Mg alloys have become a new generation of biodegradable medical materials due to their good biocompatibility. However, their rapid corrosion rate in physiological environments and the mismatch between their degradation rate and tissue reconstruction pose challenges for clinical applications. To improve the corrosion resistance and biocompatibility of Mg alloys, drug-loaded corrosion resistant coating has gradually become a research hotspot. In this work, a uniform pH-responsive ZIF-14 coating was in situ synthesized on the surface of Mg alloy via a solvothermal method. Using rapamycin, an anti-restenosis drug, as a model compound, the drug release behavior and biocompatibility of the rapamycin-loaded ZIF-14 coating were evaluated under different pH conditions. ZIF-14 coating exhibited rapid drug release under both acidic and alkaline conditions. The rapamycin-loaded ZIF-14 coating effectively inhibited the excessive proliferation of smooth muscle cells, thereby preventing vascular restenosis after device implantation. Notably, theoretical calculations and experimental characterizations revealed that Zn2+ ions in ZIF-14 precursor solution can coordinate with both imidazole ligands and Mg from the substrate, leading to the formation of a stable ZIF precursor on Mg surface. In addition, ZIF-14 coating enhanced the corrosion resistance of Mg alloy, effectively prolonging its service life. This work provides a new strategy for the design of multifunctional smart coatings on Mg alloy surfaces and shows great potential for applications in biomedical Mg alloy implants. STATEMENT OF SIGNIFICANCE: This study presents a significant advancement in addressing the limitations of biodegradable Mg alloy stents by developing a uniform, and pH-responsive ZIF-14 coating via one-step in situ solvothermal synthesis. Integrating DFT calculations with experimental validation, this research elucidates the intricate coordination mechanism among Zn2+, imidazole ligands, and Mg, offering fundamental insights into MOFs growth on reactive metal surfaces. This coating exhibits dual-trigger pH-responsive drug release, accelerating drug release under both acidic (local inflammation) and alkaline (Mg corrosion) conditions, thus providing a smart solution for localized therapeutic intervention. Furthermore, this nanostructured coating enhances the corrosion resistance and biocompatibility of Mg alloy. This work proposes a strategy for designing multifunctional smart coatings on biodegradable implants, holding potential for biodegradable implants.

Intermittent tilting pouring is widely utilized in metal casting due to its operational simplicity and cost-effectiveness. However, this method faces challenges such as difficult manual tuning and inconsistency in achieving constant flow rates. Targeting pouring equipment at a high-purity metal smelting company, this study proposes a closed-surface flux calculation method based on the Gauss divergence theorem to determine molten metal volume at any given instant. A mathematical model for pouring processes involving ladles with non-cylindrical inner surfaces is established. Based on this model, pouring characteristics are analyzed. Through piecewise fitting, angular velocity functions for constant flow rate pouring are derived, which provides theoretical guidance for practical industrial operations.

This paper presents a low-frequency vibration energy harvester based on a magnetic spring and a rolling magnet, designed to harvest energy from human motion and low-frequency mechanical vibrations. A theoretical model is established and numerically analyzed to investigate the dynamic and output characteristics, enabling the optimization of the rolling magnet dimensions and structural parameters. A prototype is fabricated and experimentally characterized under different excitation frequencies and amplitudes. The results show that a maximum output is achieved at an amplitude of 20 mm and a frequency of 6 Hz, with an RMS voltage of 8.17 V and an output power of 6.36 mW. In the frequency range of 3 6 Hz, the voltage frequency amplification factor ranges from 6.13 to 9.33, with an average value of 8.15. Application tests demonstrate that the prototype can successfully harvest kinetic energy from human body movements to power a Xiaomi temperature and humidity sensor, and when mounted on a bicycle, it captures road-induced vibrations to illuminate a LED panel consisting of 26 lights. These results confirm the feasibility of the proposed harvester for powering low-power electronics.

In this paper, an airflow energy harvester based on diamagnetic levitation is investigated to optimize the floating magnet configuration for enhanced energy conversion and harvesting performance. The influence of the notch radius of the floating magnet on its rotational characteristics is analyzed through simulation, leading to an improved structural design with the floating magnet encapsulated by a resin housing. Comparative simulation and experiment are conducted on the airflow energy harvester before and after the improvements. The results demonstrate that the corresponding steady-state levitation gap at the same upper spacing increases. The housing does not affect the energy conversion coefficient, and both the rotational speed of the combined floating magnet and the induced electromotive force (EMF) generated in the coils increase as the housing's external notch radius decreases. At an airflow rate of 3000 sccm through both nozzles, the improved harvester yields an average peak voltage of 3.463 V, an effective voltage of 2.449 V, and an average harvested power of 237.94 mW without an external circuit. The optimal output power is 112 mW, with a power density of 1.2556 mW/cm3, and an energy conversion efficiency of 28.96%. 60 LEDs are illuminated by the improved energy harvester, verifying its application feasibility.

This paper proposes a novel motion planning algorithm based on model predictive control (MPC) and fuzzy logic to address the coordinated motion planning problem in terms of optimal energy consumption while maintaining specific driving style. The MPC controller based on the linear time-varying (LTV) vehicle dynamics model is constructed to deal with the calculation of trajectory tracking accuracy, while the optimal energy consumption term is also integrated into the evaluation function. To transform the non-convex optimization problem into quadratic programming (QP), the tracking error is further linearized. Noting that differentiated control objectives lead to potential abnormal acceleration fluctuations, the weight adjustment mechanism is adopted to handle the adjustment of vehicle’s dynamic behavior. In the process of adaptive weight configuration, the fuzzy logic controller based on driving intention and deviation level is designed to achieve the goal of maintaining the preset driving style. Therefore, by leveraging the correlation between driving style definition and acceleration/deceleration decisions, the trade-off problem in motion planning and the riding comfort issue can be addressed simultaneously. Moreover, the improved algorithm under three different driving styles and the original MPC planner are tested and compared in the typical cornering scenario. By introducing the optimal energy consumption term at the cost of a 4.08% extension in scenario passage time, the proposed algorithm achieves up to a 29.76% reduction in trajectory deviation and a 38.89% decrease in approximate driving energy consumption. Visual analysis of driving objectives’ trade-off further indicates that different driving style presets lead to distinct optimization potentials, while trajectory tracking still plays a dominant role in the overall control objectives.

A four-steering-wheel heavy-duty Automated Guided Vehicle (AGV) is prone to lateral instability and wheel slippage during acceleration, climbing, and small-radius turns. To address this issue, a trajectory tracking strategy considering lateral stability and an optimal driving torque distribution strategy considering load transfer and tire adhesion coefficient are proposed. Firstly, a three-degree-of-freedom AGV trajectory tracking model is established, tracking error and sideslip angle are incorporated into the cost function, and an improved model predictive trajectory tracking controller is proposed. Secondly, the longitudinal and yaw dynamic model of AGV is established, and vertical load transfer is analyzed. With the goal of minimizing tire adhesion utilization rate, quadratic programming is used for the optimal distribution of driving torque. Finally, through co-simulation using ADAMS and MATLAB on a narrow “climbing straight+ S-curve” road, the maximum tracking error is 0.0443 m. Compared to the unimproved model predictive control and average driving torque distribution strategy, the sideslip angle is reduced by 58.18%, the maximum tire adhesion utilization rate is reduced by 6.62%, and climbing gradeability on wet roads is enhanced.

In this paper, an array of permanent magnets is proposed as a floating magnet to enhance the levitation characteristics of the diamagnetic levitation structure. Experimental results show that the maximum steady levitation gap of the diamagnetic levitation structure can be increased by 80.21% with the new floating magnet, and the axial size of the diamagnetic levitation structure can be reduced by up to 39.73%. A prototype of a vibration energy harvester based on the diamagnetic levitation structure was constructed. The experimental results show that when the external excitation frequency is 4.8 Hz and the amplitude is 6 mm, the maximum effective voltage of the vibration energy harvester is 1663 mV. Compared with the original structure, the output performance of the vibration energy harvester is improved by 33.87%. This study shows that using this permanent magnet array as a floating magnet not only improves the levitation characteristics of the diamagnetic levitation structure, but also enhances the output performance of the vibration energy harvester.

The vibration energy harvester based on diamagnetic levitation can increase the amplitude of the floating magnet by adjusting the natural frequency of the diamagnetic levitation structure. However, due to size constraints, the floating magnet frequently collides with the shell. To collect the energy generated by the collision and improve the output performance of the harvester, we introduce piezoelectric cantilever beams into the shell of the vibration energy harvester. The piezoelectric cantilever beam comprises a structural layer, a piezoelectric layer (PZT-5H) and a seismic block. This structure exhibits high energy density and excellent structural stability. The collision provides the initial velocity for the vibration of the piezoelectric cantilever beam, thereby enhancing its output voltage. The simulation results show that collision between the floating magnet and the shell can increase the output voltage of the piezoelectric cantilever beam by more than 10 times. Experimental results show that when the resonance frequency is 3.8 Hz and the external amplitude is 5 mm, the effective output voltage of the piezoelectric cantilever beam is 3034 mV, and the error between the simulation and experiment results is 8.7%. Following the addition of piezoelectric cantilever beams, the output performance of the vibration energy harvester is increased by 7.15 times. This research provides an effective solution for collecting energy generated by impacts and collisions.

In this paper, the levitation characteristics of the floating magnet in an airflow energy harvester based on diamagnetic levitation structure is studied by theoretical analysis and simulation calculation. According to the simulation with COMSOL Multiphysics, we obtained the relationship between the inductive voltage and the values of the notch radius, the floating magnet radius and the floating magnet thickness. At the same time, the coil parameters, including inner diameter, outer diameter, wire diameter and coil layer, were analyzed to study the influence of energy conversion factor (ECF) and energy conversion efficiency of the airflow energy harvester. Based on the analysis results, corresponding parameters are selected for experiment. And the results show that the peak voltage is 1.892 V, and the average power is 94.70 mW when the left and right nozzles’ gas flow rate is 3000 sccm. The simulation analysis provides a good reference for parameters selection of the floating magnet and the coil in the diamagnetic airflow energy harvester, which can increase the energy harvesting efficiency of the harvester.

During the operation of outdoor heavy-duty Automated Guided Vehicle (AGV), the stability and safety of AGV are easily reduced due to load transfer. In order to solve this problem, a trajectory tracking control strategy considering load transfer is proposed to realize the trajectory tracking of AGV and the adaptive distribution of driving torque. The three-degree-of-freedom (3-DOF) kinematics model and pose error model of heavy-duty AGV vehicles are established. The lateral load transfer and longitudinal load transfer rules are analyzed. The vehicle trajectory tracking control strategy is composed of an improved model predictive controller (IMPC) and drive motor torque adaptive distribution controller considering load transfer. By optimizing the lateral acceleration of the vehicle body, the IMPC controller improves the problem of large driving force difference between the left and right sides of the wheel caused by the lateral transfer of the load and the problem of large wheel adhesion rate caused by the longitudinal transfer of the load is improved by the speed controller and the torque proportional distribution controller. The joint simulation platform of MATLAB/Simulink and CarSim is built to simulate and analyze the trajectory tracking of heavy-duty AGV under different pavement adhesion coefficients. The simulation results have shown that compared with the control strategy without considering load transfer, on the two types of pavements with different adhesion coefficients, the maximum lateral acceleration is reduced by 19.7%, and the maximum tire adhesion rate is reduced by 11.5%.

This paper proposes an airflow energy harvester based on dual-pull diamagnetic levitation with a center-symmetric rotor, aiming to investigate its levitation stability and energy harvesting efficiency. Simulation calculations were performed to analyze how the coil’s and symmetrical rotor’s structural parameters affect the harvester’s levitation and output characteristics, thereby determining the coils’ appropriate layout and structural parameter. Subsequently, the influence of the thickness and notch radius of the symmetrical rotor on the levitation characteristics and output performance of the airflow energy harvester was analyzed by experiment. Simulation and experimental results indicate that a 4-mm-thick symmetrical rotor with a 2.5-mm notch radius is identified as the most suitable choice in the study. When left and right nozzles maintain an airflow rate of 3000 sccm, the stable rotational speed of the symmetrical rotor is 25,827 rpm, the peak output voltage of the airflow energy harvester is 3.206 V, and the power of the airflow energy harvester is 383.52 mW. The optimal external load for this airflow energy harvester is 13.4 Ω. With the load circuit connected, the total power of the airflow energy harvester is 191.76 mW, and the maximum power of the external load circuit is 95.88 mW. In practical application experiment, 60 LED lights were successfully illuminated, verifying the feasibility of the airflow energy harvester.

Anilido-oxazoline-ligated iron complexes, including bis(anilido-oxazolinate) iron(II), mononuclear iron(II) alkyl and aryloxide, as well as the dinuclear analogues, were synthesized, and their catalytic performance on ring-opening polymerization (ROP) has been studied. Transmetalation of FeCl2(THF)1.5 with in situ-generated anilido-oxazolinate lithium afforded the bis(anilido-oxazolinate) iron complexes 1 and 2. Half-sandwich anilido-oxazolinate iron trimethylsilylalkyl complexes 3 and 4 could be synthesized in good yields via taking pyridine as an L-type ligand. Treatment of 3 with benzyl alcohol and 4-phenoxyphenol, respectively, generated the dimeric alkoxide or aryloxide complexes 5 and 6, whereas the reaction with 2,4,6-trimethylphenol and 2,6-di-tert-butyl-4-methylphenol yielded the mononuclear aryloxide complexes 7 and 8, respectively. The iron alkoxide and aryloxide complexes were active single component catalysts for the ROP of ε-caprolactone (CL). Remarkably, the dinuclear complex 5 exhibited excellent controllability, livingness, and high initiation efficiency for ROP of CL. ROP of CL derivatives by 5 produced the corresponding polycyclic esters with good controllability, and the well-defined block copolymers could be generated by sequentially feeding different monomers. The chain initiation and propagation processes were investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and kinetics analysis. In addition, a computational study was conducted to rationalize the mechanism and synergistic effect of the alkoxide-bridged bimetallic iron centers.

This paper proposes a novel magnetic coupled airfoil-based flutter piezoelectric energy harvester, for decreasing the critical velocity, broadening the working bandwidth, and achieving more efficient harvesting performance at lower airflow velocity. The conceptual designing of the harvester system via coupling magnetic force is first conducted, the mathematical and simulation models of the fluid-structure-electric-magnetic coupled fields are then established, and the experimental prototypes are finally fabricated. The influences of the structural parameters of the harvester system on the vibration response and output performance are fully studied. The results show that the magnetic repulsion force decreases the equivalent stiffness of the harvester system and makes it easy to couple plunge-pitch motions. A decrease in the magnet spacing distances leads to decreasing the critical velocity and improving the output performance. Compared with the magnetic spacing distance of 25 mm, the critical velocity with the magnetic spacing distance of 17 mm decreases by 70%, and the enhancement ratio of output power increases by 50% at 13.8 m/s. The flow field demonstrates that the alternating pressure difference drives the harvester system to take place two DOF plunge-pitch motions. The experimental results are in good agreement with the theoretical values, which verified the established mathematical model. The designed magnetic coupled airfoil-based flutter harvester system achieves a larger vibration response and better harvesting performance at lower airflow velocity. This work provides essential foundations for achieving better harvesting performance via coupling magnetic force.

In this article, a new diamagnetic levitation structure is proposed to explore its potential in the application of sensors and actuators through the study of its levitation and dynamic characteristics. Compared with our old diamagnetic levitation structure, the levitation point, maximum monostable levitation space, horizontal magnetic spring stiffness, and axial resultant force distribution of the new structure are all adjustable. At the same time, the maximum horizontal radial recovery force of the floating magnet could reach 34 $780\, \mu \text{N}$ , which is 542.41% higher than that of the floating magnet in the old structure. Accordingly, when the range of the horizontal radial displacement is 0–15 mm, the maximum axial resultant force of the floating magnet is $439.7 \,\mu \text{N}$ , which is only 5.72% of that in the old structure. In the experiment, when the floating magnet is blown by nitrogen gas with a flow rate of 3000 sccm, the maximum horizontal radial displacement of the floating magnet is 2.27 mm, which is only 22.976% of that in the old structure. Under the same gas flow rate, the maximum tilt angle of the floating magnet is 0.482°, which is only 3.998% of that in the old structure. In summary, the theoretical analysis, numerical simulation, and experiment results are consistent with each other, which indicates the great potential of the new structure in the application of sensors and actuators.

In this paper, the proposed diamagnetic levitation structure was studied to explore its potential in energy harvesting. It is proved that the floating magnet rotor can be levitated stably under the joint action of two highly oriented pyrolytic graphite (HOPG) sheets and the lifting magnet. Simulation calculation was carried out to analyze the influence of different coil radius and wire diameter on peak voltage and average power in scheme A or scheme B, so as to obtain appropriate layout and wire diameter for the coils which was built the experimental platform. Subsequently, the center hole, notch radius and thickness of the floating rotor are analyzed by experiment. And the influence of different parameters on rotation speed of the rotor and peak output voltage of coils is obtained. Through experimental results, it is found that the notch radius of the floating rotor has the greatest influence on the rotation speed of the rotor. Based on the experiment, a new-type rotor was designed, with an outer shell to reduce the notch radius. Compared with the original floating rotor, there was 49.73% increase in voltage, 55.70% increase in rotation speed and 124.50% increase in power according to the experimental results. Test was performed with the optimization, the LED array of Zhengzhou University logo, which was composed of 60 LED lights, was lighting up. According to the oscilloscope measurement, the diamagnetic levitation energy harvester has an output voltage up to 1.294 V and average power of 60.67 mW under gas flow rate of 3000 sccm and nozzle exit velocity of 6.173 m/s. Obviously, the new-type rotor proposed in this paper could significantly increase the energy conversion efficiency, and make the future application of airflow energy harvester a step further.

This paper proposes a novel piezoelectric energy harvester attached with a trailing-edge flap under various installation angles, for enhancing the aeroelastic vibration and improving the harvesting performance. The mathematical models of the fluid-structure-electric coupled fields are derived, the simulation models of the multi-physical coupled fields of the harvester system with various installation angle flaps are established, and the experimental prototypes of the harvester are fabricated. The influences of the flap installation angles on the flow field and output characteristics are investigated theoretically, numerically, and experimentally. The results demonstrate that the flap stiffness and damping coefficients exert less influence on vibration characteristics and harvesting performance. The flap at a certain installation angle alters the flow field, affects the flow pattern, restricts the vortex shedding, and offsets the aerodynamic force and moment. A decrease in the flap installation angles results in increasing the vibration response and output performance. The obtained numerical results are in good agreement with the experimental and theoretical values, which verifies the effectiveness of the simulation model. The maximum plunge amplitude is 0.029 m and the output voltage is 15.51 V at 17.74 m/s and an installation angle of 0o. The enhancement ratio of the output voltage at 0o is up to 148.6% over 45o, which achieves better harvesting performance. The designed harvester system powers indirectly the pedometer for 104 s at 13.58 m/s. This research offers an essential foundation for achieving better tradeoffs in energy harvesting and vibration suppressing by appropriately selecting the flap installation angle.

In order to solve the demand for low-power microcomputers and micro-electro-mechanical system components for continuous energy supply, a magnetic coupling piezoelectric–electromagnetic composite galloping energy harvester (MPEGEH) is proposed. It is composed of a piezoelectric energy harvester (PEH) and an electromagnetic energy harvester (EEH) coupled by magnetic force. The bistable nonlinear magnetic coupling structure improves the output power of the MPEGEH. The advantages and output performance of the MPEGEH are analyzed. The prototype of the energy harvester is made, and the nonlinear output characteristics under different load resistances are analyzed. Through the experiment on the key parameters of the composite energy harvester, it is found that the higher the coupling degree of the two parts of the MPEGEH, the stronger the nonlinear characteristics and the better the output characteristics. The results show that the onset wind velocity and output power of the MPEGEH are better than the classic galloping piezoelectric energy harvester (CGPEH). At the same wind speed, with the increase in the distance d0 between magnets A and B, the output power of both the PEH and the EEH decreases. When d0 is 37 mm, the output power of the EEH is the largest. The distance s0 between magnets B and C has little influence on the output power of the PEH but has a great influence on the EEH. When s0 is 23 mm, the EEH has the best output characteristics. Compared with the CGPEH, the onset wind velocity is reduced by 28%, and the output power is increased by 136% when the wind speed is 11 m/s.

In order to solve the problem of self-energy supply of vehicle-mounted micro-sensors, bridge detection and some other low-power electronic devices in their working state, a vortex-induced flutter composite nonlinear piezoelectric energy harvester (VFPEH) with symmetrical airfoils on both sides of a cylindrical bluff body is designed. The VFPEH consists of a cantilever beam, a cylindrical bluff body connected to the free end of the cantilever beam, and two airfoil components symmetrically fixed at both ends of the shaft, which enables coupling between vortex-induced vibration and flutter. The airfoil symmetrically arranged on both sides of the cylindrical bluff body induces the cantilever beam to produce bending and torsional composite vibrations at high wind velocities, realizing energy harvest in the two degrees of freedom motion direction, which can effectively improve the output power of the energy harvester. Based on a wind tunnel experimental platform, the effect of key parameters matching impedance and the diameter of the cylindrical bluff body on the output performance of the VFPEH is investigated, together with the output performance of the classical vortex-induced energy harvester (VEH), the flutter energy harvester (FEH) and the VFPEH. The experimental results show that for the VFPEH under a combination of vortex-induced vibrations and flutter vibrations has a better output performance than the VEH and the FEH when using the same size. The coupling of vortex-induced vibration and flutter can reduce the start-up wind velocity of the VFPEH and expand the wind velocity range of the high output power of the VFPEH. The VFPEH has a better output performance at the cylindrical bluff body diameter of 30 mm and a load resistance of 140 kΩ. When the wind velocity range is 2 m/s–15 m/s, the maximum output power of the VFPEH is 6.47 mW, which is 129.4 times and 24.9 times of the maximum output power of the VEH (0.05 mW) and FEH (0.26 mW), respectively.

To widen the operation wind speed bandwidth of a classic vortex shedding induced vibration piezoelectric energy harvester, a piezoelectric-electromagnetic hybrid energy harvester based on vortex shedding induced vibration is designed. The hybrid vortex shedding induced vibration energy harvester (HVSIVEH) includes a vortex shedding induced vibration piezoelectric energy harvester (VSIVPEH) and an electromagnetic vibration energy harvester (EVEH). The electromechanical coupled vibration model of the hybrid structure was established. By comparing the variations of the output power as a function of the wind speed of the HVSIVEH and the classic VSIVPEH, it is found that the power response curve of the HVSIVEH has two peaks. The hybrid structure can broaden the working wind speed range. The lower the requirement on the output power level, the more obvious the effect of widening the wind speed range. By the solution and analysis of the electromechanical coupled model, better values of related parameters of the HVSIVEH are obtained. The first and second peaks of the output power of the HVSIVEH show better values of 1.9 and 2.2 mW, respectively, under these parameters.

This paper presents a piezoelectric-electromagnetic hybrid flutter-based energy harvester (HFEH), where the piezoelectric part and electromagnetic part are coupled with each other by magnetic forces. The working principle is explained in detail and the corresponding theoretical model of the HFEH is established based on Lagrange's equations, Newton's second law, Kirchhoff's law, a semi-empirical nonlinear aerodynamic model, and a magnetic dipole model. The advantages of the HFEH, output performance, and nonlinear output characteristics under different magnet distances and load resistances are analyzed. Results show that the cut-in wind speed and the output power of the HFEH are, respectively, lower and higher than those of the typical flutter-based piezoelectric energy harvester (FPEH). When the distance between magnets A and B and that between magnets C and D is small, the amplitude jump phenomenon occurs, and the electromagnetic part has a satisfactory output power near the jump points. The output power of the piezoelectric part and the electromagnetic part of the HFEH, respectively, reaches 1.35 mW and 36.63 mW at a wind speed of 6.70 m/s. Overall, this study provides a theoretical framework for the design of high-efficiency wind energy harvesters.