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Tessellations in GIS:Part I—putting it all together

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Geo-Spatial Information Science 2016年第1期19卷 9-25页

作者： christopher Gold Faculty of Computing Engineering and ScienceUniversity of South WalesWalesUK Faculty of Geosciences and Environmental Engineering Southwest Jiaotong UniversityChengduChina State Key Laboratory of Information Engineering in Surveying Mapping and Remote Sensing(LIESMARS)Wuhan UniversityWuhanChina

This article attempts to describe the role of tessellated models of space within the discipline of geographic information systems(GIS)—a speciality coming largely out of geography and land surveying,where there was a strong need to represent information about the land’s surface within a computer system rather than on the original paper *** look at some of the basic operations in GIS,including dynamic and kinetic *** examine issues of topology and data structures and produce a tessellation model that may be widely applied both to traditional“object”and“field”data *** on this framework,it can be argued that tessellation models are fundamental to our understanding and processing of geographical space,and provide a coherent framework for understanding the“space”in which we *** first article examines static structures,and a subsequent article looks at“change”—what happens when things move.

关键词： GIS tessellation model static structure topology data structure object and field Voronoi diagram

Science of empirical design in mining ground control

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International Journal of Mining Science and Technology 2016年第3期26卷 461-470页

作者： Mark christopher MSHA Pittsburgh Safety & Health Technology Center

Many problems in rock engineering are limited by our imperfect knowledge of the material properties and failure mechanics of rock masses. Mining problems are somewhat unique, however, in that plenty of real world experience is generally available and can be turned into valuable experimental *** pillar that is developed, or stope that is mined, represents a full-scale test of a rock mechanics design. By harvesting these data, and then using the appropriate statistical techniques to interpret them,mining engineers have developed powerful design techniques that are widely used around the *** empirical methods are readily accepted because they are simple, transparent, practical, and firmly tethered to reality. The author has been intimately associated with empirical design for his entire career, but his previous publications have described the application of individual techniques to specific problems. The focus of this paper is the process used to develop a successful empirical method. A sixstage process is described: identification of the problem, and of the end users of the final product; development of a conceptual rock mechanics model, and identification of the key parameters in that model;identification of measures for each of the key parameters, and the development of new measures(such as rating scales) where necessary; data sources and data collection; statistical analysis; and packaging of the final product. Each of these stages has its own potential rewards and pitfalls, which will be illustrated by incidents from the author's own experience. The ultimate goal of this paper is to provide a new and deeper appreciation for empirical techniques, as well as some guidelines and opportunities for future developers.

关键词： Design Pillar Stope Empirical Statistics Modeling

With the wizard of the unit circle-An appreciation of ***

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Journal of Hydrodynamics 2019年第6期31卷 1085-1088页

作者： christopher Earls Brennen Richard and Dorothy Hayman Professor of Mechanical Engineering EmeritusCalifornia Institute of TechnologyPasadenaCalifornia 91125

An account of my interactions with *** Yao-tsu Wu of the California Institute of Technology.

关键词： Caltech fluid mechanics cavitation

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

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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

Biological and cultural diversity in the context of botanic garden conservation strategies

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Plant Diversity 2017年第6期39卷 396-401页

作者： christopher P.Dunn Cornell Botanic Gardens 124 Comstock Knoll Drive Cornell University

Impacts of global climate change, habitat loss, and other environmental changes on the world's biota and peoples continue to increase, especially on islands and in high elevation areas. Just as floristic diversity is affected by environmental change, so too are cultural and linguistic diversity. Of the approximately 7000 extant languages in the world, fully 50% are considered to be at risk of extinction, which is considerably higher than most estimates of extinction risks to plants and animals. To maintain the integrity of plant life, it is not enough for botanic gardens to consider solely the effects of environmental change on plants within the context of major conservation strategies such as the Global Strategy for Plant Conservation and the Convention on Biological Diversity. Rather, botanic gardens should actively engage in understanding and communicating the broader impacts of environmental change to biological and cultural diversity.

关键词： Biocultural diversity Botanic gardens Linguistic diversity Plant diversity

Atomic layer deposition: Catalytic preparation and modification technique for the next generation

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Chinese Journal of Catalysis 2019年第9期40卷 1311-1323页

作者： Hongbo Zhang christopher L. Marshall School of Materials Science and Engineering & National Institute for Advanced Materials Nankai UniversityTianjin 300350China Chemical Sciences and Engineering Division Argonne National Laboratory9700 South Cass AvenueLemontIL60439USA

Atomic layer deposition(ALD)attracts great attention nowadays due to its ability for designing and modifying catalytic systems at the molecular *** are several reported review papers published recently discussing this technique in ***,the mechanism on how the deposited materials improve the catalyst stability and tune the reaction selectivity is still ***,catalytic systems created via ALD on stepwise preparation and/or modification under self-limiting reaction conditions are *** effects of deposited materials in terms of electronic/geometry modification over the catalytic nanoparticles(NPs)are *** effects explain the mechanism of the catalytic stability improvement and the selectivity *** unique properties of ALD for designing new catalytic systems are further investigated for building up photocatalytic reaction nanobowls,tandem catalyst and bi-active-component metallic catalytic systems.

关键词： Atomic layer deposition Catalyst modification Catalyst preparation Redox properties Terrace site Step site

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

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航空动力学报 2007年第5期22卷 683-693页

作者： christopher Long Peter Childs TFMRC Department of Engineering and Design University of Sussex Brighton BN1 9QT UK

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig. Measurements of heat transfer from the discs and tangential velocities are presented. The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine. Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air. Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows (Reφup to 5×106 and ReΦup to 2×105).Two different builds have been tested. The most significant difference between these two build configurations is the size of the annular gap between the (non-rotating) drive shaft and the bores of the discs. The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method. The velocity measurements were made using a two component, LDA system. The heat transfer results from the discs show differences between the two builds. This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity. There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig. For the narrow annular gap, there is an increase of non-dimensional tangential velocity Vφ/Ωr with radial location to solid body rotation Vφ/Ωr=*** the wider annular gap, the non-dimensional velocities show a decrease with radial location to solid body rotation.

关键词：轴向直流热转移旋转式孔进口接头

Development process for a higher capacity Propsetter~ system

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International Journal of Mining Science and Technology 2018年第1期28卷 121-126页

作者： christopher J.Brown Product Development-Strata Worldwide LLC

As longwall tailgate support technologies continue to be developed and improved, strata worldwide has worked to design and manufacture a revised Propsetter to provide additional support capacity and enable applications at greater mine *** support is targeted for tailgate applications, however, it can also be utilized for roof support in various types of mining *** paper describes the design changes for enhancing the support capacity of the Propsetter to more closely align its performance with other support technologies currently being employed in longwall *** changes to each design aspect of the Propsetter was key to successfully improving the roof support's load capacity while maintaining controlled *** the load capacity would allow a mine to improve support efficiency with a smaller, less intrusive support compared to support alternatives and reduce the cost per foot of supported *** target support capacity was 711–890 k N at 50 mm of deformation to more closely match the performance of competing tailgate supports such as the 610 mm-diameter CAN~.To achieve this goal, changes were made to all design aspects of the Propsetter: diameter, wedge cut depth and angle, pod size, and confinement *** results from the NIOSH Mine Roof Simulator verified that these design changes were successful in increasing the capacity of the Propsetter to the 711–890 k N range at fifty mms of deformation.

关键词： Propsetter Can Longwall mining Tailgate roof support Controlled deformation

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