Rhodophycean algae from the Lower Cretaceous of the Cauvery Basin, South India by P.K. Misra, S. Kishore, S.K. Singh and A.K. Jauhri. Jour. Geol. Soc. India, v.73, 2009, pp.325–334 相似文献
In light of the current problems facing the Yellow River and surrounding areas (e.g., periods of zero river discharge, increasing nitrate concentrations of the Bohai Sea), we examined the coastal mixing dynamics around the mouth of the Yellow River. Naturally occurring radium isotopes (223Ra, 224Ra, 226Ra, and 228Ra) and other geochemical tracers (Ba, Si, and salinity) were employed to determine river plume transport scales and rates. Barium and radium exhibit elevated concentrations within the salinity gradient where they are desorbed from particles via ion-exchange. Once they are added to the system, they decrease offshore from dilution with lower concentration Bohai Sea water, and in the case of 224Ra and 223Ra, by radioactive decay. Using radium “ages” to assess the dissolved material transport scales and rates proved to be a useful tool in this environment. The ages based on the 224Ra/228Ra activity ratio increased gradually until salinities reached ∼25 when they rapidly increased due to decreased mixing at higher salinities. Integrated net transport rates through the salinity front ranged from 1.4 to 1.6 cm/s and did not vary significantly with river discharge. Thus, tidal mixing appears to dominate in this system, at least over the range of discharges investigated (80–600 m3/s). Determining the temporal scale of flow across the coastal zone in this region is a valuable first step toward examining whether the Yellow River is contributing to the increasing inorganic nitrogen concentrations in the central Bohai Sea. 相似文献
The present paper reports the K-Ar ages determined on glauconitic samples collected from the Ukra Member of the Mesozoic Bhuj
Formation in two different sections, one located on the Ghuneri-Ghaduli road near Katesar Mahadeo temple and the other at
the base of the Ukra hill in the northwestern part of the Kutch Mainland area.
Three glauconite samples viz., UkraKT-1, UkraKT-4 and UkraUH-3 have yielded K-Ar ages of 107.9 ± 3.4 Ma, 105.5 ± 3.3 Ma and 103.5 ± 3.4 Ma, respectively. The sample UkraKT-l treated with 0.5N HC1 and analysed in duplicate has yielded a mean age of 104 ± 2.3 Ma while the sample UkraKT-4 treated with 0.1N HCl has given an age of 106.5 ± 3.3 Ma. The ages of the treated and untreated glauconites are indistinguishable
within 2σ uncertainty with a mean of 105.2 ± 1.3 Ma, which has been interpreted as the depositional age of the Ukra Member
of the Mesozoic Bhuj Formation. The study has further indicated that mild acid treatment (up to 0.5N HCl) does not lead to
any loss of radiogenic argon in the glauconites and can be helpful in purification of the samples. 相似文献
The effect of lunar tides on the apparent ionospheric drift velocity (V) for an equatorial station Thumba (0.6°S dip) is computed by using nearly six years of data at fixed solar hours. Significant tides are observed in the E-region drifts, particularly around 12.00 hr and in the F-region drifts around 15.00 hr.A good correlation in the phases of the lunar tides in H and V is found to exist, suggesting a strong electrojet control of the horizontal ionospheric drift around these hours. 相似文献
Accurate thematic classification is one of the most commonly desired outputs from remote sensing images. Recent research efforts
to improve the reliability and accuracy of image classification have led to the introduction of the Support Vector Classification
(SVC) scheme. SVC is a new generation of supervised learning method based on the principle of statistical learning theory,
which is designed to decrease uncertainty in the model structure and the fitness of data. We have presented a comparative
analysis of SVC with the Maximum Likelihood Classification (MLC) method, which is the most popular conventional supervised
classification technique. SVC is an optimization technique in which the classification accuracy heavily relies on identifying
the optimal parameters. Using a case study, we verify a method to obtain these optimal parameters such that SVC can be applied
efficiently. We use multispectral and hyperspectral images to develop thematic classes of known lithologic units in order
to compare the classification accuracy of both the methods. We have varied the training to testing data proportions to assess
the relative robustness and the optimal training sample requirement of both the methods to achieve comparable levels of accuracy.
The results of our study illustrated that SVC improved the classification accuracy, was robust and did not suffer from dimensionality
issues such as the Hughes Effect. 相似文献
This paper introduces an objective definition of local onset and demise of the Indian summer monsoon (ISM) at the native grid of the Indian Meteorological Department’s rainfall analysis based on more than 100 years of rain gauge observations. The variability of the local onset/demise of the ISM is shown to be closely associated with the All India averaged rainfall onset/demise. This association is consistent with the corresponding evolution of the slow large-scale reversals of upper air and ocean variables that raise the hope of predictability of local onset and demise of the ISM. The local onset/demise of the ISM also show robust internannual variations associated with El Nino and the Southern Oscillation and Indian Ocean dipole mode. It is also shown that the early monsoon rains over northeast India has a predictive potential for the following seasonal anomalies of rainfall and seasonal length of the monsoon over rest of India.
Four levels of terraces located along Siang River, north of Main Central Thrust at Tuting, NE Himalaya are dated using Optically
Stimulated Luminescence (OSL). The dating technique is applied using (1) Blue LED stimulation on Quartz (2) Infrared Stimulated
Luminescence (IRSL) stimulation on Feldspar at 50 °C and (3) Infrared Stimulated Luminescence stimulation on Feldspar at an
elevated temperature of 225 °C. The results indicated that the later two protocols on feldspars yielded overestimated ages
that suggested incomplete bleaching of luminescence signals in feldspar. The ages derived using quartz suggested a nearly
continued valley aggradation from >21–8 ka with three phases of bedrock incision. The phase of aggradation coincides with
a climatic transition from cold and dry Last Glacial phase to warm and wet Holocene Optimum. The bedrock incision phases centered
at <21 ka, ∼11 ka and ∼8 ka indicate towards major episodes of tectonic uplift in the region around Tuting. 相似文献
GRS 1915+105 is a prominent black hole system exhibiting variability over a wide range of time scales and its observed light curves have been classified into 12 temporal states. Here we undertake a complete analysis of these light curves from all the states using various quantifiers from nonlinear time series analysis, such as the correlation dimension (D2), the correlation entropy (K2), singular value decomposition (SVD) and the multifractal spectrum (f(α) spectrum). An important aspect of our analysis is ... 相似文献