In-Situ Measuring the Particle Mean Size and Dust Concentration by Near-Forward Small Angle Light Scattering

This paper presents a method of measuring the particle mean size and dust concentration by small angle near forward light scattering optics and the extinction theory. Its theory is based on Fraunhofer diffraction theory which is the approximation of Mie scattering within the forward Fraunhofer diffraction lobe, and Rosin Rammler function is introduced to describe the particle size distribution in two phase flow in advance. Compared with the values by the sample weight method, the measurement results have a reasonable agreement. The present work has demonstrated that this method will be probably used to monitor the parameters of two phase flow.

Reconstructed Light Extinction Coefficients Using Chemical Compositions of PM_(2.5) in Winter in Urban Guangzhou, China

The objective of this study was to reconstruct light extinction coefficients （b ext ） according to chemical composition components of particulate matter up to 2.5 μm in size （PM 2.5 ）. PM 2.5 samples were collected at the monitoring station of the South China of Institute of Environmental Science （SCIES, Guangzhou, China） during January 2010, and the online absorbing and scattering coefficients were obtained using an aethalometer and a nephelometer. The measured values of light absorption coefficient by particle （b ap ） and light scattering coefficient by particle （b sp ） significantly correlated （R 2 0.95） with values of b ap and b sp that were reconstructed using the Interagency Monitoring of Protected Visual Environments （IMPROVE） formula when RH was 70%. The measured b ext had a good correlation （R 2 0.83） with the calculated b ext under ambient RH conditions. The result of source apportionment of b ext showed that ammonium sulfate [（NH 4 ） 2 SO 4 ] was the largest contributor （35.0%） to b ext , followed by ammonium nitrate （NH 4 NO 3 , 22.9%）, organic matter （16.1%）, elemental carbon （11.8%）, sea salt （4.7%）, and nitrogen dioxide （NO 2 , 9.6%）. To improve visibility in Guangzhou, the effective control of secondary particles like sulfates, nitrates, and ammonia should be given more attention in urban environmental management.

Drawdown mechanism of light particles in baffled stirred tank for the KR desulphurization process

To improve the efficiency of the desulfurization process, the drawdown mechanism of light particles in stirred tank is studied in this paper. For both up and down pumping modes, the just drawdown speeds(Njd) of floating particles in transformative Kanbara Reactor(KR) are measured in one and four baffled stirred tanks experimentally. Then numerical simulations with standard k-ε model coupled with volume of fluid model(VOF) and discrete phase model(DPM) are conducted to analyze the flow field at the just drawdown speed Njd. The torques on the impeller obtained from experiments and simulations agree well with each other, which indicates the validity of our numerical simulations. Based on the simulations, three main drawdown mechanisms for floating particles, the axial circulation, turbulent fluctuation and largescale eddies, are analyzed. It's found that the axial circulation dominates the drawdown process at small submergence(S = 1/4 T and 1/3 T) and the large-scale eddies play a major role at large submergence(S = 2/3 T and 3/4 T). Besides, the turbulent fluctuation affects the drawdown process significantly for up pumping mode at small submergence(S = 1/4 T and 1/3 T) and for down pumping mode at large submergence(S = 2/3 T and 3/4 T). This paper helps to provide a more comprehensive understanding of the KR desulphurizer drawdown process in the baffled stirred tank.

Light Focusing through Scattering Media by Particle Swarm Optimization

We demonstrate light focusing through scattering media by introducing particle swarm optimization for modulat- ing the phase wavefront. Light refocusing is simulated numerically based on the angular spectrum method and the circular Gaussian distribution model of the scattering media. Experimentally, a spatial light modulator is used to control the phase of incident light, so as to make the scattered light converge to a focus. The influence of divided segments of input light and the effect of the number of iterations on light intensity enhancement are investigated. Simulation results are found to be in good agreement with the theoretical analysis for light refocusing.

Effects of geometrical and physical factors on light particles dispersion by agitation characteristic curve

In this study,the effects of geometrical and physical factors on light particles dispersion in stirred tank were investigated by agitation characteristic curve.The experiments and CFD simulations with discrete phase model(DPM)and volume of fluid model(VOF)were conducted in this paper.Five factors,which include four geometrical factors(submergence,impeller-to-tank ratio,number of impeller blades and baffling mode)and a physical factor(liquid viscosity)were considered.For each factor,the power consumption curve and agitation characteristic curve were drawn to compare the power consumption and mixing results in the stirred tank.Characteristics of the agitation characteristic curves were compared with the previous published literatures and theories.It is found that the agitation characteristic curves reflect the tendency of power consumption and particles distribution well in stirred tank.The good agreement indicates the applicability of the agitation characteristic curves for the study of light particles distribution in stirred tank.

Theoretical studies on particle shape classification based on simultaneous small forward angle light scattering and aerodynamic sizing

Particle shape contributes to understanding the physical and chemical processes of the atmosphere and better ascer- taining the origins and chemical compositions of the particles. The particle shape can be classified by the aspect ratio. which can be estimated through the asymmetry factor measured with angularly resolved light scattering. An experimental method of obtaining the asymmetry factor based on simultaneous small forward angle light scattering and aerodynamic size measurements is described briefly. The near forward scattering intensity signals of three detectors in the azimuthal angles at 120° offset are calculated using the methods of T-matrix and discrete dipole approximation. Prolate spheroid particles with different aspect ratios are used as the shape models with the assumption that the symmetry axis is parallel to the flow axis and perpendicular to the incident light. The relations between the asymmetry factor and the optical size and aerodynamic size at various equivalent sizes, refractive indices, and mass densities are discussed in this paper. The numerically calculated results indicate that an elongated particle may be classified at diameter larger than 1.0 μm, and may not be distinguished from a sphere at diameter less than 0.5 μm. It is estimated that the lowest detected aspect ratio is around 1.5： I in consideration of the experimental errors.

Shaping the Wavefront of Incident Light with a Strong Robustness Particle Swarm Optimization Algorithm

We demonstrate a modified particle swarm optimization(PSO) algorithm to effectively shape the incident light with strong robustness and short optimization time. The performance of the modified PSO algorithm and genetic algorithm(GA) is numerically simulated. Then, using a high speed digital micromirror device, we carry out light focusing experiments with the modified PSO algorithm and GA. The experimental results show that the modified PSO algorithm has greater robustness and faster convergence speed than GA. This modified PSO algorithm has great application prospects in optical focusing and imaging inside in vivo biological tissue, which possesses a complicated background.

In situ nanobubble sizing by visualization particle tracking and image-based dynamic light scattering

A novel method combining visualization particle tracking with image-based dynamic light scattering was developed to achieve the in situ and real-time size measurement of nanobubbles(NBs).First,the in situ size distribution of NBs was visualized by dark-field microscopy.Then,real-time size during the preparation was measured using image-based dynamic light scattering,and the longitudinal size distribution of NBs in the sample cell was obtained in a steady state.Results show that this strategy can provide a detailed and accurate size of bubbles in the whole sample compared with the commercial ZetaSizer Nano equipment.Therefore,the developed method is a real-time and simple technology with excellent accuracy,providing new insights into the accurate measurement of the size distribution of NBs or nanoparticles in solution.

DETERMINATION OF DROPLET SIZE DISTRIBUTION AND WETNESS OF FLOWING STEAM FROM LIGHT EXTINCTION MEASUREMENTS

提出一种新方法，用光全散射测量数据确定流动蒸汽的湿度及水滴分布，并应用于一试验汽轮机的测量结果，计算得到的汽轮机排汽湿度与测功器的结果吻合良好。该法采用线性优化及合理的物理限制条件，可推广应用于光部分散射测量分析。

Attenuation characteristics of a light attenuator combined by polarizers with different extinction ratios

This paper deals with a systematical analysis and an algorithm of attenuation characteristics of a light attenuator combined by n pieces of polarizers （n-LACP） whose extinction ratios are different from each other. The attenuation ratio expression of a two-LACP is deduced. We find that the monotonic attenuation interval depends on the first polarizer and that the attenuation range depends on the second one. For the three-LACP, a method for obtaining a monotonic attenuation interval is proposed. Moreover, the attenuation ratio expression is demonstrated. Analysis and experiment show that when the initial status of the three-LACP is at the maximum output, if the second or third polarizer rotates alone, the minimum attenuation ratios can reach K2^-1 and K3^-1, respectively, and if the first polarizer rotates, a minimum attenuation ratio of K2^-1K3^-1 can be obtained （K1, K2 and K3 represent the extinction ratios of the three polarizers in turn）. Furthermore, the attenuation ratio expression of n-LACP and the relevant attenuation characteristics are proposed. The minimum attenuation ratio of an n-LACP is （K2K3 ... Kn）-1.

Difference scattering field properties between periodic defect particles and three-dimensional slightly rough optical surface

Based on the practical situation of nondestructive examination, the calculation model of the composite scattering is established by using a three-dimensional half-space finite difference time domain, and the Monte Carlo method is used to solve the problem of the optical surface with roughness in the proposed scheme. Moreover, the defect particles are observed as periodic particles for a more complex situation. In order to obtain the scattering contribution of defects inside the optical surface, a difference radar cross section is added into the model to analyze the selected calculations on the effects of numbers, separation distances, different depths and different materials of defects. The effects of different incident angles are also discussed. The numerical results are analyzed in detail to demonstrate the best position to find the defects in the optical surface by detecting in steps of a fixed degree for the incident angle.

Comparative research on visibility and light extinction of PM_(2.5)components during 2014–17 in the North China plain

Severe air pollution with visibility deterioration has long been a focus in the North China Plain(NCP).In this study,concentration and light extinction analysis of PM_(2.5)chemical components were carried out from 2014 to 2017 to study the pollution characteristics in Baoding,a case city of the NCP.The annual average concentration of total PM_(2.5)components showed a declining trend,decreasing by 11μg m^(−3)(water-soluble inorganic ions),23μg m^(−3)(carbonaceous aerosols),and 1796 ng m^(−3)(inorganic elements).Contributing 82.9%to the concentration of total ions,the dominant components,NH 4+,NO 3−,and SO_(4)^(2−)became the main pollutants in PM_(2.5)pollution.Based on the IMPROVE algorithm,the average reconstructed PM_(2.5)mass concentration was 93±69μg m^(−3)during the observation period.Meanwhile,the light extinction coefficients were 373.8±233.6 M^(m−1),405.3±300.1M^(m−1),554.3±378.2M^(m−1)and 1005.2±750.3M^(m−1),in spring,summer,autumn,and winter,respectively.Ammonium sulfate,ammonium nitrate,and organic matter were the largest contributors to light extinction,accounting for a total of 55%–77%in the four seasons.The b sca(light scattering by particles and gases)reconstructed from PM_(2.5)components(Rb_(sca))and the b sca converted from visibility(Vb_(sca))were compared to evaluate the performance of the IMPROVE algorithm,revealing a high correlation coefficient of 0.84.The high values of Vb_(sca)were underestimated while the low values were overestimated,as determined through comparison with the one-to-ne line.Especially,when Rb_(sca)>1123M^(m−1)(corresponding to<2.0 km,approximately),Vb_(sca)was underestimated by 17.6%.PM_(2.5)mass concentration and relative humidity also had an impact on the estimation.

Study on Correlation Between Light Particles and Fragments in 25MeV／u ^（40）Ar＋^（115）In Reaction

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Correlative Measurements of Fission Fragments and Light Particles（α，p）in Reactions of ^（40）Ar＋^（209）Bi，^（nat）Ag at 25MeV／u

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Synthesis of Nanometer Cobalt Blue Pigment by Microemulsion Method and Control of Diameter of Particle

The nanometer cobalt blue pigments were prepared by microemulsion method. Using dynamic light scattering(DLS) test method, the influences of water content on the size of liquid drop of microemulsion and the liquid drop of microemulsion on the final diameter of nanometer particle were studied in the course of preparation. Accordingly, the method to control the diameter of nanometer particle by changing water content was established. The nanometer cobalt blue particles were confirmed by XRD and TEM. Color parameters of pigments were determined. The quantum size effect of the pigments was discussed.

Synthesis of Silica Particles with Precisely Tailored Diameter

A modified seeded growth process of silica particles with a continuous addition of tetraethyl orthosilicate （TEOS） was presented to control the diameter of silica particles. The diameter of particles was monitored by dynamic light scattering to control the addition of TEOS. The increase in the diameter of the silica particles with time and the addition of TEOS was investigated. The diameter of silica seeds increased from 193 nm to 446 nm in 4 h. The final diameter of silica particles was tailored within the range of ±5 nm to the target diameter. Silica particles with diameter of 446 nm were synthesized and assembled into photonic crystals with a pseudo band gap centered at just 1000 nm. The feasibility and practicability of this modified seeded growth process was verified.

VLC-Based Indoor Positioning Algorithm Combined with OFDM and Particle Filter

Visible light communications(VLC) have recently attracted a growing interest and can be a potential solution to realize indoor positioning,however,the performance of existing indoor positioning system is limited by multipath distortion inside a room.In order to combat the effect of multipath distortion,this paper proposes an LED-based indoor positioning algorithm combined with hybrid OFDM(HOFDM),in which asymmetrically clipped optical OFDM(ACOOFDM) is transmitted on the odd subcarriers while using pulse amplitude modulated discrete multitone(PAM-DMT) to modulate the imaginary part of each even subcarrier.In this scheme,we take a combined approach where a received-signal-strength(RSS) technique is employed to determine the location of the receiver and realize the 3-D positioning by Trust-region-based positioning.Moreover,a particle filter is used to further improve the positioning accuracy.Results confirm that this proposed positioning algorithm can achieve high accuracy even with multipath distortion,and the algorithm has better performance when combined with particle filter.

Approximations of the Scattering Phase Functions of Particles

Based on anomalous diffraction theory and the modified Rayleigh-Debye approximation, a physically realistic model in bridging form is described to approximate the scattering phase function of particles. When compared with the exact method, the bridging technique reported here provides a reasonable approximation to the Mie results over a broader range of angles and size parameters, and it demonstrates the advantage of being computationally economic. In addition, the new phase function model can be essentially extended to other shapes and conveniently used in more complicated scattering and emission problems related to the solutions of the radiative transfer equations.

PHOTODEGRADATION OF p-NITROCHLORBENZENE(p-NCB)USING NANOMETER-SIZED ZnO PARTICLES PREPARED BY REACTIVE EVAPORATION METHOD

Photocatalytic degradations of p-nitrochlorbenzene (p-NCB) with distilled water wereinvestigated with ZnO crystals (catalyst) of 70nm in diameter under UV irradiation.The suitable experimental conditions are determined as: ZnO 0.25g, pH 7, p-NCBconcentration 30mg/L. These variables in terms of the degradation rate have beendiscussed, which was defined as the rate of the initial degradation to the final degrada-tion of p-NCB. When all of the experimental degradation rate values are plotted as afunction of irradiation time, all of the points appeared on a single line for wide range ofp-NCB degradations. On the basis of these results, it has been concluded that at lowerZnO catalyst amount, much of the light is transmitted through the slurry in the con-tainer beaker, while at higher catalyst amount, all the incident photons are observedby the slurry. Degradation rates of p-NCB were found to decrease with increasingsolution pH. It has been concluded that the maximum degradation rate values of p-NCB under principally the same experimental conditions mentioned above are 97.4%,98.8% and 95.5% at 100min respectively. The results suggest that the photocatalyticdegradation is initiated by an oxidation of the p-NCB through ZnO surface-adsorbedhydroxyl radicals. Absorption spectra are recorded using spectrophotometer before andafter UV-irradiation in the wavelength range 200-400nm at room temperature. Itis found that the variation of irradiation time over the range 20-100min resulted inchange in the form of the spectrum linear absorption and a higher maximum valuewill be obtained at longer irradiation time.

Absorption enhancement in thin film a-Si solar cells with double-sided SiO_2 particle layers

Light absorption enhancement is very important for improving the power conversion efficiency of a thin film a-Si solar cell. In this paper, a thin-film a-Si solar cell model with double-sided SiO2 particle layers is designed, and then the underlying mechanism of absorption enhancement is investigated by finite difference time domain（FDTD） simulation;finally the feasible experimental scheme for preparing the SiO2 particle layer is discussed. It is found that the top and bottom SiO2 particle layers play an important role in anti-reflection and light trapping, respectively. The light absorption of the cell with double-sided SiO2 layers greatly increases in a wavelength range of 300 nm-800 nm, and the ultimate efficiency increases more than 22% compared with that of the flat device. The cell model with double-sided SiO2 particle layers reported here can be used in varieties of thin film solar cells to further improve their performances.