Platoon driving has potential to significantly benefit road traffic. This study presents a decoupled robust control strategy for a vehicular platoon with identical feedback controller and rigid information topology. The node dynamics of vehicle with a lower-level controller is assumed to be covered by a multiplicative uncertainty model. The vehicular platoon control system is skillfully decomposed into an uncertain part and a diagonal system by applying linear transformation and eigenvalue decomposition on information flow graph. Then the requirements of robust stability and distance tracking error are equivalent to the H-infinity norm of decoupled sub-systems. Comparative simulations with a non-robust controller and different communication topologies are conducted to demonstrate the robust stability and distance tracking performances of the proposed method. 相似文献
The hub location problem deals with finding the location of hub facilities and allocating the demand nodes to these hub facilities so as to effectively route the demand between any origin–destination pair. In the extensive literature on this challenging network design problem, it has widely been assumed that the subgraph induced by the hub nodes is complete. Relaxation of this basic assumption constitutes the starting point of the present work. In this study, we provide a uniform modeling treatment to all the single allocation variants of the existing hub location problems, under the incomplete hub network design. No network structure other than connectivity is imposed on the induced hub network. Within this context, the single allocation incomplete p-hub median, the incomplete hub location with fixed costs, the incomplete hub covering, and the incomplete p-hub center network design problems are defined, and efficient mathematical formulations for these problems with O(n3) variables are introduced. Computational analyses with these formulations are presented on the various instances of the CAB data set and on the Turkish network. 相似文献
This article examines the negative situation surrounding seafarers’ welfare in the post 9–11 shipping world. Its main focus
is the denial of shore leave which has become a prime source of disharmony since the implementation of post 9–11 security
measures. It discusses the implementation of these measures which has been at the expense of seafarers’ customary right to
shore leave. 相似文献
The traditional methods of fatigue assessment of welded joints have some limitations, and are extremely time consuming. In order to overcome these difficulties, the Thermographic Method (TM), based on thermographic analyses, has been applied to predict the fatigue behaviour of butt welded joints, made of AH36 steel, largely used in shipbuilding. Experimental tests have been carried out to assess the fatigue capability in terms of S–N curves and fatigue limits. The predictions of the fatigue capability obtained resorting to the Thermographic Method show a good agreement with those derived from the traditional procedure. Moreover, the fatigue design recommendations were compared to the experimental data in order to analyse the reliability of the codes. 相似文献
The purpose of this paper is to detect and describe general trends in the spatial distribution of epibenthic and demersal communities of Le Danois Bank (El Cachucho) in relation to the environmental variables that characterize their habitat by means of multivariate ordination. Data were derived from two multidisciplinary surveys carried out in October 2003 and April 2004 included in the ECOMARG project. The surveys were focused on the study of the physical scenario, including both geological (seabed characterization from bathymetry and backscatter data) and hydrographic features, and the different compartments of the benthic fauna (endobenthic, epibenthic, suprabenthic and demersal communities). For the present study, epibenthos and demersal species were sampled using two different gears, a 3.5 m beam trawl and a Porcupine 39/52 type baca otter trawl respectively. The total species richness combining both samplers ascended to 221, including 71 species of fishes, 65 crustaceans, 35 molluscs, 29 echinoderms, 10 cnidarians and 5 sponges.Multivariate methods were used for the study of the characteristics of communities and habitats. Hierarchical cluster analysis was applied to calculate and visualize similarities between samples in terms of species composition. To assess the amount of variation of faunal densities related to a set of eight environmental variables, a redundancy analysis (RDA) was used. The set of environmental variables used were: depth, near-bottom temperature and salinity, sedimentary typology (dry weight percentages of coarse sands, medium and fine sands, silt and organic matter) and seafloor reflectivity. Using the spatial distribution of the ranges of depth and seafloor reflectivity that characterize the habitats of the faunal assemblages we defined the spatial distribution of the different communities.The multivariate analysis of 18 beam-trawl samples and 15 otter trawl samples showed the existence of 4 main assemblages associated with the more characteristic habitats of the area. The Callogorgia–Chimaera community live mainly in the areas at the top of the Bank (425–550 m depth), where the sediment coverage is lower and there exists a high presence of rocky outcrops. The Gryphus–Galeus community were found in the areas at the top of the Bank covered by medium and fine sand sediments with low organic matter content. The Phormosoma–Trachyrincus community live on the sedimentary terraces that characterize the Bank break (550–800 m) and the Pheronema–Deania community occupy all the deeper (800–1050 m) sedimentary grounds of the inner basin. 相似文献
Road safety is a policy priority due to the high casualties and costs associated with road accidents. Since speed is a major cause of road accidents, in‐vehicle speed limiters or Intelligent Speed Adaptation (ISA), seems a promising solution. ISA implementation, however, is hindered by large uncertainties, for example about the impacts of ISA, the way users might respond to ISA, and the relationship between speed and accidents. Traditional Multi‐Criteria Analysis (MCA) has limitations in handling these uncertainties. We present an MCA approach based on exploratory modeling, which uses computational experiments to explore the multiple outcomes of ISA policies (safety, emissions, throughput, and cost) across a range of future demand scenarios, functional relationships for performance criteria, and user responses to ISA. As an illustration, by testing the impacts of different ISA penetration levels on two driver groups, we show that when compliance with ISA is expected to be low, a policy aimed only at novice drivers outperforms other ISA policies on safety improvement. 相似文献
There are many regulatory changes being imposed on tanker operators of new and existing ships. This paper provides a brief
on the main changes and their practical impact on design and operation i.e. the significant recent and upcoming revisions
to IMO MARPOL Annexes I, II and VI, SOLAS and other regulations and the IACS Common Structural Rules. 相似文献
The problem of designing network-wide traffic signal control strategies for large-scale congested urban road networks is considered. One known and two novel methodologies, all based on the store-and-forward modeling paradigm, are presented and compared. The known methodology is a linear multivariable feedback regulator derived through the formulation of a linear-quadratic optimal control problem. An alternative, novel methodology consists of an open-loop constrained quadratic optimal control problem, whose numerical solution is achieved via quadratic programming. Yet a different formulation leads to an open-loop constrained nonlinear optimal control problem, whose numerical solution is achieved by use of a feasible-direction algorithm. A preliminary simulation-based investigation of the signal control problem for a large-scale urban road network using these methodologies demonstrates the comparative efficiency and real-time feasibility of the developed signal control methods. 相似文献
The paper takes station-based bikesharing system (SBS) with docks and dockless free-floating bikesharing system (FBS) as two targets to dig out the relationship between users and use frequency of the services for each scheme, and how the relationship varies from scheme to scheme. To achieve this, studies are carried out focusing on three questions: “who are using these two bicycle services?”; “what are the factors influencing the use frequency of both bicycle systems?”; and “which specific level of the factors influencing the use frequency of both bicycle schemes?” To collect data from users, a survey was designed containing questions for user attributes and service experience and conducted jointly on-line and on-site at four locations with mixed land use in Hangzhou, China. Analysis results show that SBS and FBS have similar user structure but different factors influence use frequency. Based on analysis results, from the user perspective, SBS’s strength is to have good quality with low cost while FBS is more flexible and free to use. Finally, recommendations for SBS are to involve more technology to expand its range to aided bikes for senior citizens and open the access for a mobile renting system, whereas for FBS, it is critical to get government cooperation and for operators to add parking area restrictions into the cellphone application, and create an on-line platform where users can find all the free-floating bike information.
In this volume, Jones has made a persuasive case for considering recently observed reductions in car use (and sometimes car ownership) in a number of major northern cities as part of an evolutionary process, rather than the consequence of transient conditions such as the economic downturn of 2008 and its relatively slow recovery. In an era bringing new service models for mobility and communications that have important implications for safety, security, the environment and well-being, he points to the role of public attitudes and sentiments that may underlie changing policy priorities and an associated culture change with respect to transport in cities and the reclamation of street space. This paper briefly explores the role of public sentiments and reflects on the apparent emergence of a popular subculture that favors living, if possible, without owning or using cars, in contrast to older subcultures embracing more extreme sentiments that are either Car-centered or emphatically anti-car. 相似文献