全站仪在工程测量中的精度与误差分析

电子全站仪是光电测距仪、电子经纬仪和微处理器的集成,它能在测站上同时测量、计算显示及记录各种测量数据,在工程测量中得到广泛应用。本文结合全站仪在工程测量中的应用,谈谈降低测量误差的几种方法。     

培养观察能力对提高学习技巧的作用

学习也有技巧,观察能力也很重要,培养观察能力,要指导学生掌握有序观察,分析观察,逆向观察的观察方法;重视观察的目的性、全面性、精确性、深刻性等良好观察品质的培养。学生的数学学习水平,取决于数学观察能力的强弱。     

模糊规则中局部权重对推理精确度的影响

一组模糊规则可从训练事例中学习得到,通常这组规则的推理精度有待提高。提出一种精练模糊规则的方法,它的主要思想是通过线性推理器,把局部权重分配给模糊规则中的各前件因子,通过求解一个规划问题,得出权重的近似最优值,从而改进推理精确度。     

提高D08-32型捣固车系统精度的探讨

随着高速铁路重载铁路使用的增多,对相关养路机械设备使用的要求标准要来越高。不过从实际情况来看,现阶段使用的不少机械养路设备在使用过程中,出现较多的问题,其中主要是测量方面的精度较差,这就给很多铁路线路的维护,带来一定的问题。在本文的研究中,重点对大型养路机械D08-32捣固车系统存在的问题进行了分析,并结合实际经验,提出提高作业精度的一些方案,通过实践证明,改进后的D08-32捣固车,维修作业精度得到了很大的提高,并且相关的零点校对也变得更加快捷。     

The Impact of Refinement on the Accuracy of Time‐driven ABC

Recently, time‐driven activity‐based costing (ABC) has been developed as a cost modelling technique in which transaction times (that is, times required for particular occurrences of an activity) are calculated using time equations. This paper develops a model of the error structures in time‐driven ABC and examines the impact of adding terms to time equations on the accuracy of estimated transaction times. The results provide some fundamental insights into the balancing of errors when refining time equations and lead to some general recommendations that may be followed in the design process of a time‐driven ABC system to enhance the accuracy of times calculated by means of time equations.     

Forecasting expected shortfall: Should we use a multivariate model for stock market factors?

Is univariate or multivariate modeling more effective when forecasting the market risk of stock portfolios? We examine this question in the context of forecasting the one-week-ahead expected shortfall of a stock portfolio based on its exposure to the Fama–French and momentum factors. Applying extensive tests and comparisons, we find that in most cases there are no statistically significant differences between the forecasting accuracy of the two approaches. This result suggests that univariate models, which are more parsimonious and simpler to implement than multivariate factor-based models, can be used to forecast the downside risk of equity portfolios without losses in precision.     

矿山测量常见问题及措施探讨

矿山测量是从设计到施工的中间环节而且是极其重要的环节,起着承上启下的作用。目前,我国矿山测量事业尚处于一个不健全的阶段,矿山测量事业中由于受到施工条件的限制、技术人员专业素质不足等的影响,测量结果往往比较粗糙,进而导致较大的误差并影响矿山的开采,造成一定的经济损失。为了提高矿山测量的准确性应该采用合理科学的测量方案,及时更新测量仪器、培养测量人员的专业水平,促进我国矿山测量事业的发展。     

Hard to arbitrage,hard for analysts to forecast

This paper examines whether limits to arbitrage (LA) affect analysts' earnings forecast accuracy. Using the LA index, which is constructed from unique trading constraints in the Chinese stock market and other commonly used measures, we find that forecast accuracy is much lower for stocks with high LA. Moreover, our results are more suited to explanations of cognitive bias that turn to investor sentiment or limited attention and cannot be fully explained by more objective factors, including analyst ability, broker size, broker experience, and commission pressure. We also find that LA amplifies analyst forecast dispersion. Such results indicate that LA distorts analysts’ earnings expectations and provides new insight into how LA affects anomaly returns.     

Do survey joiners and leavers differ from regular participants? The US SPF GDP growth and inflation forecasts

If ‘learning by doing’ is important for macro-forecasting, newcomers might be different from regular, established participants. Stayers may also differ from the soon-to-leave. We test these conjectures for macro-forecasters’ point predictions of output growth and inflation, and for their histogram forecasts. Histogram forecasts of inflation by both joiners and leavers are found to be less accurate, especially if we suppose that joiners take time to learn. For GDP growth, there is no evidence of differences between the groups in terms of histogram forecast accuracy, although GDP point forecasts by leavers are less accurate. These findings are predicated on forecasters being homogeneous within groups. Allowing for individual fixed effects suggests fewer differences, including leavers’ inflation histogram forecasts being no less accurate.     

提高自动量热仪的测试精度和稳定性

对影响自动量热仪测试精度和可靠性的问题进行分析,并采取切实有效的改进措施以提高了自动量热仪的测试精度和准确度。