Turbulence modulation model for gas–particle flow based on probability density function approach

The paper focuses on the turbulence modulation problem in gas–particle flow with the use of probability density function(PDF) approach. By means of the PDF method, a general statistical moment turbulence modulation model without considering the trajectory difference between two phases is derived from the Navier–Stokes equations. A new turbulence production term induced by the dispersed-phase is analyzed and considered. Furthermore, the trajectory difference between two media is taken into account. Subsequently, a new k–ε turbulence modulation model in dilute particle-laden flow is successfully set up. Then, the changes to several terms, including the turbulence production, dissipation, and diffusion terms, are well described consequently. The promoted model provides a more probable explanation for the modification of particles on the turbulence. Finally, we applied the model to simulate a gas–particle turbulence flow case in a wall jet, and found that the simulation results agree well with the experimental data.     

Shock wave dispersion of gas–particle mixtures

The decay of a discontinuity in a two-component homogeneous gas mixture and the dispersion of a gas–particle mixture with a two-component carrier medium are numerically simulated. The mathematical model of the dynamics of heterogeneous media takes into account the interphase force interaction and interphase heat exchange. Experimental results known from the literature are compared with numerical results describing the dispersion of a gas–particle mixture in a shock tube.     

Landauer–Datta–Lundstrom model for terahertz transistor amplifier based on graphene

A transistor has been considered in the form of three electrodes connected by graphene ribbons or by metal quantum wires (nanowires) that operate on the principle of the current control by the changing voltage at the central electrode (gate). The analysis has been carried out according to the Landauer–Datta–Lundstrom model in equilibrium approximation for electrodes while fixing their potentials. We have obtained linear models and nonlinear terms in the determining current, and calculated the nonlinear current–voltage performances of graphene nanoribbons.     

Noise estimation based on time–frequency correlation for speech enhancement

As a fundamental part of speech enhancement, noise estimation is particularly challenging in highly non-stationary noise environments. In this work, we propose an effective algorithm on the basis of the “Improved Minima Controlled Recursive Averaging (IMCRA)” with the objective to improve the performance of noise estimation. The main contributions of this work are: (i) in the algorithm, a rough decision about speech presence is proposed by calculating the autocorrelation and cross-channel correlation of the T–F (Time–Frequency) units; (ii) with this decision, we refine the smoothing parameters for the smoothing of noisy power spectrum and the recursive averaging in noise spectrum estimation as well as the weighting factor for the a priori SNR (Signal to Noise Ratio) estimation in the IMCRA; (iii) we improve the search of local minima during spectral bursts by adding a minimum search with a shorter window. Extensive experiments are carried out to evaluate the performance of our proposed algorithm. The experimental results illustrate that, compared with the IMCRA, the proposed approach significantly improves the accuracy of noise spectrum estimation and the quality of enhanced speech in the typical noise situations.     

Studies on Nd:YAG Single-pass Amplifiers for High-power Q-switched Laser System

The output of Nd∶YAG single-pass laser amplifiers is studied analytically and experimentally. Methods of analysis for single-pass Nd∶YAG laser amplifier are presented. A flashlamp-pumped Q-switched Nd∶YAG oscillator/amplifier laser system has been developed with the average output power of 121.5 W.     

Studies on Nd∶YAG Single-pass Amplifiers for High-power Q-switched Laser System

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Active media for tunable blue–green lasers based on aminocoumarins in polymethylmethacrylate

The lasing characteristics of 17 aminocoumarins in solutions and polymer polymethylmethacrylate (PMMA) matrix pumped by exciplex XeCl-laser radiation (_pump=308 nm) are investigated. It is demonstrated that 4-CF₃ and 3-substituted coumarins are promising for the preparation of solid-state active media for tunable blue–green lasers. PACS 42.55.Mv; 42.55.Px     

Diluted magnetic semiconductors based on II–VI compounds for photovoltaic detector applications

Infrared photovoltaic p−n junction detectors fabricated by using ternary and quaternary diluted magnetic semiconductors (also called semimagnetic semiconductors) are reviewed. The methods of material and detector preparation are described and the experimental results of the electrical and photoelectric measurements of the detectors are briefly discussed. Some singularities of both the materials and the technological techniques as well as their impact upon the properties of the detectors are analyzed.     

Novel fusion method for visible light and infrared images based on NSST–SF–PCNN

The purpose of image fusion is to combine the source images of the same scene into a single composite image with more useful information and much better visual effects, which is undoubtedly suitable for further image processing tasks. This paper presented a novel fusion method for visible light and infrared images based on non-subsampled shearlet transform (NSST)–spatial frequency (SF)–pulse coupled neural network (PCNN). As a recently developed multi-resolution geometric analysis tool, NSST not only has remarked superiorities over other past conventional tools in terms of information capturing and computational costs saving, but also overcomes the lack of shift-invariance in shearlet transform (ST), so NSST applies to conducting the decompositions and reconstructions. Besides, traditional PCNN model is also upgraded to be an improved one called IPCNN in this paper to fuse the low-frequency and high-frequency subband coefficients. In the IPCNN structure, on the one hand, the value of the linking strength β is determined by the SF which represents the gradient features of the subband image; on the other hand, the time matrix is utilized to adaptively decide the iteration number of the IPCNN model, which is helpful to increase the function efficiency and save computational resources. Experimental results indicate that the proposed method performs well and has obvious superiorities over other current typical ones in both subjective visual performance and objective criteria.     

High-power 3.8 μm tunable optical parametric oscillator based on PPMgO:CLN

The experimental results of a high-power 3.8 μm tunable laser are presented on a quasi-phase-matched single-resonated optical parametric oscillator in PPMgO:CLN pumped by a 1064 nm laser of an elliptical beam. Theoretical analyses of the PPMgO:CLN wavelength tuning are presented. The pump source was an acousto-optical Q-switched cw-diode-side-pumped Nd:YAG laser. The beam polarization matched the e-ee interaction in PPMgO:CLN. When the crystal was operated at 90 °C and the pump power was 150 W with a repetition rate of 10 kHz, average output power of 22.6 W at 3.86 μm and 63 W at 1.47 μm was obtained. The slope efficiency of the 3.86 μm laser with respect to the pump laser was 17.8%. The M² factors of the 3.86 μm laser were 1.74 and 4.86 in the parallel and perpendicular directions, respectively. The mid-IR wavelength tunability of 3.7-3.9 μm can be achieved by adjusting the temperature of a 29.2 μm period PPMgO:CLN crystal from 200 °C to 30 °C, which basically is accorded with the theoretic calculation.     

Ultrarelativistic Bose–Einstein gas on Lorentz symmetry violation

In this paper, we study the effects of Lorentz Symmetry Breaking on the thermodynamic properties of ideal gases. Inspired by the dispersion relation coming from the Carroll–Field–Jackiw model for Electrodynamics with Lorentz and CPT violation term, we compute the thermodynamics quantities for a Boltzmann, Fermi–Dirac and Bose–Einstein distributions. Two regimes are analyzed: the large and the small Lorentz violation. In the first case, we show that the topological mass induced by the Chern–Simons term behaves as a chemical potential. For Bose–Einstein gases, a condensation in both regimes can be found.     

Preparation of poly(vinyl alcohol)–silicone based hybrid membranes for the pervaporation separation of water–acetic acid mixtures

Hybrid membranes were prepared using poly(vinyl alcohol) (PVA) and tetraethylorthosilicate (TEOS) via hydrolysis followed by condensation. The obtained membranes were characterized by Fourier transform infrared spectroscopy, wide-angle x-ray diffraction and differential scanning calorimetry. A remarkable decrease in degree of swelling was observed with increasing TEOS content in membranes and is attributed to the formation of hydrogen bonding and covalent bonds in the membrane matrix. The pervaporation performance of these membranes for the separation of water–acetic acid mixtures was investigated in terms of feed concentration and the content of TEOS used as cross-linking agent. The membrane containing 1 : 2 mass ratio of PVA and TEOS gave the highest separation selectivity of 1116 with a flux of 3.33 × 10^?2kg/m²h at 30°C for 10 mass% of water in the feed. Except for membrane M-1, the observed values of water flux are close to the values of total flux in the investigated composition range, signifying that the developed membranes are highly water selective. From the temperature dependence of diffusion and permeation values, the Arrhenius apparent activation parameters have been estimated. The resulting activation energy values obtained, showing that water permeation is lower than that of acetic acid, suggest that the membranes have higher separation efficiency. The activation energy values calculated for total permeation and water permeation are close to each other for all the membranes except membrane M-1, signifying that coupled-transport is minimal because of the higher selective nature of membranes. The negative heat of sorption values (ΔH _s) for water in all the membranes suggests a Langmuir mode of sorption.     

Structural characterization and X-ray analysis by Williamson–Hall method for Erbium doped Aluminum Nitride nanoparticles,synthesized using inert gas condensation technique

We have synthesized AlN nanoparticles (NPs) doped in-situ with Er (AlN:Er) using inert gas condensation technique. Using x-ray diffraction (XRD) peak broadening analysis with the Williamson–Hall (W–H) Uniform Deformation Model (UDM) the crystallite size of the NPs and the strain in NPs were found to be 80±38 nm and 3.07×10⁻³±0.9×10⁻³ respectively. In comparison, using the Debye–Scherrer's (DS) formula, we have inferred that the crystallite size of the NPs was 23±6 nm and the average strain was 4.3×10⁻³±0.4×10⁻³. The scanning electron microscopy images show that the NPs are spherical and have an average diameter of ∼300 nm. The crystallite size is smaller than the size of the NPs revealing their polycrystalline behavior. In addition, the NPs strain, stress and energy density were also calculated using W–H analysis combined with the Uniform Deformation Stress Model (UDSM) and the Uniform Deformation Energy Density Model (UDEDM). Suggested by the spherical geometry and polycrystalline nature of the AlN NPs, the strain computed from UDM, UDSM and UDEDM were in agreement confirming an isotropic mechanical nature of the particle. Luminescence measurements revealed the temperature dependence of the optical emission of the Er³⁺ ions, confirming the use of AlN:Er NPs for nano-scale temperature sensing.     

Development of proton conducting biopolymer membrane based on agar–agar for fuel cell

A proton-conducting polymer electrolyte based on agar and ammonium nitrate (NH₄NO₃) has been prepared through solution casting technique. The prepared polymer electrolytes were characterized by impedance spectroscopy, X-ray diffraction, and Fourier transform infra-red spectroscopy. Impedance analysis shows that sample with 60 wt.% NH₄NO₃ has the highest ionic conductivity of 6.57 × 10⁻⁴ S cm⁻¹ at room temperature. As a function of temperature, the ionic conductivity exhibits an Arrhenius behaviour increasing from 6.57 × 10⁻⁴ S cm⁻¹ at room temperature to 1.09 × 10⁻³ S cm⁻¹ at 70 °C. Transport parameters of the samples were calculated using Wagner’s polarization method and thus shows that the increase in conductivity is due to the increase in the number of mobile ions. Fuel cell has been constructed with the highest proton conductivity polymer 40agar/60NH₄NO₃ and the open circuit voltage is found to be 558 mV.

     

Accurate calibration for a camera–projector measurement system based on structured light projection

The accurate calibration for a camera–projector measurement system based on structured light projection is important to the system measurement accuracy. This study proposes an improved systematic calibration method focusing on three key factors: calibration model, calibration artifact and calibration procedures. The calibration model better describes the camera and projector imaging process by considering higher to fourth order radial and tangential lens distortion. The calibration artifact provides a sufficient number of accurate 3D reference points uniformly distributed in a common world coordinate system. And the calibration procedures calibrate the camera and projector simultaneously based on the same reference points to eliminate the influences of the camera calibration error on the projector calibration. The experiments demonstrate that our calibration method can improve the measurement accuracy by 47%.     

In-fiber Mach–Zehnder interferometer based on multi-mode fiber and up-taper for curvature sensing

A new type of curvature sensor comprises a stub of multi-mode fiber and an up-taper is proposed and demonstrated experimentally. The whole fabrication process is quite simple and the sensor head is cost effective. Measurement results show that it has a maximum curvature sensitivity of −61.877 nm/m⁻¹ at 1.1718 m⁻¹ (the highest value of reported papers among in-fiber Mach–Zehnder interferometers) and −9.2115 nm/m⁻¹ from 0.865 m⁻¹ to 1.1172 m⁻¹. Temperature sensitivity of 89.01 pm/°C within the range of 20–80 °C has also been achieved, which implies the possibility for measurement of temperature.     

Structural-colored silk based on Ti–Si bilayer

In this Letter, Ti–Si bilayer was deposited on white silk to achieve coloration of the silk. By controlling the thickness of the Ti layer and Si layer, the saturation and the hue of the color on the silk could be preciously modulated, respectively. The structural colors on the silk could cover the major colors in the International Commission on Illumination 1931 chromaticity diagram, and it exhibits good durability, which is demonstrated by rubbing and stretching treatments. The developed textile coloration method may provide an eco-friendly technology in the silk dyeing industry.