YOLOv5s-gnConv: detecting personal protective equipment for workers at height

IntroductionFalls from height (FFH) accidents can devastate families and individuals. Currently, the best way to prevent falls from heights is to wear personal protective equipment (PPE). However, traditional manual checking methods for safety hazards are inefficient and difficult to detect and eliminate potential risks.MethodsTo better detect whether a person working at height is wearing PPE or not, this paper first applies field research and Python crawling techniques to create a dataset of people working at height, extends the dataset to 10,000 images through data enhancement (brightness, rotation, blurring, and Moica), and categorizes the dataset into a training set, a validation set, and a test set according to the ratio of 7:2:1. In this study, three improved YOLOv5s models are proposed for detecting PPE in construction sites with many open-air operations, complex construction scenarios, and frequent personnel changes. Among them, YOLOv5s-gnconv is wholly based on the convolutional structure, which achieves effective modeling of higher-order spatial interactions through gated convolution (gnConv) and cyclic design, improves the performance of the algorithm, and increases the expressiveness of the model while reducing the network parameters.ResultsExperimental results show that YOLOv5s-gnconv outperforms the official model YOLOv5s by 5.01%, 4.72%, and 4.26% in precision, recall, and mAP_0.5, respectively. It better ensures the safety of workers working at height.DiscussionTo deploy the YOLOv5s-gnConv model in a construction site environment and to effectively monitor and manage the safety of workers at height, we also discuss the impacts and potential limitations of lighting conditions, camera angles, and worker movement patterns

Toward Low‐Temperature Zinc‐Ion Batteries: Strategy, Progress, and Prospect in Vanadium‐Based Cathodes

Low-temperature vanadium-based zinc ion batteries (LT-VZIBs) have attracted much attention in recent years due to their excellent theoretical specific capacities, low cost, and electrochemical structural stability. However, low working temperature surrounding often results in retarded ion transport not only in the frozen aqueous electrolyte, but also at/across the cathode/electrolyte interface and inside cathode interior, significantly limiting the performance of LT-VZIBs for practical applications. In this review, a variety of strategies to solve these issues, mainly including cathode interface/bulk structure engineering and electrolyte optimizations, are categorially discussed and systematically summarized from the design principles to in-depth characterizations and mechanisms. In the end, several issues about future research directions and advancements in characterization tools are prospected, aiming to facilitate the scientific and commercial development of LT-VZIBs

Influence of Morphology Characteristics on Shear Mechanical Properties of Sawtooth Joints

The interface problem exists widely in building. Joints are interfaces of rock mass structures. To further study the influence of morphological characteristics on the shear mechanical properties of sawtooth joints, this paper prepared rock-like materials based on the similarity principle and carried out direct shear tests of sawtooth joints. The results showed that: (1) the peak shear displacement of joints first increases and then decreases with increasing normal stress, but the normal trend of stress during turning is different under different sawtooth angles. When the sawtooth angle of the joints is small, the decrease in shear stress between shear strength and residual shear strength is not obvious, and the rate of decrease is also small. (2) The shear strength of joints is positively correlated with normal stress. Using the Mohr–Coulomb criterion to analyze the shear strength of joints, it was found that the cohesion c and internal friction angle α of joints increased nonlinearly with increasing sawtooth angle, but their increasing trends were different. By introducing the function relation between cohesion, internal friction angle, and sawtooth angle into the classical shear strength equation, an empirical equation for the shear strength of joints was established in consideration of sawtooth angle. (3) There are two modes of shear failure for serrated joints: the “saw-toothed sliding gnawing failure mechanism” (SSG) and the “tensile fracture mechanism” (TFM). In the SSG, the shear failure mode of joints evolves in a slipping–gnawing–complete gnawing mechanism with increasing sawtooth angle and normal stress. The TFM mainly occurs at high sawtooth angles. This study provides a theoretical reference for the prediction and prevention of geological disasters

Bedding Slope Destabilization under Rainfall: A Case Study of Zhuquedong Slope in Hunan Province, China

The soft interlayer and rock structure play a significant role in controlling the deformation of the bedding slope, and it is necessary to consider the phenomenon of the sudden change of local response in these key parts under rainfall conditions, and then to clarify the mechanism of rainfall infiltration and damage mechanism of such slopes. In this paper, a large red-layered flat-dipping bedding landslide was selected as the research object, and numerical calculations based on the Van Genuchten model for saturated–unsaturated flow were performed in order to investigate the hydrological response and distribution patterns of water within the slope during rainfall. Moreover, stability analysis was performed based on the seepage field results and secondary development of FLAC3D, and the landslide evolution process was simulated and reproduced using the constitutive model of double-variables and the strength reduction method (SRM). The results showed that the effects of heavy rainfall on the water distribution and stability of the highway slope are significant, while the effects on the natural slope are not significant. There are three phases of the slope destabilization: flexure and uplift state, deformation exacerbation state and shear failure state. The slope destabilization mechanism is a typical “sliding-bending-shearing” type. The results of the study can provide a theoretical basis for the study of the seepage, stability analysis and destabilization mechanism of bedding slopes

Effect of PVP Coating on LiMnBO3 Cathodes for Li-Ion Batteries

LiMnBO3 is a potential cathode for Li-ion batteries, but it suffers from a low electrochemical activity. To improve the electrochemical performance of LiMnBO3, the effect of polyvinyl pyrrolidone (PVP) as carbon additive was studied. Monoclinic LiMnBO3/C and LiMnBO3-MnO/C materials were obtained by a solid-state method at 500 °C. The structure, morphology and electrochemical behavior of these materials are characterized and compared. The results show that carbon additives and ball-milling dispersants affect the formation of impurities in the final products, but MnO is beneficial for the performance of LiMnBO3. The sample of LiMnBO3-MnO/C delivered a high capacity of 162.1 mAh g−1 because the synergistic effect of the MnO/C composite and the suppression of the PVP coating on particle growth facilitates charge transfer and lithium–ion diffusion

Expression patterns of DNA methyltransferase genes during gametogenesis and early development in rainbow trout Oncorhynchus mykiss

RésuméRésuméDNA methylation is one of the most extensively studied epigenetic mechanisms that modulate gene expression and cellular differentiation. It plays critical roles during gametogenesis and early development of vertebrates. Previous studies in mammals demonstrated that DNA methylation is accomplished through the activities of DNA methyltransferases (Dnmts). Dnmt1 is associated with the maintenance of methylation status, whereas Dnmt3a and Dnmt3b are essential for de novo methylation. The present study aimed at investigating the dynamic transcription pattern of dnmt genes during gametogenesis and early development for the first time in rainbow trout (Oncorhynchus mykiss), an economically important fish speciesDue to the fact that the teleost experienced a third round of whole genome duplication (WGD) apart from the two round of WGD that occurred at the root of the vertebrate lineage, the evolutionary of dnmt genes remains unclear. Indeed, there are three common fates for the duplicated genes after WGD: loss one of the duplicate gene, sub- or neo-functionalisation. In the present study, two ohnologs of dnmt1 (dnmt1a and dnmt1b) and eight paralogs of dnmt3 (including 3 paralogs of dnmt3a: dnmt3aa, dnmt3ab1, dnmt3ab2, and 5 paralogs of dnmt3b: dnmt3ba1, dnmt3ba2, dnmt3bba1, dnmt3bba2 and dnmt3bbb) were identified in rainbow trout. Spatial expression patterns of dnmt genes were analysed using the PhyloFish database to identify the main expression territories of these genes. Results showed that, both dnmt1 ohnologs were preferentially expressed in unfertilised eggs. dnmt3a paralogs were highly expressed in brain, whereas dnmt3ba1, dnmt3ba2, dnmt3bbb were predominantly expressed in skin, head kidney and ovary, respectively, which could be possibly linked to a sub- or neo-functionalisation after WDG.The dynamic expression patterns of dnmt genes were analysed in trout gonads during gametogenesis (between two spawn). Our results showed that there was a remarkable increase in the mRNA levels of dnmt1a and three of the five dnmt3b paralogs in oocytes compared with ovaries in females. In males, we observed the highest mRNA level of dnmt1a together with the lowest mRNA levels of dnmt3ab1 and dnmt3bba1 at the late-spermatogenesis stage. Besides, mRNA levels of dnmt genes were also analysed during early development of trout from stage 0 (oocyte) to stage 36 (alevin). All dnmt genes displayed a similar expression pattern, with no or low mRNA levels from stage 0 up to 15, followed by a sharp increase at the setting up of the most of the vital organs (stage 22/23) and then decreased after hatching. By contrast, there was relatively high transcript abundance of dnmt3bbb from the beginning of embryogenesis, suggesting its functionally importance during early development.In conclusion, the dynamic expression patterns of dnmt genes during gametogenesis and early development suggested that epigenetic mechanisms actively participated in these physiological processes in trout. The distinct transcription patterns of dnmt3b paralogs indicated that they may subject to sub- or neo-functionalisation after WDG

Evolutionary history of DNA methylation related genes in chordates: new insights from multiple whole genome duplications

DNA methylation is an important epigenetic mechanism involved in many biological processes, i.e. gametogenesis and embryonic development. However, increased copy numbers of DNA methylation related genes (dnmt, tet and tdg) have been found during chordate evolution due to successive whole genome duplication (WGD) events. Their evolutionary history and phylogenetic relationships remain unclear. The present study is the first to clarify the evolutionary history of DNA methylation genes in chordates. In particular, our results highlight the fixation of several dnmt3-related genes following successive WGD throughout evolution. The rainbow trout genome offered a unique opportunity to study the early evolutionary fates of duplicated genes due to a recent round of WGD at the radiation of salmonids. Differences highlighted in transcriptional patterns of these genes during gametogenesis and ontogenesis in trout indicated that they might be subjected to sub- or neo-functionalisation after WDG. The fixation of multiple dnmt3 genes in genomes after WGD could contribute to the diversification and plastic adaptation of the teleost

Nonlinear Strength Reduction Method of Rock Mass in Slope Stability Evaluation

As the strength parameters of rock mass degrade differently during slope instability, different factors should be considered in the strength reduction method. Previous nonlinear reduction methods were essentially implemented based on the Mohr–Coulomb criterion, which was reported not to reflect the nonlinear performance of rock mass. To address this deficiency, in this study, the Hoek–Brown criterion was combined with a nonlinear reduction technique for slope stability evaluation. Firstly, based on the classical definition of safety factors, the relationships that should be satisfied by each parameter of the critical slope were derived. The critical curve of the slope regarding the Hoek–Brown constant mb and the uniaxial compressive strength of rock mass σcmass was then obtained. On the assumption that the slope parameter deterioration conforms to the shortest path theory, the reduction ratio of σcmass to mb was determined. The more objective k-means algorithm was employed to automatically search the potential sliding surface, on which the slope safety factor was calculated as the ratio of sliding resistance to sliding force. Finally, the slopes in published literature were adopted for verification, and the calculated safety factors were compared with those by other methods, which showed better efficacy

Mechanical Characteristics and Acoustic Emission Characteristics of Mortar-Rock Binary Medium

The stability of the interface between mortar and rock is very important in engineering construction. In this paper, the all-digital acoustic emission (AE) system is used to detect the direct shear test of the mortar-rock binary medium interface with different sawtooth angles under different normal stress states. The stress-displacement information and AE signal during the whole shearing process are extracted. The coupling relationship between stress and AE characteristic parameters is discussed. The quantitative relationship between sawtooth angle and shear strength of binary medium is established, and three AE characteristic parameters that can be used to predict structural instability are proposed. The research shows that: With the increase of the normal stress and the sawtooth angle, the shear strength of the mortar-rock binary medium increases. The relationship of that is obtained by least squares fitting. The shear stress-displacement curve is divided into five stages according to the change of deformation law. Through the analysis of AE characteristic parameters, it is found that increasing the sawtooth angle makes the AE count and AE cumulative count increase. Based on the analysis of the characteristic parameters of RA-AF, the changes of shear cracks and tensile cracks within the whole shearing process were obtained, respectively. In the process of binary medium shearing, the AE peak frequency is in the range of 120–340 kHz. Three acoustic emission parameters that can predict the macroscopic damage of binary media are obtained: the AE b value, the ratio of shear crack signals, and the number of signals with a peak frequency of 220 Hz to 320 Hz

Mechanical Properties and Acoustic Emission Characteristics of Anchored Structure Plane with Different JRC under Direct Shear Test

Rock mass, the heterogeneous natural material composed of rock and discontinuities, is an important part of engineering construction. Discontinuities affect the mechanical properties of natural rock mass and further threaten the stability of rock engineering. To study the failure characteristics of anchored structure plane with different JRC, jointed specimens with four different JRC were fabricated by pouring cement mortar. Specimens were tested under four different normal loads to figure out how JRC and anchorage angle affect the mechanical properties of anchored structure plane. Besides, acoustic emission (AE) testing technology was adopted to explore the AE characteristics of anchored structural plane under shearing. The results showed that there exists a positive correlation between the peak shear strength and JRC. The undulation shape of structural plane led to an obvious downward trend in the strain softening stage of the structural plane with JRC of 6–8 and 18–20. When the anchorage angle ranged from 45° to 60°, the potentiation of bolt was the most significant. Based on the AE results, the larger the normal stress, the more likely the cumulative count curves were to enter the fast growth phase before the peak. The characteristics of b-value curves are mainly related to the topography of structural planes and whether the bolt is deformed. In the direct shear test, the cumulative proportion of shear cracks was more than 85%, which is much higher than that of tensile cracks. The variation of cumulative tensile cracks goes through three stages: slow growth, rapid growth, and slow growth. Compared with the unanchored structural plane, the variation range of real-time tensile cracks of the anchored structural plane is large, and sometimes the proportion of real-time tensile cracks may reach 80%