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 20ºC, 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 30ºC. 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 $m_{T2}$ applied for pair-produced superparticles decaying to visible particles and a pair of invisible lightest supersymmetric particles (LSPs). Analytic expressions of the maximum of $m_{T2}$ over all events ($m_{T2}^{\rm max}$) are derived. It is noticed that if the decay product of each superparticle involves more than one visible particles, $m_{T2}^{\rm max}$ being a function of the {\it trial} LSP mass ${m}_\chi$ has a kink structure at ${m}_\chi=$ true LSP mass, which can be used to determine the mother superparticle mass and the LSP mass simultaneously. To see how well $m_{T2}^{\rm max}$ can be constructed from collider data, a Monte-Carlo analysis of the gluino $m_{T2}$ 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 $(7\pi/8, 7\pi/8)$, 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 $(q=3)$. 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 $(\omega)$ and amplitude $(h/J)$ 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 $h_c$ meson via the decay chain $B^{\pm}\to h_c K^{\pm}$, \etac \gamma with $\eta_c \to K_S^0 K^{\pm} \pi^{\mp}$ and $p\bar{p}$. No significant signals are observed. We obtain upper limits on the branching fractions for $B^{\pm} \to \eta_c\gamma K^{\pm}$ in bins of the $\eta_c\gamma$ invariant mass. The results are based on an analysis of 253 fb$^{-1}$ of data collected by the Belle detector at the KEKB $e^+e^-$ collider.Comment: 12 pages, 6 figures, submitted to Phys. Rev.