Particle-Size Distribution of CdSe Quantum Dots Determined by Photoluminescence Spectroscopy

1989 ◽  
Vol 164 ◽  
Author(s):  
E.N. Prabhakar ◽  
C.A. Huber ◽  
D. Heiman
Keyword(s):  
Quantum Dots ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
State Energy ◽  
Energy Levels ◽  
Three Dimensional ◽  
Particle Diameter ◽  
Electron Hole ◽  
Electron Hole Pair

AbstractParticle-size distribution effects on the energy levels of semiconductor quantum dots are investigated. By examining the low temperature photoluminescence spectra of microcrystals of the binary semiconductor CdSe embedded in a glass matrix, the distribution of energy levels due to three-dimensional confinement is determined. Calculations of the electron-hole pair ground state energy provide a relation between confinement energy and particle diameter. This allows conversion of the photoluminescence lineshape directly into a distribution of particle radii and facilitates analysis of the observed properties of the material. With extension to other systems the technique can become a valuable tool in the study of semiconductor microparticle composites.

scholarly journals Digital microscopic image application (DMIA), an automatic method for particle size distribution analysis in waste activated sludge

2021 ◽  
Author(s):  
S. Cazares ◽  
J. A. Barrios ◽  
C. Maya ◽  
G. Velásquez ◽  
M. Pérez ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Activated Sludge ◽  
Size Distribution ◽  
Particle Diameter ◽  
Diffraction Method ◽  
Laser Diffraction ◽  
Waste Activated Sludge ◽  
Equivalent Diameter ◽  
Distribution Analysis

Abstract An important physical property in environmental samples is particle size distribution. Several processes exist to measure particle diameter, including change in electrical resistance, blocking of light, the fractionation of field flow and laser diffraction (these being the most commonly used). However, their use requires expensive and complex equipment. Therefore, a Digital Microscopic Imaging Application (DMIA) method was developed adapting the algorithms used in the Helminth Egg Automatic Detector (HEAD) software coupled with a Neural Network (NN) and Bayesian algorithms. This allowed the determination of particle size distribution in samples of waste activated sludge (WAS), recirculated sludge (RCS), and pretreated sludge (PTS). The recirculation and electro-oxidation pre-treatment processes showed an effect in increasing the degree of solubilization (DS), decreasing particle size and breakage factor with ranges between 44.29%, and 31.89%. Together with a final NN calibration process, it was possible to compare results. For example, the 90th percentile of Equivalent Diameter (ED) value obtained by the DMIA with the corresponding result for the laser diffraction method. DMIA values: 228.76 μm (WAS), 111.18 μm (RCS), and 84.45 μm (PTS). DMIA processing has advantages in terms of reducing complexity, cost and time, and offers an alternative to the laser diffraction method.

Effect Analysis of Various Gradient Particle Size Distribution on Electrical Performance of Anode-Supported SOFCs With Gradient Anode

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Pei Fu ◽  
Yuansheng Song ◽  
Jian Yang ◽  
Qiuwang Wang
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Current Density ◽  
Molar Fraction ◽  
Particle Diameter ◽  
Electrical Performance ◽  
Diameter Distribution ◽  
Functional Layer ◽  
Layer 2

Abstract Gradient particle size anode has shown great potential in improving the electrical performance of anode-supported solid oxide fuel cells (SOFCs). In this study, a 3D comprehensive model is established to study the effect of various gradient particle size distribution on the cell electrical performance for the anode microstructure optimization. The effect of homogeneous particle size on the cell performance is studied first. The maximum current density of homogeneous anode SOFC is obtained for the comparison with the electrical performance of gradient anode SOFC. Then the effect of various gradient particle size distribution on the cell molar fraction, polarization losses, and electronic current density distribution is analyzed and discussed in detail. Results show that increasing the particle diameter gradient can effectively reduce the anodic concentration overpotential. Decreasing the particle diameter of anode functional layer 2 is beneficial for reducing the activation and ohmic overpotentials. On these bases, the comprehensive electrical performance of SOFCs with gradient particle size anode and homogeneous anode is compared to highlight the optimal gradient particle diameter distribution. In the studied cases of this work, the gradient particle diameter of 0.7 μm, 0.4 μm, and 0.1 μm at anode support layer (ASL), anode functional layer 1, and anode functional layer 2 (case 3) is the optimal particle size distribution.

Estimation of particle size distribution from cross-sectional particle diameter on the cutting plane

2010 ◽  
Vol 21 (6) ◽  
pp. 676-680 ◽  
Author(s):  
Masatoshi Akashi ◽  
Tsukasa Otani ◽  
Atsuko Shimosaka ◽  
Yoshiyuki Shirakawa ◽  
Jusuke Hidaka
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particle Diameter ◽  
Cutting Plane ◽  
Cross Sectional

Sampling, testing and modeling particle size distribution in urban catch basins

2014 ◽  
Vol 70 (11) ◽  
pp. 1873-1879 ◽  
Author(s):  
G. Garofalo ◽  
M. Carbone ◽  
P. Piro
Keyword(s):  
Particle Size ◽  
Numerical Model ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particle Diameter ◽  
Experimental Treatment ◽  
Catch Basin ◽  
Traffic Intersection ◽  
Parking Lot ◽  
Catch Basins

The study analyzed the particle size distribution of particulate matter (PM) retained in two catch basins located, respectively, near a parking lot and a traffic intersection with common high levels of traffic activity. Also, the treatment performance of a filter medium was evaluated by laboratory testing. The experimental treatment results and the field data were then used as inputs to a numerical model which described on a qualitative basis the hydrological response of the two catchments draining into each catch basin, respectively, and the quality of treatment provided by the filter during the measured rainfall. The results show that PM concentrations were on average around 300 mg/L (parking lot site) and 400 mg/L (road site) for the 10 rainfall-runoff events observed. PM with a particle diameter of <45 μm represented 40–50% of the total PM mass. The numerical model showed that a catch basin with a filter unit can remove 30 to 40% of the PM load depending on the storm characteristics.

CFD Simulation of Spouted Bed Working with a Size Distribution of Sand Particles: Segregation Aspects

2017 ◽  
Vol 899 ◽  
pp. 95-100
Author(s):  
Kássia Graciele dos Santos ◽  
L.V. Ferreira ◽  
Ricardo Correa Santana ◽  
Marcos Antonio de Souza Barrozo
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Cfd Simulation ◽  
Computational Simulation ◽  
Particle Diameter ◽  
Spouted Bed ◽  
Particle Segregation ◽  
Cfd Method ◽  
Mean Particle Diameter

Spouted bed simulations are usually performed using only one granular phase with a mean particle diameter representing the entire particle mixture, instead of a particle size distribution. In this study, the effect of the particle size distribution is accounted through the simulation of a mixture with five granular phases. The results showed that the particle segregation occurs. Larger particles are more concentrated in the upper region, while the smaller particles are preferably positioned in the lower region of the bed. Computational simulation using CFD method reproduced well the segregation experiments with different participle sizes of sand.

scholarly journals Laser Triangulation in 3-Dimensional Granulometric Analysis

2016 ◽  
Vol 61 (1) ◽  
pp. 15-27 ◽  
Author(s):  
Adam Heyduk
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particle Surface ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Conveyor Belt ◽  
Laser Triangulation ◽  
Depth Maps ◽  
Coal Particles

Abstract The measurement of the particle size distribution plays an important role in mineral processing. Due to the high costs and time-consumption of the screening process, modern machine vision methods based on the acquisition and analysis of recorded photographic images. But the image analysis methods used so far, do not provide information on the three-dimensional shape of the grain. In the coal industry, the application scope of these methods is substantially limited by the low reflectivity of the black coal particle surface. These circumstances hinder proper segmentation of coal stream surface image. The limited information contained in two-dimensional image of the raw mineral stream surface, makes it difficult to identify proper size of grains partially overlapped by other particles and skewed particles. Particle height estimation based on the shadow length measurement becomes very difficult in industrial environment because of the fast movement of the conveyor belt and because of spatial arrangement of these particles, usually touching and overlapping. Method of laser triangulation connected with the movement of the conveyor belt makes it possible to create three-dimensional depth maps. Application of passive triangulation methods (e.g. stereovision) can be impeded because of the low contrast of the black coal on the black conveyor belt. This forces the use of active triangulation methods, directly identifying position of the analyzed image pixel. High contrast of the image can be obtained by a direct pointwise laser lighting. For the simultaneous identification of the entire section of the raw material stream it is useful to apply a linear laser (a planar sheet of the laser light). There have been presented basic formulas for conversion of pixel position on the camera CCD matrix to the real-word coordinates. A laboratory stand has been described. This stand includes a linear laser, two high-definition (2Mpix) cameras and stepper motor driver. The triangulation head moves on the rails along the belt conveyor section. There have been compared acquired depth maps and photographic images. Depth maps much better describe spatial arrangement of coal particles, and have a much lower noise level resulting from the specular light reflections from the shiny fragments of the particle surface. This makes possible an identification of the coal particles partially overlapped by other particles and obliquely arranged particles. It enables a partial elimination or compensation of image disturbances affecting the final result of the estimated particle size distribution. Because of the possibility of the reflected laser beam overriding by other particles it is advantageous to use a system of two cameras. Results of the experimental research confirmed the usefulness of the described method in spite of low reflectance factor of coal surface. The fast detection of changes in particle size distribution makes possible an on-line optimization of complex technological systems - especially those involving coal cleaning in jigs - thus leading to better stabilization of quality parameters of the enrichment output products. An additional application of the described method can be achieved by measuring the total volume of the stream of the transported materials. Together with the measurement signal from the belt conveyor weight it makes possible to estimate the bulk density of the raw mineral stream. The low complexity of the signal processing in the laser triangulation method is associated with the acquisition of high contrast images and analysis based on simple trigonometric dependencies.

scholarly journals Conductivity prediction of proppant-packs based on particle size distribution under variable stress conditions

2020 ◽  
Vol 205 ◽  
pp. 03010
Author(s):  
Tiancheng Liang ◽  
Jinwei Zhang ◽  
Chuanyou Meng ◽  
Nailing Xiu ◽  
Bo Cai ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Hydraulic Fracturing ◽  
Size Distribution ◽  
Particle Diameter ◽  
Particle Packing ◽  
Stress Conditions ◽  
Sieve Analysis ◽  
Proper Size ◽  
Median Diameter

The conductivity of the proppant-packs is critical in the productivity of hydraulically fractured wells. Proppants are also the best medium for studying particle packing. Sand and ceramic media are two most common proppants used for hydraulic fracturing. This study focuses on investigate the relation between conductivity and properties of proppant-packs, the particle-size distribution, porosity and mean particle diameter have been measured. The porosity of the proppant pack under zero pressure is determined from bulk density and apparent density. To accurately measure the porosity under variable closed stress conditions, the compressed width was taken into consideration. The particle size distribution was measured from sieve analysis. The paper presents results obtained by conducting routine conductivity test on a variety of proppants. The conductivity-porosity relationships are nonlinear. The conductivity is most sensitive to mean grain size, followed by closed stress, and then sorting. Larger median diameter always correlates to higher conductivity at low stress. Loss of conductivity with stress is more severe for large particles sands than small particles. The binomial method can be used to calculate the conductivity of different types and mesh proppants, which is shown to fit conductivity-mean diameter data successfully. The research is of guiding significance to choose the proper size distribution proppants in hydraulic fracturing. Meanwhile, the binomial method is a better predictor of proppant-packs conductivity based on particle size distribution.

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