Abstract Hydrokinetic energy, a vital renewable resource, holds promise for addressing fossil fuel shortages to ensure a sustainable future. This study proposes an efficient and stable ocean wave energy harvesting system that combines a triboelectric nanogenerator (TENG), an electromagnetic generator (EMG) with a planetary gear system, and a driving turbine. The turbine transforms the up‐and‐down motion in water into continuous, unidirectional rotational motion. An EMG device accelerated by a planetary gear system further ensures sustained output at very low frequencies (0.25 Hz) and boosts the upper limit of power generation at medium to high frequencies. Under water wave conditions with a 1 Hz frequency, the TENG component yields an output of up to 2200 V and 122 µA, while the average EMG output is 15 V and 80 mA. Remarkably, the entire system maintains a steady and uninterrupted output even at extremely low frequencies (0.25 Hz). The peak power outputs for the TENG and EMG components are 115 and 350 mW, respectively, with power densities of 32.55 and 329.78 W m −3 , surpassing prior achievements. This research demonstrates self‐powered applications and provides an efficient method to amplify water wave forces, enhancing energy harvesting capabilities for practical marine environmental monitoring.
The unmanned aerial vehicle (UAV) accelerometer is a sensor that measures the acceleration of the UAV by detecting the components of gravity along the three axes. The use of self-powered technology in UAV accelerometers will become inevitable. This article proposes an asymmetric electrode arc triboelectric nanogenerator (ASA-TENG) based on the single-electrode mode. It is a potential self-powered acceleration sensor that is installed on the UAV to detect the acceleration in the cruise state. It is characterized by a simple structure, low quality, high sensitivity, large detection range, low cost, and environmental friendliness. Two ASA-TENG structures are stacked into a cross along the ${x}$ -axis and ${y}$ -axis to detect the components of actual acceleration along the two axes to detect the acceleration of random directions. Finally, the actual acceleration is obtained through the principle of acceleration synthesis, which can accurately detect the direction of acceleration. The ASA-TENG acceleration sensor can detect accelerations in the range of 0.1–40 m/s2. It exhibits a high sensitivity, and its response time has a good fitting relationship with acceleration ( ${R}$ 2 = 0.997). In addition, the voltage signal amplitude generated by the ASA-TENG sensor shows negligible fluctuations after 6 h of continuous operation. Comparison experiments with commercial acceleration sensor show a maximum relative error of only 2.9%. Therefore, the ASA-TENG acceleration sensors can be potentially used under cruise conditions of UAV as it presents numerous advantages.
Mobile source emissions have already accounted for a large proportion of environmental pollution, which seriously affect the symmetric characteristics of atmosphere, and automobile emissions have extremely serious deterioration of emissions under transient operation, especially particulate emissions. These factors exacerbate the asymmetry of the environment. So, the paper reports an experiment about the improvement of post injection strategy on combustion, regulated emissions (HC, CO, and NOx), and particle number emissions especially the emissions of different size particles in the transient process of an EGR diesel engine, meanwhile, the effects of post injection on the combustion of mixture are further analyzed by numerical simulation method. The test speed was 1600 r/min, and the torque increased from 5% of the maximum torque to 100%. The results indicated that the shorter the instantaneous loading time, the more severe the deterioration of particulate emissions, HC and CO emissions, but loading time has little effect on NOx emissions. The particles with the size range of 50–100 nm, 23–50 nm, and >100 nm are greatly affected by the loading process and post injection. In comparison, it has little effect on ultrafine particles with particle size of 15–23 nm and <15 nm. With the amount of post injection increased, the in-cylinder disturbance increased, and the oxygen-rich area in cylinder increased, the particle number concentration first decreased and then slightly increased. When the amount of post injection fuel is 2 mg and the main-post injection interval is 2000 us, the effects of suppressing particulate emissions are the best, for the 50–100 nm and >100 nm particles, the peak number concentration can be reduced by 25% and 50%, respectively. Due to the turbo charging lag, the peak of NOx emissions during the unloading process were slightly larger than the loading process.
In this paper we consider the problem of a robust H/sub /spl infin// optimal estimator design for continuous-time linear systems in the presence of parameter uncertainties. A method that expresses the system uncertainty in the estimator design problem is introduced. This expression for system uncertainty does not change the structure of the standard H/sub /spl infin// optimal problem. Therefore, a complete solution is achieved by using existing results of H/sub /spl infin// optimization theory.
Rotor blades play an important role in unmanned helicopters, and it is of great significance to study the erosion of rotor blades. In this study, titanium alloy (Ti-4Al-1.5Mn) was used as the helicopter rotor blades’ surface material. The commercial software Ansys-Fluent 18.0 was mainly used to study the erosion of solid particles on the helicopter rotor blades. The moving mesh method and the discrete phase method (DPM) were used to construct an erosion model of the blades at different speeds (500, 1000, or 2000 rpm), and at different particle mass flow rates (0.5, 1, or 1.5 kg/s). The results show that the erosion of helicopter blades is mainly observed at the leading edge and at the tip of the blades. At different particle mass flow rates, greater particle mass flow rates lead to greater DPM erosion rates. As the blade speed increases, the maximum DPM erosion rate decreases, but the severely eroded area increases. Finally, the values of the severely eroded area of the helicopter rotor blades and the ratios of the severely eroded area growth are obtained through the image processing method.
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