Review Articles

Bamboo is a sustainable material that supports carbon sequestration and helps address the imbalance of timber supply vs. demand. Drying is a crucial step in bamboo processing, in the course of which shrinkage and stress accumulation can lead to defects such as cracking and deformation. Understanding stress and strain development during drying is critical for improving bamboo processing. This review paper explores bamboo’s gradient structure and moisture migration characteristics, focusing on the mechanisms behind shrinkage strain formation and the sources of stress. It reviews literature on bamboo drying and cellular structural changes, evaluating the evolution of stress and strain testing methods, from traditional sectioning techniques to advanced methods such as digital imaging and acoustic emission. The paper also summarizes progress in stress-strain research at both macroscopic and cellular scales. Current challenges include species-specific shrinkage variations, limitations in measurement techniques, and insufficient research on shrinkage above the fiber saturation point. To address these issues, the study recommends developing universal theoretical models, employing advanced detection technologies, comparing shrinkage patterns between bamboo culms and nodes, exploring drying stress composition, and adopting multi-scale research approaches. These strategies aim to enhance the quality of bamboo processing and promote higher-value applications within the industry.

In recent years, the process of optimizing the design of natural fiber reinforcement in natural fiber composites (NFCs) with distinct properties has been redefined through the application of machine learning (ML). This work elucidates the functions of the types and applications of the ML algorithms and evolutionary computing techniques, with a particular focus on their applicability within the domain of NFCs. Moreover, the solution methodologies and associated databases were employed throughout various stages of the product development journey, from the raw material selection through the final end-use application for the NFCs. The strengths and limitations of the ML in the NFCs industry, together with relevant challenges, such as interpretability of ML models, in materials science was detailed. Finally, future directions and emerging trends in the ML are discussed.

Pinus trees are widely distributed worldwide, and pine needles, pine bark, pinecones, etc., have potential medicinal value. This paper reviews the medicinal potential of extracts from different organs of three trees of the genus Pinus in East Asia. Studies have shown that pine trees are rich in bioactive compounds, and these compounds have a variety of pharmacological activities, including antioxidation, anti-inflammatory, antibacterial, antitumor, and hypolipidemic effects. The wide range of pharmacological activities of these bioactive components is helpful for the treatment of cardiovascular diseases, inflammatory diseases, tumors, and other diseases. These findings can help promote research on the medicinal potential of Pinus and its organs to realize the efficient utilization of byproducts of pine resources.

Timber-concrete composite (TCC) beams are formed by integrating timber beams and concrete slabs into a cohesive structural unit using shear connectors. This integration capitalizes on the tensile strength of timber and the compressive strength of concrete, resulting in excellent load-bearing capacity, bending stiffness, vibration comfort, sound insulation, and fire resistance. The long-term behavior of TCC beams must be emphasized, considering the significant time-dependent behaviors of timber, concrete, and the connection system. This work analyzed the long-term mechanical behavior of TCC beams and systematically reviewed the current research on the long-term performance. The primary focus was on the experimental studies of the shear performance of the shear connectors and the mechanical performance of TCC beams under long-term loads. Furthermore, theoretical methods and numerical simulation analyses for evaluating the long-term performance of TCC beams were analyzed. Strengths and weaknesses of existing theoretical methods are identified, and further research and development in the calculation method of TCC beams under long-term loads is proposed.

The impact of UV-B (Ultraviolet-B) radiation is reviewed relative to the biosynthesis and regulation of secondary metabolites (SMs) in medicinal plants. Plants sense UV-B radiation through the photoreceptor UVR8, which is present as a dimer in the absence of UV-B and monomerizes upon UV-B exposure, interacting with proteins to regulate gene expression. In medicinal plants, UVR8-mediated signaling can regulate the activity of key enzymes, thereby affecting accumulation of secondary metabolites. For instance, in Arabidopsis thaliana, UVR8-mediated signaling regulates the expression of flavonoid biosynthesis genes. UV-B radiation influences the yield of SMs in medicinal plants, impacting the biosynthesis of phenolics, terpenoids, and alkaloids, though the effects vary under different UV-B conditions. Furthermore, UV-B radiation induces gene regulation in secondary metabolism, with most genes being upregulated. UV-B interacts with other stress factors, e.g. chromium, UV-A, water availability, and temperature, which affect the accumulation of secondary metabolites. However, these mechanisms are complex and require further investigation. Current research exhibits limitations, including uneven study coverage, a lack of standardized methodologies, and insufficient exploration of interactions between UV-B and other factors. Future studies should expand the research scope, adopt multifactorial approaches, and investigate molecular mechanisms, thereby advancing agricultural practices and the development of medicinal plants.

Environmental pollution and resource waste resulting from the disposal of agricultural biomass waste have become a global issue. Consequently, the pursuit of sustainable strategies for recycling such waste biomass and achieving its efficient and high-value conversion has emerged as a critical challenge that presents for both the global academic and industrial communities. This work provides a comprehensive overview of the current advancements in recycling and conversion of agricultural biomass waste into a variety of bio-based materials, with a particular focus on the biochar, nanocellulose, and bio-based plastics. Potential applications of these bio-based materials in agriculture and beyond with high added-value, such as cosmetics and biomedicine, are discussed with representative cases study. This review also highlights the challenges and future prospects in converting agricultural residues into various bio-based materials. It is hoped that this review will contribute to the understanding and promotion of recycling and reutilization of agricultural biomass waste, offering promising solutions for sustainable development of agricultural production.

It is hard to decarbonize a passenger jet. The aviation industry contributes to approximately 2.5% of global greenhouse gas emissions, underscoring the need for decarbonization to achieve net-zero emissions by 2050. Sustainable aviation fuels (SAFs) derived from conventional biomass, i.e., agricultural residues, forestry by-products, and organic waste, present a scalable solution. Conventional biomass has the potential to produce 60 to 80 billion liters of SAF annually, meeting up to 20% of current jet fuel demand. Lifecycle assessments indicate GHG emission reductions of 70 to 85% compared to fossil fuels. Advanced conversion technologies such as gasification and fermentation have achieved efficiencies exceeding 65%, demonstrating commercial viability. Case studies highlight significant CO₂ reductions of 50 to 70% per flight using SAFs. Despite its promise, biomass-based SAFs are costlier, ranging from USD 1.10 to USD 2.40 per liter. However, policy instruments such as the U.S. SAF Grand Challenge and the EU’s RED II are accelerating adoption. Beyond environmental benefits, SAFs support socio-economic development, potentially creating 1.2 million green jobs globally while addressing waste management challenges. To realize this potential, challenges in technology, economics, and policy need to be addressed. Coordinated efforts in policy, research, and investment are essential to scale SAF deployment, enabling the aviation sector to significantly reduce lifecycle emissions and achieve its net-zero ambitions.

Vibrational methods, which are widely recognized non-destructive testing (NDT) techniques for timber, have garnered significant attention due to their ease of use, broad applicability, and reliable data output. These methods analyze the vibrational response of wood to external stimuli to assess its mechanical properties and internal structure. With advancements in sensor technology, signal processing, and computer simulation, the role of the vibrational methods in timber inspection has been largely expanded, enhancing both the scientific application and quality assurance of timber. This paper provides a comprehensive review of applications of vibrational methods in timber performance evaluation, focusing on its vibrational characteristics, underlying principles, and utility in detecting the physical and mechanical properties as well as internal defects of timber. Furthermore, potential future trends are discussed. Through analysis and research, valuable insights into the evolution of non-destructive timber testing technology are aimed to be provided by this review, and technological innovation in the timber industry is encouraged.

Continuous fiber 3D printing, as a new technology, has attracted attention in an increasing number of applications. Research on continuous fiber 3D printing is currently still in its infancy, after less than 10 years since its discovery in 2016. Many technical and fundamental questions still need to be addressed. Most literature has dealt with 3D printing employing continuous synthetic fibers (e.g., carbon and aramid fibers). This critical review summarizes the progress on the 3D printing of continuous natural plant fibers and their regenerated fibers and their use in reinforced thermoplastic composites. Their mechanical performance under extreme environmental conditions is further reviewed. These high-performance continuous fiber reinforced polymer composites have potential for high value applications such as aerospace technologies.