Study on the long‐term thermal‐oxidative aging behavior of polyamide 6

The long‐term thermal‐oxidative aging behavior of polyamide 6 (PA6) was studied by comparison with the stabilized sample in this work. The variation of mechanical properties of the pure and the stabilized samples of PA6 with aging time at 110°C, 130°C, and 150°C were investigated, respectively. The aging mechanism of PA6 under heat and oxygen was studied in terms of the reduced viscosity, crystallization behavior, dynamic mechanical behavior, and chemical composition through the methods of polarized light microscopy (PLM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X‐ray photoelectron energy spectrum (XPS), and so on. The results indicated that at the initial stage of aging, the molecular crosslinking reaction of PA6 dominated resulting in the increase of the mechanical strength, reduced viscosity, and the glass transition temperature of the sample. And the molecular degradation dominated in the subsequent aging process resulting in the decrease of the melting temperature, the increase of the crystallinity, and the formation of the oxides and peroxides products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal stabilization effect of biphenol monoacrylate on polyamide 6

Biphenol monoacrylate (AL) was combined with a traditional hindered phenolic‐based binary antioxidant system to form a ternary stabilization system for the purpose of further improving the thermal–oxidative stability of polyamide 6 (PA6). The thermal stabilization effect of the antioxidant AL on PA6 was studied in terms of the reduced viscosity, the chemical structure, the yellow index, and the mechanical properties. The results showed that the antioxidant AL, with the proper chemical structure, could improve the thermal stability of PA6 effectively through a unique bifunctional stabilizing mechanism. The interaction of the molecules of PA6 with the antioxidant AL was investigated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Global adaptive control of nonlinearly parametrized systems

In this paper, we consider global adaptive control of nonlinearly parametrized systems in parametric-strict-feedback form. Unlike previous results, we do not require a priori bounds on the unknown parameters, which is as in the linear parametrization case. We also allow unknown parameters to be time-varying provided they are bounded. Our proposed adaptive controller is a switching type controller, in which the controller parameter is tuned in a switching manner via a switching logic. Global stability results of the closed-loop system have been proved.     

固载杂多酸催化剂气相催化合成乙酸丁酯的研究

在气固相反应体系中研究了酸处理膨润士固载的具有 Keggin结构的四种杂多酸在乙酸丁酯合成中的催化性能。实验结果表明 :同一载体负载不同杂多酸催化活性相似 ;不同载体负载的同一种杂多酸的催化活性与催化剂的表面酸性呈顺变关系。同时考察了反应温度 ,空速 ,酸 /醇比对催化活性的影响。在酸 /醇比为 1 ,温度为 1 2 0℃ ,空速为 3～ 5h- 1时 ,正丁醇和乙酸有较高的转化率 ,选择性接近 1 0 0 %。     

An optimality criterion in a control problem for a Sobolev-type linear equation

The necessary and sufficient conditions for solving an optimal control problem with a quadratic cost function for a system, whose state is described by a linear confluent equation in Hilbert spaces are obtained. We apply these results for investigating an optimal control problem for the Dzektser equation of the evolution of the free surface of a filtering fluid.     

Fivefold symmetry in real and reciprocal spaces

Tetrahedrally close-packed structures with juxtaposed pentagonal antiprisms, such as the μ, C14 Laves and the newly found C phases, were studied by means of HREM and SAD. It was found that each bright spot in the structural image corresponds to an antiprism. Differently oriented domains of these phases intergrow frequently with a fairly good match at the interphase boundary. All diffraction patterns of these phases show a fivefold distribution of spot-pairs, and it is shown that this fivefold symmetry comes from the pentagons and spot-pairs from two pentagonal prisms superposed in antisymmetrical positions.     

鄱阳湖湖底沉积物放射性水平

本文报道了1985年鄱阳湖湖底沉积物放射性水平的调查结果。沉积物中 U、Th、~(226)Ra、~(40)(?)和~(137)Cs 的比活度分别为64.8、67.9,58.9、676.1和3.5Bq/kg;用~(137)Cs 测龄方法作了沉积物泥芯垂直深度的年代定位,由此得知1985—1958年对应深度沉积物中 U、Th、~(226)Ra 和~(40)K 的比活度与1957—1930年对应深度沉积物比较无显著性差异;U、Th 和~(226)Ra 的浓集因予分别为5.2×10~413.9×10~4和4.8×10~4L/kg。     

Feature Reduction via Generalized Uncorrelated Linear Discriminant Analysis

High-dimensional data appear in many applications of data mining, machine learning, and bioinformatics. Feature reduction is commonly applied as a preprocessing step to overcome the curse of dimensionality. Uncorrelated Linear Discriminant Analysis (ULDA) was recently proposed for feature reduction. The extracted features via ULDA were shown to be statistically uncorrelated, which is desirable for many applications. In this paper, an algorithm called ULDA/QR is proposed to simplify the previous implementation of ULDA. Then, the ULDA/GSVD algorithm is proposed, based on a novel optimization criterion, to address the singularity problem which occurs in undersampled problems, where the data dimension is larger than the sample size. The criterion used is the regularized version of the one in ULDA/QR. Surprisingly, our theoretical result shows that the solution to ULDA/GSVD is independent of the value of the regularization parameter. Experimental results on various types of data sets are reported to show the effectiveness of the proposed algorithm and to compare it with other commonly used feature reduction algorithms.     

Microstructure investigations of ball milled materials

HREM and FEG TEM were emphasized and extensively used to follow the most subtle changes in the structure and composition of ball-milled Cu, Fe-Cu, and thermally decomposed Fe60Cu40. Some significant results are obtained and summarized as follows: HREM shows that the deformation of ball-milled copper proceeds mainly by twinning and shear bands (SBs) formation. The nano-grains formed during ball milling (BM) contain a high density of dislocations. The grain boundaries (GBs) of nanocrystalline (NC) Cu prepared by BM are ordered, curved, and strained, but disordering, lattice distortion, and nanovoids in local regions were frequently observed. Nanoscale composition analysis on mechanically alloyed Fe16Cu84 shows that the average Fe content in both the interior of grains and the GBs is close to the designed composition, which proves that a supersaturated solid solution has really formed. However, the Fe content is rather inhomogeneous between the larger and smaller grains, which infers the inhomogeneous mixing of Fe and Cu during mechanical alloying (MA). NC structure and the mechanical force-enhanced fast diffusion are the reasons of the formation of supersaturated solid solutions in immiscible systems with positive enthalpy of mixing. HREM observations carried out with the thermally decomposed Fe60Cu40 solid solution show that the Nishiyama (N-W) or Kurdyumov-Sachs (K-S) orientation relationships exist between alpha-Fe and Cu. Energy dispersive X-ray spectra (EDXS) results show that the Cu content in these alpha-Fe grains reaches as high as 9.5 at.% even after heating to 1,400 degrees C, which is even higher than the maximum solubility of Cu in gamma-Fe at 1,094 degrees C.     

高校资产管理系统的设计与研究

设计了适合衢州职业技术学院固定资产日常管理工作的资产管理系统.对该系统作了需求分析和详细设计,采用了ASP.NET框架技术和SQL Server后台数据库相结合的设计方法.系统基本实现了资产的登记、审核、查询、变更、统计、打印报表、上报数据等功能,有效地解决了资产管理工作的数据混乱、不准确、处理流程不规范等问题,有效地提高了管理人员的工作效率.