A formula of calculating curvature radius was deduced according to the theory of rolling, together with the characteristics of rolling process. Moreover, the simulation of producing process is represented. Simulating ...A formula of calculating curvature radius was deduced according to the theory of rolling, together with the characteristics of rolling process. Moreover, the simulation of producing process is represented. Simulating results indicate that the curvature radius could be reduced by increasing friction coefficient, friction coefficient ratio, reduction or roller radius, while it could be augmented by increasing the thickness of plate. Furthermore, increasing the thickness of plate would cause more effects on front end curvature, whereas reduction would do less. The result provides theoretic basis for eliminating the front end curvature in plate and sheet rolling process, and it is important to protect controlling equipment and reduce scrap as well.展开更多
A non-resonant piezoelectric linear motor with a flexible driving end,which has an extensive working frequency range and good operation stability,is studied theoretically and experimentally.Based on the microscopic vi...A non-resonant piezoelectric linear motor with a flexible driving end,which has an extensive working frequency range and good operation stability,is studied theoretically and experimentally.Based on the microscopic vibration characteristics of the motor stator,the longitudinal vibration model is established for the whole motor system.According to the Coulomb friction model and the motor vibration model,the friction mechanism of the nonresonant piezoelectric linear motor is investigated by dynamical analysis of the whole motor system.Furthermore,the vibration characteristics and mechanical output characteristics of the stator are simulated and experimentally studied on the basis of the friction drive mechanism model.Finally,both the simulation and experimental results show that this kind of motor remain stable in the frequency domain from 2.2 kHz to 3.5 kHz and that when the pre-stress is 4 Nand the driving voltage is 90 V,the maximum velocity of the motor is above 4 mm/s and the maximum thrust is nearly 0.5 N.展开更多
Rear-end crashes are among the most common crash types at signalized intersections. To examine the risk factors for the occurrence of this crash type, this study involved the analysis of nine years of intersection cra...Rear-end crashes are among the most common crash types at signalized intersections. To examine the risk factors for the occurrence of this crash type, this study involved the analysis of nine years of intersection crash records in the state of Wyoming. With that, the contributing factors related to crash, driver, environmental, and roadway characteristics, including pavement surface friction, were investigated. A binomial logistic regression modeling approach was applied to achieve the study’s objective. The results showed that three factors related to crash and driver’s attributes (commercial vehicle involvement, speeding, and driver’s age) and four factors related to environmental and roadway characteristics (lighting, weather conditions, area type, whether urban or rural and pavement friction) are associated with the risk of rear-end crash occurrence at signalized intersections. This study provides insights into the mitigation measures to implement concerning rear-end crashes at signalized intersections.展开更多
基金Item Sponsored by Natural Science Foundation of Shaanxi Province of China (2004E19)
文摘A formula of calculating curvature radius was deduced according to the theory of rolling, together with the characteristics of rolling process. Moreover, the simulation of producing process is represented. Simulating results indicate that the curvature radius could be reduced by increasing friction coefficient, friction coefficient ratio, reduction or roller radius, while it could be augmented by increasing the thickness of plate. Furthermore, increasing the thickness of plate would cause more effects on front end curvature, whereas reduction would do less. The result provides theoretic basis for eliminating the front end curvature in plate and sheet rolling process, and it is important to protect controlling equipment and reduce scrap as well.
基金supported by the National Natural Science Foundations of China(Nos.51405420,51375224,61503319)the Natural Science Foundation of Jiangsu Province(No.BK20140474)+2 种基金the Sponsorship of Jiangsu Oversea Research and Training Program for University Prominent Young&Middle-aged Teachersthe Jiangsu Province Ordinary University Professional Degree Graduate Innovation Project(No.SJZZ16_0294)Qing Lan Project of Jiangsu Higher Education of China(No.Su-Teacher2018-12)
文摘A non-resonant piezoelectric linear motor with a flexible driving end,which has an extensive working frequency range and good operation stability,is studied theoretically and experimentally.Based on the microscopic vibration characteristics of the motor stator,the longitudinal vibration model is established for the whole motor system.According to the Coulomb friction model and the motor vibration model,the friction mechanism of the nonresonant piezoelectric linear motor is investigated by dynamical analysis of the whole motor system.Furthermore,the vibration characteristics and mechanical output characteristics of the stator are simulated and experimentally studied on the basis of the friction drive mechanism model.Finally,both the simulation and experimental results show that this kind of motor remain stable in the frequency domain from 2.2 kHz to 3.5 kHz and that when the pre-stress is 4 Nand the driving voltage is 90 V,the maximum velocity of the motor is above 4 mm/s and the maximum thrust is nearly 0.5 N.
文摘Rear-end crashes are among the most common crash types at signalized intersections. To examine the risk factors for the occurrence of this crash type, this study involved the analysis of nine years of intersection crash records in the state of Wyoming. With that, the contributing factors related to crash, driver, environmental, and roadway characteristics, including pavement surface friction, were investigated. A binomial logistic regression modeling approach was applied to achieve the study’s objective. The results showed that three factors related to crash and driver’s attributes (commercial vehicle involvement, speeding, and driver’s age) and four factors related to environmental and roadway characteristics (lighting, weather conditions, area type, whether urban or rural and pavement friction) are associated with the risk of rear-end crash occurrence at signalized intersections. This study provides insights into the mitigation measures to implement concerning rear-end crashes at signalized intersections.
