نتایج جستجو برای: acoustic wave interferometry
تعداد نتایج: 299852 فیلتر نتایج به سال:
Determination of the wave mode short-wavelength electrostatic waves along with their generation mechanism requires reliable measurement electric field. We show that for such field measured by Magnetospheric MultiScale becomes unreliable when wavelength is close to probe-to-probe separation. develop a method, based on spin-plane interferometry, reliably determine full three-dimensional vector ob...
Near-surface structure investigation plays an important role in studying shallow active faults and has various engineering applications. Therefore, we developed a near-surface method using ambient noise water environment. This newly seismic acquisition technology, fiber-optic distributed acoustic sensing (DAS), was used to acquire from the Yangtze River. The recorded data were processed reconst...
With radar interferometry, the next-generation Surface Water and Ocean Topography satellite mission will improve the measured sea surface height resolution down to 15 km, allowing us to investigate for the first time the global upper ocean variability at the submesoscale range. Here, by analysing shipboard Acoustic Doppler Current Profiler measurements along 137°E in the northwest Pacific of 20...
In the 1990s, the method of time-reversed acoustics was developed. This method exploits the fact that the acoustic wave equation for a lossless medium is invariant for time reversal. When ultrasonic responses recorded by piezoelectric transducers are reversed in time and fed simultaneously as source signals to the transducers, they focus at the position of the original source, even when the med...
Optical surface profilers are state-of-the-art instruments for measuring surface height profiles. They are not conventionally applied to nanoparticle measurements due to the presence of diffraction artifacts. Here we use a theoretical model based on wave-optics to account for diffraction-based artifacts in optical surface profilers. This then enables accurate measurement of nanoparticles size o...
Green's function approximation via ocean noise cross-correlation, referred to here as ocean acoustic interferometry, has been demonstrated experimentally for passive noise sources. Active sources offer the advantages of higher frequencies, controllability, and continuous monitoring. Experimental ocean acoustic interferometry is described here for two active source configurations: a source lower...
Stochastic backgrounds of gravitational waves are intrinsic fluctuations of spacetime which lead to an unavoidable decoherence mechanism. This mechanism manifests itself as a degradation of the contrast of quantum interferences. It defines an ultimate decoherence border for matter-wave interferometry using larger and larger molecules. We give a quantitative characterization of this border in te...
قابلیت استفاده از روش آکوستیک امیشن برای پایش فرآیندهای اصطکاکی به عنوان روشی تکمیلی در کنار سایر روشها مانند نیروسنجی توسط محققان متعددی مورد تأیید قرار گرفته است. در این پروژه به بررسی دقیق تر پدیده های اصطکاکی به کمک آکوستیک امیشن پرداخته می شود. شرایط تولید سیگنال های آکوستیک امیشن در شکل دهی ورق های فلزی از جمله مواردی است که مورد بررسی قرار گرفته است. برای انجام آزمایشات، سه مجموعه آزمایش...
In general, Green’s functions obtained with seismic interferometry are only estimates of the true Green’s function, introducing uncertainties to the information recovered from them. However, there are still many cases in which the sourcereceiver geometries are suitable for seismic interferometry, usually allowing the recovery of kinematic information. Here we show how to use the singular value ...
In this paper we have studied the effect of magneto-static field onpropagation of thermal wave generated in metal by pulsed laser. In fact this interactiongenerate acoustic wave in different mechanisms. However, always the commonmechanism in the interactions of laser pulse and metal is the thermo-elastic wavegeneration. Applying the suitable magneto-static field on the s...
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