The Experts below are selected from a list of 18048 Experts worldwide ranked by ideXlab platform
Zhike Peng - One of the best experts on this subject based on the ideXlab platform.
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local variation detection in mdof system using wavelet based Transmissibility and its application in cracked beam
Journal of Vibration and Control, 2017Co-Authors: Xinqiang Li, Zhike Peng, X J Dong, Wenming Zhang, Guang MengAbstract:Since the local stiffness or damping variation happens when damage occurs in engineer structures, it is useful to detect the local variation as a way for structural damage inspection. As a vibration based approach, Transmissibility has attracted considerable interest because of its convenience and effectiveness in damage detection. However, using the traditional Fourier transform, it should be very careful to select the frequency bands in Transmissibility calculation. Inappropriate choice of frequency band could cause a complete inaccurate result. For unknown damage detection, it is difficult to select the frequency band which eigen-frequency should be included. This paper proposes a novel method using wavelet based Transmissibility for local variation detection. Benefiting from the ability in subtle information acquisition of wavelet transform, it is useful in reducing the influence of frequency bands to the indicators. Analytical derivation using wavelet balance method and numerical studies of a multipl...
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study of the effects of cubic nonlinear damping on vibration isolations using harmonic balance method
International Journal of Non-linear Mechanics, 2012Co-Authors: Zhike Peng, Z Q Lang, Guang Meng, Wenming ZhangAbstract:Abstract In the present study, Harmonic Balance Method (HBM) is applied to investigate the performance of passive vibration isolators with cubic nonlinear damping. The results reveal that introducing either cubic nonlinear damping or linear damping could significantly reduce both the displacement Transmissibility and the force Transmissibility of the isolators over the resonance region. However, at the non-resonance region where frequency is lower than the resonant frequency, both the linear damping and the cubic nonlinear damping have almost no effect on the isolators. At the non-resonance region with higher frequency, increasing the linear damping has almost no effects on the displacement Transmissibility but could raise the force Transmissibility. In addition, the influence of the cubic nonlinear damping on the isolators is dependent on the type of the disturbing force. If the strength of the disturbing force is constant and independent of the excitation frequency, then the effect of cubic nonlinear damping on both the force and displacement Transmissibility would be negligible. But, when the strength of the disturbing force is dependent of the excitation frequency, increasing the cubic nonlinear damping could slightly reduce the relative displacement Transmissibility and increase the absolute displacement Transmissibility but could significantly increase the force Transmissibility. These conclusions are of significant importance in the analysis and design of nonlinear passive vibration isolators.
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reducing force Transmissibility in multiple degrees of freedom structures through anti symmetric nonlinear viscous damping
Acta Mechanica Sinica, 2012Co-Authors: Zhike Peng, Z Q Lang, Guang Meng, Stephen A BillingsAbstract:In the present study, the Volterra series theory is adopted to theoretically investigate the force Transmissibility of multiple degrees of freedom (MDOF) structures, in which an isolator with nonlinear anti-symmetric viscous damping is assembled. The results reveal that the anti-symmetric nonlinear viscous damping can significantly reduce the force Transmissibility over all resonance regions for MDOF structures with little effect on the Transmissibility over non-resonant and isolation regions. The results indicate that the vibration isolators with an anti-symmetric damping characteristic have great potential to solve the dilemma occurring in the design of linear viscously damped vibration isolators where an increase of the damping level reduces the force Transmissibility over resonant frequencies but increases the Transmissibility over non-resonant frequency regions. This work is an extension of a previous study in which MDOF structures installed on the mount through an isolator with cubic nonlinear damping are considered. The theoretical analysis results are also verified by simulation studies.
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the force Transmissibility of mdof structures with a non linear viscous damping device
International Journal of Non-linear Mechanics, 2011Co-Authors: Stephen A Billings, Z Q Lang, Zhike Peng, L Zhao, Geoffrey R TomlinsonAbstract:Abstract In the present study, the concept of the Output Frequency Response Function (OFRF), recently proposed by the authors, is applied to theoretically investigate the force Transmissibility of MDOF structures with a cubic non-linear viscous damping device. The results analytically show that the introduction of cubic non-linear damping can significantly reduce the Transmissibility over all resonance regions for a Multiple Degree of Freedom (MDOF) structure and at the same time leave the Transmissibility over the isolation region virtually unaffected. The analysis also indicates that a strong linear damping may shift the system resonances and compromise the beneficial effects of cubic non-linear viscous damping on the force Transmissibility of MDOF structures. This suggests that a less significant linear damping together with a strong cubic non-linear damping can be used in MDOF structures to achieve a desired vibration isolation performance. This research work has a significant implication for the design of viscously damped MDOF structures for a wide range of practical applications.
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the Transmissibility of vibration isolators with a nonlinear antisymmetric damping characteristic
Journal of Vibration and Acoustics, 2010Co-Authors: Zhike Peng, Stephen A Billings, Xingjian Jing, Z Q Lang, Geoffrey R Tomlinson, Lingzhong GuoAbstract:In the present study, the concept of the output frequency response function, recently proposed by the authors, is applied to theoretically investigate the force Transmissibility of single degree of freedom (SDOF) passive vibration isolators with a nonlinear antisymmetric damping characteristic. The results reveal that a nonlinear antisymmetric damping characteristic has almost no effect on the Transmissibility of SDOF vibration isolators over the ranges of frequencies, which are much lower or higher than the isolator's resonance frequency. On the other hand, the introduction of a nonlinear antisymmetric damping can significantly reduce the Transmissibility of the vibration isolator over the resonance frequency region. The results indicate that nonlinear vibration isolators with an antisymmetric damping characteristic have great potential to overcome the dilemma encountered in the design of passive linear vibration isolators, that is, increasing the level of damping to reduce the Transmissibility at the resonance could increase the Transmissibility over the range of higher frequencies. These important theoretical conclusions are then verified by simulation studies.
Z Q Lang - One of the best experts on this subject based on the ideXlab platform.
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generalized Transmissibility damage indicator with application to wind turbine component condition monitoring
IEEE Transactions on Industrial Electronics, 2016Co-Authors: Long Zhang, Z Q Lang, Mayorkinos PapaeliasAbstract:Frequency methods such as frequency spectrum analysis, frequency spike detection, demodulation, envelope spectrum method have been widely used for condition monitoring of engineering structural systems. Different from the conventional frequency methods, the Transmissibility function (TF) represents the relationship between different system output responses such as, e.g., vibration and acoustic emission sensor measurements. This paper introduces a simple and effective generalized Transmissibility damage indicator (GTDI) for TF-based condition monitoring. Unlike the conventional Transmissibility damage indicator, the new GTDI can improve the detection sensitivity, reduces noise effects and avoid dynamic loadings effects. This is achieved by combining multiple groups of data to obtain more accurate Transmissibility analysis, exploiting all the available TFs, and using multiple references. This has two advantages. First, it does not require any other priori knowledge about the system responses. Therefore, the method can be used for the condition monitoring of a wide range of components or systems. Furthermore, the method can be easily implemented using fast Fourier transform or power spectra density methods and therefore is computationally efficient. These make the method very suitable for implementing online real-time condition monitoring. The method is investigated by simulation studies and then applied to analyze the vibration data of the main bearing of operating wind turbines, producing very promising results.
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a new Transmissibility analysis method for detection and location of damage via nonlinear features in mdof structural systems
IEEE-ASME Transactions on Mechatronics, 2015Co-Authors: Xueyan Y Zhao, Z Q Lang, Gyuhae Park, Charles R Farrar, Michael D Todd, Zhu Mao, K WordenAbstract:In this paper, a new Transmissibility analysis method is proposed for the detection and location of damage via nonlinear features in multidegree-of-freedom (MDOF) structural systems. The method is derived based on the Transmissibility of nonlinear output frequency response functions (NOFRFs), a concept recently proposed to extend the traditional Transmissibility concept to the nonlinear case. The implementation of the method is only based on measured system output responses and by evaluating and analyzing the Transmissibility of these system responses at super-harmonics. This overcomes the problems with available techniques, which assume there is one damaged component with nonlinear features in the system and/or require loading on inspected structural systems is measurable. Both numerical simulation studies and experimental data analysis have been conducted to verify the effectiveness and demonstrate the potential practical applications of the new method.
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study of the effects of cubic nonlinear damping on vibration isolations using harmonic balance method
International Journal of Non-linear Mechanics, 2012Co-Authors: Zhike Peng, Z Q Lang, Guang Meng, Wenming ZhangAbstract:Abstract In the present study, Harmonic Balance Method (HBM) is applied to investigate the performance of passive vibration isolators with cubic nonlinear damping. The results reveal that introducing either cubic nonlinear damping or linear damping could significantly reduce both the displacement Transmissibility and the force Transmissibility of the isolators over the resonance region. However, at the non-resonance region where frequency is lower than the resonant frequency, both the linear damping and the cubic nonlinear damping have almost no effect on the isolators. At the non-resonance region with higher frequency, increasing the linear damping has almost no effects on the displacement Transmissibility but could raise the force Transmissibility. In addition, the influence of the cubic nonlinear damping on the isolators is dependent on the type of the disturbing force. If the strength of the disturbing force is constant and independent of the excitation frequency, then the effect of cubic nonlinear damping on both the force and displacement Transmissibility would be negligible. But, when the strength of the disturbing force is dependent of the excitation frequency, increasing the cubic nonlinear damping could slightly reduce the relative displacement Transmissibility and increase the absolute displacement Transmissibility but could significantly increase the force Transmissibility. These conclusions are of significant importance in the analysis and design of nonlinear passive vibration isolators.
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reducing force Transmissibility in multiple degrees of freedom structures through anti symmetric nonlinear viscous damping
Acta Mechanica Sinica, 2012Co-Authors: Zhike Peng, Z Q Lang, Guang Meng, Stephen A BillingsAbstract:In the present study, the Volterra series theory is adopted to theoretically investigate the force Transmissibility of multiple degrees of freedom (MDOF) structures, in which an isolator with nonlinear anti-symmetric viscous damping is assembled. The results reveal that the anti-symmetric nonlinear viscous damping can significantly reduce the force Transmissibility over all resonance regions for MDOF structures with little effect on the Transmissibility over non-resonant and isolation regions. The results indicate that the vibration isolators with an anti-symmetric damping characteristic have great potential to solve the dilemma occurring in the design of linear viscously damped vibration isolators where an increase of the damping level reduces the force Transmissibility over resonant frequencies but increases the Transmissibility over non-resonant frequency regions. This work is an extension of a previous study in which MDOF structures installed on the mount through an isolator with cubic nonlinear damping are considered. The theoretical analysis results are also verified by simulation studies.
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the force Transmissibility of mdof structures with a non linear viscous damping device
International Journal of Non-linear Mechanics, 2011Co-Authors: Stephen A Billings, Z Q Lang, Zhike Peng, L Zhao, Geoffrey R TomlinsonAbstract:Abstract In the present study, the concept of the Output Frequency Response Function (OFRF), recently proposed by the authors, is applied to theoretically investigate the force Transmissibility of MDOF structures with a cubic non-linear viscous damping device. The results analytically show that the introduction of cubic non-linear damping can significantly reduce the Transmissibility over all resonance regions for a Multiple Degree of Freedom (MDOF) structure and at the same time leave the Transmissibility over the isolation region virtually unaffected. The analysis also indicates that a strong linear damping may shift the system resonances and compromise the beneficial effects of cubic non-linear viscous damping on the force Transmissibility of MDOF structures. This suggests that a less significant linear damping together with a strong cubic non-linear damping can be used in MDOF structures to achieve a desired vibration isolation performance. This research work has a significant implication for the design of viscously damped MDOF structures for a wide range of practical applications.
D. J. F. Brown - One of the best experts on this subject based on the ideXlab platform.
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RNA-2 of tobacco rattle virus encodes the determinants of Transmissibility by trichodorid vector nematodes
2015Co-Authors: A. T. P Loeg, T D. J. Robinson, D. J. F. BrownAbstract:Pseudorecombinant isolates produced from an efficiently transmitted and a non-transmitted isolate of tobacco rattle tobravirus were tested for their trans-missibility by trichodorid vector nematodes. Isolates with RNA-2 originating from the non-transmissible isolate were not transmitted by the vector, whereas isolates with RNA-2 originating from the efficiently transmitted isolate were transmitted efficiently. It is therefore concluded that the factor determining vector Transmissibility is located on the RNA-2 genome segment of TRV. Because the serological properties of the isolates also correlate with ransmissibility, it is likely that the virus particle protein is involved in the transmission process. Tobacco rattle virus (TRV) is the type member of th
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rna 2 of tobacco rattle virus encodes the determinants of Transmissibility by trichodorid vector nematodes
Journal of General Virology, 1993Co-Authors: Antoon T. Ploeg, D. J. Robinson, D. J. F. BrownAbstract:Pseudorecombinant isolates produced from an efficiently transmitted and a non-transmitted isolate of tobacco rattle tobravirus were tested for their Transmissibility by trichodorid vector nematodes. Isolates with RNA-2 originating from the non-transmissible isolate were not transmitted by the vector, whereas isolates with RNA-2 originating from the efficiently transmitted isolate were transmitted efficiently. It is therefore concluded that the factor determining vector Transmissibility is located on the RNA-2 genome segment of TRV. Because the serological properties of the isolates also correlate with Transmissibility, it is likely that the virus particle protein is involved in the transmission process.
Jean Gaudart - One of the best experts on this subject based on the ideXlab platform.
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Cold and dry winter conditions are associated with greater SARS-CoV-2 transmission at regional level in western countries during the first epidemic wave
Scientific Reports, 2021Co-Authors: Jordi Landier, Eva Legendre, Laurent Lehot, Juliette Paireau, Simon Cauchemez, Stanislas Rebaudet, Arnaud Fontanet, Jean GaudartAbstract:Higher Transmissibility of SARS-CoV-2 in cold and dry weather conditions has been hypothesized since the onset of the COVID-19 pandemic but the level of epidemiological evidence remains low. During the first wave of the pandemic, Spain, Italy, France, Portugal, Canada and USA presented an early spread, a heavy COVID-19 burden, and low initial public health response until lockdowns. In a context when testing was limited, we calculated the basic reproduction number (R 0) in 63 regions from the growth in regional death counts. After adjusting for population density, early spread of the epidemic, and age structure, temperature and humidity were negatively associated with SARS-CoV-2 Transmissibility. A reduction of mean absolute humidity by 1 g/m 3 was associated with a 0.15-unit increase of R 0. Below 10 °C, a temperature reduction of 1 °C was associated with a 0.16-unit increase of R 0. Our results confirm a dependency of SARS-CoV-2 Transmissibility to weather conditions in the absence of control measures during the first wave. The transition from summer to winter, corresponding to drop in temperature associated with an overall decrease in absolute humidity, likely contributed to the intensification of the second wave in northwest hemisphere countries. Non-pharmaceutical interventions must be adjusted to account for increased Transmissibility in winter conditions.
Simon Cauchemez - One of the best experts on this subject based on the ideXlab platform.
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Cold and dry winter conditions are associated with greater SARS-CoV-2 transmission at regional level in western countries during the first epidemic wave
Scientific Reports, 2021Co-Authors: Jordi Landier, Eva Legendre, Laurent Lehot, Juliette Paireau, Simon Cauchemez, Stanislas Rebaudet, Arnaud Fontanet, Jean GaudartAbstract:Higher Transmissibility of SARS-CoV-2 in cold and dry weather conditions has been hypothesized since the onset of the COVID-19 pandemic but the level of epidemiological evidence remains low. During the first wave of the pandemic, Spain, Italy, France, Portugal, Canada and USA presented an early spread, a heavy COVID-19 burden, and low initial public health response until lockdowns. In a context when testing was limited, we calculated the basic reproduction number (R 0) in 63 regions from the growth in regional death counts. After adjusting for population density, early spread of the epidemic, and age structure, temperature and humidity were negatively associated with SARS-CoV-2 Transmissibility. A reduction of mean absolute humidity by 1 g/m 3 was associated with a 0.15-unit increase of R 0. Below 10 °C, a temperature reduction of 1 °C was associated with a 0.16-unit increase of R 0. Our results confirm a dependency of SARS-CoV-2 Transmissibility to weather conditions in the absence of control measures during the first wave. The transition from summer to winter, corresponding to drop in temperature associated with an overall decrease in absolute humidity, likely contributed to the intensification of the second wave in northwest hemisphere countries. Non-pharmaceutical interventions must be adjusted to account for increased Transmissibility in winter conditions.
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ambient ozone and influenza Transmissibility in hong kong
European Respiratory Journal, 2018Co-Authors: Sheikh Taslim Ali, Benjamin J Cowling, Vicky J Fang, Simon Cauchemez, Linwei TianAbstract:The authors found that higher levels of ambient ozone were associated with reduced influenza Transmissibility
