Browsing by Author "Rashmi, R."
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Item A study on the influence of geometric coordination of cobalt ions on the structural, physical and optical properties of borosilicate glass(Elsevier Ltd, 2025) Raghuvanshi, V.; Rashmi, R.; Ingle, A.; Shashikala, H.D.; Nagaraja, H.S.This work explores the synthesis and characterization of cobalt oxide-added borosilicate glass using the melt-quenching technique. The glass system was investigated using various methods, including X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), density measurements, UV–vis spectroscopy, photoluminescence, and electron paramagnetic resonance (EPR) spectroscopy. XRD validated the glass's amorphous nature, while FTIR results indicated significant bonding alterations, showing a transition from BO3 to BO4 units and from B3-O-Si to B4-O-Si linkages. The increased glass density further supported the formation of BO4 units. XPS analysis verified the presence of Co2+ and Co3+ ions within the glass matrix. Optical absorption studies revealed distinct electronic transitions for Co2+ ions in both tetrahedral and octahedral coordination, and for Co3+ ions in octahedral coordination, which was corroborated by EPR spectroscopy. The paramagnetic nature of Co2+ ions was analyzed, and the g-value was determined using X-band frequency. The study also noted the narrowing of the indirect band gap with the rise in the content of Co3O4, and the examination of the metallization criterion suggested a potential metallic nature for the synthesized glasses. Notably, the 0.05 mol% Co3O4-added sample exhibited a 48 % transmission rate and the highest emission, highlighting its potential as an optical bandpass filter. These findings underscore the versatility and tunability of cobalt oxide-added borosilicate glass for various optical technologies. © 2024 Elsevier Ltd and Techna Group S.r.l.Item Analysis of symbol error probability in GFDM under generalized ????? channels: An approach based on probability density function for beyond 5G wireless applications(Elsevier GmbH, 2025) Bodempudi, N.S.P.; Chaturvedi, A.; Rashmi, R.; Kulkarni, M.Generalized Frequency Division Multiplexing (GFDM) is a flexible multicarrier modulation scheme tailored to meet the diverse requirements of 5G and beyond (B5G) wireless systems. It provides flexibility to select subsymbols, subcarriers, and pulse-shaping filters, making it suitable for various B5G communication needs. Moreover, GFDM includes orthogonal frequency division multiplexing (OFDM) and single carrier frequency domain equalization (SC-FDE) as special cases. Since fading conditions greatly affect communication reliability, this paper derives a closed-form expression for the symbol error probability/symbol error rate (SEP/SER) of GFDM using M-QAM and M-PSK in generalized ????? fading channels. The study examines how fading parameters (?,?,?), pulse-shaping filters, roll-off factor, and subsymbol count influence SER performance. Results show these factors have a significant impact on error probability. This comprehensive analysis provides important insights for evaluating GFDM performance under complex fading scenarios, making it a valuable reference for GFDM system design for B5G wireless applications. © 2025Item Influence of titanium redox states on luminescence and conductivity in TiO2 -doped borophosphate glass system(Elsevier B.V., 2025) Rashmi, R.; Ingle, A.; Raghuvanshi, V.; Shashikala, H.D.; Nagaraja, H.S.Borophosphate glasses have garnered significant interest due to their potential for optical and electronic applications. This research delves into the luminescent and conductive properties of 40P2O5–25B2O3-(35-x) BaO-xTiO2 (x = 0–5 mol%) glasses synthesized via the melt-quench method. The glass doped with 4 mol% TiO2 exhibited intense luminescence within the 400–600 nm spectrum, manifesting as a vivid blue emission and the highest Ti3+ ion concentration. Beyond this threshold, the luminescence intensity waned, highlighting the significance of Ti4+/Ti3+ ratios. Absorption spectra and X-ray photoelectron spectroscopy were utilized to study these multivalent ions. Temperature-dependent AC conductivity, exhibited a linear increase, consistent with the Correlated Barrier Hopping (CBH) model. Enhanced polaron hopping between Ti3+ and Ti4+ with increasing TiO2 content improved the dielectric constant and conductivity, peaking at 4.145×10?5 Scm?1 at 5 mol% TiO2 within the 450–530 °C range. These findings underscore the tunability of TiO2-doped glasses for optoelectronic applications. © 2024 Elsevier B.V.Item Privacy-preserving searchable encryption scheme over encrypted data supporting dynamic update(2019) Rashmi, R.; Siva, Kumar, D.V.N.; Santhi Thilagam, P.With the advancement of network technology, cloud computing services have become popular due to the on-demand availability of computing resources, large-scale data storage and distribution. Many users are influenced to outsource their private data to cloud servers to cut the costs of building by storing their data locally. Security and privacy protection of such outsourced data become a major security concern. To address this, the outsourced data is encrypted before it is stored on the cloud server. At the same time, users must be enabled to retrieve the data of their interest rather than going through all documents and picking up the ones that are required. This creates a need to search the encrypted data without allowing the cloud service providers know about the search query but still provide the clients with relevant documents. With data continuously changing over time, clients wish to keep their documents updated so as to maintain data consistency and enable other users to fetch the latest relevant data. However, while adding new keywords to documents, the potential positions of newly added keywords are leaked in the existing approaches. In this paper, an efficient and secure approach is proposed that returns the latest relevant documents and also preserves the privacy of updated keywords. � Springer Nature Singapore Pte Ltd. 2019.Item Privacy-preserving searchable encryption scheme over encrypted data supporting dynamic update(Springer Verlag service@springer.de, 2019) Rashmi, R.; Siva Kumar, D.V.N.; Santhi Thilagam, P.S.With the advancement of network technology, cloud computing services have become popular due to the on-demand availability of computing resources, large-scale data storage and distribution. Many users are influenced to outsource their private data to cloud servers to cut the costs of building by storing their data locally. Security and privacy protection of such outsourced data become a major security concern. To address this, the outsourced data is encrypted before it is stored on the cloud server. At the same time, users must be enabled to retrieve the data of their interest rather than going through all documents and picking up the ones that are required. This creates a need to search the encrypted data without allowing the cloud service providers know about the search query but still provide the clients with relevant documents. With data continuously changing over time, clients wish to keep their documents updated so as to maintain data consistency and enable other users to fetch the latest relevant data. However, while adding new keywords to documents, the potential positions of newly added keywords are leaked in the existing approaches. In this paper, an efficient and secure approach is proposed that returns the latest relevant documents and also preserves the privacy of updated keywords. © Springer Nature Singapore Pte Ltd. 2019.