Variation in predicting pantograph–catenary interaction contact forces,numerical simulations and field measurements

The contact force between the pantograph and the contact wire ensures energy transfer between the two. Too small of a force leads to arching and unstable energy transfer, while too large of a force leads to unnecessary wear on both parts. Thus, obtaining the correct contact force is important for both field measurements and estimates using numerical analysis. The field contact force time series is derived from measurements performed by a self-propelled diagnostic vehicle containing overhead line recording equipment. The measurements are not sampled at the actual contact surface of the interaction but by force transducers beneath the collector strips. Methods exist for obtaining more realistic measurements by adding inertia and aerodynamic effects to the measurements. The variation in predicting the pantograph–catenary interaction contact force is studied in this paper by evaluating the effect of the force sampling location and the effects of signal processing such as filtering. A numerical model validated by field measurements is used to study these effects. First, this paper shows that the numerical model can reproduce a train passage with high accuracy. Second, this study introduces three different options for contact force predictions from numerical simulations. Third, this paper demonstrates that the standard deviation and the maximum and minimum values of the contact force are sensitive to a low-pass filter. For a specific case, an 80?Hz cut-off frequency is compared to a 20?Hz cut-off frequency, as required by EN 50317:2012; the results show an 11% increase in standard deviation, a 36% increase in the maximum value and a 19% decrease in the minimum value.     

Emissions of particulate matters from railways – Emission factors and condition monitoring

We report tunnel measurements, where abrasion particles from different types of trains are measured in two situations and emission factors are calculated from these. The measurements show significantly elevated particle concentrations in train passages that last for about a minute and are accompanied by increased airflow. The emission of particles for each train passage was obtained by summing the product of the particle concentration and the airflow and then multiplying with the tunnel area. The average emission factors were calculated for three categories freight trains, commuter trains and regional trains and found to be 2.9 g/train-km (0.7 – 9), 0.48 (0.1 – 1.6) and 0.24 (0.05–0.9), respectively. The number in brackets refers to the range of values observed. The size-resolved data showed maxima around 1 μm for all three train types.     

Opportunities for increased profit and reduced cost and emissions by service differentiation within container liner shipping

This paper investigates opportunities for increased profit and reduced emissions and cost by service differentiation within container shipping. Traditionally the strategy among the container lines has been profit maximization by utilizing economies of scale through the building of larger and faster vessels. In 2008, the financial crisis in combination with higher fuel prices put an end to this progress and in today’s market operators are basically trying to survive by providing standardized services at the lowest possible cost. This study investigates alternative strategies and the results indicate that container lines should provide two different services instead of one standardized service. A fast service to be more competitive versus air freight for fast-moving goods and a slow service to be more competitive versus traditional shipping types for transport of minor bulk, break bulk, liquid bulk and project cargo.     

Consequences of public ownership and subsidies for mass transit: Evidence from case studies and regression analysis

The trend toward public ownership, public regulation, and public subsidization of the U.S. transit industry has recently come under attack. Many argue that the result has been reduced productivity, increased costs, and very little real benefit. This article examines the impacts of subsidies and public ownership in four large transit systems that cover a range of transit system types and financing arrangements. Evidence from the case studies is compared to the results of both time-series and cross-section regression analysis of operating and financial statistics for large samples of bus systems. Although the case studies and the regressions rely on different datasets and different techniques, they support the same conclusions. Increased subsidies and public ownership have kept down fares and permitted service expansion, but have also encouraged wasteful cost escalation. Thus, transit riders unquestionably have benefited from public takeovers of transit systems and burgeoning subsidies, but not nearly as much as they would have benefited if costs had not skyrocketed at the same time.     

A return period based plastic design approach for ice loaded side-shell/bow structures

Based on the design ice load that corresponds to a certain return period, a practical approach for designing the frames behind the side-shell or the bow of a ship subject to ice loading is proposed. Four typical types of section profiles have been selected for modelling and numerical analysis. Non-linear finite element analyses that involve both the geometric and material non-linearity were performed. From the analyses, the relationships between the loads and the beam's cross-section properties were obtained for different permanent set requirements. These relationships were then used for finding the section modulus from which the cross-section of the beam can be decided. Finally, a design example is presented for illustration.     

Local public transport on the basis of social economic criteria

Applying the welfare economic approach it is demonstrated what the effects of certain supply changes in the local public transport will be and the potential of innovative demand management measures are examined. Straighter bus routes would reduce the average travel time from door to door. The travel time on the buses decreases and the frequency increases, which reduces waiting times at bus stops. Using smaller buses and more of them would also increase the net benefit, but increase the need for subsidisation. The peak within the peak in the morning is hard to handle by price policy alone. Introducing a small variation of the start of the school-day for high-school pupils would make investment- and operation cost savings possible, and the inconvenience costs for the pupils could be limited. It is only during peak hours in the main direction of peak travel and in the critical section of the line that optimal price becomes high relative to the present level. Zero fares in off-peak will be social profitable, but an increase in subsidy is needed. An introduction of these policy changes would give rise to a net social benefit of 30 million SEK per year in Linköping.     

Parametric roll mitigation using rudder control

Severe roll angles can be developed by parametric excitation in relatively moderate weather without any apparent pre-warning for the crew onboard. In this study the prospect of using rudder control to mitigate parametric roll was investigated using multi-degree of freedom simulations. A typical modern Pure Car and Truck Carrier was considered and modelled by coupling a roll model with a planar motion manoeuvring model. The combined model was calibrated using in-service, full-scale trials and model tests. Irregular variations of the metacentric height were applied to simulate recorded, full-scale events of parametric roll that have occurred with the considered design. These simulations with rudder roll control showed promising results and demonstrate that the approach could be very efficient for mitigation of parametric roll.     

Uncertainty of estimated rainflow damage for random loads

One way to assess the uncertainty in fatigue damage analysis is to use a so-called safety index. In the computation of such an index the coefficient of variation for the accumulated damage is needed. Employing the rainflow cycle count method for fatigue damage leads to, in most cases, complicated calculations. Here we present a new and simplified method to estimate the coefficient of variation for the accumulated damage when only one sample path of the load is available. Non-stationary, slowly changing, Gaussian loads are given special attention. The approach is illustrated by means of stationary Gaussian loads with nine different spectra, a measured non-Gaussian load, a skewed load and the wave load accumulated during one year in a “seasonally changing environment”.     

Day-to-day variability in travellers’ activity-travel patterns in the Jakarta metropolitan area

Using four consecutive days of SITRAMP 2004 data from the Jakarta metropolitan area (JMA), Indonesia, this study examines the interactions between individuals’ activity-travel parameters, given the variability in their daily constraints, resources, land use and road network conditions. While there have been a significant number of studies into day-to-day variability in travel behaviour in developed countries, this issue is rarely examined in developing countries. The results show that some activity-travel parameter interactions are similar to those produced by travellers from developed countries, while others differ. Household and individual characteristics are the most significant variables influencing the interactions between activity-travel parameters. Different groups of travellers exhibit different trade-off mechanisms. Further analyses of the stability of activity-travel patterns across different days are also provided. Daily commuting time and regular work and study commitments heavily shape workers’ and students’ flexibility in arranging their travel time and out-of-home time budget, leading to more stable daily activity-travel patterns than non-workers.