Metallic lithium (Li) is a promising anode material for next‐generation rechargeable batteries. However, the dendrite growth of Li and repeated formation of solid electrolyte interface during Li ...plating and stripping result in low Coulombic efficiency, internal short circuits, and capacity decay, hampering its practical application. In the development of stable Li metal anode, the current collector is recognized as a critical component to regulate Li plating. In this work, a lithiophilic Cu‐CuO‐Ni hybrid structure is synthesized as a current collector for Li metal anodes. The low overpotential of CuO for Li nucleation and the uniform Li+ ion flux induced by the formation of Cu nanowire arrays enable effective suppression of the growth of Li dendrites. Moreover, the surface Cu layer can act as a protective layer to enhance structural durability of the hybrid structure in long‐term running. As a result, the Cu‐CuO‐Ni hybrid structure achieves a Coulombic efficiency above 95% for more than 250 cycles at a current density of 1 mA cm−2 and 580 h (290 cycles) stable repeated Li plating and stripping in a symmetric cell.
A lithiophilic Cu‐CuO‐Ni hybrid structure is synthesized on a Ni foam substrate as a current collector for lithium (Li) metal anodes. The collective effects of low overpotential of the Cu‐CuO‐Ni hybrid structure for Li nucleation, nanowire array configuration, and the Cu buffer layer are demonstrated to be keys for achieving an outstanding overall performance of the current collector.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The rapidly increasing number of images on the internet has further increased the need for efficient indexing for digital image searching of large databases. The design of a cloud service that ...provides high efficiency but compact image indexing remains challenging, partly due to the well-known semantic gap between user queries and the rich semantics of large-scale data sets. In this paper, we construct a novel joint semantic-visual space by leveraging visual descriptors and semantic attributes, which narrows the semantic gap by combining both attributes and indexing into a single framework. Such a joint space embraces the flexibility of coherent semantic-visual indexing, which employs binary codes to boost retrieval speed while maintaining accuracy. To solve the proposed model, we make the following contributions. First, we propose an interactive optimization method to find the joint semantic and visual descriptor space. Second, we prove convergence of our optimization algorithm, which guarantees a good solution after a certain number of iterations. Third, we integrate the semantic-visual joint space system with spectral hashing, which finds an efficient solution to search up to billion-scale data sets. Finally, we design an online cloud service to provide a more efficient online multimedia service. Experiments on two standard retrieval datasets (i.e., Holidays1M, Oxford5K) show that the proposed method is promising compared with the current state-of-the-art and that the cloud system significantly improves performance.
Fractures play an important role in the formation of shale-gas reservoirs because they can enlarge the transport channels and aggregation spaces and increase the specific surface area of the gas ...shale. For artificial hydraulic fracturing of these reservoirs, the natural fracture system must be fully integrated with the artificial fracture system to form an intact fracture system. In this study, we first comprehensively examined the fractures in 42 shale-gas wells using several approaches, including a systematic examination and description of the cores and the casting of thin sections, a compilation of the statistics of fracture feature parameters, and observation of various analytical and test data, such as the mineral composition, the organic carbon contents, and the rock mechanics properties for specimens from the corresponding fractured intervals. The data enabled us to thoroughly explore the developmental features and major factors affecting organic-rich shale fractures in the upper Paleozoic Carboniferous–Permian marine–continental transitional coal-bearing formation, which is located in the southeastern Ordos Basin. Our results reveal that, in comparison with the Paleozoic marine shale in the United States and southern China, as well as the Paleozoic basin transitional shale in northern China, the upper Paleozoic black shale in the Ordos Basin is primarily characterized by a relatively low content of brittle minerals and a high content of clay ingredients. The total content of brittle minerals, e.g., quartz, feldspar, and siderite, was approximately 33%, which included 27% quartz and 0.3% K-feldspar but did not include carbonate. The total content of clay minerals reached 64% and was dominated by mixed-layer illite–smectite (I/S), which accounted for more than 41% of the total clay ingredients. The shale accommodated the widespread development of various types of macro- and microfractures. In the core specimens, medium-angle slip fractures and horizontal bedding cracks were the most common types of fractures, whereas vertical and high-angle fractures and horizontal bedding cracks were underdeveloped. In the thin sections, microfractures arising in organic matter laminations or at their edges as well as those of tectonic origin were the predominant type of fractures, and they were mainly short, narrow, and open. Overall, the surface/fracture ratios of the thin sections were concentrated in a range of approximately 0.1–0.3%. The developmental level of the fracture was influenced by various factors, including tectonism, lithology, rock mechanics, and organic matter and mineral content. Thus, increased developmental level of fractures was correlated with higher paleostructural elevation and increased sand content, whereas the developmental level of microfractures was correlated with high lamellation development, high level of organic carbon (leading to more pronounced laminations), and high contents of quartz, mixed-layer I/S, and illite (leading to low levels of kaolinite). These findings were corroborated by other data generated in this study, including the rock mechanics results for the upper Paleozoic black shale and silty shale, the observation results from the cores and from the thin sections sampled from more than 40 shale-gas wells, and the anomalies of gas logging.
•Characteristics of fracture development in transitional shale-gas reservoirs.•Dominant factors of fracture development in transitional shale-gas reservoirs.•Conventional log response characteristics of shale fractures in reservoirs.•Petrological characteristics of shale-gas reservoirs in the Ordos Basin.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Nickel foam supported hierarchical mesoporous Zn–Ni–Co ternary oxide (ZNCO) nanowire arrays are synthesized by a simple two-step approach including a hydrothermal method and subsequent calcination ...process and directly utilized for supercapacitive investigation for the first time. The nickel foam supported hierarchical mesoporous ZNCO nanowire arrays possess an ultrahigh specific capacitance value of 2481.8 F g–1 at 1 A g–1 and excellent rate capability of about 91.9% capacitance retention at 5 A g–1. More importantly, an asymmetric supercapacitor with a high energy density (35.6 Wh kg–1) and remarkable cycle stability performance (94% capacitance retention over 3000 cycles) is assembled successfully by employing the ZNCO electrode as positive electrode and activated carbon as negative electrode. The remarkable electrochemical behaviors demonstrate that the nickel foam supported hierarchical mesoporous ZNCO nanowire array electrodes are highly desirable for application as advanced supercapacitor electrodes.
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IJS, KILJ, NUK, PNG, UL, UM
Nitrogen and fluorine dual-doped porous graphene nanosheets (NFPGNS) have been successfully synthesized as efficient bifunctional metal-free electrocatalysts for overall water splitting via a simple ...chemical-etching method. Pyridinic N doping rich configurations have been proven beneficial for the electrochemical process. The onset voltage of water splitting on the NFPGNS is lower than 1.60 V, only slightly higher than that found for Pt/C electrocatalysts. Particularly, an onset potential of 1.45 V vs. RHE on the NFPGNS for the OER is lower than some metal based electrocatalysts, involving Pt/C. DFT calculations reveal the origin of the electrocatalytic activity on the NFPGNS for the HER and OER; heteroatom-doped graphene materials modify the electron acceptor-donor properties of carbon via a synergistic coupling effect between heteroatoms. This leads to favorable electronic structures tuning the C sites around the heteroatoms, introducing a stronger adsorption strength and consequently, a lower value for the Gibbs free energy.
Smartly designed nanoarchitectures with effective hybridization of transition metal oxides/hydroxides are promising to realize high performance electrodes for energy storage devices. To promote the ...applications of high-power supercapacitors, a seed-assisted method is firstly applied to prepare mesoporous Ni–Co–Mn hydroxide nanoflakes (NCMH) on nickel foam with practical mass loadings (higher than 5 mg cm −2 ). Further mechanism study reveals that the Ni(OH) 2 nanorod arrays, which are firstly prepared by a hydrothermal process, serve as seeds for the successful deposition of NCMH nanoflakes. Through this convenient and cost effective method, this design results in a more orderly spatial distribution, lower intrinsic resistance and shorter electron transport pathways. The proof-of-concept application of NCMH as a binder-free supercapacitor electrode reveals an impressive specific capacity of 1043.1 μA h cm −2 at a high mass loading of 5.2 mg cm −2 . The NCMH//activated carbon asymmetric device delivered a maximum energy density of 55.42 W h kg −1 at a power density of 750 W kg −1 , exhibiting great potential as an energy storage device and shedding light on the structural design of nanomaterials.
The evolution of fissures and permeability associated with mining of the upper protective layer of the coal seam is crucial for pressure relief gas drainage of the underlying seam. To understand the ...influence of mining the upper protective layer on gas drainage within the underlying coal seam, this study utilized the M16 and M18 seams in the Qinglong Coal Mine in Guizhou. Theoretical analysis, discrete element numerical simulation, and field tests were used to characterize the evolution of fractures associated with mining of the upper protective layer and the effects of pressure relief gas drainage within the protected coal seam. The results show that mining-related stress changes controlled the development of fractures, altering the permeability values of coals. An analysis of the crack development in the coal mass caused by mining of the upper protective layer shows that during the initial stage of mining, the produced cracks exhibited a butterfly shape network. Yet, with further development of the mining, these cracks and the stress changes gradually produced an inverted butterfly shape network. According to simulations, the areas of maximum deformation via expansion in the protected coal seam were located near the open cut and the mining end line of the working face. The maximum deformation values were 29.06 and 26.68 mm, respectively, and the corresponding deformation rates were 9.37‰ and 8.61‰, which are greater than the required 3‰. The findings of this study provide a new reference for gas control in pressure relief coal seams under similar working conditions.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The chemical and pore structures of coal play a crucial role in determining the content of free gas in coal reservoirs. This study focuses on investigating the impact of acidification transformation ...on the micro-physical and chemical structure characteristics of coal samples collected from Wenjiaba No. 1 Mine in Guizhou. The research involves a semi-quantitative analysis of the chemical structure parameters and crystal structure of coal samples before and after acidification using Fourier Transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) experiments. Additionally, the evolution characteristics of the pore structure are characterized through high-pressure mercury injection (HP-MIP), low-temperature nitrogen adsorption (LT-N2A), and scanning electron microscopy (SEM). The experimental findings reveal that the acid solution modifies the structural features of coal samples, weakening certain vibrational structures and altering the chemical composition. Specifically, the asymmetric vibration structure of aliphatic CH2, the asymmetric vibration of aliphatic CH3, and the symmetric vibration of CH2 are affected. This leads to a decrease in the contents of -OH and -NH functional groups while increasing aromatic structures. The crystal structure of coal samples primarily dissolves transversely after acidification, affecting intergranular spacing and average height. Acid treatment corrodes mineral particles within coal sample cracks, augmenting porosity, average pore diameter, and the ratio of macro-pores to transitional pores. Moreover, acidification increases fracture width and texture, enhancing the connectivity of the fracture structure in coal samples. These findings provide theoretical insights for optimizing coalbed methane (CBM) extraction and gas control strategies.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract As the mechanization of the CBM extraction process advances and geological conditions continuously evolve, the production data from CBM wells is deviating increasingly from linearity, ...thereby presenting a significant challenge in accurately predicting future gas production from these wells. When it comes to predicting the production of CBM, a single deep-learning model can face several drawbacks such as overfitting, gradient explosion, and gradient disappearance. These issues can ultimately result in insufficient prediction accuracy, making it important to carefully consider the limitations of any given model. It’s impressive to see how advanced technology can enhance the prediction accuracy of CBM. In this paper, the use of a CNN model to extract features from CBM well data and combine it with Bi-LSTM and a Multi-Head Attention mechanism to construct a production prediction model for CBM wells—the CNN-BL-MHA model—is fascinating. It is even more exciting that predictions of gas production for experimental wells can be conducted using production data from Wells W1 and W2 as the model’s database. We compared and analyzed the prediction results obtained from the CNN-BL-MHA model we constructed with those from single models like ARIMA, LSTM, MLP, and GRU. The results show that the CNN-BL-MHA model proposed in the study has shown promising results in improving the accuracy of gas production prediction for CBM wells. It’s also impressive that this model demonstrated super stability, which is essential for reliable predictions. Compared to the single deep learning model used in this study, its prediction accuracy can be improved up to 35%, and the prediction results match the actual yield data with lower error.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Currently, the utilization of coalbed methane resources in the Guizhou region faces challenges such as complex reservoir structure, high gas content, and microporous development. Based on these, the ...pore structure and adsorption capacity of Guizhou tectonic deformed coals (TDCs) were evaluated using a suite of integrated diagnostic techniques including low-temperature nitrogen adsorption (LT-N
A), mercury intrusion porosimetry (MIP), methane isothermal adsorption. Through the above methods, the pore structure and adsorption characteristics of the samples were characterized; The samples were divided into the range of joint pores by combining the results of MIP and LT-N
A; Using the molecular simulation software, the 2 nm, 4 nm, 10 nm pores affecting the methane endowment state were investigated respectively, and from the perspective of the heat of adsorption and energy, the concept of the three-phase transition of methane was proposed, and explore the change of the pore spacing affecting the endowment state of methane from the solid state pore to the gas state pore. The results provide new ideas for the in-depth study of gas storage in tectonic coal reservoirs in Guizhou Province.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
