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301.
Markus Röhricht Jürgen Krisam Ulrich Weise Uta R. Kraus Rolf‐A. Düring 《洁净——土壤、空气、水》2009,37(8):638-641
Most conventional wastewater treatment plants remove very small amounts of micropollutants, such as pharmaceuticals. Here, the ability of two different types of submerged nanofiltration flat sheet modules to remove pharmaceuticals from wastewater is analyzed. The two nanofiltration membranes were used at relatively low pressures of only 0.3 and 0.7 bar. At such low pressures, the membranes did not retain salts to a great extent. This is advantageous in wastewater treatment because no salt concentrate is produced. Carbamazepine was retained only slightly by the nanofiltration membranes, whereas approximately 60% of diclofenac and naproxen were retained by both membranes. This level of effectiveness might not be enough to justify the use of such a system as an additional treatment step in wastewater treatment plants. 相似文献
302.
The OSIRIS‐REx target asteroid (101955) Bennu: Constraints on its physical,geological, and dynamical nature from astronomical observations 下载免费PDF全文
D. S. Lauretta A. E. Bartels M. A. Barucci E. B. Bierhaus R. P. Binzel W. F. Bottke H. Campins S. R. Chesley B. C. Clark B. E. Clark E. A. Cloutis H. C. Connolly M. K. Crombie M. Delbó J. P. Dworkin J. P. Emery D. P. Glavin V. E. Hamilton C. W. Hergenrother C. L. Johnson L. P. Keller P. Michel M. C. Nolan S. A. Sandford D. J. Scheeres A. A. Simon B. M. Sutter D. Vokrouhlický K. J. Walsh 《Meteoritics & planetary science》2015,50(4):834-849
We review the results of an extensive campaign to determine the physical, geological, and dynamical properties of asteroid (101955) Bennu. This investigation provides information on the orbit, shape, mass, rotation state, radar response, photometric, spectroscopic, thermal, regolith, and environmental properties of Bennu. We combine these data with cosmochemical and dynamical models to develop a hypothetical timeline for Bennu's formation and evolution. We infer that Bennu is an ancient object that has witnessed over 4.5 Gyr of solar system history. Its chemistry and mineralogy were established within the first 10 Myr of the solar system. It likely originated as a discrete asteroid in the inner Main Belt approximately 0.7–2 Gyr ago as a fragment from the catastrophic disruption of a large (approximately 100‐km), carbonaceous asteroid. It was delivered to near‐Earth space via a combination of Yarkovsky‐induced drift and interaction with giant‐planet resonances. During its journey, YORP processes and planetary close encounters modified Bennu's spin state, potentially reshaping and resurfacing the asteroid. We also review work on Bennu's future dynamical evolution and constrain its ultimate fate. It is one of the most Potentially Hazardous Asteroids with an approximately 1‐in‐2700 chance of impacting the Earth in the late 22nd century. It will most likely end its dynamical life by falling into the Sun. The highest probability for a planetary impact is with Venus, followed by the Earth. There is a chance that Bennu will be ejected from the inner solar system after a close encounter with Jupiter. OSIRIS‐REx will return samples from the surface of this intriguing asteroid in September 2023. 相似文献
303.
Elaine?R.?MilesEmail author Claire?M.?Spillman John?A.?Church Peter?C.?McIntosh 《Climate Dynamics》2014,43(7-8):2131-2145
Advanced warning of extreme sea level events is an invaluable tool for coastal communities, allowing the implementation of management policies and strategies to minimise loss of life and infrastructure damage. This study is an initial attempt to apply a dynamical coupled ocean–atmosphere model to the prediction of seasonal sea level anomalies (SLA) globally for up to 7 months in advance. We assess the ability of the Australian Bureau of Meteorology’s operational seasonal dynamical forecast system, the Predictive Ocean Atmosphere Model for Australia (POAMA), to predict seasonal SLA, using gridded satellite altimeter observation-based analyses over the period 1993–2010 and model reanalysis over 1981–2010. Hindcasts from POAMA are based on a 33-member ensemble of seasonal forecasts that are initialised once per month for the period 1981–2010. Our results show POAMA demonstrates high skill in the equatorial Pacific basin and consistently exhibits more skill globally than a forecast based on persistence. Model predictability estimates indicate there is scope for improvement in the higher latitudes and in the Atlantic and Southern Oceans. Most characteristics of the asymmetric SLA fields generated by El-Nino/La Nina events are well represented by POAMA, although the forecast amplitude weakens with increasing lead-time. 相似文献
304.
Eight eclipse reappearances of the innermost Galilean satellite, Io, were observed during the fall of 1973. The measurements were made using photometers specially designed to cope with the problem of scattered light from Jupiter. Posteclipse brightening of Io was not detected and, if present, was less than our estimated detection threshold of about 0.02 mag. 相似文献
305.
K.?C.?FredrickEmail author M.?W.?Becker D.?M.?Flewelling W.?Silavisesrith E.?R.?Hart 《Environmental Geology》2004,45(8):1054-1061
Indexing methods are used for the evaluation of aquifer vulnerability and establishing guidelines for the protection of ground-water resources. The principle of the indexing method is to rank influences on groundwater to determine overall vulnerability of an aquifer to contamination. The analytic element method (AEM) of ground-water flow modeling is used to enhance indexing methods by rapidly calculating a potentiometric surface based primarily on surface-water features. This potentiometric map is combined with a digital-elevation model to produce a map of water-table depth. This is an improvement over simple water-table interpolation methods. It is physically based, properly representing surface-water features, hydraulic boundaries, and changes in hydraulic conductivity. The AEM software, SPLIT, is used to improve an aquifer vulnerability assessment for a valley-fill aquifer in western New York State. A GIS-based graphical user interface allows automated conversion of hydrography vector data into analytic elements. 相似文献
306.
307.
Widespread till and moraines record excursions of middle-Pleistocene ice that flowed up-slope into several watersheds of the Valley and Ridge Province along the West Branch of the Susquehanna River. A unique landform assemblage was created by ice-damming and jökulhlaups emanating from high gradient mountain watersheds. This combination of topography formed by multiple eastward-plunging anticlinal ridges, and the upvalley advance of glaciers resulted in an ideal geomorphic condition for the formation of temporary ice-dammed lakes. Extensive low gradient (1°–2° slope) gravel surfaces dominate the mountain front geomorphology in this region and defy simple explanation. The geomorphic circumstances that occurred in tributaries to the West Branch Susquehanna River during middle Pleistocene glaciation are extremely rare and may be unique in the world. Failure of ice dams released sediment-rich water from lakes, entraining cobbles and boulders, and depositing them in elongated debris fans extending up to 9 km downstream from their mountain-front breakout points. Poorly developed imbrication is rare, but occasionally present in matrix-supported sediments resembling debris flow deposits. Clast weathering and soils are consistent with a middle Pleistocene age for the most recent flows, circa the 880-ka paleomagnetic date for glacial lake sediments north of the region on the West Branch Susquehanna River. Post-glacial stream incision has focused along the margins of fan surfaces, resulting in topographic inversion, leaving bouldery jökulhlaup surfaces up to 15 m above Holocene channels. Because of their coarse nature and high water tables, jökulhlaup surfaces are generally forested in contrast to agricultural land use in the valleys and, thus, are readily apparent from orbital imagery. 相似文献
308.
The soil permeability of many natural marine sediments decreases with depth because of consolidation under overburden pressure. This is accompanied by a decrease in porosity and void ratio that also affect the permeability. Conventional theories for wave-induced soil response have assumed a homogeneous porous seabed. This paper presents a new approach for the wave-induced response in a soil matrix, with variable permeability as a function of burial depth. The soil matrix considered is unsaturated and anisotropic, and is subject to a three-dimensional wave system. The pore pressure and effective stresses induced by such a system are obtained from a set of equations incorporating a variable permeability. Verification is available through reduction to the simple case of uniform permeability. The results indicate that the effect of variable soil permeability on pore pressure and vertical effective stress may be significant, especially in a gravelled seabed and for unsaturated sandy soils. 相似文献
309.
Bjorn A. Lake Courtney R. Wigdahl Kristin E. Strock Jasmine E. Saros Aria Amirbahman 《Journal of Paleolimnology》2011,46(1):45-57
The frequency of nuisance algal blooms has been increasing during the last two decades in the shallow, headwater East Pond
(Smithfield, Maine, USA). Meanwhile, the hydrologically linked North Pond has not experienced an increase in algal blooms,
despite similar morphometry and higher external nutrient loads. Possible explanations for this difference include stronger
trophic cascade effects from planktivorous white perch (Morone americana) in East Pond as well as differences in phosphorus (P) release from the sediments of these two lakes. We conducted a paleolimnological
investigation of these two lakes to assess whether sedimentary evidence supported trophic cascade effects based on cladoceran
ephippia size, diatom fossils, and fossil pigments or biogeochemical controls based on potential sedimentary P release as
the primary driver of these increased algal blooms in East Pond. At the time of white perch introduction (~1930–1950), ephippia
size increases in East Pond, although no changes are observed in either diatom abundance or trends in the algal pigments.
Instead, algal pigments increase in recent decades (~1980 to present) along with an increase in diatom taxa with higher TP
optima These results suggest that predation by white perch is not resulting in top-down effects on algal abundance in East
Pond, as predicted by the trophic cascade hypothesis. While the P content of sediments from both lakes is relatively equal,
the releasable P in the top 10 cm of sediment in East Pond constitutes a greater percentage of the P extracted. Also, North
Pond sediments exhibit a greater capacity to permanently bury P via the mechanisms of sorption to Al(OH)3(s) and a slower mineralization of organic P compounds. The results of this investigation suggest that the ultimate driver of
the recent algal blooms in East Pond is internal P release from the sediments instead of trophic cascade effects. 相似文献
310.
Ü. Rannik T. Markkanen J. Raittila P. Hari T. Vesala 《Boundary-Layer Meteorology》2003,109(2):163-189
Observations of wind statistics within and above a Scots pine forest are comparedwith those predicted from an analytical second-order closure model. The roughnesssublayer (RSL) effects, and the influence of stability on similarity functions, arestudied using observations. The commonly accepted forms of similarity functionsdescribe the influence of diabatic effects above the RSL well. According to earlierstudies they are expected also to apply within the RSL. As an exception, the averagewind speed normalised with friction velocity was found to be invariant with stabilityclose to the canopy top under unstable conditions. Lagrangian stochastic trajectorysimulations were used to evaluate the influence of canopy turbulence profiles onfootprint prediction. The main uncertainty was found to arise from parameterisationof the random forcing term in the Lagrangian velocity equation. The influence ofdiabatic conditions was studied, and it was found that thermal stability affectssignificantly the footprint function above the forest canopy, but significantuncertainty exists because of uncertainties in the formulation of stability functions. 相似文献