无穷时滞泛函微分方程的正周期解

利用范数形式的锥拉伸和锥压缩不动点定理讨论具有无穷时滞泛函微分方程的周期解问题,获得了正周期解的存在性定理,并给出了定理的若干应用.     

具有相交性质的近小扭转映射的不变环面的保持性

In this paper we investigate the nearly small twist mappings with intersection property. With a certain non-degenerate condition, we proved that the most of invariant tori of the original small twist mappings will survive afer small perturtations. The persisted invariant tori are close to the unperturbed ones when the perturbation are small. The orbits reduced by those mappings are quasi-periodic in the invariant tori with the frequences closing to the original ones.     

Similarity orbits in the Calkin algebra

Let B(H) be the algebra of all bounded linear operators on a complex separable infinite dimensional Hilbert space H.Denote by π the quotient map of B(H) onto the Calkin algebra A(H).In 1984,Apostol et al.raised the following conjecture:If an operator T on H is not similar to a compact perturbation of a Jordan operator,then the similarity orbit of π(T) in A(H) coincides with the π-image of the similarity orbit of T.In this paper,we investigate the structure of similarity orbits in the Calkin algebra and give...     

基于太赫兹技术的药物检测

鉴于太赫兹辐射特有的光谱分辨性、功能性成像特点以及良好的穿透性和安全性等,太赫兹波谱技术迅速成为物质分析与检测等的重要工具。文章基于太赫兹时域光谱技术的实验数据,结合泛函密度理论(DFT)和HIPHOP模型,对一系列降糖类药物进行分子解析和功能基团识别;结合支持向量机理论(SVM),对4种郁金类中草药进行分析识别;并结合差式扫描量热法对葡萄糖—水合物的结晶水状态进行测定;最后对太赫兹时域技术在药物检测方面的优势和不足做了进一步的分析与展望。     

Monte Carlo Study of 3-d Z4 Gauge-Z2 Higgs Theory with Radial Degree of Freedom

Phase structure of the 3-d lattice Z₄ gauge-Z₂ Higgs theory is investigated by the Monte Carlo simulation. We find a new phase, named Higgs Ⅱ phaae, when λ (scalar self-coupling constant) is small. It is a result of the radial excitation of Higgs field.     

一个包含Euler函数及k阶Smarandache ceil函数的方程及其正整数解

设k≥2为给定的整数．对任意正整数n,k阶Smarandache ceil函数Sk（n）定义为Sk（n）=min{x：x∈N,n｜x^k}．本文的主要目的是利用初等方法研究函数方程Sk（n）=Ф（n）的可解性,并给出该方程的所有正整数解,其中Ф（n）为Euler函数．     

Visible Light Photocatalytic Functional TiO2/PVDF Nanofibers for Dye Pollutant Degradation

The photodegradation of poly(vinylidene fluoride) (PVDF)/titanium oxide (TiO₂) nanofibers under visible light is described, something that has not been previously reported in the literature. Visible light photocatalytic electrospun PVDF/TiO₂ nanofiber webs with anatase TiO₂ concentration varying from 0% to 20% (0%, 1%, 3%, 5%, 10%, and 20%) are produced, and their ability to degrade a toxic pollutant, Rhodamine B (RhB), is studied. Photodegradation study using UV–vis spectroscopy on PVDF/TiO₂ nanofiber webs (with TiO₂ concentration of 20%) shows that 80% of RhB is degraded within 6 h at the wavelength of 546 nm, which clearly falls within the visible spectra. The color of RhB solvent catalyzed by PVDF/TiO₂ nanofiber webs gradually changes from red to orange, then to yellow, further to light yellow till colorless, which suggests the complete photodegradation of RhB under visible light. To estimate the rate of photodegradation, the reaction constant k is calculated. Based on the k value, PVDF/TiO₂ nanofiber webs with 20% TiO₂ concentration show the highest degradation rate compared to other PVDF/TiO₂ nanofiber webs and pure TiO₂ nanoparticles. This study proves the viability of TiO₂‐based nanofibers to have catalytic capabilities under low‐energy visible light.     

基于动态线性模型的中国狭义货币需求及缺口的贝叶斯估计

本文应用动态线性模型研究我国的狭义货币需求,利用贝叶斯吉布斯抽样方法估计模型的参数和方差,获得了潜在货币需求趋势和货币缺口,对我国的货币供给进行分析并获得一些有益结论,对于央行更好地实施货币管理,保持经济平稳发展有积极意义。     

Tuning for the first 9-cell TESLA cavity of PKU

A method based on circuit model is used to tune the first home-made 9-cell TESLA type superconducting niobium cavity at Peking University.After tuning,a flat field profile with a final π-mode frequency within 3 kHz of target frequency is achieved.The field flatness is measured by a bead-pull method,and the relative electric field is calculated from the frequency shift perturbed by the bead stepping along the axis of the cavity.