Structural changes in isothermal crystallization process of polyoxymethylene investigated by time-resolved FTIR, SAXS and WAXS measurements

Structural evolution in the isothermal crystallization process of polyoxymethylene from the molten state has been investigated by carrying out the time-resolved measurements of infrared spectra and synchrotron small angle X-ray scattering (SAXS) and wide angle X-ray scattering. In case of isothermal crystallization at 130 °C, for example, the infrared bands intrinsic of folded chain crystal (FCC) morphology appeared at first, and then the bands of extended chain crystal (ECC) morphology were detected with time delay of ca. 150 s. In the SAXS experiment at 130 °C, the lamellar stacking structure of the long period of ca. 15 nm was observed at first, which changed rapidly to ca. 12 nm in a short time. The SAXS peak with the long period of ca. 6 nm started to appear with a time delay of ca. 150 s after the initial lamellae appeared and coexisted with the initially-observed 12 nm peak. Judging from the timing to detect these characteristic infrared and SAXS signals, a good correspondence was found to exist between the stacked lamellar structure of 12 nm long period and FCC morphology and between the structure of 6 nm long period and ECC morphology. The quantitative analysis was made for the SAXS data on the basis of the lamellar insertion model combined with the paracrystalline theory of the second-kind of disorder. The following structural evolution was deduced from all these results. Immediately after the temperature jump from the melt to 130 °C, the stacked lamellar structure of FCC morphology was generated at first. New lamellae were formed from the amorphous region in between the originally-existing lamellae about 150 s later, where the random chain segments bridging the adjacent lamellae were extended to form the taut tie chains, giving infrared bands of ECC morphology. This inserted lamellar structure of 6 nm long period coexisted at a population of ca. 6% with the initially-formed lamellar stacking structure of 12 nm long period. When the experiment was made at 150 °C, only the formation of stacked lamellar structure of FCC morphology was observed and the insertion of new lamella did not occur.     

与供应商的采购合作关系分析

对与供应商的采购合作关系进行了初步的分析，通过需求分析、选择供应商、正式建立合作关系、实施和加强合作关系4个过程展开，分别对筛选战略、供应管理计划流程、供应商的评估和选择、认证管理等关键问题进行初步分析，旨在使采购工作趋于完美。     

Data structure and algorithms for fast automatic differentiation

In this paper we discuss the data structure and algorithms for the direct application of generalized Leibnitz rules to the numerical computation of partial derivatives in forward mode. The proposed data structure provides constant time access to the partial derivatives, which accelerates the automatic differentiation computations. The interaction among elements of the data structure is explained by several numerical examples. The paper contains analysis of the developed data structure and algorithms. Copyright © 2003 John Wiley & Sons, Ltd.     

The magnetic structure of TbNiSiD1.78

TbNiSiD_1.78 has been studied by powder neutron diffraction below 100 K. The compound takes the hexagonal room temperature structure at 100 and 50 K (P6₃/mmc). At 2 K, below the antiferromagnetic ordering temperature of 10 K, there is a small orthorhombic distortion of the lattice. The refined unit-cell dimensions at 2 K (space group Pnma) are a=7.9505(2), b=4.02502(14), c=6.9823(2) Å. The magnetic moments of Tb are 8.71(6) μ_B, and are ordered antiferromagnetically along a.     

创建互联网业务价值链

为促进互联网的良性发展,要使设备制造商、电信运营商、虚拟运营商/集团用户、内容提供商和最终用户构成一条互联网业务价值链,价值链的创建对互联网接入设备提出了更高的要求,华为公司的Quid-wayTMA8010Expert多业务综合接入平台可构建宽带城域网分组语音解决方案、可平滑演进为下一代网络中的媒体网关、提供窄带价值链、提供唯一号码业务以及实现多业务综合接入。     

氧化锌压敏电阻的老化机理

研究了ZnO压敏电阻的老化现象,提出了一种新的老化机理-线性链理论。该理论认为,在外电场作用下,压敏电阻势垒高度降低;当降低到一定值时,晶界可变电阻转化为线性晶界电阻,从而压敏链转化为线性链。线性链是稳定的,因而压敏电阻老化到一定程度后其电性能将不能完全恢复。     

DXDK800自动充填包装机料袋长度的调整

本文主要介绍了在DXDK800自动充填包装机中 ,采用一种新型的齿轮—蜗轮、蜗杆差速器来对膜片的进给速度进行微量的调整。及采用一种新型的可调式偏心链轮来调整横封辊的瞬时线速度 ,使其与料袋膜的进给速度相一致     

界面流法计算反应堆六角形燃料组件中子通量密度分布

利用界面流法计算两维六角形轻水堆燃料组件中子通量密度分布。子区内中子源在空间上采用二次分布近似，还考虑了六角形组件周边水隙对组件内中子通量密度的影响。根据提出的模型，编制了TPHEX－E程序，并对一些轻水堆六角形组件问题作了计算，计算结果与蒙特卡罗方法计算结果进行了比较，符合良好。本程序可用于六角形轻水堆燃料组件计算。     

A Bayesian propensity score adjustment for latent variable modeling and MCMC algorithm

The estimation of the differences among groups in observational studies is frequently inaccurate owing to a bias caused by differences in the distributions of covariates. In order to estimate the average treatment effects when the treatment variable is binary, Rosenbaum and Rubin [1983. The central role of the propensity score in observational studies for causal effects. Biometrika 70, 41-55] proposed an adjustment method for pre-treatment variables using propensity scores. Imbens [2000. The role of the propensity score in estimating dose-response functions. Biometrika 87, 706-710] extended the propensity score methodology for estimation of average treatment effects with multivalued treatments.However, these studies focused only on estimating the marginal mean structure. In many substantive sciences such as the biological and social sciences, a general estimation method is required to deal with more complex analyses other than regression, such as testing group differences on latent variables. For latent variable models, the EM algorithm or the traditional Monte Carlo methods are necessary. However, in propensity score adjustment, these methods cannot be used because the full distribution is not specified.In this paper, we propose a quasi-Bayesian estimation method for general parametric models that integrate out the distributions of covariates using propensity scores. Although the proposed Bayes estimates are shown to be consistent, they can be calculated by existing Markov chain Monte Carlo methods such as Gibbs sampler. The proposed method is useful to estimate parameters in latent variable models, while the previous methods were unable to provide valid estimates for complex models such as latent variable models.We also illustrated the procedure using the data obtained from the US National Longitudinal Survey of Children and Youth (NLSY1979-2002) for estimating the effect of maternal smoking during pregnancy on the development of the child's cognitive functioning.     

未结盟大学的联盟

通过梳理管理学界对战略联盟的定义，发现价值链的鸸释同样适用于大学问的战略联盟。通过对已有的大学战略联盟的分析，提出了名校联盟与非名校联盟间的若干差异，最后提出了我国大学联盟战略的若干建议。