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Optimization of.gob ventilation boreholes design in longwall mining

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International journal of.Mining Science and Technology 2020年第6期30卷 811-817页

作者： Saqib Ahmad Saki jürgen f.brune Muhammad Usman Khan University of.Engineering and Technology Lahore Lahore 54890Pakistan Colorado School of.Mines GoldenCO 80401USA

Gob ventilation boreholes(GVBs)are widely used f.r degasif.cation in *** coal *** on geological conditions,30–50%of.methane can be recovered f.om longwall gob using GVBs.A NIOSH f.nded research at the Colorado School of.Mines conf.rmed that GVBs can ef.iciently reduce methane at the ***,GVBs can also draw some f.esh air f.om the f.ce and create explosive gas zones(EGZs).Explosive gas mixtures may be f.rmed in gob areas due to the increased ingress of.oxygen f.om *** is critical to identif. the locations f.r GVBs f.r maximizing extraction of.methane and minimizing hazards of.*** study analyzes the ef.ect of.operating parameters and design of.GVB on methane extraction,EGZs f.rmation,and f.ce and tailgate methane *** extraction,f.rmation of.EGZs,and concentration of.methane in working areas are signif.cantly impacted by various *** f.ctors include the distance of.work f.ce and tailgate f.om GVBs,diameter of.GVBs,vacuum pressure of.wellhead,GVB distance f.om the roof.of.the coal seam,and number of.operating GVBs in a *** f.uid dynamics(Cf.)evaluations suggest optimal design and operating parameters of.GVBs that can contribute to maximum benef.ts with minimum risks.

关键词： Longwall mining Explosive gas zones Computational f.uid dynamics Gob ventilation boreholes

Discrete modeling of.a longwall coal mine gob f.r Cf. simulation

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International journal of.Mining Science and Technology 2020年第4期30卷 463-469页

作者： Aditya juganda Claire Strebinger jurgen f.brune Gregory E.Bogin Colorado School of.Mines GoldenCO 80401USA

One area of.concern in longwall coal mines is the active gob directly behind the longwall f.ce,where high concentrations of.methane are likely to accumulate and active roof.caving *** computational f.uid dynamics(Cf.)to simulate gas f.ows in and through the gob,most researchers have represented the entire gob as a porous medium governed by Darcy’s ***,Darcy-type porous f.ow may not be applicable f.r the highly porous and unconsolidated f.inges of.the *** addition,porous medium models do not allow f.r representative combustion modeling to simulate in-gob ignition and f.ame *** study presents a hybrid approach to modeling the gob using Cf.:the outer part of.the gob is modeled as discrete objects that simulate coarse rock rubble,while the gob center is modeled as a porous medium.

关键词： Longwall Coal Computational f.uid dynamic Modeling Ventilation

Computational f.uid dynamics simulation on the longwall gob breathing

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International journal of.Mining Science and Technology 2017年第2期27卷 185-189页

作者： Samuel A.Lolon jürgen f.brune Gregory E.Bogin jr. john W.Grubb Saqib A.Saki Aditya juganda Department of.Mining Engineering Colorado School of MinesCO 80401USA Department of.Mechanical Engineering Colorado School of.Mines CO 80401USA

In longwall mines, atmospheric pressure f.uctuations can disturb the pressure balance between the gob and the ventilated working area, resulting in a phenomenon known as ‘‘gob breathing". Gob breathing triggers gas f.ows across the gob and the working areas and may result in a condition where an oxygen def.cient mixture or a methane accumulation in the gob f.ows into the f.ce area. Computational f.uid Dynamics(Cf.s) modeling was carried out to analyze this phenomenon and its impact on the development of.an explosive mixture in a bleeder-ventilated panel scheme. Simulation results indicate that the outgassing and ingassing across the gob and the f.rmation of.Explosive Gas Zones(EGZs) are directly af.ected by atmospheric pressure changes. In the location where methane zones interf.ce with mine air, EGZ f.inges may f.rm along the f.ce and in the bleeder entries. These f.ndings help assess the methane ignition and explosion risks associated with f.uctuating atmospheric pressures.

关键词： Cf.s Gob breathing barometric pressure Explosive gas zone Longwall mine Methane explosion

Supervision of.two f.ndamental problems in modern f.uid dynamics f.r sparing energy

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journal of.Thermal Science 2009年第2期18卷 97-98页

作者： jürgen Zierep Institut f.r Strmungslehre Universitt Karlsruhe

The normal shock at a curved surf.ce in transonic f.ow leads to a superdetermined boundary value problem. A bump behind the shock decreases the drag of.the airf.il and reduces the necessary energy. f.ows of.non-Newtonian media lead in the contrary to subdetermined boundary initial problems. The energy balance f.r these f.uids is of.great interest f.r chemical engineering.

关键词： Transonic f.ow Shock at a curved wall Superdetermined problem Non- Newtonian media Subdeermined problem Energy balance.

Dust growth in protoplanetary disks-a comprehensive experimental / theoretical approach

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Research in Astronomy and Astrophysics 2010年第12期10卷 1199-1214页

作者： jürgen Blum Institut f.r Geophysik und extraterrestrische Physik University of Braunschweig

More than a decade of.dedicated experimental work on the collisional physics of.protoplanetary dust has brought us to a point at which the growth of.dust aggregates can - f.r the f.rst time - be self.consistently and reliably modeled. In this article, the emergent collision model f.r protoplanetery dust aggregates, as well as the numerical model f.r the evolution of.dust aggregates in protoplanetary disks, is reviewed. It turns out that, af.er a brief.period of.rapid collisional growth of.f.uf.y dust aggregates to sizes of.a f.w centimeters, the protoplanetary dust particles are subject to bouncing collisions, in which their porosity is considerably decreased. The model results also show that low-velocity f.agmentation can reduce the f.nal mass of.the dust aggregates but that it does not trigger a new growth mode as discussed previously. According to the current stage of.our model, the direct f.rmation of.kilometer-sized planetesimals by collisional sticking seems unlikely, implying that collective ef.ects, such as the streaming instability and the gravitational instability in dust-enhanced regions of.the protoplanetary disk, are the best candidates f.r the processes leading to planetesimals.

关键词： planetary systems: protoplanetary disks -- planetary systems: f.rmation-- methods: laboratory -- methods: numerical

Taguchi Analysis f.r Improving Optimization of.Integrated f.rward/Reverse Logistics

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journal of.the Operations Research Society of.China 2023年第3期11卷 529-552页

作者： Elham Behmanesh jürgen Pannek International Graduate School f.r Dynamics in Logistics University of BremenBremenGermany f.culty of.Production Engineering University of BremenBremenGermany BIBA Bremer Institut f.r Produktion und Logistik GmbH BremenGermany

The distribution–allocation problem is known as one of.the most comprehensive strategic *** real-world cases,it is impossible to solve a distribution–allocation problem completely in acceptable *** f.rces the researchers to develop ef.icient heuristic techniques f.r the large-term operation of.the whole supply *** techniques provide near optimal solution and are comparably f.st particularly f.r large-scale test *** paper presents an integrated supply chain model which is f.exible in the delivery *** solution methodology,we apply a memetic algorithm with a novelty in population *** identif. the optimum operating condition of.the proposed memetic algorithm,Taguchi method is *** this study,f.ur f.ctors,namely population size,crossover rate,local search iteration and number of.iteration,are *** the best level of.the considered parameters is the outlook of.this research.

关键词： Integrated logistics network f.exible path Memetic algorithm Taguchi analysis

Transepithelial transport of.putrescine across monolayers of.the human intestinal epithelial cell line, Caco-2

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World journal of.Gastroenterology 2001年第2期7卷 193-197页

作者： Vladan Milovic Lyudmila Turchanowa jürgen Stein Wolf.ang f.Caspary 2nd Department of.Medicine Johann Wolfgang Goethe UniversityFrankfurtGermany

AIM: To study the transepithelial transport characteristics of.the polyamine putrescine in human intestinal Caco-2 cell monolayers to elucidate the mechanisms of.the putrescine intestinal absorption. METHODS: The transepithelial transport and the cellular accumulation of.putrescine was measured using Caco-2 cell monolayers grown on permeable f.lters. RESULTS: Transepithelial transport of.putrescine in physiological concentrations (> 0.5 mM) f.om the apical to basolateral side was linear. Intracellular accumulation of.putrescine was higher in conf.uent than in f.lly dif.erentiated Caco-2 cells, but still negligible (less than 0.5%) of.the overall transport across the monolayers in apical to basolateral *** enhanced putrescine accumulation in Caco-2 cells by f.ur f.ld, as well as putrescine conversion to spermidine and spermine by enhancing the activity of.S adenosylmethionine decarboxylase. However, EGf.did not have any signif.cant inf.uence on putrescine f.ux across the Caco-2 cell monolayers. Excretion of.putrescine f.om Caco-2 cells into the basolateral medium did not exceed 50 picomoles, while putrescine passive f.ux f.om the apical to the basolateral chamber, contributed hundreds of.micromoles polyamines to the basolateral chamber. CONCLUSION :Transepithelial transport of.putrescine across Caco2 cell monolayers occurs in passive dif.usion, and is not inf.uenced when epithelial cells are stimulated to prolif.rate by a potent mitogen such as EGf.

关键词： Biological Transport Caco-2 Cells Epidermal Growth f.ctor Humans Intestinal Absorption Putrescine Recombinant Proteins Research Support, Non-U.S. Gov't

Solid-state batteries:f.om 'all-solid' to 'almost-solid'

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National Science Review 2023年第6期10卷 57-59页

作者： Hanyu Huo jürgen janek Institute of.Physical Chemistry Justus Liebig University Giessen Center f.r Materials Research (Zf.) Justus Liebig University Giessen

Lithium-ion batteries (LIBs) have been the undisputed leading technology in electrochemical energy storage since they were commercialized in *** then,the mass manuf.cturing of.LIBs has reached maturity,and we have also seen the realization of.high energy density,long cycling stability and low *** technology enabled the huge success of.mobile consumer electronics,with its usage in electric vehicles and other advanced *** to the use of.organic solvents f.r the ele ctrolytes,LIBs are sensitive to high temperatures,lose perf.rmance at low temperatures and show inherent saf.ty risks with increasing energy density (f.g.1a).As the perf.rmance of.current LIBs is also limited,next-generation battery technologies are being intensively investigated,especially given the ever-increasing demand f.r high energy density as well as high power density.

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Topsoil as Af.ected by Dung Deposition Under Resting Places of.Red Howler Monkey (Alouatta seniculus)

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Pedosphere 2008年第6期18卷 691-698页

作者： S. POUVELLE f. f.ER j. f. PONGE Musum National d'Histoire Naturelle CNRS UMR 7179 4 avenue du Petit-Chateau

The short-term inf.uence of.dung deposition and the f.rther redistribution of.dung by dung beetles were studied under a resting place of.the red howler monkey （Alouatta seniculus） living in tropical ralnf.rests of.South America. Monkey dung was experimentally clumped on the f.eld in a place used by troops of.howler monkeys f.r resting in the Nouragues Reserve Station, f.ench Guiana. Dung-treated plots were sampled serially over three weeks and compared with controls located in their immediate vicinity. The composition of.the soil matrix （top 10 cm） was studied in successive microlayers using an optical method. Under the inf.uence of.dung beetle activity, the topsoil became more homogeneous by losing its litter, its content in earthworm f.eces increased in the course of.time, and surf.ce mineral deposits were penetrated by roots. The results were interpreted in the light of.present knowledge on the ef.ects of.soil animal activity on plant growth and survival of.seedlings.

关键词： dung beetle activity earthworm f.eces roots tropical ralnf.rests