Forecasting monthly and quarterly time series using STL decomposition

This paper is a re-examination of the benefits and limitations of decomposition and combination techniques in the area of forecasting, and also a contribution to the field, offering a new forecasting method. The new method is based on the disaggregation of time series components through the STL decomposition procedure, the extrapolation of linear combinations of the disaggregated sub-series, and the reaggregation of the extrapolations to obtain estimates for the global series. Applying the forecasting method to data from the NN3 and M1 Competition series, the results suggest that it can perform well relative to four other standard statistical techniques from the literature, namely the ARIMA, Theta, Holt-Winters’ and Holt’s Damped Trend methods. The relative advantages of the new method are then investigated further relative to a simple combination of the four statistical methods and a Classical Decomposition forecasting method. The strength of the method lies in its ability to predict long lead times with relatively high levels of accuracy, and to perform consistently well for a wide range of time series, irrespective of the characteristics, underlying structure and level of noise of the data.     

Booking horizon forecasting with dynamic updating: A case study of hotel reservation data

A highly accurate demand forecast is fundamental to the success of every revenue management model. As is often required in both practice and theory, we aim to forecast the accumulated booking curve, as well as the number of reservations expected for each day in the booking horizon. To reduce the dimensionality of this problem, we apply singular value decomposition to the historical booking profiles. The forecast of the remaining part of the booking horizon is dynamically adjusted to the earlier observations using the penalized least squares and historical proportion methods. Our proposed updating procedure considers the correlation and dynamics of bookings both within the booking horizon and between successive product instances. The approach is tested on real hotel reservation data and shows a significant improvement in forecast accuracy.     

Time Series Based Errors and Empirical Errors in Fertility Forecasts in the Nordic Countries*

We use ARCH time series models to derive model based prediction intervals for the Total Fertility Rate (TFR) in Norway, Sweden, Finland, and Denmark up to 2050. For the short term (5–10 yrs), expected TFR‐errors are compared with empirical forecast errors observed in historical population forecasts prepared by the statistical agencies in these countries since 1969. Medium‐term and long‐term (up to 50 years) errors are compared with error patterns based on so‐called naïve forecasts, i.e. forecasts that assume that recently observed TFR‐levels also apply for the future.     

建筑工程造价与工期的辩证关系

阐述了施工工期与造价的辩证关系。即：工期与经济效益的关系；工期与自然损耗的关系；工期与固定成本的关系；工期与投资成本的关系。     

A classification system for understanding individual differences in temporal orientation among processual researchers and organizational informants

This paper develops a classification system of temporal orientations in an effort to provide processual researchers with a framework for understanding the potential impact of temporal orientations on processual research methods and findings. In developing the classification system four general conceptions of time are reviewed, including physiological, objective, psychological, and socially constructed relative time. Specific dimensions of temporal orientation previously studied are identified, and additional dimensions are offered. It is suggested that temporal concerns are endemic to management and organizational processes, and that differences in temporal orientations among researchers and organizational informants should be considered when conducting processual research.     

Stackelberg leadership in a dynamic duopoly with stochastic capital accumulation

I propose a dynamic duopoly model where firms enter simultaneously but compete hierarchically á la Stackelberg at each instant over time. They accumulate capacity through costly investment, with capital accumulation dynamics being affected by an additive shock the mean and variance of which are known. The main findings are the following. First, the Stackelberg game is uncontrollable by the leader; hence, it is time consistent. Second, the leader invests more than the follower; as a result, in the steady state, the leader’s capacity and profits are larger than the follower’s. Therefore, the present analysis does not confirm Gibrat’s Law, since the individual growth rate is determined by the timing of moves.JEL Classification: C61, C73, D43, D92, L13Financial support within the project The post-entry performance of firms: technology, growth and survival lead by Enrico Santarelli, co-financed by the University of Bologna and MIUR, is gratefully acknowledged. I thank Uwe Cantner, Roberto Cellini, Roberto Golinelli, Helen Louri, Enrico Santarelli, Antonello Scurcu, Peter Thompson, two anonymous referees and the audience at the final workshop of the project (Bologna, November 22-23, 2002) for useful comments and discussion. The usual disclaimer applies.     

An assessment of value creation in mobile service delivery and the moderating role of time consciousness

This study focuses on the perceived utilitarian value of a new service delivery mode, the mobile channel. The authors develop a framework that incorporates three mode-specific benefits - time convenience, user control, and service compatibility - as well as two costs - perceived risk and cognitive effort - as antecedents of perceived value. Because of the pervasiveness of time criticality as a value-added characteristic of the mobile channel, they also investigate the moderating influence of consumers’ time consciousness. They empirically investigate the model using mobile brokerage services as an illustrative application. The results reveal that the identified antecedents, with the exception of service compatibility, have a strong impact on mobile channel value perceptions, which in turn influence behavioral intentions. The authors also find that time consciousness moderates the aforementioned relationships.     

用时延编码实现远程水声通信

本文研究了一种基于时延编码的远程水声通信技术，该技术利用线性调频（LFM）信号矩形脉冲的时延值进行时延编码，在接收端采用时延估计技术进行时延解码。初步的海试结果表明，该技术可以实现80km距离、4.16bit/s数据率的信息可靠传输。     

基于并行判决法的PCTH-UWB系统性能分析

伪混沌跳时序列(PCTH)最近提出应用于UWB系统。本文分析了PCTH-UWB的工作原理,提出了并行判决法,与直接判决法进行了比较,理论分析及仿真结果表明并行判决法可提高PCTH-UWB系统性能。     

农村信贷配给实证分析

信贷配给是制约我国农村信贷市场建设的重要因素,也阻碍了农村金融环境优化、影响了农村经济的良性发展。通过引入制度因子,量化信贷配给,构建了信贷配给宏观计量模型,对我国农村信贷配给状况进行实证检验,结果证明,利率和制度因子是造成我国农村信贷配给的两大因子。应合理调控利率、推进深化改革、加大三农扶持力度,实现农村经济社会的和谐发展。