Ambient suspended particulate matter(PM)(primarily with particle diameter 2.5m or less,i.e.,PM2.5)can adversely affect ecosystems and human health.Currently,optical particle sensors based on light scattering dominate ...Ambient suspended particulate matter(PM)(primarily with particle diameter 2.5m or less,i.e.,PM2.5)can adversely affect ecosystems and human health.Currently,optical particle sensors based on light scattering dominate the portable PM sensing market.However,the light scattering method has poor adaptability to different-sized PM and adverse environmental conditions.Here,we design and develop a portable PM sensing microsystem that consists of a micromachined virtual impactor(VI)for particle separation,a thermophoretic deposition chip for particle collection,and an extended-gate field-effect transistor(FET)for particle analysis.This system can realize on-site separation,collection,and analysis of aerosol particles without being influenced by environmental factors.In this study,the design of the VI is thoroughly analyzed by numerical simulation,and mixtures of different-sized silicon dioxide(SiO2)particles are used in an experimental verification of the performance of the VI and FET.Considering the low cost and compact design of the whole system,the proposed PM analysis microsystem has potential for PM detection under a wide range of conditions,such as heavily polluted industrial environments and for point-of-need outdoor and indoor air quality monitoring.展开更多
The present paper deals with the optimum shape design of an absolutely rigid impactor which penetrates into a semi-infinite concrete shield. The objective function to maximize is the depth of penetration (DOP for shor...The present paper deals with the optimum shape design of an absolutely rigid impactor which penetrates into a semi-infinite concrete shield. The objective function to maximize is the depth of penetration (DOP for short) of the impactor;in the case of impactors with axisymmetric shapes DOP is calculated using formulas obtained by Ben-Dor et al. [1-3] with the method of local variations [4] and based on the mechanical model proposed by Forrestal and Tzou [5]. In the present paper we show that using a different class of admissible functions, more general than the axisymmetric one, better results can be obtained. To solve the formulated optimization problem we used a custom version of the particle swarm optimization method (briefly denoted by PSOA), a very recent numerical optimization algorithm of guided random global search. Numerical results show the optimal shape for various types of shields and corresponding DOP;some Ben-Dor et al. [1-3] results are compared to solutions obtained.展开更多
Based on analysis of the present hydraulic impactor, a new hydraulic impactor with pressure feedback control was developed, whose structure and operation principle were introduced. The results show that the pressure o...Based on analysis of the present hydraulic impactor, a new hydraulic impactor with pressure feedback control was developed, whose structure and operation principle were introduced. The results show that the pressure of the impact system can be adjusted steplessly to change the impact energy of the impactor steplessly. By adjusting the oil flow of supply pump steplessly, the impact frequency will also be changed steplessly. So the impact energy and frequency of the new impactor can be adjusted independently and steplessly. In order to decrease the energy loss, a new kind of sleeve valve has been designed, which has features of little leakage, little pressure loss and low energy cost. The new type hydraulic impactor can be operated under various conditions with decreased energy consumption and improved operation efficiency.展开更多
Percussive-rotary drilling technology was considered many years ago as one of the best approaches for hard rock drilling. It is a key for popularizing this technology on a large scale to design and make an impactor wi...Percussive-rotary drilling technology was considered many years ago as one of the best approaches for hard rock drilling. It is a key for popularizing this technology on a large scale to design and make an impactor with excellent performance. This paper presents a suit of method to design the percussive parameters for the oil or gas field by introducing the working principle of back-pressured impactor, dividing the working periods of impactor into three phases and establishing the computer emulational model of percussive parameters. It draws a comparison between the results of model calculation and experiment on the basis of analyzing the experiment results of impactor.The conclude provides credible foundation for designing and further ameliorating the impactor.展开更多
This paper describes the preliminary study results of developing a hypervelocity terminal intercept guidance system of a multiple kinetic-energy impactor vehicle(MKIV).The proposed MKIV system is intended to fragment ...This paper describes the preliminary study results of developing a hypervelocity terminal intercept guidance system of a multiple kinetic-energy impactor vehicle(MKIV).The proposed MKIV system is intended to fragment or pulverize an asteroid of smaller than approximately 150 m in diameter that is detected with a mission lead time of shorter than 10 years,without using nuclear explosive devices.This paper focuses on the development of a new image processing algorithm based on Otsu’s method for the coordinated terminal intercept guidance and control of multiple kinetic-energy impactors employing visual and/or infrared sensors.A scaled polyhedron shape model of asteroid(216)Kleopatra is used as a fictional target asteroid.GPU-based simulation results demonstrate the feasibility of impacting a small irregular-shaped asteroid by using the proposed new image processing algorithm and a classical pulsed TPN(true proportional navigation)terminal guidance law.展开更多
Though the bumper of a vehicle plays a major role in protecting the vehicle body against damage in low speed impacts,many bumpers,particularly in large vehicles,are too stiff for pedestrian protection.In designing a b...Though the bumper of a vehicle plays a major role in protecting the vehicle body against damage in low speed impacts,many bumpers,particularly in large vehicles,are too stiff for pedestrian protection.In designing a bumper for an automobile,pedestrian protection is as important as bumper energy absorption in low speed collisions.To prevent lower extremity injuries in car-pedestrian collisions,it is important to determine the loadings that car front structures impart on the lower extremities and the mechanisms by which injury is caused by these loadings.The present work was focused on gaining more insight into the injury mechanisms leading to both ligament damage and bone fracture during bumper-pedestrian collisions.The European Enhanced Vehicle-safety Committee (EEVC) legform impactor model was introduced and validated against EEVC/WG17 criteria.The collision mechanism between a bumper and this legform impactor was investigated numerically using LS-DYNA software.To identify the effect of the bumper beam material on leg injuries,four analyses were performed on bumpers that had the same assembly but were made from different materials.展开更多
In this study the flow field and the nanoparticle collection efficiency of supersonic/hypersonic impactors with different nozzle shapes were studied using a computational modeling approach.The aim of this study was to...In this study the flow field and the nanoparticle collection efficiency of supersonic/hypersonic impactors with different nozzle shapes were studied using a computational modeling approach.The aim of this study was to develop a nozzle design for supersonic/hypersonic impactors with the smallest possible cut-off size d_(50) and rather sharp collection efficiency curves.The simulation results show that the changes in the angle and width of a converging nozzle do not alter the cut-off size of the impactor;however,using a conical Laval nozzle with an L/D_n ratio less than or equal to 2 reduced d_(50).The effect of using a cap as a focuser in the nozzle of a supersonic/hypersonic impactor was also investigated.The results show that adding a cap in front of the nozzle had a noticeable effect on decreasing the cut-off size of the impactor.Both flat disks and conical caps were examined,and it was observed that the nozzle with the conical cap had a lower cut-off size.展开更多
In this study,numerical simulation of flow field in a supersonic/hypersonic impactor with one or two nozzles was carried out using a commercial computational fluid dynamics(CFD) software FLUENT.The objective was to in...In this study,numerical simulation of flow field in a supersonic/hypersonic impactor with one or two nozzles was carried out using a commercial computational fluid dynamics(CFD) software FLUENT.The objective was to investigate the effects of working parameters such as pressure ratio(50 < P_0/P_b< 800),nozzle diameters(D = 0.23,0.27,0.45 mm),nozzle to plate distance(0.5<L/D<50),particle diameter(1 nm < dp < 100 nm) and angle between two nozzles.A single-phase 3D unsteady-state model was implemented by the software.For this purpose,a user-defined function(UDF) was employed to implement nanoparticles for different assumptions of Cunningham correction factor.An axisymmetric form of the compressible Navier-Stokes and energy equations was used for both fluid flow and temperature;Lagrangian particle trajectory analysis was used for particle motion.Using the variable Cunningham correction factor showed suitable agreement with experimental data in comparison with other methods.Results show that increase of the distance between nozzle and impaction plate causes increase of Mach number,the distance between bow shock and impaction plate,and the collection efficiency.Maximum jet velocity,distance between bow shock and impaction plate and collection efficiency increase by using two nozzles in supersonic and hypersonic impactors.展开更多
Two types of Mg-Cu composition system graded density impactors used for complex loading (shock loading and quasi-isentropic compression) are designed by the elastic-plastic hydrodynamic method in this paper. Mixtures ...Two types of Mg-Cu composition system graded density impactors used for complex loading (shock loading and quasi-isentropic compression) are designed by the elastic-plastic hydrodynamic method in this paper. Mixtures of metal powders in the Mg-Cu system are cast into a series of 17 and 25 uniform compositions ranging from 100% Mg to 100% Cu. The graded density impactors are launched to the stationary 10 m aluminum film and 12 mm LiF window targets by a two-stage light-gas gun in the National Key Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, CAEP, and the resulting wave profiles are measured with the DISAR system. Hydrodynamic simulation results are perfectly consistent with the experiments. Our work in this paper will set up a foundation for further research of controllable loading/releasing routes and rate experiments in the future.展开更多
基金supported by the National Natural Science Foundation of China(Nos.91743110,61674114,and 21861132001)the National Key R&D Program of China(Nos.2017YFF0204604 and 2018YFE0118700)+1 种基金Tianjin Applied Basic Research and Advanced Technology(No.17JCJQJC43600),the“111”Project(No.B07014)the Foundation for Talent Scientists of Nanchang Institute for Micro-technology of Tianjin University.
文摘Ambient suspended particulate matter(PM)(primarily with particle diameter 2.5m or less,i.e.,PM2.5)can adversely affect ecosystems and human health.Currently,optical particle sensors based on light scattering dominate the portable PM sensing market.However,the light scattering method has poor adaptability to different-sized PM and adverse environmental conditions.Here,we design and develop a portable PM sensing microsystem that consists of a micromachined virtual impactor(VI)for particle separation,a thermophoretic deposition chip for particle collection,and an extended-gate field-effect transistor(FET)for particle analysis.This system can realize on-site separation,collection,and analysis of aerosol particles without being influenced by environmental factors.In this study,the design of the VI is thoroughly analyzed by numerical simulation,and mixtures of different-sized silicon dioxide(SiO2)particles are used in an experimental verification of the performance of the VI and FET.Considering the low cost and compact design of the whole system,the proposed PM analysis microsystem has potential for PM detection under a wide range of conditions,such as heavily polluted industrial environments and for point-of-need outdoor and indoor air quality monitoring.
文摘The present paper deals with the optimum shape design of an absolutely rigid impactor which penetrates into a semi-infinite concrete shield. The objective function to maximize is the depth of penetration (DOP for short) of the impactor;in the case of impactors with axisymmetric shapes DOP is calculated using formulas obtained by Ben-Dor et al. [1-3] with the method of local variations [4] and based on the mechanical model proposed by Forrestal and Tzou [5]. In the present paper we show that using a different class of admissible functions, more general than the axisymmetric one, better results can be obtained. To solve the formulated optimization problem we used a custom version of the particle swarm optimization method (briefly denoted by PSOA), a very recent numerical optimization algorithm of guided random global search. Numerical results show the optimal shape for various types of shields and corresponding DOP;some Ben-Dor et al. [1-3] results are compared to solutions obtained.
文摘Based on analysis of the present hydraulic impactor, a new hydraulic impactor with pressure feedback control was developed, whose structure and operation principle were introduced. The results show that the pressure of the impact system can be adjusted steplessly to change the impact energy of the impactor steplessly. By adjusting the oil flow of supply pump steplessly, the impact frequency will also be changed steplessly. So the impact energy and frequency of the new impactor can be adjusted independently and steplessly. In order to decrease the energy loss, a new kind of sleeve valve has been designed, which has features of little leakage, little pressure loss and low energy cost. The new type hydraulic impactor can be operated under various conditions with decreased energy consumption and improved operation efficiency.
基金Supported by the Science Foundation of China National Petroleum Corporation (990407 - 06 - 02)
文摘Percussive-rotary drilling technology was considered many years ago as one of the best approaches for hard rock drilling. It is a key for popularizing this technology on a large scale to design and make an impactor with excellent performance. This paper presents a suit of method to design the percussive parameters for the oil or gas field by introducing the working principle of back-pressured impactor, dividing the working periods of impactor into three phases and establishing the computer emulational model of percussive parameters. It draws a comparison between the results of model calculation and experiment on the basis of analyzing the experiment results of impactor.The conclude provides credible foundation for designing and further ameliorating the impactor.
文摘This paper describes the preliminary study results of developing a hypervelocity terminal intercept guidance system of a multiple kinetic-energy impactor vehicle(MKIV).The proposed MKIV system is intended to fragment or pulverize an asteroid of smaller than approximately 150 m in diameter that is detected with a mission lead time of shorter than 10 years,without using nuclear explosive devices.This paper focuses on the development of a new image processing algorithm based on Otsu’s method for the coordinated terminal intercept guidance and control of multiple kinetic-energy impactors employing visual and/or infrared sensors.A scaled polyhedron shape model of asteroid(216)Kleopatra is used as a fictional target asteroid.GPU-based simulation results demonstrate the feasibility of impacting a small irregular-shaped asteroid by using the proposed new image processing algorithm and a classical pulsed TPN(true proportional navigation)terminal guidance law.
文摘Though the bumper of a vehicle plays a major role in protecting the vehicle body against damage in low speed impacts,many bumpers,particularly in large vehicles,are too stiff for pedestrian protection.In designing a bumper for an automobile,pedestrian protection is as important as bumper energy absorption in low speed collisions.To prevent lower extremity injuries in car-pedestrian collisions,it is important to determine the loadings that car front structures impart on the lower extremities and the mechanisms by which injury is caused by these loadings.The present work was focused on gaining more insight into the injury mechanisms leading to both ligament damage and bone fracture during bumper-pedestrian collisions.The European Enhanced Vehicle-safety Committee (EEVC) legform impactor model was introduced and validated against EEVC/WG17 criteria.The collision mechanism between a bumper and this legform impactor was investigated numerically using LS-DYNA software.To identify the effect of the bumper beam material on leg injuries,four analyses were performed on bumpers that had the same assembly but were made from different materials.
文摘In this study the flow field and the nanoparticle collection efficiency of supersonic/hypersonic impactors with different nozzle shapes were studied using a computational modeling approach.The aim of this study was to develop a nozzle design for supersonic/hypersonic impactors with the smallest possible cut-off size d_(50) and rather sharp collection efficiency curves.The simulation results show that the changes in the angle and width of a converging nozzle do not alter the cut-off size of the impactor;however,using a conical Laval nozzle with an L/D_n ratio less than or equal to 2 reduced d_(50).The effect of using a cap as a focuser in the nozzle of a supersonic/hypersonic impactor was also investigated.The results show that adding a cap in front of the nozzle had a noticeable effect on decreasing the cut-off size of the impactor.Both flat disks and conical caps were examined,and it was observed that the nozzle with the conical cap had a lower cut-off size.
文摘In this study,numerical simulation of flow field in a supersonic/hypersonic impactor with one or two nozzles was carried out using a commercial computational fluid dynamics(CFD) software FLUENT.The objective was to investigate the effects of working parameters such as pressure ratio(50 < P_0/P_b< 800),nozzle diameters(D = 0.23,0.27,0.45 mm),nozzle to plate distance(0.5<L/D<50),particle diameter(1 nm < dp < 100 nm) and angle between two nozzles.A single-phase 3D unsteady-state model was implemented by the software.For this purpose,a user-defined function(UDF) was employed to implement nanoparticles for different assumptions of Cunningham correction factor.An axisymmetric form of the compressible Navier-Stokes and energy equations was used for both fluid flow and temperature;Lagrangian particle trajectory analysis was used for particle motion.Using the variable Cunningham correction factor showed suitable agreement with experimental data in comparison with other methods.Results show that increase of the distance between nozzle and impaction plate causes increase of Mach number,the distance between bow shock and impaction plate,and the collection efficiency.Maximum jet velocity,distance between bow shock and impaction plate and collection efficiency increase by using two nozzles in supersonic and hypersonic impactors.
基金supported by the National Natural Science Foundation of China (Grant No. 11072228, 11002129)the Science Foundation of China Academy of Engineering Physics (Grant No. 2011B0202005)+1 种基金the Open Foundation of State Key Laboratory of Explosion Science and Technology(Grant No. KFJJ09-06)the Open Foundation of State Key Laboratory of Advanced Technology for Materials Synthesis and Process-ing, Wuhan University of Technology
文摘Two types of Mg-Cu composition system graded density impactors used for complex loading (shock loading and quasi-isentropic compression) are designed by the elastic-plastic hydrodynamic method in this paper. Mixtures of metal powders in the Mg-Cu system are cast into a series of 17 and 25 uniform compositions ranging from 100% Mg to 100% Cu. The graded density impactors are launched to the stationary 10 m aluminum film and 12 mm LiF window targets by a two-stage light-gas gun in the National Key Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, CAEP, and the resulting wave profiles are measured with the DISAR system. Hydrodynamic simulation results are perfectly consistent with the experiments. Our work in this paper will set up a foundation for further research of controllable loading/releasing routes and rate experiments in the future.
