Impacts of combining partial and general equilibrium modelling in freight transport analyses – a forest sector case study from Norway

Abstract

The forest sector in Norway is very transport intensive, accounting for approximately 14% of total domestic freight transport traffic on Norwegian roads. This paper presents an analysis linking a general equilibrium freight transport modelling tool with a partial equilibrium model of the forest sector. The freight transport model predicts transport costs, modal split and transport patterns, and the results are treated as inputs to the forest sector model. The objective of the paper is to analyse the modelling effect of taking forest sector model effects back into the freight transport model and treated as new demand. Compared to a base scenario for the year 2020, we compare analyses with and without this new demand from the forest sector model back into the freight transport modelling tool.     

Numerical simulation of flow around a smooth circular cylinder at very high Reynolds numbers

High Reynolds number flows (Re = 1 × 10⁶, 2 × 10⁶ and 3.6 × 10⁶, based on the free stream velocity and cylinder diameter) covering the supercritical to upper-transition flow regimes around a two-dimensional (2D) smooth circular cylinder, have been investigated numerically using 2D Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations with a standard high Reynolds number k ? ? turbulence model. The objective of the present study is to evaluate whether the model is applicable for engineering design within these flow regimes. The results are compared with published experimental data and numerical results. Although the k ? ? model is known to yield less accurate predictions of flows with strong anisotropic turbulence, satisfactory results for engineering design purposes are obtained for high Reynolds number flows around a smooth circular cylinder in the supercritical and upper-transition flow regimes, i.e. Re > 10⁶. This is based on the comparison with published experimental data and numerical results.     

Large eddy simulations for quasi-2D turbulence in shallow flows: A comparison between different subgrid scale models

In this study, the performance of the horizontal large eddy simulation module, developed at the University of Leuven (HLES-KULeuven module) is assessed. A comparison between different subgrid scale models has been carried out. The study is concerned with the non-rotating and unstratified flows. The results of the simulation for an oscillatory backward facing (BFS) flow are presented in case of an expanding flume based on a one-length scale approach and a two-length scale approach. Three subgrid scale (SGS) models have been tested: Smagorinsky SGS model (Smagorinsky, J., (1963). General circulation experiments with the primitive equations, I. the basic experiments. Monthly Weather Review, 91(3), 99–164), Uittenbogaard SGS model (Uittenbogaard, R.E., and van Vossen, B., (2004). Subgrid-scale model for quasi-2D turbulence in shallow water. Shallow Flows. Jirka and Uijttewaal (Eds.), Taylor & Francis Group, London, ISBN 90 5809 700 5) and a proposed two-length scale approach. The first two models are considered to be a one-length scale models. A simulation without a subgrid scale model for the horizontal mixing has also been conducted. In all simulations, a quadratic friction model parameterizes the dissipation produced by the 3D-subdepth scale turbulence. The two-length scale concept uses a newly mixing length formulation for the quasi-2D turbulence and doesn't depend on the filter width in contrast to the one-length scale approach, in which the mixing length is function of the filter width. The outputs of the HLES-KULeuven module have been compared with the experimental data taken from Stelling, G.S., and Wang, L.X., (1984). Experiments and computations on separating flow in an expanding flume. Dept. Civil Engineering, Delft University of Technology, Report 2–84.). The two-length scale approach has been validated with experimental data from SERC Flood Channel Facility at HR Wallingford. In general, there is a qualitative agreement with the experimental data. It has also been found that the two-length scale approach produces more elongated and less isotropic vortex than the one-length scale models.     

Measurements of Emissions to Air from a Marine Engine Fueled by Methanol

Emissions of exhaust gases and particulate matter from a dual fuel marine engine using methanol as fuel with marine gasoil as pilot fuel have been examined for ...     

Traveler delay costs and value of time with trip chains, flexible activity scheduling and information

The delay costs of traffic disruptions and congestion and the value of travel time reliability are typically evaluated using single trip scheduling models, which treat the trip in isolation of previous and subsequent trips and activities. In practice, however, when activity scheduling to some extent is flexible, the impact of delay on one trip will depend on the actual and predicted travel time on itself as well as other trips, which is important to consider for long-lasting disturbances and when assessing the value of travel information. In this paper we extend the single trip approach into a two trips chain and activity scheduling model. Preferences are represented as marginal activity utility functions that take scheduling flexibility into account. We analytically derive trip timing optimality conditions, the value of travel time and schedule adjustments in response to travel time increases. We show how the single trip models are special cases of the present model and can be generalized to a setting with trip chains and flexible scheduling. We investigate numerically how the delay cost depends on the delay duration and its distribution on different trips during the day, the accuracy of delay prediction and travel information, and the scheduling flexibility of work hours. The extension of the model framework to more complex schedules is discussed.     

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.     

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.     

From Titanic to Costa Concordia—a century of lessons not learned

The recent foundering of the Costa Concordia in January 2012 demonstrated that accidents can occur even with ships that are considered masterpieces of modern technology and despite more than 100?years of regulatory and technological progress in maritime safety. The purpose of this paper is, however, not to speculate about the concrete causes of the Costa Concordia accident, but rather to consider some human and organizational factors that were present in the Costa Concordia accident as well as in the foundering of the Titanic a century ago, and which can be found in many other maritime accidents over the years. The paper argues that these factors do not work in isolation but in combination and often together with other underlying factors. The paper critically reviews the focus of maritime accident investigations and points out that these factors do not receive sufficient attention. It is argued that the widespread confidence in the efficacy of new or improved technical regulations, that characterizes the recommendations from most maritime accident investigations, has led to a lack of awareness of complex interactions of factors and components in socio-technical systems. If maritime safety is to be sustainably improved, a systemic focus must be adopted in future accident investigations.     

Psychological benefits from vanpooling and group composition

Prospective carpool satisfaction varies with respect to carpool size, acquaintanceship and gender composition, at least for carpool arrangements of 2–4 members. It is not known whether such variations apply in the same kind or to the same degree for vanpools of 9–15 members. A study of 15 vanpool programs in Southern California operating over 700 vanpools with more than 8,000 members was used to test for such effects. Five measures of retrospective vanpool satisfaction were derived from 40 vanpool benefit items using factor analysis in LISREL. The five perceived vanpool satisfaction factors included reliability, social, relaxation, economic and environmental benefits. Variations in these five benefit factors were analyzed with respect to vanpool group composition using difference of means tests and correlation analysis. Perceived vanpool reliability showed the largest statistical association with most of the group composition variables studied, perhaps because it was better identified in the analysis in terms of the total number of individual items loading on it. Gender had the largest statistical association with most of the vanpool benefit factors, perhaps because it was most clearly identified with individual vanpool members in the data. Based on this analysis, it appears that perceived vanpool benefits are qualitatively as well as quantitatively different than perceived carpool benefits. Vanpool program marketing strategies may need to be rethought and recast based on these research findings.     

Network design for line-based autonomous bus services

Transportation - The maturing of autonomous driving technology in recent years has led to several pilot projects and the initial integration of autonomous pods and buses into the public transport...