Owing to a certain angle existing between a belt conveyor and the parallel hoppers,and the hoppers localizing away from the centerlines of a blast furnace,particles size segregation is likely to happen in a bell-less ...Owing to a certain angle existing between a belt conveyor and the parallel hoppers,and the hoppers localizing away from the centerlines of a blast furnace,particles size segregation is likely to happen in a bell-less top blast furnace with parallel hoppers.Mastering the law of particles size segregation in hoppers could help to choose better charging parameters and optimize production and technical indices.As for the previous works on burden segregation at a bell-less top blast furnace with parallel hoppers,more attention was paid to the falling point segregation and the circumferential mass flow segregation while charging from the tilting chute,but ignoring the particle size segregation in burden hoppers as burden falls from a belt conveyor,which is the right basis of analyzing the former,and plays a significant role in controlling the gas distribution in the blast furnace.The present work takes ternary mixtures of coke in three different particle sizes to simulate the size segregation of the coke charged into the hoppers by experiments.The effect of the main striking point on size segregation is also investigated.The research shows that there exists a good linear relation between segregation coefficient k and the dimensionless main striking point when using the equation C = C_0~k to express the degree of size segregation in hoppers.The linear relation is proposed for the first time and provides a new way to predict the size segregation in hoppers,which forms a theoretical basis and technical support for reducing the size segregation degree in hoppers.展开更多
The circumferential burden distribution of bell-less top with two parallel hoppers was analyzed to obtain the expressions of burden flux and uneven ratio. The four-batch feeding spirally with two parallel hoppers was ...The circumferential burden distribution of bell-less top with two parallel hoppers was analyzed to obtain the expressions of burden flux and uneven ratio. The four-batch feeding spirally with two parallel hoppers was proposed to realize even burden distribution by uneven flux, ensuring reasonable distribution of BF gas and effective usage of heat energy and chemical energy of gas as well as stable BF production with higher quality and lower consumption.展开更多
A two-dimensional discrete element model （DEM） simulation of cohesive polygonal particles has been developed to assess the benefit of point source vibration to induce flow in wedge-shaped hoppers. The particle-parti...A two-dimensional discrete element model （DEM） simulation of cohesive polygonal particles has been developed to assess the benefit of point source vibration to induce flow in wedge-shaped hoppers. The particle-particle interaction model used is based on a multi-contact principle. The first part of the study investigated particle discharge under gravity without vibration to determine the critical orifice size （Bc） to just sustain flow as a function of particle shape. It is shown that polygonal-shaped particles need a larger orifice than circular particles. It is also shown that Bc decreases as the number of particle vertices increases. Addition of circular particles promotes flow of polygons in a linear manner. The second part of the study showed that vibration could enhance flow, effectively reducing Bc. The model demonstrated the importance of vibrator location （height）, consistent with previous continuum model results, and vibration amplitude in enhancing flow.展开更多
This paper presents a numerical and experimental study of the discharge rate of sawdust from an aerated hopper as an important parameter in many industrial processes involving the handling of other granular materials....This paper presents a numerical and experimental study of the discharge rate of sawdust from an aerated hopper as an important parameter in many industrial processes involving the handling of other granular materials. Numerical experiments are conducted by means of an Eulerian-Eulerian approach coupled with the kinetic theory of granular flow （KTGF）. Emphasis is given to the effects of particle size, hopper outlet width, hopper half angle, aeration height and air flow rate. The results show that the discharge rate is significantly affected by hopper outlet width, particle size and air flow rate, but is not sensitive to the hopper half angle and aeration height： increasing hopper outlet width or air flow rate increases discharge rate, while increasing particle size decreases discharge rate. Close agreement between numerical predictions and experimental results is obtained.展开更多
The discharge behavior of particles is important in many industrial applications,such as in the core of a pebble bed reactor,which uses a hopper bed filled with many large particles.In this work,a mixture composed of ...The discharge behavior of particles is important in many industrial applications,such as in the core of a pebble bed reactor,which uses a hopper bed filled with many large particles.In this work,a mixture composed of two particle types,freely discharged from a pebble bed,is simulated using the discreteelement method.One is a spherical pebble of diameter equal to that of the fuel pebble of the reactor.The other is a composite particle comprising three spherical pebbles bonded together.The included angleαof the three pebbles characterized the particle conformation,which may affect the discharge behavior of the mixture.The effects of volume fraction of the multi-sphere x(equivalent to the number fraction)on the discharge are also analyzed.Flow patterns,number flow rate,discharge velocity,and mean force of the mixture are computed to help in revealing discharge features.The results show that increasing eitherαor x reduces the discharge flow rate.Fittings and correlations give a quantitative evaluation of the independent effects ofαand x.The analysis of velocity and force explains the mechanism relevant to the main influencing factorsαand x.The results are helpful in gaining a better understanding of the discharge feature of binary mixtures and in providing a quantitative evaluation of the discharge behavior of the reactor core,especially adverse failure conditions.展开更多
The article introduces the composition and working principle of the batching and weighing system underneath the blast furnace hearth.Besides,the shortcomings of the batching and weighing system during installation,deb...The article introduces the composition and working principle of the batching and weighing system underneath the blast furnace hearth.Besides,the shortcomings of the batching and weighing system during installation,debugging,and calibration,as well as the dynamic errors in the batching process are also analyzed.Corresponding solutions are then provided.展开更多
Based on the hopping principle, a miniature gas fuel-powered hopper is designed and manufactured. According to thermodynamic analysis, the pressure-displacement curve in the combustion chamber after ignition is obtain...Based on the hopping principle, a miniature gas fuel-powered hopper is designed and manufactured. According to thermodynamic analysis, the pressure-displacement curve in the combustion chamber after ignition is obtained through iterative calculation, then the work on the cylinder done by high-pressure gas is calculated and the initial hopping velocity of the hopper is obtained. The wireless control system is developed to realize the tele-control of the hopper, including fuel injection and ignition. Experimental results agree well with analytical results. The hopper has a jumping ability of height 2.2 m and distance 3.5 m, and it is more than 14 times its dimension.展开更多
The present study was conducted at the Faiz Chaman mango orchard, Multan to find out the attraction of mango hopper Idioscopus clypealis to sticky traps of different colors. The experiment was laid out in randomized c...The present study was conducted at the Faiz Chaman mango orchard, Multan to find out the attraction of mango hopper Idioscopus clypealis to sticky traps of different colors. The experiment was laid out in randomized complete block designed with three replications. The sticky traps were hung vertically with the branch/twig under the canopy of mango trees. Data were recorded under binocular stereoscope. Results indicated significant differences in the number of I. clypealis (adults) captured in the different colored sticky traps. Yellow color was found most attractive with a capture of highest number of adults of I. clypealis (11.53 adults/trap). While pink and purple colors were found less attractive. The peak population of mango hoppers was recorded at the 31.96°C during 25-April to 9-May. Yellow sticky traps were found most effective in trapping a considerably higher number of hoppers throughout the study period. Correlation analysis revealed a strong positive correlation between temperature and the mean number of I. clypealis adults. Population peaks of I. clypealis were recorded at temperatures >30°C, while at lower temperatures relatively low numbers of adults were recorded.展开更多
Flow behaviors of four kinds of granular particles(i.e. sphere,ellipsoid,hexahedron and binary mixture of sphere and hexahedron) in rectangular hoppers were experimentally studied. The effects of granular shape and ho...Flow behaviors of four kinds of granular particles(i.e. sphere,ellipsoid,hexahedron and binary mixture of sphere and hexahedron) in rectangular hoppers were experimentally studied. The effects of granular shape and hopper structure on flow pattern,discharge fraction,mean particle residence time and tracer concentration distribu-tion were tested based on the visual observation and particle tracer technique. The results show that particle shape affects significantly the flow pattern. The flow patterns of sphere,ellipsoid and binary mixture are all parabolic shape,and the flow pattern shows no significant difference with the change of wedge angle. The flowing zone be-comes more sharp-angled with the increasing outlet size. The flow pattern of hexahedron is featured with straight lines. The discharge rates are in increasing order from hexahedron,sphere,binary mixture to ellipsoid. The dis-charge rate also increases with the wedge angle and outlet size. The mean particle residence time becomes shorter when the outlet size increases. The difference of mean particle residence time between the maximum and minimum values decreases as the wedge angle increases. The residence time of hexahedron is the shortest. The tracer concen-tration distribution of hexahedron at any height is more uniform than that of binary mixture. The tracer concentra-tion of sphere in the middle is lower than that near the wall,and the contrary tendency is found for ellipsoid particles.展开更多
Beverloo's scaling law can describe the flow rate of grains discharging from hoppers. In this paper, we show that the Beverloo's scaling law is valid for varying material parameters. The flow rates from a hopp...Beverloo's scaling law can describe the flow rate of grains discharging from hoppers. In this paper, we show that the Beverloo's scaling law is valid for varying material parameters. The flow rates from a hopper with different hopper and orifice sizes(D, D_0) are studied by running large-scale simulations. When the hopper size is fixed, the numerical results show that Beverloo's law is valid even if the orifice diameter is very large and then the criteria for this law are discussed.To eliminate the effect of walls, it is found that the criteria can be suggested as D-D_0≥ 40 d or D/D_0≥ 2. Interestingly,it is found that there is still a scaling relation between the flow rate and orifice diameter if D/D_0 is fixed and less than 2.When the orifice diameter is close to the hopper size, the velocity field changes and the vertical velocities of grains above the free fall region are much larger. Then, the free fall arch assumption is invalid and Beverloo's law is inapplicable.展开更多
The dynamics of granular material discharging from a cuboid but thin hopper,including the hopper flow and granular jet,are investigated via discrete element method(DEM)simulations.The slot width is varied to study its...The dynamics of granular material discharging from a cuboid but thin hopper,including the hopper flow and granular jet,are investigated via discrete element method(DEM)simulations.The slot width is varied to study its influence on the flow.It is found the flow in the cuboid hopper has similarity with the flow in two-dimensional(2D)hopper.When the slot width is large,the flowrate is higher than the predicted value from Beverloo’s law and the velocity distribution is not Gaussian-like.For granular jet,there is a transition with varying slot width.For large slot width,there is a dense core in the jet and the variations of velocities and density are relatively small.Finally,the availability of continuum model is assessed and the results show that the performance with large slot width is better than that with small slot width.展开更多
We experimentally investigate the effect of the hopper angle on the flow rate of grains discharged from a twodimensional horizontal hopper on a conveyor belt.The flow rate grows with the hopper angle,and finally reach...We experimentally investigate the effect of the hopper angle on the flow rate of grains discharged from a twodimensional horizontal hopper on a conveyor belt.The flow rate grows with the hopper angle,and finally reaches a plateau.The curve feature appears to be similar for different orifice widths and conveyor belt-driven velocities.On the basis of an empirical law of flow rate for a flat-bottom hopper,we propose a modified equation to describe the relation between the flow rate and hopper angle,which is in a good agreement with the experimental results.展开更多
We investigated the influence of an inserted bar on the hopper flow experimentally.Three geometrical parameters,size of upper outlet D1,size of lower outlet D0,and the height of bar H,are variables here.With varying H...We investigated the influence of an inserted bar on the hopper flow experimentally.Three geometrical parameters,size of upper outlet D1,size of lower outlet D0,and the height of bar H,are variables here.With varying H we found three regimes:one transition from clogging to a surface flow and another transition from a surface flow to a dense flow.For the dense flow,the flow rate follows Beverloo’s law and there is a saturation of inclination of free surfaceθ.We plotted the velocity field and there is a uniform linear relation between the particle velocity and depth from the free surface.We also found that the required value of D_(1) to guarantee the connectivity of flow is little smaller than D_(0).For the transition from a surface flow to a dense flow,there is a jump of flow rate and the minimumθfor flowing is two degrees larger than the repose angle.展开更多
The mass flow rate of a granular flow through an aperture under gravity is a long-standing challenge issue in physical science. We show that for steady flow field close to laminar flow, the dynamical equations togethe...The mass flow rate of a granular flow through an aperture under gravity is a long-standing challenge issue in physical science. We show that for steady flow field close to laminar flow, the dynamical equations together with the continue equation and Mohr-circle description of the stress are closed, and hence solvable. In a case of streamline guided by the two-dimensional hopper, we obtain a consistent condition and use it to determine the stress and the velocity distribution. Our result indicates that 3/2 power scaling behavior is recovered with a coefficient C(μ,α) being a function of frictional coefficient and the hopper angle. It is found that the predicted coefficient C(μ,α) is compatible with previous studies.展开更多
Modern cars are mostly computerized and equipped with passive keyless entry and start(PKES) system. PKES is based on Radio Frequency Identification(RFID) technology for authentication of the authorized drivers. RFID t...Modern cars are mostly computerized and equipped with passive keyless entry and start(PKES) system. PKES is based on Radio Frequency Identification(RFID) technology for authentication of the authorized drivers. RFID technology has replaced the conventional ways of identification and authorization in order to facilitate users while introducing new security challenges. In this article, we focused on verifying the presence of authorized key in the physical proximity of car by employing multiple antennas. Application of multiple antennas to the currently developed cryptographic algorithms opens a new approach for researchers to improve security of RFID based systems. We propose an advanced security system for PKES using multiple antennas wherein an authorized key passes through multiple vicinities to allow driver to access and start the car. Furthermore, we modified a light-weight cryptographic protocol named as HB(Hopper and Blum) protocol to integrate it with the proposed design based on multiple antennas. Simulation results show improvement in security functionality while keeping in view the efficiency constraints.展开更多
Species in the genus Pyrops Spinola (Hemiptera:Fulgoridae)in Chinese fauna are studied,one new species,P.jianfenglingensis sp.nov.is described from Hainan (southern China).Morphological characters and male genitalia o...Species in the genus Pyrops Spinola (Hemiptera:Fulgoridae)in Chinese fauna are studied,one new species,P.jianfenglingensis sp.nov.is described from Hainan (southern China).Morphological characters and male genitalia of most Pyrops species in China are illustrated.A key for identifying the species of Pyrops from China is also provided.展开更多
The dubas bug Ommatissus lybicus （Debergevin） （Homoptera： Tropiduchidae） was almost absent in AI-Anbar Province during the past years, however, field survey conducted in different regions of the province during f...The dubas bug Ommatissus lybicus （Debergevin） （Homoptera： Tropiduchidae） was almost absent in AI-Anbar Province during the past years, however, field survey conducted in different regions of the province during fall of 2007 indicated the presence of heavy infestation by this pest on date palm trees in some orchards toward the east of Hit city. Infestation was highly influencing in term of affected trees and accumulation of honey dew. Scattered infestations were also recorded in some orchards west of Hit city and near the cities of Haditha, Rawa and AI-Kaim near the Syrian border. However, a sharp decline of dubas population was observed during 2008 and subsequent years as a result of the influence of sever winter in 2008 and the continuous occurrence of dust storms which showed a detrimental effect on moving stages of dubas bug. Data showed that nymphs density reached to about 50 individuals/leaflet recorded during the last week of April and early May of 2008 and was reduced to less than 5 nymphs/leaflet by the end of the third week of May of the same year as a result of the indicated climatic factors. Farther samplings conducted in Spring and Fall seasons of 2009 and 2010 indicated that insects were mainly found on offshoots near the ground with a maximum density reached to 12 individuals/tree. Since the spread of the pest occurred in a discontinuous manner with no correlation to infestations in close by provinces indicating that the arrival or transportation of the pest was happened in a way other than the normal distribution, therefore, dubas bug may not persist in date palm orchards in A1- Anbar Province.展开更多
The adhesion mechanics of coal and the behavior of the coal adhesion to the hopper are analyzed. A model coal hopper is developed, and the model experiments are made by using the surface electro osmosis technology ac...The adhesion mechanics of coal and the behavior of the coal adhesion to the hopper are analyzed. A model coal hopper is developed, and the model experiments are made by using the surface electro osmosis technology according to the processing conditions. The parameters of the surface electro osmosis technology are optimized by the method of orthogonal polynomial regression designing. The result shows that the surface electro osmosis technique is one of the good methods to solve the adhering problem of coal to the coal hopper in transfer piping.展开更多
文摘Owing to a certain angle existing between a belt conveyor and the parallel hoppers,and the hoppers localizing away from the centerlines of a blast furnace,particles size segregation is likely to happen in a bell-less top blast furnace with parallel hoppers.Mastering the law of particles size segregation in hoppers could help to choose better charging parameters and optimize production and technical indices.As for the previous works on burden segregation at a bell-less top blast furnace with parallel hoppers,more attention was paid to the falling point segregation and the circumferential mass flow segregation while charging from the tilting chute,but ignoring the particle size segregation in burden hoppers as burden falls from a belt conveyor,which is the right basis of analyzing the former,and plays a significant role in controlling the gas distribution in the blast furnace.The present work takes ternary mixtures of coke in three different particle sizes to simulate the size segregation of the coke charged into the hoppers by experiments.The effect of the main striking point on size segregation is also investigated.The research shows that there exists a good linear relation between segregation coefficient k and the dimensionless main striking point when using the equation C = C_0~k to express the degree of size segregation in hoppers.The linear relation is proposed for the first time and provides a new way to predict the size segregation in hoppers,which forms a theoretical basis and technical support for reducing the size segregation degree in hoppers.
文摘The circumferential burden distribution of bell-less top with two parallel hoppers was analyzed to obtain the expressions of burden flux and uneven ratio. The four-batch feeding spirally with two parallel hoppers was proposed to realize even burden distribution by uneven flux, ensuring reasonable distribution of BF gas and effective usage of heat energy and chemical energy of gas as well as stable BF production with higher quality and lower consumption.
文摘A two-dimensional discrete element model （DEM） simulation of cohesive polygonal particles has been developed to assess the benefit of point source vibration to induce flow in wedge-shaped hoppers. The particle-particle interaction model used is based on a multi-contact principle. The first part of the study investigated particle discharge under gravity without vibration to determine the critical orifice size （Bc） to just sustain flow as a function of particle shape. It is shown that polygonal-shaped particles need a larger orifice than circular particles. It is also shown that Bc decreases as the number of particle vertices increases. Addition of circular particles promotes flow of polygons in a linear manner. The second part of the study showed that vibration could enhance flow, effectively reducing Bc. The model demonstrated the importance of vibrator location （height）, consistent with previous continuum model results, and vibration amplitude in enhancing flow.
文摘This paper presents a numerical and experimental study of the discharge rate of sawdust from an aerated hopper as an important parameter in many industrial processes involving the handling of other granular materials. Numerical experiments are conducted by means of an Eulerian-Eulerian approach coupled with the kinetic theory of granular flow （KTGF）. Emphasis is given to the effects of particle size, hopper outlet width, hopper half angle, aeration height and air flow rate. The results show that the discharge rate is significantly affected by hopper outlet width, particle size and air flow rate, but is not sensitive to the hopper half angle and aeration height： increasing hopper outlet width or air flow rate increases discharge rate, while increasing particle size decreases discharge rate. Close agreement between numerical predictions and experimental results is obtained.
基金The authors are grateful for research support from the National Natural Science Foundation of China(Grant No.51576211)the Sci-ence Fund for Creative Research Groups of National Natural Science Foundation of China(Grant No.51621062)and the National High Technology Research and Development Program of China(863)(2014AA052701).
文摘The discharge behavior of particles is important in many industrial applications,such as in the core of a pebble bed reactor,which uses a hopper bed filled with many large particles.In this work,a mixture composed of two particle types,freely discharged from a pebble bed,is simulated using the discreteelement method.One is a spherical pebble of diameter equal to that of the fuel pebble of the reactor.The other is a composite particle comprising three spherical pebbles bonded together.The included angleαof the three pebbles characterized the particle conformation,which may affect the discharge behavior of the mixture.The effects of volume fraction of the multi-sphere x(equivalent to the number fraction)on the discharge are also analyzed.Flow patterns,number flow rate,discharge velocity,and mean force of the mixture are computed to help in revealing discharge features.The results show that increasing eitherαor x reduces the discharge flow rate.Fittings and correlations give a quantitative evaluation of the independent effects ofαand x.The analysis of velocity and force explains the mechanism relevant to the main influencing factorsαand x.The results are helpful in gaining a better understanding of the discharge feature of binary mixtures and in providing a quantitative evaluation of the discharge behavior of the reactor core,especially adverse failure conditions.
文摘The article introduces the composition and working principle of the batching and weighing system underneath the blast furnace hearth.Besides,the shortcomings of the batching and weighing system during installation,debugging,and calibration,as well as the dynamic errors in the batching process are also analyzed.Corresponding solutions are then provided.
基金Supported by the National Natural Science Foundation of China(50605031)~~
文摘Based on the hopping principle, a miniature gas fuel-powered hopper is designed and manufactured. According to thermodynamic analysis, the pressure-displacement curve in the combustion chamber after ignition is obtained through iterative calculation, then the work on the cylinder done by high-pressure gas is calculated and the initial hopping velocity of the hopper is obtained. The wireless control system is developed to realize the tele-control of the hopper, including fuel injection and ignition. Experimental results agree well with analytical results. The hopper has a jumping ability of height 2.2 m and distance 3.5 m, and it is more than 14 times its dimension.
文摘The present study was conducted at the Faiz Chaman mango orchard, Multan to find out the attraction of mango hopper Idioscopus clypealis to sticky traps of different colors. The experiment was laid out in randomized complete block designed with three replications. The sticky traps were hung vertically with the branch/twig under the canopy of mango trees. Data were recorded under binocular stereoscope. Results indicated significant differences in the number of I. clypealis (adults) captured in the different colored sticky traps. Yellow color was found most attractive with a capture of highest number of adults of I. clypealis (11.53 adults/trap). While pink and purple colors were found less attractive. The peak population of mango hoppers was recorded at the 31.96°C during 25-April to 9-May. Yellow sticky traps were found most effective in trapping a considerably higher number of hoppers throughout the study period. Correlation analysis revealed a strong positive correlation between temperature and the mean number of I. clypealis adults. Population peaks of I. clypealis were recorded at temperatures >30°C, while at lower temperatures relatively low numbers of adults were recorded.
基金Supported by the National Natural Science Foundation of China （50706007 50976025） the National Key Program of Basic Research in China （2010CB732206）+1 种基金 the Foundation of Excellent Young Scholar of Southeast University （4003001039） the Collaboration Project of China and British （2010DFA61960）
文摘Flow behaviors of four kinds of granular particles(i.e. sphere,ellipsoid,hexahedron and binary mixture of sphere and hexahedron) in rectangular hoppers were experimentally studied. The effects of granular shape and hopper structure on flow pattern,discharge fraction,mean particle residence time and tracer concentration distribu-tion were tested based on the visual observation and particle tracer technique. The results show that particle shape affects significantly the flow pattern. The flow patterns of sphere,ellipsoid and binary mixture are all parabolic shape,and the flow pattern shows no significant difference with the change of wedge angle. The flowing zone be-comes more sharp-angled with the increasing outlet size. The flow pattern of hexahedron is featured with straight lines. The discharge rates are in increasing order from hexahedron,sphere,binary mixture to ellipsoid. The dis-charge rate also increases with the wedge angle and outlet size. The mean particle residence time becomes shorter when the outlet size increases. The difference of mean particle residence time between the maximum and minimum values decreases as the wedge angle increases. The residence time of hexahedron is the shortest. The tracer concen-tration distribution of hexahedron at any height is more uniform than that of binary mixture. The tracer concentra-tion of sphere in the middle is lower than that near the wall,and the contrary tendency is found for ellipsoid particles.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11705256 and 11605264)
文摘Beverloo's scaling law can describe the flow rate of grains discharging from hoppers. In this paper, we show that the Beverloo's scaling law is valid for varying material parameters. The flow rates from a hopper with different hopper and orifice sizes(D, D_0) are studied by running large-scale simulations. When the hopper size is fixed, the numerical results show that Beverloo's law is valid even if the orifice diameter is very large and then the criteria for this law are discussed.To eliminate the effect of walls, it is found that the criteria can be suggested as D-D_0≥ 40 d or D/D_0≥ 2. Interestingly,it is found that there is still a scaling relation between the flow rate and orifice diameter if D/D_0 is fixed and less than 2.When the orifice diameter is close to the hopper size, the velocity field changes and the vertical velocities of grains above the free fall region are much larger. Then, the free fall arch assumption is invalid and Beverloo's law is inapplicable.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11705256 and 11905272)the National Postdoctoral Program for Innovative Talents,China(Grant No.BX201700258)+1 种基金Young Scholar of CAS“Light of West China”Program for Guanghui Yang(Grant No.2018-98)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21010202)。
文摘The dynamics of granular material discharging from a cuboid but thin hopper,including the hopper flow and granular jet,are investigated via discrete element method(DEM)simulations.The slot width is varied to study its influence on the flow.It is found the flow in the cuboid hopper has similarity with the flow in two-dimensional(2D)hopper.When the slot width is large,the flowrate is higher than the predicted value from Beverloo’s law and the velocity distribution is not Gaussian-like.For granular jet,there is a transition with varying slot width.For large slot width,there is a dense core in the jet and the variations of velocities and density are relatively small.Finally,the availability of continuum model is assessed and the results show that the performance with large slot width is better than that with small slot width.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11475018 and 11974044)the National Key Research and Development Program of China(Grant 2016YFC1401001)。
文摘We experimentally investigate the effect of the hopper angle on the flow rate of grains discharged from a twodimensional horizontal hopper on a conveyor belt.The flow rate grows with the hopper angle,and finally reaches a plateau.The curve feature appears to be similar for different orifice widths and conveyor belt-driven velocities.On the basis of an empirical law of flow rate for a flat-bottom hopper,we propose a modified equation to describe the relation between the flow rate and hopper angle,which is in a good agreement with the experimental results.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11705256 and 11905272)National Postdoctoral Program for Innovative Talents,China(Grant No.BX201700258)West Light Foundation of the Chinese Academy of Sciences(Grant No.2018-98)。
文摘We investigated the influence of an inserted bar on the hopper flow experimentally.Three geometrical parameters,size of upper outlet D1,size of lower outlet D0,and the height of bar H,are variables here.With varying H we found three regimes:one transition from clogging to a surface flow and another transition from a surface flow to a dense flow.For the dense flow,the flow rate follows Beverloo’s law and there is a saturation of inclination of free surfaceθ.We plotted the velocity field and there is a uniform linear relation between the particle velocity and depth from the free surface.We also found that the required value of D_(1) to guarantee the connectivity of flow is little smaller than D_(0).For the transition from a surface flow to a dense flow,there is a jump of flow rate and the minimumθfor flowing is two degrees larger than the repose angle.
基金Supported by the Key Research Program of Frontier Science of the Chinese Academy of Sciences under Grant No QYZDYSSW-SYS006
文摘The mass flow rate of a granular flow through an aperture under gravity is a long-standing challenge issue in physical science. We show that for steady flow field close to laminar flow, the dynamical equations together with the continue equation and Mohr-circle description of the stress are closed, and hence solvable. In a case of streamline guided by the two-dimensional hopper, we obtain a consistent condition and use it to determine the stress and the velocity distribution. Our result indicates that 3/2 power scaling behavior is recovered with a coefficient C(μ,α) being a function of frictional coefficient and the hopper angle. It is found that the predicted coefficient C(μ,α) is compatible with previous studies.
基金supported by the National Key Research and Development Program(No.2016YFB0800602)National Natural Science Foundation of China(NSFC)(No.61502048)Shandong provincial Key Research and Development Program of China(2018CXGC0701,2018GGX106005)
文摘Modern cars are mostly computerized and equipped with passive keyless entry and start(PKES) system. PKES is based on Radio Frequency Identification(RFID) technology for authentication of the authorized drivers. RFID technology has replaced the conventional ways of identification and authorization in order to facilitate users while introducing new security challenges. In this article, we focused on verifying the presence of authorized key in the physical proximity of car by employing multiple antennas. Application of multiple antennas to the currently developed cryptographic algorithms opens a new approach for researchers to improve security of RFID based systems. We propose an advanced security system for PKES using multiple antennas wherein an authorized key passes through multiple vicinities to allow driver to access and start the car. Furthermore, we modified a light-weight cryptographic protocol named as HB(Hopper and Blum) protocol to integrate it with the proposed design based on multiple antennas. Simulation results show improvement in security functionality while keeping in view the efficiency constraints.
基金supported by the National Natural Science Foundation of China (31672340, 31750002)
文摘Species in the genus Pyrops Spinola (Hemiptera:Fulgoridae)in Chinese fauna are studied,one new species,P.jianfenglingensis sp.nov.is described from Hainan (southern China).Morphological characters and male genitalia of most Pyrops species in China are illustrated.A key for identifying the species of Pyrops from China is also provided.
文摘The dubas bug Ommatissus lybicus （Debergevin） （Homoptera： Tropiduchidae） was almost absent in AI-Anbar Province during the past years, however, field survey conducted in different regions of the province during fall of 2007 indicated the presence of heavy infestation by this pest on date palm trees in some orchards toward the east of Hit city. Infestation was highly influencing in term of affected trees and accumulation of honey dew. Scattered infestations were also recorded in some orchards west of Hit city and near the cities of Haditha, Rawa and AI-Kaim near the Syrian border. However, a sharp decline of dubas population was observed during 2008 and subsequent years as a result of the influence of sever winter in 2008 and the continuous occurrence of dust storms which showed a detrimental effect on moving stages of dubas bug. Data showed that nymphs density reached to about 50 individuals/leaflet recorded during the last week of April and early May of 2008 and was reduced to less than 5 nymphs/leaflet by the end of the third week of May of the same year as a result of the indicated climatic factors. Farther samplings conducted in Spring and Fall seasons of 2009 and 2010 indicated that insects were mainly found on offshoots near the ground with a maximum density reached to 12 individuals/tree. Since the spread of the pest occurred in a discontinuous manner with no correlation to infestations in close by provinces indicating that the arrival or transportation of the pest was happened in a way other than the normal distribution, therefore, dubas bug may not persist in date palm orchards in A1- Anbar Province.
文摘The adhesion mechanics of coal and the behavior of the coal adhesion to the hopper are analyzed. A model coal hopper is developed, and the model experiments are made by using the surface electro osmosis technology according to the processing conditions. The parameters of the surface electro osmosis technology are optimized by the method of orthogonal polynomial regression designing. The result shows that the surface electro osmosis technique is one of the good methods to solve the adhering problem of coal to the coal hopper in transfer piping.
