Design and Dynamic Analysis of the Recirculating Planetary Roller Screw Mechanism

The recirculating planetary roller screw mechanism(RPRSM)is a transmission mechanism that engages the screw and nut threaded by multiple grooved rollers.In this paper,frstly,the design method of RPRSM nut threadless area is proposed,and the equations related to the structural parameters of nut threadless area are derived.On this basis,the cross-section design method of roller,screw and nut is constructed according to the actual situation of engagements between the screw/nut and the roller.By adjusting the gap between the two beveled edges and that between the arc and the beveled edge,the accuracy of the thread engagements between the screw/nut and the roller can be improved.Secondly,to ensure the engagements of the screw/nut and the roller,the distance equation from the center surface of the diferent rollers to the end surface of cam ring is given.Thirdly,combined with the working principle and structural composition of RPRSM,the component model is established according to its relevant structural parameters,and the virtual assembly is completed.Finally,the 3D model is imported into the ADAMS simulation software for multi-rigid body dynamics.The dynamic characteristic is analyzed,and the simulated values are compared with the theoretical values.The results show that the contact forces between the screw/nut and the roller are sinusoidal,mainly due to the existence of a small gap between the roller and the carrier.The maximum collision forces between the roller and cam ring are independent from load magnitude.Normally,the collision force between the roller and the carrier increases as the load increases.When RPRSM is in the transmission process,the roller angular speed in nut threadless area begins to appear abruptly,and the position of the maximum change is at the contact between the roller and the convex platform of cam ring.The design of the nut threadless area and the proposed virtual assembly method can provide a theoretical guidance for RPRSM research,as well as a reference for overall performance optimization.

Unveiling protein corona composition:predicting with resampling embedding and machine learning

Biomaterials with surface nanostructures effectively enhance protein secretion and stimulate tissue regeneration.When nanoparticles(NPs)enter the living system,they quickly interact with proteins in the body fluid,forming the protein corona(PC).The accurate prediction of the PC composition is critical for analyzing the osteoinductivity of biomaterials and guiding the reverse design of NPs.However,achieving accurate predictions remains a significant challenge.Although several machine learning(ML)models like Random Forest(RF)have been used for PC prediction,they often fail to consider the extreme values in the abundance region of PC absorption and struggle to improve accuracy due to the imbalanced data distribution.In this study,resampling embedding was introduced to resolve the issue of imbalanced distribution in PC data.Various ML models were evaluated,and RF model was finally used for prediction,and good correlation coefficient(R^(2))and root-mean-square deviation(RMSE)values were obtained.Our ablation experiments demonstrated that the proposed method achieved an R^(2) of 0.68,indicating an improvement of approximately 10%,and an RMSE of 0.90,representing a reduction of approximately 10%.Furthermore,through the verification of label-free quantification of four NPs:hydroxyapatite(HA),titanium dioxide(TiO_(2)),silicon dioxide(SiO_(2))and silver(Ag),and we achieved a prediction performance with an R^(2) value>0.70 using Random Oversampling.Additionally,the feature analysis revealed that the composition of the PC is most significantly influenced by the incubation plasma concentration,PDI and surface modification.

Fe_3O_4@C nanoparticles as high-performance Fenton-like catalyst for dye decoloration

Water pollution has become serious environmental problem nowadays. Advanced oxidation processes(AOP) have been widely applied in water treatment.However, traditional Fenton reaction based on Fe2﹢-H2O2 system has obvious drawbacks, which limit its applications In this study, magnetic Fe3O4core-C shell nanoparticles(Fe3O4@C NPs) were prepared for the decoloration of methylene blue(MB) via the co-precipitation followed by the hydrothermal dehydrogenation of glucose. Fe3O4@C NPs showed high catalytic activity of the decoloration of MB through the decomposition of H2O2 in Fenton-like reactions. Fe3O4@C NPs had much higher activity than bare Fe3O4 cores, suggesting the coating of carbon enhanced the catalytic activity. The performance of Fe3O4@C NPs was better at lower pH and higher temperature, but was significantly inhibited in the presence of radical scavenger tertiary butanol. Fe3O4@C NPs could be magnetic separated and regenerated, and maintained with very good catalytic activity. The implication for the applications of Fe3O4@C NP-catalyzed Fenton-like reactions in water treatment was discussed.

From common biomass materials to high-performance tissue engineering scaffold: Biomimetic preparation, properties characterization, in vitro and in vivo evaluations

Converting common biomass materials to high-performance biomedical products could not only reduce the environmental pressure associated with the large-scale use of synthetic materials,but also increase the economic value.Chitosan as a very promising candidate has drawn considerable attention owing to its abundant sources and remarkable bioactivities.However,pure chitosan materials usually exhibit insufficient mechanical properties and excessive swelling ratio,which seriously affected their in vivo stability and integrity when applied as tissue engineering scaf-folds.Thus,simultaneously improving the mechanical strength and biological compatibility of pure chitosan(CS)scaffolds becomes very important.Here,inspired by the fiber-reinforced con-struction of natural extracellular matrix and the porous structure of cancellous bone,we built silk microfibers/chitosan composite scaffolds via ice-templating technique.This biomimetic strategy achieved 500%of mechanical improvement to pure chitosan,and meanwhile still maintaining high porosity(>87%).In addition,the increased roughness of chitosan pore walls by embedded silk microfibers significantly promoted cell adhesion and proliferation.More importantly,after subcutaneous implantation in mice for four weeks,the composite scaffold showed greater struc-tural integrity,as well as better collagenation,angiogenesis,and osteogenesis abilities,suggesting its great potential in biomedicine.