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Molten salt from the service environment leaches Y2O3from yttria-stabilized zirconia (YSZ), threatening the security of thermal barrier coatings (TBCs). In this study, we compared the molten salt corrosion resistances of YSZ coatings prepared viaplasma-spraying physical vapor deposition (PS-PVD) before and after laser remelting. At 1000 °C, the molten salt reacted with YSZ particulates in the PS-PVD YSZ coating and infiltrated the gaps between quasi-columnar crystals, resulting in phase transition of the coating and column breakage. A dense glazed layer was formed on the YSZ coating surface after remelting by the low-energy-density laser, which prohibited the penetration of molten salt and improved the hot corrosion resistance of the YSZ coating. By contrast, the failure of the high-energy-density laser-treated YSZ coating was accelerated due to the significant interfacial stress from the thick glazed layer and volume expansion caused by the corrosion products. Our investigation revealed the structural evolution of the PS-PVD YSZ coating under hot corrosion conditions, emphasized the role of laser remelting, and could serve as a guideline for TBCs modification.

Recently, the Mg–Ag binary alloy has gained much attention as an antibacterial biomaterial. However, the relationships between the extrusion parameters, microstructure, and mechanical properties of Mg–Ag alloys haven't been clearly established. Therefore, in this paper, the effects of silver (Ag) content (0, 3, 6 wt%) and extrusion (as cast, extrusion ratio (ER) 7.1 and 72.2) on the microstructure and mechanical properties of Mg–Ag alloys are systematically investigated. The results indicate that for the Mg–Ag alloys with the same extrusion ratio, as the Ag increased from 0 to 3 wt%, Mg4Ag and Mg54Ag17precipitated, leading to significant precipitation strengthening and an increase in the yield strength by over 137%. As the Ag increased to 6 wt%, the yield strength increased by only ∼20%, attributable to Ag promoting dynamic recrystallization, resulting in less grain refinement, a slower amount increase and a smaller size reduction of the precipitate. For the Mg–Ag alloys with the same Ag content, as the extrusion ratio increased to 7.1, the yield strength increased significantly by over 37%, since the grain boundary strengthening and precipitation strengthening were significantly enhanced as the grains were refined, a large number of precipitates appeared, and their sizes significantly reduced. When the extrusion ratio increased to 72.2, the yield strength increased by only ∼10%, due to the weakening of both grain boundary strengthening and precipitation strengthening as the recrystallization further improved, leading to an increase in grain sizes, the redissolution of precipitates, and a lesser reduction in their sizes.

Designing a query-efficient attack strategy to generate high-quality adversarial examples under the hard-label black-box setting is a fundamental yet challenging problem, especially in natural language processing (NLP). The process of searching for adversarial examples has many uncertainties (e.g., an unknown impact on the target model's prediction of the added perturbation) when confidence scores cannot be accessed, which must be compensated for with a large number of queries. To address this issue, we propose TextCheater, a decision-based metaheuristic search method that performs a query-efficient textual adversarial attack task by prohibiting invalid searches. The strategies of multiple initialization points and Tabu search are also introduced to keep the search process from falling into a local optimum. We apply our approach to three state-of-the-art language models (i.e., BERT, wordLSTM, and wordCNN) across six benchmark datasets and eight real-world commercial sentiment analysis platforms/models. Furthermore, we evaluate the Robustly optimized BERT pretraining Approach (RoBERTa) and models that enhance their robustness by adversarial training on toxicity detection and text classification tasks. The results demonstrate that our method minimizes the number of queries required for crafting plausible adversarial text while outperforming existing attack methods in the attack success rate, fluency of output sentences, and similarity between the original text and its adversary.

3D printing techniques offer an effective method in fabricating complex radially multi-material structures. However, it is challenging for complex and delicate radially multi-material model geometries without supporting structures, such as tissue vessels and tubular graft, among others. In this work, we tackle these challenges by developing a polar digital light processing technique which uses a rod as the printing platform. The 3D model fabrication is accomplished through line projection. The rotation and translation of the rod are synchronized to project and illuminate the photosensitive material volume. By controlling the distance between the rod and the printing window, we achieved the printing of tubular structures with a minimum wall thickness as thin as 50 micrometers. By controlling the width of fine slits at the printing window, we achieved the printing of structures with a minimum feature size of 10 micrometers. Our process accomplished the fabrication of thin-walled tubular graft structure with a thickness of only 100 micrometers and lengths of several centimeters within a timeframe of just 100 s. Additionally, it enables the printing of axial multi-material structures, thereby achieving adjustable mechanical strength. This method is conducive to rapid customization of tubular grafts and the manufacturing of tubular components in fields such as dentistry, aerospace, and more.

With the advent of cross-domain interconnection, large-scale sensor network systems such as smart grids, smart homes, and intelligent transportation have emerged. These complex network systems often have a CPS (Cyber-Physical System) architecture and are usually composed of multiple interdependent systems. Minimal faults between interdependent networks may cause serious cascading failures between the entire system. Therefore, in this paper, we will explore the robustness detection schemes for interdependent networks. Firstly, by calculating the largest giant connected component in the entire system, the security of interdependent network systems under different attack models is analyzed. Secondly, a comparative analysis of the cascade failure mechanism between interdependent networks under the edge enhancement strategy is carried out. Finally, the simulation results verify the impact of system reliability under different handover edge strategies and show how to choose a better handover strategy to enhance its robustness. The further research work in this paper can also help design how to reduce the interdependence between systems, thereby further optimizing the interdependent network system's structure to provide practical support for reducing the cascading failures. In the later work, we hope to explore our proposed strategies in the network model of real-world or close to real networks.

ABSTRACTThis study evaluated the effect of monocalcium phosphate (MCP) on the mechanical and biological properties of calcium silicate (CS) cement. Cements composed of CS with different weight ratios (0–40%) of MCP were prepared and their pH and compressive strength were tested using the pH detector and Universal Testing Machine, respectively. Cell viability, migration, mineralisation and differentiation were evaluated using the Cell Counting Kit 8 (CCK-8), Transwell, alkaline phosphatase activity assay, Alizarin Red-S staining and real-time polymerase chain reaction, respectively. With the MCP content increase, the pH of the cements decreased from 11.5 to 8 and the compressive strength decreased from 25.81 to 3.45 MPa. The extracts of cements promoted cell proliferation, migration, osteoblastic differentiation and mineralisation when MCP was 10–20 wt-%. These suggested that MCP powder can regulate the properties of CS cement. Composite cement containing 10–20 wt-% MCP showed improved biocompatibility and mineralisation and promising for bone defect restoration.

This study evaluated the effect of monocalcium phosphate (MCP) on the mechanical and biological properties of calcium silicate (CS) cement. Cements composed of CS with different weight ratios (0–40%) of MCP were prepared and their pH and compressive strength were tested using the pH detector and Universal Testing Machine, respectively. Cell viability, migration, mineralisation and differentiation were evaluated using the Cell Counting Kit 8 (CCK-8), Transwell, alkaline phosphatase activity assay, Alizarin Red-S staining and real-time polymerase chain reaction, respectively. With the MCP content increase, the pH of the cements decreased from 11.5 to 8 and the compressive strength decreased from 25.81 to 3.45 MPa. The extracts of cements promoted cell proliferation, migration, osteoblastic differentiation and mineralisation when MCP was 10–20 wt-%. These suggested that MCP powder can regulate the properties of CS cement. Composite cement containing 10–20 wt-% MCP showed improved biocompatibility and mineralisation and promising for bone defect restoration.

The mechanism of the mineralization process induced by natural mineralized collagen (MC) has been investigated for decades. The purpose of this study was to investigate the efficacy of self-assembled MC for peri-implant bone defect reconstruction in a mini pig. A standardized peri-implant bone defect model was created using 14 mini pig mandibles. Two materials were evaluated, i.e. a mixture of hydroxyapatite and collagen (Type A, TA), and self-assembled MC (Type B, TB). Bio-Oss (BO) and untreated (blank control, BC) groups were used as controls. After 3- and 6-month healing periods, the mini pigs were sacrificed for histomorphometric and microcomputed tomography analysis. After 3 months of healing, the average alveolar ridge height was 3.27 ± 1.57 mm for group TA, 3.28 ± 2.02 mm for group TB and 3.37 ± 1.09 mm for group BO, while group BC showed the lowest height of 2.68 ± 0.47 mm. After 6 months of healing, the average alveolar ridge height was 2.64 ± 1.13 mm for group TA, 4.31 ± 1.80 mm for group TB and 3.87 ± 1.38 mm for group BO, while group BC showed the lowest height of 2.48 ± 1.80 mm. The experimental groups and control group showed similar bone volume density, bone complexity and histological reaction. The self-assembled MC (Type B) stimulated new bone formation in the reconstruction of deficient alveolar ridges around the dental implant; it also displayed excellent clinical operability compared with bone grafts without collagen.

•Defect free weld were obtained by parameter of 300 mm/min and 350 rpm for 7N01 aluminum.•The high temperature region and rotation particles can be used to predict void defects.•The formation of void defects is related to the plastic region around the tool.

Introduction

ABSTRACTTantalum coating for bio-medical applications is prepared by atmospheric pressure chemical vapour deposition in a TaF5–H2system on the inner wall of a stainless steel tube. The concentration of hydrogen fluoride (HF) has a significant effect on the morphology and crystallographic orientation of the tantalum coating. As the HF concentration increases, the tantalum coating gradually becomes smooth from roughness. The rougher part and the smoother part of tantalum coating reveal (200) and (110) preferred orientation, respectively. Simultaneously, the kinetic equation containing HF concentration has been developed. The calculated results from the equation show a good correspondence with the experimental results. The performance of tantalum coating with distinct morphologies on the effect of osseointegration was studied by implanting samples in vivo. The coating with a rougher surface was more osteoattractive than the one with a smoother surface.

Tantalum coating for bio-medical applications is prepared by atmospheric pressure chemical vapour deposition in a TaF5–H2system on the inner wall of a stainless steel tube. The concentration of hydrogen fluoride (HF) has a significant effect on the morphology and crystallographic orientation of the tantalum coating. As the HF concentration increases, the tantalum coating gradually becomes smooth from roughness. The rougher part and the smoother part of tantalum coating reveal (200) and (110) preferred orientation, respectively. Simultaneously, the kinetic equation containing HF concentration has been developed. The calculated results from the equation show a good correspondence with the experimental results. The performance of tantalum coating with distinct morphologies on the effect of osseointegration was studied by implanting samples in vivo. The coating with a rougher surface was more osteoattractive than the one with a smoother surface.

Cooperation in packet forwarding among users and operators of a distributed wireless network has been widely studied. However, because of the limited computational resources, users in wireless communication do not prefer to cooperate with others unless cooperation may improve their own performance. Therefore, the key problem in cooperation enforcement must be solved first to enable a wireless network to be efficient. Yet, most of the existing game-theoretic cooperation stimulation approaches assume that the interactions between any pair of players (users) are long-lasting. In this paper, we apply game theory to optimize the communication efficiency of a distributed wireless network with finite number of interactions between any pair of players. Based on the mechanism of indirect reciprocity, we theoretically analyze the optimal action rule with the method of dynamic programming, and derive the approximate threshold of benefit-to-cost ratio to achieve the optimal action rule. Furthermore, we adopt the replicator dynamics to assess the evolutionary stability of the optimal action rule against the perturbation effect. Numerical illustrations verify the performance of the proposed method on wireless cooperation.

ABSTRACTBecause of their outstanding mechanical properties, chemical stability, and biocompatibility, 3-mol % yttria-stabilised tetragonal zirconia polycrystals (3Y-TZP), known as zirconia ceramics in dentistry, are an important choice for various types of prosthesis. In addition to extensive use for crown and bridge construction, considerable interest has been generated for applications in implant dentistry, including full-contour zirconia crowns as supra-constructions, zirconia abutments, and novel zirconia implants. However, their use among dentist and researchers is controversial, especially compared with the well-established implants made of titanium alloys. As a latecomer, the merits and limitations of 3Y-TZP are awaiting careful investigation. Design, manufacturing, and clinical operation guidelines are urgently needed. The aim of this review was to address the present status of the application of zirconia ceramics related to implant dentistry by analysing the published data from both in vitroand in vivostudies. Suggestions are provided for potential improvements and suitable applications of zirconia ceramics in metal-free implant dentistry.

Because of their outstanding mechanical properties, chemical stability, and biocompatibility, 3-mol % yttria-stabilised tetragonal zirconia polycrystals (3Y-TZP), known as zirconia ceramics in dentistry, are an important choice for various types of prosthesis. In addition to extensive use for crown and bridge construction, considerable interest has been generated for applications in implant dentistry, including full-contour zirconia crowns as supra-constructions, zirconia abutments, and novel zirconia implants. However, their use among dentist and researchers is controversial, especially compared with the well-established implants made of titanium alloys. As a latecomer, the merits and limitations of 3Y-TZP are awaiting careful investigation. Design, manufacturing, and clinical operation guidelines are urgently needed. The aim of this review was to address the present status of the application of zirconia ceramics related to implant dentistry by analysing the published data from both in vitroand in vivostudies. Suggestions are provided for potential improvements and suitable applications of zirconia ceramics in metal-free implant dentistry.

In peer-to-peer (P2P) networks, each peer's trustworthiness is evaluated according to its pseudonym's rating values given by other peers. One of the fundamental challenges in peer-to-peer networks is to protect peers' identity privacy on the communication path. In this paper, we present an anonymity mechanism to achieve all the peers' anonymity in peer-to-peer networks by changing pseudonyms with the help of a trusted third party (TTP) server. Compared with the existing reputation using pseudonyms (RuP) mechanism, our mechanism has reduced TTP server's cost by more than 50% in terms of numbers of RSA and AES decryption operations and message overhead. Simulation results show the effectiveness of our proposed anonymity mechanism to counter malicious peers.

Clinically, fractures are the main cause of computer-aided design and computer-aided manufacturing (CAD/CAM) 3 mol%-yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) all-ceramic dental restorations failure because of repetitive occlusal loading. The goal of this work is to study the effect of test methods and specimen's size on the flexural strength of five ceramic products. Both bi-axial flexure test (BI) and uni-axial flexure tests (UNI), including three-point flexure test (3PF) and four-point flexure test (4PF), are used in this study. For all five products, the flexural strength is as follows: BI > 3PF > 4PF. Furthermore, specimens with smaller size (3PF-s) have higher values than the bigger ones (3PF). The difference between BI and UNI resulted from the edge flaws in ceramic specimens. The relationship between different UNI (including 3PF-s, 3PF and 4PF) can be explained according to Weibull statistical fracture theory. BI is recommended to evaluate the flexural strength of CAD/CAM Y-TZP dental ceramics.

In the binary decision diagram–based terminal-pair network reliability analysis, the size of binary decision diagram heavily depends on the chosen edge ordering. From a theoretical point of view, finding the best ordering is an intractable task. Therefore, heuristics have been used to obtain reasonably good orderings. Among them, the breadth-first search heuristic typically outperforms other heuristics by generating smaller binary decision diagram and thus has been widely used for terminal-pair network reliability analysis. However, the performance of breadth-first search is still only vaguely understood; not much formal work has been done. In this work, we investigate the selection of high-performance root node of breadth-first search ordering for both lattice networks and de Bruijn networks. Empirical study shows that using the two terminal nodes in the terminal-pair network reliability analysis as the root node of the breadth-first search heuristic can have poor performance, and the high-performance root nodes are not randomly distributed. The relationship between the distribution pattern of high-performance root nodes and the rearrangement of successors is also studied. Given that there is often a variation of several orders of magnitude between the sizes of binary decision diagram built using different root nodes for the same network, the application of our results can dramatically reduce the running time and memory usage and make the binary decision diagram–based reliability analysis of large-scale regular networks possible.

Osteoarthritis is associated with an increase in mechanical friction of the joint, which causes irreversible damage to articular cartilage. Consequently, it is crucial to restore joint lubrication for effectively treating osteoarthritis. In the present study, hyaluronic acid (HA)-based zwitterionic nanospheres with phosphocholine groups on the surface were synthesized, which achieved excellent lubrication behavior due to the hydration lubrication mechanism. Specifically, HA was initially thiolated and modified with hexadecylamine based on an amidation reaction, then it was grafted with 2-methacryloyloxyethyl phosphocholine (MPC) by the thiol–ene click reaction, and finally self-assembled into nanospheres (HA-MPC) by hydrophobic interaction and cross-linking of the thiol group. The lubrication test demonstrated that the HA-MPC nanospheres improved lubrication under shear force, with a 40% reduction in the friction coefficient compared with HA. The in vitro experiment indicated that the HA-MPC nanospheres had excellent biocompatibility, and they upregulated the cartilage anabolic gene and downregulated cartilage catabolic proteases as well as the pain-related gene. The in vivo test showed that the injection of HA-MPC nanospheres to the joint cavity could inhibit the development of osteoarthritis, which was examined based on histological staining and also morphological evaluation. In conclusion, the new self-assembled zwitterionic HA-MPC nanospheres may be intra-articularly injected for the effective treatment of osteoarthritis by restoring joint lubrication.

Exosomes derived from mesenchymal stem cells (MSCs) have demonstrated regenerative potential for cell-free bone tissue engineering, nevertheless, certain challenges, including the confined therapeutic potency of exosomes and ineffective delivery method, are still persisted. Here, we confirmed that hypoxic precondition could induce enhanced secretion of exosomes from stem cells from human exfoliated deciduous teeth (SHEDs) viacomprehensive proteomics analysis, and the corresponding hypoxic exosomes (H-Exo) exhibited superior potential in promoting cellular angiogenesis and osteogenesis viathe significant up-regulation in focal adhesion, VEGF signaling pathway, and thyroid hormone synthesis. Then, we developed a platform technology enabling the effective delivery of hypoxic exosomes with sustained release kinetics to irregular-shaped bone defects via injection. This platform is based on a simple adsorbing technique, where exosomes are adsorbed onto the surface of injectable porous poly(lactide-co-glycolide) (PLGA) microspheres with bioinspired polydopamine (PDA) coating (PMS-PDA microspheres). The PMS-PDA microspheres could effectively adsorb exosomes, show sustained release of H-Exo for 21 days with high bioactivity, and induce vascularized bone regeneration in 5-mm rat calvarial defect. These findings indicate that the hypoxic precondition and PMS-PDA porous microsphere-based exosome delivery are efficient in inducing tissue regeneration, hence facilitating the clinical translation of exosome-based therapy.

A vacuum stir casting process is developed to produce SiCpreinforced cast magnesium matrix composites. This process can eliminate the entrapment of external gas onto melt and oxidation of magnesium during stirring synthesis. Two composites with Mg-Al9Zn and Mg-Zn5Zr alloys as matrices and 15 vol.% SiC particles as reinforcement are obtained. The microstructure and mechanical properties of the composites and the unreinforced alloys in as-cast and heat treatment conditions are analyzed and evaluated. In 15 vol.% SiCpreinforced Mg-Al9Zn alloy-based composite (Mg-Al9Zn/15SiCp), SiC particles distribute homogenously in the matrix and are well bonded with magnesium. In 15 vol.% SiCpreinforced Mg-Zn5Zr alloy-based composite (Mg-Zn5Zr/15SiCp), some agglomerations of SiC particles can be seen in the microstructure. In the same stirring process conditions, SiC reinforcement is more easily wetted by magnesium in the Mg-Al9Zn melt than in the Mg-Zn5Zr melt. The significant improvement in yield strength and elastic modulus for two composites has been achieved, especially for the Mg-Al9Zn/15SiCpcomposite in which yield strength and elastic modulus increase 112 and 33%, respectively, over the unreinforced alloy, and increase 24 and 21%, respectively, for the Mg-Zn5Zr/15SiCpcomposite. The strain-hardening behaviors of the two composites and their matrix alloys were analyzed based on the microstructure characteristics of the materials.

Achieving the uniform distribution of reinforcement particles in MMCs is very important for the effect of stirring parameters and the flow action of the melt, which should be known. The effect of stirring parameters on the distribution of SiC particles in SiCp/A356 composites was studied by the experimental and numerical methods in this paper. The experimental results show the SiC distribution with different stirring parameters. In addition, the effects of the fluid velocity and volume fraction of SiC particle at different position of crucible on the SiC distribution were analyzed by numerical simulation. The velocity magnitude, axial velocity, and radial velocity were analyzed to explain theoretically the particle distribution. The shearing force, moments, and stirring power of the stirring rod were simulated based on CFD code. The numerical results show that the stirring temperature is lower, the shearing force is greater, the stirring time is longer, and particle dispersion gets better. On the other hand, the higher the stirring speed is, the more uniform the radial and axial flow are, and the better the particles were dispersed. The numerical results were in good agreement with the experimental data.