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Learning graph embeddings for high-dimensional data is an important technology for dimensionality reduction. The learning process is expected to preserve the discriminative and geometric information of high-dimensional data in a new low-dimensional subspace via either manual or automatic graph construction. Although both manual and automatic graph constructions can capture the geometry and discrimination of data to a certain degree, they working alone cannot fully explore the underlying data structure. To learn and preserve more discriminative and geometric information of the high-dimensional data in the low-dimensional subspace as much as possible, we develop a novel Discriminative and Geometry-Preserving Adaptive Graph Embedding (DGPAGE). It systematically integrates manual and adaptive graph constructions in one unified graph embedding framework, which is able to effectively inject the essential information of data involved in predefined graphs into the learning of an adaptive graph, in order to achieve both adaptability and specificity of data. Learning the adaptive graph jointly with the optimized projections, DGPAGE can generate an embedded subspace that has better pattern discrimination for image classification. Results derived from extensive experiments on image data sets have shown that DGPAGE outperforms the state-of-the-art graph-based dimensionality reduction methods. The ablation studies show that it is beneficial to have an integrated framework, like DGPAGE, that brings together the advantages of manual/adaptive graph construction.

Cement-retained restorations have the advantages of passive fit, less complexity of clinical and laboratory methods, cost, esthetics, and dimensional stability over screw-retained restorations, especially in multiple abutment implant-supported prostheses. A common and difficult technical problem with cement-retained implant prostheses is abutment screw loosening. Three-dimensional (3D) printing is a technology that has been rapidly developed and has become widely accepted in dentistry. The aim of this study was to establish a novel method of using 3D implant planning guide to locate the abutment screw in cement-retained implant prosthesis.Six standard gypsum complete denture models were used to locate the abutment screw. An implant analog (4.5 mm in diameter and 12 mm in length) was placed in the drilling hole (5 mm in diameter and 14 mm in depth). After scanning with a 3D scanner, the 3D printing software was used to design the abutment screw location guide, which was printed by a resin-based 3D printer.A total of 30 abutment screws were located and removed using the guide. The locating guide's actual diameter was 2.4 mm. The drilling point was accurate and precise, and no excessive loss of the abutment was noticed.The guide would help the dentist in locating the abutment screw access channel, resulting in a more precise and accurate drilling point. The guide for locating the abutment screw enhances the accuracy of screw channel access and reduces damage to the crown and abutment.

Polycomb group (PcG) proteins are crucial chromatin regulators during development. H2AK119ub1 (H2Aub) and H3K27me3 are catalyzed by Polycomb-repressive complex 1 and 2 (PRC1/2) respectively, and they largely overlap in the genome due to mutual recruitment of the two complexes. However, it is unclear whether PRC1/H2Aub and PRC2/H3K27me3 can also function independently. By developing an ultra-sensitive carrier-DNA-assisted chromatin immunoprecipitation sequencing method termed CATCH-Seq, we generated allelic H2Aub profiles in mouse gametes and early embryos. Our results revealed an unexpected genomewide decoupling of H2Aub and H3K27me3 in mouse preimplantation embryos, where H2Aub but not H3K27me3 was enriched at PcG targets while only H3K27me3 was deposited in the broad distal domains associated with DNA methylation-independent non-canonical imprinting. These observations suggest that H2Aub represses future bivalent genes during early embryogenesis without H3K27me3, but it is not required for the maintenance of non-canonical imprinting, which is mediated by maternal H3K27me3. Thus, our study reveals the distinct depositions and independent functions of H2Aub and H3K27me3 during early mammalian development.

Because of the intensified electrochemical activities, mixed metal oxides as a representative for pseudocapacitive materials play a key role for high performance supercapacitor electrodes. Nevertheless, low ion and electron transfer rate and poor cycling performance in the electrode practically restrict further promotion of their electrochemical performance. In order to offset the defect, a novel copper (Cu) foam-supported nickel molybdate nanosheet decorated carbon nanotube wrapped copper oxide nanowire array (NiMoO4 NSs-CNTs-CuO NWAs/Cu foam) flexible electrode is constructed. The as-prepared electrode demonstrates a unique core-shell holey nanostructure with a large active surface area, which can provide a large number of active sites for redox reactions. Besides, the CNTs networks supply improved conductivity, which can hasten electron transport. Through this simple and efficient design method, the spatial distribution of each component in the flexible electrode is more orderly, short and fast electron transport path with low intrinsic resistance. As a result, the NiMoO4 NSs-CNTs-CuO NWAs/Cu foam as an adhesiveless supercapacitor electrode material exhibits excellent energy storage performance with high specific areal capacitance of 23.40 F cm−2 at a current density of 2 mA cm−2, which outperforms most of the flexible electrodes reported recently. The assembled asymmetric supercapacitor demonstrates an energy density up to 96.40 mW h cm-3 and a power density up to 0.4 W cm-3 under a working voltage window of 1.7 V. In addition, outstanding flexibility of up to 100° bend and good cycling stability with the capacitance retention of 82.53 % after 10,000 cycles can be obtained.

This work briefly investigates the coexistence of continuous attractors in the neural networks with Rectified Linear Unit (RELU) transfer function. Memory is stored as a manifold of stable states, or a continuous attractor. Continuous attractors are some low-dimensional manifolds embedded in a high-dimensional state space. One neural network may possess more than one continuous attractors. More importantly, we found that these multiple continuous attractors may have different dimensional, some are 2-D plane attractors and others are 1-D line attractors. It is also an enlightenment to study the continuous attractors of high dimensional models.

Inspired by the recurrent highway networks, we study the coupled networks as a modular behavior of the networks, which can better improve the performance of the system. For a neural network, the non-zero continuous attractors play an important role to decode the information. The emphasis of this paper is to study the conditions for the generation of non-zero continuous attractors in the coupled new system theoretically. By exploring the relationship between network parameters, the conditions for generating non-zero continuous attractors in the new model are successfully determined. In order to verify the correctness and validity of the proposed conclusions, the results of this paper are further verified by simulation.

Multicomponent metal sulfides have been recognized as promising anode materials for lithium/sodium-ion storage given their enticing theoretical capacities. However, the simplification of synthetic processes and the construction of heterogeneous interfaces of multimetal sulfides remain great challenges. Herein, a hierarchical 1T-MoS2/carbon nanosheet decorated Co1–xS/N-doped carbon (Co1–xS/NC@MoS2/C) hollow nanofiber was designed and constructed via a one-pot hydrothermal method using a cobalt-based coordination polymer nanofiber. This nanofiber can transform in-situ into conductive N-doped carbon hollow fibers embedded with active Co1–xS nanoparticles, enabling the epitaxial growth of MoS2 nanosheets. Consequently, the Co1–xS/NC@MoS2/C composites achieve exceptional lithium/sodium-ion storage performance. Compared to MoS2/C microspheres and Co1–xS/NC hollow nanofibers alone, the Co1–xS/NC@MoS2/C hollow nanofibers deliver higher discharge capacities (1085.9 mAh g−1 for lithium-ion batteries (LIBs) and 748.5 mAh g−1 for sodium-ion batteries (SIBs) at 100 mA g−1), better capacity retention (910 mAh g−1 for LIBs and 636.5 mAh g−1 for SIBs after 150 cycles at 100 mA g−1), and increased cycling stability (407.2 mAh g−1 after 1000 cycles for SIBs at 1000 mA g−1). Furthermore, the kinetic analysis shows that the lithium/sodium-ion storage processes of the Co1–xS/NC@MoS2/C electrode are mainly controlled by pseudocapacitance behavior. The excellent electrochemical properties can thus be ascribed to the synergy of the MoS2/C nanosheets with the enlarged interlayer spacing, good conductivity of the carbon layers, and the Co1–xS nanoparticles embedded in the hollow nanofibers with extensive reaction sites.

MnO2 has received immense consideration for supercapacitors; however, its performance in energy storage is limited by its low electroconductivity and agglomeration during the charge-discharge process. This necessitates the fabrication of flexible supercapacitor with excellent electrochemical properties for application in cable-type devices. In the current study, we have fabricated a self-standing carbonized cotton yarn (CCY) and the MnO2-based electrode by using a cotton yarn derived carbon fiber as a substrate. The electrode with hierarchical porous architecture was obtained through a redox reaction between CCY and potassium permanganate (KMnO4). Field emission scanning electron microscopy showed the deposition and uniform distribution of MnO2 nanoparticles on the surface of CCY. The electrode showed excellent capacity performance and electrochemical stability. In the electrode, the combination of MnO2 nanoparticles and CCY offered enhanced kinetics, a large surface area which resulted in high energy density (16.88 μWh/cm2) and high-power density (4770 μW/cm2). Further, the fabricated electrode showed a specific area capacity of 182.94 mF/m2 at 20 mV/s. Moreover, three flexible supercapacitors were connected in series and parallel to get higher working voltage and higher capacity, respectively, which demonstrated its potential for broad-spectrum applications in flexible devices, these results demonstrate the potential of MnO2/CCY for diverse applications in the development of cable-type devices.

Flexible fiber-based supercapacitors applied in portable energy storage devices and wearable electronics have recently aroused widespread research interests. However, challenges still exist in the pursuit of facile fabrication technique for simultaneously realizing high capacitive performance and excellent mechanical stability. Here, two novel types of core-sheathed hybrid electrodes with carbon nanotube fiber (CNF) as the core and three-dimensional (3D) porous carbon nanotubes/polypyrrole (CNTs/PPy) or reduced graphene oxide (rGO) as the sheath were hierarchically constructed through one-pot electrochemical deposition. An all-solid-state asymmetric fiber-shaped supercapacitor was assembled by wrapping the gel electrolyte coated negative CNF/rGO electrode along the positive CNF/CNTs/PPy electrode. Thanks to the combination of abundant 3D pore structure and synergistic effect of different components in the fiber electrodes, the resulted supercapacitors exhibited a broadened potential window of 1.6 V, a high areal specific capacitance of 58.82 mF cm−2 and a high areal energy density of 20.91 μW h cm−2. It should be noted that 98.6% of the initial capacitance of the supercapacitor device can still be maintained after experiencing 200 reciprocating bending cycles, demonstrating outstanding mechanical stability. Moreover, the supercapacitor exhibited excellent cyclic performance, which was testified by 90% capacity retention after 10000 times of galvanostatic charge-discharge process.

An electrolyte composed of lithium difluoro(oxalate)borate (LiDFOB) as lithium salt, N-propyl-N-methylpiperidinium bis(trifuoromethansulfonyl) imide (PP13TFSI) ionic liquid and dimethylcarbonate (DMC) as co-solvent and fluoroethylene carbonate (FEC) as additive is reported in this study. It is found that the resulted ionic liquid-based electrolyte demonstrates high ionic conductivity, low polarization and high safety performance. The Li/Li1.1Ni0.25Mn0.65O2 and Li/Graphite half-cells with the electrolyte exhibit excellent electrochemical performance, retaining capacities of more than 186 mA h g−1 and 361.6 mA h g−1 after 100 cycles, respectively. Such outstanding energy storage performance is ascribed to the joint oxidative decomposition of LiDFOB and FEC, which can form stable and low impedance solid electrolyte interface (SEI) on the Li-rich cathode and graphite anode. Besides, the SEI layer can prevent transition metal dissolution, enabling excellent cycling stability for the high voltage graphite/Li1.1Ni0.25Mn0.65O2 full cell. As a result, the full cell with the ionic liquid based electrolyte maintains a discharge capacity and capacity retention of 180 mAh g−1 and 87.54% after 100 cycles at 0.5 C and 40 °C, far superior to that obtained for commercial electrolyte. All these characteristics make the electrolyte a promising candidate for safe, high performance lithium-ion battery electrolyte.

Hollow Mo2C@C core-shell nanofibers (H-Mo2C@C/NFs) have been successfully synthesized via an integrated procedure including coaxial electrospinning, oil extraction and carbonization. As an anode of lithium-ion batteries, H-Mo2C@C/NFs delivers high discharge capacity of 1176.3 mA h g−1 in the first cycle at a current density of 0.1 A g−1 and exhibits good rate capability and reversibility. The capacity can maintain at 595.1 mA h g−1 even when the current density is up to 5 A g−1. In addition, at a high current density of 1 A g−1, H-Mo2C@C/NFs also displays extraordinary long-term cycling performance with a capacity of 674.4 mA h g−1. The excellent rate performance and cycling stability result from the synergistic effect of Mo2C nanoparticles and hollow structure nanofiber matrix. Coaxial electrospinning technology can be widely extended to manufacture other metal carbide/carbon composites to achieve important energy storage and other applications.

Transition-metal oxides (TMOs) are considered as promising anode materials for lithium ion batteries. However, the poor structural stability and relatively low electronic conductivity greatly limit their application in flexible electronic devices. Herein, a 3D hierarchical high performance MnO-based flexible electrode is fabricated through vacuum-assisted layer-by-layer assembly of 1D polydopamine coated MnO2 nanowires (MnO2@PDA NWs) and 2D graphene oxide nanosheets (GO NSs), followed by a thermal reduction process. The resulting composite (MnO@C-rGO) demonstrates excellent flexibility, structure stability and manifests outstanding lithium storage performance in terms of high reversible capacity (920 mAh g−1 at 0.2 A g−1), excellent rate capability (686 mAh g−1 at 2 A g−1 and 396 mAh g−1 at 10 A g−1) and impressive cycling stability (719 mAh g−1 at 2 A g−1 without fading after 800 cycles), exceeding most of recently reported MnO-based anodes. It is proved that the freestanding flexible MnO@C-rGO anode can be successfully applied in flexible full cell, which achieves superior flexibility and maintains good electrochemical performance during mechanical deformations.

Biomass derived porous carbons are economic and attractive materials for anode electrodes in sodium-ion batteries. In this work, a novel porous carbon has been prepared through activation of longan shell, which demonstrates an interconnected hierarchical porosity comprised of macro-, meso- and micro-pores as well with a high specific surface area of 2990 m2 g−1. Benefiting from the unique pore structure and oxygen and nitrogen dual doping, a well-developed ionic and electronic conductivity is achieved. Remarkably, it exhibits an excellent cycling stability with a capacity up to 345.9 mAh g−1 at a current density of 0.1 A g−1, and maintains a capacity of 304.2 mAh g−1 even at a high current density of 5 A g−1 after 1000 cycles as anodes for sodium-ion batteries. These results indicate that the fabricated porous carbon could be a promising electrode material for sodium-ion batteries. The mechanism of such high sodium-ion storage was also discussed with the scan-rate-dependent CV curves to quantify the pseudo-capacitive contribution.

Tumor-associated macrophages (TAMs) are a major cellular component in the tumor microenvironment (TME). However, the relationship between the phenotype and metabolic pattern of TAMs remains poorly understood. We performed single-cell transcriptome profiling on hepatic TAMs from mice bearing liver metastatic tumors. We find that TAMs manifest high heterogeneity at the levels of transcription, development, metabolism, and function. Integrative analyses and validation experiments indicate that increased purine metabolism is a feature of TAMs with pro-tumor and terminal differentiation phenotypes. Like mouse TAMs, human TAMs are highly heterogeneous. Human TAMs with increased purine metabolism exhibit a pro-tumor phenotype and correlate with poor therapeutic efficacy to immune checkpoint blockade. Altogether, our work demonstrates that TAMs are developmentally, metabolically, and functionally heterogeneous and purine metabolism may be a key metabolic feature of a pro-tumor macrophage population.

MXene, as an attractive functional and structural material with high conductivity, wettability, surface activity and plenty of superior mechanical properties, is applied for the first time to directly decorate ultra-high molecular weight polyethylene fiber (UHMWPE) and fabrics with a unique bovine serum albumin (BSA)-induced technology. The adoption of BSA successfully turns UHMWPE fiber into an adhesive platform toward the efficient assembly and wrapping of MXene. The results showed that the functionalization of MXene changed the UHMWPE fiber surface topography and increased the wettability and surface activity, which can enhance the mechanical engagement and offer sufficient reactive sites with resin matrix, providing efficiently improved interfacial properties. The interfacial shear strength between the UHMWPE/BSA/MXene fiber and epoxy increased by 116% when compared with pristine UHMWPE fiber. Besides, the peeling strength of MXene decorated UHMWPE fabric/rubber laminate demonstrates more than two times higher than the untreated UHMWPE fabric reinforced rubber composite. Furthermore, with the excellent conductivity of MXene, the UHMWPE/BSA/MXene fiber exhibits an electrical conductivity of 106 S/m, which is able to work as a conductor for the application of electronic textiles.

Advanced ionic liquid-based electrolyte is herein characterized for the application in high voltage lithium-ion batteries. The electrolyte based on N-propyl-N-methylpiperidiniumdifluoro(oxalate)borate (PP13DFOB), lithium bis(trifluoromethanesulfonyl)-imide (LiTFSI) and dimethyl carbonate (DMC) is fully characterized in terms of anodic corrosion behavior, electrochemical properties and cathode-electrolyte interphase stability. Experimental and computational results show that the preferential oxidation of PP13DFOB results in a stable and low impedance solid electrolyte interface (SEI) film on the surface of LiNi0.5Mn1.5O4 (LNMO) cathode and a passivation layer on Al foil, which suppress transition metal dissolution and Al corrosion at high voltage. As a result, the Li/LNMO and Li/graphite coin cells with ionic liquid-based electrolyte achieve excellent electrochemical performance, displaying a discharge capacity of 121.2 mAh g−1 and 369.2 mAh g−1 after 100 cycles at 0.5 C respectively and demonstrating no distinct capacitance attenuation during charge-discharge cycles.

Acrylic fiber is one of three important synthetic fibers in the world. The disposal and reuse of large number of waste acrylic fibers from fabric manufacturers or waste recovery is an urgent economic and environmental issue. Here, a porous carbon was derived from waste acrylic fibers via pre-oxidized, carbonization and KOH activation. Furthermore, we adopted melamine as nitrogen source to dope the porous carbon materials. When used as the anode of lithium ion batteries, this nitrogen-doped porous carbon shows high reversible capacity of ca. 1200 mA h g−1 after 50 cycles at 0.1 A g−1. Reversible capacities of 550 and 370 mA h g−1 are obtained at higher current densities of 1 and 5 A g−1 after 500 cycles, respectively. The outstanding electrochemical performance are a result of its large mesopore volume, high-level N-doping (especially, pyridinic-N), large quantity of edge defects, and three-dimensional hierarchical porous architecture. This paper demonstrates that the reuse of waste industrial acrylic fibers as energy storage materials is a promising method for both energy and environmental fields.

Transition-metal oxide materials have gained significant attention as high-performance anode materials for lithium ion batteries. Great advances have been achieved in the development of micro/nanostructured materials with controllable shape and tunable pore size. In this work, a facile co-precipitation approach has been developed to fabricate the Ni-NiCo2O4@ZnCo2O4 yolk-shell nano-tetrahedron composites, which significantly improve the structural stability and conductivity of the material. The Ni-NiCo2O4@ZnCo2O4 is proven to exhibit excellent cycling and rate performance for lithium ion batteries, such as the charge capacity of 1571.9 mA h g−1 after 70 cycles at 0.1 A g−1, 1097.5 mA h g−1 after 600 cycles at 1.0 A g−1. This superior electrochemical performance may attribute to the yolk-shell architecture and the Ni-doping.

The rational structure design and strong interfacial bonding are crucially desired for high performance zinc oxide (ZnO)/carbon composite electrodes. In this context, micro-nano secondary structure design and strong dopamine coating strategies are adopted for the fabrication of flower-like ZnO/carbon (ZnO@C nanoflowers) composite electrodes. The results show the ZnO@C nanoflowers (2–6 μm) are assembled by hierarchical ZnO nanosheets (∼27 nm) and continuous carbon framework. The micro-nano secondary architecture can facilitate the penetration of electrolyte, shorten lithium ions diffusion length, and hinder the aggregation of the nanosheets. Moreover, the strong chemical interaction between ZnO and coating carbon layer via C-Zn bond improves structure stability as well as the electronic conductivity. As a synergistic result, when evaluated as lithium ion batteries (LIBs) anode, the ZnO@C nanoflower electrodes show high reversible capacity of ca. 1200 mA h g−1 at 0.1 A g−1 after 80 cycles. As well as good long-cycling stability (638 and 420 mA h g−1 at 1 and 5 A g−1 after 500 cycles, respectively) and excellent rate capability. Therefore, this rational design of ZnO@C nanoflowers electrode is a promising anode for high-performance LIBs.

In terms of enhancing the energy storage performance of flexible MXene electrode, both heteroatom doping and introducing electroactive “spacers” are proved to be effective strategies. In this work, a facial protective hydrothermal method is explored to synthesis nitrogen doped porous MXene/TiO2 heterostructure in one pot, which enables a well preserved conductivity of porous N-doped MXene and controlled in-situ generation of uniformly dispersed electroactive TiO2 spacers. This unique hybridized structure provides a chance to integrate several physical and chemical advantages in a complementary easy way. As a result, the assembled freestanding film electrode based on the N-doped porous MXene/TiO2 heterogeneous layers demonstrates excellent energy storage performance with an outstanding specific capacitance value of 2194.33 mF cm−2 (918.69 F g−1), which outperforms most of the heteroatom-doped MXene electrodes reported previously. Besides, the film electrode delivers excellent cycling performance with a 74.39% capacitance retention after 10,000 cycles and the as fabricated flexible supercapacitor displays almost no changes on capacitive performance when subjected to mechanical deformations, indicating its excellent flexibility and stability. This work presents a simple way of modifying MXene with N doping and inserting “spacer” for enhancing the electrochemical performance, and builds up an exciting potential for applying to highly flexible and integrated energy storage devices.

The dynamic architecture of the human brain has been consistently observed. However, there is still limited modeling work to elucidate how neuronal circuits are hierarchically and flexibly organized in functional systems. Here we proposed a reachable probability approach based on non-homogeneous Markov chains, to characterize all possible connectivity flows and the hierarchical structure of brain functional systems at the dynamic level. We proved at the theoretical level the convergence of the functional brain network system, and demonstrated that this approach is able to detect network steady states across connectivity structure, particularly in areas of the default mode network. We further explored the dynamically hierarchical functional organization centered at the primary sensory cortices. We observed smaller optimal reachable steps to their local functional regions, and differentiated patterns in larger optimal reachable steps for primary perceptual modalities. The reachable paths with the largest and second largest transition probabilities between primary sensory seeds via multisensory integration regions were also tracked to explore the flexibility and plasticity of the multisensory integration. The present work provides a novel approach to depict both the stable and flexible hierarchical connectivity organization of the human brain.

A novel two-layer reinforced carbon fiber (CF), i.e., Ag nanoparticles (Ag NPs)/graphene oxide (GO) reinforced CF (named as CF/Ag/GO) was prepared by an electrochemical deposition and electrophoretic deposition (EPD) consequently. The modified fiber showed an increased interfacial shear strength (IFSS) and tensile strength. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectrometer, atomic force microscopic (AFM) and dynamic contact angle analysis (DCA) were carried out to investigate CF reinforced composites. And test results demonstrated that the presence of Ag NPs and GO sheets increased the surface roughness and surface energy of CFs significantly. IFSS of CF/epoxy and the tensile strength of CFs were increased by 86.1% and 36.8%, respectively. Ag NPs filled in the cracks in CF effectively to enhance the tensile strength, while GO sheets improved the wettability of resin on CFs and formed mechanical interlocking between CFs and epoxy resin. These Ag NPs and GO sheets worked together in a ferocious synergy on the interface of CF and epoxy to cause the enhanced mechanical properties.

The current information era has witnessed the fast development of flexible high-performance energy storage devices for portable and wearable smart electronics. Here, tough supercapacitor with high flexibility and tear resistance based on Ag-coated Tyvek/PEDOT:PSS/carbon nanotubes (Tyvek/Ag/PCNTs) composite electrodes has been well designed and fabricated for the first time via a facile and scalable method. In the supercapacitor, Ag-coated Tyvek substrate roles as the current collector through a polymer-assisted metal deposition method while the treatment of sulfuric acid on the electrode contributes to the removal of insulating PSS part and the increase of the crystallinity of the active materials. Due to the tough and flexible substrate and the increased conductivity of the electrodes, the supercapacitor exhibits excellent stability and rate capacity as well as brilliant mechanical strength and flexibility. The prepared supercapacitor can exhibit large specific mass capacitance (138.7 F/g) and specific volume capacitance (544.2 F/cm3) at the scan rate of 50 mV/s. As far as we can concern, the Tyvek/Ag/PCNTs-based supercapacitor owns higher energy density or power density than any other CNTs-based or PEDOT-related supercapacitors. In addition, after 1000 bending cycles, the capacitance of the supercapacitor can still reach to 91.2% of the initial value. This work will help to enlarge the study in the Tyvek-based supercapacitors for the flexible and tough energy storage devices.

It is widely accepted that the interfacial properties of carbon fiber (CF) reinforced composites tend to be weak due to the poor wettability and chemically inert surface of CF, which greatly limits the reinforcement effect of CF in composites. Here, size-controllable graphene oxide sheets (GO) were grafted on CF using Poly(oxypropylene) Diamines (D 400 ) as the bridging agent to improve the interfacial properties of CF composites. It was found that the size and content of active functional groups on GO played important roles in controlling the surface morphology of GO grafted CF. Moreover, the interfacial shear strength (IFSS) of the middle sized GO sheets grafted CF/epoxy composites reached a maximum value of 82.2 MPa, with an enhancement of 75.6% compared with untreated CF. That is to say, the strong mechanical interlocking between CF and epoxy resin and the improved wettability of resin on CF surface were responsible for the enhancement of IFSS. Instead of decaying of fiber tensile strength after treatment, the tensile strength of GO grafted CF increased from 4.73 GPa to 5.02 GPa. The reason for the enhancement may be due to that GO bridged the surface defects on CF. This hierarchical reinforcement was believed to have widely potential applications in high performance polymer matrix composites.

The emerging wire-shaped supercapacitors (WSSs) have motivated tremendous research interests in energy storage devices. However, challenges still exist in the pursuit of high-rate performance WSS. Here, a graphene fiber made from chemical vapor deposition grown laminated graphene sheet is adopted to form a WSS which exhibits an exceptional rate capability with a relaxation time constant of 1.4 ms, smallest among WSSs reported to date. Furthermore, the resulting WSS can be charged-discharged at a high scan rate of 100 V s −1 while maintaining good capacitive behavior. When the scan rate increased by 5000 times, from 20 mV s −1 to 100 V s −1 , the graphene fiber based WSS maintains 38.6% of its original capacitance. After 10,000 galvanostatic charge-discharge cycles, the specific capacitance retains over 105%, demonstrating a long cycle stability.

The exploration of reaction process plays an important role in the mechanism study of plastic hydrothermal recovery. This work investigated the procedure of the efficient heterogeneous catalytic hydrolysis of waste monomer casting polyamide in subcritical water and then proposed the depolymerization mechanism. The solid products obtained before the complete hydrolysis became less thermodynamically stable than raw polyamide material as the degree of hydrolysis increased. According to the characterization of liquid phase products, the monomer casting polyamide was depolymerized to cyclic and linear oligomers, which were further converted to the target monomer e -caprolactam by gradual chain scission. As firstly applied in the waste polyamide hydrolysis, the zeolite H-Beta was proved a promising solid catalyst which increased the degree of hydrolysis from 31% to more than 60% (300 °C, 50 min) and facilitated to produce the intermediates with specific structure due to the microporous topology. The kinetic analyses showed that compared to the formation step of oligomers, the hydrolysis of oligomers into the monomer was the critical step which could be accelerated by the zeolite H-Beta catalyst.

The growing demand on flexible all-solid-state supercapacitors has accelerated the need for fundamental understanding of their response to extreme thermal environment. In this study, supercapacitors based on freestanding films composed of randomly oriented carbon nanotubes and H 2 SO 4 -PVA gel electrolyte were fabricated. The effect of temperature on their electrochemical behaviors was systematically investigated by using cyclic voltammogram, impedance spectroscopy and galvanostatic charge-discharge measurements at temperatures between −5 °C and 55 °C. The results indicated that the capacitance of the supercapacitor was enhanced by the increase of operating temperature while the internal resistance was reduced by virtue of the acceleration of transportation/adsorption of electrolyte ions and surface modification of the electrode. For instance, when charged with the current density of 0.2 mA cm −2 , the capacitance increased by 24.3% from −5 °C to 25 °C, and by 32.6% from 25 °C to 55 °C. Operating temperatures at or below 25 °C were found to facilitate the charge-discharge reversibility and long-term cycle stability. It has also been concluded that supercapacitors based on H 2 SO 4 -PVA gel electrolyte were not suitable for long term use at temperatures higher than 40 °C due to the aging of electrolyte.

In this work, a MOF-derived Co-Fe oxide porous nanorod is introduced into the freestanding MXene film to produce a high-performance flexible electrode with excellent deformability and editability. The as-prepared composite film electrode demonstrates several advantages: MXene layer functions as a binder and conductive additive to coat Co-Fe oxide, which can effectively facilitate charge transfer and maintain the excellent flexibility of the film electrode. In the meantime, Co-Fe oxide can work as a spacer, thereby expanding the interlayer distance, improving the ion transmission path in the electrode. As a result, the optimal Co-Fe oxide/Ti3C2TX composite paper manifests a remarkable volumetric capacitance of 2467.6 F cm−3 in 1 M LiCl electrolyte. When assembled into a flexible symmetrical supercapacitor, an outstanding specific areal capacitance of 356.4 mF cm−2 can be obtained. Meanwhile, the flexible supercapacitor demonstrates excellent cycling performance with a high capacitance retention of 88.2% after 10 000 charge/discharge cycles, as well as stable electrochemical energy storage stability after 100 cycles of mechanical bending, indicating its great application potential in future flexible and portable energy storage equipment.

In spite of the recent rapid growth in stretchable electronic device research, efforts have been mainly focused on material selection, device geometric design and short-term performance characterization. The present research focuses on the long-term durability of electromechanical and electrochemical performance of buckled carbon nanotube fibers based stretchable conductors and supercapacitors under cyclic deformation. The damage mode and damage evolution as a function of fatigue deformation are identified. After 10,000 stretching-releasing cycles with mechanical deformation up to 40% strain, the conductivities of buckled dry spun and aerogel spun CNT fiber based stretchable conductors exhibit excellent stability and the resistances increase by only about 0.2% and 6%, respectively. The areal specific capacitances of buckled dry spun and aerogel spun CNT fiber based stretchable supercapacitors change, respectively, from 4.42 mF cm−2 to 3.60 mF cm−2, and from 8.16 mF cm−2 to 9.95 mF cm−2 at the scan rate of 50 mV s−1 after 10,000 deformation cycles.

At present, the capacitor voltage balancing control and the closed-loop control algorithms are two important issues in a modular multilevel converter (MMC) control system. In the published papers, the majority of the proposed balancing and closed-loop control methods require the measurement of the sub-module (SM) capacitor voltages. To reduce the cost and control complexity, firstly, this paper presents a discrete-time luenberger capacitor-voltage observer to estimate the SM capacitor voltages. Concerning the difficulty of the observation system’s stability analysis caused by the time-varying input and output switching function matrices, this paper manages to obtain the observer gain matrix design method from the point of stability analysis by the passive theory. In this process, the persistently and sufficiently exciting (PSE) condition about the switching functions to ensure the uniformly asymptotic convergence of the observation errors is obtained. This condition is also necessary for the feedback control system based on the observed state variables. Secondly, this paper presents a discrete-time state-error feedback controller using the observed capacitor voltages. According to the passive theory and separation principle, the stability of the MMC closed-loop system is analyzed. Finally, the correctness of the results obtained in this paper under different conditions, including the convergence and robustness of the observer and the state-error feedback controller using the observed capacitor voltages, are verified through the simulation.

In this work, we addresses the fabrication of a flexible film electrode based on 2D MXene wrapped 3D Ni-Fe oxide nanocube mixed analogous heterostructure. The resulted composite film electrode successfully inherits the merit of different building blocks: MXene layers works as binders and conductive additives that can connect cubic Ni-Fe oxide nanoparticals, facilitate the charge transfer and avoid a significant conductivity decrease in the resulting electrode. While cubic Ni-Fe oxide serves as an active spacer inside the adjacent MXene layers to increase the interlayer space, facilitate the electrolyte diffusion and enhance the electrochemical activity of the composite film. As a result, the optimized composite film manifests excellent specific capacitance of 1038.43 mF cm−2 at current density 0.5 mA cm−2. Meanwhile by assembling into all-solid-state flexible supercapacitor, an excellent specific areal capacitance of 328.35 mF cm−2 at 0.2 mA cm−2 was achieved. Additionally, the excellent energy storage performance is well maintained with a capacitance retention of 90.9% during 10,000 charging-discharging long cycles. Furthermore, a high mechanical robustness with 88.9% capacitance remained after subjected to bending at 90° for 50 cycles, suggesting great potentials for the applications in future flexible and wearable devices.

N-doped porous carbons (NPCs) prepared via carbonization of foam polymer materials and urea are promising anode materials of lithium-ion batteries (LIBs) for their low cost and high performance. Herein, polystyrene was mixed with Melanic Mc (5 wt%) and Azobisformamide (3 wt%) to prepared the precursors of porous carbon. NPCs with different N-doping levels were then obtained by the calcination of porous carbon/urea mixture with varied weight ratios. XPS and Raman characterizations illustrate that N-doping imposes negligible effects on the chemical states of N or C, but rather promotes the formation of disordered carbon and structural defects. BET measurement confirms that N-doping enlarges the surface area. The optimized NPCs with porous carbon/urea weight ratio of 1:5 exhibits high surface area of 508.3 m2·g−1 and the pore size is found to be around 3.66 nm. The capacities of NPCs achieve 600 mAh g−1 and 443 mAh g−1 over 200 cycles at 1 A g−1 and 5 A g−1 respectively. The excellent performance of NPC is ascribed to the enhanced surface area, defects and pores, providing abundant tunnels for lithium ion diffusion. Meanwhile, N-doping improves the electrical conductivity, which also enhances the rate performance. The facile synthetic route of NPCs as well as their excellent lithium storage performance shows great potential for the application in advanced lithium-ion batteries.

Flexible energy storage electronics are gaining increasing attention in recent years, but challenge still remains in obtaining fiber-shaped devices with both high specific capacitance to provide a high energy density and mechanical stretchability/flexibility to be able to integrate under extensive bending, stretching and twisting. Here, an all-in-one fiber high performance stretchable supercapacitor is constructed based on high performance bead-like NiCo2S4@carbon nanotube and Ti3C2Tx@N/O enriched carbon cloth threads electrodes. The assembled stretchable supercapacitor demonstrates a voltage output of 1.5 V and a specific areal capacitance of 559.3 mF cm−2, resulting in a high energy density of 174.78 μWh cm−2, outperforming most of previously reported stretchable fiber-shaped supercapacitors. Moreover, the high energy storage performances are well preserved under repeatedly stretching and bending. This unique design opens up a new direction in the development of stretchable fiber-shaped energy storage devices.

Zn-air batteries have received extensive attention because of their high energy density, environmental friendliness, low cost and safety. It is vital to develop cost-effective and stable electrocatalysts for oxygen reduction reaction for Zn-air batteries. Herein, Fe 3 O 4 encapsulated in porous carbon nanobowls (Fe 3 O 4 @PCN) for oxygen reduction reaction are prepared by simple soft-template approach and calcination subsequently. The optimized catalyst 4Fe 3 O 4 @PCN-800 with uniformly doped Fe 3 O 4 nanoparticles and large surface area exhibits excellent catalytic performance and long-term durability. It displays 66 mV higher half-wave potential (0.911 V) than that of 20 wt% Pt/C catalysts in 0.1 M KOH electrolyte. It also shows excellent durability, only 5 mV attenuation of halfwave potential after 10,000 potential cycles. In addition, 4Fe 3 O 4 @PCN-800 possesses better methanol resistance than Pt/C, negligible current density fluctuation in the basic electrolyte with 3 M methanol. Impressively, when being employed as a cathode catalyst in both aqueous and solid-state Zn-air batteries, 4Fe 3 O 4 @PCN-800 presents higher open-circuit voltage, higher capacity and peak power density, and more stable discharge voltage plateaus than those of Pt/C. Furthermore, the solid-state Zn-air batteries with the optimal synthesized catalyst exhibit encouraging flexibility, which have enormous potential in the application of flexible and wearable power sources.

Polyacrylonitrile-based carbon fibers were functionalized with phenyl amine group via aryl diazonium reaction “on water” to improve their interfacial bonding with resin matrix. Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy were employed to characterize ordered degree, functional groups, chemical states and morphology of carbon fiber surface, respectively. The results showed that phenyl amine groups were grafted on the fiber surface successfully. Mechanical property test results indicated that the aryl diazonium reaction in this paper could improve the interfacial shear strength by 73%, while the tensile strength was down very slightly. Hence aryl diazonium reaction “on water” could be a facile green platform to functionalize carbon fibers for many interesting applications.

Carbon fiber reinforced composite materials can be enhanced by introducing oxygen-containing groups on the surface of the reinforcing fibers to improve the interface bonding strength between carbon fibers and polymer matrix. While the addition of oxygen-containing groups has been shown to effectively increase the interfacial interaction between fibers and matrix, the treatments tend to consume the carbon fiber tensile strength. In this work, the surface of carbon fibers is oxidized by a chemical oxidation method which employs a strong oxidant of K 2 S 2 O 8 and a catalyst of AgNO 3 to effectively creating carboxyl and hydroxy functionalized surface and the reaction is shown that it can preserve the tensile strength and morphology of the carbon fibers. The surface oxidation is investigated by X-ray photoelectron spectroscopy, which shows that the relative surface coverage by oxygen atoms is increased from an initial 4.49% up to a maximum of 14.11% while the results of single fiber tensile strength tests demonstrate that the reaction did not lead to any obvious decrease in the fiber tensile strength. After oxidation, the interfacial shear strength (IFSS) improved from 59.52 to 96.73 MPa, with a increase of 62.5%.

PAN-based carbon fibers (CF) were functionalized with generation (n) 1–3 dendritic hexamethylenetetramine (HMTA) (denoted as CF-Gn-HMTA, n = 1, 2 and 3) in an attempt to improve the interfacial properties between carbon fibers and epoxy matrix. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), dynamic contact angle analysis (DCA), interfacial shear strength (IFSS) and single fiber tensile testing were carried out to investigate the functionalization process of carbon fibers and the interfacial properties of the composites. Experimental results showed that generation (n) 1–3 dendritic hexamethylenetetramine was grafted uniformly on the fiber surface through the chemical reaction, and then it increased significantly the fiber surface polarity and roughness. The surface energy and IFSS of carbon fibers increased obviously after the graft CF-G3-HMTA, by 147.6% and 81%, respectively. Generation (n) 1–3 dendritic hexamethylenetetramine enhanced effectively the interfacial adhesion of the composites by improving resin wettability, increasing chemical bonding and mechanical interlocking, and the interfacial adhesion increased with dendritic generation number. Moreover, the grafting of generation (n) 1–3 dendritic hexamethylenetetramine on the carbon fiber surface improved the fiber tensile strength, which is beneficial to the in-plane properties of the resulting composites.

High performance flexible asymmetric supercapacitors based on carbon cloth are continuously prepared by a quick, low-cost, simple and scalable one-step electrochemical process within minutes without any other additives. The Fe2O3 is electrochemically deposition carbon cloth for the negative electrode, while the PEDOT and MnO2 are electrochemically co-deposited on carbon cloth for positive electrode. All processes take place within 1 min, therefore, this method can be applied in a continuous preparation mode for large-scale production, which implies its application potential in the industry. This is the first report of one-step continuous prepare of the flexible electrodes for supercapacitor. In addition, as assembled supercapacitors consisting of Fe2O3@carbon cloth and MnO2-PEDOT@carbon cloth, it achieves a high operating voltage of 2 V and a high energy density of 340 μW h cm−3 at a power density of 1.212 × 105 μW cm−3. This supercapacitor also possesses excellent flexibility and stability with 95% capacitance retained even after 1000 times bending. The larger-sized supercapacitor is further tested as watchband to power an electronic watch or light 41 LEDs for minutes. The low-cost continuous preparation method with high performance endows the flexible carbon cloth various promising applications, such as flexible asymmetric supercapacitors, flexible battery, catalysts and surface treatment.

Persistent activity holds the transient stimulus for up to many seconds even after the stimulus is gone. It has been implemented in a class of models known as continuous attractor neural networks, which have infinite stable states corresponding to persistent activity patterns. Continuous attractor neural network remains stable so does not change systematically in the absence of stimulus input. Continuous attractor is a set of connected stable equilibrium points and has been used to describe the storing of continuous stimuli in neural networks. The background input of the networks plays an important role in continuous attractor neural network. In this paper, dynamical properties of continuous attractor neural network with two background input tuning schemes are investigated: constant input shifting and oscillation background activity. Simulations are employed to illustrate the theory.

Multistability is an important dynamical property in neural networks in order to enable certain applications where monostable networks could be computationally restrictive. This paper studies some multistability properties for a class of bidirectional associative memory recurrent neural networks with unsaturating piecewise linear transfer functions. Based on local inhibition, conditions for globally exponential attractivity are established. These conditions allow coexistence of stable and unstable equilibrium points. By constructing some energy-like functions, complete convergence is studied.

The well known Takagi–Sugeno (T–S) model gives an effective method to combine some simple local systems with their linguistic description to represent complex nonlinear dynamic systems. By using the T–S method, a class of local nonlinear systems having nice dynamic properties can be employed to represent some global complex nonlinear systems. This paper proposes to study the periodicity of a class of global nonlinear fuzzy systems with delays by using T–S method. Conditions for guaranteeing periodicity are derived. Examples are employed to illustrate the theory.

Poly(amic acid) (PAA) and poly(amic diethyl ester) (PAE) precursors of poly( p -phenylene biphenyltetracarboximide) (BPDA–PDA), which is a representative polyimide (PI) being used widely in the microelectronic industry as an interdielectric material, were synthesized. The miscibility behavior of these precursors with poly(arylene ether benzimidazole) (PAEBI), which is known to exhibit strong cohesive adhesion to copper metal conductor, were studied in N -methyl-2-pyrrolidone (NMP) as well as the condensed state and the imidized state using light scattering technique. And, the miscibility effect on the adhesion strength of PI/PAEBI/copper joint, in which the locus of failure is known to be within the PI layer, was investigated by 90° peel test. The PAA precursor was miscible completely with PAEBI in the NMP solution as well as in the condensed state via the strong interaction between carboxylic acid groups of the precursor and imidazole groups of PAEBI. However, imidization-induced phase-separation took place during thermal imidization of the PAA precursor, leading to domains of 0.7–1.4 μm for the imidized blends containing 30–70 wt % PI. The other blend compositions still were optically transparent. In contrast, the PAE precursor was miscible with PAEBI in the NMP solution with a limited concentration of 3.6 μm. Only the 90/10 blend film was optically transparent. The difference in the miscibilities of PAEBI with the polyimide precursors was reflected on the adhesion strength of PI/PAEBI/copper joint. The PAA precursor gave a relatively high peel strength, compared to the PAE precursor. In addition, the PAEBI having a relatively low intrinsic viscosity provided a high peel strength in the adhesion joint.