| Records |
| Author |
Kurmanseiit, M.B.; Tungatarova, M.S.; Royer, J.-J.; Aizhulov, D.Y.; Shayakhmetov, N.M.; Kaltayev, A. |
| Title |
Streamline-based reactive transport modeling of uranium mining during in-situ leaching: Advantages and drawbacks |
Type |
Journal Article |
| Year |
2023 |
Publication |
Hydrometallurgy |
Abbreviated Journal |
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| Volume |
220 |
Issue |
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Pages |
106107 |
Keywords  |
3D modeling, In-situ leaching, Reactive transport model, Streamlines, Uranium recovery |
| Abstract |
Reactive transport modeling is known to be computationally intensive when applied to 3D problems. Transforming sequential computing on the computer processor units (CPU) into parallelized computation on the high-performance parallel graphic processor units (GPU) is a classical approach to increasing computational performance. Another complementary approach is to decompose a complex 3D modeling problem into a set of simpler 1D problems using streamline approaches which can be easily parallelized, therefore reducing computation time. This paper investigates solutions to the equations governing dissolution and transport using streamlines coupled with a parallelization approach. In addition, an analytical solution to the dissolution and transfer equations of uranium describing the In-Situ Leaching (ISL) mining recovery is found using an approximation series to the 2nd order. The analytical solution is compared to the 1D numerical resolution along the streamlines and to the 3D simulation results superimposed on the streamline. Both approaches give similar results with a relative error of \textless2 % (2%). The proposed methodology is then applied to a case study in which the classical 3D resolution is compared to the newly suggested streamline solution, demonstrating that the streamline approach increases computational performances by a factor ranging from hundred to thousand depending on the complexity of the grid-block model. |
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0304-386x |
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no |
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THL @ christoph.kuells @ kurmanseiit_streamline-based_2023 |
Serial |
190 |
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| Author |
Milena-Pérez, A.; Piñero-García, F.; Benavente, J.; Expósito-Suárez, V.M.; Vacas-Arquero, P.; Ferro-García, M.A. |
| Title |
Uranium content and uranium isotopic disequilibria as a tool to identify hydrogeochemical processes |
Type |
Journal Article |
| Year |
2021 |
Publication |
Journal of Environmental Radioactivity |
Abbreviated Journal |
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| Volume |
227 |
Issue |
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Pages |
106503 |
| Keywords |
234U/238U, Betic cordillera, Groundwater, Hydrogeochemistry, Uranium natural isotopes |
| Abstract |
This paper studies the uranium content and uranium isotopic disequilibria as a tool to identify hydrogeochemical processes from 52 groundwater samples in the province of Granada (Betic Cordillera, southeastern Spain). According to the geological complexity of the zone, three groups of samples have been considered. In Group 1 (thermal waters; longest residence time), the average uranium content was 2.63 ± 0.16 μg/L, and 234U/238U activity ratios (AR) were the highest of all samples, averaging 1.92 ± 0.30. In Group 2 (mainly springs from carbonate aquifers; intermediate residence time), dissolved uranium presented an average value of 1.34 ± 0.13 μg/L, while AR average value was 1.38 ± 0.25. Group 3 comes from pumping wells in a highly anthropized alluvial aquifer. In this group, where the residence time of the groundwater is the shortest of the three, average uranium content was 5.28 ± 0.26 μg/L, and average AR is the lowest (1.17 ± 0.12). In addition, the high dissolved uranium value and the low AR brought to light the contribution of fertilizers (Group 3). In the three groups, 235U/238U activity ratios were similar to the natural value of 0.046. Therefore, 235U detected in the samples comes from natural sources. This study is completed with the determination of major ions and physicochemical parameters in the groundwater samples and the statistical analysis of the data by using the Principal Component Analysis. This calculation indicates the correlation between uranium isotopes and bicarbonate and nitrate anions. |
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0265-931x |
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THL @ christoph.kuells @ milena-perez_uranium_2021 |
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112 |
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Belz, L.; Schüller, I.; Wehrmann, A.; Köster, J.; Wilkes, H. |
| Title |
The leaf wax biomarker record of a Namibian salt pan reveals enhanced summer rainfall during the Last Glacial-Interglacial Transition |
Type |
Journal Article |
| Year |
2020 |
Publication |
Palaeogeography, Palaeoclimatology, Palaeoecology |
Abbreviated Journal |
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| Volume |
543 |
Issue |
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Pages |
109561 |
| Keywords |
-Alkanes, -Alkanols, Late Quaternary, Organic geochemistry, Palaeohydrology, Southern Africa |
| Abstract |
Conventional continental geoarchives are rarely available in arid southern Africa. Therefore, palaeoclimate data in this area are still patchy and late Quaternary climate development is only poorly understood. In the western Kalahari, salt pans (playas, ephemeral lakes) are common and can feature quasi-continuous sedimentation. This study presents the first climate-related biomarker record using sediments from the Omongwa Pan, a Kalahari salt pan located in eastern Namibia. Our approach to reconstruct vegetation and hydrology focuses on biogeochemical bulk parameters and plant wax-derived lipid biomarkers (n-alkanes, n-alkanols, and fatty acids) and their compound-specific carbon and hydrogen isotopic compositions. The presented record reaches back to 27 ka. During the glacial, rather low δ2H values of n-alkanes and low sediment input exclude a strong influence of winter rainfall. n-Alkane and n-alkanol distributions and δ13C values of n-hentriacontane (n-C31) indicate a shift to a vegetation with a higher proportion of C4 plants at the end of the Last Glacial Maximum until the end of Heinrich Stadial I (ca. 18–14.8 ka), which we interpret to indicate an abrupt excursion to a short wetter period likely to be caused by a temporary southward shift of the Intertropical Convergence Zone. Shifts in δ2H values of n-C31 and plant wax parameters give evidence for changes to drier conditions during early Holocene. Comparison of this dataset with representative continental records from the region points to a major influence of summer rainfall at Omongwa Pan during the regarded time span and demonstrates the potential of southern African salt pans as archives for biomarker-based climate proxies. |
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0031-0182 |
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THL @ christoph.kuells @ belz_leaf_2020 |
Serial |
104 |
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Eliades, M.; Bruggeman, A.; Djuma, H.; Christofi, C.; Kuells, C. |
| Title |
Quantifying Evapotranspiration and Drainage Losses in a Semi-Arid Nectarine (Prunus persica var. nucipersica) Field with a Dynamic Crop Coefficient (Kc) Derived from Leaf Area Index Measurements |
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Journal Article |
| Year |
2022 |
Publication |
Water |
Abbreviated Journal |
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14 |
Issue |
5 |
Pages |
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Quantifying evapotranspiration and drainage losses is essential for improving irrigation efficiency. The FAO-56 is the most popular method for computing crop evapotranspiration. There is, however, a need for locally derived crop coefficients (Kc) with a high temporal resolution to reduce errors in the water balance. The aim of this paper is to introduce a dynamic Kc approach, based on Leaf Area Index (LAI) observations, for improving water balance computations. Soil moisture and meteorological data were collected in a terraced nectarine (Prunus persica var. nucipersica) orchard in Cyprus, from 22 March 2019 to 18 November 2021. The Kc was derived as a function of the canopy cover fraction (c), from biweekly in situ LAI measurements. The use of a dynamic Kc resulted in Kc estimates with a bias of 17 mm and a mean absolute error of 0.8 mm. Evapotranspiration (ET) ranged from 41% of the rainfall (P) and irrigation (I) in the wet year (2019) to 57% of P + I in the dry year (2021). Drainage losses from irrigation (DR_I) were 44% of the total irrigation. The irrigation efficiency in the nectarine field could be improved by reducing irrigation amounts and increasing the irrigation frequency. Future studies should focus on improving the dynamic Kc approach by linking LAI field observations with remote sensing observations and by adding ground cover observations. |
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2073-4441 |
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no |
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THL @ christoph.kuells @ Marinos2022 |
Serial |
82 |
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| Author |
Eliades, M.; Bruggeman, A.; Djuma, H.; Christofi, C.; Kuells, C. |
| Title |
Quantifying Evapotranspiration and Drainage Losses in a Semi-Arid Nectarine (Prunus persica var. nucipersica) Field with a Dynamic Crop Coefficient (Kc) Derived from Leaf Area Index Measurements |
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Journal Article |
| Year |
2022 |
Publication |
Water |
Abbreviated Journal |
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14 |
Issue |
5 |
Pages |
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Quantifying evapotranspiration and drainage losses is essential for improving irrigation efficiency. The FAO-56 is the most popular method for computing crop evapotranspiration. There is, however, a need for locally derived crop coefficients (Kc) with a high temporal resolution to reduce errors in the water balance. The aim of this paper is to introduce a dynamic Kc approach, based on Leaf Area Index (LAI) observations, for improving water balance computations. Soil moisture and meteorological data were collected in a terraced nectarine (Prunus persica var. nucipersica) orchard in Cyprus, from 22 March 2019 to 18 November 2021. The Kc was derived as a function of the canopy cover fraction (c), from biweekly in situ LAI measurements. The use of a dynamic Kc resulted in Kc estimates with a bias of 17 mm and a mean absolute error of 0.8 mm. Evapotranspiration (ET) ranged from 41% of the rainfall (P) and irrigation (I) in the wet year (2019) to 57% of P + I in the dry year (2021). Drainage losses from irrigation (DR_I) were 44% of the total irrigation. The irrigation efficiency in the nectarine field could be improved by reducing irrigation amounts and increasing the irrigation frequency. Future studies should focus on improving the dynamic Kc approach by linking LAI field observations with remote sensing observations and by adding ground cover observations. |
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2073-4441 |
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THL @ christoph.kuells @ w14050734 |
Serial |
81 |
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Aldawsari, S.; Kampmann, R.; Harnisch, J.; Rohde, C. |
| Title |
Setting Time, Microstructure, and Durability Properties of Low Calcium Fly Ash/Slag Geopolymer: A Review |
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Journal Article |
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2022 |
Publication |
Materials |
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15 |
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3 |
Pages |
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Ordinary Portland cement (OPC) is known for its significant contribution to carbon dioxide emissions. Geopolymer has a lower footprint in terms of CO2 emissions and has been considered as an alternative for OPC. A well-developed understanding of the use of fly-ash-based and slag-based geopolymers as separate systems has been reached in the literature, specifically regarding their mechanical properties. However, the microstructural and durability of the combined system after slag addition introduces more interactive gels and complex microstructural formations. The microstructural changes of complex blended systems contribute to significant advances in the durability of fly ash/slag geopolymers. In the present review, the setting time, microstructural properties (gel phase development, permeability properties, shrinkage behavior), and durability (chloride resistance, sulfate attack, and carbonatation), as discussed literature, are studied and summarized to simplify and draw conclusions. |
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1996-1944 |
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THL @ christoph.kuells @ ma15030876 |
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84 |
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Eliades, M.; Bruggeman, A.; Djuma, H.; Christofi, C.; Kuells, C. |
| Title |
Quantifying Evapotranspiration and Drainage Losses in a Semi-Arid Nectarine (Prunus persica var. nucipersica) Field with a Dynamic Crop Coefficient (Kc) Derived from Leaf Area Index Measurements |
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Journal Article |
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2022 |
Publication |
Water |
Abbreviated Journal |
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14 |
Issue |
5 |
Pages |
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| Abstract |
Quantifying evapotranspiration and drainage losses is essential for improving irrigation efficiency. The FAO-56 is the most popular method for computing crop evapotranspiration. There is, however, a need for locally derived crop coefficients (Kc) with a high temporal resolution to reduce errors in the water balance. The aim of this paper is to introduce a dynamic Kc approach, based on Leaf Area Index (LAI) observations, for improving water balance computations. Soil moisture and meteorological data were collected in a terraced nectarine (Prunus persica var. nucipersica) orchard in Cyprus, from 22 March 2019 to 18 November 2021. The Kc was derived as a function of the canopy cover fraction (c), from biweekly in situ LAI measurements. The use of a dynamic Kc resulted in Kc estimates with a bias of 17 mm and a mean absolute error of 0.8 mm. Evapotranspiration (ET) ranged from 41% of the rainfall (P) and irrigation (I) in the wet year (2019) to 57% of P + I in the dry year (2021). Drainage losses from irrigation (DR_I) were 44% of the total irrigation. The irrigation efficiency in the nectarine field could be improved by reducing irrigation amounts and increasing the irrigation frequency. Future studies should focus on improving the dynamic Kc approach by linking LAI field observations with remote sensing observations and by adding ground cover observations. |
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2073-4441 |
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THL @ christoph.kuells @ w14050734 |
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85 |
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Benites Lazaro, L.L.; Bellezoni, R.; Puppim de Oliveira, J.; Jacobi, P.R.; Giatti, L. |
| Title |
Ten Years of Research on the Water-Energy-Food Nexus: An Analysis of Topics Evolution |
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Journal Article |
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2022 |
Publication |
Frontiers in Water |
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4 |
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THL @ christoph.kuells @ article |
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86 |
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Illgen, M.; Ackermann, H. |
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Book Chapter |
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2019 |
Publication |
Urban Flood Prevention: Technical and Institutional Aspects from Chinese and German Perspective |
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173-193 |
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Today’s cities face the challenge of climate change adaptation worldwide. In this context, prevention of damage caused by flash floods plays an important role. This requires a cooperative pluvial flood risk management approach, which includes planning, technical, and administrative measures and involves preliminary flood risk analyses. This article outlines the main components of this risk management approach, which has proven its effectiveness in Europe. The recommendations formulated for this purpose are applicable or adaptable to regions with other constraints, such as China, for example. |
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Springer International Publishing |
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Cham |
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Köster, S.; Reese, M.; Zuo, J.’e |
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978-3-030-01488-9 |
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THL @ christoph.kuells @ Illgen2019 |
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87 |
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Severi, A.; Masoudian, M.; Kordi, E.; Roettcher, K. |
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Discharge coefficient of combined-free over-under flow on a cylindrical weir-gate |
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Journal Article |
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2015 |
Publication |
ISH Journal of Hydraulic Engineering |
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21 |
Issue |
1 |
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42-52 |
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Taylor & Francis |
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THL @ christoph.kuells @ doi:10.1080/09715010.2014.939503 |
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88 |
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