Performance Analysis of Subspace Based Downlink Channel Estimation for W-CDMA Systems Using Chaotic Codes

This paper presents blind channel estimation for downlink W-CDMA system that employs chaotic codes and Walsh codes for spreading information bits of the multiple users. In a W-CDMA system, while transmitting over multipath channels, both intersymbol interference (ISI) as a result of Inter Chip Interference and multiple access interference (MAI) cannot be easily eliminated. Although it is possible to design multiuser detectors that suppress MAI and ISI, these detectors often require explicit knowledge of at least the desired users’ signature waveform. Earlier work focused on a subspace based channel estimation algorithm for asynchronous CDMA systems to estimate the multiple users’ symbols, where only AWGN channel was considered. In our work, we study a similar subspace-based signature waveform estimation algorithm for downlink W-CDMA systems, which use chaotic codes instead of pseudo random codes, that provide estimates of the multiuser channel by exploiting structural information of the data output at the base station. In particular, we show that the subspace of the (data+noise) matrix contains sufficient information for unique determination of channels, and hence, the signature waveforms and signal constellation. We consider Rayleigh and Rician fading channel model to quantify the multipath channel effects. Performance measures like bit error rate and root mean square error are plotted for both chaotic codes and Walsh codes under Rayleigh and Rician fading channels.     

Fabrication of polymethyl methacrylate/polysulfone/nanoceramic composites for orthopedic applications

We report the fabrication of polymethyl methacrylate/polysulfone/nanohydroxyapatite (PMMA/PSu/nHA) and PMMA/PSu/nanotitania (PMMA/PSu/nTiO₂) composites using N′N′‐methylene‐bis‐acrylamide (MBA) to crosslink PMMA and act as a blending agent. The composite was made porous by incorporating polyethylene glycol as the pore‐forming agent. The blend between PMMA and PSu was confirmed using Fourier transform infrared spectroscopy and thermogravimetric analysis (TGA). The surface morphology of the composites analyzed using scanning electronic microscopy (SEM) revealed the porous structure and the wide distribution of the fillers that were found to aggregate at higher concentrations. The maximum tensile strength observed for composites was with 5% nHA (23 MPa) and 7.5% TiO₂ (30 MPa). The TGA of the composites showed better thermal stability with increase in the filler concentrations. The X‐ray diffraction analysis showed that appearance of new peaks in the blend polymers indicating a strong interaction between PMMA and PSu. The surface of the composites was coated with amoxicillin and its efficiency was examined by the Zone of Inhibition test using Streptococcus mutans. The bioactivity of the composites was evaluated by immersing them in simulated body fluid and examining their surface for the formation of calcium‐phosphate layer using SEM and EDAX. Bioactivity was found to increase with increase in filler content. The in vitro biocompatibility of the composites, evaluated using monkey kidney epithelial cells by MTT assay showed that the composites containing nHA showed better cell viability than the composites with nTiO₂. The study showed that the composites with nTiO₂ exhibited better strength when compared with nHA composites while the later exhibited better biocompatibility. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Carbon supported silver (Ag/C) electrocatalysts for alkaline membrane fuel cells

This study reports on the performance of activated carbon supported silver catalyst (Ag/C) as electrocatalyst in an alkaline membrane fuel cell (AMFC), using alkalized poly (styrene ethylene butylene poly styrene) [APSEBS] as the electrolyte membrane. Carbon supported silver catalyst (Ag/C) with different metal loading was synthesized by means of wet impregnation method. The prepared electrocatalyst was characterized by X-ray diffraction pattern (XRD), thermogravimetric analysis (TGA), UV–Visible diffuse reflectance spectra (DRS-UV) and Raman spectroscopy. Surface morphology analysis of the prepared electrocatalyst using scanning electron microscopy (SEM) revealed the heterogeneous distribution of Ag on carbon support. The performance of the prepared electrocatalyst was evaluated with a home made AMFC using a novel anion exchange membrane (APSEBS). A maximum cell voltage and power density of 0.69 V and 109 mW/cm², respectively, was achieved at 60 °C for the home made 10 wt% (Ag/C) cathode catalyst and anion exchange membrane. Further, the prepared electrocatalyst was subjected to cyclic voltammetry studies to evaluate the methanol oxidation for Direct methanol alkaline fuel cell (DMAFC) applications.     

Improved K-Means Based Q Learning Algorithm for Optimal Clustering and Node Balancing in WSN

Wireless Personal Communications - A wireless sensor network is a potential technique which is most suitable for continuous monitoring applications where the human intervention is not possible. It...     

Polymer nanocomposites containing β-Bi2O3 and silica nanoparticles: Thermal stability,surface topography and X-ray attenuation properties

Silicone polymer-based nanocomposites containing β-Bi₂O₃ nanoparticles with varying concentrations of silica nanoparticles are successfully prepared and characterized for thermal stability, surface topography, and X-ray attenuation property. Of all the samples studied here, silicone polymer of higher density (S1) containing β-Bi₂O₃ (50 wt%) and silica (0.025 wt%) nanoparticles is found to be thermally stable upto 424 and 375°C in argon and oxygen atmosphere, respectively. The atomic force microscopy image of top and cleaved surface of this nanocomposite exhibits an average roughness of 12 and 506 nm, respectively. It also exhibits the highest X-ray attenuation property, among the samples analyzed here, against X-rays of energies in the range of 30–66 keV. Therefore, S1 silicone polymer containing β-Bi₂O₃ and silica (0.025 wt%) nanoparticles is a potential material for the development of lead-free and X-ray opaque aprons, gloves, thyroid collar, gonad shield, and so on.     

Low velocity axial impact crushing performance of empty recyclable metal beverage cans

This paper focuses on the axial impact crushing behaviour of recyclable empty metal beverage cans available in the market. The idea is to make a macro foam (sacrificial cladding structure) out of these cans to protect the main load bearing members of civil engineering structures from the air blast load. Axial drop weight tests have been conducted to understand the crushing characteristics and the corresponding energy absorption of a single empty beverage can in detail. To conduct such tests a small-scale drop weight test set-up has been designed and manufactured. The deformation mechanisms and the corresponding energy absorption of the beverage cans were studied in detail for different initial impact velocities (1.4 m/s, 2.2 m/s, 3.1 m/s, 3.8 m/s, 4.4 m/s and 4.9 m/s). Furthermore, an analytical model is proposed to calculate the crushing parameters of empty metal beverage cans. The results from the analytical model are compared and validated with the experimental results.     

Progress of MWCNT,Al2O3, and CuO with water in enhancing the photovoltaic thermal system

Hybrid photovoltaic thermal system is an effective method to convert solar energy into electrical and thermal energy. However, its effectiveness is widely affected due to the high temperature of photovoltaic panel, and it can be minimized by employing nanofluids to the PV/T systems. In this research, the effect of various nanoparticles on the PV/T systems was studied experimentally. The nanofluids Al₂O₃, CuO, and multiwall carbon nanotube (MWCNT) were dispersed with water at different volume fractions of 0, 0.5, 1, 2.5, and 5 (vol%) using ultrasonication process. The effect of nanomaterials on viscosity and density was classified. All tests were carried out in an outdoor laboratory setup for calibrating the PV temperatures, thermal conductivity, electrical power, electrical efficiency, and overall efficiency. In addition, the energy analyses were also made to estimate the loss of heat owing to the nanofluids. Results show that use of the nanofluid increased the electric power and electrical efficiency of PV/T compared with water. Furthermore, MWCNT and CuO reduced the cell temperature by 19%. Consequently, the nanofluids MWCNT, Al₂O₃, and CuO produced the impressive values of 60%, 55%, and 52% increase in an average electrical efficiency than conventional PV. Particularly, the MWCNT produced superior results compared with other materials. It is evidently clear from the result that the introduction of the nanofluid increases the thermal efficiency without adding any extra energy to the system. Moreover, insertion of Al₂O₃, CuO, and MWCNT on PV/T system increases the exergy efficiency more than conventional PV module.     

RETRACTED ARTICLE: Power Budget Analysis of an Ultra-Dense Coherent MB-OFDM WDM Metro-Access Networks

Wireless Personal Communications - The power budget (PB) of an ultra-dense wavelength division multiplexing virtual-carrier helped coherent-detection multi-band orthogonal frequency division which...     

Silver-incorporated poly vinylidene fluoride nanofibers for bacterial filtration

An anti-bacterial filter was developed using poly vinylidene fluoride (PVDF) nanofibers using electrospinning method blended with silver nanoparticles (AgNO₃) of varying weight percentages of filler. Polypropylene (PP) non-woven substrate was used as base material for collecting the nanofibers. It also acted as a barrier to protect the fibers. UV-visible spectroscopy and fourier transform infra red spectroscopy confirmed the uniform dispersion of silver nanoparticles throughout the nanofibers. The experiment was designed using Box–Behnken statistical tool through three different variables namely, PP non-woven sheets (GSM), electrospinning time (hours), concentration of silver (wt%) in 15 runs. Surface morphology was analyzed using scanning electron microscopy and atomic force microscopy. Thermogravimetric analysis was performed for the analyses of mass decomposition of the material. Bacterial filtration efficiency and anti-bacterial activity studies were tested against Staphylococcus aureus and Escherichia coli for both PVDF + 0?wt% Ag fibers and PVDF-Ag nanofibers. This research shows the bacterial filtration efficiency for the prepared PVDF-Ag nanofibers as 99.86%. The prepared nanofilter was shown providing greater possibilities towards the application for clean air management.

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