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Deep learning has been widely applied to intelligent fault diagnosis of rotating machines. In particular, convolutional neural network (CNN) improves the accuracy of diagnosis due to automatic feature extraction ability. However, CNN cannot make full use of the temporal information of the input signals. In order to overcome the above weaknesses, a new depth diagnositic framework called two stream convolution neural network with temporal information(TITSCNN) is proposed for bearing fault diagnosis. First, we obtain tempory signal through the difference of data points in the input signal. Next, tempory signal and original signal are used as input of two CNN branches respectively. Then, an attention mechanism is used to aggregate the features and assign weights to the features extrated by CNN adaptively. Finally, the learned high-level representations are fed into full connect layer to perform fault diagnosis. Experiments are conducted and the results showed that TITSCNN has higher accuracy compared to state-of-the-art methods. Further, experimental results demonstrated that TITSCNN has excellent noise immunity and transformation performance.

In order to reduce the flow resistance on the surface of ships, the skin with quasi-periodic elastic supports is designed based on the flexible skin drag reduction technology inspired by dolphin skin. In this paper, the stability characteristic equation of fluid-structure coupling system is established based on small perturbation theory and solved by MATLAB. The results indicate that the skin with quasi-periodic elastic supports has the ability of maintaining stability of turbulent boundary layer when the structural parameters are reasonable. In addition, the drag reduction performance of the skin with quasi-periodic elastic supports is studied by immersion boundary method. The analysis results demonstrate that the skin with quasi-periodic elastic supports can show better drag reduction performance than the skin with periodic elastic supports when the structural parameters q and the support spacing L are rationally set. In a certain speed range, the relative drag reduction rate is up to 72.16%. These optimal distribution parameter data of the skin under certain speed conditions obtained in this paper provide a reference for the practical application and intelligent optimization design of the skin with quasi-periodic elastic supports.

To improve the drag reduction performance of underwater vehicles, a skin composed of micro floating raft arrays and a bionic compliant wall is proposed. The micro floating raft is a miniaturization...

Inspired by the traditional floating raft vibration suppression system, in order to solve the problem of random vibration of the plate, through miniaturizing the floating raft system and using the microfloating raft arrays to replace the distributed dynamic vibration absorbers, a plate with microfloating raft arrays is constructed in this paper. The vibration response equation of the structure under multi-point random excitation is established by using modal superposition method. The auto-power spectral density (APSD) of displacement is obtained by using MATLAB, and the influence of system parameters on the vibration response is analyzed. Optimal combination of parameters is obtained by the generalized pattern search algorithm. Vibration reduction effect of this structure is analyzed. The results show that redistribution of microfloating raft element interval and an increase in the thickness, flexural rigidity and damping of the plate could increase the vibration suppression effect. It is also shown that an increase in mass ratio and stiffness ratio of the microfloating raft element could significantly reduce the vibration of the plate. When it achieves the optimal vibration suppression effect, the mass ratio, the stiffness ratio and the damping ratio are 0.3, 8.8562 and 4.7660, respectively. Compared with other plate structures, the plate with microfloating raft arrays of optimal parameter has the minimum APSD of displacement and minimum energy.

As an intelligent material, magnetorheological fluid (MRF) is used in various applications, such as vibration dampers and automotive engine mounts. In order to study the influence of MRF composition parameters on vibration transfer characteristics, this paper proposes an MRF vibration transmission equivalent model based on the analysis of the interaction between carbonyl iron particles and carrier liquid, calculates the vibration transfer power flow level difference (PLD) of MRF with different composition parameters, and performs experimental verification. The results show that when only the particle diameter changes, the PLD peak increases with increasing particle diameter, and the PLD peak frequency shifts to lower frequencies. When the particle volume fraction gradually increases, and the remaining parameters are kept constant, the PLD peak increases first and then decreases, and the peak frequency shifts to high frequencies. When changing only the carrier liquid viscosity, the PLD peak decreases as the viscosity increases, while the peak frequency is shifted toward the high frequency. The MRF has a maximum frequency shift of 61.6 Hz when the particle diameter, particle volume fraction, and carrier liquid viscosity are 8 μm, 20% and 0.3 Pa·s, respectively. It is shown that adjusting the composition parameters can change the PLD and vibration suppression band of MRF, and using this feature can help improve the broadband vibration suppression performance of MR devices and the vibration suppression efficiency under specific working conditions, further expanding the application of MRF in the field of vibration control.

There is proposed a tunable acoustic metamaterials cell composed of a micro-electromagnetic coil as the mass element and a magnetorheological elastomer (MRE) as cladding layer. The cell resonance frequency is changed by changing the magnetic field generated by the micro-electromagnetic coil to control the shear modulus of the MRE cladding layer. The tunable bandgaps, transmission loss, and waveguides of the tunable acoustic metamaterials are investigated using the finite element method. The results show that the bandgap frequency and width, the maximum attenuation frequency and transmission loss increase with the increasing of applied magnetic field strength. Meanwhile, without changing the structure of the acoustic metamaterials, the localization, guidance, demultiplex and multiplex of elastic waves can be realized by changing the cell resonance frequency. These results will greatly contribute to the application of tunable acoustic metamaterials in vibration control, new waveguides, and filter components.

This work aims to investigate the elastic wave propagation in the periodic impedance layered structure filled with magnetorheological fluid. The periodic impedance layered structure with high and low impedance layers is constructed by using the magnetorheological fluid with the controllability of liquid–solid conversion. The principle of the periodic impedance layered structure is presented. The transfer model of elastic wave in the proposed structure is established, and the propagation velocity and attenuation coefficient of elastic wave curves of the periodic impedance layered structures with different distribution modes are obtained. The prototype of experimental setup is designed and fabricated, and the experimental testing of the vibration transmissibility is conducted. The theoretical model is validated by comparing the results with the experimental measurements. The results suggest that appropriate distribution modes and also applied magnetic field are validly showing greater attenuation for elastic wave propagation in the periodic layered structures. Theoretical and experimental studies are conducted to investigate on the vibration transmissibility of the proposed structure, the findings of which contribute to provide guidance for the future vibration isolation platforms of the power systems in aerospace and marine engineering practical applications.

The porous foam metal magnetorheological fluid damper has a broad application prospect in the field of vibration isolation of precision instruments with small damping force because it does not need complex dynamic seal structure. The traditional single-ring magnetic pole porous foam metal magnetorheological fluid damper has a small effective area for the magnetic core that affects the damper output range due to the geometric constraints of the coil and the low magnetic field utilization. Therefore, in order to increase the effective area ratio of the magnetic core, this article introduces the built-in multi-pole magnetic core into the porous metal magnetorheological fluid damper and integrates four axial wound fan-shaped magnetic poles on the magnetic core to improve the output performance of the damper. The magnetic circuit is analyzed based on Ohm’s law of magnetic circuit, and the mathematical model of damping force is established. Based on this, the important geometric parameters of the damper are determined. The finite element method is used to simulate the magnetic field of the damper, and the output performance of the damper is numerically simulated. The dynamic performance test system of the damper is set up to test the designed damper, and the test data and numerical simulation results are verified with each other. The results show that the damping force peak and dynamic regulation range of the damper designed in this article are higher than those of the traditional porous foam metal magnetorheological fluid damper with magnetic core, which effectively improves the mechanical properties of the magnetorheological fluid damper with porous foam metal.

A sensitive electrochemiluminescence (ECL) aptasensor based on 3D graphene is described for thrombin detection utilizing nitrogen-doped graphene quantum dots doped silica (NGQDs@SiO2) nanocomposite labeling as an enhancer. Ru(bpy)32+-Pt nanoparticles (Ru-PtNPs) with an ECL signal were dropped onto a 3D graphene-modified electrode, and then, a complementary thrombin aptamer (cDNA) was conjugated to the Ru-PtNPs. Finally, NGQDs@SiO2, coupled with the thrombin aptamer as the booster, was attached to the electrode surface by using hybridization with the cDNA, and the ECL intensity was efficiently enhanced. The target thrombin induced the NGQDs@SiO2 nanocomposites labeled with the thrombin (TB) aptamer to be extracted because of their strong binding with thrombin. The immobilization amount of NGQDs@SiO2 on the modified electrode decreased. Thus, the presence of thrombin could result in a decrease in the ECL signal. On the basis of the signal amplification factors, the fabricated ECL aptasensor demonstrated excellent properties with concentrations varying from 2.0 pM to 50 nM and a detection limit of 23.1 fM.

In this work, a magnetic coupling 2-degree-of-freedom bistable piezoelectric energy harvester was designed and developed. The device consisted of a primary beam with a magnet attached to the tip and a parasitic beam. The magnets between the primary beam and the pedestal generated nonlinear repulsive force. By controlling the distance between two magnets, the system could oscillate between two stable equilibrium points which allowed the device to exhibit broadband characteristics. Theoretical and experimental investigations of this energy harvester were presented over a range of excitation frequencies. Lumped-parameter nonlinear equations of the bistable Duffing oscillator with magnetic coupling were introduced to describe the broadband voltage response. Compared with the theoretical results, at an excitation acceleration of 3 m/s2, it is experimentally verified that the proposed device achieved the operation frequency bandwidth adding up to 8 Hz at around the first and second resonance regions which was about 2.7 times higher than conventional 2-degree-of-freedom linear harvester one. In addition, energy harvesting efficiency could be improved by increasing the frequency bandwidth. The results of this work can be applied to optimize the design of piezoelectric energy harvester and harvest low-frequency vibration energy in the environment to supply power for sensor network nodes.

Dissolved cobalt ions (Co2+) are an excellent catalyst for activating peroxymonosulfate (PMS) to generate SO4- for the degradation of organic pollutants, but fairly high level of Co2+ is generally required, which may cause secondary pollution due to its toxicity. Herein, we demonstrate a novel strategy for this catalytic oxidation treatment in which the required Co2+ addition is very small, being much less than the emission limit of 17 μmol L-1. This new strategy is based on the much enhanced catalytic effect by the addition of small organic acids (SOAs). In a typical case, all the added diclofenac (30 μmol L-1) was degraded in 20 min by using 2 μmol L-1 Co2+, 0.15 mmol L-1 PMS and 0.5 mmol L-1 acetate with a degradation rate constant of 0.482 min-1, which was about 10 times higher than that (0.048 min-1) of equivalent Co2+-PMS system without acetate. The formation of SO4- was greatly enhanced by introducing acetate, and this novel system is universal for enhanced degradation of various organic pollutants. Similarly, formate, propionate, and butyrate also exhibited enhancing effects on the catalytic ability of Co2+. The enhancement mechanism of SOAs on catalytic activation of PMS by low-level Co2+ was also proposed.

The design of vigorous tools for creatinine determination is extremely important in the diagnosis and treatment of kidney diseases. In the study, we examine a robust fluorescent turn-on probe (NCP-Pd) for creatinine detection in a completely aqueous solution based on the metal palladium-catalyzed reaction. In the presence of creatinine, the NCP-Pd dissociates and subsequently restores the fluorescence due to elimination of the heavy atom quenching effect and prevention of the photoinduced electron transfer effect. The probe NCP-Pd displays excellent detecting performance with respect to creatinine such as good water solubility, high selectivity, and a low detection limit (0.16 μM). Additionally, in order to ensure its clinical application, this probe is operated in blood serum samples for detecting creatinine and compared with a commercial clinical method. The results indicate an extremely high agreement with the commercial clinical method. Furthermore, the results confirm that the probe NCP-Pd exhibits satisfactory cell permeability and low cytotoxicity and can detect creatinine in L929 and HCT116 cells. The study provides a potential application for detecting creatinine and conducting pathological research on creatinine-involved diseases.

This study describes the adsorption performance of a novel ethylenediamine rosin-based resin (EDAR) for several industrially-important phenolic compounds. Its removal of 4-nitrophenol (4-NP) from water was comparable to or better than many commercial resins, although it was less effective with other phenols (i. e., phenol, 2,4-dichlorophenol, 4-chlorophenol, and 4-methylphenol). Experimental conditions for batch adsorption of 4-NP by EDAR are evaluated, the adsorption kinetics is well described by the pseudo-second-order model (R2 > 0.99) and isotherm follows the Langmuir isotherm model (R2 > 0.99), with the maximum monolayer adsorption capacity of 82 mg g−1 at pH 6.0 and 293 K. The thermodynamic parameters indicate that the adsorption is spontaneous and endothermic. Also, quantum chemistry calculations indicate involvement of hydrogen-bonding between 4-NP and amino groups of EDAR. 4-NP was efficiently desorbed from the loaded EDAR resin by 0.2 M HCl, and the resin could be recycled with only a small decrease in its initial adsorption capacities. Thus, EDAR is a promising adsorbent for the removal of 4-NP during water treatment.

Resins derived from natural rosin have been described recently as environmentally-friendly adsorbents with potential uses in the clean-up of wastewaters and the treatment of drinking waters. However, in order to improve the design of these products it is important to understand the chemical mechanisms through which they act. We now describe the combined use of EPR spectroscopy and Cu(II) to probe directly the metal coordination environment after uptake by various rosin-derived products. Clear distinctions are demonstrated between the copper bonding in different adsorbent preparations. Furthermore, in the case of nitrogen cross-linked products, the spectral parameters also provide information on the number of nitrogen atoms in the immediate atomic environment of the copper atom when covalent bonding is involved. This methodology works well for adsorption from solutions containing multiple components, because only those that are paramagnetic are detected, and different types of paramagnetic metal ion produce distinctly different EPR spectra.

This paper presents an adaptive constraint control approach for Electronic Throttle Control System (ETCS) with asymmetric throttle angle constraints. The adaptive constraint control method, which is based on barrier Lyapunov function (BLF), is designed not only to track the desired throttle angle but also to guarantee no violation on the throttle angle constraints. An ETC mathematic model with complex non-linear system is considered and the asymmetric barrier Lyapunov function (ABLF) is introduced into the design of the controller. Based on Lyapunov stability theory, it can be concluded that the proposed controller can guarantee the stability of the whole system and uniformly converge the state error to track the desired throttle angle. The results of simulations show that the proposed controller can ensure that there is no violation on the throttle angle constraints.

As the fatigue life prediction of wire rope has the defects of large samples and many interference factors, this paper takes the 6×31WS+FC type wire rope as research carrier. Based on small samples, the grey particle filter method has been creatively proposed to realize the wire rope fatigue life prediction under various load conditions. First, combining the reliability life data prediction with the equivalent alternating stress of the dangerous part during the fatigue test, the reliability stress-life curve was determined. Subsequently, the particle filter method has been used to modify the curve to obtain the modified P-S-N curve. Finally, with theory of fatigue damage accumulation, the fatigue life prediction model was established, and compared with the test results. The results show that based on small sample conditions, the proposed method can predict the fatigue life of wire ropes under various loading conditions with high precision, which proves the general applicability.

Additional file 1.

This paper presents a single-shot, 360-degree, and high-precision three-dimensional shape measurement for human heads based on digital image correlation and plane mirrors, which improves the matching speed of DIC by introducing multiple threads.

Background: The outbreak of the novel coronavirus disease COVID-19 caused panic and psychological stress throughout the World. We investigated the extent of adverse psychological reactions in two medical staff groups in China, and explored the importance of online psychological assistance for them.Methods: A cross-sectional online survey including Hospital Anxiety and Depression Scale (HADS) and Insomnia Severity Index (ISI) was utilized to assess anxiety, depression, and insomnia. Propensity score matching (PSM) was applied to match sex and age between the two groups. Differences in the prevalence of adverse psychological reactions between the two groups were compared by a Chi-square test. A multivariate logistic regression analysis was utilized to search for associated adverse psychological reaction factors of two groups.Results: A total of 2,920 medical staff took part in the survey, including 470 frontline and 2,450 non-frontline medical staff. The risk of the frontline group experiencing anxiety, depression, insomnia-early, insomnia-middle, and insomnia-late were 1.16, 1.28, 1.26, 1.22, 1.28 times those of the non-frontline group after PSM. For frontline medical staff, the spinsterhood state (OR = 1.23, 95% CI: 1.00–1.51; P = 0.05) was a risk factor for anxiety. Bachelor or college degree (OR = 2.23, 95% CI: 1.24–4.02, P = 0.01) and a contact history with COVID-19 patients (OR = 1.62, 95% CI: 1.10–2.40; P = 0.02) were risk factors for insomnia. For non-frontline medical staff, being a woman (OR = 1.49, 95% CI: 1.08–2.06, P = 0.01) was a risk factor for anxiety, whilst being in a middle age group was a protective factor for anxiety (OR = 0.70, 95% CI: 0.50–0.99, P = 0.04) and depression (OR = 0.65, 95% CI: 0.45–0.93, P = 0.02). Being a woman (OR = 1.47, 95% CI: 1.14–1.89, P = 0.003) and working in a COVID-19 unit (OR = 1.31, 95% CI: 1.11–1.54, P = 0.001) were risk factors for insomnia, whilst the spinsterhood state (OR = 0.80, 95% CI: 0.67–0.95; P = 0.01) was a protective factor for insomnia. Online forms of psychological aid were all popular with medical staff.Conclusions: The prevalence of anxiety, depression, and insomnia in frontline medical staff was significantly higher than in the non-frontline group. Appropriate intervention methods should be adopted according to the different influencing factors of the two groups. Online psychological aid was the preferred mechanism for relieving psychological problems.

Under the compression mode, the direction of force on the magnetorheological elastomer (MRE) is parallel to the direction of electromagnetic force, so the effect of electromagnetic force on its dynamic mechanical properties cannot be ignored. Therefore, this paper focuses on the effect of electromagnetic force on the dynamic mechanical properties of MRE under compression mode. A new type of testing device was designed and processed. Under a different loading frequency, strain amplitude and external magnetic field, dynamic mechanical properties of MRE were tested, respectively. The result shows that the stiffness and energy dissipation capacity of MRE increase with the current and loading frequency. The stiffness of MRE decreases with the increase in the strain amplitude, but the energy dissipation capacity increases. Comparing the force-displacement curve of MRE with or without the effect of the electromagnetic force, it shows that the electromagnetic force has a great effect on the stiffness of MRE and little effect on its energy dissipation capacity. When the electromagnetic force is removed, the stiffness of MRE decreases, and the change rate of stiffness increases with current. The maximum change rate of stiffness is 5.65%.