A dual-grating InGaAsP/InP DFB laser integrated with an SOA for THz generation

We report a dual-mode semiconductor laser that has two gratings with different periods below and above the active layer. A semiconductor optical amplifier (SOA), which is integrated with the dual-mode laser, plays an important role in balancing the optical power and reducing the linewidths of the emission modes. A stable two mode emission with the 13.92-nm spacing can be obtained over a wide range of distributed feedback and SOA injection currents. Compared with other types of dual-mode lasers, our device has the advantages of simple structure, compact size, and low fabrication cost

Knowledge Distillation for Small-footprint Highway Networks

Deep learning has significantly advanced state-of-the-art of speech recognition in the past few years. However, compared to conventional Gaussian mixture acoustic models, neural network models are usually much larger, and are therefore not very deployable in embedded devices. Previously, we investigated a compact highway deep neural network (HDNN) for acoustic modelling, which is a type of depth-gated feedforward neural network. We have shown that HDNN-based acoustic models can achieve comparable recognition accuracy with much smaller number of model parameters compared to plain deep neural network (DNN) acoustic models. In this paper, we push the boundary further by leveraging on the knowledge distillation technique that is also known as {\it teacher-student} training, i.e., we train the compact HDNN model with the supervision of a high accuracy cumbersome model. Furthermore, we also investigate sequence training and adaptation in the context of teacher-student training. Our experiments were performed on the AMI meeting speech recognition corpus. With this technique, we significantly improved the recognition accuracy of the HDNN acoustic model with less than 0.8 million parameters, and narrowed the gap between this model and the plain DNN with 30 million parameters.Comment: 5 pages, 2 figures, accepted to icassp 201

The strong vertices of charmed mesons DD, D∗D^{*} and charmonia J/ψJ/\psi, ηc\eta_{c}

In this work, the strong form factors and coupling constants of the vertices $DDJ/\psi$, $DD^{*}J/\psi$, $D^{*}D^{*}J/\psi$, $DD^{*}\eta_{c}$, $D^{*}D^{*}\eta_{c}$ are calculated within the framework of the QCD sum rule. For each vertex, we analyze the form factor considering all possible off-shell cases and the contributions of the vacuum condensate terms $\langle\overline{q}q\rangle$, $\langle\overline{q}g_{s}\sigma Gq\rangle$, $\langle g_{s}^{2}G^{2}\rangle$, $\langle f^{3}G^{3}\rangle$ and $\langle\overline{q}q\rangle\langle g_{s}^{2}G^{2}\rangle$. Then, the form factors are fitted into analytical functions $g(Q^2)$ and are extrapolated into time-like regions to get the strong coupling constants. Finally, the strong coupling constants are obtained by using on-shell cases of the intermediate mesons($Q^2=-m^2$). The results are as follows, $g_{DDJ/\psi}=5.01^{+0.58}_{-0.16}$, $g_{DD^{*}J/\psi}=3.55^{+0.20}_{-0.21}$GeV$^{-1}$, $g_{D^{*}D^{*}J/\psi}=5.10^{+0.59}_{-0.43}$, $g_{DD^{*}\eta_{c}}=3.68^{+0.39}_{-0.11}$ and $g_{D^{*}D^{*}\eta_{c}}=4.87^{+0.42}_{-0.40}$GeV$^{-1}$

Construction health and safety: A topic landscape study

We aim to draw in-depth insights into the current literature in construction health and safety and provide perspectives for future research efforts. The existing literature on construction health and safety is not only diverse and rich in sight, but also complex and fragmented in structure. It is essential for the construction industry and research community to understand the overall development and existing challenges of construction health and safety to adapt to future new code of practice and challenges in this field. We mapped the topic landscape followed by identifying the salient development trajectories of this research area over time. We used the topic modeling algorithm to extract 10 distinct topics from 662 abstracts (filtered from a total of 895) of articles published between 1991 and 2020. In addition, we provided the most cited references and the most popular journal per topic as well. The results from a time series analysis suggested that the construction health and safety would maintain its popularity in the next 5 years. Research efforts would be devoted to the topics including “Physical health and disease”, “Migrant and race”, “Vocational ability and training”, and “Smart devices.” Among these topics, “Smart devices” would be the most promising one

Tetra­kis[μ-2-(3,4-dimeth­oxy­phen­yl)acetato]-κ3 O 1,O 1′:O 1;κ3 O 1:O 1,O 1′;κ4 O 1:O 1′-bis­{[2-(3,4-dimeth­oxy­phen­yl)acetato-κ2 O 1,O 1′](1,10-phenanthroline-κ2 N,N′)erbium(III)}

In the dimeric centrosymmetric title complex, [Er2(C10H11O4)6(C12H8N2)2], the ErIII ion is nine-coordinated by five 2-(3,4-dimeth­oxy­lphen­yl)acetic acid (DMPA) ligands via seven O atoms and two N atoms from a bis-chelating 1,10-phenanthroline (phen) ligand in a distorted tricapped trigonal-prismatic geometry. The DMPA ligands are coordinated to the ErIII ion in bis-chelate, bridging and bridging tridentate modes. Relatively weak intra­molecular C—H⋯O inter­actions reinforce the stability of the mol­ecular structure. Inter­molecular C—H⋯O inter­actions are also observed

Tris{2-meth­oxy-6-[(4-methyl­phen­yl)iminiometh­yl]phenolate-κ2 O,O′}tris­(thio­cyanato-κN)europium(III)

The metal center in the structure of the title compound, [Eu(NCS)3(C15H15NO2)3], is coordinated by three Schiff base 2-meth­oxy-6-[(4-methyl­phen­yl)iminiometh­yl]phenolate (L) ligands and three independent thio­cyanate ions. In the crystal structure, the acidic H atom is located on the Schiff base N atom and hydrogen bonded to the phenolate O atom. The coordination environment of the EuIII ion is nine-coordinate by three chelating methoxy­phenolate pairs of O atoms and three N-atom terminals of the thio­cyanate ions. The compound is isostructural with the CeIII analogue [Liu et al. (2009 ▶). Acta Cryst. E65, m650]

Tris{2-meth­oxy-6-[(4-methyl­phen­yl)iminiometh­yl]phenolato-κ2 O,O′}tris­(thio­cyanato-κN)praseodymium(III) monohydrate

The asymmetric unit of title compound, [Pr(NCS)3(C15H15NO2)3]·H2O, consists of three Schiff base 2-meth­oxy-6-[(4-methyl­phen­yl)imino­meth­yl]phenol (HL) ligands, three independent thio­cyanate anions and an uncoordinated water mol­ecule. The PrIII ion is nine-coordinated. The thio­cyanate anions coordinate to the PrIII ion via the N atoms and the three HL ligands chelate the PrIII ion via the phenoxy and meth­oxy O atoms. The protonated imine N atoms are involved in intra­molecular hydrogen bonds with the phenolate groups