共查询到20条相似文献,搜索用时 0 毫秒
1.
《Current Applied Physics》2020,20(11):1253-1262
In this paper, Ag nanoparticles were deposited on Ag@cicada wing array by using the cicada wings as templates to study its optical properties, including surface enhanced Raman scattering (SERS), polarization and surface enhanced fluorescence (SEF). The nanogaps between adjacent conical protrusion can be well dominated by adjusting the sputtering time and the optimal substrate AgNPs@Ag@cicada wing arrays have a noteworthy enhancement of SERS signal. Characterization of the prepared optimal substrate certified that it possesses the excellent SERS performances. Basically consistent SERS signal strength at the different polarization angles of the optimal substrate indicates that its polarization-independence. The SEF spectra shows that the optimal substrate has a slightly lower and unstable enhancement at this initial stage of repeated examination due to the weak adhesion between the Ag@cicada wing arrays and Ag nanoparticles. The outstanding optical properties indicate that it has enormous potential in the label-free detection and biological analytes determination. 相似文献
2.
3.
Many butterfly wing scales (BWSs) possess novel periodic fine structures and can influence and manipulate the propagation of light in a certain wavelength range though an interaction similar to that occurring in photonic crystals. Such optical properties and their physical origin can be theoretically analysed by solving Maxwell’s equations. Many previous works have successfully applied a model of strict periodic pine-tree structure to the analysis of the scattering property of BWSs. However, fluctuation of the periodicity is common in the structure of BWSs. Thus clarification of the influence of size or periodicity variations on the optical properties of BWSs is then needed. In the present article, size variations have been considered and their influence on the scattering properties of BWSs is simulated in detail using a Finite-Difference-Time-Domain method (FDTD). The calculated reflectance spectrum will be more representative to the experimental result in the case where disorders, caused by size or periodicity variations, are considered. A detailed analysis shows that the main reflectance peak will be broadened and red-shifted especially when the angle of incidence is confined to a narrow range within 0° ± 10° (?10° ≤ θ ≤ 10°). The results will be stable if the maximal deviation – the pine-tree unit away from its original equilibrium position – is smaller than 50 nm. Finally, we test the visible spectrum of the butterfly Morpho Didius and compare the results to those of our simulation. It is shown that the present results are in good agreement with experimentally observed trends, and this work will be helpful for a better understanding of the colorisation mechanism of materials with the structure of BWSs. 相似文献
4.
Composite structures have been widely concerned in the preparation of surface enhanced Raman scattering (SERS) substrates. In this paper, by solving the problem that the magnetic material was difficult to glow in magnetron sputtering, ferro-nickel (NiFe) alloy was deposited on the cicada wing (CW) and the NiFe/CW substrate was obtained. The results of sliver nanoparticles (Ag NPs) modified on the substrate were subsequently compared, and the SERS properties of the new Ag/NiFe/CW substrate were analyzed. Obviously, the intensity of SERS signals has been greatly improved after the modification of Ag NPs, and the substrate exhibits excellent reproducibility. The Ag NPs modified substrates were also applied to the detection of toxic crystal violet (CV) solution, which showed remarkable SERS activity. It has been proved that the strategy of modifying Ag NPs on the substrate to form a composite structure has great potential for improving the SERS performance of the substrate. 相似文献
6.
7.
Investigation of flapping wings of insect are focused on low Reynolds number effect and the unsteady aerodynamic properties.
Interaction between flapping wing of insects and the air flow became one of important and fundamental research topics in micro
air vehicle. The present work is aim to investigate the flow behavior of flapping wings of tethered scarab beetle. The generation
mechanisms of velocity field and vortex formation are visualized with smoke-wire method. Tethered flight of the drone beetle
shows the motion with elastic deformation of flapping wing. Measured flapping frequency is about 71 Hz and its frequency is
higher than for dragonfly and butterfly. Beetle decreases negative lift by feathering motion in the upstroke process and increase
positive lift by effect of wake capture in the downstroke process. 相似文献
8.
Violas P Estivalezes E Briot J Sales de Gauzy J Swider P 《Magnetic resonance imaging》2007,25(3):386-391
The aim of this study was to quantify from magnetic resonance imaging (MRI) the volume and hydration variation of the intervertebral disc in the lumbar spine before and after surgery in severe idiopathic scoliosis cases. MRI data were posttreated using a custom-made image processing software to semiautomatically derive volume properties of disc, annulus fibrosus and nucleus pulposus. The nucleus-disc volume ratio was also an indicator of the hydration level. The MRI that was performed in the clinical protocol concerned 28 patients with severe idiopathic scoliosis; four types of surgical instrumentations were used. The reliability of the three-dimensional reconstruction process was initially verified using an intraoperator reproducibility test. Original preoperative data on disc volume properties were then derived. Postoperative volume variations were quantified in discs below spine fusion, taking into account the level of arthrodesis and the disc location. It showed that the postoperative volume criteria increased significantly for nucleus, disc and nucleus-disc volume ratio and that some magnitude modulation could be conditioned by the location of surgical instrumentation. It tended to prove that the recovery of balanced physiological positioning and inherent biomechanical loads could induce a restored hydration of disc, which should favor the remodeling of free segments. This work was the first report to deal with the consequences of scoliosis surgery on subjacent disc in terms of volume and hydration properties. The clinical outcome will follow based on the patient cohort follow-up at 1 year after surgery. 相似文献
9.
The patterns of wing rock motion at 52.5°angle of attack have already been investigated in detail(Rong,2009;Wang,2010).These patterns are completely different from those at other angles of attack.This phenomenon indicates that angle of attack affects wing rock motion.The present study aims to examine the different patterns of wing rock motion at different angles of attack.The flow mechanisms of the motion patterns are also revealed,especially the uncommanded lateral motions,including wing rock and lateral deflection,induced by regular asymmetric separated flow from wings at low angles of attack and forebody asymmetric vortices at angles of attack of 27.5°≤α≤70°.The test conditions,including the testing Reynolds number,wind tunnel,experimental techniques,and test model,are all the same as those used in a previous study at α=52.5°.Finally,the experimental technique of rotating nose of the model to suppress the wing rock or lateral deflection,which is induced by forebody asymmetric vortex flow,is applied.The uncommanded lateral motions are successfully suppressed by this technique. 相似文献
10.
11.
The unsteady flow and acoustic characteristics of the flapping wing are numerically investigated for a two-dimensional model of Bombus terrestris bumblebee at hovering and forward flight conditions. The Reynolds number Re, based on the maximum translational velocity of the wing and the chord length, is 8800 and the Mach number M is 0.0485. The computational results show that the flapping wing sound is generated by two different sound generation mechanisms. A primary dipole tone is generated at wing beat frequency by the transverse motion of the wing, while other higher frequency dipole tones are produced via vortex edge scattering during a tangential motion. It is also found that the primary tone is directional because of the torsional angle in wing motion. These features are only distinct for hovering, while in forward flight condition, the wing-vortex interaction becomes more prominent due to the free stream effect. Thereby, the sound pressure level spectrum is more broadband at higher frequencies and the frequency compositions become similar in all directions. 相似文献
12.
The dependence of the electron absorption coefficientκ for plasmon excitation on the deviationw from the exact Bragg condition in a single crystal is explained. The present theory gives the correct sign of asymmetry ofκ(w) which for plasmon excitation has been found opposite to the usual anomalous transmission effects. Quantitative agreement with experiments on Al is satisfactory. Suggestions for test of theoretical implications are made. 相似文献
13.
Emission measurements of the self-broadened Cs resonance lines have shown characteristic satellites and asymmetries in the quasistatic wings as were previously found in absorption measurements. In addition to this, Cs2 molecular bands were found on both sides of the component. 相似文献
14.
The effect of profile asymmetry, Reynolds number, and angles of deflection of high-lift devices on the hysteresis loop shape in the dependences of the static aerodynamic forces and moments on angles of attack is studied. These dependences are measured in wind tunnels during testing of rectangular wings of equal thickness but different curvature. The wings have deflectable flaps spanning the wing trailing edge. 相似文献
15.
A method for the active vibration suppression of a cantilever wing is presented. The approach is based on modal control, in which a modal feedback control law relating the motion of the control surfaces to the controlled modes is implemented. Modal displacements and velocities required for feedback are extracted from sensor measurements by means of modal filters. A numerical example is presented. 相似文献
16.
A qualitative model of the mechanism of intensification of jet noise issuing from a nozzle located near a wing is proposed. A two-dimensional model problem on the diffraction of a plane acoustic wave at the edge of a nozzle nozzle located near a half-plane simulating the wing edge is formulated. It is shown that diffraction on the wing edge of Kelvin-Helmholtz instability waves developing from the edge of the nozzle can lead to the significant intensification of the acoustic energy radiated into the far field. 相似文献
17.
Glass formers are defined as "type B" when they exhibit a distinct Johari-Goldstein (JG) relaxation, but lack an excess loss ("excess wing," EW) in their structural relaxation peak. By studying the dielectric spectra of a well-known type-B glass former under high pressure, we unequivocally show the existence of an EW, simultaneously with the JG relaxation. Moreover, at very high pressures (0.6 GPa), the EW becomes a distinct relaxation peak, although correlated with the structural relaxation. The implication is that the EW, rather than the higher frequency relaxation ascribed to the JG process, is perhaps a universal feature of glass formers, albeit not always discernible at ambient pressure. Our findings may reconcile all opposing points of view present in the literature, as well as indicate that the type-A or type-B classification of glass formers should be modified or even discontinued. 相似文献
18.
《Journal of Quantitative Spectroscopy & Radiative Transfer》1986,36(4):307-318
Absolute absorption rates of water vapor have been measured in the laboratory in the high-frequency wing of the 183 GHz line. Measurements have been carried out for pure water vapor and mixtures with N2 at atmospheric pressure. Pressure- and temperature-dependences are compared with models involving several types of lineshapes. 相似文献
19.