三江平原湿地典型草甸小叶章群落物种多样性的季节动态

本研究以三江平原湿地典型草甸小叶章群落为研究对象,从物种丰富度、均匀度和物种多样性指数等方面探讨其季节动态规律.典型草甸小叶章群落物种丰富度在7月份最高,生态优势度指数季节动态变化呈“V”型;多样性信息指数季节动态变化呈单峰型,6月末7月初群落群落的物种多样性最高,种类之间个体分配的均匀性最大;均匀度指数季节动态变化呈线型.群落α多样性的测度指标的季节动态变化表现出一致性.     

Herzberg's Two-Factor Theory of work motivation tested empirically on seasonal workers in hospitality and tourism

The objective of this study was to understand work motivation in a sample of seasonal workers at a tourism destination strongly steered by seasonality. Furthermore, it was investigated whether seasonal workers could be divided into worker subgroups on the basis of their work motivation. A structural equations model tested Herzberg's Two-Factor Theory of work motivation empirically. The findings of the study support the Two-Factor Theory of work motivation. Furthermore, results indicated that a migrant community of workers was significantly less concerned about wage level as well as significantly more concerned about meeting new people than resident workers. As a result of these findings, it is suggested that management of businesses in hospitality and tourism need to consider that the seasonal workforce consists of different kinds of worker subgroups, which have different needs to be satisfied.     

Damping seasonal factors: Shrinkage estimators for the X-12-ARIMA program

We examine the effect of damping X-12-ARIMA's estimated seasonal variation on the accuracy of its seasonal adjustments of time series. Two methods for damping seasonals are proposed. In a simulation experiment, we generated time series data for each of 90 distinct experimental conditions that, in aggregate, characterize the variety of monthly series in the M3-competition. X-12-ARIMA consistently overestimated the actual seasonal variation by an amount consistent with statistical theory. Damping seasonals reduced X-12-ARIMA's estimation error by as much as 79% and under no conditions was estimation error increased beyond a trivial amount. Improvement depended primarily on the degree to which random variation in a series dominated seasonal variation. When the multiplicative X-12-ARIMA model did not match the data-generating model, overestimation was less for trend series than for series with no trend; otherwise the presence of trend had no discernible effect. One of the proposed methods was somewhat more accurate and robust, but more complex, than the other. In an analysis of real data—the 1428 monthly series of the M3-competition-damping X-12-ARIMA seasonals prior to forecasting (1) reduced the average forecasting MAPE by 4.9–1.4% and (2) improved forecasting accuracy for 59–65% of the series, depending on the forecasting horizon. This research suggests that damping X-12-ARIMA seasonals leads to more accurate seasonal adjustments of time series, thus providing a more reliable basis for policy-making, forecasting, and the evaluation of forecasting methods by researchers.     

SAD效应：一个基于时变风险价格的条件CAPM的解释

很多实证研究都证明季节性情绪混乱(SAD)与股指收益有明显联系。本文研究了这种SAD效应能否用一个包含允许时间变化的风险价格的资产定价模型去捕捉它的存在。本文利用上证综指的日收盘数据得到的初始和超额收益率以及SAD和FALL变量,利用修正的GRACH-M模型进行了分析,认为条件CAPM可以捕捉SAD效应。这与由于日照时间变化而导致的投资者风险承受能力变化进而影响收益的认识相符合。     

Implementation issues on shrinkage estimators for seasonal factors within the X-11 seasonal adjustment method

This commentary on Miller and Williams [Intl. J. Forecast. 20 (2004)S29-49] discusses how shrinkage can be implemented within X12-ARIMA. We discuss how the seasonal factors are estimated in X12-ARIMA, how shrinkage can be translated into a moving average, if this is compatible with the philosophy behind the X12-ARIMA method, and suggest possible improvements.     

An empirical analysis of demand variations and markdown policies for fashion retailers

In this paper, using data from a leading specialty apparel retailer, we empirically examine the determinants of a retailer's dynamic pricing policy and investigate consumer response to price changes (markdowns) throughout a fashion product's selling season using a product diffusion setting. In order to do that, we first develop and estimate a markdown pricing model and a consumer demand model that capture the important characteristics of the fashion apparel market. Next, we use the estimates from these two models to design and simulate four alternative markdown pricing policies to investigate the impact of these different policies on consumer demand and retailer revenues. Our results, in line with the previous literature, show that markdowns implemented early in the season but small in magnitude generate the highest retailer revenues. Our paper not only provides a comprehensive empirical framework for fashion apparel retailers that is easy to implement, but also shows that using this framework will lead to timely decision making and will improve sale and revenue outcomes in the fast paced fashion world.     

Analysis of the optimal spatial distribution of natural gas under ‘transition from coal to gas’ in China

China has been attempting to realise green sustainable economic development. Thus, China has proposed and begun to implement the ‘switching from coal to gas’ policy to realise the energy structure transition but neglected to consider seasonal natural gas demand fluctuations, gas supply shortages, the backward gas transportation and storage infrastructure. This paper constructs a model of China’s natural gas distribution system by incorporating these four factors: ① supply factors including domestic natural gas fields, liquid natural gas receiving stations, internationally piped gas sources, ② demand factors including domestic regional demands, ③ real natural gas transportation pipeline systems in the country, and ④ the pricing mechanism of natural gas. Optimal spatial natural gas distribution with maximum social welfare under the three conditions are simulated, respectively: the ① fixed price system, ② market pricing mechanism, and ③ seasonal fluctuations. The simulation results indicate substantial changes would occur in China’s natural gas system during the switch from coal to gas, and the natural gas infrastructure requires further improvement. This paper also provides references for the natural gas storage facility location selection in China.     

Attitude towards immigrants and security: Effects on destination-loyal tourists

This study was conducted in the midst of a surge of undocumented immigrants into a popular seasonal migrant destination in the U.S. and the subsequent state response of adding security forces. Factors examined include the effects of the role of media in shaping perceptions about security forces, perceptions about security force effectiveness, perceptions of undocumented immigrants and political orientation. The study of 413 respondents found that attitudes toward undocumented immigrants affect felt safety in the region, likelihood of recommending and returning to the region. Perceptions of the effectiveness of the security forces were important in affecting likelihood of recommending the region to others but not return intention. These and other findings contribute significantly to the scant research on both effectiveness of crises management responses and on effects of perceptions of undocumented immigrants on traveler behavior.     

2006～2009年首都机场口岸蜚蠊密度监测报告

[目的]掌握首都机场口岸蜚蠊密度、季节消长和种群构成情况,为首都机场口岸的蜚蠊防治提供科学依据。[方法]统一采用粘捕法。[结果]2006、2007、2008、2009年首都机场口岸蜚蠊的年平均密度分别为0.30、0.49、0.16、0.16只/张.夜;从2008年起蜚蠊密度明显下降,下降率为62.79%;首都机场口岸目前只监测到两种蜚蠊,其中德国小蠊为优势种,占98.50%,美洲大蠊占1.50%。[结论]首都机场口岸全年均有蜚蠊孳生,没有明显的季节消长规律;种类有德国小蠊和美洲大蠊两种,其中德国小蠊为绝对优势种,应成为今后防治的重点。     

季节时间序列理论发展综述

随着社会的进步,统计数据由过去的年度数据变为如今的季度、月度和日度数据,有些以实时交易为基础的超高频金融数据达到了按秒为间隔的频率,这些数据被称为季节时间序列。季节时间序列研究已经成为近十年来经济计量学和统计学中的热点,Joumal of Econometrics（1993,volume 55）就此问题进行了专题讨论。本文按照历史发展顺序对季节性时间序列理论进行了系统地介绍,并对这一领域的前沿热点问题进行了评述和展望。