湍流不同尺度间的近程和共振作用规律及应用

从Navier-Stokes方程出发,研究了湍流不同尺度间的相互作用规律,给出相近尺度间近程粘性应力的积分和微分表达式．引入极相近尺度之间共振相互作用的概念,得到共振粘性应力的微分表达式．利用共振粘性应力张量获得不含经验关系和常数、近似封闭的大涡模拟（LES）方程组．利用近程和共振粘性应力张量获得不含经验关系和常数、近似封闭的湍流多尺度方程组．讨论了湍流多尺度方程的性质及用于湍流计算的优点,尺度间相互作用的近程特性说明:多尺度模拟是湍流计算很有价值的方法,并列举了算例．     

The closed-orbit and the photoabsorption spectra of lithium atom in varying＇magnetic fields

Using a simple analytic formula from closed orbit theory, we have calculated the photoabsorption spectra of Li atom in different magnetic fields. Closed orbits in the corresponding classical system have also been obtained for B=5.96T.We demonstrate schematically that the closed orbits disappear gradually with the decrease of the magnitude of the magnetic field. This gives us a good method to control the closed orbits in the corresponding system by changing the magnetic field, and thus changing the peaks in the photoabaorption spectra. By comparing the photoabsorption spectra of Li atom with those of hydrogen case, we find the core-scattered effects play an important role in multi-electron Rydberg atoms.     

Monte Carlo simulation of the dynamic evolution ofbinary lamellar eutectic in directional solidification

The dynamic evolution of the lamellar eutectic of binary alloys in directional solidification is studied in detail using the Monte Carlo technique. The simulated results can be summarized into two aspects: ({1}) the lamellar spacing λ is found to be inversely proportional to the chemical potential difference Δμ, predicting a linear relationship between the kinetic supercooling ΔT_k and total supercooling at the solid/liquid (S/L) interface; (2) as the solidifying velocity R is low, the dynamic product λ^{2}R shows a considerable dependence on temperature gradient G_T in the liquid in front of the S/L interface, although this dependence becomes much weaker at a high R.     

HAsS2异构体结构与稳定性

在MP2/6-311++G(d,p)和QCISD(t)/6-311++G(3df,2p)(单点)水平下计算得到9个异构体和10个过渡态的HAsS₂体系势能面.异构体cis-HSAsS(E1)的能量最低,其次是trans-HSAsS(E2)、具有AsSS三元环的立体HAs(S)S(C_{s,E3)和HAs(S)S(C2v,E4)结构的异构体,能量分别比cis-HSAsS高1.46,60.78和93.63kJ/mol.根据体系的势能面,异构体E1,E2,E3和E4具有一定的动力学稳定性.AsH和S2第一步反应产物将会异构化为具有较高动力学稳定性的异构体E3,而SH和AsS第一步反应产物将会异构化为E1.计算结果与HNO2,HNS2,HPO2,HPS2和HAsO2等价电子相同的分子的势能面进行了比较.}     

锡纳米微粒的摩擦学性能

液相分散;作用机理假设;锡纳米微粒的摩擦学性能     

色谱和毛细管电泳在中药现代化过程中的作用

近年来,中药或者传统药物的现代化受到了国内外专家学者前所未有的关注,这不仅因为它关系到各国制药行业的发展,还因为它涉及到全人类的健康。对我国来说,它更与民族利益和国民经济发展密切相关。今年全球防治SARS的“战争”也为中药的发展提供了很好的契机。我国是中药的发祥地,但目前在国际中药贸易中所占的份额尚不足10%!加快中药现代化的进程、推动中药更大规模地进入国际市场,从而造福于全人类,不仅是中医药学者、企业和管理部门的责任,也是我国分析化学家责无旁贷的任务[1]。而色谱(包括气相色谱(GC)和高效液相色谱(HPLC)和毛…     

亲水作用电色谱用于吡啶类化合物的分离

采用亲水电色谱对强极性吡啶类化合物进行了分离。以亲水性的强阳离子交换填料作固定相,乙腈-磷酸-三乙胺缓冲液作流动相,考察了流动相中有机改性剂含量、离子强度及流动相pH对吡啶类化合物保留行为的影响。结果表明,在亲水电色谱模式下,流动相中有机改性剂含量对吡啶类化合物保留有较大影响,随着流动相中乙腈含量的增加,吡啶类化合物的保留迅速增强;较高pH值有利于吡啶类化合物的峰形改善。实验证明,亲水电色谱是一种适用于极性化合物分离的新型微分离方法。     

Long—Range Effects on the Pyroelectric Coefficient of Ferroelectric Superlattice

Long-range effects on the pyroelectric coefficient of a ferroelectric superlattice consisting of two different ferroelectric materials are investigated based on the transverse Ising model.The effects of the interfacial coupling and the thickness of one period on the pyroelectric coefficient of the ferroelectric superlattics are studied by taking into account the long-range interaction.It is found that with the increase of the strength of the long-range interaction,the pyroelectric coefficient decreases when the temperature is lower than the phase transition temperature;the mumber of the pyroelectric peaks decreases gradually and the phase transition temperature increases,It is also found that with the decrease of the interfacial coupling and the thickness of one period.the phase transition temperature and the number of the pyroelectric peaks decrease.     

种间作用的二维非线性动力系统模型及其数值模拟试验研究

系统探讨了种间制约作用的二维非线性动力系统的机理与过程,从生物力学角度扩展了Lotka-Volterra模型,建立了包含种间作用与反作用的二维非线性自治、非自治动力系统新模型,分析了该动力系统平衡点的稳定性、周期解的存在性与稳定性,并对其动力学过程进行了数值模拟试验研究.结果表明两生物种群间作用效率的大小、作用系数与反作用系数变化的同向与异向性和作用力时变等对动力系统稳定性都有一定影响,种间作用效率变大或变小,以及作用系数与反作用系数的异向变化都导致动力系统的不稳定,致使两种生物难以生存,而相互作用力时变则对系统的稳定起促进作用.     

尖海龙提取物抗癌作用的研究

制备尖海龙提取物,再将其分别作用于Hela,SK-RB-3细胞系,从细胞形态变化,细胞计数,集落形成率,细胞分裂指数变化观察体外药效,结果表明,尖海龙提取物可改变肿瘤的正常生活形态,又可显著抑制肿瘤细胞的增殖,降低集落形成率,减少分裂指数,从而证实尖海龙提取物具有抗癌活性,其在癌症的治疗与预防方面具有实用价值。