A third-order correction was recently suggested to improve the accuracy of the half-power bandwidth method in estimating the damping of single DOF systems.This paper analyzes the accuracy of the half-power bandwidth m...A third-order correction was recently suggested to improve the accuracy of the half-power bandwidth method in estimating the damping of single DOF systems.This paper analyzes the accuracy of the half-power bandwidth method with the third-order correction in damping estimation for multi-DOF linear systems.Damping ratios in a two-DOF linear system are estimated using its displacement and acceleration frequency response curves,respectively.A wide range of important parameters that characterize the shape of these response curves are taken into account.Results show that the third-order correction may greatly improve the accuracy of the half-power bandwidth method in estimating damping in a two-DOF system.In spite of this,the half-power bandwidth method may significantly overestimate the damping ratios of two-DOF systems in some cases.展开更多
无损离子操纵结构(structures for lossless ion manipulations,SLIM)是一种在特殊背景气体下,利用静电场、射频电场、离子驱动电场共同作用实现对气相离子无损传输的新结构,在物质传输和分离方面有着广阔的应用前景。为了充分发挥SLIM...无损离子操纵结构(structures for lossless ion manipulations,SLIM)是一种在特殊背景气体下,利用静电场、射频电场、离子驱动电场共同作用实现对气相离子无损传输的新结构,在物质传输和分离方面有着广阔的应用前景。为了充分发挥SLIM在体积和成本上的优势,本研究研制了一款体积小、结构紧凑、成本经济的高频高压双极性射频(radio frequency,RF)电源。该电源使用隔离模块实现控制电路与功率电路的电气隔离,并采用以GaN金属-氧化物-半导体场效应管(MOSFET)为核心的半桥电路作为输出级。针对SLIM的容性负载特性,利用电阻-电感-电容(RLC)电路的滤波特性,实现双极性正弦脉冲电压的输出。经测试,该电源可输出频率1 MHz、峰-峰值420 V(±210 V)的双极性正弦射频高压信号。在实验室自建的基于行波(traveling wave,TW)的无损离子操纵结构(TW-SLIM)迁移谱实验平台上,以甲基膦酸二甲酯(DMMP)为样本,深入探究了射频电源幅值及频率对小分子离子传输效率的影响。结果表明,射频电源幅值及频率均会对TW-SLIM结构的离子传输效率产生影响,并存在1个最优值范围,这与COMSOL的仿真结果相吻合。该射频电源能够有效支持TW-SLIM平台的稳定运行,对推动基于SLIM的小分子迁移谱技术的小型化和便携化研发具有重要价值。展开更多
基金National Natural Science Foundation under Grant No. 51179093National Basic Research Program of China under Grant No. 2011CB013602Program for New Century Excellent Talents in University under Grant No.NCET-10-0531
文摘A third-order correction was recently suggested to improve the accuracy of the half-power bandwidth method in estimating the damping of single DOF systems.This paper analyzes the accuracy of the half-power bandwidth method with the third-order correction in damping estimation for multi-DOF linear systems.Damping ratios in a two-DOF linear system are estimated using its displacement and acceleration frequency response curves,respectively.A wide range of important parameters that characterize the shape of these response curves are taken into account.Results show that the third-order correction may greatly improve the accuracy of the half-power bandwidth method in estimating damping in a two-DOF system.In spite of this,the half-power bandwidth method may significantly overestimate the damping ratios of two-DOF systems in some cases.
文摘A new dispersive relation is found and a half-pow tormulas for the generalize Miodek equation under the deeaying conditions at infinity are obtained.
文摘无损离子操纵结构(structures for lossless ion manipulations,SLIM)是一种在特殊背景气体下,利用静电场、射频电场、离子驱动电场共同作用实现对气相离子无损传输的新结构,在物质传输和分离方面有着广阔的应用前景。为了充分发挥SLIM在体积和成本上的优势,本研究研制了一款体积小、结构紧凑、成本经济的高频高压双极性射频(radio frequency,RF)电源。该电源使用隔离模块实现控制电路与功率电路的电气隔离,并采用以GaN金属-氧化物-半导体场效应管(MOSFET)为核心的半桥电路作为输出级。针对SLIM的容性负载特性,利用电阻-电感-电容(RLC)电路的滤波特性,实现双极性正弦脉冲电压的输出。经测试,该电源可输出频率1 MHz、峰-峰值420 V(±210 V)的双极性正弦射频高压信号。在实验室自建的基于行波(traveling wave,TW)的无损离子操纵结构(TW-SLIM)迁移谱实验平台上,以甲基膦酸二甲酯(DMMP)为样本,深入探究了射频电源幅值及频率对小分子离子传输效率的影响。结果表明,射频电源幅值及频率均会对TW-SLIM结构的离子传输效率产生影响,并存在1个最优值范围,这与COMSOL的仿真结果相吻合。该射频电源能够有效支持TW-SLIM平台的稳定运行,对推动基于SLIM的小分子迁移谱技术的小型化和便携化研发具有重要价值。
