Missing data and forecasting in multivariate time series: An application of the common components dynamic linear model

Summary The paper deals with missing data and forecasting problems in multivariate time series making use of the Common Components Dynamic Linear Model (DLMCC), presented in Quintana (1985), and West and Harrison (1989). Some results are presented and discussed: exploiting the correlation between series, estimated by the DLMCC, the paper shows as it is possible to update state vector posterior distributions for the unobserved series. This is realized on the base of the updating of the observed series state vectors, for which the usual Kalman filter equations can be applied. An application concerning some Italian private consumption series provides an example of the model capabilities.     

大学普通物理实验教学改革

物理实验教学属于智慧智能范畴 ,是对大学生进行科学实验基本训练一门重要的基础课。针对一些大学生对物理实验缺乏学习的积极性以及他们实验时动手能力表现欠佳的现状 ,分析原因 ,探讨大学普通物理实验教学改革的途径和措施     

跨文化交际中的时空观念差异

不同文化背景的人,由于受不同文化传统的影响,其思维方式不同,在人际交往中的时间观念(如时间顺序排列、时间取向、遵守时间的态度)和空间观念(如对体距的认识、对个人领地的态度等)也存在差异。这些差异往往容易被人们忽视,从而影响交际的正常进行,甚至导致交际的失败。因此,在交往中我们应该正确对待文化差异,自觉排除文化差异的干扰。     

影响分析化学实验结果因素的探讨

本文探讨了影响分析化学实验结果的因素，指出溶液的酸度、试剂的浓度，用量、加入顺序和溶剂等都对分析实验的结果产生影响，并分析了其原因。     

Sampling Returns for Realized Variance Calculations: Tick Time or Transaction Time?

This article introduces a new model for transaction prices in the presence of market microstructure noise in order to study the properties of the price process on two different time scales, namely, transaction time where prices are sampled with every transaction and tick time where prices are sampled with every price change. Both sampling schemes have been used in the literature on realized variance, but a formal investigation into their properties has been lacking. Our empirical and theoretical results indicate that the return dynamics in transaction time are very different from those in tick time and the choice of sampling scheme can therefore have an important impact on the properties of realized variance. For RV we find that tick time sampling is superior to transaction time sampling in terms of mean-squared-error, especially when the level of noise, number of ticks, or the arrival frequency of efficient price moves is low. Importantly, we show that while the microstructure noise may appear close to IID in transaction time, in tick time it is highly dependent. As a result, bias correction procedures that rely on the noise being independent, can fail in tick time and are better implemented in transaction time.     

时间如何前进——进化论随笔

中国古代"与时偕行"、"与时俱化"的观念,以取法天地四时的运行为基准,是一种四时循环论的变化观.我党提出的"与时俱进"思想的含义,是随着时代的前进而前进,和随着时代的变化而变化,体现了鲜明的时代创新精神,它的哲学基础是科学进化论.这一特征在语词上通过一个"进"字表达出来.虽然"与时俱进"和"与时俱化"只有一字之差,却体现了本质的超越.同时,这一表述通过对中国古代<易经>、<庄子>等经典的吸收,丰富了自身的思想内涵,也建立,了联接传统与现代的一道桥梁.当然,由于现代时间观念的一维性质,使得人们在批驳"直线进化论"的同时,易于陷入"时间进化论",而时间进化论实际上也是一种直线进化论,这也是需要警醒的.     

建筑与城市设计中的时间观

时间与形式、功能、空间四要素完备才能组成一个完整的建筑 ,运用时间设计的概念 ,分析和解决当今建筑界和城市规划出现的问题是现实的需要     

力学实验教学改革的探索与实践

力学实验作为力学课程中重要的实践性教学环节,对于培养工科学生用科学的方法来研究处理实际问题的能力和创新精神,提高学生的综合素质有着极其重要的作用.文章分析了力学实验教学改革的实践,探讨了提高力学实验教学效果的改革思路;提出要通过开发综合性与研究性实验项目,探索合理的实验教学模式,加强培养学生解决工程实际问题的能力及力学建模能力.     

马克思主义与时俱进的哲学思考

马克思主义具有与时俱进的理论品质。马克思主义哲学是这个理论品质的理论基础。实践与理论的矛盾运动、对真理的探求、以及创造崭新的马克思主义话语体系,都要求马克思主义与时俱进。     

Economic Determinants of Net International Migration in Western Europe

This paper aims to estimate theinfluence of economic determinants on netinternational migration in Western Europe inthe period 1960–1998. Net migration rates(i.e., population growth minus natural increase,divided by the midyear population) constitutethe dependent variable. The economicdeterminants used in this study are GDP percapita, unemployment, and average educationallevel (amount of human capital) of thepopulation. Time series regression models havebeen used in country-specific analyses. Inaddition, a pooled cross-sectional time seriesanalysis has been made. The analyses suggestthat GDP per capita has a positive effect andunemployment a negative effect on a country'snet international migration.