2,324 research outputs found
Robust retrieval of material chemical states in X-ray microspectroscopy
X-ray microspectroscopic techniques are essential for studying morphological
and chemical changes in materials, providing high-resolution structural and
spectroscopic information. However, its practical data analysis for reliably
retrieving the chemical states remains a major obstacle to accelerating the
fundamental understanding of materials in many research fields. In this work,
we propose a novel data formulation model for X-ray microspectroscopy and
develop a dedicated unmixing framework to solve this problem, which is robust
to noise and spectral variability. Moreover, this framework is not limited to
the analysis of two-state material chemistry, making it an effective
alternative to conventional and widely-used methods. In addition, an
alternative directional multiplier method with provable convergence is applied
to obtain the solution efficiently. Our framework can accurately identify and
characterize chemical states in complex and heterogeneous samples, even under
challenging conditions such as low signal-to-noise ratios and overlapping
spectral features. Extensive experimental results on simulated and real
datasets demonstrate its effectiveness and reliability.Comment: 12 page
A Simulation Study on von Karman Vortex Shedding with Navier-Stokes and Shallow-Water Models
This study aims to investigate the advantages of employing numerical models based on Shallow-water equations for simulating von Karman vortex shedding. Furthermore, a comparative analysis with Navier-Stokes equations will be conducted to assess their effectiveness. In addition to Reynolds number (Re), Froude number (Fr), relevant to water depth, plays an important role in the Shallow-Water modeling of the von Karman vortex. In this study, simulations of 2D von Karman vortex shedding are performed using the Navier-Stokes model and Shallow-Water model, employing the least-squares finite-element method for space discretization and θ-method for time integration. The computed vortices characteristics, including the recirculation zone behind the cylinder, vortices size, and frequency, are presented. In the Navier-Stokes modeling, the computed results indicate that the size of vortices in space decreases and the Strouhal number increases as Re increases. In the Shallow-Water modeling for the same Re condition, the size of vortices increases and the Strouhal number decreases as Fr increases
A Hierarchical Context-aware Modeling Approach for Multi-aspect and Multi-granular Pronunciation Assessment
Automatic Pronunciation Assessment (APA) plays a vital role in
Computer-assisted Pronunciation Training (CAPT) when evaluating a second
language (L2) learner's speaking proficiency. However, an apparent downside of
most de facto methods is that they parallelize the modeling process throughout
different speech granularities without accounting for the hierarchical and
local contextual relationships among them. In light of this, a novel
hierarchical approach is proposed in this paper for multi-aspect and
multi-granular APA. Specifically, we first introduce the notion of sup-phonemes
to explore more subtle semantic traits of L2 speakers. Second, a depth-wise
separable convolution layer is exploited to better encapsulate the local
context cues at the sub-word level. Finally, we use a score-restraint attention
pooling mechanism to predict the sentence-level scores and optimize the
component models with a multitask learning (MTL) framework. Extensive
experiments carried out on a publicly-available benchmark dataset, viz.
speechocean762, demonstrate the efficacy of our approach in relation to some
cutting-edge baselines.Comment: Accepted to Interspeech 202
Bis{(E)-2-[(2-chloro-3-pyridyl)iminomethyl]-6-methoxyphenolato-κ2 N,O 1}copper(II)
In the title mononuclear copper(II) complex, [Cu(C13H10ClN2O2)2], the CuII ion, lying on an inversion center, is four-coordinated in a trans-CuN2O2 square-planar geometry by two phenolate O and two imino N atoms from two symmetry-related N,O-bidentate Schiff base ligands. The shortest Cu⋯Cu distance is 7.5743 (9) Å. However, there are weak intramolecular electrostatic interactions between the Cu atom and the Cl atom of the ligand, with a Cu⋯Cl distance of 3.3845 (9) Å
A Search for Double-peaked narrow emission line Galaxies and AGNs in the LAMOST DR1
LAMOST has released more than two million spectra, which provide the
opportunity to search for double-peaked narrow emission line (NEL) galaxies and
AGNs. The double-peaked narrow-line profiles can be well modeled by two
velocity components, respectively blueshifted and redshifted with respect to
the systemic recession velocity. This paper presents 20 double-peaked NEL
galaxies and AGNs found from LAMOST DR1 using a search method based on
multi-gaussian fit of the narrow emission lines. Among them, 10 have already
been published by other authors, either listed as genuine double-peaked NEL
objects or as asymmetric NEL objects, the remaining 10 being first discoveries.
We discuss some possible origins for double-peaked narrow-line features, as
interaction between jet and narrow line regions, interaction with companion
galaxies and black hole binaries. Spatially resolved optical imaging and/or
follow-up observations in other spectral bands are needed to further discuss
the physical mechanisms at work.Comment: 17 pages, 5figures, 4 tables, accepted by RA
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