The effect of modifying substituents in the rotor group of five second generation molecular motors is estimated by theoretical calculations. The rotational speed is estimated by calculating the rate limiting step, the thermal helix inversion, and the competing backward transition using harmonic transition state theory with energy and atomic forces obtained from density functional theory. First, a methyl group at the stereogenic center is replaced with a tert-butyl (tBu) group, and the rotational speed is found to increase due to reduced lifetime of the metastable state. For two of the rotors, comparison can be made with experimental measurements, and the calculated half-life is in close agreement. Second, the effect of substituting the nine hydrogen atoms in the tBu group with fluorine atoms is studied, and this is found to increase the rotational rate further without significantly altering the molecular structure. The excitation wavelength of both the stable and metastable states is calculated, and the separation of the absorption peaks is found to increase by the tBu substitution and even more so by the fluorinated tBu substitution, up to 40 nm. These findings can help to develop a strategy for designing molecular motors with a rotational speed that best fits a given application.

Abstract The precise monitoring of propeller rotational speed is crucial for ensuring the navigation stability and motion control of autonomous underwater vehicles (AUVs). Conventional speed sensors often rely on external power supplies, which limit their long-term deployment in underwater environments. To overcome this limitation, this study proposes a novel self-powered propeller speed measurement system based on a hybrid piezoelectric-electromagnetic energy harvester. The measurement system is composed of two distinct energy harvesting mechanisms: one based on the piezoelectric principle and the other on electromagnetic induction. The piezoelectric unit is used for sensing and detection, while the electromagnetic unit is used for energy harvesting and self-powering. This dual-functional integration enables the system to simultaneously extract energy from propeller rotation and generate speed-indicative electrical signals without external power. A theoretical model of this self-powered detection system was established, and simulation analysis was performed. Piezoelectric rectification and electromagnetic rectification circuits were designed, and the electrical energy of the self-powered measurement system was collected and stored. An experimental testing platform for a self-powered underwater propeller speed detection system was constructed and tested. Results show the maximum output power of the electromagnetic unit is 100.2 mW. Within the speed range of 0–360 r/min, the maximum relative error between the measured speed of the self-powered system and the reference speed provided by the servo motor is 1.3% at 210 r/min. What’s more, the designed self-powered system exhibits a linearity of 0.91%. The research results have important practical applications for achieving high-precision self-powered detection of underwater vehicle propellers.

This study evaluates the effects of ball milling parameters—duration (2–60 min), rotation speed (200–400 rpm), and use of acetone as a liquid medium—on the structural integrity of synthetic pyrrhotine (Fe₀.₉S) and molybdenite (MoS₂). Wet milling in acetone is identified as the optimal practical approach: it prevents oxidation of pyrrhotine during post-milling annealing and eliminates macro-inhomogeneities. Molybdenite, inherently stable under mechanical treatment, shows no signs of oxidation and is readily processed in acetone due to its softness and perfect basal cleavage. These findings enable the production of homogeneous, phase-pure sulfide reference materials for LA-ICP-MS.

Numerical study of dynamic characteristics of Rotor 37 induced by back pressure and rotation speed variation

Abstract Addressing issues such as dispersed ejected material and insufficient range in sand throwing fire extinguishing devices, this study systematically investigates the effects of key structural parameters on the effective ejection zone and ejection distance and proposes an optimized design scheme. First, virtual simulations of the ejection process are performed using EDEM discrete element software to construct an interaction model between the ejection assembly and sand particles. A three factor, three level orthogonal experiment is then designed, taking impeller speed, number of blades, and blade inclination angle as factors, and the core effective zone and average ejection distance as evaluation metrics. Subsequently, Design-Expert software was used to establish a regression model and carry out multi-objective parameter optimization, and the optimal parameter combinations of impeller rotational speed of 1550 rpm, the number of blades of 5, and the inclination angle of the blades of 5°, corresponding to the core effective area of 3.7 m and the average throwing distance of 17 m were determined by the response surface method, and the reliability of the model was verified by comparing the simulation and experimental results to provide a reference for the structural design and optimization of the sand-throwing fire extinguishing machine. Finally, the reliability of the model is verified by comparing the simulation and experimental results, which provides a reference for the structural design and optimization of the sand blasting machine.

Hydrodynamic instabilities and interface dynamics of two immiscible liquids driven by a rotating disk.

Optimal rotational speed rotor load reduction control in Coaxial High - Speed helicopter/engine integration system

Effect of Rotational Speed and Brush Polarity on Wear Behavior in a Slip Ring System

This study investigates the valorization of marble waste in Turkey as a high-purity calcium carbonate (CaCO₃) source for industrial applications. Marble, with its limestone-like composition, offers potential to replace natural calcite in paper, plastics, paints, adhesives, and cosmetics. The research emphasizes severe environmental impacts of marble waste—groundwater contamination, air pollution, and land degradation—and highlights EU policies promoting recycling and resource efficiency. In Turkey, nearly 70% of quarried marble becomes waste, stressing the need for sustainable solutions. Traditionally, such waste is used in low-value applications like aggregates or cement, while micronized, high-purity calcite production remains underexplored. Samples from a processing facility in Eskişehir showed 98.93% CaCO₃ content, confirming suitability as a commercial calcite substitute. Micronized calcite production was tested with a laboratory-scale vertical stirred mill, assessing effects of grinding time (15–600 seconds), rotational speed (360–1440 rpm), and filling ratio (60-140%) on particle size. Results indicated that higher speeds and longer grinding achieved finer particles (d₅₀ of 9.6 µm after 300 seconds). However, grinding beyond 180 seconds caused agglomeration and reduced efficiency due to heat, while excessive speeds increased equipment wear. The study suggests using dispersants to mitigate agglomeration and improve performance. Overall, this research demonstrates marble waste can be transformed into a valuable industrial resource, combining chemical characterization and grinding optimization. It offers recommendations for industry and policymakers to support recycling and circular economy practices.

Aluminum Nitride (AlN) thin films are widely used in microelectronics, piezoelectric sensors, and high-power devices because of their good electrical, mechanical, and thermal properties. Among various deposition methods, radio frequency (RF) magnetron sputtering is considered advantageous due to its ability to fabricate homogeneous, high-quality layers with strong adhesion. However, achieving optimal film properties in large-scale deposition, particularly with industrial-grade 12-inch sputtering targets, requires precise control over process parameters, including target and substrate rotation. While rotation dynamics significantly influence film thickness, surface topology, and crystallinity properties, their effects in large-area deposition remain insufficiently explored. This study examines how target/substrate rotation speeds (10/5, 15/5, 0/0, 5/5, 10/10, 5/10, and 5/15 rpm) affect the film thickness, surface topology, and crystallinity characteristics of AlN thin films. The results show that balanced rotation, especially at 10/10 rpm, produces films with superior thickness uniformity and crystallinity, making it optimal for large-area AlN deposition. Therefore, these findings offer valuable insights into improving AlN film quality for larger wafer sizes in industrial applications.

This study aims to address the challenge of predicting pipe sticking accidents in petroleum drilling engineering. In response to the high blindness of tradi-tional empirical qualitative operations, the difficulty of mathematical models in accurately reflecting drilling laws, and their poor operability, machine learning methods such as neural networks (NNs), support vector machines (SVM), and random forests are introduced for pipe sticking prediction re-search. Adhering to the principles of sample representativeness, category balance, and diversity, 9 drilling parameters including depth, drilling speed, weight on bit (WOB), torque, friction coefficient, outlet temperature, rota-tional speed, inlet flow rate, and outlet flow rate were selected. Drilling data from 30 wells in the Yan'an area were collected. Measurement data within a certain period before pipe sticking were used as pipe sticking samples, which were cross-arranged with normal samples to construct the training dataset. By comparing the performance of SVM (linear kernel, radial basis kernel) and random forest models, the results show that the random forest performs the best. In its confusion matrix, the number of correctly predicted samples for true labels 0 and 1 is 190 and 207 respectively, with only 9 and 5 misclassifi-cations. The accuracy rate reaches 0.966. In summary, this study confirms that the random forest has significant advantages in balancing "accuracy and efficiency" in pipe sticking prediction tasks, providing a reliable early warning model and technical support for safe drilling operations.

In vitro testing of ventricular assist devices, constructing a mock circulation system that reproduces physiological cardiac function, is critical. However, current ventricular simulators often lack biomimetic fidelity and may introduce hemolysis and coagulation risks during prolonged operation, affecting hemocompatibility assessment. This study proposes a motor-driven torsional 3D-printed left ventricular simulator to reconstruct the hemodynamics of severe heart failure and related pathological conditions. The system integrates a 3D-printed elastic ventricular model with programmable torsional actuation, allowing the simulation of various cardiac conditions by adjusting the motor torsion angle and rotational speed, peripheral resistance and compliance. Fresh porcine blood was circulated for 4 h in a closed-loop system, with periodic measurements of plasma-free hemoglobin (PfHb), thrombin–antithrombin complex (TAT), and P-selectin. The results show that the system successfully reproduces typical hemodynamic features of severe heart failure, while hemolysis and coagulation markers remain low. After 4 h, PfHb was below 20 mg/dL, with no significant platelet activation or thrombosis. This study demonstrates that the proposed system enhances biomimicry while maintaining excellent hemocompatibility, offering a reliable platform for in vitro performance and safety evaluation of ventricular assist devices.

Abstract In recent years, with the widespread application of deep learning in industrial equipment condition monitoring, data-driven bearing temperature prediction models have achieved significant progress. However, existing methods commonly suffer from a lack of physical mechanisms and insufficient interpretability, as well as difficulties in effectively integrating key physical parameters such as electromagnetic losses in complex electromechanical systems involving cross-component thermal coupling. To address these challenges, this paper proposes a hybrid modeling approach that combines multiphysics simulation with physics-informed neural networks. First, a 2D axisymmetric electromagnetic-thermal coupled finite element model of a traction motor is constructed to quantify the spatial distribution characteristics of iron and copper losses, which are then fused with bearing measurement data (rotational speed, ambient temperature, and bearing temperature). Subsequently, an LSTM model is employed to capture the temporal dependencies of bearing temperature data, and a Physics-Informed Neural Network-enhanced LSTM is designed to embed the bearing thermal equilibrium equation into the loss function as a residual term, enabling synergistic optimization between data-driven prediction and thermodynamic laws. Finally, validation is conducted on a constructed multi-source dataset, with comparisons against other methods. Experimental results demonstrate that the proposed model effectively integrates electromagnetic loss parameters, achieves superior prediction performance, and enhances the physical interpretability of the model.

To address issues such as clogging of threshing units, high grain loss rates, and elevated impurity levels in wheat breeding harvesters, this study developed a combing-type threshing and separation system for wheat plot harvesters. The system adopts a closed plate-tooth threshing drum structure, where the airflow generated by the rotation of drum blades is combined with external impurity-cleaning airflow, thereby reducing material accumulation and seed retention in the threshing and separation system. CFD-DEM coupling simulations determine the optimal parameter combination: when the drum rotational speed is 891 r/min, the feeding rate is 0.58 kg/s, and the impurity-cleaning airflow speed is 22.56 m/s, the system achieves a loss rate of 0.87% and an impurity rate of 9.06%. A field performance test using this parameter combination showed that the system’s loss rate was 1.09% and impurity rate was 11.13%. This study provides a reference for the design and research of threshing and separation systems in comb-type wheat plot harvesters.

Abstract Circular motion is one of the more challenging issues in Newtonian mechanics for teaching and learning. A small mass rotating inside an inverted cone at different speeds provides a counterintuitive problem. Indeed, the mass unexpectedly goes up as the rotation slows down, and vice versa. To find out how the rotating cone problem is conceptualized by students, we investigated the ideas of 55 participants. Our results indicate that this problem is truly challenging even for lecturers and physicists. The main misconception found among the participants is that the mass should go up as the rotation speed increases, similar to a revolving pendulum and a mass rotating in a spherical shell. Nevertheless, physical analysis of the problem is almost absent in classical mechanics textbooks. Herein, we provide an essential conceptual analysis, analyze the misconception in terms of DiDessa and suggest some pedagogic tools for instruction.

With the increase in thrust–weight ratio of advanced aeroengines, the rotor and stator often exhibit comparable stiffness characteristics, leading to significant vibration coupling which harms the safety and reliability of operations. However, an effective vibration coupling evaluation method for complex rotor–stator systems is still lacking. This paper proposes the Vibration Coupling Evaluation Factor (VCEF) to quantitatively evaluate the interaction between the rotor and stator within the framework of the linear system. Then a new evaluation procedure is established for the structural optimization during the early design phase and the fault source localization in troubleshooting scenarios in the high-speed rotating machinery. In this paper, two typical rotor–stator systems are studied with the VCEF method: a simplified rotor–stator system is studied numerically to reveal the influence pattern of different parameters, and a complex rotor–stator system is studied numerically and experimentally to examine the validity of the evaluation method. The results show that VCEF can effectively capture rotor–stator vibration coupling. The VCEF curve with rotational speed shows a significant stepped decrease, indicating a significant strengthening of the rotor–stator vibration coupling, which aligns closely with experimental data. This evaluation method quantitatively assesses the degree of rotor–stator vibration coupling by comparing the differences in modal characteristics between the rotor system and the rotor–stator system under the gyroscopic effect. Optimizing rotor–stator stiffness and mass distribution based on VCEF mitigates operational risks in high-speed regimes. This methodology provides engineers with a systematic, quantitative tool to determine when integrated rotor–stator analysis is essential for accurate dynamic prediction and offers broad applicability to aeroengine design and other high-speed rotating machinery.

In Executing aggressive maneuvers, such as the Double Lane Change (DLC), presents a significant challenge for autonomous vehicle control, particularly when dealing with highly non-linear vehicle dynamics. This paper proposes a novel path-following and planning approach based on a comparative analysis of two distinct Nonlinear Model Predictive Control (NMPC) architectures. Developed using the CasADi framework within the MATLAB environment, the controllers are applied to a high-fidelity 8-Degree-of-Freedom (8-DOF) vehicle model, solved via the ode45 function. To ensure practical robustness against sensor noise, the control loop is integrated with a Moving Horizon Estimator (MHE), which significantly enhances the accuracy of state estimation during operation. The first control architecture implements a kinematic model, defining states by vehicle position and yaw angle to control wheel rotation speeds and steering. In comparison, the second architecture utilizes a comprehensive dynamic model that incorporates higher-order states, such as yaw rate and side-slip angle, with control inputs for independent front steering angles. We rigorously evaluated both controllers across a wide spectrum of longitudinal speeds and varying road surface conditions. The results assess the capability of each system to track predefined trajectories while strictly satisfying state and control constraints, ultimately clarifying the specific trade-offs between computational simplicity and the dynamic stability required for high-speed tracking tasks.

Electrochemical turning is an efficient machining method for machining Ti80 pressure-resistant structures owing to its low tool cost and high machining flexibility. However, research has yet to explore the electrochemical turning of the Ti80 alloy, limiting its widespread application in ocean engineering. Accordingly, this study examined the anodic dissolution behavior and electrochemical turning of the Ti80 alloy in NaCl solution. Ti80 specimens underwent electrochemical tests, namely, potentiodynamic polarization and potentiostatic polarization. X-ray photoelectron spectroscopy was employed to characterize the composition of the passive film formed on the Ti80 surface when Ti80 was placed in a 20 wt % NaCl solution; this film's structure was investigated through electrochemical impedance spectroscopy (EIS) and transmission electron microscopy (TEM). The results revealed that the passive film mainly contained TiO2, Al2O3, Nb2O5, ZrO2, and MoO3 and comprised two layers: a compact inner layer and a loose outer layer. The measured thickness of the passive film was about 18 nm from TEM, which was near the predicted value (21.6 nm) calculated by EIS data. The diffraction spots obtained from Fast Fourier Transform (FFT) with interplanar spacings of 0.1238, 0.2399, 0.1039, and 0.1888 nm indicated the (024), (201), (521), and (231) crystal planes of TiO2, respectively, showing a relatively high crystallinity of TiO2 in the passive film. The dissolution morphologies of Ti80 at different current densities and processing times were analyzed; the dissolution mechanism of Ti80 in 20 wt % NaCl solution was identified. Finally, grooves with relatively sharp edges were machined on a Ti80 cylindrical workpiece through electrochemical turning at rotation speeds of 0.011 and 0.005 r/min.

ABSTRACT Polyvinylidene fluoride (PVDF), a semicrystalline polymeric material, exhibits five crystalline phases (α, β, γ, δ, and ε), with its crystalline structure altered under different fabrication conditions. This work systematically investigates the effects of extrusion temperature (190°C–210°C) and screw rotation speed (30–110 rpm) on the crystalline phases, crystallinity, and thermal stability of PVDF, while also exploring the recrystallization behavior of PVDF during solution casting. The results demonstrate that melt extrusion can convert PVDF crystal forms from the α‐phase to the β‐phase, increasing the β‐phase fraction to 75.69%–81.94%. The screw rotation speed is the primary cause of this variation. Under different processing conditions, the crystallinity of PVDF is increased by 0.93%–6.10%, and the decomposition temperature is improved by approximately 20°C through melt extrusion. For the solution casting process, it causes a β‐phase to γ‐phase transition in PVDF, achieving γ‐phase fractions of 66.23%–74.74%, with the crystallinity values of 51.05%–56.58%.

Although electric vehicles offer increased user comfort, the range limitation remains one of their most significant challenges, primarily due to battery capacity. Moreover, for electric vehicles—classified as zero-emission—it is crucial that the electricity used originates from renewable energy sources. In this study, electricity was generated using wind energy while the vehicle was in motion, enabling the batteries to be charged during operation. This approach aims to reduce charging time and extend the vehicle's range. A wind turbine was mounted on the front bumper of a sedan-type vehicle used for the experiments, without altering the total frontal projection area. The tests were conducted along the same route, in both directions, under windy conditions with wind speeds of 1 m/s. It was observed that energy production was more efficient when the wind blew against the direction of the vehicle's motion compared to when it came from behind. As the vehicle speed increased, the rotational speed of the wind turbine also increased, resulting in greater energy generation. The AC voltage generated by the wind turbine, which varied due to changes in load and vehicle speed, was rectified and stabilized at approximately 18V DC by the battery charging control unit, allowing the batteries to be charged at all vehicle speeds.