ALBERT

Description: As a common depressant, acidified water glass (AWG) has strong inhibitory effects on fluorite and calcite. The inhibited fluorite is difficult to be recovered, thus resulting in the waste of resources and low flotation efficiency. In this study, the interaction of fluoride ions with fluorite and calcite surfaces was investigated, and its effects of AWG adsorption on mineral surfaces were evaluated. Micro-flotation experiments indicated that the flotation recovery of fluorite is 88.72% after fluoride ion treatment, that is, approximately fourfold with respect to that without fluoride ion modification. The results of solution chemical calculations showed that SiO(OH)3 is the main component to inhibit fluorite, and Si(OH)4 is the main component to inhibit calcite in AWG solution. XPS and ICP-MS results showed that fluoride ions can improve the floatability of fluorite by converting CaSiO3 on the surface of fluorite into CaF2, but the conversion ability of Si(OH)4 on the surface of calcite is weak, which increases the difference in floatability between fluorite and calcite. The above results were further verified by the analysis of flotation foam image and contact angle measurement. After fluorine ion treatment, the contact angle of fluorite increased, and it was more easily adsorbed on the foam. Therefore, the interaction of the fluoride ion with the fluorite surfaces eliminated the adsorption of AWG on fluorite, thereby resulting in the enhanced hydrophobicity of fluorite. Different from the traditional metal ions modification, the idea of anion modification in this paper is expected to be further studied.

Description: Global climatic changes have been observed for all natural biomes, with the greatest impact in the permafrost zone. The short series of direct observations of air temperature and precipitation from meteorological stations for this territory make it difficult to use them in studies of the impact of climate change on forest and forest-tundra ecosystems, but only longer series of gridded data expand the temporal-spatial resolution of this analysis. We compared local and gridded air temperature, precipitation and vapor pressure deficit (VPD) data, analyzed the trends of their changes over the last century for three sites in the permafrost zone (YAK and TAY in Russia, and CAN in Canada), and estimated the effect of their variability on oxygen isotopes in the tree-ring cellulose (δ18Ocell) of three different species (Larix cajanderi Mayr, Larix gmelinii Rupr. Rupr and Piceaglauca (Moench) Voss). Climate trend analysis showed strong changes after the 1980s, and even more pronounced from 2000 to 2020. We revealed that δ18Ocell-YAK showed mixed signals of the July temperature (r = 0.49; p = 0.001), precipitation (r = −0.37; p = 0.02) and vapor pressure deficit (VPD) (r = 0.31; p = 0.02), while δ18Ocell-CAN captured longer March–May (r = 0.37, p = 0.001) and July (r = 0.32, p 〈 0.05) temperature signals as well as spring VPD (r = 0.54, p = 0.001). The δ18Ocell-TAY showed a significant correlation with air temperature in July (r = 0.23, p = 0.04) and VPD in March (r = −0.26, p = 0.03). The obtained eco-hydrological relationships indicate the importance of temperature and moisture to varying degrees, which can be explained by site- and species-specific differences.

Description: Management of mill tailings is an important part of mining operations that aims at preventing environmental dispersion of contaminants of concern. To this end, geochemical models and reactive transport modeling provide a quantitative assessment of the mobility of the main contaminants. In arid regions with limited rainfall and intense evaporation, solutes transport may significantly differ from the usual gravity-driven vertical flow. In the uranium tailings of the Cominak mine (Niger), these evaporative processes resulted in the crystallization of gypsum, and to a lesser extent jarosite, and in the formation of surface levels of sulfated gypcrete, locally enriched in uranium. We present a fully coupled reactive transport modeling approach using HYTEC, encompassing evaporation, to quantitatively reproduce the complex sequence of observed coupled hydrogeochemical processes. The sulfated gypcrete formation, porosity evolution and solid uranium content were successfully reproduced at the surface and paleosurfaces of the tailing deposit. Simulations confirm that high solubility uranyl-sulfate phase may form at the atmospheric boundary where evaporation takes place, which would then be transformed into uranyl-phosphate phases after being watered or buried under fresh tailings. As these phases usually exhibit a lower solubility, this transition is beneficial for mine operators and tailings management.

Description: Text classification is an important component in many applications. Text classification has attracted the attention of researchers to continue to develop innovations and build new classification models that are sourced from clinical trial texts. In building classification models, many methods are used, including supervised learning. The purpose of this study is to improve the computational performance of one of the supervised learning methods, namely KNN, in building a clinical trial document text classification model by combining KNN and the fine-grained algorithm. This research contributed to increasing the computational performance of KNN from 388,274 s to 260,641 s in clinical trial texts on a clinical trial text dataset with a total of 1,000,000 data.

Description: Building typification is of theoretical interest and practical significance in map generalization. It aims to transform an initial set of buildings to a subset, while maintaining the essential distribution characteristics and important individual buildings. This study focuses on buildings located in residential suburban or rural areas and generalizes them to medium or small scale, for which the typification process can be viewed as point-similar object selection that generates exemplars in local building clusters. From this view, we propose a novel building typification approach using affinity propagation exemplar-based clustering. Based on a sparse graph constructed on the input building set, the proposed approach considers all buildings as potential cluster exemplars and keeps passing messages between those objects; thus, high-quality representative objects (i.e., exemplars) of the initial building set can be obtained and further outputted as the typified result. Experiments with real-life building data show that the proposed method is superior to the two existing representative methods in maintaining the overall distribution characteristics. Meanwhile, the importance of each individual building and the constraints of the road network can be embedded flexibly in this method, which gives some advantages in terms of preserving important buildings and the local structural distribution along the road, etc.

Description: Many researchers have unraveled innovative ways of examining geographic information to better understand the determinants of crime, thus contributing to an improved understanding of the phenomenon. Property crimes represent more than half of the crimes reported in Portugal. This study investigates the spatial distribution of crimes against property in mainland Portugal with the primary goal of determining which demographic and socioeconomic factors may be associated with crime incidence in each municipality. For this purpose, Geographic Information System (GIS) tools were used to analyze spatial patterns, and different Poisson-based regression models were investigated, namely global models, local Geographically Weighted Poisson Regression (GWPR) models, and semi-parametric GWPR models. The GWPR model with eight independent variables outperformed the others. Its independent variables were the young resident population, retention and dropout rates in basic education, gross enrollment rate, conventional dwellings, Guaranteed Minimum Income and Social Integration Benefit, purchasing power per capita, unemployment rate, and foreign population. The model presents a better fit in the metropolitan areas of Lisbon and Porto and their neighboring municipalities. The association of each independent variable with crime varies significantly across municipalities. Consequently, these particularities should be considered in the design of policies to reduce the rate of property crimes.

Description: The long-term sustainability of fractures within rocks determines whether it is reasonable to utilize such formations as potential EGS reservoirs. Representative for reservoirs in Variscan metamorphic rocks, three long-term (one month each) fracture permeability experiments on saw-cut slate core samples from the Hahnenklee well (Harz Mountains, Germany) were performed. The purpose was to investigate fracture permeability evolution at temperatures up to 90 °C using both deionized water (DI) and a 0.5 M NaCl solution as the pore fluid. Flow with DI resulted in a fracture permeability decline that is more pronounced at 90 °C, but permeability slightly increased with the NaCl fluid. Microstructural observations and analyses of the effluent composition suggest that fracture permeability evolution is governed by an interplay of free-face dissolution and pressure solution. It is concluded that newly introduced fractures may be subject to a certain permeability reduction due to pressure solution that is unlikely to be mitigated. However, long-term fracture permeability may be sustainable or even increase by free-face dissolution when the injection fluid possesses a certain (NaCl) salinity.

Description: Mechanical twins are common microstructures in deformed calcite. Calcite twins have been used for a long time as indicators of stress/strain orientations and magnitudes. Developments during the last decade point toward significant improvements of existing techniques as well as new applications of calcite twin analysis in tectonic studies. This review summarises the recent progress in the understanding of twin formation, including nucleation and growth of twins, and discusses the concept of CRSS and its dependence on several factors such as strain, temperature and grain size. Classical and recent calcite twin measurement techniques are also presented and their pros and cons are discussed. The newly proposed inversion techniques allowing for the use of calcite twins as indicators of orientations and/or magnitudes of stress and strain are summarized. Benefits for tectonic studies are illustrated through the presentation of several applications, from the scale of the individual tectonic structure to the continental scale. The classical use of calcite twin morphology (e.g., thickness) as a straightforward geothermometer is critically discussed in the light of recent observations that thick twins do not always reflect deformation temperature above 170–200 °C. This review also presents how the age of twinning events in natural rocks can be constrained while individual twins cannot be dated yet. Finally, the review addresses the recent technical and conceptual progress in calcite twinning paleopiezometry, together with the promising combination of this paleopiezometer with mechanical analysis of fractures or stylolite roughness.

Description: The two-part series of papers provides a survey on recent advances in Deep Reinforcement Learning (DRL) for solving partially observable Markov decision processes (POMDP) problems. Reinforcement Learning (RL) is an approach to simulate the human’s natural learning process, whose key is to let the agent learn by interacting with the stochastic environment. The fact that the agent has limited access to the information of the environment enables AI to be applied efficiently in most fields that require self-learning. It’s essential to have an organized investigation—we can make good comparisons and choose the best structures or algorithms when applying DRL in various applications. The first part of the overview introduces Markov Decision Processes (MDP) problems and Reinforcement Learning and applications of DRL for solving POMDP problems in games, robotics, and natural language processing. In part two, we continue to introduce applications in transportation, industries, communications and networking, etc. and discuss the limitations of DRL.

Description: Chalcocite is the most abundant secondary copper sulfide globally, with the highest copper content, and is easily treated by conventional hydrometallurgical processes, making it a very profitable mineral for extraction. Among the various leaching processes to treat chalcocite, chloride media show better results and have a greater industrial boom. Chalcocite dissolution is a two-stage process, the second being much slower than the first. During the second stage, in the first instance, it is possible to oxidize the covellite in a wide range of chloride concentrations or redox potentials (up to 75% extraction of Cu). Subsequently, CuS2 is formed, which is to be oxidized. It is necessary to work at high concentrations of chloride (〉2.5 mol/L) and/or increase the temperature to reach a redox potential of over 650 mV, which in turn decreases the thickness of the elemental sulfur layer on the mineral surface, facilitating chloride ions to generate a better porosity of this. Finally, it is concluded that the most optimal way to extract copper from chalcocite is, during the first stage, to work with high concentrations of chloride (50–100 g/L) and low concentrations of sulfuric acid (0.5 mol/L) at a temperature environment, as other variables become irrelevant during this stage if the concentration of chloride ions in the system is high. While in the second stage, it is necessary to increase the temperature of the system (moderate temperatures) or incorporate a high concentration of some oxidizing agent to avoid the passivation of the mineral.