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Shale gas content data always plays an important role in the process of shale resource evaluation. However, free gas is always underestimated in the evaluation of the gas content. As a result, there are always contradictions between the on-site desorption data and actual production data. This phenomenon will lead to the evaluation process of shale gas resources; some of the potential shale gas blocks are considered to be of no development value. Through the on-site shale desorption and organic geochemical experiment on shale of Ordovician Wufeng-Silurian Longmaxi Formation in Well Z302, Sichuan Basin, the following conclusions are drawn: (1) the desorbed gas release in a sequence of N2, followed by CO2, CH4, and C2H6; (2)the δ13C of methane and ethane showed different fractionation characteristics during on-site desorption, and ethane showed “desorption hysteresis” during desorption; (3) the shale gas is formed by oil cracking under the condition of high overmaturity, and the parent material of the oil-generating gas is mainly type II; (4) in the late stage of gas desorption, carbon isotope rollover occurred due to the stronger diffusion ability of 12C-rich methane and the reversal phenomenon caused by residual enrichment of 13C methane isotopes; (5) the transition model of gas abundance during shale desorption is established. At the same time, the separation method of free gas and adsorbed gas in the shale desorption process is determined. Finally, a new calculation method of the ratio of free gas and adsorption gas is proposed to solve the problem that free gas is underestimated in the evaluation of shale gas resources.

Atomic-scale insights into the interactions between metals and supports play a crucial role in optimizing catalyst design, understanding catalytic mechanisms, and enhancing chemical conversion processes. The effects of oxide support on the dynamic behavior of supported metal species during pretreatments or reactions have been attracting a lot of attention; however, very less systematic integrations are carried out experimentally using real catalysts. In this study, we here utilized facet-controlled CeO2as examples to explore their influence on the supported Pt species (1.0 wt %) during the reducing and oxidizing pretreatments that are typically applied in heterogeneous catalysts. By employing a combination of microscopy, spectroscopy, and first-principles calculations, it is demonstrated that the exposed crystal facets of CeO2govern the evolution behavior of supported Pt species under different environmental conditions. This leads to distinct local coordinations and charge states of the Pt species, which directly influence the catalytic reactivity and can be leveraged to control the catalytic performance for CO oxidation reactions.

Abscisic acid (ABA) is a major regulator of nonclimacteric fruit ripening, with its processes involving epigenetic mechanisms. It remains unclear whether DNA methylation is associated with ABA-regulated ripening. In this study, we investigated the patterns of DNA methylation and gene expression following ABA treatment in grape berries by using whole-genome bisulfite sequencing and RNA-sequencing. ABA application changed global DNA methylation in grapes. The hyper-/hypo-differently methylated regions were enriched in defense-related metabolism, degreening processes, or ripening-related metabolic pathways. Many differentially expressed genes showed an alteration in DNA methylation after ABA treatment. Specifically, ten downregulated genes with hypermethylation in promoters were involved in the ripening process, ABA homeostasis/signaling, and stress response. Nine upregulated genes exhibiting hypo-methylation in promoters were related to the ripening process and stress response. These findings demonstrated ABA-induced DNA alteration of ripening related and stress-responsive genes during grape ripening, which provides new insights of the epigenetic regulation of ABA on fruit ripening.

Metal/metal oxide clusters possess a higher count of unsaturated coordination sites than nanoparticles, providing multiatomic sites that single atoms do not. Encapsulating metal/metal oxide clusters within zeolites is a promising approach for synthesizing and stabilizing these clusters. The unique feature endows the metal clusters with an exceptional catalytic performance in a broad range of catalytic reactions. However, the encapsulation of stable FeOxclusters in zeolite is still challenging, which limits the application of zeolite-encapsulated FeOxclusters in catalysis. Herein, we design a modified solvent-free method to encapsulate FeOxclusters in pure siliceous MFI zeolites (Fe@MFI). It is revealed that the 0.3–0.4 nm subnanometric FeOxclusters are stably encapsulated in the 5/6-membered rings intersectional voids of the pure siliceous MFI zeolites. The encapsulated Fe@MFI catalyst with a Fe loading of 1.4 wt % demonstrates remarkable catalytic activity and recycle stability in the direct oxidation of methane, while also promoting the direct oxidation of cyclohexane, surpassing the performance of conventional zeolite-supported Fe catalysts.

TiO2-supported Pt species have been widely applied in numerous critical reactions involving photo-, thermo-, and electrochemical-catalysis for decades. Manipulation of the state of the Pt species in Pt/TiO2catalysts is crucial for fine-tuning their catalytic performance. Here, we report an interesting discovery showing the epitaxial growth of PtO2atomic layers on rutile TiO2, potentially allowing control of the states of active Pt species in Pt/TiO2catalysts. The presence of PtO2atomic layers could modulate the geometric configuration and electronic state of the Pt species under reduction conditions, resulting in a spread of the particle shape and obtaining a Pt/PtO2/TiO2structure with more positive valence of Pt species. As a result, such a catalyst exhibits exceptional electrocatalytic activity and stability toward hydrogen evolution reaction, while also promoting the thermocatalytic CO oxidation, surpassing the performance of the Pt/TiO2catalyst with no epitaxial structure. This novel epitaxial growth of the PtO2structure on rutile TiO2in Pt/TiO2catalysts shows its potential in the rational design of highly active and economical catalysts toward diverse catalytic reactions.

Complete oxidation of propane has drawn great attention in the fields of automotive emission control and volatile organic compound elimination. However, it is challenging to achieve high activity of this reaction due to the stability of propane. We here utilize a facile solvothermal method to construct tri-coordinated Al (AlIII) sites on the as-synthesized ST-Al2O3support to alter the properties of supported Pt species. It is demonstrated that AlIIIsites facilitate the dispersion and electron enrichment of supported Pt sites. Thus, Pt/ST-Al2O3exhibits a superior activity toward complete propane oxidation, showing a 6.7-fold improvement in the turnover frequency over commercial Pt/Al2O3catalysts. Meanwhile, Pt/ST-Al2O3possesses a distinct reaction route originating from its stronger C–H and C–C cleavage capability, while having excellent activity not only in complete propane oxidation but also in the complete oxidation of other alkanes (CH4, C2H6, and n-C4H10). In addition, the AlIIIconstruction strategy is successfully extended to more cases, e.g., Pd/ST-Al2O3with higher Pd dispersion and electron density. This work provides a promising strategy for the control of the oxide support for advanced design and synthesis of alkane oxidation catalysts.

In this paper, combine hybrid modulation strategy and Model predictive control (MPC) for Dual active bridge (DAB) converter is presented to achieve high efficiency of wide load range and fast dynamic response for bidirectional power flow conversion. Through offline optimization of DAB converter at steady state, only one control variable is used to reduce computational burden, and without complex algorithm in the cost function for MPC strategy. In addition, based on the simpilified average mode of DAB converter, different predictive currents are derived. Besides, three scenarios of smooth mode transition for the hybrid control strategy is given in detail. Thus, fast dynamic response for mode transition and high efficiency for wide range is guaranteed by the proposed strategy. Finally, an experimental prototype of DAB converter is built and tested for verifying the steady state and fast transition with different operation modes performance.

Covalent organic frameworks (COFs) create extended two-dimensional (2D) skeletons and aligned one-dimensional (1D) channels, constituting a class of novel π architectures with predesignable structural ordering. A distinct feature is that stacks of π building units in skeletons shape the pore walls, onto which a diversity of different units can be assembled to form various pore interfaces, opening a great potential to trigger a strong structural correlation between the skeleton and the pore. However, such a possibility has not yet been explored. Herein, we report reversible three-dimensional (3D) coalescence and interlocked actions between the skeleton and pore in COFs by controlling hydrogen-bonding networks in the pores. Introducing carboxylic acid units to the pore walls develops COFs that can confine water molecular networks, which are locked by the surface carboxylic acid units on the pore walls via multipoint, multichain, and multidirectional hydrogen-bonding interactions. As a result, the skeleton undergoes an interlocked action with pores to shrink over the x–yplane and to stack closer along the zdirection upon water uptake. Remarkably, this interlocked action between the skeleton and pore is reversibly driven by water adsorption and desorption and triggers profound effects on π electronic structures and functions, including band gap, light absorption, and emission.

We propose and investigate a novel orthogonal circulant multiplexing (OCM) technology for bandwidth-limited direct detection (DD) optical systems. We analytically derive that any OCM, i.e., using any orthogonal circulant matrix for multiplexing, can redistribute the noise uniformly across the subcarriers. However, the distribution of inter-symbol interference (ISI) and inter-carrier interference (ICI) strongly depends on the design of OCM. The previously proposed orthogonal chirp division multiplexing (OCDM), although showing better ISI/ICI tolerance than discrete-Fourier-transform spread (DFT-S) orthogonal frequency division multiplexing (OFDM), is a kind of OCM with poorer performance. We propose and analytically reveal that OCM based on chirp-like polyphase sequence (CLPS), general chirp sequence (GCS), sparse CLPS (SCLPS), and sparse GCS (SGCS) can achieve flatter ISI/ICI distribution across subcarriers and so better performance than OCDM in bandwidth-limited DD systems. The optimal parameter vector of the E-parameter CLPS is a Zadoff-Chu sequence while the parameter α in GCS should be larger. The optimal performance can be achieved by either CLPS (or GCS) using a larger E (or α) or SCLPS (or SGCS) with optimized sparsity. ∼110Gbit/s experiments using Mach-Zehnder modulator or electro-absorption modulator and receiver of 10-GHz photodiode or 8-GHz avalanche photodiode are conducted. The results agree with the theory and show that the proposed OCM outperforms conventional OFDM, DFT-S OFDM, and OCDM.

Exploration and development of shale gas in China have made significant breakthroughs in recent years. Longmaxi shales in the Xiang’exi depression are the key targets for shale gas exploration in the middle Yangtze region. However, systematic studies on the authigenic minerals and their application in shale gas enrichment evaluation are insufficient. Therefore, in this study, pyrite was selected to characterize its morphology, grain size, and distribution characteristics, with the hope to identify the favorable exploration target of Longmaxi shales in the Xiang’exi depression. Herein, 44 unweathered core samples were collected from well LD-1 for experiments. The results show that Longmaxi shales can be divided into four lithological segments from the bottom to the top. L4─high-carbon clayey shale facies and high-carbon siliceous shale facies, exhibits the characteristics of an anoxic environment with a medium pyrite content, due to the insufficient supply of ferric ions. L3─medium-carbon siliceous shale facies, shows the characteristics of a hypoxic environment, with enhanced terrestrial supply and increased pyrite content. L2─low-carbon siliceous shale facies, has the characteristics of an aerobic environment with strong terrestrial supply, leading to a low content of pyrite. L1─medium-carbon clayey shale facies, shows the characteristics of a hypoxic environment similar to L3 but with the highest pyrite content among the four segments. Further research shows that the presence of pyrite is conducive to the development and preservation of organic pores, and shale with a higher pyrite content shows larger gas content and desorption gas/total gas content ratio, showing a greater exploration and development potential. Combined comprehensive analysis concludes that in the Xiang’exi depression, L4 of the Longmaxi shale is the optimal exploration target segment, followed by L1, then L3, while the L2 segment shows the lowest exploration potential.

Producing low-mature shale oil resource is becoming economically available as in situorganic matter or heavy oil conversion technologies are introduced to shale oil production. However, we still lack suitable evaluation parameters and criteria for characterizing oil content and mobility in low-mature shales, which are very important for low-mature shale oil economic production. With the aim to better understand the influence factors for low-mature shale oil content and mobility, 16 shale core samples were collected from low-mature Upper Cretaceous Nenjiang Formation (K2n), Gulong Sag, in the Songliao Basin, to investigate their mineral composition and organic geochemical and pore characteristics. The results show the following: (1) Four shale lithofacies were identified, such as mudstone, carbonate lamina shale, bioclastic shale, and mixed lamina shale. (2) Shale oil mobility [represented by the oil saturation index (OSI)] was mainly controlled by large-sized pore distribution. (3) Total organic carbon (TOC) content and lithofacies had great influence on the distribution of oil mobility in the shale. As for mudstone and bioclastic shale, TOC played the most important role in controlling shale oil mobility, whereas for carbonate lamina shale and mixed lamina shale, TOC and mineral variation both have impacts on oil mobility. (4) The average contents of TOC, S1, and OSI in K2n were higher than those in the deeper Qingshankou shale. The oil mobility controlling factors in K2n and K2qn were both TOC and preservation conditions. (5) A new index was proposed to weigh the content of shale oil, in situOSI, and multiple isothermal pyrolysis parameter S2-2. The in situOSI shows that K2n has high oil retention capacity, and the in situoil mobility is 2–3 times the movable oil content.

Series capacitor buck (SC Buck) converters are widely used in voltage regulator modules (VRMs), electric vehicle, photovoltaic (PV) systems, and so on, for the reason that these converters have the characteristics of high step-down ratio and large output current. However, these characteristics can be realized only when the converter operates in a limited duty-cycle range. In this article, a modified pulsewidth modulation (PWM) scheme based on the principle of ampere-second balance is proposed for the three-phase SC Buck converter to solve the problem. The ampere-second balance of series capacitors is used to balance the phase currents over the entire duty-cycle range. The operating modes, voltage gain and current sharing performance of the converter, control diagram of the proposed converter, and parameter variation analysis are given. Theoretical analysis shows that with the proposed PWM scheme, the converter will have a larger output voltage, unified linear voltage gain expression, and sensorless automatic current sharing over the full duty-cycle range. Moreover, the results show that the parameter variation has nearly influence on the current sharing effect and the excellent balanced current can be achieved under steady state and transient state using the proposed PWM scheme. Finally, a 100-W experimental prototype has been fabricated to verify the performance of the proposed PWM scheme.

Superhydrophobic surfaces possess enormous potential in various applications on account of their versatile functionalities. However, artificial superhydrophobic surfaces with ultralow solid/liquid adhesion often require complicated structure fabrication and surface fluorination processes. Here, we designed a superhydrophobic surface possessed of micro/nanoscale structures by employing facile and low-cost demolding and initiated chemical vapor deposition (iCVD) processes. The achieved micro/nanostructured superhydrophobic surface has a maximum static contact angle of ∼170°, a roll-off angle and contact angle hysteresis below 1°, ultralow solid/liquid adhesion for water droplets, and maintains excellent superhydrophobicity after exposure to strongly corrosive species, like strong acid/base and salt solutions, for 60 h. This reasonability-designed method of creating the superhydrophobic surface could provide valuable guidelines for the manufacture of transferable superhydrophobic surfaces and facilitate potential applications extending from optoelectronic devices to self-cleaning materials, such as solar cells, windows, and electronic displays.

A novel electrochemical microsensor was developed for the ratiometric and simultaneous determination of hydrogen peroxide (H2O2) and ascorbic acid (AA) based on the borate-phenol “switch” recognition mechanism and carbon nanotube (CNT) catalytic characteristics. First of all, a carbon fiber microelectrode (CFME) was coated with CNTs. Then, a specific probe, 9-anthraceneboronic acid pinacol ester (9-AP), was screened and decorated on CNTs through π–π stacking for the recognition of H2O2based on the transformation of boric acid ester into electroactive phenols. CNTs not only served as the amplifiers of current signals, but also as catalysts facilitating AA oxidation. Meanwhile, ferrocenecarboxylic acid (Fc), inert to H2O2and AA, was modified on another amino-functionalized CNT microelectrode viaan amide bond as an internal reference channel for avoiding errors caused by environmental discrepancies. The two-channel ratiometric microsensor enabled the sensitive and accurate detection of H2O2and AA simultaneously, and the detection limits were estimated to be 0.09 μM and 4.12 μM, respectively. The developed microsensor with remarkable analytical performance was finally applied for the simultaneous detection of H2O2and AA in the live rat brain.

The development of high-performance potassium-ion batteries (PIBs) necessitates the research of anodes with high capacity, long cycle life, and excellent rate performance. In this study, we drew inspiration from the structure of diatoms in nature. Through a simple self-template pyrolysis process, Se and S were doped into carbon matrix, leading to the synthesis of Se/S-doped diatomite-like carbon microflakes (Se, S-DCMs) for PIBs. The porous surface structure resembling diatoms, along with the interconnected carbon fibers within the pores, enhances contact between material and electrolyte, thereby accelerating diffusion of K+. Furthermore, the co-doping of S and Se introduces defects, creating additional reaction sites and increasing capacity. As anodes for PIBs, Se, S-DCMs exhibits high capacity (414 mAh g−1after 100 cycles at 100 mA g−1) and high-rate performance (198 mAh g−1at 2000 mA g−1). This study represents a promising approach for optimizing carbon structures to boosting battery performance.

Carbon dioxide (CO2) mineral trapping was considered the most secure and stable mechanism for CO2geological storage. The previous studies lacked clarity regarding the mechanisms and processes of transformation for various types of minerals involved in CO2–water–sandstone and mudstone reactions during CO2geological storage. Additionally, it didn't clear the different stages of mineral reactions in reservoir and caprock. We utilized experimental and numerical simulation methods to analyze the mechanisms, processes, and stages of CO2–water–rock reactions involving various types of minerals in the mudstone from Chang 4 + 5 members and the sandstone from Chang 6 member of the Triassic Yanchang Formation in the Ordos Basin. The experimental simulation demonstrated the dissolution of feldspar minerals in sandstone led to precipitate of carbonate, clay, and other minerals. Contrary, mudstone primarily underwent the dissolution of clay minerals and the precipitation of feldspar minerals, whereas carbonate content remained relatively stable. The numerical simulation consisted of experimental results in the short term, but over a longer timescale, The reaction processes of carbonate and clay minerals in the reservoir and caprock dissolved first and then precipitated. Conversely, other minerals behaved oppositely; feldspar minerals continuously dissolved in the reservoir but precipitated first and then dissolved in the caprock. The reaction stages of mineral change in both the reservoir and caprock could be divided into dissolution, rapid precipitation, and stable precipitation. The reservoir's dissolution stage was shorter than the caprock, which entered the stable precipitation stage earlier. With increasing storage time, continuous CO2–water–rock reactions gradually transformed physically sequestered CO2in the formation into chemically sequestered mineralized CO2.

While social media has the potential to disseminate extensive travel-related information, it may also inadvertently restrict exposure to diverse perspectives, leading to the prevalence of homogenized information among tourists. Prior research has not comprehensively explored the role of social media in shaping and constraining tourism behaviors, which can result in negative experiences at destinations. Consequently, this study represents the initial empirical endeavor to elucidate the adverse implications of echo chambers on tourism behaviors. A mixed methods approach of explanatory sequential design was employed to investigate how and why social media narrows tourism behaviors. This study collected behavioral data and conducted interviews with two groups of tourists: those who rely on social media and those who use official destination maps. It synthesized the distinctive characteristics of tourist behavioral patterns, encompassing trajectory, duration of stay, and visual content, under the influence of social media. Furthermore, this paper examined the detrimental tourism experiences stemming from these constrained behavioral patterns and probed the underlying mechanisms of echo chambers. The findings offer concrete behavioral evidence to comprehend the darker facets of social media in the context of tourism and enhance the understanding of echo chambers within a tourism context. This study also furnishes crucial insights for managing and marketing destinations via social media platforms.

Ammonia is recognized for its potential in hydrogen storage and transportation. Among methods for hydrogen production from ammonia, catalytic decomposition stands out, and developing economical alternatives to noble metal catalysts like ruthenium (Ru) is crucial. Here, we report an exsolution strategy to obtain a size-constrained Ni0-NiO small ensemble on MgO that outperforms bare Ni single atoms and particles in ammonia decomposition. Adding Ce to the NiMg catalyst significantly enhances activity, doubling the hydrogen production rate to 92 mmolH2gcat−1min−1at 550°C, surpassing most Ni-based catalysts. Characterization reveals the role of cerium in forming active Ni0-NiO ensembles by occupying specific sites on MgO. Cerium (Ce) also affects hydrogen and ammonia adsorption and alters reaction pathways. Our work highlights the structure control of transition metal sites and the promotion mechanism of rare-earth elements for ammonia conversion and hydrogen production reaction.

Unlike conventional natural gas accumulations, unconventional ones have obvious particularity in reservoir forming conditions, enrichment mechanism, distribution modes, prediction method, and exploration technology. Analyzing the reservoir forming process and main controlling factors of unconventional natural gas accumulations under the guide of the hydrocarbon accumulation system theory is of great significance for unconventional natural gas reservoir evaluation and prediction. Based on the reservoir forming mechanism and distribution mode, the unconventional natural gas accumulation systems are divided into six types, including shale gas, coalbed methane, tight carbonate gas, tight sandstone gas, water-soluble gas, and gas hydrate. According to the concept of “element–function–structure” in the hydrocarbon accumulation system theory and the relationship of “gas source rock–migration system–accumulations distribution”, the unconventional gas accumulation system is divided into six “source–location” types. The characteristics of the other five types of unconventional gas accumulation systems except gas hydrate are analyzed. The following results were obtained. (1) Shale gas, coalbed methane and tight carbonate gas belong to an intra-source type unconventional gas accumulation system, characterized by intense gas supply capacity, lack of either a transport system or secondary migration, integration of source, reservoir and caprock, in-situ accumulation, and so on. (2) Tight sandstone gas and water-soluble gas belong to a marginal unconventional gas accumulation system of source rock, characterized by diverse gas origin, near-source accumulation in adjacent layers of source rocks, internal migration within reservoirs, and so on. (3) Basin tectonic evolution, sedimentary environment and late tectonic events control the types of unconventional gas accumulation systems: The Paleozoic marine sediments in South China are conducive to the formation of shale gas and tight carbonate gas accumulation systems; The marine–continental transitional facies deposits of Upper Paleozoic distributed in the South and North China are conducive to the development of coalbed methane, shale gas and tight sandstone gas accumulation systems; In the Middle and East China, Mesozoic–Cenozoic deep-water continental deposits are more conducive to the deep tight sandstone gas and shale gas accumulation systems, while shallow water continental basins are more conducive to the formation of coalbed methane, tight sandstone gas and shale gas accumulation systems. Water-soluble gas is widely found in the Cenozoic shallow-buried areas rich in organic matter or high-pressure reservoirs adjacent to gas source rocks.

Defects in solid materials vitally determine their physicochemical properties; however, facile regulation of the defect density is still a challenge. Herein, we demonstrate that the ligand defect density of metal–organic frameworks (MOFs) with a UiO-66 structural prototype is precisely regulated by tuning the linker groups (X = OMe, Me, H, F). Detailed analyses reveal that the ligand defect concentration is positively correlated with the electronegativity of linker groups, and Ce-UiO-66-F, constructed by F-containing ligands and Ce-oxo nodes, possesses the superior ligand defect density (>25%) and identifiable irregular periodicity. The increase in ligand defect density results in the reduction of the valence state and the coordination number of Ce sites in Ce-UiO-66-X, and this merit further validates the relationship between the defective structure and catalytic performance of CO2cycloaddition reaction. This facile, efficient, and reliable strategy may also be applicable to precisely constructing the defect density of porous materials in the future.