Thorium-234 derived information on particle residence times and sediment deposition in shallow waters of the south-western Baltic Sea

Activities of the naturally occurring, short-lived and highly particle-reactive radionuclide tracer ²³⁴Th in the dissolved and particulate phase were measured at three shallow-water stations (maximum water depths: 15.6, 22.7 and 30.1 m) in Mecklenburg Bay (south-western Baltic Sea) to constrain the time scales of the dynamics and the depositional fate of particulate matter. Activities of particle-associated (> 0.4 μm) and total (particulate + dissolved) ²³⁴Th were in the range of 0.08–0.11 dpm L^− 1 and 0.11–0.20 dpm L^− 1, respectively. The activity ratio of total ²³⁴Th and its long-lived and conservative parent nuclide ²³⁸U was well below unity (range: 0.09–0.19) indicating substantial radioactive disequilibria throughout the water column, very dynamic trace-metal scavenging and particle export from the water column at all three stations. For the discussion the ²³⁴Th data of this study were combined with previously published water-column ²³⁴Th and particulate-matter data from Mecklenburg Bay (Kersten et al., 1998. Applied Geochemistry 13, 339–347). The resulting average vertical distribution of total ²³⁴Th/²³⁸U disequilibria was used to estimate the depositional ²³⁴Th flux to the sediment. There was a virtually constant net downward flux of ²³⁴Th of about 28 dpm m^− 2 d^− 1 leaving each water layer of one meter thickness. Thorium-234-derived net residence times of particulate material regarding settling from a given layer in the water column were typically on the order of days, but with maximum values of up to a couple of weeks. Based on an average ratio of particulate matter (PM) to particle-associated ²³⁴Th a net flux of about 145 mg PM m^− 2 d^− 1 was estimated to leave each water layer of one meter thickness. The estimated cumulative water-column-derived particulate-matter fluxes at the seafloor are higher by a factor of about 2 than previously published sediment-derived estimates for Mecklenburg Bay. This suggests that about half of the settling particulate material is exported from the study area and/or subject to processes such as mechanical breakdown, remineralisation and dissolution. Lateral particulate-matter redistribution and particle breakdown in the water column (as opposed to the sediment) seem to be favoured by (repeated) particle resuspension from and resettling to the seafloor before ultimate sedimentary burial. The importance of net lateral redistribution of particulate material seems to increase towards the seafloor and be particularly high within the bottommost few meters of the water column.     

New appraisal values of travel time saving and reliability in Great Britain

Transportation - This paper provides an overview of the study ‘Provision of market research for value of time savings and reliability’ undertaken by the Arup/ITS Leeds/Accent consortium...     

Cost damping and functional form in transport models

Transport models allowing for cost damping are characterised by marginally decreasing cost sensitivities in demand. As a result, cost damping is a model extension of the simple linear-in-cost model requiring an appropriate non-linear link function between utility and cost. The link function may take different forms and be represented as a non-linear-in-parameter form such as the well-known Box–Cox function. However, it could also be specified as non-linear-in-cost but linear-in-parameter forms, which are easier to estimate and improve model fit without increasing the number of parameters. The specific contributions of the paper are as follows. Firstly, we discuss the phenomenon of cost damping in details and specifically why it occurs. Secondly, we provide a test of damping and an easy assessment of the (linear) damping rate for any variable by estimating two auxiliary linear models. This turns out to be an important guidance as the damping rate largely dictates which link functions are appropriate for the data. Thirdly, inspired by the Box–Cox function, we propose alternative linear-in-parameter link functions, some of which are based on interpolation of approximate Box–Cox end points, and others which are inspired by Taylor Expansions. The different functions are tested in simulation experiments and subsequently in a large-scale demand model based on more than 22,000 revealed preference observations. It is concluded that the use of properly specified linear-in-parameter functions gives good data fit and sometimes even outperforms the Box–Cox functions without increasing the number of parameters.     

Tunnel Waterproofing with Membranes Waterproofing at Senoko Cabele Tunnel in comparison with International Standards

Waterproofing of tunnels is and has always been a challenge, worldwide: Changing Geology with hardly predictable water inflow, limited space underground and only very little intervention opportunities once the tunnel is completed. This paper elaborates such challenges and focuses on the waterproofing solutions of mined tunnels with membranes. Different standards and approaches for the waterproofing system. In Singapore, a membrane waterproofing system is used for the shafts and adits at Senoko Cable Tunnel. The paper project specific waterproofing challenges and emphasizes on solution for them.     

Cost Scenarios for Coastal Water Pollution in a Small Island Nation: A Case Study from the Cook Islands

This article presents scenarios of watershed pollution costs in Rarotonga, the largest of the Cook Islands in the South Pacific. The valuation method applied here estimates the market costs that would be avoided in the absence of watershed pollution. The study finds gross annual watershed pollution costs in Rarotonga between NZ$3.2 to NZ$17.7, with a best estimate of NZ$7.4, million. The best estimate results in household costs of NZ$2,900 per year and equates to 3.12% of gross domestic product. A wide error margin is placed around these estimates due to uncertain and incomplete datasets, a common situation for small island nations. They are presented as “cost scenarios” rather than definitive results. The article explores the practical, theoretical, and policy issues surrounding the valuation of water resources in the context of small island nations. It is argued that rough estimates of opportunity costs, limited to market goods and services, can supply governments with sufficient information to assess the relative importance of watershed pollution.     

Fatigue Life Prediction of a Railway Bogie under Dynamic Loads through Simulation

For dynamically loaded lightweight structures fatigue strength is an important design criteria. In this paper a new method to predict fatigue lifetime is shown. This is based on the combination of frequency domain and time domain calculations, which allows lifetime prediction with reduced computational effort. The method is implemented to work in a concurrent engineering software environment together with a computer aided design (CAD), a finite-element-method (FEM) and a multibody system (MBS) program. The benefits of the new approach are demonstrated by application to the bogie of a freight locomotive. The dynamic loads acting on the bogie are computed by multibody simulation. The bogie frame is considered as an elastic body of the MBS and the highly nonlinear wheel rail contact is modeled quasi-elastically. For the ride on a straight track the equations of motion can be linearized and the covariance matrix of the loads is calculated. The ride through a ramp is simulated by using the nonlinear differential equations. FEM yields the stresses in the most stressed locations of the bogie depending on the loads calculated by multibody simulation. Based on these stresses the fatigue life prediction is carried out in the MBS post-processing program FATIGUE.