Four-dimensional scanning transmission electron microscopy (4D-STEM) is a versatile analytical tool for characterizing materials structural properties. However, extending such analysis to disordered materials is challenging, especially in technologically important samples with mixed ordered and disordered phases. Here, we present a new 4D-STEM method, called fluctuation cepstral STEM (FC-STEM), based on the fluctuation analysis of cepstral transform of diffraction patterns. The peaks in the associated transformation relate to inter-atomic distances in a thin sample. By varying the real-space range over which fluctuations are calculated, distinct ordered and disordered phases can be mapped in a diffractive image reconstruction. We demonstrate the principles of FC-STEM by characterizing a silicon anode, harvested from a cycled lithium-ion battery. A mixture of amorphous and nanocrystalline silicon, graphitic carbon, and electrolyte by-products is identified and mapped. Comparisons with conventional electron imaging and energy-dispersive X-ray spectroscopy show that FC-STEM is highly effective for the structure determination of mixed-phase amorphous materials.
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http://dx.doi.org/10.1016/j.ultramic.2023.113718 | DOI Listing |
J Chem Phys
November 2023
SISSA-Scuola Internazionale Superiore di Studi Avanzati, Trieste, Italy.
We present a method, based on the classical Green-Kubo theory of linear response, to compute the heat conductivity of extended systems, leveraging energy-density, rather than energy-current, fluctuations, thus avoiding the need to devise an analytical expression for the macroscopic energy flux. The implementation of this method requires the evaluation of the long-wavelength and low-frequency limits of a suitably defined correlation function, which we perform using a combination of recently-introduced cepstral-analysis and Bayesian extrapolation techniques. Our methodology is demonstrated against standard current-based Green-Kubo results for liquid argon and water, and solid amorphous Silica, and compared with a recently proposed similar technique, which utilizes mass-density, instead of energy-density, fluctuations.
View Article and Find Full Text PDFSensors (Basel)
April 2023
Institute for Technological Development and Innovation in Communications, Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain.
In this paper, we thoroughly analyze the detection of sleep apnea events in the context of Obstructive Sleep Apnea (OSA), which is considered a public health problem because of its high prevalence and serious health implications. We especially evaluate patients who do not always show desaturations during apneic episodes (non-desaturating patients). For this purpose, we use a database (HuGCDN2014-OXI) that includes desaturating and non-desaturating patients, and we use the widely used Physionet Apnea Dataset for a meaningful comparison with prior work.
View Article and Find Full Text PDFUltramicroscopy
June 2023
Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States; Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States. Electronic address:
Four-dimensional scanning transmission electron microscopy (4D-STEM) is a versatile analytical tool for characterizing materials structural properties. However, extending such analysis to disordered materials is challenging, especially in technologically important samples with mixed ordered and disordered phases. Here, we present a new 4D-STEM method, called fluctuation cepstral STEM (FC-STEM), based on the fluctuation analysis of cepstral transform of diffraction patterns.
View Article and Find Full Text PDFSci Rep
January 2023
Mechanical Engineering Program, Physical Science and Engineering Division, Clean Combustion Research Center, King Abdullah University of Science and Technology (KAUST), 23955-6900, Thuwal, Saudi Arabia.
A mid-infrared laser-based sensor is reported for the quantification of fugitive methane emissions. The sensor is based on a distributed feedback inter-band cascade laser operating near 3.3 μm.
View Article and Find Full Text PDFJ Speech Lang Hear Res
August 2022
Department of Communication Sciences and Disorders, University of South Florida, Tampa.
Purpose: Vocal roughness is often present in many voice disorders but the assessment of roughness mainly depends on the subjective auditory-perceptual evaluation and lacks acoustic correlates. This study aimed to apply the concept of roughness in general sound quality perception to vocal roughness assessment and to characterize the relationship between vocal roughness and temporal envelop fluctuation measures obtained from an auditory model.
Method: Ten /ɑ/ recordings with a wide range of roughness were selected from an existing database.
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