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Given the fact that diverting fracturing technique can improve the effective stimulation reservoir volume, and the currently-used temporary plugging materials of chemical particles and fibers are difficult to pass through sand-control completion tools and enter into fractures due to their solid nature, this work thus developed a novel temporary plugging agent (TPA) with multiphase transition properties at different temperatures. Laboratory and field experiments were both conducted to study its feasibility on industrial field applications. Laboratory experiments were first carried out to investigate the properties of this TPA, including multiphase transition temperature and time, plugging strength, compatibility with other fluids, and core permeability damage, in order to guide the design of plugging agent dosage, fracturing construction parameters, and wellbore-fracture temperature. Then, field experiments were conducted to demonstrate its feasibility on actual field applications. Well A and Well R with almost the same geological and engineering conditions were chosen in this experiment where Well A adopted the developed novel technique and Well R, as a comparison well, adopted a conventional fracturing technique. The results from the laboratory experiments indicated that the performance of this TPA met the requirements of industrial standards. With an increase in temperature, this TPA underwent a solution (liquid state) - gel (semi-solid state) - solution (liquid state) transition to meet the needs of different stages in a fracturing treatment, and its multiphase transition speed was controllable. Its plugging strength was positively correlated with its plugging length, with a gradient of 8.9MPa/m. This TPA had good compatibility with other fluids and little damage to rock permeability, only 2%, much less than 25% specified in the standard. The results from the field experiments demonstrated that this innovative technique was feasible and effective. The construction curve of Well A indicated that the construction pressure increased by 3.1MPa and the formation broke again after injecting this TPA. The micro-seismic monitoring also supported this finding and showed that new fractures propagated to the north-by-east direction instead of the due west direction. Under the same production system, the initial daily gas production of Well A was 1.3 times that of Well R. After 100 days of production, the daily gas production of Well A was 1.5 times that of Well R.

Electrical control of magnetic order in van der Waals (vdW) two-dimensional (2D) systems is appealing for high-efficiency and low-dissipation nanospintronic devices. For realistic applications, a vdW 2D material with ferromagnetic (FM) and ferroelectric (FE) orders coexisting and strongly coupling at room temperature is urgently needed. Here we present a potential candidate for nonvolatile electric-field control of magnetic orders at room temperature. Using first-principles calculations, we predict the coexistence of room-temperature FM and FE orders in a 2D transition metal carbide, where the spatial distribution of magnetic moments strongly couples with the orientation of out-of-plane electric polarization. Furthermore, an electric-field switching between interfacial FM and ferrimagnetic orders is realizable through constructing a multiferroic vdW heterostructure based on this material. These findings make a significant step toward realizing room-temperature multiferroicity and strong magnetoelectric coupling in 2D materials.

We predict a pressure-stabilized MnB6 structure that possesses both high-temperature ferromagnetism and high ductility at ambient pressure.

It is exceedingly desired yet challenging to steer the photocatalytic overall CO2 reduction reaction (CRR) toward high-value liquid products, especially multicarbon products like ethanol. Numerous attempts have been reported such as developing new materials, cocatalyst engineering, etc. Here, we find that by just curling the superhydrophobic Cu2O to create an enclosed Cu2O hollow structure, the selectivity of ethanol (59.59%) is impressively elevated by ~ 9 times higher than that without the enclosed hollow structure. Further investigations indicate that the superhydrophobic hollow structure can efficiently repel water out and thus create an enclosed gas storage space, enabling the high concentration of CO2 molecules. With such a strategy, an impressive ethanol generation rate of 996.18 µmol g− 1 h− 1 is achieved. The mechanism is also investigated based on theoretical calculations and corresponding characterizations. This strategy provides a geometry-modulated method with high compatibility, which is promising to develop more efficient photocatalysts for multicarbon production combined with other traditional methods.

Magnetic field enhanced electrocatalysis has recently emerged as a promising strategy for the development of a viable and sustainable hydrogen economy via water oxidation. Generally, the effects of magnetic field enhanced electrocatalysis are complex including magnetothermal, magnetohydrodynamic and spin selectivity effects. However, the exploration of magnetic field effect on the structure regulation of electrocatalyst is still unclear whereas is also essential for underpinning the mechanism of magnetic enhancement on the electrocatalytic oxygen evolution reaction (OER) process. Here, it is identified that in a mixed NiFe

Half-metallic ferromagnetism in low-dimensional materials has attracted increasing attention in recent years due to its potential application in spintronics. Inspired by recent research studies, on...

Two-dimensional (2D) transition metal dinitrides (TMN2) have attracted increasing attention owing to their diverse geometry configurations and versatile properties. Because of the large electrostatic repulsion between highly charged N3− ions, TMN2 could show a low-coordination-number geometry different from transition metal dichalcogenides (e.g. MoS2), which would bring about high-temperature ferromagnetism and other unique properties. In this study, we systemically investigated the possible h-, t- and novel tetra-phases of 2D TMDNs (TM = all the 3d, 4d and 5d transition metals) via high-throughput first-principles calculations. The results show that the 2D tetra-phases for several systems are energetically preferred than their h- and t-phases. These 2D tetra-phases are dynamically and thermally stable with comparable mechanical properties to 2D MoS2 and germanene. Tetra-MoN2 and tetra-WN2 are semiconductors, while tetra-TcN2, tetra-RuN2, tetra-ReN2, tetra-OsN2 and tetra-IrN2 are metals. In particular, tetra-MnN2 exhibits ferromagnetic half-metallicity with a Curie temperature (Tc) of up to ∼360 K and out-of-plane magnetic anisotropy. These findings expand the family of 2D TMN2 and provide a material database for future theoretical and experimental studies on 2D spintronic materials.

Two-dimensional (2D) multiferroic materials with the coexistence of electric and spin polarization offer a tantalizing potential for high-density multistate data storage. However, intrinsic 2D multiferroic semiconductors with high thermal stability are still rare to date. Here, we propose a new mechanism of single-phase multiferroicity. Based on first-principles calculations, we predicted that in a CrO3 monolayer, the unconventional distortion of the square antiprismatic crystal field on Cr-d orbitals will induce an in-plane electric polarization, making this material a single-phase multiferroic semiconductor. Importantly, the magnetic Curie temperature is estimated to be ∼220 K, which is quite high as compared to those of the recently reported 2D ferromagnetic and multiferroic semiconductors. Moreover, both ferroelectric and antiferroelectric phases are observed, providing opportunities for electrical control of magnetism and energy storage and conversion applications. These findings provide a comprehensive understanding of the magnetic and electric behavior in 2D multiferroics and will motivate further research on the application of related 2D electromagnetics and spintronics.

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Two-dimensional (2D) ferromagnetic (FM) semiconductor chromium triiodide (CrI3) has attracted much attention because of its long-range two-dimensional (2D) FM order and tunable interlayer magnetic ...

Superatomic clusters, due to their unique size- and composition-specific properties, could form the building blocks of a new class of cluster-assembled materials, provided they can retain their str...

With the rapid development of Web3D technologies, sketch-based model retrieval has become an increasingly important challenge, while the application of Virtual Reality and 3D technologies has made shape retrieval of furniture over a web browser feasible. In this paper, we propose a learning framework for shape retrieval based on two Siamese VGG-16 Convolutional Neural Networks (CNNs), and a CNN-based hybrid learning algorithm to select the best view for a shape. In this algorithm, the AlexNet and VGG-16 CNN architectures are used to perform classification tasks and to extract features, respectively. In addition, a feature fusion method is used to measure the similarity relation of the output features from the two Siamese networks. The proposed framework can provide new alternatives for furniture retrieval in the Web3D environment. The primary innovation is in the employment of deep learning methods to solve the challenge of obtaining the best view of 3D furniture, and to address cross-domain feature learning problems. We conduct an experiment to verify the feasibility of the framework and the results show our approach to be superior in comparison to many mainstream state-of-the-art approaches.

Spontaneous orbital symmetry breaking in crystals gives rise to abundant novel and interesting physical properties, which sometimes are concealed by the absence of geometrical distortions. We show that a recently discovered 3d2 system, namely the layered VI3 ferromagnetic semiconductor, is a strongly correlated and orbital ordering system. Our analysis reveals that in a VI3-like system, there could be two types of orbital splitting, which are stabilized respectively by strong electronic correlation and inter-atomic exchange interactions. Consequently, on the basis of first-principles calculations, two competing low-energy phases of VI3 monolayer (denoted as twin orbital-order phases) are discovered, in which the metal–insulator transition is driven by strong electronic correlation, and the orbital symmetry breaking is robust against geometrical distortions. In addition, similar phenomena are also observed in other VI3-like systems. These findings shed light on the unusual electronic behavior of a strongly correlated 2D system and will be interesting for nanoscale multi-functional spintronic applications.

To support intelligent manufacturing, providing a unified production data view by integrating distributed data collected by different enterprise information systems is critical. Because various information systems are often heterogeneous, ontology is widely adopted to present a global reference view for data integration. However, construction and maintenance of these ontologies is difficult because of the heterogeneity and dynamism of these large-scale data. In this paper, with the objective of intelligent manufacturing application implementation, we propose a comprehensive ontology generation and evolution method that automatically abstracts ontology from raw production data and dynamically adjusts the ontology in accordance with changes in the manufacturing data environment. The proposed method comprises four phases: data extraction, ontology construction, ontology connection, and ontology evolution. In the first phase, data from different sources are mapped to data entities to form a unified data structure. In the second phase, an initial ontology is generated via instance-driven ontology construction. In the third phase, to support intelligent manufacturing, the initial ontologies are organised in terms of the dimensions of the various business elements, such as stuff, machine, product, process, and scenarios. In the fourth phase, rules regarding ontology restrictions are formulated to realise ontology evolution that respond to changes in the manufacturing environment. To verify the efficacy of the proposed method, a prototype was implemented with real data from a manufacturing factory, in which the constructed ontology was used as the metadata of product data in intelligent manufacturing.

As a fundamental thermodynamic variable, pressure can alter the bonding patterns and drive phase transitions leading to the creation of new high-pressure phases with exotic properties that are inaccessible at ambient pressure. Using the swarm intelligence structural prediction method, the phase transition of TiF3, from R–3c to the Pnma phase, was predicted at high pressure, accompanied by the destruction of TiF6 octahedra and formation of TiF8 square antiprismatic units. The Pnma phase of TiF3, formed using the laser-heated diamond-anvil-cell technique was confirmed via high-pressure x-ray diffraction experiments. Furthermore, the in situ electrical measurements indicate that the newly found Pnma phase has a semiconducting character, which is also consistent with the electronic band structure calculations. Finally, it was shown that this pressure-induced phase transition is a general phenomenon in ScF3, VF3, CrF3, and MnF3, offering valuable insights into the high-pressure phases of transition metal trifluorides.

Metal-organic frameworks (MOFs), comprised of organic ligands and metal ions/metal clusters via coordinative bonds are highly porous, crystalline materials. Their tunable porosity, chemical composition, size and shape, and easy surface functionalization make this large family more and more popular for drug delivery. There is a growing interest over the last decades in the design of engineered MOFs with controlled sizes for a variety of biomedical applications. This article presents an overall review and perspectives of MOFs-based drug delivery systems (DDSs), starting with the MOFs classification adapted for DDSs based on the types of constituting metals and ligands. Then, the synthesis and characterization of MOFs for DDSs are developed, followed by the drug loading strategies, applications, biopharmaceutics and quality control. Importantly, a variety of representative applications of MOFs are detailed from a point of view of applications in pharmaceutics, diseases therapy and advanced DDSs. In particular, the biopharmaceutics and quality control of MOFs-based DDSs are summarized with critical issues to be addressed. Finally, challenges in MOFs development for DDSs are discussed, such as biostability, biosafety, biopharmaceutics and nomenclature., Graphical abstract This review focuses on metal–organic frameworks (MOFs)-based drug delivery systems (DDSs), including classification, synthesis, characterization, applications and biopharmaceutics of MOFs for DDSs.Image 1

There is a need to develop high-capacity, stable anode materials for the next generation of lithium ion batteries that will power consumer electronics and automobiles of the future. This report des...

The integration of ferromagnetic and semiconducting properties in a single two-dimensional (2D) material has been recognized as a fertile ground for fundamental science as well as for practical app...

For the development of high-performance spintronic nanodevices, one of the most urgent and challenging tasks is the preparation of two-dimensional materials with room-temperature ferromagnetism and a large magnetic anisotropic energy (MAE). Through first-principles swarm-intelligence structural search calculations, we identify an ideal ferromagnetic Fe3P monolayer, in which Fe atoms show a perfect Kagome lattice, leading to strong in-plane Fe-Fe coupling. The predicted Curie temperature of Fe3P reaches ∼420 K, and its MAE is comparable to those of ferromagnetic materials, such as Fe and Fe2Si. Moreover, the Fe3P monolayer remains as an above room-temperature ferromagnet under biaxial strains as large as 10%. Its lattice can be retained at temperatures of ≤1000 K, exhibiting a high thermodynamic stability. All of these desirable properties make the Fe3P monolayer a promising candidate for applications in spintronic nanodevices.

Although semiconducting ferromagnetism has been experimentally discovered in two-dimensional (2D) crystals, the spin coupling is still quite weak, which leads to a rather low Curie temperature (TC)...

Since the recent experimental discovery of the CrI3 and CrGeTe3 monolayers, van der Waals (vdW) layered transition metal compounds have been recognized as promising candidates to realize 2D ferromagnetic (FM) semiconductors. However, until now, only limited compounds have been proposed to be ferromagnetic semiconductors. Here, on the basis of first-principles calculations, we report that the monolayer, Janus monolayer, and bilayer of NiX2 (X = Cl, Br, I) are intrinsic 2D FM semiconductors. Our results show that exfoliation energy of the NiX2 monolayer is smaller than that of graphene, and all studied NiX2 layers show semiconducting band gaps. The predicted Curie temperature values for NiX2 (X = Cl, Br, I) monolayers ranged from 120 to 170 K with Monte Carlo simulations. For the Janus monolayer, we found that the spin interaction shows a very strong magnetoelectric coupling under an external electric field. Furthermore, for the bilayer of NiX2, our results show that the interlayer coupling is quite weak, i...

Mobile applications are widely used to provide users convenient and friendly service experiences. Meanwhile, service logs generated by mobile applications are analyzed to obtain user behavior patterns for monitoring and optimizing mobile application performances. However, due to the frequent updates in mobile application, situations of concept drifts often occur in service log streams, which lead to challenges in mobile process mining. In this paper, a novel framework is proposed to solve the above problems by combining fog-computing-based concept drift detecting with cloud-computing-based process mining. Firstly, incomplete log data are preprocessed using fog-computing technologies to provide more accurate log contexts and lower overhead. Then, concept drift detecting methods are used in cloud computing layer to deal with the transfer of mobile applications from one version to another. Finally, experimental results demonstrate that our framework can deduce missed case identifiers for logs when concept drifts happen.

Two-dimensional (2D) ferromagnetic (FM) semiconductors with a direct electronic band gap have recently drawn much attention due to their promising potential for spintronic and magneto-optical applications. However, the Curie temperature (TC) of recently synthesized 2D FM semiconductors is too low (∼45 K) and a room-temperature 2D direct band gap FM semiconductor has never been reported, which hinders the development for practical magneto-optical applications. Here, we show that through isovalent alloying, one can increase the TC of a 2D FM semiconductor up to room temperature and simultaneously turn it from an indirect to a direct band gap semiconductor. Using the first-principles calculations, we predict that the alloyed CrMoS2Br2 monolayer is a direct band gap semiconductor with a TC of ∼360 K, whereas the pristine CrSBr monolayer is an indirect band gap semiconductor with a TC of ∼180 K. These findings provide a promising pathway to realize 2D direct band gap FM semiconductors with TC above room temperature, which will greatly stimulate theoretical and experimental interest in future spintronic and magneto-optical applications.

Electrical control of magnetism in a two-dimensional (2D) semiconductor is of great interest for emerging nanoscale low-dissipation spintronic devices. Here, we propose a general approach of tuning magnetic coupling and anisotropy of a van der Waals (vdW) 2D magnetic semiconductor via a built-in electric field generated by the adsorption of superatomic ions. Using first-principles calculations, we predict a significant enhancement of ferromagnetic (FM) coupling and a great change of magnetic anisotropy in 2D semiconductors when they are sandwiched between superatomic cations and anions. The magnetic coupling is directly affected by the built-in electric field, which lifts the energy levels of mediated ligands' orbitals and enhances the super-exchange interactions. These findings will be of interest for ionic gating controlled ferromagnets and magnetoelectronics based on vdW 2D semiconductors.

Spontaneous orbital symmetry breaking in crystals gives rise to abundant novel and interesting physical properties, which sometimes are concealed by the absence of geometrical distortions. We show that a recently discovered 3d2 system, namely the layered VI3 ferromagnetic semiconductor, is a strongly correlated and orbital ordering system. Our analysis reveals that in a VI3-like system, there could be two types of orbital splitting, which are stabilized respectively by strong electronic correlation and inter-atomic exchange interactions. Consequently, on the basis of first-principles calculations, two competing low-energy phases of VI3 monolayer (denoted as twin orbital-order phases) are discovered, in which the metal-insulator transition is driven by strong electronic correlation, and the orbital symmetry breaking is robust against geometrical distortions. In addition, similar phenomena are also observed in other VI3-like systems. These findings shed light on the unusual electronic behavior of a strongly correlated 2D system and will be interesting for nanoscale multi-functional spintronic applications.

As service-oriented computing is commonly used in industrial systems to deal with the continually changing business environment, matching processes with existing services becomes one of the most important phases in constructing, integrating and optimizing information systems. The precision of semantic service matching becomes a critical factor in ensuring the correctness of functionalities in system processes. However, the dependability of semantic service matching cannot be warranted in complex contexts. To improve semantic service matching for industrial systems, a context-based semantic service matching approach named ‘Process-Based service MatchMaker’(PBMM) is proposed in this paper. It selects the suitable services for the process from candidate services through taking the dependencies of related services process into consideration.

In spite of decades of research, a fundamental understanding of the unusual magnetic behavior of small Mn clusters remains a challenge. Experiments show that Mn2 is antiferromagnetic while small clusters containing up to five Mn atoms are ferromagnetic with magnetic moments of 5 μB/atom and become ferrimagnetic as they grow further. Theoretical studies based on density functional theory (DFT), however, find Mn2 to be ferromagnetic, with ferrimagnetic order setting in at different sizes that depend upon the computational methods used. While quantum chemical techniques correctly account for the antiferromagnetic ground state of Mn2, they are computationally too demanding to treat larger clusters, making it difficult to understand the evolution of magnetism. These studies clearly point to the importance of correlation and the need to find ways to treat it effectively for larger clusters and nanostructures. Here, we show that the DFT+U method can be used to account for strong correlation. We determine the on-...

Materials with competitive spin interactions can show multiple quantum magnetic states under external manipulation, which is important for spin-related research and applications. Although the magnetism in graphene nanoribbons has been intensively studied, robust spin interactions have not been reported. Here, we explored graphene nanoribbons modified with Ti and V atomic chains that show competitive spin interactions and robust spiral magnetism. On the basis of first-principles calculations, we systematically investigate the possibility of inducing robust and competitive magnetic ordering in graphene nanoribbons through transition-metal (TM) atomic chain decoration (denoted as TM-ZGNR, TM = Ti–Co). On the basis of the Heisenberg XY model including nearest-neighbor (NN) and next-nearest-neighbor (NNN) magnetic interactions, Ti-ZGNR and V-ZGNR are predicted to have spiral magnetic order due to spin frustration. By Monte Carlo simulations, the Neel temperatures for Ti-ZGNR and V-ZGNR are estimated to be 45 a...

Controlling magnetism of two-dimensional multiferroics by an external electric field provides special opportunities for both fundamental research and future development of low-cost electronic nanodevices. Here, we report a general scheme for realizing a magnetic phase transition in 2D type-I multiferroic systems through the reversal of ferroelectric polarization. Based on first-principles calculations, we demonstrate that a single-phase 2D multiferroic, namely, ReWCl_{6} monolayer, exhibits two different low-symmetric (C_{2}) phases with opposite in-plane electric polarization and different magnetic order. As a result, an antiferromagnetic-to-ferromagnetic phase transition can be realized by reversing the in-plane electric polarization through the application of an external electric field. These findings not only enrich the 2D multiferroic family, but also uncover a unique and general mechanism to control magnetism by electric field, thus stimulating experimental interest.

Encapsulation strategies are widely used for alleviating dissolution and diffusion of polysulfides, but they experience nonrecoverable structural failure arising from the repetitive severe volume change during lithium−sulfur battery cycling. Here we report a methodology to construct an electrochemically recoverable protective layer of polysulfides using an electrolyte additive. The additive nitrogen-doped carbon dots maintain their “dissolved” status in the electrolyte at the full charge state, and some of them function as active sites for lithium sulfide growth at the full discharge state. When polysulfides are present amid the transition between sulfur and lithium sulfide, nitrogen-doped carbon dots become highly reactive with polysulfides to form a solid and recoverable polysulfide-encapsulating layer. This design skilfully avoids structural failure and efficiently suppresses polysulfide shuttling. The sulfur cathode delivers a high reversible capacity of 891 mAh g−1 at 0.5 C with 99.5% coulombic efficiency and cycling stability up to 1000 cycles at 2 C., Inspired by the processes of thrombus formation and thrombolysis in blood vessels, the authors here construct an electrochemically recoverable protective layer of polysulfides using an electrolyte additive, realizing high performance Li–S batteries.

Ferromagnetic semiconductors exhibit novel spin-dependent optical, electrical, and transport properties, which are promising for next-generation highly functional spintronic devices. However, the possibility of practical applications is hindered by their low Curie temperature. Currently, whether semiconducting ferromagnetism can exist at room temperature is still unclear because of the absence of a solid physical mechanism. Here, on the basis of tight-binding model analysis and first-principles calculations, we report that ferromagnetism in a tetrahedral semiconductor originating from superexchange interactions can be strong enough to survive at room temperature because of the weakening of antiferromagnetic direct-exchange interactions. On the basis of the explored mechanism, a zinc-blende binary transition metal compound, chromium carbide, is predicted to be an intrinsic ferromagnetic tetrahedral semiconductor with a Curie temperature that is as high as ∼1900 K. These findings not only expand the understandings of magnetism in semiconductors but also are of great interest for room-temperature spintronic applications.

For the development of high-performance spintronic nanodevices, one of the most urgent and challenging tasks is the preparation of two-dimensional materials with room-temperature ferromagnetism and a large magnetic anisotropic energy (MAE). Through first-principles swarm-intelligence structural search calculations, we identify an ideal ferromagnetic Fe