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A novel SrSn(OH)6 photocatalyst with large plate and particle size were synthesized via a facile chemical precipitation method. The photocatalytic activity of the SrSn(OH)6 was evaluated by the removal of NO at ppb level under UV light irradiation. Based on the ESR measurements, SrSn(OH)6 photocatalyst was found to have the ability to generate the main active species of O2•−, •OH, and 1O2 during the photocatalytic process. Moreover, SrSn(OH)6 photocatalyst not only exhibits high photocatalytic activity for NO removal (79.6%), but also has good stability after five cycles. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to investigate the NOx transfer pathway and the intermediate products distribution during the adsorption and photocatalytic NO oxidation process. The present work not only provides an efficient material for air pollutants purification at room temperature but also in-depth understanding of the mechanism involved in the photocatalytic NO removal process.

Realizing efficient photocatalytic hydrogen production of graphitic carbon nitride (g-C3N4) in the absence of precious metals is one of the urgent research topics for industrial application. In this work, efficient p-n heterojunction of iron(III) hydroxide and graphitic carbon nitride (Fe(OH)3/g-C3N4) for hydrogen production were successfully constructed using the electrostatic attraction self-assembly method. The Fe(OH)3/g-C3N4 heterojunction could harvest more visible light, suppress recombination and boost transmission rate of the carriers. As expected, without participation of any precious metal, the highest hydrogen production rate (733 μmol h−1 g−1) was 51.2 folds higher than the unmodified g-C3N4 at λ > 400 nm, which is superior to many previous results. Additionally, a possible reaction mechanism was proposed according to energy band analysis as well as the experimental photocatalytic activity results. To the energy and environmental studies fields, this work suggests a novel approach to design high efficiency photocatalysts using abundant and inexpensive metals instead of precious metals.

In this paper, an improved prescribed performance anti-disturbance control is investigated for quadrotors suffering from lumped disturbances and constrained onboard communication resources. Relative threshold event-triggered based extended state observers are respectively established in trajectory and attitude subsystems to recover the immeasurable velocity and unknown lumped disturbances with a less sampling cost, while an explicit relationship between the upper bound of estimation errors and the design parameters of event-triggered condition is derived. With the aid of estimation results, an aperiodic sampling based output feedback trajectory tracking control law is developed by inserting a relative threshold sampler into the controller-to-actuator channel, such that an enhanced robustness can be realized without involving excessive resource occupations. Additionally, a modified prescribed performance control is proposed to regulate the transient profile of trajectory tracking with an arbitrarily small overshoot and a fast convergence rate even in face of triggering error. All closed-loop signals are proved to be ultimately uniformly bounded meanwhile Zeno phenomena can be eliminated. The effectiveness of presented algorithm is validated by comparable simulations.

In this paper, a fuzzy wavelet neural control scheme with improved prescribed performance is investigated for micro-electro-mechanical system (MEMS) gyroscope in the presence of uncertainties and input quantization. A hysteresis quantizer (HQ) is introduced in the controller design to generate input signal in a finite set, which can greatly reduce the actuator bandwidth without decreasing the control accuracy, and avoid the undesirable chattering occurring universally in other quantizers. To guarantee the output tracking with better prescribed transient behavior, a modified prescribed performance control (MPPC) consisting of asymmetric performance boundaries and an error transformation function is explored, such that arbitrarily small overshoot can be assured without retuning design parameters. Unlike the traditional neural network that suffers from explosion of learning, a fuzzy wavelet neural network (FWNN) based on minimal-learning-parameter (MLP) is designed to identify uncertainties with slight computational burden. A robust quantized control scheme is synthesized to compensate for quantization error and achieve prescribed ultimately uniformly bounded (UUB) tracking. Finally, extensive simulations are presented to verify the effectiveness of proposed control scheme.

Pseudomonas fragi and Escherichia coli are considered as common colonizers of fresh and spoilage meat, where they tend to live in the proximity. In this study, we primarily tested interplay patterns between different isolates of these two species in two-by-two combinations grown on stainless steel surfaces as dual-species biofilms. Results showed that these two species presented competition as major observed interplay patterns as biofilms progressed independent of bacterial strains and growth temperatures (15 °C and 25 °C). One dual-species combination was proposed as a representative to further explore dynamic patterns of interaction strength between these two species, with species colonization order taken into consideration as a biological effector. We firstly reported that prior colonization of one species significantly decreased the initiatively colonized cell counts of counterpart species by one to three orders of magnitude when competing for limited adhesion surface, under which E. coli was observed to be more aggressive in surface colonization as compared to P. fragi. However, the spatial structure and microbial composition of mature dual-species biofilms were not observed to be significantly affected. Our findings also shed new light on the evidence that E. coli and P. fragi, respectively, enhanced their biofilm formation capabilities by upregulating expression level of genes that encoded Type 1 fimbriae and phosphate response regulator as dual-species consortia progressed, which could serve as a crucial factor that improved the difficulty of food biocontrol.

Here we report a facile defect-engineering strategy on the support to optimize the metal-support interaction and enhance the metal’s electrocatalytic hydrodechlorination performance in converting 2,4-dichlorophenol (2,4-DCP) to phenol. The specific activity of the Pd nanoparticles (Pd NPs) on defective polymer carbon nitride (Pd/PCN-x) reaches 0.09 min-1 m-2Pd, which is 1.5 times that of the Pd NPs supported on the perfect PCN (Pd/PCN-0). The combined experimental and theoretical results demonstrate that the strong adsorption of phenol on Pd/PCN-0 passivates the active sites, limiting the dechlorination progress. The PCN-x containing -C≡N defects can effectively mediate the spatial configuration and electronic structure of Pd NPs, and promote the preferential adsorption of 2,4-DCP rather than phenol, resulting in an enhanced dechlorination efficiency.

To obtain profiles with sound weld seams, the effects of extrusion parameters and heat treatment on microstructures and mechanical properties of the weld seam were revealed. It was found that the high extrusion speed increases the mechanical properties and welding quality of the welding area. The micro-voids formed in low temperature and low extrusion speed could hinder the grains from growing through the welding interface during heat treatment, which caused weak bonding of the weld seam. Lots of strengthening phases precipitated during aging treatment, which leads to the disappearance of the softened welding area and the improvement of tensile strength. However, the fine grains of welding area translated to coarse grains quickly during solution treatment, and the precipitated phases coarsened and the precipitation free zone (PFZ) widened when the aging time is excessive, above reasons result in the layered fracture of welding area and poor elongation. Tensile strength and elongation were improved simultaneously because of the fine grain boundary precipitates, narrow PFZ and fine homogeneous T1 phases formed in under-aged (UA) treatment. The weld seam obtained by high extrusion speed shows a fine combination of ultimate tensile strength (UTS) and elongation after UA treatment.

Visual servoing is an effective strategy for autonomous flight of quadrotor. However, it faces the requirement of visibility constraint, i.e., holding the observed object inside the field of view (FOV) of camera. To accomplish this goal, we present an attitude restricted back-stepping anti-disturbance controller. Before the controller design, proper perspective moment features are selected to establish an uncoupled vision-quadrotor model without image singularity from a novel image plane, i.e., virtual image plane. Considering the structured vision-quadrotor model, an attitude restricted anti-disturbance control strategy is developed via back-stepping, where the unknown uncertainties are estimated via designing a model-assisted ESO and compensated in feedforward loop, and the drastic attitude motions are restricted by the designed saturation compensated integral barrier Lyapunov function(iBLF) control law. Its superiorities lie in: (1) by designing strong anti-disturbance mechanism and strict attitude limitation arithmetic, the controller can guarantee the observed object in the FOV of camera, (2) considering the deterioration of transient-state behavior due to the strict attitude constraints, a saturation compensator is constructed to improve the system transient-state performance, (3) by incorporating the model information into observer design, the estimation burden of ESO relieves greatly. Stability analysis based on the Lyapunov theory proves the boundedness of attitude states and the convergence of closed-loop system. And we design many simulations to confirm the controller performance.

The African Swine Fever (ASF) outbreaks in China since 2018 caused a more than 100 million decline in its hog inventory. Leveraging publicly available announcements of ASF outbreaks and daily stock prices data from 25 major publicly listed hog companies from China and eight major hog exporting countries, we use the event study method to estimate firm-level abnormal stock price responses to China's ASF outbreak announcements for both Chinese and foreign hog companies. This article describes the data used in the research article "A Fortune from misfortune: Evidence from hog firms' stock price responses to China's African Swine Fever outbreaks" (Xiong et al., 2021). The daily stock price data in this article can be applied to other events that also occurred during the same sample period using a similar event study approach.

Escherichia coli O157:H7 and Pseudomonas were considered as common colonizers of fresh and spoilage meat, where they tended to live in the proximity. In this study, we tested the interplay between different isolates of E. coli O157:H7 and Pseudomonas in random two-by-two combinations grown as dual-species consortia. Results showed that the growth fitness of E. coli was not facilitated by the presence of all tested Pseudomonas strains, and vice versa. Representative combinations were further selected to investigate the property changes following the time course of biofilms formation as compared to single species. Cell counting confirmed that the growth of E. coli O157:H7 was challenged by the presence of Pseudomonas strains as previously described. Our findings shed new light on the evidence that the pathogenicity of E. coli O157:H7 was negatively affected by the presence of Pseudomonas according to the evaluation of spatial organization and genetic expression of virulence factors, which might be a naturally existing biological phenomenon constraining the safety risk of former strains in meat processing and preservation. Intriguingly, we observed that E. coli managed to stably co-exist at low cellular abundance in the progress of dual-species consortia, indicating successful adaptive mechanisms that need further investigations to uncover.

The composite of gold and PDMS hold remarkable potential for surface stress-based biosensor applicaitons. However, the gold and PDMS in composite suffers from poor compatibility with each other and suppresses the performance of the biosensor. Here, we conduct two-step synthesis of the composite of gold and PDMS by in-situ reduction and glucose reduction of HAuCl4. The composite shows stable conductive gold nanoparticle network (SC-AuNW). In in-situ reduction, Au-seeds are embedded in PDMS surface. Furthermore, AuNPs are also generated inside the PDMS and enhance conductivity. The SC-AuNW plays a crucial role in tunneling conductivity of composite film and exhibits an excellent sensitivity to surface stress. We construct SC-AuNW-PDMS biosensors based on surface stress for glucose detection with a detection limit of 0.021 mM, high repeatability and specificity. Our research can promote the application of flexible conductive films in biosensors for disease diagnosis.