Empirical heat transfer and frost thickness correlations during frost deposition on a cylinder in cross-flow in the transient regime

This paper reports on results of an experimental investigation where the emphasis was placed on obtaining empirical correlations for the frost thickness–time history and the heat transfer coefficient–time history for a cylinder in humid air cross-flow. The facility employed for the investigation consisted of a low-velocity wind tunnel comprised of a rectangular test section, a transition section and a honeycomb placed at the tunnel entrance. An external refrigerator was used to cool an antifreeze solution having a mixture of 90% methanol and 10% ethylene glycol. Measured parameters included, among other things, the heat transfer coefficient as well as the frost thickness. © 1998 John Wiley & Sons, Ltd.     

Photoconductive optically driven deformable membrane for spatial light modulator applications utilizing GaAs substrates

The fabrication and characterization of an optically addressable deformable mirror for a spatial light modulator is described. Device operation utilizes an electrostatically driven pixellated aluminized polymeric membrane mirror supported above an optically controlled photoconductive GaAs substrate. A 5 microm thick grid of patterned photoresist supports the 2 microm thick aluminized Mylar membrane. A conductive ZnO layer is placed on the back side of the GaAs wafer. A standard Michelson interferometer is used to measure mirror deformation data as a function of illumination, applied voltage, and frequency. A simplified analysis of device operation is also presented.     

Real-time holographic deconvolution techniques for one-way image transmission through an aberrating medium: characterization, modeling, and measurements

We propose and demonstrate a new photorefractive real-time holographic deconvolution technique for adaptive one-way image transmission through aberrating media by means of four-wave mixing. In contrast with earlier methods, which typically required various codings of the exact phase or two-way image transmission for correcting phase distortion, our technique relies on one-way image transmission through the use of exact phase information. Our technique can simultaneously correct both amplitude and phase distortions. We include several forms of image degradation, various test cases, and experimental results. We characterize the performance as a function of the input beam ratios for four metrics: signal-to-noise ratio, normalized root-mean-square error, edge restoration, and peak-to-total energy ratio. In our characterization we use false-color graphic images to display the best beam-intensity ratio two-dimensional region(s) for each of these metrics. Test cases are simulated at the optimal values of the beam-intensity ratios. We demonstrate our results through both experiment and computer simulation.     

Effect of growth temperature on the CVD grown Fe filled multi-walled carbon nanotubes using a modified photoresist

Fe filled carbon nanotubes were synthesized by atmospheric pressure chemical vapor deposition using a simple mixture of iron(III) acetylacetonate (Fe(acac)₃) with a conventional photoresist and the effect of growth temperature (550-950 °C) on Fe filled nanotubes has been studied. Scanning electron microscopy results show that, as the growth temperature increases from 550 to 950 °C, the average diameter of the nanotubes increases while their number density decreases. High resolution transmission electron microscopy along with energy dispersive X-ray investigation shows that the nanotubes have a multi-walled structure with partial Fe filling for all growth temperatures. The graphitic nature of the nanotubes was observed via X-ray diffraction pattern. Raman analysis demonstrates that the degree of graphitization of the carbon nanotubes depends upon the growth temperature.     

Middleware to enhance mobile communications for road safety and traffic mobility applications

Middleware has emerged as an important architectural component in supporting distributed applications. The role of middleware is to present a unified programming model to application writers and to mask out problems of heterogeneity and distribution. It is motivated by the convergence of the embedded sensor and mobile communication revolutions in the automobile industry. The vehicle fleet is morphing into a vast mobile sensor fleet. The authors provide a middleware architecture and implementation that addresses the needs of a distributed system of mobile sensors comprised of vehicles and intersections producing trafficrelated data for traffic safety and operations. The authors discuss the technical challenges that the middleware addresses and describe a prototype implementation. Traffic management, intersection safety and vehicle-to-vehicle safety applications are three applications described and implemented on the middleware. The authors conclude their paper with conducting performance measures that relate to the cost of overhead incurred from using the middleware. The measurements show the middleware is efficient enough for the road safety and congestion relief applications presented.     

Characterization of Metallized Alumina Ceramics

The metallization of alumina ceramics (92 pct purity) was performed by the molybdenum-manganese (Mo−Mn) process in moist hydrogen and nitrogen atmosphere in the temperature range of 1523 K to 1673 K (1250 °C to 1400 °C) for 10 minutes with a dew point of 293 K (20 °C). The metallized alumina ceramics were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), evaluation of metallic coating adhesion by scratch test, and nanohardness measurement. XRD identified the phase composition of the metallized layer surface. The surface and cross-section microstructures of the metallized alumina ceramic specimens were observed by SEM. An EDX analysis across the metallized alumina specimens determined the elemental compositions at the selective regions. The scratch test results showed that the adhesion of the metallized layer on alumina ceramics enhanced with the increase in metallization temperature. Nanohardness measurements along the cross-sectional region of the metallized alumina ceramics exhibited the gradual change in the nanohardness values from the alumina substrate to the metallizing layer. Furthermore, it was observed that the nanohardness of interfacial and metallizing regions was enhanced slightly with increasing processing temperature.     

On-line tool condition monitoring in face milling using current and power signals

The vast majority of tool condition monitoring systems use the cutting force as the predictor signal. However, due to prohibitive cost to performance ratios and maintenance and operational problems, such methods are not favoured by industries. In this paper, a method for continuous on-line estimation of tool wear, based on the inexpensive spindle motor current and voltage measurements, is proposed for the complex and intermittent cutting face milling operation. Sensors for these signals are free from problems associated with the cutting forces and the vibration signals. Novel signal processing strategies have been proposed for on-line computation of useful features from the measured signals. Feature space filtering is introduced to obtain robust and improved predictors from the extracted features. A multiple linear regression model, built on the filtered features, is then used to estimate tool wear in real-time. Very accurate predictions are achieved for both laboratory and industrial experiments, surpassing earlier results using cutting forces and estimation methods based on complex methodologies such as artificial neural networks.     

Novel Acyl Phosphate Mimics that Target PlsY,an Essential Acyltransferase in Gram‐Positive Bacteria

PlsY is a recently discovered acyltransferase that executes an essential step in membrane phospholipid biosynthesis in Gram‐ positive bacteria. By using a bioisosteric replacement approach to generate substrate‐based inhibitors of PlsY as potential novel antibacterial agents, a series of stabilized acyl phosphate mimetics, including acyl phosphonates, acyl α,α‐difluoromethyl phosphonates, acyl phosphoramides, reverse amide phosphonates, acyl sulfamates, and acyl sulfamides were designed and synthesized. Several acyl phosphonates, phosphoramides, and sulfamates were identified as inhibitors of PlsY from Streptococcus pneumoniae and Bacillus anthracis. As anticipated, these inhibitors were competitive inhibitors with respect to the acyl phosphate substrate. Antimicrobial testing showed the inhibitors to have generally weak activity against Gram‐positive bacteria with the exception of some acyl phosphonates, reverse amide phosphonates, and acyl sulfamates, which had potent activity against multiple strains of B. anthracis.