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591.
L. Duckstein I. Bogrdi F. Szidarovszky D. R. Davis 《Journal of the American Water Resources Association》1975,11(3):425-436
ABSTRACT: Bayesian and non-Bayesian flood levee design methods that account for the uncertainty due to limited record length are compared using a case study. The first method, Bayesian decision theory (BDT), imbeds the uncertainty in the parameters of the yearly peak stage into a loss function. The optimum design of the flood levee, called Bayes design, corresponds to the minimum expected loss, called Bayes risk. The second method, induced safety algorithm (ISA), computes a margin of safety to be added to either an existing levee or a levee designed by classical benefit-cost analysis. The design decision is shown to fluctuate as different record lengths are considered. For short record lengths, BDT, which takes small sample bias into account, appears to yield a more conservative design than ISA. On the other hand, ISA, which is simple to implement, seems to be preferable to BDT for longer record lengths. 相似文献
592.
Jeff Cooper 《Local Environment》2013,18(3):325-330
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596.
Gerard F. Ricardo Andrew R. Davis Nathan A. Knott Todd E. Minchinton 《Marine Biology》2014,161(4):769-784
Variation in the release and recruitment of larvae of estuarine invertebrates affects the distribution and abundance of adults, as well as trophic interactions in both the plankton and the benthos. Larval release and supply are often timed to environmental cycles such as the diel and tidal cycles. Here, we determined using plankton tows whether the abundance of larvae spanning salt marsh and mangrove habitats across the intertidal landscape varied with diel and tidal cycles. Using three different sampling designs across two sites and within each of two estuaries over a 12-month period, we covered a range of spatial and temporal scales. This allowed us to test the general prediction that densities of meroplankton in the water column would be greater during nocturnal ebb tides than during other phases of the diel or tidal cycle. As predicted, nocturnal ebb tides yielded the highest densities of meroplanktonic larvae and were dominated by first-stage crab zoeae and this finding was most pronounced in the salt marsh. Throughout the course of the year, greater numbers of meroplankters consistently occurred during the ebb tide compared with the flood tide. The densities of other taxa (e.g. gastropods and polychaetes) showed no clear trends with diel or tidal cycles. This study highlights the effects of these pervasive physical cycles on the timing of larval release and supply in the salt marsh–mangrove complex, and emphasises their contribution to the trophic interactions and the dynamics of benthic populations within estuaries. 相似文献
597.
Jonathan L. McDonald Richard E. Sykora Paul Hixon Arsalan Mirjafari James H. Davis Jr. 《Environmental Chemistry Letters》2014,12(1):201-208
The reversible capture of CO2 from fossil-fueled industries and the absorption of CO2 for natural-gas-sweetening purposes are industrial issues closely related to very important environmental, economical, and technological concerns. Biological amino acids can be used for task-specific ionic liquids for reversible CO2 capture. Several groups have reported efficient and reversible CO2 capture by such ionic liquids under rigorously dry conditions. However, we have observed that CO2 capture by amino acid ionic liquids is hugely impacted by the presence of water. In addition, the amino acid anions appear to play only a transitory role in the CO2 capture in the first minutes of exposure to a wet CO2 stream. Here, we studied the interaction of two ionic liquids—tetramethylammonium glycinate ([N1111][Gly]) and tetraethylammonium prolinate ([N2222][Pro])—with CO2 under wet conditions, by 13C-NMR. Results show that CO2 is initially captured in a carbamate form by the amine-functionalized anions of these salts. This capture mode is unambiguously confirmed by a single-crystal X-ray study of the CO2-ionic liquid complex. However, in solution, as additional CO2 is added, the carbamate releases the covalently bound CO2, and the CO2 remaining in solution shifts in form to an equilibrium mixture of carbonate and bicarbonate. Indeed, when the amount of CO2 present in the system exceeds about one-half mole per mole of ionic liquid present, the ionic liquid–carbamate complex is detected in only trace amounts, and the neutralized amino acids are readily identifiable by NMR. 相似文献
598.
Urbanization tends to aggravate the negative effects of climate. The objective of this research is to aid in the understanding of the spatial variation of urban heat islands within selected cities in North and South Carolina. This understanding will help guide efforts to cool cities in order to increase human comfort, conserve energy and resources, and reduce air pollution in both of these states. 相似文献
599.
Nanoparticles are not specifically targeted in conventional treatment schemes; consequently, typical wastewater treatment systems are ineffective for nanoparticles removal. With rapidly increasing concern over their health effects, improved understanding of nanoparticle transport and retention in porous media filters is critical because of its application in new wastewater treatment methods and for assessment of the fate of the discharged nanoparticles in soil. In this study, a unique and robust integrated method is developed and validated. Experimentally, this approach uses an on-line, real-time, and in situ method for measuring nanoparticle retention dynamics, eliminating the laborious and less accurate sampling and off-line analysis. The data analysis part is a process simulator which provides both kinetic properties of the retention process as well as the overall capacity and loading. This technique is validated by application to the transport and retention of TiO2 nanoparticles in two vastly different porous filtration media—activated carbon and sand. TiO2 retained concentrations ranged from 0.24 to 0.37 mg g?1 for activated carbon and 0.01–0.014 mg g?1 for sand. The integrated method presented here is useful for both comparison of the filtration effectiveness of various porous materials as well as for process optimization and scale-up for industrial applications. 相似文献
600.
David Cawthon Dyron Hamlin Auburn Steward Cory Davis Finis Cavender Phillip Goad 《毒物与环境化学》2013,95(4):597-604
Ammonia is one of the most widely produced and utilized chemicals in the U.S., and while numerous lab studies have been undertaken, there is no consensus on the odor threshold. In contrast to controlled lab conditions used to determine odor thresholds, the field conditions following unintentional chemical releases are uncontrolled and highly variable due to many factors. A critical component in managing the response to these chemical spills involves understanding how lab data could be applied to uncontrolled field conditions in and around the affected community. It was postulated that analysis of field data collected following accidental releases of ammonia might augment and verify data collected in lab experiments. The widespread transport and use of ammonia has resulted in a number of unintentional releases of ammonia into the environment as a result of train derailments, tanker spills, and plant accidents. In the field studies reported here, air monitoring data were collected following a variety of accidental ammonia releases. Of 6539 readings between 0 and 1 ppm, odor was detected only in 208 samples (3.2%). Of 65 readings between 1.1 and 1.5 ppm, odor was detected in 51 samples (78.5%). These data are consistent with an ammonia odor threshold within a concentration range of 1.1–1.5 ppm. This level is consistent with the recently published odor threshold data for ammonia, but is significantly lower than frequently cited historical data. Furthermore, a review of the ammonia literature demonstrates that the ammonia odor threshold is significantly lower than levels that produce eye, nose, or throat irritation. 相似文献