A Cross-Validation Analysis of Neural Network Out-of-Sample Performance in Exchange Rate Forecasting

Econometric methods used in foreign exchange rate forecasting have produced inferior out-of-sample results compared to a random walk model. Applications of neural networks have shown mixed findings. In this paper, we investigate the potentials of neural network models by employing two cross-validation schemes. The effects of different in-sample time periods and sample sizes are examined. Out-of-sample performance evaluated with four criteria across three forecasting horizons shows that neural networks are a more robust forecasting method than the random walk model. Moreover, neural network predictions are quite accurate even when the sample size is relatively small.     

包头师范学院英语专业本科学生词汇学习策略的调查及分析

对包头师范学院英语专业本科学生词汇学习策略使用情况的调查分析表明：学生能运用包括元认知策略和认知策略在内的多种策略来学习英语词汇,但在策略的使用上,和重点院校学生使用的策略有差异;一、三年级学生在词汇学习策略和学习时间上有较大差异。     

A matter of time? Challenging and hindering effects of time pressure on work engagement

The aim of our research was to test time-exposure effects of time pressure as a stressor typically considered to be a challenge, rather than a hindrance stressor. We examined the within- and between-person effects of time pressure on work engagement in two diary/panel studies with employees using intervals of five days and three weeks, respectively (Study 1, n?=?350, and n?=?357, respectively) and six to eight weeks (Study 2, n?=?238). We assumed that it is a matter of time whether time pressure acts as a challenge (under short-term exposure) or as a hindrance stressor (under long-term exposure). We found significant positive within-person effects of time pressure on work engagement when controlling for strain in the daily and weekly diary assessment (Study 1), but a significant negative within-person effect in the six to eight weeks’ assessment (Study 2). The between-person effects were significant and negative in all studies. Although a short-term increase can be beneficial for a certain time, stable and long-time exposure of time pressure does rather reduce work engagement. Thus, employers should not keep time pressure permanently high to motivate their employees. However, short-term increases of time pressure (e.g. before a deadline) may serve as a motivating factor.     

Where does time spent on the Internet come from? Tracing the influence of information and communications technology use on daily activities

We explore from a time-use perspective how private use of computers and the Internet [information and communications technologies (ICTs)] is transforming everyday life. Data from the Swedish 2010–2011 Time-Use Survey reflect a situation in which Internet use has spread widely and become routine for many. Using covariate analysis, we analyse differences in general time use between four groups of ICT users ranging from non-users to heavy users. The theoretical departure point is a nuanced discussion of the time-displacement concept. Results indicate that private time spent using ICTs is associated primarily with individuals’ available free time, that is, elastic relative to time for paid work (i.e. contracted time). Heavy ICT users spend more time on activities carried out alone, are more home centred, and less mobile. Heavy use is associated with somewhat less committed time spent, for example, on maintenance work or taking care of children. Regarding personal time, time for meals is negatively related to heavy use, while night-time sleep is unaffected. Concerning free time, heavy use takes time from sports and outdoor recreation, but has no effect on offline media use, entertainment and cultural activities, or reading. Heavy use does not affect time spent on social activities, for example, for social interaction with family and friends or time spent on voluntary associations. Observed differences become significant at certain thresholds of ICT-related time use, involving heavy users who spend one hour or more on computers and the Internet every day.     

New block bootstrap methods: Sufficient and/or ordered

In this study, we propose sufficient time series bootstrap methods that achieve better results than conventional non-overlapping block bootstrap, but with less computing time and lower standard errors of estimation. Also, we propose using a new technique using ordered bootstrapped blocks, to better preserve the dependency structure of the original data. The performance of the proposed methods are compared in a simulation study for MA(2) and AR(2) processes and in an example. The results show that our methods are good competitors that often exhibit improved performance over the conventional block methods.     

Measuring active living in Canada: A time-use perspective

In Canada there is an increasing prevalence of chronic medical conditions and diseases related to a modifiable risk factor - physical inactivity. Therefore, it is important to have regular, robust, population-based surveillance of physical activity engagement that can be used to develop policy interventions and measure their success. The primary objective of this study is to describe the methods used to quantify the proportion of Canadians engaging in physical activities at the intensities and durations required to either maintain or enhance their health. Results indicate the overall proportion of Canadians meeting maintenance levels of physical activity has increased between 1992 (76.2%), 1998 (77.3%), and 2005 (82.5%), but over the same time the proportion meeting enhancement levels of physical activity has decreased (38.1%, 36.6%, and 30.6%, respectively). Furthermore, the results demonstrate the potential applications of time-use data for public health and quality of life research.     

Attachment Representations and Time Perspective in Adolescence

This study examines the relationship between attachment to parents and peers, time perspective and psychological adjustment in adolescence. 2,665 adolescents (M age = 17.03 years, SD = 1.48) completed self-report measures about parent and peer attachment, time perspective, sympathy and self-determination. Subjects were divided into four groups based on their parent and peer attachment scores: high parent and high peer attachment, low peer and low parent, high parent and low peer, low parent and high peer. Higher levels of negative past of the Zimbardo Time Perspective Inventory were revealed, by post hoc analyses, in the group with low attachment to parent and peer. Unlike adolescents with low attachment to parents, adolescents who reported a secure attachment to parents had higher scores on positive past, hedonistic present, and future. Adolescents with high attachment to parent and peer and adolescents with high parent but low peer attachment had the highest scores on competence and authonomy.     

Physical inactivity and working hour inflexibility: evidence from a U.S. sample of older men

Lack of time is the most frequently reported reason for lack of exercise. This study examines how restriction on the number of working hours affects individuals’ exercise decision. A structural model is constructed to describe the simultaneous decisions of employment and physical activity in the presence of working hour restriction. Using data from the 1992 Health and Retirement Study, this study finds that the working hour restriction is partly responsible for the physical inactivity among older American workers. When the working hour restriction is binding from below, an increase in the number of hours required on the job considerably reduces the probability of engaging in frequent exercise. The results imply that partial relaxation of working hour restrictions may be considered to promote frequent exercise.

试析近代工业和近代农业的关系 --以近代广东的蔗糖业为例

广东的蔗糖业,在本世纪30年代以前仍然处在传统时代的水平.民国以来广东农业界学者在蔗糖业方面的研究成果在不同程度上对30年代广东地方当局的产业决策产生影响.30年代广东的工业化运动,奠定了工业支持农业的基础.机器糖加工业迅速发展,同时有力地推动了甘蔗栽培业的技术进步.在30年代前期广东糖加工业和甘蔗栽培业的关系已经发生了一些迥异于传统时代的深刻变化.     

Fathers–participation in the domestic activities of everyday life

In this paper, the data from the multi-purpose survey on household “Time Use” conducted by Istat (the Italian National Statistical Institute) in 2002–2003 and the data from this same survey conducted in 1988–1989 will be analysed with the purpose of describing the fathers’ daily participation in the domestic activities and of highlighting the changes that have taken place during the 14 years elapsed between the two survey editions. The analysis will be carried out using standard time-use data analysis’ tool, time budget tables and by applying a multi-variate regression model with the objective of separating the relative contribution of the behavioural and structural factors to explain the variation observed.