1,284 research outputs found
Energy Data Visualization Requires Additional Approaches to Continue to be Relevant in a World with Greater Low-Carbon Generation
The hypothesis described in this article proposes that energy visualization diagrams commonly used need additional changes to continue to be relevant in a world with greater low-carbon generation. The diagrams that display national energy data are influenced by the properties of the type of energy being displayed, which in most cases has historically meant fossil fuels, nuclear fuels, or hydro. As many energy systems throughout the world increase their use of electricity from wind- or solar-based renewables, a more granular display of energy data in the time domain is required. This article also introduces the shared axes energy diagram that provides a simple and powerful way to compare the scale and seasonality of the demands and supplies of an energy system. This aims to complement, rather than replace existing diagrams, and has an additional benefit of promoting a whole systems approach to energy systems, as differing energy vectors, such as natural gas, transport fuels, and electricity, can all be displayed together. This, in particular, is useful to both policy makers and to industry, to build a visual foundation for a whole systems narrative, which provides a basis for discussion of the synergies and opportunities across and between different energy vectors and demands. The diagram’s ability to wrap a sense of scale around a whole energy system in a simple way is thought to explain its growing popularity
After the Loyalists: The Archaeology of 19th Century Kingston
No abstract available at this time
Great Britain's Energy Vectors and Transmission Level Energy Storage
As an example of the challenges facing many developed countries, the scale of daily energy flows through Great Britain's electrical, gas and transport systems are presented. When this data is expressed graphically it illustrates important differences in the demand characteristics of these different vectors; these include the scale of energy delivered through the networks on a daily basis, and the scale of variability in the different demands over multiple timescales (seasonal, weekly and daily). The paper discusses energy storage in general; the scale of within day stores of energy available to the gas and electrical transmission networks, and suggests Synthetic Natural Gas as an interesting energy carrier that could use existing natural gas infrastructure
Rapid fuel switching from coal to natural gas through effective carbon pricing
Britain’s overall carbon emissions fell by 6% in 2016 due to cleaner electricity production. This was 10 not due to a surge in low-carbon nuclear or renewable sources; instead it was the much-overlooked 11 impact of fuel switching from coal to natural gas generation. This Perspective considers the enabling 12 conditions in Britain and the potential for rapid fuel switching in other coal-reliant countries. We find 13 that spare generation and fuel supply-chain capacity must already exist for fuel switching to deliver 14 rapid carbon savings, and to avoid further high-carbon infrastructure lock-in. More important is the 15 political will to alter the marketplace and incentivise this switch, for example through a strong and 16 stable carbon price. With the right incentives, fuel switching in the power sector could rapidly achieve 17 on the order of 1 GtCO2 saving per year worldwide (3% of global emissions), buying precious time to 18 slow the growth in cumulative carbon emissions
Dendritic flux avalanches in superconducting Nb3Sn films
The penetration of magnetic flux into a thin superconducting film of Nb3Sn
with critical temperature 17.8K and critical current density 6MA/cm^2 was
visualized using magneto-optical imaging. Below 8 K an avalanche-like flux
penetration in form of big and branching dendritic structures was observed in
response to increasing perpendicular applied field. When a growing dendritic
branch meets a linear defect in the film, several scenarios were observed: the
branch can turn and propagate along the defect, continue propagation right
through it, or "tunnel" along a flux-filled defect and continue growth from its
other end. The avalanches manifest themselves in numerous small and random
jumps found in the magnetization curve.Comment: 3 pages, 4 figures, submitted to Cryogenics. Revision: M(H) data
adde
Pseudogap phase of high-Tc compounds described within the LDA+DMFT+Sigma approach
LDA+DMFT+Sigma_k approach was applied to describe pseudogap phase of several
prototype high-Tc compounds e.g. hole doped Bi2212 and LSCO systems and
electron doped NCCO and PCCO, demonstrating qualitative difference of the Fermi
surfaces (FS) for these systems. Namely for Bi2212 and LSCO the so called
"hot-spots" (intersection of a bare FS and AFM Brillouin zone (BZ) boundary),
where scattering on pseudogap fluctuations is most intensive were not observed.
Instead here we have Fermi arcs with smeared FS close to the BZ boundary.
However for NCCO and PCCO "hot-spots" are clearly visible. This qualitative
difference is shown to have material specific origin. Good agreement with known
ARPES data was demon strated not only for FS maps but also for spectral
function maps (quasiparticle bands in cluding lifetime and interaction
broadening).Comment: 4 pages, 4 figures, 1 table, SNS2010 proceedings (24-28 May 2010,
Shanghai, China
Decoherence of electron spin qubits in Si-based quantum computers
Direct phonon spin-lattice relaxation of an electron qubit bound by a donor
impurity or quantum dot in SiGe heterostructures is investigated. The aim is to
evaluate the importance of decoherence from this mechanism in several important
solid-state quantum computer designs operating at low temperatures. We
calculate the relaxation rate as a function of [100] uniaxial strain,
temperature, magnetic field, and silicon/germanium content for Si:P bound
electrons. The quantum dot potential is much smoother, leading to smaller
splittings of the valley degeneracies. We have estimated these splittings in
order to obtain upper bounds for the relaxation rate. In general, we find that
the relaxation rate is strongly decreased by uniaxial compressive strain in a
SiGe-Si-SiGe quantum well, making this strain an important positive design
feature. Ge in high concentrations (particularly over 85%) increases the rate,
making Si-rich materials preferable. We conclude that SiGe bound electron
qubits must meet certain conditions to minimize decoherence but that
spin-phonon relaxation does not rule out the solid-state implementation of
error-tolerant quantum computing.Comment: 8 figures. To appear in PRB-July 2002. Revisions include: some
references added/corrected, several typos fixed, a few things clarified.
Nothing dramati
Body Fixed Frame, Rigid Gauge Rotations and Large N Random Fields in QCD
The "body fixed frame" with respect to local gauge transformations is
introduced. Rigid gauge "rotations" in QCD and their \Sch equation are studied
for static and dynamic quarks. Possible choices of the rigid gauge field
configuration corresponding to a nonvanishing static colormagnetic field in the
"body fixed" frame are discussed. A gauge invariant variational equation is
derived in this frame. For large number N of colors the rigid gauge field
configuration is regarded as random with maximally random probability
distribution under constraints on macroscopic--like quantities. For the uniform
magnetic field the joint probability distribution of the field components is
determined by maximizing the appropriate entropy under the area law constraint
for the Wilson loop. In the quark sector the gauge invariance requires the
rigid gauge field configuration to appear not only as a background but also as
inducing an instantaneous quark-quark interaction. Both are random in the large
N limit.Comment: 29 pages LATEX, Weizmann Institute preprint WIS-93/40/Apr -P
Nonlinear Realization of Chiral Symmetry on the Lattice
We formulate lattice theories in which chiral symmetry is realized
nonlinearly on the fermion fields. In this framework the fermion mass term does
not break chiral symmetry. This property allows us to use the Wilson term to
remove the doubler fermions while maintaining exact chiral symmetry on the
lattice. Our lattice formulation enables us to address non-perturbative
questions in effective field theories of baryons interacting with pions and in
models involving constituent quarks interacting with pions and gluons. We show
that a system containing a non-zero density of static baryons interacting with
pions can be studied on the lattice without encountering complex action
problems. In our formulation one can also decide non-perturbatively if the
chiral quark model of Georgi and Manohar provides an appropriate low-energy
description of QCD. If so, one could understand why the non-relativistic quark
model works.Comment: 34 pages, 2 figures, revised version to be published in J. High
Energy Phys. (changes in the 1st paragraph, additional descriptions on the
nature of the coordinate singularities in Sec.2, references added
(Sub)mm Interferometry Applications in Star Formation Research
This contribution gives an overview about various applications of (sub)mm
interferometry in star formation research. The topics covered are molecular
outflows, accretion disks, fragmentation and chemical properties of low- and
high-mass star-forming regions. A short outlook on the capabilities of ALMA is
given as well.Comment: 20 pages, 7 figures, in proceedings to "2nd European School on Jets
from Young Star: High Angular Resolution Observations". A high-resolution
version of the paper can be found at
http://www.mpia.de/homes/beuther/papers.htm
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