336 research outputs found
Ab-initio elastic tensor of cubic TiAlN alloy: the dependence of the elastic constants on the size and shape of the supercell model
In this study we discuss the performance of approximate SQS supercell models
in describing the cubic elastic properties of B1 (rocksalt)
TiAlN alloy by using a symmetry based projection technique. We
show on the example of TiAlN alloy, that this projection
technique can be used to align the differently shaped and sized SQS structures
for a comparison in modeling elasticity. Moreover, we focus to accurately
determine the cubic elastic constants and Zener's type elastic anisotropy of
TiAlN. Our best supercell model, that captures accurately both
the randomness and cubic elastic symmetry, results in GPa,
GPa and GPa with 3% of error and for Zener's
elastic anisotropy with 6% of error. In addition, we establish the general
importance of selecting proper approximate SQS supercells with symmetry
arguments to reliably model elasticity of alloys. In general, we suggest the
calculation of nine elastic tensor elements - , , ,
, , , , and , to evaluate and
analyze the performance of SQS supercells in predicting elasticity of cubic
alloys via projecting out the closest cubic approximate of the elastic tensor.
The here described methodology is general enough to be applied in discussing
elasticity of substitutional alloys with any symmetry and at arbitrary
composition.Comment: Submitted to Physical Review
Community mapping by non-literate citizen scientists in the rainforest
Supporting local communities to share their environmental knowledge by utilizing scientifically accepted tools and methodologies can lead to improvement in environmental governance, environmental justice and management practices. Mbendjele hunter-gatherers in the rainforests of Congo are collaborating with the ExCiteS Research Group at University College London to record their local knowledge about illegal poaching activities, which will improve the control of commercial hunters and diminish the harassment they often experience at the hands of 'eco-guards' who enforce hunting regulations. Developing and deploying a system for non-literate users introduces a range of challenges that we have tried to tackle with our Anti-Poaching data collection platform
Making local knowledge matter: Supporting non-literate people to monitor poaching in Congo
This paper describes a project initiated by non-literate indigenous people to equip their own “citizen scientists” with rugged smartphones running adapted software that enable them to share some of their detailed environmental knowledge in ways that improve the sustainable management of their forest. Supporting local people to share their environmental knowledge in scientifically valid and strategically targeted ways can lead to improvement in environmental governance, environmental justice and management practices. Mbendjele hunter-gatherers in the rainforests of Congo are working together with the ExCiteS Research Group at University College London to make their local knowledge about commercial hunters’ activities improve the control of commercial hunters and diminish the harassment they often experience at the hands of “eco-guards” who enforce hunting regulations. Developing and deploying a system for non-literate users introduces a range of challenges that we have tried to solve. Our Anti-Poaching data collection platform, running on Android smartphones, is based on a decision tree of pictorial icons and employs various smartphone sensors to augment observations. We describe its development here
Supporting collaboration with non-literate forest communities in the congo-basin
Providing indigenous communities with ICT tools and methods
for collecting and sharing their Traditional Ecological
Knowledge is increasingly recognised as an avenue
for improvements in environmental governance and socialenvironmental
justice. In this paper we show how we carried
out a usability engineering effort in the “wild” context
of the Congolese rainforest – designing, evaluating and iteratively
improving novel collaborative data collection interfaces
for non-literate forest communities that can subsequently
be used to facilitate communication and information
sharing with logging companies. Working in this context
necessitates adopting a thoroughly flexible approach to the
design, development, introduction and evaluation of technology
and the modes of interaction it offers. We show that we
have improved participant accuracy from about 75% towards
95% and provide a set of guidelines for designing and evaluating
ICT solutions in “extreme circumstances” – which hold
lessons for CSCW, HCI and ICT4D practitioners dealing with
similar challenges
Transmission through correlated CuCoCu heterostructures
The effects of local electronic interactions and finite temperatures upon the
transmission across the CuCoCu metallic heterostructure are studied in
a combined density functional and dynamical mean field theory. It is shown
that, as the electronic correlations are taken into account via a local but
dynamic self-energy, the total transmission at the Fermi level gets reduced
(predominantly in the minority spin channel), whereby the spin polarization of
the transmission increases. The latter is due to a more significant
-electrons contribution, as compared to the non-correlated case in which the
transport is dominated by and electrons.Comment: 29 pages, 7 figures, submited to PR
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