K_(1,n)-free图具有给定性质的[a,b]-因子的一个充分条件

图G称为K1,n-free图,如果它不含K1,n作为其导出子图.对K1,n-free图具有给定性质的[a,b]-因子涉及到最小度条件进行了研究,得到一个充分条件.     

关于一类具有相同非负群逆和M-P逆的非负矩阵的进一步研究

1引言设A是n阶非负方阵．设矩阵方程(1)AXA=A,(2)XAX=X,(3)(AX)~T= AX,(4)(XA)~T=XA,(5)AX=XA．A具有非负广义逆是指存在非负方阵X满足方程(1)～(4),并记为A~(?)．A具有非负群逆是指存在非负方阵X满足方程(1),(2),(5),并记为A~#．在A~(?)存在的前提下,两者相同的充分必要条件有(a)AA~(?)=A~(?)A；(b)A~(?)=p(A),其     

On Dirichlet Characters of Polynomials

The main purpose of this paper is to use the properties of Gaussiansums and the analytic method to study the problem of calculatingone kind of character sums modulo q, and to give an interestingidentity. 2000 Mathematics Subject Classification 11L10, 11L40.     

Research of spatial resolution in external electro-optic probing

A new method, based on zero point of longitudinal electric field, was used to determine the spatial resolution of external electro-optic (EO) probing equipment. Considering the diffraction of Gauss beam, the result of external EO probing was simulated which was in accordance with the experiment. A spatial resolution <1 μm was demonstrated initially in our equipment using 650 nm laser diode as probe beam and semi-insulating GaP as probe tip.     

Hydrodynamic Properties of Fe3O4 Kerosene-Based Ferrofluids with Narrow Particle Size Distribution

We investigate the hydrodynamic properties of Fe3O4 kerosene-based ferrofluids with narrow particle size distribution. The ferrofluids are synthesized by improving chemical coprecipitation technique. A narrow distribution of 8.6-10.8nm particle sizes is obtained from the magnetization curve with the free-form model based on the Bayesian inference theory. The fitting result is consistent with average particle size obtained from x-ray diffraction. With the increase of applied magnetic field and magnetic particle concentration, apparent viscosity of ferrofluids increases. At concentration 4.04%, the type of flow for the ferrofluid transforms from Newtonian to Bingham plastic fluid as the applied magnetic field increases.     

Fabrication of Dendrimer－like PAMAM Based on Silica Nanoparticles

A G 4.0 dendrimer-like poly (amido amine) (PAMAM) based on silica nanoparticles was fabricated via a divergent approach.It was built from γ-aminopropyi silica nanoparfides (APSN) core via repetitive addition of acrylate (MA) and hexylenediamine (HDA). FT-IR and EA were used to monitor the progress of dendrimer during each step. The amino group content of the resulting product increased from 0.49 to 3.72 mmol/g after the 4th generation. In addition, the percentage of grafting increased with increasing generation and reached to 65.9% after 4th generation. It was found that the resulting silica nanoparticles could be dispersed in methanol with a mean hydrodynamic particle diameter of 152.7 nm although the silica nanoparticles had agglomerated during the storage period.     

A theoretical study of the ion pair SN2 reaction between lithium isocyanates with methyl fluoride with inversion and retention mechanism

This paper is devoted to a detailed theoretical study of an ion pair S_N2 reaction LiNCO+CH₃F in the gas phase and in solution at the level of MP2(full)/6-31+G**//HF/6-31+G**. Two possible reaction mechanisms, inversion and retention, are discussed. There are eight possible reaction pathways. The inversion mechanism is more favorable no matter in the gas phase or in solution based on analyses of the transition structures. Methyl isocyanate should form preferentially in the gas phase and more stable methyl cyanate is the main product in solution. The retardation of the reaction in solvents was attributed to the difference in solvation in the separated reactants and in the transition state.     

Photoluminescence linewidth broadening due to alloy/thickness fluctuation of CdxZn1 − xSe/ZnSe triple quantum wells

Photoluminescence (PL) linewidth broadening of Cd_xZn_{1 − x}Se/ZnSe triple quantum wells, grown on GaAs substrates by molecular beam epitaxy (MBE), has been investigated. Various quantum well (QW) samples have been prepared with different QW thickness and composition (Cd-composition). Measured and calculated PL linewidth are compared. Both composition and thickness fluctuations are considered for the calculation with the parameters such as the volume of exciton, nominal thickness and composition of QWs. Surface roughness measured by atomic force microscopy (AFM) is used to estimate the interface roughness. Results show that when Cd-composition increases additional linewidth broadening due to Zn/Cd interdiffusion is enhanced.     

正交各向异性矩形板受迫振动的三维分析

从正交各向异性三维弹性动力学的控制方程出发，在求得四边简支矩形板自由振动频率和位移振型的基础上，构造了受迫振动的位移函数；利用自由振动位移振型的正交性，将控制方程的空间变量和时间变量分离，得到了广义质量、广义力和频率表示的关于时间的2阶常微分方程，从而得到了正交各向异性弹性矩形板在受迫振动下的位移场和应力场．给出了本文方法与薄板理论的算例．     

介孔网络电路

用二次阳极氧化法制备纳米多孔氧化铝板,然后用磁控溅射方式在纳米多孔氧化铝板表面镀金得到介孔网络电路,对该介孔网络电路进行输运测量,发现其具有非线性电阻.