级联No序列的三项式特性研究

利用有限域GF(2n)到其子域GF(2m)上的迹函数及其性质,研究一类非线性扩频序列的密码学性质,即级联No序列的三项式特性。给出级联No序列的三项生成多项式的形式,将级联No序列三项式特性的结论应用到二元No序列中,解决了二元No序列的三项式特性问题。分析结果表明,级联No序列不仅具有三项式对,而且具有正则三项式对。     

时序最短路径算法

最短路径是指网络中两结点间阻碍强度最小的一条路径。传统的最短路径是在静态网络上进行研究的,然而现实生活中很多网络是动态的、有时序性的,因此传统的最短路径算法并不能用于解决所有最短路径问题。为了寻找时序网络上的最短路径,在Dijkstra算法思想基础上,提出一种时序最短路径的精确算法。文中利用严格的数学推导证明了本算法的可行性,并通过对构建的网络做实证分析验证了算法的正确性。     

A three-dimensional model for suspension-to-membrane-wall heat transfer in circulating fluidized beds

A three-dimensional model is proposed for both furnace-side and wall-side heat transfer in circulating fluidized beds with membrane walls. Following previous publications (Int. J. Heat Mass Transfer (2003a, b)), a core-annulus flow structure is employed in the model, with consideration of the membrane wall influence on bed hydrodynamics. The model couples radiation, conduction and convection on the furnace side to conduction and convection on the wall side. Radiation in the wall layer is simulated by the moment method. A finite-element method is employed to solve the set of non-linear, partial differential equations. The solution is demonstrated for a typical example. The model gives predictions of suspension-to-wall heat transfer which show satisfactory agreement with published experimental data.     

带隐变量的回归模型EM算法

带有隐变量的回归模型具有非常广泛的应用场合,隐回归模型的参数求解问题依赖于自变量的分布假设。基于自变量的beta分布的假设条件,给出了隐回归模型的EM算法,详细地推导了模型中的参数求解过程,给出了使用牛顿法求解beta分布参数的算法,并提出一个合适的初值选择算法。在模拟数据和真实数据的基础上进行了详细的比较性试验,结果表明,对具有不同分布特征的因变量观察值,EM算法能够有效地求解隐回归模型的参数。     

一种基于自然最近邻的离群检测算法

任何涉及k近邻求解问题的算法被应用于处理不同特征的数据集时,参数k值的选择都会明显影响算法的性能和结果。因而,如何选择k近邻算法中敏感参数k值一直是一个研究难点。提出了一种新的近邻关系———自然最近邻,它不需要设置参数k,每个节点的邻居是由算法自适应计算而形成的。针对离群点检测的特殊性,通过确定自然最近邻居搜索算法的终止条件,提出一种基于自然最近邻的新的离群检测算法ODb3N。实验表明,该算法不仅避免了k近邻中参数的选择问题,而且能够更有效地发现离群簇。     

Rhodococcus rhodochrous tg1-A6腈水解酶的表达和催化研究

采用紫外线和氯化锂诱变得到一株名为Rhodococcus rhodochrous tg1-A6的菌种,该菌经过培养基和培养条件的优化能够产生高酶活的腈水解酶.优化培养条件为温度28℃、摇床转速200r/min、种子培养20h后以6%接种量接种于产酶培养基,初始pH 7.0,300mL摇瓶装液量为40mL.酶活达到21.96 U/mL.在含一定菌体的100 mL反应体系中,经过10 h连续43次补加底物丙烯腈,能使产物丙烯酸的质量浓度累积到414.5g/L.     

Effect of H2O adsorption on the electrical transport properties of double-walled carbon nanotubes

Water molecules adsorbed on a double-walled carbon nanotube (DWCNT) serve as charge trapping centers when present in low density and as electron donors when present in high density. There is a discontinuous change between the low- and high-density regions. H₂O molecules are apt to be adsorbed on the outer surface of DWCNTs, and in this case the electrical transport properties are extremely sensitive to environment, which suggests that DWCNTs are hole doped and act as an electric dipole with the inner tube.     

Swelling behavior of poly(sodium acrylate)/kaoline superabsorbent composite

Using partly neutralized acrylic acid as monomer, kaoline ultrafine powder as filler and N,N′‐(dimethyl)acrylamide as crosslink agent, poly(sodium acrylate)/kaoline superabsorbent composite was synthesized by aqueous solution polymerization method. Using the superabsorbent composite as collagen, a hydrogel was prepared. The influence of the neutralization degree of superabsorbent collagen, the compositions, the concentration, and the pH value of exterior solution on the swelling behavior of the hydrogel was investigated. It was found that the swelling capability of the hydrogel depended on the groups on the collagen. The swelling capability of the hydrogel relied on the ionic intensity, molecular polarity, molecular volume, as well as the concentration of exterior solution. When the pH value of exterior solution was equal to seven, the hydrogel has a maximum swelling value of 800 times. POLYM. ENG. SCI. 46:324–328, 2006. © 2006 Society of Plastics Engineers     

Study on esterification of acrylic phenolic resin by maleic anhydride and photocrosslinking properties of the alkali‐soluble product

An alkali‐soluble, photocrosslinkable polymer was synthesized by esterification of OH groups of acrylic phenolic resin with maleic anhydride. The OH groups were formed by the ring‐opening reaction of epoxy groups of epoxy phenolic resin with acrylic acid. The esterification conditions were studied. The results showed that it is better to use tetramethyl ammonium bromide as catalyst than N,N‐dimethylbenzylamine. The conversion of maleic anhydride in acetone can reach about 80% at 56°C for 4 h. The purified product was characterized by IR, DSC, and TGA. The product containing acrylate and maleic acid monoester groups, above a certain content, can be dissolved in 1% Na₂CO₃ solution. The photocrosslinkable properties of the product were investigated through selection of photoinitiator, accelarator, crosslinkable diluent monomer, etc. The acrylate and maleic acid monoester group‐containing phenolic resin exhibited very good photocrosslinking behavior, since it contains double bonds from both acrylate groups and maleic acid monoester groups. The activity of photoinitiator decreases in the order: isopropylthioanthraquinone > benzoin ethyl ether (BE) > anthraquinone (AQ) > benzophenone > Michel ketone (MK) > 2,2‐diethoxyacetophenone. The combination of some photoinitiators showed synergistic effects. The order of increasing activity for the accelerator is as follows: MK > ethyl p‐(dimethylamino)benzoate > N,N‐dimethylaniline > triethanolamine. The optimum diluent monomer is trimethylolpropane trimethacrylate. The gel content of the mixture of the resin and trimethylolpropane trimethacrylate could reach 85% using the combined photoinitiators of BE and AQ under UV exposure for 120 s. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1607–1614, 2005     

硫化镉微晶掺杂玻璃及薄膜的制备与光学性能的研究

用溶胶－凝胶法制备了硫化镉微晶掺杂玻璃和薄膜材料，使用了三种不同的方法引入所需的Ｓ＾２－离子，通过Ｘ射线和透射电镜等实验手段，分析了微晶结构显微相，标定出晶体确为ＣｄＳ，并测得微晶的尺寸。从室温吸收光谱上观察到吸收截止边随着ＣｄＯ掺杂凝胶在１５０℃时通Ｈ２Ｓ气体时间的延长（１－８ｈ）而移向长波方向，从而确定其为量子尺寸效应的实验依据。在Ｎｄ：ＹＡＧ强激光光场的作用下，薄膜样品中观察到二次谐波信号，