CHEMICAL COMPOSITION AND ELECTRONIC STRUCTURE OF ZEOLITES STUDIED BY X-RAY PHOTOELECTRON SPECTROSCOPY AND 29Si MAS NMR

采用光电子能谱和Si核磁共振及化学分析方法研究了五种不同分子筛钠型和钾型的化学组成.结果发现,分子筛的表面Al/(Si+Al)比和骨架Al/(Si+Al)比与其体相Al/(Si+Al)比具有一致性,其电子结构与其组成及阳离子有关.分子筛表面晶格氧碱强度与其铝含量成正比,与阳离子的电负性成反比.     

陕西关中城市综合竞争力比较研究

在对城市竞争力内涵及其几种评价方法进行回顾的基础上,结合关中地区实际选取了8大类40个城市竞争力指标,采取主成分分析法对关中五市一区的综合竞争力进行了评定、排序和分析,从而为有关部门制定相应政策以提高城市的竞争力提供了决策依据。     

Efficient Multistep Forecast Procedures for Multivariate Time Series

Upon the evidence that infinite‐order vector autoregression setting is more realistic in time series models, we propose new model selection procedures for producing efficient multistep forecasts. They consist of order selection criteria involving the sample analog of the asymptotic approximation of the h‐step‐ahead forecast mean squared error matrix, where h is the forecast horizon. These criteria are minimized over a truncation order n_T under the assumption that an infinite‐order vector autoregression can be approximated, under suitable conditions, with a sequence of truncated models, where n_T is increasing with sample size. Using finite‐order vector autoregressive models with various persistent levels and realistic sample sizes, Monte Carlo simulations show that, overall, our criteria outperform conventional competitors. Specifically, they tend to yield better small‐sample distribution of the lag‐order estimates around the true value, while estimating it with relatively satisfactory probabilities. They also produce more efficient multistep (and even stepwise) forecasts since they yield the lowest h‐step‐ahead forecast mean squared errors for the individual components of the holding pseudo‐data to forecast. Thus estimating the actual autoregressive order as well as the best forecasting model can be achieved with the same selection procedure. Such results stand in sharp contrast to the belief that parsimony is a virtue in itself, and state that the relative accuracy of strongly consistent criteria such as the Schwarz information criterion, as claimed in the literature, is overstated. Our criteria are new tools extending those previously existing in the literature and hence can suitably be used for various practical situations when necessary. Copyright © 2015 John Wiley & Sons, Ltd.     

Does Disagreement Amongst Forecasters Have Predictive Value?

In the present study we examine the predictive power of disagreement amongst forecasters. In our empirical work, we find that in some situations this variable can signal upcoming structural and temporal changes in an economic process and in the predictive power of the survey forecasts. We examine a variety of macroeconomic variables, and we use different measurements for the degree of disagreement, together with measures for location of the survey data and autoregressive components. Forecasts from simple linear models and forecasts from Markov regime‐switching models with constant and with time‐varying transition probabilities are constructed in real time and compared on forecast accuracy. Copyright © 2015 John Wiley & Sons, Ltd.     

江西省降水中化学组分变化规律研究

通过对3年间江西省降水化学组分分析中主要离子的浓度及沉降量分析统计得出:江西省酸雨以硫酸型污染为主,但硫酸根离子在酸雨形成过程中的主导作用有下降趋势,降水中离子总浓度与降水pH值之间呈负相关关系.     

素环左理想上广义导子的复合

利用GPI素环的结构性质以及域上向量空间与其自同态环的关系证明了: 具有特殊形式的两个广义导子的复合可以在素环的非零左理想上起广义导子作用, 并对这几种特殊形式的广义导子给出了完整的描述, 从而给出了广义导子的复合在素环的非零左理想上起广义导子作用的充分必要条件.     

非二元相关免疫函数和弹性函数的特征

讨论了从[GF(q)]n到[GF(q)]m的相关免疫函数和弹性函数F的特征.首先提供了复合函数G·F的特征,其中G是从[GF(q)]m到[GF(q)]s的函数,同时得到了一些关于F的分量函数的非零线性组合的性质.给出了相关免疫函数和弹性函数的矩阵特征.利用傅里叶变换刻画了弹性函数的特征.     

天津地区蜻蜓研究

依据南开大学和天津自然历史博物馆馆藏标本及近年来在天津地区17个采样点不同时期多次调查采样结果,记述天津地区蜻蜓2亚目,7科,20属,30种,其中包括天津地区1新记录科,2个新记录属和10个新记录种,初步分析区系组成,并通过数十年来蜻蜓种群的变动对该地区环境和多样性保护问题提出新的看法.     

不同海拔区域内牦牛肠道菌群结构组成多样性研究

探索不同海拔牦牛肠道菌群结构组成,为不同海拔区域间牦牛的饲养交流提供帮助. 本研究随机采集海拔2 897~4 717 m的12头牦牛的新鲜粪便样本,用16s rDNA技术对样本宏基因组测定,比较分析高低海拔牦牛肠道菌群的OTU丰度差异,研究高低海拔区域的牦牛肠道微生物菌群结构组成. 结果显示,高海拔与低海拔地区牦牛肠道菌群在门、纲、目、科、属、种层面菌群结构组成不同. 高低海拔区域的牦牛肠道菌群有8个菌在属水平差异显著（P＜005）. 结果表明,高海拔与低海拔牦牛肠道菌群结构组成存在一定差异,低海拔地区牦牛肠道菌群OTU丰度比高海拔的更为丰富.     

天津地区鸟类组成及多样性分析

2002-2005年,采用样点和样线法对天津地区的鸟类组成及多样性进行调查.共记录到鸟类389种,隶属19目68科184属.鸟类区系以古北种类最多,203种,占总种数的52.19%;东洋种42种(10.79%)和广布种144(37.02%).居留型以旅鸟最多,234种(60.15%);夏候鸟次之,74种(19.02%);留鸟55种(14.14%);冬候鸟最少,仅26种(6.68%).基于G-F多样性指数对天津鸟类多样性进行分析,结果显示,湿地水域鸟类多样性稍高,为0.76,居民点及城市公园最低,为0.58,山地和平原田野均为0.75,表明天津地区鸟类的组成及多样性分布与其环境相关.