Consistent scale-dependency of future increases in hourly extreme precipitation in two convection-permitting climate models     

Helsen  Samuel  van Lipzig  Nicole P. M.  Demuzere  Matthias  Vanden Broucke  Sam  Caluwaerts  Steven  De Cruz  Lesley  De Troch  Rozemien  Hamdi  Rafiq  Termonia  Piet  Van Schaeybroeck  Bert  Wouters  Hendrik 《Climate Dynamics》2020,54(3):1267-1280

Climate Dynamics - Convection-permitting models (CPMs) have been proven successful in simulating extreme precipitation statistics. However, when such models are used to study climate change,...  相似文献   

Ionospheric threat simulation for GNSS using the Spirent hardware signal simulator     

Thomas Dautermann  Matteo Sgammini  Sam Pullen 《GPS Solutions》2014,18(3):365-373

Ionospheric disturbances present a considerable hazard to single-frequency satellite navigation systems for airborne users. We discuss our implementation of three ionospheric threat models in the DLR “multi-output advanced signal test environment for receivers” global navigation satellite system simulator, which is based on Spirent GSS 7780/7790 signal generator. These threat models include the standard front-based threat model developed for the integrity assessment of ground-based augmentation systems (GBAS), a simplified plasma bubble model, and ionospheric scintillation, which can be combined with either of the two previously mentioned models. These effects can now straightforwardly be simulated at the German Aerospace Center’s research facilities. As an example, we simulate a GBAS ground facility with code–carrier divergence monitoring, affected by an ionospheric front, and we show the results of a simulation with coincidental occurrence of a plasma bubble and scintillation with an S ₄ index of 0.4.  相似文献   

Water quality impacts from waste rock at a Carlin-type gold mine,Elko County,Nevada   总被引：1，自引：0，他引：1  

Sam?EarmanEmail author  Ronald?L.?Hershey 《Environmental Geology》2004,45(8):1043-1053

Changes in water quality in the North Fork of the Humboldt River, Nevada are caused by weathering of waste rock from an inactive Carlin-type gold mine. Review of historical water-quality data, monthly water sampling, and continuous monitoring of water-quality parameters were used to quantify these impacts. River water pH, which ranged between 7 and 8, did not show statistically significant variation from upstream of the mine to downstream. Several constituents, most notably sulfate, calcium, and magnesium, showed statistically significant increases in dissolved-ion concentrations. These data, along with geochemical modeling, suggest that oxidation of sulfide minerals and in situ acid neutralization by carbonate host rocks are occurring. Large increases in dissolved-ion concentrations were observed twice a year—during spring snow melt and the onset of the winter precipitation season. These spikes are likely caused by flushing of pore waters that have reacted with waste rock during months-long periods when shallow groundwater recharge is not occurring.  相似文献   

Monitoring food web changes in tide-restored salt marshes: A carbon stable isotope approach     

Andrew S. Wozniak  Charles T. Roman  Sam C. Wainright  Richard A. McKinney  Mary-Jane James-Pirri 《Estuaries and Coasts》2006,29(4):568-578

Primary producer (angiosperms, macroalgae, submerged aquatic vegetation), suspended particulate matter, andFundulus heteroclitus isotope values (δ¹³C, δ¹⁵N, δ³⁴S) were examined to assess their use as indicators for changes in food web support functions in tidally-restored salt marshes. Study sites, located throughout the southern New England region (USA), ranged fromSpartina alterniflora-dominated reference marshes, marshes under various regimes and histories of tide restoration, and a severely tide-restrictedPhragmites australis marsh.Fundulus δ¹³C values were greater for fish from referenceSpartina marshes than for fish from adjacent tide-restricted or tide-restored marshes where higher percent cover of C₃ plants, lower water column salinities, and more negative dissolved inorganic δ¹³C values were observed. The difference inFundulus δ¹³C values between a tide-restrictedPhragmites marsh and an adjacent referenceSpartina marsh was great compared to the difference between marshes at various stages of tide restoration and their respective reference marshes, suggesting that food web support functions are restored as the degree of tidal restriction is lessened. While a multiple isotopic approach can provide valuable information for determining specific food sources to consumers, this study demonstrates that monitoringFundulus δ¹³C values alone may be useful to evaluate the trajectory of ecological change for marshes undergoing tidal restoration.  相似文献   

ToF-SIMS and SEM study on the preferential oxidation of chalcopyrite     

Mohammad Al-Harahsheh  Sam Kingman  Frank Rutten  David Briggs 《International Journal of Mineral Processing》2006,80(2-4):205-214

Chalcopyrite is known to be slow reacting mineral in hydrometallurgical systems and is considered one of the most inert sulphide minerals with respect to leaching. Such character of chalcopyrite seems to be linked to a formation of a passive layer on its surface. This work reports that freshly fractured chalcopyrite surfaces exhibit highly selective reactivity depending on the exposed fracture planes. ToF-SIMS was used to qualitatively characterize various fracture planes in freshly fractured chalcopyrite particles, prior to and after hydrometallurgical treatment. It was found that, prior to treatment, certain areas exhibited pronounced contamination from atmospheric hydrocarbons; whereas, others were highly unreactive and remarkably free from adventitious hydrocarbon contamination. The positive ion spectra recorded from these areas were found to be dominated by peaks from Fe- and Cu-elements and related compounds. The negative ion spectra for the reactive areas on the other hand showed a high content of oxidized (sulphur) species.The differences between the areas of low and high reactivity, as detected after leaching, were more subtle than prior to leaching; whereas, SEM analysis showed clear evidence for selective attack of ferric sulphate to specific planes. Furthermore, it was shown that, when chalcopyrite is in intimate contact with pyrite, it experiences an enhanced oxidation compared to when there is no electric contact with pyrite.Attempts were made to explain the preferential oxidation observed based on the different chemistry of the fracture surfaces.  相似文献   

Regional innovation strategies in the knowledge-based economy   总被引：2，自引：0，他引：2  

Sam Ock Park 《GeoJournal》2001,53(1):29-38

This paper aims to examine major regional innovation strategies for regional development in the knowledge-based economy in Korea. Innovation policy and Regional Innovation Systems (RIS) are becoming important issues in Korea in both national and regional perspectives. These issues have been evolving since the mid 1990s, especially since the financial crisis of 1997 in Korea. Five major policy issues for promoting innovation and regional competitiveness are examined in this paper. The major policy issues are: promoting region-specific clustering; building habitats for innovation and entrepreneurship; collective learning processes and innovation networks; building a stock of social capital; and promoting local and global networks. Several strategies are suggested for each of these policy issues. These major policy issues and related strategies for regional innovation and competitiveness can be regarded as common issues required for the successful development of RIS. Taking these basic policy issues into account, each region can develop their own region-specific RIS, with appropriate consideration of distinctive regional characteristics such as the level of development, industrial specialization, local labor market, local business climate, local financial system, etc.  相似文献   

Characteristics of monsoon low level jet (MLLJ) as an index of monsoon activity     

N. V. Sam  K. P. R. Vittal Murty 《Journal of Earth System Science》2002,111(4):453-457

Temperature and wind data are used to describe variation in the strength of the Monsoon Low Level Jet (MLLJ) from an active phase of the monsoon to a break phase. Also estimated are the characteristics of turbulence above and below MLLJ.  相似文献   

Globalization in Korea: dream and reality     

Sam Ock Park 《GeoJournal》1998,45(1-2):123-128

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Vehicles versus conservation of invertebrates on sandy beaches: mortalities inflicted by off-road vehicles on ghost crabs     

Thomas A. Schlacher  Luke Thompson  & Sam Price 《Marine Ecology》2007,28(3):354-367

Sandy beaches face increasing anthropogenic pressures, with vehicle traffic being ecologically highly harmful. Ghost crabs (Fam. Ocypodidae) are conspicuous on many beaches, and they have been used as a bio‐monitoring tool to measure the ecological responses to human disturbance. However, the mechanisms causing declines in crab numbers are unknown, yet conservation must target the actual impact mechanisms. Therefore, we quantified the magnitude and mechanisms of off‐road vehicle (ORV) impacts on ghost crabs, addressing three key questions: (i) Does abundance of ghost crabs respond to traffic intensity?; (ii) Can burrows protect crabs from vehicles? and (iii) Can mortalities caused by vehicles contribute to population declines? ORV‐impacts were measured on North Stradbroke Island (Australia) for Ocypode cordimanus and Ocypode ceratophthalma. Crab densities were significantly lower in areas subjected to heavy beach traffic, suggesting direct crushing by vehicles. Burrows only partially protect crabs against cars: all individuals buried shallow (5 cm) are killed by 10 vehicle passes. Mortality declines with depth of burrows, but remains considerable (10–30% killed) at 20 cm and only those crabs buried at least 30 cm are not killed by ORVs: these ‘deep‐living’ crabs represent about half of the population. After crabs emerge at dusk they are killed in large numbers on the beach surface. A single vehicle can crush up to 0.75% of the intertidal population. While conservation measures should primarily regulate night traffic, our results also emphasise that the fossorial life habits of sandy beach animals cannot off‐set the impacts caused by ORVs.  相似文献   

The carbonate system in hypersaline solutions: dead sea brines     

Eytan Sass  Sam Ben-Yaakov 《Marine Chemistry》1977,5(2):183-199

Various investigators reported a decrease in pH as seawater is concentrated. A similar phenomenon was reported for Dead Sea waters which are about ten times more saline than seawater. The reasons for the low pH values of Dead Sea waters (pH 5.9–6.5), which precipitate CaCO₃, were investigated by determining the apparent dissociation constants of carbonic acid in these brines. A new method, based on alkalinity titration and least-squares fitting, was used to estimate the proton activity coefficient (γ_H+) and the first and second dissociation constants of carbonic acid (K₁′, K₂′) in natural and artificial Dead Sea waters. It was found that as the salt content increases, pK′₁ and pK′₂ values progressively decrease whereas γ_H+ sharply increase. At the highest salinity investigated (TDS = 330 gl^?1) γ_H+ pK′₁ and pK′₂ values are 24.5, 5.09 and 6.23, respectively, as compared to about 0.8, 5.9, 9.1 respectively for normal seawater (19‰ chlorinity) at the same temperature (30°C).The implication of the results of this study regarding solubility of CaCO₃ and the general behavior of the carbonate system in hypersaline solutions is discussed.  相似文献