Method to reduce errors of droplet sizing based on the ratio of fluorescent and scattered light intensities (laser-induced fluorescence/Mie technique)

The droplet sizing accuracy of the laser technique, based on the ratio of laser-induced fluorescence (LIF) and scattered light (Mie) intensities from droplets, is examined. We develop an analytical model of the ratio of fluorescent to scattered light intensities of droplets, which shows that the LIF/Mie technique is susceptible to sizing errors that depend on the mean droplet size and the spread of the droplet size distribution. The sizing uncertainty due to the oscillations of the scattered light intensity as a function of droplet size is first quantified. Then, a new data processing method is proposed that can improve the sizing uncertainty of the technique for the sprays that were examined in this study by more than 5% by accounting for the size spread of the measured droplets, while improvements of 25% are possible when accounting for the mean droplet size. The sizing accuracy of the technique is evaluated in terms of the refractive index of liquid, scattering angle, and dye concentration in the liquid. It is found that the proposed approach leads to sizing uncertainty of less than 14% when combined with light collection at forward scattering angles close to 60° and the lowest fluorescent dye concentration in the liquid for all refractive indices.     

电润湿效应控制介质上液滴运动的数值模拟

电润湿效应是利用电极阵列所产生的变化电场,改变液滴表面张力,实现控制液滴在微小通道内的运动.本文采用数值模拟方法模拟液滴在介质上的电润湿效应.用level set函数方法捕捉液滴表面,得到表面张力,通过压力方程和N-S方程依次求解压力场和速度场.采用3×3的电极方阵控制液滴运动,数值结果表明电润湿效应能在较低电压下,实现对液滴移动的控制.并给出液滴可移动的电极间距极限值100μm.     

Surface-roughness measurement based on the intensity correlation function of scattered light under speckle-pattern illumination

The statistical properties of speckle patterns generated from a rough surface under a fully developed static speckle-pattern illumination are examined. The roughness dependence of the intensity autocorrelation function is studied and utilized to characterize typical engineering surfaces with anisotropic roughness. The speckle patterns under investigation are recorded by use of a CCD technique and are then analyzed by digital image processing algorithms to obtain a parameter that describes the surface roughness. It is shown that an in-process surface inspection can be achieved by this method.     

Optimized parameters and exponents of Mie (n,m) intermolecular potential energy function based on the shape of molecules

Through the use of the second virial coefficient data, optimized parameters and exponents of the Mie (n,m) potential energy function are derived for a number of symmetric groups of molecules. In the optimizations performed, parameters of the potential function are varied for each molecule, but the exponents of the potential function are taken as functions of the shape of the groups of molecules considered. It is concluded that the attractive exponent, m = 7, is shared by all the symmetric groups considered. The repulsive exponent, n, is varied according to the shape of the molecules. Also, in this report, newly calculated parameters of the Lennard-Jones (12,6) and Mie (14,7) potential energy functions for 33 different symmetric and nonsymmetric molecules are reported. Results indicate that, generally, the Mie (14,7) pair-potential energy function is a better fit for the second virial coefficient data than the Lennard-Jones (12,6) function.     

Turn-on and near-infrared fluorescent sensing for 2,4,6-trinitrotoluene based on hybrid (gold nanorod)-(quantum dots) assembly

In this study, we design a FRET system consisting of gold nanorod (AuNR) and quantum dots (QDs) for turn-on fluorescent sensing of 2,4,6-trinitrotoluene (TNT) in near-infrared region. The amine-terminated AuNR and carboxyl-terminated QDs first form a compact hybrid assembly through amine-carboxyl attractive interaction, which leads to a high-efficiency (>92%) FRET from QDs to AuNRs and an almost complete emission quenching. Next, added TNT molecules break the preformed assembly because they can replace the QDs around AuNRs, based on the specific reaction of forming Meisenheimer complexes between TNT and primary amines. Thus, the FRET is switched off, and a more than 10 times fluorescent enhancement is obtained. The fluorescence turn-on is immediate, and the limit of detection for TNT is as low as 0.1 nM. Importantly, TNT can be well distinguished from its analogues due to their electron deficiency difference. The developed method is successfully applied to TNT sensing in real environmental samples.     

Observation of Ga droplet formation on (311)A and (511)A GaAs surfaces

Using (100) GaAs substrates as a reference, we present a study of the formation of Ga droplets on (311)A and (511)A GaAs substrates in which the effect of both the substrate temperature and the amount of Ga supplied on the droplet density and height for the three different surfaces have been investigated. Droplets on (100) substrates show a round shape; however, they appear as elongated balls with tails along the [Formula: see text] direction of the (311)A substrate and the [Formula: see text] direction of the (511)A substrate. It has been found that the Ga droplets on (511)A surfaces have lower densities and higher heights than those on (100) substrates. In contrast, Ga droplets on (311)A surfaces have lower heights and much higher densities compared to those for both (100) and (511)A. We observed that the decrease in the droplet density with increasing growth temperature for both (311)A and (511)A is more than twice that for the (100)GaAs surface due to the larger drop in the nucleation rate. Based on these observations, we offer a physical explanation based on the thermodynamics and the anisotropy of the high-index surfaces.     

磺化聚醚砜上浆剂对碳纤维/聚醚砜复合材料界面性能的影响

为了提高碳纤维(CFs)增强热塑性树脂聚醚砜(PES)复合材料的界面结合力,对PES进行磺化改性,得到磺酸基聚醚砜(SPES)制备的CFs上浆剂,研究了SPES上浆剂对CFs/PES复合材料界面性能的影响和上浆剂质量分数对CFs/PES复合材料的作用效果。结果表明:经过SPES上浆的纤维毛丝量降低、耐磨性提高。同时FTIR和XPS分析表明:SPES中的—SO3H基团与CFs表面微量的活性官能团发生了化学反应,提高了增强体CFs与基体树脂PES间的黏连。当上浆剂含量为1wt%时,CFs/PES复合材料的层间剪切强度(ILSS)提高最显著,比未上浆改性的CFs/PES复合材料的提高了24%。SEM照片证实在此浓度下CFs与PES结合更加紧密。动态力学热分析(DMTA)结果亦证明1wt%的SPES上浆剂提高了CFs/PES复合材料的玻璃化转变温度。     

An inverse light scattering technique for morphological characterization of irregular particles based on the Gaussian-random-sphere model

The Gaussian-random-sphere model is employed for morphological characterization of nonspherical, irregular particles using an inverse light scattering technique. The synthetic measurement data consist of reduced scattering spectra caused by an aggregate of irregular particles randomly oriented in turbid media and are generated using the discrete dipole approximation. The proposed method simultaneously retrieves the concentration and shape parameters of particles using the data collected at multiple wavelengths. The performance of the inverse algorithm is tested using noise-corrupted data, in which up to 50% noise may be added to the observed scattering spectra.     

Modelling of the viscoelastic behaviour of amorphous thermoplastic/glass beads composites based on the evaluation of the complex Poisson's ratio of the polymer matrix

A series of polystyrene/glass beads composites were studied by using dynamic mechanical spectrometry. From experimental data obtained under isothermal conditions, a simulation method of viscoelastic behaviour of amorphous thermoplastics reinforced by glass beads was devised. Such a theoretical approach confirmed the requirement of considering the Poisson's ratio as a complex component over all the temperature range. This could be related to the difference of many powers of ten between the moduli of the two phases. Thus, we suggest in this paper a method to evaluate the complex Poisson's ratio of the matrix. From these results, the influence of filler content on the magnitude of the mechanical relaxation related to the glass transition is taken into account.     

Incorporation of new technique for processing of Al/SiCp composites based on evaporative pattern casting (EPC) method

Abstract

A336 Al matrix composites containing different volume fraction and mean mass particle size of SiC particles as the reinforcing phase were synthesised by evaporative pattern casting (EPC) route. The process consisted of fabricating of EPS/SiC_p composite pattern followed by EPC of A336 Al alloy. The EPS/SiC_p pattern was made by blending SiC particles with expandable polystyrene (EPS) beads and placing them in expanding mould heating with steam until EPS beads expand completely. Uniform distributed SiC particles around the EPS beads and locally movement of them during pouring and degradation leads to homogenous distribution of particles in final Al/SiC_p composite. Higher modulus, strength and hardness were observed in the composites than the unreinforced Al alloy part. The fracture surfaces of the composite samples exhibited dimple surfaces and fracture in SiC particles.     

An improved algorithm of sequential number-theoretic optimization (SNTO) based on clustering technique

The sequential number-theoretic optimization (SNTO) method for global optimization is improved by means of the clustering technique. In this way the improved SNTO method can easily locate potential regions for sequential search for the global optimum, thus overcoming the difficulty of the original SNTO needing the correct number of points uniformly scattering in search space for the first search. The complexity of the studied object function can be investigated with the help of the star discrepancy D*. The identification of unimodal and multimodal objective functions seems also to be possible. These findings are supported by calculations for simulated and real systems with two-way data.     

Software design specification and analysis technique (SDSAT) for the development of safety-critical systems based on a programmable logic controller (PLC)

This paper introduces a Software Design Specification and Analysis Technique (SDSAT) for safety-critical systems based on a Programmable Logic Controller (PLC). During software development phases, the design phase performs an important role in connecting the requirements phase and the implementation phase, and it is a process of translating software requirements into software structures. In this work, the Nuclear FBD-style Design Specification and analysis (NuFDS) approach was proposed for nuclear Instrumentation and Control (I&C) software. The NuFDS approach is suggested in a straightforward manner for effective and formal software design specification and analysis. Accordingly, the proposed NuFDS approach is composed of a software design specification technique and a software design analysis technique. In addition, for tool support in the design phase, we developed the NuSDS tool based on the NuFDS approach; this tool is used specifically for generating software design specification and analysis for nuclear fields.     

Selective and sensitive fluorescent sensors for metal ions based on manipulation of side-chain compositions of poly(p-phenyleneethynylene)s

The syntheses and metal-responsive properties of poly(p-phenyleenethynylene)s with grafted new pseudo-crown-ether groups are reported. These polymers exhibit high sensitivities to alkali ions because of their collective optical properties, which are very sensitive to ion-induced conformational changes. The quenching of polymer fluorescence caused by the conformational changes is proportional to the ion concentration. The selectivity of the sensing materials toward Li(+) ions is significantly enhanced by controlling the size of the binding site via manipulation of the polymer side-chain compositions. The polymers are very stable for their six-month solid-state storage at room temperature.     

Self-sensing and dispersive evaluation of single carbon fiber/carbon nanotube (CNT)-epoxy composites using electro-micromechanical technique and nondestructive acoustic emission

Self-sensing and interfacial evaluation were investigated with different dispersion solvents for single carbon fiber/carbon nanotube (CNT)-epoxy composites by electro-micromechanical technique and acoustic emission (AE) under loading/subsequent unloading. The optimized dispersion procedure was set up to obtain improved mechanical and electrical properties. Apparent modulus and electrical contact resistivity for CNT-epoxy composites were correlated with different dispersion solvents for CNT. CNT-epoxy composites using good dispersion solvents exhibited a higher apparent modulus because of better stress transferring effects due to the relatively uniform dispersion of CNT in epoxy and enhanced interfacial adhesion between CNT and the epoxy matrix. However, good solvents exhibited a higher apparent modulus but lower thermodynamic work of adhesion, W_a for single carbon microfiber/CNT-epoxy composite. It is attributed to the fact that hydrophobic behavior with high advanced contact angle was observed for CNT-epoxy in the good solvent, which might not be compatible well with the carbon microfiber. Damage sensing was also detected simultaneously using AE combined with electrical resistance measurement. Electrical resistivity increased stepwise with progressing fiber fracture due to the decrease in electrical contact by the CNT.     

Shearing interferometer based on second-harmonic generation and a novel technique of n(2) direct measurements

We present a new wave-front sensitive interferometry technique (called dispersion shearing interferometry) for the measurement of both the sign and the magnitude of n(2). The interference pattern is produced by two laterally shifted second harmonics of the laser source. Only the fundamental wave passes through the nonlinear sample, which is placed before the interferometer. We demonstrate this technique on an aggregated colloidal silver solution using a YAG:Nd laser and KTiOPO(4) frequency doublers.     

A fluorescent probe based on visible light-emitting functionalized Graphene Quantum dots for the sensitive and selective detection of Pb (II) ions

Journal of Materials Science - We demonstrate a functionalization strategy to improve the basic fluorescence properties and to systematically customize the bandgap properties of Graphene quantum...     

Influence of Mn/S molar ratio on the microstructure and optical properties of MnS nanocrystals synthesized by wet chemical technique

Manganese sulfide (MnS) microparticles have been successfully synthesized at three different Mn/S ratios of 1:1, 1:2 and 2:1 by wet chemical technique. The effect of molar ratio on crystal structures, morphologies and optical properties of as-prepared sample has been investigated. The particle size, micro strain and dislocation density of MnS particles have been estimated by modified Scherrer formula from X-ray diffraction peak broadening analysis. It has also identified the phase transformation from the metastable β-MnS into γ-MnS microparticles. This work presents the results of morphological characterization by scanning electron microscope. It is evident from the SEM image that MnS particles are almost spherical in shape. The UV–Visible absorption study revealed to determine the optical band gap of the MnS microparticles which shows a blue shift with decreasing particle size and the observed band gap lies in the range of 6.03–4.70 eV. The photoluminescence spectrum of as-prepared samples showed that the two main emission peaks corresponding to the strong UV blue emissions.     

Fabrication and evaluation of oxidation resistance performance of open-celled Fe(Al) foam by space-holder technique

First, fabrication of Fe(Al) open-cell foams by using space-holder technique, in which NaCl powder and polyester resin were utilized as space holder and binder, was investigated. Fe(Al) powder were prepared via mechanical alloying method after 5 h milling process. Then, the influences of fabrication parameters, alloying element Al content, time of milling process, sintering temperature and soaked time on the oxidation resistance performance of foam specimens at 800 °C were mainly studied. The experimental results exhibit that alloying with 2 wt.% Al resulted in acceleration of the oxidation rate of foam samples, additionally, alloying with 4 wt.% Al had a little positive effect on oxidation rate at 800 °C. However, the oxidation resistance of the 10 wt.% Al-containing sample greatly improves compared to pure Fe. In addition, the oxidation resistance performance of prepared foam was improved by increasing the milling time up to 15 h, and followed by a decrease gradually. The increase of sintering temperature and the prolongation of soaked time to 1100 °C and 90 min, respectively had significant positive effect on the oxidation resistance.     

The effects of O2/Ar ratio on the structure and properties of hafnium dioxide (HfO2) films

HfO₂ films at various O₂/Ar flow ratios were prepared by reactive dc magnetron sputtering. The effects of O₂/Ar ratio on the structure and properties of HfO₂ films were studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and UV-Visible spectroscopy. The results showed that the HfO₂ films were amorphous at different O₂/Ar ratios, and the atomic ratio of O/Hf in the HfO₂ films at high O₂/Ar ratio was nearly to 2:1. The peaks of Hf4f and O1s shifted to higher binding energy with increasing the oxygen flow proportion. The HfO₂ films at high O₂/Ar ratio had high transmissivity at the range of 400-1100 nm.