Ultrasonic material property determinations

The use and potential offered by ultrasonic velocity and attenuation measurements to determine and/or monitor material properties is explored. The basis for such unique measurements along with examples of materials from a variety of industries are presented

Effects of Microstructure on the Speed and Attenuation of Elastic Waves: Formal Theory and Simple Approximations

The sensitivity of the propagation of an elastic wave to changes in the microstructural details of a material is well known.1 In particular, numerous experiments have shown that the attenuation of the wave is sensitive to the inclusions, voids, cracks, grain boundaries, twin boundaries, interphase boundaries, magnetic domain walls, dislocations, substitutional impurities of a material. For attenuation studies in metals, ceramics and polycrystals, three formulas, each for different wavelength regimes, are generally used in the quantitative interpretation of experimental results.1–3 If λ is the wavelength of the elastic wave and is the average grain diameter, then in the Rayleigh regime (λ≫D), α = A13λ4, in the stochastic regime (λ≃D), α = A2λ2, and in the diffusive regime (λ≪D), α = A3/-1. By fitting the data to these formulas, one tries to infer .</p

Antibacterial and antioxidant effects of five spice and herb extracts as natural preservatives of raw pork

BACKGROUND: The aim of this study was to find natural spice and herb extracts with antibacterial and antioxidant capacities that could be potentially used as natural preservatives in raw pork. RESULTS: The inhibitory effects of cinnamon stick, oregano, clove, pomegranate peel and grape seed extracts on Listeria monocytogenes, Staphylococcus aureus and Salmonella enterica were evaluated in raw pork at room temperature (~20°C). The influences of these extracts on lipid oxidation in the meat were also investigated. The pH, colour parameters and TBARS (thiobarbituric acid-reactive substances) values were tested periodically. The results showed that all five natural extracts, especially clove, were effective against the bacteria. During storage the colour parameters of the extract-treated pork samples changed slightly, in comparison with significant changes in the control. Treatments with these extracts increased the stability of raw pork against lipid oxidation. Clove was the most effective for retarding lipid oxidation and presented the highest antioxidant activity in raw pork. CONCLUSION: This study suggests that the tested extracts, especially clove, have potential as natural preservatives to reduce numbers of pathogenic bacteria, colour degradation and lipid oxidation in raw pork. © 2009 Society of Chemical Industry.link_to_subscribed_fulltex

A fast and noise-tolerant method for positioning centers of spiraling and circulating vector fields

Identification of centers of circulating and spiraling vector fields are important in many applications. Tropical cyclone tracking, rotating object identification, analysis of motion video and movement of fluids are but some examples. In this paper, we introduce a fast and noise tolerant method for finding centers of circulating and spiraling vector field pattern. The method can be implemented using integer operations only. It is 1.4 to 4.5 times faster than traditional methods, and the speedup can be further boosted up to 96.6 by the incorporation of search algorithms. We show the soundness of the algorithm using experiments on synthetic vector fields and demonstrate its practicality using application examples in the field of multimedia and weather forecasting. © Springer-Verlag Berlin Heidelberg 2007.link_to_subscribed_fulltex

Early tensile bond strengths of several enamel and dentin bonding systems.

Tensile bond strength tests are commonly used for the evaluation of adhesive dental materials. The majority of these tests are carried out after 24 h of storage in water. However, determination of the early tensile bond strength could be more important, especially in relation to gap formation between the cavity surface and the restorative material. This study investigated the tensile bond strengths of five enamel/dentin bonding systems and two experimental dentin bonding systems. Tensile bond strengths were obtained at one min, ten min, and 24 h after the resin composite was cured. Bond strengths at the early stages were always somewhat less than the 24-hour test results. For the enamel/dentin bonding systems, a significant difference was found between the enamel and dentin bond strengths at all time periods, except with Superbond D-liner and Liner Bond. The experimental group with glyceryl methacrylate as the primer produced a good 24-hour result (14.3 MPa), but the early bond strengths were no different from those in the non-primer-treated groups. It was concluded that this material may actually retard the polymerization of the bonding resin. Previous workers have suggested that a tensile bond strength in the order of 20 MPa is necessary for gap-free restorations to be obtained. Should this be the case, then all of the materials tested, from the aspect of early bond strength, lack the strength for prevention of gap formation, although Superbond D-liner and Liner Bond approached this hypothetical figure. These systems, Superbond D-liner and Liner Bond, also exhibit small differences between the enamel and dentin tensile bond strengths.link_to_subscribed_fulltex

Inhibition of enamel demineralization by glass ionomer cements

Composite materials find a number of applications nowadays in various engineering domains. The heterogeneous and anisotropic properties of the composite materials call for specific non-destructive evaluation methods and ultrasonic ones appear very suitable [ 1–3 ]