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HighlightsThe synthetic strategies and fundamental mechanisms of various asymmetric carbon- and silica-based nanomaterials were systematically summarized.The advantages of asymmetric structure on their related applications were clarified by some representative applications of asymmetric carbon- and silica-based nanomaterials.The future development prospects and challenges of asymmetric carbon- and silica-based nanomaterials were proposed.Carbon- and silica-based nanomaterials possess a set of merits including large surface area, good structural stability, diversified morphology, adjustable structure, and biocompatibility. These outstanding features make them widely applied in different fields. However, limited by the surface free energy effect, the current studies mainly focus on the symmetric structures, such as nanospheres, nanoflowers, nanowires, nanosheets, and core–shell structured composites. By comparison, the asymmetric structure with ingenious adjustability not only exhibits a larger effective surface area accompanied with more active sites, but also enables each component to work independently or corporately to harness their own merits, thus showing the unusual performances in some specific applications. The current review mainly focuses on the recent progress of design principles and synthesis methods of asymmetric carbon- and silica-based nanomaterials, and their applications in energy storage, catalysis, and biomedicine. Particularly, we provide some deep insights into their unique advantages in related fields from the perspective of materials’ structure–performance relationship. Furthermore, the challenges and development prospects on the synthesis and applications of asymmetric carbon- and silica-based nanomaterials are also presented and highlighted.

Asymmetric molecule strategy is considered an effective method to achieve high power conversion efficiency (PCE) of polymer solar cells (PSCs). In this paper, nine oligomers are designed by combining three new electron-deficient units (unitA)—n1, n2, and n3—and three electron-donating units (unitD)—D, E, and F—with their π-conjugation area extended. The relationships between symmetric/asymmetric molecule structure and the performance of the oligomers are investigated using the density functional theory (DFT) and time-dependent density functional theory (TD–DFT) calculations. The results indicate that asymmetry molecule PEn2 has the minimum dihedral angle in the angle between two planes of unitD and unitA among all the molecules, which exhibited the advantages of asymmetric structures in molecular stacking. The relationship of the values of ionization potentials (IP) and electron affinities (EA) along with the unitD/unitA π-extend are revealed. The calculated reorganization energy results also demonstrate that the asymmetric molecules PDn2 and PEn2 could better charge the extraction of the PSCs than other molecules for their lower reorganization energy of 0.180 eV and 0.181 eV, respectively.

It is of significance to prepare biodegradable electromagnetic interference (EMI) shielding materials with high EMI shielding effectiveness (SE) in order to solve electromagnetic and environmental pollution problems. In this paper, environmentally friendly EMI shielding silver nanowires (AgNWs)/poly(L-lactic acid) (PLLA)/poly(D-lactic acid) (PDLA)/ferroferric oxide (Fe 3 O 4 ) composites with step-wise asymmetric structures were prepared by a facile one-step non-solvent-induced phase separation method. The conductive AgNW network was constructed at a low mass fraction of 5 wt.% on the surface of stereo-complexed crystalline poly(lactic acid) (SC-PLA) film (1.08 × 10 4 S/m). Moreover, magnetic Fe 3 O 4 is mainly distributed in the skeleton of porous SC-PLA film. Due to the synergistic effect of AgNWs and Fe 3 O 4 , the EMI SE of SC-PLA films reaches up to 50.3 dB. Interestingly, SC-PLA film modified with triethoxy-1H,1H,2H,2H-tridecafluoro-n-octylsilane (TTO) demonstrates an outstanding water contact angle of about 150.2° compared with the pure PLLA film (134.7°), stemming from the synergistic effect of denser SC-PLA nano-protrusions and low-surface-energy TTO. Thus, we successfully fabricated the high EMI shielding SC-PLA film with wonderful superhydrophobicity, which extends the application performance and service life of portable electronics in moist environments.

Previous studies have investigated how the environmental vertical wind shear (VWS) may trigger the asymmetric structure in an initially axisymmetric tropical cyclone (TC) vortex and how TC intensity changes in response. In this study, the possible effect of the initial vortex asymmetric structure on the TC intensity change in response to an imposed environmental VWS is investigated based on idealized full‐physics model simulations. Results show that the effect of the asymmetric structure in the initial TC vortex can either enhance or suppress the initial weakening of the TC in response to the imposed environmental VWS. When the initial asymmetric structure is in phase of the VWS‐induced asymmetric structure, the TC weakening will be enhanced and vice versa. Our finding calls for realistic representation of initial TC asymmetric structure in numerical weather prediction models and observations to better resolve the asymmetric structure in TCs. Plain Language Summary Although a strong tropical cyclone (TC) is often treated as an axisymmetric vortex in most theoretical studies, asymmetric structure always exists in a TC in nature, such as that generated by the environmental vertical wind shear (VWS). However, it is unclear whether and how the asymmetric structure in the initial TC vortex may affect the TC intensity change in response to an imposed environmental VWS. This has been addressed in this study by conducting idealized high‐resolution numerical simulations. Results show that the asymmetric structure in the initial TC vortex can either enhance or suppress the initial weakening of the TC in response to an imposed environmental VWS depending on how the initial asymmetry is aligned with the asymmetry induced by the VWS. If they are in phase, the TC weakening would be enhanced and vice versa. Our finding highlights the importance of realistically representing the asymmetric structure in the initial TC vortex in numerical weather prediction models for TC forecasts and also the need to better resolve the TC asymmetric structure in observations. Key Points The initial asymmetric structure in a tropical cyclone (TC) vortex can either enhance or suppress the TC weakening induced by an imposed environmental vertical wind shear (VWS) If the initial asymmetric structure is in phase with the VWS‐induced asymmetric structure, the TC weakening would be enhanced and vice versa The TC asymmetric structure should be better observed in real time and realistically represented in numerical weather prediction models

HighlightsUltra-thin asymmetric composite solid-state electrolytes with ultralight areal density were designed for solid-state lithium metal batteries, achieving interfacial stability to Li metal and high-voltage cathode.The improved mechanical properties of the electrolyte contribute to the inhibition of Li dendrite growth was demonstrated by both experimental and theoretical simulations.The assembled pouch cell exhibited a high gravimetric/volume energy density of 344.0 Wh kg−1/773.1 Wh L−1.Solid-state lithium metal batteries (SSLMBs) show great promise in terms of high-energy–density and high-safety performance. However, there is an urgent need to address the compatibility of electrolytes with high-voltage cathodes/Li anodes, and to minimize the electrolyte thickness to achieve high-energy–density of SSLMBs. Herein, we develop an ultrathin (12.6 µm) asymmetric composite solid-state electrolyte with ultralight areal density (1.69 mg cm−2) for SSLMBs. The electrolyte combining a garnet (LLZO) layer and a metal organic framework (MOF) layer, which are fabricated on both sides of the polyethylene (PE) separator separately by tape casting. The PE separator endows the electrolyte with flexibility and excellent mechanical properties. The LLZO layer on the cathode side ensures high chemical stability at high voltage. The MOF layer on the anode side achieves a stable electric field and uniform Li flux, thus promoting uniform Li+ deposition. Thanks to the well-designed structure, the Li symmetric battery exhibits an ultralong cycle life (5000 h), and high-voltage SSLMBs achieve stable cycle performance. The assembled pouch cells provided a gravimetric/volume energy density of 344.0 Wh kg−1/773.1 Wh L−1. This simple operation allows for large-scale preparation, and the design concept of ultrathin asymmetric structure also reveals the future development direction of SSLMBs.

Since electromagnetic pollution is detrimental to human health and the environment, numerous efforts have been successively made to achieve excellent electromagnetic interference shielding effectiveness (EMI SE) via designing the hierarchical structures for electromagnetic interference (EMI) shielding polymer composites. Among the plentiful structures, the asymmetric structures are currently a hot spot, principally categorizing into multi-layered, porous, fibrous, and segregated asymmetric structures, which endows the high EMI shielding performance for polymer composites incorporated with magnetic, conductive, and/or dielectric micro/nano-fillers, due to the “absorption-reflection-reabsorption” shielding mechanism. Therefore, this review provides the retrospection and summary of the efforts with respect to abundant asymmetric structures and multifunctional micro/nano-fillers for enhancing EMI shielding properties, which is conducive to the booming development of polymeric EMI shielding materials for the promising prospect in modern electronics and 5-generation (5G) technology.

The complicated thin-walled components with asymmetric structure are extensively used in aerospace fields. The material of these parts is hard-to-machining (such as titanium alloy and superalloy) and the machining-induced residual stress (MIRS) is inevitable in each cutting process. The component is deformed easily after the MIRS is rebalanced, which has become one of the most important challenges for the manufacturing of these parts. To overcome this problem, a deflection control method for the asymmetric thin-walled component by optimizing the machining parameters of the finishing process is proposed, which is aimed at adjusting the distribution of MIRS and making the MIRS tends to be self-balanced. Firstly, the deflection of two typical thin-walled components, the thin-walled plate and the circular section plate, that caused by the symmetrically distributed MIRS is discussed in detail. The influence of the component structure on the deflection is revealed. Subsequently, the component is divided into different sub-regions and the optimization algorithm, includes the objective function and constraint, and is established to adjust the feed rate of each sub-region. To achieve the optimization, the mapping relationship between the deflection and the feed rate is established by combining the machining experiments and finite element method. And then, the method of adjusting the distribution of the MIRS based on the mapping relationship is presented, using which the component is divided into several sub-regions and the feed rate of each sub-region is optimized. Finally, two group machining experiments on the complex thin-walled blade are carried out. Experimental results illustrate that the proposed method can reduce the machining deflection obviously.

At present, with the rapid growth of manufacturing and big data, reliability technology has gradually become a topical issue in the industrial field. Aiming at the operation reliability assessment of rolling bearings, this paper proposes a bearings operational reliability assessment using an ensemble deep autoencoder based on asymmetric structure. In this method, an ensemble deep autoencoder is used to adaptively learn degradation features from condition monitoring data, where the ensemble deep autoencoder adopts an asymmetric structure with different activation functions in the encoder and decoder. Then, the learned features are classified by correlation analysis, and the typical features in each category are selected. Finally, the operation reliability of rolling bearings is evaluated through the definition of reliability based on Mahalanobis distance. Through the example evaluation of rolling bearing operation reliability and comparison with other feature extraction methods, it can be concluded that this method has stronger feature extraction ability and can effectively show the trend of bearing degradation.

For many real-world applications, structured regression is commonly used for predicting output variables that have some internal structure. Gaussian conditional random fields (GCRF) are a widely used type of structured regression model that incorporates the outputs of unstructured predictors and the correlation between objects in order to achieve higher accuracy. However, applications of this model are limited to objects that are symmetrically correlated, while interaction between objects is asymmetric in many cases. In this work we propose a new model, called Directed Gaussian conditional random fields (DirGCRF), which extends GCRF to allow modeling asymmetric relationships (e.g. friendship, influence, love, solidarity, etc.). The DirGCRF models the response variable as a function of both the outputs of unstructured predictors and the asymmetric structure. The effectiveness of the proposed model is characterized on six types of synthetic datasets and four real-world applications where DirGCRF was consistently more accurate than the standard GCRF model and baseline unstructured models.

The InAlN/GaN HEMT has been identified as a promising alternative to conventional AlGaN/GaN HEMT due to its enhanced polarization effect contributing to higher 2DEG in the GaN channel. However, the InAlN barrier usually suffers from high leakage and therefore low breakdown voltage. In this paper, we propose an asymmetrical GaN HEMT structure which is composed of an InAlN barrier at the source side and an AlGaN barrier at the drain side. This novel device combines the advantages of high 2DEG density at the source side and low electrical-field crowding at the drain side. According to the TCAD simulation, the proposed asymmetric device exhibits better drain current and transconductance compared to AlGaN/GaN HEMT, and enhanced breakdown voltage compared to InAlN/GaN HEMT. The current collapse effects have also been evaluated from the process-related point of view. Possible higher interface traps related to the two-step epitaxial growth for the asymmetric structure fabrication will not exacerbate the current collapse and reliability.