其量化表征的煤中微量元素酸脱除率划分,44个微量元素可分为五类,它们在元素周期表中有着明显的分布规律：Ⅰ型,为煤中典型的易酸脱除微量元素,主要占据于元素周期表中第Ⅰ、Ⅱ主族元素位置,按电子构型,属s区;Ⅱ型,为煤中较易酸脱除微量元素;Ⅲ型,为煤中较难酸脱除微量元素,主要占据在第Ⅲ、Ⅴ、Ⅵ、Ⅷ副族元素位置上,按电子构型,属d区和f区左半部;Ⅳ型,是难酸脱除的微量元素,主要占据在第Ⅳ、Ⅴ主族元素位置,（稀土元素部分在第Ⅲ副族）按电子构型,属p区和f区中部;Ⅴ型,为典型的最难酸脱除微量元素,主要占据在第Ⅱ、Ⅲ、Ⅳ副族位置,按电子构型,属d区的前半部、ds区和f区的右半部。煤中微量元素的酸脱除难易的大小,在元素周期表的横向、纵向和对角线方向,亦有一定的变化规律。     

气态环己烷催化氧化制丁二酸酐的研究一纳米催化剂活性组分对目标反应的影响

本文以气态环己烷催化氧化制丁二酸酐为目标反应，对TiO2-Al2O3纳米复合载体上的添加组分进行了研究与探索．结果表明，实验条件下，活性最好的催化剂添加物组成为：V2O5负载量为载体质量的5．0％，P与V原子个数比为1．5，催化剂中Mo、Sb、K的质量百分含量分别为1．25％、0．6％、4．0％．     

Experimental findings of the suppression of rotary sloshing on the dynamic response of a liquid storage tank

In liquid storage tanks, rotary sloshing occurs when the frequency of the lateral harmonic load is near the lowest frequency of the tank–liquid system. Rotary sloshing is a type of sloshing that modifies the tank response, which may cause instabilities of the tank wall. However, the consequences of rotary sloshing for the development of strain in the tank wall have not been elucidated. This paper presents an experimental determination of the effects of rotary sloshing on the development of strain and acceleration at various locations of a storage tank. A low-density-polyethylene tank containing water was tested using a shake table. Nine excitations with frequencies near the first free-vibration frequency of the tank–water system were employed. To suppress rotary sloshing, a high-density foam floating lid was utilised as a barrier. Results reveal rotary sloshing boosts not only the development of both hoop and axial strain but also the acceleration in the horizontal direction perpendicular to the excitation. The lid reduced the maximum hoop and axial strain by 500% and 400%, respectively compared to that when rotary sloshing occurs. Moreover, the lid suppressed the nonplanar sloshing by erasing the first three free-vibration frequencies of the tank–water system without the lid.     

Adventures of a fluorine chemist at DuPont

Fluorine chemist William J. Middleton (Bill) describes his career at DuPont, including some of his discoveries, a few anecdotes and a little of his poetry.     

点群乘法表和对称操作规定间的关系

导出了C3v群在不同对称操作规定下的两个乘法表,说明点群的乘法表在不同规定下有不同形式;并以C3v群为例给出Cnv群中Cnm操作与Cnn-m操作共轭的一个直观的解释.     

On the planar periodic table

We reconsider, in this work, the construction of the two‐dimensional (2‐D) periodic table. The two‐dimensional logarithmic Coulomb system is used to generate atomic shells for the 2‐D atoms. A q‐deformed model is developed to explain the ordering of the shells predicted by the 2‐D Madelung rule. Our model, with the value q=1.26 for the deformation parameter, reproduce very well the above rule. We also compute the key function and the address function which, together with our model for the Madelung rule, permit us to give a new format of the 2‐D periodic table. It is shown that this table is different from the one existing in the literature, and we have a new family of elements, the g family. The question of the existence of 2‐D “ions” is briefly discussed. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 78: 206–211, 2000     

新不定积分表

将传统不定积分表中的递推公式全部展开,并将近200个常用不定积分公式合并为43个积分公式,从而给出一张新不定积分表.     

三轴陀螺漂移测试转台台体动力学建模及控制系统设计

带宽的保证是三轴陀螺漂移测试转台（以下简称三轴转台）伺服系统设计的主要困难，从使用的角度出发，要求转台伺服系统有较大的带宽，以使三轴转台有较快的响应速度，对干扰有较强的抑制能力，提高三轴转台的跟踪精度，但一些客观因素使带宽指标受到限制，其中机械台体的谐振对带宽的影响是决定性的。本所讨论的三轴转台动力学模型，是三轴转台控制系统设计的依据。