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Sökning: WFRF:(Yang Qi) > Luleå tekniska universitet

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1.
  • Bentham, James, et al. (författare)
  • A century of trends in adult human height
  • 2016
  • Ingår i: eLIFE. - : eLife Sciences Publications Ltd. - 2050-084X. ; 5
  • Tidskriftsartikel (refereegranskat)abstract
    • Being taller is associated with enhanced longevity, and higher education and earnings. We reanalysed 1472 population-based studies, with measurement of height on more than 18.6 million participants to estimate mean height for people born between 1896 and 1996 in 200 countries. The largest gain in adult height over the past century has occurred in South Korean women and Iranian men, who became 20.2 cm (95% credible interval 17.5–22.7) and 16.5 cm (13.3– 19.7) taller, respectively. In contrast, there was little change in adult height in some sub-Saharan African countries and in South Asia over the century of analysis. The tallest people over these 100 years are men born in the Netherlands in the last quarter of 20th century, whose average heights surpassed 182.5 cm, and the shortest were women born in Guatemala in 1896 (140.3 cm; 135.8– 144.8). The height differential between the tallest and shortest populations was 19-20 cm a century ago, and has remained the same for women and increased for men a century later despite substantial changes in the ranking of countries.
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  • Feng, Yan, et al. (författare)
  • Mechanical Activation of Granulated Copper Slag and Its Influence on Hydration Heat and Compressive Strength of Blended Cement
  • 2019
  • Ingår i: Materials. - Basel, Switzerland : MDPI. - 1996-1944 .- 1996-1944. ; 12:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Mechanical activation of granulated copper slag (GCS) is carried out in the present study for the purposes of enhancing pozzolanic activity for the GCS. A vibration mill mills the GCS for 1, 2, and 3 h to produce samples with specific surface area of 0.67, 1.03 and 1.37 m²/g, respectively. The samples are used to replace 30% cement (PC) to get 3 PC-GCS binders. The hydration heat and compressive strength are measured for the binders and derivative thermogravimetric /thermogravimetric analysis (DTG/TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) are used to characterize the paste samples. It is shown that cumulative heat and compressive strength at different ages of hydration and curing, respectively, are higher for the binders blending the GCS milled for a longer time. The compressive strength after 90 d of curing for the binder with the longest milling time reaches 35.7 MPa, which is higher than the strength of other binders and close to the strength value of 39.3 MPa obtained by the PC pastes. The percentage of fixed lime by the binder pastes at 28 days is correlated with the degree of pozzolanic reaction and strength development. The percentage is higher for the binder blending the GCS with longer milling time and higher specific surface area. The pastes with binders blending the GCS of specific surface area of 0.67 and 1.37 m²/g fix lime of 15.20 and 21.15%, respectively. These results together with results from X-ray diffraction (XRD), FTIR, and SEM investigations demonstrate that the mechanical activation via vibratory milling is an effective method to enhance the pozzolanic activity and the extent for cement substitution by the GCS as a suitable supplementary cementitious material (SCM).
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4.
  • Guo, Lijie, et al. (författare)
  • Industrial practice on optimizing tailings composition combined with ore concentration processes
  • 2017
  • Ingår i: 12th International Conference on Mining with Backfill 2017, Minefill 2017. - Englewood, CO : Society for Mining, Metallurgy and Exploration. - 9781510835818 ; , s. 69-79
  • Konferensbidrag (refereegranskat)abstract
    • Cemented paste backfill (CPB) is increasingly applied in underground mines world-wide and has a broad prospect considering its benefits in environmental protection and ground control. During the paste production, a well-graded aggregate is critical for the achievement of CPB. Mine tailings from the outcome of ore-dressing plant are commonly used as the fill aggregate. However, it is difficult to obtain an ideal particle size distribution for the mine tailings which are roughly mixed with final residuum in ore concentration processes. In this study, a novel industrial method is proposed to select fill aggregates from different parts of ore-dressing processes. With combined design of concentration plant and backfill plant, the tailings with desired particle sizes and proportions during the mineral processing are chosen to produce CPB without disturbing the regular ore concentration. The problem of passively accepting final tailings from ore-dressing plant has been improved
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5.
  • Jia, Qi, et al. (författare)
  • Effects of Fine Content, Binder Type and Porosity on Mechanical Properties of Cemented Paste Backfill with Co-Deposition of Tailings Sand and Smelter Slag
  • 2016
  • Ingår i: Electronic Journal of Geotechnical Engineering. - : Mete Öner. - 1089-3032. ; 21:20, s. 6971-6988
  • Tidskriftsartikel (refereegranskat)abstract
    • Mine backfilling is a process where the underground voids resulted from mining are filled with waste materials. The potential of co-depositing iron sand produced from smelting process with tailings sand was investigated in the present study. Different amounts of iron sand were mixed with the tailings sand to prepare cemented paste backfill (CPB) samples. Two types of binders were used. Uniaxial compression tests were performed for the CPB samples after 28 days of curing. The porosities of the samplers after curing were calculated to correlate the porosity with the uniaxial compression strength, UCS. Results from uniaxial compression tests showed that the amount of iron sand and the type of the binder influences the UCS, as well as content values of fines and porosity. These results demonstrated the possibility for a part of Fe-sand to be deposited together with the tailings sand to increase UCS values for the CPB samples, which will be beneficial for both mining operation and environmental protection.
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  • Resultat 1-6 av 6

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