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Coal pillar mechanics of violent failure in U.S. Mines

International Journal of Mining Science and Technology 2017年第3期27卷 387-392页

作者： Maleki Hamid Maleki technologies Inc. Spokane WA 99223 USA

This paper seeks to enhance the understanding that the horizontal stresses build up and release during coal pillar loading and unloading(post-failure) drawing upon three decades of observations, geomechanical monitoring and numerical modeling in bump-prone U.S. mines. The focus is on induced horizontal stress in mine pillars and surrounding strata as highly stressed pillars punch into the roof and floor, causing shear failure and buckling of strata; under stiff stratigraphic units of some western US mines, these events could be accompanied by violent failure of pillar cores. Pillar punching eventually results in tensile stresses at the base of the pillar, facilitating transition into the post-failure regime; this transition will be nonviolent if certain conditions are met, notably the presence of interbedded mudstones with low shear strength properties and proper mine designs for controlling seismicity and dynamic loads. The study clearly shows high confining stress build-up in coal pillars resulting in up to twice higher peak vertical stress and high strain energy accumulations in some western US mines in comparison with peak stresses predicted using common empirical pillar design methods. It is the unstable release of this strain energy that can cause significant damage resulting from pillar dilation and ground movements. These forces are much greater than the capacity of most common internal support systems, resulting in horizontal stressinduced roof falls locally, in mines under unremarkable far-field horizontal stress. Attention should be placed on pillar designs as inc.easing support density may prove to be ineffective. This mechanism is analyzed using field measurements and generic finite-difference stress analyses. The study confirms the higher load carrying capacity of confinement-controlled coal seams in comparison with structurally controlled coal seams. Such significant differences in confining stresses are not taken into account when estimating peak pil

关键词： Rockburst and coal bumps Field measurements Stress analysis Mechanics Horizontal stress

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Analysis of the effect of bore centerline on projectile exit conditions in small arms

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Defence Technology（防务技术） 2022年第12期18卷 2160-2169页

作者： David Leonhardt Mark Garnich Miljenko Lucic College of Engineering University of CanterburyPrivate Bag 4800Christchurch8140New Zealand novacam technologies inc. 277 Lakeshore Road Suite#4Pointe-ClaireQuebecH9S 4L2Canada

Most finite element models of small arms focus on an idealized barrel,typically one with a perfectly straight bore *** five different experimentally measured bore centerlines,this investigation analyzes the effect centerline nonlinearity has on projectile exit *** inc.udes the effect of rotating a centerline through several *** using Abaqus/Explicit,this dynamic analysis simulates a single firing cycle for each *** jump is calculated for each model as a measure of the effects of warped *** warped centerlines have a small effect on barrel dynamics.

关键词： Finite element analysis Small arms Barrel dynamics Bore centerline

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Optimal chunk caching in network coding-based qualitative communication

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Digital Communications and Networks 2022年第1期8卷 44-50页

作者： Lijun Dong Richard Li Futurewei technologies inc. 2330 Central ExpresswaySanta Clara95050USA

Network processing in the current Internet is at the entirety of the data packet,which is problematic when encountering network *** newly proposed Internet service named Qualitative Communication changes the network processing paradigm to an even finer granularity,namely chunk level,which obsoletes many existing networking policies and schemes,especially the caching algorithms and cache replacement policies that have been extensively explored in Web Caching,Content Delivery Networks(CDN)or Information-Centric Networks(ICN).This paper outlines all the new factors that are brought by random linear network coding-based Qualitative Communication and proves the importance and necessity of considering them.A novel metric is proposed by taking these new factors into *** optimization problem is formulated to maximize the metric value of all retained chunks in the local storage of network nodes under the constraint of storage limit.A cache replacement scheme that obtains the optimal result in a recursive manner is proposed *** the help of the introduced intelligent cache replacement algorithm,the performance evaluations show remarkably reduced end-to-end latency compared to the existing schemes in various network scenarios.

关键词： Internet Qualitative communication New IP Chunk caching Random linear network coding End-to-end latency Cache replacement policy Degree of freedom Distance Packet size

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Reconfigurable intelligent surface:design the channel-a new opportunity for future wireless networks

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Digital Communications and Networks 2022年第2期8卷 87-104页

作者： Miguel Dajer Zhengxiang Ma Leonard Piazzi Narayan Prasad Xiao-Feng Qi Baoling Sheen Jin Yang Guosen Yue Wireless Access Lab Futurewei TechnologiesInc.BridgewaterNJ08807USA

In this paper,we survey state-of-the-art research outcomes in the burgeoning field of Reconfigurable Intelligent Surface(RIS),given its potential for significant performance enhancement of next-generation wireless communication networks by means of adapting a propagation *** has been placed on several aspects gating the commercial viability of future network *** summaries are provided for practical hardware design considerations and broad implications of artificial intelligence techniques,as are in-depth outlooks on the salient aspects of system models,use cases,and physical layer optimization techniques.

关键词： Reconfigurable intelligent surface MIMO Channel estimation Beamforming Reflectarray Transmitarray Machine learning Deep learning

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Key Techniques in Real Time Digital Simulation for Closed-loop Testing of HVDC Systems

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CSEE Journal of Power and Energy Systems 2017年第2期3卷 125-130页

作者： Yi Zhang Hui Ding Rick Kuffel RTDS technologies inc. WinnipegManitobaCanada

This paper introduces several key techniques in realtime digital simulation for closed-loop testing of high voltage direct current(HVDC)systems,inc.uding line commutated converter(LCC)HVDC valve group models,modular multilevel converter(MMC)HVDC models,phase domain frequency dependent transmission line models,and switchable filter *** issues such as background,algorithms,implementations,applications,and validation of these models are *** techniques represent the most advanced technology in modelling HVDC systems on a real time *** models have been implemented on the RTDS Simulator,a comprehensive real time power system digital simulation tool.

关键词： HVDC real time simulation

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Towards the development of integrated monitoring system for retreat mining operations

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Journal of Coal Science & Engineering(China) 2008年第3期14卷 477-484页

作者： HAMID Maleki Maleki technologies Inc.Spokane WA 99201USA

Through cooperative research between the government,the private sector, mining companies and equipment manufacturers,considerable progress had been made during the last decade in studying the mechanics of strata failure and acquiring the know- ledge needed to develop an integrated monitoring system for assessing local roof stability. Because of higher geotechnical risks in retreat mining operations,it was both important to develop panel layout designs that control convergence and stress and to monitor ground response during operations to verify designs and provide warning of impending stability *** detecting both localized roof stability problems and global overburden col- lapse mechanisms,the proposes an integrated panel-wide monitoring system which com- bines the capabilities of load rate monitoring of mobile roof supports (MRSs) with deforma- tion measurements using an extensive array of sensors located near the mining face and throughout the *** monitoring methods for the detection of localized roof stability problems have been evaluated on the basis of mine measurements and numerical model- ing *** are load rate monitoring of the hydraulic cylinders of mobile roof support (MRS) and re mote monitoring of roof *** of field data in retreat sections show that roof instabilities are influenced by: (1) pillar failure,(2) pillar yielding,(3) mine seismicity (bumps),(4) geologic structures,and (5) panel layout designs and practice. Pillar yielding and unloading can be conveniently monitored by the load rate monitoring device,but to detect impending localized roof falls,additional ground deformation meas- urements are needed near the mining *** inc.easing the number of deformation measurements in the entire panel,additional safeguards can be achieved for detecting overburden collapse mechanisms while continuously monitoring local roof stability close to the retreat line.

关键词： monitoring system convergence mobile roof supports

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Metal separations of interest to the Chinese metallurgical industry

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Journal of Rare Earths 2010年第S1期28卷 22-29页

作者： S.R.Izatt N.E.Izatt R.L.Bruening IBC Advanced technologies Inc.856 E.Utah Valley DriveAmerican ForkUT 84003U.S.A.

IBC Advanced technologies’ Molecular Recognition Technology(MRT) SuperLig products selectively and rapidly bind with target species enabling their selective removal from *** MRT process can produce a high purity separation product of maximum added value at a competitive *** products have high selectivity for many target species which can inc.ude metal ions,anions,and neutral *** operation,the SuperLig product is first placed in a packed column.A solution containing a mixture of the target species and other chemical species is then passed through the *** target species is removed selectively by the SuperLig product,the column is washed to remove residual feed solution,and the target species is recovered by a minimal quantity of *** result is a pure and concentrated species that can be kept for its value or disposed of *** process is environmentally and ecologically friendly with no organic solvents being *** paper provides a review of some examples of applications of MRT to separations of interest to the Chinese metallurgical *** are several applications of MRT,inc.uding Pd separations from Pt metal refinery streams and low-grade spent catalyst wastes,Rh recovery from spent auto catalyst and other feeds,Re removal from selected impurity ions,Cd removal from Co electrolyte,Bi removal from Cu electrolyte,In and Ge separations from difficult matrices,and removal of bivalent first transition series and other metal ions from acid mine drainage(Berkeley Pit,Montana).Finally,the potential application of MRT to separations involving the recovery of rare earth metals and Li from low-level waste solutions and end-of-life products is discussed.

关键词： selective and environmentally friendly metal separations molecular recognition technology SuperLig platinum group metals minor metals transition series metals rhenium cadmium indium germanium bismuth rare earth metals lithium

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Finite element analysis of chip formation and residual stresses induced by sequential cutting in side milling with microns to sub- micron uncut chip thickness and finite cutting edge radius

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Advances in Manufacturing 2015年第4期3卷 309-322页

作者： Nejah Tounsi Tahany EI-Wardany Open Manufacturing Solutions inc. Pierrefonds QC Canada United technologies Research Center East-Hartford CT US

In this paper, the effect of four sequential cuts in side milling of Ti6Al4V on chip formation and residual stresses （RS） are investigated using finite element method （FEM）. While the open literature is limited mainly to the studies of orthogonal sequential cutting with the constant uncut chip thickness greater than 0.01 mm, it is suggested herein to investigate not only the variable uncut chip thickness which characterises the down milling process, but also the uncut chip thickness in the sub-micron range using a finite cutting edge radius. For the resulting ductile machining regime, the characteristics of the chip mor- phology, the force profiles, the plastic deformation and temperature distributions have been analyzed. Furthermore, this study revealed that the RS should be extracted toward the area where the insert exits the workpiece in the FE simulation of the down-milling process. The simulation of a number of sequential cuts due to the consecutive engagements of the insert is required in order to capture the gradual accumulation of the RS before reaching an asymptotic convergence of the RS profile. The predicted RS are in reasonable agreement with the experimental results.

关键词： Finite element method (FEM) Down milling - Sequential cuts Ductile machining regime Chip formation Residual stresses (RS)

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A photolysis coefficient for characterizing the response of aqueous constituents to photolysis

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Frontiers of Environmental Science & Engineering 2016年第3期10卷 428-437页

作者： David R. HOKANSON Ke LI R. Rhodes TRUSSELL Trussell technologies Inc. Pasadena CA 91101 USA College of Engineering University of Georgia Athens GA 30602 USA

UV photolysis and UV based advanced oxidation processes （AOPs） are gaining more and more attention for drinking water treatment. Quantum yield （Ф） and molar absorption coefficient （ε） are the two critical parameters measuring the effectiveness of photolysis of a compound. The product of the two was proposed as a fundamental measure of a constituent＇s amenability to transformation by photolysis. It was shown that this product, named the photolysis coefficient, kp, can be determined using standard bench tests and captures the properties that govern a constituent＇s transformation when exposed to light. The development showed the photolysis coefficient to be equally useful for microbiological, inorganic and organic constituents. Values of kp calculated by the authors based on quantum yield and molar absorption coefficient data from the literature were summarized. Photolysis coefficients among microorganisms ranged from 8500 to more than 600000 and are far higher than for inorganic and organic compounds, which varied over a range of approximately 10 to 1000 and are much less sensitive to UV photolysis than the microorganisms.

关键词： UV photolysis disinfection advanced oxidation N-nitrosodimethylamine quantum yield absorption coefficient

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Separation of Basic Drugs Using Pressurized Capillary Electrochromatography

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Chinese Journal of Chemistry 2003年第4期21卷 419-422页

作者：张锴阎超姚传义江正瑾张智超王琴孙高如瑜 State Key Laboratory of Elemento Organic Chemistry Nankai University Unimicro technologies inc. 4713 First Street Pleasanton

A novel pressurized capillary electrochromatography (PCEC) was developed to separate basic drugs on strong cation exchange (SCX) column. The separation result by using PCEC was better than that by using micro-HPLC. The effects of electrical field and pressure on plate height and resolution were investigated. Influences of organic modifier, ionic strength and pH value of buffer on retention behavior were evaluated, and the separation mechanism was also discussed.

关键词： pressurized capillary electrochromatography strong cation exchange mixed mode basic drug

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