N-step combinations of forecasts

While there is general agreement that a linear combination of forecasts can outperform the individual forecasts, there is controversy about the appropriateness of the combination method to be used in a given situation. Hence, in any given application it may be more beneficial to combine different sets of combined forecasts rather than picking one of them. This paper introduces the concept of N-step combinations of forecasts which involves combining the combined forecasts obtained from different combination procedures used at the preceding step. Using quarterly GNP data, evidence supporting the increase in the accuracy of the one-period-ahead ex-ante forecasts as the combination step increases is provided. The MSE, MAE, MAPE and their corresponding standard deviations are used to evaluate the accuracy of the forecasts obtained.     

具有亏函数的复合整函数的性质

解决了C．C．Yang和C．T．Chuang提出的复合函数的特征函数的一个问题。     

Relative accuracy of judgemental and extrapolative methods in forecasting annual earnings

This paper identifies and analyses previously published studies on annual earnings forecasts. Comparisons of forecasts produced by management, analysts, and extrapolative techniques indicated that: (1) management forecasts were superior to professional analyst forecasts (the mean absolute percentage errors were 15.9 and 17.7, respectively, based on five studies using data from 1967–1974) and (2) judgemental forecasts (both management and analysts) were superior to extrapolation forecasts on 14 of 17 comparisons from 13 studies using data from 1964–1979 (the mean absolute percentage errors were 21.0 and 28.4 for judgement and extrapolation, respectively). These conclusions, based on recent research, differ from those reported in previous reviews, which commented on less than half of the studies identified here.     

肌纤维的结构组成与无氧功量关系的探讨

本文的主要目的是了解肌纤维的结构组成对无氧作功能力的影响。研究虽然得到快肌纤维百分比与无氧功量之间不相关的结果,但本文作者并不因此就否认肌纤维结构组成与无氧功量之间存在着的关系。然而,要强调的是对这种关系不应过分的绝对化,出现统计上的二者之间的不相关也是可能的。建议在加强研究肌纤维的结构组成与无氧功量关系的同时,还应注意研究其它因素对无氧作功能力的影响。     

市场需求Logit组合预测的研究

首先阐述了网络市场营销和传统市场营销的区别，分析了在该环境下市场需求的变化和相应的特点。其次，研究了一种利于计算机建模的市场需求组合预测方法，即采用Logit回归法训练数据的市场需求组合预测模型。最后，将该方法用于家用电冰箱市场需求趋势预测的示例研究，采用信息熵的方法，检验了组合预测模型的预测效果。实例表明，该方法可以通过调整组合权重提高预测精度。     

Cu-Zn-Al形状记忆合金的熔炼与加工

简述了Ｃｕ－Ｚｎ－Ａｌ记忆合金的熔炼工艺，提出了采用适宜的熔剂、在高频或中频感应炉中熔炼、熔化温度不超过１１５０℃，浇注温度在１０５０～１１５０℃之间．可以获得成分稳定均质的记忆合金。分析了电子浓度为１．４２左右时．最易获得有记忆效应的合金的原因。讨论了Ｃｕ－Ｚｎ－Ａｌ记忆合金的加工、退火特点。     

Optimal conditional ARIMA forecasts

An optimal univariate forecast, based on historical and additional information about the future, is obtained in this paper. Its statistical properties, as well as some inferential procedures derived from it, are indicated. Two main situations are considered explicitly: (1) when the additional information imposes a constraint to be fulfilled exactly by the forecasts and (2) when the information is only a conjecture about the future values of the series or a forecast from an alternative model. Theoretical and empirical illustrations are provided, and a unification of the existing methods is also attempted.     

乙酸乙烯酯与乙烯基吡咯烷酮共聚的研究

用游离基溶液聚合方法合成了乙酸乙烯酯—乙烯基吡咯烷酮（Ｖｐ）共聚物。研究了反应条件对共聚合反应的影响和共聚物组成与转化率的关系，并从元素分析和￣（１３）ＣＮＭＲ的结果计算得体系的竞聚率ｒ＿１，ｒ＿２分别为０．２８２±０．０３７和０．２７８±０．０４１；ｒ＿２分别为３．７５±０．２８和３．７０±０．２９．结果表明：引发剂浓度小和投料比中单体Ｖｐ的含量高，有利于生成特性粘度［η］大的共聚物，反应时间长，［η］下降，共聚物组成与转化率的关系与用Ｍａｙｏ－Ｌｅｗｉｓ式处理得到的结果基本符合；￣（１３）ＣＮＭＲ测定链段序列分布的结果与用末端基效应模型计算的结果一致。因此，认为是以末端基效应模型机理进行，ＤＳＣ测定结果显示出共聚物玻璃化温度与组成关系符合ＦＯＸ方程，说明共聚物为无规共聚物。