scholarly journals Investigation on Coal Fragmentation by High-Velocity Water Jet in Drilling: Size Distributions and Fractal Characteristics

2018 ◽  
Vol 8 (10) ◽  
pp. 1988 ◽  
Author(s):  
Songqiang Xiao ◽  
Zhaolong Ge ◽  
Yiyu Lu ◽  
Zhe Zhou ◽  
Qian Li ◽  
...  
Keyword(s):  
Particle Size ◽  
Fractal Dimension ◽  
Impact Velocity ◽  
Fragment Size ◽  
Water Jet ◽  
Particle Sizes ◽  
Size Distributions ◽  
Jet Impact ◽  
Fractal Characteristics ◽  
Coal Strength

Water jet drilling (WJD) technology is a highly efficient method to extract coalbed methane from reservoirs with low permeability. It is crucial to efficiently remove the coal fragments while drilling. In this study, to disclose coal fragmentation features and size distributions under water jet impact in drilling, the image processing method was utilized to obtain the geometric dimensions of coal fragments. The size distributions, morphologies and fractal characteristics of coal fragmentation were studied based on generalized extreme value distribution and fractal theory. The effects of the jet impact velocity and coal strength on the fragmentation features were analyzed. The results show that fine particles dominate the coal fragments in WJD for coal seams with various strengths. In experiments conducted at the Fengchun coal mine, owing to the higher coal strength of the M7 coal seam, the fragmentation degree of coal subjected to water jets during WJD is lower in the M7 coal steam than in the M8 coal seam, which results in a large dominant fragment size and small fractal dimension under the same impact energy. It was found that the higher the jet impact velocity is, the higher the quantity of fragments generated from WJD and the smaller the particle size. The NUM-based cumulative probability distribution curves of coal fragments are more intensive in the range of relatively small particle sizes and then become sparser with the increase in particle size. When the impact velocity increases, (i) the size distribution curves move toward smaller particle sizes, and the dominant fragment size decreases; (ii) the shape (major axis/minor axis) of coal fragments move toward the upper left, and the curve shape for a high impact velocity attains unity more quickly; and (iii) the fractal dimension value increases linearly. In addition, the fractal dimensions are obviously affected by the dominant fragment size; they increase with the decrease in the dominant fragment size. This study can provide a basis for further research on coal fragment transportation in WJD and parameter selection for discharging coal fragments during drilling for CBM development.

scholarly journals A Gentle Sedimentation Process for Size-Selecting Porous Silicon Microparticles to Be Used for Drug Delivery Via Fine Gauge Needle Administration

Silicon ◽  
2020 ◽  
Author(s):  
Elida Nekovic ◽  
Catherine J. Storey ◽  
Andre Kaplan ◽  
Wolfgang Theis ◽  
Leigh T. Canham
Keyword(s):  
Drug Delivery ◽  
Particle Size ◽  
Porous Silicon ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Agglomeration ◽  
Gas Generation ◽  
Intravitreal Drug Delivery ◽  
Median Diameter ◽  
Experimental Values

AbstractBiodegradable porous silicon (pSi) particles are under development for drug delivery applications. The optimum particle size very much depends on medical use, and microparticles can outperform nanoparticles in specific instances. Here we demonstrate the ability of sedimentation to size-select ultrasmall (1–10 μm) nanoporous microparticles in common solvents. Size tunability is quantified for 1–24 h of sedimentation. Experimental values of settling times in ethanol and water are compared to those calculated using Stokes’ Law. Differences can arise due to particle agglomeration, internal gas generation and incomplete wetting. Air-dried and supercritically-dried pSi powders are shown to have, for example, their median diameter d (0.5) particle sizes reduced from 13 to 1 μm and from 20 to 3 μm, using sedimentation times of 6 and 2 h respectively. Such filtered microparticles also have much narrower size distributions and are hence suitable for administration in 27 gauge microneedles, commonly used in intravitreal drug delivery.

scholarly journals Experimental Study on Limestone Cohesive Particle Model and Crushing Simulation

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Huaiying Fang ◽  
Dawei Xing ◽  
Jianhong Yang ◽  
Fulin Liu ◽  
Junlong Chen ◽  
...  
Keyword(s):  
Particle Size ◽  
Simulation Model ◽  
Impact Velocity ◽  
Distribution Curve ◽  
Particle Model ◽  
Particle Sizes ◽  
Particle Crushing ◽  
Discrete Element Method Simulation ◽  
Impact Crushing ◽  
The Impact

This study investigates the effect of impact velocity and particle size on crushing characteristics. We use a discrete-element method simulation and construct cohesive limestone particles with internal microinterfaces and cracks for impact crushing experimentation. The simulation model follows the same process as the impact crushing experiment. Results show that, after crushing at impact velocities of 30 and 40 m/s, the simulated particle-size distribution curve matches experimental results as closely as 95%. For different particle sizes, results are more than 90% in agreement. These results indicate the feasibility of the cohesive-particle crushing simulation model. When the particle size is 15 mm, an approximate linear relationship exists on impact velocity and crushing ratio. For a constant impact velocity, the particle size of 18 mm results in the maximum crushing ratio.

The Effects of Structural Characteristics of Low Seepage Sandstone Uranium Ore Rock on Permeability

2012 ◽  
Vol 524-527 ◽  
pp. 371-374
Author(s):  
Sheng Zeng ◽  
Kai Xuan Tan ◽  
Xue Ming Du ◽  
Chun Guang Li
Keyword(s):  
Particle Size ◽  
Structural Characteristics ◽  
Fractal Dimensions ◽  
Uranium Mine ◽  
Particle Sizes ◽  
Uranium Deposits ◽  
Test Device ◽  
Linear Change ◽  
Uranium Ore ◽  
Fractal Characteristics

It is great important for the development of China’s uranium mining to efficiently extract low seepage sandstone uranium ore rock. It is the objective of this paper to present the effects of the structural characteristics of the low seepage sandstone uranium ore rock on permeability. Samples of sandstone from a uranium mine in XinJiang province were used to carry out experimental research on permeability. These tests were carried out on ore rock with particle size and distribution characteristics determined by a homemade permeability test device. The research indicates that the sandstone uranium deposits may be classified as low seepage because the particle size falls within the range 0.1~1.6mm, that the distribution of particle sizes observed conforms to low seepage fractal characteristics, the permeability decreases when the value of the ore particle size distribution of fractal dimensions increases, and the permeability decreases with particle size decreasing, and that the decrease of the permeability is not a linear change, but is an obviously exponentially decreasing functional relationship.

scholarly journals Research on the Impact Loading and Energy Dissipation of Concrete after Elevated Temperature under Different Heating Gradients and Cooling Methods

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1651 ◽  
Author(s):  
Yue Zhai ◽  
Yubai Li ◽  
Yan Li ◽  
Wenqi Jiang ◽  
Xuyang Liu
Keyword(s):  
Fractal Dimension ◽  
Energy Dissipation ◽  
Loading Rate ◽  
Heating Temperature ◽  
Fragment Size ◽  
Fragment Size Distribution ◽  
Loading Rates ◽  
Heating Treatment ◽  
Fractal Characteristics ◽  
Cooling Methods

To provide theoretical basis for fire rescue, post-disaster safety evaluation, and reinforcement of concrete structures, C35 concrete materials are treated with high-temperature heating (200 °C, 400 °C, 600 °C, 800 °C) under two different heating gradients. After natural cooling and water cooling to normal temperature, an impact compression test was carried out at different loading rates using a Split Hopkinson Pressure Bar (SHPB) system with a diameter of 100 mm, and finally the crushed specimens were subjected to a sieving test. The effects of elevated temperatures, cooling methods, heating gradients, and loading rates on the fragment size distribution, fractal characteristics, and energy dissipation of impact-compressed concrete specimens were studied. The results show that with the increase of the loading rate and the rise of the heating temperature, the crushing degree of concrete specimens gradually increases, the average fragment size decreases, and the mass distribution of the fragments move from the coarse end to the fine end. The fragment size distribution of the specimen has obvious fractal characteristics. In addition, its fractal dimension increases with the increase of loading rate and heating temperature, the average size of the specimen fragments decreases correspondingly, and the fracture of the specimen becomes more serious. When the different heating gradients were compared, it was found that the fractal dimension of the specimens subjected to rapid heating treatment was larger than that of the slow heating treatment specimens, and the crushing degree of the specimens with different cooling methods was discrete. By analyzing the energy dissipation of the specimen under different conditions, it is shown that both the fractal dimension and the peak stress increase with the increase of the fragmentation energy dissipation density. It shows that there is a close correlation between the change of fractal dimension and its macroscopic dynamic mechanical properties.

Determination of Latex Particle Size Distributions by Fractional Creaming with Sodium Alginate

1961 ◽  
Vol 34 (2) ◽  
pp. 433-445 ◽  
Author(s):  
E. Schmidt ◽  
P. H. Biddison
Keyword(s):  
Particle Size ◽  
Electron Microscope ◽  
Sodium Alginate ◽  
Mass Distribution ◽  
Average Particle Size ◽  
Average Particle ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Size Distributions

Abstract Knowledge of mass distribution of particle sizes in latex is very important to the latex technologist. Therefore, it is desirable to have available a simple method for the determination of mass distribution of particle sizes. This paper presents a method, based on fractional creaming of latex with sodium alginate, which can be used in any laboratory without special equipment. The method is particularly advantageous for analyzing latexes of very wide particle size distributions. When analyzed with an electron microscope, these latexes require counting a very large number of particles. McGavack found that partial creaming of normal hevea latex with ammonium alginate gives concentrates of larger average particle size than the original latex. He found that the average particle size in the cream approaches that of the original latex as the amount of creaming agent is increased. In a previous paper from this laboratory, Schmidt and Kelsey demonstrated that the phenomenon of fractionation according to particle size with increasing amounts of creaming agent is applicable in a wide variety of anionic latex systems and in colloidal silica. Their results indicated also the existence of a quantitative relationship, independent of the nature of the dispersed particles, between the concentration of creaming agent and size of creamed particles. Maron confirmed fractionation with respect to particle size as a consequence of partial creaming with alginate. He showed that the mass average particle sizes of fractions, determined optically, cumulate to that of the original latex. Although the previous paper by Schmidt and Kelsey implied the basic concept of a method of determining particle size distribution by fractional creaming, it was not exploited at that time. In order to adapt the fractional creaming phenomenon to a quantitative method for particle size determination, we required a more precise knowledge of the relation between creaming agent concentration and size of particles creamed. It was proposed to establish this relationship with the aid of the electron microscope. Various factors influencing the creaming of latex, such as polymer concentration, electrolyte, soap content, and variability of the creaming agent, had to be considered in standardizing the creaming procedure.

scholarly journals Study on Rock-Breaking Depth and Damage Area under Particle Jet Impact

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Fushen Ren ◽  
Tiancheng Fang ◽  
Xiaoze Cheng
Keyword(s):  
Mathematical Model ◽  
Impact Velocity ◽  
Particle Diameter ◽  
Rock Breaking ◽  
Water Jet ◽  
Experimental Results ◽  
Damage Area ◽  
Jet Impact ◽  
Mathematical Calculation ◽  
The Mathematical Model

Particle jet impact drilling technology is an efficient method which mainly uses high-velocity particles to break rock. As the important criterion for evaluating rock-breaking effect, rock-breaking depth and damage area were studied in this paper. Firstly, a particle jet impact rock-breaking test device was developed, and laboratory experiments have been carried out. Then, based on the spherical cavity expansion theory, the mathematical model of rock-breaking depth and damage area under particle jet impact was established. Afterward, the effect of water-jet impact velocity, impact angle, and particle diameter on rock-breaking depth and damage area was analyzed by comparing experimental results and mathematical calculation. The results show that rock-breaking depth and damage area would increase with increase of water-jet impact velocity and decrease slightly with increase of particle diameter. And the combination of 8° and 20° is recommended for nozzle layout. The experimental results and mathematical calculation are basically consistent, which could verify the correctness of the mathematical model. The study has significance for development and application of particle jet impact rock-breaking technology and perfection of theoretical research.

Particle Size Characterisation of Tin Oxide (SnO2) Precipitated by Various Techniques: Consistency of Data

2007 ◽  
Vol 561-565 ◽  
pp. 2155-2158
Author(s):  
H. Taib ◽  
Charles C. Sorrell
Keyword(s):  
Particle Size ◽  
Light Scattering ◽  
Tin Oxide ◽  
Spherical Shape ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Oxide Powders ◽  
Spherical Agglomerates ◽  
The Individual

The particle size distributions of tin oxide powders produced from the calcining of precipitated tin oxalate were determined by four methods, these being two static and two dynamic light scattering techniques. Although the individual particle sizes were ~ 75 nm, all of the powders were heavily agglomerated as plates. The non-spherical shape resulted in the following interpretational problems: • None of the measurements was in agreement with any others. • There were very significant disagreements between the two light scattering methods. • The particle size distributions were multimodal. • The main peaks in the distribution curves, which were used to calculate the averages and standard deviations, were not Gaussian. The main uncertainty with these data is associated with the non-spherical agglomerates, which result in the multimodal size distributions. These probably were caused by variable-sized but large platy agglomerates.

Mechanics of Polishing

1998 ◽  
Vol 65 (2) ◽  
pp. 410-416 ◽  
Author(s):  
V. H. Bulsara ◽  
Y. Ahn ◽  
S. Chandrasekar ◽  
T. N. Farris
Keyword(s):  
Particle Size ◽  
Material Removal ◽  
Indentation Hardness ◽  
Particle Sizes ◽  
Size Distributions ◽  
Polishing Process ◽  
Average Force ◽  
Abrasive Particles ◽  
Effect Of Particle Size ◽  
Micro Indentation

A model has been developed to determine the number and sizes of abrasive particles involved in material removal in polishing, and the forces acting on these particles. The effect of particle size on these parameters has been simulated for a range of particle sizes. It is shown that when polishing with abrasive powders having relatively broad size distributions, only a very small percentage of the particles are involved in material removal. Further, these particles are comprised of the larger particles occurring in the tail end of the particle size distribution. The average force on a particle is found to be in the range of 5–200 mN under typical polishing conditions, which is of the order of loads used in micro-indentation hardness testing. These predictions of the model are consistent with observations pertaining to polished surfaces and the polishing process.

scholarly journals Experiment on Size Effect and Fractal Characteristics of Waste Brick and Concrete Recycled Aggregate

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Hongbo Li ◽  
Hubiao Zhang ◽  
Pengfei Yan ◽  
Yufei Tong ◽  
Changyu Yan ◽  
...  
Keyword(s):  
Particle Size ◽  
Fractal Dimension ◽  
Size Effect ◽  
Single Particle ◽  
Static Load ◽  
Impact Load ◽  
Apparent Size ◽  
Recycled Aggregate ◽  
Crushing Strength ◽  
Fractal Characteristics

Herein, the size effect of single-particle crushing of recycled brick and concrete recycled macadam under static load and the fractal characteristics of aggregate under impact load are investigated. The mechanical change law of recycled macadam after compaction crushing under static load is analyzed through single-particle load crushing and impact crushing tests with different particle groups. Furthermore, the fractal dimension D is introduced to study the effects of impact energy, particle size, and different materials on the fractal characteristics of the recycled macadam. Consequently, the material, shape, and particle size of a single-particle significantly affect the crushing strength under static loading, and there is an apparent size effect on the crushing strength. Moreover, the proportion of unbroken particles in the overall mass sieve increased with decreasing particle group order under impact loading. The proportion of unbroken particles in the 4.75–9.5-mm group constituted more than 60% of the total, indicating that its anticrushing ability was significant. In addition, the model relationship between fractal dimension D, nonuniformity coefficient, and curvature coefficient is established. When 1.887 ≤ D ≤ 2.631, the gradation of recycled macadam is superior.

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