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排序方式: 共有69条查询结果,搜索用时 15 毫秒
1.
Sanjay Kumar Jinka Venkata Aravind Santosh Kumar G 《Marine Georesources & Geotechnology》2020,38(3):291-301
AbstractThis article deals with the effect of salinity variation on underwater wireless optical communication (UWOC). Effect of different concentration of salt on underwater optical communication has been carried out experimentally in terms of received power at different link lengths. Based on the analysis of experimental data, a mathematical model has been proposed to describe the saline water channel. A simulation study is performed for different data rates and link lengths. It is seen that with increased salinity the attenuation is higher and the UWOC system performance degrades with higher data rate and increased link length. 相似文献
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Raghavendra Neeli J R K Kumar Dabbakuti V. Rajesh Chowdhary Nitin K. Tripathi Venkata Ratnam Devanaboyina 《Astrophysics and Space Science》2018,363(9):182
Singular Value Decomposition (SVD) model is implemented to recognize the Total Electron Content (TEC) time series of daily, temporal as well as seasonal characteristics throughout the 24th solar cycle period of the year 2015 in the study. The Vertical (vTEC) analysis has been carried out with Global Positioning System (GPS) data sets collected from five stations from India namely GNT, Guntur (16.44° N, 80.62° E), and IISC, Bangalore (12.97° N, 77.59° E), LCK2, Lucknow (26.76° N, 80.88° E), one station from Thailand namely AITB, Bangkok (14.07° N, 100.61° E), and one station from South Andaman Island namely PBR, Port Blair (11.43° N, 92.43° E), located in low latitude region. The first five singular value modes constitute about 98% of the total variance, which are linearly transformed from the observed TEC data sets. So it is viable to decrease the number of modeling parameters. The Fourier Series Analysis (FSA) is carried out to characterize the solar-cycle, annual and semi-annual dependences through modulating the first three singular values by the solar (F10.7) and geomagnetic (Ap) indices. The positive correlation coefficient (0.75) of daily averaged GPS–TEC with daily averaged F10.7 strongly supports the temporal variations of the ionospheric features depends on the solar activity. Further, the significance and reliability of the SVD model is evaluated by comparing it with GPS–TEC data and the standard global model (Standard Plasma-Spherical Ionospheric Model, SPIM and International Reference Ionosphere, IRI 2016). 相似文献
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Venkata Giri Raj Kumar Konda Venkatesh Reddy Chejarla Venkata Ravibabu Mandla Vani Voleti Nagaveni Chokkavarapu 《Arabian Journal of Geosciences》2018,11(2):35
Developing nations are abandoned against tropical cyclones because of climatic changeability; the atmosphere is probably going to expand the recurrence and extent of some outrageous climate and calamity occasions. Urban areas and towns arranged along the coastline front belt in Visakhapatnam region experienced serious harm because of Hudhud cyclone, which happened on October 12, 2014. The fundamental motivation behind this exploration was to distinguish the vegetation damage in Visakhapatnam and neighbouring towns. In this analysis, Landsat-8 satellite datasets procured prior and then afterward the cyclone have been utilized; image processing techniques have been completed to evaluate the progressions of pre- and post-disaster condition. Vegetation index strategy was utilized to assess the damage to vegetation. Arrangement results and land utilize land cover change investigation demonstrate that 13.25% of agriculture Kharif and 31.1% of vegetation was damaged. Normalized difference vegetation index (NDVI) maps were produced for the previously, then after the cyclone circumstance, and vegetation biomass damage was evaluated in Visakhapatnam and Bhimunipatanam. General loss of vegetation in both the spots was 30.67 and 43.37 km2. The result of this review can be utilized by decision makers for the post-disaster support for rebuilding of influenced regions. 相似文献
4.
Amartanshu Srivastava Suresh Pandian Elumalai Elluru Venkata Ramana Raju 《Arabian Journal of Geosciences》2018,11(6):120
The objective of the present study was to delineate temporal and spatial changes in the coal fire and land use/cover within Bastacolla area of Jharia coal field. Studying this variation helped to decipher interconnection among the dynamics of the coal fire and concomitant changes in land use/cover. The detection of coal fires during a span of 14 years along with transitioning land use/cover was cost-effective and enabled planning for management of coal resources and environment. Landsat series of satellite data of 2002, 2009, 2013, and 2016 were processed for generating land surface temperature profiles vis-a-vis classified land use/cover of the study area. A single cut-off temperature was derived for mapping of coal fires using land surface temperature profile from 2002 to 2016. The satellite images were classified using support vector machines, and for depicting land use/cover change, post-classification change detection was done. Classification accuracy obtained was excellent with kappa coefficient ranging from 0.897 for classified image of 2002 to 0.799 for classified image of 2016. Results revealed that coal fires had shifted to the central west part of the area. Furthermore, pockets of coal fire from northern and eastern part of the study area have diminished. OB dumps and coal quarry/coal dump may be attributed towards the spatial change in coal fire while; OB dumps showed connotation with the highest temperature zones. Ground verifications for temperature profiles and coal fires were carried out using thermal camera which enunciated good agreement with results. 相似文献
5.
Raghavendra Vishnu Tadivaka Bhanu Priyanka Paruchuri Sridhar Miriyala Padma Raju Koppireddi Venkata Ratnam Devanaboyina 《Acta Geophysica》2017,65(4):777-784
The performance and measurement accuracy of global navigation satellite system (GNSS) receivers is greatly affected by ionospheric scintillations. Rapid amplitude and phase variations in the received GPS signal, known as ionospheric scintillation, affects the tracking of signals by GNSS receivers. Hence, there is a need to investigate the monitoring of various activities of the ionosphere and to develop a novel approach for mitigation of ionospheric scintillation effects. A method based on Local Mean Decomposition (LMD)–Detrended Fluctuation Analysis (DFA) has been proposed. The GNSS data recorded at Koneru Lakshmaiah (K L) University, Guntur, India were considered for analysis. The carrier to noise ratio (C/N0) of GNSS satellite vehicles were decomposed into several product functions (PF) using LMD to extract the intrinsic features in the signal. Scintillation noise was removed by the DFA algorithm by selecting a suitable threshold. It was observed that the performance of the proposed LMD–DFA was better than that of empirical mode decomposition (EMD)–DFA. 相似文献
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