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Prevention of.gob ignitions and explosions in longwall mining using dynamic seals

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International journal of.Mining Science and Technology 2017年第6期27卷 999-1003页

作者： Brune jürgen f. Saki Saqib A. Department of.Mining Engineering Colorado School of Mines CO 80401 USA Aldea Services LLC Frederick MD 21704 USA

Most, if.not all longwall gob areas accumulate explosive methane-air mixtures that pose a deadly hazard to miners. Numerous mine explosions have originated f.om explosive gas zones(EGZs) in the longwall gob. Since 2010, researchers at the Colorado School of.Mines(CSM) have studied EGZ f.rmation in longwall gobs under two long-term research projects f.nded by the National Institute f.r Occupational Saf.ty and Health. Researchers used computational f.uid dynamics along with in-mine measurements. f.r the f.rst time, they demonstrated that EGZs f.rm along the f.inge areas between the methane-rich atmospheres and the f.esh air ventilated areas along the working f.ce and present an explosion and f.re hazard to mine workers. In this study, researchers f.und that, f.r progressively sealed gobs, a targeted injection of.nitrogen f.om the headgate and tailgate, along with a back return ventilation arrangement, will create a dynamic seal of.nitrogen that ef.ectively separates the methane zone f.om the f.ce air and eliminates the EGZs to prevent explosions. Using this f.rm of.nitrogen injection to create dynamic seals should be a consideration f.r all longwall operators.

关键词： Mine explosions f.ce ignitions Coal mining Longwall mining Methane

Interf.cial ef.ects in electromagnetic coupling within piezoelectric phononic crystals

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Acta Mechanica Sinica 2009年第1期25卷 95-99页

作者： f. j. Sabina A.B.Movchan Instituto de Investigaciones en Matematicas Aplicadas yen Sistemas Universidad Nacional Autónoma de México Department of.Mathematical Sciences University of Liverpool

In this paper, we discuss waves in piezoelectric periodic composite, with the emphasis on the connection between the electromechanical coupling and the ef.ects of.dispersion of.Bloch-f.oquet waves. A particular attention is given to structures containing interf.ces between dissimilar media and localization of.the electrical f.elds near such interf.ces.

关键词： Piezoelectric periodic composites Interf.ces Dispersion of.Bloch-f.oquet waves

An SBf.M-Based Model f.r Hydraulic f.acturing in Quasi-Brittle Materials

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Acta Mechanica Solida Sinica 2018年第4期31卷 416-432页

作者： f. Yao Z.j. Yang Y.j. Hu College of.Civil Engineering and architecture Zhejiang University Hangzhou 310058 China School of.Civil Engineering Shaoxing University Shaoxing 312000 China

A numerical model based on the scaled boundary f.nite element method is devel- oped to simulate the hydraulic f.acturing in concrete-like quasi-brittle materials using cohesive interf.ce elements. The shadow domain method developed previously （Yang and Deeks in Eng f.act Mech 143（4）：333 354, 2007） is extended to consider crack-width-dependent hydraulic pres- sure and cohesive traction, so that the stress intensity f.ctors caused by both crack-f.ce f.rces are semi-analytically calculated separately in the same way. The crack propagation is determined by the criterion of.KI ≥ 0, and the propagation direction by the linear elastic f.acture mechanics criteria. Two examples of.concrete structures are modeled, and the results are in good agreement with the experimental data and others numerical results.

关键词： Scaled boundary f.nite element method Hydraulic f.acture Cohesive crackmodel Crack propagation

A Crystallization Study of.Nanocrystalline PZT 53/47 Granular arrays Using a Sol-Gel Based Precursor

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journal of.Materials Science & Technology 2011年第6期27卷 489-496页

作者： A.Surez-Gómez j.M.Saniger-Blesa f.Calderón-Pinar CCADET-Universidad Nacional Autónoma de México Cd.UniversitariaCirc.Exterior s/nA.P.70-186Coyoacn 04510México D.F.México Laboratorio de Ingeniería Electroquímica Facultad de QuímicaUniversidad Nacional Autónoma de MéxicoCd.UniversitariaCoyoacn 04510México D.F.México f.cultad de f.sica/IMRE San Lzaro y LUniversidad de la Habana

In this work,we intend to perf.rm a detailed study on the crystallization process of.PZT 53/47 nanostructured powders by starting out with an amorphous precursor synthesized by a sol-gel based *** interests also lie in the f.asibility f.r controlling the average grain size of.the f.nal structure in the submicron range on an ab initio ***,f.urier transf.rm inf.ared spectroscopy（f.-IR）,Raman（Stokes and Anti-Stokes）,X-ray dif.raction（XRD） and scanning electron microscopy（SEM） are used to examine the microstructural characteristics based on previously reported dif.erential thermal analysis/thermal gravimetric analysis（DTA/TGA） *** results show a crystallization temperature of.800℃ to attain pure perovskite phase with excellent morphological quality,average grain size 〈DG〉〈 300 nm and with average crystallite size 〈DC〉〈15 nm.

关键词： Powders-chemical preparation PZT synthesis Sol-gel precursors Microstructure- f.nal Vibrational spectroscopies X-ray dif.raction

Oxidation and Coatings f.r Power Generation： New Super Ultra Critical Steam Turbines

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中国腐蚀与防护学报 2009年第4期29卷 318-319页

作者： f. j. PEREZ Grupo de Investigacion de Ingenieria de Superf.cies y Materiales Nanoestructurados U. C. M. N°910627 f.cultad de Ciencias Quimicas Universidad Complutense de Madrid. 28040 Madrid Spain

The steels with chromium contents between 9%and 12%wt are used f.r power plants with advanced steam oxidation *** present good creep properties as 9%Cr steels and good oxidation resistance,at the temperatures range between 500℃～600℃.In the last years numerous investigation in development of.coatings has been realized with the aim the protected them against the oxidation in order to allow operation of.steam turbines at 650℃.In this study,Al-Hf.protective coatings were deposited by CVD-f.R on f.rritic steel HCM-12A f.llowed by a dif.usion heat treatment,have shown to be protective at 650℃under steam f.r at least 3000 hours of.laboratory steam exposure under atmospheric *** and composition of.coatings were characterized by dif.erent techniques, such as scanning electron microscopy(SEM),electron probe microanalysis,and X-ray dif.raction(XRD). On the other hand,volatile species by mass spectrometry(MS) and thermogravimetric measurements (TG) during the initial stages oxidation of.the P92 f.rritic steel without and of.Al and Al/Si coating by chemical vapour deposition in f.uidized bed reactors(CVD-f.R) at 650℃in ar+20%H_2O f.r 150 h were *** order to go f.rward to coatings design the Thermocalc code is used as base f.r the MSdata. TG-MS experiments were conducted in a closed steam loop in order to obtain inf.rmation about the oxyhydroxides f.rmation as reaction between coatings and *** those results the role of.the dif.erent coating element could be established and optimized f.r the coating *** oxidation mechanism based on the TG-MS results is *** morphology/composition and structure of.the oxidized samples were also studied using SEM/EDS and XRD techniques.

关键词：氧化金属腐蚀防护

CORROSION PROTECTION Of.Al CATHODES IN ZINC ELECTROLYSIS

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Acta Metallurgica Sinica(English Letters) 1999年第3期12卷 221-228页

作者： Lu, f. Van Ooij, W.j. Beijing Inst of.Aeronautical Materials Beijing China

A new pretreatment or a coating f.r Al was developed and tested to protect the Al ef.ectively f.om corrosion when it was connected to pure zinc at electroplating potential and exposed to an acidic sulf.te solution. It was f.und out that (1) Al alloy purity and electroplating potential have a large ef.ect on galvanic corrosion between Zn-Al couples; (2) BTSE silane pretreatment and polyurethane coating have better perf.rmance in corrosion protection, which are evaluated by EIS, salt spray test and immersion test f.r Al cathodes in Zinc electrolyte; (3) BTSE treatment or BTSE plus polyurethane coating has the best anti-corrosion perf.rmance and can protect the Al cathode ef.ectively in zinc electrolysis.

关键词： Aluminum Electrolysis

The song remains the same： juvenile Richardson＇s ground squirrels do not respond dif.erentially to mother＇s or colony member＇s alarm calls

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Current Zoology 2012年第5期58卷 773-780页

作者： james f. HarE Kurtis j. WarKENTIN Department of.Biological Sciences University of Manitoba Winnipeg MB Canada R3T 2N2 Department of.Zoology Brandon University Brandon MB R7A 6A9

Alarm calls are emitted by Richardson＇s ground squirrels Urocitellus richardsonii in response to avian and terrestrial predators. Conspecif.cs detecting these calls respond with increased vigilance, promoting predator detection and evasion, but in doing so, lose time f.om f.raging. That loss can be minimized if.alarm call recipients discriminate among signalers, and weight their response accordingly. f.r juvenile ground squirrels, we predicted that the trade-of. between f.raging and vigilance could be optimized via selective response to alarm calls emitted by their own dam, and/or neighboring colony members over calls broad- cast by less f.miliar conspecif.cs. Alarm calls of.adult f.male Richardson＇s ground squirrels were elicited in the f.eld using a predator model and recorded on digital audio tape. f.ee-living f.cal juveniles were subjected to playbacks of.a call of.their mother, and on a separate occasion a call f.om either another adult f.male f.om their own colony, or an adult f.male f.om another colony. Neither immediate postural responses and escape behavior, nor the duration of.vigilance manif.sted by juveniles dif.ered with exposure to alarm calls of.the three adult f.male signaler types. Thus, juveniles did not respond pref.rentially to alarm calls emitted by their mothers or colony members, likely ref.ecting the high cost of.ignoring alarm signals where receivers have had limited opportunity to establish past signaler reliability [Current Zoology 58 （5）： 773-780, 2012].

关键词： Alarm Signal Communication Maternal Call Recognition Signal Reliability Ground Squirrel Social Discrimination

f.rmation and Microstructural Characterization of.Silicon-modif.ed Aluminide Coating on Nickel-based Superalloy IN738LC

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材料热处理学报 2004年第05B期25卷 657-660页

作者： f. Shahriari f. Ashraf.zadeh A. Monshi Materials engineering department Isfahan University of Technology Isfahan IranMaterials engineering department Isfahan University of Technology Isfahan IranMaterials engineering department Isfahan University of Technology Isfahan Iran

In this investigation, aluminide coatings used to protect industrial components at high temperature and corrosive environments were modif.ed with silicon addition and the microstructural f.atures and f.rmation mechanism were evaluated. The coating on the nickel-based superalloy IN738LC was carried out by a two stage process including siliconizing at f.rst and aluminizing thereaf.er. Pack cementation siliconizing perf.rmed at 950C f.r 2, 4 and 6 hours in several powder mixtures of.Si, A12O3 and NHiCl, then aluminum was dif.used into the surf.ce of.the specimens by an industrial aluminizing process. The modif.ed coatings were characterized by means of.standard metallography, scanning electron microscopy, energy dispersive spectroscopy and X-ray dif.raction methods. The results show that Si in the coatings mainly presents in the f.rm of.secondary phases including Cr3Si, Mo5Si3 and Nii6Ti6Si7, well distributed within the NiAl matrix. The advantages of.this two stage modif.ed coating is discussed.

关键词：显微结构 IN738LC 镍超级合金扩散渗碳处理生长机制

Magnetic Behaviour of.Sm2Co7/f./Sm2 Co7, Nanocomposite Trilayers with Cr and Ti Additions

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Chinese Physics Letters 2009年第3期26卷 255-257页

作者： f. Shahzad S. A. Siddiqi j. Zhou Advaaced Light Source Berkeley Lab University of California Berkeley CA 94720 USA Centre f.r Solid State Physics University of the Punjab Lahore-54590 Pakistan Department of.Physics University of California Berkeley California 94720 USA

Trilayered Sm2Co7/f./Sm2Co7 spring exchange magnets are f.bricated by dc magnetron sputtering on MgO substrates. Very thin layers （0.3-0.7 nm） of.Cr and Ti are added at the interf.ces of.the two magnetic phases. The thickness of.StucCo7 is kept at 20nm and f. at 6nm while the thickness of.Cr and Ti are varied as 0.3, 0.5, and 0.7nm. The base pressure of.sputtering chamber is kept below 10^-7 Torr and ar pressure at 3-8m Torr. The samples are characterized by x-ray dif.raction （XRD） and SQUID magnetometer. We report improvement in exchange coupling of.nonacomposite magnets by addition of.thin layers of.Cr at interf.ces.

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