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Multi-functionalization is the future development direction for protective coatings on metal surface, but has not yet been explored a lot. The effective integration of multiple functions into one material remains a huge challenge. Herein, a superhydrophobic multilayer coating integrated with multidimensional organic-inorganic components is designed on magnesium alloy via one-step plasma-induced thermal field assisted crosslinking deposition (PTCD) processing followed by after-thermal modification. Hard porous MgO ceramic layer and polytetrafluoroethylene (PTFE) nano-particles work as the bottom layer skeleton and filler components separately, forming an organic-inorganic multilayer structure, in which organic nano-particles can be crosslinked and cured to form a compact polymer-like outer layer with hierarchical surface textures. Remarkably, the chemical robustness after prolonged exposure to aqua regia, strong base and simulated seawater solution profits from polymer-like nanocomposite layer uniformly and compactly across the film bulk. Moreover, the self-similar multilayer structure coating endows it attractive functions of strong mechanical robustness (>100th cyclic rotary abrasion), stable and ultra-low friction coefficient (about 0.084), high-temperature endurance, and robust self-cleaning. The organic-inorganic multilayer coating also exhibits high insulating property with breakdown voltage of 1351.8 ± 42.4 V, dielectric strength of 21.4 ± 0.7 V/µm and resistivity of 3.2 × 1010 Ω·cm. The excellent multifunction benefits from ceramic bottom skeleton, the assembly and deposition of multidimensional nano-particles, and the synergistic effect of organic inorganic components. This study paves the way for designing next generation protective coating on magnesium alloy with great potential for multifunctional applications.

The cooperative bipartite containment control problem of linear multiagent systems is investigated based on the adaptive distributed observer in this article. The graph among the agents is structurally balanced. A novel distributed error term is designed to guarantee that some outputs of the followers converge to the convex hull spanned by the leaders, and the other followers' outputs converge to the symmetric convex hull. The matrices of the exosystems are not available for each follower. A general method is presented to verify the validity of a novel distributed adaptive observer rather than the previous approach. In other words, the definition of the M -matrix is not necessary in our result. Based on the distributed adaptive observer, an output-feedback control protocol is designed to solve the bipartite containment control problem. Finally, a numerical simulation is given to illustrate the effectiveness of the theoretical results.

This paper studies the exponential stability of switched positive system consisting of unstable subsystems with distributed time-varying delay. Unlike the existing results concerning delays, switching behaviors dominating the system can be either stabilizing or destabilizing. The distributed delay is supposed to be slowly varying and upper-bounded. To tackle the difficulties brought by both the switching behaviors with mixed effects and the distributed delay, a multiple discretized Lyapunov–Krasovskii functional is employed to derive sufficient conditions for the exponential stability of the system. Specifically, by adjusting the ratio of the stabilizing switching behaviors, the state divergence caused by unstable subsystems and destabilizing switching behaviors can be compensated. Simulation examples demonstrate the effectiveness of the results.

Herein, a facile synthesis of valuable pyrido[1,2-a]pyrimidine-4-thiones is reported via novel thiocarbonylation of C(sp3)-H bonds with carbon disulfide (CS2). This reaction features easy availability of substrates, good functional group tolerance, high yields, facile scalability and atom economy. Mechanistic investigations indicate that sulfate anion and sulfuric anhydride anion might be involved in this reaction.

At present, frequent outbreaks of bacteria and viruses have seriously affected people's normal lives. Therefore, the study of broad-spectrum antibacterial nanocomposites is very promising. However, most antibacterial materials have some disadvantages, such as single bactericidal mechanisms and unrepeatable use. Based on the current situation, a kind of nanocomposite with three structures of graphene oxide (GO), quaternary ammonium salt (QAs) and N-halamine was prepared, which showed synergistic effect to improve antibacterial activity and combined with a variety of sterilization mechanisms. Meanwhile, GO can provide richer ways of sterilization and high specific surface area, which is conducive to the grafting of quaternarized N-halamine. The advantages of physical sterilization of GO, charge adsorption of QAs, reuse of N-halamine and efficient sterilization are fully utilized. The results showed that the quaternarized N-halamine-grafted GO was obtained successfully. GO grafted with quaternarized N-halamine polymer showed strong speedy bactericidal activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) (99%). It had good storage and regeneration properties.

In recent years, managers have increasingly integrated sustainability into their business models. However, they might overestimate the premium that average consumers are willing to pay for the environment. In this paper, we formulate a game-theoretical model that illustrates the impacts of green optimism which refers to managers’ optimistic bias about consumer environmental awareness. We consider a sustainable supply chain in which one manufacturer invests in green product development and sells the green product through one retailer. Each firm within the supply chain is operated by one manager who is either realistic or optimistic. Contrary to conventional wisdom, we find that managers’ optimistic bias might discourage investment in green product development. We also find that green optimism is always detrimental to the upstream manufacturer, but might be beneficial to the downstream retailer. Surprisingly, under certain conditions, green optimism can be detrimental to all stakeholders, i.e., firms in the supply chain, consumers, and the environment. This study suggests an interesting link between supply chain management and human resource management; that is, within a sustainable supply chain those managers who are optimistic about the future of green business might be an obstacle to the success of green business.

Daylighting structures, including solar cells and building windows, utilize sunlight whilst suffering from undesired solar heat and outdoor dust contamination. A radiative cooling system that is transparent to sunlight and has a superhydrophobic surface would cool and clean the daylighting structures in a sustainable manner. However, the majority of the current daytime radiative cooling systems were designed to fully reflect the incident sunlight to maximize the cooling power. In this work, we optimized both the sunlight transmission and infrared thermal irradiation by modeling the size-dependent scattering and absorption of light by SiO2 spheres embedded in a polymer matrix, we found that the use of nanospheres (20 nm) enabled both high sunlight transmittance (> 90%) and infrared emissivity (~0.85). This theoretical prediction was confirmed by experimental measurements of a solution-processed nanocomposite film. When coated on a solar cell, the as-prepared film not only preserved the power conversion efficiency of the cell (14.71%, uncoated cell has an efficiency of 14.79%) but also radiatively cooled the cell by up to 5 °C under direct sunlight. This reduction of the operating temperature of the solar cell further enhanced its electrical power output, evidenced by an increase in the equilibrium temperature of the LED load by about 14 °C. The nanoscale textured surface formed by the nanospheres further led to superhydrophobicity and thus excellent self-cleaning performance (efficient removal of dust by wind and/or water droplets).

Porous polycaprolactone (PCL)/calcium sulfate hemihydrate (CSH) composite fibers with different compositions were fabricated via electrospinning by using chloroform/dimethyl sulfoxide (volume ratio = 8:2) as the co-solvent. It was found that the incorporation of fine CSH powders greatly improved the morphology of the PCL fibers and generated continuous, bead-free PCL/CSH composite fibers with the pore diameter varying from 0.2 to 1.1 μm when 20% CSH was added. As compared with the PCL fibers, the PCL/CSH composite fibers also exhibited enhanced thermal stability and hydrophilicity. The tensile strength and elastic modulus of the PCL/CSH fibrous membranes first increased and then decreased with the increase of the CSH content, while their ductility exhibited a sustained decrease. Moreover, after immersion in water, the PCL-20%CSH composite fibers presented a much higher tensile strength than the pristine ones probably due to the self-setting of the CSH powders through the porous structure. In addition, the PCL-20%CSH composite fibers displayed a strong ability to form bone-like apatite after immersion in simulated body fluid for 3 days, which suggests their potential applications in bone tissue regeneration as a novel type of substitute.

Lithium-ion batteries are widely used as power sources in industrial applications. Electrochemical models and simulations are crucial to disclose many details that cannot be directly measured through experiments. Parameter identification of an accurate electrochemical model is much more cost-effective than direct and destructive measurement methods. However, the complex structure and strong nonlinearity of electrochemical models will make the parameter identification very difficult. Additionally, time-consuming electrochemical simulations can significantly limit the identification efficiency. This article proposes a surrogate-model-based scheme to achieve high-efficiency parameter identification of an electrochemical battery model. To be specific, the proposed method is implemented by the close integration of an evolutionary algorithm and a surrogate model. A sensitivity-based identification strategy is first designed to alleviate the difficulty of optimization. Then, a surrogate model is developed from historical data to gradually approach the objective function used for parameter evaluations. Finally, an evolutionary algorithm is employed to find promising solutions by minimizing the output of the surrogate model. Simulations and experimental studies demonstrate the effectiveness and high efficiency of the proposed method.

Novel TiC-based composites were synthesized by reactive hot-pressing at 1800 °C for 1 h with ZrB2 addition as a sintering aid for the first time. The effects of ZrB2 contents on the phase composition, microstructure evolution, and mechanical properties were reported. Based on the reaction and solid solution coupling effects between ZrB2 and TiC, the product ZrC may be partially or completely dissolved into the TiC matrix, and then phase separation within the miscibility gap is observed to form lamellar nanostructured ZrC-rich (Zr, Ti)C. The TiC-10 mol.% ZrB2 (starting batch composition) exhibits good comprehensive mechanical properties of hardness 27.7 ± 1.3 GPa, flexural strength 659 ± 48 MPa, and fracture toughness of 6.5 ± 0.6 MPa m1/2, respectively, which reach or exceed most TiC-based composites using ceramics as sintering aids in the previous reports.

Through the introduction of gas-phase monomers phthalic anhydride (PA) and p-phenylenediamine (PPD), replenishment of lubricants during high-temperature friction process could be realized. In a 10-...

The development of new energy industry is a pressing issue due to the deterioration of the environment. The selection of new energy projects is a critical problem for decision makers. Incomplete and uncertain information appears in the process of new energy project selection. Compared with other linguistic expressions, probabilistic linguistic term set (PLTS) simultaneously reflects all possible linguistic terms and their corresponding weights, which conforms to the cognitive habits of people. Thus, a multi-criteria decision-making framework under PLTS environment is constructed for energy project selection. Firstly, a normalised projection model of PLTS, which considers the distance and the angle between two objects, is proposed to overcome the limitations of distance measurement. Secondly, a comprehensive weight-determination method combining the maximum deviation and expert scoring methods is developed to calculate the weight vector of the criteria. Furthermore, a projection-based VIKOR (Višekriterijumska optimizacija i kompromisno rešenje) method is established to select new energy projects, which can reflect the preferences of decision makers for group utility and individual regret. Finally, a numerical study on new energy project selection is performed to determine the validity and applicability of this method. Sensitive and comparative analyses are also conducted to reflect the rationality and feasibility of the method.

In this article, we present a comprehensive design and implementation for a micro aerial vehicle (MAV) that is able to perform 3-D autonomous navigation and obstacle avoidance in cluttered and realistic unknown environments without the aid of global positioning system and other external sensors or markers. To achieve these autonomous missions, modularized components are developed for the MAV, including visual–inertial odometry, 3-D occupancy mapping, and motion planning. The proposed system is implemented to run on a small embedded computer in real time. It is demonstrated to be robust in both simulation and real flight experiments. The demonstration video is available at: https://youtu.be/KUKzsnORm-4 .

Concentrated photovoltaic (CPV) has been identified as an effective method to further enhance the efficiency of photovoltaic cells. Previous studies on CPV mainly focused on III-V multi-junction cells. Nevertheless, III-V CPV technology is mainly used in niche applications due to its high cost. Here, we use metal-halide perovskite solar cell (PSC) to demonstrate a concentrated photovoltaic-thermoelectric tandem device. The thermoelectric generator (TEG) is utilized to reduce the effect of heat generation under concentrated solar irradiance. Our tandem system achieved a peak power conversion efficiency (PCE) of 25.0% at a solar concentration of 3 suns. This efficiency exceeded that of the single PSC by ~4.7%. Our work proves that by controlling the heat flow in concentrated PSC-TEG tandem system, the redundant heat produced by upper PSC can be effectively reused. This tandem structure provides a promising approach to improve the efficiency and stability of PSC under low-concentrated solar irradiation.

Uncovering the genetic basis of hypoxic adaptation is one of the most active research areas in evolutionary biology. Among air-breathing vertebrates, modifications of hemoglobin (Hb) play a pivotal role in mediating an adaptive response to high-altitude hypoxia. However, the relative contributions in water-breathing organisms are still unclear. Here, we tested the Hb concentration of fish at different altitudes. All species showed species-specific Hb concentration, which has a non-positive correlation with altitude. Moreover, we investigated the expression of Hb genes by the RNA-seq and quantitative real-time PCR (qRT-PCR), and Hb composition by two-dimensional electrophoresis (2-DE). The results showed that the multiple Hb genes and isoforms are co-expressed in schizothoracinae fishes endemic to the Qinghai-Tibetan Plateau (QTP). Phylogenetic analyses of Hb genes indicated that the evolutionary relationships are not easily reconciled with the organismal phylogeny. Furthermore, evidence of positive selection was found in the Hb genes of schizothoracinae fishes through the selection pressure analysis. We demonstrated that positively selected sites likely facilitated the functional divergence of Hb isoforms. Taken together, this study indicated that the long-term maintenance of high Hb concentration may be a disadvantage for physiologically acclimating to high altitude hypoxia. Meanwhile, the genetically based modification of Hb-O2 affinity in schizothoracinae fishes might facilitate the evolutionary adaptation to Tibetan aqueous environments.

Tris(dichloromethylsilylethyl)borane is a compound containing a B-C bond and Cl and H elements. Herein, we propose a novel method to synthesize polyborosilazanes using tris(dichloromethylsilylethyl)borane and boron trichlorosilane as boron sources and hexamethyldisilazane as a nitrogen source. The microstructure and chemical composition of the as-synthesized polyborosilazanes and as-annealed SiBCN ceramics were investigated using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, Raman spectroscopy, scanning electron microscope, and transmission electron microscope methods. The organic precursors were converted entirely into inorganic ceramics at 800 degrees C, and the ceramic yield of the polyborosilazanes was 88% at 1000 degrees C. SiBCN ceramics with irregular shapes contained chemical bonds of B-N, Si-N, and Si-C at 1500 degrees C and retained an amorphous structure below 1600 degrees C. After the first cycle, the fabricated SiBCN ceramic anodes exhibited a reversible capacity of 261.3 mA h/g, which was 2.6 times that reported in the literature (101 mA h/g). The discharge capacity decreased to 157.6 mA h/g after 30 cycles. The satisfactory electrochemical performance of the resulting SiBCN ceramic anodes can be attributed to the formation of conductive carbon species favoring the transport properties of lithium ion.

The concept of transparency order is introduced to measure the resistance of n , m -functions against multi-bit differential power analysis in the Hamming weight model, including the original transparency order (denoted by TO ), redefined transparency order (denoted by RTO ), and modified transparency order (denoted by MTO ). In this paper, we firstly give a relationship between MTO and RTO and show that RTO is less than or equal to MTO for any n , m -functions. We also give a tight upper bound and a tight lower bound on MTO for balanced n , m -functions. Secondly, some relationships between MTO and the maximal absolute value of the Walsh transform (or the sum-of-squares indicator, algebraic immunity, and the nonlinearity of its coordinates) for n , m -functions are obtained, respectively. Finally, we give MTO and RTO for (4,4) S-boxes which are commonly used in the design of lightweight block ciphers, respectively.

In this study, SiC whiskers (SCWS) reinforced geopolymer composites (SCWS/KGP) and their ceramic products (SCWS/leucite) were prepared, and effects of SiC whiskers contents on the microstructure and flexural strength of the SCWS/KGP and SCWS/leucite composites were investigated. The results show that the whisker addition has little influence on both phase composition and thermal shrinkage of the KGP composites, but a suitable content of whisker will result in the improved flexural strength, and when the SCWS content is 2 wt%, flexural strength of the SCWS/KGP composite is enhanced by 95% compared with the neat geopolymer. The flexural strength of the composites can be further enhanced significantly after the composites being treated at 1100 °C and 1200 °C and flexural strength of the composite with SCWS content of 2 wt% was 107% and 125% higher than the untreated counterpart, respectively. The increase in flexural strength of the composites should be attributed to the strong leucite formation, whisker debonding and pulling out from matrix during the fracturing process based on the good interfacial bonding state between whisker and leucite matrix.

Objective To observe the differences in clinical therapeutic effect on acute attack of lumbar disc herniation (LDH) treated with electroacupuncture (EA) of different wave patterns so as to optimize EA wave pattern in the treatment of acute attack of LDH. Methods A total of 108 patients were randomized into three groups, i.e., a disperse-dense wave, an intermittent wave and a continuous wave group, 36 cases in each one. In all of three groups, Shangliao (上髎BL31), Ciliao (次髎BL32), Zhōngliao (中髎BL33) and Xialiao (下髎BL34) were selected bilaterally as the main acupoints, which is generally termed as Bāliao (八髎 BL31 to BL34, bilateral). In each group, the corresponding wave pattern was used in EA. The treatment lasted 20 min each time, once daily, totally for 10 days. Before and after treatment, the score of visual analogue scale (VAS) and the score of the lower back pain of Japanese orthopedic association (JOA) were observed in the patients of three groups and the overall therapeutic effect was evaluated. Results After treatment, the VAS score was decreased and JOA score was increased in the patients of 3 groups, indicating statistical significance (all P 0.05). Conclusion Electroacupuncture of 3 different wave patterns all effectively relieves clinical symptoms of acute attack of lumbar disc herniation. Regarding pain release, electroacupuncture with disperse-dense wave is better than intermittent wave and continuous wave. Regarding the improvement of lumbar function, the effect of electroacupuncture with continuous wave is better than disperse-dense wave and intermittent wave.

The high-temperature service performance of nearly fully dense 20 wt% BNW/SiO2 ceramic was systematically investigated. The oxidation damage and strength degradation of the whiskers combined with the surface microstructures of the samples predominantly influence the flexural strength from RT to 1000 °C. In previous work, the temperature dependence of the material properties is invariably ignored when evaluating thermal stress crack initiation and propagation behaviour. In this work, modified thermal shock models that include temperature-dependent material properties were established based on thermal-shock fracture (TSF) theory and thermal-shock damage (TSD) theory. Then, the thermal shock resistance (TSR) of the BNW/SiO2 ceramic was evaluated by preforming a water quenching test. The modified models could better explain the TSR behaviour of the ceramic, indicating that considering the temperature-dependent material properties will reveal the thermal shock damage mechanism more precisely.

MAX phases are a family of ternary carbide or nitride ceramics possessing a layered crystal structure and, due to their chemical bonds having a mixed covalent-ionic-metallic nature, have unique properties combining those of metals and ceramics. In this review, the formation mechanisms of MAX phases from elemental and compound powders are reviewed in detail, as the formation mechanisms are closely related to the unique properties of well-synthesized MAX phases. The stability of MAX phases in some harsh external environments is significantly influenced by the defect population, allowing the mechanisms of defect formation and migration to strongly influence their self-healing performance and radiation tolerance. The properties of MAX phases can be tailored by creating solid solutions, which have lattice distortions, and texturing which results in the preferential orientation of plate-like grains.

SiBCN-reduced graphene oxide (SiBCN-rGO) ceramic composites with different rGO content derived from a single-source precursor were successful synthesized by polymer derived ceramics routes to tune their dielectric properties and electromagnetic wave absorption capacity. SiBCN-rGO ceramic composites with 6 wt% GO annealed at 1300 °C possessed the best microwave absorption performance obtaining the minimum reflection coefficient (RCmin) of −62.71 dB at 10.72 GHz, and the thin thickness of 2.17 mm. Adjusting its thickness to 1.58 mm could obtain the maximum effective absorption bandwidth (RC < −10 dB) of 4.32 GHz. The microwave absorption mechanisms of the as-prepared SiBCN-rGO ceramic composites were mainly attributed to the conductive loss and polarization loss induced by the synergistic effects of amorphous SiBCN matrix, rGO and SiC nanocrystals.

Large inventory and non-degradability made waste glass fiber reinforced plastics (GFRP) a heavy burden to environment. They are increasingly reclaimed through mechanical crushing and used as aggregate replacement in concrete. However, reuse of all-component recycled GFRP (rGFRP) was still limited due to the inconsistent influences of powder and fiber on cementitious materials. In this study, mortar and concrete with two different gradations of all-component rGFRP at 10 wt%, 20 wt% and 30 wt% were investigated with mechanical tests, ultrasonic pulse velocity inspection, Depth-of-Field optical microscopy, Scanning Electron Microscopy (SEM) and micro-CT. It revealed that the splitting strength of cement mortar was significantly increased while 10 wt% of rGFRP was added, whereas the compressive and flexural strength were barely affected. For concrete, the initial and final setting time were prolonged by the addition of 30 wt% rGFRP up to 93.8% and 124.3%, respectively. The mechanical strength of concrete increased with rGFRP content firstly, and then decreased, due to the reduced dispersity of rGFRP and compactness of mortar. When 10 wt% of rGFRP was added, the 28-day compressive, flexural and splitting strength of concrete were optimized to 25.8 MPa, 4.25 MPa and 3.02 MPa, respectively. The failure pattern analysis indicated that rGFRP can restrain crack propagation, reduce crack width and improve the integrity of fractured concrete. The results suggested the potential feasibility of rGFRP as fine aggregate replacement, and provided solid experimental references for practically reusing rGFRP in cementitious materials.

Three new complexes, namely, [Cu2(H2bdcpb)2(pyridine)2] (1), [Cu3(bdcpp)2(CH3NCH3)(H2O)] (2), and [Cu2(H2bdcpp)2(H2O)2]·2H2O (3), have been synthesized through the hydro/solvothermal reaction of cu...

The microstructure，texture distribution and tensile property of 7xxx ultra-thick plate was investigated by optical microscopy (OM), scanning electron microscopy (SEM), electron back scattering diffraction (EBSD), transmission electron microscopy (TEM) and tensile tests. The results show that the microstructure, texture and tensile property were inhomogeneous along the thickness direction. A large number of sub-crystals remained on the surface of the thick plate and was accompanied by much recrystallization. Most of the structures were random texture, and the proportion of typical texture was low at the edge. For the center layer, there were also a lot of recrystallized grains and typical deformed texture along the β-fiber (Brass, S, and Copper) was observed. The 1/4 layer of the plate is a transition one, and had the lowest recrystallized fraction. From surface to center, precipitation phases within grains and grain boundaries gradually coarsen, mechanical properties reduced. At the same thickness, the tensile property showed appreciable anisotropy, the L direction was the highest and the S direction was the lowest.

Laser surface modification technology is one of the most advanced technologies, which uses laser to modify the characteristics of the surface to offer superior performance for various industrial applications. In this study, laser surface hardening behavior of GM246 case iron was investigated. Result shows that excellent laser surface hardening of GM246 cast iron need low power density and scanning speed. With power of 2500 W, scanning speed of 300 mm/min and power density of 2500 W/cm2, the laser surface hardening of GM246 cast iron achieved the hardness of 790HV, which was 2-3 times higher than the hardness of base metal. Also, the depth of laser surface hardening case achieved 0.9 mm and the hardening case demonstrated three subzones.

The multifunctional metastable SiBOCN system ceramics (including SiBN, SiCN, SiON, SiBC, SiBCN, SiBON, SiBOCN, etc.) are a new type of advanced structure–function integrated materials with unique s...

Formaldehyde (HCHO) is a priority pollutant in the indoor environment, which is irritative and carcinogenic to humans. The non-noble metal oxides have a wide application prospect in the decomposition of HCHO. Defects in metal oxides have been widely accepted as active sites in heterogeneous catalysis. Compared with the extensive study of oxygen defects, the effect of cation defects has not been clearly addressed. Herein, Mn defect-rich Mn3O4 was synthesized by pyrolysis of Ce-doped MnCO3. It is found for the first time that the content of Mn defects in Mn3O4 can be adjusted by introducing Ce. The introduction of Ce resulted in the higher contents of Mn defects, which significantly enhances the HCHO decomposition. Moreover, Mn defect can effectively narrow the half-metallic gap of Mn3O4, regulate the electronic structure and coordination environment of surrounding oxygen, and further improve the activity and mobility of neighboring oxygen atoms. Importantly, Mn defects are not only beneficial to the generation of neighboring oxygen vacancy but also conducive to enhancing the activation ability of oxygen vacancy for O2. The advantages resulting from Mn defects significantly enhance the HCHO decomposition. This research proposes a strategy to adjust cation defects and deepens the comprehension of the function of cation defects.

Porous gas bearings (PGBs) have a proactive application in aerospace and turbomachinery. This study investigates the gas lubrication performance of a PGB with the condition of velocity slip boundary (VSB) owing to the high Knudsen number in the gas film. The Darcy-Forchheimer laws and modified Navier-Stokes equations were adopted to describe the gas flow in the porous layer and gas film region, respectively. An improved bearing experimental platform was established to verify the accuracy of the derived theory and the reliability of the numerical analysis. The effects of various parameters on the pressure distribution, flow cycle, load capacity, mass flow rate, and velocity profile are demonstrated and discussed. The results show that the gas can flow in both directions, from the porous layer to the gas film region, or in reverse. The load capacity of the PGB increases with an increase in speed and inlet pressure and decreases with an increase in permeability. The mass flow rate increases as the inlet pressure and permeability increase. Furthermore, the simulation results using VSB are in agreement with the experimental results, with an average error of 3.4%, which indicates that the model using VSB achieves a high accuracy. The simulation results ignoring the VSB overrate the load capacity by 16.42% and undervalue the mass flow rate by 11.29%. This study may aid in understanding the gas lubrication mechanism in PGBs and the development of novel gas lubricants.

The ablation properties and mechanisms of BN-coated Cf-reinforced SiBCNZr composites under an oxyacetylene combustion torch were investigated. The mass and linear ablation rates of the Cf/SiBCNZr ceramic matrix composites were lower than those of Cf/SiBCN and SiCf/SiBCN composites, reaching 0.0022 mg/s and 0.0136 mm/s, respectively. The ablation resistance of the SiBCN ceramics was enhanced by the addition of Zr, whereas the BN-coated Cf increased the thermal shock resistance of the SiBCNZr ceramics. No macrocracks were found on the ablation surface of the Cf/SiBCNZr specimen. The ablation mechanisms based on different ablation temperatures, phase evolution during ablation, and ablation morphologies in the different ablation regions consisted of oxidation of the carbon fibre and ceramic matrix, emission of various gases, the flow of high-viscosity SiO2, and denudation of Cf under the erosion of the ablation flame.

This brief presents a novel design method of broadband continuous-mode Doherty power amplifier (CM-DPA) using compensation susceptance. In particular, at power back-off point, the compensation susceptance is added at the current source plane of the carrier PA to make it operates in continuous mode, which thus enhances the back-off efficiency and extends the bandwidth. Meanwhile, considering the influence of the parasitic parameters of the PA in practical design, the designed compensation susceptance at the current source plane is equivalently transformed into the compensation susceptance at the package plane of the carrier PA. Additionally, at saturation point, the load impedances at the package plane of both carrier and peaking PAs can meet the impedance conditions of drain efficiency more than 60%. Based on the proposed method, a 74% fractional bandwidth CM-DPA operating from 1.1 to 2.4 GHz is designed and measured. Under the continuous-wave excitation, the measured 6-dB back-off efficiency is 46.8%–63% and the saturation efficiency is 59.1%–78.8%. The measured small-signal gain and back-off gain are 10–12 dB and 9.1–10 dB, respectively.

Ni2P nanoparticles and CdS nanorods were grew together on a mesoporous g-C3N4 through a facile in-situ solvothermal approach. Under visible light (λ > 400 nm), the as-prepared ternary PCN–CdS-5% Ni2P composite displays a high H2 evolution rate with 2905.86 μmol g−1 h−1, which is about 14, 18 and 279 times that of PCN–CdS, PCN–Ni2P and PCN, respectively. The enhanced photocatalytic activity is mainly attributed to the improved separation efficiency of the photocarriers by the type II PCN–CdS heterojunction and the effective extraction of photogenerated electrons by Ni2P. Meanwhile, Ni2P acts as co-catalyst to provide the photocatalytic active site for hydrogen reduction. In addition, PCN–CdS-5% Ni2P composite exerts good stability in 12-h cycles.

Gate reliability and its degradation mechanism were studied for the normally off high-electron-mobility transistors (HEMTs) with regrown p-GaN gate and AlN/SiN x stack passivation. Through comparing the forward leakage current in two designed structures, the conduction mechanism is determined to be Fowler-Nordheim tunneling whose current is independent of temperature when the Pd/p-GaN Schottky junction is under high electric field. Even for the regrown p-GaN gates, this Schottky junction fails at first, resulting in an abrupt increase in gate current. The maximum gate operation voltage with a failure rate of 1% for 10-year lifetime is estimated to be about 6.87 and 6.07 V at room temperature by adopting power law and exponential law as extrapolation fitting, respectively. Degradation process monitoring reveals that the net acceptor concentration $N_{\mathrm {A}}$ extracted through $C$ – $V$ fitting presents an apparent decreasing trend from $3.8\times 10^{19}$ to $1.1\times 10^{19}$ cm−3 with the stress time increased from 30 to 2600 s. This is assumed to be related with the defects generation in the Schottky depletion region under high tunneling current and high electric field. These analyses show the feasibility of the normally off HEMTs with a regrown p-GaN gate and AlN/SiN x stack passivation for practical applications, giving directions for further improving the gate breakdown voltage and lifetime.

Although solution-processed organometal halide perovskites (OHPs) have attracted much attention for solar cell applications due to their superior photoelectric properties, such as strong band-edge absorption, small exciton binding energy, balanced electron-hole transport, superb charge carrier mobility, etc., their instability in the ambient air severely limits their commercial applications. Here, we introduce 4-Trifluorophenyl methylammonium cations (CF3PMA+) on the surface of 3D MAPbI3 films. Subsequently, the hydrophobic fluorinated 2D perovskite thin film is in-situ formed on 3D MAPbI3 surface. The van der Waals interaction between water molecules and the surface of the fluorinated 2D perovskite becomes weaker, which prevents the water molecules from entering the perovskite lattice and, therefore, improves the moisture resistance of the perovskite. In addition, the lifetime of the excited photocarriers becomes longer after 4-Trifluorophenyl methylammonium iodide (CF3PMAI) modification, which is conducive to carrier extraction and interface transport. The 2D/3D perovskite based solar cell (2D/3D PSCs) finally achieves a PCE of 15.01% by introducing CF3PMAI, and the unsealed PSCs can maintain 90% initial efficiency within 500 hrs. Our approach provides a moisture-resistant 2D/3D perovskite film heterostructure, where the hydrophobic fluorinated 2D perovskite layer acts as a protective layer.

Robot-assisted physical therapy can encourage a subject's voluntary participation to achieve rapid motor function recovery. To enhance the subject's cooperation, and training safety during training sessions, we develop a new ankle robotic system with three rehabilitation training strategies based on an admittance controller, namely, patient-passive compliance exercise, isotonic exercise, and patient-active exercise, which fully consider the patient's muscle strength level, and different stages of recovery. The developed parallel two-UPS/RRR ankle rehabilitation robot is actuated by two servo linear actuators, and one servo motor, and has three rotational degrees of freedom. The mechanism is simple, and ensures that the rotation center of the ankle joint complex from different patients coincides with the robot's rotation center. All three strategies are based on the admittance controller, and its derivatives, and the controller's output is obtained based on proportional, and time-shifting methods according to the continuous measured torque. In particular, the developed two-UPS/RRR ankle robotic system covers the whole-stage compliance rehabilitation training, ensuring the safety of full-cycle training sessions. Experiments of the three rehabilitation training strategies were carried out on five healthy subjects, with the results showing good compliance, and trajectory tracking performance.

Encapsulating noble metal nanoparticles (NPs) within the zeolite framework enhances the stability and accessibility of active sites; however, direct synthesis remains a challenge because of the easy precipitation of noble metal species under strong alkali crystallization conditions. Herein, beta zeolite-encapsulated Pt NPs (Pt@Beta) were synthesized via a hydrothermal approach involving an unusual acid hydrolysis preaging step. The ligand—(3-mercaptopropyl)trimethoxysilane—and Pt precursor were cohydrolyzed and cocondensed with a silica source in an initially weak acidic environment to prevent colloidal precipitation by enhancing the interaction between the Pt and silica species. Thus, the resultant 0.2%Pt@Beta was highly active in the transformation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid (FDCA) under atmospheric O2 conditions by using water as the solvent while stably evincing a high yield (90%) associated with a large turnover number of 176. The excellent catalysis behavior is attributable to the enhanced stability that inhibits Pt leaching and strengthens the intermediates that accelerate the rate-determining step for the oxidation of 5-formyl-2-furan carboxylic acid into FDCA.

Two compact and high selectivity balanced bandpass filters with excellent common mode rejection are designed in this brief. Compared with the half-wavelength microstrip transmission line, 180° phase shift is realized by two small swap structures, which are composed by double-sided parallel-strip line (DSPSL), and this way can easily realize a wideband common mode rejection with compact circuit size. Two out-of-band transmission zeros are introduced by the dual-mode ring resonator in the first proposed structure; thus, high selectivity can be achieved. In the second filter, shorted/open coupled microstrip lines are added between the dual-mode ring resonator and 180° swap structure, two additional transmission zeros can be achieved. Finally, two prototypes center at 2.2 GHz are fabricated, and the measured 3-dB bandwidths for the differential mode are 23.6% and 11.8%, respectively.

Additive manufacturing of ceramics gains increasing attention in recent years, as ceramic material like clay processes distinctive merits, including hardness, thermal and chemical stability, etc. The customer-level extrusion-based ceramics 3D printer is getting easily achievable. However, due to its semi-liquid and highly viscoelastic properties, the clay material causes new challenges to the computational aspects. It does not dry instantly and may collapse during the accumulated force from new layers breaks the moment equilibrium, especially when adjacent layers have less overlap region. We tackle this unique problem, focusing on shell-like models in extrusion-based ceramics printing in this paper. We propose a structural analysis algorithm that considers the moment equilibrium for each layer along the fabrication process. We also present a computational framework to enhance the structural stability by local thickening of the shell models without affecting the appearance. We demonstrate the printing process and physical results to validate our method.

Narrowband radar automatic target recognition (ATR) is often implemented in a single-feature domain, where recognition performance is limited because only one target property is considered. Fusing features from multiple domains is an effective way to improve recognition accuracy. Existing fusion methods utilize simple fusion strategies, such as concatenation and addition, and the classier design is not considered. In this letter, a hierarchical fusion network (HFN) with multidomain features for narrowband radar ATR is proposed. The HFN contains an intradomain network and an interdomain network with abundant features in multiple domains from the radar echo signal as the input of the network. In the intradomain network, the autoencoder (AE) network is used to learn low-dimensional features and reduce the redundancy of features in the same domain. Moreover, the ratio of within-class distance to between-class distance is introduced into the intradomain network to increase the separability of low-dimensional features. The interdomain network fuses different domain features and obtains the classification result through neural networks. The intradomain and interdomain networks construct a whole framework with a unified loss function, which is jointly optimized via backpropagation. Experimental results on the aerial target data set (drones vs. birds) and the ground target data set (wheeled vehicles, tracked vehicles, and humans) demonstrate that the proposed method is effective for narrowband radar ATR.

Multimodal summarization aims to extract the most important information from the multimedia input. It is becoming increasingly popular due to the rapid growth of multimedia data in recent years. There are various researches focusing on different multimodal summarization tasks. However, the existing methods can only generate single-modal output or multimodal output. In addition, most of them need a lot of annotated samples for training, which makes it difficult to be generalized to other tasks or domains. Motivated by this, we propose a unified framework for multimodal summarization that can cover both single-modal output summarization and multimodal output summarization. In our framework, we consider three different scenarios and propose the respective unsupervised graph-based multimodal summarization models without the requirement of any manually annotated document-summary pairs for training: (1) generic multimodal ranking, (2) modal-dominated multimodal ranking, and (3) non-redundant text-image multimodal ranking. Furthermore, an image-text similarity estimation model is introduced to measure the semantic similarity between image and text. Experiments show that our proposed models outperform the single-modal summarization methods on both automatic and human evaluation metrics. Besides, our models can also improve the single-modal summarization with the guidance of the multimedia information. This study can be applied as the benchmark for further study on multimodal summarization task.

A multicomponent (TiZrHfNbTaMo)C ceramic has been fabricated by pressureless sintering at temperatures from 2100 °C to 2500 °C, using an equimolar multicomponent carbide powder synthesized by carbothermal reduction as the starting material. Influence of sintering temperature on densification, microstructure and mechanical properties of the ceramics was investigated. The relative density increases with increasing sintering temperature, and a nearly fully dense sample is achieved by pressureless sintering at 2500 °C. Average grain size increases from 3.7 to 15.2 μm with increasing sintering temperature from 2300 to 2500 °C. The (TiZrHfNbTaMo)C ceramic sintered at 2400 °C exhibits a single phase fcc structure with homogeneous chemical composition, an average grain size of 7.0 μm and a relative density of 96.5%, while its measured hardness is 33.2 GPa at 100 mN and 23.2 GPa at 9.8 N.

In aeroengine titanium alloy components, hard alpha (HA) inclusions strongly affect material performance, especially in terms of fatigue properties. Residual stresses caused by thermal expansion mi...

The solubility of pentaerythritol (PE) in four binary solvents (methanol + water, ethanol + water, isopropanol + water, acetonitrile + water) is determined using the gravimetric method at temperatu...

This paper presented a novel analytical method for calculating magnetic field in the slotted air gap of spoke-type permanent-magnet machines using conformal mapping. Firstly, flux density without slots and complex relative air-gap permeance of slotted air gap are derived from conformal transformation separately. Secondly, they are combined in order to obtain normalized flux density taking account into the slots effect. The finite element (FE) results confirmed the validity of the analytical method for predicting magnetic field and back electromotive force (BEMF) in the slotted air gap of spoke-type permanent-magnet machines. In comparison with FE result, the analytical solution yields higher peak value of cogging torque.

Using stacked models for 3D printing could significantly improve printing efficiency and save printing time. For standard 3D printing techniques like Fused Deposition Modeling (FDM) or Digital Light Processing (DLP), support structures are required for overhanging areas, even between the stacked models. However, there are requirements from medical applications like 3D printed dental implant guides, that support structures are not allowed to be placed on some restricted regions to maintain models’ appearance quality and accuracy. This paper introduces a constrained multi-level stacking scheme for DLP 3D printers, aiming to stack as many models as possible in the printing space; meanwhile, no support is placed on the restricted regions. We rotate each stacked model along the axis and calculate the feasible pose set that restricted regions have no overhanging surface. We further propose a level-based scaffold structure to arrange the stacked models level by level. Therefore, support structures could be generated on the scaffold, and the stacked model does not need to support each other. We employ a heuristic strategy for each level to iteratively select a candidate model and its posture to achieve a locally optimal arrangement. We then introduce perturbations in the arrangement order, using a hill-climbing method to approximate the most volume-efficient arrangement.

Developing the pure carbon materials with ultra-light and excellent electromagnetic wave absorption (EWA) performance that aims to solve signal interference or electromagnetic pollution is highly desirable. However, there still remains a huge challenge that whether the pure carbon materials with excellent conductivity can be used as EWA alone and how the performance can be optimized. Keeping the high conductivity and adjusting the relaxation intensity (Δe) at the same time are theoretically found to be the effective way to improve the attenuation of electromagnetic wave and obtain better impedance matching. Herein, the key relationship between Δe and EWA property is proved by theoretical calculation. As the experimental design, the pure carbon absorber, CMF (carbonized melamine foam, the density of 4.34 mg cm−3), which holds highly conductivity and appropriate Δe, exhibits a strong absorption (−57.3 dB) and a wide effective absorption band of 8.32 GHz. It is verified when carbon material possesses excellent conductivity, it is easy to steer the optimized design of Δe toward improving the impedance matching. Meanwhile, the strategy developed here paves a new way for the design of high conductivity and ultralight EWA materials for the practical applications.

Si2N2O composites were achieved via direct ink writing technique and pressureless sintering. The design and optimization of inks and the effect of mass ratio of Si3N4 and SiO2 on the phase composition, microstructure, mechanical properties and dielectric properties of composites were systematically investigated. The inks exhibit superior stability and printability. Increasing SiO2 content facilitated densification and enhancement of mechanical property. The generation of β-Si3N4 and Si2N2O and the nucleation of cristobalite were restrained by high content SiO2. The ceramic composites with the flexural strengths from 74.1MPa to 104.9MPa and low dielectric constant (≤4.68) were fabricated. This strategy provides a systematic reference for synthesis of high-performance porous Si2N2O composites based on the DIW.

To improve the passive radiative heat dissipation property of aluminum alloy, a novel-structural SiC/hBN nanocomposite ceramic coating with high emissivity value (>0.86) was fabricated by one-pot liquid-phase plasma assisted electrophoresis and sintering (LPES) method. The special formation conditions of nanocomposite coating were optimized as: applied voltage was not lower than 600 V, temperature of electrolyte was ranged from 70 to 90 °C and the concentrations of SiC and hBN nanoparticles were 8 g/L and 40 g/L, respectively. The unique parameters contributed to the plasma assisted SiC and hBN nanoparticles synergistic electrophoresis and then sintering together by SiO2 based glassy phase. The infrared emissivity in the wavelength of 3–20 μm was enhanced by SiC/hBN nanocomposite coating, especially the value was up to 0.86 in 3–8 μm wavelength. The nanocomposite coating enabled the temperature drop by 10.4 °C for 1 W LED compared with the bare aluminum alloy, which leds to the cooling efficiency of 19.8%, respectively. The SiC/hBN ceramic nanocomposite coating fabricated by one-pot LPES process shows a novel strategy to design excellent radiative heat dissipation property coatings.

In this paper, 15Cr-ODS steels containing 0, 1 wt%, 2 wt% and 3 wt% Al element were fabricated by combining wet-milling and spark plasma sintering (SPS) methods. The microstructure and mechanical properties of ODS steel were investigated by XRD, SEM, TEM, EBSD and tensile tests. The results demonstrate that the Al addition significantly refines the particle precipitates in the Fe−Cr matrix, leading to the obvious refinement in grain size of matrix and the improvement of mechanical properties. The dispersion particles in ODS steels with Al addition are identified as Al2O3 and Y2Ti2O7 nanoparticles, which has a heterogeneous size distribution in the range of 5 nm to 300 nm. Increasing Al addition causes an obvious increase in tensile strength and a decline in elongation. The tensile strength and elongation of 15Cr-ODS steel containing 3 wt% Al are 775.3 MPa and 15.1%, respectively. The existence of Al element improves the corrosion resistance of materials. The ODS steel containing 2 wt% Al shows corrosion potential of 0.39 V and passivation current density of 2.61×10−3 A/cm2(1.37 V). This work shows that Al-doped ODS steels prepared by wet-milling and SPS methods have a potential application in structural parts for nuclear system.

This article presents a new analytical method for calculating performance of line-start permanent-magnet synchronous motor (LSPMSM) based on multidamping-circuit model (MDCM) to take spatial harmonic components of LSPMSM into account. First, MDCM of damping bar in the rotor is established according to Kirchhoff's current law. Second, an eleven-order system of LSPMSM is deduced from a group of differential equations according to the equations of flux linkage, voltage, torque, and motion. Then, starting process of LSPMSM is simulated with the proposed analytical method, including speed, current, and electromagnetic torque waveforms versus time, respectively. The starting performance and synchronization capability are analyzed and compared under different effective value of input phase voltage, moment of inertia, and load torque. The simulation time with finite element method is about 1235 times longer than the simulation time with the proposed analytical method to calculate the starting process of LSPMSM with the same computer. Finally, the validation of the developed analytical method based on MDCM is verified by comparing simulating results with experimental results and direct axis and quadrature axis (DQ) model. The results based on this new method are reliable. It is conducive to calculate, analyze, and design LSPMSM with less time.