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1.
Minimally disruptive laser-induced breakdown in water 总被引:1,自引:0,他引:1
We produce minimally disruptive breakdown in water by using tightly focused 100-fs laser pulses and demonstrate the potential use of this technique in microsurgery of the eye. Using time-resolved imaging and piezoelectric pressure detection, we measure the magnitude and speed of propagation of the pressure wave produced in the breakdown. Compared with breakdown with longer pulses, here there is a much lower energy threshold for breakdown of 0.2microJ , a smaller shock zone diameter (11microm for 1-microJ pulses), and consistent energy deposition. 相似文献
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B. Da Silva M. Habibi S. Ognier G. Schelcher J. Mostafavi-Amjad H.R.M. Khalesifard M. Tatoulian D. Bonn 《The European physical journal. Special topics》2016,225(4):707-714
A new method for the elaboration of a novel type of catalytic microsystem with a high specific area catalyst is developed. A silver nanocluster catalytic microreactor was elaborated by doping a soda-lime glass with a silver salt. By applying a high power laser beam to the glass, silver nanoclusters are obtained at one of the surfaces which were characterized by BET measurements and AFM. A microfluidic chip was obtained by sealing the silver coated glass with a NOA 81 microchannel. The catalytic activity of the silver nanoclusters was then tested for the efficiency of water purification by using catalytic ozonation to oxidize an organic pollutant. The silver nanoclusters were found to be very stable in the microreactor and efficiently oxidized the pollutant, in spite of the very short residence times in the microchannel. This opens the way to study catalytic reactions in microchannels without the need of introducing the catalyst as a powder or manufacturing complex packed bed microreactors. 相似文献
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为了研究飞秒激光诱导水光学击穿阈值随激光脉冲参数的变化关系,采用四阶RungeKutta方法对飞秒激光诱导水光学击穿的椭球体模型进行了不同脉宽(40~540fs)、波长(400~1200nm)和光斑尺寸(0~200μm)下的数值模拟。通过控制变量法得出阈值光强与这些激光脉冲参数的关系曲线图,据此定性分析了阈值光强与激光脉冲参数的变化特征趋势。应用光强与功率、能量、辐照曝光量和电场强度之间的关系,得到了它们随激光脉冲参数脉宽、波长和光斑尺寸的动态关系,这为进一步研究飞秒激光与水和含水介质的相互作用提供了理论依据。 相似文献
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用激光光致发光光谱技术对发票真伪的快速鉴别进行了研究.首先采集80个真假发票样本的激光光致发光光谱数据,然后利用遗传算法对谱线重叠严重的566~669nm波段进行高斯拟合,提取特征参数,再结合BP神经网络技术建立鉴别模型.结果表明,从104个光谱数据提取13个特征参数,真假发票的拟合确定系数R2分别为0.997 89和... 相似文献
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为了研究飞秒激光诱导水光学击穿阈值随激光脉冲参数的变化关系,采用四阶Runge-Kutta方法对飞秒激光诱导水光学击穿的椭球体模型进行了不同脉宽(40~540 fs)、波长(400~1 200 nm)和光斑尺寸(0~200 μm)下的数值模拟。通过控制变量法得出阈值光强与这些激光脉冲参数的关系曲线图,据此定性分析了阈值光强与激光脉冲参数的变化特征趋势。应用光强与功率、能量、辐照曝光量和电场强度之间的关系,得到了它们随激光脉冲参数脉宽、波长和光斑尺寸的动态关系,这为进一步研究飞秒激光与水和含水介质的相互作用提供了理论依据。 相似文献
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利用MSC1210单片机改造了衍射条纹采集系统,设计并制作了基于MSC1210单片机的光强采集和数字式位移测量系统,上位机采用LABWINDOWS/CVI软件编程,方便实用地完成了衍射条纹采集光学实验. 相似文献
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Z. Cherkezova-Zheleva D. Paneva M. Tsvetkov B. Kunev M. Milanova N. Petrov I. Mitov 《Hyperfine Interactions》2014,226(1-3):517-527
The aim of presented paper was to study preparation of catalytic materials for water purification. Iron oxide (Fe3O4) samples supported on activated carbon were prepared by wet impregnation method and low temperature heating in an inert atmosphere. The as-prepared, activated and samples after catalytic test were characterized by Mössbauer spectroscopy and X-ray diffraction. The obtained X-ray diffraction patterns of prepared samples show broad and low-intensity peaks of magnetite phase and the characteristic peaks of the activated carbon. The average crystallite size of magnetite particles was calculated below 20 nm. The registered Mössbauer spectra of prepared materials show a superposition of doublet lines or doublet and sextet components. The calculated hyperfine parameters after spectra evaluation reveal the presence of magnetite phase with nanosize particles. Relaxation phenomena were registered in both cases, i.e. superparamagnetism or collective magnetic excitation behavior, respectively. Low temperature Mössbauer spectra confirm this observation. Application of materials as photo-Fenton catalysts for organic pollutions degradation was studied. It was obtained high adsorption degree of dye, extremely high reaction rate and fast dye degradation. Photocatalytic behaviour of a more active sample was enhanced using mechanochemical activation (MCA). The nanometric size and high dispersion of photocatalyst particles influence both the adsorption and degradation mechanism of reaction. The results showed that all studied photocatalysts effectively decompose the organic pollutants under UV light irradiation. Partial oxidation of samples after catalytic tests was registered. Combination of magnetic particles with high photocatalytic activity meets both the requirements of photocatalytic degradation of water contaminants and that of recovery for cyclic utilization of material. 相似文献
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A design of a kind of sonar transducers was presented. An experimental system was developed for producing the sound signal based on the laser-induced breakdown and bubble oscillation. The power spectrum and the ambiguity function were analyzed. The range resolution and the Doppler resolution constant of the sound signal were determined. It is basically proved in theory that both the range resolution and directivity of the sonar transducer are very high. The transducer can be a sound source of high-resolution sonars. 相似文献
12.
Bing Han Yun-Xiang Pan Ya-Li XueJun Chen Zhong-Hua ShenJian Lu Xiao-Wu Ni 《Optics and Lasers in Engineering》2011,49(3):428-433
Laser propulsions of six kinds of propelled objects in water and air are studied in this paper. The kinetic energy and momentum coupling coefficients gained by the objects after implementation of single laser pulses are investigated experimentally. It is shown that the propulsion effects are better in water than in air. Both in water and in air, the propulsion effects are better if there is a cavity on the laser irradiated surface of the object, and a hemispherical cavity works better than a 90°-conical cavity. A concept of equivalent reference pressure is proposed in this paper. It means that the asymmetry in the liquid induced by a rigid boundary near a spherical or nonspherical oscillating bubble can be approximated as the perturbation induced by a compressive stress wave passing through a bubble in the infinite static liquid. Thus, the collapse time and the pressure surrounding the nonspherical collapsing bubble can be estimated based on the maximum velocity of the liquid jet tip. Experiments also show that cavitation with oscillations and collapse can be induced at the object-water interface on the outside surface of the object head by the penetrating intensive stress wave and the elastic deformation of the object head. The bulging velocity of the object surface is calculated based on the propagation theory of stress waves at medium interfaces. 相似文献
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Ultrasound measurements of cavitation bubble radius for femtosecond laser-induced breakdown in water
A recently developed ultrasound technique is evaluated by measuring the behavior of a cavitation bubble that is induced in water by a femtosecond laser pulse. The passive acoustic emission during optical breakdown is used to estimate the location of the cavitation bubble's origin. In turn, the position of the bubble wall is defined based on the active ultrasonic pulse-echo signal. The results suggest that the developed ultrasound technique can be used for quantitative measurements of femtosecond laser-induced microbubbles. 相似文献
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We have fabricated complex helical microchannel arrays with uniform diameter in silica glass using femtosecond laser-induced breakdown in distilled water. The generated high-speed jet and shockwave cause cavitation damage in silica glass. Distilled water injected into microchannels through a rubber hose is used for effectively ejecting the debris. The low concentration of debris in the ablated area ensure continuously femtosecond laser-induced breakdown. The distribution, coil number, coil diameter and pitch of the helical microchannel arrays can be controlled. 相似文献
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Owing to its low cost and good transparency,highly purified water is widely used as a medium in large water Cerenkov detector experiments. The water circulation and purification system is usually needed to keep the water in good quality. In this work,a practical circulation model is built to describe the variation of the water resistivity in the circulation process and compared with the data obtained from a prototype experiment. The successful test of the model makes it useful in the future design and optimization of the circulation/purification system. 相似文献
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LU Hao-Qi YANG Chang-Gen WANG Ling-Yu XU Ji-Lei WANG aui-Guang WANG Zhi-Min WANG Yi-Fang 《中国物理C(英文版)》2009,33(7)
Owing to its low cost and good transparency, highly purified water is widely used as a medium in large water Cerenkov detector experiments. The water circulation and purification system is usually needed to keep the water in good quality. In this work, a practical circulation model is built to describe the variation of the water resistivity in the circulation process and compared with the data obtained from a prototype experiment. The successful test of the model makes it useful in the future design and optimization of the circulation/purification system. 相似文献
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基于LabVIEW的激光诱导击穿光谱谱线识别软件研究 总被引:1,自引:0,他引:1
介绍了自主开发的LIBS谱线识别软件,基于LabVIEW虚拟仪器开发平台,利用二次微商和阈值判定对LIBS谱数据进行降噪、寻峰,并通过参考NIST原子光谱数据库,确定了多种常见元素的特征波长,可以自动识别元素谱线,实现了对样品所含元素种类的定性分析。该软件系统定性分析元素简单、快捷,具有一定的实用性及推广价值。 相似文献
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Masafumi Kashii Yoichiroh Hosokawa Hiroshi Kitano Yusuke Mori Kazufumi Takano Hiroyoshi Matsumura Tsuyoshi Inoue Satoshi Murakami Kazuomi Sugamoto Takatomo Sasaki Hiroshi Masuhara 《Applied Surface Science》2007,253(15):6447-6450
For precise X-ray diffraction (XRD) measurement giving the three-dimensional structure of proteins, it is important to prepare high-quality single crystals with suitable shape. As a new processing technique to obtain such protein crystals, we employed femtosecond laser-induced cleaving of protein crystal in a growth vessel containing water solution. An intact protein crystal was precisely processed without mechanical contact in its sealed growth vessel by focusing femtosecond laser pulses. We confirmed that three-dimensional processing of the crystal in its supersaturated solution was realized using multiphoton absorption and that the processing was efficiently enhanced by the cleaving behavior attributed to a photomechanical mechanism of the femtosecond laser ablation. 相似文献
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Determination of detection limits for elements in water by femtosecond laser-induced breakdown spectroscopy 总被引:1,自引:0,他引:1
S. S. Golik O. A. Bukin A. A. Il’in E. B. Sokolova A. V. Kolesnikov M. Yu. Babiy Yu. N. Kul’chin A. A. Gal’chenko 《Journal of Applied Spectroscopy》2012,79(3):471-476
We have evaluated the feasibility of using femtosecond laser-induced breakdown spectroscopy with time-resolved detection of the spectra for determination of trace concentrations of chemical elements in water. The laser plasma was generated on the surface of aqueous solutions by a single pulse from a titanium:sapphire laser (pulse duration 40 fs, pulse repetition frequency up to 1 kHz). We obtained the 3σ limits of detection (LODs) for Al, Ba, Ca, Cu, Fe, K, Mg, Na, Zn in water as 0.19, 0.08, 0.01, 0.78, 3.4, 0.006, 1, 0.0009, 2.5 mg/L respectively. 相似文献