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Unanticipated multiple seam stresses from pillar systems behaving as pseudo gob–case histories

International Journal of Mining Science and Technology 2017年第1期27卷 131-137页

作者： Gauna michael Mark Christopher Pittsburgh Safety and Health Technology Center Mine Safety and Health Administration(MSHA)PittsburghPA 15236USA

Underground coal mining in the U.S. is conducted in numerous regions where previous workings exist above and/or below an actively mined seam. Miners know that overlying or underlying fully extracted coal areas, also known as gob regions, can result in abutment stresses that affect the active mining. If there was no full extraction, and the past mining consists entirely of intact pillars, the stresses on the active seam are usually minimal. However, experience has shown that in some situations there has been sufficient yielding in overlying or underlying pillar systems to cause stress transfer to the adjoining larger pillars or barriers, which in turn, transfer significant stresses onto the workings of the active seam. In other words, the overlying or underlying pillar system behaves as a ‘‘pseudo gob." The presence of a pseudo gob is often unexpected, and the consequences can be severe. This paper presents several case histories, summarized briefly below, that illustrate pseudo gob phenomenon:(1) pillar rib degradation at a West Virginia mine at 335 m depth that contributed to a rib roll fatality,(2) pillar rib deterioration at a Western Kentucky mine at 175 m depth that required pillar size adjustment and installation of supplemental bolting,(3) roof deterioration at an eastern Kentucky mine at 400 m depth that stopped mine advance and required redirecting the section development,(4) coal burst on development at an eastern Kentucky mine at 520 m depth that had no nearby pillar recovery, and(5) coal burst on development at a West Virginia mine at the relatively shallow depth of 335 m that also had no nearby pillar recovery. The paper provides guidance so that when an operation encounters a potential pseudo gob stress interaction the hazard can be mitigated based on an understanding of the mechanism encountered.

关键词： Underground mining Coal Multiple seam Gob Ground control

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Two-phase micro-and macro-time scales in particle-laden turbulent channel flows

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Acta Mechanica Sinica 2012年第3期28卷 595-604页

作者： Bing Wang michael Manhart School of Aerospace Tsinghua University100084 BeijingChina Fachgebiet Hydromechanik Technische Universitait MiinchenD-80290 MfinchenGermany

The micro- and macro-time scales in two-phase turbulent channel flows are investigated using the direct nu- merical simulation and the Lagrangian particle trajectory methods for the fluid- and the particle-phases, respectively. Lagrangian and Eulerian time scales of both phases are cal- culated using velocity correlation functions. Due to flow anisotropy, micro-time scales are not the same with the theo- retical estimations in large Reynolds number （isotropic） tur- bulence. Lagrangian macro-time scales of particle-phase and of fluid-phase seen by particles are both dependent on particle Stokes number. The fluid-phase Lagrangian inte- gral time scales increase with distance from the wall, longer than those time scales seen by particles. The Eulerian inte- gral macro-time scales increase in near-wall regions but de- crease in out-layer regions. The moving Eulerian time scales are also investigated and compared with Lagrangian integral time scales, and in good agreement with previous measure- ments and numerical predictions. For the fluid particles the micro Eulerian time scales are longer than the Lagrangian ones in the near wall regions, while away from the walls the micro Lagrangian time scales are longer. The Lagrangian integral time scales are longer than the Eulerian ones. The results are useful for further understanding two-phase flow physics and especially for constructing accurate prediction models of inertial particle dispersion.

关键词： Micro-time scale Lagrangian integral timescale ~ Moving Eulerian time scale Particle-laden turbulentflow ~ Particle Stokes number Direct numerical simulation(DNS) Lagrangian trajectory method

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3DIVE：An Immersive Environment for Interactive Volume Data Exploration

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Journal of Computer Science & Technology 2003年第1期18卷 41-47页

作者： michael Boyles 方晓芬 Advanced Visualization Laboratory Indiana University Indianapolis IN 46202 USA723 W. Michigan St. SL 280 Indianapolis IN 46202 USA Department of Computer and Information Science Indiana University Purdue University Indianapolis 723 W. Michigan St. SL 280 Indianapolis IN 46202 USA

This paper describes an immersive system, called 3DIVE, for interactive volume data visualization and exploration inside the CAVE virtual environment. Combining interactive volume rendering and virtual reality provides a natural immersive environment for volumetric data visualization. More advanced data exploration operations, such as object level data manipulation,simulation and analysis, are supported in 3DIVE by several new techniques. In particular, volume primitives and texture regions are used for the rendering, manipulation, and collision detection of volumetric objects; and the region-based rendering pipeline is integrated with 3D image filters to provide an image-based mechanism for interactive transfer function design. The system has been recently released as public domain software for CAVE/ImmersaDesk users, and is currently being actively used by various scientific and biomedical visualization projects.

关键词： volume visualization immersive environment volume rendering 3D texturemapping

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Two-phase air-water flows: Scale effects in physical modeling

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Journal of Hydrodynamics 2014年第2期26卷 291-298页

作者： PFISTER michael CHANSON Hubert Ecole Polytechnique Fédérale de Lausanne (EPFL) Laboratory of Hydraulic Constructions (LCH) The University of Queensland School of Civil Engineering

Physical modeling represents probably the oldest design tool in hydraulic engineering together with analytical approaches. In free surface flows, the similitude based upon a Froude similarity allows for a correct representation of the dominant forces, namely gravity and inertia. As a result fluid flow properties such as the capillary forces and the viscous forces might be incorrectly reproduced, affecting the air entrainment and transport capacity of a high-speed model flow. Small physical models operating under a Froude similitude systematically underestimate the air entrainment rate and air-water interfacial properties. To limit scale effects, minimal values of Reynolds or Weber number have to be respected. The present article summarizes the physical background of such limitations and their combination in terms of the Morton number. Based upon a literature review, the existing limits are presented and discussed, resulting in a series of more conservative recommendations in terms of air concentration scaling. For other air-water flow parameters, the selection of the criteria to assess scale effects is critical because some parameters （e.g., bubble sizes, turbulent scales） can be affected by scale effects, even in relatively large laboratory models.

关键词： air entrainment hydraulic structures physical modeling scale effects two-phase flow Morton number

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Inflammation and liver tumorigenesis

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Frontiers of Medicine 2013年第2期7卷 242-254页

作者： Beicheng Sun michael Karin Liver Transplantation Center of the First Affiliated Hospital and Cancer Center Nanjing Medical UniversityNanjing 210029China Laboratory of Gene Regulation and Signal Transduction Department of Pharmacology and PathologyCancer CenterUCSD School of MedicineLa JollaCA 92093-0723USA

Inflammation has been considered as one of the hallmarks of cancer,and chronic hepatitis is a major cause of liver *** review will focus on the pathogenic role of inflammation in hepatocarcinogenesis and will discuss recent advances in understanding the chronic hepatitis-liver cancer link based on hot spots in liver cancer research,including cellular interaction,cytokines,microRNA and stem *** of these mechanisms should be taken into consideration because they are crucial for the development of more efficacious therapeutic strategies for preventing and treating human chronic hepatitis and hepatocellular carcinoma.

关键词： hepatocellular carcinoma hepatitis cytokine stem cell miRNA

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INFLUENCE OF PHASE RATIO ON PACKING EFFICIENCY IN COLUMNS FOR MASS TRANSFER PROCESSES

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Chinese Journal of Chemical Engineering 1997年第2期5卷 25-34页

作者： Reinhard Billet michael Schultes Institute of Thermo-and Fluid-dynamics Ruhr-University BochumInstitute of Thermo-and Fluid-dynamicsRuhr-University Bochum D-44780 BochumGermanyD-44780 BochumGermany

The phase ratio has been found to affect the packing efficiency in packed *** ac-count for the effect,a model is set up to correlate the height of a mass transfer unit with the phaseratio with reasonable *** also is a correlation that allows to predict the efficiency inquestion at any given liquid-gas ratio using the knowledge of other efficiency values at other liquid-gas ratios.

关键词： phase ratio height of a transfer unit packings

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Concept modeling of tapered thin-walled tubes

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第1期10卷 44-53页

作者： michael L.DAY Department of Mechanical Engineering University of Louisville

This paper presents a method to create concept models for the tapered thin-walled tubes using beam elements and spring *** concept tapered beam models with different taper angles and cross sections are compared with those detailed models through impact *** crash results are recorded and compared,and the relatively good agreement is achieved between these *** modeling steps are illustrated in detail,and a general concept modeling method for such thin-walled tubes is summarized and presented.

关键词： Tapered tube Concept model Axial crushing Impact analysis Beam element Spring element

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A two dimensional Euler-Lagrangian model of wood gasification in a charcoal bed-Part II： Parameter influence and comparison

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Particuology 2017年第6期15卷 22-30页

作者： Stephan Gerber michael Oevermann Freie Universitat Berlin Arnimallee 6 14195 Berlin Germany Chalmers University of Technology Department of Applied Mechanics Division of Combustion Gothenburg Sweden

A Euler-Lagrangian simulation was employed for a comprehensive parameter study of wood gasification in a fluidized charcoal bed. The parameters that were varied include the initial bed temperature, fuel mass flow rate, inert tar fraction, and kinetic energy losses caused by particle-particle and particle-wall colli- sions. The results of each parameter variation are compared with a base scenario, previously described in detail in Part I of this study （Gerber ＆ Oevermann, 2014）. The results are interpreted by comparing the reactor outlet temperature, averaged particle temperature, overall wood mass, overall charcoal mass, concentrations of several gaseous species, and axial barycenter data for particles obtained with differ- ent sets of parameters. The inert tar fraction and fuel mass flow rate are the most sensitive parameter, while the particle-particle and particle-wall contact parameters have only a small impact on the results. Increasing the reactive tar components by 19% almost doubled the amount of reactive tars at the reac- tor outlet, while decreasing the restitution coefficients of the particle collisions by 0.2 results in higher overall gas production but almost no change in bed height. Herein, our numerical results are discussed in detail while assessing the model restrictions.

关键词： Wood gasification simulation Gas-solid flow Discrete element method Pyrolysis Gasification Charcoal

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Deep learning-driven interval uncertainty propagation for aeronautical structures

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Chinese Journal of Aeronautics 2024年第12期37卷 71-86页

作者： Yan SHI michael BEER Institute for Risk and Reliability Leibniz Universitat HannoverHannover 30167Germany Department of Civil and Environmental Engineering University of LiverpoolLiverpool L693BXUnited Kingdom International Joint Research Center for Resilient Infrastructure&International Joint Research Center for Engineering Reliability and Stochastic Mechanics Tongji UniversityShanghai 200092China

Interval Uncertainty Propagation(IUP)holds significant importance in quantifying uncertainties in structural outputs when confronted with interval input *** the aviation field,the precise determination of probability models for input parameters of aeronautical structures entails substantial costs in both time and *** an alternative,the use of interval variables to describe input parameter uncertainty becomes a pragmatic *** complex task of solving the IUP for aeronautical structures,particularly in scenarios marked by pronounced nonlinearity and multiple outputs,necessitates innovative *** study introduces an efficient deep learning-driven approach to address the challenges associated with *** proposed approach combines the Deep Neural Network(DNN)with intelligent optimization algorithms for dealing with the IUP in aeronautical *** inventive extremal value-oriented weighting technique is presented,assigning varying weights to different training samples within the loss function,thereby enhancing the computational accuracy of the DNN in predicting extremal values of structural ***,an adaptive framework is established to strategically balance the global exploration and local exploitation capabilities of the DNN,resulting in a predictive model that is both robust and *** illustrate the effectiveness of the developed approach,various applications are explored,including a high-dimensional numerical example and two aeronautical *** obtained results highlight the high computational accuracy and efficiency achieved by the proposed approach,showcasing its potential for addressing complex IUP challenges in aeronautical engineering.

关键词： Uncertainty propagation Interval variable Deep learning Optimization algorithm Aeronautical structure

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Preventing roof fall fatalities during pillar recovery:A ground control success story

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International Journal of Mining Science and Technology 2017年第1期27卷 107-113页

作者： Mark Christopher Gauna michael MSHA Pittsburgh Safety and Health Technology CenterPittsburghPA 15236USA

For decades, pillar recovery accounted for a quarter of all roof fall fatalities in underground coal *** showed that a miner on a pillar recovery section was at least three times more likely to be killed by a roof fall than other coal miners. Since 2007, however, there has been just one fatal roof fall on a pillar line. This paper describes the process that resulted in this historic achievement. It covers both the key research findings and the ways in which those insights, beginning in the early 2000 s, were implemented in mining practice. One key finding was that safe pillar recovery requires both global and local *** stability is addressed primarily through proper pillar design, and became a major focus after the2007 Crandall Canyon mine disaster. But the most significant improvements resulted from detailed studies that showed that local stability, defined as roof control in the immediate work area, could be achieved with three interventions:(1) leaving an engineered final stump, rather than extracting the entire pillar,(2) enhancing roof bolt support, particularly in intersections, and(3) increasing the use of mobile roof supports(MRS). A final component was an emphasis on better management of pillar recovery *** included a focus on worker positioning, as well as on the pillar and lift sequences, MRS operations,and hazard identification. As retreat mines have incorporated these elements into their roof control plans,it has become clear that pillar recovery is not ‘‘inherently unsafe." The paper concludes with a discussion of the challenges that remain, including the problems of rib falls and coal bursts.

关键词： Retreat mining Roof support Room-and-pillar Ground control

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