检索结果-南通市图书馆

Effect of slab width on choice of appropriate casting speed in steel production

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2022年第1期29卷 71-79页

作者： daniel Christopher Merten Marc-Thorsten hütt Yilmaz Uygun Department of Mathematics and Logistics Jacobs University BremenBremen 28759Germany Department of Life Sciences and Chemistry Jacobs University BremenBremen 28759Germany

In steel continuous casting(CC),the choice of the appropriate speed at which the slab is cast can be influenced by many different factors and *** the slab thickness seems to have the biggest impact,other features like the slab width have been consistently *** fact,the slab width practically limits the casting speed via the mass flow constraint which governs the input and output balance at the ***,we present a case study that aims at analyzing steel production data from the perspective of casting speed *** studying the speed fluctuations of an industrial CC machine,we identify a strategic regime change toward a stricter consideration of the mass flow *** regime change manifests itself in a significant increase in the correlation between the actual casting speed and the maximal speed associated with the mass flow *** the surface,taking greater account of the input and output balance at the tundish has reduced the productivity of the continuous caster;however,one can argue that the lessened yield is compensated by a diminished risk of eventual slab *** the perspective of this trade-off,we establish a visualization technique that enables us to pinpoint the boundary beyond which one strategic regime becomes economically more advantageous than the other.

关键词： Continuous casting Casting speed Slab width Slab thickness Mass flow constraint Machine length constraint

Parkland trees on smallholder farms ameliorate soil physical-chemical properties in the semi-arid area of Tigray,Ethiopia

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Arid Land 2024年第1期16卷 1-13页

作者： Selam LJALEM Emiru BIRhANE Kassa TEKA daniel h BERhE Department of Land Resources Management and Environmental Protection College of Dryland Agriculture and Natural ResourcesMekelle UniversityMekelle 231Ethiopia Institute of Climate and Society Mekelle UniversityMekelle 231Ethiopia Faculty of Environmental Sciences and Natural Resource Management Norwegian University of Life Sciences(NMBU)Ås 1432Norway Department of Natural Resources Management Adigrat UniversityAdigrat 50Ethiopia

Proposed agroforestry options should begin with the species that farmers are most familiar with,which would be the native multipurpose trees that have evolved under smallholder farms and socioeconomic *** African birch(Anogeissus leiocarpa(DC.)Guill.&Perr.)and pink jacaranda(Stereospermum kunthianum Cham.)trees are the dominant species in the agroforestry parkland system in the drylands of Tigray,*** farmers highly value these trees for their multifunctional uses including timber,firewood,charcoal,medicine,*** trees also could improve soil ***,the amount of soil physical and chemical properties enhanced by the two species must be determined to maintain the sustainable conservation of the species in the parklands and to scale up to similar agroecological ***,we selected twelve isolated trees,six from each species that had similar dendrometric characteristics and were growing in similar environmental *** divided the canopy cover of each tree into three radial distances:mid-canopy,canopy edge,and canopy gap(control).At each distance,we took soil samples from three different *** collected 216 soil samples(half disturbed and the other half undisturbed)from each canopy position and soil *** density(BD),soil moisture content(SMC),soil organic carbon(SOC),total nitrogen(TN),available phosphorus(AP),available potassium(AK),p h,electrical conductivity(EC),and cation exchange capacity(CEC)were *** revealed that soil physical and chemical properties significantly improved except for soil texture and EC under both species,CEC under ***,and soil p h under ***,all the studied soils were improved under both species canopy as compared with canopy ***,TN,AP,and AK under canopy of these trees were respectively 24.1%,11.1%,55.0%,and 9.3% higher than those soils under *** two parkland agroforestry species significantly enhanced soil fertility near the canopy of top

关键词： agroforestry bulk density carbon stock dispersed tree soil texture tree canopy

Computational modelling of magnesium degradation in simulated body fluid under physiological conditions

在线全文

学校读者我要写书评

暂无评论

Journal of Magnesium and Alloys 2022年第4期10卷 965-978页

作者： Berit Zeller-Plumhoff Tamadur AlBaraghtheh daniel höche Regine Willumeit-Römer helmholtz-Zentrum hereon Gmbh Institute of Metallic BiomaterialsMax-Planck-Straße 1Geesthacht21502Germany helmholtz-Zentrum hereon Gmbh Institute of Surface ScienceMax-Planck-Straße 1Geesthacht21502Germany

Magnesium alloys are highly attractive for the use as temporary implant materials, due to their high biocompatibility and ***, the prediction of the degradation rate of the implants is difficult, therefore, a large number of experiments are required. Computational modelling can aid in enabling the predictability, if sufficiently accurate models can be established. This work presents a generalized model of the degradation of pure magnesium in simulated body fluid over the course of 28 days considering uncertainty aspects. The model includes the computation of the metallic material thinning and is calibrated using the mean degradation depth of several experimental datasets simultaneously. Additionally, the formation and precipitation of relevant degradation products on the sample surface is modelled, based on the ionic composition of simulated body fluid. The computed mean degradation depth is in good agreement with the experimental data(NRMSE=0.07). however, the quality of the depth profile curves of the determined elemental weight percentage of the degradation products differs between elements(such as NRMSE=0.40 for phosphorus vs. NRMSE=1.03 for magnesium). This indicates that the implementation of precipitate formation may need further developments. The sensitivity analysis showed that the model parameters are correlated and which is related to the complexity and the high computational costs of the model. Overall, the model provides a correlating fit to the experimental data of pure Mg samples of different geometries degrading in simulated body fluid with reliable error estimation.

关键词： Biodegradation Magnesium Computational modelling Corrosion Uncertainty quantification Kriging

Effect of longwall-induced subsurface deformations on shale gas well casing stability under deep covers

在线全文

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2019年第1期29卷 3-8页

作者： daniel W.h.Su Peter Zhang Mark Van Dyke Todd Minoski Center for Disease Control and Prevention(CDC) National Institute for Occupational Safety and Health(NIOSH)Pittsburgh Mining Research Division(PMRD)

This paper presents the results of a 2017 study conducted by the National Institute for Occupational Safety and health(NIOSh), Pittsburgh Mining Research Division(PMRD), to evaluate the effects of longwall-induced subsurface deformations within a longwall abutment pillar under deep cover. The 2017 study was conducted in a southwestern Pennsylvania coal mine, which extracts 457 m-wide longwall panels under 361 m of cover. One 198 m-deep, in-place inclinometer monitoring well was drilled and installed over a 45 m by 84 m center abutment pillar. In addition to the monitoring well, surface subsidence measurements and underground coal pillar pressure measurements were conducted as the 457 m-wide longwall panel on the south side of the abutment pillar was being mined. Prior to the first longwall excavation, a number of simulations using FLAC3D^(TM) were conducted to estimate surface subsidence, increases in underground coal pillar pressure, and subsurface horizontal displacements in the monitoring well. Comparisons of the pre-mining FLAC3D simulation results and the surface, subsurface,and underground instrumentation results show that the measured in-place inclinometer casing deformations are in reasonable agreement with those predicted by the 3D finite difference models. The measured surface subsidence and pillar pressure are in excellent agreement with those predicted by the 3D *** from this 2017 research clearly indicate that, under deep cover, the measured horizontal displacements within the abutment pillar are approximately one order of magnitude smaller than those measured in a 2014 study under medium cover.

关键词： Longwall Deformations Shale gas wells Casing Safety and health