Numerical and experimental study on the response characteristics of warhead in the fast cook-off process

The response characteristics of the warhead under thermal stimuli conditions are important to the safety improvement.The goal of this study is to obtain data on the warhead in the fast cook-off process.In this paper,a numerical calculation method is proposed,whose reliability is supported by comparison with experimental results.Through the numerical calculation,the temperature distribution,temperature change,and ignition time are acquired.The numerical results show that the ignition time is 76 s after the warhead started to burn and that the maximum temperature of the explosive’s outer surface is 238.3℃ at the ignition time.The fast cook-off experiment of the warhead is implemented so as to get the flame temperature and reaction grades that are not available through numerical calculation.The experimental results show that the overpressure fails to reach the preset minimumvalue which is equivalent to 6 kg of TNT and that the reaction grade is deflagration.The research results have reference value for the design of the warhead and the reduction of detonation risks.

FAST宁静区生态脆弱性时空演变及情景模拟

[目的]揭示FAST宁静区2000—2020年的生态脆弱性时空变化特征,为维护该区域的生态安全提供科学参考。[方法]基于FAST宁静区生态本底特征,从“敏感性—恢复力—压力度”角度构建生态脆弱性评价体系,运用AHP-熵权法和GIS技术等对FAST宁静区2000—2020年生态脆弱性时空演变及未来预设情景进行了量化分析。[结果](1)研究区脆弱性以中度脆弱为主,轻度、中度、重度脆弱区合计占75%左右,微度和极度脆弱区合计只占约25%。(2) 20年间研究区生态脆弱性整体下降,高强度生态脆弱区主要向较低等级转化,前10 a生态脆弱性略有上升,而后10 a生态脆弱性明显降低,研究区生态环境整体呈改善的趋势。(3)从FAST圈层(核心区、中间区、边远区)动态变化看,核心区的生态得到较好的改善,恶化区面积占比由前10 a的19.57%降至7.12%,而稳定区和低度改善区的面积在上升,由前10 a的79.88%增至92.50%;中间区和边远区变化趋于稳定,中间区稳定区和低度改善区面积占比由68.36%增至87.10%,而边远区稳定区占比由40.78%增至59.50%,但边远区局部存有恶化风险。(4)基于生态优先保护和乡村振兴需求两种情景模拟,2030年FAST宁静区的生态脆弱性整体指数分别下降5.91%和2.22%,前者生态保护效果较优,但后者更好地兼顾生态保护和乡村发展需要,综合考虑建议推荐乡村振兴发展模式。[结论]研究时段内,FAST宁静区生态脆弱性整体降低,核心区生态环境改善明显,中间区、边远区后10 a相比前10 a整体生态在缓慢转好。

Construction of 3D porous Cu_(1.81)S/nitrogen-doped carbon frameworks for ultrafast and long-cycle life sodium-ion storage

Transition metal sulfides have great potential as anode mterials for sodium-ion batteries(SIBs)due to their high theoretical specific capacities.However,the inferior intrinsic conductivity and large volume variation during sodiation-desodiation processes seriously affect its high-rate and long-cyde performance,unbeneficial for the application as fast-charging and long-cycling SIBs anode.Herein,the three-dimensional porous Cu_(1.81)S/nitrogen-doped carbon frameworks(Cu_(1.81)S/NC)are synthesized by the simple and facile sol-gel and annealing processes,which can accommodate the volumetric expansion of Cu_(1.81)S nanoparticles and accelerate the transmission of ions and electrons during Na^(+)insertion/extraction processes,exhibiting the excellent rate capability(250.6 mA·g^(-1)at 20.0 A·g^(-1))and outstanding cycling stability(70% capacity retention for 6000 cycles at 10.0 A·g^(-1))for SIBs.Moreover,the Na-ion full cells coupled with Na_(3)V_(2)(PO_(4))_(3)/C cathode also demonstrate the satisfactory reversible specific capacity of 330.5 mAh·g^(-1)at 5.0 A·g^(-1)and long-cycle performance with the 86.9% capacity retention at 2.0 A·g^(-1)after 750 cycles.This work proposes a promising way for the conversionbased metal sulfides for the applications as fast-charging sodium-ion battery anode.

Study on cook-off characteristics and thermal safety venting area of RBOE charge

RBOE is a new type of DNAN-based high-energy melt-cast mixed explosive,whose safety under thermal stimulation is significantly affected by heating conditions and venting area of the warhead.Based on the thermal decomposition reaction characteristics and combustion characteristics of each component of RBOE explosive,the cook-off calculation models of RBOE warhead before and after ignition were established.In addition,closed and vented warheads were designed,as well as fast and slow cook-off test devices.The cook-off characteristics and thermal safety venting area of RBOE warhead were extensively studied.The results showed that the closed RBOE warhead underwent deflagration reaction under both slow and fast cook-off conditions.The calculation result of the shell wall temperature before slow cookoff ignition response of the warhead was 454.06 K,with an error of+1.75%compared to the test result of462.15 K,and the temperature rise rate calculated was in good agreement with the test.The calculated ignition time of RBOE warhead under fast cook-off was 161 s,with an error of+8.8%compared to the test result of 148 s,which verified the accuracy of cook-off model of RBOE warhead before ignition.According to the cook-off calculation model of the warhead after ignition and cook-off test of the vented warhead,it was determined that the thermal safety venting area was 1124.61 mm^(2)for fast cook-off and 530.66 mm~2 for slow cook-off,effectively preventing the reaction of warhead above combustion.Therefore,this study provides a scientific basis for the thermal safety design and evaluation of insensitive warheads.

基于灰度均值的自适应FAST角点检测优化算法

光照不均、突变引起的灰度变化会影响图像特征检测效果。为此,设计一种基于灰度均值的自适应FAST-9-12角点检测算法。首先,利用特征点的延展性设计一种小面积双重检测模板,减少像素点与中心点的比较次数,提高区域正检率和检测速度;其次,依据图像局部灰度均值,在每个像素点检测模板内自适应调整阈值,避免灰度变化影响检测效果;最后,根据柔性非极大值抑制的思想设计角点半径抑制原则,筛选鲁棒性更强的角点。在Inria遥感影像数据集上的实验结果表明,FAST-9-12角点检测速度比FAST-12-16,FAST-9-16两种模板提高22%左右,因自适应阈值的提取方式不易受光照影响,检测准确率分别提高4.16和3.11个百分点,实现了图像特征快速和精准检测。

基于Kano-FAST的瓦楞纸激光印刷设备设计研究

目的推动印刷行业朝更高效的方向迈进,提高印刷设备的易操作性和视觉识别性。方法将Kano和FAST(Function Analysis System Technique)模型引入瓦楞纸激光打印设备设计的前期应用需求分析中,通过问卷的方法获取用户的基本要求,并划分为几个子类型,进而建立Kano的二维功能属性模型。采用FAST法建立功能树,辅助使用Kano模型,从而更精准地分析用户需求,并更好地根据其需求进行优化设计。结果综合运用设计原理,针对性地挖掘瓦楞纸激光印刷设备在造型识别性、操作易用性、生产安全性上存在的问题,进而输出更优解。结论该设计方法的引入有助于为同类型的印刷设备设计提供参考,并引起更多相关厂家的重视,推动印刷行业向更积极的方向发展。

CEEMD-FastICA-CWT联合瞬态响应阶次的电驱总成噪声源识别

以某增程式电驱动总成为研究对象,提出基于联合算法的噪声分离识别模型。首先,采用互补集合经验模态分解(complementary ensemble empirical mode decomposition,CEEMD)联合快速独立分量分析(fast independent component analysis,FastICA)方法提取纯电模式稳态工况下单一通道噪声信号特征,利用复Morlet小波变换及FFT对各分量信号时频特性进行识别。其次,采用阶次分析法和声能叠加法对稳态分量信号对应的各瞬态响应阶次能量进行对比分析,并结合皮尔逊积矩相关系数(Pearson product moment correlation coefficient,PPMCC)相似性识别确定不同噪声激励源贡献度。结果表明:减速齿副啮合噪声对该增程式电驱总成纯电模式运行噪声整体贡献度最大。

基于FAST和Sobol指数法的雷达系统效能敏感性分析

为了以较小的代价快速提升对空探测雷达系统的综合效能,首先搭建了对空探测雷达系统综合效能的评估指标体系,在此基础上完成了综合效能评估模型的建立。选择两种基于方差原理的全局敏感性分析方法,即傅里叶幅度敏感性测试(Fourier amplitudes sensitivity test,FAST)和Sobol指数法,分别从频域和时域对建立的评估模型进行敏感性分析。在基于FAST进行敏感性分析时,提出了21维输入指标所对应的特征频率集的选取方法;在基于Sobol指数法进行敏感性分析时,考虑了二阶及高阶敏感性指数的影响。对比FAST和Sobol指数法的分析结果,两种方法获得的敏感性分析结果具有较好的一致性。其中,功率和频率为对空探测雷达系统的主要影响指标,为雷达系统的研发和升级提供了可靠性依据。

面向FAST的卫星电磁干扰监测技术研究与实现

来自人造卫星的信号是射电天文观测面临的主要射频干扰(radio frequency interference,RFI)之一,这些RFI会将天文信号掩埋,为天文信号的搜寻和分析带来困扰。为了缓减卫星对天文观测的影响,我们在之前的工作中为500 m口径球面射电望远镜(Five-hundred-meter Aperture Spherical radio Telescope,FAST)开发了卫星电磁干扰监测软件,主要包括卫星数据库、观测模块和监测模块。近年来随着多个巨型卫星星座的规划发射以及望远镜观测模式的增多,卫星对射电天文观测的影响更为复杂,已有的软件已经不能满足实际的需要。为此,本文在单个卫星干扰分析的基础上提出了卫星星座的干扰评估方法,并对已有监测软件进行了升级,升级后卫星数据库覆盖更多的在轨卫星及星座信息且能够自动化更新,观测模块能够支持更多种观测模式下的卫星过境预测和干扰评估。在实际天文观测中,通过接在FAST接收机上的频谱仪数据对软件的干扰预测结果进行了实验验证,结果证明升级后的软件能够在多种观测模式下预测可能威胁的卫星以及对应的过境时间,为望远镜观测规划的调整、卫星干扰的规避和接收系统的保护提供重要的支撑。

500m口径射电望远镜(FAST)索网结构风致破坏概率评估

大跨空间索网结构风敏感性突出,极易遭受风荷载影响。针对目前缺乏此类结构抗风性能评估方法的问题,以大跨空间索网结构FAST为例,提出一种基于实测风场数据的风致破坏概率分析方法。采集1971年~2020年结构所处地区的大量实测风速数据,通过概率分布拟合建立场地的风灾危险性模型。建立FAST的精细化有限元分析模型并模拟风荷载时程输入,采用非线性动力时程分析对结构的风振反应进行计算,基于概率性需求模型绘制易损性曲线。最后,结合得出的风灾危险性和结构易损性,计算得出FAST结构在所处场地实际风灾环境中的破坏概率。研究表明:该地极限风速为17m/s,风速在0~10m/s的概率最大;在120°、210°和300°风向角下,下拉索均为易损构件,210°风向角上吸风对索网结构最不利;在最不利风向角下,结构达到轻微破坏、中等破坏和严重破坏的总破坏概率分别为1.8359×10^(-4)、1.1499×10^(-5)和1.3202×10^(-6)。

基于BP神经网络的FAST馈源舱融合测量预测研究

500 m口径球面射电望远镜(Five-hundred-meter Aperture Spherical Radio Telescope,FAST)的跟踪观测需要馈源的空间运动配合,馈源舱主要用于实现馈源的精调定位,因此馈源舱位置的高精度测量对FAST望远镜的高效运行意义重大。但当全站仪设备失效时,无法对采用Kalman算法的GPS/IMU融合测量结果进行修正,导致馈源舱测量精度下降。为了解决这个问题,设计了基于BP(back propagation)神经网络的预测模型,包括数据预处理、模型设计和模型训练验证。模型训练数据为FAST真实测量数据,数据量为40 GB左右。为了验证模型的泛化能力,选取三种运动轨迹数据对模型预测精度进行测试,结果显示,三种运动轨迹下精度都满足15 mm要求。

基于Kano-FAST-FBS的智能扫地机改良设计研究

目的智能扫地机是智能家居生活中不可或缺的产品,但现有扫地机交互性和功能性趋于一致,为了有效识别居家清扫需求,进一步提升交互性和趣味性,并将其科学转化为产品的功能要素及结构参数,提出一种基于Kano-FAST-FBS模型的产品改良设计方法,以提升智能家居产品的满意度。方法首先,基于Kano模型量化评估智能家居产品的用户需求属性,获得用户需求优先级;其次,运用功能分析系统技术(FAST)将用户需求分别转化为对应的产品功能要素;最后,以功能-行为-结构(FBS)设计模型为基础,实现了产品功能到结构参数的合理映射,进而得到改良产品的各个结构模块,输出最终设计方案。结果以扫地机器人为例,验证了基于Kano-FAST-FBS模型的设计流程。结论在该方法指导下的产品设计能系统地解决用户需求和功能结构模块之间的匹配问题,从而得出更符合用户功能预期的设计方案,并可以为其他类似产品设计提供参考思路。

基于FastICA-LDA的光伏并网逆变器故障诊断

为了实现逆变器开路故障诊断,提出了一种新的诊断方法。该方法采用快速独立成分分析算法判定逆变器是否发生单管开路故障,如果发生单管开路故障,计算旋转电流Id频域下的特征值,将这些特征值作为线性判别分析模型的输入值,最后由LDA模型输出逆变器工作状态编号,从而实现单管开路定位。经过MATLAB仿真验证表明,所提方法对光伏并网逆变器故障的诊断效果较好。

FAST所受PMT基站电磁干扰及用频防护方法综述

为确定500 m口径球面射电望远镜(Five-hundred-meter Aperture Spherical radio Telescope,FAST)与其周边公众移动通信(Public Mobile Telecommunications,PMT)系统的电磁兼容(electromagnetic compatibility,EMC)特性,本文综合论述了FAST宁静区内中国移动、中国联通和中国电信三大运营商所属PMT基站对其产生的电磁干扰。首先,从射电天文业务的频谱划分谈起,论述了射电天文业务干扰源类型,引出了其运行保护标准,进而针对FAST详细说明了FAST宁静区的用频法规和保护要求;其次,分析了ITU-R建议电波传播预测与干扰分析方法,并通过实地测量验证了该方法的适用性,进一步针对性地分析了PMT基站的电磁辐射传播特性,综合评估了FAST宁静区内PMT基站的干扰情况:FAST宁静区域90.24%的PMT基站在一定程度上均会对FAST产生干扰,而在所选分析条件下,仅有43.14%的数据符合FAST保护要求;最后,针对PMT基站干扰信号的抑制和消除,分析了常用的射电天文射频干扰抑制方法,同时为保障FAST免受PMT基站干扰,从FAST和PMT基站的角度出发论述了可行的用频防护措施,并基于实施难度、经济成本、策略收益和通信质量4类指标建立了防护方法的评估体系,对所提防护方法进行了实例说明。上述研究成果可为保障FAST的安全观测提供技术基础。

基于DAN与FastText的藏文短文本分类研究

随着藏文信息不断融入社会生活,越来越多的藏文短文本数据存在网络平台上。针对传统分类方法在藏文短文本上分类性能低的问题,文中提出了一种基于DAN-FastText的藏文短文本分类模型。该模型使用FastText网络在较大规模的藏文语料上进行无监督训练获得预训练的藏文音节向量集,使用预训练的音节向量集将藏文短文本信息转化为音节向量,把音节向量送入DAN(Deep Averaging Networks)网络并在输出阶段融合经过FastText网络训练的句向量特征,最后通过全连接层和softmax层完成分类。在公开的TNCC(Tibetan News Classification Corpus)新闻标题数据集上所提模型的Macro-F1是64.53%,比目前最好评测结果TiBERT模型的Macro-F1得分高出2.81%,比GCN模型的Macro-F1得分高出6.14%,融合模型具有较好的藏文短文本分类效果。

Dual-single-atoms of Pt-Co boost sulfur redox kinetics for ultrafast Li-S batteries

Applications of lithium-sulfur(Li-S)batteries are still limited by the sluggish conversion kinetics from polysulfide to Li_(2)S.Although various single-atom catalysts are available for improving the conversion kinetics,the sulfur redox kinetics for Li-S batteries is still not ultrafast.Herein,in this work,a catalyst with dual-single-atom Pt-Co embedded in N-doped carbon nanotubes(Pt&Co@NCNT)was proposed by the atomic layer deposition method to suppress the shuttle effect and synergistically improve the interconversion kinetics from polysulfides to Li_(2)S.The X-ray absorption near edge curves indicated the reversible conversion of Li_(2)Sx on the S/Pt&Co@NCNT electrode.Meanwhile,density functional theory demonstrated that the Pt&Co@NCNT promoted the free energy of the phase transition of sulfur species and reduced the oxidative decomposition energy of Li_(2)S.As a result,the batteries assembled with S/Pt&Co@NCNT electrodes exhibited a high capacity retention of 80%at 100 cycles at a current density of 1.3 mA cm^(−2)(S loading:2.5 mg cm^(−2)).More importantly,an excellent rate performance was achieved with a high capacity of 822.1 mAh g^(−1) at a high current density of 12.7 mA cm^(−2).This work opens a new direction to boost the sulfur redox kinetics for ultrafast Li-S batteries.

Unraveling the Fundamental Mechanism of Interface Conductive Network Influence on the Fast‑Charging Performance of SiO‑Based Anode for Lithium‑Ion Batteries

Progress in the fast charging of high-capacity silicon monoxide(SiO)-based anode is currently hindered by insufficient conductivity and notable volume expansion.The construction of an interface conductive network effectively addresses the aforementioned problems;however,the impact of its quality on lithium-ion transfer and structure durability is yet to be explored.Herein,the influence of an interface conductive network on ionic transport and mechanical stability under fast charging is explored for the first time.2D modeling simulation and Cryo-transmission electron microscopy precisely reveal the mitigation of interface polarization owing to a higher fraction of conductive inorganic species formation in bilayer solid electrolyte interphase is mainly responsible for a linear decrease in ionic diffusion energy barrier.Furthermore,atomic force microscopy and Raman shift exhibit substantial stress dissipation generated by a complete conductive network,which is critical to the linear reduction of electrode residual stress.This study provides insights into the rational design of optimized interface SiO-based anodes with reinforced fast-charging performance.

Multilevel carbon architecture of subnanoscopic silicon for fast‐charging high‐energy‐density lithium‐ion batteries

Silicon(Si)is widely used as a lithium‐ion‐battery anode owing to its high capacity and abundant crustal reserves.However,large volume change upon cycling and poor conductivity of Si cause rapid capacity decay and poor fast‐charging capability limiting its commercial applications.Here,we propose a multilevel carbon architecture with vertical graphene sheets(VGSs)grown on surfaces of subnanoscopically and homogeneously dispersed Si–C composite nanospheres,which are subsequently embedded into a carbon matrix(C/VGSs@Si–C).Subnanoscopic C in the Si–C nanospheres,VGSs,and carbon matrix form a three‐dimensional conductive and robust network,which significantly improves the conductivity and suppresses the volume expansion of Si,thereby boosting charge transport and improving electrode stability.The VGSs with vast exposed edges considerably increase the contact area with the carbon matrix and supply directional transport channels through the entire material,which boosts charge transport.The carbon matrix encapsulates VGSs@Si–C to decrease the specific surface area and increase tap density,thus yielding high first Coulombic efficiency and electrode compaction density.Consequently,C/VGSs@Si–C delivers excellent Li‐ion storage performances under industrial electrode conditions.In particular,the full cells show high energy densities of 603.5 Wh kg^(−1)and 1685.5 Wh L^(−1)at 0.1 C and maintain 80.7%of the energy density at 3 C.

基于动物创伤模型试验培训FAST超声技术在急诊本科实习生中的应用研究

目的评价基于动物创伤模型试验培训创伤超声重点评估法(FAST)超声技术在急诊本科实习生临床技能培训中的应用效果。方法选取我院2022年1月至2024年3月在我院急诊科的本科实习生65名作为研究对象,随机分为对照组和实验组。对照组采用传统教学方法,实验组按照动物创伤模型教学模式实施教学,比较两组本科实习生出科理论及操作成绩、学习满意度、学习能力和学习行为。结果两组实习生的理论及操作成绩均较培训前有所提高,实验组实习生的理论及操作成绩均明显高于对照组,差异均有统计学意义(均P<0.05)。两组实习生培训后的学习满意度均有所提高,实验组实习生的学习满意度得分明显高于对照组,差异均有统计学意义(均P<0.05)。两组实习生培训后的学习能力得分和学习行为得分均有所提高,实验组得分均明显高于对照组,差异均有统计学意义(均P<0.05)。结论基于动物创伤模型试验培训FAST超声技术能有效提高急诊本科实习生的学习成绩和学习满意度,学习能力明显提高,对提高本科实习生的成长与急诊诊疗水平具有积极意义。

基于FAST评分的分级管理模式在急性脑卒中患者急救中的应用

目的:探讨基于FAST评分的分级管理模式在急性脑卒中患者急救中的应用效果。方法:选取2022年1月1日~12月31日收治的126例急性脑卒中患者为研究对象,随机分为对照组和研究组各63例,对照组给予常规急救管理模式,研究组给予基于FAST评分的分级管理模式;比较两组救治时间(包括就诊至评估时间、就诊至接诊时间、就诊至CT检查时间、CT检查至用药时间)、干预前后上下肢Fugl-Meyer评分、神经功能[采用美国国立卫生院卒中量表(NIHSS)]、日常生活活动能力(采用Barthel指数),不良事件发生情况和护理满意度。结果:研究组就诊至评估时间、就诊至接诊时间、就诊至CT检查时间、CT检查至用药时间均短于对照组(P<0.05);干预后,两组上下肢Fugl-Meyer评分、Barthel指数均高于干预前(P<0.05),且研究组高于对照组(P<0.05);干预后,两组NIHSS评分低于干预前(P<0.05),且研究组低于对照组(P<0.05);研究组不良事件发生率低于对照组(P<0.05),护理满意度高于对照组(P<0.05)。结论:将基于FAST评分的分级管理模式应用于急性脑卒中患者急救中,可提高日常生活能力及护理满意度,恢复肢体运动能力、神经功能,减少不良事件的发生。