GPS销售渠道：4股飓风抢滩登陆

2008年的GPS导航市场，是一个从上到下都不平静的战场，从地图供应商的产权纷争，到硬件商的价格大战，GPS导航销售渠道也出现了4股飓风抢滩登陆的场面。虽然4个渠道看起来都有不同的消费群，但在用户基数还不大的情况下，其相互间的激烈竞争还是难免。而这4个销售渠道，谁将更有实力在未来的导航市场分得更多甜头呢？     

CTRL应用纤维混凝土管片的经验

海峡隧道铁路联络线2区段上的运营隧道包括2.52km长的泰晤士河双洞隧道(Thames Tunnel)和17.5km长的伦敦双洞隧道(London Tunnels)(CTRL 2区段隧道,T&TI杂志2003年9月,增刊).     

提高大型逆变器输出电压的控制方法

日本研制的超导磁悬浮系统使用了带有地面电枢线圈的直线同步电动机(LSM).其功率变流器能根据列车速度和牵引力提供电压和频率可变的电源.因此为山梨磁悬浮试验线开发了脉宽调制(PWM)逆变器.另外,为了降低制造成本,开发了几种控制方法,在不改变逆变器电路配置的情况下能提高其输出电压.文章叙述了这些控制方法的特性及部分试验结果.     

实用感应电机饱和模型

文章提出了基于H-G图建立感应电机饱和模型的新方法,它只需用H-G图中每个饱和点对应的3个参数来描述电机的饱和.另外这种方法还可以推广到考虑其他影响因素的电机,比如温度和集肤效应时的电机建模.文章将这种模型与感应电机有、无交叉耦合的两种传统模型进行了比较.仿真结果显示,这种方法较交叉耦合饱和模型在精度和准确度上有更多优点,特别是在启动和满负载运行时.     

A system dynamics approach to land use / transportation system performance modeling Part II: Application

This paper presents a system dynamics approach to simultaneous land use/transportation system performance modeling. A model is designed based on the causality functions and feedback loop structure between a large number of physical, socioeconomic, and policy variables. The model system consists of 7 sub‐models: population, migration of population, household, job growth‐employment‐land availability, housing development, travel demand, and traffic congestion level. The model is formulated in DYNAMO simulation language, and tested on a data set from Montgomery County, MD. In Part I: Methodology, the overall approach and the structure of the model system is discussed and the causal‐loop diagrams and major equations are presented. In Part II: Application, the model is calibrated and tested with data from Montgomery County, MD. Least square method and overall system behavior are used to estimate the model parameters. The model is fitted with the 1970–80 data and validated with the 1980–1990 data. Robustness and sensitivities with respect to input parameters such as birth rate or regional economy growth are analyzed. The model performance as a policy analysis tool is also examined by predicting the year by year impacts of highway capacity expansion on land use and transportation system performance. While this is a first attempt in using dynamic system simulation modeling in simultaneous treatment of land use and transportation system interactions, and model development and application are limited to some extent due to data availability, the results clearly indicate that the proposed method is a promising approach in dealing with complex urban land use/transportation modeling     

新型快餐盒生物降解性能试验方法研究

通过固体培养微生物侵蚀试验、液体培养微生物侵蚀试验、降解过程中纤维素酶活性测定、纤维素酶侵蚀试验和降解过程中 Ｃ Ｏ２ 生成体积分数的测定等试验结果分析，认为固体培养微生物侵蚀试验、纤维素酶侵蚀试验及 Ｃ Ｏ２ 生成量测定试验可用于评价新型快餐盒生物降解性能。     

A “horizontal Sverdrup mechanism” may control the spring bloom around small oceanic islands and over banks

One of the most basic paradigms in marine ecology is the “Sverdrup mechanism,” where the spring bloom is retarded if the surface mixed layer is too deep, due to the algae being mixed vertically out of the euphotic layer. A similar mechanism may operate in vertically homogeneous water over a small shallow area, surrounded by deep waters, if the horizontal exchange is sufficiently intense. In systems with inter-annual variations in the horizontal exchange rate, this may induce inter-annual variations in the timing and intensity of the spring bloom. A numerical primary production model with circular symmetry and prescribed horizontal exchange rate is developed. Using the Faroe Shelf as an example, the model and observations show that the timing and intensity of the spring bloom in the shallow parts of the system may be critically dependent upon the rate of the horizontal exchange. Numerical experiments confirm that the effect of horizontal exchange on the spring bloom is less pronounced for banks than for shelf systems around islands of similar scales, and that the effect increases in importance as the horizontal scale is reduced.     

Calibration of large-scale transport planning models: a structured approach

Transportation - Traditionally, transport planning model systems are estimated and calibrated in an unstructured way, which does not allow for interactions among included parameters to be...