5,372 research outputs found
Transient non-isothermal model of a polymer electrolyte fuel cell
In this paper we present a one-dimensional transient model for the membrane electrode assembly of a polymer-electrolyte fuel cell. In earlier work we established a framework to describe the water balance in a steady-state, non-isothermal cathode model that explicitly included an agglomerate catalyst layer component. This paper extends that work in several directions, explicitly incorporating components of the anode, including a micro-porous layer, and accounting for electronic potential variations, gas convection and time dependence. The inclusion of temperature effects, which are vital to the correct description of condensation and evaporation, is new to transient modelling. Several examples of the modelling results are given in the form of potentiostatic sweeps and compared to experimental results. Excellent qualitative agreement is demonstrated, particularly in regard to the phenomenon of hysteresis, a manifestation of the sensitive response of the system to the presence of water. Results pertaining to pore size, contact angle and the presence of a micro-porous layer are presented and future work is discussed
D-SLATS: Distributed Simultaneous Localization and Time Synchronization
Through the last decade, we have witnessed a surge of Internet of Things
(IoT) devices, and with that a greater need to choreograph their actions across
both time and space. Although these two problems, namely time synchronization
and localization, share many aspects in common, they are traditionally treated
separately or combined on centralized approaches that results in an ineffcient
use of resources, or in solutions that are not scalable in terms of the number
of IoT devices. Therefore, we propose D-SLATS, a framework comprised of three
different and independent algorithms to jointly solve time synchronization and
localization problems in a distributed fashion. The First two algorithms are
based mainly on the distributed Extended Kalman Filter (EKF) whereas the third
one uses optimization techniques. No fusion center is required, and the devices
only communicate with their neighbors. The proposed methods are evaluated on
custom Ultra-Wideband communication Testbed and a quadrotor, representing a
network of both static and mobile nodes. Our algorithms achieve up to three
microseconds time synchronization accuracy and 30 cm localization error
Spin rotation and oscillations for high energy particles in a crystal and possibility to measure the quadrupole moments and tensor polarizabilities of elementary particles and nuclei
It is shown that particle motion in a bent (straight) crystal is accompanied
by particle spin rotation and oscillations that allows to measure the tensor
electric and magnetic polarizabilities of nuclei and elementary particles. It
is shown that channelling of particles in either straight or bent crystal with
the polarized nuclei could be used both to analyze polarization of high energy
particles and polarize them.Comment: reported at RC2005; prepared in the framework of INTAS
Project#03-52-615
An ARPES view on the high-Tc problem: phonons vs spin-fluctuations
We review the search for a mediator of high-Tc superconductivity focusing on
ARPES experiment. In case of HTSC cuprates, we summarize and discuss a
consistent view of electronic interactions that provides natural explanation of
both the origin of the pseudogap state and the mechanism for high temperature
superconductivity. Within this scenario, the spin-fluctuations play a decisive
role in formation of the fermionic excitation spectrum in the normal state and
are sufficient to explain the high transition temperatures to the
superconducting state while the pseudogap phenomenon is a consequence of a
Peierls-type intrinsic instability of electronic system to formation of an
incommensurate density wave. On the other hand, a similar analysis being
applied to the iron pnictides reveals especially strong electron-phonon
coupling that suggests important role of phonons for high-Tc superconductivity
in pnictides.Comment: A summary of the ARPES part of the Research Unit FOR538,
http://for538.wmi.badw.d
Damping mechanism for the strongly renormalized -axis charge transport in high- cuprate superconductors
We analyze the -axis infrared reflectivity of
LaSrCuO single crystals. The plasma edge near 6 meV,
observed below , is due to Cooper-pair tunneling. This low value of the
plasma edge is consistent with the -axis plasma frequency () obtained
from LDA calculations ( eV) if we take into account that the
single-particle charge transport along the axis is strongly incoherent both
above and below . We find no evidence for a reduction of the -axis
scattering rate () below . Our investigation suggests
, which is exactly opposite to the clean limit.
VSGD.94.6.1Comment: 4 pages, figures on request. Revtex, version 2, Materials Science
Center Internal Report Number VSGD.94.6.
Tachyon Kinks in Boundary String Field Theory
We study tachyon kinks with and without electromagnetic fields in the context
of boundary string field theory. For the case of pure tachyon only an array of
kink-antikink is obtained. In the presence of electromagnetic coupling, all
possible static codimension-one soliton solutions such as array of
kink-antikink, single topological BPS kink, bounce, half kink, as well as
nonBPS topological kink are found, and their properties including the
interpretation as branes are analyzed in detail. Spectrum of the obtained kinks
coincides with that of Dirac-Born-Infeld type effective theory.Comment: LaTex, 29 pages, 17 Figure
Gravitational Wave Spectrum in Inflation with Nonclassical States
The initial quantum state during inflation may evolve to a highly squeezed
quantum state due to the amplification of the time-dependent parameter,
, which may be the modified dispersion relation in
trans-Planckian physics. This squeezed quantum state is a nonclassical state
that has no counterpart in the classical theory. We have considered the
nonclassical states such as squeezed, squeezed coherent, and squeezed thermal
states, and calculated the power spectrum of the gravitational wave
perturbation when the mode leaves the horizon.Comment: 21 page
Organic geochemistry of Palaeozoic source rocks, central North Sea (CNS)
This report details a regional analysis of the source rock quality and potential of Palaeozoic rocks of the UK Central North Sea for the 21CXRM Palaeozoic project. The objective was to undertake a regional screening of all intervals to identify source rocks using new and legacy datasets of all Carboniferous and Devonian samples. In addition, a literature review (Appendix 1) summarises source and kerogen typing information from legacy reports. The background and stratigraphic nomenclature are given in Monaghan et al. (2016), details on individual well interpretations and stratigraphy are given in Kearsey et al. (2015). Geological context on the results of this work are included in basin modelling (Vincent, 2015) and were synthesised into a petroleum systems analysis in Monaghan et al. (2015).
New and legacy Carboniferous and Devonian source rock geochemical data were examined per well using industry standard criteria to give an overview of the source rock quality, type (oil or gas prone) and maturity. The aims of this study were to classify the source rock quality of 33 wells, to examine if intervals were ‘gas-prone’ or ‘oil-prone’, and to ascertain the hydrocarbon generation stage of each well based on Rock-Eval pyrolysis, vitrinite reflectance (VR, where available) and total organic carbon (TOC) data. The term ‘gas prone’ was used to describe source rocks that have or could generate gas; ‘oil prone’ for source intervals that have or could generate oil. This study was a rapid screening exercise to identify intervals or areas of interest, and as such the data and inferences must be used concomitantly with other geological data to fully assess the source rock potential within the studied wells. It should be noted that the wells studied penetrate different parts of the geological succession and in many cases only small sections of the Devonian and Carboniferous interval.
An initial sift through the wells with available geochemical data indicated that 33 wells had enough data to be usefully evaluated. Subsequently it was found that 8 of the 33 wells had incomplete, unreliable or otherwise poor source rock quality data sets and therefore were not analysed further; the reasons are detailed in this report.
The remaining 25 wells selected for analysis were: 43/28-2, 26/07-1, 26/08-1, 36/13-1, 36/23-1, 38/16-1, 38/18-1, 39/07-1, 41/08-1, 42/10a-1, 42/10b-2ST, 42/09-1, 41/10-1, 42/10b-2, 41/15-1, 43/21-2, 41/01-1, 41/20-1, 41/14-1, 43/02-1, 43/17-2, 43/20b-2, 43/28-1, 43/28-2, 44/13-1, 44/16-1. Samples analysed from the majority of these wells were interpreted to be gas prone in the Carboniferous succession (Figure 1).
1. 41/10-1, 41/14-1 and 41/20-1 contained source rocks that were both gas window mature (e.g. VR >1.3) and can be regarded as excellent gas source. Strata in 43/17-2, 44/16-1 and 43/28-1 were also gas mature in all or parts of the section of interest, but with variable source rock quality. The six wells all had low S2 peaks: this may be due to either prior hydrocarbon generation and depletion or the initial presence of low amounts of non-inert kerogen.
2. 41/15-1, 42/10b-2 and 43/21-2 were also identified as possessing good gas-prone source rocks with elevated S2 values and also a high maturity attained by the source rocks. 41/01-1 was identified as a good for gas generation in the deeper section.
3. 26/07-1, 26/08-1, 36/13-1, 38/16-1, 39/07-1, 41/08-1, 42/10a-1, 42/10b-2ST, 42/09-1, 43/02-1, 43/20b-2, 43/28-2 and 44/13-1, contain good to excellent quality source rocks, but have not matured sufficiently to generate significant amount of gas, so these can be regarded as poor gas sources based on their current maturity. If present, in deeper basins some of these intervals will have generated significant quantities of gas
On the asymptotic expansion of the solutions of the separated nonlinear Schroedinger equation
Nonlinear Schr\"odinger equation (with the Schwarzian initial data) is
important in nonlinear optics, Bose condensation and in the theory of strongly
correlated electrons. The asymptotic solutions in the region ,
, can be represented as a double series in and .
Our current purpose is the description of the asymptotics of the coefficients
of the series.Comment: 11 pages, LaTe
Effect of magnetic and non-magnetic impurities on highly anisotropic superconductivity
We generalize Abrikosov-Gor'kov solution of the problem of weakly coupled
superconductor with impurities on the case of a multiband superconductor with
arbitrary interband order parameter anisotropy, including interband sign
reversal of the order parameter. The solution is given in terms of the
effective (renormalized) coupling matrix and describes not only
suppression but also renormalization of the superconducting gap basically at
all temperatures. In many limiting cases we find analytical solutions for the
critical temperature suppression. We illustrate our results by numerical
calculations for two-band model systems.Comment: 18 pages (12pt) RevTeX, 4 postscript figure
- …