Sr3GeMgN4: new quaternary nitride containing Mg

A new Mg-containing quaternary nitride, Sr₃GeMgN₄, was obtained as single crystals from constituent elements in molten Na. It crystallizes in space group Pnna (No. 52) with a=5.939(1) Å, b=10.320(2) Å, c=9.618(2) Å, and Z=6. It is isostructural with Sr₃Ga₂N₄, both of which contain one-dimensional chains of edge-sharing tetrahedra.     

Semantic interoperability: A central issue for sharing geographic information

Technical interoperability has provided geographic information communities with substantial improvements for constructing GIS capable of very low friction and dynamic data exchanges. These technical advances stand to provide substantial advantages for sharing geographic information, however reaping these advantages in highly heterogeneous operational and organizational environments requires the understanding and resolution of semantic differences. While the OpenGIS consortium has made important progress on technical interoperability, semantic interoperability still remains an unpassed hurdle for efforts to share geographic information across organizational and institutional boundaries at the local, regional, and other levels. Identifying and resolving semantic interoperability issues is especially pertinent for data sharing and considering future developments of standards. This paper presents an overview of semantic interoperability and through case studies shows the breadth and depth of issues and approaches in different countries and at different levels of organizations. These cases illustrate the importance of developing flexible approaches to practical data sharing problems that merge semantical with technical considerations. Based on our examinations of semantic issues and approaches in ongoing research projects, we propose cognitive, computer science, and socio-technical frameworks for examining semantic interoperability.     

Accurate time-dependent analysis of concrete bridges considering concrete creep, concrete shrinkage and cable relaxation

This paper proposes a new relaxation model for steel tendons based on the equivalent creep coefficient to enable the accurate estimation of losses of cable forces. The equivalent creep coefficient works not only in the case of intrinsic relaxation but also under various boundary conditions. Based on the proposed relaxation model, an accurate finite element analysis of the time-dependent behavior of concrete bridges considering concrete creep, concrete shrinkage and cable relaxation is devised based on the time integration method. Concrete members are modeled by beam elements while tendons are modeled by truss elements with nodes connected to the beam axis by perpendicular rigid arms. Then the individual and combined effects of concrete creep, concrete shrinkage and cable relaxation on the long-term performance of concrete structures are investigated. It is found that the proposed relaxation model and time integration method can provide a reliable method for time-dependent analysis. The numerical results obtained indicate that the interactions among these factors should be considered carefully in analyzing the long-term performance of concrete bridges.     

Solid-wall U-values: heat flux measurements compared with standard assumptions

The assumed U-values of solid walls represent a significant source of uncertainty when estimating the energy performance of dwellings. The typical U-value for UK solid walls used for stock-level energy demand estimates and energy certification is 2.1?Wm^?2?K^?1. A re-analysis (based on 40 brick solid walls and 18 stone walls) using a lumped thermal mass and inverse parameter estimation technique gives a mean value of 1.3?±?0.4?Wm^?2?K^?1 for both solid wall types. Among the many implications for policy, this suggests that standard UK solid-wall U-values may be inappropriate for energy certification or for evaluating the investment economics of solid-wall insulation. For stock-level energy modelling, changing the assumed U-value for solid walls reduces the estimated mean annual space heating demand by 16%, and causes a proportion of the stock to change Energy Performance Certification (EPC) band. The analysis shows that the diversity of energy use in domestic buildings may be as much influenced by heterogeneity in the physical characteristics of individual building components as it is by variation in occupant behaviour. Policy assessment and guidance material needs to acknowledge and account for this variation in physical building characteristics through regular grounding in empirical field data.     

Experimental study of pollutant accumulation on an urban road surface

An understanding of pollutant characteristics on impervious surfaces is essential to estimate pollutant washoff characteristics and to design methods to minimise the impacts of pollutants on the environment. This paper presents data on surface pollutant characteristics on an urban road surface in Melbourne, Australia, from samples collected over a 36 day period. The data indicate that buildup over the dry days occurs relatively quickly after a rain event, but slows down after several days as redistribution occurs. The surface pollutant also becomes finer over the dry days as it is disintegrated. The washoff of surface pollutant is dependent on the rainfall and runoff characteristics, but the results here show that common storms only remove a small proportion of the total surface pollutant load. The data also show that street sweeping may have an adverse impact on pollutant washoff because the street sweeper releases the finer material but only removes some of them, making the fine sediment available for washoff by the next storm. The data also show that most of the nutrients are attached to the finer sediments, and to effectively reduce nutrient loads in particulates, treatment facilities must be able to remove the finer particles (down to 50 μm for TP and down to 10 μm for TN), and not just the total sediment or suspended solid load.