23,765 research outputs found
An investigation of condensation heat transfer in a closed tube containing a soluble noncondensable gas
A more exact one-dimensional condensation heat transfer model for insoluble gases was developed and compared with experimental data. Modifications to this model to accommodate soluble gas behavior were also accomplished, and the effects on gas front behavior demonstrated. Analytical models for condensation heat transfer are documented, and an optical method used for measuring gas concentration profiles is outlined. Experimental data is then presented and interpreted
DSIF station schedules
System manages Deep Space Instrumentation Facilities /DSIF/ equipment construction and modification planning. Versatile program applies to such tasks as employee time and task schedules, pay schedules, operations schedules, and plant and equipment procurement, construction, modification or service
Derivation of reduced two-dimensional fluid models via Dirac's theory of constrained Hamiltonian systems
We present a Hamiltonian derivation of a class of reduced plasma
two-dimensional fluid models, an example being the Charney-Hasegawa-Mima
equation. These models are obtained from the same parent Hamiltonian model,
which consists of the ion momentum equation coupled to the continuity equation,
by imposing dynamical constraints. It is shown that the Poisson bracket
associated with these reduced models is the Dirac bracket obtained from the
Poisson bracket of the parent model
U-Pb ages and Sr, Pb and Nd isotope data for gneisses near the Kolar Schist Belt: Evidence for the juxtaposition of discrete Archean terranes
Uranium-lead ages and Sr, Pb, and Nd isotopic data for gneisses near the Kolar Schist Belt and their interpretation as evidence for the juxtaposition of discrete Archean terranes were presented. The granodioritic Kambha gneiss east of the schist belt has a zircon age of 2532 + or - 3 Ma and mantle-like initial Sr, Pb, and Nd isotopic ratios. Therefore these gneisses are thought to represent new crust added to the craton in the latest Archean. By contrast, more mafic Dod gneisses and leucocratic Dosa gneisses west of the schist belt (2632 + or - 7 and 2610 + or - 10 Ma) show evidence for contamination of their magmatic precursors (LREE-enriched mantle-derived for the Dod gneisses) by older (greater than 3.2 Ga) continental crust. Fragments of this older crust may be present as granitic and tonalitic inclusions in the 2.6-Ga gneisses and in shear zones. The antiquity of these fragments is supported by their Nd, Sr, and Pb isotopic compositions and by 2.8 to greater than 3.2 Ga zircon cores
Tectonic setting of the Kolar Schist Belt, Karnataka, India
The tectonic setting of the Kolar Schist Belt and why the belt may represent a late Archean suture was discussed. The isotopic and chronological evidence that suggest diverse origins of the various packages of supracrustal rocks within the schist belt and the two gneiss terrains adjoining the belt were summarized. The eastern and western amphibolites were derived from sources at similar depths in the mantle (probably at similar ages, ca. 2.7 Ga), but these sources had distinct trace element compositions and histories. A distinctive feature of these differences was shown by the differences between the east and west amphibolites on a Ce vs. Nd diagram. In the gneisses the age and isotopic evidence suggest that the two terranes had distinct histories until after 2520 Ma and by 2420 Ma (Ar-40/Ar-39 age of muscovite in the sheared margin of the schist belt). Based on these data, the schist belt probably represents the site of accretion of diverse fragments (terrains) to the margin of the craton in the latest Archean, possibly as an Archean analog to the Phanerozoic North American Cordillera
The Kolar Schist Belt: A possible Archaean suture zone
The Kolar Schist Belt represents a N-S trending discontinuity in the structures, lithologies, and emplacement and metamorphic ages of late Archean gneisses. The suggestion of a much older basement on the west side of the belt is not seen on the east. Within the schist belt amphibolites from each side have distinctly different chemical characteristics, suggesting different sources at similar mantle depths. These amphibolites were probably not part of a single volcanic sequence, but may have formed about the same time in two completely different settings. Could the amphibolites with depleted light REE patterns represent Archean ocean floor volcanics which are derived from a mantle source with a long term depletion of the light REE? Why are the amphibolites giving an age which may be older than the exposed gneisses immediately on either side of the belt? These results suggest that it is necessary to seriously consider whether the Kolar Schist Belt may be a suture between two late Archean continental terranes
Changing Consumer Food Prices: A User's Guide to ERS Analyses
USDA's Economic Research Service (ERS) uses different economic models to estimate the impact of higher input prices on consumer food prices. The present study compares three ERS models. In the first two models, neither consumers nor food producers respond to market prices. We refer to these two models as short-run models. In the third model, both consumers and food producers respond to changing prices, and we refer to this model as a long-run model. Given published parameter estimates, we simulate the impact of a higher energy price on consumer food prices, and our empirical findings are consistent with our understanding of market responses. In the short run, we find that the full effect of an increase in the price of energy is fully (or nearly fully) passed on to consumers, because neither food producers nor consumers can immediately respond to changing prices. In the long run, however, the price response of food producers and consumers serves to mitigate the increase in consumer food prices.price-spread model, input-output model, variable-proportions model, food prices, energy prices, input prices, Demand and Price Analysis,
On the use of projectors for Hamiltonian systems and their relationship with Dirac brackets
The role of projectors associated with Poisson brackets of constrained
Hamiltonian systems is analyzed. Projectors act in two instances in a bracket:
in the explicit dependence on the variables and in the computation of the
functional derivatives. The role of these projectors is investigated by using
Dirac's theory of constrained Hamiltonian systems. Results are illustrated by
three examples taken from plasma physics: magnetohydrodynamics, the
Vlasov-Maxwell system, and the linear two-species Vlasov system with
quasineutrality
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