Search Results (7)

The construction sector’s increasing eco-consciousness is driving the need for higher-performance wood-based engineered products from underutilized timber resources, such as small-diameter trees from hazardous fuel treatments of our forests. Strand-based products, including oriented strand board (OSB) and lumber (OSL), are widely used. However, hot-pressing during their manufacturing generates approximately 10% waste, which includes a substantial amount of resinated strands that are landfilled. The huge potential of using strand-based products has led to many studies and growing interest in strand-based three-dimensional sandwich panels that can be used as wall, floor, or roofing panels. As the market grows, understanding the recyclability of these resinated strands becomes crucial. This study investigates the feasibility of using re-resinated waste strands that were collected during lab-scale production of strand-based panels. Results demonstrate significant improvements in dimensional stability, mechanical properties, and fire resistance. Specifically, recycling increased internal bond strength, flexural strength, time to ignition, time to flameout, mass loss, and time to peak heat release rate by 107%, 44%, 58%, 35%, 51%, and 27%, respectively, and helped decrease water absorption and thickness swell by 51% and 58%, respectively. Full article

Firefighting foam is widely recognized for its excellent fire suppression performance. However, research on the effect of foam expansion ratio on the suppression efficiency of forest surface fires remains limited. In this study, the expansion ratio was adjusted by varying the air-to-liquid ratio in a compressed air foam system, and laboratory-scale foam suppression experiments were conducted. Key performance indicators, including extinguishing coverage time, internal cooling rate, and resistance to reignition, were systematically measured. The effects of expansion ratio on the diffusion and penetration behavior of foam on the fuel bed surface were then investigated to understand how these characteristics influence suppression performance. The results indicate that both excessively low and high expansion ratios can weaken fire suppression effectiveness. Low-expansion foam, characterized by low viscosity and high water content, exhibits strong local penetration and cooling capabilities. However, it struggles to rapidly cover the fuel bed surface and isolate oxygen, thereby reducing the overall suppression efficiency. In contrast, high-expansion foam has greater viscosity, allowing it to spread across the fuel bed surface under pressure gradient forces and form a stable coverage layer, effectively limiting the oxygen supply required for combustion. However, its limited depth penetration and lower water content reduce internal cooling efficiency, increasing the risk of reignition. The optimal expansion ratio was determined to be 15.1. Additionally, increasing the liquid supply flow rate significantly improved suppression performance; however, this improvement plateaued when the flow rate exceeded 10 L/min. Full article

Statistics indicate that over 90% of large forest fires experience re-ignition after initial extinction. However, research on the mechanisms triggering forest fire rekindling remains largely empirical, lacking an intuitive 3D mathematical model to elucidate the process. To fill this gap, this study proposes a digital twin-based forest fire re-ignition trigger model to investigate the transition from smoldering to flaming combustion. Leveraging digital twin technology, a virtual forest environment was constructed to assess the influence of ambient wind conditions and terrain slope on the smoldering-to-flaming (StF) transition based on historical rekindling data. Subsequently, logistic regression was employed in a reverse iterative process to update the model parameters, thereby establishing a matching mechanism between the model predictions and the observed rekindling states. This approach enables the adaptive adjustment of the weights assigned to key variables (e.g., wind speed and slope) and facilitates the prediction of forest fire rekindling probability within the virtual environment. Additionally, digital twin simulations are employed to assess the 3D firefighting effectiveness of unmanned aerial vehicles (UAVs) deploying hydrogel and solidified foam extinguishing agents. This visualization of the firefighting process provides valuable insights, aiding in the development of more effective strategies for preventing and controlling fire re-ignition. Full article

Forest fires often pose serious hazards, and the timely monitoring and extinguishing of residual forest fires using unmanned aerial vehicles (UAVs) can prevent re-ignition and mitigate the damage caused. Due to the urgency of forest fires, drones need to respond quickly during firefighting operations, while traditional drone formation deployment requires a significant amount of time. This paper proposes a pure azimuth passive positioning strategy for circular UAV formations and utilizes the Deep Q-Network (DQN) algorithm to effectively adjust the formation within a short timeframe. Initially, a passive positioning model for UAVs based on the relationships between the sides and angles of a triangle is established, with the closest point to the ideal position being selected as the position for the UAV to be located. Subsequently, a multi-target optimization model is developed, considering 10 UAVs as an example, with the objective of minimizing the number of adjustments while minimizing the deviation between the ideal and adjusted UAV positions. The DQN algorithm is employed to solve and design experiments for validation, demonstrating that the deviation between the UAV positions and the ideal positions, as well as the number of adjustments, are within acceptable ranges. In comparison to genetic algorithms, it saves approximately 120 s. Full article

Wildfires play a critical role in re-shaping boreal ecosystems and climate. It was projected that, owing to the Arctic amplification, boreal wildfires would become more frequent and severe in the coming decades. Although provoking concern, the spatiotemporal changes in boreal wildfires remain unclear, and there are substantial inconsistencies among previous findings. In this study, we performed a comprehensive analysis to determine the spatiotemporal changes in wildfires over Northern Eurasia (NEA) from 2003 to 2020 using a reconstructed Moderate Resolution Imaging Spectroradiometer (MODIS) active fire product. We found that wildfires in NEA exhibited contrasting changes in different latitudinal zones, land cover types, and seasons from 2003 to 2020. Cropland wildfires, mainly distributed at low latitudes (50–60°N), considerably decreased by 81% during the study period. Whereas forest wildfires ignited at high latitudes (north of 60°N) have nearly tripled (increasing at rate of 11~13% per year) during the past two decades. The southwestern and northeastern NEA regions exhibited contrasting patterns of wildfire changes. The active fire counts in the southwestern NEA decreased by 90% at a rate of 0.29(±0.12) × 10⁵ per year, with cropland fires contributing to ~66% of the decrease. However, the fire counts in the northeastern NEA increased by 292% at a rate of 0.23(±0.12) × 10⁵ per year, with boreal forests contributing to ~97% of the increase. It is worth noting that the contrasting changes in wildfires during the past two decades have led to significant structural alternation in the NEA wildfire composition. Forest fires, contributing over 60% of the total fire counts in NEA nowadays, have become the predominant component of the NEA wildfires. The contrasting changes in NEA wildfires imply that more forest fires may emerge in far northern regions of the North Hemisphere as the Arctic becomes progressively warmer in the coming decades. As wildfires continue to increase, more gases and aerosols would be released to the atmosphere and cause considerable feedback to the Arctic climate. The increased wildfire-related climate feedbacks should, therefore, be seriously considered in climate models and projections. Full article

In 2022 the US Forest Service launched an ambitious 10-year strategy to address the escalating wildfire danger in the U.S. “Confronting the Wildfire Crisis: A Strategy for Protecting Communities and Improving Resilience in America’s Forests” includes a 10-year plan to substantially increase the scale of forest health and risk reduction fuel treatments over the next decade. The plan expands and prioritizes treatments on 20 million acres on National Forest System lands, and 30 million acres of other federal, state, tribal, and private lands, targeting lands where wildfire ignitions will potentially impact communities. In this talk, we describe the core science components supporting the treatment plan, and its evolution through interactions between our research team and Forest Service leadership. We highlight key science advancements and contributions, including: (1) the development of a multiscale planning framework based on wildfire risk transmission to communities that recognizes the scale of wildfire risk in the western U.S.; (2) scenario planning models that optimized and scheduled treatments over the first 20 years of the plan and re-treatments for an additional 10 years; (3) methods to incorporate the future effect of wildfire during plan implementation, i.e. “planning risk”; (4) an online geospatial registry to track progress; and (5) use of extreme event assessments rather than average burn probability to communicate risk. We describe how these tools and methods could be used in other fire-prone regions to build and test national scale fuel management strategies to guide current and new policy initiatives in response to recent trends in wildfire losses. Full article

This study analyses the smouldering combustion on soils that took place during the wildfires that occurred in Rocallaura (Northeastern Spain). The smouldering combustion after the first event, 23 June, was the potential source of flaming fire re-ignition of the second event, 19 July 2016. Re-ignitions are an important challenge for the firefighting system. Budget and efforts are spent on controlling these re-ignitions that can ultimately cause the collapse of the response system if the re-ignitions happen during periods of simultaneous fire events. Our objective is to contribute to better understand the dynamics of the smouldering combustion of organic soils associated with these wildfires and the impact on the Pinus halepensis Mill. forest ecosystem. Transects were established in adjacent control and post-fire zones. Laboratory analyses were conducted to determine some physical and chemical properties of both the duff and mineral soil. Using these variables, we estimate thresholds of duff ignition probability, percentage of duff consumption and smouldering combustion spread rates. Overall, we provide a set of tools for evaluating re-ignitions in forest ecosystems. We conclude that the concept of fire persistence should be a new variable for consideration in present and future analysis of fire regimes and demonstrates the significance of introducing smouldering combustion and re-ignition within the strategic framework of the wildfire hazard and integrating these phenomena into forest planning and management. Full article