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101.
M.G. Spagnuolo F. Grings P. Perna M. Franco H. Karszenbaum V.A. Ramos 《Planetary and Space Science》2011,59(11-12):1222-1230
SHARAD (SHAllow RADar) is a nadir-looking Synthetic Aperture Ground Penetrating Radar on board NASA's 2005 Mars Reconnaissance Orbiter. There are three main characteristics that define the performance of this instrument: ground penetration (due to the operational frequency, the observed echoes can be related to reflections from surface or subsurface), spaceborne operation (the first reflection does not necessarily correspond to the nadir reflection), and nadir looking SAR (there will always be left/right ambiguities). All this implies that there will be surface/subsurface range ambiguity and the geological interpretation of the radargrams cannot be straightforward. In order to avoid data misinterpretation, a simulator of SHARAD’s expected response for a given observation geometry and topography is needed. Simulations can take into account all surface/subsurface reflections in order to identify common families of ambiguities and facilitate the interpretation. In this work we present SHARSIM (SHARAD Radargram SIMulator), a software tool designed to simulate SHARAD radargrams taking as inputs Mars surface information and hypothetical subsurface structure. Its performance is analyzed by investigating typical artifacts and by a direct comparison with real radargrams. We show that SHARSIM simulations can help to discern between artifacts and real subsurface features in order to make accurate geological interpretations. 相似文献
102.
The Sardinia Radio Telescope (SRT) is a challeging scientific project managed by the National Institute for Astrophysics (INAF),
it is being developed at 30 km North of the city of Cagliari, Italy. The goal of the SRT project is to build a general purpose,
fully steerable, 64 m diameter radio telescope, capable of operating with high efficiency in the centimeter and millimeter
frequency range (0.3–100 GHz). In portions of this frequency range, especially towards the high end, astronomical observations
can be heavily deteriorated by non-optimal atmospheric conditions, especially by water vapor content. The water molecule permanent
electric dipole in fact, leads to pressure broadened rotational transitions around the 22.23 GHz spectral line. Furthermore,
water vapor’s continuum absorption and emission may influence higher frequency observations too. To a lower degree, cloud
liquid black body radiation can also affect centimeter and millimeter observations. In addition to this, inhomogeneities in
water vapor distributions can cause signal phase errors which introduce a great amount of uncertainty to VLBI mode observations.
The Astronomical Observatory of Cagliari (OA-CA) has obtained historical timeseries of radiosonde profiles conducted at the
airport of Cagliari. Through the radiosonde measurements and an appropriate radiative transfer model, we have performed a
statistical analysis of the SRT site’s atmosphere which accounts for atmospheric opacity at different frequencies, integrated
water vapor (IWV), integrated liquid water (ILW) and cloud cover distributions during the year. This will help to investigate
in which period of the year astronomical observations at different frequencies should be performed preferably. The results
show that, at the SRT site, K-band astronomical observations are possible all year round, the median opacity at 22.23 GHz
is 0.10 Np in the winter (Dec-Jan-Feb) and 0.16 Np in the summer (Jun-Jul-Aug). Integrated water vapor during winter months
ranges, on average, between 7 and 15 mm. Cloud cover is usually not present for more than 36% of the time during the year.
The atmospheric opacity study indicates that observations at higher frequencies (50–100 GHz) may be performed usefully: the
median opacity at 100 GHz is usually below or equal to 0.2 Np in the period that ranges from January to April. 相似文献
103.
Abstract A long history of overt discrimination left an enduring racialized imprint upon the geography of the East Bay. While the benefits of a metropolitan decentralization of jobs, housing, and public investment fell to Whites, discrimination in employment and housing trapped African Americans in urban neighborhoods burdened by infrastructure encroachment and divestment. By circa 1970, overt discrimination succumbed to new, racially neutral, legal, and administrative forms, including regional planning processes. Using an environmental racism framework, we show that these new forms reproduced the existing racialized geography by means of new inequalities in representation and transportation service provision. These new regional transportation policies, like those challenged by a 2005 civil rights lawsuit, favored the mobility needs of more affluent suburbanites over those of African American East Bay bus riders. These policies, layered onto an existing racialized geography, reinforced existing inequalities by failing to address racial barriers to opportunity in the built environment. [Key words: transportation, race, segregation, Oakland] 相似文献
104.
Soil samples extracted from a contaminated landfill with hexavalent chromium, Cr(VI), were treated in a packed-bed column reactor applying different reductant solutions under controlled flow conditions. In all cases, the kinetic study concerning removal of Cr(VI) from packed soil revealed the overall process (leaching and redox reaction) is described by pseudo-first order kinetics. The complexity of the process taking place in non-isotropic medium (packed soil) was evidenced by dependence of the overall pseudo-first order kinetic rate constant, k*, on treatment time, volumetric flow rate, and composition and concentration of the reductant solution. A phenomenological equation was proposed in order to represent k* in non-ideal conditions. The comparative study concerning the use of different reductants revealed application of ferrous sulphate, Fe(II), under flow conditions furnished the best results, since in this case the redox process reached a considerable extent and the reduced chromium, Cr(III), was immobilized in packed soil as an insoluble mixed compound. 相似文献
105.
Wen-Yi CHANG Jihn-Sung LAI Teng-Yi YU Franco LIN Lung-Cheng LEE Whey-Fone TSAI Chin-Hsiung LOH 《国际泥沙研究》2014,29(2):269-277
A scour monitoring system with a micro camera tracking the bed-level images is proposed in this study.Two image recognition algorithms have been developed to support the bed-level image tracking approach.Through the laboratory experiments of pier scour,this study demonstrates that the proposed system is able to accurately monitor the scour-depth evolution in real time.In addition,five commonly-used temporal scour models are employed to simulate scour-depth evolution and their results are compared with monitoring data.In general,the results indicate that the proposed scour monitoring system has the potential for further applications in the field. 相似文献
106.
107.
Evolution of fluid geochemistry at the Turrialba volcano (Costa Rica) from 1998 to 2008 总被引:3,自引:1,他引:2
O. Vaselli Franco Tassi E. Duarte E. Fernandez R. J. Poreda A. Delgado Huertas 《Bulletin of Volcanology》2010,72(4):397-410
Turrialba (10°02′N, 83°45′W) is a 3,349-m high stratovolcano belonging to the Holocene “Cordillera Central” volcanic belt
of Costa Rica. The summit consists of three EW-oriented craters (East, Central, and West). Since its last eruptive phase (1864–1866),
the Central and West craters have displayed modest fumarolic activity, with outlet temperatures clustering around 90°C. In
2001, seismic swarms, ground deformation, and increasing fumarolic activity occurred. From 2005 to 2008, new fumarolic vents
opened between and within the Central and West craters, and along the western and southwestern outer flanks of the volcanic
edifice. These physical changes were accompanied by a drastic modification in the gas chemistry that can be divided in three
stages: (1) hydrothermal (from 1998 to autumn 2001), characterized by the presence of H2O, CO2, H2S, and, to a very minor extent, HCl and HF; (2) hydrothermal/magmatic (autumn 2001–2007), with the appearance of SO2 and a significant increase of HCl and HF; and (3) magmatic-dominated (2007–2008), characterized by increased SO2 content, SO2/H2S > 100, and temperatures up to 282°C. Accordingly, gas equilibrium in the CO2-CH4-H2 system suggests a progressive evolution of the deep fluid reservoir toward higher temperatures and more oxidizing conditions.
The chemical–physical modifications of Turrialba in the last decade can be interpreted as part of a cyclic mechanism controlling
the balance between the hydrothermal and the magmatic systems. Nevertheless, the risk of rejuvenation of the volcanic activity
cannot be excluded, and an appropriate seismic, ground deformation, and geochemical monitoring program is highly recommended.
Turrialba lies at a distance of 35 and 15 km from San José and Cartago, respectively, the two largest cities in Costa Rica. 相似文献
108.
Biochemical and microbial features of shallow marine sediments along the Terra Nova Bay (Ross Sea,Antarctica) 总被引:1,自引:0,他引:1
Franco Baldi Davide Marchetto Francesco Pini Renato Fani Luigi Michaud Angelina Lo Giudice Daniela Berto Michele Giani 《Continental Shelf Research》2010
Shallow marine sediments were collected from seven stations (three of which located at Gerlache Inlet, two at Tethys Bay, one at Adelie Cove and one just beneath the Italian Research Base) along the Terra Nova Bay coast (Ross Sea, Antarctica). Their chemical, biochemical and microbiological properties were studied in order to provide further insights in the knowledge of this Antarctic benthic ecosystem. Overall, the organic carbon (OC) represented the major fraction of total carbon (TC) and displayed concentrations similar to or slightly lower than those previously measured in Antarctic bottom sediments. The biopolymeric carbon within OC ranged from 4.1% to 19.9% and showed a wide trophic range (65–834 μg g−1 d.w.). Proteins (PRT) represented on average the main biochemical class contributing to labile organic carbon, followed by lipids (LIP) and carbohydrates (CHO). The activity of aminopeptidase, β-d-glucosidase, alkaline phosphatase and esterase was checked, giving the highest values at Tethys Bay and at the deepest water sediments. The principal component analysis, which was computed considering physical, chemical (elemental and biochemical sedimentary composition) and microbiological parameters (including bacterial abundance, ectoenzymatic activities, T-RFs richness and diversity indices), allowed to obtain two main clusters (“Tethys Bay” and “other stations”). Based on data obtained, two representative 16S rRNA clone libraries using samples from Tethys Bay and Gerlache Inlet were constructed. The sequences of 171 clones were compared to those available in public databases to determine their approximate phylogenetic affiliations. Both aerobic and anaerobic bacteria were disclosed, with the majority of them affiliated with the Gamma- and Deltaproteobacteria, Bacteroidetes and Acidobacteria. The occurrence of strictly anaerobic bacteria suggests that sediments might also undergo anoxic conditions that, in turn, could favor the accumulation of PRT in respect to CHO, assuming that fermentation of amino acids is slower than that of sugars from decomposing polysaccharides. 相似文献
109.
Débora V. Franco Wilson F. Jardim Julien F. C. Boodts Leonardo M. Da Silva 《洁净——土壤、空气、水》2008,36(1):34-44
Perspectives, advances and environmental aspects concerning electrochemical ozone production applied to water purification are presented and discussed in relation to the conventional corona process (silent electric discharge). Ozone generated using a laboratory‐made electrochemical reactor was applied for the discoloration/degradation of dyes used in the Brazilian textile industry and for degradation of endocrine disruptors. A constant ozone load of 0.35 ± 0.02 g/h was used throughout. The study, concerning color removal from dye solutions, revealed that total discoloration is rapidly achieved. The degradation rate of the textile dyes evaluated by TOC is little affected by the dye composition and considerably influenced by the pH and ozonation time. Analysis of the COD/TOC‐ratio indicates that ozonation increases oxidation feasibility of the organic matter (dye by‐products) when compared to the original compounds. Ozonation of mixed aqueous solutions containing different endocrine disruptors revealed these compounds are totally degraded with a very high removal rate. 相似文献
110.
Maria de Assunção Franco Jan Vanaverbeke Dick Van Oevelen Karline Soetaert Maria José Costa Magda Vincx Tom Moens 《Marine Ecology》2010,31(2):276-290
Biomass and respiration rates of bacteria, nematodes and macrobenthos were estimated in relation to the deposition of the spring phytoplankton bloom at two contrasting sites in the Southern North Sea: one with fine‐grained sediment close to the coastline and another with highly permeable sediments. Sediment community oxygen consumption (SCOC) was also measured. Bacterial biomass was relatively similar at both stations, whereas nematode and macrobenthic biomass were higher in fine‐grained sediment. In fine sediments, bacterial biomass increased quickly after deposition of the phytoplankton bloom, whereas the response of nematodes and macrobenthos was delayed. In coarser sediments, nematodes and macrobenthos also showed a fast response in terms of density and biomass. Respiration in permeable sediments was mainly dominated by bacteria at all periods of the year. Hence, nematode and macrobenthic respiration did not contribute strongly to SCOC. This is in contrast to the patterns observed in finer sediments, where both macrofauna and nematodes were important oxygen consumers as well. Macrobenthos contributed more to total SCOC than did nematodes in winter. However, shortly after the arrival of phytodetritus at the sea floor, nematodes and macrobenthos contributed equally to the total SCOC, indicating that all benthic size classes should be taken into account when investigating marine benthic respiration rates. 相似文献