Ammonium phosphate-based fire extinguishers are widely used in forest fires due to their low cost and effectiveness against solid combustibles. However, the mechanism by which ammonium phosphate ...interacts with pyrolysis gas flames is not well understood, and there is a lack of precise experimental validation and correction of the chemical kinetics models regarding the suppression mechanism. Therefore, this study utilized NH4H2PO4 powder as a fire extinguishing agent and constructed a PLIF experimental system suitable for NH4H2PO4/red pine pyrolysis gas/air interactions. Through experiments, the changes in the concentration of OH radicals with different amounts of extinguishing agent at various equivalence ratios were measured. By employing Chemkin software, the study comprehensively analyzed the kinetic regulation mechanism of NH4H2PO4 on red pine pyrolysis gas flames from aspects such as chemical inhibition, sensitivity of elementary reactions, chemical reaction pathways, and chemical thermodynamics. The study revealed the characteristics and mechanisms of NH4H2PO4 powder inhibition, identifying R1092, R1098, R1116, and R1120 as the primary elementary reactions suppressing flame combustion. The mutual inhibition cycles formed among these reactions were found to be the main reasons for the suppression of H and OH radicals in the flame. Moreover, PO2 was identified as the primary phosphorus-containing fire extinguishing agent responsible for extinguishing the flame.
Display omitted
•A literature review to occupant-centric thermal comfort studies was performed.•Many variables and data-collecting sensors were utilized to support the approach.•Data-driven thermal ...comfort models got a median predicting accuracy of 84%•Occupant-centric thermal comfort control could save 22% energy and improve 29.1% thermal comfort.•Challenges and opportunities in the field were discussed.
Ensuring occupants’ thermal comfort and work performance is one of the primary objectives for building environment conditioning systems. In recent years, there emerged many occupant-orientated technologies aiming to optimize thermal comfort while saving energy. These attempts offered opportunities to move the indoor thermal environment control from the one-fits-all approach toward a new paradigm with occupant-centric merits. A timely review of this emerging field would help to fill the knowledge gap and provide new insights for future research and practice. This study performed a literature review to summarize recent occupant-centric thermal comfort practices following a framework with three themes: sensing, predicting, and controlling. The results show that occupant-centric thermal comfort control has become a hot research topic in recent years. A wide range of variables and data-collecting sensors were utilized to support the concept. Among all the potential variables, occupants’ comfort feedback, skin temperature, and air temperature are the top three popular input features for thermal comfort prediction. Using different machine learning algorithms, data-driven thermal comfort models were reported to have a median predicting accuracy of 84% and some of them can predict thermal comfort at a personal level. Cases implementing occupant-centric thermal comfort control strategy were reported to save air-conditioning energy by 22% and improve thermal comfort by 29.1%. These observations from the literature support the prospects of the new thermal comfort paradigm. Additionally, the challenges and opportunities in this emerging field were discussed.
Ammonium phosphate fire extinguishing agents, due to their excellent cost-effectiveness and suitability for forest fires, have become one of the most commonly used fire suppressants for forest fire ...control. Among them, NH4H2PO4 fire extinguishing agent is the most widely applied. In this study, NH4H2PO4 (>90%) as the main component of dry powder fire extinguishers was selected as the suppressant to investigate the reaction mechanism of NH4H2PO4 interacting with red pine wood pyrolysis gas flames. Initially, we constructed a Bunsen burner experimental system suitable for NH4H2PO4/red pine wood pyrolysis gas/air. Although experimental methods yield the most intuitive empirical conclusions, measuring only the laminar flame speed of red pine wood pyrolysis gas/NH4H2PO4/air mixture does not adequately analyze the inhibitory mechanism of NH4H2PO4 on red pine wood pyrolysis gas flames. Additionally, due to limitations in experimental equipment and methods, it is not feasible to extend equivalence ratios and NNH4H2PO4 doses to large or small working conditions. Therefore, in this study, we utilized Chemkin software to construct theoretical models of flames under different conditions and performed calculations. We comprehensively analyzed the kinetic regulatory mechanisms of NH4H2PO4 interacting with red pine wood pyrolysis gas flames from aspects such as chemical inhibition, sensitivity of elementary reactions, elementary reaction yields, and chemical reaction pathways.
•The laminar flame velocity of NH4H2PO4 interacting with the pyrolysis gas flame of red pine was measured.•A comprehensive analysis of the dynamic regulation mechanism of NH4H2PO4 interaction with pyrolysis gas flame of red pine.•The inhibition mechanism of phosphorus-containing active substances on pyrolysis gas flame of red pine wood was elucidated.•Provide theoretical and experimental reference for development of more efficient fire extinguishing agents for forest fires.
Forest fires are characterized by hidden ignition points, rapid spread, large burning areas, intense flames, and significant influence from meteorological conditions. Due to the complexity of terrain ...and surrounding environments, conventional firefighting equipment often struggles to reach the core ignition areas from the ground, greatly increasing the difficulty and cost of forest fire prevention and control. Fire suppression munition, due to their ability to control fires at medium and long distances, are commonly used in the field of forest firefighting. This paper conducts research and experiments on the development of new fire suppression munition after analyzing the advantages and disadvantages of current fire suppression munition, aiming to effectively suppress forest fires. Through experiments, it was found that the fire suppression aerial munition were stable and reliable throughout the entire test process. The dispersal range and concentration of the fire suppressant after explosion met the expected requirements. Good suppression effects were achieved in field tests on large ground fires and crown fires, with flames being extinguished and no reignition occurring within 10 min.
Subprime lending in the United States was a major concern after the 2008 financial crisis. While Covid-19 is sweeping the world, how will the US government and financial institutions deal with the ...potential crisis of subprime mortgage will be discussed in this study. Financial market institutions and the US government should both change their strategies to deal with the crisis. In addition to controlling the spread of the epidemic, the US government should temporarily lower the minimum wage and provide a series of quantitative financial subsidies. Financial institutions should also update loan data and use better monitoring and regulation to reduce subprime risk to cope with this potential crisis.
Spatial transcriptomics technologies are used to profile transcriptomes while preserving spatial information, which enables high-resolution characterization of transcriptional patterns and ...reconstruction of tissue architecture. Due to the existence of low-resolution spots in recent spatial transcriptomics technologies, uncovering cellular heterogeneity is crucial for disentangling the spatial patterns of cell types, and many related methods have been proposed. Here, we benchmark 18 existing methods resolving a cellular deconvolution task with 50 real-world and simulated datasets by evaluating the accuracy, robustness, and usability of the methods. We compare these methods comprehensively using different metrics, resolutions, spatial transcriptomics technologies, spot numbers, and gene numbers. In terms of performance, CARD, Cell2location, and Tangram are the best methods for conducting the cellular deconvolution task. To refine our comparative results, we provide decision-tree-style guidelines and recommendations for method selection and their additional features, which will help users easily choose the best method for fulfilling their concerns.
Object detection has made tremendous progress in natural images over the last decade. However, the results are hardly satisfactory when the natural image object detection algorithm is directly ...applied to satellite images. This is due to the intrinsic differences in the scale and orientation of objects generated by the bird’s-eye perspective of satellite photographs. Moreover, the background of satellite images is complex and the object area is small; as a result, small objects tend to be missing due to the challenge of feature extraction. Dense objects overlap and occlusion also affects the detection performance. Although the self-attention mechanism was introduced to detect small objects, the computational complexity increased with the image’s resolution. We modified the general one-stage detector YOLOv5 to adapt the satellite images to resolve the above problems. First, new feature fusion layers and a prediction head are added from the shallow layer for small object detection for the first time because it can maximally preserve the feature information. Second, the original convolutional prediction heads are replaced with Swin Transformer Prediction Heads (SPHs) for the first time. SPH represents an advanced self-attention mechanism whose shifted window design can reduce the computational complexity to linearity. Finally, Normalization-based Attention Modules (NAMs) are integrated into YOLOv5 to improve attention performance in a normalized way. The improved YOLOv5 is termed SPH-YOLOv5. It is evaluated on the NWPU-VHR10 dataset and DOTA dataset, which are widely used for satellite image object detection evaluations. Compared with the basal YOLOv5, SPH-YOLOv5 improves the mean Average Precision (mAP) by 0.071 on the DOTA dataset.
The function of Toll pathway defense against bacterial infection has been well established in shrimp, however how this pathway responds to viral infection is still largely unknown. In this study, we ...report the Toll4-Dorsal-AMPs cascade restricts the white spot syndrome virus (WSSV) infection of shrimp. A total of nine Tolls from Litopenaeus vannamei namely Toll1-9 are identified, and RNAi screening in vivo reveals the Toll4 is important for shrimp to oppose WSSV infection. Knockdown of Toll4 results in elevated viral loads and renders shrimp more susceptible to WSSV. Furthermore, Toll4 could be a one of upstream pattern recognition receptor (PRR) to detect WSSV, and thereby leading to nuclear translocation and phosphorylation of Dorsal, the known NF-κB transcription factor of the canonical Toll pathway. More importantly, silencing of Toll4 and Dorsal contributes to impaired expression of a specific set of antimicrobial peptides (AMPs) such as anti-LPS-factor (ALF) and lysozyme (LYZ) family, which exert potent anti-WSSV activity. Two AMPs of ALF1 and LYZ1 as representatives are demonstrated to have the ability to interact with several WSSV structural proteins to inhibit viral infection. Taken together, we therefore identify that the Toll4-Dorsal pathway mediates strong resistance to WSSV infection by inducing some specific AMPs.
Understanding and modeling flows over porous layers are of great industrial significance. To accurately solve the turbulent multi-scale flows on complex configurations, a rescaling algorithm designed ...for turbulent flows with the Chapman-Enskog analysis is proposed. The mesh layout and the detailed rescaling procedure are also introduced. Direct numerical simulations (DNSs) for a turbulent channel flow and a porous walled turbulent channel flow are performed with the three-dimensional nineteen-velocity (D3Q19) multiple-relaxation-time (MRT) lattice Boltzmann method (LBM) to validate the accuracy, adaptability, and computational performance of the present rescaling algorithm. The results, which are consistent with the previous DNS studies based on the finite difference method and the LBM, demonstrate that the present method can maintain the continuity of the macro values across the grid interface and is able to adapt to complex geometries. The reasonable time consumption of the rescaling procedure shows that the present method can accurately calculate various turbulent flows with multi-scale and complex configurations while maintaining high computational efficiency.
PDF
