A Magnetorheological Damper with Embedded Piezoelectric Force Sensor: Experiment and Modeling

This chapter describes configuration, fabrication, calibration and performance tests of the devised self-sensing MR damper firstly. Then, a black-box identification approach for modeling the forward and inverse dynamics of the self-sensing MR damper is presented, which is developed with the synthesis of NARX model and neural network within a Bayesian inference framework to have the ability of enhancing generalization.Department of Civil and Environmental Engineerin

Tunneling conductance in strained graphene-based superconductor: Effect of asymmetric Weyl-Dirac fermions

Based on the BTK theory, we investigate the tunneling conductance in a uniaxially strained graphene-based normal metal (NG)/ barrier (I)/superconductor (SG) junctions. In the present model, we assume that depositing the conventional superconductor on the top of the uniaxially strained graphene, normal graphene may turn to superconducting graphene with the Cooper pairs formed by the asymmetric Weyl-Dirac electrons, the massless fermions with direction-dependent velocity. The highly asymmetrical velocity, vy/vx>>1, may be created by strain in the zigzag direction near the transition point between gapless and gapped graphene. In the case of the highly asymmetrical velocity, we find that the Andreev reflection strongly depends on the direction and the current perpendicular to the direction of strain can flow in the junction as if there was no barrier. Also, the current parallel to the direction of strain anomalously oscillates as a function of the gate voltage with very high frequency. Our predicted result is found as quite different from the feature of the quasiparticle tunneling in the unstrained graphene-based NG/I/SG conventional junction. This is because of the presence of the direction-dependent-velocity quasiparticles in the highly strained graphene system.Comment: 18 pages, 7 Figures; Eq.13 and 14 are correcte

Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.</p

Modelling of a Self-sensing Magnetorheological Damper Using Bayesian Regularized NARX Neural Network

The magnetorheological (MR) damper has been demonstrated to be one of the most promising semiactive control devices to suppress structural vibration. Recently, a novel self-sensing MR damper has been fabricated by integrating an actuation-only MR damper with a piezoelectric force sensor. Possessing the sensing-while-damping function, the damper offers a cost-effective innovation for real-time semiactive structural vibration control. However, due to its intrinsic nonlinear characteristics, modelling of the damper to adequately describe its hysteresis dynamics has been one of the prerequisite and challenging tasks for fully exploring its capabilities in real-time control implementation. In this paper, forward and inverse dynamic models of the self-sensing MR damper are developed based on the combined NARX (nonlinear autoregressive model with exogenous inputs) and neural network techniques. Experiments are performed to collect training and validation data for the NARX neural networks. The Bayesian regularization is adopted in the training phase to prevent over-fitting. Validation results indicate that the trained NARX neural network models accurately represent the forward and inverse dynamics of the damper, exhibit good generalization capability, and are adequate for control design and analysis

A magnetorheological damper capable of force and displacement sensing

A magnetorheological (MR) damper with embedded force and displacement sensors is devised to facilitate closed-loop structural vibration control. A piezoelectric force sensor and a linear variable differential transformer (LVDT) have been integrated with a conventional MR damping device. The piezoelectric sensor is used to sense the damping force produced by the damper, while the LVDT is employed to measure the displacement of the vibrating structure at the damper location and the movement of the damper piston. Calibration of the piezoelectric force sensor is conducted through force-controlled tests with sinusoidal force excitations of different amplitudes and frequencies. The sensing and damping performances of the devised MR damper are evaluated under displacement-controlled excitations, with different current inputs being commanded to the damper. The experimental results demonstrate reliable displacement/force sensing and controllable damping capabilities of the devised damper. The sensing-while-damping function of the damper hence offers its potential for real-time feedback structural vibration control

The effects of thermal annealing on ZnO thin films grown by pulsed laser deposition

Journal of Applied Physics881498-502JAPI

Electronic transport and layer engineering in multilayer graphene structures

10.1063/1.2840713Applied Physics Letters925-APPL

Mid-infrared spectroscopy tracing of channel erosion in highly erosive catchments on the Chinese Loess Plateau

Whether channel erosion or topsoil erosion constitutes the dominant erosion process throughout in the hilly region of the Chinese Loess Plateau (CLP),which suffers perhaps themost severe soil erosion in theworld, had been controversial for a long time. The present article attempts to use the mid-infrared (MIR) spectroscopy fingerprinting method to trace sediment sources within nine small catchments in the hilly region of the CLP. Two major categories of sediment sources are identified: channel sediment and topsoil. Sediments trapped by check dams are used as the final sediment transferred by soil erosion. Discriminant analysis shows thatMIR spectroscopy can differentiate between the two kinds of source sediments very well. The contributions of channel sediment and topsoil to the total final sediment are quantified using partial least squares regression (PLSR) analyses of MIR spectra to compare the trapped sediment samples with experimental models. The results of the root mean square error of calibration, root mean square error of validation and coefficient of determination for 18 models all show that the MIR-PLSR models boast very high prediction abilities in the nine catchments. A comparison between the geochemical fingerprinting method and the MIR spectroscopy method in one catchment reveals that although the two methods agree well on the channel sediment contributions, the two methods produce a significant difference (R2=0.4). Overall, theMIR-PLSR results showthat channel sediments contribute 19% to 66% of the total sediment with an average of 33&plusmn; 16% in the nine small catchments. Our results indicate&nbsp;that although channel bank sediment is important, topsoil erosion is the predominant process in small damcontrolled catchments on the CLP. Furthermore, the MIR spectroscopy fingerprinting method can provide a useful, non-destructive, rapid and inexpensive tool for tracing sediment sources from different kinds of loess.</p

A Tailor-made MR Damper for Bridge Cable Vibration Control: Experiment and Modelling

Magnetorheological (MR) dampers have emerged as one of the most promising devices to suppress cable vibration in cable-stayed bridges, owing to their attractive features of minute power requirement, controllability, fail-safe operation, rapid response and low environmental sensitivity. While possessing controllable damping capability, the MR dampers are unable to monitor cable vibrations for implementing semi-active closed-loop controls, and are used merely as adjustable passive dampers in an open-loop mode in the current practices. Hence, a novel self-sensing MR damper system with an embedded PZT sensor has been tailor-made for real-time cable vibration control. Its laboratorial fabrication and characterization are to report