A fog-based security framework for intelligent traffic light control system

Multimedia Tools and Applications - The world is facing many problems including that of traffic congestion. To highlight the issue of traffic congestion worldwide specially in urban areas and to...     

Cure characterization of Cycom 977‐2A carbon/epoxy composites for quickstep processing

In this effort, Quickstep, a relatively a new technique, have been employed for manufacturing of composite materials. The cure schedule provided by a prepreg manufacturer is usually designed for autoclave or other traditional processing techniques and thermosetting resin systems are formulated for ramp rate curing 2–3 K min^?1. While in case of Quickstep processing, ramp rates of 15 K min^?1 can be achieved, thus changing the chemorheology of resin. The cure process of 977‐2A carbon/epoxy composites was evaluated for Quickstep processing using differential scanning calorimetry (DSC), dynamic mechanical and thermal analysis, and Fourier transformed infrared and results were compared with cure cycle employed for autoclave curing. Optimum hold time for Quickstep processing at upper curing temperature (180°C) was determined using DSC. The hold time of 120 min at 180°C was found to be suitable for Quickstep cure cycle, producing a panel of similar degree of cure to that achieved through autoclave processing schedule. Final degree of cure was dependent on time spent at upper cure temperature and slightly on initial steps of the cure cycle which was used to control the resin flow, fiber wetting, and void removal. Quickstep processed samples exhibited higher T_g and crosslink density and similar molecular network structure to the autoclave cured samples. POLYM. ENG. SCI., 54:887–898, 2014. © 2013 Society of Plastics Engineers     

Laser Heating of Tungsten Carbide-Coated Steel Surface: Influence of Coating Thickness on Temperature Field and Melt Depth

Laser repetitive pulse heating of tungsten carbide coating formed at a steel sheet surface is examined. Temperature field and melt pool formed in the coating and steel sheet are simulated for different coating thicknesses. The influence of laser power intensity distribution on the melt pool formation is incorporated in the analysis through introducing the laser pulse parameter. The control volume method is used to predict temperature field while the enthalpy–porosity method is incorporated to account for the phase change during the heating process. It is found that temperature predictions at the coating surface agree with the thermocouple data. The melt pool width formed in the coating is smaller than that corresponding to the steel sheet. Increasing coating thickness reduces the peak temperature at the surface. The Marangoni flow results in a toroid shape of rotating cells in the melt pool of the coating.     

Laser Assisted Nitriding of Ti-6Al-4V Alloy: Metallurgical and Electrochemical Properties

The surface properties of Ti-6Al-4V alloy, such as wear resistance, are inadequate for many applications. To improve the surface properties of the alloy, many techniques have been considered. One of the promising techniques is to form a nitride layer on the surface of the workpiece by a laser beam. In the present study, laser assisted nitriding of the Ti-6Al-4V alloy surface is carried out under a nitrogen gas flow environment. A CO₂ laser is used to irradiate the Ti-6Al-4V alloy surface while nitrogen is introduced co-axially with the laser beam onto the workpiece surface. The resulting surface cross section is examined metallurgically. SEM and XRD were carried out for material characterization. The study is extended to include the electrochemical response of the resulting surfaces. The surface morphology of the electrochemically treated workpieces are examined. It is found that in the laser treated region dendritic structures occur and TiN forms in the surface vicinity. The density of pit formation at the surface of the treated region reduces considerably.     

Flow emerging from annular-conical nozzle combinations and impinging onto a cylindrical cavity

Flow emerging from a combination of annular and conical nozzles and impinging onto a cylindrical cavity at elevated all temperature is considered, and the flow field and heat transfer rates from the cavity are computed. In the simulations, two cavity depths and four average jet velocities at nozzle exit are accommodated. Reynolds Stress Turbulence model is introduced to account for the turbulence. Air is used as working fluid while steel is considered as the cavity material. It is found that the Nusselt number attains high values in the neighborhood of the stagnation zone at the cavity bottom surface, which is more pronounced for 1 mm depth cavity.     

Nano-second laser pulse heating and assisting gas jet considerations

The nano-second laser pulse gas assisting processing method offers considerable advantages in the heat treatment process. In the present study gas assisted nano-second pulse laser heating of a stationary surface is considered. The gas, which is air, impinging onto the workpiece surface is modelled using flow equations, while the low Reynolds number k–ε model is employed to account for the turbulence. A heat conduction equation is introduced for the solid heating. A numerical scheme using a control volume approach is employed when discretizing the governing equations. The simulation is repeated for two gas jet velocities. To validate the present predictions, an analytical solution accommodating the convection losses is introduced for the workpiece heating. It is found that the temperature profiles predicted from the simulations agree well with the analytical solutions. Moreover, impinging gas jet velocity has no significant effect on the temperature distribution in the workpiece. As the heating progresses, the equilibrium heating initiates, in which case the internal energy gain of the solid increases at an almost constant rate.     

Investigation of charge and current dynamics in PVA–KOH gel electrolyte-based supercapacitor

Journal of Materials Science: Materials in Electronics - Poly-vinyl alcohol (PVA)-based electrolytes can play a vital role in the development of supercapacitors by providing a desirable charge...     

Flow over porous blocks in a square cavity: Influence of heat flux and porosity on heat transfer rates

The heat transfer due to the flow over two porous blocks situated in a square cavity is investigated and the effects of heat flux and the porosity on the flow structure and the heat transfer in the cavity are examined. In the simulations, four heat fluxes and three porosities are accommodated while air is used as the working fluid. The flow conditions at the cavity inlet are kept the same for all the cases simulated. The equilibrium equations pertinent to the flow over porous blocks in the cavity are used to predict the velocity and temperature fields. It is found that increasing porosity of the blocks modifies the flow field in the cavity, which is more pronounced as the heat flux increases. The Nusselt number enhances with the increasing porosity and heat flux.     

Optimization of a finned heat sink array based on thermoeconomic analysis

The design and specification of heat sinks for electronic systems is not easily accomplished through the use of standard thermal design and analysis tools since geometric and boundary conditions are not typically known in advance. A second-law based thermoeconomic optimization procedure is presented for a finned heat sink array. This involves including costs associated with material, and irreversible losses due to heat transfer and pressure drop. The influence of important physical, geometrical and unit cost parameters on the overall finned array are optimized for some typical operating conditions that are representative of electronic cooling applications. The optimized cost results are presented in terms of Re_D, Re_L, λ_P / λ_H, and q for a finned system in a graphical form. In addition the methodology of obtaining optimum parameters for a finned heat sink system which will result in minimum operating cost is demonstrated. Copyright © 2006 John Wiley & Sons, Ltd.