New delay range–dependent stability criteria for interval time‐varying delay systems via Wirtinger‐based inequalities

Stability conditions for time‐delay systems using the Lyapunov‐based methodologies are generically expressed in terms of linear matrix inequalities. However, due to assuming restrictive conditions in deriving the linear matrix inequalities, the established stability conditions can be strictly conservative. This paper attempts to relax this problem for linear systems with interval time‐varying delays. A double‐integral inequality is derived inspired by Wirtinger‐based single‐integral inequality. Using the advanced integral inequalities, the reciprocally convex combination techniques and necessary slack variables, together with extracting a condition for the positive definiteness of the Lyapunov functional, novel stability criteria, have been established for the system. The effectiveness of the criteria is evaluated via 2 numerical examples. The results indicate that more complex stability criteria not only improve the stability region but also bring computational expenses.     

Computational completeness of simple semi-conditional insertion–deletion systems of degree (2,1)

Natural Computing - Insertion–deletion (or ins–del for short) systems are simple models of bio-inspired computing. They are well studied in formal language theory, especially regarding...     

Kinetics of cupric oxide catalysed oxidation of propylene in a stirred reactor

The catalytic air oxidation of propylene to acrolein over a supported copper oxide catalyst was investigated in a continuous stirred vessel reactor between 375° and 450°C at atmospheric pressure. The effect of temperature, ratio of oxygen to propylene in feed and total feed rate (or contact time) on the conversion of propylene and the yield of acrolein were determined. It was found that with an increase in temperature, ratio of oxygen to propylene and contact time, the yield drops considerably though conversion increases. A study of the mixing characteristics of the stirred vessel reactor was carried out by following the conversion at various stirrer speeds. The kinetic data obtained were tested to determine the most probable model by the Hougen-Watson method. The model that satisfactorily correlated the data describes the rate-controlling step as the surface reaction occurring between adsorbed propylene, a vacant site and oxygen in the gas phase. The following Hougen-Watson type rate equation has been proposed The constants in the rate equation have been expressed as a function of temperature.     

Magnetoelastic biosensor for the detection of Salmonella typhimurium in food products

In this article, a magnetoelastic sensor immobilized with polyclonal antibody for the detection of Salmonella typhimurium in food products is described. The remote query nature of magnetoelastic sensors enables the detection of bacterial species in sealed and opaque containers. Bacterial binding to the antibody on the sensor surfaces changed the resonance parameters, and these changes were quantified by the shift in the sensor’s resonance frequency. Response of the sensors to increasing concentrations (5 × 10¹–5 × 10⁸ cfu/ml) of S. typhimurium in three different food products (water, fat-free milk and apple juice) was studied and similar responses were observed. These results were also further ascertained by Scanning Electron Microscopy (SEM) studies. A detection limit of 5 × 10³ cfu/ml, with a sensitivity of 139 Hz/decade was obtained for the sensors tested in water samples, as compared to 129 Hz/decade in apple juice and 127 Hz/decade in fat free milk. A 2 × 0.4 × 0.015 mm sensor was employed in all the investigations. The dissociation constant K _d and the binding valencies for S. typhimurium spiked in water samples was 435 cfu/ml and 2.33 respectively; as compared to 309 cfu/ml and 2.38 for apple juice; and 1389 cfu/ml and 1.85 for fat free milk samples. Bacterial binding was specific and a divalent binding was observed.     

Plasma treated fabrics coated with naturally derived Ag‐NPs for biomedical application

Ethnic value of many known plants are underexploited for medicinal application besides their proven traditional qualities. One such plant known for wound healing is Tridax procumbens. This plant has wound healing property and is commercially unexploited. Silver nanoparticle (Ag‐NP) were synthesized using this plant extracts using different solvents (methanol, ethyl acetate and aqueous), which exhibit resonance at 426, 424 and 418 nm, respectively. This plant‐mediated Ag‐NPs have strong anti‐bactericidal activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Streptococcus pyogenes, Klebsiella pneumonia, Serratia marcescens and Bacillus subtilis with methanol extract. Further instance, elemental composition was confirmed by energy dispersive X‐ray analysis and particle size ranges were observed at 80–200 nm with spherical shape nanoparticles by scanning electron microscopy and transmission electron microscopy analysis. The biocompatibility of Ag‐NPs was assessed using fibroblast cell line (L929) by MTT assay with 109.35 µg IC₅₀ value. The oxygen plasma treated and non‐treated bamboo spunlaced nonwoven fabrics were coated with the Ag‐NPs by exhaust method. Contact angle and water retention revealed significant difference in absorption ability of plasma treated fabric. Field emission scanning electron microscopy revealed the presence of Ag‐NPs in plasma coated fabrics. The fabricated cloth was studied for anti‐microbial and microbial penetration ability.Inspec keywords: solvents (industrial), organic compounds, woven composites, field emission scanning electron microscopy, plasma materials processing, contact angle, transmission electron microscopy, X‐ray diffraction, fabrics, biomedical materials, wounds, silver, nanoparticles, particle size, nanofabrication, thermal analysis, antibacterial activity, microorganisms, X‐ray chemical analysisOther keywords: biomedical application, ethnic value, medicinal application, wound healing property, silver nanoparticle synthesis, methanol, ethyl acetate, Escherichia coli, Pseudomonas aeruginosa, Streptococcus pyogenes, Klebsiella pneumonia, nonwoven fabrics, field emission scanning electron microscopy, plasma coated fabrics, fabricated cloth, solvents, antibactericidal activity, Staphylococcus aureus, particle size, transmission electron microscopy, oxygen plasma treatment, bamboo material, Tridax procumbens extracts, Serratia marcescens, Bacillus subtilis, elemental composition, energy dispersive X‐ray analysis, scanning electron microscopy, material biocompatibility, fibroblast cell line, exhaust method, contact angle, water retention, absorption ability, antimicrobial property, microbial penetration ability, size 424.0 nm, size 418.0 nm, size 80.0 nm to 200.0 nm, size 426.0 nm, Ag     

An Investigation on the Sensitivity of Wavelet Packet Modulation to Time Synchronization Error

Wavelet Packet based Multi-Carrier Modulation (WPMCM) offers an alternative to the well-established OFDM as an efficient multicarrier modulation technique. It has the advantage of being a generic transmission scheme whose actual characteristics can be widely customized to fulfill several requirements and constraints of advanced communication systems. In the last decades wavelets have been favorably applied in signal and image processing fields but only recently have they attracted the attention of the telecommunication community. A lot of research questions remain to be addressed before the novel WPMCM can be used in practice. One of the major concerns is the performance of WPMCM transceivers under time synchronization errors. This is important because WPMCM symbols overlap in the time domain. In this paper, we analyze the interference in WPMCM transmission caused by the time synchronization errors. The expressions for Inter Carrier Interference (ICI) and Inter Symbol Interference (ISI) in WPMCM transmission are derived and then through simulation studies, the ability of wavelet-based systems to cope with time synchronization errors is evaluated.     

An innovative gas-solid torbed reactor for the recycling industries

Gas-solid Torbed reactors have been developed for processing a wide range of materials. The reactors have facilitated several novel recycling projects in countries where they are used. One of the major advantages of these reactors when applied to the recycling industries is the compactness of the plant and its inherent ability to be scaled down and fully automated to better match the volume requirements of this sector. Authors’ Note: Torbed is a registered trademark of Torftech Ltd. V.I. Lakshmanan earned his Ph.D. in chemistry at Bombay University, India, in 1968. He is currently program director of process technologies with Ortech Corporation. C.E. Dodson earned his diploma in mechanical engineering at Polytechnic of the South Bank, London, in 1968. He is currently president of Torftech Ltd. Mr. Dodson is a member of TMS.     

Assessment of white layer in hardened AISI 52100 steel and its prediction using grinding power

In the present work, the effect of various grinding mechanisms on white layer (WL) formation in AISI 52100 steel is studied using two types of alumina grains, one produced by sol–gel process and the other by conventional fusion. Further, a novel approach is proposed on predicting the WL formation using grinding power. This study correlates the power variation with the change in the metallurgical aspects of the work material. WL of about 56 µm thickness is observed in the material ground by worn out sol–gel alumina wheel. However, no WL is present in the material ground by fused alumina wheel. High toughness in sol–gel alumina led to generation of wear flats with increasing grinding passes and transformed the dominant grinding mechanism from shearing to plowing and sliding. This increases the temperature in the grinding zone, which was the reason for WL formation. Change in the dominant grinding mechanisms from shearing is found to increase the grinding power. Since the change in dominant grinding mechanisms is the cause for WL formation, the increase in grinding power is found to be a good measure in predicting the WL formation. The predictability of WL formation by grinding power is further validated by comparing the power variation in grinding process by both the grinding wheels.     

Multi-gateway association in wireless mesh networks

Most traditional models of wireless mesh networks involve a mobile device connecting to the backbone through one of the available gateways in a wireless mesh network. In this paper, we present an alternate model, in which mobile devices are allowed to connect through more than one of the available gateways. We call the model multi-gateway association (MGA). We present arguments for why such a model can result in better capacity, fairness, diversity and security when compared to the default single-association model. We also identify the primary challenges that need to be addressed when using multiple-gateway associations, and propose solutions to handle these challenges. Using simulations, we show that throughput benefits ranging from 10% to 125% can be obtained by the proposed model as compared to a default single association model with just two gateways and more importantly, benefits linear in the number of gateways are obtainable. Through simulations and analysis, we establish why only intelligent multi-gateway association and neither single or simple multi-gateway association strategies can yield significant benefits.