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A case study of the stability of a non-typical bleeder entry system at a U.S.longwall mine

International Journal of mining Science and technology 2020年第1期30卷 25-31页

作者： t.m.klemetti m.A.Van Dyke I.B.tulu D.tuncay NIOSH Pittsburgh mining Research Division Pittsburgh 15236USA Department of mining Engineering West Virginia UniversityMorgantown 26505USA

Longwall abutment loads are influenced by several factors,including depth of cover,pillar sizes,panel dimensions,geological setting,mining height,proximity to gob,intersection type,and size of the gob.How does proximity to the gob affect pillar loading and entry condition?Does the gob influence depend on whether the abutment load is a forward,side,or rear loading?Do non-typical bleeder entry systems follow the traditional front and side abutment loading and extent concepts?If not,will an improved understanding of the combined abutment extent warrant a change in pillar design or standing support in bleeder entries?this paper details observations made in the non-typical bleeder entries of a moderate depth longwall panel—specifically,data collected from borehole pressure cells and roof extensometers,observations of the conditions of the entries,and numerical modeling of the bleeder entries during longwall extraction.the primary focus was on the extent and magnitude of the abutment loading experienced due to the extraction of the longwall panels.Due to the layout of the longwall panels and bleeder entries,the borehole pressure cells(BPCs)and roof extensometers did not show much change due to the advancing of the first longwall.However,they did show a noticeable increase due to the second longwall advancement,with a maximum of about 4 mPa of pressure increase and 5mmof roof deformation.the observations of the conditions showed little to no change from before the first longwall panel extraction began to when the second longwall panel had been advanced more than 915 m.Localized pillar spalling was observed on the corners of the pillars closest to the longwall gob as well as an increase in water in the entries.In addition to the observations and instrumentation,numerical modeling was performed to validate modeling procedures against the monitoring results and evaluate the bleeder design.ItASCA Consulting Group’s FLAC3D numerical modeling software was used to evaluate the bleeder entries.the results of the models indicate

关键词： Abutment loading Longwall Instrumentation Bore hole pressure cells Pillar loading Yield pillar Bleeder pillar

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Analysis of global and local stress changes in a longwall gateroad

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International Journal of mining Science and technology 2018年第1期28卷 127-135页

作者： I.B.tulu G.S.Esterhuizen D.Gearhart t.m.klemetti K.m.mohamed D.W.H.Su Department of mining Engineering West Virginia University NIOSH Pittsburgh Mining Research Division

A numerical-model-based approach was recently developed for estimating the changes in both the horizontal and vertical loading conditions induced by an approaching longwall face.In this approach, a systematic procedure is used to estimate the model's inputs.Shearing along the bedding planes is modeled with ubiquitous joint elements and interface elements.Coal is modeled with a newly developed coal mass model.the response of the gob is calibrated with back analysis of subsidence data and the results of previously published laboratory tests on rock fragments.the model results were verified with the subsidence and stress data recently collected from a longwall mine in the eastern United States.

关键词： Longwall mining Gateroad design Flac3D Horizontal angle Gob loading Hollow inclusion cells

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Distribution, health and ecological risk assessments of trace elements in Nigerian oil sands

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Acta Geochimica 2024年第1期43卷 59-71页

作者： Odunayo t.Ore Festus m.Adebiyi Department of Chemistry Obafemi Awolowo UniversityIle-Ife 220005Nigeria Department of Chemical Sciences Achievers UniversityOwoNigeria

the Nigerian oil sands represent the largest oil sand deposit in Africa, yet there is little published information on the distribution and potential health and ecological risks of trace elements in the oil resource. In the present study, we investigated the distribution pattern of 18trace elements(including biophile and chalcophile elements) as well as the estimated risks associated with exposure to these elements. the results of the study indicated that Fe was the most abundant element, with a mean concentration of 22,131 mg/kg while Br had the lowest mean concentration of 48 mg/kg. the high occurrence of Fe and ti suggested a possible occurrence of ilmenite(Fe tiO_(3)) in the oil sands. Source apportionment using positive matrix factorization showed that the possible sources of detected elements in the oil sands were geogenic, metal production, and crustal. the contamination factor, geo-accumulation index, modified degree of contamination, pollution load index, and Nemerow pollution index indicated that the oil sands are heavily polluted by the elements. Health risk assessment showed that children were relatively more susceptible to the potentially toxic elements in the oil sands principally via ingestion exposure route(HQ > 1E-04). Cancer risks from inhalation are unlikely due to CR t ingestion and dermal contact pose severe risks(CR > 1E-04). the high concentrations of the elements pose serious threats due to the potential for atmospheric transport, bioaccessibility, and bioavailability.

关键词： Biophile Chalcophile Oil sand Risk assessment trace element

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QCD sum rule study of J^(P)=1^(±)exotic states with two heavy quarks in the molecular picture

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Chinese Physics C 2024年第6期48卷 31-37页

作者： t.m.Aliev S.Bilmis m.Savcı Department of Physics Middle East Technical UniversityAnkara06800Turkey tUBItAK ULAKBIm Ankara06510Turkey

In this study,the spectroscopic parameters of exotic molecular states composed of mesons containing two heavy quarks(scalar-axial and pseudoscalar-axial meson combinations)are investigated within the QCD sum rules.Our findings reveal that molecular states containing charm quarks do not form bound states,whereas states with b-quarks can form exotic molecular states.this observation has significant implications for understanding the structure of these exotic states.

关键词： QCD sum rules exotic mesons molecular states

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Supposition of graphene stacks to estimate the contact resistance and conductivity of nanocomposites

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Applied mathematics and mechanics(English Edition) 2024年第4期45卷 663-676页

作者： Y.ZARE m.t.mUNIR G.J.WENG K.Y.RHEE Biomaterials and tissue Engineering Research Group Department of Interdisciplinary TechnologiesBreast Cancer Research CenterMotamed Cancer InstituteTehran ***Iran College of Engineering and technology American University of the Middle EastEgaila 54200Kuwait Department of mechanical and Aerospace Engineering Rutgers UniversityNew BrunswickNJ 08903U.S.A. Department of mechanical Engineering(BK21 Four) College of EngineeringKyung Hee UniversityYongin 446701Republic of Korea

In this study,the effects of stacked nanosheets and the surrounding interphase zone on the resistance of the contact region between nanosheets and the tunneling conductivity of samples are evaluated with developed equations superior to those previously reported.the contact resistance and nanocomposite conductivity are modeled by several influencing factors,including stack properties,interphase depth,tunneling size,and contact diameter.the developed model's accuracy is verified through numerous experimental measurements.to further validate the models and establish correlations between parameters,the effects of all the variables on contact resistance and nanocomposite conductivity are analyzed.Notably,the contact resistance is primarily dependent on the polymer tunnel resistivity,contact area,and tunneling size.the dimensions of the graphene nanosheets significantly influence the conductivity,which ranges from 0 S/m to90 S/m.An increased number of nanosheets in stacks and a larger gap between them enhance the nanocomposite's conductivity.Furthermore,the thicker interphase and smaller tunneling size can lead to higher sample conductivity due to their optimistic effects on the percolation threshold and network efficacy.

关键词： graphene polymer composite stacked nanosheet tunneling conductivity contact resistance interphase

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Late Ordovician mass Extinction: Earth, fire and ice

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National Science Review 2024年第1期11卷 51-65页

作者： David A.t.Harper Palaeoecosystems Group Department of Earth SciencesDurham University

the Late Ordovician mass Extinction was the earliest of the ‘big’ five extinction events and the earliest to affect the trajectory of metazoan life. two phases have been identified near the start of the Hirnantian period and in the middle. It was a massive taxonomic extinction, a weak phylogenetic extinction and a relatively benign ecological extinction. A rapid cooling, triggering a major ice age that reduced the temperature of surface waters, prompted a drop in sea level of some 100 m and introduced toxic bottom waters onto the shelves. these symptoms of more fundamental planetary processes have been associated with a range of factors with an underlying driver identified as volcanicity. Volcanic eruptions, and other products, may have extended back in time to at least the Sandbian and early Katian, suggesting the extinctions were more protracted and influential than hitherto documented.

关键词： Ordovician LOmE paleoecology palaeobiogeography biotas

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Search for production of dark fermion candidates in association with heavy neutral gauge boson decaying to dimuon in proton-proton collisions at√s=8 teV using CmS open data

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Chinese Physics C 2024年第4期48卷 6-13页

作者： Y.mahmoud H.Abdallah m.t.Hussein S.Elgammal Centre for theoretical physics The British University in EgyptEgypt Physics Department Faculty of ScienceCairo UniversityEgypt

In this study,we conducted a search for dark matter using a part of the data recorded by the CmS experiment during run-I of the LHC in 2012 with a center of mass energy of 8 teV and an integrated luminosity of 11.6 fb−1.these data were gathered from the CmS open data.Dark matter,in the framework of the simplified model(mono-Z′),can be produced from proton-proton collisions in association with a new hypothetical gauge boson,Z′.thus,the search was conducted in the dimuon plus large missing transverse momentum channel.One benchmark scenario of mono-Z′,which is known as light vector,was used for interpreting the CmS open data.No evidence of dark matter was observed,and exclusion limits were set on the masses of dark matter and Z′at 95%confidence level.

关键词： dark matter large hadron collider CmS open data search for new physics dark fermion

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SmILE soft X-ray Imager flight model CCD370 pre-flight device characterisation

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Earth and Planetary Physics 2024年第1期8卷 25-38页

作者： S.Parsons D.J.Hall O.Hetherington t.W.Buggey t.Arnold m.W.J.Hubbard A.Holland Centre for Electronic Imaging the Open UniversityMilton KeynesMK76AAUK

throughout the SmILE mission the satellite will be bombarded by radiation which gradually damages the focal plane devices and degrades their performance.In order to understand the changes of the CCD370s within the soft X-ray Imager,an initial characterisation of the devices has been carried out to give a baseline performance level.three CCDs have been characterised,the two flight devices and the flight spa re.this has been carried out at the Open University in a bespo ke cleanroom measure ment facility.the results show that there is a cluster of bright pixels in the flight spa re which increases in size with tempe rature.However at the nominal ope rating tempe rature(-120℃) it is within the procure ment specifications.Overall,the devices meet the specifications when ope rating at -120℃ in 6 × 6 binned frame transfer science mode.the se rial charge transfer inefficiency degrades with temperature in full frame mode.However any charge losses are recovered when binning/frame transfer is implemented.

关键词： CCD soft X-ray imager characterisation SmILE

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management of male obesity-related secondary hypogonadism:A clinical update

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World Journal of Experimental medicine 2024年第2期14卷 11-28页

作者： mohan t Shenoy Sunetra mondal Cornelius James Fernandez Joseph m Pappachan Department of Endocrinology Sree Gokulam Medical Collegeand Research FoundationTrivandrum 695607KeralaIndia Department of Endocrinology NRS Medical College and HospitalKolkata 700014West BengalIndia Department of Endocrinology&metabolism Pilgrim HospitalUnited Lincolnshire Hospitals NHS TrustBoston PE219QSUnited Kingdom Department of Endocrinology and metabolism Lancashire Teaching Hospitals NHS TrustPreston PR29HTUnited Kingdom Faculty of Science Manchester Metropolitan UniversityManchester M156BHUnited Kingdom Faculty of Biology Medicine&HealthThe University of ManchesterManchester M139PLUnited Kingdom

the global obesity pandemic has resulted in a rise in the prevalence of male obesity-related secondary hypogonadism(mOSH)with emerging evidence on the role of testosterone therapy.We aim to provide an updated and practical approach towards its management.We did a comprehensive literature search across mEDLINE(via Pubmed),Scopus,and Google Scholar databases using the keywords“mOSH”OR“Obesity-related hypogonadism”OR“testosterone replacement therapy”OR“Selective estrogen receptor modulator”OR“SERm”OR“Guidelines on male hypogonadism”as well as a manual search of references within the articles.A narrative review based on available evidence,recommendations and their practical implications was done.Although weight loss is the ideal therapeutic strategy for patients with mOSH,achievement of significant weight reduction is usually difficult with lifestyle changes alone in real-world practice.therefore,androgen administration is often necessary in the management of hypogonadism in patients with mOSH which also improves many other comorbidities related to obesity.However,there is conflicting evidence for the appropriate use of testosterone replacement therapy(tRt),and it can also be associated with complications.this evidence-based review updates the available evidence including the very recently published results of the tRAVERSE trial and provides comprehensive clinical practice pearls for the management of patients with mOSH.Before starting testosterone replacement in functional hypogonadism of obesity,it would be desirable to initiate lifestyle modification to ensure weight reduction.tRt should be coupled with the management of other comorbidities related to obesity in mOSH patients.Balancing the risks and benefits of tRt should be considered in every patient before and during longterm management.

关键词： male obesity-related secondary hypogonadism Androgen therapy testosterone replacement therapy Obesity Cardiovascular benefits

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Aerodynamics of a tandem-Bladed Axial Compressor Rotor under Circumferential Distortion at Different Rotational Speeds

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Journal of thermal Science 2024年第4期33卷 1340-1356页

作者： Amit KUmAR Jerry t.JOHN A.m.PRADEEP R.A.D.AKKERmANS Dragan KOZULOVIC Department of Aerospace Engineering Indian Institute of Technology Bombay Department of Automotive and Aeronautical Engineering Hamburg University of Applied Sciences Institute of Jet Propulsion Bundeswehr University Munich

For most aircraft engines,inflow distortion is inevitable.Inflow distortion is known to degrade the aerodynamic performance and stable operating limits of a compressor.tandem rotor configuration is an arrangement that effectively controls the growth of the boundary layer over the suction surface of the blade.therefore,a higher total pressure rise can be achieved through this unconventional design approach involving the splitting of the blade into forward and aft sections.It is expected that the effect of inlet flow distortion would be more severe for a tandem-rotor design due to the greater flow turning inherent in such designs.However,this aspect needs to be thoroughly examined.the present study discusses the effect of circumferential distortion on the tandem-rotor at different rotational speeds.Full-annulus RANS simulations using ANSYS CFX are used in the present study.the performance of the rotor at a particular flow coefficient and different rotational speeds is compared.the total pressure and efficiency are observed to drop at lower mass flow rates under the influence of circumferential distortion.the loss region in each blade passage is mainly associated with the blade wake,tip leakage vortex,secondary flow,and boundary layer.However,their contribution varies from passage to passage,particularly in the distorted sector.At the lower span,the wake width is found to be higher than that at a higher span.Due to the redistribution of the mass flow,the circumferential extent reduces at a higher span.In the undistorted sector,the strength of the tip leakage vortex is significantly higher at the design rotational speed than at lower speeds.the distortion near the tip region promotes an early vortex breakdown even at the design operating condition.this adversely affects the total pressure,efficiency,and stall margin.Under clean flow conditions,this phenomenon is only observed near the stall point.At the design operating condition,the breakdown of the forward rotor tip leakage vortex is detected in four blade passages

关键词： tandem rotor circumferential distortion loss tip leakage vortex vortex breakdown diffusion factor aerodynamics of compressor blade

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