金轩大邸7号楼抗扭结构设计

平面不规则的高层建筑结构在地震作用下会发生扭转振动效应.通过合理布置结构平面,减小结构的质心与刚心的距离,合理控制一阶扭振周期与一阶侧振周期的比值,可以有效地减小结构的扭振效应.结合上海金轩大邸7号楼结构设计,介绍了合理有效地减小平面不规则高层剪力墙结构的扭转效应的方法.     

Estimation of Common Factors under Cross‐Sectional and Temporal Aggregation Constraints

The paper estimates a large‐scale mixed‐frequency dynamic factor model for the euro area, using monthly series along with gross domestic product (GDP) and its main components, obtained from the quarterly national accounts (NA). The latter define broad measures of real economic activity (such as GDP and its decomposition by expenditure type and by branch of activity) that we are willing to include in the factor model, in order to improve its coverage of the economy and thus the representativeness of the factors. The main problem with their inclusion is not one of model consistency, but rather of data availability and timeliness, as the NA series are quarterly and are available with a large publication lag. Our model is a traditional dynamic factor model formulated at the monthly frequency in terms of the stationary representation of the variables, which however becomes nonlinear when the observational constraints are taken into account. These are of two kinds: nonlinear temporal aggregation constraints, due to the fact that the model is formulated in terms of the unobserved monthly logarithmic changes, but we observe only the sum of the monthly levels within a quarter, and nonlinear cross‐sectional constraints, since GDP and its main components are linked by the NA identities, but the series are expressed in chained volumes. The paper provides an exact treatment of the observational constraints and proposes iterative algorithms for estimating the parameters of the factor model and for signal extraction, thereby producing nowcasts of monthly GDP and its main components, as well as measures of their reliability.     

气轨上耦合振子的受迫振动

本文叙述了在气轨上两耦合振子的受迫振动实验。该实验物理现象直观、清晰,便于测量,实验结果与理论上吻合。该设计合理,优化,简单易行,仅在原有的气垫导轨基础上增加一驱动器即可实现,效果良好。     

应用型土木工程专业人才培养力学课程体系的研究

从新时期对应用型本科土木工程专业人才的知识、素质、能力结构的要求,按照“重基础、宽口径、多方向、强应用”的原则,构建了力学课程的课程体系。     

焊接钢结构的脆性断裂分析

通过简述钢结构的脆性断裂事故,应用断裂力学的原理对结构发生断裂的因素进行分析,指出其主要影响因素.最后,分别从焊接钢结构的设计,施工工艺、质量控制以及维修监控等方面对钢结构的脆性断裂提出防治措施,以期为实际工程提供参考.     

Model selection for nonlinear time series

We investigate the finite-sample performance of model selection criteria for local linear regression by simulation. Similarly to linear regression, the penalization term depends on the number of parameters of the model. In the context of nonparametric regression, we use a suitable quantity to account for the Equivalent Number of Parameters as previously suggested in the literature. We consider the following criteria: Rice T, FPE, AIC, Corrected AIC and GCV. To make results comparable with other data-driven selection criteria we consider also Leave-Out CV. We show that the properties of the penalization schemes are very different for some linear and nonlinear models. Finally, we set up a goodness-of-fit test for linearity based on bootstrap methods. The test has correct size and very high power against the alternatives investigated. Application of the methods proposed to macroeconomic and financial time series shows that there is evidence of nonlinearity.First version received: September 2002/Final version received : October 2003I would like to thank Cees Diks, Cars Hommes and an anonymous referee for useful comments that significantly improved the paper.     

材料力学实验教学的改革与创新

该文对当前材料力学实验教学中存在的不足进行了总结并分析了原因。指出材料力学实验教学的目的是培养学生的动手能力和创新能力，介绍了材料力学实验教学改革中的一些举措，分析了结合实验教学开展大学生科研创新项目的可行性，并介绍了部分项目内容，为材料力学实验教学改革提供借鉴。     

腐败不会阻止FDI?——腐败和FDI关系的实证研究

理论模型和实证研究表明,腐败和FDI之间存在二次非线性关系,腐败并不一定会阻止FDI的流入,仅仅在某一阶段会产生这种关系;而在另一阶段,腐败和FDI之间确实存在着负相关的关系.     

Forecasting tourism: a combined approach

In this article, we employ a combined seasonal nonseasonal ARIMA and sine wave nonlinear regression forecast model to predict international tourism arrivals, as represented by the number of world-wide visitors to Singapore. Compared with a similar study of the accuracy of international tourist arrivals forecasts by Chan (Journal of Travel Research, 1993, 31, 58–60)¹ and Chu (Journal of Travel Research, 1998, 36, 79–84)² using other univariate time series models, our proposed model has the smallest mean absolute percentage error.     

基于电磁直线作动器的主动悬架控制方法研究

为了实现电磁直线作动器主动悬架中电磁阻力的有效跟踪输出,进一步提高悬架的性能,利用1/4主动悬架系统的动力学模型和作动器驱动电路模型,设计了LQG控制器和Fuzzy-PID控制器相结合的主动悬架分层控制系统。给出了电磁直线作动器主动悬架控制系统的设计方案,利用MATLAB/Simulink搭建模型进行仿真,并通过具体的台架试验验证。结果表明,主动悬架的减振性能得到了明显改善,其车身加速度和悬架动行程得到了大幅降低。研究结果对电磁悬架的主动控制方法研究具有一定的参考价值。