Children’s travel to school: satisfaction,current mood,and cognitive performance

We investigate whether travel mode, travel time, and activities during travel influence children’s satisfaction with their travel to school, their current mood, and their cognitive performance after arriving at school. A sample of 344 children (165 girls) between the ages of 10 and 15 years were recruited at five public schools in Värmland County, Sweden. Directly after arriving at school, the children rated how they felt on two scales ranging from very sad to very happy and from very tired to very alert, filled out the Satisfaction with Travel Scale adapted for children (STS-C), reported details about their journeys, and took a word-fluency test. The results for STS-C showed that traveling by school bus and walking or cycling was experienced as having a higher quality than traveling by car. Children who engaged in conversation during their journeys reported a higher quality and more positive feelings than children who were engaged in solitary activities during their journeys. A shorter journey was experienced as having a higher quality and resulting in more positive feelings. Children traveling for longer durations performed better in the word-fluency test if using their smartphones or doing a combination of activities during their journeys.     

The results of the pantograph–catenary interaction benchmark

This paper describes the results of a voluntary benchmark initiative concerning the simulation of pantograph–catenary interaction, which was proposed and coordinated by Politecnico di Milano and participated by 10 research institutions established in 9 different countries across Europe and Asia. The aims of the benchmark are to assess the dispersion of results on the same simulation study cases, to demonstrate the accuracy of numerical methodologies and simulation models and to identify the best suited modelling approaches to study pantograph–catenary interaction. One static and three dynamic simulation cases were defined for a non-existing but realistic high-speed pantograph–catenary couple. These cases were run using 10 of the major simulation codes presently in use for the study of pantograph–catenary interaction, and the results are presented and critically discussed here. All input data required to run the study cases are also provided, allowing the use of this benchmark as a term of comparison for other simulation codes.     

Changes in apparent oxygen removal in the Baltic proper deep water

By developing a steady state diagnostic model for a stratified deep-water mass, one is able to quantify both the mass flows and apparent oxygen removal in the Baltic proper deep water. The model is based on continuity of the assumed conservative observable volume, salinity and temperature. Second degree polynomials are fitted to observed vertical profiles of temperature as well as oxygen concentration to give a functional correspondence with the used spatial variable salinity. These relations are used in the model that calculate the water flows, oxygen flows and oxygen removal during four periods between 1959 and 1997. The model forms a boundary value problem, which is solved with a finite difference scheme. The model seems to give reasonable estimates of the flows. The oxygen removal is mainly balanced by inflow of oxygen with incoming water. The oxygen consumption is 4–8 μl O₂ l⁻¹ day⁻¹, which corresponds to a degradation of organic matter in the range 30–60 g C m⁻² year⁻¹.     

Past, present and future state of the biogeochemical Si cycle in the Baltic Sea

The Baltic Sea is one of many aquatic ecosystems that show long-term declines in dissolved silicate (DSi) concentrations due to anthropogenic alteration of the biogeochemical Si cycle. Reductions in DSi in aquatic ecosystems have been coupled to hydrological regulation reducing inputs, but also with eutrophication, although the relative significance of both processes remains unknown for the observed reductions in DSi concentrations. Here we combine present and historical data on water column DSi concentrations, together with estimates of present river DSi loads to the Baltic, the load prior to damming together with estimates of the long-term accumulation of BSi in sediments. In addition, a model has been used to evaluate the past, present and future state of the biogeochemical Si cycle in the Baltic Sea. The present day DSi load to the Baltic Sea is 855 ktons y^− 1. Hydrological regulation and eutrophication of inland waters can account for a reduction of 420 ktons y^− 1 less riverine DSi entering the Baltic Sea today. Using published data on basin-wide accumulation rates we estimate that 1074 ktons y^− 1 of biogenic silica (BSi) is accumulating in the sediments, which is 36% higher than earlier estimates from the literature (791 ktons y^− 1). The difference is largely due to the high reported sedimentation rates in the Bothnian Sea and the Bothnian Bay. Using river DSi loads and estimated BSi accumulation, our model was not able to estimate water column DSi concentrations as burial estimates exceeded DSi inputs. The model was then used to estimate the BSi burial from measured DSi concentrations and DSi load. The model estimate for the total burial of BSi in all three basins was 620 ktons y^− 1, 74% less than estimated from sedimentation rates and sediment BSi concentrations. The model predicted 20% less BSi accumulation in the Baltic Proper and 10% less in the Bothnian Bay than estimated, but with significantly less BSi accumulation in the Bothnian Sea by a factor of 3. The model suggests there is an overestimation of basin-wide sedimentation rates in the Bothnian Bay and the Bothnian Sea. In the Baltic Proper, modelling shows that historical DSi concentrations were 2.6 times higher at the turn of the last century (ca. 1900) than at present. Although the DSi decrease has leveled out and at present there are only restricted areas of the Baltic Sea with limiting DSi concentrations, further declines in DSi concentrations will lead to widespread DSi limitation of diatoms with severe implications for the food web.     

The effects of an acceleration advisory tool in vehicles for reduced fuel consumption and emissions

This study evaluates whether the use of an acceleration advisor leads to fuel savings, to determine the change in traffic-related emissions and to analyse changes in driving patterns on various routes. The acceleration advisor provides advice to drivers through resistance in the accelerator pedal when they try to accelerate rapidly. In a test carried out in Southern Sweden, the acceleration advisor was installed in four postal delivery vehicles. The driving pattern parameters show that strong acceleration was significantly reduced, which indicated that the drivers had complied with the advisor. On two of the three routes, the acceleration advisor had a positive effect on emissions. In general, no significant reduction in fuel consumption was observed when driving with the acceleration advisor activated.     

Hazardous material incidents: Some key results of a risk analysis

Human safety and health, environmental and property protection and security concerning hazardous materials supply chain are important issues for many countries, industries and organisations around the world. This paper presents some key results of a comprehensive risk study on hazardous materials supply chain incidents. Based on a risk analysis framework adapted for maritime transport of packaged dangerous goods, this study combines qualitative and quantitative analysis of large and diverse datasets collected from some of the U.S.’s best and largest data sources. The study may be one of the largest of its kind, and some of the results might not be found elsewhere. Incidents have occurred in every system of the hazardous materials supply chain, including platforms, all modes of transport, chemical plants, terminals and storages. The results show that more than half (52.1 %) of incidents are attributed to the transport system. The study largely considers incidents happening during maritime transport, which account for 18% of transport incidents. In absolute terms, the FN curves of maritime transport human risks are generally found to be well below the corresponding FN curves of aggregated supply chain human risks.     

Wave analysis of porous geometry with linear resistance law

The wave diffraction-radiation problem of a porous geometry of arbitrary shape located in the free surface of a fluid is formulated by a set of integral equations, assuming a linear resistance law at the geometry. The linear forces, the energy relation and the mean horizontal drift force are evaluated for non-porous and porous geometries. A geometry of large porosity has an almost vanishing added mass. The exciting forces are a factor of 5–20 smaller compared to a solid geometry. In the long wave regime, the porous geometry significantly enhances both the damping and the mean drift force, where the latter grows linearly with the wavenumber. The calculated mean drift force on a porous hemisphere and a vertical truncated cylinder, relevant to the construction of fish cages, is compared to available published results.     

Analysis and optimisation of objective vehicle dynamics testing in winter conditions

Objective testing of vehicle handling in winter conditions has not been implemented yet because of its low repeatability and its low signal-to-noise ratio. Enabling this testing, by identifying robust manoeuvres and metrics, was the aim of this study. This has been achieved by using both experimental data, gathered with steering-robot tests on ice, and simulation models of different complexities. Simple bicycle models with brush and MF-tyre models were built, both optimally parameterised against the experimental data. The brush model presented a better balance in complexity performance. This model was also implemented in a Kalman filter to reduce measurement noise; however, a simpler low-pass filter showed almost similar results at lower cost. A more advanced full vehicle model was built in VI-CarRealTime, based on kinematics and compliance data, damper measurements, and real tyre measurements in winter conditions. This model offered better results and was therefore chosen to optimise the initial manoeuvres through test design and simulations. A sensitivity analysis (ANOVA) of the experimental data allowed one to classify the robustness of the metrics. Finally, to validate the results, the proposed and the initial manoeuvres were tested back to back in a new winter campaign.     

Voluntary internalization of speeding externalities with vehicle insurance

High speed is an important determinant of accidents for speeders as well as for other motorists. This paper develops a framework for analyzing instruments that encourage drivers to internalize the full consequences of their behavior with respect to choice of speed using Pay-As-You-Speed (PAYS) insurance, possibly as an extension of Pay-As-You-Drive (PAYD) insurance. We demonstrate how the combination of a Pigovian taxation scheme and PAYS can be designed in a setting involving two principals (the state and an insurance company) that affect the incentives of commuters to choose between driving and other modes of transport and for those that use the car mode to drive carefully. While the government is assumed to maximize overall social efficiency and therefore wants to implement marginal cost pricing, insurance companies do actuarial pricing, i.e. average cost pricing within risk classes that are homogeneous to the degree that the insurers have information about actual behavior. PAYS insurance improves the insurance industry’s possibility to differentiate premiums according to behavior and therefore to target risk classes in a better way than today. Moreover, since our framework is designed to accomplish differentiation by self-selection, compulsory regulation is not necessary, although there may be reason for the government to facilitate the implementation of the new technology.     

An experimental/numerical approach for evaluating skin friction on full-scale ships with surface roughness

For an accurate evaluation of the increase in skin friction due to various surface topographies on ships, i.e. plate roughness, coatings, or bio fouling, both experimental measurements and a numerical evaluation of those measurements are necessary. The measurements are necessary as no other practical method exists to evaluate the skin friction coefficient on most surface topographies, and numerical evaluation is required to compute the roughness effects of varying ship types and speeds. Therefore, a method for measuring the skin friction coefficient for bio-fouled and structured surfaces at full-scale friction velocity is presented, and a validation of the design and measuring procedures is given. For the ship frictional resistance calculations, the Computational Fluid Dynamics (CFD) code ShipFlow has been modified to take the added friction into account.