Humidity-Sensing Characteristics of Divalent-Metal-Doped Indium Oxide Thin Films

Metal-doped indium oxide thin films that have been prepared on glass substrates via a dip-coating method from an aqueous sol show a rapid decrease in electrical conductivity at room temperature (by approximately three orders of magnitude) when brought into contact with moist air. This observation is in contrast to the conductivities of nondoped indium oxide films that are independent of moisture. Thus, the doped films can be applied as a humidity sensor. The film thickness has no substantial effect on the sensing properties, probably because of the porous nature of the films that are prepared by a sol-gel process. To examine the effects of film morphology, a comparison between the humidity-sensing properties of the films that have been prepared from organic and aqueous sols also has been conducted. The roles of the doped metal ions are also discussed.     

Kinetics of tungsten‐catalyzed sunflower oil epoxidation studied by 1H NMR

Sunflower oil (SO) is a renewable resource that can be epoxidized, and the epoxidized SO has potential uses as an environmentally friendly and reactive material in polymeric formulations, especially for polyvinyl chloride. SO was epoxidized with peracetic acid, which was either preformed or prepared in situ. In order to optimize the formation of oxirane rings, the epoxidation and the extent of the side reactions were studied at different temperatures. The peracetic acid was obtained by acidic catalysis in the presence of a cation‐exchange resin. The optimum conversions were obtained within a 4‐h reaction period at 55 °C by the in situ epoxidation technique. The epoxidation was also carried out with hydrogen peroxide in the presence of peroxotungstic acid complexed with lipophilic phosphorus‐based ligands. ¹H NMR was used to define the new indices Δ and Ω, which are the mean numbers of C=C double bonds and oxirane rings per fatty acid chain, respectively. This allowed monitoring of the reaction and quantification of the results. Peroxotungstic catalysts appeared less performing than peracids in the epoxidation of SO, but were found very efficient for the epoxidation of the SO methyl esters.     

ACOUSTIC ANALYSIS OF HYDRODYNAMIC AND ELASTO-HYDRODYNAMIC OIL LUBRICATED JOURNAL BEARINGS

The purpose of the present paper is to investigate the effect of elastic deformation of bearing liner on the acoustic behavior of oil lubricated journal bearings.Analysis is performed for hydrodynamic(HD) and elasto-hydrodynamic (EHD) lubrications.Dynamic behavior and acoustical properties are investigated through an analysis of pressure fluctuation calculated from the Reynolds equation governing the flow in the clearance space of the journal bearing.This is solved numerically using the finite difference method with the successive over relaxation technique.In elasto-hydrodynamic lubrication,the finite element method with in iteration scheme is adopted to solve both Reynolds equation and the three-dimensional elasticity equation representing the displacement field in the bearing shell.The results show that the sound pressure level of the bearing is markedly influenced by the flexibility of the bearing liner,the viscosity of lubricant and the load applied to journal.HD analysis shows that the journal centre’s orbit,from a disturbed position,converges to the static equilibrium position faster than EHD lubrication.The results of the present paper could aid in the design of low-noise rotor-bearing systems supported by oil lubricated journal bearings.     

Estimation de la résistance thermique de contact durant la solidification du verre

Estimation of the thermal contact resistance during glass solidification. This paper presents an experimental study of thermal contact conditions during glass moulding. Our goal was to develop an experimental setup to simulate the real contact conditions during the glass solidification and to build a numerical procedure to estimate the thermal parameters characterizing heat transfer at the contact interface (mould–glass). The semi-transparent character of glass was taken into account when building the theoretical heat transfer model. Thus a heat radiation–conduction model was built to simulate heat transfer at the interface during the glass cooling. The study shows that when the coupled conduction–radiation effect is taken into account, the parameter estimation is better. Thermal contact resistance mold–glass was estimated and the quality of heat transfer at the interface was analyzed.     

Free convection enhancement in an annulus between horizontal confocal elliptical cylinders using hybrid nanofluids

ABSTRACT

In the present paper, natural convection in an annulus between two confocal elliptic cylinders filled with a Cu-Al₂O₃/water hybrid nanofluid is investigated numerically. The inner cylinder is heated at a constant surface temperature while the outer wall is isothermally cooled. The basic equations are formulated in elliptic coordinates and developed in terms of the vorticity-stream function formulation using the dimensionless form for 2D, laminar and incompressible flow under steady-state condition. The governing equations are discretized using the finite volume method and solved by an in-house FORTRAN code. Numerical simulations are performed for various volume fractions of nanoparticles (0?≤???≤?0.12) and Rayleigh numbers (10³?≤?Ra?≤?3?×?10⁵). The eccentricity of the inner and outer ellipses and the angle of orientation are fixed at e₁?=?0.9, e₂?=?0.6 and γ?=?0° respectively. It is found that employing a Cu-Al₂O₃/water hybrid nanofluid is more efficient in heat transfer rate compared to the similar Al₂O₃/water nanofluid.     

HYDRODYNAMIC AND ELASTOHYDRODYNAMIC STUDIES OF A CYLINDRICAL JOURNAL BEARING

In this article, the effect of the bearing elastic deformation on the performance characteristics of a cylindrical journal bearing is analyzed. The variety of simulation models covers hydrodynamic (HD) and elastohydrodynamic (EHD) lubrication theories. The Reynolds equations governing the flow in the clearance space of the journal bearing are obtained by considering the effect of mass transfer across the fluid film. The finite element method with an iteration scheme was employed to solve both the Reynolds equation and the three-dimensional elasticity equation representing the displacement field in the bearing shell. The converged solutions for the lubricant flow and elastic deformation vector are obtained. Dynamic characteristics of the journal bearing are computed for HD and EHD theories. Numerical simulation results show that the flexibility of bearing liner has a significant influence on the performance of a cylindrical journal bearing. Indeed, the elastic deformations of the bearing liner extend the pressure area in the bearing and increase the minimum film thickness. Although, dynamic coefficient, load capacity and attitude angle decrease.     

Adaptation of a routing algorithm in wireless video sensor network for disaster scenarios using JPEG 2000

In this work we will develop an extension of one of existing routing algorithm in wireless sensor network. This new adaptation will permit the sensor node to save more energy and transmit images in wireless mode. This situation will be strategic and helpful especially in disaster scenario, where groups of rescuers must be on site to accomplish emergency tasks; therefore it’s very important and necessary to establish a wireless communication in real time between individuals or groups. The nature of wireless video sensor network makes it suitable to be used in the context of emergencies because introducing a video give more information in precise time and this is very advantageous when the existing infrastructure is down or severely overloaded. In emergencies the network topology may change rapidly and randomly. The increasing mobility of terminals makes them progressively dependent on their autonomy from the power source. This is illustrated by introducing many mobility models and using many scenarios of mobility in emergency situation, where image transmission via sensor node is used. Low complexity algorithm in image processing in order to reduce time transfer of selected data by this way allows saving energy. Efficiency in emergency scenario is the main objective of this work, achieved by the combination of three strategies: low-power mode algorithm, a power-aware routing strategy and compression technique in image processing used in sensor node. A selected set of simulations studies and real test bed on sensor node platform (Telos-B) indicate a reduction in energy consumption and a significant increase in node lifetime whereas network performance is not affected significantly. This is the big interest of our work in emergency situation, by increasing life time of node, individual can communicate longer and give more chance to rescuers to find them.     

Interference between reactants in simultaneous interpenetrating polymer network formation. II. Influence of the presence of a free‐radical initiator on polyurethane formation

Polyether polyurethane networks were prepared in solution at 25 and 60°C, using various organotin catalysts. The presence of a free‐radical initiator [viz. azobisisobutyronitrile (AIBN)] in the reaction media has no effect on the catalytic efficiency of organotin(IV) compounds, whereas it causes severe deactivation of organotin(II) compounds. This effect was explained by the following mechanism: formation of a cyclic 1 : 1 complex by coordination of the nitrile groups of AIBN with the tin(II) atom, which both reduces the effective catalyst concentration and allows the early decomposition into radicals, as previously seen, leading to tin oxidation. The addition of a free‐radical scavenger such as 3‐tert‐butyl pyrocatechol allows the maintenance of the catalyst efficiency of organotin(II) compounds at their reference level. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1929–1937, 2002     

Targets Classification Based on Multi-sensor Data Fusion and Supervised Learning for Surveillance Application

Wireless Personal Communications - In surveillance application scenarios, like border security and area monitoring, potential targets to be detected may be either an unarmed person, a soldier...