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In recent years, research has focused heavily on the investigation of functionalized ammonium polyphosphate (APP) flame retardants to improve the fire safety of epoxy resins (EP). The reason for this is the dual nature of APP's performance in fire protection of EP. This article provides a comprehensive overview of the advances in the use of functionalized APP flame retardants to improve the fire resistance of EP materials. It then presents the improvement of the modification of the functionalized APP flame retardants in terms of the hydrophobicity, compatibility and catalytic ability of the flame retardants, as well as the effects on the fire resistance, heat resistance, smoke reduction and mechanical properties of the EP composites. After the summary and comparison of the relevant studies, it is clear that the functionalized APP flame retardants can effectively improve the fire safety of EP composites and offset the adverse effects of APP in EP flame retardant applications. In addition, APP flame retardants can obtain various excellent functions through the use of materials with different properties, and the interaction between APP and materials can also lead to more efficient fire protection. However, the current problem is to find ways to streamline the process and minimise the costs associated with functionalized APP flame retardants, as well as to use them effectively in industrial production. We hope that this review can provide valuable hints and insights for the practical application of functionalized APP in EP and perspectives for future research.

Abstract A multi-element synergistic flame retardant with double-bond structure was synthesized and added to epoxy resin (EP) to obtain EP composites with high flame retardant and mechanical properties. The study demonstrated that the DOPO-KhCPA-5 composite, containing 5 wt% of DOPO, exhibits the limiting oxygen index (LOI) value of 32%, indicating a high resistance to combustion. Additionally, it successfully meets the UL-94 V-0 grade, indicating excellent self-extinguishing properties. The DOPO-KhCPA-5 compound exhibited a 48.7% decrease in peak heat release rate (PHRR) and a 7.2% decrease in total heat release (THR) compared to pure EP. The inclusion of double-bonded architectures in the DOPO-KhCPA-5 composites led to a significant enhancement in both the tensile strength and tensile modulus. Specifically, the tensile strength increased by 38.5% and the tensile modulus by 57.9% compared to pure EP. This improvement can be attributed to the formation of a fully interpenetrating network of macromolecular chain structures by DOPO-KhCPA within the EP matrix. This network increased the entanglement between molecular chains, resulting in positive effects on the mechanical properties of the EP. Multi-element of DOPO-KhCPA exhibits a synergistic effect, providing condensed and noncombustible gas-phase flame retardancy. Additionally, the mechanical properties were improved with the introduction of flame retardants due to the good impact of double-bond cross-linking. The effectiveness of DOPO-KhCPA as an additive for developing high-performance EP with significant potential applications has been proven.

Pedestrian safety evacuation in aircraft cabins has been a challenging problem because of the aircraft's unique characteristics, such as the diversity of passengers and the restricted evacuation environment. It is difficult to reproduce evacuation activities in aircraft cabin due to safety concerns and cost constraints. To fill this gap, an improved cellular automaton model of crowd evacuation for aircraft cabin is established by incorporating the characteristics of cabin space structures and passenger attributes. Passengers are divided into healthy individual passengers and disabled-healthy group passengers, whose movement mechanisms are quantified. Based on the constructed model, simulation experiments are conducted using the configuration cabin layout of B737-800 as an example. The results show that the evacuation time is prolonged with increased passenger density and the number of disabled passengers. Moreover, the overall evacuation time is insignificantly affected by whether disabled-healthy group passengers' seats are close to the aisle or window, and the evacuation efficiency is best when their seats are evenly distributed in the cabin. The evacuation time is the shortest when all cabin doors are open, and pedestrians are evacuated the slowest when the central emergency doors are closed. This study provides valuable insights into effective strategies for pedestrian evacuation and crowd emergency management of civil aircraft.

Planets may be rotationally flattened, and their oblateness thus provides useful information on their formation and evolution. Here, we develop a new algorithm that can compute the transit light curve due to an oblate planet very efficiently and use it to study the detectability of planet oblateness (and spin obliquity) with the James Webb Space Telescope (JWST). Using the Jupiter analog, Kepler-167e, as an example, we show that observations of a single transit with JWST are able to detect a Saturn-like oblateness ( f = 0.1) with high confidence, or set a stringent upper limit on the oblateness parameter, as long as the planetary spin is slightly misaligned (≳20°) with respect to its orbital direction. Based on known obliquity measurements and theoretical arguments, it is reasonable to believe that this level of misalignment may be common. We estimate the sensitivity limit of JWST in oblateness detections and highlight the importance of better characterizations of cold planets in planning future JWST transit observations. The potential to detect rings, moons, and atmospheric species of the cold giants with JWST is also discussed.

The occurrence of pool fires adjacent to a sidewall poses significant risks. To investigate fire source combustion characteristics and thermal feedback of sidewall-attached fires, experiments involving rectangular heptane pool fires with varying aspect ratios and pool orientation relative to sidewall were conducted. The flame tilting behavior, temperature near sidewall, thermal transfer process and air entrainment effects of rectangular pool fires were studied. The findings show that triangular flame shape in parallel arrangements and flame separation of perpendicular setups attribute to the unbalanced air entrainment near sidewall. Perpendicular pools lead to lower temperatures near sidewall surface caused by flame separation. The mass loss rate (MLR) of parallel pool fires initially decreases with n driven by thermal radiation from the flame. It is followed by an increase due to thermal conduction and thermal radiation through the sidewall, with a threshold value at n = 3. The MLR of perpendicular pools decreases continuously owing to the dominance of total thermal radiation. Finally, based on the air entrainment theory, a quantitative correlation between the flame height and n relative to sidewall is proposed. This is also validated by experimental and previous research data.

Object detection methods can be used to detect flames and smoke from images or videos for the identification and exploration of fire. In this paper, an improved YOLOv5s algorithm, called GAM-ASFF-YOLOv5s is proposed, which introduces an attention mechanism and feature fusion layer. A global attention mechanism (GAM) is introduced into the backbone network of YOLOv5s to focus on the detection information that is conducive to flames and smoke, while suppressing unimportant information. A head network with adaptive spatial feature fusion (ASFF) was designed to extract more complete image features of flame and smoke. In addition, the original object bounding box regression loss function the complete IoU (CIoU) of YOLOv5s was replaced by repulsion loss to enhance the generalization ability of the model and further improve the detection performance of the flame and smoke. The experimental results show that the precision of the GAM-ASFF-YOLOv5s+REP algorithm was 5.7% higher than that of the original YOLOv5s algorithm on the VOC2007 dataset and it also performed well on the flame and smoke dataset, that is, the precision, recall, and mean average precision (mAP) were improved by 0.5 %, 2.1 % and 2.9 % respectively, compared to the original YOLOv5s algorithm.

Fire-detection technology plays a critical role in ensuring public safety and facilitating the development of smart cities. Early fire detection is imperative to mitigate potential hazards and minimize associated losses. However, existing vision-based fire-detection methods exhibit limited generalizability and fail to adequately consider the effect of fire object size on detection accuracy. To address this issue, in this study a decoder-free fully transformer-based (DFFT) detector is used to achieve early smoke and flame detection, improving the detection performance for fires of different sizes. This method effectively captures multi-level and multi-scale fire features with rich semantic information while using two powerful encoders to maintain the accuracy of the single-feature map prediction. First, data augmentation is performed to enhance the generalizability of the model. Second, the detection-oriented transformer (DOT) backbone network is treated as a single-layer fire-feature extractor to obtain fire-related features on four scales, which are then fed into an encoder-only single-layer dense prediction module. Finally, the prediction module aggregates the multi-scale fire features into a single feature map using a scale-aggregated encoder (SAE). The prediction module then aligns the classification and regression features using a task-aligned encoder (TAE) to ensure the semantic interaction of the classification and regression predictions. Experimental results on one private dataset and one public dataset demonstrate that the adopted DFFT possesses high detection accuracy and a strong generalizability for fires of different sizes, particularly early small fires. The DFFT achieved mean average precision (mAP) values of 87.40% and 81.12% for the two datasets, outperforming other baseline models. It exhibits a better detection performance on flame objects than on smoke objects because of the prominence of flame features.

The escalating impacts of human activities on the ecological environment underscore the significance of valuing ecological resources within the paradigm of sustainable development. In this context, the ecological service value (ESV) of the Danjiangkou watershed (Hubei section) was assessed using a revised equivalent factor evaluation method. Additionally, the study determined the human activity intensity (HAI) and employed GeoDetector to delineate the spatial heterogeneity of ESV, thereby investigating the underlying causes. Results show that vegetation coverage attains a high level of 94%, with a minor 1.37% land use change between 2016 and 2020. Secondly, ESV exhibited a substantial variation, rising from 75.55 billion to 79.81 billion yuan, a growth rate of 5.64%. Lastly, the explanatory degree for the synergistic interplay of HAI and expenditure on the spatial variation of ESV surpassed 30%, and the average sensitivity coefficient of up to 0.82 further indicated the apparent impacts of land use and human interference activities on ESV. The study makes an excellent effort to clarify the complex coupling relationships between different land use types and ESV, which could serve as an example and model for other studies in the field.

This study primarily investigates the combustion characteristics of full-scale cabin fires under different fire source positions based on the pyrolysis and burnout of the typical cabin combustibles. The flame spread, mass loss rate (MLR), heat release rate (HRR), smoke movement characteristics and temperature decay were analyzed. Results showed that the cabin flame spread under different fire source positions could be divided into four stages. The fire source position significantly influenced the growth rate of MLR and HRR, but had little effect on the peak value. Comparison of the theoretical HRR based on fuel and ventilation control with the simulation data verified the dynamic change of cabin fire. The confined space and continuous intense combustion made the smoke movement driven by weak and strong plume in cabin fire. The fire source position had the great influence on TBL in the initial stage of cabin fire. The temperature decay correlation ln(ΔTmax(abs(x−a)/L)ΔTmax)∝C(abs(x−a)/L) considering the flame spread was proposed, which was well consistent with the simulation results. The conclusions would be helpful to understand the cabin fire and provide the theoretical reference for evacuation.

We present constraints on the shape of Kepler-51d, which is a superpuff with a mass ∼6 M _⊕ and a radius ∼9 R _⊕ , based on detailed modeling of the transit light curve from James Webb Space Telescope (JWST) NIRSpec. The projected shape of this extremely low-density planet is consistent with being spherical, and a projected oblateness f _⊥ > 0.2 can be excluded regardless of the spin obliquity angles. If this is taken as the limit on the true shape of the planet, Kepler-51d is rotating at ≲50% of its breakup spin rate, or its rotation period is ≳33 hr. In the more plausible situation that the planetary spin is aligned with its orbital direction to within 30°, then its oblateness is

The supply and demand of ecosystem services (ES) present apparent spatial heterogeneities within cities, with a higher demand but limited supply in urban centers, and vice versa in suburban and rural areas. However, there is still a lack of theory and relevant quantitative tools to quantify the distribution patterns and spatial mismatches of ES supply and demand across space, e.g., along urban-rural gradients. Here, we adopt a modified sigmoid function to quantify spatial gradients of ES supply and demand of six cities within the Danjiangkou Basin in Hubei Province, China. ES supply and demand are calculated using the value equivalent method and the land development index model, respectively. Results show that as the distance from the city center increases, there is a decrease in ES demand, while ES supply exhibits a gradual increase through the gradient analysis. We then utilized the modified sigmoid model to accurately quantify the S-shape curve for ES supply and the inverse S-shape curve for ES demand. We further observed that the balance point (the intersection of the ES supply and demand curves) of ES supply and demand gradually moved towards the outskirts of the city as it expanded. Our study introduces a quantitative tool for analyzing the spatial gradients of ES supply and demand within cities.

One-dimensional (1D) van der Waals (vdW) materials have garnered significant attention for their unique structures and properties, making them promising candidates for various applications in optoelectronics, catalysis, energy storage, and sensors. However, further advancements are required to fully exploit their potential as energy storage devices. This study presents an anode design paradigm utilizing 1D vdW-based V2PS10 crystals characterized by large vdW gaps, a small bandgap, and distinctive chemical compositions that favor lithium storage. To enhance their performance, we employ surface modification techniques to create V2PS10 @C composites, where conductive carbon is integrated with V2PS10 crystals. This modification significantly improves electron transport and Li-ion diffusion within the composite anodes. The resulting composite anodes exhibit exceptional electrochemical properties, including a high discharge capacity of 1154 mAh g−1 after the 50th cycle at 0.1 A g−1, superior rate performance with a current density of 561 mAh g−1 at 10 A g−1, and prolonged cycling stability, maintaining a capacity of 605 mAh g−1 for up to 800 cycles at 5 A g−1. These remarkable electrochemical performances underscore the immense potential of 1D vdW-based materials as next-generation anodes for lithium-ion batteries.

The isothermally hot compression tests of Incoloy 925 were conducted over a temperature range of 900–1150 °C and strain rate of 0.01–10 s−1 to investigate the dynamic recrystallization (DRX) kinetics behavior and its effect on the microstructure evolution. The values of DRX fraction under different deformation conditions were evaluated through electron backscatter diffraction analysis combined with artificial neural network approach. The DRX behavior was also investigated based on the traditional Avrami-DRX kinetics model and the strain-rate dependent Avrami-DRX kinetics model modified by genetic algorithm & BiHill function, respectively. The results reflected that the modified model shows a better robustness to describe the DRX behavior under the deformation condition with a relatively low DRX fraction or at the domain with higher strain rate. Besides, the crystallographic orientation parallel to the compressive direction tends to form the fiber highlighted by the deformed grains, while the predominant orientations of DRX grains show a tendency towards fiber. Moreover, the transition rule of the main DRX mechanism was further studied by discussing the linear relationship between the Z parameter and DRX grain size.

Abstract Background Neurocognitive disorders and psychosocial difficulties are common in patients with Turner syndrome and multiple neurodegenerative diseases, yet there is no effective cure. Human primordial germ cells (hPGCs) are pluripotent germline stem cells in early embryo, which pass genetic information from one generation to the next, whereas all somatic cells will die along with the end of life. However, it is not known whether patient hPGCs with Turner syndrome contain information of neurocognitive and psychosocial illness. Results In this report, we used a high-density of culture system of embryoids derived from iPSCs of a patient with Turner syndrome to ask how pathogenetic pathways are associated with onset of neurocognitive and psychosocial disorders. The hPGC-Like Cells (hPGCLCs) were in vitro specified from iPSCs of 45,XO, 46,XX and 46,XY by the high-density induction of embryoids. Amazingly, we found that the specification process of the hPGCLCs in 45,XO, compared to those in 46,XX and 46,XY, enriched several common pathogenetic pathways regulating neurocognitive and psychosocial disorders, that shared among multiple neurodegenerative diseases and Turner syndrome. The downregulated chemical synaptic transmission pathways, including glutamatergic, GABAergic, and nicotine cholinergic synapses, indicated synaptic dysfunctions, while upregulated pathways that were associated with imbalance of mitochondrial respiratory chain complexes and apoptosis, may contribute to neuronal dysfunctions. Notably, downregulation of three types of ubiquitin ligases E1-E2-E3 and lysosome-associated sulfatases and RAB9A, owing to haploinsufficiency and parental preference of the X chromosome expression, indicated that two pathways of cellular degradation, lysosome and ubiquitin–proteasome, were impaired in the specification process of 45,XO hPGCLCs. This would lead to accumulation of undesired proteins and aggregates, which is a typically pathological hallmark in neurodegenerative diseases. Conclusions Our data suggest that the specification process of the hPGCLCs in 45,XO, compared to those in 46,XX and 46,XY, enriched pathogenetic pathways that are associated with the onset of neurocognitive and psychosocial disorders.

The effect of microalloyed Ca on the microstructure, mechanical properties and aging precipitation of Mg–6Zn–1Mn–4Sn (wt.%, ZMT614) alloy were investigated. The as-cast ZMT614 alloy was mainly composed of α-Mg, Mg–Zn and Mg2Sn phase, and a new CaMgSn phase with high melting point was formed with Ca addition. The CaMgSn phase was easier to form than Mg2Sn during solidification, so the formation of Mg2Sn was suppressed. Undissolved CaMgSn phases after solution treatment played an important role in pinning grain boundary migration and grain growth, and can act as nucleation sites promoting precipitation during aging process. CaMgSn particles also retarded the recovery process and the retained dislocations could act as additional heterogeneous nucleation sites for precipitation. β′ precipitates along [0001]α were finer and disc-like precipitates β'' on (0001)α were denser for Ca-containing alloys after aging treatment. The peak-aged ZMT614-0.5Ca alloy exhibited the optimum mechanical properties and its yield strength, ultimate tensile strength and elongation were 345 MPa, 378 MPa and 6.5%, respectively. The strengthening mechanism was mainly attributed to the grain refinement and precipitation strengthening.

Developing hydrolytic nanozymes remains challenging. Here the authors present a rational methodology to design hydrolytic nanozyme by developing a data-informed strategy to screen and identify potential scaffold and active sites of hydrolase-like nanozyme.

The accurate analysis of multi-scale flame development plays a crucial role in improving firefighting decisions and facilitating smart city establishment. However, flames’ non-rigid nature and blurred edges present challenges in achieving accurate segmentation. Consequently, little attention is paid to extracting further flame situation information through fire segmentation. To address this issue, we propose Flame-SeaFormer, a multi-scale flame situation detection model based on the pixel-level segmentation of visual images. Flame-SeaFormer comprises three key steps. Firstly, in the context branch, squeeze-enhanced axial attention (SEA attention) is applied to squeeze fire feature maps, capturing dependencies among flame pixels while reducing the computational complexity. Secondly, the fusion block in the spatial branch integrates high-level semantic information from the contextual branch with low-level spatial details, ensuring a global representation of flame features. Lastly, the light segmentation head conducts pixel-level segmentation on the flame features. Based on the flame segmentation results, static flame parameters (flame height, width, and area) and dynamic flame parameters (change rates of flame height, width, and area) are gained, thereby enabling the real-time perception of flame evolution behavior. Experimental results on two datasets demonstrate that Flame-SeaFormer achieves the best trade-off between segmentation accuracy and speed, surpassing existing fire segmentation methods. Flame-SeaFormer enables precise flame state acquisition and evolution exploration, supporting intelligent fire protection systems in urban environments.

Abstract A hyperbranched phosphorus-containing copper phthalocyanine compound (DOPO-CuPc) was successfully synthesized and used as the flame-retardant additive to prepare flame-retarded epoxy thermosets. The addition of DOPO-CuPc led to a significant enhancement of the flame retardant properties of the epoxy resin. The 15DOPO-CuPc/EP composite obtained a LOI value of 35.8%, and the UL-94 rose from NR to V-0 rating. And the addition of DOPO-CuPc resulted in early decomposition of the epoxy thermoset, but the residual char at 700 °C reached 27.7%. The flame retardant mechanism was further investigated. It was found that DOPO-CuPc could release phosphorus-containing radicals and non-combustible gases in the gas phase to exert gas-phase flame retardant activity. In the condensed phase, the epoxy thermoset formed the expanded honeycomb-like char layer during combustion and the presence of copper phthalocyanine contributed to the stability of the char layer.

Abstract A new method for studying the two-dimensional spreading properties and sealing characteristics of surfactant solution on oil surface was provided. The actual spreading situation of the C4-Br/oil systems in axisymmetric geometry was observed directly using HD camera for the first time and the results showed that the aqueous film expanded outwards in a circle with the guiding device as the center. Meanwhile, the relation between spreading radius and time was investigated and evaluated using the model for surface-tension-viscous regime. The root-mean-square deviation (RMSD) values obtained from the correlation for all of the systems we studied below 1.64, indicating a good agreement between the experimental and theoretical values. The results of sealing experiments showed that the aqueous film could absolutely seal the oil surface for 27–65 s and the sealing effect would be lost after 216–742 s for different systems. The stronger the volatility was, the shorter the sealing time was. Additionally, the volume percentage of oil vapor with film was always lower than that without film even when the evaporation was saturated. These findings were of great significance to guide the preparation of efficient AFFF.

To better understand the thermal runaway characteristics of lithium-ion batteries in civil aviation transportation environments, an experimental platform for the fire and explosion of lithium-ion batteries was designed and built. The 18650 NCM lithium-ion battery was selected as the test sample to study the influence of different initial pressures on the thermal runaway characteristics of the lithium-ion battery pack in a confined space. The results showed that, under 61 kPa, the initial thermal runaway triggering time is longer, the initial thermal runaway temperature is higher, and the explosion pressure and TNT equivalent are lower than that under 96 kPa. The mass loss increased with the increase of pressure and the number of batteries. In addition, the initial thermal runaway triggering time and temperature are affected by the number of batteries. These results could provide some support for civil aviation transportation safety.

With the improvement of lithium-ion batteries in civil aviation transportation, the thermal safety of lithium-ion batteries can not be ignored. Especially in a battery pack, the thermal runaway of batteries can spread from cell to cell, resulting in catastrophic hazards. This work focuses on the experimental setup and analysis of the experimental parameters of lithium-ion batteries with different thicknesses of aerogel felt to study the blocking effect of barrier materials on thermal runaway propagation of lithium-ion batteries in civil aviation transport. The aerogel felt was selected as the barrier material and a series of experiments were carried out with different thicknesses of 1 mm, 3 mm, and 6 mm. The results demonstrated that the increase of aerogel felt thickness exhibited excellent performance in delaying lithium-ion battery thermal runaway. Additionally, a simplified thermal model of thermal runaway propagation was proposed to explain the thermal runaway propagation in the battery to adjacent batteries. These results provide valuable suggestions and enlightenment for the aviation safety transportation of lithium-ion batteries.

Proton exchange membrane fuel cells (PEMFCs) have received considerable interest due to their low operating temperature and high energy conversion rate. However, their practical implement suffers from significant performance challenge. In particular, proton exchange membrane (PEM) as the core component of PEMFCs, have shown a strong correlation between its properties (e.g., proton conductivity, dimensional stability) and the performance of fuel cells. Metal-organic frameworks (MOFs) as porous inorganic-organic hybrid materials have attracted extensive attention in gas storage, gas separation and reaction catalysis. Recently, the MOFs-modified PEMs have shown outstanding performance, which have great merit in commercial application. This manuscript presents an overview of the recent progress in the modification of PEMs with MOFs, with a special focus on the modification mechanism of MOFs on the properties of composite membranes. The characteristics of different types of MOFs in modified application were summarized.

Metal-organic frameworks (MOFs), as newly emerging filler materials for polyelectrolytes, show many compelling intrinsic features, such as variable structural designability and modifiability of proton conductivity. In this manuscript, UiO-66-NH2, a stable MOF with -NH2 functional groups in its ligands, was selected to achieve a high-performance sulfonated poly(arylene ether nitrile)s (SPENs)/UiO-66-NH2-x covalent-ionically cross-linked composite membrane. Simultaneously, the obtained composite membranes displayed excellent thermal stability and dimensional stability. The as-prepared SPEN/UiO-66-NH2-x cross-linked membranes exhibited higher proton conductivity than recast SPENs, which can be attributed to the construction of ionic clusters and well-connected ionic nanochannels along the interface between UiO-66-NH2-x and SPEN matrix via molecular interactions. Meanwhile, the methanol permeability of the SPEN/UiO-66-NH2-x composite membrane had been effectively reduced due to the barrier effect of cross-linking and the addition of UiO-66-NH2-x. The SPEN/UiO-66-NH2-5 composite membrane had the highest selectivity of 6.42 × 105 S·s·cm−3: 14.3-times higher than that of Nafion 117. The preparation of cross-linked UiO-66-NH2/SPEN composite was facile, which provides a new strategy for preparing high performance proton exchange membrane.

The existing equipment of civil aircraft cargo fire detection mainly uses photoelectric smoke detectors, which has a high false alarm rate. According to Federal Aviation Agency’s (FAA) statistics, the false alarm rate is as high as 99%. 1 In the cargo of civil aircraft, the traditional photoelectric detection technology cannot effectively distinguish interference particles from smoke particles. Since the video smoke detection technology has proven to be reliable in many large scenarios, a deep learning method of image processing for fire detection is proposed. The proposed convolutional neural network is constructed of front end network and back end network cascaded with the capsule network and the circularity computation for the dynamic infrared fire image texture extraction. In order to accurately identify whether there is a fire in the area and give the kind of burning substances, a series of fuels are selected, such as n -heptane, cyclohexane, and carton for combustion reaction, and infrared camera is used to take infrared images of all fuel combustion. Experimental results show that the proposed method can effectively detect fire at the early stage of fire which is applicable for fire detection in civil aircraft cargoes.