Applied Sciences

This study assessed the toxic effects of bisphenol A (BPA) on the microbial community and the function of activated sludge in sequencing batch reactors (SBRs). The toxicity of BPA was mitigated through dosing sludge with Rhodococcus Req-001. BPA reduced the biomass of sludge, and the proportion of viable bacteria decreased with the aggravation of BPA pollution. BPA affected the secretion of extracellular polymeric substances (EPSs), increased the ratio of polysaccharide to protein, and deteriorated the sedimentation performance of sludge. BPA decreased the abundances of functional bacteria involved in the degradation of organic matter and water purification, including Polaromonas, Dechloromonas, and Nitrospira, and the water purification capacity of the reactor decreased. Req-001 enhanced the BPA removal efficiency by 15%, and increased ammonia nitrogen and phosphorus removal by 8.8% and 22.7%, respectively. The functional recovery ability of the sludge system and the high removal ability of Req-001 make it a promising specie for use in BPA bioremediation. This study combined the effect of BPA on activated sludge and reactor performance with the microbial community, clarified the toxic mechanism of BPA on activated sludge, and therefore provides a theoretical basis and potential solutions to help WWTPs cope with the toxic effects of BPA. Full article

Knowing particle penetration efficiencies and concentration distributions in an inlet channel of a sampling device is beneficial for the robust assessment, attribution and quantification of nanoparticles produced by various activities. The aim of this research is to evaluate the effect of the presence or absence of a conical column inside a hollow tapered cylinder on the nanoparticle penetration efficiency and its outlet concentration profile for different flow rates. The particle penetration characteristics of various sizes from 3 nm to 20 nm were numerically investigated by using the flow field and convection diffusion equations within the hollow tapered cylinder. Firstly, the proposed model of the nanoparticle penetration efficiency for the hollow tapered cylinder with the conical column is validated with the experimental data in the literature. Then, the results indicate that the concentration at the outlet of the hollow tapered cylinder with the conical column exhibits annular profiles for 3 nm and 5 nm nanoparticles at a flow rate of 2.0 L/min, which is found to avoid centralizing the particles in the exit area. In addition, the penetration efficiency of nanoparticles can be improved by increasing flow rates or removing the conical column inside the hollow tapered cylinder. Finally, the ring-shaped concentration profile of the 10 nm nanoparticles at the outlet of the hollow conical cylinder with the conical column becomes more obvious as the flow rate decreases. This study interprets and quantitatively decides the nanoparticle penetration efficiency and its exit concentration profile for the hollow tapered cylinder with or without the conical column. Therefore, the results can provide some useful design references for the transport of nanoparticles in the hollow tapered cylinder. Full article

For any rural area, a suitable ecological civilization model is of great significance and must be recommended taking into account its natural, social, and cultural characteristics so that the model is conducive to the sustainable development of its economy, environment, and industrial structure. However, the rural attribute data required for such a recommendation are often missing, and the data sparsity leads to the low accuracy of and poor training effect issues in recommendation algorithms. To address this issue, this paper proposes a geographic data augmentation method, namely the spatial factor on generative adversarial networks (S-GANs), which combines the generative adversarial network (GAN) with the Third Law of Geography. Specifically, the GAN is used to generate data for the rural ecological civilization recommender system, while the Third Law of Geography is used to ensure that the generated data conform to the real geographical environment. To test the effectiveness of the S-GAN method, the experiment used the enhanced rural attribute data as the input of three recommendation systems: RippleNet, KGCN, and KGNN-LS. Compared with the data before argumentation, the recommendation accuracy increased by 55.49%, 25.12%, and 27.14% in RippleNet, KGCN, and KGNN-LS, respectively. The experimental results show that the S-GAN is effective in geographic data argumentation for recommendation and is expected to be widely used in other geographic data argumentation fields. Full article

In recent years, graph convolutional networks (GCNs) have been extensively applied in numerous fields, demonstrating strong performances. Although existing GCN-based models have extraordinary feature representation capabilities in spatial modeling and perform exceptionally well in skeleton-based action recognition, they work poorly for fine-grained recognition. The key issue involves tiny distinctions between multiple classes. To address this issue, we propose a novel module named the topology-embedded temporal attention module (TE-TAM). Through embedding the temporal-different topology modeled with local area skeleton points in spatial and temporal dimensions, the TE-TAM achieves dynamical attention learning for the temporal dimensions of distinct data samples, to capture minor differences among intra-frames and inter-frames, making the characteristics more discriminating, and increasing the distances between various classes. To verify the validity of the proposed module, we inserted the module into the GCN-based models and tested them on FSD-30. Experimental results show that the GCN-based models with TE-TAMs outperformed the property of pred GCN-based models. Full article

Traditional techniques for detecting materials have been unable to coordinate with the advancement of material science today due to their low accuracy and high cost. Accordingly, machine learning (ML) improves prediction efficiency in material science and high-entropy alloys’ (HEAs’) phase prediction. Unlike traditional alloys, HEAs consist of at least five elements with equal or near-equal atomic sizes. In a previous approach, we presented an HEA interaction network based on its descriptors. In this study, the HEA phase is predicted using a graph-based k-nearest neighbor (KNN) approach. Each HEA compound has its phase, which includes five categories: FCC, BCC, HCP, Multiphase and Amorphous. A composition phase represents a state of matter with a certain energy level. Phase prediction is effective in determining its application. Each compound in the network has some neighbors, and the phase of a new compound can be predicted based on the phase of the most similar neighbors. The proposed approach is performed on the HEA network. The experimental results show that the accuracy of the proposed approach for predicting the phase of new alloys is 88.88%, which is higher than that of other ML methods. Full article

The inclusion of training in the Sustainable Development Goals (SDGs) in higher education is essential to achieve them. In addition, labor market reintegration or improvement of older workers is a goal that an increasing number of people have set for themselves, especially in countries severely affected by crises. The union of these two premises has given rise to the application of a methodology in a master’s degree in engineering. This manuscript makes a double contribution: on the one hand, it presents the methodology with its application through a practical case; on the other hand, it covers how students perceive the application of non-traditional training techniques. The methodology is based on student-centered learning, using case-based teaching and inquiry-based learning. The students’ perception of this change in training was evaluated through a qualitative methodological approach for five consecutive years and through two types of surveys carried out each year, one of which involves comparison with traditional training methodologies. The results of the surveys show the favorable acceptance of this form of teaching, surpassing the results of traditional teaching methods by more than 25%. As a practical implication, this research identifies new ways of teaching complex subjects that facilitate training in SDGs and the subsequent labor market reintegration of older people. Full article

Augmented reality (AR) applied in education provides learners a possible way for better understanding and thorough learning. Although the traditional projector is used to integrate the augmented information with real objects without wearing AR glasses, the projector-based AR system is unlikely to be adopted widely in education due to the cost, heavy weight, and space issues. In this paper, an alternative projector-camera AR platform, utilizing a digital light processing (DLP) module matched with a Beaglebone Black (BB) controller, is proposed for AR physical experiments. After describing the DLP-based AR learning design method, the algorithm of pre-deforming projection content with simulation-based poly fitting is presented to keep the virtual asset consistent with the user action; and then a prototype with the content regarding the thermal management of power devices is illustrated to validate the performance of the AR experimental platform. The result shows that the DLP-based AR platform is an accurate and interactive AR system with a response time of 1 s, and a registration deviation of 3 mm. It is also an affordable AR learning design tool with a bill of materials of about $200, and thus casts light on creating AR-based physical experiments to explore more physical phenomena. Full article

The additive technologies widely used in recent years provide enormous flexibility in the production of cellular structures. Material extrusion (MEX) technology has become very popular due to the increasing availability of relatively inexpensive desktop 3D printers and the capability of fabricating parts with complex geometries. Poly-lactic acid (PLA) is a biodegradable and commonly applied thermoplastic material in additive manufacturing (AM). In this study, using a simulation method based on the user subroutine titled “user subroutine to redefine field variables at a material point” (USDFLD) in the finite element method (FEM) ABAQUS software, the elastic stiffness (ES) of a cylindrical lightweight cellular PLA sample with a 2.4 mm infill line distance (ILD), which was designed as a layered structure similar to the laboratory mode with a MEX method and was subjected to cyclic compressive loading, was investigated by considering the variation of the Young’s modulus depending on the variation of the equivalent plastic strain (PEEQ). It was observed that the PLA sample’s elastic stiffness increases during cyclic loading. This increase is high in the initial cycles and less in the subsequent cycles. It was also observed that the simulation results are in good agreement with the experimental results. Full article

An intercomparison study was conducted to evaluate the contributions of carboxylic acids to m/z 44 (COO⁺) signals obtained by an on-line aerosol mass spectrometer (AMS) during a field campaign at Cape Hedo, Okinawa, in the western North Pacific Rim. We report for the first time that carboxylic acids (diacids, oxoacids, benzoic acid, and fatty acids) significantly contribute to m/z 44 signals with a strong correlation (R = 0.93); oxalic acid accounts for 16 ± 3% of the m/z 44 signals and 3.7 ± 0.9% of organic mass measured by AMS. We also found that about half of AMS m/z 44 signals can be explained by diacids and related compounds, suggesting that the remaining signals may be derived from other organic acids including monocarboxylic acids (e.g., formate and acetate) in aerosol phase. This study confirms that AMS-derived m/z 44 can be used as a surrogate tracer of carboxylic acids, although the signals cannot specify the types of carboxylic acids and their molecular compositions. Full article

A helmet is the main protective equipment for a child pillion passenger. A safe helmet must be able to mitigate head and brain injuries resulting from high head impact loading. A lightweight helmet is preferable, especially for children. This paper proposed to study the effect of materials, liner thickness, and friction at the head–helmet interface on linear and rotational accelerations using reduced-order modelling. A child head–helmet finite element model was developed and validated against an experiment. Finite element simulations were conducted to generate training data for the establishment of reduced-order models which were subsequently used to predict the linear and rotational accelerations for various helmet parameters. The prediction could be performed in a very short time compared to its corresponding finite element simulation. The use of aluminium foam enhanced mitigation of the linear and rotational accelerations as well as weight reduction. This study also revealed that the head–helmet friction coefficient had a strong effect on the rotational acceleration, while the liner thickness predominantly affected the linear acceleration. However, the liner thickness had less influence on the rotational acceleration when the head–helmet friction was low. The risk of brain concussion as well as diffusional injury could be reduced by enabling low friction at head–helmet surface. Full article

Displacements induced by mineral dissolution and subsurface volume contraction affect overlying soils. In this study, we examine the consequences of mass loss or volume contraction at shallow depths using a discrete element method. The goal of the study is to identify particle-scale and global effects as a function of the relative depth of a dissolving inclusion, initial soil density, and granular interlocking. There are successive arch formation and collapse events, and a porosity front propagates upwards as grains slide down to refill the space. Grains around and within the refilled cavity are loosely packed and have small contact forces that are sufficient to avert the buckling of granular arches that form around the dissolving zone. Denser packings and interlocking combine to exacerbate rotational frustration and lead to more pronounced force chains along granular arches, looser fill, and reduced surface settlement. In fact, surface settlement vanishes, and the sediment hides the localized dissolution when deep inclusions z/D ≥ 5 dissolve within dense sediments. While scaling relations limit the extrapolation of these numerical results to tunneling and mining applications, macroscale trends observed in the field resemble results gathered in this study. Full article

Surveillance cameras are increasingly prevalent in public places, and security services urgently need to monitor violence in real time. However, the current violent-behavior-recognition models focus on spatiotemporal feature extraction, which has high hardware resource requirements and can be affected by numerous interference factors, such as background information and camera movement. Our experiments have found that violent and non-violent video frames can be classified by deep-learning models. Therefore, this paper proposes a keyframe-based violent-behavior-recognition scheme. Our scheme considers video frames as independent events and judges violent events based on whether the number of keyframes exceeds a given threshold, which reduces hardware requirements. Moreover, to overcome interference factors, we propose a new training method in which the background-removed and original image pair facilitates feature extraction of deep-learning models and does not add any complexity to the networks. Comprehensive experiments demonstrate that our scheme achieves state-of-the-art performance for the RLVS, Violent Flow, and Hockey Fights datasets, outperforming existing methods. Full article

With the emergence of high-performance infrared detectors and the latest progress in grating manufacturing technology, high-resolution and high-sensitivity infrared spectrometers provide new methods for application to many fields, including astronomy and remote sensing detection. Spectral detection has attracted considerable attention due to its advantages of noncontact and stability. To obtain the detailed features of the missile’s tail flame spectrum, traditional plane reflection gratings are used as the main dispersive element; however, the instrument’s volume will increase with increasing resolution, which is not conducive to remote sensing detection from airborne platforms. Such spectrometers cannot meet high-resolution spectroscopy requirements. To address this problem, this paper proposes an immersion echelle spectrometer combined with a three-mirror astigmatism optical system. High resolution and compact size were achieved. In this paper, a small high-resolution infrared echelle spectrometer optical system was created by combining an off-axis three-mirror anti-astigmatism system, a Littrow structure, and a concave grating Wadsworth imaging device. The optical system operated in the 3.7–4.8 μm band; the echelle grating worked under quasi-Littrow conditions, while the concave grating was used for auxiliary dispersion to separate overlapping orders. The resolution of the optical system in the entire working band was 23,000–45,000. The optical plane size of the spectrometer was around 360 mm × 165 mm. The results show that the Mid-IR echelle spectrometer achieved high spectral resolution, better than 0.25 cm⁻¹, meeting missile tail flame detection requirements. This device has the potential for real-time long-range target detection when warheads are destroyed. While this study focuses on the mid-wave infrared band, its approach can also be extended to other infrared bands. Full article

Coral reefs are the most diverse and productive marine ecosystems on earth. The National Museum of Marine Biology and Aquarium has cultured more than 35 species of corals for research. When we conducted the asexual propagation of corals, the octocoral Sinularia flexibilis released a black pigment that stained the operator’s hands black. This is the first reported case of the skin being dyed black while propagating corals. We quantified the blackness of the stain by using the RGB value of the color. The longer the coral contacted the skin, the darker the skin became. Incubating the tentacles of S. flexibilis in high-salinity filtered seawater increased the amount of the black pigment released. However, collecting 100% of the black pigment was exceedingly challenging because it was very sticky and was constantly entangled with Symbiodiniaceae. Furthermore, we were unable to identify any solvents that could dissolve the pigment. The structure and function of the black pigment merit further study as it has the potential to become a new black dye for human industries. Full article

In this paper, a four-degree-of-freedom camellia-pollen-picking manipulator is proposed and designed. It can solve the problem of having no mechanized equipment for picking camellia pollen in agricultural machinery as the labor intensity of manual pollen extraction is high. To make the manipulator reach the target space quickly and efficiently, a structural-parameter-optimization method that reduces the working space to a more versatile cube is proposed. The numerical optimization algorithm is used to calculate the optimization result. Through the static analysis of the manipulator, the stability of the manipulator structure is verified. The working space of the manipulator is simulated and analyzed, and the simulation results are further verified by experiments. This research provides reliable technical support for the structural optimization, manufacturing, and intelligent upgrading of the camellia-pollen-picking robot. Full article

The emergence and popularization of various fifth-generation fighter jets with supersonic cruise, super maneuverability, and stealth functionalities have raised higher and more comprehensive challenges for the tactical performance and operational indicators of air defense weapon systems. The training of air defense systems requires simulated targets; however, the traditional targets cannot simulate the radar cross-section (RCS) distribution characteristics of fifth-generation fighter aircrafts. In addition, the existing target aircrafts are expensive and cannot be mass-produced. Therefore, in this paper, a corner reflector and a Luneburg ball reflector with RCS distribution characteristics of a fifth-generation fighter in a certain spatial area are designed for target simulation. Several corner reflectors and Luneburg balls are used to form an array to realize the simulations. The RCS value and distribution characteristics of the target can be combined with fuzzy clustering and a single-chip microcomputer to design an intelligent switching system, which improves the practicability of the intelligent target design proposed in this paper. Full article

The framework of this paper is the study of gas treatments (NOx abatement) by dielectric barrier discharge (DBD) at atmospheric pressure. To investigate the impact of various solutions for electrical energy injection on the treatment process, two diagnostic methods are considered to evaluate the discharging ratio on the reactor surface: an image processing method and a DBD equivalent circuit analysis, both presented in this paper. For the image analysis, the discharge area is first translated into gray levels, then segmented using the Otsu’s method in order to perform the discharging ratio diagnostic. The equivalent circuit approach, derived from the classical Manley’s diagram analysis, includes the behavior of the part of the reactor in which no discharge is happening. The identification of its parameters is used to estimate the discharging ratio, which evaluates the percentage of the reactor surface covered by the discharge. Experimental results with specifically developed power supplies are presented: they show a good agreement between the two methods. To allow a quantitative comparison of the discharge uniformity according to the operating conditions, the statistical analysis of gray level distribution is performed: non-uniform discharges with intense energy channels are shown to be clearly distinguished from more diffuse ones. Full article

Background: In the literature, there are few studies on included mandibular canines and possible therapeutic solutions for arch restoration. The aim of this review was to evaluate how the recovery of included mandibular canines is performed in adolescent patients with mixed or permanent dentition. The clinical case reported is that of successful orthodontic surgical treatment in an 11-year-old mixed-dentition patient with an included mandibular right canine. Methods: A literature search was performed using the PubMed/Medline, Scopus, Web of Science, and Cochrane Library databases with the following Boolean indicators: canine, mandibular, impacted. The inclusion criteria were year of publication between 2017 and 2022, orthodontic canine surgical approach included, age between 9 and 18 years, free full text, and English language. Results: A total of 536 articles was identified through the electronic search, and 11 articles published between 2017 and 2022 were ultimately included in the qualitative analysis. Conclusions: In the majority of cases, combined surgical–orthodontic therapy, as reported in the studies that we reviewed, is successful in correcting the eruption defect, restoring the canine to occlusion and the physiological arch perimeter, and maintaining the health of the periodontal supporting tissues. Full article