Chalk River Laboratories

About: Chalk River Laboratories is a based out in . It is known for research contribution in the topics: Neutron diffraction & Neutron scattering. The organization has 2297 authors who have published 2700 publications receiving 73287 citations.

Streamflow generation in a headwater basin on the precambrian shield

Abstract: Current conceptual runoff models hypothesize that stormflow generation on the Canadian Shield is a combination of subsurface stormflow and saturation overland flow. This concept was tested during spring runoff in a small (3.3 ha) headwater basin using: (1) isotopic and chemical hydrograph separation and (2) field mapping and direct tracing of saturated areas. Isotopic and chemical hydrograph separation indicated three runoff components: (1) pre-melt subsurface flow; (2) subsurface flow of new (event) water; and (3) direct precipitation on to saturated areas (DPS). During early thaw-freeze cycles, their relative contributions to total flow remained constant (65 per cent, 30 per cent, and 5 per cent respectively). It is hypothesized that lateral flow along the bedrock/mineral soil interface, possibly through macropores, supplied large volumes of subsurface flow (of both old and new water) rapidly to the stream channel. Much higher contributions of DPS were observed during an intensive rain-on-snow event (15 per cent of total flow). Mapping and direct tracing of saturated areas using lithium bromide, suggested that saturated area size was positively correlated to stream discharge but its response lagged behind that of discharge. These observations suggest that the runoff mechanisms, and hence the sources of stream flow, will vary depending on storm characteristics.

Improving microstructure and ductility in the Mg–Zn alloy system by combinational Ce–Ca microalloying

Abstract: A strategy is proposed to enhance the microstructure and mechanical properties of Mg–Zn alloys by combining microalloying additions of the rare earth element Ce and the non-rare earth element Ca. The double additions of Ce–Ca are found to significantly increase tensile elongation compared to binary Mg–Zn, or single additions of either Ce or Ca. Microstructure analysis reveals that the Ce–Ca additions increase ductility by modifying texture and refining grain size. Texture modification is attributed to solute effects from the microalloying elements, particularly Ca, while grain refinement is additionally influenced by a fine dispersion of Mg6Ca2Zn3 precipitates that form during rolling and pin grain boundaries. The microalloying element additions also lead to large secondary phase particles in the alloys, which can limit ductility enhancement by promoting early fracture. By scaling Zn content in the Mg–Zn–Ce–Ca alloys, the Mg6Ca2Zn3 phase fraction and Zn solute content can be controlled for optimum ductility or strengthening potential.