空泡流非稳态现象的流动控制

处于跨临界阶段的空泡流必然导致强烈的周期性冲击和振动,空泡流的激振来源于空泡云的周期性大规模脱落,空泡云的形成和发展与流动的边界层效应有着强烈的相关性,且空泡末端的局部流动直接影响空泡流的整体稳定性,本试验在NACA16012水翼表面粘附一条展向1mm厚10mm宽的挡流条,尝试以干扰水翼上表面局部流动的方法来影响整个空泡流的形态及其流动稳定性,最终在一定的空泡数范围内抑制了空泡流激振现象,并从试验研究的角度探索了空泡云脱落的机理。     

高强聚焦超声(HIFU)无创外科─21世纪治疗肿瘤的新技术

本文从简要回顾超声治疗的发展历史开始,重要介绍了90年代初在国际上兴起的HIFU无创外科技术及我国在该领域中的成就。文章继而对HIFU“切除”肿瘤的机理,治疗质量及其发展前景做了讨论。     

Degradation of Rhodamine B in aqueous solution by laser cavitation

A novel method of laser cavitation (LC) was proposed for degrading organic dye wastewater. Rhodamine B (RhB) aqueous solution was employed as the simulated organic dye wastewater, and a LC system was designed to conduct the experiments of degrading RhB. The effects of laser energy, initial concentration and cavitation time on the degradation were investigated. Moreover, the degradation kinetics, degradation mechanism and energy efficiency were analyzed. The experimental results indicate that RhB aqueous solution can be degraded effectively by LC and the degradation follows the pseudo-first-order kinetics. The extent of degradation increases by 27.6% with the rise of laser energy (50–100 mJ) while it decreases by 7.8% with increasing the initial concentration from (20–40 mg/L), but RhB can not be degraded when exceeding 100 mg/L. The degradation extent of RhB at 100 mJ and 20 mg/L for 3 h is 81.11%, and the RhB solution is almost completely degraded at 150 mJ (98.4%). The degradation velocity of RhB rises firstly and then decreases as the cavitation time increases. The degradation of RhB by LC can be attributed to the N-de-ethylation and chromophore cleavage caused by oxidation of hydroxyl (OH) radical and thermal decomposition. LC has a higher energy efficiency compared with other methods and is more energy efficient at lower laser energy.     

Liposome destruction by hydrodynamic cavitation in comparison to chemical,physical and mechanical treatments

Liposomes are widely applied in research, diagnostics, medicine and in industry. In this study we show for the first time the effect of hydrodynamic cavitation on liposome stability and compare it to the effect of well described chemical, physical and mechanical treatments. Fluorescein loaded giant 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipid vesicles were treated with hydrodynamic cavitation as promising method in inactivation of biological samples. Hydrodynamic treatment was compared to various chemical, physical and mechanical stressors such as ionic strength and osmolarity agents (glucose, Na⁺, Ca²⁺, and Fe³⁺), free radicals, shear stresses (pipetting, vortex mixing, rotational shear stress), high pressure, electroporation, centrifugation, surface active agents (Triton X-100, ethanol), microwave irradiation, heating, freezing-thawing, ultrasound (ultrasonic bath, sonotrode). The fluorescence intensity of individual fluorescein loaded lipid vesicles was measured with confocal laser microscopy. The distribution of lipid vesicle size, vesicle fluorescence intensity, and the number of fluorescein loaded vesicles was determined before and after treatment with different stressors. The different environmental stressors were ranked in order of their relative effect on liposome fluorescein release. Of all tested chemical, physical and mechanical treatments for stability of lipid vesicles, the most detrimental effect on vesicles stability had hydrodynamic cavitation, vortex mixing with glass beads and ultrasound. Here we showed, for the first time that hydrodynamic cavitation was among the most effective physico-chemical treatments in destroying lipid vesicles. This work provides a benchmark for lipid vesicle robustness to a variety of different physico-chemical and mechanical parameters important in lipid vesicle preparation and application.     

The role of bulk micro-nanobubbles in reagent desorption and potential implication in flotation separation of highly hydrophobized minerals

Micro-nanobubbles (MNBs) generated during hydrodynamic cavitation (HC) have been extensively studied in mineral processing field in the past two decades. Many researchers have claimed that MNBs can effectively promote the collection of fine particles in flotation, while studies on MNBs assisted mineral separation are rare. In this study, the role of bulk MNBs in desorbing flotation reagent was investigated, with the aim of illustrating the potential effects of MNBs on minerals separation. The results showed that bulk MNBs could efficiently remove the sodium oleate (NaOl) from diaspore surfaces, reducing the residual concentration of NaOl on solids, which was more significant when the amount of NaOl pre-adsorbed was relatively small. Furthermore, lower residual concentration of NaOl on solids caused by MNBs cleaning made the particles less hydrophobic and flocs more friable. Given that gangue entrapment in flocs was one of the main limits for high-selective flotation, the roles of MNBs in enhancing reagent desorption and associated flocs breakup and reorganization probably contribute to higher separation efficiency of different minerals, which was confirmed by the flotation results of diaspore/kaolinite mixture.     

Influence of co-existing cations and anions on removal of direct red 89 dye from synthetic wastewater by hydrodynamic cavitation process: An empirical modeling

In the present study the evaluation of Direct Red 89 (DR89) dye removal from synthetic wastewater by a lab-scale hydrodynamic cavitation (HC) process has been investigated under different operational conditions; the influence of co-existing cations and anions was applied using synthetic wastewater to assess whether the DR89 removal was enhanced. To study the effect of operational parameters, an empirical approach was adopted for the modeling of the HC process. The results showed that the DR89 degradation rate was strongly influenced by solution pH, reaction time and initial DR89 concentration. The removal efficiencies of DR89 were enhanced remarkably with the reaction time increment. When the initial concentration of DR89 increased from 30 to 90 mg/L, the DR89 removal efficiency decreased from 36.3 ± 3.8% to 17.5 ± 2.5%. In addition, the highest DR89 removal efficiency (75.4 ± 3.4%) was observed at a solution pH of 3. At a solution pH of 8, the DR89 removal efficiency was 18.4 ± 1.1%. An initial DR89 concentration of 80 mg/L was 75.4 ± 5.1% degraded after 130 min at a solution pH of 3. The results indicated that a synergistic effect occurred due to the added ions except for HCO₃^–. The removal of DR89 by the HC process was extremely enhanced with NO₃‾ ions with synergetic index higher than 2.5. Kinetic studies revealed that the decolorization of DR89 by HC followed a first order kinetic mechanism. The comparison between the predicted results of the empirical model and experimental data was also conducted. The empirical model described the DR89 removal efficiency under different conditions (R²: 0.93) and the results showed the HC reaction to be a useful technology for the treatment of dye in the textile wastewater.     

Ultrasound-assisted electrodeposition and synthesis of alloys and composite materials: A review

The development of electrodeposited materials with improved technological properties has been attracting the attention of researchers and companies from different industrial sectors. Many studies have demonstrated that the electrodeposition and synthesis of alloys and composite materials assisted by ultrasound may promote the de-agglomeration of particles in the electrolytic solution due to microturbulence, microjets, shock waves, and breaking of Van der Waals forces. The sonoelectrochemical technique, in which the ultrasound probe acts as a working electrode, also has been used for the formation of nanostructures in greater quantity, in addition to accelerating the electrolysis process and eliminating the reaction products on the electrode surface. Regarding the morphological aspects, the acoustic cavitation promotes the formation of smooth and uniform surfaces with incorporated particles homogeneously distributed. These changes have a direct impact on the composition and physical properties of the material, such as corrosion resistance, magnetization, wear, and microhardness. Despite the widespread use of acoustic cavitation in the synthesis of nanostructured materials, the discussion of how process variables such as acoustic power, frequency, and type of ultrasound device, as well as their effects still are scarce. In this sense, this review discusses the influence of ultrasound technology on obtaining electrodeposited coatings. The trends and challenges in this research field were reviewed from 2014 to 2019. Moreover, the effects of process variables in electrodeposition and how these ones change the technological properties of these materials were evaluated.     

Bubble phenomena in sould fields: part two

Large-amplitude radial oscillations of gas bubbles are briefly illustrated with the aid of numerical examples. The origin and possible effects of pressure-radiation forces are considered and an estimate of the coalescence time under their action is given. Non-spherical oscillations, the related problem of the fragmentation of oscillating bubbles by instability of the spherical shape, and sound propagation in bubbly liquids conclude the review.