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Light-emitting diodes (LEDs) based on metal halide perovskite quantum dots (QDs) have achieved impressive external quantum efficiencies; however, the lack of surface protection of QDs, combined with efficiency droop, decreases device operating lifetime at brightnesses of interest. The epitaxial incorporation of QDs within a semiconducting shell provides surface passivation and exciton confinement. Achieving this goal in the case of perovskite QDs remains an unsolved challenge in view of the materials' chemical instability. Here, we report perovskite QDs that remain stable in a thin layer of precursor solution of perovskite, and we use strained QDs as nucleation centers to drive the homogeneous crystallization of a perovskite matrix. Type-I band alignment ensures that the QDs are charge acceptors and radiative emitters. The new materials show suppressed Auger bi-excition recombination and bright luminescence at high excitation (600 W cm-2), whereas control materials exhibit severe bleaching. Primary red LEDs based on the new materials show an external quantum efficiency of 18%, and these retain high performance to brightnesses exceeding 4700 cd m-2. The new materials enable LEDs having an operating half-life of 2400 h at an initial luminance of 100 cd m-2, representing a 100-fold enhancement relative to the best primary red perovskite LEDs.

Developing bifunctional electrocatalysts with both high catalytic activity and high stability is crucial for efficient water splitting in alkaline media. Herein, a Fe-incorporated dual-metal selenide on nickel foam (Co0.9Fe0.1-Se/NF) is synthesized via a facile one-step electrodeposition method. As-synthesized materials could serve as self-supported bifunctional electrocatalysts with excellent catalytic activity towards oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media. Experimental results show that delivering a 10 mA cm−2 water splitting current density only requires a cell voltage of 1.55 V. In addition, a very stable performance could be kept for about 36 hours, indicating their excellent working stability. Moreover, by means of phase analysis, we have identified that the evolution of the synthesized Co0.9Fe0.1-Se/NF experiences two entirely different processes in HER and OER, which hydroxide and oxyhydroxide are regarded as the real active sites, respectively. This work may pave the way to further understanding the relationships between the reactivity and stability of chalcogenide-based electrocatalysts and facilitating the rational design of efficient electrocatalysts for future renewable energy system applications.

The all-inorganic nature of CsPbI3 perovskites allows to enhance stability in perovskite devices. Research efforts have led to improved stability of the black phase in CsPbI3 films; however, these strategies-including strain and doping-are based on organic-ligand-capped perovskites, which prevent perovskites from forming the close-packed quantum dot (QD) solids necessary to achieve high charge and thermal transport. We developed an inorganic ligand exchange that leads to CsPbI3 QD films with superior phase stability and increased thermal transport. The atomic-ligand-exchanged QD films, once mechanically coupled, exhibit improved phase stability, and we link this to distributing strain across the film. Operando measurements of the temperature of the LEDs indicate that KI-exchanged QD films exhibit increased thermal transport compared to controls that rely on organic ligands. The LEDs exhibit a maximum EQE of 23 % with an electroluminescence emission centered at 640 nm (FWHM: ≈31 nm). These red LEDs provide an operating half-lifetime of 10 h (luminance of 200 cd m-2 ) and an operating stability that is 6× higher than that of control devices.

Microcrystalline graphite (MG) is a major form of natural graphite and an important raw material with various applications in advanced technologies, such as lithium-ion battery anodes and isotropic graphite filler particles. MG is known to be an aggregate of graphite crystallites with a lateral dimension of less than 1 μm. However, the microstructure of MG remains unclear. In this study, we report the porous structure of a purified Chinese MG with an apparent density of 1.3–1.4 g/cm3. MG typically contains many microslits that are approximately 1–2 μm in length and up to 200 nm in width. The microslits provide MG with a stronger ability to accommodate c-axis thermal expansion than Mrozowski cracks, resulting in a low coefficient of thermal expansion (CTE) of approximately 2 × 10−6/K. This unique thermal expansion behavior makes MG a promising filler material for developing artificial graphite with a low CTE, and enables the modulation of the CTE of nuclear graphite.

The transmission and distribution of moisture in cement-based materials are of great significance to the properties and durability of materials. Traditional macro-humidity monitoring equipment in civil engineering cannot capture the microscale humidity inside cement-based materials in situ. In this paper, a method of using rhodamine 6G fluorescence to characterize the change in relative humidity in cement-based materials is proposed. Two kinds of moulding processes are designed, which are premixed and smeared after moulding, and the optimal preparation concentration is explored. The results showed that rhodamine 6G can reflect the relative humidity of cement-based materials in situ by its fluorescence intensity and had little effect on the hydration heat release and hydration products of cement-based materials; the fluorescence intensity was much higher when the internal relative humidity was 63% and 75%. The research results lead the application of polymer materials in the field of traditional building materials, help to explore the performance evolution law of cement-based materials in micro scale, and have important significance for the evolution from single discipline to interdisciplinary.

Natural graphite such as flake graphite and microcrystalline graphite have important applications in nuclear engineering, especially in high-temperature gas-cooled reactors. Owing to requirements for low ash content and total equivalent boron content, thermal and gas purification is necessary for producing natural graphite powder with nuclear-grade purity. In this study, representative Chinese flake graphite and microcrystalline graphite were purified thermally or with halogens at graphitization temperatures. By thermal purification at 3000 °C, natural flake graphite and microcrystalline graphite containing at least 99.9% carbon was achieved. The metallic impurities remaining after thermal purification were mainly elements that formed carbides with extraordinarily high melting/boiling points, such as B, Ti, Ta, V, W, and Mo. Gas purification with halogens further increased the purity of natural flake graphite and microcrystalline graphite to nuclear grade, that is, the ash content and total equivalent boron content were less than 50 ppm and 0.01 ppm, respectively. Meanwhile, an investigation of the purification mechanism helped to understand the chemistry and thermodynamics of thermal purification of natural graphite.

The effect of fluid turbulence models on the coarse-grid simulation for the mesoscale gas-solid flow system is not as clear as that for gas-liquid/single flows. In this study, the effect of different turbulence models on predictions of riser-only, turbulent and bubbling flow hydrodynamics is quantified. Then the selected turbulence models are examined by coarse-grid simulations in a full-loop circulating fluidized bed (CFB) with a proposed hybrid drag model which integrates two SGMs and Hulin-Gidaspow model. Results show that the standard k-epsilon and k-omega models fail to capture a correct fluidization pattern in riser. Meanwhile, the RNG and realizable k-epsilon models and SST k-omega model enable satisfactory predictions which are highly comparable to discrete model predictions and experiments over different flow regimes. However, the realizable k-epsilon model produces more pronounced flow fluctuations causing computational instability. Using superior turbulence closures, full-loop simulations with the proposed hybrid model can predict desirable hydrodynamics.

Herein is developed a ternary heterostructured catalyst, based on a periodic array of 1D TiN nanotubes, with a TiO2 nanoparticulate intermediate layer and a In2O3-x(OH)y nanoparticulate shell for improved performance in the photocatalytic reverse water gas shift reaction. It is demonstrated that the ordering of the three components in the heterostructure sensitively determine its activity in CO2 photocatalysis. Specifically, TiN nanotubes not only provide a photothermal driving force for the photocatalytic reaction, owing to their strong optical absorption properties, but they also serve as a crucial scaffold for minimizing the required quantity of In2O3-x(OH)y nanoparticles, leading to an enhanced CO production rate. Simultaneously, the TiO2 nanoparticle layer supplies photogenerated electrons and holes that are transferred to active sites on In2O3-x(OH)y nanoparticles and participate in the reactions occurring at the catalyst surface.

Colloidal quantum dot (CQD) solar cells are solution-processed photovoltaic devices that exhibit promise in harvesting the infrared solar spectrum. Solid-state ligand exchange is the method employe...

The chirality feature of C1 and C3 boron subphthalocyanines (BsubPcs) is an attractive property in material science and supramolecular chemistry. Normally in the field, enantiomeric mixtures are separated through a standard process. The goal of this study was to determine if the mixture of BsubPc enantiomers could form a mixed alloyed composition in the solid state, which is very relevant to their potential application in the organic electronic field. We present the synthesis and physical characteristics of a selection of four chiral BsubPc mixtures. These BsubPcs are specifically trichlorinated and trifluorinated in the periphery, such as Cl-βF3BsubPc, Cl-αF3BsubPc, Cl-βCl3BsubPc and Cl-αCl3BsubPc. The isomeric (C1/C3) ratios of each BsubPc were determined by NMR. Single-crystal XRD of all four BsubPc mixtures showed that the C1 and C3 isomers co-crystallized within their respective lattices forming solid-state mixed alloyed compositions. The structures of Cl-αF3BsubPc and Cl-βF3BsubPc crystallized in the same lattice as Cl-BsubPc, with some expansion of the unit cell volume, while the trichlorinated BsubPcs did not due to the large van der Waals radii of the chlorine atoms. This set of mixed alloyed BsubPcs was also integrated into organic solar cells/photovoltaics (OSCs/OPVs) as both non-fullerene electron acceptors and as electron donors. It was confirmed that these BsubPc isomers/enantiomers are applicable in OPVs as mixed alloyed compositions, with more promising functionality as non-fullerene electron acceptors given their significant contribution to the EQE spectra. Further molecular engineering of these materials will be made to enhance their OPV performance and to explore their bifunctional charge carrier mobility roles.

Scramjet is the key technology to achieve long-endurance and supersonic flight in the future. With air flowing through the interior of a Scramjet in milliseconds, the rapid mixing of fuel and air becomes one of the great challenges of engine design. Among the various methods of improving fuel-air mixing, shock wave enhancement is an effective technical approach. Based on this, a new method is proposed in this paper to enhance the mixing efficiency of the supersonic mixing layer by using unsteady shock wave. The feasibility of the method is verified by comparing the effects of three conditions on the mixing efficiency of the mixing layer, which are shock-free mixing layer, steady shock/mixing layer interaction, and unsteady shock/mixing layer interaction. The shock wave structures and vortex structures in the three conditions are compared and the vorticity and turbulence intensity are calculated. The results indicate that the shock waves have a significant effect on the mixing layer, especially the unsteady shock. The unsteady shock will cause periodic changes in the shock wave structures and the direction of mainstream flow. Moreover, the shock waves will increase the averaged vorticity at the interaction point and the unsteady shock can greatly enhance the evolution of the vortex structures. The periodic changes of the flow field will cause the oscillation of the mixing layer, resulting in an increase in the averaged vorticity and its fluctuation range of vertical distribution. Furthermore, the unsteady shock wave can significantly increase the turbulence intensity of the mixing layer, and the contribution of the oscillation to the turbulence intensity will counteract the reduction caused by the compression effect of the shock wave. In conclusion, the unsteady shock waves can enhance the mixing efficiency more effectively.

The adipic acid is an important intermediate in the production of nylon, polyurethane and polyester resins. The industrial approach for preparing adipic acid is through the liquid catalytic oxidation of KA oil with nitric acid. In this work, a comprehensive model is developed for this reaction based on the kinetic study conducted in a continuous flow tubular reactor. The kinetic model fits well with the experimental results across the experimental conditions, and the average relative error between the calculated and experimental values is 5.7%. Results show that there was an induction period at the early stage of reaction. Moreover, it is found that at temperature range of 328–358 K, the formation rate of adipic acid strongly dependents on the temperature and nitric acid concentration. The developed model is used to predict the yield of adipic acid at 359–368 K. The work in this study could provide much knowledge for industrial tubular reactor design.

Exfoliated graphite (EG) is promising oil sorbent as well as an intermediate product for the preparation of flexible graphite films (FGFs). It has been a critical challenge to energy conservation and pollution abatement for the traditional EG production technique. Here, we propose a simple and effective preparation method to acquire EG in which flake graphite is intercalated and exfoliated at room temperature, not involving any pollutant emission. The influence factors in the preparation process were explored, such as the amount of H2SO4 and H2O2, the temperature for the preparation of room temperature exfoliated graphite (RTEG). In contrast to the EG by high temperature exfoliation (HTEG), RTEG exhibits a homogeneous structure and a significantly increased volume and surface area. Moreover, EG blocks with high oil sorption capacity and excellent reuse performance can be obtained by RTEG method. Especially, FGFs fabricated by RTEG has high flexibility, thermal conductivity and electrical conductivity. It suggests that this environment-friendly technology is suitable for large-scale industrial implementation of graphite-based oil sorbents and flexible materials.

One of the challenges for modelling of polymerization kinetics is the detailed description of the molecular build-up of both linear and non-linear chains, specifically those with many grafts and crosslinks. Such grafted/crosslinked (co)polymers are relevant as emulsifiers, surface-modifying agents, coating materials, and compatibilizers. In the present work, we put forward a coupled matrix-based Monte Carlo (CMMC) concept to be successful in this respect, avoiding computational stiffness. The CMMC concept is illustrated for single phase grafting of polybutadiene (PB) with styrene (St) at 343 K by limiting the St conversion to 30%. Considering literature kinetic parameters, a benchmark for average characteristics as obtainable by deterministic method of moments simulations is first presented to then gradually extend the level of modelling output addressing (i) conventional grafting performance indicators (e.g. the grafting yield and mass ratio); (ii) univariate chain length distributions for all macrospecies types (polystyrene, PB, PB with only T grafts, PB with at least one H graft, etc.); (iii) bivariate St–butadiene distributions showing a compositional drift, due to the kinetic tendency to attack longer chains if they are sufficiently present and the competition between grafting and crosslinking; (iv) the explicit molecular build-up of individual molecules predicting the positioning of the St–Bd and St–St connectivity points and the chain formation history. It is demonstrated that the CMMC tool allows the simulation of the contribution and structure of molecules that are hard to access purely experimentally, so that in the long run, novel structure–property relationships are within reach. It is also showcased that consideration of elementary reactions is highly recommended and that even at 343 K, thermal self-initiation with St and related chain transfer reactions matter for a full appreciation of molecular variations. The current work also opens the pathway to identifying pragmatic equations for the experimentalist and online control benefiting from a detailed CMMC solution under any desired conditions.

The quantification of dispersity is an indispensable part of characterizing polymers. In this work, general dispersity equations for “living” polymers obtained by nitroxide-mediated polymerization ...

As the information technology rapidly develops, many network applications appear and their communication protocols are unknown. Although many protocol keyword recognition based protocol reverse engineering methods have been proposed, most of the keyword recognition algorithms are time consuming. This paper firstly uses the traffic clustering method F-DBSCAN to cluster the unknown protocol traffic. Then an improved CFSM (Closed Frequent Sequence Mining) algorithm is used to mine closed frequent sequences from the messages and identify protocol keywords. Finally, CFGM (Closed Frequent Group Mining) algorithm is proposed to explore the parallel, sequential and hierarchical relations between the protocol keywords and obtain accurate protocol message formats. Experimental results show that the proposed protocol formats extraction method is better than Apriori algorithm and Sequence alignment algorithm in terms of time complexity and it can achieve high keyword recognition accuracy. Additionally, based on the relations between the keywords, the method can obtain accurate protocol formats. Compared with the protocol formats obtained from the existing methods, our protocol format can better grasp the overall structure of target protocols and the results perform better in the application of protocol reverse engineering such as fuzzing test.

Colloidal quantum dot (CQD) solar cells composed of ionic halide passivated active layers benefit from improved passivation and high carrier mobility because of short interparticle distance. Howeve...

We report a simple process to connect graphene sheets forming graphene hollow microtubes (GHMs), where the tube diameter can be adjusted in the 100–500 nm range by changing reaction conditions. We discovered that graphene sheets can be seamlessly linked to each other if C atoms are substituted for N atoms at the edges of the sheets during annealing of graphene oxide(G-O)-coated electrospun PAN carbon fibers in ammonia atmosphere. The G-O/carbon hybrid nanofibers framework served as a confining template around which graphene sheets curved to form tubular structures. The GHMs formed by this process are similar to (very) large diameter carbon nanotubes (CNTs) with relatively low curvature whose electron field-emission properties include a low turn-on voltage of 0.18 V/μm (at J = 10 μA/cm2), low threshold field of 0.35 V/μm (at J = 10 mA/cm2), and high field-emission stability. This process to produce GHMs can be scaled up to fabricate GHMs of variable diameter in bulk quantities.

In this work, the effect of non-drag forces (lift force, turbulent dispersion force, wall lubrication force and virtual mass force) and bubble induced turbulence (BIT) on the CFD-PBM simulation of ...

Colloidal quantum dot (QD) solids are emerging semiconductors that have been actively explored in fundamental studies of charge transport1 and for applications in optoelectronics2. Forming high-quality QD solids—necessary for device fabrication—requires substitution of the long organic ligands used for synthesis with short ligands that provide increased QD coupling and improved charge transport3. However, in perovskite QDs, the polar solvents used to carry out the ligand exchange decompose the highly ionic perovskites4. Here we report perovskite QD resurfacing to achieve a bipolar shell consisting of an inner anion shell, and an outer shell comprised of cations and polar solvent molecules. The outer shell is electrostatically adsorbed to the negatively charged inner shell. This approach produces strongly confined perovskite QD solids that feature improved carrier mobility (≥0.01 cm2 V−1 s−1) and reduced trap density relative to previously reported low-dimensional perovskites. Blue-emitting QD films exhibit photoluminescence quantum yields exceeding 90%. By exploiting the improved mobility, we have been able to fabricate CsPbBr3 QD-based efficient blue and green light-emitting diodes. Blue devices with reduced trap density have an external quantum efficiency of 12.3%; the green devices achieve an external quantum efficiency of 22%. A solution-based ligand-exchange strategy enables the realization of close-packed quantum dot solid films with near-unity photoluminescence quantum yield and high charge carrier mobility.

A flexible graphite sheet can be used as a self-supported substrate material for sensors owing to its excellent conductivity and flexibility. Copper nanoparticle/flexible graphite sheet self-supporting enzyme-free glucose sensors were prepared by a hydrothermal method using copper sulfate as the elemental copper source and ascorbic acid as the reducing agent. Results indicate that both the molar ratio of copper sulfate to ascorbic acid and the hydrothermal temperature affect the microstructure and sensor performance. The optimal sensor obtained with a ratio of 1:0.5 at 150 oC has a low detection limit of 1.05 μmol/L, and high sensitivities of 7 254.1 μA·mM-1·cm-2 R2 = 0.996 1 from 0.1 to 3.4 mmol/L and 3 804.5 μA·mM-1·cm-2 (R2 = 0.999 5) from 3.4 to 5.6 mmol/L The sensor possesses excellent anti-interference properties against sodium chloride, acetaminophenol, ascorbic acid, dopamine, and uric acid, and has good reproducibility.

This paper focus on the wing shape related drag reduction measures of normal layout civil aircraft, through the drag reduction to improve the aircraft performance. Mainly by the laminar flow wing to reduce skin drag and weak shock wave wing to reduce shock drag, to keep a section of laminar zone on the wing leading edge to reduce skin drag, the wing profile's pressure distribution transit from the middle part's tonsure pressure zone to the trailing edge's inverse pressure gradient zone gentle to reduce the shock drag. The wing body junction plus the body belly fairing to increase the junction flow velocity, through increase flow velocity to weak the boundary layer stacked at the junction, improve the drag performance. The blended winglet to reduce the wing tip induced drag, study the shape parameters impact on the drag reduction, longitudinal moment and directional moment, attain the winglet model with drag reduction effect, suitable pitching moment and directional moment. For the wing body fairing have significant impact on the wing shape lower surface pressure distribution, the winglet have important impact on the wing tip flow, so the single part drag reduction measure is not feasible, need to carry out integrated drag reduction study on the wing related three drag reduction measures, and study the drag reduction measure's drag reduction decrement, put a reference for the normal layout civil aircraft's drag reduction. Through the above drag reduction measure's assessment attain the effect of drag reduction and rising the normal layout civil aircraft's cruise ratio, improving the cruise performance.

Nitrogen oxides (NOx: NO2 and NO) are the main pollutants produced in combustion. Previous studies have focused on the NOx forming mechanism and control strategies but have paid less attention to t...

Low-dimensional copper halides with high luminance have attracted increasing interest as heavy-metal-free light emitters. However, the optical mechanisms underpinning their excellent luminescence r...

How to correctly acquire the appropriate features is a primary problem in network protocol recognition field. Aiming to avoid the trouble of artificially extracting features in traditional methods and improve recognition accuracy, a network protocol recognition method based on Convolutional Neural Network (CNN) is proposed. The method utilizes deep learning technique, and it processes network flows automatically. Firstly, normalization is performed on the intercepted network flows and they are mapped into two-dimensional matrix which will be used as the input of CNN. Then, an improved classification model named PtrCNN is built, which can automatically extract the appropriate features of network protocols. Finally, the classification model is trained to recognize the network protocols. The proposed approach is compared with several machine learning methods. Experimental results show that the tailored CNN can not only improve protocol recognition accuracy but also ensure the fast convergence of classification model and reduce the classification time.

Intensive attempts have been devoted to solving the inferior cycling stability of Si-based electrode induced by the large volume change of Si. However, the complex synthesis procedures make many strategies much low practical significances. Together with the inferior cycling stability, an easy and scalable fabrication strategy is still a great challenge for implementing Si anode in commercial batteries. This work uses a simple water steam selective etching method to simultaneously engineer the pores and the confinement of commercial Si/SiOx in carbon paper electrodes, leading to a significant improvement in electrode flexibility and cycle life. The as-prepared freestanding lotus-seed-pod-like steam-etched Si/SiOx@CNF electrode shows a high capacity retention of 137% after 1000 cycles at 3 A g−1. It also possesses outstanding electrochemical performance in a flexible lithium-ion full battery with LiCoO2/steam-etched CNF as the cathode, even under bended condition. This simple approach may offer a pathway for the application of Si-based anode in commercialization and/or flexible energy storage devices.

Lithium-ion hybrid supercapacitors (Li-HSCs) and dual-ion batteries (DIBs) are two types of energy storage devices that have attracted extensive research interest in recent years. Li-HSCs and DIBs have similarities in device structure, tendency for ion migration, and energy storage mechanisms at the negative electrode. However, these devices have differences in energy storage mechanisms and working potentials at the positive electrode. Here, we first realize the integration of a Li-HSC and a DIB to form a dual-ion hybrid supercapacitor (DIHSC), by employing mesocarbon microbead (MCMB)-based porous graphitic carbon (PGC) with a partially graphitized structure and porous structure as a positive electrode material. The MCMB-PGC-based DIHSC exhibits a novel dual-ion battery-capacitor hybrid mechanism: it exhibits excellent electronic double-layer capacitor (EDLC) behavior like a Li-HSC in the low-middle wide potential range and anion intercalation/de-intercalation behavior like a DIB in the high-potential range. Two types of mechanisms are observed in the electrochemical characterization process, and the energy density of the new DIHSC is significantly increased.

Blue-emitting perovskites can be easily attained by precisely tuning the halide ratio of mixed halide (Br/Cl) perovskites (MHPs). However, the adjustable halide ratio hinders the passivation of Cl ...

Na-ion capacitors (NICs) are promising energy storage devices in virtue of their merits in combining the high energy densities of secondary batteries and the high power densities of supercapacitors. However, it is still very challenging to achieve a balanced energy-power performance in NIC device due to the kinetic imbalance between the battery-type anode and the capacitive-type cathode. In this work, an NIC device based on carbon materials for both anode and cathode has been reported. As-prepared (polyimide/graphene oxide)-derived carbon (PIGC) anode material shows excellent rate capability, which can deliver a specific capacity of 110 mAh g−1 at high current densities of 5 A g−1. In addition, the N, B co-doped expanded reduced graphite oxide (NBEG) cathode demonstrates a high specific capacitance of 328 F g−1. Due to the improved rate capability of PIGC anode and specific capacitance of NBEG cathode, the imbalance on the energy and power densities between anode and cathode is well addressed. As-assembled PIGC//NBEG device can deliver an energy density of 55 W h kg−1 even at a high power density of 9500 W kg−1. The energy-power properties of PIGC//NBEG are superior to many state-of-the-art NIC devices that using carbon or non-carbon based electrodes. This work offers not only a promising device configuration with superior energy-power properties, but also a guidance for the design strategies on electrode materials for high-throughput energy storage systems. Keywords: Carbon materials, Doping, Porous structure, Sodium ion capacitors, Energy storage

Light-emitting diodes (LEDs) based on excitonic material systems, in which tightly bound photoexcited electron–hole pairs migrate together rather than as individual charge carriers, offer an attractive route to developing solution-processed, high-performance light emitters. Here, we demonstrate bright, efficient, excitonic infrared LEDs through the incorporation of quantum dots (QDs)1 into a low-dimensional perovskite matrix. We program the surface of the QDs to trigger fast perovskite nucleation to achieve homogeneous incorporation of QDs into the matrix without detrimental QD aggregation, as verified by in situ grazing incidence wide-angle X-ray spectroscopy. We tailor the distribution of the perovskites to drive balanced ultrafast excitonic energy transfer to the QDs. The resulting LEDs operate in the short-wavelength infrared region, an important regime for imaging and sensing applications, and exhibit a high external quantum efficiency of 8.1% at 980 nm at a radiance of up to 7.4 W Sr−1 m−2. Embedding perovskite quantum dots in perovskite leads to bright, efficient 980 nm LEDs with applications in imaging and sensing.

In this work, a three-dimensional coarse-grid two-fluid model (TFM) simulation by varying granular properties like granular viscosity, frictional viscosity, and solids pressure has been performed. Simulated predictions were subsequently compared with experimental results in the case of Geldart A or B particles. Laminar flow behavior is also studied and coarse-grid simulation predictions were less realistic for laminar flow. This flow regime which although consumes less computational resources falls short for large-scale riser scale up. Flow regime in our simulation was fast fluidization and simulation predicts with minimum error near riser inlet. More specifically, granular viscosity, frictional viscosity and solids pressure for Type A particles predict with minimum error especially near riser inlet at a lower height. For Type B particles, these three solid properties correspond closely with experimental results near inlet at a lower height whereas, at a higher height, turbulence increases and simulation results deviate from experimental studies.

Shock trains are formed by shock wave boundary layer interaction in isolator to match the pressure between inlet and combustor. However, the complexity of this problem has primarily restricted to rigid isolators without deformation. A little is known regarding the impact of wall vibration, due to structural elasticity, on the flow in isolator. The current study focuses on this problem by comparing changes of 13 parameters regarding separation zone, shock structure, flow asymmetry and isolator performance. Results examine the differences due to one-wall vibration, two-wall vibration and short panel vibration. Analyses indicate that one-wall vibration will cause the upstream movement and length decrease of separation zone, upstream movement and length growth of shock trains, increase of flow asymmetry with large transient side loads and decrease of performance. Moreover, compared to one-wall vibration, two walls vibrating in opposite direction leads to a larger influence on flow structures and isolator performance, while the effect of two-wall vibration in the same direction is relative minor on flow structures and significant on flow asymmetry as well as isolator performance. Furthermore, by placing vibrating panels at different locations, analyses identify that the influence of upstream and midstream vibrations is stronger than downstream vibration in wall vibration. The upstream vibration has a greater impact on flow structures while the midstream vibration has a greater effect on flow asymmetry and isolator performance. The current study emphasizes the importance of future investigations on aeroelastic problem in isolator and provides primary knowledge for flow control by considering flexible or vibrating panel.

Engineering the size, shape and crystallinity of organic semiconductor nanostructures (OSNs) offers the opportunity of fine tuning their optoelectronic properties for photocatalytic applications. Here, we report a facile and general ‘ice-melting’ kinetic control strategy to synthesize OSNs with excellent photocatalytic performance. The ultraslow release and interaction of organic molecules from ice melting yields an ultralow local concentration (∼five orders of magnitude fewer molecules), fundamentally enhancing the energy barrier thus leading to their relaxed and ordered assembly into refined nanocrystals (∼one order of magnitude smaller in size, morphological change from amorphous to crystalline); such nanocrystals display improved light-harvesting and charge transfer properties and consequent photocatalytic efficiency towards degrading organic pollutants compared to standard OSNs, or even commercial titania photocatalysts (Degussa P25); we also generalize the ‘ice-melting’ kinetic control strategy to synthesize a series of highly photoactive organic nanocrystals.

Deep-blue light-emitting diodes (LEDs) (emitting at wavelengths of less than 450 nm) are important for solid-state lighting, vivid displays and high-density information storage. Colloidal quantum dots, typically based on heavy metals such as cadmium and lead, are promising candidates for deep-blue LEDs, but these have so far had external quantum efficiencies lower than 1.7%. Here we present deep-blue light-emitting materials and devices based on carbon dots. The carbon dots produce emission with a narrow full-width at half-maximum (about 35 nm) with high photoluminescence quantum yield (70% ± 10%) and a colour coordinate (0.15, 0.05) closely approaching the standard colour Rec. 2020 (0.131, 0.046) specification. Structural and optical characterization, together with computational studies, reveal that amine-based passivation accounts for the efficient and high-colour-purity emission. Deep-blue LEDs based on these carbon dots display high performance with a maximum luminance of 5,240 cd m−2 and an external quantum efficiency of 4%, notably exceeding that of previously reported quantum-tuned solution-processed deep-blue LEDs. Deep-blue high-colour-purity light-emitting materials are developed by using amine-based edge passivation. The light-emitting diodes based on the carbon dots exhibit a maximum luminance of 5,240 cd m–2 and an external quantum efficiency of 4%.

Ultrafine hierarchically porous carbon fibers (HPCFs) were produced by electrospinning from phenolic resin and Fe(acetylacetonate)3, carbonization under an NH3 atmosphere and HCl/water leaching to remove the Fe species. Their adsorption performance for ethanol and acetone and their pore structure were compared with fibers produced from polyacrylonitrile (PAN) and Fe(acetylacetonate)3 (HPCFs(PAN)), and phenolic resin without the Fe(acetylacetonate)3 addition (PCFs). Results indicate that HPCFs and HPCFs(PAN) are hierarchically porous with abundant micropores and mesopores while PCFs are dominantly microporous. The addition of Fe(acetylacetonate)3 promotes graphitization. The hierarchical pore structure increases the uptake of both ethanol and acetone vapors at high pressures by multilayer adsorption while the microporous structure contributes to the uptake at low pressures by monolayer adsorption. The highest ethanol and acetone adsorption uptakes were found for the HPCFs, and are 7.55 and 12.56 mmol g−1 at 25 °C, respectively. Superiority of phenolic resin to PAN as the carbon precursor is demonstrated. The freestanding characteristic of the ultrafine carbon fibers as a result of their electrospining is advantageous as an adsorbent for the removal of volatile organic compounds.

Usually, the dynamic equations of tethered systems are derived using Lagrangian formulation. However, Hamiltonian formulation is also widely used for mechanical systems because of its well-known symplectic structure property. In this paper, the dynamic equations of the tethered system are deduced using Hamiltonian formulation. The goodness of the Hamiltonian formulation is intuitive to reveal the energy balance property that corresponds to the passive property. Furthermore, the Hamiltonian function of the tethered system is employed to facilitate the design of the controller. The energy-based control is to achieve the tether deployment/retrieval with suppressing the tether liberation. Numerical simulations are used to demonstrate the effectiveness of the designed controller.

Ti3C2Tx MXene has drawn considerable attention as anode materials to store sodium ions because of the capability of accommodating the large sodium ions, enabling their intercalation without substantial structural change. However, the limited sodium-ion storage capacity of Ti3C2Tx hinders its real application in sodium-ion batteries (SIBs). To enhance its performance as anode materials in SIBs, here, we introduce nanopores into Ti3C2Tx sheets by sonication, and after which we assemble them with rGO and cellulose nanofibers into an elastic freestanding composite structure by mimicking the wasp nest. The wasp nest-like structure endows the resulting composite with more accessible surfaces of electrode materials to the electrolyte. Further, the nanopores on the Ti3C2Tx sheets and the TiO2 formed from the sonication provide more active sites for sodium storage. As a result, the resulting composite shows a high capacity of 280 mAh g−1 at 100 mA g−1 and remarkable cyclic life with a capacity retention of 84.8% after 1000 cycles at 1 A g−1.

This work aims at comparing surface tension models in VOF (Volume of Fluid) modeling and investigating the effects of gas distributor and gas velocity. Hydrodynamics of a continuous chain of bubbles inside a bubble column reactor was simulated. The grid independence study was first conducted and a grid size of 1.0 mm was adopted in order to minimize the computing time without compromising the accuracy of the results. The predictions were validated by comparing the experimental studies reported in the literature. It was found that all surface tension models can describe the bubble rise and bubble plume in a column with slight deviations.

Particle-resolved (PR) high-fidelity simulations, e.g., direct numerical simulation (DNS), have emerged as a powerful tool to precisely capture the full details of complex fluid-particle heat and mass transfer behaviors. The captured information can be used to constitute closures for unresolved conservation equations. However, such simulations are commonly performed under a specific variety of operating conditions. To broaden the range of closure model applicability, this fundamental study develops an enhanced correlation for the gas-particle transport rate in terms of Nusselt (Sherwood) number via collecting data points (e = [0.35, 1], Rep = [0, 550]) from open sources. The collected data are predicted with a mean relative error of 9.3%. The extended correlation is then systematically validated by comparison with experimental data and PR-DNS results. Finally, the correlation is applied to integrate with a macroscopic computational fluid dynamics (CFD) reactor model. Validation results reveal an enhanced improvement in mass and heat transfer predictions. Moreover, the overall thermal and reactive behaviors computed from the coupled reactor model achieve reasonably good accordance with PR-DNS predictions over various process conditions. The developed correlation is hopeful to improve the accuracy of coarse-grained simulation of interphase heat and mass transfer accompanied by heterogeneously catalyzed chemical reaction.

Stress-absorption interlayer (SAI) is one of the most important methods to prevent reflection cracking. This paper analyzed the properties of SAI with the waste tire rubber (WTR) and amorphous ploy alpha olefin (APAO) complex modified asphalt binder. Research found that WTR/APAO modified asphalt works excellently as a binder in SAI. The SAI with base asphalt, WTR/APAO, WTR and SBS modified asphalt mixture were prepared for comparative analysis. The mechanical properties and durability of four SAIs were determined using Marshall stability, Indirect tensile (IDT) strength, immersion Marshall and Marshall stability after aging procedure. The bond strength and shear resistance of three SAIs with modified asphalt were determined using slant shear tests under different conditions. The overlay tests (OT) were used to characterize the fatigue and anti-reflection cracking performance. Besides, the Paris’ Law was used to characterize the fracture properties based on OT. Research found that WTR/APAO SAI had the strongest high temperature stability, deformation resistance, bond strength and shear resistance. WTR/APAO and SBS SAIs had excellent water stability and anti-aging performance. WTR/APAO SAI had the highest bond strength at both high and normal temperatures. The OT number of cycles of all three SAIs reached 1200 times. This indicator showed that all three SAIs had excellent fatigue and anti-reflection cracking performance. Further research found that the fracture properties n in Paris’ Law showed that WTR/APAO and SBS SAIs had better cracking resistance. The addition of APAO improved the cracking resistance of WTR SAI.

Vanadium trioxide material have attracted enormous attention recently, owing to their high theoretical capacity for use as anodes in lithium ion batteries. However, the unstable structure of V2O3 limits its practical application. It is challenge to develop a simple, scalable and economical technique to produce 3D porous carbon-based V2O3 materials with high structure stability. In this work, a facile NaCl template-assisted freeze-drying strategy was used to produce 3D porous carbon-encapsulated V2O3 (3D porous V2O3@C) composites with highly crystalline architecture, uniformly carbon-encapsulated V2O3 nanoparticles and interconnected conductive carbon networks. The resultant 3D porous V2O3@C anode exhibits significantly enhanced rate performance (797 mAh/g at 0.1 A/g, 715 mAh/g at 0.3 A/g, 658 mAh/g at 0.5 A/g, 598 mAh/g at 1 A/g, 480 mAh/g at 3 A/g and 426 mAh/g at 5 A/g) and long-term cycling stability (506 mAh/g at 5A/g after 2000 cycles). The present work suggests a scalable preparation of the 3D porous carbon-based V2O3 materials, which may be extended to preparing other 3D porous materials for potential applications in energy storage, catalysis and sensors.

An electrochemically mediated atom transfer radical polymerization (eATRP) of methyl acrylate (MA) in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) ionic liquid (IL) was reported. Remarkably, the kinetic results revealed an extremely fast and well controlled polymerization in the presence of tris(2-(dimethylamino)ethyl)amine (Me6TREN). The monomer conversion reached more than 90% within a period of 300 s. Computational and simulation results indicated that the IL induced acceleration of polymerization can be attributed to the increased value of k t / k p 2 compared to the associated literature value. Additionally, polymerizations under different conditions, including ligand types, monomer/IL ratios, catalyst loadings, and targeted degrees of polymerization were explored. All the kinetic plots suggested superfast polymerization rates with good control over molecular weight and dispersity. Furthermore, the livingness of MA polymerization was confirmed by chain extension experiment. This work provides a new insight into eATRP in IL through experimentation and simulation and thus enriches the knowledge of reaction features of eATRP.

Multicloud access control is important for resource sharing and security interoperability across different clouds, and heterogeneity of access control policy is an important challenge for cloud mashups. XAC-ML is widely used in distributed environment as a declaratively fine-grained, attribute-based access control policy language, but the policy integration of XACML lacks formal description and theory foundation. Multicloud Access Control Policy Integration Framework (MACPIF) is proposed in the paper, which consists of Attribute-based Policy Evaluation Model (ABPEM), Four-value Logic with Completeness (FLC) and Four-value Logic based Policy Integration Operators (FLPIOs). ABPEM evaluates access control policy and extends XACML decision to four-value. According to policy decision set and policy integration characteristics, we construct FLC and define FLPIOs including Intersection, Union, Difference, Implication and Equivalence. We prove that MACPIF can achieve policy monotonicity, functional completeness, canonical suitability and canonical completeness. Analysis results show that this framework can meet the requirements of policy integration in Multicloud.

Developing, verifying and validating sub-grid methods is of crucial significance for enabling accurate coarse-grained two-fluid modeling of rapid gas-fluidized flows. However, very few studies in the literature so far have been focused on how the sub-grid modification depends on material properties. As an extension of previous sub-grid efforts, this fundamental investigation attempts to derive a material-property-dependent drag modification based on generated data from an initially homogeneous state of periodic gas-particle suspensions. The newly constituted model is then verified by highly-resolved two-fluid simulation results. We further validate the accuracy of model predictions via systematic assessments to experimental results that encompass a wide variety of material properties in five three-dimensional large-scale circulating fluidized bed (CFB) risers. Besides, we introduce a deviation index (DI) to quantify the predictive capability of the extended model. Computational results demonstrate an essential dependence of drag correction on material properties as an additional factor. Hydrodynamic validation predictions achieve satisfactory accordance with experiments. The current model is potential to serve as a more general tool for efficiently reducing the number of pilot-scale tests and effectively designing and controlling industrial process devices.

Radiation intensity is commonly assumed to be the same for simplification in a lab-scale photoreactor, however, the radiation along propagating direction attenuates exponentially owing to the absorption and scattering of photons by catalysts and bubbles. Hence, it is necessary to develop a model that can predict the spatial radiation distribution (SRD), which is a critical factor in designing industrial-scale photoreactors. In this study, a SRD model was developed to compute the radiation intensity as a function of the volume fraction of the medium and the distance between the observation point and the source. Subsequently, numerical simulations and analyses for the gas-liquid-solid mini-fluidized bed were performed by coupling the proposed SRD model with the reaction kinetic model based on a three-dimensional hybrid Euler-Lagrange method. The simulation results fit well with experimental data. Furthermore, the radiation intensity and the hydrodynamic factors exert different impacts on the degradation ratio with increasing reaction time, respectively. Under low concentration, the main influence on the degradation ratio is hydrodynamics, including reactant mass fraction, air volume fraction and catalyst volume fraction. The developed model is of potential value in industrial photocatalytic reactors.

Sulfur cathodes in lithium-sulfur batteries (LSBs) have received a boost in electrochemical performance through developing various sulfur hosts. However, it remains great challenges in achieving fast electron and ion conduction while accommodating the dramatic volume change and suppressing severe intermediate polysulfide dissolution under practically necessary ‘3H’ conditions (high areal sulfur loading, high electrode compactness and high sulfur content). Here a compact 3D interconnected sulfur cathode is reported to satisfy the above requirements. It is constructed by self-assembly of Zn,Co-bimetallic ZIF nanoparticles, following pyrolysis and subsequent melt-diffusion of high-content sulfur. Sulfur filled into an open porous 3D carbon network (3DCN) with abundant N, Co doping and graphitic carbon species and produced a thin sulfur-coating layer on the macroporous surface of 3DCN. Such smart architecture provides multidimensional electron and ion transport pathways and shortened mass and ion diffusion length. The close contact of sulfur species with carbon-based polar host provides facilitated physiochemical adsorption and conversion reaction of polysulfides. At high areal sulfur loading of 10.9 mg cm-2, high sulfur content of 74 wt% in the whole cathode and low electrolyte/sulfur ratio of 6 µL/mg, it delivers high gravimetric/volumetric/areal capacities of 945 mA h g-1/867 mA h cm-3/10.3 mA h cm-2 at 0.1 C (1.83 mA cm-2). At a high rate of 0.5 C (9.13 mA cm-2), it still presents a high capacity of 8.73 mA h cm-2 and maintains 6.35 mA h cm-2 after 200 cycles. Therefore this work provides an instructive paradigm of rational architecture design to fabricate sulfur cathodes for practically viable Li-S batteries.

Hydrogenation of CO2 into methanol is promising for achieving the sustainable energy economy, but still has some problems, e.g. low methanol selectivity and high operation pressures (>10 atm). Herein, we prepared a Pt/film hybrid with highly dispersed Pt nanoparticles, and combined Pt/film with In2O3 to form a Pt/film/In2O3 catalyst. By using a dielectric barrier discharge (DBD) plasma reactor, a CO2 conversion of 37.0% and a methanol selectivity of 62.6% are achieved in the hydrogenation of CO2 with H2 on Pt/film/In2O3 at 1 atm and 30 °C. These are higher than those on Pt/In2O3 prepared by the conventional high-temperature H2 reduction (24.9% and 36.5%) and commercial Cu/ZnO/Al2O3 (25.6% and 35.1%). The high-energy electrons of the DBD plasma trigger the CO2 hydrogenation at 1 atm and 30 °C. The higher Pt nanoparticles dispersion, film and In2O3 promote the adsorption of CO2 on Pt/film/In2O3, thus enhancing the hydrogenation of CO2 into methanol. These results are helpful for efficient methanol production from CO2 hydrogenation under atmospheric pressure.

Herein, hierarchical porous carbon derived from polyethylene waste (plastic bags etc.) has been synthesized by ball-milling and carbonization with a flame-retardant agent, basic magnesium carbonate pentahydrate (MCHP:4MgCO3·Mg(OH)2·5H2O). The presence of MCHP not only provides in-situ MgO template during pyrolysis, but also greatly enhances the thermal stability of polyethylene for carbonization. After subsequent NH3 activation, the polyethylene waste derived carbon (PE-HPC-900NH3) shows a high surface area and a unique property of meso-porosity, which contribute to the excellent capacitive performance. Remarkably, the obtained PE-HPC-900NH3 electrode displays a relatively high specific capacitance with excellent cycling stability (about 97.1% of capacitance retention after 10,000 cycles at 2 A g−1). A high energy density of 43 Wh kg−1 can be achieved for the PE-HPC-900NH3 symmetrical supercapacitor at an extremely wide voltage of 4 V in EMIMBF4 due to the high purity and low ratio of O/N. This work provides a promising approach to disposal of waste plastics and opens new applications in various energy fields.