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Abstract Background Pangolin is one of the most endangered mammals with many peculiar characteristics, yet the understanding of its sensory systems is still superficial. Studying the genomic basis of adaptation and evolution of pangolin’s sensory system is expected to provide further potential assistance for their conservation in the future. Results In this study, we performed a comprehensive comparative genomic analysis to explore the signature of sensory adaptation and evolution in pangolins. By comparing with the aardvark, Cape golden mole, and short-beaked echidna, 124 and 152 expanded gene families were detected in the genome of the Chinese and Malayan pangolins, respectively. The enrichment analyses showed olfactory-related genomic convergence among five concerned mammals. We found 769 and 733 intact OR genes, and 704 and 475 OR pseudogenes in the Chinese and Malayan pangolin species, respectively. Compared to other mammals, far more intact members of OR6 and OR14 were identified in pangolins, particularly for four genes with large copy numbers (OR6C2, OR14A2, OR14C36, and OR14L1). On the genome-wide scale, 1,523, 1,887, 1,110, and 2,732 genes were detected under positive selection (PSGs), intensified selection (ISGs), rapid evolution (REGs), and relaxed selection (RSGs) in pangolins. GO terms associated with visual perception were enriched in PSGs, ISGs, and REGs. Those related to rhythm and sound perception were enriched in both ISGs and REGs, ear development and morphogenesis were enriched in ISGs, and mechanical stimulus and temperature adaptation were enriched in RSGs. The convergence of two vision-related PSGs (OPN4 and ATXN7), with more than one parallel substituted site, was detected among five concerned mammals. Additionally, the absence of intact genes of PKD1L3, PKD2L1, and TAS1R2 and just six single-copy TAS2Rs (TAS2R1, TAS2R4, TAS2R7, TAS2R38, TAS2R40, and TAS2R46) were found in pangolins. Interestingly, we found two large insertions in TAS1R3, distributed in the N-terminal ectodomain, just in pangolins. Conclusions We found new features related to the adaptation and evolution of pangolin-specific sensory characteristics across the genome. These are expected to provide valuable and useful genome-wide genetic information for the future breeding and conservation of pangolins.

TPMS structures possess immense potential in terms of lightweight and multifunctional applications. However, previous studies have predominantly focused on aspects such as wall thickness, unit cell size, periodicity, and level set values. The impact of amplitude factors on the topological shape and mechanical properties of TPMS has not been fully elucidated. Here, primitive (P), gyroid (G), and diamond (D) structures were initially examined to explore the effects of amplitude factors on the topological shape and relative density of TPMS structures. The mechanical properties and energy absorption capability of the variable amplitude structures were investigated, with emphasis on a gyroid structure, using both experiments and numerical simulations. It was found that the amplitude does not alter the deformation pattern of the structure. However, the mechanical properties of the structure can be regulated over a relatively large range. Specifically, the elastic modulus and yield strength at an amplitude of 1.6 were observed to be approximately 1.5 times those at an amplitude of 0.4, and the plateau stress was approximately 1.33 times that of 0.4. Additionally, with increasing amplitude factor, there was a slight decrease in the densification strain of the structure but a significant increase in its energy absorption capability. Such findings offer a novel means by which the mechanical properties of TPMS structures can be modulated, providing new opportunities for the development of tissue scaffolds or energy-absorbing devices.

Abstract Background Pleistocene climate fluctuations have strongly modified species genetic diversity and distributions. The Chinese pangolin (Manis pentadactyla) has been recognized as a critically endangered animal due to heavy poaching and trafficking. However, the effect of Pleistocene climate fluctuations on the genetic diversity and spatial distribution of the Chinese pangolin remains largely unknown. Here, we combined whole genome sequencing data, analysis of complete mitochondrial genomes, and a large amount of occurrence data from field surveys to infer the ancestral demographic history and predict the past spatial dynamics of the Chinese pangolin in Guangdong Province, China. Results Our results indicated that there were two subpopulations, which showed similar trends of population size change in response to past climatic changes. We estimated a peak effective population size (N e) during the last interglacial (LIG), followed by a marked decrease (~ 0.5 to fivefold change) until the last glacial maximum (LGM) and a rebound to a small peak population size during the Mid-Holocene (MH). The estimated time of the separation event between two subpopulations was approximately 3,000–2,500 years ago (ka). We estimated that the distribution of suitable areas shrank by 14.4% from the LIG to LGM, followed by an expansion of 31.4% from the LGM to MH and has been stable since then. In addition, we identified an elevational shift and suitable area decreased significantly during the LGM, but that the geographic extent of suitable areas in the western region increased from the LIG to present. The eastern region of Guangdong Province had the highest habitat suitability across all the climate scenarios. Conclusions Our results suggested that Pleistocene climate fluctuations played an important role in shaping patterns of genetic diversity and spatial distribution, and that human stressors likely contributed to the recent divergence of two Chinese pangolin subpopulations sampled here. We argue that a key protected area should be established in the eastern region of Guangdong Province. As such, this study provides a more thorough understanding of the impacts of Pleistocene climate fluctuations impacts on a mammalian species in southern China and suggests more robust management and conservation plans for this Critically Endangered species of special interest.

Abstract Scanning electron microscopy (SEM) was used to observe the macroscopic, microscopic, and cross‐sectional structures of the claws of Cyrtotrachelus buqueti Guer (Coleoptera: Curculionidae), and a mathematical model of a claw was used to investigate the structure–function relationships. To improve the quality of the SEM images, a non‐local means (NLM) algorithm and an improved NLM algorithm were applied. After comparison and analysis of five classical edge‐detection algorithms, the boundaries of the structural features of the claw were extracted based on a B‐spline wavelet algorithm, and the results showed that the variable curvature of the beetle claw enhances its adhesion force and improves its strength. Adhesion models of the claw were established, and the mechanical properties of its biomaterials were measured using nanoindentation. Considering that the presence of water can affect the hardness and Young's modulus, both ‘dry’ and ‘wet’ samples were examined. For the dry samples, the hardness and Young's modulus were 0.197 ± 0.074 GPa and 1.105 ± 0.197 GPa, respectively, whereas the respective values for the wet samples were both lower at 0.071 ± 0.030 GPa and 0.693 ± 0.163 GPa. This study provides data that can inform the design of climbing robots.

In order to enhance the theory and process of magnetorheological polishing fluid (MRPF) preparation, the bubble models of MRPF under ultrasonic preparation and mechanical preparation were established by considering the mixture continuity equation and the VAND viscosity equation. The bubble motion of MRPF was investigated numerically by using the fourth-order Runge-Kutta algorithm, and the influence of liquid phase and liquid-solid two-phase on the bubble of MRPF was discussed. The results show that the bubble in MRPF undergoes the dynamic processes of growth, expansion, compression, collapse, and rebound under ultrasonic preparation, while it only undergoes the dynamic processes of compression and rebound under mechanical preparation. For the ultrasonic preparation process, the addition of solid particles of MRPF significantly weakens the original cavitation effect of liquid phase, while for the mechanical preparation process, the addition of solid particles of MRPF enhances the original cavitation effect of liquid phase. The pressure inside bubble and the wall velocity of bubble produced by ultrasonic preparation of MRPF were 104 times higher than those of the mechanical preparation. The analysis results of the bubble dynamics of MRPF fit the experimental results of sedimentation rate of MRPF well. The superiority of ultrasonic preparation of MRPF was theoretically verified, providing a theoretical basis for further insight into the homogenization mechanism of MRPF.

The lattice sandwich structure has become a focus of research in aerospace and other fields because of its light weight and high impact resistance. However, research on the impact resistance of lattice sandwich structures is still focused on simulations and experiments and presently lacks theoretical models. In this paper, we proposed a toughening design method based on the failure modes of lattice sandwich structures. The toughening model was established, the dimensional effect was analysed, and the mechanism of synergistic toughening was studied. The results show that the mass of the sandwich structure we designed is reduced by 67.7% compared with the solid part, which has the same outline sizes, and its impact toughness is increased by 119.0%.

Abstract In the electronics industry environment, rapid recognition of objects to be grasped from digital images is essential for visual guidance of intelligent robots. However, electronic components have a small size, are difficult to distinguish, and are in motion on a conveyor belt, making target detection more difficult. For this reason, the YOLOv4-tiny method is used to detect electronic components and is improved. Then, different network structures are built for the adaptive integration of middle- and high-level features to address the phenomenon in which the original algorithm integrates all feature information indiscriminately. The method is deployed on an electronic component dataset for validation. Experimental results show that the accuracy of the original algorithm is improved from 93.74 to 98.6%. Compared with other current mainstream algorithms, such as Faster RCNN, SSD, RefineDet, EfficientDet, and YOLOv4, the method can maintain high detection accuracy at the fastest speed. The method can provide a technical reference for the development of manufacturing robots in the electronics industry.

Lodging in wheat (Triticum aestivum L.) is a complicated phenomenon that is influenced by physiological, genetics, and external factors. It causes a great yield loss and reduces grain quality and mechanical harvesting efficiency. Lodging resistance is contributed by various traits, including increased stem strength. The aim of this study was to map quantitative trait loci (QTL) controlling stem strength-related features (the number of big vascular bundles, stem diameter, stem wall thickness) using a doubled haploid (DH) population derived from a cross between Baiqimai and Neixiang 5. Field experiments were conducted during 2020–2022, and glasshouse experiments were conducted during 2021–2022. Significant genetic variations were observed for all measured traits, and they were all highly heritable. Fifteen QTL for stem strength-related traits were identified on chromosomes 2D, 3A, 3B, 3D, 4B, 5A, 6B, 7A, and 7D, respectively, and 7 QTL for grain yield-related traits were identified on chromosomes 2B, 2D, 3D, 4B, 7A, and 7B, respectively. The superior allele of the major QTL for the number of big vascular bundle (VB) was independent of plant height (PH), making it possible to improve stem strength without a trade-off of PH, thus improving lodging resistance. VB also showed positive correlations with some of the yield components. The result will be useful for molecular marker-assisted selection (MAS) for high stem strength and high yield potential.

Fish skin is a biological material with high flexibility and compliance and can provide good mechanical protection against sharp punctures. This unusual structural function makes fish skin a potential biomimetic design model for flexible, protective, and locomotory systems. In this work, tensile fracture tests, bending tests, and calculation analyses were conducted to study the toughening mechanism of sturgeon fish skin, the bending response of the whole Chinese sturgeon, and the effect of bony plates on the flexural stiffness of the fish body. Morphological observations showed some placoid scales with drag-reduction functions on the skin surface of the Chinese sturgeon. The mechanical tests revealed that the sturgeon fish skin displayed good fracture toughness. Moreover, flexural stiffness decreased gradually from the anterior region to the posterior region of the fish body, which means that the posterior region (near the tail) had higher flexibility. Under large bending deformation, the bony plates had a specific inhibition effect on the bending deformation of the fish body, especially in the posterior region of the fish body. Furthermore, the test results of the dermis-cut samples showed that the sturgeon fish skin had a significant impact on flexural stiffness, and the fish skin could act as an external tendon to promote effective swimming motion.

Inspired by the macro/microstructures of starfish and beetle elytra, a series of bio-inspired structures (BSs) with improved comprehensive mechanical performance were proposed and fabricated. In the BS design, the principle of the branching structure of starfish was borrowed and each arm was endowed with calcified exoskeletons that can bend autonomously, enabling the starfish to move flexibly and adapt to changing shapes. At the same time, inspiration was taken from the concave-convex structure design principle of beetle elytra to enhance the internal complexity and mechanical performance of the BS. By increasing the number of polygons inside the thin-walled tubes, the performance of the BS in torsion and three-point bending was effectively improved. To evaluate the mechanical properties of the BS, finite element models were constructed using ANSYS and verified through experimental measurements. Universal testing machines and electronic torsion testers controlled by a microcomputer were used to study the compression, bending, and torsion properties of the BS. The results indicated that the differences in maximum compressive load-bearing capacity between each BS were small, and their lightweight compression values (LWN-C) remained unchanged, around 310 N/g. Increasing the number of polygons inside the thin-walled tubes effectively improved the performance of the BS in torsion and three-point bending. Moreover, the crashworthiness behaviors of the bio-inspired lightweight tube were also studied using a drop hammer impact tester. These findings have significant implications for the development of bio-inspired designs, particularly in the fields of machine arms, vehicle shafts, and bumpers, where lightweight yet high-strength structures are highly desirable.

Abstract The green bacterial biosynthesis of lead sulfide nanocrystallites by l-cysteine-desulfurizing bacterium Lysinibacillus sphaericus SH72 was demonstrated in this work. Nanocrystals formed by this bacterial method were characterized using the mineralogical and morphological approaches. The results revealed that the microbially synthesized PbS nanocrystals assume a cubic structure, and are often aggregated as spheroids of about 105 nm in size. These spheroids are composed of numerous nanoparticles with diameter 5–10 nm. Surface characterization of the bacterial nanoparticles with FTIR spectroscopy shows that the l-cysteine coats the surface of PbS nanoparticle as a stabilizing ligand. The optical features of the PbS nanocrystallites were assessed by UV–Vis spectroscopy and PL spectroscopy. The maximum absorption wavelength of the bacterial PbS particles occurs at 240 nm, and the photoluminescence emission band ranges from 375 to 550 nm. The band gap energy is calculated to be 4.36 eV, compared to 0.41 eV for the naturally occurring bulk PbS, with this clear blue shift attributable to the quantum size effect.

The article selects socioeconomic data related to 146 prefecture-level cities included in nine city clusters from 2014 to 2018 to establish a city-level socioeconomic system in China. A sensitivity analysis of regional entrepreneurship and economic quality development based on system dynamics was conducted to explore the changes in regional entrepreneurship and economic quality development over time and their sensitivity factors. In this way, the dynamic evolution mechanism of the system can be portrayed, and the optimization of the system can be achieved through the coordination of the factors within the system. The article sets up three scenarios to explore the fluctuations in regional entrepreneurship and economic quality development when three sensitive factors, namely, business environment, financial services scale, and innovation environment, change. Findings: There are differences in the development of cities within city clusters. The business environment and high-quality economic development of the central cities within the city cluster are stronger than those of the non-central cities. Therefore, regions should focus on synergistic development within city clusters when formulating related policies. The variation of regional entrepreneurship development and economic quality development, after a factor in the system is changed, is asymmetric. Because the sensitivity of different urban clusters and the way they are affected by sensitive factors varies, the state should pay more attention to the adaptability of cities when formulating corresponding policy measures and adapt its policy measures to the sensitivity characteristics of each region according to local conditions.

The camera tracking systems based on visual image processing face a problem that they are completely ineffective in their blind zones. To address this problem, a design of acoustic enhanced tracking system combining visual and auditory target tracking methods is reported in this article. The system holds the abilities of performing sound direction estimation and target tracking in real-time. Estimating direction of arrival of the sound accompanied with the target helps the camera turn towards the target outside the field of view. This sound-triggered mode of camera operation makes a significant supplement to conventional cameras' working state. Considering the embedded system is necessary in consideration of the cost and size of the system in practical application, we designed a small aperture array with 7 digital omnidirectional MEMS microphones and built the overall system based on FPGA and ARM. The experiments were carried out in a normal indoor environment and the results confirmed that the system can perform auditory and visual tracking in real-time.

Benefiting from their unique morphological characteristics and structural properties, the ventral bony plates of the Chinese sturgeon are excellent biological protective tissue. In this work, we studied the micro- and macro-morphology and mechanical properties of the ventral bony plates of the Chinese sturgeon to elucidate the special protective mechanisms of the bony plates. Experiments involving scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed that the bony plates possess a hierarchical structure and a ridge-like shape. This structure comprises a surface layer containing mineralized nanocrystals and an internal layer containing mineralized collagen fibers. From the surface layer to the internal layer, the degree of mineralization decreases gradually. Nanoindentation, tension, and compression tests demonstrated that the bony plates feature excellent mechanical properties and a high specific tensile strength comparable to that of stainless steel. Moreover, water can significantly improve the fracture toughness and deformability of the bony plates and effectively enhance the damage tolerance of the structures. The obtained results concerning the microstructure–property–function relationships of the ventral bony plates of the Chinese sturgeon may provide novel insights for designing protective structures that are both lightweight and high strength.

In the ultrasonic dispersion process, the ultrasonic cavitation effect can seriously affect the dispersion efficiency of magnetorheological polishing fluid (MRPF), but the mechanism remains unclear now. Through considering the continuity equation and Vand viscosity equation of the suspension, a revised cavitation bubble dynamic model in the MRPF was developed and calculated. The effects of presence or absence of solid particles, the volume fraction of solid particles, and viscosity on the cavitation bubble motion characteristics in the MRPF were discussed. Settlement experiments of the MRPF under ultrasonic and mechanical dispersion were observed. Analysis of particle dispersion is made by trinocular biomicroscope and image processing of the microscopic morphology of the MRPF. The results show that the high volume fraction of carbonyl iron particle (CIP) will significantly weaken the cavitation effect, and the low volume fraction of green silicon carbide (GSC) has a negligible effect on the cavitation effect in the MRPF. When the liquid viscosity is greater than or equal to 0.1 Pa·s, it is inconvenient to produce micro-jets in the MRPF. The sedimentation rate of the MRPF prepared by ultrasonic dispersion is lower than mechanical dispersion when the volume fraction of CIP is between 1% and 25%. The dispersion ratio under ultrasonic dispersion is lower than that under mechanical dispersion. The experimental results fit the simulation well. It offers a theoretical basis for exploring the ultrasonic cavitation effect in the industrial application of the MRPF.

High strength and tough structures are beneficial to increasing engineering components service span. Nonetheless, improving structure strength and, simultaneously, toughness is difficult, since these two properties are generally mutually exclusive. Biological organisms exhibit both excellent strength and toughness. Using bionic structures from these biological organisms can be solutions for improving these properties of engineering components. To effectively apply biological models to design biomimetic structures, this paper analyses strengthening and toughening mechanisms of six fundamentally biological models obtained from biological organisms. Numerical models of three-point bending test are established to predict crack propagation behaviors of the six biological models. Furthermore, the strength and toughness of six biomimetic composites are experimentally evaluated. It is identified that the helical model possesses the highest toughness and satisfying strength. This work provides more detailed evidence for engineers to designate bionic models to the design of biomimetic composites with high strength and toughness.

The finite element method is a powerful tool for evaluating the experimental results. It can help to study the flight mechanism of insects and the structural characteristics of flying wings. Therefore, the research object based on the hind wings of Cyrtotrachelus buqueti (C. buqueti) was completed here. A finite element model with a length of 45 mm in the spanwise direction and a 16 mm width in the chordwise direction were established. We used a three‐dimensional (3D) scanner to scan a real hind wing to obtain point cloud images. The physical model of the hind wing was carried out by using both the software Imageware and Unigraphics NX. To quantify the quality of the finite element model of the hind wing, the material properties of the wing membranes and veins were conducted by the tensile testing machine. The structural static properties of the hind wing, including static characteristics analysis and natural vibration modal analysis, were analysed by ANSYS; the stress and deflection under uniformly distributed load, bending moment, and torque were, respectively, shown. It was found that the model only had a small deformation, which shows that the hind wings of C. buqueti have excellent structural properties.

Research data of the microstructure and surface morphology of insect wings have been used to help design micro air vehicles (MAV) and coating materials. The present study aimed to examine the microstructure and morphology of the hind wings of Cyrtotrachelus buqueti using inverted fluorescence microscopy (IFM), scanning electron microscopy (SEM), and a mechanical testing system. IFM was used to investigate the distribution of resilin in the hind wing, and SEM was performed to assess the functional characteristics and cross-sectional microstructure of the wings. Moreover, mechanical properties regarding the intersecting location of folding lines and the bending zone (BZ) were examined. Resilin, a rubber-like protein, was found in several mobile joints and in veins walls that are connected to the wing membranes. Taken together, structural data, unfolding motions, and results of tensile testing suggest two conclusions on resilin in the hind wing of C. buqueti: firstly, the resilin distribution is likely associated with specific folding mechanisms of the hind wings, and secondly, resilin occurs at positions where additional elasticity is needed, such as in the bending zone, in order to prevent structural damage during repeated folding and unfolding of the hind wings. The functional significance of resilin joints may shed light on the evolutionary relationship between morphological and structural hind wing properties.

Pitting, which results from contact fatigue, is a common failure mode in gear transmission systems and is influenced by the material strength and stress state of the contact area, which is further influenced by lubrication and roughness because of stress fluctuations. In this study, a comparative contact-fatigue test was conducted on two types of gears with different terminal machining processes. The contact stress of the tooth surface considering the microtopography was analyzed using the fractal method based on surface microtopography data measured from the surface formed by the two processes. Test results show that the average service life of gears machined using the barrel-finishing process was approximately 5–7 times that of gears machined using grinding. The pitting morphologies of gears fabricated using different processes exhibited evident differences. The maximum stress level of the gears machined with barrel finishing was approximately twice that of the gears machined through grinding. Different stress levels resulted in different micropitting load-bearing capacities, which could be attributed to the different service lives of gears manufactured through different machining processes. The different presence features of the pitting morphology were due to the different micromorphologies of the surface formed by the different finishing processes. In particular, the randomly distributed pitting morphology of the gear surface machined using the barrel-finishing process was due to its flattening and polishing effect. Optimization of the surface-microgeometry distribution via the finishing process is an effective method for prolonging the service life of gears.

Jumping mechanisms constitute an important means of resolution in applications such as crossing uneven terrain and space exploration. However, the traditional design mainly uses engineering design thinking, but seldom studies the structural characteristics of organisms themselves and lacks biomimetic research basis, which leads to the difference between jumping mechanism and biological structure and its jumping ability. On the other hand, it lacks in-depth study on biological jumping mechanism from the view of engineering. Weevil has excellent jumping performance, and its key jumper structure is specially designed by biologist. To investigate the motion mechanism and working mechanism of the jumping mechanisms, this paper takes the weevil as the bionic object, and designs a weevil-inspired jumping mechanism. A miniature prototype is designed to reproduce weevil’s jumping mechanism with its working principle and anatomical structure to verify how weevil’s jumping mechanisms work, and turns out to perform well at jumping height. This paper is presented the anatomical structure and working principle of the weevil jumping mechanism, followed by explanation and analysis of its kinematics and dynamics, then performing virtual prototype simulations to compare different design schemes, with results guiding the parameter optimization and subjecting a prototype machine into a height test. In comparisons among existing jumping mechanisms whose jumping method is bio-inspired, the present design, which weighs 44.7 g and can jump to a maximum height of 2 m. The present research establishes a biologically inspired working principle and provides a new practical archetype in biologically inspired studies.

As an important field of computer vision, object detection has been studied extensively in recent years. However, existing object detection methods merely utilize the visual information of the image and fail to mine the high-level semantic information of the object, which leads to great limitations. To take full advantage of multi-source information, a knowledge update-based multimodal object recognition model is proposed in this paper. Specifically, our method initially uses Faster R-CNN to regionalize the image, then applies a transformer-based multimodal encoder to encode visual region features (region-based image features) and textual features (semantic relationships between words) corresponding to pictures. After that, a graph convolutional network (GCN) inference module is introduced to establish a relational network in which the points denote visual and textual region features, and the edges represent their relationships. In addition, based on an external knowledge base, our method further enhances the region-based relationship expression capability through a knowledge update module. In summary, the proposed algorithm not only learns the accurate relationship between objects in different regions of the image, but also benefits from the knowledge update through an external relational database. Experimental results verify the effectiveness of the proposed knowledge update module and the independent reasoning ability of our model.

The rostrum of Cyrtotrachelus buqueti Guer has excellent mechanical properties, such as high-specific strength and high-specific stiffness, and it is an example of successful evolution in nature. In this paper, based on the biological structural characteristics of the rostrum, bionic variable-density lightweight structures of varying layer number are designed, and their mechanical properties are analyzed under different helix angles. The results show that when the helix angle is greater than or equal to 40°, the maximum compressive load borne by the three-layer tube is 30.75 N, which is 1.89 times that of the single-layer tube. Through calculation, at a helix angle of 15°, the torsion lightweight coefficient of the single-layer, double-layer, and three-layer structures is 0.99 ± 0.03 N·M g ^−1 , 1.75 ± 0.05 N·M g ^−1 , and 2.32 ± 0.06 N·M g ^−1 , respectively, where that of the three-layer structure was approximately 2.34 times that of the single-layer structure. Further calculations show that the bending lightweight factor of the single-layer, double-layer, and three-layer tubes is 17.89 ± 0.20 N g ^−1 , 33.16 ± 0.45 N g ^−1 , 41.33 ± 0.55 N g ^−1 , respectively, where that of the three-layer tube is 2.31 times that of the single-layer tube. In addition, this paper also investigates the cushioning energy absorption characteristics of the bionic lightweight tubes by using an impact testing machine. The results show that under the same conditions, as the number of layers of the lightweight tube increases, the buffering energy absorption also increases. The total energy absorption and specific energy absorption of the three-layer lightweight tube are approximately 10 times those of the single-layer tube. Finally, a response surface-based optimization method is proposed to optimize the bionic structures under a combined compression-torsion load. The results lay the foundation for the lightweight design of thin-walled tube structures.

This paper focuses on generating distributed flocking strategies via imitation learning. The primary motivation is to improve the swarm robustness and achieve better consistency while respecting the communication constraints. This paper first proposes a quantitative metric of swarm robustness based on entropy evaluation. Then, the graph importance consistency is also proposed, which is one of the critical goals of the flocking task. Moreover, the importance-correlated directed graph convolutional networks (IDGCNs) are constructed for multidimensional feature extraction and structure-related aggregation of graph data. Next, by employing IDGCNs-based imitation learning, a distributed and scalable flocking strategy is obtained, and its performance is very close to the centralized strategy template while considering communication constraints. To speed up and simplify the training process, we train the flocking strategy with a small number of agents and set restrictions on communication. Finally, various simulation experiments are executed to verify the advantages of the obtained strategy in terms of realizing the swarm consistency and improving the swarm robustness. The results also show that the performance is well maintained while the scale of agents expands (tested with 20, 30, 40 robots).

Many biological architectures are Bouligand structures, which comprise uniaxial fiber layers stacked in a periodic helical arrangement and are characterized by high damage resistance. As an effective flexible protective structure, fish skin is a Bouligand structure that protects the body while ensure flexibility during swimming and predation. In this paper, an analytical model inspired by fish skin is established based on previous studies, and the parameters for describing crack growth are determined. Then, mathematical expressions for the local stress intensity factors and plastic zone are used to predict how the helical stacking angle α influences the crack propagation. The results show that crack deflection and twisting improve the fracture toughness of the composite structure greatly, with the optimal fracture toughness being that for α = 60° – 70°. Moreover, biomimetic flexible composite structures inspired by fish skin are produced using silicone and Kevlar fibers. Scanning electron microscopy is used to observe the cross-sectional morphology of the composite structures, showing that the interfaces between the silicone and Kevlar fibers are highly compact. Results from experimental impact tests agree well with the predicted results.

Owing to insufficient illumination of the space station, the image information collected by the intelligent robot will be degraded, and it will not be able to accurately identify the tools required for the robot’s on-orbit maintenance. This situation increases the difficulty of the robot’s maintenance in a low-illumination environment. We proposes a novel enhancement method for images under low-illumination, namely, a deep learning algorithm based on the combination of deep convolutional and Wasserstein generative adversarial networks (DC-WGAN) in CIELAB color space. The original low-illuminance image is converted from the RGB space to the CIELAB color space which is relatively close to human vision, to accurately estimate the illumination image, and effectively reduce the effect of uneven illumination. DC-WGAN is applied to enhance the brightness component by increasing the width of the generation network to obtain more image features. Subsequently, the LAB is converted into RGB space to obtain the final enhanced image. The feasibility of the algorithm is verified by experiments on low-illuminance image under general, special, and actual conditions and comparing the experimental results with four commonly used algorithms. This study lays a technical foundation for robot target recognition and on-orbit maintenance in a space environment.

This article examines the career development of international football coaches in the context of their transnational migration. Previous research has mainly relied on the normative stages models to explain coaching career development, which has limitations in capturing the complexity and diversity of coach career trajectories, particularly in terms of unique individual experiences and contextual impacts on their career development. Drawing upon the theory of careership, this article seeks to bridge the gap by focusing on how individual coaches navigate their careers according to their horizon for action. Careership theory provides a useful lens through which to examine the interactions between individuals and their contexts, in gaining a more nuanced understanding of how these interactions shape career trajectories. Semi-structured interviews were conducted with eight international coaches who worked in China to gather qualitative data. The results show that the migration of coaches closely intertwined with their career development in a variety of ways, which were manifested in different career horizons for migration within two distinct stages of career development: (1) 'career-consolidation' reflecting the willingness to stabilise and solidify the career pathways, and (2) 'career-reformulation' highlighting the desires or needs to change the current career trajectories. The findings of this article suggest that career development is a multifaceted process encompassing normative, longitudinal steps, individualised approaches, objectives, constraints and unexpected events. Analysing coaches' horizons for action allows researchers and practitioners (e.g. coach educators) to gain a holistic picture of individual and contextual distinctions within the longitudinal stages of coaching career development.

A total of 114 moderately halophilic bacteria were isolated from marine sediment environments. The isolates are belonged to 23 species based on the 16S rRNA sequence analysis. 63, 52, 47, 57, 74, 15 and 4 isolates are able to produce protease, amylase, lipase, pectinase, pulluanase, xylanase, cellulase, respectively. Combined hydrolytic enzyme activity analysis show that 15 strains present 1 hydrolytic activity, 32 strains present 2 hydrolytic activities, 21 strains present 3 hydrolytic activities, 26 strains present 4 hydrolytic activities, 11 strains present 5 hydrolytic activities and 2 strains present 6 hydrolytic activities. Hydrolase activities are widely distributed in a variety of species. The highest rates for production of protease, amylase, lipase, pectinase, pullanase, xylanase and cellulase were observed in species of B. baekryungensis, Hallobacillus sp., B. pumilus, B. megaterium or P. chungwhensis, B. amyloliquefaciens, B. pumilus, B. baekryungensis, respectively. However, the higher activities of protease, pectinase and pulluanase are frequently produced by the species of Halomonas sp. B. amyloliquefaciens or P. chungwhensis, and Vibrio sp. respectively. This investigation show that the diversity of halophilic bacteria from marine sediments could serve as a potential source of hydrolytic enzymes for industrial applications.

Although use of fenvalerate has increased dramatically over the past decade, little is known about their potential adverse effects on growth and development. The purpose of this study was to examine the effects of maternal fenvalerate exposure during pregnancy on growth and neurobehavioral development in the offspring. Pregnant mice were orally administered to fenvalerate (0.2, 2.0, and 20 mg/kg) daily throughout pregnancy. The tests of growth and neurobehavioral development were performed during lactation period. A series of neurobehavioral tasks were carried out from lactation to puberty. Anxiety-related behaviors were evaluated by open-field and elevated plus maze. Morris Water Maze was used to assess spatial learning and memory ability. Results showed that maternal fenvalerate exposure during pregnancy markedly delayed growth development of neonatal offspring during lactation. In addition, anxiety-like behaviors were increased in fenvalerate-exposed male offspring. Moreover, spatial learning and memory was severely impaired in female offspring. Taken together, maternal fenvalerate exposure during pregnancy delayed growth and neurobehavioral development in a gender-dependent manner. Additional study is required to explore the underlying mechanism through which maternal fenvalerate exposure during pregnancy induces impairment of growth and neurobehavioral development.