机械产品精度的并行优化设计——数学模型

介绍机械产品精度设计后一种新方法－产品精度的并行优化设计,这种新方法非常适合于产品并行设计的环境,与常规的顺序精度设计方法不同,这种方法将产品的工作精度与零件的加工精度直接联系起来,于是在产品设计阶段就可直接求出满足产品工作精度要求的最佳加工公差来,应用这种方法,不仅可以大大缩短产品的设计和制造周期,还可以保证产品的设计质量,降低产品的设计和制造成本。     

直齿锥齿轮齿形加工精度的研究

研究了刨齿机可调参数对直齿锥齿轮齿形加工精度的影响规律。通过分析齿形加工误差产生的原因，对滚切比、摇台摆角等调整参数进行了重新计算与比较，试切结果表明，齿形加工精度有明显提高，并达到使用要求。     

The impact of forecasting methodology on the accuracy of national population forecasts: evidence from the Netherlands and Czechoslovakia

"This study considers the accuracy of national population forecasts of the Netherlands and the Czechoslovak Socialist Republic.... We look at the demographic components employed in each forecast, the procedure to extrapolate fertility and the level at which assumptions for each component are formulated. Errors in total population size, fertility, mortality and foreign migration, and age structure are considered. We discuss trends in errors and methodology since 1950 and compare the situations in the two countries. The findings suggest that methodology has only a very limited impact on the accuracy of national population forecasts."     

DME/P精度评估

精密测距系统(DME/P)是国际上新开发的无线电导航系统,它与微波着陆系统配合,为进场飞机提供精密进场着陆引导。介绍了对DME/P系统进行测试的3种典型测试飞行剖面图。对测距误差的划分方法以及精度的分布特点作了详细分析,提出用合理的数字滤波软件和数据处理软件方法对其误差实现有效分离,并进行了飞行验证,对其测距精度进行了连续动态的准确评估。     

Modeling of Selective Availability for Global Positioning System

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碱性苦味酸法测定血清肌酐试剂的配制

目的 :配制直接测定血清肌酐的试剂碱性苦味酸 ,使得方法简单 ,结果可靠。方法 :改变氢氧化钠与苦味酸的浓度及配比 ,采用固定时间法测定。结果 :本法测定两种批号 RANDOX质控血清与其靶值比较 P>0 .0 5 ,精密度批内分别是 CV=3.4%和 2 .7% ,批间分别是 CV=3.96 %和 3.34%。本法与除蛋白滤液法 ,上海试剂 (速率法 )测定 10 0份血清结果分别是 113± 71μm ol/ L,110± 70 μmol/ L,115± 6 4μmol/ L.P>0 .0 5。结论 :本法准确度 ,精密度 ,回收率 ,线性均良好。     

有限差分法在静态电磁场计算中的应用

利用有限差分法求解二维静电场问题,所得的数值结果与解析结果相一致,分析讨论了有限差分法的精度和收敛性问题。分析结果表明：当α取最佳值时收敛最快,步长越小精度越高。     

提高紫外分光光度法测定总氮质量的措施研究

采用 GB1 1 894- 89紫外分光光度法测定水体中的总氮时 ,测定结果的质量受消解温度与时间、玻璃器皿的洁净度、分析仪器的精密度以及试剂质量的影响。针对以上问题进行质量保证措施研究 ,在实际测定中提高了分析结果的准确度和灵敏度     

Judgemental revision of sales forecasts: A longitudinal eetension

When quantitative models are used for short-term multi-item sales forecasts it is possible that the managers who use such forecasts may disagree with at least some of the estimates obtained, and wish to change them so that they become more consistent with their own (subjective) evaluation of the marketplace. This study reports on an analysis of the effectiveness of judgemental revision of sales forecasts over six quarterly forecasting periods. The results give general support for the practice of forecast manipulation as a means of improving forecasting accuracy. It is also observed that the effectiveness of revision activity varies across different time periods.     

Towards a taxonomy of forecast error measures a factor-comparative investigation of forecast error dimensions

This study explores the nature of information conveyed by 14 error measures drawn from the literature, using real-life forecasting data from 691 individual product items over six quarterly periods. Principal components analysis is used to derive factor solutions that are subsequently compared for two forecasting methods, a version of Holt's exponential smoothing, and the random walk model (Naive 1). The results reveal four underlying forecast error dimensions that are stable across the two factor solutions. The potentially confounding influence of sales volume on the derived error dimensions is also explored via correlation analysis.