The Effect of Electromagnetic Stirrer on the Size and Morphology of Intermetallic Particles in Al-Si Metal Matrix Composite

Silicon - The electromagnetic stirrer method was developed to overcome the problems caused by the presence of a mechanical stirrer in the slurry; this method is nowadays considered to be the most...     

Development of Antibacterial Carboxymethyl Cellulose‐Based Nanobiocomposite Films Containing Various Metallic Nanoparticles for Food Packaging Applications

In this study, silver (Ag), zinc oxide (ZnO), and copper oxide (CuO) metallic nanoparticles were used in preparation of carboxymethyl cellulose (CMC) nanobiocomposite films. Scanning electron microscopy (SEM), X‐ray diffraction (EDXA), water vapor permeability (WVP), ultraviolet and visible light (UV–Vis) spectroscopy, and mechanical and microbial tests were used to determine the characteristics of the obtained active films. SEM results showed that the CMC nanobiocomposite films had roughness deflection levels and the EDXA test confirmed the presence of Ag, ZnO, and Cuo nanoparticles in the biopolymer tissue. UV–Vis spectroscopy confirmed that with addition of metallic nanoparticles to the pure CMC film, absorption rate increased and WVP decreased. In the mechanical tests, addition of nanoparticles also increased the tensile strength of the films, and the nanobiocomposite films exhibited higher resistance compared to the pure CMC film. Films incorporating metallic nanoparticles showed antibacterial properties against Escherichia coli and Staphylococcus aureus growth. Thus, nanobiocomposite films can be used as active packaging films and could increase the shelf‐life of the food.     

A fully integrated SOC for 802.11b in 0.18-/spl mu/m CMOS

A fully integrated system-on-a-chip (SOC) intended for use in 802.11b applications is built in 0.18-/spl mu/m CMOS. All of the radio building blocks including the power amplifier (PA), the phase-locked loop (PLL) filter, and the antenna switch, as well as the complete baseband physical layer and the medium access control (MAC) sections, have been integrated into a single chip. The radio tuned to 2.4 GHz dissipates 165 mW in the receive mode and 360 mW in the transmit mode from a 1.8-V supply. The receiver achieves a typical noise figure of 6 dB and -88-dBm sensitivity at 11 Mb/s rate. The transmitter delivers a nominal output power of 13 dBm at the antenna. The transmitter 1-dB compression point is 18 dBm and has over 20 dB of gain range.     

Hedonic and sensory characteristics of odors conditioned by pairing with tastants in humans.

Animals readily acquire positive odor-taste hedonic associations, but evidence for this in humans remains weak and was explored further. Retronasal pairing of odors with sucrose or salty stimuli (Experiment 1) increased the rated sweetness of sucrose-paired odors without altering liking, although changes in odor pleasantness correlated with sucrose liking. Experience of odors with sucrose or quinine by sweet likers (Experiment 2) found increased pleasantness and sweetness for sucrose-paired odors, whereas quinine-paired odors became less liked and more bitter. Odor-sucrose pairings in sweet likers and dislikers (Experiment 3) found increased sweetness in both groups but increased odor liking only in likers. These data suggest that evaluative and sensory learning are dissociable and that evaluative changes are sensitive to individual differences in sweet liking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Synthesis and physicochemical characterization of nanostructured Pd/ceria‐clinoptilolite catalyst used for p‐xylene abatement from waste gas streams at low temperature

BACKGROUND: The effect of Pd loading, xylene concentration and GHSV on xylene oxidation was tested over Pd/CeO₂(30%)‐clinoptilolite nanocatalysts at low temperatures. The catalysts were prepared by acid treatment of clinoptilolite, followed by the incipient wetness method of synthesized ceria and modified clinoptilolite in PdCl₂ solution. The synthesized nanocatalysts were characterized by XRD, FESEM, EDAX, TEM, BET, FTIR and TG‐DTG analysis. RESULTS: The XRD patterns confirmed the formation of crystalline ceria with an average crystallite size of 11.8 nm. FESEM images showed nanostructures in cavities of natural zeolite, brought about by ceria incorporation and acid activation. TEM analysis showed high dispersion of Pd with a size distribution between 6.6 and 36.7 nm. The quantitative analysis showed that the specific surface area of Pd(1%)/CeO₂(30%)‐clinoptilolite was 77 m² g^?1. The results showed that Pd(1%)/CeO₂(30%)‐clinoptilolite is the most appropriate catalyst, with the conversion more than 90% at 275 °C. CONCLUSIONS: Experimental results established effective performance and durability for the catalysts. As a result, clinoptilolite modification and ceria incorporation significantly altered the samples' morphology at nanoscale, improving the structure of composites and distribution of noble metals. A reaction path was suggested based on the adsorption‐migration of species to reveal the mechanism of p‐xylene oxidation over nanocatalysts. © 2012 Society of Chemical Industry     

Comparison studies between two wavelet based crack detection methods of a beam subjected to a moving load

In this paper, the performances of two wavelet based damage detection approaches to find the location and the size of a crack in a beam subjected to a moving load are compared. In the first approach, designated as ‘Fixed Sensor Approach’, a sensor is assumed to be located at the mid span of the beam. Thus in this approach, Continuous Wavelet Transform (CWT) coefficient of the time varying deflection attributed to the beam at mid span is used. In the second approach, the sensor is attached to the moving load and CWT coefficient of moving sensor is analyzed. The crack is modeled as a rotational spring which its stiffness is obtained from fracture mechanics, and modal expansion theory is used to find the deflection of cracked beam. The two approaches are compared for several cases of moving load speeds, crack sizes and crack locations, and also several scales of CWT. In the both approaches, wavelet Gaussian 4 is employed. It is shown that, the highest magnitude of CWT coefficient occurs at the exact location of crack and its value depends on damage size. As a result, it can be considered as a damage index. It is found that the moving sensor approach is more effective than the fixed sensor. Thereafter, the effect of beam parameters such as length, width, modulus of elasticity and density and also, crack size and location on the damage index were investigated based on the moving sensor approach. The obtained damage index has two significant features: (a) it has an explicit expression and shows the effects of all parameters clearly, (b) it is not dependent upon the response of the undamaged beam. From the obtained explicit relation for damage index, it is illustrated that the damage index does not depend on material properties of a homogeneous beam. Moreover in a rectangular cross section beam, the damage index is independent of width and has a linear relationship with the height to length ratio. It is shown that using this damage index, small cracks with a depth more than 10% of the beam height can be detected.     

Polymer Nanocomposites Containing N-Trimellitylimido-L-phenylalanine Dicarboxylic Acid Moieties Reinforced with α-Al2O3 Nanoparticles Modified with Citric Acid: Synthesis and Characterization

In field of nanotechnology, polymer based nanocomposites (NCs) with inorganic nanoparticles (NPs) have become a noticeable area of recent researches. In this work, citric acid (CA) was used as a biocompatible “modifier” for the alumina (α-Al₂O₃) NPs to prevent their agglomeration and create effective interaction with polymer matrix. In addition, chiral poly(amide-imide) (PAI) was synthesized by a direct polycondensation of N-trimellitylimido-L-phenylalanine dicarboxylic acid and 1,5-naphthalenediamine in ionic liquid as green solvent. Then modified (α-Al₂O₃-CA) NPs were incorporated into the obtained PAI through ultrasonic process for the preparation of PAI/α-Al₂O₃-CA NCs. Finally, the PAI/α-Al₂O₃-CA NCs were characterized by different methods.     

Hydrophilic drug release from bioerodible polyanhydride microspheres

The present investigation was carried out to develop bioerodible drug delivery systems. Copolymers of fumaric anhydride and isophthalic anhydride were synthesized by melt polycondensation. To synthesize a copolymer with known composition, soluble in common organic solvents, a prepolymer of each monomer was first prepared. Copolymers were synthesized by mixing two prepolymers followed by melt polycondensation of the resulting mixture with a specific ratio of each prepolymer. Microspheres loaded with theophylline and diltiazem hydrochloride (DHC) were obtained using the solvent removal method in an oil‐in ‐oil (O/O) emulsion system. The size of the drug loaded microspheres was less than 75 μm, which is suitable for subcutaneous or intramuscular injection. DHC was incorporated in a polymeric carrier better than theophylline because of its solubility in chloroform and dichloromethane. In vitro release of two drugs in the phosphate buffer solution indicated that the release profile of DHC was closer to a zero‐order kinetic profile compared with theophylline. Finally, drug release data was compared with three semiempirical models. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1457–1464, 2002     

Non-thermal plasma assisted synthesis and physicochemical characterizations of Co and Cu doped Ni/Al2O3 nanocatalysts used for dry reforming of methane

Ni/Al₂O₃ nanocatalysts doped with Co and Cu were prepared by co-impregnation and modified by non-thermal plasma. The nanocatalysts were characterized by XRD, FESEM, TEM, EDX dot-mapping, BET, FTIR, TGA-DTG, and XPS analysis. According to XRD and XPS results, good interaction between active phase and support can be observed in both Ni–Co/Al₂O₃ and Ni–Cu/Al₂O₃ nanocatalysts. A uniform morphology, high surface area, and well dispersed particles of active sites in Ni–Co/Al₂O₃ nanocatalyst were observed that shows the effect of cobalt in controlling Ni ensemble size. In contrast Ni–Cu/Al₂O₃ nanocatalyst had no homogenous dispersion of active phase due to sintering of copper particles. The activity measurements illustrated better Ni–Co/Al₂O₃ nanocatalyst activity in comparison to Ni/Al₂O₃ and Ni–Cu/Al₂O₃ in terms of CH₄ and CO₂ conversion. H₂ and CO yield were higher for Ni–Co/Al₂O₃ and higher H₂/Co ratio was obtained as well. Whereas Ni/Al₂O₃ and Ni–Co/Al₂O₃ did not experience deactivation, Ni–Cu/Al₂O₃ suffered from activity loss by ca. 22% and 16% for CH₄ and CO₂ conversion, respectively. Sintering most likely happened in Ni–Cu/Al₂O₃ nanocatalyst due to high temperature of calcination while cobalt by controlling the size of Ni particles, alternated the size of active sites to a size range in which carbon formation was suppressed. Ni/Al ratio from XPS analysis which signifies Ni dispersion on alumina support was 5.15, 9.16, and 6.35 for Ni/Al₂O₃, Ni–Co/Al₂O₃, and Ni–Cu/Al₂O₃ nanocatalysts respectively. The highest ratio of Ni/Al was for Ni–Co/Al₂O₃ nanocatalyst that shows the best coverage of support by Ni active phase in this nanocatalyst.