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• The magnesium alloy and 304 stainless steel were successfully joined via nanosecond pulsed laser welding. • Highest tensile shear force of 298.7 N was obtained at the speed of 30 mm/s. • Three fracture modes produced at various welding speeds were clarified. • The welding temperature field of magnesium/steel joint was simulated. Nanosecond pulse laser welding was performed on AZ31B magnesium alloy and 304 stainless steel to investigate the impact of welding speed on the joining process. The temperature field of the magnesium/steel laser welding process was simulated using COMSOL software. The findings revealed that a welding speed of 10 mm/s resulted in significant spattering and larger porosity defects in the joint due to excessive heat input. However, when the welding speed was increased to 30 mm/s, these defects disappeared, and the porosity decreased to a minimum, leading to an increased bonding area at the interface. As the speed increased, the heat input decreased, making it more challenging for the porosity to escape from the molten pool and resulting in the formation of larger pores. The shear force test results indicated that the highest shear force was 298.7 N at a welding speed of 30 mm/s. The reduction in porosity and greater penetration depth of the magnesium alloy contributed to the desired mechanical performance. Additionally, the fracture modes were classified as button pullout failure (BPF), base material tearing failure (BTF), and interface failure (IF). The outermost weld seam served as the initial fracture path for both BPF and BTF modes, with BTF ultimately fracturing in the steel base material during tearing. Oxide inclusions, porosity, and the angle of distortion contributed to the fracture path of IF. [ABSTRACT FROM AUTHOR]

Abstract In this manuscript, the longest O/N and S/N atoms containing heteroacenes (tetraazatetraoxodecacene (TAOD) and tetraazatetrathiodecacene (TATD)) with ten linearly fused rings have been synthesized and fully characterized. The X-ray crystal structures show that O/N atoms containing TAOD exhibits a linear structure, while S/N atoms containing TATD bends in S atom containing heterorings. Obviously, TAOD shows a higher fluorescence quantum yield in solution than that of S atom containing compound TATD. By simple reprecipitation method, TAOD and TATD self-assembly into different microstructures with microwires and microrods, respectively, which demonstrate distinctive non-linear optical properties depending on the orientation of transition dipoles. Graphical abstract Image 1 Highlights • The longest O/N (TAOD) and S/N (TATD) atoms containing heteroacenes with ten linearly fused rings were successfully prepared. • TAOD and TATD show different photophysical and electrochemical properties. • The microcrystals of TAOD and TATD exhibit distinctive non-linear optical properties depending on the orientation of transition dipoles. [ABSTRACT FROM AUTHOR]

Abstract: Spherical Fe3O4 nanocrystal clusters were prepared via a simple solvothermal method using FeCl2·4H2O and NaOH as starting materials. When sodium acetate (NaAc) was added into the reaction system, the final products turned from sphere to cube. The as-prepared clusters are uniform in size. The possible mechanism was proposed to elucidate the changes of the clusters shape. The chemical compositions were characterized by X-ray diffraction (XRD). The morphology was determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The magnetic properties were investigated on a superconducting quantum interference device (SQUID) magnetometer. [Copyright &y& Elsevier]

Abstract: Superparamagnetic magnetite microspheres with a hydrophobic surface were successfully prepared through a simple solvothermal method based on hydrolysis of iron–oleate complex in diphenyl ether in the presence of oleic acid as the ligands. The microspheres size and size distribution were analyzed by a laser diffraction particle size analyzing method using ZETASIZER. The morphology and crystalline structure of the products were characterized using transmitting electron microscopy (TEM), scanning electron microscopy (SEM), X-Ray diffraction (XRD), and the magnetic property was studied by a Quantum Design MPMS SQUID. TEM and SEM images showed that as-prepared spherical nanostructures are of about 140nm in sizes, which self-assembled by many 10nm primary magnetic nanoparticles. The XRD analysis revealed that the magnetic microspheres are composed of magnetite. The magnetic measurements demonstrated that the spherical nanostructures are superparamagnetic at room temperature with no magnetic remanence and coercive force. In addition, the microspheres can be well dispersed in various non-polar solvents due to their surfaces capped of hydrophobic surfactants in situ. [Copyright &y& Elsevier]

Abstract: Fe3O4@ZnO core–shell structured nanoparticles have been synthesized by a simple one-pot sequential polyol process. The nanoparticles have been investigated by powder X-ray diffraction (XRD), transmission electron microscope (TEM), energy-dispersive X-ray spectrometer (EDS) and physical properties measurement system (PPMS) of Quantum Design. [Copyright &y& Elsevier]

Engineered Cementitious Composites (ECC) utilize the bridging effect of high toughness fibers to improve the brittle failure of concrete materials, achieve the effective control of cracks in cementitious materials, and significantly improve the deformation capacity. In view of the multi-stage crack-blocking effect of different fibers incorporated in ECC materials, 91 ECC specimens of steel-polypropylene hybrid fiber by mixing steel fiber (SF) and polypropylene fiber (PPF) into cement-base are made in this paper. The specimens are tested in compression, tensile, bending and damping properties, respectively, which is of great significance to study the response of ECC structures under the earthquake action. The effects of the volume content of SF and PPF on the mechanical properties of ECC are studied in this paper. The results show that the cube specimen has better ductility than the prismatic specimen under monotonic compression, and there is no obvious brittle failure. With the increase of the volume content of SF to PPF, the compressive strength and elastic modulus of hybrid fiber ECC gradually increase, while the corresponding strain and axial compressive toughness gradually decrease; the tensile strength and tensile modulus increase, while the bending strength and damping ratio decrease. According to the test results, constitutive models of monotonic and repeated loading of hybrid fiber ECC suitable for finite element (FE) analysis are proposed. This investigation provides a theoretical basis and an experimental reference for further study of steel-polypropylene hybrid fiber ECC. • Steel fiber and polypropylene fiber are mixed as hybrid fiber of ECC. • The mechanical properties of ECC are investigate. • Volume content of steel-polypropylene hybrid fiber has influence on concrete material. • The hybrid fiber ECC cube has better ductility than that of prismatic. • Constitutive models of hybrid fiber ECC are suitable for finite element analysis. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tube (CFST) columns are widely used in structures where high bearing capacity and ductility are crucial. They offer several advantages over conventional steel or concrete columns, such as a high strength-weight ratio, better ductility, and increased resistance to buckling and compression. Also, seismic damage in CFST columns primarily occurs within the plastic hinge region at their base. Therefore, by improving the ductility specifically in this plastic hinge region, the seismic resilience of CFST columns can be significantly enhanced. In this paper, the use of steel-polypropylene hybrid fiber engineered cementitious composites (HECC) in the plastic hinge region of square CFST columns is proposed to improve their hysteretic performance. This paper presents an experimental study of the hysteretic behavior with three different local HECC-enhanced CFST (LHECFST) columns. Based on the test results, modeling was performed using ABAQUS, and the reliability of the FE model was verified. Following this, FE models with smaller HECC pouring height gradients were developed, and these CFST columns were parametrically analyzed. The results show that the seismic performance of CFST columns is improved by local enhancement with HECC. The pouring of HECC will reduce the slope of the peak load descending stage of the CFST column. In addition, the formulas for calculating the peak load of LHECFST columns with different axial compression ratios and HECC pouring heights were developed and the accuracy was verified by contrasting the data. • Hysteresis tests on concrete-filled steel tube (CFST) columns were performed. • The validation data were established by finite element analysis. • Engineered cementitious composites (ECC) reduce damage in plastic hinge region. • The deterioration of peak loads in CFST columns with ECC localized pouring is slow. • Methods are proposed for calculating the peak load of two-material CFST columns. [ABSTRACT FROM AUTHOR]

• A lightweight onboard measurement system for micro-UAV swarms based on sensor fusion and neural networks is proposed. • A collaborative relative positioning method based on DGO and DEKF is developed. • The system is implemented on a 150 g micro-UAV platform, demonstrating high precision and real-time capability. In recent years, the swarm of micro Unmanned Aerial Vehicles (micro-UAVs) is becoming a research hotspot. As the basis of swarm autonomous flight, traditional relative positioning methods typically rely on external base stations or onboard sensors of high power consumption, the vast majority of which are not feasible on resource-constrained micro-UAVs flying in a complex environment. This article proposes a lightweight relative positioning system implemented on a micro-UAV platform weighing 150 g. We have developed a distributed graph optimization (DGO) scheme fusing the results of the onboard Ultra-Wideband (UWB) module, camera, and inertial sensors. A Delay Extended Kalman Filter (DEKF) is utilized to mitigate communication delays and enhance accuracy. This scheme enables micro-UAVs to collaboratively compute the relative position graph in real-time. Through real-world experiments, our system has achieved a relative positioning accuracy of 0.167 m, exhibiting significant potential for future swarm applications. [ABSTRACT FROM AUTHOR]

Abstract Owing to their special optical and chemical properties, polymers with helical nanostructures are good candidates for constructing building blocks for various applications in analytical and biomedical science. While the chirality of conjugated polymers has been well studied, there are few reports on the chirality of polyurethanes (PUs). In particular, direct morphological observations of their chiral nanostructures are rare. In this work, PUs were synthesized using isosorbide (ISO) and isomannide (ISOM), derived from renewable feedstocks, as chiral building segments and 1,4-phenylenediisocyanate (4,4′-MDI) and para -phenylenediisocyanate (PPDI), which have rigid structures, as hard segments. The molecular structures and thermal properties of the PUs were characterized, as well as the nanostructures formed following their deposition on solid surfaces. Polymers with 4,4′-MDI segments had plate-like structures, whereas those with PPDI segments had rod-like structures, with ISO-PPDI-PU and ISOM-PPDI-PU exhibiting helical nanostructures, as confirmed by transmission electron microscopy and atomic force microscopy. Graphical abstract ISO-PPDI-PU polymers were synthesized and self-assembled to helical nanostructures, which were confirmed by atomic force microscopy. Image 1 Highlights • Polyurethanes with various chiral units and hard segments were fabricated. • The chiral building blocks were derived from renewable feedstocks. • The nanostructures formed by the polymers depended on the type of hard segment. • The formation of helical nanostructures was confirmed by atomic force microscopy. [ABSTRACT FROM AUTHOR]

Abstract: Biodegradable poly(l-lactide) (PLLA) has been covalently grafted onto the surface of magnetic multiwalled carbon nanotubes (m-MWCNTs) by in-situ ring-opening polymerization of lactide. The content of grafting PLLA can be controlled by adjusting the feed ratio of monomer to m-MWCNTs. FT-IR and Raman spectroscopy confirm that PLLA have been covalently attached to the sidewalls of m-MWCNTs. Thermal gravimetric analysis (TGA) indicates that the composites of PLLA grafted m-MWCNTs have a polymer weight percentage of ca. 25.6–33.7wt%. The scanning eletron microscopy (SEM) and transmission electron microscopy (TEM) are utilized to image the PLLA grafted m-MWCNTs, showing relatively uniform polymer layer coated on the surface of m-MWCNTs. The composites of PLLA grafted m-MWCNTs exhibit superparamagnetic behavior at room temperature and are aligned under a low magnetic field. [Copyright &y& Elsevier]