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Large eddy simulation of room fire spread using a medium scale compartment made of medium density fibreboard (MDF) panels

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Building Simulation 2022年第4期15卷 495-510页

作者： Jiayidaer Baolati kaiyuan li Yanyan Zou Kevin Frank George Hare Jiaqing Zhang Fanliang Ge School of Safety Science and Emergency Management Wuhan University of TechnologyLuoshi Road 122Wuhan 430070China BRANZ Private Bog 50908Porirua 5240New Zealand Electric Power Research Institute State Grid Anhui Electric Power Co.LTDHefei 230601China State Key Laboratory of Fire Science University of Science and Technology of ChinaHefei 230027China

At present,there is a shortage of experimental and simulation studies on fire spread in medium-and large-scale compartments while the existing models of the fire spread are limited for typical engineering applications.This paper proposes a new model for large-scale fire spread on medium density fibreboard(MDF)panels.Validating the model with single burning item(SBI)experiments,it is found that the numerical simulation closely predicts the experimental heat release rate(HRR)with some error near the peak.The predicted heat flux and distance of lateral flame spread are consistent with the experiments and an existing model.The effects of kinetic properties and heat of combustion are identified through a sensitivity analysis.The decrease of activation energy and increase of pre-exponential factor make the MDF easier to pyrolyze and the increase of heat of combustion enhances the flame temperature and thus provide more heat feedback to the sample surface.The low activation energy(71.9 kJ/mol)and high heat of combustion(46.5 MJ/kg)of the model ensure the occurrence of flame spread.Furthermore,the model was validated using medium-scale compartment fire experiments and the results showed that the model can accurately predict the HRR after flashover(the error is within 7%).While the burner is ignited,the predictions of in-compartment gas temperature and heat flux are more accurate.However,when the burner is extinguished,the modelled in-compartment gas temperature is lower than the experimental values,resulting in a lower heat flux prediction.The model leads to easier flame spread;therefore,the modelled flame spreads faster in the compartment compared to the experiment,and thus the HRR increases more rapidly.

关键词： flame spread compartment fire SBI numerical simulation MDF activation energy

Borate-Modified,Flame-Retardant Paper Packaging Materials for Archive Conservation

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Journal of Renewable Materials 2022年第4期10卷 1125-1136页

作者： Juanli Wang Ming Cao Jiaxin li kaiyuan li Xiaolian Chao Bingjie Mai Yuhu li Jing Cao Engineering Research Center of Historical and Cultural Heritage Protection Ministry of EducationSchool of Materials Science and EngineeringShaanxi Normal UniversityXi’an710119China Ningbo University of Finance&Economics Ningbo315175China

Paper packaging materials like cardboards are widely used to protect archives which are a major kind of cultural relics.Unfortunately,paper is a combustible material,and thus exploring environment-friendly flame retardant for paper-based archive packaging material plays an important role.Herein,boric acid,borax and disodium octaborate are used to modify the craft paper-based packaging materials for archive conservation to improve fire safety.The modified craft paper exhibits much higher flame retardancy than the pristine one dose based on vertical burning tests,without much influence on mechanical properties such as tensile strength and elongation at break.Thermogravimetric analysis(TGA),scanning electron microscope(SEM),and X-ray photoelectron spectroscopy(XPS)reveal that porous glass structure is formed during the combustion,because thermal decomposition of boric acid,borax and disodium octaborate will produce porous glassy matter as B_(2)O_(3).The porous glass covers the paper surface as an insulating layer which retards the further pyrolysis and combustion,resulting in a denser carbon layer.Our study provides a robust way to reduce the fire hazard of the archive packaging material by applying environment-friendly boron-based fire retardants.

关键词： Paper packaging materials archive conservation flame retardant

MPFracNet:A Deep Learning Algorithm for Metacarpophalangeal Fracture Detection with Varied Difficulties

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Computers, Materials & Continua 2023年第4期75卷 999-1015页

作者： Geng Qin Ping Luo kaiyuan li Yufeng Sun Shiwei Wang Xiaoting li Shuang liu linyan Xue College of Quality and Technical Supervision Hebei UniversityBaoding071002China Hebei Technology Innovation Center for lightweight of New Energy Vehicle Power System Baoding071002China National&Local Joint Engineering Research Center of Metrology Instrument and System Hebei UniversityBaoding071002China

Due to small size and high occult,metacarpophalangeal fracturediagnosis displays a low accuracy in terms of fracture detection and locationin X-ray images.To efficiently detect metacarpophalangeal fractures on Xrayimages as the second opinion for radiologists,we proposed a novel onestageneural network namedMPFracNet based ***,a deformable bottleneck block(DBB)was integrated into the bottleneckto better adapt to the geometric variation of the fractures.Furthermore,an integrated feature fusion module(IFFM)was employed to obtain morein-depth semantic and shallow detail features.Specifically,Focal Loss andBalanced L1 Loss were introduced to respectively attenuate the imbalancebetween positive and negative classes and the imbalance between detectionand location tasks.We assessed the proposed model on the test set andachieved an AP of 80.4%for the metacarpophalangeal fracture detection.To estimate the detection performance for fractures with different difficulties,the proposed model was tested on the subsets of metacarpal,phalangeal andtiny fracture test sets and achieved APs of 82.7%,78.5%and 74.9%,respectively.Our proposed framework has state-of-the-art performance for detectingmetacarpophalangeal fractures,which has a strong potential application valuein practical clinical environments.

关键词： Deep learning small object detection metacarpophalangeal fractures computer-aided diagnosis(CAD)

An efficient recycling strategy to eliminate the residual“impurities”while heal the damaged structure of spent graphite anodes

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Green Energy & Environment 2024年第6期9卷 1027-1034页

作者： Dan Yang Ying Yang Haoran Du Yongsheng Ji Mingyuan Ma Yujun Pan Xiaoqun Qi Quan Sun kaiyuan Shi Long Qie Institute of New Energy for Vehicles School of Materials Science and EngineeringTongji UniversityShanghai201804China State Key Laboratory of Material Processing and Die&Mold Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan430074China Shuangdeng Group Co. Ltd.Taizhou225500China School of Materials Science and Engineering Sun Yat-Sen UniversityGuangzhou510275China

The recycling of graphite from spent lithium-ion batteries(liBs)is overlooked due to its relatively low added value and the lack of efficient recovering methods.To reuse the spent graphite anodes,we need to eliminate their useless components(mainly the degraded solid electrolyte interphase,SEI)and reconstruct their damaged structure.Herein,a facile and efficient strategy is proposed to recycle the spent graphite on the basis of the careful investigation of the composition of the cycled graphite anodes and the rational design of the regeneration processes.The regenerated graphite,which is revitalized by calcination treatment and acid leaching,delivers superb rate performance and a high specific capacity of 370 mAh g^(-1)(~99% of its theoretical capacity)after 100 cycles at 0.1 C,superior to the commercial graphite anodes.The improved electrochemical performance could be attributed to unchoked li^(+) transport channels and enhanced charge transfer reaction due to the effective destruction of the degraded SEI and the full recovery of the damaged structure of the spent graphite.This work clarifies that the electrochemical performance of the regenerated graphite could be deteriorated by even a trace amount of the residual“impurity”and provides a facile method for the efficient regeneration of graphite anodes.

关键词： Graphite Anode Regeneration Solid electrolyte interphase Spent lithium-ion battery

燃烧室百叶与双排孔冷气对透平端壁冷却性能影响研究

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西安交通大学学报 2024年第6期58卷 65-76页

作者：张垲垣栗智宇李志刚李军西安交通大学能源与动力工程学院西安710049

针对燃烧室与透平冷气掺混导致实际二次流发展及端壁冷却性能偏离设计值的问题,综合考虑燃烧室百叶冷气尾迹与双排孔射流,数值研究了多源冷气射流在燃烧室与透平交界区的掺混机制,分析了其对透平静叶端壁气膜冷却与流动特性的影响规律... 详细信息

针对燃烧室与透平冷气掺混导致实际二次流发展及端壁冷却性能偏离设计值的问题,综合考虑燃烧室百叶冷气尾迹与双排孔射流,数值研究了多源冷气射流在燃烧室与透平交界区的掺混机制,分析了其对透平静叶端壁气膜冷却与流动特性的影响规律。研究结果表明:空腔涡卷吸大部分百叶冷气,并跨越双排孔冷气向下游发展,马蹄涡卷吸限制大部分双排孔冷气,并向空腔涡外侧发展;当双排孔冷气吹风比M_h=0.5,1.0较小时,马蹄涡导致冷气形成楔形高冷效区域,空腔涡的附着侧和分离侧分别产生了高、低冷效区,随着百叶冷气吹风比M_l的增加,空腔涡强度显著降低,导致位于楔形中心的分离侧冷却效率有所提升;当双排孔冷气吹风比M_h为1.5时,双排孔冷气部分跨越马蹄涡,静叶端壁可实现完全冷气覆盖,此时百叶冷气吹风比M_l从0.5增加到1.5,静叶端壁平均冷却效率可从0.4提升到0.63。该研究为考虑燃烧室与透平交界区实际流动掺混情况的静叶端壁冷却结构与布局设计提供理论基础。

关键词：透平静叶端壁燃烧室百叶冷气双排孔射流气膜冷却

Multi-Classification of Polyps in Colonoscopy Images Based on an Improved Deep Convolutional Neural Network

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Computers, Materials & Continua 2023年第6期75卷 5837-5852页

作者： Shuang liu Xiao liu Shilong Chang Yufeng Sun kaiyuan li Ya Hou Shiwei Wang Jie Meng Qingliang Zhao Sibei Wu Kun Yang linyan Xue College of Quality and Technical Supervision Hebei UniversityBaoding071002China Hebei Technology Innovation Center for lightweight of New Energy Vehicle Power System Baoding071002China National&Local Joint Engineering Research Center of Metrology Instrument and System Hebei UniversityBaoding071002China College of Electronic Information Engineering Hebei UniversityBaoding071002China Department of Orthopedics Affiliated Hospital of Hebei UniversityBaoding071002China State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics Center for Molecular Imaging and Translational MedicineDepartment of Laboratory MedicineSchool of Public HealthXiamen UniversityXiamen361102China

Achieving accurate classification of colorectal polyps during colonoscopy can avoid unnecessary endoscopic biopsy or resection.This study aimed to develop a deep learning model that can automatically classify colorectal polyps histologically on white-light and narrow-band imaging(NBI)colonoscopy images based on World Health Organization(WHO)and Workgroup serrAted polypS and Polyposis(WASP)classification criteria for colorectal polyps.White-light and NBI colonoscopy images of colorectal polyps exhibiting pathological results were firstly collected and classified into four categories:conventional adenoma,hyperplastic polyp,sessile serrated adenoma/polyp(SSAP)and normal,among which conventional adenoma could be further divided into three sub-categories of tubular adenoma,villous adenoma and villioustublar adenoma,subsequently the images were re-classified into six categories.In this paper,we proposed a novel convolutional neural network termed Polyp-DedNet for the four-and six-category classification tasks of colorectal polyps.Based on the existing classification network ResNet50,Polyp-DedNet adopted dilated convolution to retain more high-dimensional spatial information and an Efficient Channel Attention(ECA)module to improve the classification performance further.To eliminate gridding artifacts caused by dilated convolutions,traditional convolutional layers were used instead of the max pooling layer,and two convolutional layers with progressively decreasing dilation were added at the end of the network.Due to the inevitable imbalance of medical image data,a regularization method DropBlock and a Class-Balanced(CB)Loss were performed to prevent network overfitting.Furthermore,the 5-fold cross-validation was adopted to estimate the performance of Polyp-DedNet for the multi-classification task of colorectal polyps.Mean accuracies of the proposed Polyp-DedNet for the four-and six-category classifications of colorectal polyps were 89.91%±0.92%and 85.13%±1.10%,respectively.The metrics of precision,recall and F1-score wer

关键词： Colorectal polyps four-and six-category classifications convolutional neural network dilated residual network

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氨-生物燃料双燃料发动机的燃烧与排放特性

汽车工程 2024年第4期46卷 626-633,681页

作者：蔡开源王巍赵自庆马骁齐运亮李莉王志清华大学车辆与运载学院北京100084 西安交通大学城市学院机械工程系西安710018

针对双碳目标,应用低碳/零碳燃料是实现内燃机高效清洁燃烧的有效途径。本研究基于一个双燃料柴油机台架开展,缸内直喷燃料分别选用柴油、生物柴油/汽油混合燃料(BG70)和生物柴油/汽油/乙醇混合燃料(BG50E20);氨为进气道喷射,能量替代率... 详细信息

针对双碳目标,应用低碳/零碳燃料是实现内燃机高效清洁燃烧的有效途径。本研究基于一个双燃料柴油机台架开展,缸内直喷燃料分别选用柴油、生物柴油/汽油混合燃料(BG70)和生物柴油/汽油/乙醇混合燃料(BG50E20);氨为进气道喷射,能量替代率为0~28%。试验工况为1200 r/min、0.8 MPa指示平均有效压力(IMEP)。对比分析了不同燃料的一氧化碳(CO)、总碳氢(THC)、氮氧化物(NOx)排放以及颗粒物粒径分布。结果表明:单燃料模式下,BG70和BG50E20的指示热效率高于柴油。BG70的CO排放相比柴油降低30%,但THC和NOx排放在3种燃料中最高。BG70和BG50E20的总颗粒物数量(TPN)排放低于柴油。相比各燃料单燃料模式的燃烧与排放性能,添加氨后的3种燃料的指示热效率降低1%~2%;CO排放增加约1倍;柴油和BG70的NOx排放减少接近50%,BG50E20的NOx排放减少约30%。另外,氨的加入对BG70和BG50E20的TPN有显著影响,当氨能量替代率从0增长至28%时,BG70的TPN排放增加20倍。

关键词：氨生物柴油乙醇燃烧排放

TiB_(2)/B_(4)C复相陶瓷自蔓延热爆炸烧结与性能表征

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兵工学报 2024年第1期45卷 26-34页

作者：李云飞高鑫陈鹏万刘开源北京理工大学爆炸科学与技术国家重点实验室北京100081 北京理工大学前沿技术研究院山东济南250307

为了探究高硬度复相陶瓷高效且低成本的制备方法,利用自蔓延高温合成结合爆炸烧结技术,开展制备二硼化钛/碳化硼(TiB_(2)/B_(4)C)复相陶瓷的研究,成功制备厚度约为1 cm、直径约为5 cm的TiB_(2)/B_(4)C复相陶瓷块体。烧结样品物相和微观... 详细信息

为了探究高硬度复相陶瓷高效且低成本的制备方法,利用自蔓延高温合成结合爆炸烧结技术,开展制备二硼化钛/碳化硼(TiB_(2)/B_(4)C)复相陶瓷的研究,成功制备厚度约为1 cm、直径约为5 cm的TiB_(2)/B_(4)C复相陶瓷块体。烧结样品物相和微观结构分析表征结果表明:烧结样品中TiB_(2)相和B_(4)C相分布均匀,截面观察到致密的微米级颗粒。该方法制备的样品致密度和硬度较高,随冲击压力不同,致密度范围在90%~93%之间,相应平均维氏硬度为16.64~17.35 GPa;根据不同条件下回收样品的微结构、致密度等分析,冲击压力和起爆时刻生坯温度对TiB_(2)/B_(4)C复相陶瓷烧结质量有重要影响;冲击压力为40 GPa,生坯温度为1800 K时,烧结致密度为93%;为进一步提高烧结质量,应提高冲击压力或冲击波作用时间。研究表明自蔓延热爆炸烧结技术是一种高效且低成本的高硬度复相陶瓷的制备方法。

关键词： TiB_(2)/B_(4)C 复相陶瓷自蔓延高温合成爆炸烧结微观结构

Decorating ketjen black with ultra-small Mo_(2)C nanoparticles to enhance polysulfides chemisorption and redox kinetics for lithium-sulfur batteries

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Journal of Energy Chemistry 2020年第12期29卷 207-215页

作者： Nan Jiang Guangyu Jiang Dechao Niu Jiayi Mao Meiwan Chen kaiyuan li Yongsheng li Lab of Low-Dimensional Materials Chemistry Key Laboratory for Ultrafine Materials of Ministry of Education.School of Materials Science and EngineeringEast China University of Science and TechnologyShanghai 200237China

The low sulfur utilization and fast capacity fading resulting from the sluggish redox reaction and abominable polysulfides shuttle greatly hinder the practical applications of lithium-sulfur(li-S) batteries.Herein, we develop a facile "in-situ growth" method to decorate ultra-small Mo2 C nanoparticles(USMo2 C) on the surface of Ketjen Black(KB) to functionalize the commercial polypropylene(PP) separators,which can accelerate the redox kinetics of lithium polysulfides conversion and effectively increase the utilization of sulfur for li-S batteries. Importantly, the US-Mo2 C nanoparticles have abundant sites for chemical adsorption towards polysulfides and the conductive carbon networks of KB have cross-linked pore channels, which can promote electron transport and provide physical barrier and volume expansion space for polysulfides. Due to the combined effects of the US-Mo2 C and KB, li-S cells employing the multifunctional PP separators modified with KB/US-Mo2 C composite(KB/US-Mo2 C@PP) exhibit a high specific capacity(1212.8 mAh g^(-1) at 0.2 C), and maintain a reversible capacity of 1053.3 m Ah g^(-1) after 100 cycles.More importantly, the KB/US-Mo2 C@PP cells with higher sulfur mass loading of 4.9 mg cm^(-2) have superb areal capacity of 2.3 mAh cm^(-2). This work offers a novel and promising perspective for high-performance li-S batteries from both the shuttle effect and the complex polysulfides conversion.

关键词： in-situ growth Ultra-small Mo_(2)C Catalytic effect Chemisorption Multifunctional separator lithium-sulfur batteries