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Geometrically nonlinear analysis of Timoshenko piezoelectric nanobeams with flexoelectricity effect based on Eringen's differential model
摘要： This study analyzes the nonlinear free vibration and post-buckling of nanobeams with flexoelectric effect based on Eringen’s differential model. The nanobeam is modeled based on Timoshenko beam's theory. The von-Kármán strain-displacement relation together with the electrical Gibbs free energy and Hamilton's principle are employed to derive equations of motion. The nonlinear free vibration frequencies are obtained for pinned-pinned (P-P) and clamped-clamped(C-C) boundary conditions. Multiple scales method is employed to obtain the closed-form solution for the nonlinear governing equations. By employing this methodology, the natural frequencies of nanobeams are obtained and their post-buckling behavior is examined. The influence of nonlocal parameter, amplitude ratio, and input voltage on the top surface and flexoelectricity constant on nonlinear free vibration and post-buckling characteristics of nanobeamis investigated. In this paper, it is concluded that the flexoelectricity has a significant effect on free vibration of the beams in nano scale and its effect has to be considered in designing nano-electro-mechanical systems (NEMS) such as nano- generators and nano-sensors.
关键词： Nonlinear vibration,Flexoelectricity,Nonlocal elasticity,Postbuckling
更新于2025-09-23 15:22:29
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Subsea Cable Condition Monitoring with Distributed Optical Fibre Vibration Sensor
摘要： A novel subsea cable condition monitoring technique based on embedded optical fibre inside the cable is demonstrated. It is shown that a distributed optical fibre vibration sensor can be used to map dynamic strains all along the cable simultaneously. It is experimentally shown that such system can fully quantify the location and strain level at each point on the cable as a function of time for both abrupt impact and cyclical loading. The sensing system demonstrated a spatial and strain resolution of 1m and 4με, respectively, over a 10km sensing range.
关键词： Offshore wind farm,Cable fault monitoring,Subsea cable monitoring,Distributed Vibration Sensor (DVS),Submarine cable installation,Distributed Acoustic Sensor (DAS)
更新于2025-09-23 15:22:29
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[IEEE 2018 41st International Conference on Telecommunications and Signal Processing (TSP) - Athens, Greece (2018.7.4-2018.7.6)] 2018 41st International Conference on Telecommunications and Signal Processing (TSP) - Experimental Verification of the Optimum Diagonal Loading Level for Adaptive Matched Filtering with ?-OTDR System
摘要： Recently, a temporal adaptive matched filtering technique has been proposed to reduce the background noise in phase-sensitive optical time domain reflectometry (φ-OTDR) systems deployed for fibre optic distributed acoustic sensing (DAS) applications. This technique utilizes noise covariance matrix inversion which is estimated from signal-free assumed training samples. The detection performance degradation due to desired signal presence in the training data and the ill-conditioning of the matrix because of the limited training data are conventionally avoided by adding some amount of white noise on the diagonal elements of the covariance matrix. In this paper, the optimum level for this diagonal loading (DL) is investigated for DAS applications and verified with real φ-OTDR data. The optimum DL level which has been analytically proven in beamforming applications is shown to be applicable in the temporal domain noise filtering for DAS applications. The experimental results validate that the optimum DL value is negative.
关键词： diagonal loading,phase-sensitive optical time domain reflectometry (OTDR),distributed vibration sensors,optimum filtering.,Adaptive matched filter
更新于2025-09-23 15:22:29
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[ASME ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference - Boston, Massachusetts, USA (Sunday 2 August 2015)] Volume 8: 27th Conference on Mechanical Vibration and Noise - Nonlinear Free Vibration of Piezoelectric Functionally Graded Beams in Thermal Environment
摘要： Nonlinear free vibration analysis of piezoelectric functionally graded (PFG) beams in thermal environment with any boundary conditions are investigated. The nonlinear governing Equation of motion is derived based on the Euler-Bernoulli beam theory and Von Karman's strain-displacement relation. Simple analytical expression is presented for the nonlinear natural frequency using energy balanced method (EBM). Results are validated and compared with available results in the literature. Effects of different parameters such as vibration amplitude, boundary conditions, material inhomogenity, electrical and thermal loading on the nonlinear behavior of PFG beams are presented.
关键词： Boundary conditions,Energy balanced method,Piezoelectric functionally graded beams,Nonlinear free vibration,Thermal environment
更新于2025-09-23 15:22:29
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The Transitional Transmittance Response of ZIF-8 Gas Adsorption Observed Using Terahertz Waves
摘要： In this study, we recorded the transitional response in terms of terahertz transmittance of zeolitic imidazole framework-8 [Zn(2-methylimidazolate)2, ZIF-8] at 2.0 THz as a function of exposure time to gaseous propane and n-butane. The transmittance at 2.0 THz increased as gas adsorbed onto the ZIF-8. Conversely, during a nitrogen purge, transmittance decreased as the alkane gas desorbed. We estimated time constants for the adsorption and desorption of the two gases by comparing the plots of their responses. We also demonstrated the potential of using a combination of ZIF materials and terahertz technology as a novel gas analyzer.
关键词： Adsorption kinetics,Terahertz vibration,Metal-organic frameworks,Porous solids,Infrared absorption spectroscopy
更新于2025-09-23 15:22:29
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Vibration sensing based on macrobending loss in a standard single mode fiber loop structure
摘要： A new optical fiber sensor for vibration measurement has been proposed and demonstrated. This paper realizes vibration sensing based on the macrobending loss in a standard single-mode fiber loop. The experiments shows the suggested sensor enable us to measure multi-frequency vibrations with the resolution as high as 0.04 Hz. The crosstalk between temperature and vibration can be ignored because the macrobending loss is insensitive to the ambient temperature.
关键词： Bend loss,Vibration sensor,Fiber optic sensor
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - High-Speed Railway Bridge Vibration Measurement and Analysis Based on Radar Interferometry
摘要： A newly designed radar based on interferometry is proposed and well designed in the paper. The designed radar can detect the vibration of the railway bridge with a super-resolution and a high precision, which also has remote sensing ability. The general bridge monitoring methods are expensive and time-consuming since it is difficult to install sensors that should be directly contact with the bridge, such as accelerometer and dynamometer. Based on the designed radar, experiments are constructed on a Beijing-Tianjin Inter-City high-speed railway bridge to prove that the radar interferometry can be used to preciously and accurately monitor the railway bridge’s vibration.
关键词： Vibration,Railway bridge,Interferometry
更新于2025-09-23 15:21:21
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Stereo Applications Need a Dedicated Lens Choosing
摘要： Stereo cameras perceive the world in a manner similar to humans; this similarity allows machines using stereo technology to perform and interact like human partners. Robots equipped with a stereo camera can grasp objects autonomously, without the need for additional sensors or lights. Autonomous cars can have the ability to detect a human crossing the street and accurately determine their distance from the moving car, and their walking speed. The selection of the correct lens for a stereo application is much more important than for a setup with a single camera. The position and perspective of each camera with respect to the other determines the system’s accuracy. Environmental parameters require consideration, in addition to temperature, shock, and vibration.
关键词： lens selection,Stereo cameras,shock,temperature,stability,vibration,system environment
更新于2025-09-23 15:21:21
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A comparative study of laser metal deposited and forged Ti-6Al-4V alloy: Uniaxial mechanical response and vibration fatigue properties
摘要： This paper conducts a comparative study on mechanical properties of LMD and forged Ti-6Al-4V, focusing on uniaxial compression, tension and shear response with different strain rates, and vibration fatigue behaviors with 45–50 Hz in frequency. The micro-observation on initial microstructures and fractures explains the mechanism of lower uniaxial strength, shorter fatigue life, and larger dispersion in fatigue life and fracture position of LMD sample compared with the forged counterpart. Initial void defects within LMD sample tend to be stress-concentration zone, further initiating fatigue cracks. The columnar β grains leads to anisotropy of fatigue life and crack propagation for LMD sample.
关键词： Fracture analysis,Laser metal deposition,Vibration fatigue,Initial defect,Ti-6Al-4V
更新于2025-09-23 15:21:01
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Gradient microstructure and vibration fatigue properties of 2024-T351 aluminium alloy treated by laser shock peening
摘要： To investigate the improvement in vibration fatigue and the strengthening mechanism of laser shock peening, a nanosecond laser was used to strengthen the 2024-T351 aluminium alloy. Accordingly, the microstructure, residual stress, nanohardness and surface roughness of the treated alloy were measured. Subsequently, the vibration fatigue damage and fatigue life were evaluated, and the vibration fracture morphology was observed. The results showed that the grains in the peened surface were re?ned. A residual stress of ?141 MPa and a nanohardness of 3.1 GPa were obtained by laser shock peening. Based on the relationship between the peened microstructure and fracture morphology, it was deduced that an increase in the grain boundaries led to a lower crack initiation rate and a higher crack initiation life. The compressive residual stress decreased the crack growth rate and increased the crack growth life. Therefore, laser shock peening increases the total vibration fatigue life by about 63.5%.
关键词： Laser shock peening,Vibration fatigue,2024-T351 aluminium,Compressive residual stress,Microstructure
更新于2025-09-23 15:21:01