Network availability prediction with hidden context

Modern mobile devices are increasingly capable of simultaneously connecting to multiple access networks with different characteristics. Restricted coverage combined with user mobility will vary the availability of networks for a mobile device. Most proposed solutions for such an environment are reactive in nature, such as performing a vertical handover to the network that offers the highest bandwidth. But the cost of the handover may not be justified if that network is only available for a short time. Knowledge of future network availability and their capabilities are the basis for proactive schemes which will improve network selection and utilization. We have previously proposed a prediction model that can use any available context such as GSM Location Area, WLAN presence or even whether the power cable is plugged in, to predict network availability.As it may not be possible to sense all of the context variables that influence future network availability, in this paper we introduce a generic, new model incorporating a hidden variable to account for this. Specifically, we propose a Dynamic Bayesian Network based context prediction model to predict network availability. Predictions performed for WLAN availability with the real user data collected in our experiments show 20% or more improvement compared to both of our earlier proposals of order 1 and 2 semi-Markov models.     

Effect of Temperature on Hydraulic Parameters of Cable-In-Conduit-Conductor of SST-1

Stable operation of superconducting magnets depend critically on the balance of heat deposition rate versus heat extraction rate by the cryo-coolant. Thus, the mass flow rate of the coolant in case of force-flow cooled superconducting magnet with Cable-In-Co-nduit-Conductor (CICC) construction becomes an important factor for optimum stability of magnets. The Toroidal and Poloidal Field magnets of Steady-state Superconducting Tokamak-1 (SST-1) is made of superconducting CICC with a void fraction of 40 %±2 %. For adequate cooling of magnets, supercritical helium at 4 bar and 4.5 K is forced-flown through the voids. Effect of temperature on mass flow rate and pressure drop in SST-1 CICC is studied in a 7 m long piece wound helically. The experimental friction factor of the CICC is also measured at different temperatures and flow rates and is compared with the standard Katheder equation and Tada equation. Also, based on the new findings obtained from the experimental results, the dimensionless Reynolds number has been slightly modified. This new number is used to propose a modified Katheder correlation for the friction factor in CICCs similar to that of SST-1.     

Investigation of structural,optical, and magnetic properties of Nd-doped Sr2SnO4 Ruddlesden Popper oxide

The samples of Sr_2-xNd_xSnO₄ with x = 0, 0.01, 0.02, 0.04, 0.06, and 0.10 were synthesized by a high-temperature solid-state ceramic route. Rietveld refining of X-ray diffraction results showed that all the synthesized compositions are single phase under tetragonal crystal structure. The presence of functional group and local structure has been studied using FTIR and Raman spectroscopy, respectively. XPS study of samples showed the presence of oxygen vacancy and interstitial oxygen in the sample. Optical band gap of samples analyzed by UV-Vis spectra gradually increases with dopant concentration, and Photoluminescence (PL) spectroscopy study showed most intense emission around 1064 nm. Room-temperature magnetic hysteresis curve in sample SSN2 showed ferromagnetism, slowly decreasing with Nd and becoming antiferromagnetic for higher compositions. Utilizing the absorption state observed in PL as metastable state makes it promising candidate for laser and IR detector application and the ferromagnetic/antiferromagnetic nature of sample makes it suitable candidate for spintronics device applications.     

The critical organic modifier aliphatic tail length for the formation of poly(methyl methacrylate)-montmorillonite nanocomposites

In this article, we report the influence of organic modifier structure (alkyl chain length C8-C20, single vs ditallow) and thereby, the effect of hydrophobicity on the structure, thermal and mechanical properties of poly(methyl methacrylate) (PMMA)-clay hybrids. Melt processed PMMA-clay hybrids were characterized using wide-angle X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. The organoclays having an alkyl chain length of more than 12 CH₂ groups resulted in the formation of nanocomposites. The glass transition temperature (T_g) of PMMA increased in the presence of clay. The mean-field lattice model was used to predict the free energy for nanocomposite formation, which showed a reasonable match with the experimental results and provided a general guideline for the proper selection of polymer and organoclay (ie, organic modifier) to obtain nanocomposite. Tensile modulus showed maximum improvement of 58% for the nanocomposites compared to 9% improvement for the composites. Tensile modulus increased with increases in the alkyl chain length of the organic modifier and clay loading. The level of improvement for the tensile properties of nanocomposites prepared from primary and secondary ammonium-modified clay is the same as that obtained with the commercial organoclays.     

Atomistic simulations of the surfaces of thin films of random copolymers

Amorphous thin films of styrene-butadiene and styrene-butadiene-acrylonitrile copolymers containing a small amount of acrylic acid are generated using molecular dynamics and energy minimization simulations. The structure of the films shows an interior region of bulk density and a thin outer surface layer where the density falls to zero. The surface layer over which the density changes is approximately 5 Å in thickness. The film mass density at its center of mass is close to the bulk values. The orientation function parameter of the backbone carbon-carbon bonds, averaged over the ensemble of representative cells, shows a random nature in the dense region and an inclination towards an orientation somewhat along the plane of the surface layer in the external parts of the film. The styrene rings are mostly located in the bulk region, with random spatial and orientation distributions. The polar groups in the acrylonitrile segment of the SBA films are mostly found in the surface region, where they contribute to the marked enhancement in the surface energy for SBA films compared to SB films. The surface energy values deduced from the models are systematically slightly lower than independent estimates.     

The effect of platinum on the performance of WO3 nanocrystal photocatalysts for the oxidation of Methyl Orange and iso‐propanol

BACKGROUND: This research investigated the effect of platinum (Pt) on the reactivity of tungsten oxide (WO₃) for the visible light photocatalytic oxidation of dyes. RESULTS: Nanocrystalline tungsten oxide (WO₃) photocatalysts were synthesised by a sol‐gel process and employed for the photocatalytic degradation of Methyl Orange under visible light. For comparison commercial bulk WO₃ materials were also studied for the same reaction. These materials were fully characterised using X‐ray diffraction (XRD), UV‐visible diffuse reflection spectroscopy and transmission electron microscopy (TEM). The photocatalytic oxidation of iso‐propanol was used as a model reaction to follow the concomitant reduction of molecular oxygen. No reactions occured in the absence of platinum, which is an essential co‐catalyst for the multi‐electron reduction of oxygen. The platinised WO₃ catalysts were stable for multiple oxidation–reduction cycles. The results from the catalytic activity measurements showed that platinised nanocrystalline WO₃ is a superior oxidation photocatalyst when compared with bulk WO₃. Methyl Orange was completely decolourised in 4 h. CONCLUSIONS: The enhanced performance of nanocrystalline Pt‐WO₃ is attributed to improved charge separation in the nanosized photocatalyst. Platinum is an essential co‐catalyst to reduce oxygen. This photocatalyst could be applied to the treatment of organic pollutants in wastewater, with the advantage of using visible light compared with the widely studied TiO₂, which requires UV light. Copyright © 2011 Society of Chemical Industry     

Effect of Ethrel and 1-methylcyclopropene (1-MCP) on antioxidants in mango (Mangifera indica var. Dashehari) during fruit ripening

Ripening affects the quality and nutritional contents of fleshy fruits. Mango, a climacteric fruit, is very susceptible to post-harvest losses, due to fast softening. In the present paper we report the effect of 1-methylcyclopropene (1-MCP) and Ethrel on antioxidant levels in mango fruit during ripening. Use of 1-MCP is applied commercially to delay ripening while Ethrel is used to accelerate ripening of climacteric fruits. 1-MCP treatment led to decreased levels of H₂O₂ and lipid peroxidation, concomitant with increased activities and isozymes of catalase (CAT) and superoxide dismutase (SOD), as compared to respective controls. On the other hand, Ethrel treatment led to an increase in H₂O₂ and lipid peroxidation, concomitant with a decrease in the activities and isozymes of catalase and SOD. Guaiacol peroxidase (GPX) could not be detected in the control or in treated fruits. Activity of ascorbate peroxidase (APX) was found to drastically increase in the presence of Ethrel while 1-MCP treatment led to only a marginal increase in APX.     

Intratumoral Thermal Reading During Photo‐Thermal Therapy by Multifunctional Fluorescent Nanoparticles

The tremendous development of nanotechnology is bringing us closer to the dream of clinical application of nanoparticles in photothermal therapies of tumors. This requires the use of specific nanoparticles that must be highly biocompatible, efficient light‐to‐heat converters and fluorescent markers. Temperature reading by the heating nanoparticles during therapy appears of paramount importance to keep at a minimum the collateral damage that could arise from undesirable excessive heating. In this work, this thermally controlled therapy is possible by using Nd³⁺ ion‐doped LaF₃ nanocrystals. Because of the particular optical features of Nd³⁺ ions at high doping concentrations, these nanoparticles are capable of in vivo photothermal heating, fluorescent tumor localization and intratumoral thermal sensing. The successful photothermal therapy experiments here presented highlight the importance of controlling therapy parameters based on intratumoral temperature measurements instead of on the traditionally used skin temperature measurements. In fact, significant differences between intratumoral and skin temperatures do exist and could lead to the appearance of excessive collateral damage. These results open a new avenue for the real application of nano­particle‐based photothermal therapy at clinical level.     

Dechlorination of chlorophenols using magnesium-palladium bimetallic system

Ninety-four percent removal of 10 mg L(-1) of pentachlorophenol (PCP) was achieved by treatment with 154.5mM Mg(0) and 0.063 mM K(2)PdCl(6) in the presence of 175 mM acetic acid in 1h reaction time. Dechlorination of PCP was found to be sequential and phenol was identified as the end product along with accumulation of trace concentrations of tetra- and trichlorophenols. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) revealed that palladium in its metallic form (Pd(0)) produced by reduction of Pd4+, was spatially separated from magnesium granules when acid was included in the reaction. These colloidal palladium particles generated active reductive species of hydrogen and dechlorinated chlorophenols. In the absence of acid, the efficiency of dechlorination of PCP by Pd/Mg(0) system was very low and chief mechanism of removal of the compound was through sorption onto solid surfaces. Thus, it was important to include acid in the system to: (a) facilitate corrosion of Mg(0) and reduction of Pd4+ to Pd(0), (b) provision of protons to produce H2, (c) retard formation of insoluble oxides and hydroxides that may deposit on the magnesium granules and sorb PCP and its partially dechlorinated products and. Application of 154.5 mM Mg(0)/0.063 mM K(2)PdCl(6) on PCP, 2,4,5-trichlorophenol (TCP) and 2-chlorophenol (MCP) with organic chloride equivalence showed that the rate and extent of removal increased with decrease in number of chlorine atoms on phenol.