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1.
The sonochemical degradation of a variety of chemical contaminants in aqueous solution has been investigated. Substrates such as chlorinated hydrocarbons, pesticides, phenols, explosives such as TNT, and esters are transformed into short-chain organic acids, CO2, and inorganic ions as the final products. Time scales of treatment in simple batch reactors over the frequency range of 20 to 500 kHz are reported to range from minutes to hours for complete degradation. Ultrasonic irradiation appears to be an effective method for the rapid destruction of organic contaminants in water because of localized high concentrations of oxidizing species such as hydroxyl radical and hydrogen peroxide in solution, high localized temperatures and pressures, and the formation of transient supercritical water.

The degradation of chemical compounds by acoustic cavitation is shown to involve three distinct pathways: 1) oxidation by hydroxyl radicals, 2) pyrolytic decomposition and 3) supercritical water oxidation. Detailed reaction mechanisms for the degradation of p-nitrophenol, carbon tetrachloride, parathion, p-nitrophenyl acetate and trinitrotoluene are presented.  相似文献

2.
超声空化的研究方法及进展   总被引:15,自引:5,他引:10       下载免费PDF全文
综述了超声空化研究的各种方法及研究进展,总结了空化研究中存在的问题,简要介绍了超声空化在基因导入方面应用的新进展。  相似文献
3.
Bubble population phenomena in acoustic cavitation   总被引:11,自引:0,他引:11  
Theoretical treatments of the dynamics of a single bubble in a pressure field have been undertaken for many decades. Although there is still scope for progress, there now exists a solid theoretical basis for the dynamics of a single bubble. This has enabled useful classifications to be established, including the distinction between stable cavitation (where a bubble pulsates for many cycles) and transient cavitation (where the bubble grows extensively over time-scales of the order of the acoustic cycle, and then undergoes an energetic collapse and subsequent rebound and then, potentially, either fragmentation, decaying oscillation or a repeat performance). Departures from sphericity, such as shape and surface oscillations and jetting, have also been characterized. However, in most practical systems involving high-energy cavitation (such as those involving sonochemical, biological and erosive effects), the bubbles do not behave as the isolated entities modelled by this single-bubble theory: the cavitational effect may be dominated by the characteristics of the entire bubble population, which may influence, and be influenced by, the sound field.

The well established concepts that have resulted from the single-bubble theory must be reinterpreted in teh light of the bubble population, an appreciation of population mechanisms being necessary to apply our understanding of single-bubble theory to many practical applications of ‘power’ ultrasound. Even at a most basic level these single-bubble theories describe the response of the bubble to the local sound field at the position of the bubble, and that pressure field will be influenced by the way sound is scattered by neighbouring bubbles. The influence of the bubble population will often go further, a non-uniform sound field creating an inhomogeneous bubble distribution. Such a distribution can scatter, channel and focus ultrasonic beams, can acoustically shield regions of the sample, and elsewhere localize the cavitational activity to discrete ‘hot spots’. As a result, portions of the sample may undergo intense sonochemical activity, degassing, erosion, etc., whilst other areas remain relatively unaffected. Techniques exist to control such situations where they are desirable, and to eliminate this localization where a more uniform treatment of the sample is desired.  相似文献

4.
冯若 《应用声学》2001,20(2):38-42
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。  相似文献
5.
空化单气泡外围压强分布   总被引:7,自引:0,他引:7       下载免费PDF全文
刘海军  安宇 《物理学报》2004,53(5):1406-1412
通过数值计算非线性谐振的气泡外围流场中的Navier Stokes方程 ,给出详细的空化单气泡外围压强分布 .数值计算发现当气泡处于压缩相 ,那些最大半径比较大的气泡 ,其外围紧邻气泡壁处出现负压区 ,这将使气泡在这段时间处于力的非稳定平衡点 .计算还发现 ,当气泡接近它的最小半径处 ,气泡外围形成很薄的高压区 ,这个高压区域随后向外传播 ,这就形成冲击波 .分析表明 ,冲击波对Mie散射法测量气泡最小半径有一定影响 ,但不是主要影响 .  相似文献
6.
Cavitation mechanism of ultrasonic melt degassing   总被引:5,自引:0,他引:5  
The real melt always contains non-wettable fine inclusions which are potential nuclei for cavitation and degassing. This paper deals with the nature of ultrasonic degassing and the industrial application of a relevant technology.  相似文献
7.
This paper describes investigations of the spatial distribution of cavitation activity generated within an ultrasonic cleaning vessel, undertaken using a novel cavitation sensor concept. The new sensor monitors high frequency acoustic emissions (>1 MHz) generated by micron-sized bubbles driven into acoustic cavitation by the applied acoustic field. Novel design features of the sensor, including its hollow, cylindrical shape, provide the sensor with spatial resolution, enabling it to associate the megahertz acoustic emissions produced by the cavitating bubbles with specific regions of space within the vessel. The performance of the new sensor has been tested using a 40 kHz ultrasonic cleaner employing four transducers and operating at a nominal electrical power of 140 W under controlled conditions. The results demonstrate the ability of the sensors to identify 'hot-spots' and 'cold-spots' in cavitation activity within the vessel, and show good qualitative agreement with an assessment of the spatial distribution of cavitation determined through erosion monitoring of thin sheets of aluminium foil. The implications of the studies for the development of reliable methods of quantifying the performance of cleaning vessels are discussed in detail.  相似文献
8.
功率超声在废水处理中的应用   总被引:5,自引:0,他引:5       下载免费PDF全文
熊宜栋 《应用声学》2002,21(4):33-35,32
采用不同强度和频率的超声波,对几种生物难降解的有毒污染物(苯胺,硝基苯)废水进行超声处理,实验表明,降解效果主要取决于超声波在反应液中的声强及处理时间,同时,若辅以通氧气或加入催化剂,处理效果更好,这就为设计相应的超声废水处理设备提供了实验基础。  相似文献
9.
超声波强化超滤过程   总被引:5,自引:0,他引:5       下载免费PDF全文
陈健  肖凯军  郭祀远  李琳 《应用声学》2002,21(5):45-48,39
本文综述了超声波强化超滤的实验方法,超声波对越滤膜结构的影响及超声波强化清洗超滤膜等方面的研究进展,论述了超声波强化超滤的作用机理,声冲流和空化作用在超声波强化超滤中起到主要作用。  相似文献
10.
声空化场下单相对流传热的实验研究   总被引:4,自引:0,他引:4  
以水、乙醇和丙酮为工质,首次通过实验研究了声空化场的热效应、单相对流换热受空化时间.纳米颗粒和实验工质的影响及恒热流密度下单相对流换热系数随声空化强度的变化,并就其强化传热机理进行了分析。  相似文献
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