New chelating resin for preconcentration and determination of molybdenum by inductive couple plasma atomic emission spectroscopy     

H. Sid Kalal Ph.D.  H. Ahmad Panahi Ph.D.  N. Framarzi  E. Moniri Ph.D.  A. Naeemy  H. Hoveidi Ph.D.  A. Abhari 《International Journal of Environmental Science and Technology》2011,8(3):501-512

A chelating resin is prepared by condensation polymerization of aniline with formaldehyde and characterized by Fourier transform infrared spectrometer, elemental analysis and thermogravimetric analysis and studied for the preconcentration and determination of trace Molybdate ion from environmental water sample using inductive couple plasma atomic emission spectroscopy. The optimum pH value for sorption of the metal ion was 5. The sorption capacity of functionalized resin is 3.1 mg/g. The chelating sorbent can be reused for 20 cycles of sorption-desorption without any significant change in sorption capacity. The best desorption of the metal ions from resin was obtained by 0.5 mol/L nitric acid as eluting agent. The profile of molybdenum uptake on this sorbent reflects good accessibility of the chelating sites in the aniline-formaldehyde. Scatchard analysis revealed that the homogeneous binding sites were formed in the polymers. The equilibrium adsorption data of Molybdate ion modified resin were analyzed by five isotherm models such as Langmuir, Freundlich and Temkin. Langmuir isotherm parameters obtained from the four Langmuir linear equations by using linear method. Based on the Langmuir isotherm analysis, the monolayer adsorption capacity was determined to be 4.03 mg/g at 20 °C. The method was applied for molybdenum ions determination from river water sample.  相似文献   

Turbulent Transfer Between Street Canyons and the Overlying Atmospheric Boundary Layer   总被引：1，自引：1，他引：0  

Pietro Salizzoni  Massimo Marro  Lionel Soulhac  Nathalie Grosjean  Richard J. Perkins 《Boundary-Layer Meteorology》2011,141(3):393-414

The turbulent exchange of momentum between a two-dimensional cavity and the overlying boundary layer has been studied experimentally, using hot-wire anemometry and particle image velocimetry (PIV). Conditions within the boundary layer were varied by changing the width of the canyons upstream of the test canyon, whilst maintaining the square geometry of the test canyon. The results show that turbulent transfer is due to the coupling between the instabilities generated in the shear layer above the canyons and the turbulent structures in the oncoming boundary layer. As a result, there is no single, unique velocity scale that correctly characterizes all the processes involved in the turbulent exchange of momentum across the boundary layer. Similarly, there is no single velocity scale that can characterize the different properties of the turbulent flow within the canyon, which depends strongly on the way in which turbulence from the outer flow is entrained into the cavity and carried round by the mean flow. The results from this study will be useful in developing simple parametrizations for momentum exchange in the urban canopy, in situations where the street geometry consists principally of relatively long, uniform streets arranged in grid-like patterns; they are unlikely to be applicable to sparse geometries composed of isolated three-dimensional obstacles.  相似文献   

The Barny Sentinel trawl-resistant ADCP bottom mount: design,testing, and application     

Perkins  H. de Strobel  F. Gualdesi  L. 《Oceanic Engineering, IEEE Journal of》2000,25(4):430-436

A trawl-resistant bottom mount (TRBM) has been developed to meet the needs of long-term deployment of Acoustic Doppler Current Profilers (ADCPs) and Wave-Tide Gauges in water depths up to 300 m. This paper describes the unit's construction and operation together with practical lessons learned during development, testing, and use that can be applied to comparable platforms. The Barny Sentinel is derived from a larger version developed several years ago at SACLANT Center, now extensively redesigned to incorporate an RDI Sentinel ADCP and a Sea-Bird Wave-Tide Gauge. A concrete ring surrounding the fiberglass instrument housing serves as ballast and impact protection. Two independent recovery modes may be activated by acoustic commands, one of which can operate whether or not the platform is upright. Features have also been included to facilitate recovery by remotely operated underwater vehicle. A sending unit, temporarily attached during launch, provides real time information on platform depth and tilt, and confirms that the platform is properly positioned on the bottom before a launch commitment is made. A series of tests and applications have validated all basic functions and trawl resistance. Platform cost has been kept below that of the on-board instruments, while still maintaining the required high level of recoverability  相似文献   

Seasonal distribution and growth of larval herring (Clupea harengus L.) in the Georges Bank-Gulf of Maine area from 1962 to 1970     

Boyar  H. C.; Marak  R. R.; Perkins  F. E.; Clifford  R. A. 《ICES Journal of Marine Science》1973,35(1):36-51

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Circulation and currents in the southwestern East/Japan Sea: Overview and review     

K.-I. Chang  W.J. Teague  S.J. Lyu  H.T. Perkins  D.-K. Lee  D.R. Watts  Y.-B. Kim  D.A. Mitchell  C.M. Lee  K. Kim 《Progress in Oceanography》2004,61(2-4):105

A review is made of circulation and currents in the southwestern East/Japan Sea (the Ulleung Basin), and the Korea/Tsushima Strait which is a unique conduit for surface inflow into the Ulleung Basin. The review particularly concentrates on describing some preliminary results from recent extensive measurements made after 1996. Mean flow patterns are different in the upstream and downstream regions of the Korea/Tsushima Strait. A high velocity core occurs in the mid-section in the upstream region, and splits into two cores hugging the coasts of Korea and Japan, the downstream region, after passing around Tsushima Island located in the middle of the strait. Four-year mean transport into the East/Japan Sea through the Korea/Tsushima Strait based on submarine cable data calibrated by direct observations is 2.4 Sv (1 Sv = 10⁶ m³ s⁻¹). A wide range of variability occurs for the subtidal transport variation from subinertial (2–10 days) to interannual scales. While the subinertial variability is shown to arise from the atmospheric pressure disturbances, the longer period variation has been poorly understood.Mean upper circulation of the Ulleung Basin is characterized by the northward flowing East Korean Warm Current along the east coast of Korea and its meander eastward after the separation from the coast, the Offshore Branch along the coast of Japan, and the anticyclonic Ulleung Warm Eddy that forms from a meander of the East Korean Warm Current. Continuous acoustic travel-time measurements between June 1999 and June 2001 suggest five quasi-stable upper circulation patterns that persist for about 3–5 months with transitions between successive patterns occurring in a few months or days. Disappearance of the East Korean Warm Current is triggered by merging the Dok Cold Eddy, originating from the pinching-off of the meander trough, with the coastal cold water carried Southward by the North Korean Cold Current. The Ulleung Warm Eddy persisted for about 20 months in the middle of the Ulleung Basin with changes in its position and spatial scale associated with strengthening and weakening of the transport through the Korea/Tsushima Strait. The variability of upper circulation is partly related to the transport variation through the Korea/Tsushima Strait. Movements of the coastal cold water and the instability of the polar front also appear to be important factors affecting the variability.Deep circulation in the Ulleung Basin is primarily cyclonic and commonly consists of one or more cyclonic cells, and an anticyclonic cell centered near Ulleung Island. The cyclonic circulation is conjectured to be driven by a net inflow through the Ulleung Interplain Gap, which serves as a conduit for the exchange of deep waters between the Japan Basin in the northern East Sea and the Ulleung Basin. Deep currents are characterized by a short correlation scale and the predominance of mesoscale variability with periods of 20–40 days. Seasonality of deep currents is indistinct, and the coupling of upper and deep circulation has not been clarified yet.  相似文献   

Smoothed Particle Hydrodynamics for modelling landslide–water interaction problems     

Mahallem  Abderrahmane  Roudane  Mohamed  Krimi  Abdelkader  Gouri  Sid Ahmed 《Landslides》2022,19(5):1249-1263

Landslides - This work aims to develop a Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) in-house code for modelling landslide–water interaction problems. While we consider the...  相似文献   

Climate variability,snow, and physiographic controls on storm hydrographs in small forested basins,western Cascades,Oregon     

Reed M. Perkins  Julia A. Jones 《水文研究》2008,22(25):4949-4964

Large floods are often attributed to the melting of snow during a rain event. This study tested how climate variability, snowpack presence, and basin physiography were related to storm hydrograph shape in three small (<1 km²) basins with old‐growth forest in western Oregon. Relationships between hydrograph characteristics and precipitation were tested for approximately 800 storms over a nearly 30‐year period. Analyses controlled for (1) snowpack presence/absence, (2) antecedent soil moisture, and (3) hillslope length and gradient. For small storms (<150 mm precipitation), controlling for precipitation, the presence of a snowpack on near‐saturated soil increased the threshold of precipitation before hydrograph rise, extended the start lag, centroid lag, and duration of storm hydrographs, and increased the peak discharge. The presence of a snowpack on near‐saturated soil sped up and steepened storm hydrographs in a basin with short steep slopes, but delayed storm hydrographs in basins with longer or more gentle slopes. Hydrographs of the largest events, which were extreme regional rain and rain‐on‐snow floods, were not sensitive to landform characteristics or snowpack presence/absence. Although the presence of a snowpack did not increase peak discharge in small, forested basins during large storms, it had contrasting effects on storm timing in small basins, potentially synchronizing small basin contributions to the larger basin hydrograph during large rain‐on‐snow events. By altering the relative timing of hydrographs, snowpack melting could produce extreme floods from precipitation events whose size is not extreme. Further work is needed to examine effects of canopy openings, snowpack, and climate warming on extreme rain‐on‐snow floods at the large basin scale. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Whipple telescope observations of LS I +61 303: 2004–2006     

A. Smith  R. W. Atkins  S. Bradbury  O. Celik  Y. C. K. Chow  P. Cogan  C. Dowdall  S. J. Fegan  P. Fortin  D. Gall  G. H. Gillanders  J. Grube  K. J. Gutierrez  T. A. Hall  D. Hanna  J. Holder  D. Horan  S. B. Hughes  T. B. Humensky  I. Jung  P. Kaaret  G. Kenny  M. Kertzman  D. B. Kieda  A. Konopelko  H. Krawczynski  F. Krennrich  M. J. Lang  S. Le Bohec  G. Maier  J. Millis  P. Moriarty  R. A. Ong  J. S. Perkins  K. Ragan  G. H. Sembroski  J. A. Toner  L. Valcarcel  V. V. Vassiliev  R. G. Wagner  S. P. Wakely  T. C. Weekes  R. J. White  D. A. Williams 《Astrophysics and Space Science》2007,309(1-4):299-303

In this paper we present the results of the past two years observations on the galactic microquasar LS I +61 303 with the Whipple 10 m gamma-ray telescope. The recent MAGIC detection of the source between 200 GeV and 4 TeV suggests that the source is periodic with very high energy (VHE) gamma-ray emission linked to its orbital cycle. The entire 50-hour data set obtained with Whipple from 2004 to 2006 was analyzed with no reliable detection resulting. The upper limits obtained in the 2005–2006 season covered several of the same epochs as the MAGIC Telescope detections, albeit with lower sensitivity. Upper limits are placed on emission during the orbital phases of 0→0.1 and 0.8→1, phases which are not included in the MAGIC data set.   相似文献   

Arsenic within the secondary environment resulting from geogenic inputs,Harlech Dome,United Kingdom     

Graham Bird  Hannah E. G. Bell  William T. Perkins 《Environmental Earth Sciences》2014,72(9):3521-3530

There has been a growing awareness of As in the environment due to both anthropogenic and geogenic loading. This study quantifies the presence of As in river water, river sediment and groundwater within the Harlech Dome region of the UK, an area underlain by Cambro–Ordovician aged mineralization. Published data regarding As levels in UK groundwater are relatively rare compared to elsewhere. Arsenic levels in groundwater (0.1–18 µg l^?1) and river sediment (1.5–142 mg kg^?1) exceed environmental quality guidelines and indicate the release of As into the secondary environment from predominantly geogenic sources. Modelling of dissolved As speciation using ORP–pH diagrams predicts the presence of As in both arsenate (As⁵⁺) and arsenous acid (As³⁺) species, which possess differing solubilities and mobilities. Calculation of enrichment factors (EFs) for As in river sediments, using Al as a reference element, indicates highest EFs, and therefore As release, occurs in streams draining the Coed-y-Brenin region in the south-east of the Harlech Dome. This area is underlain by an as yet unexploited porphyry copper deposit. Data indicate that the presence of potentially harmful elements within the environment may occur with or without the presence of major anthropogenic activity.  相似文献   

Multistage evolution of the European lithospheric mantle: new evidence from Sardinian peridotite xenoliths     

Luigi Beccaluva  Gianluca Bianchini  Massimo Coltorti  William Perkins  Franca Siena  Carmela Vaccaro  Marjorie Wilson 《Contributions to Mineralogy and Petrology》2001,142(3):284-297

Peridotite xenoliths entrained in Plio-Pleistocene alkali basalts from Sardinia represent fragments of the uppermost lithospheric mantle, and are characterised by an anhydrous four-phase mineral assemblage. They range in bulk rock composition from fertile spinel-lherzolites to residual spinel-harzburgites. The Sr-Nd isotope and trace element composition of clinopyroxene mineral separates varies between LREE-depleted samples with ⁸⁷Sr/⁸⁶Sr as low as 0.70262 and ¹⁴³Nd/¹⁴⁴Nd up to 0.51323 and LREE-enriched samples with ⁸⁷Sr/⁸⁶Sr up to 0.70461 and ¹⁴³Nd/¹⁴⁴Nd down to 0.51252. The available data suggest that all the studied peridotite samples suffered variable degrees of partial melting during Pre-Mesozoic times (based on Nd model ages relative to CHUR and DMM). The overprinted enrichment is related to a subsequent metasomatism, induced by fluids rising through the lithosphere that preferentially percolated the originally most depleted domains. Despite the occurrence of orogenic volcanism in the area, preferential enrichment in elements typically associated with slab derived fluids/melts (K, Rb, Sr, Th) relative to LREE has not been detected, and metasomatism seems to be more likely related to the infiltration of highly alkaline basic melts characterised by an EM-like Sr-Nd isotopic composition. Similar ⁸⁷Sr/⁸⁶Sr-¹⁴³Nd/¹⁴⁴Nd compositions, characterised by an EM signature, are observed in anorogenic mafic lavas and peridotite xenoliths from widespread localities within the "European" plate, whereas they have not previously been recorded in peridotite xenoliths and associated alkaline mafic lavas from the stable "African" lithospheric domain.  相似文献