What are the implications of climate change for trans-Atlantic aircraft routing and flight time?

The effect of wind changes on aircraft routing has been identified as a potential impact of climate change on aviation. This is of particular interest for trans-Atlantic flights, where the pattern of upper-level winds over the north Atlantic, in particular the location and strength of the jet stream, strongly influences both the optimal flight route and the resulting flight time. Eastbound trans-Atlantic flights can often be routed to take advantage of the strong tailwinds in the jet stream, shortening the flight time and reducing fuel consumption. Here we investigate the impact of climate change on upper-level winds over the north Atlantic, using five climate model simulations from the Fifth Coupled Model Intercomparison Project, considering a high greenhouse-gas emissions scenario. The impact on aircraft routing and flight time are quantified using flight routing software. The climate models agree that the jet stream will be on average located 1° further north, with a small increase in mean strength, by 2100. However daily variations in both its location and speed are significantly larger than the magnitude of any changes due to climate change. The net effect of climate change on trans-Atlantic aircraft routes is small; in the annual-mean eastbound routes are 1 min shorter and located further north and westbound routes are 1 min longer and more spread out around the great circle. There are, however, seasonal variations; route time changes are larger in winter, while in summer both eastbound and westbound route times increase.     

中国至尼泊尔跨境铁路最大坡度研究

中国至尼泊尔跨境铁路穿越喜马拉雅山脉,具有显著的地形高差,海拔从佩枯错4 600 m急骤下降至加德满都1 360 m,部分地段自然纵坡达50‰及以上,需要采用较大坡度以适应地形。在分析国内外大坡度铁路使用及发展的基础上,结合项目地形特点对坡度方案进行分段研究,重点对佩枯错至加德满都段最大坡度方案从运输安全性、运输质量、运输能力和运输经济性等方面综合分析论证。结合长大下坡紧急制动距离的要求,分析客货列车下坡限速,考虑牵引力、制动力、黏着力和车钩强度等限制条件,检算满足长大坡道客货列车牵引、制动安全的牵引质量和编挂辆数,并结合运输需求分析不同坡度方案能力适应性,通过模拟牵引计算比较列车运行速度,计算工程投资、机车购置费和运营费的费用现值,进行经济性比较。综合分析,本项目最大坡度日喀则至佩枯错段暂推荐采用13‰,佩枯错至加德满都段采用30‰。     

Optimization of traffic demand management policy in China: towards a sustainable mode split

The rapid increase in private car use in large metropolitan areas has led to irrational travel mode splits and severe traffic problems. Traffic demand management (TDM) is an effective policy to achieve a more sustainable development of traffic systems. This study analyzes the relationships between TDM policy, mode split, and travel mode choice using Stackelberg game theory. Then, using 0–1 programming, it establishes a combination of TDM policy instruments that can achieve a more sustainable mode split in a city and provides a case study in China. The method presented in this research has strong theoretical implications for TDM policymakers.     

基于l1范数稀疏解的水下双层圆柱壳振动声辐射预报影响因素研究

基于模态叠加法理论,采用l1范数稀疏解方法,实现了水下双层圆柱壳由内壳有限测点振速值重构得到内、外壳振速空间分布,进而基于边界元理论对结构水下辐射声场进行预报。通过数值计算,分析了模态数目、测点数目和模态振型误差等因素对振动声辐射预报结果的影响,为指导速度场重构时模态数目、测点数目的选取提供了一定的理论依据;结果表明基于l1范数稀疏解声学预报方法对模态振型误差有一定的鲁棒性。最后开展了水下典型双层圆柱壳结构振动声辐射预报的试验研究,可为工程领域结构的声振预报提供一定的指导思路。     

DK-1型制动机适用于CIS制动系统的初探

根据DK-1型制动机制动指令范围与CIS制动系统动作区域之间的关系,研究DK-1型制动机适用于CIS制动系统的可行性,并分析DK-1型制动机全面适用于CIS制动系统还需要改动之处。     

灰色系统模型在内河港口吞吐量预测中的应用

根据淮南港吞吐量实际调查资料,选择灰色系统理论对其进行吞吐预测研究,结果表明,对不同的预测时期应采用不同的灰色系统预测模型。对于短期预测,采用GM(1,1)模型与Verhulst模型的组合模型;对于长期预测,采用Verhulst模型并用GM(1,1)模型对其残差进行修正。实例验证以上两种模型是可行性的。     

广州地铁1号线谐波测量及分析

介绍了在不同运行方式下，广州地铁1号线供电系统110KV侧的谐波测量结果，并对测量结果进行了分析。指出广州地铁1号线供电系统中主要存在11次、13次谐波电流。在目前负荷水平不高的情况下，在滤波器退出运行时，其谐波电流尚未超过国际限制值；但在未来高峰负荷期间，需将滤波器投入运行。另外，还介绍了在广州地铁1号线挂网试运行的24脉波整流变压器对改善地铁供电系统谐波的情况。最后说明需经理论分析、计算及经济比较后，方可决定是否采用滤波器或24脉波整流变压器来抑制地铁系统的谐波。     

基于CDMA的铁路10kV配变监控系统的研究与实现

设计了基于CDMA2000-1X分组数据网络构建的铁路10kV配变监控系统。该系统利用CDMA 1X分组域的VPDN专线网,结合传统的调度自动化技术,在调度中心构建数字化多功能信息平台,实现了对区间信号点处变压器运行状态的实时监测与控制,同时也为铁路10kV自闭/贯通线上故障测距和故障诊断提供了相关的有效依据。     

车辆段5T、AEI探测站维修作业通道开设方式探讨

本文针对铁路全封闭后,车辆段5T、AEI探测站维修人员进出困难的问题,提出了设置探测站作业通道需遵守的三条原则。归纳了栅栏直开、探测站双开门、围墙开门三种探测站作业通道的开设方式,比较各自优缺点和适用条件。建议在既有探测站增设作业通道时,需因地制宜,选择合理方案。在新建探测站工程时应同步进行作业通道的设计和施工。     

A study of the response of chlorophyll-a biomass to a winter upwelling event off Western Iberia using SeaWiFS and in situ data

Observations of a winter upwelling event off Western Iberia shelf/slope in the area of influence of the Western Iberia Buoyant Plume (WIBP) were conducted in February 2000. Spatial patterns and time evolution of the chlorophyll-a (chl-a) biomass are analysed, based on in situ and satellite data. SeaWiFS-derived chl-a concentration L2 products were used to track the chlorophyll front and estimate its westward migration velocity (maximum up to 29 km day⁻¹), as well as to characterize the frontal system and its evolution. A method associating the type of spectral signature of a pixel to the fraction of chlorophyll probed by SeaWiFS enabled the estimation of the chl-a biomass within error intervals. High chlorophyll concentrations (for wintertime) were observed over the shelf and slope, up to large distances to the coast. Due to the WIBP, a shallow Ekman layer developed, being nearly coincident with the stratified upper meters. The transport comprised westward advection and stretching of the plume, with little entrainment with the offshore deep mixed layer waters. The relative enlargement of the total area of the Inside-Front Zone (IFZ) during the upwelling event was roughly accompanied by the maintenance of the average biomass per unit of area, considering the water column up to depths of interest. This suggests that there was a net increase of chl-a biomass inside the water column associated with the IFZ, roughly proportional to the increase in the IFZ area. Retention of phytoplankton in the shallow stratified nutrient-rich waters of the WIBP was a key factor for this increase in chl-a biomass.