Development of ultrafine grained high strength age hardenable Al 7075 alloy by cryorolling

High strength age hardenable Al 7XXX series alloys are difficult to process by many of the severe plastic deformation processes at room temperature. The Al 7075 alloy has been processed at cryogenic temperature and room temperature up to different rolling strains, in the present work, with the objective of developing a processing strategy to obtain ultrafine grained microstructure with enhanced mechanical properties in the alloy. It has been identified that the Al 7075 alloy samples can be successfully cryorolled to higher strains (up to 3.4) if the reduction per pass is less than 0.3 mm, however it was found to be difficult to deform the samples at room temperature. A cryorolling strain of 3.4 has been found to be desirable for producing the ultrafine grained Al 7075 alloys with the high angle grain boundaries. However, the subgrains are not recrystallized up to this strain in the case of room temperature rolled Al alloys. The strength and hardness of the cryorolled Al 7075 alloy samples are higher than that of the room temperature rolled samples as observed in the present work. The improved strength and hardness of cryorolled samples are due to the grain size effect and higher dislocation density. The reduction in dimple size of cryorolled Al 7075 alloy upon failure confirms the grain refinement and strain hardening mechanism operating in the heavily deformed samples.     

Simultaneous Determination of 23 Azo Dyes in Paprika by Gas Chromatography-Mass Spectrometry

The present work describes the development and validation of a simple, quick and precise gas chromatography-mass spectrometry (GC-MS) method for the analysis of 23 azo dye breakdown products in paprika samples. After the extraction procedure, dyes were identified on an Agilent J&W DB-5ms Ultra Inert capillary column using dichloroethane as a sample dissolvent. Limits of detection (LODs) were comprised between 10.6 and 84.4 ng/mL. Accuracy values in the range of 90–104 % for the 23 azo dye breakdown products were obtained, and RSD% for the analysis of 2.4 μg/mL of each compound was below 4.6 % (n = 9). The recovery for the azo dyes in paprika samples was comprised between 71.2 ± 3.5 % (benzidine) and 118.9 ± 2.5 % (para-cresidine). Results of this study suggest that the developed method is suitable for detection and quantification of azo dye breakdown products in the range of 60–240 μg/kg paprika. In addition, this GC-MS method allowed the simultaneous determination of disperse orange 3 (azo dye) with high accuracy and precision. The method has numerous advantages such as simplicity, low cost, easy operation and short analysis time and constitutes an efficient method for the monitoring of a large number of azo dyes in food matrices.     

Relative performance of chelated zinc and zinc sulphate for lowland rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Field experiments were conducted during the wet seasons of 2005–2006 and 2006–2007 on an Aeric Endoaquept (pH 7.2) to study the relative performance of chelated zinc [Zn ethylene diamine tetra-acetic acid (EDTA)] and zinc sulphate (ZnSO₄) on the growth and yield of rice (cv. IET 4094). The diethylene triamine penta-acetic acid (DTPA) extractable (available) Zn concentration in soil and total Zn content in dry matter of rice increased initially up to 28 days of crop growth when Zn was applied as a single basal source, being greater with chelated Zn compared with ZnSO₄ application. The highest mean Zn uptake by rice grain and straw was found to be 209.2 and 133.8 g ha⁻¹, respectively, in the treatment T₇ (1 kg Zn ha⁻¹ as Zn-EDTA at basal). The mean filled grain percentage, thousand grain weight and number of panicles m⁻² were highest with 90.4%, 25.4 g and 452, respectively, in treatment T₇ where 1 kg ha⁻¹ Zn as Zn-EDTA was applied. The highest yield of grain and straw was 5.5 and 7.3 t ha⁻¹, respectively, in treatment T₇, resulting in a 37.5 and 43.1% increase in yield over that of the control during both the years.     

Design of compact bandpass filter for WiMAX and UWB application using asymmetric SIRs and DGS

This paper considers a novel compact tri-band microstrip bandpass filter, the design of which employs asymmetric SIRs and DGS for achieving the characteristics of low insertion loss, high selectivity, wider range of bandwidth, and low group delay for 2.5/3.4 GHz (WiMAX) and 4.14–5.32 GHz (UWB) bands. The novel filter design implies the intentional selection of impedance ratio R and the length of the microstrip of asymmetric SIRs; in addition, DGS is used to improve the coupling strength of the last band. The scattering parameters of the three passbands have the following values: insertion losses S₂₁ are–0.26/–0.07/–0.05 dB, and return losses S₁₁ are–11.29/–19.25/–22.64 dB, respectively. The response of the filter was simulated using Ansoft HFSS simulator.     

Role of gamma radiation and EGDMA on the physico–mechanical properties of jute fabrics/polypropylene composites

Jute fabrics reinforced polypropylene (PP) composites (45 wt % fiber) were prepared by compression molding and their mechanical properties were investigated. Both jute fabrics and PP sheets were treated with gamma radiation (250–1,000 krad dose) at a rate of 350 krad/h. Irradiated jute fabrics were soaked into ethylene glycol dimethacrylate (EGDMA) solutions (5–40% by weight) and cured in an oven at different temperatures (40–100°C) for 60 min. The percentage of polymer loading (PL) was evaluated and found that 20% EGDMA‐treated jute fabrics contains the highest PL. Composites made of 20% EGDMA‐treated jute fabrics were studied further. It was found that the treatment using the EGDMA improved the mechanical properties of the composites significantly. Scanning electron microscopy and aging properties of untreated and treated composites were performed. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Molecular characterization of biosurfactant producing Bacillus cereus strain DRDU1 for its potential application in bioremediation and further EOR studies

Abstract

Environmental pollution by crude oil during petroleum exploration is a global issue of concern. It largely alters the physicochemical property of soil and water which makes them toxic for crops and aquatic organisms to survive. Bacillus cereus strain DRDU1 (Genbank accession no. KF273330.1) is an endospore forming potential hydrocarbon degrader which was isolated from an automobile engine. The isolate could achieve up to 96 and 84% kerosene and crude oil degradation with respective cfu of (6.3?±?2.31)?×?10⁹ and (13.67?±?2.52)?×?10⁸ cells/mL. On the other hand it also showed its potential to degrade 74 and 67% of kerosene and crude oil in nitrate (N) and phosphate (P) deficient media with corresponding cfu (10?±?1.73)?×?10⁸ and (6?±?2.65)?×?10⁶ cells/mL. This indicates its potential to survive under nutrient stress condition. The strain was reported to be capable of producing biosurfactant which may play role in petroleum biodegradation and may be a potential tool for Microbial Enhanced Oil Recovery (MEOR) studies in future. Herein the presence of sfp gene in the isolate was confirmed which may be responsible for its ability to synthesize biosurfactant for hydrocarbon degradation and also for its stress tolerant potential. It was further characterized and the hypothetical protein sequence encoded by this gene is also proposed.     

Preparation of ordered porous carbon from tea by chemical activation and its use in Cr(VI) adsorption

Ordered porous carbon was prepared from a new carbon precursor??the tea leaves, the most widely used beverage worldwide by a chemical activation process. We obtained well developed spherical interlinked meso and micro pores with uniform pore morphology and high surface area from green, black and waste tea by NaOH as well as H₃PO₄ activation process. The carbon obtained from green tea by H₃PO₄ activation had the highest BET surface area of 1,285?m²g^?1 with total pore volume of 0.6243?mL?g^?1. The as prepared porous carbon showed high adsorption efficiency of Cr(VI) adsorption from aqueous solution.     

Convergecast tree management from arbitrary node failure in sensor network

The efficiency and reliability of convergecast in sensor network depends on the correct and efficient accumulation of data to the sink. A tree, rooted at the sink, that utilizes sensor resources properly is an ideal topology for data gathering. Resource constrained sensor nodes are highly prone to sudden crash. So the application demands a quick and efficient repairing of the tree when a node dies. The proposed scheme builds a data gathering tree rooted at the sink. The tree eventually becomes a Breadth First Search (BFS) tree where each node maintains the shortest hop-count to the root to reduce the routing delay. Each node collects some extra neighborhood information during the tree construction. Thus a little pre-processing at each node helps in taking prompt actions to repair the tree through local adjustment if any arbitrary single or multiple nodes fail in future. On failure of a node, each affected node in its vicinity fixes the parent through a pair of control message transmissions. Simulation results show that the repairing delay is significantly less in average and the convergecast messages are delivered with minimum data loss and no redundancy even in presence of node crash.     

Banana/Glass Fiber-Reinforced Polypropylene Hybrid Composites: Fabrication and Performance Evaluation

Hybrid composites of Polypropylene (PP) reinforced with intimately mixed short banana and glass fibers were fabricated using Haake twin screw extruder followed by compression molding with and without the presence maleic anhydride grafted polypropylene (MAPP) as a coupling agent. Incorporation of both the fibers into PP matrix resulted in an increase in tensile, flexural and impact strength with an increasing level of fiber content upto 30 wt% at banana: glass fiber ratio of 15:15 wt% and 2 wt% of MAPP. The rate of water absorption for the hybrid composites decreased due to the presence of glass fiber and coupling agent. The effect of fiber loading in presence of coupling agent on the dynamic mechanical properties has also been analyzed to investigate the interfacial properties. An increase in the storage modulus (E′) of the treated composite indicates higher stiffness. The tan δ spectra confirms a strong influence of fiber contents and coupling agent on the α and β relaxation processes of PP. The nature of fiber matrix adhesion was examined through scanning electron microscopy (SEM) of the tensile fractured specimen. Thermal measurements were carried out employing differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA) which indicated a decrease in the crystallization temperature and thermal stability of PP with the incorporation of MAPP treated banana and Glass fiber.     

Sorption of As(V) from aqueous solution using acid modified carbon black

The sorption performance of a modified carbon black was explored with respect to arsenic removal following batch equilibrium technique. Modification was accomplished by refluxing the commercial carbon black with an acid mixture comprising HNO(3) and H(2)SO(4). Modification resulted in the substantial changes to the inherent properties like surface chemistry and morphology of the commercial carbon black to explore its potential as sorbent. The suspension pH as well as the point of zero charge (pH(pzc)) of the material was found to be highly acidic. The material showed excellent sorption performance for the removal of arsenic from a synthetic aqueous solution. It removed approximately 93% arsenic from a 50mg/L solution at equilibration time. The modified carbon black is capable of removing arsenic in a relatively broad pH range of 3-6, invariably in the acidic region. Both pseudo-first-order and second-order kinetics were applied to search for the best fitted kinetic model to the sorption results. The sorption process is best described by the pseudo-second-order kinetic. It has also been found that intra-particle diffusion is the rate-controlling step for the initial phases of the reaction. Modelling of the equilibrium data with Freundlich and Langmuir isotherms revealed that the correlation coefficient is more satisfactory with the Langmuir model although Freundlich model predicted a good sorption process. The sorption performance has been found to be strongly dependent on the solution pH with a maximum display at pH of 5.0. The temperature has a positive effect on sorption increasing the extent of removal with temperature up to the optimum temperature. The sorption process has been found to be spontaneous and endothermic in nature, and proceeds with the increase in randomness at the solid-solution interface. The spent sorbent was desorbed with various acidic and basic extracting solutions with KOH demonstrating the best result ( approximately 85% desorption).