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Local Influence on the Error-Correction Variable in a Cointegrated System

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Journal of Systems Engineering and Electronics 2001年第3期12卷 1-8页

作者： zhang, X. Yang, B. zhang, t. zhang, S. School of Management Tianjin University Tianjin 310072 China

the concept of cointegration describes an equilibrium relationship among a set of time-varying variables, and the cointegrated relationship can be represented through an error-correction model (ECM). the error-correction variable, which represents the short-run discrepancy from the equilibrium state in a cointegrated system, plays an important role in the ECM. It is natural to ask how the error-correction mechanism works, or equivalently, how the short-run discrepancy affects the development of the cointegrated system? this paper examines the effect or local influence on the error-correction variable in an error-correction model. Following the argument of the second-order approach to local influence suggested by reference [5], we develop a diagnostic statistic to examine the local influence on the estimation of the parameter associated with the error-correction variable in an ECM. An empirical example is presented to illustrate the application of the proposed diagnostic. We find that the short-run discre pancy may have strong influence on the estimation of the parameter associated with the error-correction model. It is the error-correction variable that the short-run discrepancies can be incorporated through the error-correction mechanism.

关键词： Computer simulation Error correction Mathematical models Parameter estimation Program diagnostics Statistical methods time series analysis time varying control systems

Expression and regulation of plasminogen activator and plasminogen activator inhibitor type-1 in rat epididymis

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Chinese Science Bulletin 1997年第9期42卷 779-783页

作者： Zhou, HM zhang, t Liu, YX CHINESE ACAD SCI INST ZOOLSTATE KEY LAB REPROD BIOLBEIJING 100080PEOPLES R CHINA

EPIDIDYMIS is the site where spermatozoa released from testis undergo maturation and become capable of fertilizing *** epididymal secretions including enzymes,nutrients and hor-mones are believed to be essential for sperm *** proteolysis contributes toloss or modification of surface molecules of spermatozoa,which is an important aspect of

关键词： plasminogen activator plasminogen activator inhibitor human chorionic gonadotropin/luteinizing hormone epi-didymis.

OpenIFEM:A High Performance Modular Open-Source Software of the Immersed Finite Element Method for Fluid-Structure Interactions

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Computer Modeling in Engineering & Sciences 2019年第4期119卷 91-124页

作者： Jie Cheng Feimi Yu Lucy t.zhang Department of Mechanical Aerospace and Nuclear Engineering Rensselaer Polytechnic InstituteTroyNY12180USA

We present a high performance modularly-built open-source *** is a C++implementation of the modified immersed finite element method(mIFEM)to solve fluid-structure interaction(FSI)*** software is modularly built to perform multiple tasks including fluid dynamics(incompressible and slightly compressible fluid models),linear and nonlinear solid mechanics,and fully coupled fluid-structure *** of open-source software packages are restricted to certain discretization methods;some are under-tested,under-documented,and lack modularity as well as *** is designed and built to include a set of generic classes for users to adapt so that any fluid and solid solvers can be coupled through the FSI *** addition,the package utilizes well-developed and tested *** also comes with standard test cases that serve as software and algorithm *** software can be built on cross-platform,i.e.,Linux,Windows,and Mac OS,using *** parallelization is also implemented for high-performance computing for large-sized *** is documented using Doxygen and publicly available to download on *** is expected to benefit the future development of FSI algorithms and be applied to a variety of FSI applications.

关键词： Immersed finite element method open-source parallelization fluid-structure interaction adaptive mesh refinement

PRECIPItAtION AND GROWtH OF PEROVSKItE PHASE IN tItANIUM BEARING BLASt FURNACE SLAG

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Acta Metallurgica Sinica(English Letters) 2007年第1期20卷 9-14页

作者： Z.Z. Guo t.P. Lou L. zhang L.N. zhang Z.t. Sui School of Materials and Metallurgy Northeastern University Shenyang 110006 Ghina

the effects of transformation of slag composition and additive agents on the morphology, the precipitation behavior, the crystal growth, and the volume fraction (VF) of perovskite (CaO·¤tiO_2) crystal in the ti-bearing blast furnace slags were investigated. As the morphology of perovskite is dispersed in molten slags, the crystal growth mechanism of the melting of fine dendrites and the coarsening of large grains exist throughout the solidification of molten slags. With the increase of CaO and Fe_2O_3 content, VF of perovskite obviously increases. However, high basicity leads to the viscosity of slag, which results in the reduction of the average equivalent diameter (AED). the experimental results showed that the presence of the additives CaF_2 and MnO efficiently decreased the viscosity of the slags, and obviously improved the morphology of perovskite and promoted its growth.

关键词： perovskite phase ti-bearing blast furnace slag precipitation additive agent

Achieving superior strength-ductility synergy in a heterostructured magnesium alloy via low-temperature extrusion and low-temperature annealing

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Journal of Materials Science & technology 2023年第32期163卷 32-44页

作者： H.Wang D.t.zhang C.Qiu W.W.zhang D.L.Chen Guangdong Key Laboratory for Advanced Metallic Materials Processing and Forming National Engineering Research Center of Near-net-shape Forming for Metallic MaterialsSouth China University of TechnologyGuangzhou 510640China Department of Mechanical and Industrial Engineering Toronto Metropolitan University(formerly Ryerson University)350 Victoria StreetTorontoON M5B 2K3Canada

A low-alloyed Mg-1.2Zn-0.1Ca(wt.%)alloy was fabricated via low-temperature extrusion and annealing at 250℃for different times(10,30,and 90 min)to attain heterostructures with different fine-grained fractions,focusing on the effect of heterostructure on the mechanical *** dynamic recrystallization(RX)occurred during extrusion at 150℃,and a lamellar structure consisting of fine RX grains and coarse unRX grains was *** subsequent annealing promoted static RX in the as-extruded alloy,leading to an increased fine-grained fraction from 67%to 95%.Meanwhile,the co-segregation of Zn and Ca atoms impeded the migration of grain boundaries,thus achieving a fine grain size of 0.8–1.6μ*** sample annealed for 10 min with a fine-grained fraction of 73%and an average RX grain size of 0.9μm exhibited a superior combination of high yield strength(305 MPa)and good ductility(20%).In comparison,an excellent elongation of 30%was achieved in the alloy with a nearly fully-RXed microstructure and an average grain size of 1.6μm after 90 min annealing,despite a lower yield strength of 228 *** unRX grains,the hard orientation with(01–10)parallel to the extrusion direction and high-density dislocations made it more difficult to deform compared with the RX grains,thus producing hetero-deformation induced(HDI)*** fine grains and high-density dislocations,HDI strengthening is the key to achieving the superior mechanical properties of the low-alloyed Mg alloy.

关键词： Low-alloyed magnesium alloy Low-temperature extrusion Annealing Heterostructure Mechanical properties

Hierarchical fractal structure of perfect single-layer graphene

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Frontiers of Mechanical Engineering 2013年第4期8卷 371-382页

作者： t.zhang K.Ding Research Center for Solid Mechanics Beihang University School of Engineering Brown University School of Instrument Science and Opto-electronic Engineering Beihang University

the atomic lattice structure of perfect singlelayer graphene that can actually be regarded as a kind of hierarchical fractal structure from the perspective of fractal geometry was studied for the first *** novel and special discoveries on hierarchical fractal structure and sets were unveiled upon examination of the regular crystal lattices of the single-layer *** interior fractaltype structure was discovered to be the fifth space-filling curve from physical *** efficient methods for calculating the fractal dimension of this fresh member was also *** outer boundary curve had a fractal dimension equal to one,and a multi-fractal structure from a naturally existing material was found for the first time.A series of strict self-similar hexagons comprised a rotating fractal *** hexagons slewed at a constant counterclockwise angle α of 19.1° when observed from one level to the next higher *** the perspective of fractal geometry,these pioneering discoveries added three new members to the existing regular fractal structures and sets.A fundamental example of a multi-fractal structure was also presented.

关键词： hierarchical fractal structure fractal dimension the fifth space-filling curve multi-fractal structure

StUDY ON tHE tEXtURE OF A FRICtION StIR WELDED Mg-Al-Ca ALLOY

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Acta Metallurgica Sinica(English Letters) 2006年第5期19卷 335-340页

作者： D. t. zhang M. Suzuki K. Maruyama Graduate School of Environmental Studies Tohoku University 6-6-02 Aoba-yamaAoba-ku Sendai 980-8579 Japan College of Mechanical Engineering South China University of TechnologyGuangzhou 510640 China

Macro-texture of an Mg-Al-Ca alloy prepared by friction stir welding （FSW） was investigated through pole figure measurement and X-ray diffraction （XRD） pattern analysis. It was found that at the top and bottom surfaces of friction stir zone （FSZ）, （0002） basal planes of magnesium tend to be arranged parallel to the plate surface. In the cross section of FSZ, no obvious texture had evolved and （0002） basal planes showed a random distribution.

关键词： friction stir welding (FSW) Mg-Al-Ca alloy texture microstructure

training β relaxation to rejuvenate metallic glasses

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Journal of Materials Science & technology 2023年第27期158卷 53-62页

作者： L.t.zhang Yun-Jiang Wang Y.Yang J.C.Qiao School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China Department of Mechanical Engineering College of EngineeringCity University of Hong KongTat Chee AvenueKowloon TongKowloonHong Kong SARChina Department of Materials Science and Engineering College of EngineeringCity University of Hong KongTat Chee AvenueKowloon TongKowloonHong Kong SARChina Innovation Center NPU-ChongqingChongqing 401135China

In the current work,we demonstrated that the rejuvenation of metallic glasses can be achieved through training theβrelaxation *** the increase in the training frequency,a transition from structural relaxation to rejuvenation can be *** rejuvenation treatment is unexpected due to it occurs at a relatively small cyclic strain of 0.2%.Rejuvenation is beneficial to increase the relaxation enthalpy and promotes the decoupling of theβrelaxation process andαrelaxation process.A cluster ofβrelaxation time curves are formulated to describe any energetic state between ultrastable and ultimately rejuvenated metallic *** addition,rejuvenation expands the distribution ofβrelaxation process,anelastic and viscoplastic components during the deformation process.

关键词： Metallic glass βrelaxation Rejuvenation Structural heterogeneity

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美国页岩油气地质特征及勘探开发进展

石油勘探与开发 2024年第4期51卷 807-828页

作者： MCMAHON t P LARSON t E zhang t SHUStER M 美国德克萨斯大学奥斯汀分校杰克逊地质科学学院经济地质局奥斯汀78758-4445德克萨斯州美国

基于美国页岩油气勘探开发历程的回顾,对主要页岩盆地的地质演化、主要页岩层系的油气地质特征及勘探开发进展进行系统梳理和总结。美国重要页岩盆地的富烃页岩主要发育于6个地质时期:中奥陶世、中—晚泥盆世、早石炭世(中—晚密西西比... 详细信息

基于美国页岩油气勘探开发历程的回顾,对主要页岩盆地的地质演化、主要页岩层系的油气地质特征及勘探开发进展进行系统梳理和总结。美国重要页岩盆地的富烃页岩主要发育于6个地质时期:中奥陶世、中—晚泥盆世、早石炭世(中—晚密西西比世)、早二叠世、晚侏罗世和晚白垩世(塞诺曼期—土伦期),构造沉积环境主要包括克拉通内盆地、前陆盆地和被动大陆边缘盆地。古生界富烃页岩主要分布于以下6个盆地:阿巴拉契亚盆地(尤蒂卡页岩和马塞勒斯页岩)、阿纳达科盆地(伍德福德页岩)、威利斯顿盆地(巴肯页岩)、阿卡马盆地(费耶特维尔页岩)、沃思堡盆地(巴内特页岩)和二叠盆地(狼营组和斯帕瑞组/骨泉组页岩)。中生界富烃页岩主要发育在西墨西哥湾盆地(海恩斯维尔组和鹰滩组)和落基山盆地群(以丹佛和粉河盆地的尼尔布拉勒组页岩为主)。通过对各页岩区带的详细分析发现,页岩的岩相和矿物成分存在差异,“页岩储层”并非只是页岩,很多情况下页岩油气还产自粉砂岩和碳酸盐岩等多种岩石类型。美国的页岩油气资源丰富,页岩油地质资源量超过0.246×1012 t,页岩气地质资源量超过290×1012 m3。在开启“页岩革命”的水平井水力压裂技术出现之前,美国经过了长达20年的勘探开发实践和理论技术积累。自2007年至2023年,美国页岩油气产量从约11.2×104t/d油当量增加到超过300.0×104t/d油当量,2017年页岩油气产量超过了常规油气,2023年在油气总产量中的占比增加到60%以上。页岩油气的开发主要得益于钻完井技术的改进,“立体开发”的攻关,以及重复压裂、提高原油采收率和“U”形井等技术的应用。基于美国丰富的页岩资源基础和技术的不断进步,页岩油气的产量将继续为全美的油气生产做出更大贡献。

关键词：美国页岩油页岩气页岩储层非常规储层油气产量资源评价

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