What do numerical (climate) models really represent?

The translation of a mathematical model into a numerical one employs various modifications in order to make the model accessible for computation. Such modifications include discretizations, approximations, heuristic assumptions, and other methods. The paper investigates the divergent styles of mathematical and numerical models in the case of a specific piece of code in a current atmospheric model. Cognizance of these modifications means that the question of the role and function of scientific models has to be reworked. Neither are numerical models pure intermediaries between theory and data, nor are they autonomous tools of inquiry. Instead, theory and data are transformed into a new symbolic form of research due to the fact that computation has become an essential requirement for every scientific practice. Therefore the question is posed: What do numerical (climate) models really represent?     

基于元模型的复杂产品虚拟样机建模方法研究

新技术环境下复杂产品对数字化设计质量的要求不断提升,需要进一步提高建模的质量和效率,解决复杂产品虚拟样机多学科模型的一体化信息集成问题,以实现复杂产品系统设计及优化。本文以航天制造领域广泛存在的复杂产品为对象,对元模型、建模方法以及多学科建模过程进行研究与分析,将多学科优化设计与元模型建模方法相结合,建立了复杂产品的虚拟样机元模型,并构建了元模型与学科元模型的转换关系,形成了虚拟样机多学科建模优化设计方案。     

XB4450型仿型铣床数控化伺服改造

将XB4450仿型铣床改造为四轴三联动的数控铣床,可以加工复杂的曲线、曲面。配上数控分度头可以加工齿轮、蜗轮等机械零件,且有较高的加工精度．同时以伺服进给系统为例,对改造后伺服系统的工作原理和数学模型进行了详细的介绍。     

Henderson‐Trending of Macroeconomic Variables and Forecasting Accuracy

Using a structural time‐series model, the forecasting accuracy of a wide range of macroeconomic variables is investigated. Specifically of importance is whether the Henderson moving‐average procedure distorts the underlying time‐series properties of the data for forecasting purposes. Given the weight of attention in the literature to the seasonal adjustment process used by various statistical agencies, this study hopes to address the dearth of literature on ‘trending’ procedures. Forecasts using both the trended and untrended series are generated. The forecasts are then made comparable by ‘detrending’ the trended forecasts, and comparing both series to the realised values. Forecasting accuracy is measured by a suite of common methods, and a test of significance of difference is applied to the respective root mean square errors. It is found that the Henderson procedure does not lead to deterioration in forecasting accuracy in Australian macroeconomic variables on most occasions, though the conclusions are very different between the one‐step‐ahead and multi‐step‐ahead forecasts. Copyright © 2011 John Wiley & Sons, Ltd.     

浅论轻集料混凝土的应用与发展

轻集料混凝土是具有轻质高强、保温，耐火耐热、抗震等众多优点的一种新型建筑材料。本文就轻集料混凝土的技术性能、国内外的发展状况，在工程中的应用与以及其发展趋势做了介绍和分析。     

贵州红粘土的工程特性研究

贵州为典型的喀斯特地貌,广泛分布的碳酸盐岩、亚热带的温湿季风气候,为红粘土的形成提供了良好条件,文章结合工程实际描述了贵州红粘土的工程特性以及研究。     

RBF神经网络在商品住宅投资估算中的应用

投资估算是建筑工程项目可行性研究中关键性的工作,其结果直接影响投资决策的判断。针对现行人工神经网络估算方法,输入向量的选择依据科学性不足的缺陷,笔者拟应用解释结构模型(Interpretatiue Sructral Modelling,ISM),分析影响商品住宅造价的因素,对造价影响程度不同的影响因素划分层级,以选出对造价影响较大的因素作为输入向量,使人工神经网络在投资估算中的应用更有可靠性。     

仿生裂缝自愈合混凝土

文章介绍了一种新型的工程建筑材料——仿生裂缝自愈合混凝土，这种材料的特性是，当混凝土材料出现裂缝时，部分液芯纤维或胶囊破裂，黏结液流出渗入裂缝，黏结液可以使混凝土重新愈合。     

多种印刷体汉字识别的一种方法

本文提出了一种新的描述多种印刷体汉字的方法——特征链码法.使用该方法无需先对汉字图像进行细化和平滑处理,可以克服汉字图像位移、不同大小以及一些噪声的影响.实验中针对常用的一级字库约3700个仿宋体、宋体、黑体(理论上还可以扩充到二级字库6700多个印刷体汉字,字体还可以增加楷体等),以及相应的尺寸出现的变化如24×24、24×48、48×48等做了特征抽取和识别试验,实验中还对链码特征库进行了几种预分类.     

隐式PID自校正控制器及其应用

针对某化工厂间歇化学反应器模型难以建立与控制的问题，本文提出一种隐式ＰＩＤ自校正控制算法。该算法克服了常规ＰＩＤ算法参数整定难且整定周期长的问题，可实现在线实时辨识被控对象的参数，并具备ＰＩＤ控制器参数的自校正功能，经计算机仿真研究表明该算法具有较强的鲁棒性，是一种较有应用价值的算法。