Kinetic theory for strong uniform shear flow of granular media at high density

We discuss the uniform shear flow of a fluidized granular bed composed of monodisperse Hertzian spheres. Considering high densities around the glass transition density of inelastic Hertzian spheres, we report kinetic theory expressions for the Newtonian viscosity as well as the Bagnold coefficient. We discuss the dependence of the transport coefficients on density and coefficient of restitution.Comment: Powders & Grains 201

Estimating flow and transport parameters in the unsaturated zone with pore water stable isotopes

The first author was funded by the DFG Research Group: From Catchments as Organised Systems to Models based on Functional Units (FOR 1598). The second author was funded by the DFG project Coupled soil-plant water dynamics – Environmental drivers and species effects (contract numbers: GE 1090/10-1 and WE 4598/2-1). The isotope data in the precipitation for Roodt were provided by FNR/CORE/SOWAT, project of the Luxembourg Institute of Science and Technology – LIST. Sampling of the isotope profiles was made possible by the support of the CAOS Team and Begona Lorente Sistiaga, Benjamin Gralher, Andre Böker, Marvin Reich and Andrea Popp. Special thanks to Britta Kattenstroth and Jean Francois Iffly for their technical support in the field and Barbara Herbstritt for her support in the laboratory. For Roodt, soil texture and hydraulic parameter information were provided by Conrad Jackisch and Christoph Messer (KIT, Karlsruhe, Germany) and hydraulic conductivity data were provided by Christophe Hissler and Jérôme Juilleret (LIST). Pore water isotope and soil moisture data for Hartheim were provided by Steffen Holzkämper and Paul Königer. Temperature and precipitation data for Hartheim were provided by the Chair of Meteorology and Climatology, University of Freiburg.Peer reviewedPublisher PD

Exploiting Transaction Accumulation and Double Spends for Topology Inference in Bitcoin

Bitcoin relies on a peer-to-peer network for communication between participants. Knowledge of the network topology is of scientific interest but can also facilitate attacks on the users’ anonymity and the system’s availability. We present two approaches for inferring the network topology and evaluate them in simulations and in real-world experiments in the Bitcoin testnet. The first approach exploits the accumulation of multiple transactions before their announcement to other peers. Despite the general feasibility of the approach, simulation and experimental results indicate a low inference quality. The second approach exploits the fact that double spending transactions are dropped by clients. Experimental results show that inferring the neighbors of a specific peer is possible with a precision of 71 % and a recall of 87 % at low cost

Spatial Interpolation of Air Quality Data with Multidimensional Gaussian Processes

The central question of this paper is whether interpolation techniques applied to a distributed sensor network can indeed provide more information than using the constant background of an urban reference station to measure air pollution. We compare different interpolation techniques based on temporal-spatial machine learning in terms of their applicability for correctly predicting personal exposure. Using a dataset of stationary low-cost sensors, we estimate exposure on a route through the city and compare it to mobile measurements. The results show that while different machine learning-based interpolation methods yield quite different results, validation of machine learning-based approaches is still challenging

High-Temperature Thermal Storage System for Solar Tower Power Plants with Open-Volumetric Air Receiver Simulation and Energy Balancing of a Discretized Model

This paper describes the modeling of a high-temperature storage system for an existing solar tower power plant with open volumetric receiver technology, which uses air as heat transfer medium (HTF). The storage system model has been developed in the simulation environment Matlab/Simulink®. The storage type under investigation is a packed bed thermal energy storage system which has the characteristics of a regenerator. Thermal energy can be stored and discharged as required via the HTF air. The air mass flow distribution is controlled by valves, and the mass flow by two blowers. The thermal storage operation strategy has a direct and significant impact on the energetic and economic efficiency of the solar tower power plants

High-Temperature Thermal Storage System for Solar Tower Power Plants with Open-Volumetric Air Receiver Simulation and Energy Balancing of a Discretized Model

This paper describes the modeling of a high-temperature storage system for an existing solar tower power plant with open volumetric receiver technology, which uses air as heat transfer medium (HTF). The storage system model has been developed in the simulation environment Matlab/Simulink®. The storage type under investigation is a packed bed thermal energy storage system which has the characteristics of a regenerator. Thermal energy can be stored and discharged as required via the HTF air. The air mass flow distribution is controlled by valves, and the mass flow by two blowers. The thermal storage operation strategy has a direct and significant impact on the energetic and economic efficiency of the solar tower power plants

The reproduction of educational inequalities - do parenting and child behavioural problems matter?

The strong link between parental socioeconomic status (SES) and children’s success in school is well established. However, mechanisms that underpin this association remain a major issue in current research on social inequality. Using data from the Families in Germany Study and structural equation modelling, this study demonstrates that parenting styles and child behavioural problems explain, in part, the association between parental SES and child school grades for mathematics and German between the ages of 9 and 10. We found that parents with a low SES are more likely to be inconsistent in their parenting and to use psychological control with their children more often, these two factors being linked to child behavioural problems. Adverse parenting and behavioural problems are, in turn, associated with low school grades. Our findings also show that behavioural problems in children are associated with lower school grades independent of parenting style. These findings suggest that parenting styles and child behavioural problems and their interplay may be potential pathways that underpin the influence of parental SES on children’s school achievement