The traditional standard wet sieving method uses steel sieves with aperture?0.063 mm and can only determine the particle size distribution(PSD)of gravel and sand in general soil.This paper extends the traditional meth...The traditional standard wet sieving method uses steel sieves with aperture?0.063 mm and can only determine the particle size distribution(PSD)of gravel and sand in general soil.This paper extends the traditional method and presents an extended wet sieving method.The extended method uses both the steel sieves and the nylon filter cloth sieves.The apertures of the cloth sieves are smaller than 0.063 mm and equal 0.048 mm,0.038 mm,0.014 mm,0.012 mm,0.0063 mm,0.004 mm,0.003 mm,0.002 mm,and 0.001 mm,respectively.The extended method uses five steps to separate the general soil into many material sub-groups of gravel,sand,silt and clay with known particle size ranges.The complete PSD of the general soil is then calculated from the dry masses of the individual material sub-groups.The extended method is demonstrated with a general soil of completely decomposed granite(CDG)in Hong Kong,China.The silt and clay materials with different particle size ranges are further examined,checked and verified using stereomicroscopic observation,physical and chemical property tests.The results further confirm the correctness of the extended wet sieving method.展开更多
The effects of high-volume slag-fly ash cement with different particle sizes on hydration degree,microstructure and mechanical properties were systematically studied,by means of laser particle size(DLS),X-ray diffract...The effects of high-volume slag-fly ash cement with different particle sizes on hydration degree,microstructure and mechanical properties were systematically studied,by means of laser particle size(DLS),X-ray diffraction (XRD),comprehensive thermal analysis (TG-DTA),scanning electron microscopy(SEM) and mechanical properties tests.The results show that suitable particle size distribution of cementitious material has significantly promoting effects on hydration reaction rate and mechanical properties.Compared with slag without further grinding,the slag after ball milling for 4 h has an obvious improvement in reactivity,which also provides a faster hydration rate and higher compressive strength for the cementitious material.When the slag milled for 1 and 4 h is mixed at a mass ratio of 2:1 (i e,slag with D_(50) of 7.4μm and average size of 9.9μm,and slag with D_(50) value of 2.6μm and average size of 5.3μm),and a certain amount of fly ash is added in,the most obvious improvement of compressive strength of cement is achieved.展开更多
The particle size distribution of polymer always develops in emulsion polymerization systems,and certain key phenomena/mechanisms as well as properties of the final product are significantly affected by this distribut...The particle size distribution of polymer always develops in emulsion polymerization systems,and certain key phenomena/mechanisms as well as properties of the final product are significantly affected by this distribution.This review mainly focuses on the measurement methods of particle size distribution rather than average particle size during the emulsion polymerization process,including the existing off-line,on-line,and in-line measurement methods.Moreover,the principle,resolution,performance,advantages,and drawbacks of various methods for evaluating particle size distribution are contrasted and illustrated.Besides,several possible development directions or solutions of the in-line measurement technology are explored.展开更多
Internal erosion occurs when fine particles escape from the soil driven by seepage flow,which is considered to be the crucial factor causing the failure of earth structures filled with gravelly soil.The objective of t...Internal erosion occurs when fine particles escape from the soil driven by seepage flow,which is considered to be the crucial factor causing the failure of earth structures filled with gravelly soil.The objective of this paper is to suggest an appropriate method to assess internal erosion potential of gravelly soil.By analyzing the sensitivity of soil material to internal erosion,the variable(Dc15/df85)max and the content of coarse particles(Pc)are selected as the evaluation indexes(Dc15 and df85 are the diameters of 15%mass passing in the coarse component and 85%mass passing in the fine component,respectively).A series of gravelly soils with different particle size distributions are tested for internal erosion by the self-made permeameter.Based on the test results,an evaluation method for the internal erosion of gravelly soil is proposed.Gravelly soil is prone to internal erosion when 60%≤Pc<95%and(Dc15/df85)max≥9.5.The proposed method shows good accuracy in evaluating the internal erosion of 36 soil samples from other studies,which confirms the reliability of the method.The proposed method makes it possible to accurately assess internal erosion of gravelly soil,and an alternative method is provided for engineers to determine whether there is a risk of internal erosion in earth structures consisting of gravelly soil.展开更多
The weighted-sum-of-gray-gas(WSGG)model and Mie theory are applied to study the influents of particle size on the radiative transfer in high temperature homogeneous gas-particle mixtures,such as the flame in aero-engi...The weighted-sum-of-gray-gas(WSGG)model and Mie theory are applied to study the influents of particle size on the radiative transfer in high temperature homogeneous gas-particle mixtures,such as the flame in aero-engine combustor.The radiative transfer equation is solved by the finite volume method.The particle size is assumed to obey uniform distribution and logarithmic normal(L-N)distribution,respectively.Results reveal that when particle size obeys uniform distribution,increasing particle size with total particle volume fraction fvunchanged will result in the decreasing of the absolute value of radiative heat transfer properties,and the effect of ignoring particle scattering will also be weakened.Opposite conclusions can be obtained when total particle number concentration N0 is unchanged.Moreover,if particle size obeys L-N distribution,increasing the narrowness indexσor decreasing the characteristic diameter Dˉwith the total particle volume fraction fvunchanged will increase the absolute value of radiative heat transfer properties.With total particle number concentration N0 unchanged,opposite conclusions for radiative heat source and incident radiation terms can be obtained except for radiative heat flux term.As a whole,the effects of particle size on the radiative heat transfer in the high-temperature homogeneous gas-particle mixtures are complicated,and the particle scattering cannot be ignoring just according to the particle size.展开更多
An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has be...An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has been made.展开更多
Based on the laser diffraction and Shifrin transform,the measurement method of particle size distribution has been improved extensively.While in real measurements,some noise peaks exist in the inversion data and are e...Based on the laser diffraction and Shifrin transform,the measurement method of particle size distribution has been improved extensively.While in real measurements,some noise peaks exist in the inversion data and are easily to be misread as particle distribution peaks.The improved method used a truncation function as a filter is hard to distinguish adjacent peaks.Here,by introducing the bimodal resolution criterion,the filter function is optimized,and to a quasi truncation function with the optimized filter function is studied to achieve optimal bimodal resolution and to remove noise peaks.This new quasi truncation function fits multimode distribution very well.By combining the quasi truncation function with Shifrin transform,noise peaks are removed well and the adjacent peaks are distinguished clearly.Finally,laser diffraction experiments are conducted and the particle size distribution is analyzed by adoping the method.The results show that the quasi truncation function has better bimodal resolution than the truncation function.Generally,by combining the quasi truncation function with the Shifrin transform,in particle size distribution measurements with laser diffraction,the bimodal resolution is greatly increased and the noise is removed well.And the results can restore the original distribution perfectly.Therefore,the new method with combination of the quasi truncation function and the Shifrin transform provides a feasible and effective way to measure the multimode particle size distribution by laser diffraction.展开更多
Particle size distributions(PSDs) of bottom sediments in a coastal zone are generally multimodal due to the complexity of the dynamic environment. In this paper, bottom sediments along the deep channel of the Pearl Ri...Particle size distributions(PSDs) of bottom sediments in a coastal zone are generally multimodal due to the complexity of the dynamic environment. In this paper, bottom sediments along the deep channel of the Pearl River Estuary(PRE) are used to understand the multimodal PSDs′ characteristics and the corresponding depositional environment. The results of curve-fitting analysis indicate that the near-bottom sediments in the deep channel generally have a bimodal distribution with a fine component and a relatively coarse component. The particle size distribution of bimodal sediment samples can be expressed as the sum of two lognormal functions and the parameters for each component can be determined. At each station of the PRE, the fine component makes up less volume of the sediments and is relatively poorly sorted. The relatively coarse component, which is the major component of the sediments, is even more poorly sorted. The interrelations between the dynamics and particle size of the bottom sediment in the deep channel of the PRE have also been investigated by the field measurement and simulated data.The critical shear velocity and the shear velocity are calculated to study the stability of the deep channel. The results indicate that the critical shear velocity has a similar distribution over large part of the deep channel due to the similar particle size distribution of sediments. Based on a comparison between the critical shear velocities derived from sedimentary parameters and the shear velocities obtained by tidal currents, it is likely that the depositional area is mainly distributed in the northern part of the channel, while the southern part of the deep channel has to face higher erosion risk.展开更多
Despite international efforts to limit worker exposure to coal dust,it continues to impact the health of thousands of miners across Europe.Airborne coal dust has been studied to improve risk models and its control to ...Despite international efforts to limit worker exposure to coal dust,it continues to impact the health of thousands of miners across Europe.Airborne coal dust has been studied to improve risk models and its control to protect workers.Particle size distribution analyses shows that using spraying systems to suppress airborne dusts can reduce particulate matter concentrations and that coals with higher ash yields produce finer dust.There are marked chemical differences between parent coals and relatively coarse deposited dusts(up to _(500)μm,DD_(500)).Enrichments in Ca,K,Ba,Se,Pb,Cr,Mo,Ni and especially As,Sn,Cu,Zn and Sb in the finest respirable dust fractions could originate from:(i)mechanical machinery wear;(ii)variations in coal mineralogy;(iii)coal fly ash used in shotcrete,and carbonates used to reduce the risk of explosions.Unusual enrichments in Ca in mine dusts are attributed to the use of such concrete,and elevated K to raised levels of phyllosilicate mineral matter.Sulphur concentrations are higher in the parent coal than in the DD_(500),probably due to relatively lower levels of organic matter.Mass concentrations of all elements observed in this study remained below occupational exposure limits.展开更多
In this paper,the power law of particle size distributions (PSDs) in conventional water treatment processes is developed. After measuring the particle size distributions of raw-water,settled water and filtered water,a...In this paper,the power law of particle size distributions (PSDs) in conventional water treatment processes is developed. After measuring the particle size distributions of raw-water,settled water and filtered water,a mathematical model between particle diameter and the amount of particles was studied. The value of collision frequency factor β in the PSDs model can be used to represent the collision behavior of particles ,and can be used as foundation exponent to choose suitable coagulation to accelerate particles aggregation. At the same time,the relationship between the value of parameter K and the total particles volume V was deduced. K is defined as particle volume exponent,which can represent the total volume of particles. The degression degree of K shows the removal efficiency of potable water treatment units.展开更多
Atmospheric aerosol concentrations have been found to change constantly due to the influence of source,winds and human activities over short time periods.This has proved to be a constraint to the study of varied aeros...Atmospheric aerosol concentrations have been found to change constantly due to the influence of source,winds and human activities over short time periods.This has proved to be a constraint to the study of varied aerosol concentrations in urban atmosphere alongside changing relative humidity and how it affects visibility and aerosol particle size distribution.In this research simulation was carried out using Optical Properties of Aerosols and Clouds(OPAC 4.0)average concentration setup for relative humidity(RH)0-99%at visible wavelength 0.4-0.8μm to vary the concentrations of three aerosol components:WASO(Water-soluble),INSO(Insoluble)and SOOT.The Angstrom exponents(α),the curvatures(α2)and atmospheric turbidities(β)were obtained from the regression analysis of Kaufman’s first and second order polynomial equations for visibility.The research determined the mean exponent of the aerosol size growth curve(μ)from the effective hygroscopic growth(geff)and the humidification factors(γ)from visibility enhancement f(RH,λ).The mean exponent of aerosol size distributions(υ)was determined fromμandγ.The results showed that with varied WASO,INSO and SOOT concentrations respectively at different RH,aerosol particle size distributions showed bimodal characteristics with dominance of fine mode particles.Hazy atmospheric conditions prevailed with increasing turbidity.展开更多
Gap debris as discharge product is closely related to machining process in electrical discharge machining(EDM). A lot of recent researches have focused on the relationship among debris size, surfaces texture, remove r...Gap debris as discharge product is closely related to machining process in electrical discharge machining(EDM). A lot of recent researches have focused on the relationship among debris size, surfaces texture, remove rate, and machining stability. The study on statistical distribution of debris size contributes to the research, but it is still superficial currently. In order to obtain the distribution law of the debris particle size, laser particle size analyzer(LPSA) combined with scanning electron microscope(SEM) is used to analyze the EDM debris size. Firstly, the heating dried method is applied to obtain the debris particles. Secondly, the measuring range of LPSA is determined as 0.5-100 μm by SEM observation, and the frequency distribution histogram and the cumulative frequency distribution scattergram of debris size are obtained by using LPSA. Thirdly, according to the distribution characteristic of the frequency distribution histogram, the statistical distribution functions of lognormal, exponentially modified Gaussian(EMG), Gamma and Weibull are chosen to achieve curve fitting of the histogram. At last, the distribute law of the debris size is obtained by fitting results. Experiments with different discharge parameters are carried out on an EDM machine designed by the authors themselves, and the machining conditions are tool electrode of red-copper material, workpiece of ANSI 1045 material and working fluid of de-ionized water. The experimental results indicate that the debris sizes of all experiment sample truly obey the Weibull distribution. The obtained distribution law is significantly important for all the models established based on the debris particle size.展开更多
Particle size distribution of coarse aggregates through mechanical sieving gives results in terms of cumulative mass percent. But digital image processing generated size distribution of particles, while being fast and...Particle size distribution of coarse aggregates through mechanical sieving gives results in terms of cumulative mass percent. But digital image processing generated size distribution of particles, while being fast and accurate, is often expressed in terms of area function or number of particles. In this paper, a mass model is developed which converts the image obtained size distribution to mass-wise distribution, making it readily comparable to mechanical sieving data. The concept of weight/particle ratio is introduced for mass reconstruction from 2D images of particle aggregates. Using this mass model, the effects of several particle shape parameters(such as major axis, minor axis, and equivalent diameter) on sieve-size of the particles is studied. It is shown that the sieve-size of a particle strongly depend upon the shape parameters, 91% of its variation being explained by major axis, minor axis, bounding box length and equivalent diameter. Furthermore, minor axis gives an overall accurate estimate of particle sieve-size, error in mean size(D-50) being just 0.4%. However, sieve-size of smaller particles(<20 mm) strongly depends upon the length of the smaller arm of the bounding box enclosing them and sieve-sizes of larger particles(>20 mm) are highly correlated to their equivalent diameters. Multiple linear regression analysis has been used to generate overall mass-wise particle size distribution, considering the influences of all these shape parameters on particle sieve-size. Multiple linear regression generated overall mass-wise particle size distribution shows a strong correlation with sieve generated data. The adjusted R-square value of the regression analysis is found to be 99 percent(w.r.t cumulative frequency). The method proposed in this paper provides a time-efficient way of producing accurate(up to 99%) mass-wise PSD using digital image processing and it can be used effectively to replace the mechanical sieving.展开更多
The quantitative change and size distribution of particles in the effluents from a sand filter and a granular activated carbon (GAC) filter in a drinking water treatment plant were investigated. The average total conc...The quantitative change and size distribution of particles in the effluents from a sand filter and a granular activated carbon (GAC) filter in a drinking water treatment plant were investigated. The average total concentration of particles in the sand filter effluent during a filter cycle was 148 particles/mL, 27 of which were larger than 2 μm in size. The concentration in the GAC effluent (561 particles/mL) was significantly greater than that in the sand filter effluent. The concentration of particles larger than 2 μm in the GAC filter effluent reached 201 particles/mL, with the amount of particles with sizes between 2 μm and 15 μm increasing. The most probable number (MPN) of carbon fines reached 43 unit/L after six hours and fines between 0.45 μm and 8.0 μm accounted for more than 50%. The total concentration of outflowing bacteria in the GAC filter effluent, 350 CFU (colony-forming units) /mL, was greater than that in the sand filter effluent, 210 CFU/mL. The desorbed bacteria concentration reached an average of 310 CFU/mg fines. The disinfection efficiency of desorbed bacteria was lower than 40% with 1.5 mg/L of chlorine. The disinfection effect showed that the inactivation rate with 2.0 mg/L of chloramine (90%) was higher than that with chlorine (70%). Experimental results indicated that the high particle concentration in raw water and sedimentation effluent led to high levels of outflowing particles in the sand filter effluent. The activated carbon fines in the effluent accounted for a small proportion of the total particle amount, but the existing bacteria attached to carbon fines may influence the drinking water safety. The disinfection efficiency of desorbed bacteria was lower than that of free bacteria with chlorine, and the disinfection effect on bacteria attached to carbon fines with chloramine was better than that with only chlorine.展开更多
Based on various ultrasonic loss mechanisms, the formula of the cumulative mass percentage of minerals with different particle sizes was given, with which the particle size distribution was integrated into an ultrason...Based on various ultrasonic loss mechanisms, the formula of the cumulative mass percentage of minerals with different particle sizes was given, with which the particle size distribution was integrated into an ultrasonic attenuation model. And then the correlations between the ultrasonic attenuation and the pulp density, and the particle size were obtained. The derived model was combined with the experiment and the analysis of experimental data to determine the inverse model relating ultrasonic attenuation coefficient with size distribution. Finally, an optimization method of inverse parameter, genetic algorithm was applied for particle size distribution. The results of inverse calculation show that the precision of measurement was high.展开更多
Background: Particle size distribution and hydraulic conductivity of coastal no-agricultural lands are not available. This study characterized the particle size distribution and hydraulic conductivity on coastal non-a...Background: Particle size distribution and hydraulic conductivity of coastal no-agricultural lands are not available. This study characterized the particle size distribution and hydraulic conductivity on coastal non-agricultural land along the coastal plain of Gaza. Materials and Methods: Six soil profiles were digged along the coastal plain in Gaza Strip and soil samples were collected from 0 - 150 cm depth. Four soil plots around each site were used to determine the hydraulic conductivity using Infiltrometer method. Four particle size groups were identified, group 1 (630 nm), group 2 (200 nm), group 3 (63 nm) and group 4 (20 nm). Results: Dominancy of particle size group 2 was noticed in all sites followed by group 3. Groups 1 and 4 were less dominant in all sites. Hydraulic conductivity ranged from lower value 0.27 in the control soil plot in Khan Younis (site 1) to the highest value 1.76 m/s in disturbed soil plot in Shakhejjlen (site 3) with regression coefficient (R2) range of 0.9725 - 0.997 indicating strong positive association. Conclusion: It can be concluded that the coastal non-agricultural land is sandy with various hydraulic conductivity values due to different particle size distribution. These data are useful to the scientific community around the world and will be helpful to speculate potential risk factors to life of ecosystem.展开更多
A closed or semi\|closed plateau lake, whose sediment records can provide us with plenty of fine and high resolution information, is a sensitive indicator of climatic and environmental changes. During the reconstructi...A closed or semi\|closed plateau lake, whose sediment records can provide us with plenty of fine and high resolution information, is a sensitive indicator of climatic and environmental changes. During the reconstruction of various short\|time\|scale climatic and environmental changes, the geochemical records in plateau\|lake sediments are superior to other natural files. Based on fine dissection of the vertical profile of sediment particle sizes, this paper reveals the quasi\|periodical changes of sediment particle sizes, which indicates the quasi\|periodical fluctuations of the regional climate. A synthetic analysis of multiple indexes shows that sediment particle size is a more sensitive and more effective index of climatic and environmental changes than other geochemical indexes. High content of >20 μm sediment particles and low content of 2-10 μm sediment particles indicate a warm\|dry climate and conversely a cold\|humid climate, and their ratio can be used as an effective index of climatic changes. The basic climate succession in the region of Lake Erhai is characterized as being alternatively warm\|dry and cold\|humid and it has been developing into a warm\|dry climate as a whole. There exist at least 2 time\|scale quasi\|periodical fluctuations of the regional climate in Lake Erhai. At present, the region of Lake Erhai is at the end of the warm\|dry period and at the beginning of a cold\|humid period, so the temperature will go down and the water level will rise.展开更多
Several industrial coal processes are largely determined by the distribution of particle sizes in their feed.Currently these parameters are measured by manual sampling,which is time consuming and cannot provide real t...Several industrial coal processes are largely determined by the distribution of particle sizes in their feed.Currently these parameters are measured by manual sampling,which is time consuming and cannot provide real time feedback for automatic control purposes.In this paper,an approach using image segmentation on images of overlapped coal particles is described.The estimation of the particle size distribution by number is also described.The particle overlap problem was solved using image enhancement algorithms that converted those image parts representing material in lower layers to black.Exponential high-pass filter(EHPF) algorithms were used to remove the texture from particles on the surface.Finally,the edges of the surface particles were identified by morphological edge detection.These algorithms are described in detail as is the method of extracting the coal particle size.Tests indicate that using more coal images gives a higher accuracy estimate.The positive absolute error of 50 random tests was consistently less than 2.5% and the errors were reduced as the size of the fraction increased.展开更多
On the basis of population balance a mathematical model is developed to describe the formation of polymer partlcle in styrene suspension polymerization. The characteristics of coalescence and breakage of droplets and ...On the basis of population balance a mathematical model is developed to describe the formation of polymer partlcle in styrene suspension polymerization. The characteristics of coalescence and breakage of droplets and the gel effect are analyzed in particular. Parameters of the models are esthnztted by experimental. on reaction conversion and particle size distributlon. The results show that the model is suitable for predicting polymerization processes.展开更多
The effect of particle size distribution of alumina has been investigated for silica-free tabular alumina low cement castables( LCC). Three different combinations of alumina have been included in the matrix formulatio...The effect of particle size distribution of alumina has been investigated for silica-free tabular alumina low cement castables( LCC). Three different combinations of alumina have been included in the matrix formulation of the castables. All the three combinations are composed of a bimodal reactive alumina and a fine ground monomodal reactive alumina. The first A1 and second A2 combinations are respectively composed of bimodal and monomodal aluminas from Alteo,with a different fine /coarse particles ratio for the bimodal alumina. The two Alteo combinations have been compared with a third combination C composed of a bimodal commercially available grade and a monomodal commercially available grade. Optimization of particle size packing has been performed for the three different formulations using the Dinger and Funk model. With this optimization,the two formulations based on Alteo material( PFR,PBR and PFR40) achieve the same level of performance in applicative tests( flowability,cold physical properties,mechanical resistance,crystalline phases,thermal shocks and corrosion) as reference solutions on the market.展开更多
基金The work described in this paper was partially supported by grants from the Research Grant Council of the Hong Kong Special Administrative Region,China(Project Nos.HKU 17207518 and R5037-18).
文摘The traditional standard wet sieving method uses steel sieves with aperture?0.063 mm and can only determine the particle size distribution(PSD)of gravel and sand in general soil.This paper extends the traditional method and presents an extended wet sieving method.The extended method uses both the steel sieves and the nylon filter cloth sieves.The apertures of the cloth sieves are smaller than 0.063 mm and equal 0.048 mm,0.038 mm,0.014 mm,0.012 mm,0.0063 mm,0.004 mm,0.003 mm,0.002 mm,and 0.001 mm,respectively.The extended method uses five steps to separate the general soil into many material sub-groups of gravel,sand,silt and clay with known particle size ranges.The complete PSD of the general soil is then calculated from the dry masses of the individual material sub-groups.The extended method is demonstrated with a general soil of completely decomposed granite(CDG)in Hong Kong,China.The silt and clay materials with different particle size ranges are further examined,checked and verified using stereomicroscopic observation,physical and chemical property tests.The results further confirm the correctness of the extended wet sieving method.
基金Funded by the National Natural Science Foundation of China(No.52172025)。
文摘The effects of high-volume slag-fly ash cement with different particle sizes on hydration degree,microstructure and mechanical properties were systematically studied,by means of laser particle size(DLS),X-ray diffraction (XRD),comprehensive thermal analysis (TG-DTA),scanning electron microscopy(SEM) and mechanical properties tests.The results show that suitable particle size distribution of cementitious material has significantly promoting effects on hydration reaction rate and mechanical properties.Compared with slag without further grinding,the slag after ball milling for 4 h has an obvious improvement in reactivity,which also provides a faster hydration rate and higher compressive strength for the cementitious material.When the slag milled for 1 and 4 h is mixed at a mass ratio of 2:1 (i e,slag with D_(50) of 7.4μm and average size of 9.9μm,and slag with D_(50) value of 2.6μm and average size of 5.3μm),and a certain amount of fly ash is added in,the most obvious improvement of compressive strength of cement is achieved.
基金The National Key Research and Development Program(2020YFA0906804)the National Natural Science Foundation of China(22078325,22035007,91934301)+1 种基金the NSFC-EU project(31961133018)the Special Project of Strategic Leading Science and Technology,CAS(XDC06010302)are gratefully acknowledged.
文摘The particle size distribution of polymer always develops in emulsion polymerization systems,and certain key phenomena/mechanisms as well as properties of the final product are significantly affected by this distribution.This review mainly focuses on the measurement methods of particle size distribution rather than average particle size during the emulsion polymerization process,including the existing off-line,on-line,and in-line measurement methods.Moreover,the principle,resolution,performance,advantages,and drawbacks of various methods for evaluating particle size distribution are contrasted and illustrated.Besides,several possible development directions or solutions of the in-line measurement technology are explored.
基金financially supported by the National Natural Science Foundation of China(Grant No.41790432)Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA20030301)。
文摘Internal erosion occurs when fine particles escape from the soil driven by seepage flow,which is considered to be the crucial factor causing the failure of earth structures filled with gravelly soil.The objective of this paper is to suggest an appropriate method to assess internal erosion potential of gravelly soil.By analyzing the sensitivity of soil material to internal erosion,the variable(Dc15/df85)max and the content of coarse particles(Pc)are selected as the evaluation indexes(Dc15 and df85 are the diameters of 15%mass passing in the coarse component and 85%mass passing in the fine component,respectively).A series of gravelly soils with different particle size distributions are tested for internal erosion by the self-made permeameter.Based on the test results,an evaluation method for the internal erosion of gravelly soil is proposed.Gravelly soil is prone to internal erosion when 60%≤Pc<95%and(Dc15/df85)max≥9.5.The proposed method shows good accuracy in evaluating the internal erosion of 36 soil samples from other studies,which confirms the reliability of the method.The proposed method makes it possible to accurately assess internal erosion of gravelly soil,and an alternative method is provided for engineers to determine whether there is a risk of internal erosion in earth structures consisting of gravelly soil.
基金supported by the National Natural Science Foundation of China (No: 51806103)Jiangsu Provincial Natural Science Foundation(No: BK20170800)Open Funds of Aero-engine Thermal Environment and Structure Key Laboratory of Ministry of Industry and Information Technology (No. CEPE2018005)
文摘The weighted-sum-of-gray-gas(WSGG)model and Mie theory are applied to study the influents of particle size on the radiative transfer in high temperature homogeneous gas-particle mixtures,such as the flame in aero-engine combustor.The radiative transfer equation is solved by the finite volume method.The particle size is assumed to obey uniform distribution and logarithmic normal(L-N)distribution,respectively.Results reveal that when particle size obeys uniform distribution,increasing particle size with total particle volume fraction fvunchanged will result in the decreasing of the absolute value of radiative heat transfer properties,and the effect of ignoring particle scattering will also be weakened.Opposite conclusions can be obtained when total particle number concentration N0 is unchanged.Moreover,if particle size obeys L-N distribution,increasing the narrowness indexσor decreasing the characteristic diameter Dˉwith the total particle volume fraction fvunchanged will increase the absolute value of radiative heat transfer properties.With total particle number concentration N0 unchanged,opposite conclusions for radiative heat source and incident radiation terms can be obtained except for radiative heat flux term.As a whole,the effects of particle size on the radiative heat transfer in the high-temperature homogeneous gas-particle mixtures are complicated,and the particle scattering cannot be ignoring just according to the particle size.
文摘An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has been made.
基金financially supported by the National Natural Science Foundation of China(No.51376095)the Jiangsu Province Environmental Research Projects(No.2014049)
文摘Based on the laser diffraction and Shifrin transform,the measurement method of particle size distribution has been improved extensively.While in real measurements,some noise peaks exist in the inversion data and are easily to be misread as particle distribution peaks.The improved method used a truncation function as a filter is hard to distinguish adjacent peaks.Here,by introducing the bimodal resolution criterion,the filter function is optimized,and to a quasi truncation function with the optimized filter function is studied to achieve optimal bimodal resolution and to remove noise peaks.This new quasi truncation function fits multimode distribution very well.By combining the quasi truncation function with Shifrin transform,noise peaks are removed well and the adjacent peaks are distinguished clearly.Finally,laser diffraction experiments are conducted and the particle size distribution is analyzed by adoping the method.The results show that the quasi truncation function has better bimodal resolution than the truncation function.Generally,by combining the quasi truncation function with the Shifrin transform,in particle size distribution measurements with laser diffraction,the bimodal resolution is greatly increased and the noise is removed well.And the results can restore the original distribution perfectly.Therefore,the new method with combination of the quasi truncation function and the Shifrin transform provides a feasible and effective way to measure the multimode particle size distribution by laser diffraction.
基金supported by the National Natural Science Foundation of China(Grant Nos.41676078,51409088 and41506100)the Natural Science Foundation of Jiangsu Province(Grant No.BK20151499)+1 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.2015B16114,2015B26414 and 2015B34914)the Project of Jiangsu Provincial Six Talent Peaks(Grant No.XXRJ-008)
文摘Particle size distributions(PSDs) of bottom sediments in a coastal zone are generally multimodal due to the complexity of the dynamic environment. In this paper, bottom sediments along the deep channel of the Pearl River Estuary(PRE) are used to understand the multimodal PSDs′ characteristics and the corresponding depositional environment. The results of curve-fitting analysis indicate that the near-bottom sediments in the deep channel generally have a bimodal distribution with a fine component and a relatively coarse component. The particle size distribution of bimodal sediment samples can be expressed as the sum of two lognormal functions and the parameters for each component can be determined. At each station of the PRE, the fine component makes up less volume of the sediments and is relatively poorly sorted. The relatively coarse component, which is the major component of the sediments, is even more poorly sorted. The interrelations between the dynamics and particle size of the bottom sediment in the deep channel of the PRE have also been investigated by the field measurement and simulated data.The critical shear velocity and the shear velocity are calculated to study the stability of the deep channel. The results indicate that the critical shear velocity has a similar distribution over large part of the deep channel due to the similar particle size distribution of sediments. Based on a comparison between the critical shear velocities derived from sedimentary parameters and the shear velocities obtained by tidal currents, it is likely that the depositional area is mainly distributed in the northern part of the channel, while the southern part of the deep channel has to face higher erosion risk.
基金European Commission Research Fund for Coal and Steel(Grant Agreement Number–754205)Generalitat de Catalunya(SGR41).Centre of Excellence Severo Ochoa—Spanish Ministry of Science and Innovation(Project CEX2018-000794-S).
文摘Despite international efforts to limit worker exposure to coal dust,it continues to impact the health of thousands of miners across Europe.Airborne coal dust has been studied to improve risk models and its control to protect workers.Particle size distribution analyses shows that using spraying systems to suppress airborne dusts can reduce particulate matter concentrations and that coals with higher ash yields produce finer dust.There are marked chemical differences between parent coals and relatively coarse deposited dusts(up to _(500)μm,DD_(500)).Enrichments in Ca,K,Ba,Se,Pb,Cr,Mo,Ni and especially As,Sn,Cu,Zn and Sb in the finest respirable dust fractions could originate from:(i)mechanical machinery wear;(ii)variations in coal mineralogy;(iii)coal fly ash used in shotcrete,and carbonates used to reduce the risk of explosions.Unusual enrichments in Ca in mine dusts are attributed to the use of such concrete,and elevated K to raised levels of phyllosilicate mineral matter.Sulphur concentrations are higher in the parent coal than in the DD_(500),probably due to relatively lower levels of organic matter.Mass concentrations of all elements observed in this study remained below occupational exposure limits.
基金Sponsored by the National Basic Research Program of China(973)(Grant No.2004CB41850)the Natural Science Foundation of Heilongjiang Prov-ince(Grant No.E200609)
文摘In this paper,the power law of particle size distributions (PSDs) in conventional water treatment processes is developed. After measuring the particle size distributions of raw-water,settled water and filtered water,a mathematical model between particle diameter and the amount of particles was studied. The value of collision frequency factor β in the PSDs model can be used to represent the collision behavior of particles ,and can be used as foundation exponent to choose suitable coagulation to accelerate particles aggregation. At the same time,the relationship between the value of parameter K and the total particles volume V was deduced. K is defined as particle volume exponent,which can represent the total volume of particles. The degression degree of K shows the removal efficiency of potable water treatment units.
文摘Atmospheric aerosol concentrations have been found to change constantly due to the influence of source,winds and human activities over short time periods.This has proved to be a constraint to the study of varied aerosol concentrations in urban atmosphere alongside changing relative humidity and how it affects visibility and aerosol particle size distribution.In this research simulation was carried out using Optical Properties of Aerosols and Clouds(OPAC 4.0)average concentration setup for relative humidity(RH)0-99%at visible wavelength 0.4-0.8μm to vary the concentrations of three aerosol components:WASO(Water-soluble),INSO(Insoluble)and SOOT.The Angstrom exponents(α),the curvatures(α2)and atmospheric turbidities(β)were obtained from the regression analysis of Kaufman’s first and second order polynomial equations for visibility.The research determined the mean exponent of the aerosol size growth curve(μ)from the effective hygroscopic growth(geff)and the humidification factors(γ)from visibility enhancement f(RH,λ).The mean exponent of aerosol size distributions(υ)was determined fromμandγ.The results showed that with varied WASO,INSO and SOOT concentrations respectively at different RH,aerosol particle size distributions showed bimodal characteristics with dominance of fine mode particles.Hazy atmospheric conditions prevailed with increasing turbidity.
基金supported by Research Fund for the Doctoral Program of Ministry of Education of China(Grant No.20090041110031)National Natural Science Foundation of China(Grant No.50575033)
文摘Gap debris as discharge product is closely related to machining process in electrical discharge machining(EDM). A lot of recent researches have focused on the relationship among debris size, surfaces texture, remove rate, and machining stability. The study on statistical distribution of debris size contributes to the research, but it is still superficial currently. In order to obtain the distribution law of the debris particle size, laser particle size analyzer(LPSA) combined with scanning electron microscope(SEM) is used to analyze the EDM debris size. Firstly, the heating dried method is applied to obtain the debris particles. Secondly, the measuring range of LPSA is determined as 0.5-100 μm by SEM observation, and the frequency distribution histogram and the cumulative frequency distribution scattergram of debris size are obtained by using LPSA. Thirdly, according to the distribution characteristic of the frequency distribution histogram, the statistical distribution functions of lognormal, exponentially modified Gaussian(EMG), Gamma and Weibull are chosen to achieve curve fitting of the histogram. At last, the distribute law of the debris size is obtained by fitting results. Experiments with different discharge parameters are carried out on an EDM machine designed by the authors themselves, and the machining conditions are tool electrode of red-copper material, workpiece of ANSI 1045 material and working fluid of de-ionized water. The experimental results indicate that the debris sizes of all experiment sample truly obey the Weibull distribution. The obtained distribution law is significantly important for all the models established based on the debris particle size.
基金Indian Institute of Technology,Kharagpur in India for supporting this work
文摘Particle size distribution of coarse aggregates through mechanical sieving gives results in terms of cumulative mass percent. But digital image processing generated size distribution of particles, while being fast and accurate, is often expressed in terms of area function or number of particles. In this paper, a mass model is developed which converts the image obtained size distribution to mass-wise distribution, making it readily comparable to mechanical sieving data. The concept of weight/particle ratio is introduced for mass reconstruction from 2D images of particle aggregates. Using this mass model, the effects of several particle shape parameters(such as major axis, minor axis, and equivalent diameter) on sieve-size of the particles is studied. It is shown that the sieve-size of a particle strongly depend upon the shape parameters, 91% of its variation being explained by major axis, minor axis, bounding box length and equivalent diameter. Furthermore, minor axis gives an overall accurate estimate of particle sieve-size, error in mean size(D-50) being just 0.4%. However, sieve-size of smaller particles(<20 mm) strongly depends upon the length of the smaller arm of the bounding box enclosing them and sieve-sizes of larger particles(>20 mm) are highly correlated to their equivalent diameters. Multiple linear regression analysis has been used to generate overall mass-wise particle size distribution, considering the influences of all these shape parameters on particle sieve-size. Multiple linear regression generated overall mass-wise particle size distribution shows a strong correlation with sieve generated data. The adjusted R-square value of the regression analysis is found to be 99 percent(w.r.t cumulative frequency). The method proposed in this paper provides a time-efficient way of producing accurate(up to 99%) mass-wise PSD using digital image processing and it can be used effectively to replace the mechanical sieving.
基金supported by the National Natural Science Foundation of China (Grant No 50638020)the National Key High-Tech Program (863) of China (Grant No 2006AA06Z311)the Natural Science Foundation of Jiangsu Province (Grant No BK2006170)
文摘The quantitative change and size distribution of particles in the effluents from a sand filter and a granular activated carbon (GAC) filter in a drinking water treatment plant were investigated. The average total concentration of particles in the sand filter effluent during a filter cycle was 148 particles/mL, 27 of which were larger than 2 μm in size. The concentration in the GAC effluent (561 particles/mL) was significantly greater than that in the sand filter effluent. The concentration of particles larger than 2 μm in the GAC filter effluent reached 201 particles/mL, with the amount of particles with sizes between 2 μm and 15 μm increasing. The most probable number (MPN) of carbon fines reached 43 unit/L after six hours and fines between 0.45 μm and 8.0 μm accounted for more than 50%. The total concentration of outflowing bacteria in the GAC filter effluent, 350 CFU (colony-forming units) /mL, was greater than that in the sand filter effluent, 210 CFU/mL. The desorbed bacteria concentration reached an average of 310 CFU/mg fines. The disinfection efficiency of desorbed bacteria was lower than 40% with 1.5 mg/L of chlorine. The disinfection effect showed that the inactivation rate with 2.0 mg/L of chloramine (90%) was higher than that with chlorine (70%). Experimental results indicated that the high particle concentration in raw water and sedimentation effluent led to high levels of outflowing particles in the sand filter effluent. The activated carbon fines in the effluent accounted for a small proportion of the total particle amount, but the existing bacteria attached to carbon fines may influence the drinking water safety. The disinfection efficiency of desorbed bacteria was lower than that of free bacteria with chlorine, and the disinfection effect on bacteria attached to carbon fines with chloramine was better than that with only chlorine.
基金Project supported by Technology Development and Research Special Foundation of National Science Research Academicand Institute , China
文摘Based on various ultrasonic loss mechanisms, the formula of the cumulative mass percentage of minerals with different particle sizes was given, with which the particle size distribution was integrated into an ultrasonic attenuation model. And then the correlations between the ultrasonic attenuation and the pulp density, and the particle size were obtained. The derived model was combined with the experiment and the analysis of experimental data to determine the inverse model relating ultrasonic attenuation coefficient with size distribution. Finally, an optimization method of inverse parameter, genetic algorithm was applied for particle size distribution. The results of inverse calculation show that the precision of measurement was high.
文摘Background: Particle size distribution and hydraulic conductivity of coastal no-agricultural lands are not available. This study characterized the particle size distribution and hydraulic conductivity on coastal non-agricultural land along the coastal plain of Gaza. Materials and Methods: Six soil profiles were digged along the coastal plain in Gaza Strip and soil samples were collected from 0 - 150 cm depth. Four soil plots around each site were used to determine the hydraulic conductivity using Infiltrometer method. Four particle size groups were identified, group 1 (630 nm), group 2 (200 nm), group 3 (63 nm) and group 4 (20 nm). Results: Dominancy of particle size group 2 was noticed in all sites followed by group 3. Groups 1 and 4 were less dominant in all sites. Hydraulic conductivity ranged from lower value 0.27 in the control soil plot in Khan Younis (site 1) to the highest value 1.76 m/s in disturbed soil plot in Shakhejjlen (site 3) with regression coefficient (R2) range of 0.9725 - 0.997 indicating strong positive association. Conclusion: It can be concluded that the coastal non-agricultural land is sandy with various hydraulic conductivity values due to different particle size distribution. These data are useful to the scientific community around the world and will be helpful to speculate potential risk factors to life of ecosystem.
文摘A closed or semi\|closed plateau lake, whose sediment records can provide us with plenty of fine and high resolution information, is a sensitive indicator of climatic and environmental changes. During the reconstruction of various short\|time\|scale climatic and environmental changes, the geochemical records in plateau\|lake sediments are superior to other natural files. Based on fine dissection of the vertical profile of sediment particle sizes, this paper reveals the quasi\|periodical changes of sediment particle sizes, which indicates the quasi\|periodical fluctuations of the regional climate. A synthetic analysis of multiple indexes shows that sediment particle size is a more sensitive and more effective index of climatic and environmental changes than other geochemical indexes. High content of >20 μm sediment particles and low content of 2-10 μm sediment particles indicate a warm\|dry climate and conversely a cold\|humid climate, and their ratio can be used as an effective index of climatic changes. The basic climate succession in the region of Lake Erhai is characterized as being alternatively warm\|dry and cold\|humid and it has been developing into a warm\|dry climate as a whole. There exist at least 2 time\|scale quasi\|periodical fluctuations of the regional climate in Lake Erhai. At present, the region of Lake Erhai is at the end of the warm\|dry period and at the beginning of a cold\|humid period, so the temperature will go down and the water level will rise.
基金the Creative Research Groups Science Fund of the National Natural Science Foundation of China(No.50921002)
文摘Several industrial coal processes are largely determined by the distribution of particle sizes in their feed.Currently these parameters are measured by manual sampling,which is time consuming and cannot provide real time feedback for automatic control purposes.In this paper,an approach using image segmentation on images of overlapped coal particles is described.The estimation of the particle size distribution by number is also described.The particle overlap problem was solved using image enhancement algorithms that converted those image parts representing material in lower layers to black.Exponential high-pass filter(EHPF) algorithms were used to remove the texture from particles on the surface.Finally,the edges of the surface particles were identified by morphological edge detection.These algorithms are described in detail as is the method of extracting the coal particle size.Tests indicate that using more coal images gives a higher accuracy estimate.The positive absolute error of 50 random tests was consistently less than 2.5% and the errors were reduced as the size of the fraction increased.
文摘On the basis of population balance a mathematical model is developed to describe the formation of polymer partlcle in styrene suspension polymerization. The characteristics of coalescence and breakage of droplets and the gel effect are analyzed in particular. Parameters of the models are esthnztted by experimental. on reaction conversion and particle size distributlon. The results show that the model is suitable for predicting polymerization processes.
文摘The effect of particle size distribution of alumina has been investigated for silica-free tabular alumina low cement castables( LCC). Three different combinations of alumina have been included in the matrix formulation of the castables. All the three combinations are composed of a bimodal reactive alumina and a fine ground monomodal reactive alumina. The first A1 and second A2 combinations are respectively composed of bimodal and monomodal aluminas from Alteo,with a different fine /coarse particles ratio for the bimodal alumina. The two Alteo combinations have been compared with a third combination C composed of a bimodal commercially available grade and a monomodal commercially available grade. Optimization of particle size packing has been performed for the three different formulations using the Dinger and Funk model. With this optimization,the two formulations based on Alteo material( PFR,PBR and PFR40) achieve the same level of performance in applicative tests( flowability,cold physical properties,mechanical resistance,crystalline phases,thermal shocks and corrosion) as reference solutions on the market.
