With the recent observational evidence in extragalactic astronomy,the interpretation of the nature of quasar redshift continues to be a research interest.Very high redshifts are being detected for extragalactic object...With the recent observational evidence in extragalactic astronomy,the interpretation of the nature of quasar redshift continues to be a research interest.Very high redshifts are being detected for extragalactic objects that are presumably very distant and young while also exhibiting properties that are characteristic of a more mature galaxy such as ours.According to Halton Arp and Geoffrey Burbidge,redshift disparities consist of an intrinsic component and are related to an evolutionary process.Karlsson observed redshift periodicity at integer multiples of0.089 in log scale and Burbidge observed redshift periodicity at integer multiples of 0.061 in linear scale.Since Singular Value Decomposition based periodicity estimation is known to be superior for noisy data sets,especially when the data contain multiple harmonics and overtones,mainly irregular in nature,we have chosen it to be our primary tool for analysis of the quasar-galaxy pair redshift data.We have observed a fundamental periodicity of0.051 with a confidence interval of 95%in linear scale with the site-available Sloan Digital Sky Survey Data Release 7(SDSS DR7)quasar-galaxy pair data set.We have independently generated quasar-galaxy pair data sets from both 2d F and SDSS and found fundamental periodicities of 0.077 and 0.089,respectively,in log scale with a confidence interval of 95%.展开更多
In this paper, we report the development of the design verification model (DVM) of Rb atomic frequency standard for the Indian Regional Navigational Satellite System (IRNSS) programme. Rb atomic clock is preferred for...In this paper, we report the development of the design verification model (DVM) of Rb atomic frequency standard for the Indian Regional Navigational Satellite System (IRNSS) programme. Rb atomic clock is preferred for the space applications as it is light-weight and small in size with excellent frequency stability for the short and medium term. It has been used in all other similar navigation satellite systems including GPS, GLONASS Galileo etc. The Rb atomic frequency standard or clock has two distinct parts. One is the physics package where the hyperfine transitions produce the clock signal in the integrated filter cell or separate filter cell configuration and the other is the electronic circuits which include frequency synthesizer for generating the resonant microwave hyperfine frequency, phase modulator and phase sensitive detector. In this paper, the details of the Rb physics package and the electronic circuits are given. The reasons for the mode change in Rb lamp have been revisited. The effect of putting the photo detector inside the microwave cavity is studied and reported with its effect on the resonance signal profile. The Rb clock frequency stability measurements have also been discussed.展开更多
Recently,the increasing demand of radio spectrum for the next generation communication systems due to the explosive growth of applications appetite for bandwidths has led to the problem of spectrum scarcity.The potent...Recently,the increasing demand of radio spectrum for the next generation communication systems due to the explosive growth of applications appetite for bandwidths has led to the problem of spectrum scarcity.The potential approaches among the proposed solutions to resolve this issue are well explored cognitive radio(CR)technology and recently introduced non-orthogonal multiple access(NOMA)techniques.Both the techniques are employed for efficient spectrum utilization and assure the significant improvement in the spectral efficiency.Further,the significant improvement in spectral efficiency can be achieved by combining both the techniques.Since the CR is well-explored technique as compared to that of the NOMA in the field of communication,therefore it is worth and wise to implement this technique over the CR.In this article,we have presented the frameworks of NOMA implementation over CR as well as the feasibility of proposed frameworks.Further,the differences between proposed CR-NOMA and conventional CR frameworks are discussed.Finally,the potential issues regarding the implementation of CR-NOMA are explored.展开更多
The changes in species composition, abundance and forest stand structure were analyzed across altitudinal regimes in tropical forests of Eastern Ghats of northern Andhra Pradesh, India. Three 1-ha plots were establish...The changes in species composition, abundance and forest stand structure were analyzed across altitudinal regimes in tropical forests of Eastern Ghats of northern Andhra Pradesh, India. Three 1-ha plots were established with one each in low, medium and high altitudes. A total of 153 species, 2129 stems （709 stems .ha^-1） of ≥10 cm girth were enumerated. Species richness and diversity pattern varied along altitudinal gradient and increased with the altitude. Species richness varied from 52 to 110 species-ha^-1 and stand density from 639 to 836 stems.ha^-1 with average basal area of 34.39 m^2.ha^-1. Shannon-Wiener index （H＇） ranged from 4.55 to 5.17. Low altitude （i.e., Site 1） is dominated byXylia xylocarpa （59.22） and Lagerstroemia parviflora （23.90）, medium altitude （i.e., Site 2） by Xylia xylocarpa （45;50） Bursera serrata （17.29）, and high altitude （i.e., Site 3） has Schleichera oleosa （28.25） Pterocarpus marsupium （26.55） as predominant species. Taxonomically, Rubiaceae （12 species）, Fabaceae （12）, Euphorbiaceae （11）, Rutaceae （7） and Lanraceae （7） were dominant families. Density-wise, Fabaceae, Combretaceae, Euphorbiaceae, Anacardiaceae and Myrtaceae were abundant. Thus, conservation assessment based on altitudinal regimes and the information on species structure and function can provide baseline information for monitoring and sustaining the biodiversity.展开更多
A magnitude M;7.8 earthquake occurred on 25 April 2015(referred as Gorkha earthquake).We have analyzed the spatial variation of b-value and two-dimensional strain within Nepal Himalaya before and after the Gorkha eart...A magnitude M;7.8 earthquake occurred on 25 April 2015(referred as Gorkha earthquake).We have analyzed the spatial variation of b-value and two-dimensional strain within Nepal Himalaya before and after the Gorkha earthquake.We have used continuous Global Navigation Satellite System(GNSS)data from 30 stations in the Nepal region for geodetic strain estimation and earthquake data for b-value estimation.The GNSS data were processed using double differencing technique for the accurate position of each station.The precise velocity vectors show a general azimuth of north east for all the stations and have been used to derive two-dimensional strain.Between epicenters of Gorkha(25 April 2015)and Dolakha earthquakes(12 May 2015),we observed high co-seismic horizontal displacements(0.2 m to 2 m).In the Pre-seismic deformation study,maximum strain accumulation(56.40×10;)and low bvalue(0.79-0.89)was observed in and around the Western Nepal region,which may be responsible for the 2015 Gorkha earthquake.The potential seismic zones were identified by GIS based integration of geodetic strain and b-value map and superimposition using weighted overlay method.The Maximum strain and low b-value are now observed in the eastern part of Nepal.Hence,the spatial disposition of elastic energy has changed after the two major earthquakes and continuous seismic hazard assessment is required in the eastern Nepal.展开更多
In an era of climate change,the availability of empirical data on alpine summit vegetation in the Himalaya is still scarce.Here we report the assessment of alpine summit flora in Gulmarg Wildlife Sanctuary,Kashmir Him...In an era of climate change,the availability of empirical data on alpine summit vegetation in the Himalaya is still scarce.Here we report the assessment of alpine summit flora in Gulmarg Wildlife Sanctuary,Kashmir Himalaya.We employed a globally standardized Multi-Summit Approach and four spatially isolated summits spanning an elevation gradient of 210 m(between 3530-3740 m a.s.l.)from natural treeline to nival zone were studied.Sampling of the summits was carried out in the year 2018 to collect floristic data together with records of soil temperature.A total of 142 vascular plant species were recorded in the sampled summits.Majority of the species were of herbaceous growth form and with perennial life span.Based on Raunkiaer’s life form,hemicryptophytes were the most dominant followed by therophytes and phanerophytes.The summit flora showed the predominance of narrow-endemic species,with broad-and non-endemics declining with elevation.A significant relationship between growth form,Raunkiaer’s life form,and the degree of endemism with elevation was observed.Both species diversity and soil temperature showed a monotonic decrease with increasing elevation.Interestingly,soil temperature clearly determined the magnitude of species diversity on the summits.Furthermore,based on floristic composition,the lowest summit had the highest dissimilarity with the rest of the summits.The present study employed globally standardized protocol to scientifically assess the patterns of plant diversity on the alpine mountain summits of Kashmir Himalaya,which in turn has wide implications towards long-term monitoring of climate change impact on alpine biodiversity in the rapidly warming Himalaya.展开更多
To investigate the geometry of the accretion disk in the source H1743-322, we have carried out a detailed X-ray temporal and spectral study using RXTE pointed observations. We have selected all data pertaining to the ...To investigate the geometry of the accretion disk in the source H1743-322, we have carried out a detailed X-ray temporal and spectral study using RXTE pointed observations. We have selected all data pertaining to the Steep Power Law （SPL） state during the 2003 outburst of this source. We find anti-correlated hard X-ray lags in three of the observations and the changes in the spectral and timing parameters （like the QPO frequency） confirm the idea of a truncated accretion disk in this source, Compiling data from similar observations of other sources, we find a correlation between the fractional change in the QPO frequency and the observed delay. We suggest that these observations indicate a definite size scale in the inner accretion disk （the radius of the truncated disk） and we explain the observed correlation using various disk parameters like Compton cooling time scale, viscous time scale etc..展开更多
Development of asymptotic magnitude Bode plots for integer-order transfer functions is a well-established topic in the control theory.However,construction of such plots for the fractional-order transfer functions has ...Development of asymptotic magnitude Bode plots for integer-order transfer functions is a well-established topic in the control theory.However,construction of such plots for the fractional-order transfer functions has not received much attention in the existing literature.In the present paper,we investigate in this direction and derive the procedures for sketching asymptotic magnitude Bode plots for some of the popular fractional-order controllers such as PI^α,[PI]^α,PD^β,[PD]^β,and PI^αD^β.In addition,we deduce these plots for general fractional commensurate-order transfer functions as well.As applications of this work,we illustrate 1)the analysis of the designed fractional-control loop and 2)the identification of fractional-order transfer function from a given plot.展开更多
The present study was carried out in Tungnath alpine meadows of Kedarnath Wild Life Sanctuary, Western Himalaya from subalpine to upper alpine zone. A total of four summits were selected along an altitudinal gradient ...The present study was carried out in Tungnath alpine meadows of Kedarnath Wild Life Sanctuary, Western Himalaya from subalpine to upper alpine zone. A total of four summits were selected along an altitudinal gradient and sampled for detailed vegetation analysis using multi summit approach as per Global observation research initiative in alpine environments(GLORIA). Species richness, diversity, and evenness among four summits as well as the interaction between environmental variables with plant communities were assessed. Monthly mean soil temperature was calculated using data retrieved from geo-precision temperature logger in order to identify the trend of soil temperature among different season and altitudinal gradient and its implications to plant communities. Soil samples were analyzed fromeach summit by collecting randomized composite soil samples. The indirect non-metric multidimensional scaling(NMDS) and direct canonical correspondence analysis(CCA) tools of ordination techniques to determine the linkage between plant species from various sample summits and biotic/abiotic environmental gradients were used in the present study. The results of the study demonstrated increase in species richness as soil temperature increases, the ecotone representing summits were found most warm summits followed by highest species richness. Annual soil temperature increased by 1.43°C at timberline ecotone. Whereas, at upper alpine zone the soil temperature increased by 0.810 C from year 2015 to 2016. S?rensen's similarity index was found to be increased between subalpine and upper alpine zone with increase in the presence of subalpine plant species at upper alpine zone. Both the ordination tools separate the subalpine summit and their respective vegetation from summits representingtimberline ecotone and upper alpine zone. Soil p H, altitude, soil cation exchange capacity were found as the key abiotic drivers for distribution of plant species.展开更多
TCP performance degrades when end-to-end connections extend over wireless links which are characterized by high Bit Error Rate and intermittent connectivity. Such degradation is mainly accounted for TCP’s unnecessary...TCP performance degrades when end-to-end connections extend over wireless links which are characterized by high Bit Error Rate and intermittent connectivity. Such degradation is mainly accounted for TCP’s unnecessary congestion control actions while attempting TCP loss recovery. Several independent link loss recovery approaches are proposed by researchers to reduce number of losses visible at TCP. In this paper we first presented a survey of loss mitigation techniques at wireless link layer. Secondly performance evaluation for TCP through Type 0 Automatic Retransmission Request mechanism in erroneous Wireless LAN is presented. In particular, simulations are performed taking into account the wireless errors introduced over IEEE 802.11 link using a well-established 2-State Markov model. TCP performance is evaluated under different settings for maximum link retransmissions allowed for each frame. Simulation results show that, link retransmission improves TCP performance by reducing losses perceived at TCP sender. However, such improvement is often associated with adverse effect on other TCP parameters that may cost a lot in return under extreme network conditions. In this paper an attempt is made to observe impact of link retransmissions on the performance of multiple TCP flows competing with each other. The analysis presented in this paper signifies the scope for maximizing TCP’s throughput at the least possible cost.展开更多
The desert locust, <em>Schistocerca gregaria</em> Forsk. (Orthoptera: Acrididae) is a peculiar insect that exhibits density-dependent phase polyphenism. Gregarious phase enables desert locust to form a lar...The desert locust, <em>Schistocerca gregaria</em> Forsk. (Orthoptera: Acrididae) is a peculiar insect that exhibits density-dependent phase polyphenism. Gregarious phase enables desert locust to form a large groups and mass migrations during which significant crop loss and food security issues may occur. Currently, the most recent upsurge of desert locust is prevailing across Eastern Africa and Southwestern Asia. Usually desert locusts are restricted to regions like semi-arid and arid regions. A super cyclonic storm, namely Amphan originated during May 2020, in the Bay of Bengal of North Indian Ocean has influenced numerous swarms to migrate from the Thar desert region to other parts of India. In this research, satellite data were used to investigate the reasons for this sudden swarm migration. The results that revealed the wind jets passing above the Thar desert region have integrated with the cyclogenesis of Amphan and led to the formation of conduits. The favorable conditions in the conduits include the open sky conditions, air temperature and fresh vegetation availability. Moreover, the wind settings in the conduits have enabled the swarm migrate to follow the downwind facing the sunrays during early mornings for an easy and successful take-off. It is observed that during the take-off session the wind speed at 850 hPa pressure level is mostly double than that of surface wind in both the conduits.展开更多
Present study attempts to understand the potential of multispectral ASTER (Advanced space borne thermal emission and reflection radiometer) data for spatial mapping of kimberlite. Kimberlite is an economic rock known ...Present study attempts to understand the potential of multispectral ASTER (Advanced space borne thermal emission and reflection radiometer) data for spatial mapping of kimberlite. Kimberlite is an economic rock known for hosting diamond. Kimberlite also has petrogenetic importance for giving us clue on the composition of lower part of the mantle. Kimberlites often contain serpentine, carbonate minerals;which have their diagnostic spectral signatures in short wave infrared (SWIR) domain. In the present study, attempt is made to delineate kimberlite from adjacent granite-granodiorite gneiss based on processing of the ASTER data as ASTER’s spectral channels can detect some of the diagnostic absorption features of kimberlites. But it has been observed that the kimberlites are difficult to be delineated by processing the ASTER data using correlative information of both sub-pixel and per-pixel mapping. Moreover, smaller spatial size of kimberlites with respect to pixel size of ASTER SWIR channels further obscures the spectral feature of kimberlite. Therefore, an attempt is also made to understand how intra pixel spectral mixing of kimberlite and granite granodiorite-gneiss modifies the diagnostic spectral feature of kimberlite. It is observed that spectral feature of kimberlites would be obscured when it is has very small spatial size (one-tenth of pixel) with respect to pixel size. Moreover, calcrete developed in the adjacent soil has identical absorption feature similar to the spectral features of kimberlites imprinted in the respective ASTER convolved spectral profiles. This also has resulted false-positives in ASTER image when we use spectral feature as a tool for spatial mapping of kimberlite. Therefore hyperspectral data with high spatial and spectral resolution is required for targeting kimberlites instead of using broad band spectral feature of kimberlites.展开更多
Aeolian process leads to the transportation and accumulation of sand particles that result in sand dune landforms. The structure and shape of the sand dunes are driven by the parameters of interacting wind force and t...Aeolian process leads to the transportation and accumulation of sand particles that result in sand dune landforms. The structure and shape of the sand dunes are driven by the parameters of interacting wind force and the material composition of sand within. Cross-section profiles over the sand dunes will essay the geomorphological parameters through which the steady state and rate of sand transport can be computed. National Aeronautics and Space Administration’s novel satellite namely Ice, Cloud and land Elevation Satellite-2 (ICESat-2) hosts a solo sensor namely Advanced Topographic Laser Altimeter System (ATLAS) which is a photon counting instrument that measures the round-trip time of the light pulse being emitted and reflected back from the surface determines the true height of the topographic feature on the Earth. In this article, cross-section profiles generated from the beams of ICESat-2 ground-tracks acquired over sand dunes of the Thar Desert region were analysed for detecting the geomorphological parameters. Observations from the cross-section profiles have resulted in giving unprecedented details about the shapes and morphological settings of various types of sand dunes like barchanoids, parabolic, longitudinal, and transverse dunes. Morphological parameters of sand dunes like the length of the stoss slope, crest height, slip face details, inter-arms spacing, height of the trailing arms, length of the depositional lobes, and sinuosity of the recurring crest lines were retrieved with ease from the Level-2A data product namely ATL03 of ICESat-2/ATLAS.展开更多
The projection for groundwater states that the total domestic water demand for greater Bangalore would increase from 1,170 MLD in 2010 to 1,336 MLD in 2016. Dependence on groundwater is ever increasing due to rapid In...The projection for groundwater states that the total domestic water demand for greater Bangalore would increase from 1,170 MLD in 2010 to 1,336 MLD in 2016. Dependence on groundwater is ever increasing due to rapid Industrialization ＆ Urbanization. It is estimated that almost 40% of the population of Bangalore is dependent on groundwater. Due to the unscientific disposal of domestic and industrial waste generated, groundwater is getting highly polluted in the city. The scale of this impact will depend mainly upon the water-service infrastructure, the superficial geology and the regional setting. The quality of ground water is equally important as that of quantity. Jointed and fractured granites and gneisses constitute the major aquifer system of BBMP （Bruhat Bengaluru Mahanagara Palike） area. Two new observatory borewells were drilled and lithology report has been prepared. Petrographic Analysis （XRD/XRF） and Water Quality Analysis were carried out as per the standard methods. Petrographic samples were analysed by collecting chip of rock from the borewell for every 20 ft depth, most of the samples were similar and samples were identified as Biotite-Gneiss, Schistose Amphibolite. Water quality analysis was carried out for individual chemical parameters for two borewells drilled. The 1st Borewell struck water at 150 ft （total depth-200 ft） ＆ 2nd struck at 740 ft （total depth-960 ft）. Five water samples were collected till end of depth in each borewell. Chemical parameter values such as, Total hardness （360-348, 280-320） mg/ltr, Nitrate （12.24-13.5, 45-48） mg/ltr, Chloride （104-90, 70-70） mg/ltr, Fe （0.75-0.09, 1.288-0.312） mg/ltr etc. are calculated respectively. Water samples were analysed from various parts of BBMP covering 750 sq kms, also thematic maps （IDW method） of water quality are generated for these samples for post-monsoon season. The study aims to explore the sub-surface lithological layers and the thickness of weathered zone, which indirectly helps to know the groundwater pollution source near surface water bodies, dug wells, etc. The above data are interpreted for future ground water resources planning and management.展开更多
Various spacecraft and satellites from the world’s best space agencies are exploring Mars since 1970, constantly with great ability to capture the maximum amount of dataset for a better understanding of the red plane...Various spacecraft and satellites from the world’s best space agencies are exploring Mars since 1970, constantly with great ability to capture the maximum amount of dataset for a better understanding of the red planet. In this paper, we propose a new method for making a mosaic of Mars Reconnaissance Orbiter (MRO) spacecraft payload Context Camera (CTX) images. In this procedure, we used ERDAS Imagine for image rectification and mosaicking as a tool for image processing, which is a new and unique method of generating a mosaic of thousands of CTX images to visualize the large-scale areas. The output product will be applicable for mapping of Martian geomorphological features, 2D mapping of the linear feature with high resolution, crater counting, and morphometric analysis to a certain extent.展开更多
Hydrological modelling of large river catchments has become a challenging task for water resources engineers due to its complexity in collecting and handling of both spatial and non-spatial data such as rainfall,gauge...Hydrological modelling of large river catchments has become a challenging task for water resources engineers due to its complexity in collecting and handling of both spatial and non-spatial data such as rainfall,gauge-discharge data,and topographic and hydraulic parameters.In this article,a flood forecast model is developed for the Godavari Basin,India through a distributed modelling approach using space inputs.The approach includes rainfall runoff modelling,hydrodynamic flow routing,calibration,and validation of the model with field discharge data.The study basin is divided into 128 subbasins to improve the model accuracy.Topographic and hydraulic parameters of each subbasin and channel are computed using the land use/land cover grid that is derived from the Indian Remote Sensing Satellite(IRS–P6) AWi FS sensor data(56 m resolution),Shuttled Radar Topographic Mission(SRTM) Digital Elevation Model(DEM),and the soil textural grid.The model is calibrated using the field hydrometeorological data of 2000 and validated with the data of 2001.The model was tested during the 2010 floods with real-time 3-hour interval hydrometeorological and daily evapotranspiration data.Accuracy in estimating the peak flood discharge and lag time was found to be very good.Flood forecast lead time is increased by 12 hours compared to conventional methods of forecasting.展开更多
Rapid satellite-based flood inundation mapping and delivery of flood inundation maps during a flood event can provide crucial information for planners and decision makers to prioritize relief and rescue operations. Th...Rapid satellite-based flood inundation mapping and delivery of flood inundation maps during a flood event can provide crucial information for planners and decision makers to prioritize relief and rescue operations. The present study is undertaken to optimize the threshold ranges for the classification of flood water in Synthetic Aperture Radar(SAR) images(of 20° to 49° incidence angles) for quick flood inundation mapping and response during flood disasters. This is done through assessing the signature of flood water in Horizontal transmit and Horizontal received(HH), Horizontal transmit and Vertical received(HV), Vertical transmit and Horizontal received(VH), and Vertical transmit and Vertical received(VV) polarization radar data. The mean backscattering signature profiles of various water bodies were analyzed to discriminate flood water from other water bodies. The study shows that there is better demarcation of land-water surface in HH polarization. VV polarization has the potential to identify partially submerged features, which can be useful in flood damage assessments. The backscatter of flood water in HV and VH is the same and both HV and VH polarizations are adequate for the mapping of flood water. At near range to far range,-8 to-12 d B,-15 to-24 d B, and-6 to-15 d B can be used as optimum ranges for the classification of flood water in HH, HV, and VV polarizations. These optimum threshold ranges can be applied to the automation of flood mapping using SAR images in near-real time, where much time was often spent on finding the thresholds in order to produce flood inundation maps in a short time from the onset of flood disasters and deliver such maps to the concerned agencies.展开更多
Transient numerical simulations are carried out to investigate the liquid-gas interfacecharacteristics associated with liquid film cooling flows.A two-dimensional axisymmetricmulti-phase numerical model using finite v...Transient numerical simulations are carried out to investigate the liquid-gas interfacecharacteristics associated with liquid film cooling flows.A two-dimensional axisymmetricmulti-phase numerical model using finite volume formulation is developed.The model hasbeen validated against available experimental data for liquid-film cooling flows inside tubes.The model has been used to predict the interface characteristics for a variety of imposedparameters and momentum flux ratios under cold flow conditions wherein both the coolant andmainstream are maintained at the same temperature.Disturbance waves are observed at theliquid-gas interface for coolant flows above a critical value and after a finite distance from theinlet.The distance toward the wave inception point increased with the increase of momentumflux ratio.However,at higher momentum flux ratios,the properties of the disturbance wavesdid not vary significantly.The parameters related to the liquid-gas interface waves,namely,wave velocity,frequency,amplitude and wave length have been analyzed in detail.Analysisindicates that the liquid entrainment is due to the shearing of the disturbance wave crest.展开更多
Groundwater assists farmers to irrigate crops for fulfilling the crop-water requirement.Indian agriculture system is characterized by three cropping seasons known as Kharif(monsoon),Rabi(post-monsoon)and summer(pre-mo...Groundwater assists farmers to irrigate crops for fulfilling the crop-water requirement.Indian agriculture system is characterized by three cropping seasons known as Kharif(monsoon),Rabi(post-monsoon)and summer(pre-monsoon).In tropical countries like India,monitoring cropping practices using optical remote sensing during Kharif and Rabi seasons is constraint due to the cloud cover,which can be well addressed by microwave remote sensing.In the proposed research,the strength of C-band polarimetric Synthetic Aperture Radar(SAR)time series images were evaluated to classify groundwater irrigated croplands for the Kharif and Rabi cropping seasons of the year 2013.The present study was performed in the Berambadi experimental watershed of Kabini river basin,southern peninsular India.A total of fifteen polarimetric variables were estimated includes four backscattering coefficients(HH,HV,VH,VV)and eleven polarimetric indices for all Radarsat-2 SAR images.The cumulative temporal sum(seasonal and dual-season)of these parameters was supervised classified using Support Vector Machine(SVM)classifier with intensive ground observation samples.Classification results using the best equation(highest accuracy and kappa)shows that the Kharif,Rabi and irrigated double croplands are respectively 9.58 km2(20.6%),16.14 km2(34.7%)and 6.22 km2(13.4%)with a kappa coefficient respectively 0.84,0.74 and 0.94.展开更多
Global warming resulting from greenhouse effect has threatened to the sustainability of agriculture,forest and land surface globally.A significant rise in extreme weather events has been observed worldwide,particularl...Global warming resulting from greenhouse effect has threatened to the sustainability of agriculture,forest and land surface globally.A significant rise in extreme weather events has been observed worldwide,particularly in developing countries[1].In the changing climatic era,the economic importance of the remote sensing and geographical information system(GIS)to monitoring forests and agricultural resources is imperative to the development of agro-ecosystem services and the products responding to user needs[2].The applications of the remote sensing for forestry and agriculture,including the estimation of the land surface,biophysical variables,forest vegetation’s,methods for mapping land cover,primary soil properties,the estimation of the forest cover area,and the contribution of remote sensing for crop and water monitoring to manage adverse conditions.展开更多
文摘With the recent observational evidence in extragalactic astronomy,the interpretation of the nature of quasar redshift continues to be a research interest.Very high redshifts are being detected for extragalactic objects that are presumably very distant and young while also exhibiting properties that are characteristic of a more mature galaxy such as ours.According to Halton Arp and Geoffrey Burbidge,redshift disparities consist of an intrinsic component and are related to an evolutionary process.Karlsson observed redshift periodicity at integer multiples of0.089 in log scale and Burbidge observed redshift periodicity at integer multiples of 0.061 in linear scale.Since Singular Value Decomposition based periodicity estimation is known to be superior for noisy data sets,especially when the data contain multiple harmonics and overtones,mainly irregular in nature,we have chosen it to be our primary tool for analysis of the quasar-galaxy pair redshift data.We have observed a fundamental periodicity of0.051 with a confidence interval of 95%in linear scale with the site-available Sloan Digital Sky Survey Data Release 7(SDSS DR7)quasar-galaxy pair data set.We have independently generated quasar-galaxy pair data sets from both 2d F and SDSS and found fundamental periodicities of 0.077 and 0.089,respectively,in log scale with a confidence interval of 95%.
文摘In this paper, we report the development of the design verification model (DVM) of Rb atomic frequency standard for the Indian Regional Navigational Satellite System (IRNSS) programme. Rb atomic clock is preferred for the space applications as it is light-weight and small in size with excellent frequency stability for the short and medium term. It has been used in all other similar navigation satellite systems including GPS, GLONASS Galileo etc. The Rb atomic frequency standard or clock has two distinct parts. One is the physics package where the hyperfine transitions produce the clock signal in the integrated filter cell or separate filter cell configuration and the other is the electronic circuits which include frequency synthesizer for generating the resonant microwave hyperfine frequency, phase modulator and phase sensitive detector. In this paper, the details of the Rb physics package and the electronic circuits are given. The reasons for the mode change in Rb lamp have been revisited. The effect of putting the photo detector inside the microwave cavity is studied and reported with its effect on the resonance signal profile. The Rb clock frequency stability measurements have also been discussed.
文摘Recently,the increasing demand of radio spectrum for the next generation communication systems due to the explosive growth of applications appetite for bandwidths has led to the problem of spectrum scarcity.The potential approaches among the proposed solutions to resolve this issue are well explored cognitive radio(CR)technology and recently introduced non-orthogonal multiple access(NOMA)techniques.Both the techniques are employed for efficient spectrum utilization and assure the significant improvement in the spectral efficiency.Further,the significant improvement in spectral efficiency can be achieved by combining both the techniques.Since the CR is well-explored technique as compared to that of the NOMA in the field of communication,therefore it is worth and wise to implement this technique over the CR.In this article,we have presented the frameworks of NOMA implementation over CR as well as the feasibility of proposed frameworks.Further,the differences between proposed CR-NOMA and conventional CR frameworks are discussed.Finally,the potential issues regarding the implementation of CR-NOMA are explored.
文摘The changes in species composition, abundance and forest stand structure were analyzed across altitudinal regimes in tropical forests of Eastern Ghats of northern Andhra Pradesh, India. Three 1-ha plots were established with one each in low, medium and high altitudes. A total of 153 species, 2129 stems （709 stems .ha^-1） of ≥10 cm girth were enumerated. Species richness and diversity pattern varied along altitudinal gradient and increased with the altitude. Species richness varied from 52 to 110 species-ha^-1 and stand density from 639 to 836 stems.ha^-1 with average basal area of 34.39 m^2.ha^-1. Shannon-Wiener index （H＇） ranged from 4.55 to 5.17. Low altitude （i.e., Site 1） is dominated byXylia xylocarpa （59.22） and Lagerstroemia parviflora （23.90）, medium altitude （i.e., Site 2） by Xylia xylocarpa （45;50） Bursera serrata （17.29）, and high altitude （i.e., Site 3） has Schleichera oleosa （28.25） Pterocarpus marsupium （26.55） as predominant species. Taxonomically, Rubiaceae （12 species）, Fabaceae （12）, Euphorbiaceae （11）, Rutaceae （7） and Lanraceae （7） were dominant families. Density-wise, Fabaceae, Combretaceae, Euphorbiaceae, Anacardiaceae and Myrtaceae were abundant. Thus, conservation assessment based on altitudinal regimes and the information on species structure and function can provide baseline information for monitoring and sustaining the biodiversity.
文摘A magnitude M;7.8 earthquake occurred on 25 April 2015(referred as Gorkha earthquake).We have analyzed the spatial variation of b-value and two-dimensional strain within Nepal Himalaya before and after the Gorkha earthquake.We have used continuous Global Navigation Satellite System(GNSS)data from 30 stations in the Nepal region for geodetic strain estimation and earthquake data for b-value estimation.The GNSS data were processed using double differencing technique for the accurate position of each station.The precise velocity vectors show a general azimuth of north east for all the stations and have been used to derive two-dimensional strain.Between epicenters of Gorkha(25 April 2015)and Dolakha earthquakes(12 May 2015),we observed high co-seismic horizontal displacements(0.2 m to 2 m).In the Pre-seismic deformation study,maximum strain accumulation(56.40×10;)and low bvalue(0.79-0.89)was observed in and around the Western Nepal region,which may be responsible for the 2015 Gorkha earthquake.The potential seismic zones were identified by GIS based integration of geodetic strain and b-value map and superimposition using weighted overlay method.The Maximum strain and low b-value are now observed in the eastern part of Nepal.Hence,the spatial disposition of elastic energy has changed after the two major earthquakes and continuous seismic hazard assessment is required in the eastern Nepal.
基金Financial supports to A.A.K.under the HIMADRI project(SAC/EPSA/ABHG/ALPINE/PRACRITI-II/01/13)by Space Applications Centre(SAC)-ISRO Ahmedbad(India)AICOPTAX project(F No.22018/12/2015/RE(Tax)by Mo EFCC,New Delhi(India)。
文摘In an era of climate change,the availability of empirical data on alpine summit vegetation in the Himalaya is still scarce.Here we report the assessment of alpine summit flora in Gulmarg Wildlife Sanctuary,Kashmir Himalaya.We employed a globally standardized Multi-Summit Approach and four spatially isolated summits spanning an elevation gradient of 210 m(between 3530-3740 m a.s.l.)from natural treeline to nival zone were studied.Sampling of the summits was carried out in the year 2018 to collect floristic data together with records of soil temperature.A total of 142 vascular plant species were recorded in the sampled summits.Majority of the species were of herbaceous growth form and with perennial life span.Based on Raunkiaer’s life form,hemicryptophytes were the most dominant followed by therophytes and phanerophytes.The summit flora showed the predominance of narrow-endemic species,with broad-and non-endemics declining with elevation.A significant relationship between growth form,Raunkiaer’s life form,and the degree of endemism with elevation was observed.Both species diversity and soil temperature showed a monotonic decrease with increasing elevation.Interestingly,soil temperature clearly determined the magnitude of species diversity on the summits.Furthermore,based on floristic composition,the lowest summit had the highest dissimilarity with the rest of the summits.The present study employed globally standardized protocol to scientifically assess the patterns of plant diversity on the alpine mountain summits of Kashmir Himalaya,which in turn has wide implications towards long-term monitoring of climate change impact on alpine biodiversity in the rapidly warming Himalaya.
基金support of the NASA High Energy Astrophysics Programssupported by UGC through the RFSMS scheme
文摘To investigate the geometry of the accretion disk in the source H1743-322, we have carried out a detailed X-ray temporal and spectral study using RXTE pointed observations. We have selected all data pertaining to the Steep Power Law （SPL） state during the 2003 outburst of this source. We find anti-correlated hard X-ray lags in three of the observations and the changes in the spectral and timing parameters （like the QPO frequency） confirm the idea of a truncated accretion disk in this source, Compiling data from similar observations of other sources, we find a correlation between the fractional change in the QPO frequency and the observed delay. We suggest that these observations indicate a definite size scale in the inner accretion disk （the radius of the truncated disk） and we explain the observed correlation using various disk parameters like Compton cooling time scale, viscous time scale etc..
文摘Development of asymptotic magnitude Bode plots for integer-order transfer functions is a well-established topic in the control theory.However,construction of such plots for the fractional-order transfer functions has not received much attention in the existing literature.In the present paper,we investigate in this direction and derive the procedures for sketching asymptotic magnitude Bode plots for some of the popular fractional-order controllers such as PI^α,[PI]^α,PD^β,[PD]^β,and PI^αD^β.In addition,we deduce these plots for general fractional commensurate-order transfer functions as well.As applications of this work,we illustrate 1)the analysis of the designed fractional-control loop and 2)the identification of fractional-order transfer function from a given plot.
基金conducted as a part of the project Alpine Ecosystem Dynamicssupported by SAC,ISRO,Ahmedabad,India(EPSA/ABHG/ALPINE/PRACRITI-II 01/13)
文摘The present study was carried out in Tungnath alpine meadows of Kedarnath Wild Life Sanctuary, Western Himalaya from subalpine to upper alpine zone. A total of four summits were selected along an altitudinal gradient and sampled for detailed vegetation analysis using multi summit approach as per Global observation research initiative in alpine environments(GLORIA). Species richness, diversity, and evenness among four summits as well as the interaction between environmental variables with plant communities were assessed. Monthly mean soil temperature was calculated using data retrieved from geo-precision temperature logger in order to identify the trend of soil temperature among different season and altitudinal gradient and its implications to plant communities. Soil samples were analyzed fromeach summit by collecting randomized composite soil samples. The indirect non-metric multidimensional scaling(NMDS) and direct canonical correspondence analysis(CCA) tools of ordination techniques to determine the linkage between plant species from various sample summits and biotic/abiotic environmental gradients were used in the present study. The results of the study demonstrated increase in species richness as soil temperature increases, the ecotone representing summits were found most warm summits followed by highest species richness. Annual soil temperature increased by 1.43°C at timberline ecotone. Whereas, at upper alpine zone the soil temperature increased by 0.810 C from year 2015 to 2016. S?rensen's similarity index was found to be increased between subalpine and upper alpine zone with increase in the presence of subalpine plant species at upper alpine zone. Both the ordination tools separate the subalpine summit and their respective vegetation from summits representingtimberline ecotone and upper alpine zone. Soil p H, altitude, soil cation exchange capacity were found as the key abiotic drivers for distribution of plant species.
文摘TCP performance degrades when end-to-end connections extend over wireless links which are characterized by high Bit Error Rate and intermittent connectivity. Such degradation is mainly accounted for TCP’s unnecessary congestion control actions while attempting TCP loss recovery. Several independent link loss recovery approaches are proposed by researchers to reduce number of losses visible at TCP. In this paper we first presented a survey of loss mitigation techniques at wireless link layer. Secondly performance evaluation for TCP through Type 0 Automatic Retransmission Request mechanism in erroneous Wireless LAN is presented. In particular, simulations are performed taking into account the wireless errors introduced over IEEE 802.11 link using a well-established 2-State Markov model. TCP performance is evaluated under different settings for maximum link retransmissions allowed for each frame. Simulation results show that, link retransmission improves TCP performance by reducing losses perceived at TCP sender. However, such improvement is often associated with adverse effect on other TCP parameters that may cost a lot in return under extreme network conditions. In this paper an attempt is made to observe impact of link retransmissions on the performance of multiple TCP flows competing with each other. The analysis presented in this paper signifies the scope for maximizing TCP’s throughput at the least possible cost.
文摘The desert locust, <em>Schistocerca gregaria</em> Forsk. (Orthoptera: Acrididae) is a peculiar insect that exhibits density-dependent phase polyphenism. Gregarious phase enables desert locust to form a large groups and mass migrations during which significant crop loss and food security issues may occur. Currently, the most recent upsurge of desert locust is prevailing across Eastern Africa and Southwestern Asia. Usually desert locusts are restricted to regions like semi-arid and arid regions. A super cyclonic storm, namely Amphan originated during May 2020, in the Bay of Bengal of North Indian Ocean has influenced numerous swarms to migrate from the Thar desert region to other parts of India. In this research, satellite data were used to investigate the reasons for this sudden swarm migration. The results that revealed the wind jets passing above the Thar desert region have integrated with the cyclogenesis of Amphan and led to the formation of conduits. The favorable conditions in the conduits include the open sky conditions, air temperature and fresh vegetation availability. Moreover, the wind settings in the conduits have enabled the swarm migrate to follow the downwind facing the sunrays during early mornings for an easy and successful take-off. It is observed that during the take-off session the wind speed at 850 hPa pressure level is mostly double than that of surface wind in both the conduits.
文摘Present study attempts to understand the potential of multispectral ASTER (Advanced space borne thermal emission and reflection radiometer) data for spatial mapping of kimberlite. Kimberlite is an economic rock known for hosting diamond. Kimberlite also has petrogenetic importance for giving us clue on the composition of lower part of the mantle. Kimberlites often contain serpentine, carbonate minerals;which have their diagnostic spectral signatures in short wave infrared (SWIR) domain. In the present study, attempt is made to delineate kimberlite from adjacent granite-granodiorite gneiss based on processing of the ASTER data as ASTER’s spectral channels can detect some of the diagnostic absorption features of kimberlites. But it has been observed that the kimberlites are difficult to be delineated by processing the ASTER data using correlative information of both sub-pixel and per-pixel mapping. Moreover, smaller spatial size of kimberlites with respect to pixel size of ASTER SWIR channels further obscures the spectral feature of kimberlite. Therefore, an attempt is also made to understand how intra pixel spectral mixing of kimberlite and granite granodiorite-gneiss modifies the diagnostic spectral feature of kimberlite. It is observed that spectral feature of kimberlites would be obscured when it is has very small spatial size (one-tenth of pixel) with respect to pixel size. Moreover, calcrete developed in the adjacent soil has identical absorption feature similar to the spectral features of kimberlites imprinted in the respective ASTER convolved spectral profiles. This also has resulted false-positives in ASTER image when we use spectral feature as a tool for spatial mapping of kimberlite. Therefore hyperspectral data with high spatial and spectral resolution is required for targeting kimberlites instead of using broad band spectral feature of kimberlites.
文摘Aeolian process leads to the transportation and accumulation of sand particles that result in sand dune landforms. The structure and shape of the sand dunes are driven by the parameters of interacting wind force and the material composition of sand within. Cross-section profiles over the sand dunes will essay the geomorphological parameters through which the steady state and rate of sand transport can be computed. National Aeronautics and Space Administration’s novel satellite namely Ice, Cloud and land Elevation Satellite-2 (ICESat-2) hosts a solo sensor namely Advanced Topographic Laser Altimeter System (ATLAS) which is a photon counting instrument that measures the round-trip time of the light pulse being emitted and reflected back from the surface determines the true height of the topographic feature on the Earth. In this article, cross-section profiles generated from the beams of ICESat-2 ground-tracks acquired over sand dunes of the Thar Desert region were analysed for detecting the geomorphological parameters. Observations from the cross-section profiles have resulted in giving unprecedented details about the shapes and morphological settings of various types of sand dunes like barchanoids, parabolic, longitudinal, and transverse dunes. Morphological parameters of sand dunes like the length of the stoss slope, crest height, slip face details, inter-arms spacing, height of the trailing arms, length of the depositional lobes, and sinuosity of the recurring crest lines were retrieved with ease from the Level-2A data product namely ATL03 of ICESat-2/ATLAS.
文摘The projection for groundwater states that the total domestic water demand for greater Bangalore would increase from 1,170 MLD in 2010 to 1,336 MLD in 2016. Dependence on groundwater is ever increasing due to rapid Industrialization ＆ Urbanization. It is estimated that almost 40% of the population of Bangalore is dependent on groundwater. Due to the unscientific disposal of domestic and industrial waste generated, groundwater is getting highly polluted in the city. The scale of this impact will depend mainly upon the water-service infrastructure, the superficial geology and the regional setting. The quality of ground water is equally important as that of quantity. Jointed and fractured granites and gneisses constitute the major aquifer system of BBMP （Bruhat Bengaluru Mahanagara Palike） area. Two new observatory borewells were drilled and lithology report has been prepared. Petrographic Analysis （XRD/XRF） and Water Quality Analysis were carried out as per the standard methods. Petrographic samples were analysed by collecting chip of rock from the borewell for every 20 ft depth, most of the samples were similar and samples were identified as Biotite-Gneiss, Schistose Amphibolite. Water quality analysis was carried out for individual chemical parameters for two borewells drilled. The 1st Borewell struck water at 150 ft （total depth-200 ft） ＆ 2nd struck at 740 ft （total depth-960 ft）. Five water samples were collected till end of depth in each borewell. Chemical parameter values such as, Total hardness （360-348, 280-320） mg/ltr, Nitrate （12.24-13.5, 45-48） mg/ltr, Chloride （104-90, 70-70） mg/ltr, Fe （0.75-0.09, 1.288-0.312） mg/ltr etc. are calculated respectively. Water samples were analysed from various parts of BBMP covering 750 sq kms, also thematic maps （IDW method） of water quality are generated for these samples for post-monsoon season. The study aims to explore the sub-surface lithological layers and the thickness of weathered zone, which indirectly helps to know the groundwater pollution source near surface water bodies, dug wells, etc. The above data are interpreted for future ground water resources planning and management.
文摘Various spacecraft and satellites from the world’s best space agencies are exploring Mars since 1970, constantly with great ability to capture the maximum amount of dataset for a better understanding of the red planet. In this paper, we propose a new method for making a mosaic of Mars Reconnaissance Orbiter (MRO) spacecraft payload Context Camera (CTX) images. In this procedure, we used ERDAS Imagine for image rectification and mosaicking as a tool for image processing, which is a new and unique method of generating a mosaic of thousands of CTX images to visualize the large-scale areas. The output product will be applicable for mapping of Martian geomorphological features, 2D mapping of the linear feature with high resolution, crater counting, and morphometric analysis to a certain extent.
文摘Hydrological modelling of large river catchments has become a challenging task for water resources engineers due to its complexity in collecting and handling of both spatial and non-spatial data such as rainfall,gauge-discharge data,and topographic and hydraulic parameters.In this article,a flood forecast model is developed for the Godavari Basin,India through a distributed modelling approach using space inputs.The approach includes rainfall runoff modelling,hydrodynamic flow routing,calibration,and validation of the model with field discharge data.The study basin is divided into 128 subbasins to improve the model accuracy.Topographic and hydraulic parameters of each subbasin and channel are computed using the land use/land cover grid that is derived from the Indian Remote Sensing Satellite(IRS–P6) AWi FS sensor data(56 m resolution),Shuttled Radar Topographic Mission(SRTM) Digital Elevation Model(DEM),and the soil textural grid.The model is calibrated using the field hydrometeorological data of 2000 and validated with the data of 2001.The model was tested during the 2010 floods with real-time 3-hour interval hydrometeorological and daily evapotranspiration data.Accuracy in estimating the peak flood discharge and lag time was found to be very good.Flood forecast lead time is increased by 12 hours compared to conventional methods of forecasting.
文摘Rapid satellite-based flood inundation mapping and delivery of flood inundation maps during a flood event can provide crucial information for planners and decision makers to prioritize relief and rescue operations. The present study is undertaken to optimize the threshold ranges for the classification of flood water in Synthetic Aperture Radar(SAR) images(of 20° to 49° incidence angles) for quick flood inundation mapping and response during flood disasters. This is done through assessing the signature of flood water in Horizontal transmit and Horizontal received(HH), Horizontal transmit and Vertical received(HV), Vertical transmit and Horizontal received(VH), and Vertical transmit and Vertical received(VV) polarization radar data. The mean backscattering signature profiles of various water bodies were analyzed to discriminate flood water from other water bodies. The study shows that there is better demarcation of land-water surface in HH polarization. VV polarization has the potential to identify partially submerged features, which can be useful in flood damage assessments. The backscatter of flood water in HV and VH is the same and both HV and VH polarizations are adequate for the mapping of flood water. At near range to far range,-8 to-12 d B,-15 to-24 d B, and-6 to-15 d B can be used as optimum ranges for the classification of flood water in HH, HV, and VV polarizations. These optimum threshold ranges can be applied to the automation of flood mapping using SAR images in near-real time, where much time was often spent on finding the thresholds in order to produce flood inundation maps in a short time from the onset of flood disasters and deliver such maps to the concerned agencies.
文摘Transient numerical simulations are carried out to investigate the liquid-gas interfacecharacteristics associated with liquid film cooling flows.A two-dimensional axisymmetricmulti-phase numerical model using finite volume formulation is developed.The model hasbeen validated against available experimental data for liquid-film cooling flows inside tubes.The model has been used to predict the interface characteristics for a variety of imposedparameters and momentum flux ratios under cold flow conditions wherein both the coolant andmainstream are maintained at the same temperature.Disturbance waves are observed at theliquid-gas interface for coolant flows above a critical value and after a finite distance from theinlet.The distance toward the wave inception point increased with the increase of momentumflux ratio.However,at higher momentum flux ratios,the properties of the disturbance wavesdid not vary significantly.The parameters related to the liquid-gas interface waves,namely,wave velocity,frequency,amplitude and wave length have been analyzed in detail.Analysisindicates that the liquid entrainment is due to the shearing of the disturbance wave crest.
基金Indo-French collaboration research projects such as IFCPAR/CEFIPRA AICHA(2013-2016),ANR ATCHA(2017-2020)VIGISAT programme,IISc-STC ISRO-098(2010-2013)+1 种基金UBL Ph.D.student grant for mobility(2017)CNES/TOSCA(Irriga-Detection project(2017-2019).
文摘Groundwater assists farmers to irrigate crops for fulfilling the crop-water requirement.Indian agriculture system is characterized by three cropping seasons known as Kharif(monsoon),Rabi(post-monsoon)and summer(pre-monsoon).In tropical countries like India,monitoring cropping practices using optical remote sensing during Kharif and Rabi seasons is constraint due to the cloud cover,which can be well addressed by microwave remote sensing.In the proposed research,the strength of C-band polarimetric Synthetic Aperture Radar(SAR)time series images were evaluated to classify groundwater irrigated croplands for the Kharif and Rabi cropping seasons of the year 2013.The present study was performed in the Berambadi experimental watershed of Kabini river basin,southern peninsular India.A total of fifteen polarimetric variables were estimated includes four backscattering coefficients(HH,HV,VH,VV)and eleven polarimetric indices for all Radarsat-2 SAR images.The cumulative temporal sum(seasonal and dual-season)of these parameters was supervised classified using Support Vector Machine(SVM)classifier with intensive ground observation samples.Classification results using the best equation(highest accuracy and kappa)shows that the Kharif,Rabi and irrigated double croplands are respectively 9.58 km2(20.6%),16.14 km2(34.7%)and 6.22 km2(13.4%)with a kappa coefficient respectively 0.84,0.74 and 0.94.
文摘Global warming resulting from greenhouse effect has threatened to the sustainability of agriculture,forest and land surface globally.A significant rise in extreme weather events has been observed worldwide,particularly in developing countries[1].In the changing climatic era,the economic importance of the remote sensing and geographical information system(GIS)to monitoring forests and agricultural resources is imperative to the development of agro-ecosystem services and the products responding to user needs[2].The applications of the remote sensing for forestry and agriculture,including the estimation of the land surface,biophysical variables,forest vegetation’s,methods for mapping land cover,primary soil properties,the estimation of the forest cover area,and the contribution of remote sensing for crop and water monitoring to manage adverse conditions.
