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Ultrasonic Waves (ultrasonic + wave)
Selected AbstractsDETERMINATION OF ULTRASONIC-BASED RHEOLOGICAL PROPERTIES OF DOUGH DURING FERMENTATION,JOURNAL OF TEXTURE STUDIES, Issue 1 2004SUYONG LEE ABSTRACT An ultrasonic technique was used to study the changes of the rheological properties of dough during fermentation at 37C and compared with the extensional properties of fermented dough obtained from tensile tests carried out in a Universal Testing Maching. The velocity and attenuation of a longitudinal wave (P-wave) propagated through the dough samples were measured and analyzed to obtain the viscoelastic moduli of the dough; the storage modulus M' and the loss modulus M". These moduli include both the bulk and the shear moduli. A wavelet analysis also was used to determine the effect of frequency on the ultrasonic-based viscoelastic moduli and the effect of the fermentation process on the ultrasonic velocity dispersion. A decrease in ultrasonic velocity was observed with increasing fermentation times. Ultrasonic waves were strongly attenuated in the dough subjected to long fermentation times and fermentation had a large influence on the viscoelastic moduli of the dough. The ultrasonic velocity increased with increasing frequency, clearly showing the viscoelastic nature of the fermented dough. The analysis also showed significant ultrasonic velocity dispersion upon fermentation. Ultrasonic measurements yielded results that agreed with those obtained from conventional rheology commonly used to characterize the extensional properties of dough. Both tests clearly showed the loss of elasticity by the dough samples upon fermentation. [source] Ultrasonic welding of advanced thermoplastic composites: An investigation on energy-directing surfacesADVANCES IN POLYMER TECHNOLOGY, Issue 2 2010Irene Fernandez Villegas Abstract Ultrasonic welding is considered as one of the most promising welding techniques for continuous fiber-reinforced thermoplastic composites. Intermolecular friction within the bulk, resulting from the application of ultrasonic waves applied on the surfaces, generates the heat required for welding to take place at the interface of the joining members via the so-called "energy directors" (EDs). Energy directors consist of resin protrusions or artificially produced asperities on the composite surfaces and play an important role both in the welding process and in the quality of the resulting welds. This paper presents the results of a study on the effects of configuration of different EDs on the ultrasonic welding of carbon fiber/polyetherimide advanced thermoplastic composites in a near-field setup. Triangular EDs were molded on the surface of consolidated composite laminates with a hot platen press. Single lap-shear-welded samples were produced to investigate the influence of the orientation of the EDs with respect to the load direction, as well as the configuration of multiple EDs. The results indicate that the configuration of multiple transverse EDs was more effective in covering the overlap area, once the resin has melted, causing only a minimum fiber disruption at the welding interface. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:112,121, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20178 [source] Polymer characterization by ultrasonic wave propagationADVANCES IN POLYMER TECHNOLOGY, Issue 2 2008Francesca Lionetto Abstract The propagation of low-intensity ultrasound in polymers, acting as a high-frequency dynamic mechanical deformation, can be successfully used to monitor changes in the modulus of polymers associated with glass transition, crystallization, cross-linking, and other chemical and physical phenomena related to changes in the viscoelastic behavior, such as gelation phenomena. The velocity of sound is related to the polymer storage modulus and density, whereas the absorption of ultrasonic waves is related to the energy dissipation in the material and, therefore, to the loss modulus. Accordingly, ultrasonic measurements have been used by several authors to monitor the evolution of the viscoelastic moduli of polymers as a function of time or temperature and, recently, become a characterization technique of its own right, generally known as ultrasonic dynamic mechanical analysis (UDMA). Often the technique is used in conjunction with rheological methods as a means of providing a better insight into the viscoelastic behavior of polymer systems. As yet UDMA is underutilized primarily because of the low operating temperatures (usually below 100,C) of commercially available ultrasonic transducers, and also due to the requirement of a coupling medium to ensure an efficient energy transfer mechanism between the transducer and the test material. Despite these limitations, this paper shows that the use of ultrasonics is potentially a powerful method for the characterization of polymers, particularly as a tool for online monitoring of events occurring during polymer processing and in the manufacture of polymer matrix composites. The aim of this paper is to review the progress made in recent years, highlighting the potential and reliability of UDMA for monitoring physical transitions in polymers such as glass transition, melting, crystallization, as well as physical changes taking place during curing of thermosetting resins. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:63,73, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20124 [source] Application of ultrasonic waves in activation of microcrystalline celluloseJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Xianling Wang Abstract In this work, microcrystalline cellulose (MCC) was activated with ultrasonic waves. The influences of ultrasonic treatment on the changes of supramolecular structures and morphology structure were studied by WAXS and SEM. The accessibility of the MCC was characterized by water retention value (WRV) and specific surficial area. The influence of ultrasonic treatment on the reactivity of MCC was investigated through the reaction of MCC being oxidized into 2,3-diadehyde cellulose (DAC) by periodate sodium. The mechanism of the reactivity change of ultrasonically treated MCC was examined. The results showed that the degree of crystallinity of MCC decreased and the degree of polymerization showed little change after treatment with ultrasonic waves. The morphologial variation of the treated MCC was significant when compared with the untreated MCC, which contribute to the improvement of accessibility. The aldehyde content of DAC prepared from ultrasonically treated MCC was improved from 64.19 to 85.00%, indicating that the regioselective oxidation reactivity of MCC was significantly improved. The aldehyde content was found to first increase with time of ultrasonic treatment to a point, and then decrease as time progressed. In addition, the aldehyde content was found to increase with an increase in ultrasonic power. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Ultrasonic-activated micellar drug delivery for cancer treatmentJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2009Ghaleb A. Husseini Abstract The use of nanoparticles and ultrasound in medicine continues to evolve. Great strides have been made in the areas of producing micelles, nanoemulsions, and solid nanoparticles that can be used in drug delivery. An effective nanocarrier allows for the delivery of a high concentration of potent medications to targeted tissue while minimizing the side effect of the agent to the rest of the body. Polymeric micelles have been shown to encapsulate therapeutic agents and maintain their structural integrity at lower concentrations. Ultrasound is currently being used in drug delivery as well as diagnostics, and has many advantages that elevate its importance in drug delivery. The technique is noninvasive, thus no surgery is needed; the ultrasonic waves can be easily controlled by advanced electronic technology so that they can be focused on the desired target volume. Additionally, the physics of ultrasound are widely used and well understood; thus ultrasonic application can be tailored towards a particular drug delivery system. In this article, we review the recent progress made in research that utilizes both polymeric micelles and ultrasonic power in drug delivery. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:795,811, 2009 [source] Characteristics of polystyrene/polyethylene/clay nanocomposites prepared by ultrasound-assisted mixing processPOLYMER ENGINEERING & SCIENCE, Issue 7 2004J. G. Ryu In this study, polymer-clay nanocomposites of various concentrations were prepared by ultrasonically assisted polymerization and melt-mixing processes. A sonication process using power ultrasonic waves was employed to enhance nano-scale dispersion during melt-mixing of polymer blends and organically modified clay. We expected enhanced breakup of layered silicate bundles and further reduction in the size of the dispersed phase, with better homogeneity compared to the different immiscible blend pairs. X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to characterize the structures of the nanocomposites. The rheological behaviors of the obtained nanocomposites were measured with parallel plate rheometry. It was found that the ultrasound-assisted process successfully generated exfoliated nanocomposites and promoted in-situ compatibilization of the matrix comprising an immiscible pair of polymers in a blend. The resulting nanocomposite exhibited superior thermal stability and elastic modulus compared to the base polymer. Polym. Eng. Sci. 44:1198,1204, 2004. © 2004 Society of Plastics Engineers. [source] Functionalization of high density polyethylene with maleic anhydride in the melt state through ultrasonic initiationPOLYMER ENGINEERING & SCIENCE, Issue 4 2003Yuncan Zhang Grafting of maleic anhydride (MAH) onto high density polyethylene (HDPE) performed in the melt state through ultrasonic initiation by a laboratory-scale ultrasonic extrusion reactor was studied in this paper. The effect of sonic intesity on the amount of grafted MAH, viscosity-average molecular weight and melt flow index of the grafted product was investigated. The results show that the ultrasonic waves can obviously decrease the molecular weight of the grafted product and cause the increase of the amount of grated MAH, implying that the grafting reaction consists of the chain scission and the grafting reaction of the produced macroradicals with MAH. The percentage of grafting of the product amounts to 0.6%; its melt-flow index is between 0.5 and 2.0 g/10 min, depending upon ultrasonic intensity, MAH content and grafting temperature. Compared with the method of peroxide initiation, in this method the crosslinking reaction can be prevented easily through the allocation of ultrasonic intensity. The mechanical properties of the improved HDPE/GF composite produced by ultrasonic initiatives are higher than in those produced by peroxide initiatives. [source] | |||||||||||||