Preparation and properties of rice starch–chitosan blend biodegradable film

Biodegradable blend films from rice starch–chitosan were developed by casting film-solution on leveled trays. The influence of the ratio of starch and chitosan (2:1, 1.5:1, 1:1, and 0.5:1) on the mechanical properties, water barrier properties, and miscibility of biodegradable blend films was investigated. The biodegradable blend film from rice starch–chitosan showed an increase in tensile strength (TS), water vapor permeability (WVP), lighter color and yellowness and a decreasing elongation at the break (E), and film solubility (FS) after incorporation of chitosan. The introduction of chitosan increased the crystalline peak structure of starch film; however, too high chitosan concentration yielded phase separation between starch and chitosan. The amino group band of the chitosan molecule in the FTIR spectrum shifted from 1541.15 cm⁻¹ in the chitosan film to 1621.96 cm⁻¹ in the biodegradable blend films. These results pointed out that there was a molecular miscibility between these two components. The properties of rice starch–chitosan biodegradable blend film and selected biopolymer and synthetic polymer films were compared; the results demonstrated that rice starch–chitosan biodegradable blend film had mechanical properties similar to the other chitosan films. However, the water vapor permeability of rice starch–chitosan biodegradable blend film was characterized by relatively lower water vapor permeability than chitosan films but higher than polyolefin.     

BER performance of MQAM with L‐branch MRC diversity reception over correlated Nakagami‐m fading channels

Exact and closed form generalized expressions for bit error rate (BER) of M‐ary quadrature amplitude modulation (MQAM) with L‐branch maximal ratio combining (MRC) space diversity reception in fading channels are derived and analyzed. The fading channels are modeled as identical but correlated frequency‐nonselective slow Nakagami‐m fading channels corrupted by additive white Gaussian noise (AWGN). Analytical results obtained are in terms of few finite range integrals with an integrand composed of elementary functions. Because of their simple form, these analytical results readily allow numerical evaluation in cases of practical interest. The results are also general enough to include Nakagami‐m fading channels with and without correlation, no diversity system, Rayleigh fading channels with and without correlation, and AWGN as special cases. The numerical results for the case of 16QAM are shown graphically and also in tabular form in order to examine the effects of fading severity, order of diversity, and branch correlation on the BER performance. The two correlation models considered are constant correlation model and exponential correlation model. One may be interested to know how the BER of MQAM is related to symbol error rate (SER) of MQAM. Therefore, the BER results obtained in this paper are also compared with that obtained directly from the SER. It is expected that the analytical results presented in this paper will provide a convenient tool for design and analysis of a radio communication system with space diversity reception in uncorrelated and correlated fading environment. Copyright © 2002 John Wiley & Sons, Ltd.     

SnO2 based sensors with improved sensitivity and response‐recovery time

The objective of this work is to develop gas sensors using tin oxide (SnO₂) based thin films doped by Iron (Fe) and Indium (In) for good sensitivity and better response–recovery time. The structural properties and crystalline behavior of the synthesized films is studied by X-ray diffraction (XRD). The surface morphology and particle size is investigated by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The studies performed with energy-dispersive X-ray spectroscopy (EDS) confirmed the composition of the films. The sensitivity measurements are carried out as a function of operating temperature (50–350 °C) and at 400, 600 and 800 ppm partial pressure of chemical inputs. The In-doped sensors exhibit maximum sensitivity for ethanol, while Fe-doped sensors showed maximum sensitivity for CO gas at its working temperatures. Most importantly, both of these sensors exhibited faster response time of the order of 1–2 s and short recovery time of the order of 15–25 s. Increase of texture coefficient of less dense (200) plane and reduction in band gap upon doping is found to have influence on better sensitivity.     

Structure and Properties of β Nucleated Polypropylene Film Prepared by Tubular Water Quench Process

β-Nucleated isotactic polypropylene (iPP) films were prepared by tubular quench process. The stretching of the film during the process resulted in the formation of different polymorphs in nucleated iPP, whereas meso phase alone resulted in unnucleated iPP. The process conditions determine the formation of β crystals transforming into α crystals on stretching. The crystalline content and β phase decrease as the stretching speed increases. The β nucleated film samples are found to have voided surface. The degree of crystallinity and crystalline content define physical properties of the film.     

Fat reduction affects quality of akara (fried cowpea paste)

Akara, a fried finger food made from cowpeas (Vigna unguiculata), is popular in West Africa and has been shown to be acceptable to American consumers. Akara is, however, a high‐fat food (about 31%, dry wt basis). We determined the effects of incorporating two modifiers, high amylose cornstarch or extruded cowpea flour, on akara fat content and consumer acceptability. The modifiers were used at the 10% level. Akara fat content was reduced by 26.1% with cornstarch and by 36.8% with extruded cowpea flour. There were no significant differences in sensory ratings among samples, and all samples received acceptable ratings (6 = like slightly) for overall liking.     

Vinyl ester resins, 3. Effect of ethyl methacrylate on thermal and mechanical properties

This paper describes the effect of ethyl methacrylate (EMA) on the thermal and mechanical properties of glass fibre-reinforced laminates of vinyl ester resins derived from diglycidyl ether of bisphenol-A and methacrylic acid. The thermal stability and the curing characteristic of the resins were investigated by thermogravimetric analysis and differential scanning calorimetry. The glass transition temperature of the laminates decreased with increase in EMA content. Dilution of vinyl ester resin with EMA resulted in a decrease in flexural strength and flexural modulus of the laminates.     

A linear antenna array failure correction using improved bat algorithm

The failure of antenna array elements causes disturbance in the sidelobe power level. In this article, an improved flexible approach that use bat algorithm is proposed and applied to solve the problem of antenna array failure by controlling only the amplitude excitation of array elements. An adaptive inertia weight approach is applied to the standard bat algorithm to improve the quality of the solution and the speed of convergence. The effectiveness of the proposed improved bat algorithm (IBA) is verified on different standard test functions. Numerical examples of element failure correction are presented to show the capability of this flexible approach in antenna array failure correction.     

Optimization of Cognitive Radio System Using Simulated Annealing

Cognitive radio (CR) technology has introduced a revolution in wireless communication network and it is capable to operate in a continuously varying radio frequency environment that depends on multiple parameters. In this paper, optimization of CR system has been achieved using simulated annealing (SA) Technique. SA is a stochastic global optimization technique that exploits an analogy between the way in which a metal cools and freezes into a minimum energy crystalline structure. SA has been used to meet the quality of service (QoS) that is defined by the user in terms of minimum transmit power, minimum bit error rate, maximum throughput, minimum interference and maximum spectral efficiency. The results obtained by SA are compared with the genetic algorithm (GA) results for the various QoS parameters and it has been observed that SA is outperforming GA in CR system optimization.     

pH‐responsive fibers based on acrylonitrile acrylic acid block copolymers: Effect of spinning conditions and postspinning operations on response and mechanical properties

pH sensitive poly(acrylonitrile‐co‐acrylic acid) having ～50 mol % acrylic acid with block type structure (AA50B) was synthesized by controlled dosing method of free radical polymerization. The polymer was converted into fibers by wet solution spinning technique in DMF‐water system. The resulting block type copolymer could generate a domain type morphology with segregated domains of acrylonitrile and acrylic acid on heat‐setting. The drawing ratio and heat‐setting temperature had a significant effect on the formation of these domains and their stability. The domain formation was more pronounced when the fibers could be drawn to higher draw ratios during coagulation or heat‐set at higher temperature. The stability of the fibers, which is influenced by domain formation, was lowest (at few cycles of transitions) when the fibers were heat‐set at 100°C, while it is improved significantly to more than 50 cycles as the heat‐setting temperature was increased to 150°C. The coagulation conditions, drawing and the heat‐setting also greatly influenced the mechanical properties, transition behavior, and retractive stresses of the responsive fibers. The tenacity improved by 6.6 times in swollen state and 1.4 times in deswollen state, while the retractive stresses during deswelling were significantly increased to about 4.7 times. However, the increased heat‐setting temperature was also found to have a negative effect on the equilibrium swelling values as well as the response rate. The effect of heat‐setting on chemical structure of the copolymer was also investigated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008