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Digital twin (DT) technology has become an effective means of industrial digital transformation due to its ability to realize virtual-real mapping, data fusion, etc. In recent years, the application of DT technology to the assembly process of complex mechanical products in multiple fields can effectively overcome the drawbacks of the current assembly method, which is a new strategy for achieving high-precision and high-efficiency intelligent assembly. However, there are few reviews of DT's intelligent assembly technology and application for complex mechanical products. Based on the composition of the DT assembly system, the paper systematically summarizes the critical technologies of DT assembly, including DT model representation of the assembly objects, DT model construction of the assembly process, and DT data collection/management. The application of the DT assembly model based on virtual and real fusion in online monitoring, quality prediction, process planning, real-time control, etc. is comprehensively reviewed. Finally, the challenges faced by DT intelligent assembly of complex mechanical products are described, and future research directions are predicted. [ABSTRACT FROM AUTHOR]

In order to harmonize the functions of both anticoagulation and accelerating endothelialization simultaneously, the micropatterns were fabricated by photoimmobilizing heparin, functionalized with a photoreactive moiety, on 3-aminopropylphosphonic acid modified titanium oxide (Ti-O) substrates. The amount of heparin immobilized on the surfaces was determined using the toluidine blue assay. And the surface morphology of the patterns was examined using scanning electron microscopy and surface profiler. The platelet adhesion and endothelial cell behavior in terms of adhesion, proliferation, and orientation were investigated in vitro. It is clear that the heparin patterns can reduce the platelet adhesion, and promote endothelial cells spreading and proliferation compared to nonpatterned heparin sample. Furthermore, the microstripes with appropriate size can induce the cells to elongate and arrange along the stripe direction. This may suggest a new modification method for blood-contacting device. [ABSTRACT FROM AUTHOR]

The driving factors of runoff changes can be divided into precipitation factor and non-precipitation factor, and they can also be divided into natural factor and human activity factor, In this paper, the ways and methods of these driving factors impacting on runoff changes are analyzed at first, and then according to the relationship between precipitation and runoff, the analytical method about impacts of precipitation and non-precipitation factors on basin’s natural runoff is derived. The amount and contribution rates of the two factors impacting on natural runoff between every two adjacent decades during 1956–1998 are calculated in the Yellow River Basin (YRB). The results show that the amount and contribution rate of the two factors impacting on natural runoff are different in different periods and regions. For the YRB, the non-precipitation impact is preponderant for natural runoff reduction after the 1970s. Finally, by choosing main factors impacting on the natural runoff, one error back-propagation (BP) artificial neural network (ANN) model has been set up, and the impact of human activities on natural runoff reduction in the YRB is simulated. The result shows that the human activities could cause a 77 × 108 m3·a-1 reduction of runoff during 1980–1998 according to the climate background of 1956–1979. [ABSTRACT FROM AUTHOR]

Uniform monodisperse nanospheres of tetra-kis(4-methoxylphenyl) porphynatemanganese (III) chloride [MnIII(TMOPP)Cl] of about 200 nm have been synthesized through a facile surfactant-assisted reprecipitation method at room temperature. Scanning electron microscopy, transmission electron microscope, infrared spectrum, ultraviolet-visible spectrum, and elemental analysis were adopted to characterize the as-prepared metalloporphyrin nanostructures. The influence factors in the reaction to the sizes and morphologies of porphyrin nanoparticles were discussed. The sizes of porphyrin nanoparticles were affected mainly by the porphyrin concentration and only monodisperse nanoshperes with high uniformity in sizes and shapes can self-assemble to form order two-dimensional superstructures. [ABSTRACT FROM AUTHOR]