Industry-Scale and Environmentally Stable Ti3C2Tx MXene Based Film for Flexible Energy Storage Devices

MXenes, 2D transition metal carbides, and nitrides have attracted tremendous interest because of their metallic conductivity, solution processability, and excellent merits in energy storage and other applications. However, the pristine MXene films often suffer from poor ambient stability and mechanical properties that stem from their polar terminal groups and weak interlayer interactions. Here, a heteroatom doping strategy is developed to tailor the surface functionalities of MXene, followed by the addition of large-sized reduced graphene oxide (rGO) as conductive additives to achieve a scalable production of S, N-MXene/rGO (SNMG-40) hybrid film with high mechanical strength ( ≈ 45 MPa) and energy storage properties (698.5 F cm⁻³). Notably, the SNMG-40 film also demonstrates long-term cycling stability ( ≈ 98% capacitance retention after 30 000 cycles), which can be maintained under ambient condition or immersed in H₂SO₄ electrolyte for more than 100 days. The asymmetric supercapacitor (aMGSC) based on SNMG-40 film shows an ultrahigh energy density of 22.3 Wh kg⁻¹, which is much higher than those previously reported MXene-based materials. Moreover, the aMGSC also provides excellent mechanical durability under different deformation conditions. Thus, this strategy makes MXene materials more competitive for real-world applications such as flexible electronics and electromagnetic interference shielding.     

分布式视频编码中关键帧丢失错误保护

目的 分布式视频编码较其传统视频编码具有编码简单、误码鲁棒性高等特点,可以很好地满足如无人机航拍、无线监控等新型视频业务的需求。在分布式视频编码中,视频图像被交替分为关键帧和Wyner-Ziv帧,由于受到信道衰落和干扰等因素的影响,采用传统帧内编码方式的关键帧的误码鲁棒性远不如基于信道编码的Wyner-Ziv帧。关键帧能否正确传输和解码对于Wyner-Ziv帧能否正确解码起着决定性的作用,进而影响着整个系统的压缩效率和率失真性能。为此针对关键帧在异构网络中的鲁棒性传输问题,提出一种基于小波域的关键帧质量可分级保护传输方案。方法 在编码端对关键帧同时进行传统的帧内视频编码和基于小波域的Wyner-Ziv编码,解码端将经过错误隐藏后的误码关键帧作为基本层,Wyner-Ziv编码产生的校验信息码流作为增强层。为了提高系统的分层特性以便使系统的码率适应不同的网络条件,进一步将小波分解后图像的各个不同层的低频带和高频带组合成不同的增强层,根据不同信道环境,传输不同层的Wyner-Ziv校验数据。同时对误码情况下关键帧的虚拟噪声模型进行了改进,利用第1个增强层已解码重建的频带与其对应边信息来获得第2个和第3个增强层对应频带的更加符合实际的虚拟信道模型的估计。结果 针对不同的视频序列在关键帧误码率为1%20%时,相比较于传统的帧内错误隐藏算法,所提方案可以提高视频重建图像的主观质量和整体系统的率失真性能。例如在关键帧误码率为5%时,通过传输第1个增强层,不同的视频序列峰值信噪比（PSNR）提升可达25 dB左右;如果继续传输第2个增强层的校验信息,视频图像的PSNR也可以提升0.51.6 dB左右;如果3个增强层的校验信息都传输的话,基本上可以达到无误码情况下关键帧的PSNR。结论 本文所提方案可以很好地解决分布式视频编码系统中的关键帧在实际信道传输过程中可能出现的误码问题,同时采用的分层传输方案可以适应不同网络的信道情况。     

Air–water interfacial synthesis of metal–organic framework hollow fiber membranes for water purification

In this study, we report a novel air–water interfacial self-crystallization (AWISC) method for scalable depositing continuous metal–organic framework (MOF) layers on modification-free polyvinylidene fluoride (PVDF) hollow fibers. Through importing MOF precursors into porous hollow fiber substrates with outer diameters of 1.2 mm and evaporating aqueous solutions under mild conditions, the metal ions and linkers close to solution surface can be concentrated firstly, thus the crystallization of MOFs will preferentially occur at interface of air and liquid precursors. The formed crystals can block off the pores of substrates to form defect-free MOF membranes. The prepared ZIF-8 membranes exhibit superior performance in molecular separation, with high rejections of 94.1 ∼ 99.5% for small molecules (molecular weight: 320 ∼ 800 Da) and large permeance up to 50 L m⁻² h⁻¹ bar⁻¹. Moreover, by combining AWISC and microfluidic processing, the high-performance ZIF-8 hollow fiber membranes with long length of 30 cm can be easily fabricated in scalability.     

基于H.264SVC的可分级视频会议系统的实现

介绍了在网络异构和用户异构环境中部署网络视频会议系统的挑战,阐述了H.264 SVC可分级视频编码技术优势,最后详细给出了面向异构环境的可分级网络视频会议系统的实现方法.     

质量可伸缩编码技术在视频会议系统的应用

文章结合湖北电网应急指挥中心高清视频会议系统、视频监控系统的实际应用,围绕应用质量可伸缩的视频编码,开展了如下工作：采用一种小波编码器来实现质量可伸缩的视频编码,着力解决高清视频会议系统在有限通信带宽、复杂网络环境和终端设备异构性等现状下出现图像画面抖动的实际问题。     

A reconfigurable real-time neuromorphic hardware for spiking winner-take-all network

The central nervous system receives a vast amount of sensory inputs, and it should be able to discriminate and recognize different kinds of multisensory information. Winner-take-all (WTA) consists of a simple recurrent neural network carrying out discrimination of input signals through competition. This paper presents a real-time scalable digital hardware implementation of the spiking WTA network. The need for concurrent computing, real-time performance, proper accuracy, and the reconfigurable device has led to the field-programmable gate array (FPGA) as the target hardware platform. A set of techniques is employed to lessen memory and resource usage. The proposed architecture consists of multiprocessing elements, which share hardware resources between a specific number of neurons. We introduce a novel connectivity array for neurons (dedicated to the WTA network) to cut down memory usage. Also, a multiplier-less method in the neuron model and a novel tree adder in the synapse processing unit are designed to improve computational efficiency. The proposed network simulates 4,500 neurons in real time on a Xilinx Artix-7 FPGA, while a scalable architecture facilitates the implementation of up to 20,000 neurons on this device. The pipeline structure can guarantee real-time performance for large-scale networks. Based on simulation and physical synthesis results, the presented network mimics biological WTA dynamics and consumes efficient hardware resources.     

20kN-9m伸缩折叠起重机设计

该起重机是中小型船用起重装置。在设计中巧妙地将调幅臂设计成开口型截面,并使基本臂与调幅臂不在同一中心线上连接。实现基本臂与调幅臂折叠,调幅臂与回转支座二次折叠,成功的将起重机收到最小的外形尺寸。     

Scalable models of microwave system responses using sequential sampling on unstructured grids

This paper presents two sequential sampling algorithms for the macromodeling of parameterized system responses in model‐dependent sampling frameworks. The construction of efficient algorithms for the automatic selection of samples for building scalable macromodels of frequency‐domain responses is addressed in this paper. The sequential sampling algorithms proposed here are tailored toward the application of local scalable macromodeling schemes on unstructured design space grids. Two pertinent examples are considered. For the first one, different algorithms are applied, and a comparison is made in terms of the number of samples generated, accuracy and CPU time. As a second example, four design variables are taken into account with one of the proposed algorithms, and the generated model is used in a frequency‐domain optimization. Copyright © 2013 John Wiley & Sons, Ltd.     

基于有符号数字系统的Montgomery模逆算法及其硬件实现

 在椭圆曲线密码中,模逆运算是有限域运算中最复杂、最耗时且硬件实现难度最大的运算.本文在Kaliski算法的基础上,提出了基于有符号数字系统的Montgomery模逆算法,它支持素数域和二进制域上任意多精度参数的求模逆运算.据此算法,设计了相应的硬件结构方案,并给出了面积复杂度和时间复杂度分析.仿真结果表明,相比于其它模逆算法硬件设计方案,本文提出的基于有符号数字系统的Montgomery模逆算法在运算速度、电路面积、灵活性等方面具有显著的优越性.