Bamboo is a typical natural fiber-reinforced composite with excellent mechanical properties, which are determined by its special micro-structure. As the reinforcing phase, the vascular bundles play a central role in the control of the mechanical properties of bamboo macro-structure. To find the exact gradient variation of the mechanical properties of these continuously distributed vascular bundles within the bamboo culm, 4-year-old Moso bamboo was chosen to investigate the variation of locate-distribution, cross-section area, and mechanical properties of single vascular bundles along the longitudinal and radial directions with respect to their location from the base, middle, and top sections of bamboo culm, respectively. It shows that the spatial distribution of vascular bundles along the column is distributed exponentially from the inside to the outside of the culm. The cross-section area of the vascular bundles decreased exponentially from the inside to the outside along the radial direction. All the vascular bundles were then carefully separated from bamboo strips and tested via the tensile tests. Test results show that the longitudinal tensile strengths of vascular bundles ranged from 180.44 to 774.10 MPa, and the longitudinal Young’s modulus ranged from 9.00 to 44.76 GPa. The tensile strength of vascular bundles at the outer side was three times higher than that of the inner side, while Young’s modulus at the outer side was three to four times higher than that of the inner side. For all three height positions, the strengths and Young’s modulus of vascular bundles are all exponentially increased from the inner side to the outer side along the radial direction. This work will provide a basis for the highly processed product’s application of bamboo resources and a reference for further study on the trans-scale analysis of the mechanical properties of bamboo.

Using bamboo residue and high-density polyethylene (HDPE) as the main raw materials, core–shell structured wood plastic composites (WPCs) with nano-CaCO₃ filling shell were prepared by coextruded technology. The effect of nano-CaCO₃ contents on the flexural properties, impact strength and dynamic thermo-mechanical properties of the core–shell structured WPCs were investigated. And the value of core–shell interface interaction parameter was calculated by dynamic thermodynamic parameters. The results showed that the flexural strength increased by 48.1% and 40.3% when it was loaded with 10%–15% nano-CaCO₃, compared to the HDPE shell composites, respectively. While nano-CaCO₃-filled HDPE shell had lower impact strength in comparison with HDPE shell, the field emission scanning electron microscope revealed proper interfacial adhesion between the core and shell layers. The storage modulus of core–shell structured WPCs increased as nano-CaCO₃ contents increased, but the values were lower than that of the HDPE shell. Addition of nano-CaCO₃ caused an increase in the glass transition temperature (T_g) of the core–shell structured WPCs, loss factor (tanδ) of the core–shell structured WPCs decreased. The value of the core–shell interface interaction parameter of the core–shell structured WPCs increased significantly after the nano-CaCO₃ loading reached 15%, which was consistent with the bending test results. These findings demonstrate that the core–shell structured WPCs have excellent properties filling with nano-CaCO₃ in the shell layer, and bamboo residue is added to the core layer.

To solve the problem of large sowing amount and poor sowing uniformity for millet, according to the physical characteristics of the millet seed and its sowing agronomic requirements, an electromagnetic vibration type fine and small-amount seeder was designed, and the main technical parameters of the seeder were determined, in order to realize the functions of furrow opening, electronically controlled seed metering, soil covering and pressing. Based on the principle of electromagnetic vibration, an electromagnetic vibration type seed metering device was designed to achieve uniform seeding of the millet seed with a small sowing amount; a seeding amount electronic control device was designed using an STM32 microcontroller, which realized the switching to sowing agronomic mode and the adjustment of the seeding amount with sowing operation speed; a vibration experimental bench was set up to simulate the vibration state of field operation, and studies on the seeding performance and vibration damping of the seed metering device by the isolation spring were carried out, as well as field sowing tests for verification. When the working voltage of the seed metering device is 80–160 V, the coefficients of variation for seeding uniformity per row and for total seeding uniformity are not greater than 3.57% and 2.39%, respectively, and the seed damage rate is less than 0.5%. The installation of isolation springs can increase the maximum vibration acceleration of the seed metering device by 10.61–28.20%, significantly reducing the impact of external vibrations on the seed metering device. Within the range of suitable sowing operation speeds, the electronic control device can meet the seeding amounts along with sowing operation speed in the 6, 7.5 and 9 kg/hm² sowing agronomic modes, and the coefficient of variation for seeding uniformity per row, for total seeding uniformity and for sowing uniformity are not greater than 4.63%, 2.48% and 23.38%, respectively. This study provides a reference for the development of sowing machinery for millet crop.

Mechanized harvesting is a crucial step in the agricultural production of foxtail millet (Setaria italica), as its peduncles are susceptible to bending and breaking during the harvesting process, leading to yield losses and deterioration in grain quality. To evaluate the suitability of foxtail millet for mechanical harvesting, this study comprehensively analyzed the biomechanical properties of the peduncles and related biological morphological characteristics of 116 foxtail millet accessions, establishing a system for indicator screening and comprehensive evaluation. Using partial correlation analysis and R-type cluster analysis, four biomechanical and seven related morphological indices of the peduncle were screened from 22 candidate indicators, with their coefficient of variation ranging from 6% to 80%. The entropy method was used to assign weights to the selected indices, with biomechanical factors contributing 47.4%, peduncle morphology 20.2%, spike morphology 27.6%, and plant height 4.8%. The Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and Rank-Sum Ratio (RSR) methods were applied to rank and grade the classification of the 116 foxtail millet varieties into four performance groups: Excellent (8 varieties), Good (50 varieties), Moderate (51 varieties), and Poor (7 varieties). This study provides a scientific basis for the selection and evaluation of foxtail millet varieties.

Chitosan films have attracted increasing attention as biodegradable packaging materials; however, their relatively low stiffness and limited mechanical stability restrict their practical application. In this study, ramie elementary fiber-reinforced chitosan composite films were prepared using ramie elementary fiber suspensions at concentrations of 0, 0.5, 1.0, and 1.5 g/L. The mechanical properties, chemical interactions, crystalline structure, and surface morphology of the composite films were systematically investigated by tensile testing, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The results showed that the incorporation of ramie elementary fibers significantly affected the mechanical behavior of chitosan films. Among the tested concentrations, the composite film with 0.5 g/L ramie elementary fibers exhibited the best overall performance, with the elastic modulus increasing by 130% from 67.46 MPa to 155.14 MPa compared with the pure chitosan film. FTIR analysis indicated that the formation of hydrogen-bonding between ramie elementary fibers and the chitosan matrix, while XRD results showed that the incorporation of ramie elementary fibers enhanced the structural ordering of the chitosan-based composite films without forming a new crystalline phase. SEM observations further confirmed that an appropriate fiber content promoted uniform dispersion and good interfacial bonding, whereas excessive fiber addition led to aggregation, surface roughening, and interfacial defects. These findings demonstrate that low-content ramie elementary fibers can effectively improve the stiffness and structural stability of chitosan composite films, providing a potential strategy for developing biodegradable fiber-reinforced packaging materials.

In this study, poplar wood flour was modified with alkyl ketene dimer (AKD), and poplar wood flour/polylactic acid (PLA) composites with 0–5% AKD were prepared. Effects of AKD content on wettability, water absorption kinetics, dimensional stability, flexural properties, and microscopic interface were investigated. AKD likely consumed hydroxyl groups through esterification and/or hydrogen bonding, as reported in the literature, and introduced hydrophobic alkyl chains. The 5% AKD sample exhibited the highest contact angle, while the 3% AKD sample showed the lowest total surface free energy (24.73 mJ·m⁻²). AKD content significantly changed the water diffusion mode: at 0–3% AKD, water absorption followed non-Fickian diffusion, with 2% AKD showing the highest n value (0.7132), indicating swelling-controlled diffusion and the lowest apparent saturation water absorption. At 4% AKD, n decreased to 0.4786, approaching Fickian diffusion, and agglomerated pores accelerated water transport. The 2% AKD sample exhibited optimal interfacial bonding and the highest flexural strength retention (46.29%). The 5% AKD sample showed the lowest steady-state thickness swelling coefficient (10.03%), indicating the best dimensional stability, but agglomeration defects weakened mechanical properties. Interfacial bonding strength, rather than low water absorption or low swelling, was key to mechanical retention. An optimal AKD content range exists when “optimal” is defined by the balance between mechanical retention and dimensional stability: 2% AKD is preferred for mechanical retention, while 5% AKD is preferred for dimensional stability under humid service scenarios. These findings support the water-resistant modification of PLA-based wood–plastic composites.