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11.
A.R. Mosier J.A. Delgado V.L. Cochran D.W. Valentine W.J. Parton 《Nutrient Cycling in Agroecosystems》1997,49(1-3):71-83
Increasing concentrations of methane (CH4) in the atmosphere are projected to account for about 25% of the net radiative forcing. Biospheric emissions of CH4 to the atmosphere total approximately 400 Tg C y-1. An estimated 300 Tg of CH4-C y-1 is oxidized in the atmosphere by hydroxyl radicals while about 40 Tg y-1 remains in the atmosphere. Approximately 40 Tg y-1 of the atmospheric burden is oxidized in aerobic soils. Research efforts during the past several years have focused on quantifying
CH4 sources while relatively less effort has been directed toward quantifying and understanding the soil sink for atmospheric
CH4.
Recent research has demonstrated that land use change, including agricultural use of native forest and grassland systems has
decreased the soil sink for atmospheric methane. Some agricultural systems consume atmospheric CH4 at rates less than 10% of those found in comparable undisturbed soils.
While it has been necessary to change land use practices over the past centuries to meet the required production of food and
fiber, we need to recognize and account for impacts of land use change on the biogeochemical nutrient cycles in the biosphere.
Changes that have ensued in these cycles have and will impact the atmospheric concentrations of CH4 and N2O. Since CH4 and N2O production and consumption are accomplished by a variety of soil microorganisms, the influence of changing agricultural,
forest, and, demographic patterns has been large. Existing management and technological practices may already exist to limit
the effect of land use change and agriculture on trace gas fluxes. It is therefore important to understand how management
and land use affect trace gas fluxes and to observe the effect of new technology on them.
This paper describes the role of aerobic soils in the global CH4 budget and the impact of agriculture on this soil CH4 sink. Examples from field studies made across subarctic, temperate and tropical climate gradients in grasslands are used
to demonstrate the influence of nutrient cycle perturbations on the soil consumption of atmospheric CH4 and in increased N2O emissions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
M.D. Foster I. Rivin M.M.J. Treacy O. Delgado Friedrichs 《Microporous and mesoporous materials》2006,90(1-3):32-38
We have applied Delaunay triangulation to models of the known zeolite frameworks. We show that this well-established technique from computational geometry provides for each framework; (i) the location and shape of the open pores and channels, (ii) the diameter of the largest possible included sphere, and indirectly (iii) the diameter of the largest-free-sphere that can diffuse through the framework by at least one lattice translation. Since Delaunay triangulation naturally locates the empty spaces within a set of points, it provides a powerful computer-automated tool for determining the physical characteristics of pores and channels of zeolite frameworks. Such tools will further enhance the usefulness of large databases of hypothetical framework materials.
Here, we tabulate results for the 165 zeolite frameworks that are presently listed in the Atlas of Zeolite Frameworks. Of the known zeolites, refined as pure silicates, the largest included sphere occurs in the TSC framework, with a diameter of 16.39 Å. The largest-free-sphere has a diameter of 11.33 Å, for diffusion along the [0 0 1] direction in the VFI framework. 相似文献
13.
In the present study, different types of 75% Cr3C2-25% NiCr coatings were applied on a steel substrate by means of high velocity oxygen fuel spraying (HVOF), and studied using ac and dc electrochemical measurements in an aerated and unstirred 0.5 M H2SO4 solution. Structural characterization was determined before and after electrochemical tests. Differences between all sprayed systems are related to the gun transverse speed and number of deposited layers, which strongly affected the electrochemical characteristics of the coated steels. The coating obtained with a higher torch speed showed better resistance against corrosion. The electrochemical impedance results were analyzed using an equivalent circuit where porosity of the coatings and substrate oxidation were considered. 相似文献
14.
Procopio Lorenzo M. Delgado Francisco Enríquez Marco Belabas Nadia 《Quantum Information Processing》2021,20(6):1-3
Quantum Information Processing - A Correction to this paper has been published: https://doi.org/10.1007/s11128-019-2234-5 相似文献
15.
Nirvana Delgado Otalvaro Pembe Gül Bilir Karla Herrera Delgado Stephan Pitter Jörg Sauer 《化学,工程师,技术》2021,93(5):754-761
Artificial neural networks (ANNs) are designed and implemented to model the direct synthesis of dimethyl ether (DME) from syngas over a commercial catalyst system. The predictive power of the ANNs is assessed by comparison with the predictions of a lumped model parameterized to fit the same data used for ANN training. The ANN training converges much faster than the parameter estimation of the lumped model, and the predictions show a higher degree of accuracy under all conditions. Furthermore, the simulations show that the ANN predictions are also accurate even at some conditions beyond the validity range. 相似文献
16.
T. E. Howson D.E.Sc. H. E. Delgado Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1989,41(2):32-34
By simulating the flow of metal in forging, engineers can eliminate defects and undesirable flow patterns. Localized deformation heating of the forging can be predicted and avoided, with a resulting improvement of quality. 相似文献
17.
Gerti Daschiel Milovan Perić Jovan Jovanović Antonio Delgado 《Microfluidics and nanofluidics》2013,15(5):675-687
The sub-laminar drag effect of microgroove surfaces was studied numerically in a steady two-dimensional channel flow at subcritical Reynolds numbers. Considerations are restricted to grooves of a few viscous length scales in depth, which are assumed not to promote the laminar to turbulent transition process. It was found that the drag reduction effect is due to the layout of grooves with respect to the flow direction and contour geometry. Results of computations show that for grooves of curved contour placed normal to the flow direction, drag arising from viscous and pressure forces is modulated due to the functional dependence of forces on the surface area projected in the flow direction. Such a groove layout leads to a large skin-friction reduction, but a comparable increase in pressure drag results in sub-laminar drag if drag over flat surface is considered as a reference. For a curved groove contour, the drag reduction increases with increasing Reynolds number and reaches about 5 % at Reynolds numbers approaching critical. 相似文献
18.
M Delgado EJ Munoz-Elias Y Kan I Gozes M Fridkin DE Brenneman RP Gomariz D Ganea 《Canadian Metallurgical Quarterly》1998,273(47):31427-31436
19.
Generated interfacial waves are under investigation in this paper. The flow field and the movement of the interface between two stratified newtonian fluids will be considered. Cylindrical geometry is examined. All results are given in an analytical form. With the help of an algebraic computation programm it is possible to reduce computation time for parameter studies. The dependence of the wavenumber of several dimensionless groups are studied intensively.List of symbols
a(
j
), b(
j
)
integration constants
-
Â
wave amplitude at the origin
-
g
acceleration due to gravity
-
h
interface distortion
-
i
imaginary unit
-
J
0, J
1
zero/first order Bessel function
-
k
1, k
1(
j
), k
2(
j
)
complex wave numbers
-
p(
j
)
pressure
-
t
time
-
v
r
j
, v
z
j
velocity component in r and z direction
-
Re(
j
), Bo, We
Reynolds, Bond and Weber number
-
R
density ratio
-
wavelength
- µ
j
, v
j
dynamic/kinematic fluid viscosity
-
j
fluid density
-
interfacial tension
-
non dimensional time
-
j
potential function
-
j
stream function
J=1, 2, where the index 1 refers to the upper fluid and the index 2 refers to the lower fluid. In the text the asterisk indicates non dimensional quantities. 相似文献
20.