检索结果-南通市图书馆

Influences of microstructure and texture on crack propagation path of X70 acicular ferrite pipeline steel

在线全文

学校读者我要写书评

暂无评论

Journal of University of Science and Technology Beijing 2008年第6期15卷 683-687页

作者： hao Yu School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

The aspects of two pipeline steels with different technologies were investigated by using transmission electron microscopy （TEM） and electron back-scattered diffraction （EBSD）. The microstructure presents a typical acicular ferrite characteristic with fine particles of martensite/austenite （M/A） constituent, which distributes in grains and at grain boundaries. The bulk textures of the pipeline steel plate are {112}〈110〉 and 〈111〉 fibers, respectively, and the {112}〈110〉 component is the favorable texture benefiting for drop weight tear test. Moreover, low angle boundaries and low coincidence site lattice boundaries are inactive and more resistant to fracture than high energy random boundaries.

关键词： pipeline steel acicular ferrite microstructure texture crack propagation

在线全文

学校读者我要写书评

暂无评论

爆炸作用下建筑结构高效毁伤评估方法

爆炸与冲击 2025年第1期45卷 133-150页

作者：吕晋贤吴昊卢永刚陈德同济大学土木工程学院上海200092 中国工程物理研究院总体工程研究所四川绵阳621999

为综合评估战后建筑结构的毁伤等级,针对爆炸作用下典型地面建筑,即含填充墙钢筋混凝土(reinforced concrete,RC)框架结构,提出了损伤破坏和倒塌的高精度数值仿真分析方法,并通过RC结构爆炸试验、倒塌事故和砌体墙爆炸试验进行了充分验... 详细信息

为综合评估战后建筑结构的毁伤等级,针对爆炸作用下典型地面建筑,即含填充墙钢筋混凝土(reinforced concrete,RC)框架结构,提出了损伤破坏和倒塌的高精度数值仿真分析方法,并通过RC结构爆炸试验、倒塌事故和砌体墙爆炸试验进行了充分验证;开展了典型3层原型RC框架结构在不同爆炸当量(25~200 kg TNT)下的内爆炸数值仿真,定量分析了爆炸冲击波在建筑结构内部的传播、结构损伤破坏和墙体飞散等。爆炸作用下建筑结构的高效毁伤评估流程为:结合镜像爆源和非线性叠加原理确定内爆炸荷载,基于等效单自由度方法评估梁、板、柱及墙体构件的毁伤等级,引入构件重要性系数加权确定房间毁伤等级,考虑房间功能及位置重要性评估整体结构的毁伤等级。高精度数值仿真分析与毁伤评估方法计算的典型RC框架结构的整体毁伤等级一致,即在25、100和200 kg TNT爆炸下RC结构分别呈现轻度、中度和重度毁伤,毁伤评估方法可缩短99%以上的计算耗时,兼具可靠性与时效性。

关键词：爆炸荷载建筑结构毁伤评估方法损伤破坏

Achievement of chaotic synchronization trajectories of master-slave manipulators with feedback control strategy

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2010年第3期26卷 433-439页

作者： Qingkai Han Lina hao hao Zhang Bangchun Wen School of Mechanical Engineering and Automation Northeastern University 110004 Shenyang China

This paper addresses a master-slave synchro- nization strategy for complex dynamic systems based on feedback control. This strategy is applied to 3-DOF pla- nar manipulators in order to obtain synchronization in such complicated as chaotic motions of end-effectors. A chaotic curve is selected from Duffing equation as the trajectory of master end-effector and a piecewise approximation method is proposed to accurately represent this chaotic trajectory of end-effectors. The dynamical equations of master-slave manipulators with synchronization controller are derived, and the Lyapunov stability theory is used to determine the stability of this controlled synchronization system. In numer- ical experiments, the synchronous motions of end-effectors as well as three joint angles and torques of master-slave manipulators are studied under the control of the proposed synchronization strategy. It is found that the positive gain matrix affects the implementation of synchronization con- trol strategy. This synchronization control strategy proves the synchronization＇s feasibility and controllability for com- plicated motions generated by master-slave manipulators.

关键词： Master-slave manipulators - Chaoticsynchronization trajectory - Feedback control

Full waveform inversion based on the ensemble Kalman filter method using uniform sampling without replacement

在线全文

学校读者我要写书评

暂无评论

Science Bulletin 2019年第5期64卷 321-330页

作者： Jian Wang Dinghui Yang hao Jing hao Wu Department of Mathematical Sciences Tsinghua University

Full waveform inversion(FWI) has been increasingly more and more important in seismology to better understand the interior structure of the Earth. FWI, by taking advantage of both the traveltime and amplitude in the data, provides high-resolution model parameters of the earth which can produce images with high resolution. However, this inversion method conventionally suffers from non-uniqueness due to many local minima of the objective function and large computing costs. In this study, we propose a new FWI method in a semi-random framework by integrating the ensemble Kalman filter and uniform sampling without replacement. Numerical results demonstrate that the new method can achieve highresolution results and a wider convergence domain. Accordingly, the new method overcomes the disadvantage of conventional FWIs that depend strongly on the initial model.

关键词： Data assimilation Ensemble Kalman filter Uniform sampling without replacement Full waveform inversion

侵彻爆炸联合作用下超高性能混凝土遮弹层设计

在线全文

学校读者我要写书评

暂无评论

爆炸与冲击 2025年第1期45卷 88-101页

作者：程月华吴昊岑国华张瑜同济大学土木工程学院上海200092

为了准确评估超高性能混凝土(ultra-high performance concrete,UHPC)遮弹层在战斗部侵彻爆炸作用下的损伤破坏并建立可靠的计算方法,首先,开展了UHPC靶体抗105 mm口径弹体侵彻和5 kg TNT炸药爆炸联合作用试验,获取了侵彻作用后以及侵... 详细信息

为了准确评估超高性能混凝土(ultra-high performance concrete,UHPC)遮弹层在战斗部侵彻爆炸作用下的损伤破坏并建立可靠的计算方法,首先,开展了UHPC靶体抗105 mm口径弹体侵彻和5 kg TNT炸药爆炸联合作用试验,获取了侵彻作用后以及侵彻与爆炸联合作用后弹靶的损伤破坏数据;然后,建立了UHPC靶体抗弹体侵彻与爆炸作用的有限元模型,通过对上述试验和已有的有限厚UHPC板埋置装药爆炸试验进行数值仿真分析,验证了有限元模型和分析方法的可靠性;最后,对比了SDB、WDU-43/B和BLU-109/B等3种典型原型战斗部侵彻与爆炸联合作用下,UHPC遮弹层和普通混凝土遮弹层的临界贯彻和震塌厚度。结果表明:3种战斗部侵彻爆炸联合作用下,遮弹层的临界贯穿厚度和震塌厚度范围分别为1.30~2.60 m和1.70~5.00 m,相应的临界贯穿系数和震塌系数范围分别为1.81~2.17和2.46~4.17;与普通混凝土遮弹层对比,3种战斗部侵彻爆炸联合作用下UHPC遮弹层的开坑直径减小了34.4%~42.4%,临界贯穿和震塌厚度分别减小了7.1%~31.6%和39.7%~52.8%。研究结果可为UHPC遮弹层的抗力评估和设计提供参考。

关键词：超高性能混凝土遮弹层侵彻爆炸防护设计

Analysis of the ionospheric variability based on wavelet decomposition

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2015年第1期58卷 174-180页

作者： SHI hao ZHANG DongHe LIU YuMei hao YongQiang Department of Geophysics Peking University National Key Laboratory of Electromagnetic Environment China Research Institute of Radio Wave Propagation

In this work,the ionospheric variability is analyzed by applying the wavelet decomposition technique to the noontime fo F2,F10.7,interplanetary magnetic field(IMF)Bz,Ap,and lower thermospheric temperature at pressure of 10?4 h Pa in *** show that the variance of periodic oscillations in the ionosphere is largest in the 2–4-day period and declines with the increase of the *** maximum variance of the periodic oscillations in solar irradiation is in the 16–32-day *** geomagnetic activities,most of the variance is about equally distributed on intervals of periods shorter than 32 *** distributions of IMF Bz and lower thermospheric temperature are similar to those of the *** show the maximum in the 2–4-day period and decline with the increase of the *** analyzing the distributions of the variances,the potential connections between the ionosphere and the external sources are discussed.

关键词： ionosphere variability fo F2 Wavelet decomposition 2–32-day period

Hour-to-hour variability of the ionosphere: An application of the classical multidimensional scaling method

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2015年第7期58卷 1243-1250页

作者： SHI hao ZHANG DongHe hao YongQiang XIAO Zuo Department of Geophysics Peking University

The classical multidimensional scaling(MDS) method is introduced and applied in the study of the hour-to-hour ionospheric variability based on the ionospheric fo F2 observed at three ionosonde stations in East-Asia in 2002 and 2007. Results from the matrix eigen decompositions indicate that the annual part of the ionospheric variation is large in middle latitude and solar maximum period(2002) while low in the low latitude and solar minimum period(2007). The connectivity maps of the hour-to-hour ionospheric variability based on MDS method show some common diurnal features. The ionospheric connectivity between adjacent hours near noon hours and near midnight hours is high. The ionospheric connectivity between adjacent hours near sunrise hours and near sunset hours is poor, especially for the sunrise hours. Also there are latitudinal and solar activity dependences in this kind of connectivity. These results revealed from the ionospheric connectivity maps are useful physically and in practice for the ionospheric forecasting on the hour-to-hour scale.

关键词： ionospheric variability classical multidimensional scaling connectivity map

A Chemical Reactor Network for Oxides of Nitrogen Emission Prediction in Gas Turbine Combustor

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2014年第3期23卷 279-284页

作者： Nguyen Thanh hao Industrial University of HoChiMinh City

This study presents the use of a new chemical reactor network(CRN) model and non-uniform injectors to predict the NOx emission pollutant in gas turbine combustor. The CRN uses information from Computational Fluid Dynamics(CFD) combustion analysis with two injectors of CH4-air mixture. The injectors of CH4-air mixture have different lean equivalence ratio, and they control fuel flow to stabilize combustion and adjust combustor's equivalence ratio. Non-uniform injector is applied to improve the burning process of the turbine combustor. The results of the new CRN for NOx prediction in the gas turbine combustor show very good agreement with the experimental data from Korea Electric Power Research Institute.

关键词： Chemical Reactor Networks (CRN) Computational Fluid Dynamics (CFD) Perfectly Stirred Reactor (PSR) Plug Flow Reactor (PFR) Gas Turbine Combustor Oxides of Nitrogen Emission (NOx).

Numerical investigation of the failure mechanism of cubic concrete specimens in SHPB tests

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2022年第1期18卷 1-11页

作者： Mei Li Hong hao Jian Cui Yi-fei hao Labomtory of Coast Civil Structure Safety of Ministry of Education Tianjin UniversityTiarjin300072China chool of Civil Engineering.Tianin University Tianjin300072China entre for Infrastructural Monitoring and Protection School of Civil and Mechanical Engineering Curtin UniversityPerth Western Australia6845Australia

Cylindrical specimens are commonly used in Split Hopkinson pressure bar(SHPB)tests to study the uniaxial dynamic properties of concrete-like *** recent years,true tri-axial SHPB equipment has also been developed or is under development to investigate the material dynamic properties under tri-axial impact *** such tests,cubic specimens are *** is well understood that static material strength obtained from cylinder and cube specimens are *** factors are obtained and adopted in some guidelines to convert the material streng th obtained from the two types of *** uniaxial impact tests have also demonstrated that the failure mode and the strain rate effect of cubic specimens are very different from that of cylindrical ***,the mechanical background of these findings is *** an extension of the previous laboratory study,this study performs numerical SHPB tests of cubic and cylindrical concrete specimens subjected to uniaxial impact load with the validated numerical *** stress states of cubic specimens in relation to its failure mode under different strain rates is analyzed and compared with cylindrical *** detailed analyses of the numerical simulation results show that the lateral inertial confinement of the cylindrical specimen is higher than that of the cubic specimen under the same strain *** cubic specimen,the corners aremore severely damaged because of the lower lateral confinement and the occurrence of the tensile radial stress which is not observed in cylindrical *** results explain why the dynamic material strengths obtained from the two types of specimens are different and are strain rate *** on the simulation results,an empirical formula of conversion factor as a function of strain rate is proposed,which supplements the traditional conversion factor for quasi-static material *** can be used for transforming the dynamic compressive strength from

关键词： Concrete Lateral inertial confinement Shape effet Dynamic failure mechanism Strain rate