Laser triangulation theory was used to develop a novel contact-free method for measuring the coal level in a silo under harsh environmental conditions found in coal mines, such as the presence of dense dust, high humi...Laser triangulation theory was used to develop a novel contact-free method for measuring the coal level in a silo under harsh environmental conditions found in coal mines, such as the presence of dense dust, high humidity, and low illumination. A laser source and a camera were mounted at the top of the silo. The laser spot projected into the silo was imaged by the camera. The pinhole imaging principle allows the level to be found from the lateral shift of the spot image on the sensor. A pre-calibrated look-up table of the coal depth versus spot position was used to obtain the depth. The measurement accuracy depends on the step size used during pre-calibration. The actual application of a device designed according to these principles shows that it is easy to implement. The detection of the coal level in a silo at the low illumination level found in coal mines is demonstrated.展开更多
Due to the fact that rolling contact fatigue is not easily detected, and residual life is not easily evaluated in the early stage of bearing life, a nondestructive testing method based on initial permeability is propo...Due to the fact that rolling contact fatigue is not easily detected, and residual life is not easily evaluated in the early stage of bearing life, a nondestructive testing method based on initial permeability is proposed. By analyzing the crack propagation mechanism, a fatigue state detection system based on differential signals is designed. A simulation model of the detection of the inner ring of the pulse signal is established by using the electromagnetic field simulation software. The effects of the height of the coil, the inner and outer diameter, the number of coil turns, the diameter and the height of the ferrite core of the probe on the differential value of the detection signal are simulated. The parameter combination of the maximum difference value of the signal is used as the structural size of the sensor, and the detection sensor is designed and fabricated. Moreover, the bearing fatigue test system is designed, and the bearing is tested. The results show that the system has good detection ability for rolling contact fatigue and verifies the mechanism and trend of crack propagation in the inner ring of the bearing.展开更多
The most general contact in mechanical transmission is the elliptical one. In particular, a toroidal continuously variable transmission (CVT) has an elliptical shape in the contact area under the elastohydrodynamic lu...The most general contact in mechanical transmission is the elliptical one. In particular, a toroidal continuously variable transmission (CVT) has an elliptical shape in the contact area under the elastohydrodynamic lubrication regime, where the shearing of the fluid subjects to high contact stress and transmits the power. Many parameters affect the contact service performance of the half toroidal CVT, which include the properties of the contacting material (Young抯 modulus), operating parameters (input torque and maximum traction coefficient) and geometrical parameters (aspect cavity ratio, curvature ratio and half cone angle of the power roller). In this paper, the contacts between the input disk, the power roller and the output disk are formulated using the classical Hertzian contact theory. Based on the formulated equations, different system parameters, which affect the maximum Hertzian stresses, are compared. The comparative results will provide some observations of the relations between the maximum Hertzian stresses and transmission ratios in the form of graphs. These graphs give useful information for designer to know the maximum Hertzian stress during operation in such systems.展开更多
In this paper, we derive a unified scattering theory model for current noise based on the equivalent contact model of the scattering region. Our model seamlessly covers the whole range of transport regimes from cohere...In this paper, we derive a unified scattering theory model for current noise based on the equivalent contact model of the scattering region. Our model seamlessly covers the whole range of transport regimes from coherent transport to incoherent transport and it also includes the effects of Pauli exclusion and Coulomb interaction on shot noise.展开更多
基金supported by the National Natural Science Foun-dation of China (No. 51074169)
文摘Laser triangulation theory was used to develop a novel contact-free method for measuring the coal level in a silo under harsh environmental conditions found in coal mines, such as the presence of dense dust, high humidity, and low illumination. A laser source and a camera were mounted at the top of the silo. The laser spot projected into the silo was imaged by the camera. The pinhole imaging principle allows the level to be found from the lateral shift of the spot image on the sensor. A pre-calibrated look-up table of the coal depth versus spot position was used to obtain the depth. The measurement accuracy depends on the step size used during pre-calibration. The actual application of a device designed according to these principles shows that it is easy to implement. The detection of the coal level in a silo at the low illumination level found in coal mines is demonstrated.
基金The Science and Technology Innovation Committee(STIC)of Shenzhen(No.JCYJ20180306174455080)
文摘Due to the fact that rolling contact fatigue is not easily detected, and residual life is not easily evaluated in the early stage of bearing life, a nondestructive testing method based on initial permeability is proposed. By analyzing the crack propagation mechanism, a fatigue state detection system based on differential signals is designed. A simulation model of the detection of the inner ring of the pulse signal is established by using the electromagnetic field simulation software. The effects of the height of the coil, the inner and outer diameter, the number of coil turns, the diameter and the height of the ferrite core of the probe on the differential value of the detection signal are simulated. The parameter combination of the maximum difference value of the signal is used as the structural size of the sensor, and the detection sensor is designed and fabricated. Moreover, the bearing fatigue test system is designed, and the bearing is tested. The results show that the system has good detection ability for rolling contact fatigue and verifies the mechanism and trend of crack propagation in the inner ring of the bearing.
基金the Ford-NSFC Foundation of China (No. 50122151).
文摘The most general contact in mechanical transmission is the elliptical one. In particular, a toroidal continuously variable transmission (CVT) has an elliptical shape in the contact area under the elastohydrodynamic lubrication regime, where the shearing of the fluid subjects to high contact stress and transmits the power. Many parameters affect the contact service performance of the half toroidal CVT, which include the properties of the contacting material (Young抯 modulus), operating parameters (input torque and maximum traction coefficient) and geometrical parameters (aspect cavity ratio, curvature ratio and half cone angle of the power roller). In this paper, the contacts between the input disk, the power roller and the output disk are formulated using the classical Hertzian contact theory. Based on the formulated equations, different system parameters, which affect the maximum Hertzian stresses, are compared. The comparative results will provide some observations of the relations between the maximum Hertzian stresses and transmission ratios in the form of graphs. These graphs give useful information for designer to know the maximum Hertzian stress during operation in such systems.
基金This research was financially supported by Scientific Research Fund of Shaanxi Provincial Education Department （Grant No. 2013K1115） ,the National Natural Science Foundation of China （Grant No. 61106062）, the Fundamental Research Funds for the Central Universities （Grant No. K50511050007）, and the Fundamental Research Funds for AnKang University （Grant No. AYQDZR201206）.
文摘In this paper, we derive a unified scattering theory model for current noise based on the equivalent contact model of the scattering region. Our model seamlessly covers the whole range of transport regimes from coherent transport to incoherent transport and it also includes the effects of Pauli exclusion and Coulomb interaction on shot noise.
