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Evaluation and prediction of the effect of load frequency on the wear properties of pre-cracked nylon 66

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Friction 2014年第3期2卷 240-254页

作者： A.ABDELBARY m.n.ABOUELWAFA i.m.EL FAHHam mechanical Engineering Department Faculty of EngineeringAlexandria UniversityAlexandriaEgypt

nylon 66 has been widely used for numerous mechanical applications but its sliding wear mechanisms are not fully *** particular,limited attention has been paid to the generation of fatigue surface cracks under constant and cyclic load *** present work focuses on the effect of load frequency on the wear behavior of a polymer with surface defects in dry sliding *** defects were imposed vertical deep cracks perpendicular to the direction of *** studies were conducted against a steel counterface at constant loads,and in cyclic loads at different *** neural network(Ann)models were examined to identify one that optimally simulates wear under the applied load *** cracks were found to have a remarkable adverse effect on the wear behavior of the *** wear rates were influenced by the number of cracks as well as the type of applied ***,results suggest that the presence of surface cracks is attributable to the section B wear ***,acceptable predicted wear rate values were obtained by introducing the Ann wear model.

关键词： nylon wear surface defects wear model

numerical analysis and centrifugal modeling of LnAPLs transport in subsurface system

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Progress in natural Science:materials international 2006年第4期16卷 416-424页

作者： LO i.m.C. mEEGODA J.n. Department of Civil Engineering Hong Kong University of Science and Technology Hong Kong SARChina Department of Civil and Environmental Engineering new Jersey institute of Technology USA

The transport of non-aqueous phase liquids (nAPLs) in unsaturated soils and groundwater is an important research topic in geo-environmental engineering. in this paper, the mechanism of light nAPLs (LnAPLs) transport in subsurface system is briefly introduced, and the mass transport equations, fluid flow equations, and the constitutive model of relative permeability - saturation - capillary pressure are discussed. Then the numerical method is introduced to simulate the multiphase flow problems in porous media, and the tempospatial distribution of LnAPLs is obtained. moreover, different boundary conditions are employed in numerical simulation to investigate its effect on transport behavior. To verify the numerical data, centrifugal tests are conducted to model the LnAPLs migration in unsaturated soils and groundwater. The calculation results are agreeable with the experimental findings of centrifugal modeling, which indicates that LnAPLs from leaking point move downwards due to gravity force, and form a high concentration zone above the capillary fringe, and then spread out laterally along the groundwater table. Some LnAPL enters groundwater system to further migrate. The combination of numerical simulation and centrifuge modeling can be a useful means to study the transport behavior of LnAPLs in subsurface system.

关键词： geo-environmental engineering subsurface contamination multiphase flow light non-aqueous phase liquids (LnAPLs) centrifugal modeling technique numerical simulation.

Approximation of Rainfall Erosivity Factors in north Jordan

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Pedosphere 2010年第6期20卷 711-717页

作者： n.i.ELTAiF m.A.GHARAiBEH F.AL-ZAiTAWi m.n.ALHamad Department of natural Resources and Environment Faculty of AgricultureJordan University of Science and Technology

Despite being in arid and semi-arid areas,erosion is largely a result of infrequent but heavy rainfall events; therefore,rainfall erosivity data can be used as an indicator of potential erosion *** purpose of this study was to investigate the spatial distribution of annual rainfall erosivity in north Jordan.A simplified procedure was used to correlate erosivity factor R values in both the universal soil loss equation (USLE) and the revised universal soil loss equation (RUSLE) with annual rainfall amount or modified Fournier index (F mod ).Pluviometric data recorded at 18 weather stations covering north Jordan were used to predict R *** annual values of erosivity ranged between 86-779 mJ mm ha ?1 h ?1 year ?1 .The northwest regions of Jordan showed the highest annual erosivity values,while the northeastern regions showed the lowest annual erosivity values.

关键词： erosion Fournier index iso-erodent map universal soil loss equation

Variation in Salt Tolerance of Wheat Cultivars:Role of Glycinebetaine and Ethylene

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Pedosphere 2012年第6期22卷 746-754页

作者： m.i.R.KHAn n.iQBAL A.mASOOD n.A.KHAn Department of Botany Aligarh Muslim UniversityAligarh 202002(India)

Four wheat （Triticum aestivum L.） cultivars 711, PBW343, 3765 and WH542 were screened for studying variations in glycinebetaine （GB） content and plant dry mass under 100 mmol L-1 naCl stress. A tolerance index was calculated using plant dry mass data to select salt-tolerant and salt-sensitive types and find association between tolerance index and GB content. Tolerance index has been used as a good criterion to select the tolerant types under high salinity stress. Further, physiological differences in salt-tolerant cultivar 711 and salt-sensitive cultivar WH542 were examined. The salt-tolerant cultivar exhibited greater CB content, which was found correlative with ethylene. The cultivar also showed higher nitrogen （n） content and nitrate reductase activity, reduced glutathione and higher redox state resulting in maximal protection of plant dry mass than the salt-sensitive type. Thus, the content of CB may be considered as important physiological criteria for selecting salt-tolerant wheat types.

关键词： glutathione nitrogen assimilation salt stress

Chirping instabilities produced by a runaway electron beam at a spherical tokamak

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Plasma Science and Technology 2023年第7期25卷 19-24页

作者： i m BALACHEnKOV n n BAKHAREV V K GUSEV m V iLiASOVA E m KHiLKEViCH P S KOREnEV A E KOnKOV V B minAEV Yu V miTRiZHKin m i PATROV Yu V PETROV n V SAKHAROV A E SHEVELEV O m SKREKEL ioffe institute Saint-Petersburg 194021Russia Lomonosov moscow State University Moscow 119991Russia

Two different types of mHD instabilities with rapidly chirping frequency were found to arise in the Globus-m2 spherical tokamak in substantially different frequency *** first type arises at frequencies of an order of 1 mHz in ohmic plasmas at relatively low density(n_(e))m^(-3) in a wide range of toroidal magnetic fields and plasma *** type of instability was identified as compressional Alfven waves,driven by electrons,accelerated during a sawtooth *** was found that the mode frequency is sweeping in time,according to the Berk-Breizman hole-clump nonlinear chirping *** second type of wave arises in a specific single-swing regime of the central solenoid current with a very narrow plasma column,when the plasma tends to decay at extremely low density(n_(e))m^(-3) and,in fact,is an instability of the runaway electron *** exited modes cover the whole observed frequency range and are divided into several(two or three)frequency regions:approximately 0-30 mHz,60-120 mHz and sometimes 30-60 *** of the branches was also *** chirps are more rapid than for 1 mHz Alfven instability and follow an exponential *** paper,to our knowledge,is the first report of frequency chirping instabilities excited by accelerated electrons at a spherical tokamak.

关键词： Alfvén waves chirping instability spherical tokamak runaway electrons

Utilization of traditional healers for treatment of malaria among female residents in makurdi city and its environs

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Asian Pacific Journal of Tropical medicine 2010年第7期3卷 563-566页

作者： Jombo GTA mbaawuaga em Denen Akaa P Dauda am Eyong Ki Akosu JT Etukumana EA Department of medical microbiology and Parasitology College of Health SciencesBenue State UniversityPMB 102119 MakurdiNigeria Department of Biological Sciences Faculty of ScienceBenue State UniversityPMB 102119 MakurdiNigeria Department of Surgery College of Health SciencesBenue State University MakurdiNigeria Department of Histopathology Faculty of Medical SciencesUniversity of JosJosNigeria Department of Paediatrics College of Medical SciencesUniversity of CalabarCalabarNigeria Department of Community medicine College of Medical SciencesUniversity of JosNigeria Department of Family medicine University of Uyo Teaching Hospital UyoNigeria

Objective:To ascertain the role of traditional healers in malaria treatment and its impact on control of the ***:The study was cross-sectional in ***-run structured and semi-structured questionnaires were either interviewer or self administered to adult women aged 18 years old and *** holds were selected using systematic random sampling *** such as age,educational level,marital status,occupation and methods of malaria treatment were *** group discussions about beliefs and perceptions on utilization of traditional healers and in depth discussions on treatment and control of malaria were also carried ***:Of the 2 075 respondents studied,49.7%(n=1 031) utilized traditional healers for treatment of malaria,including 16.7%(n=172) utilizing traditional healers strictly while 83.3%(n=859) combining it with other treatment methods such as hospital/clinic, pharmacy/chemist shop,herbs or spiritual *** major contributors to utilization of traditional healers were:illiteracy and ignorance,poverty,unemployment/underemployment and slow pace of the comprehensive package implem.ntation of the "roll back malaria"(RBm) programme initiate in the ***:Health education should be intensified while adequate facilities put in place to commence home managem.nt of malaria and probable free distribution of the artemisinin-based combination therapy(ACT).

关键词： Traditional healers Utilization malaria treatment adult-women

Effectiveness of external prestressing in enhancing the non-ductile hanger failure mechanism in reinforced concrete inverted T-beams

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Frontiers of Structural and Civil Engineering 2024年第7期18卷 1050-1065页

作者： Ahmed m.ATTA Reda n.BEHiRY mohammed i.HARAZ Structural Engineering Department Faculty of EngineeringTanta UniversityTanta 33511Egypt nile Higher institute for Engineering and Technology Mansoura 11001Egypt

Recently,inverted T-beams have been used in reinforced concrete(RC)bridges to support transverse precast *** T-beams,contrary to practice with conventional beams,are loaded on the flanges upper *** loading configuration causes hanger failure due to the generation of vertical tensile stresses near the bottom of the *** key purpose of this study is to investigate the efficiency of vertical external prestressing stainless-steel bars in mitigating non-ductile hanger failure in reinforced concrete inverted *** experimental study on six inverted-T beams,including two un-strengthened specimens,was carried *** study showed that the value of the prestressing level had a considerable impact on the performance of hanger mechanism in relation to crack pattern,ultimate loads,cracking behavior,load-deflection,strains,and *** experimental results indicated that the suggested method for strengthening inverted T-beams had efficacy in reducing the seriousness of the non-ductile hanger failure and resulted in a strength increase of up to 53% when compared to that of the un-strengthened ***,two analytical models for estimating the hanger capacity and the average crack width of the strengthened RC inverted T-beams were *** models that were proposed exhibited a high degree of agreem.nt with the experimental results.

关键词： RC bridges inverted T-beams strengthening hanger failure external prestressing

Environmental screening and ligand-field effects to magnetism in Cri_(3) monolayer

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npj Computational materials 2021年第1期7卷 1481-1490页

作者： D.Soriano A.n.Rudenko m.i.Katsnelson m.Rösner Radboud University Institute for Molecules and MaterialsHeyendaalseweg 1356525 AJ NijmegenThe Netherlands Universitàdi Pisa Dipartimento di Ingegneria dell’InformazioneVia Caruso56122 PisaItaly Department of Theoretical Physics and Applied mathematics Ural Federal University620002 EkaterinburgRussia

We study the microscopic origin of magnetism in suspended and dielectrically embedded Cri_(3)monolayer by down-folding minimal generalized Hubbard models from ab initio calculations using the constrained random phase *** models are capable of describing the formation of localized magnetic moments in Cri_(3)and of reproducing electronic properties of direct ab initio *** the magnet force theorem,we find a multi-orbital super-exchange mechanism as the origin of magnetism in Cri_(3)resulting from an interplay between ferro-and anti-ferromagnetic Cr-Cr d coupling channels,which is decisively affected by the ligand p *** show how environmental screening,such as resulting from encapsulation with hexagonal boron nitride,affects the Coulomb interaction in the film and how this controls its magnetic *** by a non-monotonic interplay between nearest and next-nearest neighbor exchange interactions we find the magnon dispersion and the Curie temperature to be non-trivially affected by the environmental screening.

关键词： properties monolayer exchange

Assessing fracturing mechanisms and evolution of excavation damaged zone of tunnels in interlocked rock masses at high stresses using a finitediscrete elem.nt approach

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Journal of Rock mechanics and Geotechnical Engineering 2019年第4期11卷 701-722页

作者： i.Vazaios n.Vlachopoulos m.S.Diederichs Arup LondonW1T 4BQUnited Kingdom Department of Geological Sciences and Geological Engineering Queen’s UniversityKingstonOntarioK7L 3N6Canada Department of Civil Engineering Royal Military College of CanadaKingstonOntarioK7L 4V3Canada

Deep underground excavations within hard rocks can result in damage to the surrounding rock mass mostly due to redistribution of *** within rock masses with non-persistent joints,the role of the pre-existing joints in the damage evolution around the underground opening is of critical importance as they govern the fracturing mechanisms and influence the brittle responses of these hard rock masses under highly anisotropic in situ *** this study,the main focus is the impact of joint network geometry,joint strength and applied field stresses on the rock mass behaviours and the evolution of excavation induced damage due to the loss of confinem.nt as a tunnel face *** of such a phenomenon was conducted using the finite-discrete elem.nt method (FDem).The numerical model is initially calibrated in order to match the behaviour of the fracture-free,massive Lac du Bonnet granite during the excavation of the Underground Research Laboratory (URL) Test Tunnel,*** influence of the pre-existing joints on the rock mass response during excavation is investigated by integrating discrete fracture networks (DFns) of various characteristics into the numerical models under varying in situ *** numerical results obtained highlight the significance of the pre-existing joints on the reduction of in situ rock mass strength and its capacity for extension with both factors controlling the brittle response of the ***,the impact of spatial distribution of natural joints on the stability of an underground excavation is discussed,as well as the potentially minor influence of joint strength on the stress induced damage within joint systems of a non-persistent nature under specific ***,the in situ stress-joint network interaction is examined,revealing the complex fracturing mechanisms that may lead to uncontrolled fracture propagation that compromises the overall stability of an underground excavation.

关键词： Excavation damaged zone (EDZ) Brittle failure Finite-discrete elem.nt method (FDem) Tunnelling Discrete fracture network (DFn)