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971.
T. Zhu Ph.D. Y. D. Wan M.Sc. J. Li Ph.D. X. W. He Ph.D. D. Y. Xu Ph.D. X. Q. Shu Ph.D. W. J. Liang Ph.D. Y. Q. Jin 《International Journal of Environmental Science and Technology》2011,8(3):621-630
A series of experiments were performed for toluene decomposition from a gaseous influent at normal temperature and atmospheric pressure by nonthermal plasma coupled with a combination of catalysts technology. Nonthermal plasma was generated by dielectric barrier discharge. γ-Al2O3 was used to be a sorbent and a catalyst carrier. Nanocatalysts were MnO2/γ-Al2O3 coupled with modified ferroelectric of nano-Ba0.8Sr0.2Zr0.1Ti0.9O3. γ-Al2O3 played an important role in prolonging reaction time of nonthermal plasma with volatile organic compounds molecules. MnO2/γ-Al2O3 has an advantage for ozone removal, while nano-Ba0.8Sr0.2Zr0.1Ti0.9O3 is a kind of good ferroelectric material for improving energy efficiency. Thus these packed materials were incorporated together to strengthen nonthermal plasma power for volatile organic compounds decomposition. The results showed the synergistic technology resulted in greater enhancement of toluene removal and energy efficiencies and a better inhibition for ozone formation in the gas exhaust. Based on the data analysis of the Fourier transforms infrared spectrum, the reaction process of toluene decomposition and the mechanism of synergistic effect are discussed. The results showed in a complex oxidation mechanism of toluene via several pathways, producing either ringretaining or ringopening products. The final products were carbon dioxide and water. 相似文献
972.
The Sumatra–Andaman Tsunami left distinctive sedimentological and geomorphological signatures in the area of Khao Lak. Fine-grained
sediments, predominantly layers of cohesive, carbonate-rich, fine-sandy silt with thicknesses of 1–10 cm, erosionally overlying
pre-tsunami sandy soils and sediments, represent the most common tsunami deposits in the study area. Petrographically, they
differ significantly from other coastal sediments and affiliated soils. Due to their grain size and corresponding clay mineral
content, muddy shelf sediments (sub-wave base) are indicated as a main source. The present results suggest that indications
of shelf influence, although varying regionally, might contribute to the identification of fine-grained tsunami sediments
and their differentiation from storm sediments. However, the observed differences of tsunami sediments to soils and other
coastal sediments, especially with respect to carbonate mineralogy, might disappear in short geological time under conditions
of intensive weathering and bioturbation. At Cape Pakarang, hundreds of boulders with up to 24 tons were deposited on the
foreshore and upper shoreface. Applying Nott’s (Earth Planet Sci Lett 210:269–276, 2003) formulas, minimum flow velocities of 3.9 m/s are required to transport the largest boulders. The devastating tsunami effect
of both, onshore flow and backflow, is documented by damaged human constructions. Geomorphological effects include intensive
widening of estuary mouths and the development of erosional channels. Now, estuary mouths are reduced, and erosional channels
cut off from the sea due to the formation of a post-tsunami beach ridge. 相似文献
973.
José D. Carriquiry Julio A. Villaescusa Víctor Camacho-Ibar L. Walter Daesslé Pedro G. Castro-Castro 《Environmental Earth Sciences》2011,62(7):1407-1418
During the last century, the Colorado River delta (CRD) has been dramatically altered by the diversion of river water for
use in human activities. This alteration has eliminated the delivery of fresh water to the Gulf of California radically transforming
the former estuary into an inverse-estuary. Under the new conditions, the new materials budget was estimated at the mouth
of the Colorado River in terms of salts, total suspended sediments, organic suspended matter and nutrients. The results of
this study show that, because of the asymmetry of the tidal wave, the variability of seston concentration follows a sedimentation
pattern of three successive stages: re-suspension (erosion at ebb flow) > dilution (during flood flow) > sedimentation (at
the end of the flood stage). The tidal asymmetry during neap tides was characterized by longer ebb (at least, 30 min longer)
than flood and more intense ebb currents (as much as 43% higher), hence characterizing an ebb-dominated system. The CRD is
characterized by high nutrients concentrations. Maximal levels are: nitrates (41 μM), phosphates (2.6 μM) and silicates (68 μM),
nitrite (15 μM). The mass balance indicates that the system acts as a net exporter of suspended sediment with rates as high
as 7 tons per tidal cycle. This behavior indicates that the CRD is in a destructive stage as a result of the lack of freshwater
inflow and supply of sediment into the system. 相似文献
974.
Resolving scales of aquifer heterogeneity using ground penetrating radar and borehole geophysical logging 总被引:1,自引:1,他引:0
Accurate and reliable characterization of aquifer heterogeneity remains one of the foremost problems in hydrogeology. In this
study, ground penetrating radar (GPR) and borehole geophysical logging are used to investigate scales of heterogeneity present
locally (<500 m laterally) within an outwash deposit comprised of inter-bedded and cross-bedded sands and gravels of glaciofluvial
origin. At a small scale (<15 m laterally), gamma log data in adjacent boreholes show evidence of fining upward sequences,
occasional coarsening upward sequences, and abrupt changes in grain sizes, which appear to be laterally continuous at scales
of 10 m. At the site scale (<500 m laterally), GPR profiles show a strong reflection interpreted as the water table. Reflectors
in the unsaturated zone are more clearly defined than those beneath the water table due to signal attenuation within the saturated
sediments. Undulating to discontinuous reflectors at scales of 10–15 m are interpreted to result from interbedded and cross-bedded
sands and gravels. A few laterally continuous horizontal to sub-horizontal reflectors, which extend at least up to 360 m,
are interpreted as unconformities, based on evidence of gravel bars, truncation of underlying units, as well as scour and
fill features in a nearby gravel pit exposure. Overall, the integration of these two geophysical methods provided evidence
of unit correlation at the two scales of investigation. 相似文献
975.
The objective of a field development optimization process, or workflow, is to investigate various options and determine a course of action that will deliver the largest expected value from an asset. The analysis is often complicated by uncertainty in important inputs. Ideally, operators desire workflows and tools that integrate reservoir engineering and optimization principles in a fast-solving model that can be used to explore the full range of the uncertain inputs. This need is acute in the screening and concept selection stage where the primary objective is to determine the sensitivity of competing concepts to the sources of uncertainty. In these early stages, model results can be used to determine whether additional information should be collected, and to narrow down the number of competing options. The objective of this research is the development of a workflow and tool that integrates reservoir response surfaces within a project optimization model that contains facility and operational options, and to use this model to investigate the impacts of uncertainty on decision making. The integration of technical options is critical because a static view of capital investment and facility constraints causes a systematic undervaluation and can introduce error to development decisions. The new workflow and integrated reservoir-economic optimization tool developed in this research leverage methods and engineering work products that are already known to industry, for example, experimental design (ED) and response surface methods (RSMs). A demonstration is provided for a gas flood project using a stylized reservoir. Specifically, we investigate the selection of initial well configurations and injection capacities while simultaneously accounting for the options to update these decisions after production information is acquired in the early periods of production. The workflow is used to optimize the development of a gas flood. As a second step, the workflow is used to solve a value of information problem. 相似文献
976.
Animal treading can change soil physical properties, and thus is an important factor in hydrological modelling. We investigated the impacts of animal treading on infiltration by using a series of rainfall simulation experiments at Whatawhata Research Center, Waikato, New Zealand. The study identified significant variables for estimating soil steady‐state infiltration at a micro‐site (0·5 m2) and fitted the Green and Ampt equation by modifying or including variables for soil and water parameters and animal activities on grazing paddocks. A regression function for estimating steady‐state infiltration rate was created for each of four scenarios: between tracks (inter‐track), track, easy slope with ash soil, and easy slope with clay soil. Significant variables included the number of days after treading, antecedent soil moisture, field capacity, percentage of bare ground, bulk density, and the high degree of soil damage (damage not compacted). Regression models explained more than 71% of the variance in steady‐state infiltration for three scenarios, but only 53% for the easy slope with clay soil. The remodified Green and Ampt equation provided satisfactory estimation of infiltration for all scenarios (accuracy > 80%), and thus enables us to use the modified model for Waikato hill country pastures of different topography, soil physical condition, season and grazing management. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
977.
978.
P. Erdodu J. P. Huchra O. Lahav M. Colless R. M. Cutri E. Falco T. George T. Jarrett D. H. Jones C. S. Kochanek L. Macri J. Mader N. Martimbeau M. Pahre Q. Parker A. Rassat W. Saunders 《Monthly notices of the Royal Astronomical Society》2006,368(4):1515-1526
We estimate the acceleration on the Local Group (LG) from the 2 Micron All-Sky Redshift Survey (2MRS). The sample used includes about 23 200 galaxies with extinction-corrected magnitudes brighter than K s = 11.25 and it allows us to calculate the flux-weighted dipole. The near-infrared flux-weighted dipoles are very robust because they closely approximate a mass-weighted dipole, bypassing the effects of redshift distortions and require no preferred reference frame. This is combined with the redshift information to determine the change in dipole with distance. The misalignment angle between the LG and the cosmic microwave background (CMB) dipole drops to 12°± 7° at around 50 h −1 Mpc , but then increases at larger distances, reaching 21°± 8° at around 130 h −1 Mpc . Exclusion of the galaxies Maffei 1, Maffei 2, Dwingeloo 1, IC342 and M87 brings the resultant flux dipole to 14°± 7° away from the CMB velocity dipole. In both cases, the dipole seemingly converges by 60 h −1 Mpc . Assuming convergence, the comparison of the 2MRS flux dipole and the CMB dipole provides a value for the combination of the mass density and luminosity bias parameters Ω0.6 m / b L = 0.40 ± 0.09 . 相似文献
979.
980.