基于粒子群优化算法的机场群航班优化配置研究

针对我国机场群发展不平衡、航线同质化程度高等问题,建立了以航班准点率、航空公司市场份额、旅客损失时间和航班功能定位指标最大化的航班时刻优化模型,将一级国际枢纽机场运行效果差的航班分配至周边机场.笔者在满足机场群内各机场起降容量限制、航班唯一性和航班连续性的条件下,设计改进的粒子群优化算法进行求解.以长三角机场群的航班时刻资源为例进行实例验证.研究表明:模型能够有效调整枢纽机场的低效航班至周边机场,使得机场群内各机场航班分布较为均衡,有效控制各时段航班架次的变化趋势,优化效果显著.     

Detection and Classification of Vehicles by Measurement of Road-Pavement Vibration and by Means of Supervised Machine Learning

Road vehicle detection and, to a lesser extent, classification have received considerable attention, in particular for the purpose of traffic monitoring by transportation authorities. A multitude of sensors and systems have been developed to assist people in traffic monitoring. Camera-based systems have enjoyed wide adoption over the last decade, partially substituting for more traditional techniques. Methods based on road-pavement vibration are not as common as camera-based systems. However, vibration sensors may be of interest when sensors must be out of sight and insensitive to environmental conditions, such as fog. We present and discuss our work on detection and classification of vehicles by measurement of road-pavement vibration and by means of supervised machine learning. We describe the entire processing chain from sensor data acquisition to vehicle classification and discuss our results for the task of vehicle detection and the task of vehicle classification separately. Using data for a single vibration sensor, our results show a performance ranging between 94% and near 100% for the detection task (1340 samples) and between 43% and 86% for the classification task (experiment specific, between 454 and 1243 samples).     

The influence of the material relation on the accuracy of collision simulations

The non-linear finite element method is widely used to simulate marine structures subjected to collisions. Furthermore, common to all non-linear finite element simulations is the need to implement the non-linear material behaviour including failure. However, the influence of the material relation on the accuracy of numerical results is not presented in detail in the present literature even though different material relations are used. Additionally, the material relation needs to include an appropriate criterion for treating the occurrence of fracture within the marine structure. Thereby, the crash resistance until inner hull failure should be predicted reliable and realistic. Therefore, this article seeks to describe the common choice of a material relation and compares this with a recent finite element-length dependent material relation based on optical measurements. As a result, this comparison gives an insight into the influence of the material relation on the accuracy of non-linear finite element simulations. Hence, this comparison can support the future use of an appropriate material relation for collision simulations.     

Road network vulnerability analysis of area-covering disruptions: A grid-based approach with case study

We present an approach to systematically analysing the vulnerability of road networks under disruptions covering extended areas. Since various kinds of events including floods, heavy snowfall, storms and wildfires can cause such spatially spread degradations, the analysis method is an important complement to the existing studies of single link failures. The methodology involves covering the study area with grids of uniformly shaped and sized cells, where each cell represents the extent of an event disrupting any intersecting links. We apply the approach to the Swedish road network using travel demand and network data from the Swedish national transport modelling system Sampers. The study shows that the impacts of area-covering disruptions are largely determined by the level of internal, outbound and inbound travel demand of the affected area itself. This is unlike single link failures, where the link flow and the redundancy in the surrounding network determine the impacts. As a result, the vulnerability to spatially spread events shows a markedly different geographical distribution. These findings, which should be universal for most road networks of similar scale, are important in the planning process of resource allocation for mitigation and recovery.     

Modelling and forecasting the demolition market in shipping

ABSTRACT

We model the demolition market, an integral part of the international shipping industry. It is shown through the implementation of a Vector Autoregressive (VAR) model that international steel-scrap prices contribute decisively towards price discovery in the ship-demolition industry. Our finding is explained and attributed to the fact that the growth models of Southeast Asian countries, where the ship-demolition market is primarily located, rely on scrap metal imports. These are mainly obtained from the developed economies rather than the recycling of vessels. We then proceed to test the forecasting ability of our model and use it for price prediction in the ship-demolition market. We establish that it provides the decision-makers with a useful prediction tool which enables all stakeholders involved, the ship owner, the recycler and the cash buyer alike, to gain valuable insights of the underlying trend in the sector.     

Applying measures of modelling quality to a national time series: a benchmark for transport demand models

ABSTRACT

In current urban planning practice, macroscopic transport demand and assignment models are essential for the evaluation of mid- and long-term land use developments and infrastructure investments. The credibility of their projections strongly depends on their ability to reproduce present day traffic volumes. Obviously, a simplified model of reality will display some shortcomings, and the effect of these is asserted by quality measures that quantify the divergence from observed traffic volumes. There is, however, only rough guidance regarding acceptable ranges of these measures. Most of the literature on this subject approach these ranges from below, by discussing measures attained by operational models and using these as a benchmark, or by using the adverse effects of modelling errors to derive a minimum quality level. On the contrary, this study suggests upper limits for quality measures by analysing year-on-year variations in traffic volumes that result from changing land use and infrastructure.     

俄罗斯的铁路改革

俄罗斯铁路为适应市场经济的需要所进行的改革进展顺利。随着机构分离的完成私人对车辆投资不断增加．铁路货运的竞争力大大提高；     

锰粉加工工人心血管功能的调查研究

对 ５５ 名锰粉加工工人和 ５６ 名对照工人的调查结果显示，工人工作地点 Ｍｎ Ｏ２ 浓度几何均值为 １９６ ｍ ｇ／ｍ ３ （锰尘 ０１７～２２．２４ ｍ ｇ／ｍ ３ ），样品超标率 ８８７％ 。接触组头晕头痛、睡眠障碍、容易疲劳和记忆不良的主诉率明显高于对照组（ Ｐ＜００５～００１）。接触组和对照组的心电图异常、高血压和低舒张压检出率未见显著性差异，其心率、 Ｐ Ｒ间期、 Ｑ Ｒ Ｓ波、收缩压和舒张压的均值比较也没有显著性差异。接触组心电图异常和低舒张压的 Ｏ Ｒ分别是 １．５６（９５％ 可信区间为 ０７０～３．５０）和 ２．０８（９５％ 可信区间为 ０１８～２３．５７）。