Improvements on Deep Bottleneck Network based I-Vector Representation for Spoken Language Identification

Recently, the i-vector representation based on deep bottleneck networks (DBN) pre-trained for automatic speech recognition has received significant interest for both speaker verification (SV) and language identification (LID). In particular, a recent unified DBN based i-vector framework, referred to as DBN-pGMM i-vector, has performed well. In this paper, we replace the pGMM with a phonetic mixture of factor analyzers (pMFA), and propose a new DBN-pMFA i-vector. The DBN-pMFA i-vector includes the following improvements: (i) a pMFA model is derived from the DBN, which can jointly perform feature dimension reduction and de-correlation in a single linear transformation, (ii) a shifted DBF, termed SDBF, is proposed to exploit the temporal contextual information, (iii) a senone selection scheme is proposed to improve the i-vector extraction efficiently. We evaluate the proposed DBN-pMFA i-vector on the most confused six languages selected from NIST LRE 2009. The experimental results demonstrate that DBN-pMFA can consistently outperform the previous DBN based framework. The computational complexity can be significantly reduced by applying a simple senone selection scheme

Improved language identification using deep bottleneck network

Effective representation plays an important role in automatic spoken language identification (LID). Recently, several representations that employ a pre-trained deep neural network (DNN) as the front-end feature extractor, have achieved state-of-the-art performance. However the performance is still far from satisfactory for dialect and short-duration utterance identification tasks, due to the deficiency of existing representations. To address this issue, this paper proposes the improved representations to exploit the information extracted from different layers of the DNN structure. This is conceptually motivated by regarding the DNN as a bridge between low-level acoustic input and high-level phonetic output features. Specifically, we employ deep bottleneck network (DBN), a DNN with an internal bottleneck layer acting as a feature extractor. We extract representations from two layers of this single network, i.e. DBN-TopLayer and DBN-MidLayer. Evaluations on the NIST LRE2009 dataset, as well as the more specific dialect recognition task, show that each representation can achieve an incremental performance gain. Furthermore, a simple fusion of the representations is shown to exceed current state-of-the-art performance

Deep Bottleneck Network based i-vector representation for Language Identification

This paper presents a unified i-vector framework for language identification (LID) based on deep bottleneck networks (DBN) trained for automatic speech recognition (ASR). The framework covers both front-end feature extraction and back-end modeling stages.The output from different layers of a DBN are exploited to improve the effectiveness of the i-vector representation through incorporating a mixture of acoustic and phonetic information. Furthermore, a universal model is derived from the DBN with a LID corpus. This is a somewhat inverse process to the GMM-UBM method, in which the GMM of each language is mapped from a GMM-UBM. Evaluations on specific dialect recognition tasks show that the DBN based i-vector can achieve significant and consistent performance gains over conventional GMM-UBM and DNN based i-vector methods. The generalization capability of this framework is also evaluated using DBNs trained on Mandarin and English corpuses. Index Terms: Language Identification, Deep Neural Network, Deep Bottleneck Feature, i-vector representatio

Conjugation of Inulin Improves Anti-Biofilm Activity of Chitosan

Bacteria biofilm helps bacteria prevent phagocytosis during infection and increase resistance to antibiotics. Staphylococcus aureus is a Gram-positive pathogenic bacterium and is tightly associated with biofilm-related infections, which have led to great threat to human health. Chitosan, the only cationic polysaccharide in nature, has been demonstrated to have antimicrobial and anti-biofilm activities, which, however, require a relative high dosage of chitosan. Moreover, poor water solubility further restricts its applications on anti-infection therapy. Inulins are a group of polysaccharides produced by many types of plants, and are widely used in processed foods. Compared to chitosan, inulin is very soluble in water and possesses a mild antibacterial activity against certain pathogenic bacteria. In order to develop an effective strategy to treat biofilm-related infections, we introduce a method by covalent conjugation of inulin to chitosan. The physicochemical characterization of the inulin-chitosan conjugate was assayed, and the anti-biofilm activity was evaluated against S. aureus biofilm. The results indicated that, as compared to chitosan, this novel polysaccharide-polysaccharide conjugate significantly enhanced activities against S. aureus either in a biofilm or planktonic state. Of note, the conjugate also showed a broad spectrum anti-biofilm activity on different bacteria strains and low cellular toxicity to mammalian cells. These results suggested that chitosan conjugation of inulin was a viable strategy for treatment against biofilm-related infections. This finding may further spread the application of natural polysaccharides on treatments of infectious disease

Distribution and source appointment of rare earth elements in offshore sediments of Western Xiamen Bay, Southeast China

The REEs concentrations in offshore sediments (surface sediments and core sediments) of Western Xiamen Bay and some potential sources (parent materials, Pb-Zn deposit, vehicle exhaust, atmospheric dust, ship paint, coal combustion and domestic sewage sludge) were determined to investigate the geochemical characteristics and major sources of REEs in the sediments of Western Xiamen Bay. The results showed that the mean concentrations of REEs in surface sediments and core sediments were 245.9 mg.kg(-1) and 220.0 mg.kg(-1), respectively, which were close to the background value of topsoil in Xiamen City. There were negative Eu anomaly and no Ce anomaly in general and LREEs had a significant enrichment relative to HREEs. The results of enrichment factor showed that REEs were slightly enriched in surface sediments. The patterns of chondrite-normalized REE exhibited a negative slope, indicating that the REEs in surface sediments were mainly from the continental crust. Parameters and normalized patterns of REEs suggested that the sediments in Western Xiamen Bay were mainly from terrestrial sources and also affected by anthropogenic activities such as domestic sewage sludge and coal combustion. The results of Pearson's correlations, chondrite-normalized REEs distribution patterns and ternary plot of (La/Yb)(N-)(La/Sm)(N-)(Gd/Yb)(N) for the surface sediments and some potential sources indicated that the REEs accumulated in the surface sediments might be related to natural sources (parent materials and Pb-Zn deposit) and anthropogenic activities (coal combustion and domestic sewage sludge)

Transparent ββ-SiN4_4 and γγ-Si3_3N4_4 compacts synthesized with mixed-size precursor under high pressure and high temperature

Transparent polycrystalline ceramics exhibit improved mechanical and optical properties. However, synthesizing transparent ceramics without additives is nontrivial. Herein, we report the synthesis of two transparent ceramics ($β$-SiN$_4$ and $γ$-Si$_3$N$_4$) under high pressure and high temperature from a pure Si$_3$N$_4$ precursor with nano-/micro-dual grain sizes. Synthesized $β$-SiN$_4$ exhibited a significantly enhanced Vickers hardness reaching 24.2 GPa (at 10 N load) when transparency was achieved. Transparent nano-grained $γ$-Si$_3$N$_4$ exhibited a Vickers hardness of 37.3 GPa. These are the highest hardness values reported for these two phases at a 10 N load. Density and microstructure measurements suggest that the hardness and transparency of the specimens correlate with both the grain size and porosity/density. The negligible amount of pores accounts for the superior optical transparency and high hardness of two Si$_3$N$_4$ allotropes. As higher pressures can effectively suppress grain growth and minimize pores between grains, high-pressure sintering is demonstrated as an effective way to realize highly dense transparent ceramics

Conjugation of Inulin Improves Anti-Biofilm Activity of Chitosan

Bacteria biofilm helps bacteria prevent phagocytosis during infection and increase resistance to antibiotics. Staphylococcus aureus is a Gram-positive pathogenic bacterium and is tightly associated with biofilm-related infections, which have led to great threat to human health. Chitosan, the only cationic polysaccharide in nature, has been demonstrated to have antimicrobial and anti-biofilm activities, which, however, require a relative high dosage of chitosan. Moreover, poor water solubility further restricts its applications on anti-infection therapy. Inulins are a group of polysaccharides produced by many types of plants, and are widely used in processed foods. Compared to chitosan, inulin is very soluble in water and possesses a mild antibacterial activity against certain pathogenic bacteria. In order to develop an effective strategy to treat biofilm-related infections, we introduce a method by covalent conjugation of inulin to chitosan. The physicochemical characterization of the inulin-chitosan conjugate was assayed, and the anti-biofilm activity was evaluated against S. aureus biofilm. The results indicated that, as compared to chitosan, this novel polysaccharide-polysaccharide conjugate significantly enhanced activities against S. aureus either in a biofilm or planktonic state. Of note, the conjugate also showed a broad spectrum anti-biofilm activity on different bacteria strains and low cellular toxicity to mammalian cells. These results suggested that chitosan conjugation of inulin was a viable strategy for treatment against biofilm-related infections. This finding may further spread the application of natural polysaccharides on treatments of infectious disease