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Effects of overburden characteristics on dynamic failure in underground coal mining

International Journal of Mining Science and technology 2017年第1期27卷 121-129页

作者： Lawson Heather E. tesarik Douglas larson Mark K Abraham Habte NIOSH Office of Mine Safety and Health ResearchGround Control BranchSpokane WA 99207USA

Dynamic failures, or ‘‘bumps", remain an imperative safety concern in underground coal mining, despite significant advancements in engineering controls. the presence of spatially discrete, stiff roof units are one feature that has been linked to these events. However, an empirical stratigraphic review indicates that no significant difference exists in the relative commonality of discrete units between bumping and non-bumping deposits. Instead an apparent relationship exists between reportable bumping and the overall stiffness of the host rock. However, this initial study is too simplistic to be conclusive; to weight the relative impact of changes in a single variable, such as the thickness or location of sandstone members, it must be examined in isolation—i.e., in a setting where all other variables are held *** modelling provides this setting, and the effects of variability in a stiff discrete member in a hypothetical longwall mining scenario are investigated within the context of three stratigraphic ‘‘types",compliant, Intermediate and Stiff. A modelling experiment examines changes in rupture potential in stiff roof units for each stratigraphic type as discrete unit thickness and location are manipulated through a range of values. Results suggest that the stiff-to-compliant ratio of the host rock has an impact on the relative stress-inducing effects of discrete stiff members. In other words, it is necessary to consider both the thickness and the distance to the seam, within the context of the host rock, to accurately anticipate areas of elevated rupture-induced hazard; acknowledging the presence of a discrete unit within the overburden in general terms is an insufficient indicator of risk. this finding helps to refine our understanding of the role of individual stiff, strong roof members in bumping phenomena, and suggests that a holistic view of overburden lithology and site-specific numerical modelling may be necessary to improve miner safety.

关键词： Dynamic failure coal mining Bumps Bounces

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the P-t-t-D evolution of the Mahabharat,east-central Nepal:the out-of-sequence development of the Himalaya

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Geoscience Frontiers 2022年第2期13卷 372-382页

作者： Kyle P.larson Sudip Shrestha Mathieu Soret Matthijs Smit Department of Earth Environmental and Geographic SciencesUniversity of British Columbia Okanagan3247 University WayKelownaBC V1V 1V7Canada Department of Earth Ocean and Atmospheric SciencesUniversity of British Columbia Vancouver2020-2207 Main MallVancouverBC V6T 1Z4Canada

A garnet-bearing schist from the southernmost such exposure along the Himalaya in east central Nepal records prograde metamorphism at 32.4±0.3 *** equilibria modelling,combined with ti-in-biotite and quartz caxis thermometry,outline a tight-to-hairpin pressure-temperature(P-t)path extending from~515℃ and 5.5 kbar to peak conditions at~575℃ and 7 kbar followed by deformation during the retrograde phase at 480-515℃ and 6-7 *** new geochronology data place an upper bound on the evolution of metamorphism and deformation in the frontal-most part of the Himalaya,which lasted until 17.5 Ma,as indicated by previously published ^(40)Ar/^(39)Ar *** P-t-time data from this part of the Himalaya,as well as that from more hinterlandward portions of the orogen,outline a progressive,stepwise,commonly out-of-sequence *** data from along the orogen indicates that this evolution is not a local phenomenon,but instead characterizes the tectonics of this system as a whole.

关键词： Himalaya Metamorphism Kinematics Lu-Hf Geochronology Nepal

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Microstructural Evolution of Infrared Brazed cP-ti Using ti-cu-Ni Brazes

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Journal of Materials Science & technology 2011年第2期27卷 131-138页

作者： c.t.chang t.Y.Yeh R.K.Shiue c.S.chang Department of Mechanical Engineering National Hualien Industrial Vocational Senior High SchoolHualien 970TaiwanChina Department of Materials Science and Engineering National Taiwan UniversityTaipei 106TaiwanChina Engineered Materials Solutions 39 Perry AvenueMS 4-1AttleboroMA 02703-2410USA

Microstructural evolution of infrared vacuum brazed cP-ti using two ti-based braze alloys,ti-15cu-15Ni and ti-15cu-25Ni,has been *** infrared brazed joint consisted of eutectic ti 2 cu/ti 2 Ni intermetallic compounds and ti-rich *** eutectic ti 2 cu/ti 2 Ni intermetallic compounds disappeared from the joint after being annealed at 900 c for 1 *** contrast,the depletion rate of both cu and Ni from the braze alloy into cP-ti substrate at 750 c annealing was greatly decreased as compared with that annealed at 900 *** ti 2 cu/ti 2 Ni phases were observed even if the specimen was annealed at 750 c for 15 *** the Ni content of the ti-15cu-25Ni braze alloy is much higher than that of the ti-15cu-15Ni alloy,the amount of eutectic ti 2 cu/ti 2 Ni phases in ti-15cu-25Ni brazed joint is more than that in ti-15ci-15Ni brazed ***,similar microstructural evolution can be obtained from the infrared brazed joint annealed at various temperatures and/or time for both filler metals.

关键词： Infrared Brazing cP-ti ti-cu-Ni fillers Microstructure

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Structural Properties of Homomorphism Dilation Systems

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chinese Annals of Mathematics,Series B 2020年第4期41卷 585-600页

作者： Deguang HAN David R.larson Bei LIU Rui LIU Department of Mathematics University of Central FloridaOrlando 32816USA. Department of Mathematics Texas A&M UniversityCollege Station 77843USA. School of Science Tianjin University of TechnologyTianjin 300384China. corresponding author.School of Mathematical Sciences and LPMc Nankai UniversityTianjin 300071China.

Inspired by some recent development on the theory about projection valued dilations for operator valued measures or more generally bounded homomorphism dilations for bounded linear maps on Banach algebras,the authors explore a pure algebraic version of the dilation theory for linear systems acting on unital algebras and vector *** introducing two natural dilation structures,namely the canonical and the universal dilation systems,they prove that every linearly minimal dilation is equivalent to a reduced homomorphism dilation of the universal dilation,and all the linearly minimal homomorphism dilations can be classified by the associated reduced subspaces contained in the kernel of synthesis operator for the universal dilation.

关键词： Linear systems Linearly minimal homomorphism dilation systems Principle and universal dilations Equivalent dilation systems

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Structural modeling of sandwich structures with lightweight cellular cores

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Acta Mechanica Sinica 2007年第5期23卷 545-559页

作者： t.Liu Z.c.Deng t.J.Lu Department of Engineering Mechanics Northwestern Polytechnical UniversityXi'an 710072China MOE Key Laboratory of Strength and Vibration School of AerospaceXi'an Jiaotong UniversityXi'an 710049China

An effective single layered finite element （FE） computational model is proposed to predict the structural behavior of lightweight sandwich panels having two dimensional （2D） prismatic or three dimensional （3D） truss cores. three different types of cellular core topology are considered： pyramidal truss core （3D）, Kagome truss core （3D） and corrugated core （2D）, representing three kinds of material anisotropy： orthotropic, monoclinic and general anisotropic. A homogenization technique is developed to obtain the homogenized macroscopic stiffness properties of the cellular core. In comparison with the results obtained by using detailed FE model, the single layered computational model can give acceptable predictions for both the static and dynamic behaviors of orthotropic truss core sandwich panels. However, for non-orthotropic 3D truss cores, the predictions are not so well. For both static and dynamic behaviors of a 2D corrugated core sandwich panel, the predictions derived by the single layered computational model is generally acceptable when the size of the unit cell varies within a certain range, with the predictions for moderately strong or strong corrugated cores more accurate than those for weak cores.

关键词： cellular material Sandwich panel Homogenization Finite element

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Dirac-like cone-based electromagnetic zero-index metamaterials

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Light(Science & Applications) 2021年第11期10卷 2048-2066页

作者： Yang Li c.t.chan Eric Mazur State Key Laboratory of Precision Measurement technology and Instrument Department of Precision InstrumentTsinghua UniversityBeijingChina Department of Physics Hong Kong University of Science and TechnologyKowloonHong KongChina John A.Paulson School of Engineering and Applied Sciences Harvard UniversityCambridgeMAUSA

Metamaterials with a Dirac-like cone dispersion at the center of the Brillouin zone behave like an isotropic and impedance-matched zero refractive index material at the Dirac-point *** metamaterials can be realized in the form of either bulk metamaterials with efficient coupling to free-space light or on-chip metamaterials that are efficiently coupled to integrated photonic *** materials enable the interactions of a spatially uniform electromagnetic mode with matter over a large area in arbitrary *** unique optical property paves the way for many applications,including arbitrarily shaped high-transmission waveguides,nonlinear enhancement,and phase mismatch-free nonlinear signal generation,and collective emission of many *** review summarizes the Dirac-like cone-based zero-index metamaterials’fundamental physics,design,experimental realizations,and potential applications.

关键词： index collective realization

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Re-evaluating monazite as a record of metamorphic reactions

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Geoscience Frontiers 2022年第2期13卷 237-254页

作者： Kyle P.larson Sudip Shrestha John M.cottle carl Guilmette t.Alex Johnson H.Daniel Gibson Félix Gervais Department of Earth Environmental and Geographic SciencesUniversity of British Columbia Okanagan3247 University WayKelownaBC V1V 1V7Canada Fipke Laboratory for trace Element Research University of British Columbia Okanagan3247 University WayKelownaBC V1V 1V7Canada Department of Earth Science University of CaliforniaSanta BarbaraSanta BarbaraCA 93106-9630USA Géologie et Génie Géologique UniversitéLavalQuébec CityQuebecCanada Department of Earth Sciences Simon Fraser University8888 University DriveBurnabyBC V5A 1S6Canada Départment des Génies civil Géologique et des MinesPolytechnique MontréalMontréalQC H3T 1J4Canada

this study presents a re-examination of historical specimens(DG136 and DG167)from the Monashee complex in the southeastern canadian cordillera that are critical to the current understanding of rare earth element(REE)distribution between garnet and monazite(and other accessory minerals)during ***-hundred and fifty-one new monazite petrochronology spot analyses on 29 different grains across two specimens outline detailed(re)crystallization *** element data collected from the same ablated volume,interpreted in the context of new phase equilibria modelling that includes monazite,xenotime and apatite,link ages to specific portions of the pressure-temperature(P-t)paths followed by the *** linkages are further informed by garnet Lu-Hf geochronology and xenotime *** clockwise P-t paths indicate prograde metamorphism was ongoing by ca.80 Ma in both *** structurally deeper specimen,DG136,records peak P-t conditions of~755-770℃and 8.8-10.4 kbar,interpreted to coincide with(re-)crystallization of low Y monazite at~75-70 ***-rim garnet isopleths from DG167 cross in the observed peak assemblage field at~680℃ and 9.3 *** conditions are interpreted to correspond with low Y monazite(re-)crystallisation at~65 *** specimens record decompression along their retrograde path coincident with high Y 70-55 Ma and 65-55 Ma monazite populations in DG136 and DG167,*** findings broadly agree with those initially reported~20 years ago and confirm early interpretations using trace elements in monazite as generally reliable markers of metamorphic *** phase equilibria modelling and in situ petrochronological analysis,however,provide additional insight into monazite behaviour during anatexis and the effects of potential trace element buffering by REE-bearing phases such as apatite.

关键词： Monazite petrochronology Phase equilibria modelling Geochronology P-t-t paths

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Behavior modeling and verification of movement authority scenario of chinese train control System using AADL

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Science china(Information Sciences) 2015年第11期58卷 125-144页

作者： AHMAD Ehsan DONG YunWei larson Brian Lü JiDong tANG tao ZHAN NaiJun School of computer Science Northwestern Polytechnical University State Key Laboratory of computer Science Institute of Software Chinese Academy of Sciences computing and Information Systems Kansas State University State Key Laboratory of Rail traffic control and Safety Beijing Jiaotong University

train control systems like most digital controllers are, by definition, hybrid systems as they interact with or try to control some aspects of the physical world. Detailed behavior modeling with constraints specification and formal verification, required for reliability prediction, is a great challenge for hybrid system *** control systems further intensify this challenge with extensive interaction between computing units and their physical environment and their mutual dependence on each other. In this paper, we investigate behavior modeling and formal verification of chinese train control System Level 3(ctcS-3) using Architectural Analysis & Design Language(AADL) to cope with this challenge. AADL is an architecture description language for embedded systems and is based on model-based engineering paradigm. Along with structural modeling of embedded systems using the core language constructs, AADL also provides support for language extension through annex sublanguages. In system requirements specification document, the behavior of the ctcS-3 is specified as a set of basic operation scenarios that cooperate with each other to achieve safe and secure functionality of *** Authority(MA) scenario, explored in this paper, is considered as a basic and most crucial scenario to prevent trains from colliding with each other. the detailed discrete behavior of control system is modeled and verified using the Behavior Language for Embedded Systems with Software(BLESS) annex sublanguage of AADL, and the continuous behavior of train with the cyber–physical interaction(communication between train and control system) is modeled using the Hybrid annex sublanguage. the behavior of the MA scenario at system level is verified using the Hybrid Hoare Logic theorem prover. Behavior constraints are specified as assertions using first-order logic formulas augmented with a simple temporal operator.

关键词： AADL behavior modeling BLESS annex ctcS hybrid annex train control system

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Influences of residual stress and micro-deformation on microstructures and mechanical properties for ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy produced by laser powder bed fusion

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Journal of Materials Science & technology 2021年第16期75卷 174-183页

作者： c.c.Zhang H.L.Wei t.t.Liu L.Y.Jiang t.Yang W.H.Liao National Joint Engineering Research center of Nc Forming technology and Equipment School of Mechanical EngineeringNanjing University of Science and TechnologyNanjing 210094China

Laser powder bed fusion(LPBF)yields unique advantages during the fabrication of titanium *** the present work,ti-6.5 Al-3.5 Mo-1.5 Zr-0.3 Si alloy specimens with excellent mechanical performances were fabricated by *** as-built specimens displayed relatively high strength and ductility under modest volume energy densities(VEDs),whereas they manifested high strength with low ductility under high *** investigate the key reason of this phenomenon,the specimens were designed with two VEDs ranges of 60 J/mm^(3) and 85 J/mm^(3).Special attention was paid to the influences of residual stress and micro-deformation on microstructures and mechanical properties for the first *** results indicated that the residual stresses and relative density of the 60 J/mm^(3) range specimens were higher than that of the 85 J/mm3 range *** multiplication and dislocation movement promoted by the residual stress were hindered by the initialα’phase grain boundary(prior-α’GB),leading to the formation ofα’metastable *** mean tensile strength and elongation of the 60 J/mm^(3) range specimens were 1248.1 MPa and 12.3%,respectively,whereas the corresponding values for the 85 J/mm^(3) range specimens were 1405.3 MPa,5.0%,*** deformation,the strength and ductility of the specimens were first improved by lamellar structures generated from prior-α’phases,and then effectively enhanced by the interaction between the{10–12}twins and ***,pores significantly reduced the ductility;hence,high VED specimens with large twins and numerous large pores increased the strength and reduce the ductility.

关键词： Laser powder bed fusion ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy Residual stress twin Mechanical properties

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A correlation between pulse diagnosis of human body and health monitoring of structures

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Earthquake Engineering and Engineering Vibration 2004年第1期3卷 117-125页

作者： c.c.chang Henry t.Y.Yang Department of civil Engineering Hong Kong University of Science and TechnologyHong Kong Department of Mechanical and Environmental EngineeringUniversity of California Department of Mechanical and Environmental Engineering University of California

the concept of health monitoring is a key aspect of the field of medicine that has been practiced for a long time. A commonly used diagnostic and health monitoring practice is pulse diagnosis, which can be traced back approximately five thousand years in the recorded history of china. With advances in the development of modern technology, the concept of health monitoring of a variety of engineering structures in several applications has begun to attract widespread attention. Of particular interest in this study is the health monitoring of civil structures. It seem natural, and even beneficial, that these two health-monitoring methods, one as applies to the human body and the other to civil structures, should be analyzed and compared. In this paper, the basic concepts and theories of the two monitoring methods are first discussed. Similarities are then summarized and commented upon. It is hoped that this correlation analysis may help provide structural engineers with some insights into the intrinsic concept of using pulse diagnosis in human health monitoring, which may of be some benefit in the development of modern structural health monitoring methods.

关键词： human health monitoring pulse diagnosis structural health monitoring vibration-based techniques local detection techniques

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