A new and generic strategy to construct interwoven carbon nanotube (CNT) branches on various metal oxide nanostructure arrays (exemplified by V2O3 nanoflakes, Co3O4 nanowires, Co3O4–CoTiO3 composite ...nanotubes, and ZnO microrods), in order to enhance their electrochemical performance, is demonstrated for the first time. In the second part, the V2O3/CNTs core/branch composite arrays as the host for Na+ storage are investigated in detail. This V2O3/CNTs hybrid electrode achieves a reversible charge storage capacity of 612 mAh g−1 at 0.1 A g−1 and outstanding high‐rate cycling stability (a capacity retention of 100% after 6000 cycles at 2 A g−1, and 70% after 10 000 cycles at 10 A g−1). Kinetics analysis reveals that the Na+ storage is a pseudocapacitive dominating process and the CNTs improve the levels of pseudocapacitive energy by providing a conductive network.
Chemical vapor deposition synthesis of carbon nanotube (CNT) branches is demonstrated on four types of metal oxide arrays. High‐performance Na ion storage is proven in the V2O3/CNTs system long cycle stability and high rates.
Based on joint media engagement (JME) and parental mediation theory (PMT), this study conducted a textual and thematic analysis of 360 user-generated content videos to explore, in the family ...scenario, smart speaker use behavior between Chinese children and parents. The findings reveal the following: (a) smart speakers create a new JME model and new co-use scenarios; (b) the mediation strategy used by parents differs from the mediation strategies in traditional PMT; (c) smart speakers are social actors and play a mediating role in the construction of family relationships; and (d) smart speaker use behavior between parents and children is characterized by a return to the living room era, which creates a new family dynamic and a reshaping of family politics.
For a stand-alone microgrid, the reliability criterion is often taken into account to guarantee the supply adequacy. This paper proposes a mixed integer linear programming (MILP) based model to ...determine the optimal sizing of a photovoltaic/diesel/battery stand-alone microgrid considering the reliability. Firstly, an economic-oriented microgrid planning model is developed. Subsequently, a rolling horizon based Sequential Monte Carlo method is developed to evaluate the system reliability. In particular, a multidimensional piecewise linearization method is proposed to approximate the nonlinear and implicit reliability evaluation function. Therefore the reliability criterion can be safely integrated into the microgrid planning model as an MILP problem which can be solved easily. The advantage of this method is that the costly reliability evaluation is calculated offline. Consequently, the time consumption of the online implement of the model becomes much less. The conventional techniques, however, integrate the reliability evaluation into the procedure. Thus a lot of iterations are needed to search for a solution that satisfies the reliability criterion. Finally, numerical experiments based on one microgrid test system are performed. The results indicate that larger sized DERs are deployed if a higher reliability criterion is required. Additionally, the proposed method is much faster than conventional evolutionary algorithms.
Due to the demand for high reliability, modular multilevel converters (MMCs) are designed with redundant submodules. Redundant submodules can be integrated into the converter by employing different ...redundancy schemes: the conventional active scheme, the load-sharing active scheme, and the passive scheme. Different schemes have different impacts on the improvement of converter reliability. The contributions of this paper include that an analytical method is proposed to evaluate the reliability of MMCs under different redundancy schemes and the factors' influence on the converter reliability is analyzed to determine the proper redundancy scheme. Reliability models of MMCs under different redundancy schemes are built using Markov chains and the iteration method. Based on the proposed models, the effects of redundant schemes are evaluated in terms of the converter reliability. A case study is conducted to validate the feasibility and robustness of proposed models and to specify the conditions in the favor of each redundancy scheme. The benefits of sharing redundancy among arms are also explored from the reliability point of view. If insulated-gate bipolar transistors (IGBTs) and capacitors are dominant components in a submodule in terms of failure rates, the load-sharing active scheme performs better; otherwise, setting the redundant submodules in an idle state is more effective. It is also found that the number of required redundant submodules is greatly reduced by sharing redundancy among arms.
Papilla and skin are two important organs of the sea cucumber. Both tissues have ectodermic origin, but they are morphologically and functionally very different. In the present study, we performed ...comparative transcriptome analysis of the papilla and skin from the sea cucumber (Apostichopus japonicus) in order to identify and characterize gene expression profiles by using RNA-Seq technology. We generated 30.6 and 36.4 million clean reads from the papilla and skin and de novo assembled in 156,501 transcripts. The Gene Ontology (GO) analysis indicated that cell part, metabolic process and catalytic activity were the most abundant GO category in cell component, biological process and molecular funcation, respectively. Comparative transcriptome analysis between the papilla and skin allowed the identification of 1,059 differentially expressed genes, of which 739 genes were expressed at higher levels in papilla, while 320 were expressed at higher levels in skin. In addition, 236 differentially expressed unigenes were not annotated with any database, 160 of which were apparently expressed at higher levels in papilla, 76 were expressed at higher levels in skin. We identified a total of 288 papilla-specific genes, 171 skin-specific genes and 600 co-expressed genes. Also, 40 genes in papilla-specific were not annotated with any database, 2 in skin-specific. Development-related genes were also enriched, such as fibroblast growth factor, transforming growth factor-β, collagen-α2 and Integrin-α2, which may be related to the formation of the papilla and skin in sea cucumber. Further pathway analysis identified ten KEGG pathways that were differently enriched between the papilla and skin. The findings on expression profiles between two key organs of the sea cucumber should be valuable to reveal molecular mechanisms involved in the development of organs that are related but with morphological differences in the sea cucumber.
2D layered perovskites have emerged as potential alternates to traditional 3D analogs to solve the stability issue of perovskite solar cells (PSCs). However, van der Waals gaps in reported ...Ruddlesden-Popper (RP) phase 2D perovskites with monoammonium cations provide weak interactions between layers, potentially destabilizing the layered perovskite structure and thus the device. Here we eradicate such gaps by incorporating diammonium cations into MAPbI3, developing a series of Dion-Jacobson phase 2D perovskites that afford a cell efficiency of 13.3% with ultrahigh device stability. Unencapsulated devices retain over 95% efficiency upon exposure to various harsh stresses including ambient air (40%–70% relative humidity RH) for 4,000 hr, damp heat (85°C and 85% RH) for 168 hr, and continuous light illumination for 3,000 hr. The improved device stability over the RP counterpart is attributed to alternating hydrogen bonding interactions between diammonium cations and inorganic slabs, strengthening the 2D layered perovskite structure.
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•Dion-Jacobson (DJ) phase 2D perovskites without the van der Waals gap are developed•A maximum PCE of 13.3% is achieved from the DJ phase 2D perovskite solar cells•Unsealed devices are extremely stable, subjected to various harsh testing conditions•Hydrogen bonds at both sides of diammonium cations strengthen 2D layered structure
Perovskite solar cells (PSCs) have attracted tremendous academic and industrial interests because of their rapidly increased power conversion efficiency (PCE) in the past few years, but the intrinsic instability of commonly used 3D perovskites induces the issue of low device stability. Ruddlesden-Popper (RP) phase 2D layered perovskites have recently been reported to show enhanced stability. However, weak van der Waals interactions between interlayers cannot sufficiently stabilize their 2D layered structure. By removing the van der Waals gaps in the RP case, we herein develop a series of Dion-Jacobson phase (DJ) 2D layered perovskites with higher structural stability for PSCs. A maximum PCE of 13.3% is achieved from the DJ phase 2D PSCs, and unencapsulated devices are extremely stable, retaining more than 95% of initial PCE upon exposure to ambient air (4,000 hr), damp heat (85°C and 85% RH, 168 hr), and continuous light illumination (3,000 hr).
Dion-Jacobson (DJ) phase 2D layered perovskites are developed by removing the van der Waals gap between organic layers and inorganic slabs in Ruddlesden-Popper (RP) phase counterparts. The hydrogen bonding formed at both sides of diammonium cations with perovskite layers in the DJ phase 2D perovskite endows it with extremely high structural stability, compared with that at only one side in the RP phase one. The devices exhibit a PCE of 13.3% with unprecedented stability, even when subjected to very harsh testing conditions.
K metal battery is a kind of high‐energy‐density storage device with economic advantages. However, due to the dendrite growth and difficult processing characteristics, it is difficult to prepare ...stable K metal anode with thin thickness and fixed area capacity, which severely limits its development. In this work, a multi‐functional 3D skeleton (rGCA) is synthesized by simple vacuum filtration and thermal reduction, and K metal anodes with controllable thickness and area capacity (K content) can be fabricated by changing the raw material mass and graphene layer spacing of rGCA. Moreover, the graphene sheet layer of rGCA can relax stress and relieve volume expansion; carbon nanotubes can serve as the fast transport channel of electrons, reducing internal impedance and local current density; Ag nanoparticles can induce the uniform nucleation and deposition of K+. The K metal composite anodes (rGCA‐K) based on the conductive skeleton can effectively suppress dendrites and exhibit excellent electrochemical performance in symmetric and full cells. The controllable fabrication process of stable K metal anode is expected to help K metal batteries move toward the stage of commercial production.
K metal anodes with thin thickness (10–200 µm) and fixed area capacity (0.47–3.54 mAh cm‐2) can be fabricated by changing the raw material mass and graphene layer spacing of rGCA. Moreover, the K metal composite anodes (rGCA‐K) based on the multi‐functional skeleton can effectively suppress dendrites and exhibit excellent electrochemical performance in symmetric and full cells.
•A Self-assembly method was used to prepare 1-octadecanol/graphene composite PCMs.•1-octadecanol/graphene composite PCMs possess three-dimensional network structure.•1-octadecanol/graphene composite ...PCMs showed superior thermal performances than the pure 1-otadecanol.
A self-assembly method is introduced to prepare composite phase change materials (PCMs) consisting of 1-octadecanol (OD) and graphene. The shape stability and thermal properties of 1-octadecanol/graphene composite PCMs with three-dimensional network structure are investigated. Graphene is dispersed evenly in OD matrix and the three-dimensional network structure is getting tighter with increasing ratio of graphene. OD is completely encapsulated at relatively low amount of graphene about 1.5 wt%. XRD and Raman results show that the combination between OD and graphene is physical adsorption. The 1-octadecanol/graphene (OG) composite phase change materials possess excellent shape stability, which can prevent the leakage of molten OD during phase transition. In addition, around 99.3% phase change enthalpy of pure OD is maintained by connected network structure of graphene while the melting and solidifying temperature merely have small fluctuations. The thermal conductivity of composite phase change material with 1.5 wt% graphene increases to 0.358 W/(m K), which is 1.5 times higher than that of pure OD. Furthermore, the porous network of graphene can delay the evaporation and thermal decomposition point of the composite phase change materials, thus extending the operating temperature of OD efficiently. This work provides a promising way to encapsulate low-temperature organic phase change materials with little carbon additives, and enhance the thermophysical properties of base materials simultaneously.
Due to the high theoretical capacity and low reduction potential, metallic lithium is a promising anode material for the next generation of high‐energy‐density batteries. However, the dynamic Li ...plating/stripping process can easily destroy the unstable solid electrolyte interphase (SEI) and cause dendrite growth. Here, an artificial lithium sulfide nanoparticle composed SEI layer with superior stability and high ionic conductivity is designed by a spray quenching method. The artificial SEI layer on Li surface can effectively minimize the side reactions and suppress Li dendrite growth, and the metal electrode delivers stable cycling for 500 cycles in the symmetrical cell with carbonate electrolyte. Moreover, when this SEI‐modified Li anode is coupled with a LiFePO4 cathode, the full cell shows promoted cycling stability and rate capability. This work provides a broadly applicable and facile strategy to address the intrinsic issues of lithium metal anodes.
An artificial lithium sulfide nanoparticles (LSNP) composed solid electrolyte interphase (SEI) layer with superior stability and high ionic conductivity is prepared via a facile spray quenching method. This artificial SEI layer on Li surface could effectively minimize the side reactions and suppress Li dendrite growth. Thus, the LSNP layer‐protected anodes showed superior cycling performance both in the symmetrical cells and full cells.
To enhance the comprehension of the cavitation mechanism and explore its practical use in industrial production, this study developed models involving oxygen, varying bubble radii, and bubble ...quantities. This study uses molecular dynamics simulations coupled with the momentum mirror method to examine the collapse characteristics of bubbles during ultrasonic cavitation. The investigation uncovers patterns in the fluctuation of the maximum local density of water molecules, released pressure, and temperature. The findings demonstrate that, when oxygen-containing bubbles collapse at identical radii, the local density is notably higher and diminishes more rapidly. Moreover, the changes in the shape exhibit greater regularity. During the bubble collapse, a depression forms on the bubble’s surface, coinciding with a notable surge in local density around the depression. As bubble radii and quantities increase, so does the local density along with a concurrent rise in the maximum pressure. Intriguingly, the model demonstrates the lowest pressure at Z = 35 Å accompanied by the emergence of a small crescent-shaped region with a reduced density. Throughout the pressure ascension phase, the rate of the maximum pressure change escalates with an increase in the number of bubbles. Conversely, during the pressure descent phase, the rate of the maximum pressure change diminishes with a growing number of bubbles. However, it is important to note that the maximum pressure does not exhibit a direct correlation with the number of bubbles. Ultimately, this study provides valuable technical guidance and a theoretical foundation for the integration of ultrasonic cavitation in industrial production processes.
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