Design of a wideband microstrip antenna and the use of artificial neural networks in parameter calculation

This paper deals with the design of a multi-slot hole-coupled microstrip antenna on a substrate of 2 mm thickness that gives multi-frequency (wideband) characteristics. The Method of Moments (MoM)-based IE3D software was used to simulate the results for return loss, VSWR, the Smith chart, and the radiation patterns. A tunnel-based artificial neural network (ANN) was also developed to calculate the radiation patterns of the antenna. The radiation patterns were measured experimentally at 10.5 GHz and 12 GHz. The experimental results were in good agreement with the simulated results from IE3D and those of the artificial neural network. A new method of using a genetic algorithm (GA) in an artificial neural network is also discussed. This new method was used to calculate the resonant frequency of a single-shorting-post microstrip antenna. The resonant frequency calculated using the genetic-algorithm-coupled artificial neural network was compared with the analytical and experimental results. The results obtained were in very good agreement with the experimental results.     

Polymers from renewable resources. I. Castor oil-based interpenetrating polymer networks: Thermal and mechanical properties

A number of polyurethanes (PUs) were synthesized by reacting castor oil with toluene-2,4-diisocyanate and hexamethylene diisocyanate and varying the NCO/OH ratio. All these polyurethanes were reacted with some acrylic monomers like ethyl acrylate, n-butyl acrylate, ethyl methacrylate, and butyl methacrylate using a crosslinker ethylene glycol dimethyl-acrylate and benzoyl peroxide as the initiator. The physicochemical properties of interpenetrating polymer networks (IPNs) are reported. Thermogravimetric analysis was used to study the thermal behavior of IPNs and the evaluation of kinetic parameters. Degradation mechanism has also been investigated. Some of the mechanical properties viz. tensile strength, shore-A hardness, elongation at break, etc. are also reported. © 1993 John Wiley & Sons, Inc.     

Physicochemical Characterization of Interaction of Ibuprofen by Solid-State Milling with Aluminum Hydroxide

This present study is a preliminary exploration of the affinity between a carboxylic model drug ibuprofen and aluminum hydroxide. Ibuprofen was comilled with aluminum hydroxide in different weight ratios in the solid state and was characterized by scanning electron microscopy (SEM), X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and in vitro dissolution studies. XRD and SEM studies indicated complete interaction of ibuprofen with aluminum hydroxide and complete amorphization of aluminum hydroxide–ibuprofen complexed salt as well, on comilling with aluminum hydroxide at 1:2 ratio. FTIR data showed the disappearance of acid carbonyl peak with the appearance and the corresponding increase in absorbance of new signal at 1,682 cm^?1 in the 1:1 and 1:2 ibuprofen–aluminum hydroxide-comilled powder. The accompanied increase in the absorbance of carboxylate peak in the ibuprofen–aluminum hydroxide physical mixture, and 1:0.1, 1:0.5, 1:1, and 1:2 (IBA_pm, and IB₁A_0.1, IB₁A_0.5, IB₁A₁, and IB₁A₂, respectively) comilled powder indicated an acid–base reaction between ibuprofen and aluminum hydroxide. On storage at 40°C and 75% relative humidity (RH) for 10 weeks, XRD study showed the absence of reversion to the crystalline state and FTIR data revealed continued increase of new signal at 1,682 cm^?1 relative to carboxylic acid peak and no reappearance of carboxylic acid peak. In vitro dissolution studies revealed that the percent release of ibuprofen from the aluminum hydroxide-comilled powder is in the following order: IB₁A₂ < IB₁A₁ < ibuprofen crystal < ibuprofen milled alone < IB₁A_0.1 < IB₁A_0.5. Aluminum metal cation might have interacted to form a complex through the carboxyl and carbonyl groups of ibuprofen. Improved dissolution of drug associated with IB₁A_0.1 and IB₁A_0.5 is because of the absence of a new signal at 1,682 cm^?1 and improved amorphization of the drug to some extent. Dissolution of drug affected in IB₁A₂ and IB₁A₁ may be because of the insoluble stable complex formation.     

Dry machining of aluminum for proper selection of cutting tool: tool performance and tool wear

Machining of aluminum and its alloy is very difficult due to the adhesion and diffusion of aluminum, thus the formation of built-up edge (BUE) on the surface. The BUE, which affects the surface integrity and tool life significantly, affects the service and performance of the workpiece. The minimization of BUE was carried out by selection of proper cutting speed, feed, depth of cut, and cutting tool material. This paper presents machining of rolled aluminum at cutting speeds of 336, 426, and 540 m/min, the feeds of 0.045, 0.06, and 0.09 mm/rev, and a constant depth of cut of 0.2 mm in dry condition. Five cutting tools WC SPUN grade, WC SPGN grade, WC + PVD (physical vapor deposition) TiN coating, WC + Ti (C, N) + Al₂O₃ PVD multilayer coatings, and PCD (polycrystalline diamond) were utilized for the experiments. The surface roughness produced, total flank wear, and cut chip thicknesses were measured. The characterization of the tool was carried out by a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) pattern. The chip underface was analyzed for the study of chip deformation produced after machining. The results indicated that the PCD tool provides better results in terms of roughness, tool wear, and smoother chip underface. It provides promising results in all aspects.     

Effect of elevated temperature exposure on the structure,stability, and mechanical behavior of aluminum-stainless steel composites

The effect of elevated temperature exposure on subsequent ambient temperature tensile behavior of aluminum-stainless steel composities (V _f= 6.5 pct) has been studied. In particular, ambient temperature tensile yielding, flow, and fracture were correlated with the associated interface microstructures, matrix substructure, and fracture morphology in the as-pressed condition and following elevated-temperature exposure at 550°C (823 K) or 625°C (898 K) for 24 h (86.4 ks). Compared to the as-pressed condition, exposure at either temperature results in a small increase (?4 pet) in initial modulus, and a decrease in the level of residual stress (tensile) in the matrix; tensile stress-strain behavior in stage II (matrix plastic, reinforcement elastic) is essentially unaffected. Lower strength levels in stage III (matrix and reinforcement plastic) after exposure are due to premature cracking in the interface reaction zone, primarily a ternary (Fe, Cr) Al intermetallic, with associated notch effects on the wire reinforcement. Changes in fracture surface morphology of the composites confirm the degradation. Wires extracted from composites after hot pressing or following exposure at 550°C (823 K) possess a unique strength. Exposure at 625°C (898 K) leads to a bimodal distribution in the strength of extracted wires. In each condition, a matrix dislocation cell structure develops in stage III; the invariant form and size of the cell structure withV _f and distance from the matrix wire interface confirm isostrain conditions.