具有辛群对称性的一类价激发n电子波函数的性质和应用

讨论了具有辛群对称性的一类价激发n电子波函数 ψ_(a,s_1,s_2)=N(multiply from t=s_1 to s_1+s_2-1)(a_1+(a_t))(multiply from k=s_1+s_2 to s_1+s_2+m-1)G+(ζ,k,V_(s+1))|0>的性质,它们对闭壳层和开壳层体系均适用.用此类函数计算了Li_2,LiH_2^-和CH_3^+,结果表明这类函数能较好地描述电子相关作用,并且变分得到的轨道都是自然轨道。

Direct and Indirect Excitons in Two-Dimensional Covalent Organic Frameworks

Highly luminescent bulk two-dimensional covalent organic frameworks(COFs)attract much attention recently.Origin of their luminescence and their large Stokes shift is an open question.After first-principles calculations on two kinds of COFs using the GW method and Bethe-Salpeter equation,we find that monolayer COF has a direct band gap,while bulk COF is an indirect band-gap material.The calculated optical gap and optical absorption spectrum for the direct excitons of bulk COF agree with the experiment.However,the calculated energy of the indirect exciton,in which the photoelectron and the hole locate at the conduction band minimum and the valence band maximum of bulk COF respectively,is too low compared to the fluorescence spectrum in experiment.This may exclude the possible assistance of phonons in the luminescence of bulk COF.Luminescence of bulk COF might result from exciton recombination at the defects sites.The indirect band-gap character of bulk COF originates from its AA-stacked conformation.If the conformation is changed to the AB-stacked one,the band gap of COF becomes direct which may enhance the luminescence.

On the Construction and Development of Strategies to Stimulate Learners＇ Motivation Concept and Evaluation Model

This paper starts from the theoretical basis of constructivism and development evaluation study that learns the principles of communication, the use of educational psychology and other disciplines of knowledge. It is to build a developmental evaluation and characteristics for the idea to the attention of the relevant confidence to meet and the evaluator＇ s expectations as of the five elements to stimulate learning motivation, build developmental evaluation principles to stimulate learning motivation of process model. Seven strategies are to stimulate and sustain the motivation of college students, while emphasizing mentor in the process of converting role as learner and developmental evaluation. Related strategies are used in the actual teaching of ＂Mechanical Engineering Materials＂ , ＂Graduation Design＂ , ＂Engineer Training＂ course, and it achieved satisfactory teaching effect, playing a role in promoting real learning and comprehensive evaluation of the development of college students.

Leaky modes and the first arrivals in cased boreholes with poorly bonded conditions

The generation mechanism of the first arrivals in the cased boreholes for the poorly bonded conditions is investigated. Based on the analyses of the Riemann surface structure of the characteristic function, the dispersion features, excitation spectra and contributions of modes excited in the cased boreholes with different cementing types are studied. The phase velocity dispersion studies of leaky modes show that high-order modes form "plateau" regions with one approximate velocity denoted by v separated by their cutoff frequencies, in which the phase velocity changes little with a considerable frequency range, while the group velocity keeps a relatively constant high value. Usually, the operation frequency range of a specific cementing evaluation acoustic logging tool is covered by such a "plateau" region. Mode excitation and contribution analyses show that the first arrivals in the cased boreholes for the poorly bonded conditions are the contributions from leaky modes, where the traveling velocity of the first arrivals processed by slowness time coherence(STC) method is equal to the approximated velocity v. Analyses on generation of leaky modes in the cased boreholes supplement the understanding of the generation mechanism of the first arrivals.

Evaluating Soil Dissolved Organic Matter Extraction Using Three-Dimensional Excitation-Emission Matrix Fluorescence Spectroscopy

Soil dissolved organic matter （DOM） consists of many organic compounds and plays an important role in contaminant transport in the ecosystem. However, the effects of different extraction conditions on contents of different DOM components are poorly understood. We extracted DOM from three soils using different extraction times, solid to liquid ratios （SLR）, and extraction solution （KC1） concentrations, and evaluated the extractions using three-dimensional excitation-emission matrix （EEM） fluorescence spectroscopy. The sum of the contents of the main DOM components （protein-, fulvic-, and humic-like compounds） increased by 0.6-3.5, 2.5-3.9, and 0.11 0.37 times （P 〈 0.05） when SLR decreased from 1：2 to 1：10, the extraction solution concentration increased from 0.01 to 1.5 mol L-1, and extraction time increased from 10 to 300 rain, respectively. The three-dimensional EEM fluorescence spectroscopy is a useful tool to characterize the components of DOM and evaluate DOM extraction in soils.

Rotating deformed halo nuclei and shape decoupling effects

To explore the rotational excitation of deformed halo nuclei,the angular momentum projection(AMP)has been implemented in the deformed relativistic Hartree-Bogoliubov theory in continuum(DRHBc),in which both the mean field and collective wave functions are expanded in terms of Dirac WoodsSaxon basis.The DRHBc+AMP approach self-consistently describes the coupling between single particle bound states and the continuum not only in the ground state but also in rotational states.The rotational modes of deformed halos in ^(42,44)Mg are investigated by studying properties of rotational states such as the excitation energy,configuration,and density distribution.Our study demonstrates that the deformed halo structure persists from the ground state in the intrinsic frame to collective states.Especially,the typical behavior of shape decoupling effects in rotating deformed halo nuclei is revealed.