This paper proposes a multifunction radar that can not only measure sea currents but also perform sea-surface imaging.The fundamental aspect of the proposed radar comprises transmitting time-shifted up-and-down contin...This paper proposes a multifunction radar that can not only measure sea currents but also perform sea-surface imaging.The fundamental aspect of the proposed radar comprises transmitting time-shifted up-and-down continuous wave linear frequency modulated signals that allow for the offset of two one-dimensional range images of the sea surface that respectively correspond to the upward linear frequency modulated(LFM)signal and the downward LFM signal.Owing to the Doppler frequency shift from the sea surface,a range offset,which is proportional to the radial velocity of the sea surface,occurs between the upward and downward LFM signals.By using the least-squares linear fitting method in the transformed domain,the range offset can be measured and the current velocity can be retrieved.Finally,we verify the accuracy of current measurement with simulation results.展开更多
近年来 ,通过影像学及眼眶的组织学研究证实在眼球赤道部附近有一个由胶原、弹性蛋白和平滑肌构成的 pulley。Pulley作为眼外肌的功能性起点决定着直肌作用力的方向和大小。本文就 pul ley的提出、组织结构、位置及对于非共同性斜视的...近年来 ,通过影像学及眼眶的组织学研究证实在眼球赤道部附近有一个由胶原、弹性蛋白和平滑肌构成的 pulley。Pulley作为眼外肌的功能性起点决定着直肌作用力的方向和大小。本文就 pul ley的提出、组织结构、位置及对于非共同性斜视的意义等作一综述。展开更多
In conventional modeling of a cable-pulley system, the cable must be finely meshed with Lagrangian elements for valid contact detections with pulleys, leading to extremely low efficiency. The sliding joint method base...In conventional modeling of a cable-pulley system, the cable must be finely meshed with Lagrangian elements for valid contact detections with pulleys, leading to extremely low efficiency. The sliding joint method based on the arbitrary-Lagrangian- Eulerian （ALE） formulation still lacks an efficient cable element, and in particular, modeling of friction between a sliding joint and the cable has not been studied. This paper presents efficient multi-body modeling of a cable-pulley system with friction. A variable- length cable element with a node movable along the cable, which is described with ALE, is developed to mesh the cable. A transitional cable element is then proposed to model the contact part of the cable by fixing its two nodes to the two corresponding locations of the pulley. Friction of the cable-pulley is derived as a simple law of tension decay and embedded in the multi-body system modeling. It is simplified as a generalized friction force acting only on the arc-length coordinate. This approach can use a rough mesh on the cable, and is free of contact detections, thus significantly saving computation time. Several examples are presented to validate the proposed method, and show its effectiveness in real engineering applications.展开更多
According to the requirements of designing V-groove pulley transmission, an application development based on AutoCAD environment and using AutoLISP language is presented. As an example of effective solution for CAD ap...According to the requirements of designing V-groove pulley transmission, an application development based on AutoCAD environment and using AutoLISP language is presented. As an example of effective solution for CAD application, the CAD system for V-groove pulley transmission is established.展开更多
为了解决传统式调谐质量阻尼器(tuned mass damper, TMD)在控制低频桥梁结构中弹簧静伸长过长的问题,介绍了滑轮式TMD及其用于结构振动控制时的特点,指出滑轮式TMD可以有效减小弹簧静伸长量。以一座人行景观桥为例,研究了采用气动措施...为了解决传统式调谐质量阻尼器(tuned mass damper, TMD)在控制低频桥梁结构中弹簧静伸长过长的问题,介绍了滑轮式TMD及其用于结构振动控制时的特点,指出滑轮式TMD可以有效减小弹簧静伸长量。以一座人行景观桥为例,研究了采用气动措施和滑轮式TMD对该桥的涡振控制效果。风洞试验结果显示,在最优气动措施下,主梁的涡振振幅减少了一半以上,但仍未达到行人舒适性要求。基于Scanlan线性涡激力模型进行滑轮式TMD的优化设计,在气动措施的基础上进一步辅以滑轮式TMD进行涡振控制。分析结果表明,气动措施结合滑轮式TMD进行涡振控制能够满足行人舒适性要求,并确保滑轮式TMD质量块的工作行程不超过限值。通过同时采用气动措施和滑轮式TMD,可以满足主梁涡振限值、TMD弹簧静伸长量和工作行程等多重要求,从而有效控制主梁的涡振现象。本文提出的混合控制方案为类似工程中的涡振控制提供了有益参考,可为工程实践提供指导。展开更多
基金The National Key Research and Development Program under contract No.2016YFC1401002the National Natural Science Foundation of China under contract Nos 41606201,41576173,41620104003 and 41706202.
文摘This paper proposes a multifunction radar that can not only measure sea currents but also perform sea-surface imaging.The fundamental aspect of the proposed radar comprises transmitting time-shifted up-and-down continuous wave linear frequency modulated signals that allow for the offset of two one-dimensional range images of the sea surface that respectively correspond to the upward linear frequency modulated(LFM)signal and the downward LFM signal.Owing to the Doppler frequency shift from the sea surface,a range offset,which is proportional to the radial velocity of the sea surface,occurs between the upward and downward LFM signals.By using the least-squares linear fitting method in the transformed domain,the range offset can be measured and the current velocity can be retrieved.Finally,we verify the accuracy of current measurement with simulation results.
基金Project supported by the National Natural Science Foundation of China(No.11302114)the Major State Basic Research Development Program(No.2012CB821203)the Guangdong Provincial Key Laboratory Construction Project of China(No.2011A060901026)
文摘In conventional modeling of a cable-pulley system, the cable must be finely meshed with Lagrangian elements for valid contact detections with pulleys, leading to extremely low efficiency. The sliding joint method based on the arbitrary-Lagrangian- Eulerian （ALE） formulation still lacks an efficient cable element, and in particular, modeling of friction between a sliding joint and the cable has not been studied. This paper presents efficient multi-body modeling of a cable-pulley system with friction. A variable- length cable element with a node movable along the cable, which is described with ALE, is developed to mesh the cable. A transitional cable element is then proposed to model the contact part of the cable by fixing its two nodes to the two corresponding locations of the pulley. Friction of the cable-pulley is derived as a simple law of tension decay and embedded in the multi-body system modeling. It is simplified as a generalized friction force acting only on the arc-length coordinate. This approach can use a rough mesh on the cable, and is free of contact detections, thus significantly saving computation time. Several examples are presented to validate the proposed method, and show its effectiveness in real engineering applications.
文摘According to the requirements of designing V-groove pulley transmission, an application development based on AutoCAD environment and using AutoLISP language is presented. As an example of effective solution for CAD application, the CAD system for V-groove pulley transmission is established.
文摘为了解决传统式调谐质量阻尼器(tuned mass damper, TMD)在控制低频桥梁结构中弹簧静伸长过长的问题,介绍了滑轮式TMD及其用于结构振动控制时的特点,指出滑轮式TMD可以有效减小弹簧静伸长量。以一座人行景观桥为例,研究了采用气动措施和滑轮式TMD对该桥的涡振控制效果。风洞试验结果显示,在最优气动措施下,主梁的涡振振幅减少了一半以上,但仍未达到行人舒适性要求。基于Scanlan线性涡激力模型进行滑轮式TMD的优化设计,在气动措施的基础上进一步辅以滑轮式TMD进行涡振控制。分析结果表明,气动措施结合滑轮式TMD进行涡振控制能够满足行人舒适性要求,并确保滑轮式TMD质量块的工作行程不超过限值。通过同时采用气动措施和滑轮式TMD,可以满足主梁涡振限值、TMD弹簧静伸长量和工作行程等多重要求,从而有效控制主梁的涡振现象。本文提出的混合控制方案为类似工程中的涡振控制提供了有益参考,可为工程实践提供指导。
