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11.
Ian M. Davies 《Marine environmental research》1991,32(1-4)
Surveys of imposex in dogwhelk (Nucella lapillus) populations around oil terminals in Sullom Voe (Shetland) and Scapa Flow (Orkney) have confirmed that the effects of tributyltin (TBT) released from large vessels in coastal waters can be recognised. The impact of large vessels can be separated from the effects of other inputs of TBT in the areas studied. The intensity of the effects was greater in Shetland than in Orkney, reflecting the higher exposure to TBT resulting from the greater volume of traffic using the Shetland terminal, and the more restricted water exchange in that area. A large proportion of the female dogwhelks in Sullom Voe were unable to reproduce. Females in Scapa Flow were still able to reproduce, except for a small proportion close to two fish farm sites where TBT net-treatments were used prior to 1987. 相似文献
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K. S. Rao Y. S. Rao H. K. Al Jassar 《Journal of the Indian Society of Remote Sensing》2008,36(2):123-136
Spaceborne Imaging Radar (SIR-C) data acquired over Gujarat, India in 1994 were processed and analysed using differnet techniques
applicable to polarimetric SAR data such as polarization signatures, polarization index, decomposition of the signal and polarization
phase difference and limited groundtruth data. It has been observed that multi-frequency polarimetric data enhances the potential
of retrieving geo-physical parameters. The polarization signatures are found to vary with the nature of the target. Target
decomposition of the returned signal will be useful for the classification of various features. Polarization Phase Difference
(PPD) gives good information about the vegetation parameters. 相似文献
14.
This paper introduces a new method for GPS signal acquisition, which is based on the repeatability of successive code phase
measurements and the M-of-N search algorithm. The performance of the proposed method in terms of probability of signal detection
is similar to that of traditional methods, except that the calculation of the probability of detection does not rely on the
noise distribution or the Carrier-to-Noise ratio (C/N0). The code phase repeatability-based method is presented along with equations for probability of detection and probability
of false detection. If the distribution of the noise is known, it also provides an estimate of the C/N0. The proposed method is illustrated for coherent and non-coherent acquisition and C/N0 estimation. 相似文献
15.
An important task in modern geostatistics is the assessment and quantification of resource and reserve uncertainty. This uncertainty
is valuable support information for many management decisions. Uncertainty at specific locations and uncertainty in the global
resource is of interest. There are many different methods to build models of uncertainty, including Kriging, Cokriging, and
Inverse Distance. Each method leads to different results. A method is proposed to combine local uncertainties predicted by
different models to obtain a combined measure of uncertainty that combines good features of each alternative. The new estimator
is the overlap of alternate conditional distributions. 相似文献
16.
The occasional occurrence of brief but intense bursts of cosmic gamma-rays was disclosed through a systematic search of data acquired from the Vela satellites. Confirmation of the nature of the events and additional detail of their characteristics has subsequently been provided by 15 other groups of experimenters with instruments on 13 spacecraft. Thirty-nine such events have been identified from data spanning a period of four and a half years. The record of intensity as a function of time varies considerably for different events, with total durations ranging from 0.1 to 60s. Time-integrated flux density ranges from 10–6 to 10–3 erg cm–2. Spectral measurements have been accomplished by several groups of experimenters, showing a broad maximum in the energy distribution at about 150 keV. The distribution of source directions implies either near galactic or extragalactic locations. The existing data are not sufficient to distinguish between the various models proposed to explain the phenomenon; no model is completely consistent with all observed characteristics.Work performed under the auspices of the United States Energy Research and Development Administration.Paper presented at the COSPAR Symposium on Fast Transients in X-and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975. 相似文献
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Peter G. Verity 《Estuaries and Coasts》2002,25(5):944-960
The Skidaway River estuary is a tidally-dominated subtropical estuary in the southeastern USA surrounded by extensiveSpartina salt marshes. Weekly smapling at high and low tide began in 1986 for hydrography, nutrients, chlorophylla, particulate matter, and microbial and plankton biomass and composition; hydrographic and nutrient data during 1986–1996
are reported here. Salinity varied inversely with river discharge and exhibited variability at all time scales but with no
long-term trend. Water temperature typically ranged over 25°C and was without apparent long-term frend. Seasonal cycles in
concentrations of NO3, NH4, PO4, Si(OH)4, and DON were observed, with annual maxima generally occurring in late summer. Superimposed on seasonal cycles, all five
nutrients exhibited steady increases in minimum, mean, and maximum concentrations; mean concentrations increased c. 50–150%
during the decade. Nutrient concentrations were highly correlated with water temperature over the ten-year period, but weakly
related to salinity and discharge. Nutrients were strongly correlated with one another, and the relative ratios among inorganic
nutrients showed little long-term trend. Correlations among temperature and nutrient concentrations exhibited considerable
inter-annual variability. Major spikes in organic and inorganic nutrient concentrations coincided with significant rainfall
events; concentrations increased hyperbolically with rainfall. Although pristine compared to more heavily impacted waterways
primarily outside the region, residential development and population density have been increasing rapidly during the past
15–20 years. Land use is apparently altering nutrient loading over the long-term (months-years), and superimposed on this
are stochastic meteorological events that accelerate these changes over the short term (days-weeks). 相似文献