Comparison of two non‐parametric models for daily traffic forecasting in Hong Kong

The most up‐to‐date annual average daily traffic (AADT) is always required for transport model development and calibration. However, the current‐year AADT data are not always available. The short‐term traffic flow forecasting models can be used to predict the traffic flows for the current year. In this paper, two non‐parametric models, non‐parametric regression (NPR) and Gaussian maximum likelihood (GML), are chosen for short‐term traffic forecasting based on historical data collected for the annual traffic census (ATC) in Hong Kong. These models are adapted as they are more flexible and efficient in forecasting the daily vehicular flows in the Hong Kong ATC core stations (in total of 87 stations). The daily vehicular flows predicted by these models are then used to calculate the AADT of the current year, 1999. The overall prediction and comparison results show that the NPR model produces better forecasts than the GML model using the ATC data in Hong Kong. Copyright © 2006 John Wiley _ Sons, Ltd.     

细菌培养模型极限环的唯一性

分析了一类细菌培养模型,证明了在一定参数范围内极限环是唯一的。     

Working Within Organizational Cycles—A More Suitable Way to Manage Action Research Projects in Large Organizations?

This article proposes that action research projects in a large business context may need to fit within organizational funding and political cycles. It outlines some of the problems that may occur in attempting to implement an action research project in a large organization. It gives a case study of such a project that aimed to introduce a systemic human resource strategy to bring about organizational cultural change. Part way through the completion of the project the cycle changed, funds were cut, and the project was abolished, although significant portions of it had been implemented and other parts were later reestablished. The article establishes a link to punctuated equilibrium theory in exploring the political and funding cycles that influenced the decision to cut funding. It considers whether this could have been foreseen, and gives some recommendations for future action research projects.     

HOPF分叉定理在非线性振荡电路中的应用

利用李雅普诺夫函数推导的HOPF分叉定理时域型式中的综合参数－曲率系数a0和其二维系统中的局部型式来分析二阶自治非线性电路中的振荡问题。通过列出电路的状态方程计算其雅可比矩阵共轭复数特征值和求出曲率系数，并判别系统是否具有稳定的极限环来判断电路是否会出现自激振荡，从而为电子线路的振荡分析提供一种新的分析方法。     

插电式混合动力汽车能耗及其影响因素分析

通过建立插电式混合动力汽车(plug-in hybrid electric vehicle,PHEV)的前向仿真模型,对其能耗进行仿真,并分析PHEV能耗的使用影响因素.基于Modelica物理建模语言,搭建PHEV整车动力传动及纵向动力学模型,并在标准测试工况下仿真整车各部分能耗变化.针对影响PHEV能耗的使用因素,重点仿真分析表征行驶工况的平均车速和驾驶激进性对电量消耗(charge deplete,CD)阶段电耗和电量保持(charge sustain,CS)阶段油耗的影响规律.通过分析不同车速与驾驶激进性下各部分能耗以及动力部件工作效率的影响,揭示了行驶工况对能耗影响规律的内在机理.     

超过指数增长速度的年度用电量曲线拟合预测

为有效预测超过指数增长速度的年度用电量,选用超阶乘、二重指数等可线性化的函数,对年度用电量进行曲线直接拟合外推预测．采用这些新的数学函数预测北京年度用电量,拟合平均相对误差绝对值小于4．2%,2006年校验误差小于1．9％．超阶乘、二重指数函数不仅可用于超过指数增长的负荷预测,还可用于纠正线性回归、指数平滑和移动平均等方法对增长负荷预测值偏小的系统误差     

Occurrence of two types of El Niño events and the subsurface ocean temperature anomalies in the equatorial Pacific

The relationships between the evolution of two types of E1 Nifio events and the subsurface ocean temperature anomaly （SOTA） in the equatorial Pacific are compared in this study. The results show that both types of E1 Nifio are negatively correlated to the SOTA in the equatorial western Pacific, but relationships are different in different phases of E1 Nifio. Furthermore, the occurrence of different types of E1 Nifio is related to different features of the equatorial thermocline, e.g. its zonal gradient, significant variation area, amplitude and duration of thermocline oscillation. The propagation of SOTA in the equator plays an important role during the evolution of both types of E1 Nifio, but shows dramatic differences in intensity, duration and phase reverse of warm SOTA. Moreover, the pathways of SOTA signal are different between these two types of E1 Nifio. The dominant pathway in the life cycle of Eastern Pacific （EP）-E1 Nifio lies on the equator and to its north, but there is no loop to the south of the equator. In contrast, the dominant pathway in Central Pacific （CP）-E1 Nifio is located on the equator and to its south, and the propagation signal of SOTA to the north of the equator is very weak. The relationships between the zonal wind anomalies and the two types of E1 Nifio are also preliminarily discussed. It is shown that EP-E1 Nifio is more likely to respond to the westerly anomalies over the equatorial central and western Pacific, while CP-E1 Nifio is more likely to respond to the westerly anomalies over the equatorial western Pacific and need the cooperation of easterly anomalies over the equa- torial eastern Pacific to certain extent.     

Numerical Analysis of Moisture Influential Depth in Concrete During Drying-Wetting Cycles

The influential depth of moisture transport in a concrete surface subject to drying-wetting cycles was analyzed numerically. The moisture transport was described by a diffusion model with different diffusivities for drying and wetting. A finite difference scheme was developed to solve the partial differential equations The influential depth was then investigated numerically for initially saturated and unsaturated concretes exposed to drying-wetting actions in marine environments using an equilibrium time ratio concept. The equilibrium time ratio was calculated numerically for a saturated condition and the moisture influential depth is shown to be a linear function of the square root of the drying time. However, this equilibrium time ratio does not exist for an unsaturated condition and the moisture influential depth depends on the initial saturation as well as the drying-wetting time ratio. The results indicate that this model gives more realistic predictions of moisture transport of in situ structural concrete and its durability.     

Entransy dissipation and irreversibility of some thermodynamic processes

The relationship between entransy dissipation and the irreversibility of some thermodynamic processes, such as heat transfer, work-heat conversion, free expansion, isothermal diffusion etc., are analyzed in this paper. The results show that there is entropy generation but no entransy dissipation in irreversible work-heat conversion, free expansion and isothermal diffusion. Therefore, entransy dissipation cannot be used to describe the irreversibility of these processes. Both entropy generation and entransy dissipation exist in heat transfer process, which indicates that the entransy dissipation can be used to describe the irreversibility of heat transfer processes. Furthermore, the irreversibility of endoreversible cycles is analyzed. As all the irreversibility in endoreversible cycles is attributed to heat transfer between the heat sources and the working medium, entransy dissipation can be used to describe the irreversibility of this kind of cycles. To verify this conclusion, numerical examples of the endoreversible Carnot cycle are discussed.     

2008中国有数专利年度报告

基于2008年我国有效专利的统计数据，分析我国有效专利的国内外分布状况，探讨有效专利维持年限，以及有效发明专利的技术领域分布，并对我国有效专利的主要特点进行总结。