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Structural, optical, and morphological stability of ZnO nano rods under shock wave loading conditions
摘要： Shock wave recovery experiment on crystalline materials is a hot research topic for aerospace applications. In this research article, authors present and demonstrate the stability of physical properties of ZnO nano rods (ZnO NRs) under shock wave loaded conditions. The test sample is synthesized by hydrothermal method and the shock waves were generated using a table top semi automatic pressure driven shock tube. A shock wave of 2.2 Mach number which has a transient pressure of 2.0 MPa and temperature 864 K was made to strike four test samples for the counts of 50,100,150 and 200, respectively. The shock loaded samples were subjected to XRD and optical analysis so as to understand the influence of shock waves in the structural and optical properties. The results show that ZnO NRs have magnificent molecular, optical, structural and morphological stability for 50,100 and 150 shocks. Though, when the number of shock pulses was increased to 200 and a blue shift was observed in UV-Vis spectrum, no changes in structural properties took place which was evidenced from XRD. From this shock wave recovery experiment, it is clear that ZnO NRs are highly stable against shock waves and hence this material is suggested for the aerospace and military applications.
关键词： ZnO nano rods,Aerospace applications,Structure stability,Shock waves
更新于2025-09-23 15:23:52
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Shock wave induced enhancement of optical properties of benzil crystal
摘要： In this article, we present the results of the experimental work on the impact of shock waves on optical properties of benzyl crystalline material. Test material of benzil crystal is grown along [100] plane by Sankaranarayana - Ramasamy method. In the present work, the functional shock waves of Mach number 1.7 are generated from pressure driven shock tube. The optical properties of test material are investigated by UV-Visible spectrometer over the range between 200 and 800nm. The observed results show that the intensity of the absorption spectrum is inversely proportional to the number of exposed shock waves. The direct and indirect optical band gap energy (Eg) and Urbach tail energy (Ug) are determined from the optical absorption spectrum for pre and post shock wave loaded condition and found that shock wave loaded test crystal has high band gap energy. The optical constants namely extinction coefficient, real and imaginary parts of the dielectric constant, skin depth, optical density, optical conductivity and electrical conductivity are investigated and the obtained results are compared with post shock wave loaded benzil crystal with the incident light possessing wavelength at 700 nm. The results are found to be very impressive for the shock wave recovery experiments that are to be clearly discussed.
关键词： Transmission,Shock Waves,Re-crystallization,Benzil crystal,Optical properties
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference on Electromagnetics in Advanced Applications (ICEAA) - Cartagena des Indias (2018.9.10-2018.9.14)] 2018 International Conference on Electromagnetics in Advanced Applications (ICEAA) - Exact Solution for the Electromagnetic Field Excited by a Pulsed Filamentary Electric Current in a Nonlinear Nondispersive Medium
摘要： Radiation from a pulsed ?lamentary electric current immersed in a nonlinear nondispersive medium is studied. Two cases where such a medium is homogeneous or has a power-law permittivity pro?le in the linear limit are considered and the spatial distributions of the source-excited ?elds in the nonlinear regime are analyzed in these cases. Concerning the propagation of pulsed signals excited by the source, the emphasis is placed on the formation of cylindrical electromagnetic shock waves and the behavior of the propagation velocities of wave pro?les in the nonlinear medium. Special attention is also paid to the in?uence of the pulse shape on the manifestation of the studied nonlinear phenomena.
关键词： pulsed electric current,nonlinear nondispersive medium,electromagnetic shock waves
更新于2025-09-23 15:22:29
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Oral ascorbic acid 2-glucoside prevents coordination disorder induced via laser-induced shock waves in rat brain
摘要： Oxidative stress is considered to be involved in the pathogenesis of primary blast-related traumatic brain injury (bTBI). We evaluated the effects of ascorbic acid 2-glucoside (AA2G), a well-known antioxidant, to control oxidative stress in rat brain exposed to laser-induced shock waves (LISWs). The design consisted of a controlled animal study using male 10-week-old Sprague-Dawley rats. The study was conducted at the University research laboratory. Low-impulse (54 Pa?s) LISWs were transcranially applied to rat brain. Rats were randomized to control group (anesthesia and head shaving, n = 10), LISW group (anesthesia, head shaving and LISW application, n = 10) or LISW + post AA2G group (AA2G administration after LISW application, n = 10) in the first study. In another study, rats were randomized to control group (n = 10), LISW group (n = 10) or LISW + pre and post AA2G group (AA2G administration before and after LISW application, n = 10). The measured outcomes were as follows: (i) motor function assessed by accelerating rotarod test; (ii) levels of 8-hydroxy-2’-deoxyguanosine (8-OHdG), an oxidative stress marker; (iii) ascorbic acid in each group of rats. Ascorbic acid levels were significantly decreased and 8-OHdG levels were significantly increased in the cerebellum of the LISW group. Motor coordination disorder was also observed in the group. Prophylactic AA2G administration significantly increased the ascorbic acid levels, reduced oxidative stress and mitigated the motor dysfunction. In contrast, the effects of therapeutic AA2G administration alone were limited. The results suggest that the prophylactic administration of ascorbic acid can reduce shock wave-related oxidative stress and prevented motor dysfunction in rats.
关键词： ascorbic acid 2-glucoside,laser-induced shock waves,traumatic brain injury,Oxidative stress,motor dysfunction
更新于2025-09-23 15:21:01
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Probing dissipation mechanisms in BL Lac jets through X-ray polarimetry
摘要： The dissipation of energy ?ux in blazar jets plays a key role in the acceleration of relativistic particles. Two possibilities are commonly considered for the dissipation processes, magnetic reconnection – possibly triggered by instabilities in magnetically dominated jets – or shocks – for weakly magnetized ?ows. We consider the polarimetric features expected for the two scenarios analyzing the results of state-of-the-art simulations. For the magnetic reconnection scenario we conclude, using results from global relativistic MHD simulations, that the emission likely occurs in turbulent regions with unstructured magnetic ?elds, although the simulations do not allow us to draw ?rm conclusions. On the other hand, with local particle-in-cell simulations we show that, for shocks with a magnetic ?eld geometry suitable for particle acceleration, the self-generated magnetic ?eld at the shock front is predominantly orthogonal to the shock normal and becomes quasi-parallel downstream. Based on this result we develop a simpli?ed model to calculate the frequency-dependent degree of polarization, assuming that high-energy particles are injected at the shock and cool downstream. We apply our results to HBLs, blazars with the maximum of their synchrotron output at UV-soft X-ray energies. While in the optical band the predicted degree of polarization is low, in the X-ray emission it can ideally reach 50 per cent, especially during active/?aring states. The comparison between measurements in the optical and in the X-ray band made during active states (feasible with the planned IXPE satellite) is expected to provide valuable constraints on the dissipation and acceleration processes.
关键词： radiation mechanisms: non-thermal,X-rays: galaxies,magnetic reconnection,galaxies: jets,shock waves
更新于2025-09-23 15:21:01
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Tuning of surface plasmon resonance of silver nano particles by shock waves for plasmonic device applications
摘要： The present research article demonstrates the findings of the fine tuning of surface plasmon resonance (SPR) and the relationship between structural, optical and morphological properties of shock wave loaded silver nano-particles (Ag NPs). The characteristics of structural, optical and morphological properties of Ag NPs are evaluated by powder XRD (X-ray powder diffraction), UV–Vis (ultra violet- visible) spectroscopy and SEM (scanning electron microscopy) technique, respectively. The test material of Ag NPs is subjected to the shock wave loading with 50,100 and 150 shock pulses, respectively. The PXRD results reveal that the degree of crystalline nature and grain size of the crystal is significantly reduced by the impact of shock waves. The UV–Visible spectrum reveals that the control Ag NPs absorption band at 514 nm has given rise to blue shift (514–403 nm) at 150 shock wave loaded samples. The SEM images reveal that the particle size is considerably reduced by the impact of shock waves with respect to number of shock waves. The tri-angle correlation of structural, optical and morphological properties of shock wave loaded Ag NPs is explored.
关键词： Impact of shock waves,Tuning of SPR,Silver nano particles
更新于2025-09-23 15:21:01
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Calibration and verification of streaked optical pyrometer system used for laser-induced shock experiments
摘要： Although the streaked optical pyrometer (SOP) system has been widely adopted in shock temperature measurements, its reliability has always been of concern. Here, two calibrated Planckian radiators with different color temperatures were used to calibrate and verify the SOP system by comparing the two calibration standards using both multi-channel and single-channel methods. A high-color-temperature standard lamp and a multi-channel filter were specifically designed for the measurement system. To verify the reliability of the SOP system, the relative deviation between the measured data and the standard value of less than 5% was calibrated out, which demonstrates the reliability of the SOP system. Furthermore, a method to analyze the uncertainty and sensitivity of the SOP system is proposed. A series of laser-induced shock experiments were conducted at the ‘Shenguang-II’ laser facility to verify the reliability of the SOP system for temperature measurements at tens of thousands of kelvin. The measured temperature of the quartz in our experiments agreed fairly well with previous works, which serves as evidence for the reliability of the SOP system.
关键词： shock temperature measurement,laser-induced shock waves,streaked optical pyrometer
更新于2025-09-23 15:19:57
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Interaction of two counterpropagating laser induced plasmas and shock waves in air
摘要： The interaction of two counterpropagating plasmas and shockwaves due to a 7 ns laser induced breakdown (LIB) of ambient atmospheric air was studied using the 2D emission and shadowgraphic imaging technique. The effect of separation distance (d) between the two plasma sources and their energy ratio on plasma and shockwave evolution is presented. These low density and low temperature plasma sources form a stagnation layer in the interaction zone that showed an interesting dependence on the input energy of the sources. The interaction dynamics of the two counterpropagating plasma plumes and the shock waves in ambient air are compared with that of the respective single plasma source to explicitly bring out the energy exchange during the interaction. The evolution of a plasma jetlet, studied by 2D emission images and shadowgraphic imaging, has shown very good correlation giving valuable insight into the role of a plasma induced shockwave on the expanding plasma. The propagation of the shock front of the high energy source through the plasma of a low energy source is observed to predominantly lead to the formation of a jetlet and its evolution.
关键词： laser induced plasmas,plasma jetlet,plasma interaction,shock waves,counterpropagating,stagnation layer
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Anisotropic Dispersive Shock Waves in Highly Nonlinear M-Cresol/Nylon
摘要： M-Cresol/Nylon is a chemical solution, which is made up of an organic solvent (m-cresol) and a synthetic polymeric solute (nylon). Recent experiments showed that this solution exhibits an isotropic giant self-defocusing nonlinearity, tunable by varying the nylon concentration [1]. When it is enlightened by a continuous-wave laser beam, light absorption induces heat gain, which reduces the refractive index: the material experiences a nonlinear thermo-optical effect, made nonlocal by the heat diffusion. Since the temperature changes with the beam intensity, this nonlinearity follows a nonlocal Kerr model, expressed by the nonlinear Schroedinger equation (NLSE) [2]. In particular, V. Smith et al. measured the m-cresol/nylon nonlinear Kerr coef?cient n2 and found that, if for pure m-cresol it is ?9 × 10?8cm2/W , for a nylon mass concentration of 3.5% it is ?1.6 × 10?5cm2/W , a magnitude higher than most of the other thermal nonlinear materials reported in literature. In optics, many phenomena are ruled by NLSE, such as soliton propagation and dispersive shock wave (DSW) generation [1,2]. We report experimental evidence of two-dimensional optical DSWs with an anisotropic zero-singularity (Fig. 1). Fixing z as the longitudinal and x, y as the transverse directions, we start with a beam that has a Gaussian pro?le along y but a Gaussian ?rst derivative along x, thus the intensity is null for x = 0. This speci?c initial condition causes a new phenomenon, reported here for the ?rst time: the shock develops undular bores on the beam external borders (as already known in literature [2]), but around the singularity it presents an abrupt intensity discontinuity. We theoretically analyze the wave breaking along all the propagation. By a hydrodynamic model, we study the beam before the shock point: the WKB approach and the characteristic method let us predict the wave breaking both in phase and in intensity [2]. In order to model the beam propagation beyond the shock point, we use mathematical tools of time asymmetric quantum mechanics and uncover the mechanism how such an abrupt intensity discontinuity is generated [3]. We numerically simulate these results and ?nd remarkable agreement both with experiments and with theoretical predictions. Our outcome not only con?rms previous studies on the giant nonlinear response of m-cresol/nylon, but also discloses fundamental insights on propagation of DSWs with a singular initial intensity pro?le.
关键词： Dispersive shock wave generation,Anisotropic Dispersive Shock Waves,Highly Nonlinear M-Cresol/Nylon,Nonlinear Schroedinger equation,Thermo-optical effect
更新于2025-09-16 10:30:52
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Spatial confinement effects of bubbles produced by laser ablation in liquids
摘要： The paper deals with the influence of the spatial confinement on the evolution of laser bubbles and shock waves by means of the shadowgraphy technique. Due to the constraint of walls, the bubble center shrinks faster than the bubble edge and collapses before the edge of the bubble, splitting into left and right small bubbles that continue to shrink down. The result validates that the Bjerknes force has little effect on bubble evolution at the expansion stage but a great influence on it at the collapse stage. We study the evolution of laser bubbles with different Al-plate intervals for displaying a gradual transition from constrained conditions to unconstrained conditions. In addition, we describe the dynamics of the first bubble at the expansion stage using the Rayleigh-Plesset equation. The pressure and temperature inside laser bubbles are calculated in the meanwhile.
关键词： spatial confinement,Rayleigh-Plesset equation,shock waves,laser ablation,bubbles
更新于2025-09-16 10:30:52