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Mechanical behaviors of deep pillar sandwiched between strong and weak layers

Journal of Rock Mechanics and Geotechnical Engineering 2023年第5期15卷 1111-1126页

作者： Sahendra Ram Petr Waclawik Jan Nemcik radovan kukutsch Ashok Kumar Arun Kumar Singh Libin Gong Department of Mining Engineering National Institute of TechnologyRourkelaOdishaIndia Institute of Geonics The Czech Academy of SciencesOstravaCzech Republic University of Wollongong WollongongAustralia CSIR-Central Institute of Mining and Fuel Research DhanbadJharkhandIndia Department of Mining Engineering Indian Institute of Technology(Indian School of Mines)DhanbadJharkhandIndia

A variety of coal room and pillar mining methods have been efficiently practiced at depths of up to 500 m with least strata mechanics ***,for the first time,this method was trialled at depths of 850 e900 m in CSM mine of Czech *** rhomboid-shaped coal pillars with acute corners of 70,surrounded with 5.2 m wide and 3.5e4.5 m high mine roadways,were *** were developed in a staggered manner with their size variation in the Panel II from 83 m×25 m to 24 m×20 m(corner to corner)and Panel V from 35 m×30 m to 26 m×16 *** seam inclined at 12was affected by the unusual slippery slickenside roof bands and sometimes in the floor levels with high vertical stress below strong and massive sandstone *** order to ensure safety,pillars in both the panels were continuously monitored using various geotechnical instruments measuring the induced stresses,side spalling and roof *** panels suffered high amounts of mining induced stress and pillar failure with side-spalling up to 5 m from all *** fracturing of coal pillar sides was controlled by fully encapsulated steel *** induced stress kept increasing with the progress of development of pillars and *** installed in the pillar failed to monitor actual induced stress due to fracturing of coal mass around it which created an apprehension of pillar failure up to its core due to high vertical mining induced *** risk was reduced by carrying out scientific studies including the three-dimensional numerical models calibrated with data from the instrumented *** attempt has been made to study the behavior of coal pillars and their yielding characteristics at deeper cover based on field and simulation results.

关键词： Pillar yielding mechanisms Great depth Numerical modeling Induced stress Pillar dilation Slippery slickenside layer

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Oxidized organic molecules in the tropical free troposphere over Amazonia

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National Science Review 2024年第1期11卷 174-184页

作者： Qiaozhi Zha Diego Aliaga radovan Krejci Victoria A.Sinclair Cheng Wu Giancarlo Ciarelli Wiebke Scholz Liine Heikkinen Eva Partoll Yvette Gramlich Wei Huang Markus Leiminger Joonas Enroth Otso Per?kyl? Runlong Cai Xuemeng Chen Alkuin Maximilian Koenig Fernando Velarde Isabel Moreno Tuukka Pet?j? Paulo Artaxo Paolo Laj Armin Hansel Samara Carbone Markku Kulmala Marcos Andrade Douglas Worsnop Claudia Mohr Federico Bianchi Institute for Atmospheric and Earth System Research/Physics University of Helsinki Joint International Research Laboratory of Atmospheric and Earth System Sciences Nanjing University Department of Environmental Science & Bolin Centre for Climate Research Stockholm University Department of Chemistry and Molecular Biology University of Gothenburg Institute for Ion and Applied Physics University of Innsbruck Ionicon Analytik GmbH Laboratory for Atmospheric Physics Institute for Physics Research Universidad Mayor de San Andrés Institute of Physics University of Sao Paulo Institute for Geosciences and Environmental Research (IGE) University of Grenoble Alpes Agrarian Sciences Institute Federal University of Uberl?ndia Beijing Advanced Innovation Center for Soft Matter Science and Engineering Beijing University of Chemical Technology Department of Atmospheric and Oceanic Sciences University of Maryland Aerodyne Research Inc. Department of Environmental System Science ETH Zürich Switzerland and Laboratory of Atmospheric Chemistry Paul Scherrer Institute

New particle formation(NPF) in the tropical free troposphere(FT) is a globally important source of cloud condensation nuclei, affecting cloud properties and climate. Oxidized organic molecules(OOMs)produced from biogenic volatile organic compounds are believed to contribute to aerosol formation in the tropical FT, but without direct chemical observations. We performed in situ molecular-level OOMs measurements at the Bolivian station Chacaltaya at 5240 m above sea level, on the western edge of Amazonia. For the first time, we demonstrate the presence of OOMs, mainly with 4–5 carbon atoms, in both gas-phase and particle-phase(in terms of mass contribution) measurements in tropical FT air from Amazonia. These observations, combined with air mass history analyses, indicate that the observed OOMs are linked to isoprene emitted from the rainforests hundreds of kilometers away. Based on particle-phase measurements, we find that these compounds can contribute to NPF, at least the growth of newly formed nanoparticles, in the tropical FT on a continental scale. Thus, our study is a fundamental and significant step in understanding the aerosol formation process in the tropical FT.

关键词： oxidized organic molecules tropical aerosol formation Amazon free troposphere

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Dependence of epoch-wise two-way nested ANOVA estimates of variances of unmodeled effects present in relative GPS positioning on satellite elevation cutoff angle and PDOP mask

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Geodesy and Geodynamics 2022年第5期13卷 473-491页

作者： Darko Andic radovan Durovic Cadastre and State Property Administration Department of State Survey and MappingPodgoricaMontenegro University of Montenegro Faculty of Civil EngineeringPodgoricaMontenegro

Impact of satellite elevation cutoff angle and position dilution of precision(PDOP)mask change on epoch-wise variance components of unmodeled effects that accompany relative Global Positioning System(GPS)positioning is presented *** used for this study refer to the winter and summer periods of the years with minimal(2008)and maximal(2013)solar *** data were collected every 30 s in static mode,at two permanent GPS stations located in Montenegro,establishing a mediumdistance(116-km-long)baseline with a height difference of approximately 760 m between its *** study showed that changing satellite elevation cutoff angle,with a fixed PDOP mask,affects epochwise two-way nested ANOVA estimates of variances related to the‘far-field’multipath(considered as the nested factor herein)and the combined unmodeled effect of tropospheric and ionospheric refraction(considered as the nesting factor herein).However,changing of PDOP mask,with a fixed satellite elevation cutoff angle,doesn’t affect epoch-wise two-way nested ANOVA estimate of variance of the combined unmodeled effect of tropospheric and ionospheric refraction,but,generally,affects the estimate of variance of the‘far-field’multipath(possibly mixed with a part of a‘shorter-term’ionospheric refraction),which is especially pronounced for the summer *** should also be noted that there is a significant influence of satellite elevation cutoff angle change on both epoch-wise horizontal and vertical position accuracy,only for the summer period,especially in the presence of maximal solar activity,while there is no significant impact of PDOP mask change on epoch-wise positional accuracy.

关键词： Unmodeled effects in relative GPS positioning 2-way nested ANOVA Epoch-wise variance components Satellite elevation cutoff angle change PDOP mask change

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Effects of solid friction modifier on friction and rolling contact fatigue damage of wheel-rail surfaces

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Friction 2022年第4期10卷 597-607页

作者： Jingdong SONG Lubing SHI Haohao DING radovan GALAS Milan OMASTA Wenjian WANG Jun GUO Qiyue LIU Martin HARTL Tribology Research Institute State Key Laboratory of Traction PowerSouthwest Jiaotong UniversityChengdu 610031China School of Mechanical Engineering Xi’an Jiaotong UniversityXi’an 710049China Faculty of Mechanical Engineering Brno University of TechnologyBrno 61669Czech Republic

In railway network,friction is an important factor to consider in terms of the service behaviors of wheel-rail *** objective of this study was to investigate the effect of a solid friction modifier(FM)in a railway *** was achieved by studying the friction,wear,and rolling contact fatigue(RCF)damage on the wheel-rail materials at different slip *** results showed that when a solid FM was applied,the friction coefficient *** the solid FM was separated from the wheel-rail interface,the friction coefficient gradually increased to its original *** the application of the solid FM,the wear rates of the wheel-rail *** addition,the thickness and hardness of the plastic deformation layers of the wheel-rail materials were *** worn surfaces of the wheel-rail were dominated by pits and RCF *** the FM,RCF cracks ranged from 84 to 120μm,and subsurface cracks were ***,with the FM,RCF cracks ranged from 17 to 97μm and no subsurface cracks were *** findings indicate possible methods of improving the performance of railway rolling stock by managing friction,and reducing wear and permanent RCF damage affecting both the wheels and rails.

关键词： wheel-rail solid friction modifier(FM) friction wear rolling contact fatigue(RCF)damage

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Hybrid Laser-GMAW Welding of High Strength Quenched-Tempered Steels

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稀有金属材料与工程 2011年第S4期40卷 102-105页

作者： radovan Kovacevic Research Center for Advanced Manufacturing Southern Methodist UniversityTexas 75205United States

High-strength quenched and tempered (HSQT) steels have been widely used in structural applications where light weight is of primary design *** metal arc welding is a common way to join QT *** GMAW is used to join the HSQT steel,multi-pass is usually required to achieve full *** addition,weld crack is often observed because of HSQT steel's high susceptibility to hydrogen *** addition,due to the large amount of heat input from the arc,the heat affected zone is often *** reduces the ductility and strength of welds and makes the weld weaker than the base *** this study,a hybrid laser/GMAW process is proposed to produce butt joint for 6.5mm thick HSQT A514 steel *** diffusion mechanism is first discusses for GMAW and hybrid laser-GMAW welding *** transfer mode during the hybrid laser/GMAW welding process is also analyzed.A high speed CCD camera with 4000 frame/second is used to monitor the welding process in real *** obtained by GMAW and hybrid laser/GMAW techniques are compared and tested by static lap shear and dynamic *** of gap between two metal plates and laser beam/GMAW torch spacing on weld property are *** appropriately choosing these two parameters,crack-free butt joints with full penetration can be successfully obtained by the hybrid laser/GMAW welding process for HSQT A514 steel plate.

关键词： hybrid laser-GMAW welding high strength quenched and tempered steels hydrogen induced cracking

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Greenhouse gas emissions from thermal treatment o non-recyclable municipal waste

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Frontiers of Chemical Science and Engineering 2018年第4期12卷 815-831页

作者： Tomas Ferdan Martin Pavlas Vlastimlr Nevrly radovan Sompllak Petr Stehllk Institute of Process Engineering Faculty of Mechanical EngineeringBmo University of Technology61669 BmoCzech Republic Sustainable Process Integration Laboratory-SPIL NETME CentreFaculty of Mechanical Engineering Bmo University of Technology61669 BmoCzech Republic

This paper analyses factors affecting the production of greenhouse gases from the treatment of residual municipal waste. The analysis is conducted so that the environmentally-friendly decision-making criteria may be later implemented into an optimisation task, which allocates waste treatment capacities. A simplified method of life cycle assessment is applied to describe environmental impact of the allocation. Global warming potential (GWP) is employed as a unit to quantify greenhouse gases (GHG) emissions. The objective is to identify the environmental burdens and credits measured by GWP for the three fundamental methods for treatment of residual waste unsuitable for material recovery. The three methods are waste-to-energy (WTE), landfilling and mechanical-biological treatment (MBT) with subsequent utilization of refuse-derived fuel. The composition of the waste itself and content of fossil-derived carbon and biogenic carbon are important parameters to identify amounts of GHG. In case of WTE, subsequent use of the energy, e.g., in district heating systems in case of heat, is another important parameter to be considered. GWP function dependant on WTE capacity is introduced. The conclusion of this paper provides an assessment of the potential benefits of the results in optimisation tasks for the planning of overall strategy in waste management.

关键词： waste management greenhouse gases global warming potential allocation planning waste-to-energy

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Macroscopically-Zoned Grandite from the Garnetite Skarn of Meka Presedla(Kopaonik Mountain,Serbia)

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Acta Geologica Sinica(English Edition) 2012年第2期86卷 393-406页

作者： Pavle TANCIC Predrag VULIC Reinhard KAINDL Bernhard SARTORY radovan DIMITRIJEVIC Geological Institute of Serbia BelgradeSerbia Department of Crystallography Faculty of Mining and GeologyUniversity of BelgradeBelgradeSerbia 3 Institute of Mineralogy and Petrography University of InnsbruckInnsbruckAustria

The macroscopically-zoned grandite from the garnetite skarn of Meka Presedla （Kopaonik Mountain, Serbia） was studied with optical microscopy, electron microprobe analysis （EMPA）, Fourier transform infra-red （FT-IR）, and Raman methods. The EMPA results indicate that the main core-rim compositional variations （Ca2.93-2.97Mn0.05-0.06Mg0.00-0.01AI1.14-L26 Fe0.72-0.83 Ti0.00-0.02Si2.97-3.02012） slightly differ along the zones, showing evidence for a quasi-cyclic alternation of the oscillatory zoning nature. Among this, considerable variation is observed only by the AI-Fe3＋ substitutions in the octahedral site. The EMPA also indicate that the grandite zones compositionally vary, mostly within ＋1 and ±2 mol% of the homogeneity level range, that is, Grs64±1Adra36±1SpS2 （A）, Grs62±1Adra38±1Sps2 （B）, Grs59±2Adr40±2Sps2 （C）, Grs58±2Adr41±2Sps2 （D）, and Grss±1Adr41±1Sps2 （E）. Therefore, the investigated garnet can be considered as relatively highly homogeneous. The majority of compositions lie within the narrow miscibility region of 0.58±2〈XGrs〈0.64±1, without gaps, and with only three outliers near the zone boundaries of approximately 0.38〈XGrs〈0.52. FT-IR and Raman bands are almost constant within the zones and adequate to the chemical compositions. All of the zones should be considered as anhydrous. From the results, formation temperatures between -600 and 720℃ and pressures 0f-2-3 kbars, are derived. Among five possible causes for the slightly optical anisotropy of grandite, three were reconsidered, and consequently rejected.

关键词： grandite anisotropy compositional variation zone homogeneities miscibility region

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Crystal Structure and Chemical Composition of Ludwigite from Vranovac Ore Deposit (Boranja Mountain,Serbia)

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Acta Geologica Sinica(English Edition) 2012年第6期86卷 1524-1538页

作者： Pavle TANCIC radovan DIMITRIJEVIC Maja POZNANOVIC Aleksandar PACEVSKI Slobodanka SUDAR Geological Institute of Serbia Faculty of Mining and Geology Department of Mineralogy and Crystallography

The crystal structure of ludwigite from Vranovac ore deposit （Boranja Mt., Serbia） was refined using the X-ray powder diffraction （XRPD） Rietveld method in the space group Pbam to a final RB=7.45% and RF=5.26%. It has the unit cell dimensions of： a=9.2515（2） A; b=12.3109（2） A; c=3.03712 （7） A; and V=345.91（1） A3. The calculated distances and angles are mostly in good agreement with the Mg2＋-Fe2＋ substitutions across the M（1） and M（3） sites, as well as with the Fe3＋-AI3＋ replacement in the M（4） site. However, the mean observed M（2）-O distance is considerably shorter than prescribed, due to a slight increase of the Fe3＋ content in the M（2） site. Such replacement was compensated by slight increase of the Fe2＋ content in the M（4） site, resulting in the （Mg1.4sFe2＋o.46Fe3＋***.o2）2.o1 （Fe3＋o.94Fe2＋0.04Al0.02）1.00B1.00Os composition. The formation temperature was estimated to be about 500- 600C. The influences of the various chemical compositions to the crystallographic parameters, M-O distances, M（3） and M（4） sites shift, distortion parameters and estimated valences, were also studied and compared with other reference samples.

关键词： ludwigite crystal structure chemical composition M-O distances distortion parameters,ions valences comparison formation temperature

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Proteomic analysis of gastric cancer and immunoblot validation of potential biomarkers

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World Journal of Gastroenterology 2012年第11期18卷 1216-1228页

作者： Nina Kocevar Federico Odreman Alessandro Vindigni Snjezana Frkovic Grazio radovan Komel Medical Centre for Molecular Biology Institute of BiochemistryFaculty of MedicineUniversity of Ljubljana International Centre for Genetic Engineering and Biotechnology Trieste AREA Science ParkTrieste 34149Italy Department of Obstetrics and Gynecology Department of Gynecological Pathology and Cytology University Clinical Hospital LjubljanaLjubljana 1000Slovenia

AIM:To search or and validate di erentially expressed proteins in patients with gastric ***:We used two-dimensional gel electrophoresis and mass spectrometry to search or di erentially expressed proteins in patients with gastric adenocarcinoma.A set o proteins was validated with ***:We identified 30 di erent proteins involved in various biological processes:metabolism,development,death,response to stress,cell cycle,cell communication,transport,and cell *** proteins were chosen or urther validation by *** results show that gastrokine-1,39S ribosomal protein L12(mitochondrial precursor),plasma cell-induced resident endoplasmic reticulum protein,and glutathione S-trans erase mu 3 were signi icantly underexpressed in gastric adenocarcinoma relative to adjacent non-tumor tissue *** the other hand,septin-2,ubiquitin-conjugating enzyme E2 N,and transaldolase were significantly *** controlled tumor protein was shown to be di erentially expressed only in patients with cancer o the gastric cardia/esophageal ***:This work presents a set o possible diagnostic biomarkers,validated or the first *** might contribute to the e orts o understanding gastric cancer carcinogenesis.

关键词：蛋白质组生物标志物验证胃癌免疫学分双向凝胶电泳差异表达

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Nutrients accumulation in drainage channel sediments

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International Journal of Sediment Research 2017年第2期32卷 180-185页

作者： radovan Savic Gabrijel Ondrasek Ljubomir Letic Vesna Nikolic Vjekoslav Tanaskovik Faculty of Agriculture University of Novi Sad Faculty of Agriculture University of Zagreb Faculty of Forestry University of Belgrade Faculty of Agricultural Sciences and Food Ss.Cyril and Methodius University in Skopje

The drainage channel network in Vojvodina,northern part of the Republic of Serbia,in total length of around 20,000 km,transfers excessive(under)ground waters from around 2.15 million ha of *** are mostly in direct connection with the surrounding arable agricultural land and are exposed to different run-off,leaching and/or wind erosion *** to urban areas,some channel sections serve as recipients of unrefined sewage and industrial waste *** flows and velocities,as well as the transportable capacity of fluvial materials(sediments) are relatively ***,in combination with other natural and anthropogenic impacts,contributes to sediment generation in the drainage channel *** on around 100 sediment samples from 46 channels,concentrations of primary nutrients(N,P and K) were elaborated in this *** concentrations of macronutrients in the channel sediments(e.g.N 1-1.2%,P 100-265 and K 100-380 mg 100 g-1) exceeded their content in surrounding arable land by a few ***,significantly higher nutrient concentrations(in average by 50%) were detected in downstream(***) channel *** excessive presence of observed elements in channel sediments,due to interactive processes between water and sediment material,can adversely influence the water quality and life conditions for channel biota and caused other negative environmental impacts such as *** results clearly confirm that the processes of nutrient accumulation in channel sediments are greater than those in the surrounding,mostly intensively arable land *** erosion of unprotected agricultural areas and sediment transport as the most important pollution pathways from the drainage basin to channel network may be essential factors responsible for detected condition of nutrient accumulation.

关键词： Drainage channels Sediments,N,P,K Erosion

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