Anti-Roll and Active Roll Suspensions

Full car roll model is used to show an anti-roll control like that in Citroen's Xantia Activa and the proposed active roll with an in-series active suspension. Computed responses to pulse-shaped anti-phase road unevenness as well as to lateral acceleration in comparison with passive suspension are given in the paper. Also stability values for all parameters can be found.     

New methodology for fast prediction of wheel wear evolution

In railway applications wear prediction in the wheel–rail interface is a fundamental matter in order to study problems such as wheel lifespan and the evolution of vehicle dynamic characteristic with time. However, one of the principal drawbacks of the existing methodologies for calculating the wear evolution is the computational cost. This paper proposes a new wear prediction methodology with a reduced computational cost. This methodology is based on two main steps: the first one is the substitution of the calculations over the whole network by the calculation of the contact conditions in certain characteristic point from whose result the wheel wear evolution can be inferred. The second one is the substitution of the dynamic calculation (time integration calculations) by the quasi-static calculation (the solution of the quasi-static situation of a vehicle at a certain point which is the same that neglecting the acceleration terms in the dynamic equations). These simplifications allow a significant reduction of computational cost to be obtained while maintaining an acceptable level of accuracy (error order of 5–10%). Several case studies are analysed along the paper with the objective of assessing the proposed methodology. The results obtained in the case studies allow concluding that the proposed methodology is valid for an arbitrary vehicle running through an arbitrary track layout.     

基于Biba模型的三权分立分析

强制访问控制是建设高级别安全信息系统的必要条件.本文基于Biba模型,重点给出了信息系统中系统管理员、安全管理员和安全审计员三权分立的形式化分析.通过分析,给出三权分立管理机制下,保障信息系统安全管理的条件.本文的结果在某国家级信息系统的具体建设中得到了应用.     

Performance analysis of a CVT clutch system for a hybrid electric vehicle

In this study, the performance of a CVT clutch system for a hybrid electric vehicle was investigated. To analyzed the vehicle performance at restart, the restart delay and driveshaft torque was investigated by simulations and experiments. It was found from the simulation results that the vehicle restart response depends on the clutch pressure buildup time to the point where the clutch torque begins to overcome the vehicle road load, and driving comfort at restart is directly related to the rate change of the clutch pressure.     

Memory properties and fractional integration in transportation time-series

In transportation analyses, autoregressive integrated moving average (ARIMA) and generalized autoregressive conditional heteroskedasticity (GARCH) models have been widely used mainly because of their well established theoretical foundation and ease of application. However, they lack the ability to capture long memory properties and do not jointly treat the mean and variance (variability) of a time-series. We employ fractionally integrated dual memory models and compare results to classical time-series models in a traffic engineering context. Results indicate that dual memory models offer better representation of the original time-series than classical models; further, forcing the differentiation parameter of ARIMA model to equal 1 leads to over-inflated moving average terms and, consequently, to questionable models with artificial correlation structures.     

Ranking of factors contributing to higher performance in the ocean transportation industry: a multi-attribute utility theory approach

Ocean transportation has been mainly studied from an economic and strategic point of view. This paper adopts an operations management approach aiming at the identification of the value-adding attributes that characterize the ocean transportation industry. This is achieved by using Johansson et al.'s 1 four value metrics—service, quality, cost, time—which are used for the identification of the contribution that different factors make to the total created value. In this paper, multi-attribute utility theory (MAUT) has been used to measure and compare the value of different processes of various sectors of the ocean transportation industry. The application of MAUT methodology is illustrated with an example from the four sectors of the industry: liner, dry bulk, liquid bulk and specialized. Results suggest that there is strong emphasis placed by ocean transportation companies on quality and that there is differentiating importance put on service and cost by different sectors. Time is seen as the lowest value contributor by all four sectors of the surveyed companies.     

Error quantification of a high resolution coupled hydrodynamic-ecosystem coastal-ocean model: Part3, validation with Continuous Plankton Recorder data

Data collected during the Continuous Plankton Recorder (CPR) survey has been used to validate a three-dimensional hydrodynamic ecosystem model simulation of the North-west European Shelf for the years 1988–89. The CPR time series is unique to the North Atlantic region as a validation tool. Data were extracted from the model to correspond with those collected by the CPR survey, and both the model and survey plankton data were standardised to allow the comparison of model biomass with survey counts. Simple linear regression and absolute error maps provide a qualitative evaluation of spatio-temporal model performance of simulated diatoms, flagellates, total phytoplankton and omnivorous mesozooplankton. Comparisons of z-scores indicate that the model reproduces the main pelagic seasonal features, and there is good correlation between magnitudes of these features with respect to standard deviations from a long-term mean. The model is replicating up to 62% of the mesozooplankton seasonality across the domain, with variable results for the phytoplankton. There are, however, differences in the timing of patterns in plankton seasonality. The validation exercise has highlighted that the spring diatom bloom in the model is too early, suggesting the need to reparameterise the response of phytoplankton to changing light levels in the model. Errors in the north and west of the domain imply that model turbulence and vertical density structure need to be improved to more accurately capture plankton dynamics.     

Recent sedimentary study of the shelf of the Basque country

The Northern Iberian margin of the Spanish Basque country (provinces of Gipuzkoa and Viscaia) is characterized by a narrow continental platform, which receives inputs of riverine particulate matter from the numerous riverine systems located within the Basque country. This particulate matter is subsequently deposited within the Bay of Biscay, and Gouf de Capbreton [Frouin, R., Fiuza, A.F.G., Ambar, I., Boyd, T.J., 1990. Observations of a poleward surface current off the coasts of Portugal and Spain during winter. Journal of Geophysical Research 95 (C1), 679–691]. The main goal of this study is to establish a map of the surface sediment distribution of the Basque continental shelf and more specifically to map the muddy patch located at the eastern side of that continental shelf.Three oceanographic cruises were conducted in 2003 and 2004. From these campaigns 340 surface samples, 12 short cores and 3 gravity cores have been collected over the mid and outer shelf from depths ranging between 50 m and 150 m deep. 3 seismic profiles were obtained across the shelf mud patch using a Sparker device.Sediment grain-size analyses were performed by the classical physical method of sieving and use of settling columns. The POC (Particular Organic Carbon) amounts in sediment and water samples were determined using the Strickland and Parsons' method [Strickland, J.D.H., Parsons, T.R., 1972. Determination of particulate carbon. In : A practical handbook of seawater analysis. Fisheries ResearchBoard of Canada, Ottawa, pp. 207−211] as adapted by Etcheber [Etcheber, H., 1981. Comparaison des diverses méthodes d'évaluation des teneurs en matières en suspension et en carbone organique particulaire des eaux marines du plateau continental aquitain. Journal de Recherche Océanographique VI (2), 37−42]. Radioisotopic measurements (²¹⁰Pb_exc) were made using a semi-planar germanium detector coupled to a multichannel analyser. Radiographical analysis was performed with an X-ray equipment (SCOPIX®) coupled with a radioscopy instrumentation and processing unit.Firstly, a detailed sedimentological map of this shelf has been produced and secondly, geophysical surveys have precisely mapped the geometry of the main mud patch on the continental shelf. In the mud patch itself the rates of sedimentation are between 0.13 and 0.50 cm yr^− 1. The maximum rate of sedimentation is located in the central mud patch, whereas the minimum rate of deposition occurs close to the rocky outcrops. These results seem to be in agreement with the estimation of the total thickness of the mud patch revealed by seismic profiles. The central part corresponds to the maximum thickness of 7 m.Interpretations of the associated oceanic current forcing factors (current direction, wave fetch and wind directional modes) relating to the identified sediment depositional zones are also undertaken.     

Assimilation of sea surface temperature in the POL Coastal Ocean Modelling System

A one-dimensional scheme is used to assimilate satellite Sea Surface Temperature data into the Proudman Oceanographic Laboratory Coastal Ocean Modelling System, set up in the Irish Sea with a fine resolution ( 1.8 km). The capabilities of the assimilation scheme are investigated using two different sets of satellite data, of lower and similar resolution to that of the model respectively. Comparison of results with independent data show that assimilation improves the modelled Sea Surface Temperature, but does not address model representation of the temperature vertical structure. It is concluded that for the Irish Sea and at the scales resolved by the model, the assimilation problem cannot be approached in a one-dimensional framework. It is also pointed out that forecast error needs to account explicitly for errors in the representation of the vertical structure of the thermal field.Three-dimensional methods that are suited for coastal systems are then suggested.