To study the distribution and dissipation of braking power of wet multidisc brake and determine thermal load and thermal flux distribution between mated discs, the concept of distributing brake power four times was pu...To study the distribution and dissipation of braking power of wet multidisc brake and determine thermal load and thermal flux distribution between mated discs, the concept of distributing brake power four times was put forward. The third and the fourth distribution of brake power were calculated by using finite element(FE) software ANSYS. The third and the fourth distribution of wet multidisc brake are mainly related to material characteristics of discs during emergency braking, while most of the braking power is carried off during continuous braking. Basis is provided for further analysis of disc failure and applicability of different friction materials.展开更多
This study aims to introduce a novel hybrid design with a combination of two more common mechanisms for improving the capacity of systems in absorbing the kinetic energy of moving vehicles or devices. This new model c...This study aims to introduce a novel hybrid design with a combination of two more common mechanisms for improving the capacity of systems in absorbing the kinetic energy of moving vehicles or devices. This new model consists of two individual mechanisms, i.e., expansion of a circular tube accompanied by crushing of an inner tube, which dissipate the energy through friction, plastic deformations and failures of inner tube. This study comprises 24 case studies surveyed under two different design controls, constant mass and constant volume, for comparing purposes. Finite element simulations are utilized so as to investigate models’ deformations and to extract some crashworthiness parameters in aid of representing the efficiency of the mechanism as well as conducting a parametric study between three different profiles of inner tube. This study shows that models with inner circular and hexagonal tube profile absorb higher amount of energy due to experiencing three different modes of energy dissipation systems, including folding, shear and ductile damages.展开更多
The finiteness of superstring theory at each order in perturbation theory is considered with respect to the ten-dimensional effective action. The quantum consistency of the ten-dimensional superstring effective action...The finiteness of superstring theory at each order in perturbation theory is considered with respect to the ten-dimensional effective action. The quantum consistency of the ten-dimensional superstring effective action is confirmed with an analysis of the perturbative expansion of the quartic sector. It is found to be compatible with the finiteness of reduced four-dimensional theory. Furthermore, implications for the validity of superstring perturbation theory at lower energies is considered.展开更多
In this paper, the buckling behavior of zigzag BN (Boron Nitride) nanotubes under bending is studied through molecular dynamics finite element method with Tersoff potential. The tube with namely (15, 0) BN zigzag ...In this paper, the buckling behavior of zigzag BN (Boron Nitride) nanotubes under bending is studied through molecular dynamics finite element method with Tersoff potential. The tube with namely (15, 0) BN zigzag tube is investigated. The critical bending buckling angle, moment and curvature are studied and examined with respect to the tube length-diameter ratios from 5 to 30. Effects of a SW (Stone-Wales) defect in the middle tube on the bending behavior are also discussed. The results show that the tube length affects significantly the bending behavior of these tubes. All tubes exhibit brittle fracture under bending. The buckling takes place at the middle in the compressive side of these tubes. These results are important information on the buckling behaviors of pristine and Stone-Wales BN nanotubes, which will be useful for their future applications.展开更多
Rotating machines are very sensitive to mass unbalance which has a harmful effect on its running accuracy and service life. Therefore,a variety of dynamic balancing methods and devices are studied to reduce the vibrat...Rotating machines are very sensitive to mass unbalance which has a harmful effect on its running accuracy and service life. Therefore,a variety of dynamic balancing methods and devices are studied to reduce the vibration caused by mass unbalance. On-line active balancing is a new balancing procedure which is more convenient and precise than the previous methods. In this paper,an electromagnetic balancer based on ring coils and permanent magnets is presented. The balancer has a simple structure and the self-locking function without clutch,and transfers power by the non-contact electromagnetic field. In order to justify the rationality of its design,a two-dimension(2D) electromagnetic finite element model is conducted to verify that this magnetic circuit has no flux leakage and saturation. A three-dimension (3D) 1/10 model of the balancer is built to obtain the self-locking torque and driving torque. Based on the research work above,an electromagnetic balancer is developed. By testing the balancer using COCO80,it is verified effective to reduce the rotor unbalance at the speed of 1300 r/min.展开更多
A recently emerging family of smart materials,photostrictive materials,exhibit large photostriction under uniform illumination of high-energy light.This photostriction mechanism arises from a superposition phenomenon ...A recently emerging family of smart materials,photostrictive materials,exhibit large photostriction under uniform illumination of high-energy light.This photostriction mechanism arises from a superposition phenomenon of photovoltaic and converse piezoelectric effects.A photostrictive type of opto-electromechanical actuator activated by high-energy lights can introduce actuation and control effects without hard-wired connections.The control light intensity applied to the actuator is proportional to the transverse velocity at a positioned point,which is measured by a laser vibrometer.In this paper,photostrictive films are numerically analyzed to evaluate their use as wireless actuators for future remote vibration control of flexible structures.A novel opto-electromechanical solid shell finite element formulation is developed for accurate analysis of the multiple physics effects of photovoltaic,pyroelectric and thermal expansion of photostrictive materials.Available experimental data and analytical solutions have been used to verify the present finite element results.The simulation in this study demonstrates that the present formulation is very reliable,accurate and also computationally efficient and that the use of photostrictive actuators can provide good controllability of structural vibration.展开更多
We review the construction of gravitational solutions holographically dual to N=1 quiver gauge theories with dynamical flavor multiplets.We focus on the D3-D7 construction and consider the finite temperature,finite qu...We review the construction of gravitational solutions holographically dual to N=1 quiver gauge theories with dynamical flavor multiplets.We focus on the D3-D7 construction and consider the finite temperature,finite quark chemical potential case where there is a charged black hole in the dual solution.Discussed physical outputs of the model include its thermodynamics (with susceptibilities) and general hydrodynamic properties.展开更多
文摘To study the distribution and dissipation of braking power of wet multidisc brake and determine thermal load and thermal flux distribution between mated discs, the concept of distributing brake power four times was put forward. The third and the fourth distribution of brake power were calculated by using finite element(FE) software ANSYS. The third and the fourth distribution of wet multidisc brake are mainly related to material characteristics of discs during emergency braking, while most of the braking power is carried off during continuous braking. Basis is provided for further analysis of disc failure and applicability of different friction materials.
文摘This study aims to introduce a novel hybrid design with a combination of two more common mechanisms for improving the capacity of systems in absorbing the kinetic energy of moving vehicles or devices. This new model consists of two individual mechanisms, i.e., expansion of a circular tube accompanied by crushing of an inner tube, which dissipate the energy through friction, plastic deformations and failures of inner tube. This study comprises 24 case studies surveyed under two different design controls, constant mass and constant volume, for comparing purposes. Finite element simulations are utilized so as to investigate models’ deformations and to extract some crashworthiness parameters in aid of representing the efficiency of the mechanism as well as conducting a parametric study between three different profiles of inner tube. This study shows that models with inner circular and hexagonal tube profile absorb higher amount of energy due to experiencing three different modes of energy dissipation systems, including folding, shear and ductile damages.
文摘The finiteness of superstring theory at each order in perturbation theory is considered with respect to the ten-dimensional effective action. The quantum consistency of the ten-dimensional superstring effective action is confirmed with an analysis of the perturbative expansion of the quartic sector. It is found to be compatible with the finiteness of reduced four-dimensional theory. Furthermore, implications for the validity of superstring perturbation theory at lower energies is considered.
文摘In this paper, the buckling behavior of zigzag BN (Boron Nitride) nanotubes under bending is studied through molecular dynamics finite element method with Tersoff potential. The tube with namely (15, 0) BN zigzag tube is investigated. The critical bending buckling angle, moment and curvature are studied and examined with respect to the tube length-diameter ratios from 5 to 30. Effects of a SW (Stone-Wales) defect in the middle tube on the bending behavior are also discussed. The results show that the tube length affects significantly the bending behavior of these tubes. All tubes exhibit brittle fracture under bending. The buckling takes place at the middle in the compressive side of these tubes. These results are important information on the buckling behaviors of pristine and Stone-Wales BN nanotubes, which will be useful for their future applications.
基金The National Science and Technology Major Project of China(No.2010ZX04012-014)
文摘Rotating machines are very sensitive to mass unbalance which has a harmful effect on its running accuracy and service life. Therefore,a variety of dynamic balancing methods and devices are studied to reduce the vibration caused by mass unbalance. On-line active balancing is a new balancing procedure which is more convenient and precise than the previous methods. In this paper,an electromagnetic balancer based on ring coils and permanent magnets is presented. The balancer has a simple structure and the self-locking function without clutch,and transfers power by the non-contact electromagnetic field. In order to justify the rationality of its design,a two-dimension(2D) electromagnetic finite element model is conducted to verify that this magnetic circuit has no flux leakage and saturation. A three-dimension (3D) 1/10 model of the balancer is built to obtain the self-locking torque and driving torque. Based on the research work above,an electromagnetic balancer is developed. By testing the balancer using COCO80,it is verified effective to reduce the rotor unbalance at the speed of 1300 r/min.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10872090, 50830201)NUAA Research Funding (Grant No. NJ2010011)
文摘A recently emerging family of smart materials,photostrictive materials,exhibit large photostriction under uniform illumination of high-energy light.This photostriction mechanism arises from a superposition phenomenon of photovoltaic and converse piezoelectric effects.A photostrictive type of opto-electromechanical actuator activated by high-energy lights can introduce actuation and control effects without hard-wired connections.The control light intensity applied to the actuator is proportional to the transverse velocity at a positioned point,which is measured by a laser vibrometer.In this paper,photostrictive films are numerically analyzed to evaluate their use as wireless actuators for future remote vibration control of flexible structures.A novel opto-electromechanical solid shell finite element formulation is developed for accurate analysis of the multiple physics effects of photovoltaic,pyroelectric and thermal expansion of photostrictive materials.Available experimental data and analytical solutions have been used to verify the present finite element results.The simulation in this study demonstrates that the present formulation is very reliable,accurate and also computationally efficient and that the use of photostrictive actuators can provide good controllability of structural vibration.
基金supported by the European Community Seventh Frame work Programme FP7/2007-2013,under grant agreements n. 253534 and 253937. J.T.supported by the Netherlands Organization for Scientic Research (NWO) under the FOM Foundation research program+3 种基金supported by the MICINN and FEDER (grant FPA2008-01838)the Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042)the Xunta de Galicia (Conselleria de Educacion and grant INCITE09-206-121-PR)KITPC Beijing for hospitality and financial support (this last under grant KJCX2.YW.W10 of the Chinese Academy of Sciences)
文摘We review the construction of gravitational solutions holographically dual to N=1 quiver gauge theories with dynamical flavor multiplets.We focus on the D3-D7 construction and consider the finite temperature,finite quark chemical potential case where there is a charged black hole in the dual solution.Discussed physical outputs of the model include its thermodynamics (with susceptibilities) and general hydrodynamic properties.