Improved model selection criteria for SETAR time series models

The purpose of this paper is threefold. First, we obtain the asymptotic properties of the modified model selection criteria proposed by Hurvich et al. (1990. Improved estimators of Kullback-Leibler information for autoregressive model selection in small samples. Biometrika 77, 709–719) for autoregressive models. Second, we provide some highlights on the better performance of this modified criteria. Third, we extend the modification introduced by these authors to model selection criteria commonly used in the class of self-exciting threshold autoregressive (SETAR) time series models. We show the improvements of the modified criteria in their finite sample performance. In particular, for small and medium sample size the frequency of selecting the true model improves for the consistent criteria and the root mean square error (RMSE) of prediction improves for the efficient criteria. These results are illustrated via simulation with SETAR models in which we assume that the threshold and the parameters are unknown.     

Applicability of a Neuroprobabilistic Integral Risk Index for the Environmental Management of Polluted Areas: A Case Study

Recently, we developed a GIS-Integrated Integral Risk Index (IRI) to assess human health risks in areas with presence of environmental pollutants. Contaminants were previously ranked by applying a self-organizing map (SOM) to their characteristics of persistence, bioaccumulation, and toxicity in order to obtain the Hazard Index (HI). In the present study, the original IRI was substantially improved by allowing the entrance of probabilistic data. A neuroprobabilistic HI was developed by combining SOM and Monte Carlo analysis. In general terms, the deterministic and probabilistic HIs followed a similar pattern: polychlorinated biphenyls (PCBs) and light polycyclic aromatic hydrocarbons (PAHs) were the pollutants showing the highest and lowest values of HI, respectively. However, the bioaccumulation value of heavy metals notably increased after considering a probability density function to explain the bioaccumulation factor. To check its applicability, a case study was investigated. The probabilistic integral risk was calculated in the chemical/petrochemical industrial area of Tarragona (Catalonia, Spain), where an environmental program has been carried out since 2002. The risk change between 2002 and 2005 was evaluated on the basis of probabilistic data of the levels of various pollutants in soils. The results indicated that the risk of the chemicals under study did not follow a homogeneous tendency. However, the current levels of pollution do not mean a relevant source of health risks for the local population. Moreover, the neuroprobabilistic HI seems to be an adequate tool to be taken into account in risk assessment processes.     

接触式低温固定中样品内部传热过程的分析

建立了用于电子显微镜生物样品制备的接触式低温固定法中的传热过程模型,并求得了一维常物性条件下的精确解。讨论了样品内部冷却速率的一些变化规律及其与样品初始温度和固化温度的关系,为实际的低温固定操作提供了理论指导。     

文化资源的整合&海河文化带的建设

一、文物遗迹的保护开发与海河文化带的建设 人文历史景观是城市极具活力的视觉要素,是构成城市视觉形象的精神和灵魂.可以说,人文识别(与地缘识别相对的包括历史、文化、风俗、民族等人文状况的识别系统)是一个城市最持久、最具资源潜力和最有文化人类学意义的识别系统.人文历史景观最重要的要素是城市的文化遗迹,它们是城市发展历史形态在物质实体上的表现,是城市的一笔宝贵的文化遗产,是不可再生的文化资源.一棵古树、一座桥梁、一条小街、一座建筑物,都是城市历史发展的文化符号,是城市文化特色的生动体现,都在不经意间透露出城市发展的信息,烙上了时代前进的印迹.通过文物遗迹的保护与开发,可以丰富城市的文化内涵,提升城市形象,为城市创造财富.     

基于虚拟仪器的土壤水分测试系统开发

采用PCl-812PG数据采集卡,基于虚拟仪器技术,以Delphi作为平台开发了土壤含水量测试系统,对AZS -2土壤水分传感器的功能进行了扩展。标定结果及实际应用表明,此系统性能稳定,精度较高。     

“换词求雅”的修辞作用及衔接功能

“换词求雅”作为一种消极修辞手段,在避免重复、增加文章的文体色彩方面起到了积极的作用。不仅如此,作为一种衔接手段,“换词求雅”也在保证语篇的衔接与连贯上发挥着不可替代的作用。本文通过对这种辞手段的应用原则及分类方法的阐述,试图表明“换词求雅”并不是为了语言花哨的目的而存在的,无论从修辞还是语法意义角度上看,这一修辞方法的作用都是其他方法难以替代的。     

浅谈现代篮球持球突破技术及运展

对篮球运动持球突破技术的分类与结构,持球突破技术的运用方法和持球突破后应注意的要素进行分析。