Search Results (460)

The drastic changes in the marine environment can induce the instability of seabed sediments, threatening the safety of marine engineering facilities such as offshore oil platforms, oil pipelines, and submarine optical cables. Due to the lack of long-term in situ observation equipment for the engineering properties of seabed sediments, most existing studies have focused on phenomena such as the erosion suspension of the seabed boundary layer and wave-induced liquefaction, leading to insufficient understanding of the dynamic processes affecting the seabed environment. In this study, a long-term in situ observation system for subsea engineering geological environments was developed and deployed for 36 days of continuous monitoring in the offshore area of Qingdao. It was found that wave action significantly altered sediment mechanical properties, with a 5% sound velocity increase correlating to 39% lower compression, 7% higher cohesion, 11% greater internal friction angle, and 50% reduced excess pore water pressure at 1.0–1.8 m depth. suggesting sustained 2.2 m wave loads of expelled pore water, driving dynamic mechanical property variations in seabed sediments. This long-term in situ observation lays the foundation for the monitoring and early warning of marine engineering geological disasters. Full article

This experimental study investigates the aerothermodynamic performance of a turbocharger turbine under steady and pulsating flow conditions across various turbine inlet temperatures (TITs) and pulsation frequencies. A power-based approach was implemented to quantify turbine heat transfer for diabatic scenarios over a range of operating turbocharger speeds. The results reveal that higher TITs significantly increase heat transfer under steady flow, driven by enhanced thermal gradients; while pulsating flow amplifies heat transfer by up to 63.6% due to intensified turbulence and frequent boundary layer disruptions. The exergy analysis shows that pulsating flow increases exergy destruction compared to steady flow, primarily due to pressure and velocity fluctuations that intensify flow friction and turbulence. At higher pulsation frequencies, exergy destruction decreases slightly, while heat transfer exergy loss becomes more prominent, reflecting a shift in the exergy balance. These higher frequencies, representative of real engine conditions, drive the flow toward quasi-steady behavior, further shaping the aerothermodynamic performance of the turbine. These findings provide valuable insights into the effects of pulsating flow on turbine heat transfer and exergy losses, offering practical implications for optimizing turbocharger turbine performance under realistic operating conditions. Full article

Surface roughness and sliding friction are pivotal in determining the dynamic meshing performance of helical gears, especially under conditions of flexible support. In addition, the meshing parameters influenced by gear vibrations exhibit time-varying characteristics under flexible support stiffness, which is disregarded by many scholars. Based on this, a nonlinear dynamic model of a helical cylindrical gear system under flexible support conditions is developed, considering the coupling effects of dynamic friction and backlash influenced by fractal surface roughness. The motion differential equations of the system are derived using the Lagrange method, and numerical solutions are obtained through the Runge–Kutta method. The effect of several control parameters (driving speed, surface roughness and fractal dimension) on the dynamic response of gear system is studied, and the proposed dynamic model is compared with the traditional model under different support stiffness to demonstrate its adaptability to highly flexible support scenarios. The results indicate that the proposed dynamic model is better suited for flexible support structures. Moreover, the coupling effects of sliding friction and fractal backlash amplify the dynamic response of the gear system and introduce complex spectrum characteristics. This study provides theoretical guidance for the optimization of vibration and noise reduction designs in helical gear systems. Full article

Force-projecting bilateral control is an effective method for enhancing the positioning rigidity and stability of teleoperation systems equipped with compliant pneumatically driven followers. However, friction in the pneumatic actuation mechanism has caused a deterioration in force reproducibility between the leader and follower. To solve this problem, this study proposes a practical method of nonlinear friction compensation in force-projecting bilateral control to improve the force reproducibility. The proposed method generates two friction compensation forces: one based on the target admittance velocity from the leader and the other based on the actual velocity of the follower. These forces are seamlessly switched according to the dynamic state of the system to compensate for the follower’s driving force. This enables improved force reproducibility in any motion states of the system while maintaining the advantage of force-projecting bilateral control, which eliminates the need for external force measurement on the follower side. Experiments were conducted using a 1-DOF bilateral control device consisting of an electric linear motor and a pneumatic cylinder, including free motion and contact operations with two types of environments, demonstrating the effectiveness of the proposed method. Full article

To enhance the driving experience for drivers, making it more realistic and comfortable, this study proposes a simulation control strategy for steering-by-wire road sense based on sliding mode control. Firstly, a dynamic model is constructed for the steering wheel module and the steering actuator, building upon this, a methodology for calculating the self-aligning torque is formulated, utilizing the linear two-degree-of-freedom vehicle model in conjunction with the Magic Formula. The approach incorporates the influences of assistive forces, damping, and frictional torque, thereby providing an accurate simulation of the steering road feel. On this basis, a sliding mode control algorithm is developed to achieve the necessary road-sensing motor current, guaranteeing system stability and rapid response across various driving scenarios. To validate the simulation, MATLAB/Simulink in conjunction with Carsim is employed. The outcomes from tests involving dual lane shifts and step inputs demonstrate that the introduced control approach effectively follows the target current, featuring swift convergence and minimal response latency. Full article

In this paper, TC4 titanium alloy pipes were achieved by continuous drive friction welding, metallographic microscope and microhardness tester were used to evaluate the microstructure and the hardness of the joints, and the effect of friction pressure on the microstructure was studied. Under the selected welding parameters, all the joints have good morphology. The martensite is formed at the weld zone and the flash, which leads to a higher hardness on the weld zone. With the increase of friction pressure, the width of the weld zone, the grain size and LAGB (low angle grain boundary) at the weld zone decreases. In addition, dynamic recrystallization increases first, but when the friction pressure reaches 65 MPa, the deformation dominates. Full article

Hardness and wear resistance are the requirements of nickel-based superalloys used in gas turbine blades. This study uses laser cladding technology to develop three types of wear-resistant coatings—NiCr-2%hBN, NiCr-12%cBN, and NiCr-2%hBN-12%cBN—on GTD-111 superalloy. The above coatings’ microstructure, microhardness, and tribological behavior were systematically characterized by scanning electron microscope, hardness tester, pin-on-disc wear device, and three-dimensional profiles. The hardness test results showed that the hBN coating has the lowest hardness (692 HV) due to its layered structure, and the hBN-cBN coating has the highest hardness (992 HV) due to its complex structure and the creation of inhomogeneous nucleation centers in the coating. The wear test results showed that the hBN coating has a lower coefficient of friction (COF) (0.49) than the hard cBN coating (0.53) due to its lubricating properties. Meanwhile, the wear rate of the hBN coating is lower than the wear rate of the hard cBN due to the weak forces of one in the B-N bond. However, the wear test results of hBN-cBN coating showed that the effects of hBN and the high hardness of cBN cause the formation of a coating with the lowest wear rate (0.22 × 10⁻⁶ mm³/N·m), COF (0.41), fluctuation, wear depth (17.2 µm), and wear volume loss (0.32 × 10⁵ µ³) compared to the other two coatings. In addition, in the hBN-cBN coating, due to the greater driving force for the inhomogeneous nucleation of the melt, a larger area of equiaxed grains was formed, which in turn had a significant effect on increasing the wear resistance. Full article

Conventional machines often face limitations due to complex controllers and bulky power supplies, which can hinder their reliability and operability. In contrast, self-excited movements can harness energy from a stable environment for self-regulation. In this study, we present a novel model of a self-rowing boat inspired by paddle boats. This boat is powered by a liquid crystal elastomer (LCE) turntable that acts as a motor and operates under consistent illumination. We investigated the dynamic behavior of the self-rowing boat under uniform illumination by integrating the photothermal reaction theory of LCEs with a nonlinear dynamic framework. The primary equations were solved using the fourth-order Runge–Kutta method. Our findings reveal that the model exhibits two modes of motion under steady illumination: a static pattern and a self-rowing pattern. The transition between these modes is influenced by the interaction of the driving and friction torques generated by photothermal energy. This study quantitatively analyzes the fundamental conditions necessary for initiating a self-rowing motion and examines how various dimensionless parameters affect the speed of the self-rowing system. The proposed system offers several unique advantages, including a simple structure, easy control, and independence from electronic components. Furthermore, it has the potential for miniaturization and integration, enhancing its applicability in miniature machines and systems. Full article

The requirement to improve energy efficiency is constantly driving the development of high-performance and eco-friendly friction modifiers (FMs). Herein, two innovative sulfur- and phosphorus-free melamine long-chain alcohol esters (Dodec-EG-CC and Dodec-CC) are reported as novel organic friction modifiers (OFMs). Over a wide temperature range of 100 °C to 200 °C, the synthesized melamine long-chain alcohol esters, which have exceptional thermal stability, dramatically lessen wear and friction of PAO4 base oil. Dodec-EG-CC particularly reduces friction by up to 50% and wear rate by approximately 92% within this temperature range. Detailed studies of the tribological properties at elevated temperatures demonstrate that the synergistic effect of the melamine structural unit coupled with ester groups significantly enhances adsorption properties of additives on metal surfaces, improving adsorption strength and lubricating film stability. The adsorption of additives on the metal surfaces is further confirmed by surface analysis and adsorption energy calculation, which serve as a key parameter for characterizing the binding strength between molecules and surfaces. These findings demonstrate the potential of the designed triazine-based derivatives, especially Dodec-EG-CC, as OFMs in effectively reducing friction losses in motor vehicle engines. This highlights their significant potential for industrial applications in improving energy efficiency and extending engine lifespan. These in-depth studies not only provide valuable insights for the molecular structure design of OFMs, but also advances the development of sustainable lubrication technologies. Full article

Worm drive belongs to the inclined plane transmission principle, and there is severe wear on the conjugate tooth surface. To reveal the wear mechanism and realize steel–steel meshing in the spiroid worm drive, the meshing performance model of conjugate tooth surface is established based on differential geometry theory and gear meshing principle, and the wear performance model is inferred by the Archard model and microscopic meshing performance. The wear performance of conjugate tooth surface is analyzed through the digital calculation, the pin-disk friction, and wear testing, as well as the spiroid worm drive prototype performance testing. The results show that there are good lubrication and anti-wear characteristics between the conjugate tooth surfaces, the wear amount on the right flank is twice that of the left flank, the wear depth at the loaded flank of the spiroid gear surface is smaller than that at the unloaded flank, as well as the feasibility of steel–steel meshing in worm drive has been confirmed. Full article

An ultra-low-power implantable body temperature sensor with a power consumption of 40.9 nW is presented. Deep body temperature measurement can be utilized for diseases such as inflammatory response due to implantable devices, treatment of traumatic brain injury, early monitoring of rejection after kidney transplantation, and monitoring of frictional heat in artificial joints, as well as health management such as ovulation cycles. Since it is implanted in the body and operated by a battery, it is very important to minimize power consumption. For low power consumption, we propose a dynamic virtual Wheatstone bridge technology for low-power transducer driving, and the simplified architecture is designed to operate at 0.6 V. The chip fabricated in a 180 nm CMOS process meets the ASTM E1112-00 specification for medical thermometers. That is, it can measure from 34 °C to 43 °C and meets the accuracy of ±0.1 °C between 37 °C and 39 °C. The measured power consumption at 37 °C is 40.9 nW. To verify practical application, a temperature sensor was implanted in a rat and body temperature changes before and after anesthesia were observed. Full article

The sliding electric contact that is established between the catenary wire and pantograph slider serves as the primary mechanism through which contemporary high-speed railway trains obtain their driving energy. The wear resistance of both the sliders and contact wires significantly influences their service life. This paper reports an experimental investigation into the electrical tribological characteristics of a copper–silver alloy contact wire in conjunction with a novel pure carbon slider, conducted under AC 300–500 A at sliding velocities ranging from 150 to 250 km/h. The experimental tests reveal that the coefficient of friction changes from 0.20 to 0.28, and the wear rate of the sliders varies from 0.0028 to 0.0147 g/km. The observed wear mechanisms for the slider encompass arc ablation, abrasive wear, delamination wear, and adhesive wear. Full article

This paper examines the energy efficiency of smart electric vehicles equipped with regenerative braking systems under challenging weather conditions. While Advanced Driver Assistance Systems (ADAS) are primarily designed to enhance driving safety, they often overlook energy efficiency. This study proposes a Weather-Adaptive Regenerative Braking Strategy (WARBS) system, which leverages onboard sensors and data processing capabilities to enhance the energy efficiency of regenerative braking across diverse weather conditions while minimizing unnecessary alerts. To achieve this, we develop driving style recognition models that integrate road conditions, such as weather and road friction, with different driving styles. Next, we propose an adaptive deceleration plan that aims to maximize the conversion of kinetic energy into electrical energy for the vehicle’s battery under varying weather conditions, considering vehicle dynamics and speed constraints. Given that the potential for energy recovery through regenerative braking is diminished on icy and snowy roads compared to dry ones, our approach introduces a driving context recognition system to facilitate effective speed planning. Both simulation and experimental validation indicate that this approach can significantly enhance overall energy efficiency. Full article

This article offers a clear and approachable introduction to the evolving landscape of money and the frictions developing between traditional government control and decentralized finance (DeFi). Tailored for readers with a basic awareness of cryptocurrency but limited familiarity with its broader implications, the article demystifies DeFi by explaining its core concepts including blockchain, Centralized Bank Digital Currencies (CBDCs), and the historical role of government regulation of money through central banking. Against this backdrop, it examines the transformative potential of DeFi, emphasizing the growing tension between the centralized authority of governments and the decentralized ideals driving this new financial model. While governments seek to maintain stability and control, individuals increasingly gravitate toward the more affordable, efficient, and inclusive solutions promised by DeFi. Designed to empower readers with a better grasp of the forces shaping the future of finance, this article underscores the importance of understanding the delicate interplay between governmental oversight and decentralized innovation. As the digital economy expands, this dynamic struggle will influence not only economic policies but also personal financial choices and access to resources. Full article

Soft robots have shown great application potential in human–computer interaction, scientific exploration, and biomedical fields. However, they generally face issues like poor load capacity. Inspired by the propagation and movement mechanisms of ocean waves, this study proposes a novel type of pneumatically driven crawling soft robot. An automated pneumatic drive system was first constructed for driving and controlling the crawling soft robot, and then the soft robot body was made using additive manufacturing and silicone molding. Experimental testing of the robot’s performance revealed that it can move efficiently on surfaces with varying friction coefficients and has a strong load-bearing capacity. This work is expected to provide a reference for the design of other soft robots. Full article