http://nopr.niscpr.res.in/handle/123456789/63092 2026-10-06T19:19:00Z http://nopr.niscpr.res.in/handle/123456789/65063 Title: Precipitable Water Vapour Retrieval Modelling Using Indian Regional Navigation Satellite System (IRNSS) Observations over Dehradun Authors: Srivastava, Ashutosh Abstract: In the present work, a maiden attempt has been made to derive precipitable water vapour (PWV) using IRNSS datasets. A least square differential correction approach is used in modelling to process datasets. PWV is estimated for different days of January, April, July, and November of the year 2019 to observe its variation over different seasons. Meteorological datasets used in the estimation of zenith hydrostatic delay (ZHD) and weighted mean temperature estimation are taken from the National Centers for Environmental Prediction (NCEP) at the location. The obtained PWV values are validated with GPS-derived PWV and Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis datasets. The results show that PWV derived using IRNSS datasets are close to the other reference values. The difference of 3 mm to 7 mm was observed if compared with GPS-derived PWV and MERRA PWV values. Since each satellite signal is available at all times, PWV is estimated using the individual satellite data and combined data from all the IRNSS satellites. As the IRNSS constellation includes both geostationary and geosynchronous satellites, it is observed that PWV estimated using geostationary satellite datasets is close to the reference datasets having a difference of 3 to 5 mm. However, estimated PWV using geosynchronous satellite data have more variation with differences within 3 to 7 mm. Combined data from all the satellites was also used to derive the PWV which has a difference of close to 5 mm in all the cases. The obtained PWV values using IRNSS data show a good correlation with GPS PWV and MERRA PWV values and provide a good estimate of PWV. Page(s): 1061-1073 2024-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/65062 Title: Thermal Conductivity Enhancement of Phase Change Materials Using Metal Wire Woven Porous Structures for Thermal Energy Storage Authors: Khare, Anup Kumar; Sharma, Mohit; Gupta, Gaurav Kumar; Gupta, Manoj Kumar; Prasanth, N; Bhargaw, Hari N Abstract: In the present work, the thermal conductivity of paraffin wax has been increased using low-cost and lightweight aluminium wire metal foam structures. The designed metal wire foam structures have uniform-sized circular pores forming a convective spring-like network for faster heat transfer. The paraffin wax can easily infiltrate the designed wire woven foam structures even at a lower porosity (~75 vol %). The latent heat thermal energy storage (LHTES) systems which can store up to 500 kJ of thermal energy have been designed using the PCM-wire-woven metal foam composite material. The heating of these composites is carried out both in convection and conduction modes, and their effect has been studied. The effect of using a polymer (acrylic), and a galvanized iron (GI) sheet to encapsulate PCM-metal wire foam composites is also evaluated. Increasing the pore diameters in the wire woven structures, and its effect on the thermal efficiencies of the LHTES system is calculated. The thermal efficiency of the LHTES ranged from 67 to 92 % using an acrylic sheet, and 72 to 77 % using the GI sheet. The heat extraction using cold water could be continued for 8-9 cycles in acrylic, and 5-6 cycles in GI sheet capsulation. Page(s): 1074-1090 2024-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/65061 Title: Advancing Terahertz Connectivity of Innovative Design of a Directional Cross-Dipole Antenna with Conformal Graphene-Based Reconfigurable Intelligent Surface Authors: Yadav, Harshmani; Kumar, Nitin; Meena, Mahesh C.; Jewariya, Mukesh; Yaduvanshi, Rajveer Singh Abstract: In contemporary systems, there is a growing emphasis on harnessing tunable terahertz (THz) waves to advance wireless communication swiftly. Furthermore, reconfigurable intelligent surfaces (RISs) have noticeably enhanced the performance of THz components and devices that enabling them to control electromagnetic waves effectively. Within the domain of wireless systems operating within the THz frequency range, a demand has arisen for adjustable directional antennas. This paper presents a novel approach that suggests a solution involving a customizable directional antenna design which utilizing a cross-dipole configuration with a central graphene-based dipole element. The electrical conductivity of these dipole elements can be adjusted independently by applying a bias voltage via the graphene's chemical potential. The concept of employing a graphene-based Reconfigurable Intelligent Surface (RIS) to actively manipulate Terahertz (THz) waves. By carefully engineering the reflection characteristics of the individual unit cells, the overall system performance can be enhanced. The proposed conformal RIS design comprises a repetitive arrangement of rectangular graphene meta-atoms positioned on a silicon substrate grounded with metal. The paper also provides a model featuring an equivalent circuit for the RIS design and its solution. Furthermore, an implementation of tunable surfaces featuring the conformal graphene-based RIS. It is developed to be placed beneath the cross-dipole antenna at an appropriate distance. This setup enables the control of radiated patterns through a reconfigurable process that involves changing the states of the meta-atoms to achieve specific codes with corresponding patterns. The antenna can achieve various gains that ranging from 8.3 to 9.3 dBi. The results of this study demonstrate the promising potential of the proposed antenna structure for efficient and intelligent THz wireless communications. Page(s): 1091-1097 2024-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/65060 Title: Crystal Growth and Characterization of an Efficient Nonlinear Optical Material: ƒ×-Glycine Crystal Authors: Juliana, S Gracelin; Sathishkumar, p; Durai, S C Vella Abstract: In an aqueous solution of ferrous chloride,  - Glycine Crystal (-GC), an efficient nonlinear optical (NLO) material, was created. AR grade glycine and ferrous chloride in a molar ratio of 1: 0.5 were employed to grow the title sample. The lattice properties of -GC were determined using a single crystal X-ray diffraction method. High transmittance in the visible area and a UV-visible spectrum make -GC excellent for optical applications. Using a Nd:YAG laser, the produced crystal's LDT value was ascertained. The crystal's hardness was assessed using the Vickers test, and other mechanical properties were determined. The electrical properties of -GC were examined by measuring the dielectric constant and dielectric loss at various frequencies, and temperatures. Using TG/DTA tests to gauge the sample's thermal stability, the functional groups of the -GC were identified by FTIR analysis. The material also underwent SHG and LDT testing. Page(s): 1098-1105 2024-12-01T00:00:00Z