检索结果-南通市图书馆

A unified viscoplasticity constitutive model based on irreversible thermodynamics

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2008年第4期51卷 378-385页

作者： LIU ChangChun Lü HeXiang guan ping State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian 116024China Prediction&Control Key Laboratory on Complicated Structure System Dalian UniversityDalian 116622China

A unified viscoplasticity constitutive model for metal materials is developed within the framework of irreversible thermodynamics, and an expression for the Helmholtz free energy function involving the parameters reflecting kinematic hardening and isotropic hardening is given. At the same time a non-associated flow potential function including the corresponding state variables is also given, from which the flow equation and the evolution equations of the internal state variables are derived. Thus, a general theoretical framework constructing a unified viscoplasticity constitutive model is given. Compared with the typical unified viscoplasticity constitutive models, the presented model evidently satisfies the irreversible thermodynamics laws. Moreover, this method not only provides a new theoretical foundation for further development of the unified viscoplasticity constitutive model, but also gives a new theoretical framework for the stress-strain analysis of more materials.

关键词： irreversible thermodynamics viscoplasticity unified constitutive kinematic hardening isotropic hardening

Volcanic structure of the Tarim flood basalt revealed through 3-D seismological imaging

在线全文

学校读者我要写书评

暂无评论

Science Bulletin 2015年第16期60卷 1448-1456页

作者： Lei Wang Wei Tian Yongmin Shi ping guan School of Earth and Space Sciences Peking University

The detailed structures of the volcanic edifice and plumbing system of the early Permian Tarim flood basalt were investigated by three-dimensional seismic imaging. The images show that the Tarim flood basalt erupted from central volcanoes distributed along major faults. The uppermost magma formed a single lava lobe with a volume of *0.74 km3 and an aspect ratio of 50,implying a sheet flow eruption with a high effusion rate. At the subsurface level, all central volcanoes, irrespective of size, had a separate pipe-like feeder vent. Only thirteen dikes were identified at shallow depths of \100 m below the lava surface; deeper dikes were even rarer. The pipelike plumbing system and the paucity of dilational dikes were different from the typical plumbing system of flood basalt provinces on Earth, which are normally buoyancycontrolled dike–sill networks. A gas-driven vigorous eruption can be inferred from the imaged structure, which means that the Tarim flood basalt may have carried and released a large proportion of volcanic gas, similar to some mafic volcaniclastic deposit-bearing continental flood basalt provinces.

关键词： Tarim flood basalt - 3-D seismicimaging Central volcano Lava lobe Plumbing system Eruption style

Hot tensile deformation behavior and constitutive model of ZK61M high-strength magnesium alloy sheet

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2021年第5期40卷 1182-1190页

作者： Liu Yang Yong-Chuan Duan Ying-ping guan Zhen-Hua Wang Key Laboratory of Advanced Forging&Stamping Technolnology and Science Ministry of Education of ChinaYanshan UniversityQinhuangdao 066004China School of Mechanical Engineering Yanshan UniversityQinhuangdao 066004China

Hot deformation behavior of the annealed ZK61 M magnesium alloy sheet was explored using tensile tests with strain rates varying from 0.001 to 0.030 s^(-1) in temperatures range of 423-513 *** obtained results indicate that the flow stress increased with deformation temperature decreasing and strain rate *** recrystallization(DRX)occurs when the temperature is higher than 423 K,and the recrystallization volume fraction increases with temperature *** a given temperature,the measured DRX volume fraction at a higher strain rate is smaller than that at a lower strain *** are observed throughout the tested temperature ***,they grow larger as temperature *** average absolute relative error(AARE)of 2.65%proves that the peak stress predicted by the constitutive model is in good agreement with the experimental *** correlation coefficient(R’)obtained for the predicted stress and the experimental value considering the strain on the material constant are between 0.9831 and *** addition,AARE and root mean square error(RMSE)are less than 6.5%and 8.5 MPa,*** indicates that the deviation of the predicted value from the experimental value is small and the predictions of the proposed model are reliable.

关键词： ZK61M magnesium alloy sheet Hot tensile deformation Microstructure Constitutive model

Isotopic composition charac-teristics and identification of immature and low-mature oils

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2001年第22期46卷 1923-1929页

作者： XU Yongchang SHEN ping LIU Wenhui guan ping HUANG Difan State Key Laboratory of Gas Geochemistry Lanzhou Institute of GeologyChinese Academy of SciencesLanzhou 730000China Department of Geology Peking UniversityBeijing 100871China Institution of Exploration&Development China Petroleum&NaturalGas Corporation LimitedBeijing 100083China

Isotopic composition characteristics and the significance of immature and low-mature oils are first systematically discussed. The carbon isotopes of the whole oil can be divided into two groups, one has δ13C main peak values ranging from -30‰ to -29 and the other from -27‰ to -25‰, they are related to lacustrine and salt-lake facies or swamp facies, respectively. The carbon isotopic fractionation among different group components is relatively small, usually less than 2‰ and the biggest difference in fractionation often occurs between saturated and aromatic fractions. Their δD values vary between -180‰ and -130‰. The main peak of their δD values concentrates between -170‰ and -150‰, suggesting a domination of lacustrine facies. However, the secondary peak ranges from -160‰ to -150‰, showing a frequent salinization of paleo-water bodies. The average δ13C values of the methane vary between -50‰ and -52‰, about 10‰ lighter than those of mature oils. There is a relatively good

关键词： immature and low-mature oil isotope associated gas.

A model for carbon isotope distribution of methane duringdiagenesis

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 1998年第7期43卷 576-578页

作者： ping guan Yongchang Xu Wenhui Liu Darui Wang Peking Univ Dept Geol Beijing 100871 Peoples R China Chinese Acad Sci Lanzhou Inst Geol Lanzhou 730000 Peoples R China Res Inst Petr Explorat & Dev Beijing 100083 Peoples R China

The evolution of methane carbon isotope with depth has been discussed based on diagenetic reaction kinetics and isotopic Rayleigh fractionational theory. A mathematical model to describe data of methane carbon isotope... 详细信息

关键词： methane carbon isotope maturity Rayleigh fractionation.

Finite-time Consensus for Multi-agent Systems via Nonlinear Control Protocols

在线全文

学校读者我要写书评

暂无评论

International Journal of Automation and computing 2013年第5期10卷 455-462页

作者： Ya-Kun Zhu Xin-ping guan Xiao-Yuan Luo Institute of Electrical Engineering Yanshan University School of Electronic Information and Electrical Engineering Shanghai Jiao Tong University

This paper investigates the fnite-time consensus problem of multi-agent systems with single and double integrator dynamics,*** novel nonlinear protocols are constructed for frst-order and second-order leader-follower multi-agent systems,*** on the fnite-time control technique,the graph theory and Lyapunov direct method,some theoretical results are proposed to ensure that the states of all the follower agents can converge to its leader agent s state in fnite ***,some simulation results are presented to illustrate the efectiveness of our theoretical results.

关键词： Finite-time consensus multi-agent systems nonlinear control protocol leader-follower single and double integratordynamics

Finite-time Control for a Class of Networked Control Systems with Short Time-varying Delays and Sampling Jitter

在线全文

学校读者我要写书评

暂无评论

International Journal of Automation and computing 2015年第4期12卷 448-454页

作者： Chang-Chun Hua Shao-Chong Yu Xin-ping guan Department of Electrical Engineering University of Yanshan Department of Automation Shanghai Jiaotong University

This paper is concerned with the finite-time control problem for a class of networked control systems(NCSs) with short time-varying delays and sampling *** a state feedback controller,the closed-loop NCS is described as a discrete-time linear system model,and the uncertain parts reflect the effect of the the network-induced delays and short sampling jitter of the system *** a robust approach is proposed to solve the finite-time stability and stabilization problems for the considered *** illustrative example is provided to demonstrate the effectiveness of the proposed theoretical results.

关键词： Networked control system(NCS) time-varying delay sampling jitter finite-time stability state feedback.

Natural gas geochemistry of low evolutionary stage of mediumand small-sized basins in Yunnan Province, southwestern China

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 1999年第18期44卷 1709-1712页

作者： Yongchang Xu ping Shen Jiangjing Zhen Wenhui Liu ping guan Chinese Acad Sci Lanzhou Inst Geol Lanzhou 730000 Peoples R China Peking Univ Dept Geol Beijing 100871 Peoples R China

The biogenic gas and premature-low mature associated gases in some medium and small-sized basins of Yannan Province, such as Luliang, Yanglin, Baoshan and Jinggu basins, have beed researched. The results show that the biogenic-gas consists mainly of methane which is more than 99% in gasous hydrocarbons and of lighter carbon isotopic composition with δ13C1 values from -60.0‰ to - 75.4‰. The methane carbon isotopic compositions in the Baoshan Basin is relatively heavy (δ13C1, - 60‰-- 65‰), but those in Luliang and

关键词： low-evolution natural gas carbon isotope.

Modeling and Control for Wireless Networked Control System

在线全文

学校读者我要写书评

暂无评论

International Journal of Automation and computing 2011年第3期8卷 357-363页

作者： Chang-Chun Hua Ying Zheng Xin-ping guan Department of Electrical Engineering Yanshan University Qinhuangdao 066004 PRC Department of Automation Shanghai Jiao Tong University Shanghai 20024 PRC

In this paper, the stabilization problem is considered for the class of wireless networked control systems （WNCS）. An indicator is introduced in the WNCS model. The packet drop sequences in the indicator are represented as states of a Markov chain. A new discrete Markov switching system model integrating 802.11 protocol and new scheduling approach for wireless networks with control systems are constructed. The variable controller can be obtained easily by solving the linear matrix inequality （LMI） with the use of the Matlab toolbox. Both the known and unknown dropout probabilities are considered. Finally, a simulation is given to show the feasibility of the proposed method.

关键词： Wireless networked control systems (WNCS) packet dropout sequences controller network scheduling stability.