10,653 research outputs found
Experimental Design of a Prescribed Burn Instrumentation
Observational data collected during experiments, such as the planned Fire and
Smoke Model Evaluation Experiment (FASMEE), are critical for progressing and
transitioning coupled fire-atmosphere models like WRF-SFIRE and WRF-SFIRE-CHEM
into operational use. Historical meteorological data, representing typical
weather conditions for the anticipated burn locations and times, have been
processed to initialize and run a set of simulations representing the planned
experimental burns. Based on an analysis of these numerical simulations, this
paper provides recommendations on the experimental setup that include the
ignition procedures, size and duration of the burns, and optimal sensor
placement. New techniques are developed to initialize coupled fire-atmosphere
simulations with weather conditions typical of the planned burn locations and
time of the year. Analysis of variation and sensitivity analysis of simulation
design to model parameters by repeated Latin Hypercube Sampling are used to
assess the locations of the sensors. The simulations provide the locations of
the measurements that maximize the expected variation of the sensor outputs
with the model parameters.Comment: 35 pages, 4 tables, 28 figure
Field theoretic calculation of scalar turbulence
The cascade rate of passive scalar and Bachelor's constant in scalar
turbulence are calculated using the flux formula. This calculation is done to
first order in perturbation series. Batchelor's constant in three dimension is
found to be approximately 1.25. In higher dimension, the constant increases as
.Comment: RevTex4, publ. in Int. J. Mod. Phy. B, v.15, p.3419, 200
Long-range Ni/Mn structural order in epitaxial double perovskite La2NiMnO6 thin films
We report and compare the structural, magnetic, and optical properties of
ordered La2NiMnO6 thin films and its disordered LaNi0.5Mn0.5O3 counterpart. An
x-ray diffraction study reveals that the B-site Ni/Mn ordering induces
additional XRD reflections as the crystal symmetry is transformed from a
pseudocubic perovskite unit cell in the disordered phase to a monoclinic form
with larger lattice parameters for the ordered phase. Polarized Raman
spectroscopy studies reveal that the ordered samples are characterized by
additional phonon excitations that are absent in the disordered phase. The
appearance of these additional phonon excitations is interpreted as the
clearest signature of Brillouin zone folding as a result of the long-range
Ni/Mn ordering in La2NiMnO6. Both ordered and disordered materials display a
single ferromagnetic-to-paramagnetic transition. The ordered films display also
a saturation magnetization close to 4.8 mB/f.u. and a transition temperature
(FM-TC) around 270 K, while the disordered ones have only a 3.7 mB/f.u.
saturation magnetization and a FM-TC around 138 K. The differences in their
magnetic behaviours are understood based on the distinct local electronic
configurations of their Ni/Mn cations.Comment: 15 pages, 5 fig
Phase formation, phonon behavior, and magnetic properties of novel ferromagnetic La3BAlMnO9 (B = Co or Ni) triple perovskites
In the quest for novel magnetoelectric materials, we have grown, stabilized
and explored the properties of La3BAlMnO9 (B = Co or Mn) thin films. In this
paper, we report the influence of the growth parameters that promote B/Al/Mn
ordering in the pseudo-cubic unit cell and their likely influence on the
magnetic and multiferroic properties. The temperature dependence of the
magnetization shows that La3CoAlMnO9 is ferromagnetic up to 190 K while
La3NiAlMnO9 shows a TC of 130 K. The behavior of these films are compared and
contrasted with related La2BMnO6 double perovskites. It is observed that the
insertion of AlO6 octahedra between CoO6 and MnO6 suppresses significantly the
strength of the superexchange interaction, spin-phonon and spin-polar coupling.Comment: 13 pages, 3 fig
Multi-locus phylogeny of Pleosporales: a taxonomic, ecological and evolutionary re-evaluation
Five loci, nucSSU, nucLSU rDNA, TEF1, RPB1 and RPB2, are used for analysing 129 pleosporalean taxa representing 59 genera and 15 families in the current classification of Pleosporales. The suborder Pleosporineae is emended to include four families, viz. Didymellaceae, Leptosphaeriaceae, Phaeosphaeriaceae and Pleosporaceae. In addition, two new families are introduced, i.e. Amniculicolaceae and Lentitheciaceae. Pleomassariaceae is treated as a synonym of Melanommataceae, and new circumscriptions of Lophiostomataceae s. str, Massarinaceae and Lophiotrema are proposed. Familial positions of Entodesmium and Setomelanomma in Phaeosphaeriaceae, Neophaeosphaeria in Leptosphaeriaceae, Leptosphaerulina, Macroventuria and Platychora in Didymellaceae, Pleomassaria in Melanommataceae and Bimuria, Didymocrea, Karstenula and Paraphaeosphaeria in Montagnulaceae are clarified. Both ecological and morphological characters show varying degrees of phylogenetic significance. Pleosporales is most likely derived from a saprobic ancestor with fissitunicate asci containing conspicuous ocular chambers and apical rings. Nutritional shifts in Pleosporales likely occured from saprotrophic to hemibiotrophic or biotrophic
Typologie morpho-génétique des marelles du marais littoral de la baie de Kangiqsualujjuaq, estuaire du George, Québec nordique
Des marĂ©es d'un trĂšs grand marnage (12 m aux vives-eaux) caractĂ©risent l'estuaire du George. Dans la partie supĂ©rieure des marais littoraux, la faible frĂ©quence des submersions et l'importance des surfaces Ă dĂ©couvert permettent la croissance de gel intertidal sous forme de buttes de pergĂ©lisol et de gel saisonnier Ă©pais. Sur le marais littoral de la baie de Kangiqsualujjuaq, la dynamique du gel intertidal, l'activitĂ© glacielle et l'action sĂ©dimentaire des vagues, de la marĂ©e et de l'eau de ruissellement sont responsables de la formation et du dĂ©veloppement de plus de 170 marelles littorales. On peut distinguer 10 types de marelles se rĂ©partissant selon le gradient inondation sur le marais, qui se divise topographiquement en marais infĂ©rieur, en marais supĂ©rieur sans gel intertidal et en marais supĂ©rieur avec gel intertidal. Les marelles crĂ©Ă©es par l'action du gel se trouvent dans les parties les plus hautes du marais qui sont protĂ©gĂ©es de l'action des vagues et des glaces flottantes. Les marelles produites par la dynamique sĂ©dimentaire de la baie se situent dans les secteurs exposĂ©s aux agents littoraux, surtout dans l'axe de l'ouverture de la baie sur l'estuaire. Le rĂ©gime de tempĂ©rature et de salinitĂ© des marelles dĂ©pend de facteurs externes, comme la frĂ©quence de submersion par la marĂ©e ou les prĂ©cipitations, mais Ă©galement de facteurs internes, comme la situation topographique et la morphologie des bassins.Very large spring tides with a range of 12 m characterize the George River Estuary. In the upper marsh, unfrequent tidal covering and significant unsheltered areas permit the development of small mounds and heaved marsh surfaces. In the Kangiqsualujjuaq salt marsh, processes related to intertidal ground frost, shore-ice processes and sedimentological processes due to waves, tidal currents and overland flow are responsible of the existence of 170 pans. Ten types of pans are defined. They are distributed along the intertidal topographical gradient including three zones : lower marsh, upper marsh without frost and upper marsh underlain by permafrost. Pans formed by processes related to permafrost are located at the highest parts on the intertidal zone in areas sheltered from waves and ice drifting. Pans originating from hydraulic and sedimentological processes are concentrated in exposed sites that lie opposite of the opening of the bay. Temperature and salinity regimes of the pans depend on the frequency of tidal submersions and precipitations, as well as on topographic situation and basin morphology.Gezeiten mit sehr hoher FluthĂŽhe (12 m Springtiden) charakterisieren die Mundung des George-Flusses. Im oberen Teil der Kusten-Moraste ermoglichen die geringe Ăberschwemmungs-frequenz und erhebliche ungeschutzte Oberflachen die Zunahme von Gezeitenfrost in Form von Dauerfrost-Hugeln und von dichtem, saisonbedingtem Frost. Auf dem Kiisten-Morast der Bucht von Kangiqsualujjuaq sind die Dynamik des Frosts zwischen den Gezeiten, die Frost-AktivitĂ t und die sedimentologische Wirkung der Wellen, der Gezeiten und des rieselnden Wassers verantwortlich fur die Bildung und Entwicklung von mehr als 170 kleinen Kusten-Pfuhlen. Man kann 10 Typen von kleinen Pfuhlen unterscheiden, die sich entsprechend dem ĂberschwemmungsgefĂ lle Ăčber den Morast verteilen, welcher sich topographisch in unteren Morast, hĂŽheren Morast ohne Zwischengezeitenfrost und hĂŽheren Morast mit Zwischengezeitenfrost teilt. Die kleinen, durch Frostwirkung geformten PfĂčhle befinden sich in den hĂŽchsten Teilen des Morasts, die vom Einflup der Wellen und des Treibeises geschĂčtzt sind. Die durch die Sediment-Dynamik der Bucht geschaffenen kleinen PfĂčhle befinden sich in den Abschnitten, die den Einflussen der Kuste ausgesetzt sind, vor allem in der Achse der Ăffnung der Bucht auf die Flufi-Mundung. Das System der Temperatur und des Salzgehalts der kleinen PfĂčhle hĂ ngt von Ăąuperen Faktoren ab, wie die HĂ ufigkeit der Uberschwemmung durch die Flut oder die NiederschlĂ ge, aber auch von inneren Faktoren, wie die topographische Lage und die Morphologie der Becken
Calculation of renormalized viscosity and resistivity in magnetohydrodynamic turbulence
A self-consistent renormalization (RG) scheme has been applied to nonhelical
magnetohydrodynamic turbulence with normalized cross helicity and
. Kolmogorov's 5/3 powerlaw is assumed in order to compute the
renormalized parameters. It has been shown that the RG fixed point is stable
for . The renormalized viscosity and resistivity
have been calculated, and they are found to be positive for all
parameter regimes. For and large Alfv\'{e}n ratio (ratio of
kinetic and magnetic energies) , and . As
is decreased, increases and decreases, untill where both and are approximately zero. For large ,
both and vary as . The renormalized parameters for
the case are also reported.Comment: 19 pages REVTEX, 3 ps files (Phys. Plasmas, v8, 3945, 2001
A Study of Temperature Set Point Strategies for Peak Power Reduction in Residential Buildings
AbstractThis paper presents an experimental and theoretical study of the dynamic response of residential buildings with different levels of thermal mass and their respective space heating peak demands for different room temperature set point profiles. Experiments were conducted at two identical and highly instrumented houses. One of them is modified with different floor coverings, while the other one is kept unchanged and used for reference. Their dynamic response to a night time setback set point profile with step changes is monitored and analyzed. Equivalent RC network thermal models are developed for a north zone of the houses. These models are then used to study the impact of set point ramping lengths and ânear-optimalâ transition curves between two temperatures on the peak demand reductions, while maintaining thermal comfort. It was found that, while taking into consideration the thermal response of the building due to the level of mass, an appropriate yet simple set point strategy to reduce peak electricity demand can be established. For a room with wood flooring, by replacing the conventional night time setback temperature profile with a one hour or two hour ramp, peak demand reductions of up to 10% and 25% can be achieved, respectively
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