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Nagaraja B.B.,PESIT Bangalore South Campus | Nagananda K.G.,Bangalore University
2015 IEEE Global Communications Conference, GLOBECOM 2015 | Year: 2015

A heterogenous network is considered where the base stations (BSs), small base stations (SBSs) and users are distributed according to independent Poisson point processes (PPPs). We let the SBS nodes to posses high storage capacity and are assumed to form a distributed caching network. Popular data files are stored in the local cache of SBS, so that users can download the desired files from one of the SBS in the vicinity subject to availability. The offloading-loss is captured via a cost function that depends on a random caching strategy proposed in this paper. The cost function depends on the popularity profile, which is, in general, unknown. In this work, the popularity profile is estimated at the BS using the available instantaneous demands from the users in a time interval [0,τ]. This is then used to find an estimate of the cost function from which the optimal random caching strategy is devised. The main results of this work are the following: First it is shown that the waiting time τ to achieve an ε > 0 difference between the achieved and optimal costs is finite, provided the user density is greater than a predefined threshold. In this case, τ is shown to scale as N^2, where N is the support of the popularity profile. Secondly, a transfer learning based approach is proposed to obtain an estimate of the popularity profile used to compute the empirical cost function. A condition is derived under which the proposed transfer learning-based approach performs better than the random caching strategy. © 2015 IEEE. Source

Prasanna B.P.,Tumkur University | Prasanna B.P.,Bangalore University | Avadhani D.N.,Rashtreeya Vidyalaya College of Engineering | Muralidhara H.B.,Bangalore University | And 4 more authors.
Bulletin of Materials Science | Year: 2016

Polyaniline/zirconium oxide (PANI/ZrO2) nanocomposites have been synthesized by incorporating ZrO2 nanoparticles into the PANI matrix via liquid-liquid interfacial polymerization method. The composite formation and structural changes in PANI/ZrO2 nanocomposites were investigated by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). PXRD pattern of PANI/ZrO2 nanocomposites exhibited sharp and well-defined peaks of monoclinic phase of ZrO2 in PANI matrix. SEM images of the composites showed that ZrO2 nanoparticles were dispersed in the PANI matrix. The FT-IR analysis revealed that there was strong interaction between PANI and ZrO2. AC conductivity and dielectric properties of the nanocomposites were studied in the frequency range, 50-106 Hz. AC conductivity of the nanocomposites obeyed the power law indicating the universal behaviour of disordered media. The nanocomposites showed high dielectric constant in the order of 104, which could be related to dielectric relaxation phenomenon. Further, the materials were checked for their supercapacitance performance by using cyclic voltammetry (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). Among the synthesized nanocomposites, PANI/ZrO2-25 wt.% showed a higher specific capacitance of 341 F g-1 at 2 m Vs-1 and good cyclic stability with capacitance retention of about 88% even after 500 charge-discharge cycles. © Indian Academy of Sciences. Source

Nagesa Sastry D.,Vijayanagara Sri Krishnadevaraya University | Revanasiddappa M.,PESIT Bangalore South Campus | Basavaraja C.,Inje University | Suresh T.,Vijayanagara Sri Krishnadevaraya University | Raghavendra S.C.,Higher Colleges of Technology
Indian Journal of Engineering and Materials Sciences | Year: 2013

Camphor sulfonic acid (CSA) doped polyaniline (PANI) and tungsten oxide (WO3) composites (PANI/CSA/WO3) have been prepared by in situ deposition technique by placing different wt% of fine grade nano powder of WO3(PANI/CSA/WO3-10,-20,-30,-40 and-50%) during polymerization of polyaniline. The polymerization of aniline is carried by using ammonium peroxydisulfate as oxidizing agent. The composites are characterized by various physical methods such as Fourier transform infrared spectra (FTIR), X-ray diffractogram (XRD), thermo-gravimetric analysis (TGA), scanning electron micrograph (SEM) and transmission electron micrographs (TEM). The FTIR spectral data shows the homogeneous distribution of WO3 nano particles in PANI/CSA polymer matrix. The TGA reveals that PANI interacted strongly with the WO3-SO3H, enhancing the thermal stability of polyaniline. The SEM images indicate that increase of WO3 wt% in PANI/CSA/WO3 composites, enhances the compactness of the matrix. The TEM image clearly shows the size distribution of WO3 nanoparticles formed during the reaction and ranges from 150 to 200 nm. The temperature dependent DC conductivity of PANI/CSA/WO3 composites is studied in the temperature range 308-433 K. The results of PANI/CSA/WO3 indicate strong interaction of PANI/CSA with WO3 in the composites. The study of DC conductivity shows an evidence for the transport properties of the composites. Due to the positive temperature coefficient of resistance of WO3, these composites can signify in development of new materials in temperature dependent applications. Source

Begum A.,PESIT Bangalore South Campus
International Journal of ChemTech Research | Year: 2014

A polynomial equation is developed to relate the concentration of hydrochloric acid as corrosive medium for mild steel to the variables like inhibitor concentration, temperature and time. The inhibitor used is castor seed oil. The effect of variables has been investigated and these are optimized using 3 level full factorial design method. The model allows the prediction of the extent of corrosion inhibition at different conditions. ANOVA is used to evaluate the validity of model. The correlation coefficient between the calculated and the experimental data indicates good performance of the model. From ANOVA, the variables and their interaction effect on the corrosion rate were significant. A maximum of 84.1% of Inhibition efficiency was achieved under the optimum conditions of 50%v/v inhibitors concentration, 48 hours time and at 303K temperature. Source

Sarasvathi V.,PESIT Bangalore South Campus | Iyengar N.C.S.N.,Vellore Institute of Technology | Saha S.,PESIT Bangalore South Campus
International Journal of Communication Networks and Information Security | Year: 2014

In recent years, multi-channel multi-radio wireless mesh networks are considered a reliable and cost effective way for internet access in wide area. A major research challenge in this network is, selecting a least interference channel from the available channels, efficiently assigning a radio to the selected channel, and routing packets through the least interference path. Many algorithms and methods have been developed for channel assignment to maximize the network throughput using orthogonal channels. Recent research and test-bed experiments have proved that POC (Partially Overlapped Channels) based channel assignment allows significantly more flexibility in wireless spectrum sharing. In this paper, first we represent the channel assignment as a graph edge coloring problem using POC. The signal-to-noise plus interference ratio is measured to avoid interference from neighbouring transmissions, when a channel is assigned to the link. Second we propose a new routing metric called signal-to-noise plus interference ratio (SINR) value which measures interference in each link and routing algorithm works based on the interference information. The simulation results show that the channel assignment and interference aware routing algorithm, proposed in this paper, improves the network throughput and performance. Source

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