检索结果-南通市图书馆

Particuology 2022年第6期20卷 39-50页

作者： Peyman Aela Lu Zong Morteza Esmaeili Mohammad Siahkouhi Guoqing Jing School of Civil Engineering Beijing Jiaotong UniversityBeijing 100044China School of Railway Engineering Iran University of Science and TechnologyTehran 16846-13114Iran

The discrete element method(DEM)is widely used in the realistic simulation of the shapes of particles.Researchers have considered the simplification of particle shapes owing to the high computational cost of such simulation.In this regard,the modeling of calibrated particles is a major challenge owing to the simultaneous effects of particle properties.The angle-of-repose test is a standard test method used to calibrate the bulk behavior of simulated particles.In the present study,the hollow-cylinder(slump)test was modeled for the verification of discrete element simulations.In this regard,a sensitivity analysis was conducted for all effective parameters,namely the static friction,rolling friction,restitution coefficient,sphericity,roundness,particle size distribution,and number of ballast particles.The results indicate that the rolling friction,roundness,number of particles,and size of particles are the most important parameters in the determination of the angle of repose(AOR).For particles in the range of ballast(20-60 mm),the effect of the number of particles on the angle of repose is reduced when the number is greater than 426.Additionally,it is concluded that angular particles can be replaced with sub-angular particles(R≈0.2-0.45)with a higher rolling friction coefficient(μ_(r)>0.14).

关键词： Ballast angle of repose Calibration Hollow cylinder test Friction coefficients Shape factors

DEM investigation of angle of repose for super-ellipsoidal particles

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Particuology 2020年第3期18卷 53-66页

作者： Hao Chen Shiwei Zhao Xiaowen Zhou State Key Laboratory of Subtropical Building Science South China University of TechnologyGuangzhou 510641China

We explore the effect of particle shape on the angle of repose (AoR) in granular packing using a three-dimensional discrete element method.Non-spherical particles were modeled using super-ellipsoids characterized by aspect ratio and blockiness.The relationship between AoR and particle shape was examined,followed by a series of analyses on the origin of AoR from a microscopic perspective.Results show that,with blockiness deviating from unity,AoR has an approximate "M" shape that exhibits a strong to weak trend with aspect ratio,matching results of previous reports.Another finding suggests a parabolic relationship between normalized AoR and normalized coordination number,AoR increases with anisotropy related more with the anisotropy of particle orientation than with the anisotropy of contact normal.Particle shape is more likely to affect AoR by affecting the tangential force than the normal contact force.An analysis based on traction indicates that dips in stress associated with the tangential force (compared with the normal force) and non-spherical particles (compared with spheres) are more significant.For various particle shapes,AoR is positively correlated with friction mobilization but is negatively correlated with friction mobilization for various coefficient of friction.

关键词： Discrete element angle of repose Non-spherical particles Granular fabric Packing

Difference between static and dynamic angle of repose of uniform sediment grains

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2017年第2期32卷 149-154页

作者： Nian-Sheng Cheng Kuifeng Zhao School of Civil and Environmental Engineering Nanyang Technological University

In the investigation of sediment transport,it is necessary to differentiate various definitions of angle of repose(AoR) available in the literature.The static AoR,composed of upper and lower angle of slope,forms just before and after slope instability,while the dynamic AoR can be observed when sediment grains are moving continuously down an inclined plane.In the present study,a series of laboratory experiments was conducted to measure static and dynamic angle of repose for uniform natural sediments with median diameter of 0.28-4.38 mm.The results show that the different slope angles have different characteristics.The upper and dynamic AoR increase slightly with increasing grain diameter,while the lower AoR is not sensitive to changes in sediment size and may assume a constant value.The average of the upper and lower AoR is equivalent to the dynamic AoR,and the difference between them increases with increasing grain diameter.The present study suggests that the different angles of repose should be treated with caution when applying in investigations of bedload transport,dune migration and local scour development.

关键词： angle of repose Avalanche Sediment transport

The effect of hemicellulose on the interparticle frictional behavior of lignocellulosic biomass particulates

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Particuology 2021年第2期19卷 16-22页

作者： Ekramul Haque Ehite Eric Drumm Nourredine Abdoulmoumine Biosystems Engineering and Soil Science Department University of TennesseeKnoxvilleTN 37996USA Center for Renewable Carbon University of TennesseeKnoxvilleTN 37996USA

Lignocellulosic biomass material sourced from plants and herbaceous sources is considered as a prospective feedstock of inexpensive,potentially carbon-neutral energy.Lignocellulosic biomass is structurally built on cellulose,hemicellulose,and lignin,which are present in varying concentrations based on the feedstock type and play distinct and not well understood mechanical functions in the flow behavior.The frictional characteristics of lignocellulosic biomass particulates influence their flow behavior in biorefineries.Thus,it is important to fundamentally investigate the relative contribution of cellulose,hemicellulose,and lignin to the frictional behavior.However,these three biopolymers are interwoven into a complex matrix in the lignocellulosic biomass,thus making it hard to quantify the contribution of each biopolymer.In this study,we selectively remove hemicellulose from switchgrass and investigate the effects of its diminishing concentration on the coefficient of friction.We observed that the angle of repose and,therefore,the coefficient of friction for a loose assembly of the control and treated switchgrass samples decrease with decreasing hemicellulose content.This indicates the frictional resistance to flow for biomass particulate assemblies is at least proportional to the hemicellulose content.We also established that the observed changes in the frictional behavior were not due to particle morphological characteristics.

关键词： Lignocellulosic biomass Frictional behavior angle of repose Hot water extraction Switchgrass Hemicellulose removal

Moisture dependent physical properties of Lagenaria siceraria seed

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Agricultural and Biological Engineering 2013年第4期6卷 111-120页

作者： Prashant Pandharinath Said Rama Chandra Pradhan Department of Farm Engineering Institute of Agricultural SciencesBanaras Hindu UniversityVaranasiUttar Pradesh 221005India

The investigation was done to evaluate the effect of moisture content on some physical properties of Lagenaria siceraria seed.The study was conducted at five moisture levels including 8.84%,10.10%,11.89%,12.60%and 15.10%(w.b.).Results showed that the mean value of principal dimensions,average diameters,surface area and 1000 seed mass increased linearly but aspect ratio decreased with increase in moisture content.The sphericity increased in the moisture range of 8.84%to 11.89%but decreased with further raise in the moisture up to 15.10%.Gravimetric properties like bulk density increased with increase in moisture content however true density and porosity decreased linearly with increase in moisture content.angle of repose and terminal velocity increased linearly with moisture content of the seed.The coefficient of friction increased linearly with seed moisture content on five experimental surfaces(plywood,galvanized iron,glass and plastic).The information pertaining to moisture dependant physical properties of Lagenaria siceraria seeds may become an essential part in design of processing machines and its unit operations,design of dehulling,oil expression and other processing equipments.

关键词： Lagenaria siceraria physical properties angle of repose aspect ratio gravimetric properties sphericity

Contact parameter analysis and calibration in discrete element simulation of rice straw

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Agricultural and Biological Engineering 2021年第4期14卷 72-81页

作者： Honglei Jia Jiayu Deng Yanling Deng Tianyou Chen Gang Wang Zaijin Sun Hui Guo College of Biological and Agricultural Engineering Jilin UniversityChangchun 130022China Technical Center for Soil Agricultural and Rural Ecology and EnvironmentMinistry of Ecology and Environment of the People’s Republic ChinaBeijing 100012China College of Mechanical Engineering Harbin Institute of PetroleumHarbin 150028China

Discrete element method was used to study and analyze the interaction between rice straws and between rice straw and agricultural machinery parts,thereby providing a scientific basis for post-harvest paddy field processing.Calibrations of rice straw-rice straw,rice straw-agricultural machinery part contact parameters(collision recovery coefficient,static friction coefficient and rolling friction coefficient)constitute an important prerequisite for the discrete element research process.In this study,the collision recovery coefficients of rice straw-steel and rice straw-rice straw were 0.230 and 0.357,respectively,which were calibrated by the collision method.The static friction coefficient and rolling friction coefficient of rice straw-steel were 0.363 and 0.208 respectively,which were calibrated by the inclined plate method and the slope method.The static friction coefficient and rolling friction coefficient of rice straw-rice straw were 0.44 and 0.07,respectively,which were calibrated by the split cylinder method.The paired t-test showed insignificant differences between calibration parameter simulation results and the physical test values(p>0.05).Taking the angle of repose that reflecting rice straw flow and friction characteristics as the evaluation index,the verification tests of the above calibration values indicated that the simulated angle of repose has no significant difference from the physical test value(p>0.05).The side plate lifting test on rice straw of different lengths showed no significant difference between the simulated angle of repose and the physical test value(p>0.05).This study can provide a basis for contact parameters choice in discrete element simulation analysis with rice straw-rice straw and rice straw-agricultural machinery parts as the research object.The calibration method can provide a reference for the contact parameter calibration of other crop straws.

关键词： rice straw discrete element simulation contact parameter parameter calibration angle of repose

Determination of the coefficient of rolling friction of irregularly shaped maize particles by using discrete element method

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Agricultural and Biological Engineering 2020年第2期13卷 15-25页

作者： Linrong Shi Wuyun Zhao Bugong Sun Wei Sun School of Mechanical and Electrical Engineering Gansu Agricultural UniversityLanzhou 730070China

The coefficient of rolling friction is a foundation parameter for conducting particles simulation,however,which of irregularly shaped maize seeds is difficult to measure.Furthermore,the coefficient of rolling friction between the simulation particles and the actual seeds is inconsistent due to the shaped difference of model and different position of gravity center.This paper use two methods to determinate the coefficient of rolling friction based on discrete element method(DEM)and physical experiments.Three types of maize models from five different shaped maize samples(including horse-tooth shape,spherical cone shape,spherical shape,oblate shape,irregular shape)were developed with the help of slice modeling and 3D modeling technology.Aluminum cylinder container is used to arrange the simulation experiments of angle of repose with taking the coefficient of rolling friction as independent variables and the simulation angle of repose as target values.After predicting detailed the coefficient of rolling friction(including horse-tooth shape,spherical cone shape,spherical shape,between horse-tooth shape and spherical cone shape,between horse-tooth shape and spherical shape,between spherical shape and spherical cone shape maize models),and forecasting a unified the coefficient of rolling friction among horse-tooth shape,spherical cone shape and spherical shape maize models,two types of materials(aluminum cylinder container and organic glass container)were used to validate the difference the angle of repose between the simulation maize models and actual maize seeds.Results show the relative error of the angle of repose between the maize models controlled by the coefficient of rolling friction through the detailed method and the actual maize seeds is 0.22%,0.33%in aluminum cylinder,organic glass container,respectively.The relative error of the angle of repose between the simulation maize models controlled by the coefficient of rolling friction through the united method and actual maize seeds is 2.47%,2.97%in aluminum cyli

关键词： coefficient of rolling friction maize irregularly shaped model angle of repose discrete element method

STABILITY ANALYSIS OF RIVERBANK SUBJECT TO SEEPAGE

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2007年第4期22卷 282-291页

作者： Yan LU1, Yongjun LU2, and Xingnong ZHANG3 1 Postdoctoral Fellow, Nanjing Hydraulic Research Institute, State Key Laboratory of Hydrology Water Resources and Hydraulic Engineering Science, Nanjing, China 210029. 2 Prof., Nanjing Hydraulic Research Institute, Nanjing, China 210029 3 Prof., Nanjing Hydraulic Research Institute, Nanjing, China 210029. Nanjing Hydraul Res Inst Nanjing 210029 Peoples R China

The stability of riverbanks subject to seepage is studied experimentally and theoretically in this paper. By including seepage in a 3-dimensional theoretical analysis, the study first shows how the critical slope or angle of repose of a cohesionless material is related to the ratio of the hydraulic gradient of seepage to its critical value under the fluidization condition. The critical stable slope is shown to be related to not only the hydraulic gradient but also the seepage direction. Measured laboratory data reasonably fit well with the theoretical relationship for the case of injection and suction. The data reveal that the slope is reduced with injection and increased with suction, respectively. Additionally, the study identifies the seepage direction which results in a minimum critical stable slope for a certain hydraulic gradient of seepage.

关键词： Seepage Riverbank Stability Critical stable slopes angle of repose Erosion

Drying Technology and Formation Process of Naomai Xingshen Capsules

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Medicinal Plant 2022年第2期13卷 8-11页

作者： Congyan ZENG Yu ZHANG Bin ZHUO Shi LIANG Yuliang HU Zhongshan Hospital of Traditional Chinese Medicine Affiliated to Guangzhou University of Chinese Medicine Zhongshan 528400 China

[Objectives]To optimize the drying technology and formation process of Naomai Xingshen Capsules.[Methods]The yield of paste powder and moisture content as evaluation indicators were taken as indicators,the relative density of feed liquid,inlet air temperature and dosage of excipients were selected as investigation factors,the orthogonal experiment method was used to optimize the spray drying process.The moisture absorption rate and angle of repose were taken as evaluation indicators,the types of forming excipient were screened,and the critical relative humidity was determined.[Results]The optimum spray drying process was that the relative density of liquid medicine was 1.05(60℃),the air inlet temperature was 200℃,and the dosage of excipients was 2%.The effect of using dextrin as a forming excipient was better,and the relative humidity of the production environment should be controlled below 65%.[Conclusions]The optimized process is stable,feasible,scientific and reasonable,and can be used for large-scale industrial production.

关键词： Naomai Xingshen Capsules Orthogonal experiment Spray-drying Forming process angle of repose Moisture absorption rate Critical relative humidity

Moisture-dependent physical properties of barley grains

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Agricultural and Biological Engineering 2009年第4期2卷 84-91页

作者： Mahmoud Tavakoli Hamed Tavakoli Ali Rajabipour Hojat Ahmadi Seyed Mohammad Taghi Gharib-Zahedi Department of Food Science and Technology Faculty of AgricultureUniversity of ZabolZabolIran Department of Agricultural Machinery Engineering Faculty of Agricultural Engineering&TechnologyUniversity of TehranP.O.Box 4111Karaj 31587-77871Iran Department of Food Science and Engineering Faculty of Agricultural Engineering&TechnologyUniversity of TehranKarajIran

Designing equipment for processing,sorting,sizing and other post-harvest operations of agricultural products requires information about their physical properties.This study was carried out to evaluate the effect of moisture content on some physical properties of barley grains.Four levels of moisture content ranging from 7.34%to 21.58%(d.b.)were used.The average length,width,thickness,arithmetic mean diameter,geometric mean diameter,thousand grain mass,sphericity,surface area and repose angle increased from 8.91 to 9.64 mm,3.30 to 3.74 mm,2.58 to 2.98 mm,4.93 to 5.45 mm,4.23 to 4.75 mm,44.48 to 51.30 g,47.55%to 49.35%,56.66 to 71.09 mm2 and 31.16°to 36.90°,respectively,as moisture content increased from 7.34%to 21.58%(d.b.).The bulk density,true density and porosity were found to decrease with increasing moisture content.The static friction coefficient of the grains increased linearly against various surfaces(plywood,glass and galvanized iron sheet)as the moisture content increased.At all moisture content,the maximum friction was offered by plywood,followed by galvanized iron sheet and glass surface.

关键词： barley moisture content angle of repose coefficient of friction