Journal Articles
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884
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Item Dynamic pricing of call rates: Bayesian approach(Elsevier B.V., 2015) Dugar, C.; Jain, A.; Rajawat, A.; Bhattacharya, S.In this paper, we present different cases and their possible solutions in the telecommunications market by incorporating dynamically changing call rates over the channel depending upon the network congestion. Since dynamic pricing of call rates is beneficial from both the perspectives of subscribers and service providers, our solution can significantly help to adapt this pricing mechanism in real market scenario. In order to deploy this scheme, we have incorporated the competing network provider's strategy into the mechanism of deciding dynamic price. Establishment of Nash equilibrium with the competing network provider has stabilized our pricing mechanism. © 2014 Elsevier B.V. All rights reserved.Item Scalable and fair forwarding of elephant and mice traffic in software defined networks(Elsevier, 2015) Hegde, S.; Koolagudi, S.; Bhattacharya, S.A software defined network decouples the control and data planes of the networking devices and places the control plane of all the switches in a central server. These flow based networks do not scale well because of the increased number of switch to controller communications, limited size of flow tables and increased size of flow table entries in the switches. In our work we use labels to convey control information of path and policy in the packet. This makes the core of the network simple and all routing and policy decisions are taken at the edge. The routing algorithm splits the elephant traffic into mice and distributes them across multiple paths, thus ensuring latency sensitive mice traffic is not adversely affected by elephant traffic. We observed that label based forwarding and traffic splitting work well together to enable scalable and fair forwarding. Our approach is topology independent. We present here a few preliminary simulation results obtained by running our routing algorithm on random network topologies. © 2015 Elsevier B.V.Item Social network pruning for building optimal social network: A user perspective(Elsevier B.V., 2017) Sumith, N.; Annappa, B.; Bhattacharya, S.Social networks with millions of nodes and edges are difficult to visualize and understand. Therefore, approaches to simplify social networks are needed. This paper addresses the problem of pruning social network while not only retaining but also improving its information propagation properties. The paper presents an approach which examines the nodal attribute of a node and develops a criterion to retain a subset of nodes to form a pruned graph of the original social network. To authenticate feasibility of the proposed approach to information propagation process, it is evaluated on small world properties such as average clustering coefficient, diameter, path length, connected components and modularity. The pruned graph, when compared to original social network, shows improvement in small world properties which are essential for information propagation. Results also give a significantly more refined picture of social network, than has been previously highlighted. The efficacy of the pruned graph is demonstrated in the information diffusion process under Independent Cascade (IC) and Linear Threshold (LT) models on various seeding strategies. In all size ranges and across various seeding strategies, the proposed approach performs consistently well in IC model and outperforms other approaches in LT model. Although, the paper discusses the problem with the context of information propagation for viral marketing, the pruned graph generated from the proposed approach is also suitable for any application, where information propagation has to take place reasonably fast and effectively. © 2016 Elsevier B.V.Item A holistic approach to influence maximization in social networks: STORIE(Elsevier Ltd, 2018) Sumith, N.; Annappa, B.; Bhattacharya, S.Crowd sourcing techniques are used in social networks to propagate information at a faster pace through campaigns. One of the challenges of crowd sourcing system is to recruit right users to be a part of successful campaigns. Fetching this right group of people, who influence a vast population to adopt information, is termed as influence maximization. Concerns of scalability and effectiveness need an effective and a viable solution. This paper proposes the solution in three stages. At the first stage, the large social network is pruned based on the nodal properties to make the solution scalable. At the second stage, Outdegree Rank (OR), is proposed and at the third stage, Influence Estimation (IE) approach estimates user influence. This work amalgamates aspects of structure, heuristic and user influence, to form STORIE. The proposed approach is compared to standard heuristics, on various experimental setups such as RNNDp, RNUDp and TVM. The spread of information is observed for HEP, PHY, Twitter, Infectious and YouTube data, under Independent Cascade model and STORIE gives optimal results, with an increase up to 50%. Although the paper discusses influence maximization, the proposed approach is also applicable to understand the spread of epidemics, computer virus, and rumor spreading in the real world and can also be extended to detect anomalies in web and social networks. © 2017 Elsevier B.V.Item Optical and structural properties of BCBS glass system with and without alumina(Elsevier B.V., 2018) Bhattacharya, S.; Shashikala, H.D.BaO–CaO–Al2O3–SiO2 (BCAS) glass and their derivatives have gained extreme importance for their high endurance to elevated temperatures and being suitable for various electrochemical applications. Two glass systems, one being 50mol% [SiO2–B2O3]-xBaO-(45-x)CaO–5Al2O3 called as BCBSA and another without Al2O3 termed as BCBS were synthesized using melt quenching technique in the present work. Addition of ZnO and MgO as flux helped in melting them at 1300 °C which is much lower than the usual melting temperature of these glasses [1–4]. Density of the quenched glasses was measured by Archimedes method and structural bond vibrations were confirmed through FTIR. UV Visible spectroscopy was used to determine band gap energy and confirm the insulating nature of the synthesized glasses. The samples were isothermally heated at 700 °C, 800 °C for 50 h and at 900 °C for 50 and 100 h duration in air to allow the devitrification process to take place. The heat treated samples were analyzed by X-ray diffraction to identify the developed phases. Five Al2O3 free samples synthesized at 1300 °C by regular melt quenching technique were found to be devoid of the monocelsian phase. This is a detrimental phase for high temperature sealant applications as it has a very low coefficient of thermal expansion (CTE). Al2O3 free BCBS glasses, properties of which are being reported for the first time and glasses with low BaO concentrations are found to meet the requirements for high temperature applications as sealants in Solid Oxide Fuel Cell (SOFC). © 2018 Elsevier B.V.Item Influence maximization in large social networks: Heuristics, models and parameters(Elsevier B.V., 2018) Sumith, N.; Annappa, B.; Bhattacharya, S.Online social networks play a major role not only in socio psychological front, but also in the economic aspect. The way social network serves as a platform of information spread, has attracted a wide range of applications at its doorstep. In recent years, lot of efforts are directed to use the phenomenon of vast spread of information, via social networks, in various applications, ranging from poll analysis, product marketing, identifying influential users and so on. One such application that has gained research attention is the influence maximization problem. The influence maximization problem aims to fetch the top influential users in the social networks. The aim of the paper is to provide a comprehensive analysis on the state of art approaches towards identifying influential users. In this review, we discuss various challenges and approaches to identify influential users in online social networks. This review concludes with future research direction, helping researchers to bring possible improvements to the existing body of work. © 2018 Elsevier B.V.Item Effect of BaO on thermal and mechanical properties of alkaline earth borosilicate glasses with and without Al2O3(Elsevier B.V., 2019) Bhattacharya, S.; Shashikala, H.D.BaO-CaO-Al2O3-SiO2 (BCAS) glass and their derivatives have gained extreme importance for their high endurance to elevated temperatures and suitability for various electrochemical applications. Two glass systems, one being 50 mol%[SiO2-B2O3]-xBaO-(45-x)CaO-5Al2O3 with x = 0, 10, 20, 25, 30, 35 and 40 mol%, represented as BCBSA and another without Al2O3 termed as BCBS, synthesized using melt quenching technique are considered here. The authors focus on the thermal and mechanical properties of these glasses. Reducing BaO concentrations improve the coefficient of thermal expansion (CTE/?) and other characteristic temperatures of glasses. Compacted glass pellets made of the water quenched frits show maximum shrinkage at 700 °C. Dilatometric analysis were conducted on compacts showing maximum shrinkage. CTE of these pellets are more than the bulk glasses. Glasses with low BaO concentrations exhibit high hardness and Young's modulus. Glasses bearing 20 mol% BaO, or even lesser, meet the thermal and mechanical properties required for high temperature sealants. © 2019 Elsevier B.V.Item Synthesis and characterization of zinc oxide incorporated iron borate glass-ceramic(Elsevier Ltd, 2019) Ramteke, R.; Kumari, K.; Bhattacharya, S.; Rahman, M.R.Here, zinc oxide (ZnO) incorporated iron borate (Fe3BO6) glass-ceramics have been synthesized using the traditional melt-quenching technique, and the role of ZnO has been investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveals that the prepared samples have a single crystalline phase and crystalline nanostructures, respectively. The orthorhombic crystal structure has been retained without the formation of a new crystalline phase. The addition of ZnO is found to distort the Fe3BO6 lattice by substituting Zn2+ in the Fe3+ sites, with the formation of ZnO6 structural units as revealed by Fourier transform infrared spectroscopy (FTIR). FTIR and Raman spectroscopy conducted to study the structure of glass-ceramic, have also revealed the formation of other structural units like ZnO4, BO3, BO4, and FeO6 in the system. Surface analysis conducted by X-ray photoelectron spectroscopy (XPS) reveals that the addition of ZnO diminishes the formation of surface B2O3 layer which forms over the Fe3BO6 phase in the Fe3BO6 iron borate glass-ceramic system. ZnO addition has also shown a remarkable difference in the volume of the crystallization in the system, thereby paving the way for controlled crystallization in the iron borate glass-ceramic system. The controlled crystallization was achieved through additive content, retaining the iron borate (Fe3BO6) glass-ceramic system without the evolution of any secondary phases even with large additive concentrations up to 10 mol%. © 2019 Elsevier B.V.Item Impedance spectroscopy study of zinc oxide incorporated iron borate glass-ceramic(Elsevier B.V., 2021) Ramteke, R.; Kumari, K.; Bhattacharya, S.; Sharma, S.K.; Rahman, M.R.Here, the effects of zinc oxide (ZnO) on impedance and dielectric properties of the ZnO incorporated iron borate (Fe3BO6) glass-ceramics were studied using impedance spectroscopy in a wide range of frequency (1 Hz – 1 MHz) and temperature (25 °C–250 °C). With ZnO addition, the ?? and tan? values were reduced significantly, the strength of the relaxation process also decreased, along with a decrease in conductivity. Activation energies associated with modulus and conductivity plots suggest that similar type of charge carriers was responsible for the relaxation and conduction processes. The analysis of both complex impedance and conductivity show the negative temperature coefficient of resistance (NTCR) behavior of the samples. The thermistor constant B-values of 5ZnO and 10ZnO were found to be 7223 and 7088 respectively. The study of the NTCR properties suggests a potential candidate for thermistor applications. © 2021 Korean Physical SocietyItem High figure-of-merit in Zn, Sb co-doped Mg2Si0.3Sn0.7 alloy through simultaneous optimization of electrical and thermal transports(Elsevier Ltd, 2025) Sarkar, P.; Gupta, P.; Shenoy, U.S.; Singh, S.; Kundu, S.; Kumawat, N.; Kedia, D.K.; Bhat, D.K.; Bhattacharya, S.; Singh, A.The derivatives of Mg2Si have recently attracted wide attention as promising thermoelectric materials due to earth abundant and environment friendly low-cost constituents. The main challenge in optimizing the thermoelectric figure of merit ZT, is the low electrical and high thermal conductivities of Mg2Si. The present study demonstrates high ZT of ?1.55 at 673 K in Mg2Si0.3Sn0.7 through simultaneous optimization of electrical and thermal transport through Sb and Zn co-doping. The ultra-low deformation and alloy scattering potentials in Sb and Zn co-doped samples helps in maintaining record high Hall mobility ?70–90 cm2/V.s. The doping induced pudding mold band structure with hyperconvergence in conduction band balances high Seebeck coefficient and high electrical conductivity. The point defects and dislocations created by doping helps in lowering of lattice thermal conductivity as well. The uni-leg power generator fabricated using optimized Mg1.96Zn0.04(Si0.3Sn0.7)0.98Sb0.02 exhibits a record efficiency of ?9.5 % at ?T ? 329 K. © 2025