517 research outputs found
Observations on metallurgical bonding between plasma sprayed tungsten and hot tungsten substrates
Metallurgical bonding between plasma sprayed tungsten & hot tungsten substrates - interface & recrystallizatio
An Investigation of the Loss of Planet-Forming Potential in Intermediate Sized Young Embedded Star Clusters
A large fraction of stars forming in our galaxy are born within clusters
embedded in giant molecular clouds. In these environments, the background UV
radiation fields impinging upon circumstellar disks can often dominate over the
radiation fields produced by each disk's central star. As a result, this
background radiation can drive the evaporation of circumstellar disks and lead
to the loss of planet forming potential within a cluster. This paper presents a
detailed analysis of this process for clusters whose stellar membership falls
within the range . For these intermediate-sized clusters,
the background UV field is often dominated by the most massive stellar member.
Due to the steep slope of the initial mass function, the amount of background
UV light that bathes clusters of similar size displays significant variance. As
a result, we perform a statistical analysis of this problem by calculating
distributions of FUV flux values impinging upon star/disk systems for several
cluster scenarios. We find that in the absence of dust attenuation, giant
planet formation would likely be inhibited in approximately half of systems
forming within intermediate-sized clusters regardless of stellar membership. In
contrast, the presence of dust can significantly lower this value, with the
effect considerably more pronounced in more populated clusters.Comment: Accepted for publication in PAS
Processing and mechanical properties of magnesium-lithium composites containing steel fibers
Deformation-processed metal-metal composites (DMMC) of Mg-Li alloys containing steel reinforcing fibers were prepared by infiltrating a preform of steel wool with the molten matrix. The Li content was varied to control the crystal structure of the matrix; Mg-4 wt pct Li is hexagonal close packed (hcp), while Mg-12 wt pct Li is body-centered cubic (bcc). The low carbon steel used as the reinforcing fiber is essentially bcc. The hcp/bcc and bcc/bcc composites were subsequently deformed by rolling and by extrusion/swaging and mechanically tested to relate the tensile strength of the composites to true deformation strain. The hcp/bcc composites had limited formability at temperatures up to 400 °C, while the bcc/bcc composites had excellent formability during sheet rolling at room temperature but limited formability during swaging at room temperature. The tensile strengths of the hcp/bcc composite rod and the bcc/bcc composite sheet and rod increased moderately with deformation, though less than predicted from rule-of-mixtures (ROM) calculations. This article presents the experimental data for these DMMC materials and comments on the possible effect of texture development in the matrix and fiber phases on the deformation characteristics of the composite material
Terrorism and Anti-Terrorism Legislation in Canada
The events of September 11, 2001 drastically altered the political climate in North America. The atmosphere of fear, mainly instilled by the hegemonic influence of American mass media outlets and government, allowed the Canadian government to take advantage of citizen unease and pass controversial legislation, such as the Anti-Terrorism Act (2001) and the Combating Terrorism Act (2013). This critical analysis attempts to divulge into the root meaning of “terror†in order to unpack the motivations of terrorism, and understand how it really operates. Particular attention is placed on the role of the media and the Canadian and American governments in instilling a psychological phenomenon of terror into society. This article seeks to answer whether terrorism poses any real threat to North Americans, and whether the legislation passed by the Canadian government stands up to the Charter of Rights and Freedoms and democracy itself
Laying the Groundwork for a Community Risk Assessment of the Ring of Fire and Related Infrastructure
Tree Island Response to Fire and Flooding in the Short-Hydroperiod Marl Prairie Grasslands of the Florida Everglades
Within the marl prairie grasslands of the Florida Everglades, USA, the combined effects of fire and flooding usually lead to very significant changes in tree island structure and composition. Depending on fire severity and post-fire hydroperiod, these effects vary spatially and temporally throughout the landscape, creating a patchy post-fire mosaic of tree islands with different successional states. Through the use of the Normalized Difference Vegetation Index (NDVI) and three predictor variables (marsh water table elevation at the time of fire, post-fire hydroperiod, and tree island size), along with logistic regression analysis, we examined the probability of tree island burning and recovering following the Mustang Corner Fire (May to June 2008) in Everglades National Park. Our data show that hydrologic conditions during and after fire, which are under varying degrees of management control, can lead to tree island contraction or loss. More specifically, the elevation of the marsh water table at the time of the fire appears to be the most important parameter determining the severity of fire in marl prairie tree islands. Furthermore, in the post-fire recovery phase, both tree island size and hydroperiod during the first year after the fire played important roles in determining the probability of tree island recovery, contraction, or loss
High strength-high conductivity Cu--Fe composites produced by powder compaction/mechanical reduction
A particulate mixture of Cu and Fe is compacted and mechanically reduced to form an in-situ Cu-Fe composite having high strength and high conductivity. Compaction and mechanical reduction of the particulate mixture are carried out at a temperature and time at temperature selected to avoid dissolution of Fe into the Cu matrix particulates to a harmful extent that substantially degrades the conductivity of the Cu-Fe composite
Recommended from our members
Hall effect and transmission electron microscopy of epitaxial MnSi thin films
We present Hall effect measurements on MnSi/Si(111) epilayers and find an anomalous Hall contribution that is significantly smaller than in bulk crystals, which enables the observation of an additional contribution to the anomalous signal previously overlooked in MnSi. Our measurements indicate the signal is not due to skyrmions in MnSi thin films, which are absent in out-of-plane fields, but rather are the result of scattering from the cone phase. The absence of magnetic contrast in the transmission electron microscopy (TEM) measurements are consistent with this interpretation. We provide a method to model TEM images of skyrmions lattices to determine the conditions necessary for their observation in other B20 epilayers with an anisotropy that is favourable to their formation.T.L.M. and M.N.W. acknowledge support from NSERC and the support of the Canada Foundation for Innovation, the Atlantic Innovation Fund, and other partners which fund the Facilities for Materials Characterization, managed by the Institute for Research in Materials. Work done by J.C.L. was funded by the Royal Society. The work of F.N.R. was supported by RFBR, research project No. 14-02-31012.This is the accepted manuscript of a paper published in Physical Review B (SA Meynell, MN Wilson, JC Loudon, A Spitzig, FN Rybakov, MB Johnson, TL Monchesky, Physical Review B 2014 90, 224419)
Everglades Ridge, Slough, and Tree Island Mosaics: Year 2 Annual Report
Status and history of the Ridge-Slough Mosaic The Florida Everglades is a large subtropical wetland with diverse hydrologic, edaphic, and vegetative characteristics. Historically, a significant portion of this system was a slow moving river originating from the Kissimmee River floodplain, flowing into the vast but shallow Lake Okeechobee, and draining south-southwest over extensive peatlands into Florida Bay (McVoy 2011). Human-induced alterations to the hydrologic regime, including reduction, stabilization, and impoundment of water flow through diversion and compartmentalization of water via canals and levees have degraded pre-drainage vegetation patterns and microtopographic structure (Davis and Ogden 1994, Ogden 2005, McVoy 2011). The Everglades peatland emerged 5,000 years ago with the stabilization of sea level at approximately current elevations (Loveless 1959, Gleason and Stone 1994). This, combined with subtropical rainfalls, allowed a vast mass of water to slowly flow over a limestone bedrock platform 160 km long and 50 km wide at a near uniform descent totaling about 6 m, ultimately reaching Florida Bay (Stephens 1956, Gleason and Stone 1994, McVoy 2011). Vegetation quickly colonized the area, and peat, in the absence of adequate respiration, accumulated on the limestone bedrock to a depth of 3-3.7 m (Gleason and Stone 1994, McVoy et al. 2011). The “River of Grass” referenced by Douglas (1947) alludes to the dually intertwined processes of the historic riverine nature of the Everglades and the vast sawgrass (Cladium jamaicense) communities that have dominated the landscape for about the last 1,000 years (Bernhardt and Willard 2009)
- …