Devices on aircraft are subjected to complex environmental excitations that pose risks to their operational safety.Passive vibration isolation techniques are extensively employed due to their advantage of not requirin...Devices on aircraft are subjected to complex environmental excitations that pose risks to their operational safety.Passive vibration isolation techniques are extensively employed due to their advantage of not requiring additional energy sources.This paper introduces a novel metallic vibration isolator based on zigzag structures.The proposed isolator features a compact design and can be manufactured using additive manufacturing techniques,allowing for the integration of structural and functional elements.Firstly,the vibration response of the single-degree-of-freedom(SDOF)system is analyzed.To achieve effective vibration reduction,it is crucial for the isolator's stiffness to be sufficiently low.Secondly,to obtain a structure with high compliance,the traversal algorithm and the finite element method(FEM)are applied.The results confirm that the zigzag structure is a reliable high-compliance configuration.Thirdly,the parametric geometric model of the zigzag structure is developed and its stiffness is calculated.Quasi-static compression experiments validate the accuracy of the calculations.Finally,a specific engineering example is considered,where a zigzag vibration isolator is designed and fabricated.Vibration experiments demonstrate that the zigzag isolator effectively reduces both the stiffness and the fundamental frequency of the vibration system,achieving a vibration isolation efficiency exceeding 60%.展开更多
文摘水声网络(underwater acoustic network,UAN)具有长传播时延、高误码率、半双工通信等特性,这些特性严重影响了UAN中数据的可靠传输。而在线喷泉码具有在线控制、编解码复杂度低、码率自适应等诸多优势,在线喷泉码适合于保障UAN中数据的可靠传输。针对递归与限制反馈的在线喷泉码(recursive OFC with limited feedback,ROFC-LF)存在不理想覆盖和4元环问题导致略高的开销和频繁的反馈,提出适用于UAN的基于优先级与可Zigzag解码的ROFC-LF(priority-based and zigzag-decodable ROFC-LF,P-ZROFC-LF)。P-ZROFC-LF在建立阶段选取具有最高优先级的原始包进行编码直至所有原始包均参与编码。同时,引入可Zigzag解码编码,将无用编码包进行移位异或转换为有用编码包来提高解码性能。通过随机图理论,分析P-ZROFC-LF所需编码包数与原始包数之间的关系。理论分析与仿真结果表明,与大部分在线喷泉码相比,P-ZROFC-LF显著提高了反馈和开销性能。其中P-ZROFC-LF相比于ROFC-LF的反馈和开销分别减少了18%和0.0176,更适用于UAN。
基金supported by the National Key Research and Development Program of China(Nos.2023YFB4603900,2023YFB4603901)the National Natural Science Foundation of China(No.52275255)。
文摘Devices on aircraft are subjected to complex environmental excitations that pose risks to their operational safety.Passive vibration isolation techniques are extensively employed due to their advantage of not requiring additional energy sources.This paper introduces a novel metallic vibration isolator based on zigzag structures.The proposed isolator features a compact design and can be manufactured using additive manufacturing techniques,allowing for the integration of structural and functional elements.Firstly,the vibration response of the single-degree-of-freedom(SDOF)system is analyzed.To achieve effective vibration reduction,it is crucial for the isolator's stiffness to be sufficiently low.Secondly,to obtain a structure with high compliance,the traversal algorithm and the finite element method(FEM)are applied.The results confirm that the zigzag structure is a reliable high-compliance configuration.Thirdly,the parametric geometric model of the zigzag structure is developed and its stiffness is calculated.Quasi-static compression experiments validate the accuracy of the calculations.Finally,a specific engineering example is considered,where a zigzag vibration isolator is designed and fabricated.Vibration experiments demonstrate that the zigzag isolator effectively reduces both the stiffness and the fundamental frequency of the vibration system,achieving a vibration isolation efficiency exceeding 60%.
