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In this work, the second harmonic generation (SHG) technique based on embedded piezoelectric (PZT) sensors is developed for the defect assessment of concrete samples. Three different imperfection f...

This paper presents the development of a nonlinear vibro-acoustic modulation technique based on non-contact piezoelectric sensors to detect the crack progression of concrete subjected to both mechanical and thermal load. Two types of crack are investigated in the work including the isolated single crack induced by the three point bending test and distributed mapping cracks caused by heating treatment. Experimental results show that the damage index defined in the air-coupled wave modulation method – ultrasonic nonlinear parameter presents a positive correlation with the growth of single crack in bending test and the accumulation of mapping crack in thermal test. The sensitivity of developed method is validated through a comparison between the ultrasonic nonlinear parameter and two traditional linear parameters namely the phase velocity of Rayleigh wave and resonance frequency of vibrations. X-ray Computed Tomography (CT) technique and three-dimensional (3D) image reconstruction method are used to visualize microstructure of thermal damage. The CT images show that proposed nonlinear parameter is reliable and well correlated with the microstructural defects of concrete specimen. The repeatability of the air-coupled method is better than the contact method because the coefficient of variation of non-contact measurements is averagely about 43.2% of the contact measurements. Due to the advantage of removable characteristic of non-contact ultrasonic measurements, the developed air-coupled nonlinear wave modulation method could be promising for fast damage assessment of concrete structures in engineering practice.

In this paper, a novel nonsingular finite-time backstepping controller is constructed for trajectory tracking of marine vessel subject to unknown external disturbances. Firstly, in the presence of disturbances, a disturbance observer (DO) is proposed to estimate and compensate the disturbances exactly in finite time. Secondly, a finite-time tracking controller is designed in the classical backstepping procedure, however, the inevitable singularity appears in calculating the derivative of virtual control. Furthermore, for overcoming this singularity, a nonsingular finite-time backstepping controller is designed by adopting a finite-time command filter to estimate the derivative, instead of calculating it directly. Theoretical analysis demonstrates the closed-loop system is finite-time stable. Finally, simulation results and comparisons illustrate the effectiveness of the proposed method.

Plant diseases reduce crop yield and quality, hampering the development of agriculture. Fungicides, which restrict chemical synthesis in fungi, are the strongest controls for plant diseases. However, the harmful effects on the environment due to continued and uncontrolled utilization of fungicides have become a major challenge in recent years. Plant-sourced fungicides are a class of plant antibacterial substances or compounds that induce plant defenses. They can kill or inhibit the growth of target pathogens efficiently with no or low toxicity, they degrade readily, and do not prompt development of resistance, which has led to their widespread use. In this study, the growth inhibition effect of 24 plant-sourced ethanol extracts on rice sprigs was studied. Ethanol extract of gallnuts and cloves inhibited the growth of bacteria by up to 100%. Indoor toxicity measurement results showed that the gallnut and glove constituents inhibition reached 39.23 μg/mL and 18.82 μg/mL, respectively. Extract treated rice sprigs were dry and wrinkled. Gallnut caused intracellular swelling and breakage of mitochondria, disintegration of nuclei, aggregation of protoplasts, and complete degradation of organelles in hyphae and aggregation of cellular contents. Protection of Rhizoctonia solani viability reached 46.8% for gallnut and 37.88% for clove in water emulsions of 1000 μg/mL gallnut and clove in the presence of 0.1% Tween 80. The protection by gallnut was significantly stronger than that of clove. The data could inform the choice of plant-sourced fungicides for the comprehensive treatment of rice sprig disease. The studied extract effectively protected rice sprigs and could be a suitable alternative to commercially available chemical fungicides. Further optimized field trials are needed to effectively sterilize rice paddies.

A bacterial strain (BGf-2) with anti-Beauveria bassiana activity was obtained from the feces of Blattella germanica (L.) and identified as Pseudomonas aeruginosa based on biochemical tests and 16S rRNA sequence analysis. An antifungal protein (A0A0H2ZK06) was purified with Sephadex G-100 column and DEAE-sepharose Fast Flowanion exchange from sterile BGf-2 fermentation liquid. Based on MALDI-TOF MS analysis and protein model building, A0A0H2ZK06 showed homology with Pyrrolidone carboxyl peptidases (pcps). Fermentation liquid and antifungal proteins not only reduced the B. bassiana conidial germination rate but also inhibited hyphal growth. A per os test showed that the mortality of cockroaches decreased after treatment with BGf-2 suspension compared with control. We hypothesized that gut microbes with antifungal activity might play an important role in protect cockroaches from pathogenic fungi.

We described herein a unique dual emission switching process from o-carborane–tetraphenylethene (TPE) dyads induced by twisted intramolecular charge transfer (TICT) in the crystalline state. Two novel o-carborane–tetraphenylethylene dyads, composed of a TPE core bearing o-carborane units, were designed, synthesized and characterized. Crystalline o-1 and o-2 were obtained with mono-substituted and bi-substituted o-carborane units, respectively. Both dyads presented locally excited (LE) emission and TICT induced emission in solutions. Crystalline o-1 demonstrated aggregation-induced emission (AIE), crystallization-induced emission (CIE), thermochromism, vapochromism, and mechanical luminescence (MCL) properties via TICT, while crystalline o-2 showed only the AIE and CIE properties orginating from the inherent ICT states. From the mechanistic investigations and theoretical calculations, it was demonstrated that the emission was reversible and switchable between green and orange colors for o-1, which was assigned to the facile TICT modulation in the solid state. The results manifest that the unique three-dimensional o-carborane cluster's structure plays an important role in precisely controlling the molecular packing patterns and conformations to achieve TICT emission.

Reduced graphene oxide wrapped hollow molybdenum trioxide nanorods (MoO 3 @rGO) have been fabricated by a facile process. The MoO 3 @rGO shows improved lithium storage performance. It could deliver a high reversible capacity (842 mAh/g at 0.1 A/g), excellent cycling stability (778 mAh/g at 0.1 A/g after 200 cycles) and excellent rate capability (455 mAh/g at 2 A/g). The excellent electrochemical performance could be attributed as the special core (MoO 3 )/sheath (rGO) structure, which could accommodate the volume change of MoO 3 during lithiation/delithiation process. In addition, the rGO coating layer could improve the electronic conductivity of MoO 3 .

To design and synthesize materials for alkaline hydrogen evolution is favorable for industrial hydrogen cycle operation. In this study, we present a facile approach to synthesize free-standing ruthenium-beryllium (RuBe) nanosheets, which possess amorphous phase state and associated with holey structures due to the molten method. The two-dimensional RuBe nanosheets exhibit improved activity than pure Ru counterpart and comparable properties to commercial Pt toward hydrogen evolution reaction in both of alkaline and neutral electrolytes. Based on the experiments and density functional theory calculations, it is suggested that the adsorption and dissociation of water molecules on Ru-based catalyst are much enhanced with the assistance of Be modulation, which are essential for the improved hydrogen production capability under alkaline condition. This work broadens the Ru-based catalyst family and may provide new insights for electrocatalyst development.

Heteroatom-doped carbon nanomaterials with well-defined porous are used as anode materials for SIBs due to their exceptional structural characteristics. In this work, porous N-doped carbon networks composed with ultrathin carbon nanosheets were synthesized via the direct pyrolysis of Vitamin B5. The content of nitrogen, specific surface area, porous structure of the N-doped carbon nanosheet networks were adjusted by changing reaction temperatures. The formation mechasim of the ultrathin N-doped carbon nanosheet networks was also proposed. The generation of calcium carbonate/calcium oxide used as a self-template renders the formation of the porous structure via thermal treatment. The optimized samples possess a superior lithium and sodium storage: 1534 mAh g −1 at 100 mA g −1 vs. Li/Li + and 335 mAh g −1 at 100 mA g −1 vs. Na/Na + , with nearly 100% cycling Coulombic efficiency, remarkable cycling retention and high rate capacity. Additionally, good electrocatalytic activity for ORR via a 4e −1 pathway determines that the resulting primary Zn-air battery showed high discharge power energy density (80 mW cm −2 ), high reversibility and stability over continuous cycles.

The photoluminescence (PL) and circularly polarized luminescence (CPL) of ((R)-1-phenyl-N-(pyren-1-ylmethyl)ethanamine) P-R were successfully modulated via fine-tuning and precise control of excited conformation of dimer/excimer by external stimuli. The resulting aggregation-induced emission (AIE)-active material (P-R) exhibited CPL with a low dissymmetry factor (∼10−4) in monomeric form, while demonstrating a prominent CPL signal with a higher dissymmetry factor (∼10−3) in thin solid films even without annealing processes.

An experimental study on a rotating detonation engine model using hydrogen/air mixture as propellant was conducted to analyze the initiation characteristics of detonation wave. Three ignition methods, including the ordinary spark plug, high-energy spark plug and thermal-jet tube, were used in the tests. The initiation process of rotating detonation wave was recorded and analyzed by a high frequency pressure measurement system and high-speed photographs. Operating range of the model engine was determined by series of experiments. Results indicate that the model engine could be successfully run by all the three ignition methods. Although the detonation formation time using spark plugs is quite stochastic, increasing the ignition energy can reduce the formation time of the detonation wave. Among the three ignition methods, thermal-jet provides the shortest detonation formation time. It is also found that the operating characteristic of the model engine is independent of the ignition device in the same operating condition. Three operation modes of the engine model have been observed, which are failed initiation of the detonation, unstable detonation and continuous rotating detonation. The experimental results show that the stable operating range can be extended by increasing the fuel mass flow rate.

Germanium (Ge) has been considered as a promising anode material for Li-ion batteries because of its theoretical capacity (1600 mA h g−1). However, its poor electrochemical performances resulting from the large volume variation during Li–Ge alloy/dealloy processes prevent its practical application. Herein, we designed a 3D core/shell structure by encapsulation of Ge in a sulfur (S) and nitrogen (N) co-doped three-dimensionally (3D) interconnected macroporous carbon matrix (denoted as Ge@S,N-3DPC). The 3D porous structure can not only buffer the volume change during alloy/dealloy processes, but also facilitate the electrolyte to soak in, offering fast ion/electron pathways. What's more, the co-doping of S and N in carbon could introduce more defects and active sites, which can also help to improve the interfacial adsorption and electrochemical behaviors. When used as an anode material for LIBs, the Ge@S,N-3DPC shows excellent electrochemical performances (1000 mA h g−1 at 200 mA g−1), outstanding cycling stability (94% capacity retention after 300 cycles) and high rate capability (358 mA h g−1 at 10 A g−1). This work develops a general strategy to improve the electrochemical performance of these alloy-type electrode materials with huge volume change in the energy storage area.

Solvent-dependent self-assemblies of an amphiphilic molecule based on perylene bisimide were employed in the fabrication of well-defined millimeter long nanorods and high density nanofibers, respectively. Moreover, the fabricated memory device demonstrated good behaviours with a low operating voltage, high ON/OFF ratio, long retention time, and good stability.

In this paper, a fully non-contact second harmonic generation (SHG) technique using a pair of air-coupled ultrasonic transducers is developed and the feasibility of the technique is investigated through the evaluation of surface cracks of concrete beams subjected to the bending load. The reliability of developed technique is subsequently validated by comparing the non-contact nonlinear ultrasonic measurements with measurement results based on contact-type sensors, where the coefficient of variation of non-contact measurements is averagely about 46% of the contact measurements. The defined nonlinear parameter is found to have a monotonically increasing trend with the growth of concrete crack, and the nonlinear parameter corresponding to the largest crack increases about 7 times from its initial value corresponding to the sample in intact state. In contrast, the increase of linear parameter namely the time-of-flight of surface wave is only about 40%. The difference as high as one order of magnitude verifies the high sensitivity of developed air-coupled SHG technique. With consideration of the easily removable characteristic of air-coupled ultrasonic measurements, the developed SHG technique could be promising for the large scale quality control of concrete structures in engineering practice.

The plant Na+/H+ antiporter (NHX) plays a significant role in cellular ion homeostasis. Herein, an Na+/H+ antiporter gene, SpNHX1 from the Sesuvium portulacastrum plant, was obtained by homology-cloning method. The SpNHX1 gene contains 2113 bp with an open-reading frame encoding a polypeptide of 554 amino acid residues with an estimated molecular mass of 61.27 kDa and an isoelectric point of 7.24. The amino acid sequences of SpNHX1 shared a high similarity with Arabidopsis thaliana AtNHX1 (75.81%), AtNHX2 (77.12%) and Oryza sativa OsNHX1 (73.10%). SpNHX1 contains an amiloride-binding region (FFIYLLPPI), which is a highly-conserved domain in plant Na+/H+ antiporters. RT-PCR (reverse transcriptional PCR) analysis showed that the SpNHX1 gene had a high expression level in roots compared to other tissues under normal conditions. The qRT-PCR (quantitative real-time PCR) results indicated that NaCl treatment induced the expression of SpNHX1 gene in the roots, but its transcriptional levels were not influenced by the ABA, PEG, H2O2, heat (42 °C) or cold (4 °C) stresses. The growth of yeast cells expressing SpNHX1 was better than the non-transgenic control cells in the presence of 30 mM NaCl, 0.4 M KCl, or 0.5 mM LiCl. Furthermore, transgenic yeast cells with SpNHX1 accumulated more Na+ relative to control cells under salinity stress. These results suggested that SpNHX1 was a key determinant in the salt-stress response in Sesuvium portulacastrum.

Stimuli-responsive circularly polarized luminescence (CPL) was successfully achieved through fine-tuning the conformation of a perylenyl dyad by using external stimuli. Monomer CPL was clearly detected from an inherent achiral monochromophore system in a simple perylene–carbazole dyad, and concentration-dependent CPL was observed from ‘good solvent’, giving an excimer-like CPL emission with a peak maximum at 643 nm. Moreover, the CPL bands depended on the aggregated state, which was identical to the emission changes in the THF–H2O system. It is noteworthy that the perylene–carbazole dyad emitted efficient CPL in thin films even without annealing processes. The specific perylenyl–carbazole structure plays a crucial role in CPL in response to the external environment. This novel molecular design strategy opens up a new perspective for the future development of smart CPL-active organic dyads.

3D hierarchical flower-like carbon coated MoO3−x nanosheets (denoted as MoO3−x NS@C) have been successfully fabricated by a simple hydrothermal method. When used as anode for Li-ion batteries, the MoO3−x NS@C electrode exhibits excellent cycle performance and outstanding rate capabilities. The charge capacity can reach 1025 mAh g−1 over 150 cycles, and 62% of the charge capacity is retained when the current density increases to 2000 mA g−1. The improved lithium storage performance of MoO3−x NS@C is attributed to the synergistic effect of oxygen vacancies and the carbon coating, which not only enhance the electric conductivity and Li-ion diffusion coefficient but also lead to superior structural stability and cyclability of the MoO3−x NS@C electrode during repeated lithiation/delithiation process.