THG in dielectrics using low-energy tightly-focused ir femtosecond laser: third-order nonlinearity measurements and the evolution of laser-induced plasma

The third-order nonlinearity x ⁽³⁾ and other optical properties of LiF, CaF₂, fused silica, and free standing polymeric thin film are studied using a diagnostic technique based on the third-harmonic generation of tightly-focused femtosecond Cr:forsterite laser radiation. Time-resolved measurements of the plasma evolution in the bulk of a fused silica sample are performed by a pump-probe technique using the fundamental and third-harmonic radiation as a probe. With the use of the pump-probe technique, two types of the relaxation processes are registered.     

Improved delay-dependent stability criterion for neural networks with time-varying delays

In this Letter, the problem of stability analysis for neural networks with time-varying delays is considered. By constructing a new Lyapunov functional, a new delay-dependent stability criterion for the network is established in terms of LMIs (linear matrix inequalities) which can be easily solved by various convex optimization algorithms. Two numerical examples are included to show the effectiveness of proposed criterion.     

Effect of strain and nonparabolicity on interband transition energies of InAs/GaAs coupled double quantum dots

Strained potential profiles and electronic subband energies of InAs/GaAs coupled double quantum dots (DQDs) were calculated by using a three-dimensional finite-difference method (FDM) taking into account shape-based strain and nonparabolic effects. The interband transition energies from the ground electronic subband to the ground heavy-hole band (E₁-HH₁) in the InAs/GaAs DQDs, as determined from the FDM calculations taking into account strain and nonparabolic effects, were in reasonable agreement with the experimental peaks corresponding to the (E₁-HH₁) interband transition energies at several temperatures, as determined from the temperature-dependent photoluminescence spectra.     

A high-order incompressible flow solver with WENO

A numerical method for solving the incompressible Navier–Stokes equations with a 5th-order weighted essentially non-oscillatory (WENO) scheme is presented. The method is not based on artificial compressibility and is free of tunable parameters such as the artificial compressibility parameter. The method makes use of the fractional-step method in conjunction with the low-dissipation and low-dispersion Runge–Kutta (LDDRK) scheme to improve temporal accuracy of the scheme. The use of a WENO scheme makes it possible to obtain stable solutions for discontinuous initial data and resolve difficult applications with strong shear such as Kelvin–Helmholtz instability or turbulence. Good convergence rate is established for the velocity variables and numerical solutions of the present method compare well with exact solutions and other numerical results.     

Dominant frequencies of train-induced vibrations

This paper investigates the dynamic characteristics of ground vibrations induced by moving vehicles including the mass rapid transit system, high-speed train railway, and general railway on bridges, embankments, and in tunnels using field experiments and theoretical solutions. The results indicate that train-induced ground vibrations at the trainload dominant frequencies are significantly large for both subsonic and supersonic train speeds, and the vibrations from carriage natural frequencies and engine frequencies are minor. For trains moving on bridges, the resonant vibrations are serious when the natural frequencies of the bridge are close to the trainload dominant frequencies, but resonance does not occur when the carriage natural frequencies and trainload dominant frequencies match. The trainload dominant frequency and its influence factor can be computed using the two simple equations deducted in this paper.     

10吉比特长途DWDM系统工程设计中关键问题的探讨

本文从色散、色散斜率、光信噪比和可升级性等方面论述了10Gbit/s长途DWDM系统工程设计应该关注的问题.     

New route synthesis of indolizines via 1,3-dipolar cycloaddition of pyridiniums and alkynes

A convenient synthesis of 2,3-di and 1,2,3-trisubstituted indolizines has been achieved via a 1,3-dipolar cycloaddition of pyridiniums and alkynes. Various alkynes and diynes were used instead of dimethyl acetylenedicarboxylate (DMAD) and its analogues in the traditional method. The corresponding 1,2,3-trisubstituted indolizines are useful building blocks for the construction of complex indolizine derivatives.     

Morphological Transformation of Co(OH)2 Microspheres from Solid to Flowerlike Hollow Core–Shell Structures

Co(OH) ₂ that blooms : Flowerlike hollow spherical architectures of cobalt hydroxide obtained through a facile solvothermal process are reported for the first time (see picture). Their growth process involves aggregation of cobalt hydroxide nanoparticles into solid spheres and a hollowing effect through subsequent dissolution‐diffusion‐redeposition of the smaller crystallites under the surface layer.

     

Functionalization of Carbon Nanotubes with Water‐Insoluble Porphyrin in Ionic Liquid: Direct Electrochemistry and Highly Sensitive Amperometric Biosensing for Trichloroacetic Acid

A functional composite of single‐walled carbon nanotubes (SWNTs) with hematin, a water‐insoluble porphyrin, was first prepared in 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM][PF₆]) ionic liquid. The novel composite in ionic liquid was characterized by scanning electron microscopy, ultraviolet absorption spectroscopy, and electrochemical impedance spectroscopy, and showed a pair of direct redox peaks of the Fe^III/Fe^II couple. The composite–[BMIM][PF₆]‐modified glassy carbon electrode showed excellent electrocatalytic activity toward the reduction of trichloroacetic acid (TCA) in neutral media due to the synergic effect among SWNTs, [BMIM][PF₆], and porphyrin, which led to a highly sensitive and stable amperometric biosensor for TCA with a linear range from 9.0×10^?7 to 1.4×10^?4 M . The detection limit was 3.8×10^?7 M at a signal‐to‐noise ratio of 3. The TCA biosensor had good analytical performance, such as rapid response, good reproducibility, and acceptable accuracy, and could be successfully used for the detection of residual TCA in polluted water. The functional composite in ionic liquid provides a facile way to not only obtain the direct electrochemistry of water‐insoluble porphyrin, but also construct novel biosensors for monitoring analytes in real environmental samples.     

Single-phased white-light emitting CaAl<Subscript>2</Subscript>Si<Subscript>2</Subscript>O<Subscript>8</Subscript>: Eu<Superscript>2+</Superscript>, Mn<Superscript>2+</Superscript> phosphors prepared by a sol–gel method

CaAl₂Si₂O₈: Eu²⁺, Mn²⁺ phosphors have been prepared by a sol–gel method. X-ray diffractometer, spectrofluorometer and UV–Vis spectrometer were used to characterize structural and optical properties of the samples. The results indicate that anorthite (CaAl₂Si₂O₈) directly crystallizes at 1000 °C in the sol–gel process. CaAl₂Si₂O₈: Eu²⁺, Mn²⁺ phosphors show two emission bands excited by ultraviolet light. Blue (around 415 nm) and yellow (around 575 nm) emissions originate from Eu²⁺ and Mn²⁺, respectively. With appropriate tuning of Mn²⁺ content, CaAl₂Si₂O₈: Eu²⁺, Mn²⁺ phosphors exhibit different hues and relative color temperatures.