10,560 research outputs found
Modeling the underlying mechanisms for organic memory devices: Tunneling, electron emission and oxygen adsorbing
We present a combined experimental and theoretical study to get insight into
both memory and negative differential resistance (NDR) effect in organic memory
devices. The theoretical model we propose is simply a one-dimensional metallic
island array embedding within two electrodes. We use scattering operator method
to evaluate the tunneling current among the electrode and islands to establish
the basic bistable I-V curves for several devices. The theoretical results
match the experiments very well, and both memory and NDR effect could be
understood comprehensively. The experimental correspondence, say, the
experiment of changing the pressure of oxygen, is addressed as well.Comment: 5 pages, 3 figure
Experimental Study on the Effect of Nano-silica on Mud Density in Synthetic Based Mud
Drilling fluids play important roles in drilling operations to suspend cuttings, counter high formation pressure and to ensure wellbore stability. Amongst the different types
of drilling fluids, currently synthetic based muds are the choice drilling fluid due to its high performance in HPHT wells in terms of wellbore stability and high penetration rates. However, under HPHT conditions, the well will encounter thermal degradation of mud properties, which will affect the performance of the mud, such as fluid loss, unstable rheology and barite sag. Barite sag is an effect of high density and high solid content in muds, in which the heavy solids in the mud settle at the bottom of the wellbore causing pipe sticking and lost of circulation. The experiment was carried out at LPLT, starting of HPHT and extreme HPHT conditions with a varying nano-silica concentration of 0%(base case) to 40%. At different mud weights, the formulated drilling fluid will be tested for HPHT filtrate loss, stable rheology and static sag at a 45° tilt. Nano-silica has been proven in this project to be only effective for fluid loss and improve mud rheology due to the nature of nano-silica as a plugging agent. The nano-silica had no effect on barite sag as proven in this experiment. Nevertheless, the newly formulated mud is still effective for solving and preventing downhole problems
Natural constraints on the gluon-quark vertex
In principle, the strong-interaction sector of the Standard Model is
characterised by a unique renormalisation-group-invariant (RGI) running
interaction and a unique form for the dressed--gluon-quark vertex,
; but, whilst much has been learnt about the former, the latter is
still obscure. In order to improve this situation, we use a RGI
running-interaction that reconciles both top-down and bottom-up analyses of the
gauge sector in quantum chromodynamics (QCD) to compute dressed-quark gap
equation solutions with 1,660,000 distinct Ansaetze for . Each one
of the solutions is then tested for compatibility with three physical criteria
and, remarkably, we find that merely 0.55% of the solutions survive the test.
Plainly, therefore, even a small selection of observables places extremely
tight bounds on the domain of realistic vertex Ansaetze. This analysis and its
results should prove useful in constraining insightful contemporary studies of
QCD and hadronic phenomena.Comment: 6 pages, 7 figure
Phase diagram and critical endpoint for strongly-interacting quarks
We introduce a method based on the chiral susceptibility, which enables one
to draw a phase diagram in the chemical-potential/temperature plane for
strongly-interacting quarks whose interactions are described by any reasonable
gap equation, even if the diagrammatic content of the quark-gluon vertex is
unknown. We locate a critical endpoint (CEP) at (\mu^E,T^E) ~ (1.0,0.9)T_c,
where T_c is the critical temperature for chiral symmetry restoration at \mu=0;
and find that a domain of phase coexistence opens at the CEP whose area
increases as a confinement length-scale grows.Comment: 4 pages, 3 figure
Quark spectral density and a strongly-coupled QGP
The maximum entropy method is used to compute the dressed-quark spectral
density from the self-consistent numerical solution of a rainbow truncation of
QCD's gap equation at temperatures above that for which chiral symmetry is
restored. In addition to the normal and plasmino modes, the spectral function
also exhibits an essentially nonperturbative zero mode for temperatures
extending to 1.4-1.8-times the critical temperature, T_c. In the neighbourhood
of T_c, this long-wavelength mode contains the bulk of the spectral strength
and so long as this mode persists, the system may fairly be described as a
strongly-coupled state of matter.Comment: 4 pages, 2 figure
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