Local Trends in Price‐to‐Dividend Ratios—Assessment,Predictive Value,and Determinants

Persistent variations of the log price‐to‐dividend ratio (PD) and their economic determinants have attracted a lively discussion in the literature. We suggest a gradually time‐varying state process to govern the persistence of the PD. The adopted state‐space approach offers favorable model diagnostics and finds particular support in out‐of‐sample stock return prediction. We show that this slowly evolving mean process is jointly shaped by the consumption risk, the demographic structure, and the proportion of firms with traditional dividend payout policy during the past 60 years. In particular, the volatility of consumption growth plays the dominant role.     

现代农业信息系统研究

结合信息技术与传统农业，分析了我国现代化农业信息的发展状况，并对农业信息系统的形式提出了建议，构建了现代农业信息系统的框架，引入了信息过滤和数据挖掘相结合的思想，并分析了这些技术的结合，表明了这样的系统对进行农业决策起到了很大的作用，从而说明了现代化农业信息系统对农业发展的重要性。     

中间件与多层分布式体系技术

传统两层模式已无法适应开放系统中实现大规模的关键业务的要求,以交易中间件为基础框架的多层分布式体系应运而生,它支持分布计算,提供跨网络、硬件和OS平台的透明性的应用或服务的交互、且支持标准的协议、接口等。     

Trends and cycles in economic time series: A Bayesian approach

Trends and cyclical components in economic time series are modeled in a Bayesian framework. This enables prior notions about the duration of cycles to be used, while the generalized class of stochastic cycles employed allows the possibility of relatively smooth cycles being extracted. The posterior distributions of such underlying cycles can be very informative for policy makers, particularly with regard to the size and direction of the output gap and potential turning points. From the technical point of view a contribution is made in investigating the most appropriate prior distributions for the parameters in the cyclical components and in developing Markov chain Monte Carlo methods for both univariate and multivariate models. Applications to US macroeconomic series are presented.     

Detecting shocks: Outliers and breaks in time series

A single outlier in a regression model can be detected by the effect of its deletion on the residual sum of squares. An equivalent procedure is the simple intervention in which an extra parameter is added for the mean of the observation in question. Similarly, for unobserved components or structural time-series models, the effect of elaborations of the model on inferences can be investigated by the use of interventions involving a single parameter, such as trend or level changes. Because such time-series models contain more than one variance, the effect of the intervention is measured by the change in individual variances.We examine the effect on the estimated parameters of moving various kinds of intervention along the series. The horrendous computational problems involved are overcome by the use of score statistics combined with recent developments in filtering and smoothing. Interpretation of the resulting time-series plots of diagnostics is aided by simulation envelopes.Our procedures, illustrated with four example, permit keen insights into the fragility of inferences to specific shocks, such as outliers and level breaks. Although the emphasis is mostly on parameter estimation, forecast are also considered. Possible extensions include seasonal adjustment and detrending of series.     

基于改进粒子群算法的SVR参数优化选择的研究

支持向量回归机(SVR)模型的拟合精度和泛化能力取决于其相关参数的选取,由于在参数的选择范围内可选择的数量是无穷的,在多个参数中盲目搜索最优参数是需要极大的时间代价,并且很难逼近最优。因此提出了基于改进粒子群算法的SVR参数优化选择方法。仿真结果表明:该改进粒子群算法优化SVR参数方法可行、有效,由此得到的SVR模型具有更好的学习精度和推广能力。     

基于量子微粒群算法的车辆路径问题研究

提出一种基于量子行为的微粒群智能优化算法。使用量子角表示量子比特的状态,并引入微粒群算法中,对量子群中的各量子角进行自适应动态调整．设计一种新的编码方式,用于求解车辆路径问题,通过计算表明,该算法是解决车辆路径问题的有效方法。     

AZ91D镁合金粉末粒度分布对其选区激光熔化成形的影响

为了解决AZ91D镁合金粉末选区激光熔化(SLM)成形过程中产生的烟尘问题,从粉末粒度分布的角度着手,将粉末筛分成不同规格,并按一定比例混合后进行SLM成形实验,探究其对成形过程烟尘产生的影响规律,在保证制件较高拉伸强度的条件下,找出烟尘产生量较少的粒度分布.实验结果表明:镁合金粉末粒径分布对其SLM成形过程中产生的烟尘量有明显的影响作用;SLM成形相同的制件,20 pm以下的细粉末对烟尘的产生作用显著,适当增大大粒径粉末所占比例,能有效减少烟尘的产生量;同时,筛除20 μm以下的细粉末后,制件的抗拉强度提升了 6％,大粒径粉末比例的增加,使得制件的抗拉强度有所降低,但这一影响并不显著.研究结果所确定的优选粉末粒度分布区间,可为进一步减少SLM成形过程中的烟尘产生量、获得高性能镁合金制件提供方法创新和技术支撑.     

On the comparison of Schwartz and Smith’s two- and three-factor models on commodity prices

Since Schwartz and Smith (2000) published their study on two-factor model on commodity prices, many studies have used this model and others have extended it. The authors also proposed the three-factor model due to the poor fitting of the two-factor one on long-term futures prices. At that time the authors had only long-term prices from a private source to calibrate, test and compare these models. No public data on long-term future contracts were available. On the other hand, during the last decade the commodity prices soared as did the liquidity of long-term contracts. This means that the interest of the agents in the management of their risk on long-term positions increased the same way and this is the motivation for this study. In this article, we revisit the comparison between two- and three-factor models using public data for short- and long-term contracts (we use up to the 67-month-ahead contract). We also provide a detailed derivation of the three-factor model differently from that of the original article. Following the original article of Schwartz and Smith, we used oil futures prices traded on the New York Mercantile Exchange to calibrate the model. The results show a better fit of the three-factor model for the term structure of prices and volatilities mainly for long maturities contracts, while the two-factor model in most portions of the curve underestimates the risk premiums. This type of analysis is important not only for daily agents negotiating the physical commodities through long-term contracts but also for investment decisions on development of real projects.     

Excel在工程造价管理预结算阶段的具体应用

Excel是微软公司推出的数据处理软件,其强大的数学、统计等函数为造价人员提供了统计数据的便利条件。本文采用知识点讲解与上机练习相结合的方式,介绍Excel在工程造价管理结算阶段中的部分使用方法与操作技巧。