631 research outputs found
Leaching of a Cu-Co ore from Congo using sulphuric acidhydrogen peroxide leachants
A Cu-Co ore from Katinga Province, the Republic of Congo containing 1.5% Co and 1.6% Cu was tested to determine the leachability of Cu and Co using sulphuric acid and hydrogen peroxide mixtures at different conditions. Without hydrogen peroxide, the maximum extraction of copper and cobalt were found to be ~80% and ~15%, respectively when the acid concentration was varied between 0.36 - 1.1M. When hydrogen peroxide was added (0.008-0.042M), Cu recovery was enhanced to ~90%. Recoveries of ~90% of Co could be achieved at 20ÂșC, using leachants consisting of 0.36M sulphuric acid and 0.025M hydrogen peroxide after 3 hours. The reaction time to reach 90% Co extraction was reduced to less than 2 hours at 30ÂșC. Stabcal modelling of the Eh-pH diagrams shows the importance of hydrogen peroxide as a reductant. The decrease of solution potential (300-350 mV) by adding hydrogen peroxide was confirmed by Eh measurements during the tests. The leaching follows the shrinking core model kinetics, where the rate constant is linearly dependent on hydrogen peroxide concentration in the range 0-0.025M and proportional to (1/r2) where r is the average radius of the mineral particles. The activation energy for the leaching process is 72.3 kJ/mol
TeV scale partial mirage unification and neutralino dark matter
We study the TeV scale partial mirage unification scenario, where the gluino
and wino masses are degenerate around a TeV scale, but the bino mass is not
degenerate. This scenario has phenomenologically interesting aspects. First,
because of the degeneracy between the gluino and wino masses, this scenario
does not have the little hierarchy problem, that is, the higgisino mass is
around 150 GeV. The lightest superparticle is a mixture of the bino and
higgsino, and can lead to a right amount of thermal relic density as a dark
matter candidate
Sparticle masses in deflected mirage mediation
We discuss the sparticle mass patterns that can be realized in deflected
mirage mediation scenario of supersymmetry breaking, in which the moduli,
anomaly, and gauge mediations all contribute to the MSSM soft parameters.
Analytic expression of low energy soft parameters and also the sfermion mass
sum rules are derived, which can be used to interpret the experimentally
measured sparticle masses within the framework of the most general mixed
moduli-gauge-anomaly mediation. Phenomenological aspects of some specific
examples are also discussed.Comment: 43 pages, 17 figures, references adde
Extreme waves generated by Typhoon Bolaven (201215) in Southern Korean waters
Unusual extreme waves were generated by Typhoon Bolaven (201215) in the Southern Korean Waters\ud
(SKW) and gave destructive damages to the breakwaters of Seogwipo Harbor at Jeju Island. The waves were far\ud
exceeding the design wave height (Hs50yrs 9.3m) and their duration was 14hours. The duration is a very significant\ud
factor as much as the design wave height for breakwater armor stability in terms of cumulative damages. A significant\ud
increase in strong typhoon intensity and duration in North West Pacific (NWP) due to global warming has been reported\ud
and also in landfall typhoons on Korea/Japan in a recent decade. The frequency of typhoon passed SKW region had an\ud
inter-annual and also a decadal variation and decreased in recent years, but several strong typhoons were occurred.\ud
Bolaven was affected by high pressure distribution located above the warm eddy region to track toward NNW rather\ud
than NE as usual in August. The extreme waves were analyzed with respect to typhoon genesis, evolution of the waves\ud
through extensive measured data and model simulation. Numerical models of TC96 for the wind fields and WAM4.5.2\ud
for the waves were used after calibration with measured data and correction of Cd in wave growth term. They produced\ud
reasonably good results. It was found that the extreme waves were evolved by combination of distant large swell and\ud
strong wind seas generated by consistent strong winds from front right quadrant of typhoon track for such a long time.\ud
The variation of those waves was relatively small as 1-2m, which might be due to limitation of wave growth for\ud
U>30m/s and bottom energy dissipation of long period waves in the region. It is essential to hindcast accurately the\ud
extreme waves for design of the breakwaters and also for assessment of coastal flooding and coastal erosion in a\ud
warming climate
Toward Green Synthesis of Graphene Oxide Using Recycled Sulfuric Acid via Couette-Taylor Flow
Developing eco-friendly and cost-effective processes for the synthesis of graphene oxide (GO) is essential for its widespread industrial applications. In this work, we propose a green synthesis technique for GO production using recycled sulfuric acid and filter-processed oxidized natural graphite obtained from a Couette-Taylor flow reactor. The viscosity of reactant mixtures processed from Couette-Taylor flow was considerably lower (???200 cP at 25 ??C) than that of those from Hummers' method, which enabled the simple filtration process. The filtered sulfuric acid can be recycled and reused for the repetitive GO synthesis with negligible differences in the as-synthesized GO qualities. This removal of sulfuric acid has great potential in lowering the overall GO production cost as the amount of water required during the fabrication process, which takes a great portion of the total production cost, can be dramatically reduced after such acid filtration. The proposed eco-friendly GO fabrication process is expected to promote the commercial application of graphene materials into industry shortly
Measuring superparticle masses at hadron collider using the transverse mass kink
We present a detailed study of the collider observable applied for
pair-produced superparticles decaying to visible particles and a pair of
invisible lightest supersymmetric particles (LSPs). Analytic expressions of the
maximum of over all events () are derived. It is
noticed that if the decay product of each superparticle involves more than one
visible particles, being a function of the {\it trial} LSP
mass has a kink structure at true LSP mass, which can be
used to determine the mother superparticle mass and the LSP mass
simultaneously. To see how well can be constructed from
collider data, a Monte-Carlo analysis of the gluino is performed for
some superparticle spectra.Comment: Typos corrected. A few references added. Figures update
Test for entanglement using physically observable witness operators and positive maps
Motivated by the Peres-Horodecki criterion and the realignment criterion we
develop a more powerful method to identify entangled states for any bipartite
system through a universal construction of the witness operator. The method
also gives a new family of positive but non-completely positive maps of
arbitrary high dimensions which provide a much better test than the witness
operators themselves. Moreover, we find there are two types of positive maps
that can detect 2xN and 4xN bound entangled states. Since entanglement
witnesses are physical observables and may be measured locally our construction
could be of great significance for future experiments.Comment: 6 pages, 1 figure, revtex4 styl
The fermi arc and fermi pocket in cuprates in a short-range diagonal stripe phase
In this paper we studied the fermi arc and the fermi pocket in cuprates in a
short-range diagonal stripe phase with wave vectors , which
reproduce with a high accuracy the positions and sizes of the fermi arc and
fermi pocket and the superstructure in cuprates observed by Meng et
al\cite{Meng}. The low-energy spectral function indicates that the fermi pocket
results from the main band and the shadow band at the fermi energy. Above the
fermi energy the shadow band gradually departs away from the main band, leaving
a fermi arc. Thus we conclude that the fermi arc and fermi pocket can be fully
attributed to the stripe phase but has nothing to do with pairing.
Incorporating a d-wave pairing potential in the stripe phase the spectral
weight in the antinodal region is removed, leaving a clean fermi pocket in the
nodal region.Comment: 5 pages, 6 figure
Stationary State Solutions of a Bond Diluted Kinetic Ising Model: An Effective-Field Theory Analysis
We have examined the stationary state solutions of a bond diluted kinetic
Ising model under a time dependent oscillating magnetic field within the
effective-field theory (EFT) for a honeycomb lattice . Time evolution of
the system has been modeled with a formalism of master equation. The effects of
the bond dilution, as well as the frequency and amplitude of
the external field on the dynamic phase diagrams have been discussed in detail.
We have found that the system exhibits the first order phase transition with a
dynamic tricritical point (DTCP) at low temperature and high amplitude regions,
in contrast to the previously published results for the pure case \cite{Ling}.
Bond dilution process on the kinetic Ising model gives rise to a number of
interesting and unusual phenomena such as reentrant phenomena and has a
tendency to destruct the first-order transitions and the DTCP. Moreover, we
have investigated the variation of the bond percolation threshold as functions
of the amplitude and frequency of the oscillating field.Comment: 8 pages, 4 figure
Search for the h_c meson in B^+- ->h_c K^+-
We report a search for the meson via the decay chain , \etac \gamma with and
. No significant signals are observed. We obtain upper limits on the
branching fractions for in bins of the
invariant mass. The results are based on an analysis of 253
fb of data collected by the Belle detector at the KEKB
collider.Comment: 12 pages, 6 figures, submitted to Phys. Rev.
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