Application of signal processing techniques to ultrasonic testing of plates by S0 Lamb wave mode

In recent years, much attention has been paid to the use of Lamb waves for structural health monitoring. This choice is prompted by the high speed of Lamb wave inspection, although their dispersive nature can complicate the interpretation of results, especially when dealing with closely-spaced reflectors. In this paper, the objective is to improve the time resolution and signal-to-noise ratio of signals obtained from inspection of plates by the S₀ Lamb mode. The signal processing scheme used is based on deconvolution of the measured signal by Wiener filtering, followed by autoregressive spectral extrapolation. The deconvolution technique is applied to signals obtained from finite element models and also to experimentally measured signals; both sets of data are based on plates with various types of notch discontinuities. Using this technique, the separation distance between adjacent notches was estimated with high accuracy in both simulated and experimental ultrasonic signals.     

Radiation‐induced graft copolymerization of MMA monomer onto UHMWPE: Adhesion improvement

Graft copolymerization of methyl methacrylate monomer onto ultra high molecular weight polyethylene (UHMWPE) and acid‐etched UHMWPE was conducted using preirradiation method in air in the presence of a Mohr salt and sulfuric acid to improve adhesion to the bone cement. The grafted samples were characterized by Fourier transform infrared (FTIR) spectroscopy, gravimetric method, goniometry, and interfacial bonding strength measurements. The FTIR results showed the presence of ether, carbonyl, and hydroxyl groups for grafted films. The gravimetric results showed that the chromic acid etching and graft copolymerization had a synergetic effect so, the irradiated, then chromic acid etched at room temperature and grafted sample (Rad etch25) had the highest grafting degree. The interfacial bonding strength between UHMWPE and poly methyl methacrylate bone cement was considerably improved by graft copolymerization and chromic acid etching. The surface morphology was studied by scanning electron microscopy. The substitution of polar groups into the backbone of UHMWPE by chromic acid etching and graft copolymerization changed its contact angles with water and methylene iodide and increased its surface energy, as evidenced by contact angle measurements. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Resource sharing among real-time components under multiprocessor clustered scheduling

In this paper we propose a general synchronization protocol for resource sharing among independently-developed real-time applications (components) on multi-core platforms. This protocol is a generalization of a previously proposed synchronization protocol (MSOS). In our proposed protocol, each component is statically allocated on a dedicated subset of processors (called cluster). A component has its own internal scheduler by which its tasks are scheduled. In this paper we focus on multiprocessor global fixed-priority preemptive scheduling algorithms to be used to schedule the tasks inside each component. Sharing the local resources is handled by the Priority Inheritance Protocol (PIP). For sharing the global resources (inter-component resource sharing) we have studied usage of FIFO and Round-Robin queues for access the resources across the components and usage of FIFO and prioritized queues inside the components. We have derived schedulability analysis for the different queue handling alternatives and compared their performance by using experimental evaluations. Finally, we have shown that the integration phase can be formulated in the form of a nonlinear integer programming problem where solution techniques in this domain can be used to minimize the total number of processors required to guarantee the schedulability of all components. As a proof of concept we have only provided the formulation for FIFO queues.     

Cure kinetics of a polymer‐based composite friction material

In the present article, cure kinetics of a commercially available composite friction material used in railroad vehicles is investigated using the rheometer measurements. Effect of ingredients of friction material compound, including rubber matrix, phenolic resin, and fillers, on overall cure kinetics of friction compound is also investigated by comparing the cure kinetics of friction material and rubber matrix compound. A phenomenological model and an Arrhenius‐type equation is developed for cure kinetics and induction time of both friction material and rubber matrix. The parameters of the models are extracted from experimental data, using the rheometer at different temperatures and utilizing appropriate optimization method. The good agreement between experimental measurement and models prediction indicates the good performance of the models developed in this study. The results demonstrate that phenolic resin and fillers have dominant effects on the overall cure behavior of the friction material compound. A comparison between the present results and other published data based on the differential scanning calorimetry (DSC) shows a reasonable agreement as well. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 100: 9–17, 2006     

A focus on the features of polyaniline nanofibres prepared via developing the single crystals of their block copolymers with poly(ethylene glycol)

Poly(ethylene glycol) (PEG)–polyaniline (PANI) diblock and triblock copolymers were synthesized via copolymerization of aniline with amine-terminated PEG by interfacial polymerization using sulphuric acid as dopant and ammonium peroxydisulfate (APS) as well as potassium hydrogen diiodate (PHD) as oxidants. The PHD-based synthesized PANI nanorods possessed longer lengths, narrower diameter distribution and higher conductivity. The electroactivity of synthesized copolymers was characterized using ultraviolet–visible (UV–Vis) spectrometry, cyclic voltammetry (CV) and resistivity measurement. Even in the presence of dielectric PEG blocks, the synthesized block copolymers had a conductivity around 3 S \(\hbox {cm}^{-1}\). In a further step, the solution-grown single crystals were prepared to investigate the general features of grafted PANI nanorods using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Based on AFM and SAXS analyses, the bimodal gel permeation chromatography (GPC) traces obtained from the block copolymers were originated from the diameter distribution of nanofibres, not from the dispersity of their lengths and molecular weights.     

Multiple Protective Roles of Nanoliposome-Incorporated Baicalein against Alpha-Synuclein Aggregates

Nanoparticles are useful for increasing drug stability, solubility, and availability. The small molecule baicalein inhibits fibrillation, and detoxifies aggregates of α-synuclein (αSN) associated with Parkinson's disease (PD), but it suffers from instability, low solubility and consequent low availability. Here it is demonstrated that incorporation of baicalein into zwitterionic nanoliposomes (NLP-Ba) addresses these problems. NLP-Ba inhibits αSN fibril initiation, elongation, secondary nucleation, and also depolymerizes mature fibrils more effectively than free baicalein and prevents soluble αSN aggregates from seeding new fibrils. Importantly, NLP-Ba perturbs oligomers’ capacity to permeabilize the membrane. The interaction between NLP-Ba and αSN is confirmed by different biophysical techniques. This nanosystem crosses the blood-brain barrier in vitro and is effective against rotenone neurotoxicity in vivo. The effect of NLP-Ba on αSN fibrillation/cytotoxicity is attributed to a combination of free baicalein and empty NLPs. The results indicate a neuroprotective role for NLP-Ba in decreasing αSN pathogenicity in PD and highlight the use of nanoliposomes to mobilize poorly soluble hydrophobic drugs.     

Finite element simulation of the punchless piercing process with Lemaitre damage model

The punchless piercing is a process that uses highly pressurized fluid instead of the conventional punch to make holes into the sheet metal. This process has many advantages over the conventional method for piercing various shaped holes into very thin strips of metal, composite, etc. An important cost advantage comes from not having to use a punch. Another important advantage comes from the top quality of pierced holes produced by punchless piercing, as no secondary finishing process will be needed for removing burrs typically found in conventional cutting processes.The ABAQUS/Explicit FEM code coupled with Lemaitre damage model has been used to more precisely characterize the punchless piercing process of a copper sheet. The formulation adopted for this purpose uses an established and efficient stress integration algorithm and development of a user material subroutine (VUMAT).For verification, the computed results have been compared with those of the experimental results in the literature and shown to be in good agreement with each other.The results obtained from this work are expected to be of significant interest to automotive and aerospace industries interested in using the punchless piercing process.     

Mixed extracts of green tea and orange peel encapsulated and impregnated on black tea bag paper to be used as a functional drink

Herbal drinks have been considered among the known groups of functional drinks. The aim of this study was to encapsulate green tea and orange peel extracts using double emulsion followed by complex coacervation to be used in the preparation of a functional drink. All of the microcapsule formulations were spherically prepared without cracks in the walls and their sizes increased by decreasing the ratio of the core to the wall. Microcapsules under the best conditions of this study were used to coat the paper of a bag containing black tea. The results showed that theaflavin and its ratio to thearubigin as the quality indices for black tea have increased in comparison with the sample without encapsulation. This study resulted in the production of encapsulated mixed extracts of green tea and orange peel that can be used later for the preparation of a functional drink.     

Combustion synthesis of titanium aluminides via co-reduction of oxides

In this study, Ti-50Al and Ti-48Al-2Cr powders were produced via reduction of TiO₂/Al₂O₃ and TiO₂/Al₂O₃/Cr₂O₃ mixtures with Ca. Upon addition of KClO₄ to the above mixtures, a combustion synthesis process was initiated in the systems. In the presence of KClO₄, the reduction temperature decreased from 1000 to 550°C.