Methods of Reducing the Response of Integrally Stiffened Structures to Random Pressures

1969 ◽  
Vol 91 (4) ◽  
pp. 1203-1209 ◽  
Author(s):  
B. L. Clarkson ◽  
F. Cicci
Keyword(s):  
Spectral Density ◽  
Broad Band ◽  
Experimental Results ◽  
Significant Response ◽  
Theoretical Studies ◽  
Frequency Range ◽  
Efficient System ◽  
Stiffened Structures ◽  
Experimental And Theoretical Studies

Experimental and theoretical studies of the response of integrally stiffened skin structures to random acoustic pressures are described. Typical structures are lightly damped and show significant response in the frequency range 100 to 2000 Hz. Some methods of increasing the damping are described and experimental results quoted. In the most efficient system investigated a damping treatment adding only 2 percent by weight to the structure reduced the rms stress by a factor of approximately three for the case of broad band excitation having a constant spectral density in the range 100 to 1000 Hz.

Hydrodynamic Fluid Pressure in Grinding Zone During Grinding With Metal-Bonded Diamond Wheels

1999 ◽  
Vol 122 (3) ◽  
pp. 603-608 ◽  
Author(s):  
Bo Zhang ◽  
Akira Nakajima
Keyword(s):  
Theoretical Analysis ◽  
Hydrodynamic Force ◽  
Fluid Pressure ◽  
Hydrodynamic Pressure ◽  
Grinding Force ◽  
Experimental Results ◽  
Theoretical Studies ◽  
Wheel Surface ◽  
Grinding Fluid ◽  
Experimental And Theoretical Studies

Experimental and theoretical studies on hydrodynamic fluid pressure were conducted for the cases of plane grinding with nonporous metal bonded diamond wheels of SD140 and SD4000. Hydrodynamic force was successfully separated from the actual grinding force using the device developed in this study. Both experimental results and theoretical analysis showed that the effect of side leakage of grinding fluid on hydrodynamic pressure is negligible under grinding condition and therefore the infinite width cylindrical bearing theory is applicable. The effective clearance includes the effects of both the protrusion of cutting points and the waviness of the wheel surface for SD140. However, for a fine wheel such as SD4000, the waviness is predominant. Hydrodynamic force predominates normal grinding force even for a coarse wheel as SD140. [S0742-4787(00)01302-3]

scholarly journals Broadband bifunctional Luneburg–Fisheye lens based on anisotropic metasurface

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Jiaqing Chen ◽  
Yongjiu Zhao ◽  
Lei Xing ◽  
Zheng He ◽  
Luyang Sun
Keyword(s):  
High Efficiency ◽  
Broad Band ◽  
Dipole Antenna ◽  
Wide Frequency Range ◽  
Experimental Results ◽  
Frequency Range ◽  
Fisheye Lens ◽  
Low Profile ◽  
Theoretical Predictions ◽  
Fisheye Lenses

AbstractLuneburg lenses and Maxwell fisheye lenses possess distinct properties of focusing, well beyond conventional lenses made of uniform materials. In this paper, a planar broadband bifunctional Luneburg-fisheye lens synthesized by gradient anisotropic metasurface is proposed. The proposed anisotropic metasurface is formed by non-resonant anisotropic cells, so that it can independently realize the equivalent gradient refractive indexes of Luneburg lens and Maxwell fisheye lens along orthogonal directions in a broad band, respectively. To verify the performance of the bifunctional lens, a prototype associated with a feeding log-periodic dipole antenna has been fabricated. Experimental results show that the proposed lens functions well over a wide frequency range with high efficiency and low profile, which coincides well with theoretical predictions and simulated results. It is expected that the proposed design will facilitate the applications of multifunctional metadevices in microwave and optical ranges.

The Stabilizing Effect of Pre-Equilibria: A Trifluoromethyl Complex as CF2 Reservoir in Catalytic Olefin Difluorocarbenation

2020 ◽  
Author(s):  
Thomas Louis-Goff ◽  
Huu Vinh Trinh ◽  
Eileen Chen ◽  
Arnold L. Rheingold ◽  
Christian Ehm ◽  
...  
Keyword(s):  
High Selectivity ◽  
Side Reactions ◽  
Theoretical Studies ◽  
Attractive Feature ◽  
Catalyst Recovery ◽  
Wide Range ◽  
Stabilizing Effect ◽  
Experimental And Theoretical Studies

A new, efficient, catalytic difluorocarbenation of olefins to give 1,1-difluorocyclopropanes is presented. The catalyst, an organobismuth complex, uses TMSCF<sub>3</sub> as a stoichiometric difluorocarbene source. We demonstrate both the viability and robustness of this reaction over a wide range of alkenes and alkynes, including electron-poor alkenes, to generate the corresponding 1,1-difluorocyclopropanes and 1,1-difluorocyclopropenes. Ease of catalyst recovery from the reaction mixture is another attractive feature of this method. In depth experimental and theoretical studies showed that the key difluorocarbene-generating step proceeds through a bismuth non-redox synchronous mechanism generating a highly reactive free CF<sub>2</sub> in an endergonic pre-equilibrium. It is the reversibility when generating the difluorocarbene that accounts for the high selectivity, while minimizing CF<sub>2</sub>-recombination side-reactions.

Strong coupling: resonant effects

2017 ◽  
Author(s):  
Alexey V. Kavokin ◽  
Jeremy J. Baumberg ◽  
Guillaume Malpuech ◽  
Fabrice P. Laussy
Keyword(s):  
Strong Coupling ◽  
Experimental Studies ◽  
Strong Coupling Regime ◽  
Theoretical Studies ◽  
Stimulated Scattering ◽  
Quantum Theories ◽  
Pump Probe ◽  
Exciton Polaritons ◽  
Linear Optical Properties ◽  
Experimental And Theoretical Studies

This chapter presents experimental studies performed on planar semiconductor microcavities in the strong-coupling regime. The first section reviews linear experiments performed in the 1990s that evidence the linear optical properties of cavity exciton-polaritons. The chapter is then focused on experimental and theoretical studies of resonantly excited microcavity emission. We mainly describe experimental configuations in which stimulated scattering was observed due to formation of a dynamical condensate of polaritons. Pump-probe and cw experiments are described in addition. Dressing of the polariton dispersion and bistability of the polariton system due to inter-condensate interactions are discussed. The semiclassical and the quantum theories of these effects are presented and their results analysed. The potential for realization of devices is also discussed.

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