Stellar spectra classification with twin hypersphere model     

《New Astronomy》2021

With the increase of stellar spectra, how to automatically classify these spectra have attracted astronomer's attention. Support Vector Machine (SVM), as a typical classifier, has widely used in stellar spectra classification. Due to its limited performance in various classification problems and higher training time, a model with a pair of hyperspheres named Twin Hypersphere Model (THM), proposed by Peng and Xu, is utilized for stellar spectra classification in this paper. In THM, the samples in one hypersphere is far from another according to the Euclidean distance. The comparative experiments with SVM and Twin Support Vector Machine (TWSVM) on the SDSS datasets shows that the THM model gives the best classification accuracy of 0.8836 for type F, 0.9446 for type G, and 0.9509 for type K, which are better than the classification accuracies of 0.8000, 0.8484, 0.8911 obtained by SVM and 0.8413, 0.8699, 0.9109 obtained by TWSVM. It can be concluded that THM perform better than traditional techniques such as SVM and TWSVM on the K-, F-, G- type stellar spectra classification.  相似文献   

Socio-economic and Environmental Implications of the Hydroelectric Projects in Uttarakhand Himalaya, India   总被引：1，自引：1，他引：0  

Naresh Rana S.P. Sati Y.P. Sundriyal Madan Mohan Doval Navin Juyal 《山地科学学报》2007,4(4):344-353

This paper deals with detailed analysis of the fiasco created by the Tehri High Dam in Uttarakhand, India, particularly in terms of resettlement and rehabilitation of the local inhabitants. Aspects pertaining to the environmental issues are also discussed. Currently, the river valleys in Uttarakhand state of India are the targets of increasing hydroelectric projects. Virtually all rivers are being exploited for generating environmental friendly power. Having being learned the hard lesson from Tehri Dam, it has been decided to opt for such schemes in which comparatively little submergence and tempering with the fragile eco-systems is involved.However, our observations suggest that even in such schemes if due care is not taken they may turn out to be a failure.  相似文献   

Land cover dynamics in Garhwal Himalayas — a case study of balkhila sub-watershed   总被引：1，自引：1，他引：1  

P. K. Joshi  Sushma Gairola 《Journal of the Indian Society of Remote Sensing》2004,32(2):199-208

The present paper focuses on land cover dynamics pattern in Balkhila sub-watershed situated in Garhwal Himalayas. This study contributes example from human shaped ecosystem in mountainous regions where fragmentation of natural resources is active. The remote sensing and GIS has been used to understand the land cover dynamics along the topography. The results report that the land cover dynamics is dependent on the aspect due to sun illumination. The altitude and slope are no more a barrier for resource extraction and the human activity zone is shifting towards higher altitudes and slopes. The changes are also defined along the road and settlements.  相似文献   

Reactive transport impacts on recovered freshwater quality during multiple partially penetrating wells (MPPW-)ASR in a brackish heterogeneous aquifer     

《Applied Geochemistry》2016

The use of multiple partially penetrating wells (MPPW) during aquifer storage and recovery (ASR) in brackish aquifers can significantly improve the recovery efficiency (RE) of unmixed injected water. The water quality changes by reactive transport processes in a field MPPW-ASR system and their impact on RE were analyzed. The oxic freshwater injected in the deepest of four wells was continuously enriched with sodium (Na⁺) and other dominant cations from the brackish groundwater due to cation exchange by repeating cycles of ‘freshening’. During recovery periods, the breakthrough of Na⁺ was retarded in the deeper and central parts of the aquifer by ‘salinization’. Cation exchange can therefore either increase or decrease the RE of MPPW-ASR compared to the RE based on conservative Cl⁻, depending on the maximum limits set for Na⁺, the aquifer’s cation exchange capacity, and the native groundwater and injected water composition. Dissolution of Fe and Mn-containing carbonates was stimulated by acidifying oxidation reactions, involving adsorbed Fe²⁺ and Mn²⁺ and pyrite in the pyrite-rich deeper aquifer sections. Fe²⁺ and Mn²⁺ remained mobile in anoxic water upon approaching the recovery proximal zone, where Fe²⁺ precipitated via MnO₂ reduction, resulting in a dominating Mn²⁺ contamination. Recovery of Mn²⁺ and Fe²⁺ was counteracted by frequent injections of oxygen-rich water via the recovering well to form Fe and Mn-precipitates and increase sorption. The MPPW-ASR strategy exposes a much larger part of the injected water to the deeper geochemical units first, which may therefore control the mobilization of undesired elements during MPPW-ASR, rather than the average geochemical composition of the target aquifer.  相似文献   

Analysis of dry and wet climate characteristics at Uttarakhand (India) using effective drought index     

Malik  Anurag  Kumar  Anil  Kisi  Ozgur  Khan  Najeebullah  Salih  Sinan Q.  Yaseen  Zaher Mundher 《Natural Hazards》2021,105(2):1643-1662

Natural Hazards - Drought is a complex natural disaster that adversely affects human life and the ecosystem. A variety of drought indexes are available for monitoring meteorological drought events....  相似文献   

Sensitivity of tanaid Apseudes latreillei (Milne-Edwards) populations to sewage pollution     

《Marine environmental research》2010,70(5):309-317

Apseudes latreillei (Milne-Edwards) is a common and abundant tanaid in soft-bottom communities from waters off East Atlantic and Mediterranean coasts. Its sensitivity to pollution is not clear despite being an abundant and widely distributed crustacean, since it has been reported as both a tolerant and sensitive species. This paper tests the sensitivity of A. latreillei to sewage discharges in fine-sand communities along the Castellon coast (W. Mediterranean). We analysed variation in tanaid populations between sites at varying distances from sewage outfalls with respect to population density, size distribution, sex ratio and their correlation with different abiotic factors of waste water and sediment. Results showed clearly that A. latreillei populations were affected by the presence of sewage outfalls, to such an extent that sewage disposal outlets produced a decrease in population density and changes in size spectra.  相似文献   

Evaluation of a probabilistic approach to simulation of alkalinity and electrical conductivity at a river bank filtration site     

A. K. Thakur  V. P. Singh  C. S. P. Ojha 《水文研究》2012,26(22):3362-3368

In river bank filtration, impurities present in the river water travel with the bank filtrate towards the pumping well. During this passage, certain types of impurities, such as turbidity, total coliform, and so forth, may get attenuated; however, it is interesting to note that some of the instant raw river water quality parameters, such as alkalinity and electrical conductivity, increase after the passage of water through the porous medium. This occurs because water, when passing through the soil pores, absorbs many of the solutes that cause an increase in alkalinity and electrical conductivity. Measurements at a river bank filtration site for a year showed that alkalinity of 116–32 mg l^?1 in river water increased to 222.4–159.9 mg l^?1 in the river bank filtered water. Likewise, the electrical conductivity increased from 280–131 μS cm^?1 to 462–409.6 μS cm^?1. This study uses a probabilistic approach for investigating the variation of alkalinity and electrical conductivity of source water that varies with the natural logarithm of the concentration of influent water. The probabilistic approach has the potential of being used in simulating the variation of alkalinity and electrical conductivity in river bank filtrate. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Primary to re-equilibrated fluids and geochemical signatures for the evolution of the Nagthat siliciclastics in the Tons valley,Lesser Himalaya,India     

《Journal of Asian Earth Sciences》2007,29(2-3):440-454

Medium to coarse-grained Neo-Proterozoic Nagthat siliciclastic rocks form a part of the Krol Formation in the Lesser Himalayan geotectonic zone. Fluid inclusion and geochemical studies have been carried out on the Nagthat siliciclastics from the Tons valley to determine their provenance during the Proterozoic and their recrystallisation during maximum burial to uplift. Fluid inclusion studies have been carried out on detrital, recrystallised quartz grains and quartz overgrowths. Major and trace element analyses of the siliciclastics, the relationships of SiO₂ with various trace elements, and the association of various trace elements with mineral species suggest a granitic source for these siliciclastics. Primary Q1 aqueous brine inclusions and Q3 H₂O–CO₂ fluid with 0.9 gm/cm³ CO₂ density in detrital quartz grains characterised the protolith of the sandstone as granite or metamorphic rocks. H₂O–NaCl fluids participated in the cementation history, temperatures of quartz overgrowth from 198 to 232 °C show the effect of maximum burial. The re-equilibration of the primary fluid due to elevated internal pressure > confining pressure is evident from features like ‘C’ shaped cavities, stretching of the inclusions, their migration, decrepitation clusters, etc. During recrystallisation these inclusions were equilibrated at 187 ° and 235 °C in a restricted fluid of aqueous, moderately saline composition. The observed inclusion morphology is attributed to a decrease in external pressure related to isothermal decompression uplift.  相似文献   

HACC: Simulating sky surveys on state-of-the-art supercomputing architectures     

《New Astronomy》2016

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On the observations of unique low latitude whistler-triggered VLF/ELF emissions     

《Physics and Chemistry of the Earth》2013

A detailed analysis of the VLF/ELF wave data obtained during a whistler campaign under All India Coordinated Program of Ionosphere Thermosphere Studies (AICPITS) at our low latitude Indian ground station Jammu (geomag. lat. = 22° 26′ N, L = 1.17) has yielded two types of unusual and unique whistler-triggered VLF/ELF emissions. These include (1) whistler-triggered hook emissions and (2) whistler-triggered long enduring discrete chorus riser emissions in VLF/ELF frequency range during night time. Such types of whistler-triggered emissions have not been reported earlier from any of the ground observations at low latitudes. In the present study, the observed characteristics of these emissions are described and interpreted. Dispersion analysis of these emissions show that the whistlers as well as emissions have propagated along a higher geomagnetic field line path with L-values lying ∼L = 4, suggesting that these triggered emissions are to be regarded as mid-latitude emissions. These waves could have propagated along the geomagnetic field lines either in a ducted mode or in a pro-longitudinal (PL) mode. The measured intensity of the triggered emissions is almost equal to that of the source waves and does not vary throughout the period of observation on that day. It is speculated that these emissions may have been generated through a process of resonant interaction of the whistler waves with energetic electrons. Parameters related to this interaction are computed for different values of L and wave amplitude. The proposed mechanism explains some aspects of the dynamic spectra.  相似文献