Evaluation of slurry settling rate using fuzzy rule-based modeling     

Shahid Azam  Rehan Sadiq 《Acta Geotechnica》2006,1(3):149-156

The pressure acid leach process is the most widely used method of metal extraction from laterite ores. The self-weight settling rate of the ore slurries governs the throughput of the process and is improved by adding synthetic polymers. The charge density, molecular weight, and dosage of the polymers are the key factors influencing the settling rate of the slurries. This interdisciplinary paper uses the geotechnical understanding of hindered sedimentation for a mining engineering application. A conceptual fuzzy rule-based model was developed to evaluate the initial hydraulic conductivity of polymer-modified laterite ore slurries. Identification of control parameters and selection of the model architecture (fuzzy rule-base) were based on expert judgment. The developed model was trained and validated using bench-scale settling test data. The model reasonably predicts the initial hydraulic conductivity of polymer-added laterite ore slurry with a coefficient of determination of 0.75. Rank correlation coefficient-based sensitivity analyses indicated that charge density was the most significant polymer parameter followed by molecular weight and then by dosage. Charge density accounted for more than 97% of variability in the initial hydraulic conductivity estimates for both anionic and cationic polymers.  相似文献   

Effect of Secondary Circulations on the Surface–Atmosphere Exchange of Energy at an Isolated Semi-arid Forest     

Konstantin Kröniger  Frederik De Roo  Peter Brugger  Sadiq Huq  Tirtha Banerjee  Judith Zinsser  Eyal Rotenberg  Dan Yakir  Shani Rohatyn  Matthias Mauder 《Boundary-Layer Meteorology》2018,169(2):209-232

Afforestation in semi-arid regions can potentially enhance the global carbon sink by increasing the terrestrial biomass. However, the survival of planted forests under such extreme environmental conditions is not guaranteed a priori, and critically depends on the surface–atmosphere exchange of energy. We investigate the pine forest Yatir in Israel, an example of a man-made semi-arid ecosystem, by means of large-eddy simulations. We focus on the interaction between surface–atmosphere exchange and secondary circulations that couple the isolated forest to the surrounding shrubland. The large-eddy simulations feature a grid resolution that resolves the forest canopy in several layers, and are initialized by satellite data and Doppler lidar, eddy-covariance and radiosonde measurements. We perform three large-eddy simulations with different geostrophic wind speeds to investigate the influence of those wind speeds on the surface–atmosphere exchange. We reproduce the measured mean updrafts above the forest and mean downdrafts above the shrubland, which increase in strength with decreasing geostrophic wind speed. The largest updrafts emerge above the older, denser part of the forest, triggering secondary circulations. The spatial extent of these circulations does not cover the entire forest area, although we observe a reduced aerodynamic resistance in the regions of updraft. Our simulations indicate that the enhanced surface–atmosphere exchange of the Yatir forest is not sufficient to compensate for the increased net radiation, due to the lower albedo of the forest with respect to the surroundings, resulting in higher air temperatures inside the forest. However, the difference between the forest and shrubland temperatures decreases with increasing geostrophic wind speed due to reduction in the aerodynamic resistance.  相似文献   

Seasonal evaluation of evapotranspiration fluxes from MODIS satellite and mesoscale model downscaled global reanalysis datasets     

Prashant K. Srivastava  Dawei Han  Tanvir Islam  George P. Petropoulos  Manika Gupta  Qiang Dai 《Theoretical and Applied Climatology》2016,124(1-2):461-473

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Exploration of the high-redshift universe enabled by THESEUS     

Tanvir  N. R.  Le Floc’h  E.  Christensen  L.  Caruana  J.  Salvaterra  R.  Ghirlanda  G.  Ciardi  B.  Maio  U.  D’Odorico  V.  Piedipalumbo  E.  Campana  S.  Noterdaeme  P.  Graziani  L.  Amati  L.  Bagoly  Z.  Balázs  L. G.  Basa  S.  Behar  E.  De Cia  A.  Valle  M. Della  De Pasquale  M.  Frontera  F.  Gomboc  A.  Götz  D.  Horvath  I.  Hudec  R.  Mereghetti  S.  O’Brien  P. T.  Osborne  J. P.  Paltani  S.  Rosati  P.  Sergijenko  O.  Stanway  E. R.  Szécsi  D.  Tot́h  L. V.  Urata  Y.  Vergani  S.  Zane  S. 《Experimental Astronomy》2021,52(3):219-244

Experimental Astronomy - At peak, long-duration gamma-ray bursts are the most luminous sources of electromagnetic radiation known. Since their progenitors are massive stars, they provide a tracer...  相似文献   

The THESEUS space mission: science goals,requirements and mission concept     

Amati  L.  O’Brien  P.T.  Götz  D.  Bozzo  E.  Santangelo  A.  Tanvir  N.  Frontera  F.  Mereghetti  S.  Osborne  J. P.  Blain  A.  Basa  S.  Branchesi  M.  Burderi  L.  Caballero-García  M.  Castro-Tirado  A. J.  Christensen  L.  Ciolfi  R.  De Rosa  A.  Doroshenko  V.  Ferrara  A.  Ghirlanda  G.  Hanlon  L.  Heddermann  P.  Hutchinson  I.  Labanti  C.  Le Floch  E.  Lerman  H.  Paltani  S.  Reglero  V.  Rezzolla  L.  Rosati  P.  Salvaterra  R.  Stratta  G.  Tenzer  C. 《Experimental Astronomy》2021,52(3):183-218

Experimental Astronomy - THESEUS, one of the two space mission concepts being studied by ESA as candidates for next M5 mission within its Comsic Vision programme, aims at fully exploiting Gamma-Ray...  相似文献   

The evolution of barred spiral galaxies in the Hubble Deep Fields North and South     

R. G. Abraham  M. R. Merrifield  R. S. Ellis  N. R. Tanvir  J. Brinchmann 《Monthly notices of the Royal Astronomical Society》1999,308(2):569-576

The frequency of barred spiral galaxies as a function of redshift contains important information on the gravitational influence of stellar discs in their dark matter haloes and may also distinguish between contemporary theories for the origin of galactic bulges. In this paper we present a new quantitative method for determining the strength of barred spiral structure, and verify its robustness to redshift-dependent effects. By combining galaxy samples from the Hubble Deep Field North with newly available data from the Hubble Deep Field South, we are able to define a statistical sample of 46 low-inclination spiral systems with I _814 W<23.2 mag. Analysing the proportion of barred spiral galaxies seen as a function of redshift, we find a significant decline in the fraction of barred spirals with redshift. The redshift distribution of 22 barred and 24 non-barred spirals with suitable inclinations is inconsistent with their being drawn from the same distribution at the 99 per cent confidence level. The physical significance of this effect remains unclear, but several possibilities include dynamically hotter (or increasingly dark-matter-dominated) high-redshift discs, or an enhanced efficiency in bar destruction at high redshifts. By investigating the formation of the 'orthogonal' axis of Hubble's classification tuning fork, our result complements studies of evolution in the early–late sequence, and pushes to later epochs the redshift at which the Hubble classification sequence is observed to be in place.  相似文献   

Deep Gemini/GMOS imaging of an extremely isolated globular cluster in the Local Group     

A. D. Mackey  A. M. N. Ferguson  M. J. Irwin  N. F. Martin  A. P. Huxor  N. R. Tanvir  S. C. Chapman  R. A. Ibata  G. F. Lewis  A. W. McConnachie 《Monthly notices of the Royal Astronomical Society》2010,401(1):533-546

We report on deep imaging of a remote M31 globular cluster, MGC1, obtained with Gemini/GMOS. Our colour–magnitude diagram for this object extends ∼5 mag below the tip of the red-giant branch and exhibits features consistent with an ancient metal-poor stellar population, including a long, well-populated horizontal branch. The red-giant branch locus suggests MGC1 has a metal abundance  [M/H]≈−2.3  . We measure the distance to MGC1 and find that it lies ∼160 kpc in front of M31 with a distance modulus  μ= 23.95 ± 0.06  . Combined with its large projected separation of   R _p= 117 kpc  from M31, this implies a deprojected radius of   R _gc= 200 ± 20 kpc  , rendering it the most isolated known globular cluster in the Local Group by some considerable margin. We construct a radial brightness profile for MGC1 and show that it is both centrally compact and rather luminous, with   M_V =−9.2  . Remarkably, the cluster profile shows no evidence for a tidal limit and we are able to trace it to a radius of at least 450 pc, and possibly as far as ∼900 pc. The profile exhibits a power-law fall-off with exponent  γ=−2.5  , breaking to  γ=−3.5  in its outermost parts. This core-halo structure is broadly consistent with expectations derived from numerical models, and suggests that MGC1 has spent many gigayears in isolation.  相似文献   

Radar rainfall uncertainty modelling influenced by wind          下载免费PDF全文

Qiang Dai  Dawei Han  Miguel A. Rico‐Ramirez  Lu Zhuo  Nergui Nanding  Tanvir Islam 《水文研究》2015,29(7):1704-1716

Radar‐based estimates of rainfall are affected by many sources of uncertainties, which would propagate through the hydrological model when radar rainfall estimates are used as input or initial conditions. An elegant solution to quantify these uncertainties is to model the empirical relationship between radar measurements and rain gauge observations (as the ‘ground reference’). However, most current studies only use a fixed and uniform model to represent the uncertainty of radar rainfall, without consideration of its variation under different synoptic regimes. Wind is such a typical weather factor, as it not only induces error in rain gauge measurements but also causes the raindrops observed by weather radar to drift when they reach the ground. For this reason, as a first attempt, this study introduces the wind field into the uncertainty model and designs the radar rainfall uncertainty model under different wind conditions. We separate the original dataset into three subsamples according to wind speed, which are named as WDI (0–2 m/s), WDII (2–4 m/s) and WDIII (>4 m/s). The multivariate distributed ensemble generator is introduced and established for each subsample. Thirty typical events (10 at each wind range) are selected to explore the behaviours of uncertainty under different wind ranges. In each time step, 500 ensemble members are generated, and the values of 5th to 95th percentile values are used to produce the uncertainty bands. Two basic features of uncertainty bands, namely dispersion and ensemble bias, increase significantly with the growth of wind speed, demonstrating that wind speed plays a considerable role in influencing the behaviour of the uncertainty band. On the basis of these pieces of evidence, we conclude that the radar rainfall uncertainty model established under different wind conditions should be more realistic in representing the radar rainfall uncertainty. This study is only a start in incorporating synoptic regimes into rainfall uncertainty analysis, and a great deal of more effort is still needed to build a realistic and comprehensive uncertainty model for radar rainfall data. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Tracking a tropical cyclone through WRF–ARW simulation and sensitivity of model physics     

Tanvir Islam  Prashant K. Srivastava  Miguel A. Rico-Ramirez  Qiang Dai  Manika Gupta  Sudhir K. Singh 《Natural Hazards》2015,76(3):1473-1495

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Dynamics of tilted cylindrical geometry     

M. Sharif  Sobia Sadiq 《Astrophysics and Space Science》2016,361(9):278

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