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Besides improving the generator torque and blade pitch controller, incorporating additional control actuations, such as a vibration absorber and active ballast, into the floating offshore wind turbine (FOWT) system is also promising for the motion mitigation of FOWTs. This work aims to study the catenary mooring length re-configuration effect on the dynamic behaviours of semi-submersible FOWTs. The mooring length re-configuration mentioned here is achieved by altering the mooring length with winches mounted on the floating platform, which is in a period of minutes to hours, so that the mooring tensions could be adjusted to reduce the aerodynamic load induced platform mean pitch. Control designs for both single mooring line and multiple mooring lines have been described and studied comparatively. In order to assess the motion mitigation performance of the proposed mooring line length re-configuration methods, fully coupled numerical simulations under different environmental cases have been conducted. Results indicate that the catenary mooring length re-configuration is able to reduce the platform pitch motion by up to 15.8% under rated condition, while careful attention must be paid to the scenarios where the catenary moorings become taut, which may lead to large load variations. [ABSTRACT FROM AUTHOR]

Nanomaterials based pressure sensors have obtained world‐wide research interest due to their promising potential applications in health monitoring, artificial intelligence, and electronic skin (e‐skin). Despite the recent progress in sensitivity and detection range of the pressure sensors, the relatively high thickness of the active films has obstructed their applications for e‐skin and degraded the comfortability as wearable devices. We hereby report for the first time a novel pressure sensor based on two‐dimensional metal oxide nanosheets where the gaps between neighboring nanosheets are adjustable. The pressure sensors show a sensitivity of up to 7.2 × 106 kPa–1, which is the highest value ever reported for a pressure sensor. Additionally, the sensor shows good repeatability and excellent stability. The pressure‐sensing ranges can be tuned by adjusting the coverage of the nanosheet film. This work presents an effective strategy to develop ultrathin pressure sensors. [ABSTRACT FROM AUTHOR]

Layered materials are promising candidates to serve for thermal insulation coatings because of their low out‐of‐plane thermal conductivity. The thin film preparation of the layered materials in layer‐by‐layer fashion can be realized by several solution processes. However, the layered materials suffer low thermal stability after the solution processes. Herein, we report a strategy to improve the thermal stability of the layered materials processed in solution. In this work, we studied the thermal stability of the lepidocrocite‐type titanate with various interlayer ions (Li+, Na+, K+, and Cs+) at elevated temperatures. We proved that the thermal stability of the titanate increased with the increase of the ionic radius. The Cs+ intercalated titanate can remain in its layered structure up to 1000°C, while the Li+ interacted titanate loses its structural stability at ~280°C. Our work suggests that increasing the size of the interlayer ions is an effective strategy to enhance the structural stability of layered titanates. [ABSTRACT FROM AUTHOR]

Insertion type material has been attracted plenty of attentions as the anode of sodium ion batteries (SIBs) due to the low volume change induced long cycle stability. H1.07Ti1.73O4 (HTO), a two‐dimensional layered material, is a new insertion type anode material for SIBs reported in this study. Layered HTO composites were decorated with rGO nanosheets via an electrostatic assembly method followed by hydrothermal treatment. When adapted as the anode material of SIBs, HTO@rGO composite exhibits an enhanced sodium ion storage behavior, including high rate capability and long cycle stability. It can deliver high capacities of 142.8 and 66.7 mA h g−1 at 100 and 10 000 mA g−1, respectively. Moreover, it can keep a capacity of 75.1 mA h g−1 at 5 A g−1 after even 5000 cycles, corresponding to a high capacity retention of 70.8% (0.0058% capacity decay per cycle). HTO exhibits a small volume expansion of 19.6% by in‐situ transmission electron microscopy (in‐situ TEM). The diffusion coefficient of sodium ions is increased from 1.77 × 10−14 cm2 s−1 in HTO composites to 4.80 × 10−14 cm2 s−1 in HTO@rGO composites. Our designed and synthesized HTO@rGO provides a new route for high rate and long cycle stable SIBs anode materials. [ABSTRACT FROM AUTHOR]

For main bearings of internal combustion engines, most of the wear occurs during the start-ups and stops. The popularity of the start–stop system in automobile engines, which is used to save fuel consumption during idling stage, makes the working condition of main bearings severer because more frequent starts and stops will be generated. Changes in the bearing surface caused by wear will directly affect the bearing's working performance. So in this study a transient mixed lubrication model and a wear model are coupled to analyze the influence of numerous start-ups and stops on the tribological performance evolution of engine main bearings. Starved lubrication of bearings before the oil supply is considered. The wear process is studied on the scale of surface topography and geometry. A main bearing in a four-stroke four-cylinder gasoline engine is studied under engine start–stop cycle conditions. The effects of temperature and lubricant grade on the transient tribodynamic behavior during the start-ups and stops are first investigated. Then the evolutions of surface characteristics and tribological performance of main bearings after numerous engine start-ups and stops are simulated. Results show that the temperature and lubricant grade can significantly affect the friction and wear of bearings. Hot start–stop condition leads to more serious asperity contact friction in the early stage of start-up, while cold start–stop condition generates more friction loss. The wear process of bearing surface is faster when applying oil with lower viscosity. And the impacts of engine start-ups and stops on bearing working performance are mainly seen in contact friction. [ABSTRACT FROM AUTHOR]

Cotton fabrics with hydrophilic-to-hydrophobic asymmetric surfaces are attractive as potential utilizable structures for functional garments. The spray-coating route could be deemed as a fast and simple way to achieve asymmetric surfaces. In this paper, SiO2 nanoparticles with size ∼ 205 nm were synthesized via the modified sol-gel method, and then modified with poly(vinylidene fluoride) (PVDF) to form a hydrophobic surface. The SiO2 nanoparticles modified with PVDF were uniformly deposited on the outer surface of cotton fabric aided with the robust air flow force from the sprayer. The morphology and chemical structures were characterized by scanning electron microscopy, mapping, atomic force microscopy, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. The results indicated that SiO2 nanoparticles were evenly deposited on the surface of cotton fibers and stable interfacial interaction occurred between SiO2 and PVDF molecular chains. The existence of SiO2 could increase the roughness of the fabric surface, which could enhance the water-repellent property of the coated fabrics. Furthermore, the water-repellent property and thermal insulation properties were evaluated via the water contact angle and thermal conductivity tests, respectively, and the results showed that 20 wt.% SiO2/PVDF fabric achieved a desirable level of contact angle, 136.6°, which was the largest water contact angle among all the samples, and the lowest thermal conductivity of 0.033 W/mK, resulting from the existence of SiO2 nanoparticles. Such a fast and simple spray-coating strategy could be widely introduced into asymmetric fabric modification, and such asymmetric fabrics with reasonable water-repellent and thermal insulating outer surfaces could act as candidates in the field of functional garments. [ABSTRACT FROM AUTHOR]