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We present a further analysis for the second-harmonic generation of Bessel beams in lossy media.The emphasis is put on the effect of absorption to the radial pattern of the second-harmonic beam.It is shown that within the absorption length of the second harmonic,the Bessel second-harmonic beam approaches limited diffraction in the radial direction and behaves as in the case of lossless media. 相似文献
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本文利用5,5-dimethy1-1-purrolinel-oxide(DMPO)自旋捕集剂及电子自旋共振(ESR)技术研究证明,理疗级超声辐照可在自然空气饱和的水溶液中导致OH及H自由基的形成。认为这是超声瞬态空化过程产生局部高温高压的结果。当超声辐照时间取3min时,发现超声阈值空化强度在0.537W/cm~2—0.632W/cm~2间。随着辐照声强的增加,OH自由基产量在声强为1W/cm~2—2W/cm~2间迅速增长,大约在3W/cm~2以上,产量将不再增加。OH产量D与辐照声强τ的关系可近似用拟合方程D=8.1I(1/2)1/2I(1/2)来描述。取声强一定时,OH产量随辐照时间呈单调增长趋势。 相似文献
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