共查询到20条相似文献,搜索用时 15 毫秒
1.
JETP Letters - The ranges of energies of femtosecond laser pulses and distances from the focusing point of intense (up to 1013 W/cm2) femtosecond laser radiation to a silicon sample in which phase... 相似文献
2.
Zygmunt J. Jakubek S.G. Nakhate Benoit SimardWalter J. Balfour 《Journal of Molecular Spectroscopy》2002,211(1):135-146
The yttrium monohydride spectrum in the range 12 500-25 000 cm−1 has been studied by various laser-induced fluorescence (LIF) techniques. YH (YD) molecules have been produced in a free jet molecular beam apparatus by a laser vaporizing yttrium metal in the presence of He doped with H2 (D2) or NH3 (ND3). Low-resolution (∼0.04 cm−1) excitation spectra have been recorded in the entire studied range. Four green bands (19 300-19 900 cm−1) of the YH isotopomer have been studied in more detail: (1) high-resolution (∼120 MHz, ∼0.004 cm−1) excitation spectra have been recorded, (2) dispersed fluorescence spectra have been obtained, and (3) lifetimes of the selected rotational levels of the upper states have been measured. Our observations have confirmed that the ground state of yttrium monohydride has 1Σ+ symmetry and have provided a link between the singlet and triplet manifolds. The upper states of the observed transitions have been tentatively assigned to five electronic states, d0+, f3Π, f′1, D1Π, E0+, and Fl. The low-energy excited electronic state observed in the dispersed fluorescence experiment has been assigned as the a3Δ state. 相似文献
3.
S. G. Chefranov 《Journal of Experimental and Theoretical Physics》2020,130(4):633-642
A new condition is obtained for the linear instability of a plane front of an intense shock wave in an arbitrary medium, which is determined by the finiteness of the viscosity. It is shown that the shock front instability occurs due to dissipative instability of the flow behind the front, which is analogous to the flow instability in the boundary layer. It is found that in the low-viscosity limit, one-dimensional longitudinal perturbations increase much faster than two-dimensional (corrugation) perturbations. The results are compared with the available data of experimental observation and numerical simulation of instability of shock waves. The comparison shows a better agreement between the new absolute shock instability as compared to the condition of such instability in the classical D’yakov theory disregarding viscosity. 相似文献
4.
ZHANG Yongkang 《Chinese Journal of Lasers》1997,6(1):81-85
1.IntroductionThewideapplicationsoflaser-inducedshockwaveshadbeendeveloPed,forexam-ple,materialprocessing[1~'J,mediCaltreatment[4],measuring['J,etc.Alltheseinvesti-gationswerestronglyrelatedtotheprofi1eofpressurepulseinducedbythelaserradiationandthePeakpressureonthesurfaceoftargetmaterials.InthisP8Per,theshockpressuremeasurementshavebeenPerformedbyusingaNd-glasslaserwithapulsedurationof5onsasanexcitingbeamandaPVDFtransducerasadetector.2.ExPeriments2.lhoerAhighpowerNd-glass1aserisusedint… 相似文献
5.
6.
We introduce three new models for a binary mixture which have only 6+5, 8+5, and 12+5 velocities and study the properties of the first two. The models are plane and have five conservation laws as expected for a binary mixture in the plane case. We look for exact solutions corresponding to traveling waves, which turn out to have the properties of a structured shock wave, and study their properties. Particular attention is paid to the overshoots in the profiles of internal energy for the mixture and the two components. 相似文献
7.
在激光偏转原子束实验中若使激光频率适当失谐,并令光束稍许偏离正交方向,则可偏转热原子束中具有特写速度的原子群。本文给出了这一简单选择方法的理论和初步实验结果。 相似文献
8.
Gianluca Gemelli 《General Relativity and Gravitation》1997,29(9):1163-1180
Gravitational shock waves are defined in the framework of space-times with distribution-valued curvature tensors. Then different kinds of motion in the presence of a gravitational shock wave are investigated. In an earlier paper the same investigation was carried out for an ordinary gravitational discontinuity wave. Discontinuity effects due to gravitational shock waves are compared to those due to ordinary waves. 相似文献
9.
10.
采用激光粒度扫描仪测量了二元混合物铝热剂(Al+Fe2O3)原料的粒径分布,在电子显微镜下观察了铝颗粒、氧化铁颗粒的颗粒形状及两者按照化学配比混合后的颗粒接触状态。综合粒径分布和反应体系的化学配比关系,得到两种反应物的特征粒径和混合物的颗粒布局。根据特征粒径和颗粒布局,建立了该反应体系的等效细观模型,该细观模型能够保证得到与实际颗粒体系相一致的具有统计意义的孔穴结构。采用无网格粒子方法,数值模拟了铝热剂体系在不同冲击速度作用下,基本氧化铁颗粒排列形成的热点特征。研究表明,氧化铁三颗粒紧密排列的模式为形成单独热点的最基本排列,在平面冲击作用下,二元不同粒径的含能材料混合物形成热点的尺寸由初始孔穴尺寸确定,而热点温度受冲击速度影响较大。采用轻气炮对不同密度和配比的铝热剂进行了冲击点火实验,并将测量和数值计算结果进行了对比分析,结果表明,两者的定性结论吻合较好。 相似文献
11.
Propagation of Laser-Induced Hypersound Waves in Polycrystalline Diamond with Submicron Crystallites
Klokov A. Yu. Sharkov A. I. Ralchenko V. G. Sedov V. S. 《Journal of Russian Laser Research》2021,42(5):580-585
Journal of Russian Laser Research - We investigate the propagation of laser-induced hypersound waves in polycrystalline diamond films by analyzing the spatial changes in the phase and amplitude of... 相似文献
12.
A pseudo arc-length method is proposed for the numerical simulation of shock wave propagations. This method passes the discontinuities and establishes adaptive moving meshes in the physical space by introducing the arc-length parameter and transforming the computational domain. Numerical experiments of the Sod problem, double Mach reflection problem and explosion problem demonstrate that this approach is more efficient than traditional numerical methods in capturing and tracking discontinuous solutions of singular or nearly singular problems. 相似文献
13.
用数值方法研究铁-铍介质界面上的激波折射现象.运用激波极曲线理论分析不同强度的激波从正规折射过渡到非正规折射的临界角变化.运用一个具有二阶精度和波传播性质的激波捕捉法,数值求解激波折射运动的流体力学方程组.对正规折射,数值结果与激波极曲线理论一致;对非正规折射,不同强度的激波大都存在前驱的折射激波,并且入射激波的强度不同、入射角度不同,激波折射的图像也不同. 相似文献
14.
为研究A型钝感炸药冲击起爆反应演化过程,进行了火炮驱动蓝宝石飞片的一维平面冲击实验。实验中采用光子多普勒测速仪(Photonic Doppler velocimetry,PDV)技术测量冲击起爆后台阶型炸药的粒子速度。在炸药不同厚度台阶的后界面固定镀铝膜的楔形氟化锂(LiF)窗口,利用阻抗匹配将PDV测量的LiF窗口波后粒子速度转化为炸药样品波后粒子速度。比较组合式电磁粒子速度计和PDV两种测速技术,结果表明,相较于组合式电磁粒子速度计,PDV测量的粒子精度更高。简要分析了PDV测速探头角度、探头孔径、窗口折射率等影响,得到PDV测速的相对不确定度小于1%。 相似文献
15.
《中国物理快报》2017,(3)
Nonlinear features of electron-acoustic shock waves are studied.The Burgers equation is derived and converted to the time fractional Burgers equation by Agrawal's method.Using the Adomian decomposition method,the shock wave solutions of the time fractional Burgers equation are constructed.The effect of time fractional parameter on the shock wave properties in auroral plasma is investigated. 相似文献
16.
17.
用线性稳定性理论,分析粘性物质中的正激波稳定性问题.粘性物质中任意强度的一维激波,其稳定性问题可归结为处理复数范围内的特征值问题,该特征值问题由两个一阶常微分方程及一个二阶常微分方程构成.这些常微分方程的系数依赖于流动的基本流场的物理量及其梯度.所获得的特征值问题由一个四阶精度的有限差分离散求解.分析考虑物质粘性的金属铝中的正激波稳定性,可以看出,正激波运动是稳定的,并且激波速度对波前和波后的小扰动量的衰减有相反的作用,而物质粘性有致稳的作用. 相似文献
18.
Structures of strong shock waves in dense plasmas are investigated via the steady-state Navier-Stokes equations and Poisson equation. The structures from nuid simulation agree with the ones from kinetic simulation. The effects of the transport coeffcients on the structures are analysed. The enhancements of the electronic heat conduction and ionic viscosity both will broaden the width of the shock fronts, and decrease the electric fields in the fronts. 相似文献
19.
We consider the Hammersley interacting particle system starting from a shock initial profile with densities \(\rho ,\lambda \in {\mathbb R}\) (\( \rho < \lambda \)). The microscopic shock is taken as the position of a second-class particle initially at the origin, and the main results are: (i) a central limit theorem for the shock; (ii) the variance of the shock equals \(2[\lambda \rho (\lambda - \rho )]^{-1}t + O(t^{2/3})\). By using the same method of proof, we also prove similar results for first-class particles. 相似文献
20.
P. Mali S. K. Sarkar A. B. Bhattacharya 《International Journal of Infrared and Millimeter Waves》2001,22(1):153-171
Radio wave operating in millimetrewave and microwave frequency bands are adversely affected due to rain. Particularly the attenuation is of immense significance for sensitive remote measurements by satellites using frequencies greater than 10 GHz. Maintenance of an uninterrupted communication link requires a precise knowledge of the attenuation effect due to rain for commissioning right kind of transmitting sources for various purposes required in present day situation. Precise measurement of attenuation at various frequencies will enable us to choose the right frequency, polarization, incident angle and power of the source for different purposes. In this paper we have compared the results of earlier works using aRb Olsen et al, (1) and the formulation by Moupfouma, (2) on the basis of theoretical analysis for explaining the observed results. Effect of temperature, considered in detail in this communication, has contributed the necessary correction factor of the rain attenuation for explaining the observed results. Theoretical analyses to measure the attenuation of the propagating wave due to temperature variation in the rain path have been presented. Correction factor due to temperature profile (temperature from the ground to the rain height within which the radio wave traces its path) has been incorporated in two models by using the concept of dipole energy changes. The effect of this temperature is noted to be quite significant and incorporates an error to the extent of 7–8%. 相似文献