20,781 research outputs found
Subject-specific finite element modelling of the human hand complex : muscle-driven simulations and experimental validation
This paper aims to develop and validate a subject-specific framework for modelling the human hand. This was achieved by combining medical image-based finite element modelling, individualized muscle force and kinematic measurements. Firstly, a subject-specific human hand finite element (FE) model was developed. The geometries of the phalanges, carpal bones, wrist bones, ligaments, tendons, subcutaneous tissue and skin were all included. The material properties were derived from in-vivo and in-vitro experiment results available in the literature. The boundary and loading conditions were defined based on the kinematic data and muscle forces of a specific subject captured from the in-vivo grasping tests. The predicted contact pressure and contact area were in good agreement with the in-vivo test results of the same subject, with the relative errors for the contact pressures all being below 20%. Finally, sensitivity analysis was performed to investigate the effects of important modelling parameters on the predictions. The results showed that contact pressure and area were sensitive to the material properties and muscle forces. This FE human hand model can be used to make a detailed and quantitative evaluation into biomechanical and neurophysiological aspects of human hand contact during daily perception and manipulation. The findings can be applied to the design of the bionic hands or neuro-prosthetics in the future
Strong Correlations and Magnetic Frustration in the High Tc Iron Pnictides
We consider the iron pnictides in terms of a proximity to a Mott insulator.
The superexchange interactions contain competing nearest-neighbor and
next-nearest-neighbor components. In the undoped parent compound, these
frustrated interactions lead to a two-sublattice collinear antiferromagnet
(each sublattice forming a Neel ordering), with a reduced magnitude for the
ordered moment. Electron or hole doping, together with the frustration effect,
suppresses the magnetic ordering and allows a superconducting state. The
exchange interactions favor a d-wave superconducting order parameter; in the
notation appropriate for the Fe square lattice, its orbital symmetry is
. A number of existing and future experiments are discussed in light of
the theoretical considerations.Comment: (v2) 4+ pages, 4 figures, discussions on several points expanded;
references added. To appear in Phys. Rev. Let
Tractable approximate deduction for OWL
Acknowledgements This work has been partially supported by the European project Marrying Ontologies and Software Technologies (EU ICT2008-216691), the European project Knowledge Driven Data Exploitation (EU FP7/IAPP2011-286348), the UK EPSRC project WhatIf (EP/J014354/1). The authors thank Prof. Ian Horrocks and Dr. Giorgos Stoilos for their helpful discussion on role subsumptions. The authors thank Rafael S. Gonçalves et al. for providing their hotspots ontologies. The authors also thank BoC-group for providing their ADOxx Metamodelling ontologies.Peer reviewedPostprin
Thorium-doping induced superconductivity up to 56 K in Gd1-xThxFeAsO
Following the discovery of superconductivity in an iron-based arsenide
LaO1-xFxFeAs with a superconducting transition temperature (Tc) of 26 K[1], Tc
was pushed up surprisingly to above 40 K by either applying pressure[2] or
replacing La with Sm[3], Ce[4], Nd[5] and Pr[6]. The maximum Tc has climbed to
55 K, observed in SmO1-xFxFeAs[7, 8] and SmFeAsO1-x[9]. The value of Tc was
found to increase with decreasing lattice parameters in LnFeAsO1-xFx (Ln stands
for the lanthanide elements) at an apparently optimal doping level. However,
the F- doping in GdFeAsO is particularly difficult[10,11] due to the lattice
mismatch between the Gd2O2 layers and Fe2As2 layers. Here we report observation
of superconductivity with Tc as high as 56 K by the Th4+ substitution for Gd3+
in GdFeAsO. The incorporation of relatively large Th4+ ions relaxes the lattice
mismatch, hence induces the high temperature superconductivity.Comment: 4 pages, 3 figure
Possibility of Unconventional Pairing Due to Coulomb Interaction in Fe-Based Pnictide Superconductors: Perturbative Analysis of Multi-Band Hubbard Models
Possibility of unconventional pairing due to Coulomb interaction in
iron-pnictide superconductors is studied by applying a perturbative approach to
realistic 2- and 5-band Hubbard models. The linearized Eliashberg equation is
solved by expanding the effective pairing interaction perturbatively up to
third order in the on-site Coulomb integrals. The numerical results for the
5-band model suggest that the eigenvalues of the Eliashberg equation are
sufficiently large to explain the actual high Tc for realistic values of
Coulomb interaction and the most probable pairing state is spin-singlet s-wave
without any nodes just on the Fermi surfaces, although the superconducting
order parameter changes its sign between the small Fermi pockets. On the other
hand the 2-band model is quite insufficient to explain the actual high Tc.Comment: 2 pages, 3 figures. Proceedings of the Intl. Symposium on
Fe-Oxypnictide Superconductors (Tokyo, 28-29th June 2008
Scaling behavior of temperature-dependent thermopower in CeAu2Si2 under pressure
We report a combined study of in-plane resistivity and thermopower of the
pressure-induced heavy fermion superconductor CeAu2Si2 up to 27.8 GPa. It is
found that thermopower follows a scaling behavior in T/T* almost up to the
magnetic critical pressure pc ~ 22 GPa. By comparing with resistivity results,
we show that the magnitude and characteristic temperature dependence of
thermopower in this pressure range are governed by the Kondo coupling and
crystal-field splitting, respectively. Below pc, the superconducting transition
is preceded by a large negative thermopower minimum, suggesting a close
relationship between the two phenomena. Furthermore, thermopower of a variety
of Ce-based Kondo-lattices with different crystal structures follows the same
scaling relation up to T/T* ~ 2.Comment: 6 pages, 4 figures. Supplementary Material available on reques
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Sustainable design approach underpinned with Life Cycle Impact Assessment(LCIA) and ontology
Sustainable development has been a subject of global interest when people shift the focus from the economy and productivity only to the economy with consideration of the environment and resources on the earth. Manufacturing industry is one of the most crucial sectors that people focused on to make it more sustainable. However, the sustainability for current existing products are not enough to satisfy the requirement of sustainable development within the modern society. Therefore, an approach to design and to optimise product considering ecological impact is to be developed by this research. After review and comparison of popular LCIA methods and tools, the three-tier sustainable design approach considering human labour ecological impact is developed. Design optimisation with eco-constraints using genetic algorithm is followed. Moreover, from a product life cycle point of view, production may not be the least sustainable section. Use and disposal also play important roles in the whole product life cycle. In this case, Ontology is proposed in the research. It is a powerful tool to collect and exchange data of products and manage the relationships among different parts, properties of products, and suppliers in one specific area such as a factory or an industrial estate. Afterwards, The approach is validated by case study. Finally, the sustainable design approach underpinned with life cycle impact assessment (LCIA) and ontology is developed
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