The paper investigates the micro asperity contact load ratios and lubrication states of the water-lubricated bearing. New coupled models with consideration of micro-scale asperity contact effects are ...put forward. The relevance of load ratio with transition of lubrication regimes under multi coupled structural parameters and operating conditions are established. The three-dimensional relationships between typical parameters and contact ratio under typical working conditions have been further studied. Characteristic parameters of lubrication regimes transition under multi coupled factors are investigated. The mechanism of regimes transition is revealed at the micro level. Experimental measurements verify the correctness of the revised model. Researches are beneficial for the definition of micro asperity contact load ratio and lubrication regimes transition for such bearings.
•The relevance of load ratio with transition of lubrication regimes under multi coupled structural parameters and operating conditions is explored.•The three-dimensional relationship between typical parameters and contact ratio under typical working conditions has also been studied.•Characteristic parameters of lubrication regimes transition under multi coupled factors is investigated.
Long non-coding (lnc) RNAs are non-coding RNAs longer than 200 nt. lncRNAs primarily interact with mRNA, DNA, protein, and miRNA and consequently regulate gene expression at the epigenetic, ...transcriptional, post-transcriptional, translational, and post-translational levels in a variety of ways. They play important roles in biological processes such as chromatin remodeling, transcriptional activation, transcriptional interference, RNA processing, and mRNA translation. lncRNAs have important functions in plant growth and development; biotic and abiotic stress responses; and in regulation of cell differentiation, the cell cycle, and the occurrence of many diseases in humans and animals. In this review, we summarize the functions and mechanisms of lncRNAs in plants, humans, and animals at different regulatory levels.
Among all inorganic halide perovskite photovoltaic materials, CsPbIBr2 exhibits the most balanced features in terms of bandgap and stability. However, the poor quality of solution‐processed CsPbIBr2 ...films impedes further optimization of cells performance. Herein, a facile intermolecular exchange strategy for CsPbIBr2 film is demonstrated, wherein an optimized methanol solution of CsI is spin‐coated on CsPbIBr2 precursor film in conventional one‐step solution route. It surprisingly produces full‐coverage and pure‐phase CsPbIBr2 films featured with average grain size of ≈0.65 µm, few grain boundaries, high crystallinity, preferable (100) orientation, stoichiometric composition along with favorable electronic structures for effective dissociation and transfer of carriers. Hence, the cost‐effective, carbon‐based all‐inorganic planar perovskite solar cells based on them, yield an optimized efficiency of 9.16% with a stabilized value of 8.46% in ambient air conditions that highlight a particularly superb open‐circuit voltage of 1.245 V, all of which represent the highest values reported in pure CsPbIBr2 based cells so far. Moreover, the optimized cell without encapsulation shows excellent long‐term stability because it can retain 90% over 60 days and 97% over 7 days of its initial efficiency, when is stored controllably in ≈45% relative humidity at 25 or 85 °C at zero humidity, respectively.
A carbon‐based all‐inorganic planar CsPbIBr2 solar cell with a record efficiency of 9.16%, an extremely high open‐circuit voltage of 1.245 V, and excellent long‐term stability is achieved by a facile intermolecular exchange strategy. Its impressive performance mainly derives from the desirable features of CsPbIBr2 film including full coverage, high crystallinity, preferable (100) orientation, and stoichiometric composition along with favorable electronic structure.
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•Transverse mechanical properties of unidirectional composites with microvoids are evaluated by finite element simulation.•Reduced order quantification of microstructures is ...established using two-point statistics and principal component analysis.•A machine learning and materials informatics approach is developed to predict the transverse mechanical properties.
The mechanical properties of composites are traditionally measured using numerical and experimental approaches, which impede the innovation of materials due to the cost, time, or effort involved. This study for the first time develops a machine learning-assisted model, which aims at predicting the transverse mechanical properties of unidirectional (UD) carbon fiber reinforced polymer (CFRP) composites with microvoids. To this end, the stochastic microstructures are generated by random sequential expansion (RSE) and hard-core model. And the transverse elastic modulus, transverse tensile strength and transverse compressive strength are computed by micromechanics-based finite element (FE) method. Then, the reduced order representation of microstructures is determined using 2-point spatial correlations and principal component analysis (PCA). Finally, a genetic algorithm (GA) optimized back propagation (BP) neural network is implemented to capture the potential nonlinear relationship between microstructure and transverse mechanical properties. The presented data-driven techniques can reproduce the FE simulation results with an R-value of 0.89 or greater. The excellent agreement between the predicted results and test datasets verifies the successful application of data science methodologies in elucidating the microstructure-property linkages of UD-CFRP composites with microvoids, and thus provides a promising tool for accelerating the smart design and optimization of composites.
Clinically, it is difficult to endow implants with excellent osteogenic ability and antibacterial activity simultaneously. Herein, the self-activating implants modified with hydroxyapatite (HA)/MoS
...coating are designed to prevent Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) infections and accelerate bone regeneration simultaneously. The electron transfer between bacteria and HA/MoS
is triggered when bacteria contacted with the material. RNA sequencing data reveals that the expression level of anaerobic respiration-related genes is up-regulated and the expression level of aerobic respiration-related genes is down-regulated when bacteria adhere to the implants. HA/MoS
presents a highly effective antibacterial efficacy against both S. aureus and E. coli because of bacterial respiration-activated metabolic pathway changes. Meanwhile, this coating promotes the osteoblastic differentiation of mesenchymal stem cells by altering the potentials of cell membrane and mitochondrial membrane. The proposed strategy exhibits great potential to endow implants with self-activating anti-infection performance and osteogenic ability simultaneously.
This paper presents a review-based comparative study of state-of-the-art technologies, technical challenges and research barriers, and development trends of gearboxes used in tidal current energy ...converters (TCECs). Currently, the development of commercial projects using TCECs is still in the demonstration phase. While many drivetrain designs and configurations of TCECs inherit from those of wind turbines, different operational constraints, e.g., high-torque and low-speed conditions, make TCECs potentially suffer from high failure rates in harsh deep-sea environments. Evidence of these potentially high failure rates highlights the need for adopting the most resilient drivetrain options with a high degree of maintainability. The gearbox option is a critical issue that needs to be addressed for the choice of the drivetrain configuration due to its longest downtime per failure among all drivetrain components of TCECs. The main purpose of this study is to review current gearbox technologies of TCECs with advantages and disadvantages as well as to identify future technical challenges and research barriers. Gearbox maintenance is also a focal point in this study. We present a discussion of the operation phase to highlight operational maintenance methods currently used in the tidal energy industry. This study will, therefore, address the critical issue by proposing a review-based gearbox option comparison and discussing potential solutions to reduce operation and maintenance costs of gearboxes of TCECs.
Ultrasmall palladium nanoparticles (1.5-2.5 nm) encapsulated in metal-organic frameworks (MOFs) have been prepared by introducing a palladium precursor into a highly porous and hydrothermally stable ...amine-functionalized UiO-66 (NH sub(2)-UiO-66) via a direct anionic exchange and subsequent H sub(2) reduction. The prepared PdatNH sub(2)-UiO-66 catalyst was then applied in the hydrodeoxygenation of vanillin (a typical model compound of lignin) at a low H sub(2) pressure in aqueous media. Excellent catalytic results (100% conversion of vanillin with exclusive selectivity for 2-methoxy-4-methylphenol) could be achieved over the developed 2.0 wt% PdatNH sub(2)-UiO-66 catalyst under mild conditions. Furthermore, the catalytic activity and selectivity were not affected after six reaction cycles indicating excellent stability and reproducibility of this catalyst system. It was found that the presence of free amine groups in the framework of NH sub(2)-UiO-66 plays a key role in the formation of uniform, well-dispersed and leaching resistant palladium nanoparticles within the MOF host. Moreover, the developed PdatNH sub(2)-UiO-66 exhibits a novel synergetic catalysis in the hydrodeoxygenation due to the cooperation between the well-dispersed metallic Pd sites and the amine-functionalized MOF support, in which Pd offers hydrogenation activity and the MOF support facilitates hydrogenolysis of the intermediate vanillin alcohol to the 2-methoxy-4-methylphenol product.
This article presents a stabilized level‐set topology optimization method for the design of a thermal‐fluid system. The steady‐state laminar Navier–Stokes equation and the convection–diffusion ...equation are used to model the thermal‐fluid problem. The compactly supported radial basis functions are employed to describe the fluid–solid interfaces. The extended finite element method is used to interpolate the material domain and the non‐slip interface conditions are weakly enforced by the Nitsche's method. To overcome the numerical instabilities during the optimization process, a distance‐regularized method based on adopting a modified energy potential functional is proposed and the signed distance property around the structural boundaries is obtained. In the numerical experiments, two‐dimensional numerical models considering minimizing the average or maximum temperature are used to reveal the validity and merits of the proposed method.
•A new method is proposed to improve the efficiency of error compensation for robots in aircraft industry.•The two-dimensional manifolds reduce the workspace's dimensionality from 6 to 2 to avoid the ...curse of dimensionality.•The continuity of robot's kinematic parameters and positioning errors in the new workspace are mathematically proved.•The feasibility of proposed method is validated by experiments conducted on a typical industrial robot.•The whole process of error compensation can be performed with the help of the integrated controlling system quickly.
To improve the efficiency of error compensation for robotic machining, this paper proposes a new method which contains the two-dimensional manifold that reduces the dimensionality of the workspace. The theory for error compensation in two-dimensional workspace is briefly described, which is based on the continuity of positioning errors. With two-dimensional manifold developed from robot posture optimization, the continuity of positioning errors and robot's kinematic parameters is theoretically proved in the two-dimensional space. The continuity of robot's kinematic parameters such as joint angles is also verified by simulations performed in Delmia and Matlab. To verify the effectiveness of proposed method, experiments have been conducted on a typical industrial robot. The results show that positioning errors are continuous in two-dimensional space which validates the feasibility of theory, and the average positioning error of end effector is decreased by more than 70% after compensation which meets the requirement of robotic machining.
The suitability of vertical axis wind turbines (VAWTs) in harnessing energy within a complex wind environment has increased their renewed interest. However, there still exists a huge knowledge gap ...about the aerodynamic performance of VAWTs operating in a turbulent flow regime. In this paper, an experimental method is presented for a deeper understanding of unsteady rotor aerodynamics under turbulent flow operating conditions. To carry out the investigation, we developed and tested a small-scale Savonius turbine in a wind tunnel. A systematic analysis of torque and power coefficients, including their variations at uniform flow, was also presented to predict the power performance. A mechanism to generate a turbulent flow was then created to analyze the effect of induced turbulence intensity on the aerodynamics and performance of the VAWT. Results revealed that the turbulence of the inflow impacted fluctuating aerodynamic loads on the turbine blade and, ultimately, its aerodynamic performance. In addition, simulations using a CFD code were performed to compare numerical data with experimental measurements. This analysis shows the effect of turbulence intensity on performance of small wind turbines, and the aerodynamics that causes the behavior.
•A wind tunnel mechanism to generate turbulent inflow is developed.•Effect of induced turbulent intensity on VAWT aerodynamic performance is analyzed.•CFD simulations are performed to compare numerical data with experimental measurements.•Turbulent inflow impacts fluctuating aerodynamic loads on turbine blade.
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