The dolomite problem has confused scientists for nearly two centuries because the classic saturation index cannot explain the failure of dolomite precipitation in carbonate solutions including ...1000-fold super saturation for 32 years and oversaturation of modern seawater for millions of years. Although the dolomite problem is still controversial, the chemistry of a global set of surface water samples reported in dolomitization (N = 54) and dedolomitization (N = 433) is indispensable, and firstly summarized to explore the mechanism of dolomite inorganic precipitation. This study indicates that: (1) saturation index of dolomite in the surface water of dolomitization is closing to dedolomitization, suggesting the failure of SI to reflect the real precipitation driving force of dolomite; (2) the primary difference is that most of water in dedolomitization has negative SI of gypsum, while most of water in dolomitization has positive SI of gypsum; (3) the inherent stoichiometry competition relationship between calcite and dolomite is proposed to explain the incompleteness of classic saturation index model in predicting inorganic dolomitization; (4) A multi-component calcite - dolomite - gypsum phase equilibrium (CDGPE) model is recommended to replace SI in predicting the dolomitization and dedolomitization of a global set of surface waters; (5) CDGPE model is proved reliable and useful in predicting the surface water reported in dolomitization and dedolomitization (including the modern seawater); (6) the evaporation modelling of the modern seawater through the stepwise detraction of water shows that the surface waters (Persian Gulf, Mediterranean, Abu Dhabi, Coorong Region at Southern Australia, and LagoaVermelha at Brazil) observed with abundant dolomitization are all located at the different evaporation paths of modern seawater, suggesting that the dolomitization at these seawater are resulted by the evaporation, which is consistent with the recent finding that the dolomitization event at the oceanic chemocline occurred during the Permian-Triassic transition period when the temperature was hot on the earth surface.
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•CDGPE model is proposed to replace SI to predict the dolomitization and dedolomitization.•Database of global surface water in dolomitization and dedolomitization (GSWDD) is constructed.•CDGPE model can divide the global surface water reported in dolomitization and dedolomitization.•A new insight is proposed to explain failure of dolomitization in laboratory and modern seawater.
In recent years, blind source separation (BSS) has received much attention in the hyperspectral unmixing field due to the fact that it allows the simultaneous estimation of both endmembers and ...fractional abundances. Although great performances can be obtained by the BSS-based unmixing methods, the decomposition results are still unstable and sensitive to noise. Motivated by the first law of geography, some recent studies have revealed that spatial information can lead to an improvement in the decomposition stability. In this paper, the group-structured prior information of hyperspectral images is incorporated into the nonnegative matrix factorization optimization, where the data are organized into spatial groups. Pixels within a local spatial group are expected to share the same sparse structure in the low-rank matrix (abundance). To fully exploit the group structure, image segmentation is introduced to generate the spatial groups. Instead of a predefined group with a regular shape (e.g., a cross or a square window), the spatial groups are adaptively represented by superpixels. Moreover, the spatial group structure and sparsity of the abundance are integrated as a modified mixed-norm regularization to exploit the shared sparse pattern, and to avoid the loss of spatial details within a spatial group. The experimental results obtained with both simulated and real hyperspectral data confirm the high efficiency and precision of the proposed algorithm.
Rechargeable aqueous zinc-ion batteries are promising energy storage devices due to their high safety and low cost. However, they remain in their infancy because of the limited choice of positive ...electrodes with high capacity and satisfactory cycling performance. Furthermore, their energy storage mechanisms are not well established yet. Here we report a highly reversible zinc/sodium vanadate system, where sodium vanadate hydrate nanobelts serve as positive electrode and zinc sulfate aqueous solution with sodium sulfate additive is used as electrolyte. Different from conventional energy release/storage in zinc-ion batteries with only zinc-ion insertion/extraction, zinc/sodium vanadate hydrate batteries possess a simultaneous proton, and zinc-ion insertion/extraction process that is mainly responsible for their excellent performance, such as a high reversible capacity of 380 mAh g
and capacity retention of 82% over 1000 cycles. Moreover, the quasi-solid-state zinc/sodium vanadate hydrate battery is also a good candidate for flexible energy storage device.
The Na/K ratio in feldspars in sediment has been proven to be a stable and predictable index. The relationship between the sediment and its source in terms of the Na/K ratio in feldspars can be ...defined using the mass-balance model combined with the feldspar weathering kinetics asK1=γ∗K0γ=1−ttNa−L0.391−ttK−L0.39
where K0 and K1 are the Na/K ratios in feldspars in the parent rocks and sediment, respectively; t represents the time interval; γ is the ratio of K1 to K0; and tNa-L and tK-L are the lifetimes of Na-containing and K-containing feldspars, respectively. According to this model, the change in the Na/K ratio in feldspars as a function of time for different combinations of feldspars can be predicted. Further, tNa-L and tK-L can be replaced by the lifetimes of the Na-containing and K-containing feldspars with the shortest lifetimes, respectively, if there are other types of feldspars. The ratio depends on the time interval and feldspar lifetime. The Na/K ratio in feldspars changes by <5% over nearly 104 years for nine selected combinations of Na-containing and K-containing feldspars (microcline–labradorite, microcline–sanidine, microcline–K-feldspar, albite–labradorite, albite–sanidine, albite–K-feldspar, oligoclase–labradorite, oligoclase–sanidine, oligoclase–K-feldspar), although ~20% of these feldspars is lost over 104 years. A case study of a lake affected by the slow lake filling between the 1960s and 1980s showed that the Na/K ratio in feldspar is more sensitive than major elements to changes in the sediment source and more stable than trace metals, which are easily affected by human activities.
•The Na/K ratio in feldspars is proposed as a predictable index to trace sediment.•The ratio changes ≤5% over nearly 104 years for nine selected combinations.•The stability of this index depends on the time interval and feldspar's lifetime.•A case study is used to test its stability and predictability.
Sorption of Mo to goethite and related iron (hydr)oxides plays an important role in controlling the mobility of Mo in soil and aquatic environments. We first performed ab-initio molecular dynamics ...(MD) simulations of Mo complexation at the goethite {1 0 1}-water interface. We find that molybdenum adsorbed on goethite mainly exists as the inner-sphere tetrahedral bidentate and monodentate corner-sharing complex, instead of the previous argued bidentate edge-sharing or outer-sphere complex. Different from previous literature, we didn’t find any distorted octahedral structure of Mo on goethite. The predicted Mo-Fe distances of bidentate and monodentate corner-sharing complex based on ab-initio MD is 3.53 and 3.38 Å, respectively, which are consistent with the fitted Mo-Fe distances: 3.40 ± 0.15 Å and 3.41 ± 0.1 Å from EXAFS.
We measured the adsorption of Mo (VI) on goethite (α-FeOOH) at different initial concentration and pH from 3 to 11 under N2 atmosphere and constructed a surface complexation model that is consistent with the molecular speciation based on ab-initio MD, XANES, EXAFS and reported in-situ ATR-IR analysis (Davantes and Lefevre, 2015, 2016). Application of SCM for Mo on goethite assuming iron oxides as the principal component of ferromanganese crust (containing average 276 mg/kg Mo) will have ∼0.3 μg/l Mo in seawater in equilibrium. The observed ∼10 μg/l Mo in seawater (c a. 400–800 yr) is between 0.3 (adsorption equilibrium by marine goethite) and 23 μg/l (adsorption equilibrium by marine birnessite, Kashiwabara et al., 2011), suggesting that molybdenum in seawater has reached equilibrium with ferromanganese crust, and goethite (57%) probably plays a more important role than birnessite (43%) in regulating molybdenum abundance in the ocean, which has not been fully recognized in past.
Observed molybdenum isotopic fractionation between seawater and ferromanganese crust excesses the experimental molybdenum isotopic fractionation range during adsorption by birnessite and goethite (Goldberg et al., 2009). Based on reported experimental molybdenum isotopic fractionation values and our SCM prediction, the molybdenum isotopic fractionation δ98/95Mo value should vary between 1.6 and 2.3‰, which is lower than the observed range between seawater and ferromanganese crust: 2.7–3.2‰ about 1‰, suggesting the disequilibrium of molybdenum isotopic fractionation in ocean. To clarify the discrepancy, this study highlights the necessity of clarifying the molybdenum source in hydrogenic and hydrothermal ferromanganese crusts before understanding molybdenum isotopic fractionation between seawater and ferromanganese crust.
•An ensemble model AdaBoost-CART is proposed to predict rock mass classification.•SMOTE is utilized to address the imbalance ratio of rock mass classifications.•The AdaBoost-CART model performs ...better than conventional machine learning methods.•The variable importance of the model is analyzed.
The real-time acquisition of surrounding rock information is important for the efficient tunneling and hazard prevention in tunnel boring machines (TBMs). This study presents an ensemble learning model based on classification and regression tree (CART) and AdaBoost algorithm to predict the classification of surrounding rock mass. Statistical indicators (i.e., mean value and standard deviation) of TBM operational parameters were calculated and used as input variables, and the rock mass classification obtained by the hydropower classification (HC) method was used as output variable. To develop the model, a database was established, consisting of 3166 samples collected from the Songhua River Water Conveyance Tunnel. The synthetic minority over-sampling technique (SMOTE) was utilized to address the imbalance ratio of rock mass classifications in the database. The results of the testing set showed that the accuracy and F1-measure of AdaBoost-CART were 0.865 and 0.770, respectively, which are better than the results of the standard CART (0.753 and 0.629, respectively). The application of SMOTE improves the recall of minority classes. Compared with artificial neural networks, k-nearest neighbor, and support vector classifier, the developed AdaBoost-CART model achieves better performance. The variable importance was analyzed to distinguish key features; the results showed that rock mass boreability may not be a major consideration of the HC method. The presented model can provide significant guidance for the real-time acquisition of surrounding rock information during TBM tunneling.
A near infrared (NIR) light-responsive supramolecular hydrogel consisting of α-cyclodextrin and poly(ethylene glycol)-modified dendrimer-encapsulated platinum nanoparticles was developed. Upon NIR ...irradiation, this hydrogel underwent a photothermo-sensitive degradation to release the entrapped therapeutic agents in an on-demand and dose-tunable fashion.
The impact of siblings on the executive functioning and theory of mind in children is a complex and multifaceted phenomenon. Siblings have the potential to influence each other’s cognitive ...development through various forms of interaction, such as negotiation, cooperation, and conflicts. This paper summarizes the relationship between siblings, executive functioning, and theory of mind through reviewing previous research. It discusses whether siblings directly contribute to changes in executive functioning and theory of mind or if other factors, such as age difference and gender, play a role. This article discusses the importance of identifying the significant role of siblings in shaping executive functioning and theory of mind and provides an overview of research findings and potential influencing factors. By focusing on processes influenced by older siblings, this review article will provide a deeper understanding of how sibling interactions may impact younger children’s cognitive functioning. Future research should encompass different cultural backgrounds, socioeconomic statuses, and family structures to increase generalizability and can help to understand the contexts of the correlation between siblings and cognitive functioning.
Silicon and lithium metal are considered as promising alternatives to state-of-the-art graphite anodes for higher energy density lithium batteries because of their high theoretical capacity. However, ...significant challenges such as short cycle life and low coulombic efficiency have seriously hindered their practical applications. In the past decades, various strategies have been proposed to address the major problems of Si and Li anodes. In this review, we summarize the understanding on Si and Li anodes, highlight the recent progress in the development and introduce advanced characterization techniques. We also indicate the remaining challenges of Si and Li anodes requiring more efforts for future widespread applications. We expect that this review provides an overall picture of the recent progress and inspires more efforts in the fundamental understanding and practical applications of Si and Li anodes.
This review summarizes the important progress of Si and Li anodes and discusses the remaining essential issues towards their applications.
In this paper, a neural networks (NNs) enhanced telerobot control system is designed and tested on a Baxter robot. Guaranteed performance of the telerobot control system is achieved at both kinematic ...and dynamic levels. At kinematic level, automatic collision avoidance is achieved by the control design at the kinematic level exploiting the joint space redundancy, thus the human operator would be able to only concentrate on motion of robot's end-effector without concern on possible collision. A posture restoration scheme is also integrated based on a simulated parallel system to enable the manipulator restore back to the natural posture in the absence of obstacles. At dynamic level, adaptive control using radial basis function NNs is developed to compensate for the effect caused by the internal and external uncertainties, e.g., unknown payload. Both the steady state and the transient performance are guaranteed to satisfy a prescribed performance requirement. Comparative experiments have been performed to test the effectiveness and to demonstrate the guaranteed performance of the proposed methods.
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