检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

基于小波变换的信号奇异度指标计算方法

探测与控制学报 2012年第6期34卷 62-67页

作者：马锐张天军乔宝明崔巍西安科技大学理学院陕西西安710054

小波变换在信号奇异性检测的应用研究主要表现在突变点测试、声源定位、奇异间断点判断方面。针对声发射信号在时空域准确定位中存在的问题,提出基于小波变换的信号奇异度指标计算方法对声发射信号进行奇异性检。该方法采用小波变换对... 详细信息

小波变换在信号奇异性检测的应用研究主要表现在突变点测试、声源定位、奇异间断点判断方面。针对声发射信号在时空域准确定位中存在的问题,提出基于小波变换的信号奇异度指标计算方法对声发射信号进行奇异性检。该方法采用小波变换对实际采集的声发射信号进行多尺度分析,通过对奇异度指标的计算来确定突变发生的时间和位置。工程实例表明:小波变换的信号奇异度指标计算方法在声发射信号奇异性检测的误差仅相差一个采样点的位置,且不存在累计误差,其中db3、sym2、coif1小波基更适合声发射畸变信号的检测,为煤岩体受压损伤破坏全过程的检测提供了有效的思路。

关键词：信号处理声发射信号小波变换奇异度指标奇异性检测

在线全文

学校读者我要写书评

暂无评论

煤层冲击倾向性指标体系研究及实验验证

湖南科技大学学报（自然科学版） 2019年第3期34卷 1-10页

作者：张天军包若羽王乾羽玥西安科技大学理学院陕西西安710054 西安科技大学安全科学与工程学院陕西西安710054

针对传统煤层冲击倾向性指标存在的局限性,基于考虑残余强度的损伤统计本构模型,从损伤因子、损伤速率和损伤速率加速度3个角度分别研究峰值强度点、损伤速率最值点、损伤速率加速度最值点处的损伤规律,对残余强度和动态损伤应变进行了... 详细信息

针对传统煤层冲击倾向性指标存在的局限性,基于考虑残余强度的损伤统计本构模型,从损伤因子、损伤速率和损伤速率加速度3个角度分别研究峰值强度点、损伤速率最值点、损伤速率加速度最值点处的损伤规律,对残余强度和动态损伤应变进行了修正,提出了新的煤层冲击倾向性指标—盈余能指数变化率,建立冲击倾向性指标体系,并开展冲击倾向性实验对新指标体系合理性进行验证.结果表明:考虑残余强度的损伤统计本构模型能较好地反映煤岩体峰值强度后应力—应变曲线变化趋势及残余强度特点,得到峰值强度点、损伤速率最值点和损伤速率加速度最值点处的损伤规律及损伤速率最大值表达式;根据修正后动态损伤应变的力学意义得到动态损伤应变与动态破坏时间关系式,采用动态损伤应变来表征动态破坏时间,从而使冲击倾向性实验不再受加载方式的限制;采用盈余能指数变化率指标可综合衡量盈余能、峰后破坏过程损耗应变能、动态破坏时间的变化情况;由最大损伤速率、动态损伤应变、盈余能指数变化率构成的新冲击倾向性指标体系更为有效和全面,为准确评价煤层冲击倾向性工作提供新方法.

关键词：冲击倾向性损伤统计本构模型最大损伤速率动态损伤应变盈余能指数变化率

Advances and challenges on springback control for creep age forming of aluminum alloy

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2022年第10期35卷 8-34页

作者： Liwen zhang Heng LI tianjun BIAN Changhui WU Yang GAO Chao LEI Taicang Yangtze River Delta Research Institute of NPU Northwestern Polytechnical UniversityTaicang 215400China State Key Lab of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi'an 710072China Shanghai Aerospace Equipments Manufacturer Co. Ltd.Shanghai 200245China School of Materials Science and Engineering Xi'an University of TechnologyXi'an 710048China

Creep age forming(CAF)is an advanced forming technology that combines creep deformation and age hardening *** compared with the conventional forming technologies including roll bending and shot-peen forming,CAF has many advantages of low residual stress,excellent dimensional stability,good service performance and short production *** is an optimal technique for precise manufacturing for shape and properties of large-scale complicated thinwalled components of light-weight and high strength aluminum alloys in the aviation and aerospace ***,CAF has an inevitable disadvantage that a large amount of springback occurs after unloading,which brings a challenge on the accurate shape forming and property tailoring of ***,how to achieve accurate prediction and control of springback has always been a bottleneck hindering the development of CAF to more industrial *** the factors of affecting springback and measures of reducing springback are summarized from the internal and external aspects,constitutive models for predicting springback and springback compensation methods for CAF of aluminum alloy panel components are ***,a review of research progresses on tool design for CAF is ***,in view of the key issue that it is difficult to predict and control the shape and properties of components during CAF,the technical challenges are discussed and future development trends of CAF are prospected.

关键词： Aluminum alloy Creep age forming Integrated manufacturing Springback compensation Tool design

不同产状裂隙煤样三轴承压下非Darcy渗流特性

在线全文

学校读者我要写书评

暂无评论

煤炭学报 2019年第1期44卷 246-253页

作者：张天军庞明坤彭文清陈佳伟潘红宇西安科技大学理学院西安科技大学安全科学与工程学院

裂隙产状是影响瓦斯抽采钻孔孔周煤体渗流状态的重要因素之一。为探究裂隙的不同产状对煤体渗流特性的影响,分别制作了含有1,2,3条裂隙共5种产状的煤样;利用自主设计的三轴渗流试验系统,采用稳态渗透法对煤样进行渗流试验研究,得到了三... 详细信息

裂隙产状是影响瓦斯抽采钻孔孔周煤体渗流状态的重要因素之一。为探究裂隙的不同产状对煤体渗流特性的影响,分别制作了含有1,2,3条裂隙共5种产状的煤样;利用自主设计的三轴渗流试验系统,采用稳态渗透法对煤样进行渗流试验研究,得到了三轴应力下裂隙煤体的渗流雷诺数、渗透率和Forchheimer数变化趋势,并分析了裂隙煤体非Darcy渗流的演化规律。结果表明:(1)渗流试验过程中,42%的渗流雷诺数分布在10～100,且渗流趋势符合非线性渗流特点;说明随着裂隙面面积的增大,流动过程中黏滞阻力和惯性力对流速的影响越来越大,其发生非Darcy渗流的可能性就越高;(2)通过分析裂隙煤体受力状况,得到裂隙煤样渗透率k随着有效应力σ的增加呈下降趋势,且符合k=aσ-b关系;说明随着应力水平的增加,煤样内部部分裂隙发生闭合、渗流通道数目和宽度的减少,最终导致渗透率急剧降低;(3)通过计算各个阶段的Forchheimer数Fo,得到Fo与渗流速度v符合二次曲线规律增长,且随着Fo的增加非Darcy渗流效应也越来越显著,说明裂隙煤样渗透性的增强是导致发生高速非Darcy渗流的根本原因。结合以上结论,可在煤层瓦斯预抽工作中,依据钻孔孔周煤体瓦斯流动规律准确确定抽采钻孔影响范围,从而为钻孔布孔方式的设计提供重要的理论依据。

关键词：贯穿裂隙产状非Darcy流三轴承压渗流特性瓦斯抽采

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

海洋石油完井技术现状及发展趋势研究

化工设计通讯 2024年第7期50卷 40-42,50页

作者：秦天军张涛左翊寅中法渤海地质服务有限公司湛江分公司广东湛江524057

在全球能源需求的不断增长和陆地石油资源的逐步枯竭的背景下,海洋石油资源的开发成为现行石油开采的主要组成部分,其中,海洋石油完井技术作为提高油气田开发效率和生产效益的关键技术,针对其进行研究具有重要意义。就海洋石油完井的技... 详细信息

在全球能源需求的不断增长和陆地石油资源的逐步枯竭的背景下,海洋石油资源的开发成为现行石油开采的主要组成部分,其中,海洋石油完井技术作为提高油气田开发效率和生产效益的关键技术,针对其进行研究具有重要意义。就海洋石油完井的技术创新、绿色环保技术的发展,以及数字化和智能化技术的应用等方向进行了深入探讨,以期望为海洋石油开发领域提供前瞻性的见解和参考,促进该领域的技术进步和可持续发展。

关键词：海洋石油石油开采技术现状发展趋势

Understanding and building upon pioneering work of Nobel Prize in Physics 2021 laureates Syukuro Manabe and Klaus Hasselmann:From greenhouse effect to Earth system science and beyond

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2022年第4期65卷 589-600页

作者： tianjun ZHOU Wenxia zhang Deliang CHEN Xuebin zhang Chao LI Meng ZUO Xiaolong CHEN State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100049China Department of Earth Sciences University of GothenburgGothenburg 40530Sweden Environment and Climate Change Canada Toronto M3H 5T4Canada Max Planck Institute for Meteorology Hamburg 20146Germany

The Nobel Prize in Physics 2021 was awarded jointly to Syukuro Manabe,Klaus Hasselmann,and Giorgio Parisi for their groundbreaking contributions to our understanding of complex *** is the first time that climate scientists were awarded the Nobel Physics ***,we present the evolution of climate science in the past~200 years and highlight the landmarks of the developments in advancing our understanding of climate change,placing the pioneering contributions of Manabe and Hasselmann into a historical *** backbone of modern climate science is further discussed in the context of the development of the discipline from the discovery of the greenhouse effect to the formation of Earth system *** on the future development of climate science are also`presented.

关键词： Greenhouse gases Climate change General Circulation Model Detection and attribution Climate science Earth system science

Investigation of Nuclear Binding Energy and Charge Radius Based on Random Forest Algorithm

在线全文

学校读者我要写书评

暂无评论

原子能科学技术 2023年第4期57卷 704-712页

作者： CAI Boshuai YU tianjun LIN Xuan zhang Jilong WANG Zhixuan YUAN Cenxi Sino-French Institute of Nuclear Engineering and Technology Sun Yat-sen UniversityZhuhai 519082China

The random forest algorithm was applied to study the nuclear binding energy and charge *** regularized root-mean-square of error(RMSE)was proposed to avoid overfitting during the training of random *** for nuclides with Z,N>7 is reduced to 0.816 MeV and 0.0200 fm compared with the six-term liquid drop model and a three-term nuclear charge radius formula,*** interest is in the possible(sub)shells among the superheavy region,which is important for searching for new elements and the island of *** significance of shell features estimated by the so-called shapely additive explanation method suggests(Z,N)=(92,142)and(98,156)as possible subshells indicated by the binding *** the present observed data is far from the N=184 shell,which is suggested by mean-field investigations,its shell effect is not predicted based on present *** significance analysis of the nuclear charge radius suggests Z=92 and N=136 as possible *** effect is verified by the shell-corrected nuclear charge radius model.

关键词： nuclear binding energy nuclear charge radius random forest algorithm

Understanding and Attribution of Extreme Heat and Drought Events in 2022: Current Situation and Future Challenges

在线全文

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2023年第11期40卷 1941-1951页

作者： Lixia zhang Xiaojing YU tianjun ZHOU Wenxia zhang Shuai HU Robin CLARK State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and TechnologyNanjing 210044China Key Laboratory of Citie’s Mitigation and Adaptation to Climate Change in Shanghai China Meteorological AdministrationShanghai 200030 College of Geography and Remote Sensing Sciences Xinjiang UniversityUrumqi 830046China Met Office Hadley Centre ExeterEX13PBUK

Extreme weather events and their consequential impacts have been a key feature of the climate in recent years in many parts of the world,with many partly attributed to ongoing global-scale *** past year,2022,has been no exception,with further records being *** year was marked by unprecedented heatwaves and droughts with highly unusual spatial extent,duration and intensity,with one measure indicating an aggregated and overall intensity of extreme heat events worldwide not seen since at least *** extreme drought measured by surface soil moisture covered 47.3%of global land areas in 2022,which was the second most widespread year since ***,we examine notable events of the year in five major regions of the world:China’s Yangtze River region,western Europe,the western U.S.,the Horn of Africa and central South *** each event,we review the potential roles of circulation,oceanic forcing(especially the“triple-dip”La Niña)and anthropogenic climate change,with an aim of understanding the extreme events in 2022 from a global *** will serve as a reference for mechanism understanding,prediction and attribution of extreme events.

关键词： extreme event in 2022 heatwave drought detection and attribution

在线全文

学校读者我要写书评

暂无评论

瓦斯抽采钻孔孔周裂纹扩展规律

辽宁工程技术大学学报（自然科学版） 2018年第3期37卷 499-507页

作者：张天军张磊李树刚张超潘红宇董晓刚西安科技大学理学院陕西西安710054 西安科技大学安全科学与工程学院陕西西安710054 西部矿井开采及灾害防治教育部重点实验室陕西西安710054

为研究瓦斯抽采钻孔孔周裂纹扩展规律,制作不同抗压强度的含钻孔试样并进行全应力—应变单轴压缩试验,采用数字散斑相关测量方法获取试样表面破坏图像序列及其表面破坏过程中的全场应变.研究不同强度试样破坏过程中的裂纹分布,孔周位移... 详细信息

为研究瓦斯抽采钻孔孔周裂纹扩展规律,制作不同抗压强度的含钻孔试样并进行全应力—应变单轴压缩试验,采用数字散斑相关测量方法获取试样表面破坏图像序列及其表面破坏过程中的全场应变.研究不同强度试样破坏过程中的裂纹分布,孔周位移及裂纹张开位移.结果表明:低抗压强度试样较高抗压强度试样的破坏形式更加多样,裂纹分布形式也更加繁杂;两种试样的孔顶和孔底始终保持相对收缩的趋势,孔洞断面形状在试样破坏的过程中逐渐由圆形变为椭圆形;试样强度对裂纹扩展的影响较大,低强度试样孔周位移约为高强度试样的2~4倍,其裂纹扩展开始时间早于高强度试样,且裂纹张开位移高1~2个数量级;轴向应力σ在0.2σmax^0.5σmax时T类裂纹首先扩展,σ>0.8σmax时I类和N类裂纹扩展并逐渐连通.

关键词：裂纹扩展数字散斑孔周位移单轴压缩裂纹张开位移