Papers by Keyword: Ultrasound

Abstract: Ultrasonic melt processing of light alloys has enjoyed a revival in the last 15 years. Although the scientific foundation and first examples of industrial application date back to the 1950s–1970s, the technological application of ultrasound in melt and solidification processing has not been fully accomplished. In recent years, the availability of advanced reliable equipment, new basic knowledge gained through modeling and dedicated experiments, and the industrial demand for clean, environment friendly technology sparked an interest in this technology and ensuing research. This paper reports on the currently achieved level of ultrasound application in light metal processing, i.e. degassing and grain refinement of light alloys and metal-matrix composite material manufacturing, and discusses challenges that still prevent large-scale implementation, both from fundamental and applied points of view. The main mechanisms underlying the effects of ultrasonic processing such as cavitation in melts, nucleation and fragmentation of solid phases, forced convection induced by cavitation zone and acoustic streaming, and mixing and distribution of solid inclusions are explained. The paper is illustrated by examples of research done under the supervision of the author.

Abstract: Chitosan is a natural biopolymer derived by deacetylation of chitin from the two main sources of crustaceans, shrimp and crabs. Chitosan, which is soluble in acidic solutions, is used in many applications (biomedical/pharmaceutical, water engineering, food, cosmetics). There have been many researchers who have developed a process of deacetylation of chitin from shrimp shells waste by thermochemical or enzymatic methods. However, application of ultrasonic irradiation for chitin deacetylation has received little attention. In this work, the deacetylation of chitin with concentrated sodium hydroxide was performed using ultrasound irradiation (80 W, 42 kHz). The reaction time and degree of deacetylation were compared with conventional process. Results showed that under the same condition, the degree of deacetylation was similar. However, the use of ultrasonic irradiation decreased the reaction time, showing that this method may be a promising alternative method to the conventional method.

Abstract: The searching of environmentally friendly materials that have potential to replacement mineral oil is currently being considered a top priority research topic in the fuel and energy sector. This paper presents the influence of ultrasound-assisted transesterification of jatropha oil to isopropyl ester and the optimum condition. The transesterification was performed by using isopropyl alcohol as solvent in the presence of ultrasound operating frequency constant at 35 kHz. The isopropyl ester content of product was 97.80 % under the the reaction temperature of 60 °C, isopropyl alcohol to jatropha oil molar ratio of 8 : 1 within the reaction time of 15 minutes.

Abstract: The injection of ozone into the air mixture for a barbotage of electrolyte at anodization of an aluminum alloy D16 in 5 % aqueous solution of sulfuric acid increases final thickness of oxide coating by 45 - 53 %, and simultaneous ultrasonic affecting and bubbling of electrolyte by the ozone-aerial mixture - only on 30 - 35 %, however in the latter case microhardness and wear resistance of coating increase. The additional applying of vibration decreases thickness, microhardness and wear resistance of an oxide layer.

Abstract: We focused on the effects of ultrasound and Fenton reagent in ultrasonic coupling Fenton oxidation (U+F) pre-treatment processes on the disintegration of wastewater treatment plant sludge. The results demonstrated that U+F treatment could significantly increase SCOD, TOC, total N, proteins, total P and PO₄^3- concentrations in sludge supernatant. This method was more effective than ultrasonic (U) or Fenton oxidation (F) treatment alone. U+F treatment increased the SCOD by 2.1-and 1.4-fold compared with U and F alone, respectively. U+F treatment increased the total N and P by 1.7-and 2.2-fold, respectively, compared with F alone. This demonstrated that U+F treatment induces disintegration of sludge and release of organic carbon, nitrogen and phosphorus better.

Abstract: This paper presents some non-destructive evaluation methods of materials and structures, such as: pulse method, resonance method, direct measurement of the propagation velocity, pulse-echo method, impact-echo method, acoustic emission evaluation, interferometry and infrared thermography. The methods are suitable for non-metallic materials, with rugged and non-homogeneous structure, high attenuation coefficients for ultrasound propagation waves into materials, composites multilayer structures, etc. Some relevant measurement parameters are presented too.

Abstract: Fused deposition modeling (FDM) is an additive manufacturing (AM) process that has been used in various manufacturing fields. However, the drawback of FDM is poor surface finish of parts produced, leading to surface roughness and requires hand finishing. In this study, ultrasonic technology will be integrated into a desktop FDM system.Ultrasound has been applied in various conventional machining processes and shows good machined surface finish. However, very little research regarding the application of ultrasound to AM has been carried out. Our previous research found that the extrusion nozzle of the FDM system could withstand the high vibration transmitted at 40 kHz of frequency from an ultrasonic transducer. The aim of this paper is to discuss three novel setups of using ultrasound devices attached to a desktop FDM system to study its feasibility to improve the surface finish of parts produced. A comparative study was made and it was found that the second setup (Concept 2) was most suitable due to its safety and reliability aspects.

Abstract: The paper analyzes the forms of different probe pole distribution automatic detection equipment inspection speed setting principle; Combined the common failure modes of several kinds of probe or channel, in order to ensure the detection achieve 100% scanning coverage and discusses the detection speed setting problem.

Abstract: Uniform Microbubbles (MBs) were routinely used as ultrasound contrast agents, but the MBs served for drug carrier showed well-marked advantage. In this study, we prepared a novel docetaxel–loaded microbubbles by carboxymethyl chitosan with W/O/W emulsion technique. Then, the surface morphology was characterized by scanning electron microscope (SEM). Ultrasound-triggered drug release experiments were performed with adjustable intensity and time. In the antitumor experiment in vitro, Ultrasound-assisted drug release from MBs exhibited good treatment of tumor. The results proved the combination of ultrasound and drug-loaded carboxymethyl chitosan microbubbles could be used as a potential strategy for anti-tumor therapy.

Abstract: The objective of this study is to realize a non-destructive characterization of cementitious materials using ultrasonic method. The motivation of our work is to show that the ultrasound can be applied not only in medical imaging but also in the assessment of construction materials, which is not widely known in this domain. In order to solve the problem, the ultrasonic velocity measurement was performed on the samples before and after carbonation of a standardized mortar at different periods. The results offer the possibility to determine the mechanical properties such as Young modulus E, shear modulus G and Poisson's ratio. This is an advantage for in-situ structures in comparison with destructive methods that require destroying the samples. The main contributions of this study are: 1) Ultrasonic occultation of cement materials is a reliable method with a small margin of error; 2) The values ​​of mechanical properties found by ultrasonic method are consistent with theoretical values ​​found in the literature; 3) The evolution of these mechanical properties is consistent with the densification of the microstructure during carbonation due to the formation of CaCO₃.