Consistent link flow estimation from counts

Partly because of counting errors and partly because counts may be carried out on different days, traffic counts on links of a network are unlikely to satisfy the flow conservation constraint “flow IN = flow out” at every node of the network. Van Zuylen and Willumsen (1980) have described a method of eliminating inconsistencies in traffic counts when a single count is available for each link in the network. In this paper, the method is extended to the case when more than one count is available on some links of the network. In addition, an algorithm is described for application of the method.     

Preview-Based Control of Suspension Systems for Commercial Vehicles

An active suspension with preview is developed for the rear axle of a commercial vehicle. The obtained improvements are promising and justify further investigation of the more feasible semi-active suspensions with preview. The inherent non-linearity of semi-active suspensions with switching shock absorbers and the need for controllers that can handle a broad class of control objectives has led to the development of several numerical control methods for both multi-level and continuously variable shock absorbers. The most promising control method and shock absorber type are selected and mounted in a test vehicle. Some first experimental results are discussed.     

The effect of resuspension on chemical exchanges at the sediment-water interface in the deep sea — A modelling and natural radiotracer approach

We review the processes responsible for the formation of vertical gradients in the chemical composition of suspended particles across the benthic nepheloid layer. Such gradients have usually explained by resuspension of surface sediments, but it is shown here that these gradients can only be understood as part of a dynamic exchange between the water column and the sediments. A coupled model, developed in a companion paper, is expanded to include chemical reactions above and below the sediment-water interface. Three cases are discussed: A tracer with first-order decay (Model 1), the dissolution of a major constituent (Model 2), and a particle-reactive tracer with first-order decay and production in the water column (Model 3). Using typical parameter values for a well-developed benthic nepheloid layer, the three models reproduce typical distributions of C_org (organic carbon), opal, and ²³⁴Th, respectively, on particles above and below the sediment-water interface. Sensitivity analyses illustrate how bioturbation can cause the large discrepancy observed between suspended and surface sediment C_org values (Model 1). The model also reconciles this observed discrepancy with observations that the major part of the decomposition takes place within the sediment. For opal (Model 2), the influence of resuspension on the burial rate of opal is shown to be negligible, as long as dissolution follows first-order kinetics and is not enhanced by turbulence in the suspended phase. The modelling of ²³⁴Th (Model 3) successfully links the depletion of ²³⁴Th in bottom waters with the distribution of excess ²³⁴Th in surface sediments and on resuspended particles.²³⁴Th is a powerful example of the tools supplied by the radioactive daughters of the natural U and Th decay series in studying fluxes and exchange rates of solutes and particles across the sediment-water interface. A short review is given of these tools, and it is shown how they can be used to obtain rate information required to apply and calibrate specific resuspension models.     

A well-functioning port is a stimulus for economy

Until just a few years ago, ports in Europe had a rather wishy-washy image. In the eyes of both the public and politicians, ports were a necessary fact of life.     

Consumer car preferences and information search channels

In this paper, we measure the relations between stated and revealed car preferences and the use of information sources in the car-purchasing process, based on a survey of households in the Netherlands. The analysis showed that attitudinal and behavioral constructs are found for ‘environmental’, ‘performance’, and ‘convenience’ preferences, but that there is a ‘gap’ between attitude and behavior. The results show that people with a positive environmental attitude who also show environmentally friendly behavior have more involvement with cars than people who do not translate their environmental attitude into the corresponding behavior. This leads to the idea that not only environmental knowledge but also involvement with cars is a prerequisite for buying an environmentally friendly car.