Simulating an optical guidance system for the recovery of anunmanned underwater vehicle     

Deltheil  C. Didier  L. Hospital  E. Brutzman  D.P. 《Oceanic Engineering, IEEE Journal of》2000,25(4):568-574

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Detection of Hg pollution by stream sediment geochemistry in the Bisagno valley (Genoa, Italy)     

L. Marini  G. Ottonello  M. Canepa  F. Cipolli  M. Vetuschi Zuccolini 《Environmental Geology》2000,40(1-2):234-242

 Systematic stream sediment investigation in a periurban area surrounding Genoa (Italy) revealed the existence of a significant mercury anomaly localized on the main (3rd rank) bed of the Bisagno river. Statistical multivariate analysis of elemental abundances points out the anthropic nature of this contamination. Because of the well-known bioaccumulation of Hg in contaminated media, attention must be focused on the risks associated with the discovered pollution. Received: 30 November 1999 · Accepted: 22 March 2000  相似文献   

Surface current measurements by HF radar in freshwater lakes     

Fernandez  D.M. Meadows  L.A. Vesecky  J.F. Teague  C.C. Paduan  J.D. Hansen  P. 《Oceanic Engineering, IEEE Journal of》2000,25(4):458-471

HF radar has become an increasingly important tool for mapping surface currents in the coastal ocean. However, the limited range, due to much higher propagation loss and smaller wave heights (relative to the saltwater ocean), has discouraged HF radar use over fresh water, Nevertheless, the potential usefulness of HF radar in measuring circulation patterns in freshwater lakes has stimulated pilot experiments to explore HF radar capabilities over fresh water. The Episodic Events Great Lakes Experiment (EEGLE), which studied the impact of intermittent strong wind events on the resuspension of pollutants from lake-bottom sediments, provided an excellent venue for a pilot experiment. A Multifrequency Coastal HF Radar (MCR) was deployed for 10 days at two sites on the shore of Lake Michigan near St. Joseph, MI. Similarly, a single-frequency CODAR SeaSonde instrument was deployed on the California shore of Lake Tahoe. These two experiments showed that when sufficiently strong surface winds (2 about 7 m/s) exist for an hour or more, a single HE radar can be effective in measuring the radial component of surface currents out to ranges of 10-15 km. We also show the effectiveness of using HF radar in concert with acoustic Doppler current profilers (ADCPs) for measuring a radial component of the current profile to depths as shallow as 50 cm and thus potentially extending the vertical coverage of an ADCP array  相似文献   

Peperite: a useful genetic term     

James D. L. White  Jocelyn McPhie  Ian Skilling 《Bulletin of Volcanology》2000,62(1):65-66

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Chemical composition and leaching characteristics of granules made of wood ash and dolomite     

S. L. Holmberg  B. B. Lind  T. Claesson 《Environmental Geology》2000,40(1-2):1-10

 In 1995, the central heating plant Draken in Kalmar, Sweden, started manufacturing a granular ash product for nutrient recycling to forest soil, instead of dumping the ash in landfills. Chemical composition, leaching and dissolution characteristics were determined for the Draken wood ash, the dolomite used in granule manufacturing and the final granule product. The heavy metal concentrations in fly ash were within the limit values recommended by the Swedish National Board of Forestry for ash recycling, except for Cd and As levels which occasionally exceeded the limit values. The Ca, Mn and P levels were too low for nutrient recycling at the time. Adding dolomite insures that the levels of the important nutrients Ca and Mg are sufficient in the granules. After 7 months in the field, about 60 % of Na and K was leached out from granules. Between 20 and 60% of trace elements Mo, Sc, V, Y and Zr were leached out after 7 months. The release of Ca and Mg was low, 1–5% during 7 months. Received: 12 July 1999 · Accepted: 31 August 1999  相似文献   

Hydrogeology of limited aquifer in a granitic terrain     

V. S. Singh  V. Krishnan  M. R. K. Sarma  C. P. Gupta  R. L. Dhar 《Environmental Geology》1999,37(1-2):90-95

 Detailed hydrogeological studies in a granitic micro-watershed have been carried out to determine the extent, behavior, and characteristics of the aquifer. The study includes analysis of lithologs, drill time log, pumping tests, and slug tests. Realistic field conditions have been taken into account for characterizing the aquifer system. Slug tests were carried out to estimate aquifer parameters at the wells which could not sustain pumping. Received: 20 November 1997 · Accepted: 23 February 1998  相似文献   

Evolution of the Australian lithosphere     

P. G. Betts  D. Giles  G. S. Lister  L. R. Frick 《Australian Journal of Earth Sciences》2013,60(4):661-695

The evolution of the Australian plate can be interpreted in a plate‐tectonic paradigm in which lithospheric growth occurred via vertical and horizontal accretion. The lithospheric roots of Archaean lithosphere developed contemporaneously with the overlying crust. Vertical accretion of the Archaean lithosphere is probably related to the arrival of large plumes, although horizontal lithospheric accretion was also important to crustal growth. The Proterozoic was an era of major crustal growth in which the components of the North Australian, West Australian and South Australian cratons were formed and amalgamated during a series of accretionary events and continent‐continent collisions, interspersed with periods of lithospheric extension. During Phanerozoic accretionary tectonism, approximately 30% of the Australian crust was added to the eastern margin of the continent in a predominantly supra‐subduction environment. Widespread plume‐driven rifting during the breakup of Gondwana may have contributed to the destruction of Archaean lithospheric roots (as a result of lithospheric stretching). However, lithospheric growth occurred at the same time due to mafic underplating along the eastern margin of the plate. Northward drift of Australia during the Tertiary led to the development of a complex accretionary margin at the leading edge of the plate (Papua New Guinea).  相似文献   

Observed intra-seasonal to interannual variability of the upper ocean thermal structure in the southeastern Arabian Sea during 2002–2008     

V.V. Gopalakrishna  F. Durand  K. Nisha  M. Lengaigne  T.P. Boyer  J. Costa  R.R. Rao  M. Ravichandran  S. Amrithash  L. John  K. Girish  C. Ravichandran  V. Suneel 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(6):739-754

The southeastern Arabian Sea (SEAS), located in the Indian Ocean warm pool, is a key-region of the regional climate system. It is suspected to play an important role in the dynamics of the Asian summer monsoon system. The present study reports the salient features derived from a newly harvested observational dataset consisting of repeated fortnightly XBT transects in the SEAS over the period 2002–2008. The fortnightly resolution of such a multi-year record duration is unprecedented in this part of the world ocean and provides a unique opportunity to examine the observed variability of the near-surface thermal structure over a wide spectrum, from intra-seasonal to interannual timescales. We find that most of the variability is trapped in the thermocline, taking the form of upwelling and downwelling motions of the thermal stratification. The seasonal variations are consistent with past studies and confirm the role of the monsoonal wind forcing through linear baroclinic waves (coastally-trapped Kelvin and planetary Rossby waves). Sub-seasonal variability takes the form of anomalous events lasting a few weeks to a few months and occurs at two preferred timescales: in the 30–110 day band, within the frequency domain of the Madden–Julian oscillation and in the 120–180 day band. While this sub-seasonal variability appears fairly barotropic in the offshore region, the sign of the anomaly in the upper thermocline is opposite to that in its lower part on many occasions along the coast. Our dataset also reveals relatively large interannual temperature variations of about 1 °C from 50 to 200 m depth that reflect a considerable year-to-year variability of the magnitude of both upwelling and downwelling events. This study clearly demonstrates the necessity for sustained long-term temperature measurements in the SEAS.  相似文献   

A proposal for a new statistic and technique development for the design and evaluation of cloud seeding experiments     

A.A. Tsonis  G.L. Austin  S. Lovejoy 《大气与海洋》2013,51(1):67-82

Abstract

The use of short‐term predictions of rain flux from isolated showers is discussed in the context of the design and evaluation of cloud‐seeding experiments. It is found that for a sample of 85 seeded convective clouds a seeding effect of 25% could be detected at the 10% significance level.  相似文献   

Crustal structure of the Ordovician Macquarie Arc,Eastern Lachlan Orogen,based on seismic‐reflection profiling     

R. A. Glen  R. J. Korsch  N. G. Direen  L. E. A. Jones  D. W. Johnstone  K. C. Lawrie 《Australian Journal of Earth Sciences》2013,60(2):323-348

In the Eastern Lachlan Orogen, the mineralised Molong and Junee‐Narromine Volcanic Belts are two structural belts that once formed part of the Ordovician Macquarie Arc, but are now separated by younger Silurian‐Devonian strata as well as by Ordovician quartz‐rich turbidites. Interpretation of deep seismic reflection and refraction data across and along these belts provides answers to some of the key questions in understanding the evolution of the Eastern Lachlan Orogen—the relationship between coeval Ordovician volcanics and quartz‐rich turbidites, and the relationship between separate belts of Ordovician volcanics and the intervening strata. In particular, the data provide evidence for major thrust juxtaposition of the arc rocks and Ordovician quartz‐rich turbidites, with Wagga Belt rocks thrust eastward over the arc rocks of the Junee‐Narromine Volcanic Belt, and the Adaminaby Group thrust north over arc rocks in the southern part of the Molong Volcanic Belt. The seismic data also provide evidence for regional contraction, especially for crustal‐scale deformation in the western part of the Junee‐Narromine Volcanic Belt. The data further suggest that this belt and the Ordovician quartz‐rich turbidites to the east (Kirribilli Formation) were together thrust over ?Cambrian‐Ordovician rocks of the Jindalee Group and associated rocks along west‐dipping inferred faults that belong to a set that characterises the middle crust of the Eastern Lachlan Orogen. The Macquarie Arc was subsequently rifted apart in the Silurian‐Devonian, with Ordovician volcanics preserved under the younger troughs and shelves (e.g. Hill End Trough). The Molong Volcanic Belt, in particular, was reworked by major down‐to‐the‐east normal faults that were thrust‐reactivated with younger‐on‐older geometries in the late Early ‐ Middle Devonian and again in the Carboniferous.  相似文献