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A computational particle fluid-dynamics simulation of hydrodynamics in a three-dimensional full-loop circulating fluidized bed: Effects of particle-size distribution

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Particuology 2020年第2期18卷 134-145页

作者： Hang Zhang Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049ShaanxiChina

A computational particle fluid-dynamics model coupled with an energy-minimization multi-scale(EMMS)drag model was applied to investigate the influence of particle-size distribution on the hydrodynamics of a three-dimensional full-loop circulating fluidized *** particle systems,including one monodisperse and two polydisperse cases,were *** numerical model was validated by comparing its results with the experimental axial voidage distribution and solid mass *** EMMS drag model had a high accuracy in the computational particle fluid-dynamics simulation of the three-dimensional full-loop circulating fluidized *** total number of parcels in the system(Np)influenced the axial voidage distribution in the riser,especially at the lower part of the *** numerical simulation results showed that axial segregation by size was predicted in the two polydisperse cases and the segregation size increased with an increase in the number of size *** axial voidage distribution at the lower portion of the riser was significantly influenced by particle-size ***,radial segregation could only be correctly predicted in the upper region of the riser in the polydisperse case of three solid species.

关键词： Circulating fluidized bed Computational particle fluid dynamics particle-size distribution Energy-minimization multiscale model Three-dimensional full-loop simulation

Multifractal features of the particle-size distribution of suspended sediment in the Three Gorges Reservoir, China

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International Journal of Sediment Research 2021年第4期36卷 489-500页

作者： Jinlin Li Xiubin He Jie Wei Yuhai Bao Qiang Tang Jean de Dieu Nambajimana Gratien Nsabimana Dil Khurram Key Laboratory of Mountain Surface Processes and Ecological Regulation Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chongqing Key Laboratory of Earth Surface Processes and Environmental Remote Sensing in the Three Gorges Reservoir Area University of Chinese Academy of Sciences School of Geographical Sciences Southwest University

The Three Gorges Reservoir(TGR) in China is the largest hydroelectric project in the world,but the threat of sediment affecting ecological sustainability of the reservoir is a topic of *** particlesize distribution(PSD) is informative in understanding sediment transport dynamics and biochemical *** is,therefore,important to quantitatively characterize the distribution of sediment *** the current study,fractal theory is applied to determine the PSD of suspended sediment in the *** results show that the volumetric fractal dimension(Dv) exhibits a significant seasonal difference(p particles are coarser in the wet season than in the dry season for the Yangtze River,and the opposite is true for the Ruxi River,an important *** generalized dimension spectrum,D(q)-q,and multifractal singularity spectrum,f[α(q)]-α(q),were calculated for each suspended sediment ***,the parameters,D(0),D(1),D(2),α(0),Δα(q),and Δf [α(q)],were determined to characterize the *** a result,the coarser suspended sediment during the wet season is characterised by a more complex PSD pattern,with a wider range of particle sizes,greater heterogeneity,and greater homogeneity of distribution over the measurement ***,the multifractal structure of the PSD of suspended sediment is more complex during the dry season than during the wet season,with higher local dispersion and *** findings of the current study highlight that multifractal analysis provides important insight for understanding the PSD of suspended sediment in the TGR.

关键词： particle-size distribution Suspended sediment Multifractal features Flow regulation Three Gorges Reservoir

Applicability of Fractal Models in Estimating Soil Water Retention Characteristics from particle-size distribution Data

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Pedosphere 2002年第4期12卷 301-308页

作者： LIU JIANLI and XU SHAOHUIInstitute of Soil Science, the Chinese Academy of Sciences, Nanjing 210008 (China) Institute of Soil Science the Chinese Academy of Sciences Nanjing 210008

Soil water retention characteristics are the key information required in hydrological modeling. Frac-tal models provide a practical alternative for indirectly estimating soil water retention characteristics fromparticle-size distribution data. Predictive capabilities of three fractal models, i.e, Tyler-Wheatcraft model,Rieu-Sposito model, and Brooks-Corey model, were fully evaluated in this work using experimental datafrom an international database and literature. particle-size distribution data were firstly interpolated into20 classes using a van Genuchten-type equation. Fractal dimensions of the tortuous pore wall and the poresurface were then calculated from the detailed particle-size distribution and incorporated as a parameter infractal water retention models. Comparisons between measured and model-estimated water retention cha-racteristics indicated that these three models were applicable to relatively different soil textures and pressurehead ranges. Tyler-Wheatcraft and Brooks-Corey models led to reasonable agreements for both coarse- andmedium-textured soils, while the latter showed applicability to a broader texture range. In contrast, Rieu-Sposito model was more suitable for fine-textured soils. Fractal models produced a better estimation of watercontents at low pressure heads than at high pressure heads.

关键词： fractal model particle-size distribution soil water retention characteristics

DESCRIPTION OF G-S particle size distribution OF ROCK COMMINUTION WITH FRACTAL GEOMETRY

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Transactions of Nonferrous Metals Society of China 1991年第1期1卷 35-38页

作者： Li Gongbo Tang Chunan Xu Xiaohe Northeast University of Technology Shenyang 110006China

The fractal model of rock comminution is presented with Mandelbrot's fractal *** results show that it is difficult for those with only a linear similarity ratio to fit practical *** comminution prob ability of the central part should be considered so the geometric meaning of the constant in Gaudin-Schuhmann's distribution function can be explained more clearly.

关键词： fractal dimension comminution engineering particle-size distribution

Interactions between wind and water erosion change sediment yield and particle distribution under simulated conditions

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Journal of Arid Land 2015年第5期7卷 590-598页

作者： TUO Dengfeng XU Mingxiang ZHAO Yunge GAO Liqian State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Institute of Soil and Water ConservationNorthwest A&F University Institute of Soil and Water Conservation Chinese Academy of Sciences and Ministry of Water Resources

Wind and water erosion are among the most important causes of soil loss, and understanding their interactions is important for estimating soil quality and environmental impacts in regions where both types of erosion occur. We used a wind tunnel and simulated rainfall to study sediment yield, particle-size distribution and the fractal dimension of the sediment particles under wind and water erosion. The experiment was conducted with wind ero- sion firstly and water erosion thereafter, under three wind speeds （0, 11 and 14 m/s） and three rainfall intensities （60, 80 and 100 ram/h）. The results showed that the sediment yield was positively correlated with wind speed and rain- fall intensity （P〈0.01）. Wind erosion exacerbated water erosion and increased sediment yield by 7.25%-38.97% relative to the absence of wind erosion. Wind erosion changed the sediment particle distribution by influencing the micro-topography of the sloping land surface. The clay, silt and sand contents of eroded sediment were also posi- tively correlated with wind speed and rainfall intensity （P〈0.01）. Wind erosion increased clay and silt contents by 0.35%-19.60% and 5.80%-21.10%, respectively, and decreased sand content by 2.40%-8.33%, relative to the absence of wind erosion. The effect of wind erosion on sediment particles became weaker with increasing rainfall intensities, which was consistent with the variation in sediment yield. However, particle-size distribution was not closely correlated with sediment yield （P〉0.05）. The fractal dimension of the sediment particles was significantly different under different intensities of water erosion （P〈0.05）, but no significant difference was found under wind and water erosion. The findings reported in this study implicated that both water and wind erosion should be controlled to reduce their intensifying effects, and the controlling of wind erosion could significantly reduce water erosion in this wind-water erosion crisscross region.

关键词： sediment yield particle-size distribution fractal dimension wind and water erosion

Prediction of particle size and layer-thickness distributions in a continuous horizontal fluidized-bed coating process

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Particuology 2020年第3期18卷 1-12页

作者： P.Bachmann K.Chen A.Buck E.Tsotsas Thermal Process Engineering Otto-von-Guericke UniversityUniversit(a)tsplatz 2Magdeburg D-39106Germany Institute of particle Technology Friedrich-Alexander University Erlangen-NurembergCauerstr.4Erlangen D-91058Germany

To predict the particle size and layer-thickness distributions(LTDs)in a continuously operated horizontal fluidized-bed granulation process,two alternative models were considered.A one-dimensional two-zone model was proposed,which describes with population-balance equations the particle growth in a spraying zone that is separated from the drying *** residence-time distribution(RTD)was calculated from a literature correlation and was coupled with a population-balance model via a tank-in-series model with reflux.A two-dimensional,one-zone population-balance model,which was based directly on the RTD and the feed particle-size distribution(PSD)was also *** experiments were conducted and analyzed microscopically and with a camera optical device to determine the sample *** over the particle population were derived from the PSDs and were analyzed directly by *** compare the simulated data with the experimentally determined distributions,the PSDs were converted to *** good agreement shows that both methods are suitable to determine the PSD from an RTD of an arbitrary granulation process in a horizontal fluidized *** appears necessary with regards to the LTD spread.

关键词： Fluidized bed Continuous process Coating,Residence-time distribution particle-size distribution Layer-thickness distribution

Novel Approach for Automatic Region of Interest and Seed Point Detection in CT Images Based on Temporal and Spatial Data

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Computers, Materials & Continua 2019年第5期59卷 669-686页

作者： Zhe Liu Charlie Maere Yuqing Song School of Computer Science and Telecommunication Jiangsu UniversityZhenjiangChina

Accurately finding the region of interest is a very vital step for segmenting organs in medical image *** propose a novel approach of automatically identifying region of interest in Computed Tomography Image(CT)images based on temporal and spatial *** method is a 3 stages approach,1)We extract organ features from the CT images by adopting the Hounsfield filter.2)We use these filtered features and introduce our novel approach of selecting observable feature candidates by calculating contours’area and automatically detect a seed point.3)We use a novel approach to track the growing region changes across the CT image sequence in detecting region of interest,given a seed point as our *** used quantitative and qualitative analysis to measure the accuracy against the given ground truth and our results presented a better performance than other generic approaches for automatic region of interest detection of organs in abdominal CT *** the results presented in this research work,our proposed novel sequence approach method has been proven to be superior in terms of accuracy,automation and robustness.

关键词： Computed tomography image continuously adaptive mean-shift hounsfield particle-size distribution

Mapping Soil Texture Based on Field Soil Moisture Observations at a High Temporal Resolution in an Oasis Agricultural Area

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Pedosphere 2016年第5期26卷 699-708页

作者： YANG Renmin LIU Feng ZHANG Ganlin ZHAO Yuguo LI Decheng YANG Jinling YANG Fei YANG Fan State Key Laboratory of Soil and Sustainable Agriculture Institute of Soil ScienceChinese Academy of SciencesNanjing 210008(China) University of Chinese Academy of Sciences Beijing 100049(China)

Due to the almost homogeneous topography in low relief areas, it is usually difficult to make accurate predictions of soil properties using topographic covariates. In this study, we examined how time series of field soil moisture observations can be used to estimate soil texture in an oasis agricultural area with low relief in the semi-arid region of northwest China. Time series of field-observed soil moisture variations were recorded for 132 h beginning at the end of an irrigation event during which the surface soil was *** correlation between two time-adjacent soil moisture conditions was used to select the factors for fuzzy c-means clustering. In each of the ten generated clusters, soil texture of the soil sample with the maximum fuzzy membership value was taken as the cluster centroid. Finally, a linearly weighted average was used to predict soil texture from the centroids. The results showed that soil moisture increased with the increase of clay and silt contents, but decreased with the increase of sand content. The spatial patterns of soil moisture changed during the entire soil drying phase. We assumed that these changes were mainly caused by spatial heterogeneity of soil texture. A total of 64 independent samples were used to evaluate the prediction accuracy. The root mean square error(RMSE)values of clay, silt and sand were 1.63, 2.81 and 3.71, respectively. The mean relative error(RE) values were 9.57% for clay, 3.77% for silt and 12.83% for sand. It could be concluded that the method used in this study was effective for soil texture mapping in the low-relief oasis agricultural area and could be applicable in other similar irrigation agricultural areas.

关键词： digital soil mapping fuzzy c-means clustering low relief particle-size distribution semi-arid region water content

Effects of Vegetation Cover and Rainfall Intensity on Sediment-Bound Nutrient Loss,size Composition and Volume Fractal Dimension of Sediment particles

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Pedosphere 2011年第5期21卷 676-684页

作者： ZHANG Guan-Hua LIU Guo-Bin WANG Guo-Liang WANG Yu-Xia College of Resource and Environment Northwest A&F University Yangling 712100 (China) Institute of Soil and Water Conservation Chinese Academy of Sciences and Ministry of Water Resources Yangling 712100 (China)

Vegetation and rainfall are two important factors affecting soil erosion and thus resulting in nutrient loss in the Chinese Loess Plateau.A field experiment was conducted to investigate the effects of rainfall intensities(60,100 and 140 mm h-1) and vegetation(Caragana korshinskii) coverages(0%,30% and 80%) on soil loss,nutrient loss,and the composition and volume fractal dimension of eroded sediment particles under simulated rainfall *** results showed that vegetation cover,rainfall intensity and their interaction all had significant effects on sediment transport and the sedimentbound nutrient *** rainfall intensity and lower coverage led to higher sediment and nutrient *** linear relationships were observed between soil loss and nutrient *** treatments showed more significant effects on the enrichment ratio(ER) of nitrogen(ERN) than organic matter(EROM) and phosphorus(ERP).Compared with the original surface soil,the eroded sediment contained more fine *** the same coverage,the clay content significantly decreased with increasing rainfall *** ER of sediment-bound nutrients was positively correlated with that of clay,suggesting that the clay fraction was preferentially eroded and soil nutrients were mainly adsorbed onto or contained within this *** were increments in the fractal dimension of the sediment particles compared to that of the original surface ***,the fractal dimension was positively correlated with clay,silt,and sediment-bound OM,N,and P contents,whereas it was negatively correlated with sand *** study demonstrated that fractal dimension analysis can be used to characterize differences in particle-size distribution and nutrient loss associated with soil erosion.

关键词： fractal features Loess Plateau particle-size distribution runoff nutrients simulated rainfall