Degradable and Fully Recyclable Dynamic Thermoset Elastomer for 3D-Printed Wearable Electronics

Wearable electronics have become an important part of daily lives. However, its rapid development results in the problem of electronic waste (e-waste). Consequently, recyclable materials suitable for wearable electronics are highly sought after. In this study, a conductive recyclable composite (PFBC) is designed based on a dynamic covalently cross-linked elastomer and hierarchical hybrid nanofillers. The PFBC shows excellent wide-ranging properties including processability, elasticity, conductivity, and stability, which are superior to previous materials used for recyclable electronics, and exhibits outstanding mechanical properties and environmental tolerance including high temperature, high humidity, brine, and ethanol owing to its covalent cross-linking. Reversible dissociation of Diels–Alder networks allows for convenient processing and recycling. After three recycles, the toughness of the PFBC remained at 10.1 MJ m⁻³, which is conspicuous among the reported recyclable electronic materials. Three types of PFBC-based wearable electronics including a triboelectric nanogenerator, a capacitive pressure sensor, and a flexible keyboard, are successfully 3D printed with excellent performance. The PFBC possessed both recyclability and degradability, the combination of which provides a new way to reduce e-waste. This is the first work to recycle electronics using direct 3D printing and presents promising new design principles and materials for wearable electronics.     

Poly(2,5-Dihydroxy-1,4-Benzoquinonyl Sulfide) As an Efficient Cathode for High-Performance Aqueous Zinc–Organic Batteries

Aqueous rechargeable zinc-ion batteries (ZIBs) have attracted considerable attention as a promising candidate for low-cost and high-safety electrochemical energy storage. However, the advancement of ZIBs is strongly hindered by the sluggish ionic diffusion and structural instability of inorganic metal oxide cathode materials during the Zn²⁺ insertion/extraction. To address these issues, a new organic host material, poly(2,5-dihydroxy-1,4-benzoquinonyl sulfide) (PDBS), has been designed and applied for zinc ion storage due to its elastic structural factors (tunable space and soft lattice). The aqueous Zn-organic batteries based on the PDBS cathode show outstanding cycling stability and rate capability. The coordination moieties (O and S) display the strong electron donor character during the discharging process and can act as the coordination arms to host Zn²⁺. Also, under the electrochemical environment, the malleable polymer structure of PDBS permits the rotation and bending of polymer chains to facilitate the insertion/extraction of Zn²⁺, manifesting the superiority and uniqueness of organic electrode materials in the polyvalent cation storage. Finally, quasi-solid-state batteries based on aqueous gel electrolyte demonstrate highly stable capacity under different bending conditions.     

Origin of High Ionic Conductivity of Sc-Doped Sodium-Rich NASICON Solid-State Electrolytes

Substitution of liquid electrolyte with solid-state electrolytes (SSEs) has emerged as a very urgent and challenging research area of rechargeable batteries. NASICON (Na₃Zr₂Si₂PO₁₂) is one of the most potential SSEs for Na-ion batteries due to its high ionic conductivity and low thermal expansion. It is proven that the ionic conductivity of NASICON can be improved to 10⁻³ S cm⁻¹ by Sc-doping, of which the mechanism, however, has not been fully understood. Herein, a series of Na_3+xSc_xZr_2−xSi₂PO₁₂ (0 ≤ x  ≤  0.5) SSEs are prepared. To gain a deep insight into the ion transportation mechanism, synchrotron-based X-ray absorption spectroscopy (XAS) is employed to characterize the electronic structure, and solid-state nuclear magnetic resonance (SS-NMR) is used to analyze the dynamics. In this study, Sc is successfully doped into Na₃Zr₂Si₂PO₁₂ to substitute Zr atoms. The redistribution of sodium ions at certain specific sites is proven to be critical for sodium ion movement. For x ≤ 0.3, the promotion of sodium ion movement is attributed to sodium ion concentration increase at the Na2 sites and decrease at the Na1 and Na3 sites. For x > 0.3, the inhibition of sodium ion movement is due to the phase change from monoclinic to rhombohedral and an increasing impurity content.     

基于二维极化特征的PolSAR图像决策分类

决策树模型在极化SAR数据分类中有着极大的应用价值,既能描述分类结果的极化散射机制,又能获得较好的分类精度。但在对散射机制相似的地物进行分类时,由于经典决策树模型的节点采用的是单个特征,分类精度不理想。因此,该文提出了节点采用2维特征的方法,即在特征集相同的前提下,每次取两个特征组成特征矢量用于节点,提高了经典决策树难以区分的地物的分类精度;并且利用分类结果的混淆矩阵准确定位了导致分类误差的节点,进而对节点进行有针对性的反馈调整,进一步提高了指定地物的分类精度。利用AIRSARFlevoland数据验证了该方法的有效性,并结合极化特征描述了Flevoland地区多种植被的极化散射机制。      

Four-junction AlGaAs/GaAs laser power converter

Four-junction A1GaAs/GaAs laser power converters (LPCs) with n+-GaAs/p+-Al0.37Ga0.63As heterostructure tunnel junctions (TJs) have been designed and grown by metal-organic chemical vapor deposition (MOCVD) for converting the power of 808 nm lasers.A maximum conversion efficiency ηc of 56.9％ + 4％ is obtained for cells with an aperture of 3.14 mm2 at an input laser power of 0.2 W,while dropping to 43.3％ at 1.5 W.Measured current-voltage (I-V) characteristics indicate that the performance of the LPC can be further improved by increasing the tunneling current density of TJs and optimizing the thicknesses of sub-cells to achieve current matching in LPC.     

Porous Iron–Cobalt Alloy/Nitrogen‐Doped Carbon Cages Synthesized via Pyrolysis of Complex Metal–Organic Framework Hybrids for Oxygen Reduction

Efficient and stable nonprecious metal electrocatalysts for oxygen reduction are of great significance in some important electrochemical energy storage and conversion systems. As a unique class of porous hybrid materials, metal–organic frameworks (MOFs) and their composites are recently considered as promising precursors to derive advanced functional materials with controlled structures and compositions. Here, an “MOF‐in‐MOF hybrid” confined pyrolysis strategy is developed for the synthesis of porous Fe–Co alloy/N‐doped carbon cages. A unique “MOF‐in‐MOF hybrid” architecture constructed from a Zn‐based MOF core and a Co‐based MOF hybrid shell encapsulated with FeOOH nanorods is first prepared, followed by a pyrolysis process to obtain a cage‐shaped hybrid material consisting of Fe–Co alloy nanocrystallites evenly distributed inside a porous N‐doped carbon microshell. Of note, this strategy can be extended to synthesize many other multifunctional “nanosubstrate‐in‐MOF hybrid” core–shelled structures. Benefiting from the structural and compositional advantages, the as‐derived hybrid cages exhibit superior electrocatalytic performance for the oxygen reduction reaction in alkaline solution. The present approach may provide some insight in design and synthesis of complex MOF hybrid structures and their derived functional materials for energy storage and conversion applications.     

SIR-C data quality and calibration results

The SIR-C/X-SAR imaging radar took its first flight on the Space Shuttle Endeavour in April 1994 and flew for a second time in October 1994. This multifrequency radar has fully polarimetric capability at L- and C-band, and a single polarization at X-band (X-SAR). The Endeavour missions were designated the Space Radar Laboratory-1 (SRL-1) and -2 (SRL-2). Calibration of polarimetric L- and C-band data for all the different modes SIR-C offers is an especially complicated problem. The solution involves extensive analysis of pre-flight test data to come up with a model of the system, analysis of in-flight test data to determine the antenna pattern and gains of the system during operation, and analysis of data from over fourteen calibration sites distributed around the SIR-C/X-SAR orbit track. The SRL missions were the first time a multifrequency polarimetric imaging radar employing a phased array antenna has been flown in space. Calibration of SIR-C data products involved some unique technical problems given the complexity of the radar system. In this paper, the approach adopted for calibration of SIR-C data is described and the calibration performance of the data products is presented     

电子束图形转移过程中的数据分割和压缩算法

研究了电子束曝光机图形数据各式转换软件的分割、压缩算法,针对传统的图形数据分割、压缩算法存在的主要缺点,提出了新的分割算法和压缩算法,并对压缩算法进行了详细的论述和研究。     

圆阵相位模式空间波束输出的高分辨目标方位估计算法研究

本文推导了均匀圆阵作为接收阵时的相位模式空间,证明圆阵在相位模式空间可以等效为一个虚拟线阵,并把高分辨方位估计算法应用到均匀圆阵相位模式空间虚拟线阵波束输出。计算机仿真结果显示,波束域Root－MUSIC算法应用到虚拟线阵时可以获得良好的解不相关信源的能力,而波束域WSF算法则具有比模式平滑算法更佳的解相干信源性能。     

微电脑时控系统

介绍的微电脑时控系统主要是按学校、工厂、机关等单位的供电要求而设计的,以实现对电能及设备的合理应用,避免繁杂的工人操作,它以８０３１单片机为核心,通过键盘实现人机对话,可完成日在、电子表功能及实时控制功能。