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A seaweed-like porous carbon anode, prepared using fish scale as the precursor and K2SO4 as the auxiliary, achieves high capacities and superior stability for KIC.

This paper presents the design and fabrication of a magnetic double network (DN) composite, which consists of permanent magnet chains embedded in an elastomer matrix, and was capable of large yet fully recoverable deformation. The initially connected magnets served as reusable sacrificial components in the composite. The strong magnetic attraction between neighboring magnetics endowed the composite with the high strength while the compliance of the elastomer matrix provided the high extensibility. Having a similar mechanism as DN gels, the composite was found to be significantly tougher than either of the constituents. The nonlinear behavior in the composite separated it into two coexisting phases - a softer phase with separated magnet links and a stiffer phase with connected magnet links - which led to the stress plateau on the tensile curve. Further stretching was manifested by the growth of the disconnected softer phase at the expense of the linked stiffer phase, until all magnets were separated. The unloading curves appeared drastically different from the loading curves, as the force needed to separate two magnets was much higher than the force at which two separated magnets snapped back. Such asymmetry between loading and unloading was the main cause of the hysteresis in the stress-strain curve and the energy dissipation. To further understand the physical mechanism and the damage process of the magnetic DN composite, a simple model was developed to examine the deformation and damage dissipation process of composite. With very few parameters, the model predictions agree qualitatively with the measured properties of the material, and the difference can be further reduced by accounting for the interfacial friction/adhesion, a second means of energy dissipation. With a combination of desired properties including high stretchability, self-healing, and high toughness, the magnetic DN composite is a viable candidate for various applications.

Modulation pattern recognition is an important part of underwater acoustic communication. Due to the complexity of underwater acoustic media (propagation loss, ocean noise, multipath effect and Doppler effect), underwater acoustic channel is considered to be one of the most challenging wireless communication channels. This paper proposed an intelligent underwater acoustic signal processing and recognition method based on artificial neural network (ANN) and signal feature extraction. Firstly, the real part and imaginary part of the signal are extracted by fast Fourier transform (FFT), the variance, mean and other eigenvalues of the real part and imaginary part are calculated, respectively. Secondly, the extracted signal features are used to train ANN classifier to realize the classification and recognition of different signals. In this way, the intelligent recognition of underwater acoustic signal by data-driven method is realized. Finally, the effectiveness of the proposed method is verified by simulation, and the good recognition effect is achieved.

In the field of underwater acoustic communication, some underwater devices often operate voice communication and digital communication separately when communicating, and the existing analog modulated voice communication and digital coded voice communication cannot distinguish between digital communication and voice communication in time, resulting in data The transmission speed is slower and the voice quality is lower. In order to solve this problem, the design proposes the use of hybrid communication for information transmission, and designs a special communication protocol system. At the same time, the system adopts positive and negative hyperbolic frequency modulation in the synchronization head and synchronization tail, and adds a spread spectrum communication data header after the synchronization head. The system uses cyclic redundancy check (CRC) to distinguish between voice information and digital information and to synchronize them. The system uses data communication to aid voice communication. The communication system makes the communication process less affected by the channel, has strong anti-interference ability, and realizes better data transmission. Simulation and laboratory tests show that the system can effectively improve the quality of voice communication.

In order to study how dolphins transmit information through sound, a dolphin sound-triggered underwater acoustic recorder was designed to collect sound samples of dolphins communicating. When working underwater for a long time, the dolphin voice signal recorder often faces the problem of insufficient power and limited storage space. In response to this problem, this paper proposes a dolphin sound signal recorder with STM32F407 as the main processor and MSP430F5438A as the coprocessor, which can work on the seabed for a long time and store sufficient samples of dolphins' communication sounds for scientific analysis. The recorder first uses short-term energy to detect whether the dolphin is coming, and then uses a function that describes the correlation between two different signals to calculate the degree of similarity between the sound feature parameters extracted at the sound collection site and the sound feature parameters extracted at the dolphin sound sample, then the similarity value is compared with the set similarity threshold. If the similarity value is greater than or equal to the threshold, the sound signal is stored in the SD card. If the similarity value is less than the threshold, it will not be stored. The paper specifically introduces the design of acoustic triggering algorithm and the design of dolphin sound signal recorder.

Shape memory polymers (SMPs) have been applied in aerospace engineering as deployable space structures. In this work, the coupled finite element method (FEM) was established based on the generalized Maxwell model and the time–temperature equivalence principle (TTEP). The thermodynamic behavior and shape memory effects of a single-arm deployment structure (F-DS) and four-arm deployment structure (F-DS) based on SMPs were analyzed using the coupled FEM. Good consistency was obtained between the experimental data and simulation data for the tensile and S-DS recovery forces, verifying that the coupled FEM can accurately and reliably describe the thermodynamic behavior and shape memory effects of the SMP structure. The step-by-step driving structure is suitable for use as a large-scale deployment structure in space. This coupled FEM provides a new direction for future research on epoxy SMPs.

The center of gravity (CG) has a significant influence on the controllability, stability, and fuel efficiency of the aircraft. For the aircraft with multiple fuel tanks, the CG position can be controlled by the fuel quality of different fuel tanks during flight. In this paper, an optimization method based on discrete cosine transform (DCT) compression is proposed to solve the optimization strategy of aircraft multi-tank fuel supply according to the current aircraft mission and engine working requirements. The transform coefficients of the low frequency components are used as design variables to represent the fuel supply curves. The improved KS function is proposed to deal with constraints. The numerical example is demonstrated to verify the effectiveness of the proposed method.

Printed active composites (PACs) are capable of deforming from an initial shape to a target shape via spatial arrangements of active materials within a passive matrix. Multi-material polymer printers allow precise placement of multiple materials in the design space. However, Single active material is difficult to satisfy the demand in the high-precision matching of more complex target shape. Hence, a multi-material topology optimization approach for the design of PACs is proposed to achieve a target shape under a given stimulus. A multi-material interpolation function for active materials is established, and continuum mechanics modeling is used for simulating active material behaviors on a voxel basis to compute deformations for a given material distribution. The adjoint method is used for sensitivity analysis. Numerical simulations, of different target shapes with the same initial shape, verify the effectiveness of the method. The proposed method is feasible in the conceptual designs of PAC material distributions benefit with stable convergence, ease of implementation, and low computational costs.

The ground-dwelling arthropods is a key component in grassland ecosystem. Many studies have been done on the effects of grazing intensity and grazer species on arthropods in grassland ecosystems, but the information on the effects of grazing timing and frequency are less available. We investigated the abundance of ground-dwelling arthropods in spring, summer and autumn in an experimental steppe grassland that had experienced four grazing management (no-grazed control (T0), June-and-August grazing (T1), July-and-September grazing (T2) and plant growing season grazing (T3)) over four years in central Inner Mongolia. We found that (i) Phytophagous, parasitic and detritivore arthropods were more abundant in autumn than spring, whereas predatory and omnivorous arthropods were less abundant in autumn than spring and summer. (ii) Grazing reduced the abundance of detritivore or predatory arthropods, but not that of omnivorous arthropods. (iii) Grazing had no effects on the relative abundance of different arthropod guilds in spring, but T2 and T3 reduced the relative abundance of detritivore or predatory arthropods, but increased that of omnivorous arthropods in summer. (iv) The variations in the abundance of arthropod guilds was closely associated with the changes in vegetation attributes induced by current-year grazing (height, standing biomass and quality), not by grazing over multiple years (relative biomass of dominant plant species, soil available N and total C:N ratio). Our results provide new insights into the mechanisms of the biological interactions across tropic levels under different management and is helpful to the development of management regimes for steppe ecosystem conservation.

Inspired by the toughening mechanism of double-network (DN) hydrogels, a soft composite consisting of a fabric mesh and VHB tape layers was fabricated. The composite was as stiff as the fabric mesh, and as stretchable as the VHB tape. At certain compositions, the composite was significantly stronger and tougher than the base materials. The extensibility and toughness of the composite can be attributed to a damage delocalization mechanism similar to that of the DN gels. In the partially damaged regions, the fabric mesh fragmented into small islands, surrounded by the highly stretched VHB tapes. Accommodated by the finite sliding at the interface, the large deformation of the composite is highly non-affine. Just as the DN gels, the coexistence of the partially damaged and intact regions resulted in a stable necking in the composite when subjected to uniaxial tension. The propagation of the necking zone corresponded to a plateau on the stress-stretch curve. During cyclic loading, the composite also exhibited stress hysteresis with almost recoverable strain, similar to that in a DN gel. To rationalize these observations and to better understand the underlying physical mechanism, a simple 1D model has been developed for the damage evolution process in the composite. The predictions of the model have achieved good agreement with the measured properties of the composite of various compositions. Furthermore, the composite itself may also be regarded as a macroscopic model when studying the properties and toughening mechanism of the DN gels.

Consisting of stretchable and flexible cell walls or ligaments, soft elastic foams exhibit extremely high fracture toughness. Using the analogy between the cellular structure and the network structure of rubbery polymers, this paper proposes a scaling law for the fracture energy of soft elastic foam. To verify the scaling law, a phase-field model for the fracture processes in soft elastic structures is developed. The numerical simulations in two-dimensional foam structures of various unit-cell geometries have all achieved good agreement with the scaling law. In addition, the dependences of the macroscopic fracture energy on geometric parameters such as the network connectivity and spatial orientation have also been revealed by the numerical results. To further enhance the fracture toughness, a type of soft foam structures with nonstraight ligaments or folded cell walls has been proposed and its performance studied numerically. Simulations have shown that an effective fracture energy one order of magnitude higher than the base material can be reached by using the soft foam structure.