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The self-tapping screw connectors are widely used in Cold-formed Steel (CFS) construction due to their rapid fastening with automatic power driving and ease of installation via a self-drilling process. However, there is a lack of a robust numerical method for the modelling of behaviours of screw fasteners bearing against steel sheets, where the connections can undergo different failure modes including fracture, bearing, tilting, pull-out and shear failure, particularly for CFS thin plates. A nonlinear explicit dynamic finite element (FE) model is developed in this paper to address this issue by validating the modelled load-deformation relationships and failure modes with available tests in literature. The proposed numerical model is improved in two aspects comparing to available research: firstly, a ductile fracture criterion was proposed that could address the fracture of ply metals subjected to complex stress state with less trial-and-error process. Secondly, the threads in the screw fasteners and ply sheets were carefully modelled where the inter-locking capacity between the screws and steel sheets were better taken into account, eliminating the need for an artificial friction factor. The FE modelled results were compared against the test results and showed good agreement in terms of connection strength and failure modes, including fracture, bearing, tilting, pull-out and shear failure. Finally, parametric studies were carried out to investigate the influence of steel sheet thickness and the screw outer diameter on the force–displacement relationships of the steel lap joints.

Hierarchical nitrogen-rich porous carbon (HNPC) was prepared by a simple and effective method using standard wheat straw as raw material. The as-synthesized HNPC material was found to possess high specific surface area. Because of its hierarchical porous structure, the HNPC material enables highly efficient lithium-ion transport through the electrolyte to the negative electrode, which shortens the diffusion path of the lithium-ion channel and reduces the internal resistance. The initial reversible capacity of the HNPC battery reaches 792.41 mAh·g−1 with coulombic efficiency of 88.61%. This type of HNPC material provides a potential anode for lithium-ion batteries with high specific capacity.

The ultrasonic annular array transducer usually has a stronger focusing acoustic field than the linear array and matrix transducer with the same number of array elements, and is more suitable for the detection of large thickness and high attenuation components. However, due to the special arrangement of array elements, the focusing beam cannot be deflected and has a large near field, which limits its application in practical detection. The element parameters of annular array transducer are often designed and analyzed according to the 2-D acoustic field model of a linear array transducer. Therefore, the 3-D acoustic field distribution model of the annular array transducer is established, and the influence of the element parameters on its spatial acoustic field focusing characteristics is analyzed. The design criteria of the array element division mode and element size are proposed, which can avoid the generation of high-energy side lobe and grating lobe, and have good axial acoustic field. Then, the influence of excitation aperture on the energy and size of focal spot at different depths is discussed. The dynamic focusing method with variable aperture of annular array is established, and the C-scan detection experiment is carried out on the addictive manufacturing titanium alloy specimen. The detection results show that the variable aperture method has better central amplitude consistency and imaging accuracy for different depth defects, and has better near surface detection ability than the fixed aperture method.

Electrohydrodynamic jet printing (EJP) is a developing additive manufacture technology that enables the fabrication of fine scaffolds directly from polymer solutions or melt. Timely solidification of the polymer jet is the key factor for the success of EJP process. In conventional solution-based EJP methods, it is usually achieved by rapid solvent evaporation and producing a scaffold with smooth filaments. In current study, by combining solution-based EJP with a cryogenic workbench, a cryogenic electrohydrodynamic jet printing (CEJP) system was developed, in which the polymer jet was frozen and solidified quickly at the freezing temperature rather than solvent evaporation. The feasibility and versatility of the CEJP system were verified by successful printing of scaffolds with different hole shapes and pore sizes. Meanwhile, the resulting scaffolds not only had a resolution in the range of 50–80 μm but also possessed oriented “ridges” and “valleys” on surface of the filaments, which was conductive to cell orientation. Therefore, this work provides a novel method to print fine scaffolds with extra surface topography.

A new and precise control printing method was developed for preparing homogeneous microspheres. Hydroxyapatite-sodium alginate (HA-SA) mixed suspension was used as printing material and CaCl2 solution was used as solidifying liquid to prepared ceramic microspheres by pneumatic extrusion printing technology. By adjusting the positive pressure, dwell time, and hydroxyapatite concentration, the influence of each parameter on the shape of printed microspheres was studied, and the suitable preparation parameters were determined. Then, the microspheres with uniform particle size distribution were successfully prepared in large quantities by selecting appropriate printing parameters. Then, the microspheres were dried and sintered at different temperatures. During the drying and sintering process, the microspheres showed obvious shrinkage, but still keep good sphericity. The phases of sintered microspheres are hydroxyapatite and calcium oxide. The microstructure shows typical hydroxyapatite grain characteristics.

The current study involves fabrication and characterization of HA scaffolds containing different copper (Cu) content by ion exchange and 3D extrusion deposition technique. The fabricated pure HA and Cu-doped scaffolds (Cu–HA) were characterized by mechanical behavior, SEM, EDS, XRD, and FT-IR studies. The results show that the Cu-doped HA scaffolds show stronger compressive strength. In addition, the antibacterial properties and biological properties of these scaffolds were investigated in vitro. The antibacterial test results show that the addition of Cu in the HA scaffolds increased antibacterial activity, and the antibacterial properties of scaffolds significantly increased with the addition of Cu. The biocompatibility test results show that the 15Cu–HA scaffolds treated with 15% CuSO4 curing solution significantly inhibited of cell growth on day 7, while the 5Cu–HA scaffolds treated with 5% CuSO4 curing solution the cells observed good grown state on day 7. The 5Cu–HA scaffolds show stronger mechanical behavior, increased antibacterial properties and lower toxicity rat bone marrow mesenchymal stem cells (BMSCs) on day 7. So, the developed 5Cu–HA scaffolds can be used as a good biomaterial for bone tissue engineering.

We propose a method for low-concentration detection of sodium chloride based on surface plasmon resonance (SPR). A novel prism coupling structure is designed for the sodium chloride concentration sensor, where a TiO2–ZnO composite film and a MoS2–GO hybrid nanosheet are chosen to enhance the surface plasmon resonance based on an Au nanowire array because of their unique properties in metal nanowire arrays and two-dimensional nanomaterials. Using the finite element method, we analyze the thickness of each medium layer for the structure designed in order to obtain the optimum value, so that the sensitivity of the sodium chloride concentration sensor designed is substantially enhanced. The optimum thickness of each medium layer is given, and the sensitivity of the sodium chloride concentration sensor based on the surface plasmon resonance can reach 0.260°/ (g/100 ml) concentration in the detection range of the sodium chloride concentration from zero to 15 g/100 ml. We derive the relationship between the sodium chloride concentration and the surface plasmon resonance angle in the detection range of the sodium chloride concentration.

An experimental program investigating the flexural behavior of an innovative dovetail ultra-high performance concrete joint for connecting precast ultra-high performance concrete slabs in composite bridges is reported in this study. Test parameters included interface treatment method, joint material, reinforcing bar overlapping form, and prestressing level. Specifically, a new steel wire mesh interface treatment was proposed, which could generate an additional fiber-bridging mechanism in the joint surface. An enhancement of 17.4%, 20.1%, and 50% on flexural cracking strength, ultimate strength, and ductility were obtained by using the steel wire mesh. Joint material showed no significant influence, while prestressing had obvious influence on the flexural behavior of ultra-high performance concrete joints. The post-cracking behavior, ductility performance, and stiffness degradation of the tested specimens were analyzed. Good deformability was obtained for the jointed ultra-high performance concrete slabs as the ratio of deflection to span was about 1/50 at failure. The post-cracking stiffness was retained at about 90% of the initial stiffness, while the ultimate stiffness was retained at about 10% of the initial stiffness. The research findings are useful in popularizing and applying the proposed innovative dovetail ultra-high performance concrete joints in composite bridges.

In this work, the polycaprolactone (PCL) scaffold with specific surface morphology was prepared by cryogenic printing technique. Biocompatible hydroxyapatite (HA) was added to the PCL matrix to enhance the surface properties and bioactivity of the scaffolds. The effects of HA on the mechanical strength and surface morphology were studied systematically. It was found that the extra surface morphology of filament enhanced the exposure of the HA particles, which induced a positive synergistic effect on surface properties. The wettability and bio-mineralization were significantly improved, and the protein adsorption capacity was 4.5 and 3.9 times than the ones of sample with 20%HA and smooth surface, respectively. Rat bone mesenchymal stem cells (rBMSCs) were used as the cell model to evaluate the cellular response to the specific surface of the scaffolds. The results showed that the scaffolds with 20–40% HA and extra surface had better proliferation ratio. The ALP assay also demonstrated that the synergistic effect was beneficial to cell osteogenic differentiation, and the ALP level was significantly higher than that of pure PCL and smooth PCL/HA composite scaffold samples at the 14th day. Therefore, the PCL/HA composite scaffold with extra surface morphology had better potential for bone tissue engineering.

Extrusion dripping is a facile method for the preparation of millimetre-size macrobeads. In this work, a pneumatic extrusion dripping system has been established to fabricate hydroxyapatite macrobeads with a controlled size. The size of the hydroxyapatite spherical beads could be tailored by adjusting the dripping parameters. This work is believed to provide an alternative method for the fabrication of hydroxyapatite macrobeads that can be used in bone regeneration.

In this study, a novel hybrid surface plasmon waveguide structure based on CdS nanowires and metal ridges was designed. The waveguide structure was simulated and analysed at a working wavelength of 490 nm based on the finite element method. The electric field distribution, mode characteristics, transmission length and quality factor of the waveguide were studied with geometric parameters. Results show that the comprehensive performance of the waveguide can be significantly optimised by appropriately adjusting the geometric parameters of the structure. Through the optimal parameter design, the effective mode field area reaches 0.008 λ 2 , the transmission length is 21,289 nm, and the quality factor is 702.12. This waveguide structure has great potential in the fields of optoelectronic communication and optical sensing technology.

This study presents an experimental and numerical investigation on the static behavior of headed stud shear connectors in ultra-high performance concrete (UHPC) of composite bridges. Four push-out specimens were tested. It was found that no cracking, crushing or splitting was observed on the concrete slab, indicating that UHPC slab exhibited good performance and could resist the high force transferred from the headed studs. The numerical and experimental results indicated that the shear capacity is supposed to be composed of two parts stud shank shear contribution and concrete wedge block shear contribution. The stiffness increment of a stud in UHPC was at least 60% higher than that in normal strength concrete. Even if the stud height was reduced from 6d to 2d, there was no reduction in the shear strength of a stud. Short stud shear connectors with an aspect ratio as small as 2 could develop full strength in UHPC slabs. An empirical load-slip equation taking into account stud diameter was proposed to predict the load-slip response of a stud. The reliability and accuracy of the proposed load-slip equation was verified by the experimental and numerical load-slip curves.

Porous fibers had better performance in many application fields for their larger surface area or extra nano topography than smooth ones. However, high vapor pressure solvents or selective removal of one phase from fastidious blended fibers were mostly used to fabricate porous fibers in electrospinning process, which made the process unfriendly and inconveniently. Here, a facial process on fabrication of porous fibers was developed by integrating the principles of thermally induced phase separation with the self-made cryogenic electrospinning system (CES) which can provisional solidify the polymer jet on the freezing collector. For demonstration, the polymer solution of Polycaprolactone (PCL) with solvent of glacial acetic acid was chosen. The PCL porous fibers with diameter of 3.29 ± 0.42 μm were successfully prepared at the height of 90 mm and freezing temperature of −3.6 ± 0.3℃ on collector in room environment. Furthermore, the pores on the surface of fibers exhibited two types: pits and polygon concaves. The pits were induced by phase separation at freezing temperature and the polygon concaves were due to the interaction of residual solvent with ice crystals on surface of silicon wafer or metal collector recruited from the air moisture. Generally, this process was suitable to polymer solutions with solvents of low vapor pressure but high freezing point.

In this paper, the electromagnetically induced transparency (EIT) effect of graphene nanostructures was studied by numerical methods. Numerous branch structures were added to the sides of the graphene/medium/graphene waveguide, and the Fabry-Perot resonators were formed between adjacent branches due to the phase coupling effect. The back and forth oscillation of electromagnetic waves in the cavity significantly enhanced the transmitted light in a narrow band. Thus, an output spectrum similar to the EIT effect was produced. The output spectrum can be further adjusted by the gate voltage with the unique electrically adjustable properties of graphene. The surface of plasmon exhibited stronger locality in graphene nanostructures than metals. Thus, graphene-based electro-optical devices were more compact and integrated in the deep sub-wavelength scale. The proposed graphene nanostructures facilitated the implementation of a variety of high performance electro-optical devices, including multi-channel selective filters, sensors, and modulators.

The bovine hydroxyapatite (BHA) was applied to prepare biological tissue engineering scaffolds by the method of extrusion freeforming. To achieve this goal, BHA were added to sodium alginate (SA) solution to form a slurry system in appropriate proportion. The resulting mixtures were fabricated to be a kind of controllable and porous scaffolds followed with cross-linking in 5% calcium chloride (CaCl2) solution for 24 h. After that, the scaffolds were sintered in air at 1 000, 1 100, 1 200 and 1 300 °C for 5 h. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies were performed on the scaffolds to analyze its microstructure and constituent. To explore the effect of sintering temperature on scaffolds, the compressive strength, volume shrinkage and water absorptivity of BHA-SA composite scaffolds after sintering were investigated. The research tests indicated the feasibility of applying BHA powder to 3D printing. Besides, the scaffolds sintered in a respectively lower temperature possess much more pores and performed higher water absorptivity, which means better cellular affinity. And scaffolds sintered between 1 100 and 1 200 °C presents higher compressive strength.

An in-fiber integrated sensor array with the embedded weakly reflective joint surface is proposed and demonstrated. The weak reflector is formed of a single-mode fiber (SMF) and a double-cladding fiber (DCF), whose cores have different refractive index. A sensor array based on this structure is sensitive to strain and temperature, and it has the ability to achieve quasi-distributed measurements. Therefore, it can be used for structural health monitoring. Besides that, without any connector, the sensors were integrated in a fiber. Consequently, they are more suitable for a harsh test environment (space limitation or high temperature).

Electrical treatment is a useful method for reducing viscosity of waxy crude oil. Molecular dynamics simulation was employed to study the influence of electric field on viscosity of waxy crude oil and micro properties of paraffin. The waxy crude oil model consists of light oil and 24.9% by weight of paraffin. The simulation results show that viscosity decreases when electric field is applied. The larger the electric field intensity, the greater the decreasing extent of viscosity. The electrical viscosity-reducing effect is better at lower temperatures. The radial distribution function and diffusion coefficient were analyzed for explaining the reason of viscosity decreasing. The radial distribution function results confirm that electric field promotes aggregation of paraffin molecules. Diffusion coefficient increases with the increase of electric field intensity. At the same temperature, the higher the electric field strength, the larger the increasing extent of diffusion coefficient. In a certain electric field intensity, the lower the temperature, the greater the increasing extent. The changing tendency of diffusion coefficient is consistent with the trend of viscosity reduction under electrical treatment. It is suggested that the change of diffusion coefficient is the main reason for electrical viscosity-reducing effects, the contribution of aggregation is smaller than increasing of diffusion coefficient.

In human, strontium (Sr) follows the same physiological pathway as calcium and thus could be used for improving the bioactivity and osteoconductivity of hydroxyapatite (HAp) in bone tissues. Similarly, iron (Fe) can potentially play an important role in bone remodeling due to its magnetic properties. Therefore, the current study was aimed to simultaneously co-substitute Sr2+/Fe3+ in HAp nanoparticles for various potential biomedical applications. The Sr2+/Fe3+ co-substituted HAp nanoparticles were systematically synthesized through sonication-assisted aqueous precipitation method. The as-synthesized nanoparticles were evaluated for different physicochemical and biological properties. X-ray diffraction (XRD) patterns of Sr2+/Fe3+ co-substituted HAp nanoparticles confirmed their phase purity and showed hexagonal-like structure. Scanning electron microscope (SEM) micrographs showed an agglomerated rod-like morphology of HAp nanoparticles which contained pores consisted of small spheroids. The nanoparticles displayed magnetization (Ms) reliance on the loading level of mole % (X = Fe3+) and exhibited tunable porosity and microhardness (Hv) upon heat treatment. The nanoparticles showed less than 5% hemolysis demonstrating high blood compatibility with high in vitro bioactivity performance. The multifunctional properties of synthesized nanoparticles make them a potential candidate for various biomedical applications; including bone grafting and guided bone regeneration, targeted drug delivery, magnetic resonance imaging, and hyperthermia based cancer treatment.

This paper uses the linear-elastic Theory of Critical Distances (TCD) to verify and quantify the analysis of a particular central fracture mode occurring in the classical double-cracked flat plate specimen subjected to mixed mode I/mode II loading. Analytical formulae for estimating the critical loading condition for such a special central fracture mode of double-cracked flat plate specimen are derived using both standard elastic beam theory and the TCD. The influence of the crack length, specimen geometry and material parameters on the critical loading angle for such a special central fracture mode is discussed in detail. Finally, in order to verify the proposed central fracture prediction formulae, linear elastic stress analyses for two double-cracked flat plate specimens made of different materials and having different loading angles were conducted using finite element analysis. The results in this study confirm the possibility of interior fracture modes and provide insight on the mechanism of analogous interior fracture occurring in practical applications.

Surface states on TiO2 photoanodes are usually considered to hinder the photoelectrochemical (PEC) water splitting via slowing charge transport and increasing charge recombination. Here, we found that electrochemically doping the TiO2 nanotubes electrode at a potential negative than its flat band potential will induce the insertion of protons into the lattice of TiO2 via a reaction of TiIVO2 + e− + H+ = TiIIIO(OH) to form the surface states. Photoelectrochemical/electrochemical tests confirmed that the surface states (Ti-OH) are an important photogenerated electron transfer route, significantly increasing charge separation efficiency, and hence contributing to the PEC performance enhancement. In addition, we have made a self-consistent explanation on Mott-Schottky (M–S) plots of the TiO2 nanotubes electrode, demonstrating that the M–S measurement is able to accurately describe electron filling and extraction into/from surface states and not suitable to determine the flat band potential of nanostructured TiO2 electrodes. Our results offer a new insight to understanding the role of surface states during the charge separation, transfer, and injection processes of the water splitting reaction.

A novel perovskite hybrid surface plasmon waveguide structure is designed. Established its physical model and introduced its theoretical basis in detail. Based on the finite element method, the mode characteristics, quality factor, and gain threshold of the waveguide structure are analyzed with geometric parameters. The results show that the optical field constraint of the waveguide can reach a good deep sub-wavelength level under the optimal operating wavelength of 1550nm. By adjusting the waveguide design parameters, the high quality factor, low energy loss, low threshold limit and ultra small effective mode field area are obtained. Compared with the hybrid waveguide structure proposed in the current research results, this structure has stronger optical field limiting ability and microcavity binding ability. The waveguide structure can provide theoretical and technical support for the development of new efficient nano laser devices, and has a good application prospect.

Fiber-reinforced polymer (FRP) bar-reinforced unsaturated polyester resin concrete (UPC) can solve the problem of rebar corrosion in ordinary reinforced concrete members. However, it has not been widely used in engineering practice because there have been few studies conducted on the bond behaviors of FRP bar and UPC, and the interaction mechanisms between FRP bar and UPC have not been well understood. A series of pull-out tests are conducted on FRP bar-UPC specimens to study the bond behaviors between these two materials. Parametric studies are also carried out to investigate the effects of FRP bar diameter, fiber type, type of surface treatment, concrete cover thickness, and interfacial bond length between the two. Three failure modes of the specimens are observed from pull-out tests, i.e., FRP bar pull-out, tensile failure of FRP bar, and UPC split. A new constitutive model is, therefore, proposed to predict the bond stress of FRP bar and UPC in the residual stage, and the proposed model is finally verified by test data reported in this study.

Graft reconstruction of the mandible is an important approach that aims at improving the appearance and functionality of defected mandibles. The traditional implant materials are generally bioinert, non-degradable, and that they lack favorable pore structures for cell proliferation, which limit their clinical application. In this study, we used boron-containing bioactive glass which was combined with a three-dimensional (3D) printing technology to construct an osteoinductive implant scaffold, according to the imaging instructions of CT scan on bone defects. Here, the boron-containing bioglass scaffold (B-BGs) was prepared through sol-gel processing and a 3D print technique. Different boron content of borosilicate bioglass was prepared by incorporating B2O3 (molar: 19.4 and 38.8%) into 58S bioglass to replace parts of SiO2. For fabricated mandible implants through three-dimensional 3D printing of B-BGs (size: 8 × 2 mm; pore size: 250 μm) modified with borosilicate bioglass powder and sodium alginate. Notably, the compressive strength of the B-BGs was about 3.8 Mpa, which supported mandibular activity. Subsequently, the excellent biocompatibility of B-BGs was confirmed using cytotoxicity in vitro studies. Finally, data from in vivo experiments demonstrated that the B-BGs could promote bone regeneration and they could almost get completely degraded within 4 weeks. Our results showed that the boron-containing bioglass could repair mandibular defects.

A tunable Fano resonance based on a microring resonator is proposed. The double microring is nested in parallel in the U-shaped feedback waveguide with the graphene embedded in part of the waveguide as the active modulation region of Fano resonance. When different voltages are applied to the graphene in the feedback waveguide or microrings, the Fano resonance exhibits different and asymmetrical shapes and has a larger extinction ratio than the traditional Lorentz shape. The maximum extinction ratio of the proposed device is up to 71.50 dB. The proposed structure will have a wide application in sensors, switches, and integrated optoelectronic devices.

In the current study, Sr/Fe co-substituted hydroxyapatite (HAp) bioceramics were prepared by the sonication-assisted aqueous chemical precipitation method followed by sintering at 1100 °C for bone tissue regeneration applications. The sintered bioceramics were analyzed for various structural and chemical properties through X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy, which confirmed the phase purity of HAp and Sr/Fe co-substitution into its lattice. The Vickers hardness measurement, high blood compatibility (less than 5% hemolysis), and ability to support the adhesion, proliferation, and osteogenic differentiation of human mesenchymal stem cells suggest the suitability of Sr/Fe:HAp bioceramics for bone implant applications. The physicochemical analysis revealed that the developed Sr/Fe:HAp bioceramics exhibited a polyphasic nature (HAp and βTCP) with almost identical structural morphology having a particle size less than 0.8 μm. The dielectric constant (ε') and dielectric loss (ε″) were potentially affected by the incorporated foreign ions together with the polyphasic nature of the material. The Sr/Fe co-substituted samples demonstrated extended drug (5-fluorouracil and amoxicillin) release profiles at the pH of physiological medium. The multifunctional properties of the developed HAp bioceramics enabled them to be an auspicious candidate for potential biomedical applications, including targeted drug-delivery applications, heating mediator in hyperthermia, and bone tissue repair implants.

In this study, borosilicate bio-glass (BG) was incorporated into magnesium phosphate cement (MPC) for the purpose of developing an injectable and bioactive composite cement with suitable physicochemical and biocompatible performance. Results show that the BG-incorporated MPC possesses an excellent injectability, and can be used to fill in different 3D printed defect models using a syringe with a moderate setting time. Meanwhile, BG can retard the setting time and adjust the exothermic temperature of MPC. When the MPC/BG ratio was 3:1 (MPC3-BG), its corresponding setting time, peak temperature, anti-washout ratio and compressive strength were 9.9 ± 0.7 min, 45.8 ± 1.6 °C, 87%-90% and 13.5 MPa, respectively, which were suitable for injection and bone reparation. Characterizations of MPC3-BG showed that it had a faster degradation rate than MPC and the functional ions of boron and silicon could be released from the dissolution of the composite cement. In vitro and in vivo experiments also demonstrated that MPC3-BG had a stimulatory effect on the cell proliferation and new bone regeneration.

In this paper, a grating-coupled surface plasmon resonance concentration sensor employing a gold and indium tin oxide (Au/ITO) nanoparticle composite instead of metal is proposed. The structure and material parameters of the sensor are discussed and analyzed. Taking the ethylene glycol concentration as an example, the influence of the nanocomposite on the wave vector matching, the influence of the refractive index of the medium to be tested and the influence of the concentration on the refractive index were analyzed in detail. The experimental results show that when the sensor is used for the measurement of ethylene glycol concentration, the correlation coefficient between the concentration and the refractive index is as high as 0.999995. The fitting curve and data correlation are good, and the sensitivity has a good linear relationship with the sensitivity. Therefore, the sensor structure proposed in this paper can be used to accurately measure the trace concentration of liquid, and its sensing mode has certain reference value for the measurement of general trace fluid concentration.

Earlier reports of fabricating 3D porous PCL scaffolds for tissue engineering applications were overshadowed by several limitations such as additional molds cost, relatively low efficiency, and lacking process control. In present study, combined extrusion-based cryogenic 3D printing (ECP) (−20 °C) and subsequent freeze-drying approaches were employed to facilely fabricate polycaprolactone (PCL) scaffolds, with high porosity and fidelity. Freeze-drying caused shrinkage of the scaffolds along X, Y, and Z-axes to some extent. The porosities of CP600, CP800, and CP1000 were found to be 64.0 ± 1.2%, 70.1 ± 1.3%, and 74.3 ± 0.6%, respectively. The fabricated scaffolds were characterized for various structural features and compared with the ones fabricated through traditional extrusion-based melt 3D printing (EMP). The crystallinity of PCL in ECP scaffolds was lower (57.1 ± 2.2%) than EMP scaffolds (69.8 ± 1.3%). The ECP scaffolds showed high alkaline degradation, but low compression properties. The ECP scaffolds promoted the adhesion and proliferation of MCT3T-E1 cells with well-spread morphology on the porous filaments. Together, these features justify the suitability of printed PCL scaffolds for potential TE applications. Keywords: Extrusion-based cryogenic 3D printing, Polycaprolactone, Glacial acetic acid, 3D scaffold, Tissue engineering

Sluggish water dissociation kinetics on nonprecious metal electrocatalysts limits the development of economical hydrogen production from water–alkali electrolyzers. Here, using Co3N electrocatalyst as a prototype, we find that during water splitting in alkaline electrolyte a cobalt-containing hydroxide formed on the surface of Co3N, which greatly decreased the activation energy of water dissociation (Volmer step, a main rate-determining step for water splitting in alkaline electrolytes). Combining the cobalt ion poisoning test and theoretical calculations, the efficient hydrogen production on Co3N electrocatalysts would benefit from favorable water dissociation on in-situ formed cobalt-containing hydroxide and low hydrogen production barrier on the nitrogen sites of Co3N. As a result, the Co3N catalyst exhibits a low water-splitting activation energy (26.57 kJ mol–1) that approaches the value of platinum electrodes (11.69 kJ mol–1). Our findings offer new insight into understanding the catalytic mechanism...

The Polycaprolactone (PCL) fibrous scaffolds in nano to micro scale have been considered as excellent templates for cell culture and tissue growth. The hydrophobic nature of the PCL, however, yields low initial cell seeding density, heterogeneous cell spreading and slow cell growth rate. Therefore, in this study the surface hydrophilic fibrous scaffolds were directly fabricated by the electrospinning of PCL solutions with small quantities (0.5–5%) of Pluronic F127 (PEO100-PPO65-PEO100) dissolved in benign solvent of glacial acetic acid. The clear and miscible solutions were achieved by controlling the proper F127 content in the blend solutions. The continuous and smooth fibers with average diameters from 0.71 to 1.43 μm made up the fibrous scaffolds in non-woven mode. Then the water wetting angle of the scaffolds could be adjusted from 126° to 0° by varying F127 content owing to its hydrophilic PEO chains presented on surface the blended fibers. Finally, it was demonstrated that the blended fibrous scaffolds with the F127 content less than 1% exhibited better cell attachment, proliferation and spreading performance than those of pure PCL scaffolds.

For photoelectrochemical (PEC) water splitting, the interface interactions among semiconductors, electrocatalysts, and electrolytes affect the charge separation and catalysis in turn. Here, through the changing of the bath temperature, Co-based oxygen evolution catalysts (OEC) with different crystallinities were electrochemically deposited on Ti-doped Fe2O3 (Ti–Fe2O3) photoanodes. We found: (1) the OEC with low crystallinity is highly ion-permeable, decreasing the interactions between OEC and photoanode due to the intimate interaction between semiconductor and electrolyte; (2) the OEC with high crystallinity is nearly ion-impermeable, is beneficial to form a constant buried junction with semiconductor, and exhibits the low OEC catalytic activity; and (3) the OEC with moderate crystallinity is partially electrolyte-screened, thus contributing to the formation of ideal band bending underneath surface of semiconductor for charge separation and the highly electrocatalytic activity of OEC for lowering over-pot...

Magnetic treatment is a widely used physical treatment technique in oilfields. The influencing mechanism of magnetic field on waxy crude oil has drew much attention in recent years. Molecular dynamics simulation was employed in this paper to study the influence of magnetic field on waxy crude oil. The waxy crude oil model consists of light oil and 24.9% by weight of paraffin. The simulation results showed that the density of waxy crude oil model firstly decreased and then increased with the strengthening of magnetic field intensity, while the diffusion coefficient increased in low magnetic field intensity and decreased in high intensity. Viscosity was calculated by Rouse Model. The reduction of viscosity only appeared within a specific range of magnetic field intensities, mainly concentrated on the low intensities. The viscosity increases when the range is overstepped, which is supposed to be the reason of the unstable effects of magnetic treatment. The aggregation of paraffin molecules in magnetic field was proved by analysing the radial distribution function. The analysis of energy represented that the magnetic field had greater influence on molecular morphology than distances between molecules. The simulation results provide micro-perspective of waxy crude oil in the presence of magnetic field, which help to offer the mechanism explanation of magnetic treatment effects.

Graphene-based electrocatalytic materials are potential low-cost electrocatalysts for the oxygen evolution reaction (OER). However, substantial overpotentials above thermodynamic requirements limit their efficiency and stability in OER-related energy conversion and storage technologies. Here, we embedded CrN crystals into graphene and in situ electrochemically oxidized them to construct graphene materials with encapsulated Cr6+ ions (Cr6+@G). These Cr6+@G materials exhibit the lowest OER overpotential of 197 mV at 10 mA cm−2 and excellent stability over 200 h at a high current density of about 120 mA cm−2 in an alkaline electrolyte. Spectroscopic and computational studies confirm a stable ion coordination environment significantly benefiting the downshift of the graphene Fermi level via hybridization of C p orbitals with d orbitals of Cr6+ ions that enhances the OER activity and stability.

The control of interfacial interaction between polymers and fillers is essential for the fabrication of high-performance polymer composites. In this work, poly(ether-ether-ketone)/silica (PEEK/SiO2) and PEEK/SiO2/graphene oxide (GO) composite were prepared by ball milling-ultrasonic dispersion combined with melt extrusion injection molding. GO nanosheets were introduced as the interfacial enhancer to improve interfacial binding between SiO2 and PEEK. Mechanical tests showed that the incorporation of SiO2 and GO greatly optimized the modulus, strength, and fracture toughness of the composites. The tensile strength and Young's modulus of the PEEK/SiO2 composites increases with the increase of SiO2 content. The maximum tensile strength and Young's modulus of the PEEK/SiO2 composites are approximate 95.9 ± 0.6 MPa and 4.007 ± 0.005 GPa at 30 wt% of SiO2, an increase of 6.4% and 21.2% than that of pure PEEK. The maximum tensile strength and Young's modulus of the PEEK/SiO2/GO composite are further improved to approximate 101.5 ± 0.7 MPa and 4.62 ± 0.08 GPa at a GO content of 1.5% wt, which is 12.6% and 39.4% higher than that of pure PEEK. In addition, SEM images show that numerous HA formed on the surface of the PEEK/SiO2/GO composite after immersion in SBF for 7 days, and the HA layer becomes gradually thicker after 14 days, implying the good osteogenic activity of PEEK/SiO2/GO composites. Therefore, these results suggest that the use of GO as a novel filler surface modifier for the preparation of high-performance composites may become a novel interfacial design strategy for the development of high-performance composites.

The plasmon resonance effect of metal nanoparticles (NPs) offers a promising route to improve the solar energy conversion efficiency of semiconductors. In this study, it is revealed that hot electrons generated by the plasmon resonance effect of Au NPs tend to inject into the surface states instead of the conduction band of Fe2 O3 photoanodes, and then severe surface recombination occurs. Such an electron-transfer process seems to be independent of external applied potentials, but is sensitive to metal-semiconductor interface properties. Passivating the surface states of Fe2 O3 with a noncatalytic Al2 O3 layer can construct an effective resonant energy-transfer interface between Ti-doped Fe2 O3 (Ti-Fe2 O3 ) and Au NPs. In such a Ti-Fe2 O3 /Al2 O3 /Au electrode configuration, the enhanced photoelectrochemical (PEC) water-splitting performance can be attributed to the following two factors: 1) in the non-light-responsive wavelength range of Au NPs, both the relaxing Fermi pinning effect of the Al2 O3 passivation layer and the higher work function of Au enlarge band bending; thus promoting the charge separation; and 2) in the light-responsive wavelength range of Au NPs, the effective resonant energy transfer contributes to light harvesting and conversion. The interface manipulation proposed herein may provide a new route to design efficient plasmonic PEC devices for energy conversion.

Pyrolysis of supramolecular assembly precursor is a promising method to prepare graphite carbon nitride (g-C3N4), and the topological structure of the precursor assemblies largely determine the morphology and photoelectric properties of g-C3N4. In this paper, uniformly and highly porous g-C3N4 nanotubes were synthesized under the assistance of 1,5-naphthalene disulfonic acid (NA) through the melamine (MA)-cyanuric acid (CA) precursor self-assembly strategy. The as-synthesized g-C3N4 nanotubes in the presence of 75 mg/L NA (MNCA-75) exhibited the highest BET surface area (SBET) of 100.40 m2/g, and the smallest band gap (Eg) of 2.31 eV. 10 mg/L of sulfamethoxazole (SMX) was completely degraded within 120 min with the MNCA-75, and the degradation reaction conformed to pseudo-first-order kinetics. This paper reported a facile but effective method to prepare highly porous g-C3N4 nanotubes with large surface area and excellent photocatalytic performance.

The Fifth Nanjing Yangtze River Bridge had adopted accelerated bridge construction utilizing precast systems to connect the prefabricated plate with the cast-in-place ultra-high performance concrete (UHPC) wet joint. Wet joints are prone to crack under fatigue load. In this study, the steel wire mesh (SWM) treatment method was adopted to enhance the interface crack resistance, and add coarse aggregate (CA) to UHPC to reduce cost. Decks were tested under static and fatigue loadings to study the effects of CA, SWM interface treatment, and stress level on fatigue performance. Results indicate that the fatigue performance of wet joints using UHPC with CA was similar to that using regular UHPC. Dovetail wet joints using SWM interface treatment effectively guarantee the bridging effect of the fiber at the interface and disperse fatigue cracks. Overloading affected the fatigue performance, and the fatigue damage was linear to the upper limit of stress when the stress ratio was fixed. Secant stiffness was used to evaluate the fatigue damage of decks, and the calculated damage was in good agreement with the actual bearing capacity loss. This study verified that the innovative dovetail wet joint is practical, economical, and guarantees fatigue performance.

Recently, additive manufacturing is one of the most focused research topics due to its explosive development, especially in manufacturing engineering and medical science. In order to build 3D complex scaffolds with multi-biomaterials for clinical application, a new 3D multi-nozzle system with dual-mode drives, i.e. ejection and extrusion was developed. In this paper, much effort was made to gain fine control of droplet and excellent coordination during fabrication. Specifically, the parameters that influence the size and stability of droplet most was intensively studied. Considering that the biomaterials used in the future may have much difference in properties, the combination of parameters was investigated to facilitate the settings for certain-sized droplets, which are potentially eligible for bio-printing. The dispensing nozzles can work well both in independent and convergent mode, which can be freely switched. Outstanding to the most currently used 3D bio-printing techniques, this system can fabricate scaffolds with multimaterials of both low viscosity (by pneumatic dispensing) and high viscosity (through motor extrusion). It is highly expected that this system can satisfy clinical application in the near future.

This paper assesses and evaluates the detrimental effect of standard and complex geometrical features on the static strength of samples made of Q460 steel. The experimental results generated by testing four types of notched specimens were analyzed using the Theory of Critical Distances (TCD). The considered configurations included uniaxial tension tests on standard notched round bars and double-side U-notched flat plate specimens. In particular, our attention was focused on the fracture behavior of two specimens containing complex geometrical features subjected to pure-shear and tensile-shear local stress states. The common feature of these two notched specimens was that cracks were seen to initiate, within the material, away from the stress raisers, even though obvious stress concentrations existed at notch tip. The performed validation exercise confirms the accuracy and reliability of the linear-elastic TCD in estimating the fracture initiation position and static strength of standard notched round bars and double-side U-notched flat plate specimens. In the meantime, the linear-elastic method proposed in this paper can also be used as an effective approach to assess the fracture behavior of metallic components having complex geometry.

Copper is an indispensable micronutrient in human health, which has important effects on the promotion of angiogenesis and thus contributes to bone formation and antimicrobial activity. We used ion exchange and pneumatic printing methods to prepare hydroxyapatite (HA) microspheres with different copper content. The microspheres were characterized by scanning electron microscope (SEM), X-ray diffractometry (XRD) and X-Ray photoelectron spectroscopy (XPS). Considering the resistance of hydroxyapatite to biodegradation in vivo, the degradation rate of microspheres in modified simulated body fluids was studied. In addition, cell proliferation and antibacterial experiments were carried out to study the biological properties of microspheres. HA-1.5MCu microbeads treated by 1.5 mol/L CuSO4 curing solution have good performance on degradation, antibacterial properties and cell survival rate on day 7. The results showed that HA-1.5MCu microbeads may be used as a good repair material for bone defects.

In this paper, diffusion bonding was adopted to join 9Cr martensitic/ferritic heat-resistant steels using an electrodeposited Ni interlayer with a thickness of 40 &mu, m. In addition, the effect of tempering treatment after diffusion bonding on the microstructure evolution and mechanical properties of the bonding joints was investigated. It was found that a transition region with face-centered cubic (FCC) structure was formed between the steel and Ni interlayer. The transition region was the solid solution of (&gamma, Fe,Ni) rich in Ni component, being related to martensite in the base metal by the Kurdjumov&ndash, Sachs (K-S) orientation relationship. No intermetallic compounds were detected at the bonding joints before and after tempering treatment. After tempering treatment, the transition region had higher dislocation density than other regions, due to the higher pinning effect of solute atoms acting on the dislocation than that of the matrix. Tensile tests indicated that tempering treatment improved the mechanical properties of the joint, since the samples after tempering treatment fractured in the base metal, whereas the specimens without tempering treatment fractured at the joint interface.

Semiconductor photocatalysts facilitate solar energy conversions via reduction–oxidation (redox) reactions. This requires the bandgaps of semiconductors to straddle the redox potentials of half-reactions. Such inherent thermodynamic prerequisite greatly limits utilization of visible or near-IR light. Thus, controllable redox potentials are highly desirable to obtain favorable band alignment. Here a simple thermodynamic approach was proposed to quantitatively predict temperature dependent behavior of energetics of redox half-reactions. Distinguished trends were observed at a temperature range of 298.15–1500 K for representative photocatalytic processes: H2O splitting was relatively temperature insensitive than CO2 reduction and NH3 synthesis, and the shifts in negative or positive directions as a function of temperature depend on the Gibbs energy change of the reactions. Furthermore, thermodynamic and kinetic implications on photocatalysis were discussed based on band alignment and overpotential. Understanding those thermodynamic characteristics is important for prediction and manipulation of physiochemical properties for more efficient photocatalysis.

Wound healing is a dynamic and well-orchestrated process that can be promoted by creating an optimal environment with wound dressing. An ideal wound dressing material should possess a suitable matrix, structure and bioactive components, functioning synergistically to accelerate wound healing. Wound dressings that allow reproducibility and customizability are highly desirable in clinical practice. In this study, using chitosan (CS) as the matrix and bioglass (BG) as the biological component, a spatially designed dressing scaffold was fabricated from a home-made cryogenic printing system. The micro- and macro-structures of the scaffold were highly controllable and reproducible. The printed scaffold exhibited interconnected and hierarchical pore structures, as well as good flexibility and water absorption capacity, and these properties were not affected by the content of BG. Nevertheless, when the content of BGs exceeded 20% that of CS, the tension strength and elongation rate reduced, but in vitro antibacterial, cell proliferation and migration performance were enhanced. In vivo examinations revealed that the composite scaffold significantly promoted wound healing process, with the group having 30% bioglass showing better wound closure, neovascularization and collagen deposition than other groups. These results indicate that the 3D printed CS/BG composite scaffold is a promising dressing material that accelerates wound healing.

The ductile fracture characteristics of Chinese Q460 high strength structural steel under quasi-static condition were studied by using mechanical tests of four types of notched specimens. The influence of stress state on fracture mechanism of the material was investigated by observing the fracture surfaces of all test specimens using the Scanning Electron Microscope. Meanwhile, corresponding numerical simulations were conducted to collect the critical stress and strain at notch for all test specimens. The effects of stress triaxiality and Lode angle parameter, which were found to be the key parameters governing the ductile fracture of metallic material in many studies, on fracture strain of the Q460 structural steel were investigated. The analysis results show that different fracture mechanisms were observed in different stress triaxiality regions. At high stress triaxialities, Q460 steel exhibits a typical mechanism of “void nucleation, growth and coalescence”. When stress triaxiality equals to zero, a shear fracture mechanism was observed. At low stress triaxiality values, fracture develops as a combination of shear and void growth modes. In addition, the ductility of Q460 structural steel under pure shear or plane strain is lower than that under axisymmetric tension, especially at low stress triaxiality.

To make full use lignocellulosic biomass resources, comprehensive utilization of this renewable energy resource was proposed. In this work, Amygdalus pedunculata shell served as typical lignocellulosic biomass was used for ethanol production and activated carbon preparation, and the maximum ethanol yield 0.0158 g g−1 and activated carbon with maximum BET surface 2059 m2 g−1 were obtained. Additionally, the porous carbon was systematically characterized and applied as electrode material for supercapacitor which exhibits high specific capacitance of 358.4 F g−1 at a current density of 0.5 A g−1. After 1000 cycles, the capacitor still exhibited a stable performance with capacitance retention of 86.3% at a current density of 5 A g−1. The conversion of Amygdalus pedunculata shell to bioethanol and activated carbon applied as electrode material in high performance supercapacitor offers significant potentials for comprehensive utilization of lignocellulosic biomass.

In this paper, a novel hybrid plasmonic waveguide with a metal ridge and an MgF2 dielectric layer is demonstrated at ultraviolet band. We investigate the propagation distance, the scaling factor and the figure of merit by using the finite element method. The structure enables low scaling factor and long propagation distance. Compared to the previous structure with a metal plate, this waveguide has better performance. And the structure can be used as a nanolaser and has broad application prospects in optoelectronic integrated circuits, biological detection and so on.

Extrusion freeforming is a facile approach to produce complex 3D structures with controlled architecture and porosity. In this work, a new slurry system, mainly containing hydroxyapatite (HA) and sodium alginate (SA), has been used to fabricate porous hydroxyapatite scaffolds. After cross-linking in 5% calcium chloride (CaCl 2 ) solution for 24 h, HA–SA composite scaffolds were sintered at 1000–1300 °C for 2 h. The properties of HA–SA composite scaffolds before and after sintering have been investigated. The new slurry system has greatly improved the quality of porous hydroxyapatite scaffolds.