1,722 research outputs found

    Analysis of friction-induced vibration leading to brake squeal using a three degree-of-freedom model

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    Friction-induced vibration is a common phenomenon in nature and thus has attracted many researchers’ attention. Many of the mathematical models that have been proposed on the basis of mode coupling principle, however, cannot be utilized directly to analyse the generation of friction-induced vibration that occurs between two bodies because of a difficulty relating model parameters to definite physical meaning for real friction pairs. In this paper, a brake squeal experiment is firstly carried out by using a simple beam-on-disc laboratory apparatus. Experimental results show that brake squeal correlates with the bending mode of the beam and the nodal diameter out-ofplane mode of the disc as well as the cantilever length of the beam. Then, a specific three degree-of-freedom dynamic model is developed of the beam-on-disc system and the vibration behaviour is simulated by using the complex eigenvalue analysis method and a transient response analysis. Numerical simulation shows that the bending mode frequency of the beam a little greater than the frequency of the nodal diameter out-of-plane mode and a specific incline angle of the leading area to the normal line of the disc as well as a certain friction coefficient, are necessary conditions for the mode coupling of a frictional system. Results also show that when the frictional system is transited from a steady state to an unstable state for the variation of parameters, its kinetic and potential energy increase with time due to continuous feed-in energy from the friction force while the dynamic responses of the system change from the beating oscillation to the divergent, which leads to the friction-induced vibration and squeal noise

    A novel robust reversible watermarking scheme for protecting authenticity and integrity of medical images

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    It is of great importance in telemedicine to protect authenticity and integrity of medical images. They are mainly addressed by two technologies, which are region of interest (ROI) lossless watermarking and reversible watermarking. However, the former causes biases on diagnosis by distorting region of none interest (RONI) and introduces security risks by segmenting image spatially for watermark embedding. The latter fails to provide reliable recovery function for the tampered areas when protecting image integrity. To address these issues, a novel robust reversible watermarking scheme is proposed in this paper. In our scheme, a reversible watermarking method is designed based on recursive dither modulation (RDM) to avoid biases on diagnosis. In addition, RDM is combined with Slantlet transform and singular value decomposition to provide a reliable solution for protecting image authenticity. Moreover, ROI and RONI are divided for watermark generation to design an effective recovery function under limited embedding capacity. Finally, watermarks are embedded into whole medical images to avoid the risks caused by segmenting image spatially. Experimental results demonstrate that our proposed lossless scheme not only has remarkable imperceptibility and sufficient robustness, but also provides reliable authentication, tamper detection, localization and recovery functions, which outperforms existing schemes for protecting medical image

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    laser pulling of graphene nanosheets with wavelength of 488 nm and the irradiation direction is from right to lef

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    laser pulling of graphene nanosheets with wavelength of 650 nm and the irradiation direction is from left to righ

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    laser pulling of graphene nanosheets with wavelength of 488 nm and the irradiation direction is from left to righ

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    laser pulling of graphene nanosheets with wavelength of 405 nm and the irradiation direction is from left to righ

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    laser pulling of graphene nanosheets with wavelength of 532 nm and the irradiation direction is from left to righ

    Weighted associations between the dietary Cu intake and all-cause and cardiovascular mortality in the multivariable, and crude analyses.

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    Weighted associations between the dietary Cu intake and all-cause and cardiovascular mortality in the multivariable, and crude analyses.</p

    The weighted features of the subjects were stratified based on their dietary Cu intake quartiles.

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    The weighted features of the subjects were stratified based on their dietary Cu intake quartiles.</p

    Generalized additive models were employed to show the link between Cu consumption in the diet and cardiovascular-related mortality.

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    Generalized additive models were employed to show the link between Cu consumption in the diet and cardiovascular-related mortality.</p
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