268,190 research outputs found
Magnetic correlations on the full chains of Ortho-II YBaCuO
We propose that the NMR line shape on the chain Cu in the stoichiometric
high- superconductor Ortho-II YBaCuO is determined by the
magnetization induced on Cu near O vacancies, due to strong magnetic
correlations in the chains. An unrestricted Hartree-Fock calculation of a
coupled chain-plane Hubbard model with nearest-neighbor d-wave pairing
interaction shows that the broadening of NMR lines is consistent with
disorder-induced magnetization at low temperatures. In addition, we give a
possible explanation of the anomalous bimodal line shape observed at high
temperatures in terms of nonuniform Cu valence in the chains. The proximity
between chains and CuO plane induces anisotropic magnetization on the planar
Cu, and broadens the plane NMR lines in accordance with that of the chain
lines, in agreement with experiment. We discuss implications of the model for
other experiments on underdoped YBCO.Comment: 8 pages, 8 figures, submitted to PR
Evolutionary computation enabled game theory based modelling of electricity market behaviours and applications
The collapse of the Californian electricity market system in 2001 has highlighted urgency in research in intelligent electricity trading systems and strategies involving both suppliers and customs. In their trading systems, power generation companies under the new electricity trading arrangement (NETA) of the UK are now developing gaming strategies. However, modelling of such "intelligent" market behaviours is extremely challenging, because traditional mathematical and computer modelling techniques cannot cope with the involvement of game theory. In this paper, evolutionary computation enabled modelling of such system is presented. Both competitive and cooperative game theory strategies are taken into account in evolving the intelligent model. The model then leads to intelligent trading strategy development and decision support. Experimental tests, verification and validation are carried out with various strategies, using different model scales and data published by NETA. Results show that evolutionary computation enabled game theory involved modelling and decision making provides an effective tool for NETA trading analysis, prediction and support
Carfentrazone-ethyl Pond Dissipation and Efficacy on Floating Plants
Carfentrazone-ethyl (CE) is a reduced risk herbicide that
is currently being evaluated for the control of aquatic weeds.
Greenhouse trials were conducted to determine efficacy of
CE on water hyacinth (
Eichhornia crassipes
(Mart.) Solms-
Laub.), water lettuce (
Pistia stratiotes
L.), salvinia (
Salvinia
minima
Baker) and landoltia
(Landoltia punctata
(G. Mey.)
Les & D. J. Crawford
)
. CE controlled water lettuce, water hyacinth
and salvinia at rates less than the maximum proposed
use rate of 224 g ha
-1
. Water lettuce was the most susceptible
to CE with an EC
90
of 26.9 and 33.0 g ha
-1
in two separate trials.
Water hyacinth EC
90
values were calculated to be 86.2 to
116.3 g ha
-1
, and salvinia had a similar susceptibility to water
hyacinth with an EC
90
of 79.1 g ha
-1
. Landoltia was not adequately
controlled at the rates evaluated. In addition, CE was
applied to one-half of a 0.08 ha pond located in North Central,
Florida to determine dissipation rates in water and hydrosoil
when applied at an equivalent rate of 224 g ha
-1
. The
half-life of CE plus the primary metabolite, CE-chloropropionic
acid, was calculated to be 83.0 h from the whole pond,
and no residues were detected in water above the limit of
quantification (5 μg L
-1
) 168 h after treatment. CE dissipated
rapidly from the water column, did not occur in the sediment
above the levels of quantification, and in greenhouse
studies effectively controlled three species of aquatic weeds
at relatively low rates.(PDF contains 6 pages.
Crossover from Kramers to phase-diffusion switching in hysteretic DC-SQUIDs
We have measured and propose a model for switching rates in hysteretic
DC-SQUID in the regime where phase diffusion processes start to occur. We show
that the switching rates in this regime are smaller than the rates given by
Kramers' formula due to retrapping of Josephson phase. The retrapping process,
which is affected by the frequency dependent impedance of the environment of
the DC-SQUID, leads to a peaked second moment of the switching distribution as
a function of temperature. The temperature where the peaks occur are
proportional to the critical current of the DC- SQUID.Comment: 4 pages, 4 figure
Strategy for Cost-Effective Reduction of the Sum of Health Risk Estimates for Exposures to Mixtures of Toxic Substances
The authors argue that a minimization approach can provide guidance for effective use of funds to reduce the sum of estimated risks or the upper limit of the sum of risk estimates for mixtures of chemicals
Delayed fracture of silicon: Silicon sheet growth development for the large area silicon sheet task of the low cost silicon solar array project
Bar specimens were cut from ingots of single crystal silicon, and acid etched prior to testing. Artificial surface flaws were introduced in specimens by indentation with a Knoop hardness tester. The specimens were loaded in four-point bending to 95 percent of the nominal fracture stress, while keeping the surface area, containing the flaw, wet with test liquids. No evidence of delayed fracture, and, therefore stress corrosion, of single crystal silicon was observed for liquid environments including water, acetone, and aqueous solutions of NaCl, NH4OH, and HNO3, when tested with a flaw parallel to a (110) surface. The fracture toughness was calculated
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Semantics-Space-Time Cube. A Conceptual Framework for Systematic Analysis of Texts in Space and Time
We propose an approach to analyzing data in which texts are associated with spatial and temporal references with the aim to understand how the text semantics vary over space and time. To represent the semantics, we apply probabilistic topic modeling. After extracting a set of topics and representing the texts by vectors of topic weights, we aggregate the data into a data cube with the dimensions corresponding to the set of topics, the set of spatial locations (e.g., regions), and the time divided into suitable intervals according to the scale of the planned analysis. Each cube cell corresponds to a combination (topic, location, time interval) and contains aggregate measures characterizing the subset of the texts concerning this topic and having the spatial and temporal references within these location and interval. Based on this structure, we systematically describe the space of analysis tasks on exploring the interrelationships among the three heterogeneous information facets, semantics, space, and time. We introduce the operations of projecting and slicing the cube, which are used to decompose complex tasks into simpler subtasks. We then present a design of a visual analytics system intended to support these subtasks. To reduce the complexity of the user interface, we apply the principles of structural, visual, and operational uniformity while respecting the specific properties of each facet. The aggregated data are represented in three parallel views corresponding to the three facets and providing different complementary perspectives on the data. The views have similar look-and-feel to the extent allowed by the facet specifics. Uniform interactive operations applicable to any view support establishing links between the facets. The uniformity principle is also applied in supporting the projecting and slicing operations on the data cube. We evaluate the feasibility and utility of the approach by applying it in two analysis scenarios using geolocated social media data for studying people's reactions to social and natural events of different spatial and temporal scales
Waveguide cooling system
An improved system is described for cooling high power waveguides by the use of cooling ducts extending along the waveguide, which minimizes hot spots at the flanges where waveguide sections are connected together. The cooling duct extends along substantially the full length of the waveguide section, and each flange at the end of the section has a through hole with an inner end connected to the duct and an opposite end that can be aligned with a flange hole in another waveguide section. Earth flange is formed with a drainage groove in its face, between the through hole and the waveguide conduit to prevent leakage of cooling fluid into the waveguide. The ducts have narrowed sections immediately adjacent to the flanges to provide room for the installation of fasteners closely around the waveguide channel
Business integration models in the context of web services.
E-commerce development and applications have
been bringing the Internet to business and marketing
and reforming our current business styles and
processes. The rapid development of the Web, in
particular, the introduction of the semantic web and
web service technologies, enables business
processes, modeling and management to enter an
entirely new stage. Traditional web based business
data and transactions can now be analyzed,
extracted and modeled to discover new business
rules and to form new business strategies, let alone
mining the business data in order to classify
customers or products. In this paper, we investigate
and analyze the business integration models in the
context of web services using a micro-payment
system because a micro-payment system is
considered to be a service intensive activity, where
many payment tasks involve different forms of
services, such as payment method selection for
buyers, security support software, product price
comparison, etc. We will use the micro-payment case
to discuss and illustrate how the web services
approaches support and transform the business
process and integration model.
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