A coupled discrete element model for the simulation of soil and water flow through an orifice

Soil erosion around defective underground pipes can cause ground collapses and sinkholes in urban areas. Most of these soil erosion events are caused by fluidization of the surrounding soil with subsequent washing into defective sewer pipes. In this study, this soil erosion process is simplified as the gradual washout of sand particles mixed with water through an orifice. The discrete element method is used to simulate the large deformation behavior of the sand particles, and the Darcy fluid model is coupled with this approach to simulate fluid flow through porous sand media. A coupled 3D discrete element model is developed and implemented based on this scheme. To simulate previous experiments using this coupled model considering the current computing capacity, we incorporated a ‘supply layer’ to study the continuous erosion process. The coupled model can predict the erosion flow rates of sand and water and the shape of erosion void. Thus, the model can be used as an effective and efficient tool to investigate the soil erosion process around defective pipes. Copyright © 2017 John Wiley & Sons, Ltd.     

Neptune: A marine micropaleontology database

Marine micropaleontology must in the future provide more precise chronologic and paleoenvironmental information, which in turn must be based on better, more consistent taxonomic and distributional data. Better tools for synthesis and standardization of this data are needed, as the ever expanding published literature is rapidly becoming unmanageable by purely manual compilation methods. The micropaleontology group at the ETH has developed a large relational database of marine microfossil data to partially meet this need. It currently contains biogeographic data on the distribution in Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) holes of nearly 8,000 species of Cenozoic planktonic foraminifera, radiolaria, diatoms and calcareous nannofossils. The database also includes full stratigraphic occurrence (range chart) data for these fossil groups from more than 100 selected Neogene holes. A particular feature of the database is that all sample information and species names in the original reports are linked to newly created, updatable, comprehensive age models and synonymy lists which reflect modern chronology and taxonomic usage. Searches of the database automatically make use of this information in producing reports. Species ' occurrences, including first and last occurrence information, can be further analyzed using external spreadsheet and statistics packages; plotted by mapping programs; or displayed by a new program which creates composite age-range charts.     

Eccentric geomagnetic dipole drift

A recalculation of the rate of westward drift of the eccentric geomagnetic dipole since 1900 has confirmed its correlation with irregularities in the excess length-of-day (LOD) as originally reported by Vestine. The major changes in the LOD curve since 1900 are shown to be well correlated with the westward drift rate from a number of magnetic models covering the interval. A new Magsat model of secular variation for 1980.0 shows no increase in the drift rate which dropped by a factor of three in the interval 1965–1970.     

A Framework and Software Tool to Support Collaborative Landscape Analysis: Fitting Square Pegs into Square Holes

For landscape models to be applied successfully in management situations, models must address appropriate questions, include relevant processes and interactions, be perceived as credible and involve people affected by decisions. We propose a framework for collaborative model building that can address these issues, and has its roots in adaptive management, computer‐supported collaborative work and landscape ecology. Models built through this framework integrate a variety of information sources, address relevant questions, and are customized for the particular landscape and policy environment under study. Participants are involved in the process from the start, and because their input is incorporated, they feel ownership of the resulting models, increasing the chance of model acceptance and application. There are two requirements for success: a tool that supports rapid model prototyping and modification, that makes a clear link between a conceptual and implemented model, and that has the ability to implement a wide range of model types; and a core team with skills in communication, research and analysis, and knowledge of ecology and forestry in addition to modelling. SELES (Spatially Explicit Landscape Event Simulator) is a tool for building and running models of landscape dynamics. It combines discrete event simulation with a spatial database and a relatively simple modelling language to allow rapid development of landscape simulations, and provides a high‐level means of specifying complex model behaviours ranging from management actions to natural disturbance and succession. We have applied our framework in several forest modelling projects in British Columbia, Canada. We have found that this framework increases the interest by local experts and decision‐makers to participate actively in the model building process. The workshop process and resulting models have efficiently provided insight into the dynamics of large landscapes over long time frames. The use of SELES has facilitated this process by providing a flexible, transparent environment in which models can be rapidly implemented and refined. As a result, model findings may be more readily incorporated into decision‐support systems designed to assist resource managers in making informed decisions.     

The frequency response of the horizontal magnetic field for a conductive channel

Summary. Babour & Mosnier's results showing no frequency dependence between the anomalous horizontal magnetic field above a conductor and the difference between the horizontal magnetic fields above and below the conductor over a wide range of frequencies led them to conclude that this effect is due to current channelling. A two-dimensional numerical model of a conductive channel, with a uniform horizontal source field, shows the same effect over a wide range of frequencies. Thus local induction can show the same effect.