A theoretical study of the TiC5 cluster

The geometric and electronic properties of the titanium carbide TiC(5) cluster in its neutral and anionic charge states have been investigated using density functional theory (DFT) at the B3LYP level. The nonplanar six-membered ring-type or "butterflylike" structures are found to be the equilibrium geometric structures of TiC(5) and TiC(5) (-). Time-dependent DFT is used in the calculation of the excited states. The theoretical assignment at the B3LYP level for the features in the photoelectron spectrum is given. All results obtained are in good agreement with the available experimental data.     

BCKLUND TRANSFORMATION ON SURFACESWITH CONSTANT MEAN CURVATURE IN R~(2.1)

In this paper, the authors obtain the Backlund transformation on time-likesurfaces with constant mean curvature in R~(2,1). Using this transformation, families ofsurfaces with constant mean curvature from known ones can be constructed.     

Separation and determination of 2,4-D, dicamba and 2,4,5-T in tobacco by nonaqueous capillary electrophoresis

A practical method for residue analysis of 2,4-D, dicamba and 2,4,5-T in baked tobacco leaves has been developed using nonaqueous CE (NACE). The herbicide residues of 2,4-D, dicamba and 2,4,5-T in tobaccos were extracted by ultrasonication with ethyl acetate, followed by a cleanup procedure with gel permeation chromatography. The separation of 2,4-D, dicamba and 2,4,5-T by NACE was optimized based on orthogonal experiment design with four factors at three levels. The optimal NACE condition was established with the running buffer of 40.0 mmol/L ammonium acetate in 90% CH3CN (apparent pH 10.2), and the applied voltage of -25 kV over a capillary of 50 microm id x 46 cm (37.5 cm to the detector window), which gave a baseline separation of 2,4-D, dicamba and 2,4,5-T within 15 min. The LOD were ca. 0.4-0.6 microg/mL for the three herbicides, whereas the overall recovery ranged from 80.8 to 84.1%. The proposed method has been successfully applied to measure 300 real tobacco samples, and the residue profiles of the three herbicides in tobacco samples were obtained and evaluated.     

基于声发射技术的钢丝绳断丝模式识别

基于大量实验及波形分析,给出钢丝绳断丝事件的声发射（ＡＥ）定量化表征形式．采用类内类间距离和二维图示方法综合选择ＡＥ特征,并根据其分布情况建立起基干Ｆｉｓｈｅｒ准则的分段线性分类器,以实现断丝事件的自动检测．