308 research outputs found
Theory and experiment of differential acoustic resonance spectroscopy
Abstract Recent advances in Differential Acoustic Resonance Spectroscopy (DARS) techniques have given rise to applications in the field of poromechanics. We report on the experimental demonstration of bulk modulus measurements on poroelastic samples at sonic frequencies (1 kHz) with DARS. Normal mode perturbation is due to scattering of a foreign object (i.e., a rock sample) within an otherwise fluid-filled resonator. The perturbation theory on an elastic object determines its bulk modulus (inverse compressibility). The experimental bulk modulus of medium-to high-permeability (>10 mD) poroelastic samples is in agreement with predictions from quasi-static loading of a porous sphere using the Biot theory. This result demonstrates that pore fluid flow governs the dominant relaxation process of the rock during compression. For low-permeability samples (<10 mD), pressure equilibration via slow wave diffusion is limited, and only qualitative agreement is found between the upper bound (Gassmann undrained modulus) and the lower bound (volume-weighted compressibilities of the two constituents). DARS experiments, in conjunction with the poroelastic theory presented here, allow one to infer such rock physical properties as the effective bulk modulus at sonic frequencies
Long-Term Visual Object Tracking Benchmark
We propose a new long video dataset (called Track Long and Prosper - TLP) and
benchmark for single object tracking. The dataset consists of 50 HD videos from
real world scenarios, encompassing a duration of over 400 minutes (676K
frames), making it more than 20 folds larger in average duration per sequence
and more than 8 folds larger in terms of total covered duration, as compared to
existing generic datasets for visual tracking. The proposed dataset paves a way
to suitably assess long term tracking performance and train better deep
learning architectures (avoiding/reducing augmentation, which may not reflect
real world behaviour). We benchmark the dataset on 17 state of the art trackers
and rank them according to tracking accuracy and run time speeds. We further
present thorough qualitative and quantitative evaluation highlighting the
importance of long term aspect of tracking. Our most interesting observations
are (a) existing short sequence benchmarks fail to bring out the inherent
differences in tracking algorithms which widen up while tracking on long
sequences and (b) the accuracy of trackers abruptly drops on challenging long
sequences, suggesting the potential need of research efforts in the direction
of long-term tracking.Comment: ACCV 2018 (Oral
Hydrothermal saline promoted grafting of periodic mesoporous organic sulfonic acid silicas for sustainable FAME production
Hydrothermal saline promoted grafting of sulfonic acid groups onto SBA-15 and periodic mesoporous organic silica analogues affords solid acid catalysts with high acid site loadings (>2.5 mmol g-1 H+), ordered mesoporosity and tunable hydrophobicity. The resulting catalysts show excellent activity for fatty acid esterification and tripalmitin transesterification to methyl palmitate, with framework phenyl groups promoting fatty acid methyl esters production. (Chemical Equation Presented
Experimental Observation of Differences in the Dynamic Response of Newtonian and Viscoelastic Fluids
In this paper we present an experimental study of the dynamic responses of a
Newtonian fluid and a Maxwellian fluid under an oscillating pressure gradient.
We use laser Doppler anemometry in order to determine the velocity of each
fluid inside a cylindrical tube. In the case of the Newtonian fluid, the
dissipative nature is observed and the response obeys the Zhou and Sheng
universality (PRB 39, 12027 (1989)). In the dynamic response of the Maxwellian
fluid an enhancement at the frequencies predicted by the corresponding theory
(PRE 58, 6323 (1998)) is observed.Comment: 5 pages, 4 Figures, paper to be published in Phys. Rev.
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