Search

The fracture and mechanics response during fracturing simulation for the heterogeneous glutenite is crucial for reservoir stimulation. In this work, a non-overlapping algorithm for the generation of non-concave gravels is proposed to reproduce the heterogeneous glutenite models in the DEM. Based on heterogeneous glutenite models, the effect of gravel size distribution, gravel cementation strength and stress difference on micro-cracking response during injection were investigated. The micro-cracking mechanism and geological application of heterogeneous glutenite were discussed. The results show that the increasing of gravel size distribution and gravel cementation strength leads to an increase in breakdown pressure in hydraulic fracturing, with a decrease in stress difference. In terms of the interaction mechanism, the increase in gravel size distribution leads to a change from deflection, penetration to termination when cracks encounter the gravel, while gravel cementation strength is penetration to deflection, with penetration being dominated in the stress difference effect. It is mainly due to the uncoordinated deformation between the gravel and the matrix, the inter-gravel becomes the preferred direction of micro-cracks initiation and propagation, leading to the evolution of the interaction mechanism. The research results may improve understanding of the hydrocarbon exploitation for unconventional glutenite reservoirs.

Poor interfacial quality and low refractive index contrast (Δn) are critical challenges for the development of high-performance one-dimensional photonic crystals (1DPhCs) via solution methods that impede their optical efficiency. Herein, we introduce an innovative approach by hybridizing hollow SiO2with poly(vinyl alcohol), referred to as PHS, followed by alternate assembly with TiO2via spin-coating, achieving a 1DPhC with Δn= 0.76 at the wavelength of 550 nm. This method circumvents the need for high-temperature treatment and complex curing conditions, resulting in a 1DPhC with superior interfacial and optical characteristics. By adjusting the thickness of the PHS layers, we can finely tune the reflectance spectrum, attaining over 99% reflectance at the photonic band gap. Furthermore, 1DPhC demonstrates excellent adhesion to polycarbonate substrates and retains its optimal optical performance even after rigorous environmental testing, including hygrothermal cycles, exposure to hot water, friction, and solvent sonication. This research paves the way for the facile fabrication of high-performance 1DPhCs under mild conditions, offering new perspectives for photonic material processing.

This note characterizes the set of Fréchet-differentiable points of the projection operator on a polyhedral set and the B-subdifferential of this projection operator at any point.

Oxidative cross-coupling is a powerful strategy to form C–heteroatom bonds. However, oxidative cross-coupling for constructing C–S bond is still a challenge due to sulfur overoxidation and poisoning transition-metal catalysts. Now, electrochemical redox relay using sulfur radicals formed in situ from inorganic sulfur source offers a solution to this problem. Herein, electrochemical redox relay-induced C–S radical cross-coupling of quinoxalinones and ammonium thiocyanate with bromine anion as mediator is presented. The electrochemical redox relay comprised initially the formation of sulfur radical via indirect electrochemical oxidation, simultaneous electrochemical reduction of the imine bond, electro-oxidation-triggered radical coupling involving dearomatization–rearomatization, and the reformation of the imine bond through anodic oxidation. Applying this strategy, various quinoxalinones bearing multifarious electron-deficient/-rich substituents at different positions were well compatible with moderate to excellent yields and good steric hindrance compatibility under constant current conditions in an undivided cell without transition-metal catalysts and additional redox reagents. Synthetic applications of this methodology were demonstrated through gram-scale preparation and follow-up transformation. Notably, such a unique strategy may offer new opportunities for the development of new quinoxalinone-core leads.

Polymer foams are widely used as cushioning and impact protective materials, while the single foam is susceptible to densification by concentrating pressure at the point of impact, thus reducing the protection effect. Herein, inspired by the tortoise shell, a composite structure composed of a poly(vinyl chloride) (PVC) hard layer and a thermoplastic polyurethane (TPU) foam soft layer was developed, which demonstrated significantly enhanced impact protection and energy absorption performance. The numerical model and finite element model were developed by adopting the Storakers model and the Rayleigh damping model to represent the hyperelastic behavior and energy dissipation of the elastic foam. Macroscopic and mesoscopic theoretical analyses revealed the mechanism of excellent cushioning and protection performance. The model is also capable of simulating the effects of the foam thickness, the modulus of the rigid plate, and the free-falling sphere on the cushioning performance. Therefore, this work provides a rational design of the buffering material and a numerical model that is capable of directing the material selection, design, and optimization of the composite material configuration depending on the requirements of different impact protection situations.

Labeling the genome and envelope of a virus with multicolor quantum dots (QDs) simultaneously enables real-time monitoring of viral uncoating and genome release, contributing to our understanding of virus infection mechanisms. However, current labeling techniques require genetic modification, which alters the virus’s composition and infectivity. To address this, we utilized the CRISPR/Cas13 system and a bioorthogonal metabolic method to label the Japanese encephalitis virus (JEV) genome and envelopes with different-colored QDs in situ. This technique allows one-step two-color labeling of the viral envelope and intraviral genome with QDs harnessing virus infection. In combination with single-virus tracking, we visualized JEV uncoating and genome release in real time near the endoplasmic reticulum of live cells. This labeling strategy allows for real-time visualization of uncoating and genome release at the single-virus level, and it is expected to advance the study of other viral infection mechanisms.

This article is concerned with the optimized tracking control problem of high-order strict-feedback nonlinear systems with full-state constraints via dynamical event-triggered strategy. An adaptive optimized control algorithm is proposed using the backstepping technique and reinforcement learning method. The algorithm incorporates an identifier–critic–actor architecture and features a flexible design of dynamic event-triggered mechanism (ETM) to decrease signal transmission. The ETM is adaptively adjusted by the estimated fuzzy adaptive weights and design parameters, making it more efficient in terms of communication resources. Moreover, to ensure the system states do not exceed their constrained sets while achieving the optimization objective, a novel performance index function based on the barrier Lyapunov function is constructed. Finally, it can be demonstrated that the system output accurately tracks the desired reference signal, while ensuring that all closed-loop signals remain bounded. Simulation example confirms the validity of the developed design methodology.

Abstract: Karst groundwater is the main water supply source for human consumption and living, and it is important to study the karst groundwater resources to ensure people’s water supply needs. In this study, the northern part of the Baiquan spring area in Hebei Province was taken as a research object. Based on the hydrogeochemical approach, the characteristics and mechanism of seasonal variations of karst groundwater in the area were studied, and the groundwater quality was evaluated. This paper mainly uses multivariate statistics, the Piper trilinear diagram, the ion ratio coefficient, and the water quality index (WQI) as water quality assessment methods. The sequence of the main ion abundance is as follows: Ca2+> Mg2+> Na+> K+, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{HCO}}_{3}^{ - }$$\end{document}> \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{SO}}_{4}^{{2 - }}$$\end{document}> Cl–, and the ion content showed a downward trend from the dry season to the wet season. The hydrochemical type in the dry season has changed compared with that in the wet season. The rate of carbonate rock dissolving in most of the study area waters in the wet season was higher than in the dry season. WQI calculation results show that most of the groundwater belongs to class II water quality, and the water quality in the wet season is better than that in the dry season. Studying different seasonal changes in groundwater chemistry can provide a reference for an in-depth understanding of karst groundwater chemistry characteristics and water resources protection in the spring area.

This article is aimed at studying the concept of multihyperuniformity and applying it to the design of shared-aperture antenna arrays for ultrawideband, broadside unidirectional emission. In this study, we present our work on the design of multiple frequency helical antenna arrays within a shared-aperture configuration, incorporating multihyperuniform disorder. The array consists of seven different intercalated helical subarrays and is optimized to cover a 35:1 continuous bandwidth at 0.4–14 GHz. We provide comprehensive details regarding the fabrication process and present measurement results. Our work provides a new alternative to existing solutions of antenna array designs and has wider applicability in electromagnetics. The proposed methodology extends the limitations for the realization of multiband antenna arrays, surpassing the previously reported designs that operated in a maximum of three frequency bands, by incorporating naturally optimized disordered distributions.

Graphical Abstract:

Two-dimensional (2D) atomically thin quantum dots (QDs) possess extraordinary electrical and optical properties. However, fabricating high quality 2D QDs viaa universal and reliable technique remains a challenge. Here, we report a simple strategy to prepare high quality, monolayer single crystal 2D QDs viaultrathin cutting 2D bulk single crystals by ultramicrotome, followed by an exfoliation process. The as-prepared 2D QDs have pristine surface, high quality, high monolayer yield and high photoluminescence quantum yield (the highest photoluminescence quantum yield of WS2is 18%), which can be used as promising, low toxic, biocompatible, and good cell-permeability fluorescent labeling agents for in vitroimaging.

Tomato cultivars with contrasting resistance to pathogens regulate root exudates differentially in response to Ralstonia solanacearumattacks. However, strategies using innate root exudates against infection remain unknown. This study analyzed the innate root exudates of two tomato cultivars and their functions in regulating R. solanacearuminfection. The innate root exudates differed between the two cultivars. Astaxanthin released from resistant plants inhibited colonization by R. solanacearumbut promoted motility, while neferine released from susceptible plants suppressed motility and colonization. The secretion of astaxanthin in resistant tomatoes promoted the growth of biocontrol fungi in soil and reduced the abundance of pathogenic fungi. Neferine secreted by the susceptible cultivar inhibited the relative abundance of the bacterial-biocontrol-related Bacillusgenus, indirectly reducing the soil’s immune capacity. This study revealed contrasting strategies using root exudates in resistant and susceptible tomato cultivars to cope with R. solanacearuminfection, providing a basis for breeding disease-resistant cultivars.

View synthesis methods using implicit continuous shape representations learned from a set of images, such as the Neural Radiance Field (NeRF) method, have gained increasing attention due to their high quality imagery and scalability to high resolution. However, the heavy computation required by its volumetric approach prevents NeRF from being useful in practice; minutes are taken to render a single image of a few megapixels. Now, an image of a scene can be rendered in a level-of-detail manner, so we posit that a complicated region of the scene should be represented by a large neural network while a small neural network is capable of encoding a simple region, enabling a balance between efficiency and quality. Recursive-NeRF is our embodiment of this idea, providing an efficient and adaptive rendering and training approach for NeRF. The core of Recursive-NeRF learns uncertainties for query coordinates, representing the quality of the predicted color and volumetric intensity at each level. Only query coordinates with high uncertainties are forwarded to the next level to a bigger neural network with a more powerful representational capability. The final rendered image is a composition of results from neural networks of all levels. Our evaluation on public datasets and a large-scale scene dataset we collected shows that Recursive-NeRF is more efficient than NeRF while providing state-of-the-art quality. The code will be available at https://github.com/Gword/Recursive-NeRF

The integrated sensing and communication (ISAC) refers to the integration of radio sensing and wireless communications to realize the multiplexing of space, time, and frequency resources. In the sixth generation (6G) wireless networks, ISAC is considered as one of the most promising technologies. In this paper, a novel ISAC channel model combining forward and backward scattering is proposed. In addition to the non-stationarity caused by motions, the correlations between sensing and communication channels are investigated. The channel characteristics of sensing such as forward scattering and backward scattering are introduced into the communication channel model. Utilizing the correlations between sensing and communication channels, the communication channel model is divided into line-of-sight (LOS), forward scattering, and backward scattering components. These three components are summed according to probability weighting to obtain a more accurate channel model for sensing assisted communication systems. Moreover, important statistical properties of the proposed ISAC channel model are derived and simulated. The analytical and simulation results match well, demonstrating the correctness of derivations and simulations. Some derived/simulated statistical properties are verified by corresponding measurement data, which indicates the utility of the proposed ISAC channel model.

The Cu–15Ni–8Sn alloy ingot was prepared in the medium-frequency induction melting furnace. The hot extruded alloy was treated by solid solution at 840 °C for 60 min and aging at 400 °C for different times (0 miñ480 min). The effect of aging time on the evolution of the nanophase of Cu–15Ni–8Sn alloy and the strengthening-toughening mechanism were studied. The results show that at the beginning of aging, the alloy undergoes spinodal decomposition, the wavelength of the modulated structure is approximately 3∼7 nm, the ordered phase transformation of D022and L12occurs simultaneously, and the ordered phase size is approximately 5 nm. With the extension of aging time, the modulated structure became coarser, and the wavelength of the modulated structure increased to 5–9 nm. At the same time, the D022ordered phase changed to the L12ordered phase, and a continuous distribution of elliptical discontinuous precipitation appeared at the grain boundary. The ratio of the long and short axes of the discontinuous precipitation was approximately 4.7. In the late aging period, the D022ordered phase was basically transformed into the L12ordered phase, and discontinuous precipitation, which is incompatible with the matrix, extended into the crystal. After 120 min of aging at 400 °C, the hardness, strength, and elongation of the alloy are 105.4 HRB, 839.8 MPa and 9.6 %, respectively. The peak-aging states D022and L12coexist in an orderly phase at the nanoscale, and this nanoscale strengthening phase is completely integrated with the matrix, which improves the strength and toughness of the alloy. The research results can provide support for the development of high-performance copper alloys in the ocean.

The distribution of sulfur and heavy metals in char of Gansu lignite and Shanxi subbituminous coal was studied by means of pyrolysis and magnetic separation at different pyrolysis temperatures. The contents of sulfur and heavy metal elements in char were analyzed and determined by ICP-OES and ICP-MS, and the mineral composition and apparent morphology of char were characterized by XRD and SEM-EDS. The results show that the highest desulfurization rates of Gansu lignite and Shanxi Subbituminous coal can reach 52.37% and 17.54% respectively under optimal conditions. This is related to the phase transition behavior of pyrite during pyrolysis. The desulphurization rate of Shanxi subbituminous char is lower than that of Gansu lignite char mainly because the occurrence and inclusion of associated minerals and the organic matter influence the transformation of pyrite during pyrolysis. Ni and Cr have a strong affinity with Fe−S minerals, which are enriched into magnetic char with sulfur. At 800 °C, Cr content in magnetic char of Gansu coal and Shanxi coal is 8698.25 and 32327.47 μg/g higher than that in non-magnetic char, respectively. The pyrolytic magnetization of low-rank coal and the distribution of sulfur and heavy metals in its char products provide data support and a new idea for removal of sulfur and heavy metals from coal.

The past century has witnessed remarkable progress in antennas and propagation (A&P) research, which has made dramatic changes to our society and life and has led to paradigm shifts in engineering and technology. Although the underlying theory of electromagnetics is well established and mature, research on A&P will continue to play a paramount role in the Fourth Industrial Revolution. In this article, we present an approach based on natural language processing (NLP) and machine learning (ML) techniques to review A&P research based on large-scale unstructured data from openly published scientific papers and patents and, in turn, provide meaningful summative and predictive information. We particularly screen 159,000 research papers published between 1981 and 2021 and extract a pool of 2,415 significant keywords reflecting past and present key research topics in A&P. We then apply an encoder–decoder long short-term memory (LSTM) network with an integrated attention mechanism to predict the future trends of A&P research in the form of a Gartner’s hype cycle.

Seawater desalination is one of the effective means to efficiently consume renewable energy and to improve the flexibility of system control in the new power system. In the optimal operation of new power systems, seawater desalination is usually considered as an entirety, and a motor equivalent model is used to simulate the overall external characteristics of seawater desalination. The characteristics of multiple sets of motors with multiple equipment processes inside the seawater desalination are neglected, which makes operation control characteristics inaccurate. In order to solve the above-mentioned problems, this paper firstly studies a seawater desalination system composed of 12 motors, and introduces the specific parameters of these 12 motors in detail. Secondly, after comprehensively considering the constraints of water flow, water pressure, and other factors, three control strategies are proposed for the 12 motors, respectively. Then, a detailed mathematical model of seawater desalination units and an optimal operation model of a new power system with seawater desalination are established. The optimization model aims at the minimum operating cost of seawater desalination, and considers the constraints of practical problems comprehensively such as motor power requirements and water storage capacity. Finally, the grey wolf optimization algorithm (GWO) is used in this paper to solve the optimization problem. The simulation results show that the model proposed in this paper can precisely control each unit in the seawater desalination system and improve the economic benefits of the system. Compared with the Particle Swarm Optimization algorithm (PSO) and the Moth-flame Optimization algorithm (MFO), the algorithm used in this paper can find the global optimal solution, and has both faster convergence speed and wider practicability.

This article investigates the event-triggered optimized tracking control problem for stochastic nonlinear systems based on reinforcement learning (RL). By using the backstepping strategy, an adaptive RL algorithm is performed under the identifier-critic-actor architecture to achieve event-triggered optimized control (ETOC). Moreover, a novel dynamically adjustable event-triggered mechanism is delicately designed, which adjusts the triggering threshold online to economize communication resources and reduce the computation burden. To overcome the difficulty that the virtual control signals are discontinuous due to the state-triggering, the virtual controllers are designed with the continuous sampling states signals, and the actual optimal controller is redesigned by using the triggered states in the last step. Furthermore, the proposed ETOC in this article has significant advantages in terms of saving network resources because the event-triggered mechanism is employed in the sensor-to-controller channel and the event-sampled states are utilized to directly activate the control actions. Finally, it can be guaranteed that all signals of the stochastic system are bounded under the presented ETOC method. A simulation example is carried out to illustrate the effectiveness of the proposed ETOC algorithm.

Sugarcane smut caused by Sporisorium scitamineumis a destructive disease responsible for significant losses in sugarcane production worldwide. However, the mechanisms underlying the pathogenicity of this fungus remain largely unknown. In this study, we found that the disruption of the SsRSS1gene, which encodes a salicylic acid (SA) sensing regulator, does not affect phenotypic traits such as the morphology, growth rate, and sexual mating ability of haploid basidiospores, but rather reduces the tolerance of basidiospores to SA stress by blocking the induction of SsSRG1, a gene encoding a SA response protein in S. scitamineum. SsRSS1deletion resulted in the attenuation of the virulence of the fungus. In addition to a significant reduction in whip formation, a portion of plantlets (18.3%) inoculated with the ΔSsRSS1strains were found to be infected but failed to produce whips for up to 90 days post-inoculation. However, the development of hyphae and teliospore from the ΔSsRSS1-infected plants that formed whips seemed indistinguishable from that in the wild-type-infected plants. Combined, our findings suggested that SsRss1 is required for maintaining fungal fitness in plantaby counteracting SA stress.