632 research outputs found
CODEX: mapping co-created data for speculative geographies
This paper discusses a series of artworks named CODEX produced by the authors as part of a collaborative research project between the Centre for Research in Education, Art and Media (CREAM), University of Westminster, and the Oxford Internet Institute. Taking the form of experimental maps, large-scale installations and prints, we show how big data can be employed to reflect upon social phenomena through the formulation of critical, aesthetic and speculative geographies
Cyclone.soc: an interactive artwork visualizing Internet newsgroup postings as cyclonic weather conditions
Bonding of 304L Stainless Steel to Cast Iron by Selective Laser Melting
While cast iron is widely used in industry, a major limitation is the weldability of a dissimilar material onto cast iron due to hot cracking as a result of lack of ductility from graphite flakes. Consequently, a significant amount of preheat is often employed to reduce the cooling rate in the fusion zone, which, however, may lead to distortion of the welded parts. A potential remedy could be the Selective Laser Melting (SLM) process, where only small melt pools are created and thus the overall energy input is reduced. The present paper describes an investigation of the SLM process to join 304L stainless steel with cast iron. In this study, 304L stainless steel particles ranging from 15-45 μm in size were melted on a grey cast iron substrate by the SLM process. Multiple sets of parameter values were chosen to test different energy densities on the tensile strength of the bond created. Subsequent characterization of the bonded area included energy dispersive spectroscopy (EDS) mapping for obtaining insight into the elemental diffusion, and metallography for visualization of the microstructure. A range of energy densities was identified for purposes of eliminating bond delamination and maximizing mechanical strength
The Volume of some Non-spherical Horizons and the AdS/CFT Correspondence
We calculate the volumes of a large class of Einstein manifolds, namely
Sasaki-Einstein manifolds which are the bases of Ricci-flat affine cones
described by polynomial embedding relations in C^n. These volumes are important
because they allow us to extend and test the AdS/CFT correspondence. We use
these volumes to extend the central charge calculation of Gubser (1998) to the
generalized conifolds of Gubser, Shatashvili, and Nekrasov (1999). These
volumes also allow one to quantize precisely the D-brane flux of the AdS
supergravity solution. We end by demonstrating a relationship between the
volumes of these Einstein spaces and the number of holomorphic polynomials
(which correspond to chiral primary operators in the field theory dual) on the
corresponding affine cone.Comment: 25 pp, LaTeX, 1 figure, v2: refs adde
Evidence for Anisotropic Vortex Dynamics and Pauli Limitation in the Upper Critical Field of FeSe1-xTex
We have determined HC2(T) for FeSe1-xTex (x=0.52) single crystals using
resistivity measurements at high static and pulsed magnetic field, as well as
specific heat measurements up to 9T. We find that the significant anisotropy of
the initial slope of HC2(T) determined from resistivity measurements, is not
present when HC2 is determined from the specific heat results. This suggests
that the thermodynamic upper critical field is almost isotropic, and that
anisotropic vortex dynamics play a role. Further evidence of anisotropic vortex
dynamics is found in the behaviour in pulsed field. We also find that Pauli
limiting must be included in order to fit the temperature dependence of HC2,
indicating probably higher effective mass in FeSe1-xTex than in other Fe
superconductors
On the 0-dimensional cusps of the Kahler moduli of a K3 surface
Let S be a projective K3 surface. It is proved that the 0-dimensional cusps
of the Kahler moduli of S are in one-to-one correspondence with the twisted
Fourier-Mukai partners of S. This leads to a counting formula for the
0-dimensional cusps of the Kahler moduli. Applications to rational maps between
K3 surfaces with large Picard numbers are given. When the Picard number of S is
1, the bijective correspondence is calculated explicitly.Comment: 24page
Randomizing world trade. II. A weighted network analysis
Based on the misleading expectation that weighted network properties always
offer a more complete description than purely topological ones, current
economic models of the International Trade Network (ITN) generally aim at
explaining local weighted properties, not local binary ones. Here we complement
our analysis of the binary projections of the ITN by considering its weighted
representations. We show that, unlike the binary case, all possible weighted
representations of the ITN (directed/undirected, aggregated/disaggregated)
cannot be traced back to local country-specific properties, which are therefore
of limited informativeness. Our two papers show that traditional macroeconomic
approaches systematically fail to capture the key properties of the ITN. In the
binary case, they do not focus on the degree sequence and hence cannot
characterize or replicate higher-order properties. In the weighted case, they
generally focus on the strength sequence, but the knowledge of the latter is
not enough in order to understand or reproduce indirect effects.Comment: See also the companion paper (Part I): arXiv:1103.1243
[physics.soc-ph], published as Phys. Rev. E 84, 046117 (2011
Doping dependence of upper critical field and Hall resistivity in LaFeAsO1-xFx
The electrical resistivity (Rxx) and Hall resistivity (Rxy) of LaFeAsO1-xFx
have been measured over a wide fluorine doping range 0 =< x =< 0.14 using 60 T
pulsed magnets. While the superconducting phase diagram (Tc, x) displays the
classic dome-shaped structure, we find that the resistive upper critical field
(Hc2) increases monotonically with decreasing fluorine concentration, with the
largest Hc2 >= 75 T for x = 0.05. This is reminiscent of the composition
dependence in high-Tc cuprates and might correlate with opening of a pseudo-gap
in the underdoped region. Further, the temperature dependence of Hc2(T) for
superconducting samples can be understood in terms of multi-band
superconductivity. Rxy data for non-superconducting samples show non-linear
field dependence, which is also consistent with a multi-carrier scenario.Comment: 15 pages, 5 figures, Accepted by PR
A hybrid radiation detector for simultaneous spatial and temporal dosimetry
In this feasibility study an organic plastic scintillator is calibrated against ionisation chamber measurements and then embedded in a polymer gel dosimeter to obtain a quasi-4D experimental measurement of a radiation field. This hybrid dosimeter was irradiated with a linear accelerator, with temporal measurements of the dose rate being acquired by the scintillator and spatial measurements acquired with the gel dosimeter. The detectors employed in this work are radiologically equivalent; and we show that neither detector perturbs the intensity of the radiation field of the other. By employing these detectors in concert, spatial and temporal variations in the radiation intensity can now be detected and gel dosimeters can be calibrated for absolute dose from a single irradiation
Giant magnetothermopower of magnon-assisted transport in ferromagnetic tunnel junctions
We present a theoretical description of the thermopower due to
magnon-assisted tunneling in a mesoscopic tunnel junction between two
ferromagnetic metals. The thermopower is generated in the course of thermal
equilibration between two baths of magnons, mediated by electrons. For a
junction between two ferromagnets with antiparallel polarizations, the ability
of magnon-assisted tunneling to create thermopower depends on the
difference between the size of the majority and
minority band Fermi surfaces and it is proportional to a temperature dependent
factor where is the magnon Debye
energy. The latter factor reflects the fractional change in the net
magnetization of the reservoirs due to thermal magnons at temperature
(Bloch's law). In contrast, the contribution of magnon-assisted
tunneling to the thermopower of a junction with parallel polarizations is
negligible. As the relative polarizations of ferromagnetic layers can be
manipulated by an external magnetic field, a large difference results in a magnetothermopower effect. This
magnetothermopower effect becomes giant in the extreme case of a junction
between two half-metallic ferromagnets, .Comment: 9 pages, 4 eps figure
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