Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userInfluence of electromagnetic interferences on the gravimetric sensitivity of surface acoustic waveguides
88
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Surface acoustic waveguides are increasing in interest for (bio)chemical detection. The surface mass modification leads to measurable changes in the propagation properties of the waveguide. Among a wide variety of waveguides, Love mode has been investigated because of its high gravimetric sensitivity. The acoustic signal launched and detected in the waveguide by electrical transducers is accompanied by an electromagnetic wave; the interaction of the two signals, easily enhanced by the open structure of the sensor, creates interference patterns in the transfer function of the sensor. The influence of these interferences on the gravimetric sensitivity is presented, whereby the structure of the entire sensor is modelled. We show that electromagnetic interferences generate an error in the experimental value of the sensitivity. This error is different for the open and the closed loop configurations of the sensor. The theoretical approach is completed by the experimentation of an actual Love mode sensor operated under liquid in open loop configuration. The experiment indicates that the interaction depends on the frequency and the mass modifications.
rate research
Read More
Frequency-domain expressions are found for gradiometer and satellite-to-satellite tracking measurements of a point source on the surface of the Earth. The maximum signal-to-noise ratio as a function of noise in the measurement apparatus is computed, and from that the minimum detectable point mass is inferred. A point mass of magnitude M_3=100 Gt gives a signal-to-noise ratio of 3 when a GOCE-like gradiometer passes directly over the mass. On the satellite-to-satellite tracking mission GRACE-FO M_3=1.3 Gt for the microwave instrument and M_3=0.5 Gt for the laser ranging interferometer. The sensitivity of future GRACE-like missions with different orbital parameters and improved accelerometer sensitivity is explored, and the optimum spacecraft separation for detecting point-like sources is found. The future-mission benefit of improving the accelerometer sensitivity for measurement of non-gravitational disturbances is shown by the resulting reduction of M_3 to as small as 7 Mt for 500 km orbital altitude and optimized satellite separation of 900 km.
We analyze planar electromagnetic waves confined by a slab waveguide formed by two perfect electrical conductors. Remarkably, 2D Maxwell equations describing transverse electromagnetic modes in such waveguides are exactly mapped onto equations for acoustic waves in fluids or gases. We show that interfaces between two slab waveguides with opposite-sign permeabilities support 1D edge modes, analogous to surface acoustic plasmons at interfaces with opposite-sign mass densities. We analyze this novel type of edge modes for the cases of isotropic media and anisotropic media with tensor permeabilities (including hyperbolic media). We also take into account `non-Hermitian edge modes with imaginary frequencies or/and propagation constants. Our theoretical predictions are feasible for optical and microwave experiments involving 2D metamaterials.
Dynamical instrument limitations, such as finite detection bandwidth, do not simply add statistical errors to fluctuation measurements, but can create significant systematic biases that affect the measurement of steady-state properties. Such effects must be considered when calibrating ultra-sensitive force probes by analyzing the observed Brownian fluctuations. In this article, we present a novel method for extracting the true spring constant and diffusion coefficient of a harmonically confined Brownian particle that extends the standard equipartition and power spectrum techniques to account for video-image motion blur. These results are confirmed both numerically with a Brownian dynamics simulation, and experimentally with laser optical tweezers.
Acoustic emission (AE) characterization is an effective technique to indirectly capture the progressive failure process of the brittle rock. In previous studies, both the experiment and numerical simulation were adopted to investigate AE characteristics of the brittle rock. However, as the most popular numerical model, the moment tensor model (MTM) did not reproduce the monitoring and analyzing manner of AE signals from the physical experiment. Consequently, its result could not be constrained by the experimental result. It is thus necessary to evaluate the consistency and compatibility between the experiment and MTM. To fulfill this, we developed a particle-velocity-based model (PVBM) which enabled directly monitor and analyze the particle velocity in the numerical model and had good robustness. The PVBM imitated the actual experiment and could fill in gaps between the experiment and MTM. AE experiments of Marine shale under uniaxial compression were carried out, of which results were simulated by MTM. In general, the variation trend of the experimental result could be presented by MTM. Nevertheless, magnitudes of AE parameters by MTM presented notable differences with more than several orders compared with those by the experiment. We sequentially used PVBM as a proxy to analyze these discrepancies quantitatively and make a systematical evaluation on AE characterization of brittle rocks from the experiment to numerical simulation, considering the influence of wave reflection, energy geometrical diffusion, viscous attenuation, particle size as well as progressive deterioration of rock material. It was suggested that only the combination of MTM and PVBM could reasonably and accurately acquire AE characteristics of the actual AE experiment of brittle rocks by making full use of their respective advantages.
Long-term monitoring of organic pollutants in the soil is a major environmental challenge. We propose to meet this issue by the development of a polymer dedicated to selectively react with H2S, coating surface acoustic wave transducers designed as passive cooperative targets with the compound, and probing their response using Ground Penetrating RADAR, thus providing the capability to monitor the presence of H2S in the subsurface environment. The selectivity is brought by including lead(II) cation in a reticulated polymer matrix which can be deposited as a thin layer on a surface acoustic wave sensor. We demonstrate a signal enhancement mechanism in which water absorption magnifies the signal detection, making the sensor most sensitive to H2S in an underground environment saturated with moisture.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
