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International Journal of Minerals,Metallurgy and Materials 2020年第10期27卷 1332-1340页

作者： N.Malatji A.P.I.Popoola T.Lengopeng S.Pityana Tshwane university of Technology PretoriaSouth Africa Council for Scientific and Industrial Research PretoriaSouth Africa

AlCrFeNiCuNbx(x=0.05,0.15,and 0.26)high-entropy alloys(HEAs)were successfully fabricated using the laser metal deposition *** laser power of 1600 W and scanning speed of 1.2 m/min were used during laser processing of the *** microstructural,mechanical,and electrochemical characteristics of the alloys were evaluated using various advanced characterization *** showed that the alloys exhibited a dual-phase structure with dendritic *** inclusion of Nb in the AlCrFeNiCu alloy matrix promoted the formation of fine eutectic structures and changed the shape of the grains from columnar to *** Cu content decreased with the increase in the content of Nb,whereas the Al content increased with the increase in the content of *** findings indicated that the presence of Nb in the alloy promoted the formation and enhanced the stability of the body-centered cubic(bcc)*** of the alloys that contained Nb also exhibited high hardness,compressive strength,and wear ***,the low current density and positive shift in potential exhibited by HEAs with appropriate addition of Nb highlighted the superior anticorrosive properties.

关键词： high-entropy alloys microstructure microhardness friction wear loss corrosion resistance

Mate-recognition and species boundaries in the ascomycetes

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Fungal Diversity 2013年第1期58卷 1-12页

作者： Simon H.Martin Emma T.Steenkamp Michael J.Wingfield Brenda D.Wingfield Department of Genetics Forestry and Agricultural Biotechnology InstituteUniversity of PretoriaPretoria 0002South Africa Department of Microbiology and Plant Pathology Forestry and Agricultural Biotechnology InstituteUniversity of PretoriaPretoria 0002South Africa

Reproductive gene evolution is commonly invoked as a source of reproductive isolation during *** possibility has not been adequately explored in the Ascomycota,the most species-rich fungal *** mechanisms of mate-recognition in this group are relatively simple:a“mating type”locus determines reproductive mode and sexual compatibility,and two pheromone/receptor pairs control sexual ***,ascomycete reproductive genes can experience unique and interesting evolutionary forces,which could lead to rapid *** this review,we examine the mechanisms of sexual interaction in ascomycetes and explore current evidence as to whether these mechanisms allow for species-specificity in *** discuss the evolutionary forces that can drive reproductive gene divergence,how these may apply in the world of ascomycetes,and their possible consequences for speciation.

关键词： Ascomycota Speciation Mating type Pheromone Receptor

Guidelines for the use of accelerated pavement testing data in autonomous vehicle infrastructure research

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Journal of Traffic and Transportation Engineering(English Edition) 2019年第3期6卷 273-281页

作者： WynAND J.vdM.Steyn James W.Maina Department of Civil Engineering University of Pretoria

There is much research conducted on the vehicle technologies required for operation of autonomous vehicles(AV) on public roads, as well as analysis of the interaction between AV and the road environment. However, limited research exists on the impact of AV on road pavement structures. The research includes issues such as the effect of more channelized traffic loading, shorter inter-vehicle following distances and potential higher traffic volumes of more uniform vehicle types and loads. This paper discusses the application of existing and generation of new, relevant accelerated pavement testing(APT) data in understanding the effects of AV on pavement infrastructure. The paper presents development of provisional guidelines for the use and application of APT data to ensure that road pavement structures cope with anticipated increase in AV use. It is concludes that the use of AV fleets on existing road pavement infrastructure may lead to different behaviors and responses than what became the norm under non-autonomous vehicle fleets;appropriate analysis of existing APT data will contribute to the improved understanding of these expected changes in behaviors and responses; appropriate planning of AV operations-focused APT is possible with existing technology to contribute to the provision of economic and durable road pavement infrastructure in future.

关键词： Autonomous vehicles Accelerated pavement testing Vehicle-pavement interaction Road infrastructure

Hyper-chaos encryption using convolutional masking and model free unmasking

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Chinese Physics B 2014年第5期23卷 161-166页

作者：齐国元 Sandra Bazebo Matondo Department of Electrical Engineerin Tshwane University of Technology Pretoria

In this paper, during the masking process the encrypted message is convolved and embedded into a Qi hyper-chaotic system characterizing a high disorder degree. The masking scheme was tested using both Qi hyper-chaos and Lorenz chaos and indicated that Qi hyper-chaos based masking can resist attacks of the filtering and power spectrum analysis, while the Lorenz based scheme fails for high amplitude data. To unmask the message at the receiving end, two methods are proposed. In the first method, a model-free synchronizer, i.e. a multivariable higher-order differential feedback controller between the transmitter and receiver is employed to de-convolve the message embedded in the receiving signal. In the second method, no synchronization is required since the message is de-convolved using the information of the estimated derivative.

关键词： Qi hyper-chaos masking high-order differentiator chaos-based encryption

Monitoring the effects of land transformation on African clawless otters(Aonyx capensis)using fecal glucocorticoid metabolite concentrations as a measure of stress

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Integrative Zoology 2020年第4期15卷 293-306页

作者： Tshepiso L.MAJELANTLE Trevor MCINTYRE Andre GANSWINDT Mammal Research Institute Department of Zoology and EntomologyUniversity of PretoriaPretoriaSouth Africa Department of Life and Consumer Sciences University of South AfricaPretoriaSouth Africa Endocrine Research Laboratory Department of Anatomy and PhysiologyUniversity of PretoriaOnderstepoortSouth Africa Centre for Veterinary Wildlife Studies Faculty of Veterinary ScienceUniversity of PretoriaOnderstepoortSouth Africa

In a time of increasing environmental change caused by anthropogenic disturbance,there is a greater need to understand animal adaptations to manmade *** this regard,the measurement of stress-related endocrine markers provides a useful tool to examine the impact of environmental challenges and the physiological consequences for wildlife occupying such *** aims of the present study were to validate fecal glucocorticoid metabolite(fGCM)concentrations as a measure of stress using samples from a male African clawless otter(Aonyx capensis;n=1)and to compare fGCM concentrations of otters occurring in a transformed and in 2 natural areas in South *** the 5 different enzyme-immunoassays(EIA)tested,a cortisol and oxoetiocholanolone(measuring 11,17 dioxoandrostanes)EIA revealed the highest response(74%and 48%increase,respectively)30 and 24 hours after a stress event(translocation of a captive individual as part of its rehabilitation prior to release),respec*** both EIAs,fGCM concentrations were comparable for samples collected up to 3 h *** the cortisol EIA for subsequent analyses,fGCM concentrations of animals from the transformed area(n=20;mean[±SD]:0.468[±0.539]µg/g dry weight[DW])were significantly higher(P=0.013)than those from otters in the natural areas(n=17;0.242[±0.226]µg/g DW).These preliminary results suggest that African clawless otters may have increased adrenocortical activity that could be due to conditions linked to living in a transformed environment.

关键词： African clawless otter fecal glucocorticoid metabolites non-invasive hormone measurement stress urbanization

Preliminary examination of electrochemical and spectroscopic features of trithiocarbonate collectors for sulfide mineral flotation

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中国有色金属学会会刊：英文版 2000年第S1期10卷 12-18页

作者： R. Du Plessis 1, J.D. Miller 1, J.C.Davidtz 2 1. Department of Metallurgical Engineering, university of Utah, Salt Lake City, Utah 84102, USA 2. Department of Materials Science and Metallurgical Engineering, university of pretoria, pretoria 0002 univ Utah Dept Met Engn Salt Lake City UT 84102 USA univ pretoria Dept Met Engn & Mat Sci ZA-0002 Pretoria South Africa

The redox potentials of xanthate/dixanthogen (dithiocarbonate/di dithiocarbonate, DTC/(DTC) 2) and trithiocarbonate/di trithiocarbonate (TTC/(TTC) 2) couples have been measured for the potassium salts. The spectroscopic characteristics of these sulfide mineral collectors were determined by FTIR and UV analysis. Electrochemically controlled contact angle measurements at a pyrite surface provided the basis to analyze the effect of the functional group ( O CS 2 versus S CS 2) on the hydrophobic surface state. Results from this preliminary examination are discussed with respect to the nature of collector adsorption and the pyrite flotation response.

关键词： redox potential trithiocarbonate collector sulfide mineral flotation

Socially responsive research-based desisn in an architecture studio

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Frontiers of Architectural Research 2018年第2期7卷 211-234页

作者： Carin Combrinck Department of Architecture University of Pretoria Pretoria Gauteng 2000 South Africa

Globally, the architectural profession faces complex challenges, bringing the transformation of the curriculum to the forefront of critical discourse. This article reflects on the Honors programme at the university of pretoria Architecture Department during the first semester of 2016, where a research-based design approach has been established. In particular, the focus is on the informal settlement of Woodtane Village in pretoria, situated on a contested site among private residential estates. From this study, it is argued that a research-based approach serves to prepare graduates for the complex decision-making and collaboration that is required for the development of socially responsive design.

关键词： Social responsiveness Research-baseddesign Curriculum transformation Collaboration Informat settlement upgrade

Is the soil seed bank a reliable source for passive restoration of bush-cleared semi-arid rangelands of South Africa?

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Ecological Processes 2020年第1期9卷 1-16页

作者： Mthunzi Mndela Casper Ignacio Madakadze Florence Nherera-Chokuda Sikhalazo Dube university of pretoria P/Bag X20HatfieldPretoria 0028South Africa Agricultural Research Council APIP/Bag X02IrenePretoria 0062South Africa

Background:Bush clearing of encroached rangelands is crucial for restoration of herbaceous cover and *** after bush clearing depends largely on the soil seed bank(SSB)size and *** assess the potential of the SSB to facilitate post-clearing herbaceous restoration,we examined the SSB density,composition and diversity and similarity between SSB and aboveground vegetation(AGV).Methods:The study was conducted in semi-arid rangelands of Maseding and Kgomokgomo in North-West Province of South *** each rangeland,all woody plants in three 1250 m^(2) plots were cut using saws and loppers,with the stumps treated with *** observations were conducted in cleared and uncleared *** samples were collected at three depths(0-10,10-20 and 20-30 cm)in each microsite in April(pretreatment),August,October and December 2016 and in April and August *** was assessed using seedling emergence method,whereas pre-and post-clearing surveys of AGV were conducted in February 2016 and 2017,***:Cleared microsites had significantly(p<0.01)higher seed bank densities(1872 and 693 seeds m^(-2) at Maseding and Kgomokgomo,respectively)relative to uncleared microsites in August 2017,with grasses accounting for higher densities than other plant functional groups in the upper 0-10 *** grasses(Aristida congesta ***,Brachiaria eruciformis and Tragus berteronianus)and invasive forbs(Bidens pilosa and Schkuhria pinnata)dominated the SSB in cleared microsites at Maseding,whereas succulents(Portulaca spp.)and pioneer grasses(*** and Urochloa mosambicensis)were abundant at Kgomokgomo in August *** and AGV were dissimilar until December 2016;thereafter,similarity increased significantly(p<0.05)in cleared microsites(Sørensen’s coefficient=0.60 to 0.66 at Maseding and 0.43 to 0.52 at Kgomokgomo)compared to uncleared *** diversity was highest in August 2016 and April 2017 at Maseding,but

关键词： Bush clearing Seed bank density Seed bank diversity Sørensen’s coefficient

Lakshanhatti stromatolite, India： Biogenic or abiogenic？

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Journal of Palaeogeography 2016年第3期5卷 292-310页

作者： Adrita Choudhuri Subir Sarkar Wladyslaw Altermann Soumik Mukhopadhyay Pradip K.Bose Department of Geological Sciences Jadavpur University Kolkata 700032 India Department of Geology University of Pretoria Pretoria 0002 South Africa

Abstract The extraordinary lateral continuity of isopachous stromatotite laminae in the -87 m-thick Mesoproterozoic Lakshanhatti Dolomite （India） evinces chemical precipitation. Fan-shaped crystals grown on tamina surfaces further corroborate this contention; growth of fan-shaped crystats under the overhanging stromatolite column-margin indicates direct carbonate precipitation from ambient waters. The fan-shaped crystats are stacked up, separated onty by thin dark micritic taminae. In a retativety upper stratigraphic in- terval of the formation, tighter laminae characterized by a dotted texture and traversed by numerous winding tubutar voids change graduatty upwards into dark micritic taminae. Some sporadicatty distributed lenticutar intraciastic beds also have the similarly dark micritic coatings. Ctear carbonate cement crusts atso occur between laminae and between successive dark micritic coats around intraciasts. DuU cathodotuminescence （CL） characterizes this cement as weU as the cement lining within earty dia^enetic voids, in contrast, the taminae with dotted textures show dirty orange luminescence, white the dark micritic taminae and the dark micritic grain-coats display dear bright orange luminescence. Pyrite and its pseudomorphs are preferabty concentrated along the dark micritic laminae. Carbon content in these dark micritic components, whether laminae or coats, is much higher than in the lighter components, exceeding what can be accounted for their CaMg（COs）2 composition. A large part of this carbon is kerogen, ptausibly biogenic. The dark components are, therefore, reasonably, though not unequivocally, assumed to be microbial mats. Degradation of the mats might have given rise to the tight laminae with dotted textures. The fuzzy-margin tubes within the tight laminae probabty manifest the escape of gases generated during organic matter decomposition. Si-At-rich terrigenous fines thinty draping the dark carbonaceous taminae was possibty the resutt of baft

关键词： StromatoHte Lamina continuity Mesoproterozoic Lakshanhatti Dolomite Member Inorganicprecipitation Kerogen enrichment Filamentous microbiota

Spatio-temporal patterns and changes in environmental attitudes and place attachment in Gauteng, South Africa

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Geo-Spatial Information Science 2021年第4期24卷 666-677页

作者： Simangele Dlamini Solomon G.Tesfamichael Gregory D.Breetzke Tholang Mokhele Department of Geography Environmental Management and Energy StudiesUniversity of JohannesburgJohannesburgSouth Africa Geospatial Analytics eResearch Knowledge CentreHuman Sciences Research CouncilPretoriaSouth Africa Department of Geography Geoinformatics and MeteorologyUniversity of PretoriaPretoriaSouth Africa

In this study,we employed a number of geospatial techniques to examine the spatiotemporal patterns and changes of environmental attitudes and place attachment values in the Gauteng province of South *** data were obtained from the Gauteng City Region Observatory’s Quality of Life Survey collected at three separate points in time,namely 2013,2015,and *** indicated that wards(smallest administrative and analysis units)located on the urban periphery of Gauteng,which are generally less affluent,largely held more negative environmental attitudes and place attachment values during the three time *** contrast,centrally located wards,which are generally more affluent,expressed more positive environmental attitudes but less place attachment values,especially in *** findings of this research not only highlight the complex spatio-temporal distribution of environmental attitudes and place attachment values throughout Gauteng but also empha-size the need for spatially targeted state interventions for future environmental planning within the province.

关键词： Spatio-temporal changes environmental attitudes place attachment Gauteng spatial patterns