Tunneling a crosstown highway: a natural experiment testing the longitudinal effect on physical activity and active transport

Background In the city of Maastricht in the Netherlands, a highway crossing several deprived neighborhoods was tunneled in 2016. The vacant space on top of this tunnel was redesigned and prioritized for pedestrians and cyclists. The aim of this study was to evaluate the effect of this major infrastructural change, named the Green Carpet, on total and transport-based physical activity (PA) levels. Methods Participants (≥18 years) were part of one of three area-based exposure groups. The maximal exposure group lived in neighborhoods directly bordering the Green Carpet. The minimal exposure group consisted of individuals living at the other side of the city, and the no exposure group consisted of individuals living in a nearby city. Actual use of the new infrastructure was incorporated as a second measure of exposure. Data were collected before and 3-15 months after the opening of the Green Carpet. Device-based measurements were conducted to obtain PA levels and collect location data. Changes in PA over time and intervention effects were determined using linear mixed models. Results PA levels in the Green Carpet area increased for the maximal and minimal exposure groups, but did not lead to an increase in total or transport-based PA. For the no exposure group, transport-based MVPA decreased and transport-based SB increased. The significant interaction (time x exposure) for transport-based SB, indicated differences in trends between the no exposure and maximal exposure group (B=-3.59, 95% CI - 7.15; -0.02) and minimal exposure group (B= -4.02, 95% CI -7.85, -0.19). Trends in the results based on analyses focusing on actual use and non-use of the new infrastructure were similar to those of the area-based analyses. Conclusions Results suggest that the Green Carpet led to more PA in this specific area, but did not increase the total volume of PA. The area-based differences might reflect the differences between users and non-users, but we should be careful when interpreting these results, due to possible interference of selective mobility bias. This paper reflects that the relationship between infrastructure and PA is not unambiguous. Trial registration This research was retrospectively registered at the Netherlands Trial Register (NL8108).

USE OF THE SIMPLIFIED PN EQUATIONS AND TRANSPORT CORRECTIONS IN THE WIMS/PANTHER EMBEDDED SUPERCELL METHOD

The WIMS/PANTHER Embedded Supercell Method (ESM) provides a significant improvement in prediction accuracy in radial power distributions for pressurised water reactors compared to the standard “two-step” approach, without the need for a significant increase in computational resource.A companion paper presents validation of the ESM as previously presented, using PANTHER pin-by-pin diffusion to correct interface errors arising from the standard two-step approach. However, in principle any reference method can be used to solve the embedded supercells and correct the basic solution – this is a significant advantage of the ESM.A paper presented at PHYSOR 2016 demonstrated that use of diffusion theory introduces significant error relative to transport theory only in the high energy range, due to the discontinuous fission source when modelling the interface between two types of pincell.This paper investigates further improvement of the PANTHER solution through use of simplified PN in the fast energy groups. This solution method can be implemented without the need for any significant change to the calculation route and further improves agreement with a transport reference for a small computational cost.The remaining error in the solution is examined by derivation of an effective diffusion coefficient from a heterogeneous transport reference. This suggests a simple characterisation of the discrepancy, which can be easily corrected.Results are presented in comparison to WIMS for supercells and the KAIST benchmark. For the KAIST small core benchmark assembly power errors relative to a WIMS fine group transport reference are shown to be less than 0.5 %. Results are also presented in comparison to Monte Carlo for the Watts Bar benchmark.

Application of Hybrid Subgroup Decomposition Method to Gas Cooled Thermal Reactor Problem

In this paper, a newly developed hybrid subgroup decomposition method is tested in a 1D problem characteristic of gas cooled thermal reactors (GCR). The new method couples an efficient coarse-group eigenvalue calculation with a set of fine-group transport source iterations to unfold the fine-group flux. It is shown that the new method reproduces the fine-group transport solution by iteratively solving the coarse-group quasi transport equation. The numerical results demonstrate that the new method applied to 1D GCR problem is capable of achieving high accuracy while gaining computational efficiency up to 5 times compared to direct fine-group transport calculations.