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UNSTEADY INTERACTION OF SHOCK WAVE DIFFRACTING AROUND A CIRCULAR CYLINDER IN AIR 被引量:1
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作者 黄文生 O.Onodera K.Takayama 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 1991年第4期295-299,共5页
The reflection and diffraction of a planar shock wave around a circular cylinder are a typical problem of the complex nonlinear shock wave phenomena in literature.It has long been studied experimentally,analytically a... The reflection and diffraction of a planar shock wave around a circular cylinder are a typical problem of the complex nonlinear shock wave phenomena in literature.It has long been studied experimentally,analytically as well as numerically.Takayama in 1987 obtained clear experimental pictures ofisopycnics in shock tube under the condi- tion that the impinging shock wave propagates as far as 3 diameters away from the cylinder.To know more complete- ly the whole unsteady process,it is desirable to get experimental results in a region which is more than 10 diameters away from the cylinder.This is what has been done in this paper by using the pulsed laser holographic interferometry for several shock Mach numbers of the impinging shock. Results for several moments are shown,giving more know- ledge about the whole unsteady flow field.This is useful for a reliable and complete understanding of the changing force acting on the cylinder,and provides interesting data to check the performance of many recently developed high resolution numerical methods for unsteady shock wave calculation. 展开更多
关键词 shock wave diffraction large flow field around a cylinder pulsed laser holographic interferometry isopycnics complex interaction of curved shocks
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Generation of near transform-limited ultrashort laser pulses in kilohertz chirped-pulse amplification system by compensating high order phase distortions 被引量:1
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作者 姜永亮 周冰 +3 位作者 冷雨欣 陈晓伟 李儒新 徐至展 《Chinese Optics Letters》 SCIE EI CAS CSCD 2006年第10期614-616,共3页
The effects of gain narrowing and high order dispersions on the pulse duration in our kilohertz chirpedpulse amplification system have been compensated experimentally. Using an acousto-optic programmable dispersive fi... The effects of gain narrowing and high order dispersions on the pulse duration in our kilohertz chirpedpulse amplification system have been compensated experimentally. Using an acousto-optic programmable dispersive filter (AOPDF), the spectral full-width at half-maximum (FWHM) is expanded from 30 to 50 nm. Stable laser pulses with the duration of 30 fs (FWHM), which is 1.07 times Fourier-transformlimitation, have been acquired by pre-compensating the high order phase distortions using the phase measured by spectral phase interferometry for direct electric-field reconstruction (SPIDER). 展开更多
关键词 Acoustooptical devices AMPLIFICATION Dispersion (waves) electric fields Fourier transforms laser pulses
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高压脉冲电场冲击波法的液体杀菌实验研究 被引量:10
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作者 依成武 吴春笃 +2 位作者 徐玮 储金宇 陆从相 《高电压技术》 EI CAS CSCD 北大核心 2007年第2期109-111,共3页
为研究高压脉冲电场冲击波对液体食品杀菌以实现不破坏食品的营养结构与原有风味的食品杀菌保鲜技术,阐述了在常温条件下产生高压脉冲电场冲击波的方法及其杀菌机理,介绍了以黄酒为试验原料的杀菌实验结果以及脉冲电压幅值、电容容量和... 为研究高压脉冲电场冲击波对液体食品杀菌以实现不破坏食品的营养结构与原有风味的食品杀菌保鲜技术,阐述了在常温条件下产生高压脉冲电场冲击波的方法及其杀菌机理,介绍了以黄酒为试验原料的杀菌实验结果以及脉冲电压幅值、电容容量和放电次数对杀菌效率的影响规律。结果表明,该法在常温条件下注入能量>12 J/mL时,能使菌落总数降低2个数量级,可杀死黄酒中>97%的细菌,而对山渣汁营养成分(维生素和氨基酸等)几乎无破坏作用。 展开更多
关键词 脉冲电场 冲击波 液体 食品 黄酒 杀菌
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外加电场增强激光脉冲在靶中产生的冲击波 被引量:3
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作者 谢建 曾传相 +3 位作者 周业为 姚兵 曹雁 刘迅 《激光杂志》 EI CAS CSCD 北大核心 2000年第2期17-18,共2页
本文报导了一种以外加直流电场增强Q开关激光在靶中产生冲击波的新方法。实验表明 ,当巨脉冲激光所照射靶前面外加强直流电场时 。
关键词 外加电场 激光脉冲 冲击波
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空气中平面激波同圆柱的非定常干涉 被引量:1
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作者 黄文生 小野寺収 高山和喜 《力学学报》 EI CSCD 北大核心 1992年第1期26-31,T002,共7页
平面激波在圆柱上的反射与绕射是目前国内外研究激波非线性复杂现象的典型课題。近年来,Takayama(1987)在入射激波马赫数M_i=1.3及2.6的条件下,得到了在圆柱周围的激波绕射与反射的光测实验结果。众所周知,激波在圆柱上的反射与绕射是... 平面激波在圆柱上的反射与绕射是目前国内外研究激波非线性复杂现象的典型课題。近年来,Takayama(1987)在入射激波马赫数M_i=1.3及2.6的条件下,得到了在圆柱周围的激波绕射与反射的光测实验结果。众所周知,激波在圆柱上的反射与绕射是一非定常现象,为了了解和分析整个非定常过程的发展和变化,应得到圆柱后较远区域的结果。本文利用两次曝光全息激光干涉仪不仅得到了圆柱周围的波系图案,而且也得到了激波脱离圆柱后驻点后约10倍圆柱直径的范围内的流动形态。同时也给出了不同M_i条件下的三波点轨迹和入射激波与反射激波之间夹角ω随距离变化的实验结果。 展开更多
关键词 激波绕射 流场 全息干涉仪
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Terahertz electromagnetic waves emitted from semiconductor investigated using terahertz time domain spectroscopy 被引量:2
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作者 朱亦鸣 庄松林 《Chinese Optics Letters》 SCIE EI CAS CSCD 2011年第11期33-39,共7页
Ultrafast electromagnetic waves radiated from semiconductor material under high electric fields and photoexcited by femtosecond laser pulses have been recorded by using terahertz time domain spectroscopy (THz-TDS).T... Ultrafast electromagnetic waves radiated from semiconductor material under high electric fields and photoexcited by femtosecond laser pulses have been recorded by using terahertz time domain spectroscopy (THz-TDS).The waveforms of these electromagnetic waves reflect the dynamics of the photoexcited carriers in the semiconductor material,thus,THz-TDS provides a unique opportunity to observe directly the temporal and spatial evolutions of non-equilibrium transport of carriers within sub-picosecond time scale.We report on the observed THz emission waveforms emitted from GaAs by using a novel technology,the time domain THz electro-optic (EO) sampling,which has a bipolar feature,i.e.,an initial positive peak and a subsequent negative dip that arises from its velocity overshoot.The initial positive peak has been interpreted as electron acceleration in the bottom of Γ valley in GaAs,where electrons have a light effective mass.The subsequent negative dip has been attributed to intervalley transfer from Γ to X and L valleys.Furthermore,the power dissipation spectra of the bulk GaAs in THz range are also investigated by using the Fourier transformation of the time domain THz traces.From the power dissipation spectra,the cutoff frequency for negative power dissipation (i.e.,gain) under step electric field in the bulk GaAs can also be obtained.The cutoff frequency for the gain gradually increases with increasing electric fields up to 50 kV/cm and achieves saturation at approximately 1 THz at 300 K.Furthermore,based on the temperature dependence of the cutoff frequency,we find that this cutoff frequency is governed by the energy relaxation process of electrons from L to Γ valley via successive optical phonon emission. 展开更多
关键词 Cutoff frequency electric fields electric losses Electromagnetic waves Electromagnetism Fourier analysis Fourier transforms Gallium arsenide LANDFORMS Magnetic materials Semiconducting gallium Terahertz waves Ultrafast lasers Ultrashort pulses
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