Group Divisible Codes and Their Application in the Construction of Optimal Constant-Composition Codes of Weight Three

The concept of group divisible codes, a generalization of group divisible designs with constant block size, is introduced in this paper. This new class of codes is shown to be useful in recursive constructions for constant-weight and constant-composition codes. Large classes of group divisible codes are constructed which enabled the determination of the sizes of optimal constant-composition codes of weight three (and specified distance), leaving only four cases undetermined. Previously, the sizes of constant-composition codes of weight three were known only for those of sufficiently large length.Comment: 13 pages, 1 figure, 4 table

List Decodability at Small Radii

$A'(n,d,e)$, the smallest $\ell$ for which every binary error-correcting code of length $n$ and minimum distance $d$ is decodable with a list of size $\ell$ up to radius $e$, is determined for all $d\geq 2e-3$. As a result, $A'(n,d,e)$ is determined for all $e\leq 4$, except for 42 values of $n$.Comment: to appear in Designs, Codes, and Cryptography (accepted October 2010

Modeling the gas-solid flow in diameter-changing fluidized beds

Gas-solid diameter-changing fluidized beds are usually used as either a transition section between the two parts with various diameters in circulating fluidized bed systems or a type of independent reactor in many industrial processes. This study focuses on the multiscale modeling of the former including tapered and inverted tapered structures, whose computational complexities mainly lie in addressing the problems related to the continuous variations of superficial gas and solid velocities with height as well as much more significant wall effect in diameter-changing fluidized beds than that in constant-diameter ones. By utilizing the energy-minimization multi-scale (EMMS) theory, the steady-state modeling of this type of reactor is performed to compute the spatial heterogeneous distributions of hydrodynamic parameters. A coarse-grained discrete particle method (DPM) defined by the EMMS model is also deployed for the high resolution simulation of gas-solid diameter-changing fluidized beds, in order to gain an insight into the underlying mechanisms involved in the variation of this heterogeneity with operating conditions. Both the axial and radial heterogeneous distributions of hydrodynamic parameters such as solid velocity and concentration in this type of reactor are firstly predicted in this study, which provides a quantitative reference for the design and scale-up of the tapered or inverted tapered fluidized beds. This study can be expected to further enrich the theory of full-loop modeling of complex gas-solid processes with various geometries and sizes

Momentum-dependence of ρ−ω\rho-\omega mixing in the pion vector form factor and its effect on (g−2)μ(g-2)_\mu

The inclusion of the $\rho-\omega$ mixing effect is crucial for a good description of the pion electromagnetic form factor in the $e^+e^- \rightarrow \pi^+\pi^-$ process, which quantifies the two-pion contribution to the anomalous magnetic moment of the muon $a_\mu$. In this paper, we try to analyze the impact of the momentum-dependence of the $\rho-\omega$ mixing within the framework of resonance chiral theory. The momentum-dependence of the $\rho-\omega$ mixing is incorporated due to the calculation of loop contributions at the next-to-leading order in the $1/N_C$ expansion. The work of {[}Y. H. Chen, D. L. Yao, and H. Q. Zheng, Commun. Theor. Phys. 69 (2018) 1{]} is revisited taking into account the contribution due to the kaon mass splitting in the kaon loops and the latest experimental data. We perform two kinds of fits (with momentum-independent or momentum-dependent $\rho-\omega$ mixing amplitude) describing the $e^+e^-\rightarrow \pi^+\pi^-$ and $\tau\rightarrow \nu_{\tau}2\pi$ data in the energy region of 600$\sim$900 MeV and the decay width of $\omega \rightarrow \pi^+\pi^-$, and compare their results. It is found that taking account of the momentum-dependence of $\rho-\omega$ mixing can describe the pion vector form factor data a little better. For the contribution to the anomalous magnetic moment of the muon $a_\mu^{\pi\pi}|_{[0.6,0.9]\text{GeV}}$, the values of the results in the fits considering the momentum-dependent $\rho-\omega$ mixing amplitude are agree well with those in the fits without including the momentum-dependence of the $\rho-\omega$ mixing within errors. In addition, based on the fitted values of the involved parameters, we find that in the decay width of $\omega \rightarrow \pi^+\pi^-$ the contribution from the direct $\omega_I\pi\pi$ coupling is comparable with the contribution due to the $\rho-\omega$ mixing.Comment: 21 pages, 4 figures. arXiv admin note: text overlap with arXiv:1710.1144

A Hybrid Continuity Loss to Reduce Over-Suppression for Time-domain Target Speaker Extraction

Speaker extraction algorithm extracts the target speech from a mixture speech containing interference speech and background noise. The extraction process sometimes over-suppresses the extracted target speech, which not only creates artifacts during listening but also harms the performance of downstream automatic speech recognition algorithms. We propose a hybrid continuity loss function for time-domain speaker extraction algorithms to settle the over-suppression problem. On top of the waveform-level loss used for superior signal quality, i.e., SI-SDR, we introduce a multi-resolution delta spectrum loss in the frequency-domain, to ensure the continuity of an extracted speech signal, thus alleviating the over-suppression. We examine the hybrid continuity loss function using a time-domain audio-visual speaker extraction algorithm on the YouTube LRS2-BBC dataset. Experimental results show that the proposed loss function reduces the over-suppression and improves the word error rate of speech recognition on both clean and noisy two-speakers mixtures, without harming the reconstructed speech quality.Comment: Submitted to Interspeech202

Unsupervised multiple choices question answering via universal corpus

Unsupervised question answering is a promising yet challenging task, which alleviates the burden of building large-scale annotated data in a new domain. It motivates us to study the unsupervised multiple-choice question answering (MCQA) problem. In this paper, we propose a novel framework designed to generate synthetic MCQA data barely based on contexts from the universal domain without relying on any form of manual annotation. Possible answers are extracted and used to produce related questions, then we leverage both named entities (NE) and knowledge graphs to discover plausible distractors to form complete synthetic samples. Experiments on multiple MCQA datasets demonstrate the effectiveness of our method.Comment: 5 pages, 1 figures, published to ICASSP 202