Perfluorooctane sulfonate (PFOS) and other fluorochemicals in viscera and muscle of farmed pigs and chickens in Beijing,China

Eleven perfluorinated compounds (PFCs) were determined in tissue samples from farmed pigs and chickens (n=143) that were purchased in Beijing in March 2009. The total PFCs mean concentration was the highest in pig liver (3.438 ng g^–1 wet weight (ww)), followed by pig kidney (0.508 ng g^–1 (ww)), pig heart (0.167 ng g^–1 (ww)), chicken liver (0.098 ng g^–1 (ww)), chicken heart (0.050 ng g^–1 (ww)), pork loin (0.018 ng g^–1 (ww)), and chicken breast (0.012 ng g^–1 (ww)). Among the PFCs analyzed, perfluorooctane sulfonate (PFOS) was the predominant compound in viscera and muscle of farmed pigs and chickens. In addition, a strong linear correlation (r = 0.932) was observed between the concentrations of PFOS and perfluoroundecanoic acid (PFUnDA) in pig liver. Our preliminary conclusion is that there is little potential risk of exposure to PFCs via the consumption of these products in Beijing.     

Oil financialization and volatility forecast: Evidence from multidimensional predictors

Using the generalized dynamic factor model, this study constructs three predictors of crude oil price volatility: a fundamental (physical) predictor, a financial predictor, and a macroeconomic uncertainty predictor. Moreover, an event‐triggered predictor is constructed using data extracted from Google Trends. We construct GARCH‐MIDAS (generalized autoregressive conditional heteroskedasticity–mixed‐data sampling) models combining realized volatility with the predictors to predict oil price volatility at different forecasting horizons. We then identify the predictive power of the realized volatility and the predictors by the model confidence set (MCS) test. The findings show that, among the four indexes, the financial predictor has the most predictive power for crude oil volatility, which provides strong evidence that financialization has been the key determinant of crude oil price behavior since the 2008 global financial crisis. In addition, the fundamental predictor, followed by the financial predictor, effectively forecasts crude oil price volatility in the long‐run forecasting horizons. Our findings indicate that the different predictors can provide distinct predictive information at the different horizons given the specific market situation. These findings have useful implications for market traders in terms of managing crude oil price risk.     

含锡不锈钢溶质偏析模型计算

结合微观偏析模型及Thermo-calc软件,考虑了Mn S的析出,用微观偏析理论研究了含锡铁素体不锈钢中溶质的偏析行为.主要讨论了铁素体不锈钢中C,Mn,S,P,Cr在凝固过程中的偏析程度,研究了溶质偏析对零强度温度(ZST)、零塑形温度(ZDT)的影响规律.分析了锡在铁素体钢和低碳钢中偏析行为的差异,解释了低碳钢的热加工塑形凹槽现象,理论分析了微量元素对热塑性的影响.结果表明,Sn的凝固偏析比远大于除P,S外的其他元素,Mn对S元素凝固偏析有抑制作用.锡为易偏析元素,其在奥氏体相中的凝固偏析比大于在铁素体相中的偏析比.     

Fabrication and characterization of electrospun TiO2/CuS micro-nano-scaled composite fibers

A process to fabricate a kind of novel micro-nano scaled TiO2/CuS composite fibers by electrospinning technique and chemical precipitation method was developed in the present study.The microstructures ...     

园艺作物种质资源管理及数据库建设研究综述

简述了国内外园艺种质数据库的现状,主要分析了数据库建设中的关键技术,尤其是数据采集标准的制定,并就未来数据库的发展和存在问题进行了展望.认为应加快园艺种质数据库的建设,增加作物收集的种类,并建立信息共享系统.涉及作物更广泛、共享性更强.     

Softev: UML-based PSEE environment

Software development processes, as a mean to ensure software quality and productivity, have been widely accepted within the software development community. This research introduces how to assist developers to establish quality management plan and monitor the implementation of software processes quantitatively in a CASE environment. A PSEE (process-centered software engineering environment) named Softev has been brought forward to provide developers the environment to define, execute and monitor their processes. As UML is becoming a standard diagrammatic notation for object-oriented modeling and is spreading rapidly, it has been chosen to express the artifacts developed during the requirement analysis and system design stages. In the early products of software process engineering, most research mainly focus on the representations of complex organizational processes and architectures for process-centered application support environment. However, the metrics of software processes and artifacts was not paid sufficient attention to. This research proposes the attributes to be measured during the development period which enable managers to predict and supervise the software project more precisely.     

判别分析中基于总体可分性的变量选择

讨论了判别分析中变量选取的方法，文中首先定义了反映总体间区另别的总体可分性，然后在此基础上给出了总体可分性函数，并且讨论了该函数的三个性质，根据此函数可以定义一个判别变量选取的目标函数，最后给出了可行的选取判别变量的算法过程。     

农牧业基地水资源可持续开发利用程度分析方法研究

水资源的可持续开发利用是可持续发展的一个重要组成部分，在我国农牧业基地，缺水问题是制约农牧业发展的“瓶颈”。文中提出了一种新的决策方法来评价农牧业基地水资源的可持续开发利用程度，对于指导农业基地水资源的合理开发与利用提供了新的研究思路与方法。     

基于物联网的安全信息管理模型研究

为明确物联网环境下安全信息管理的开展依据，根据安全信息传递规律，本文对基于物联网的安全信息管理模型进行研究。首先，明确相关概念；其次，以物联网结构为基础，搭建由“感知层-网络层-应用层”构成的安全信息管理模型，并分析其基本内涵；最后，将安全信息在模型中的传递过程看作水流，分析模型的延伸内涵与应用前景。研究表明，基于物联网的安全信息管理模型能有效弥补目前安全信息管理实践的不足，有助于完善安全信息的收集机制，保证安全信息传递的时效性，是未来安全信息管理的重要理论依据。     

装配式板桥的横向预应力设计

基于摩擦抗剪的概念,提出一种确定横向预应力张拉设计值的方法.计算表明:在考虑板间铰缝及混凝土桥面板纵向开裂的情形下,装配式板桥的横向联结性能随着横向预应力的增大而增加;但是当横向预应力水平达到一定的程度(如NPO)之后,其横向联结性能基本不变,横向预应力的设计张拉值应大干NPO.通过美国马里兰州的一座装配式实心板桥的车载试验,研究了横向预应力对桥梁横向联结性能的影响.理论及试验表明,当桥面板及铰缝没有纵向开裂时,板间具备了足够的荷载横向传递能力,横向预应力对桥梁的横向联结性能影响不大.但横向预应力的存在,保证了铰缝和铺装层开裂后桥梁具有良好的横向联结性能,可以有效地抑制纵向裂缝病害的发展,确保桥梁的使用性能和安全性.