基于头部运动轨迹和3D视觉的跌倒检测系统

为了实现自动识别人体跌倒行为的目的,采用深度摄像头同时获取彩色图像和深度图像,并对其进行校正;对深度图像采用背景差分法提取运动人体前景;利用彩色图像和深度图像的融合、肤色检测以及距离加权面积法进行头部的检测与定位;最后将头部运动速度作为判断跌倒的依据,对人体不同运动行为的头部速度进行采集,利用支持向量机对跌倒进行检测。以5个志愿者的步行、蹲下、坐下和跌倒等4类动作为实验样本,运用交叉比对确定最优化参数,最后采用本文提出的方法进行测试。实验结果表明,系统能够有效识别跌倒,总体识别率超过95％。其中,跌倒／步行行为分类识别率达100％;针对跌倒／蹲下和跌倒／坐下的系统平均识别率分别为94．4％和98．8％。     

多环谐振式微机械陀螺频率跟踪电路研究

由于多环谐振式微机械陀螺的谐振频率较高,传统的数字控制电路对陀螺幅点信号的频率跟踪难以同时兼顾精度和速度的要求。在传统半球陀螺数字控制电路的基础上,提出了一种适用于多环谐振式微机械陀螺仪的频率跟踪电路,并首次运用于多环谐振式微机械陀螺。该电路以高速A/D转换电路为基础,通过对幅点信号高速采样计算频率和相位信息,并通过CORDIC算法产生输出信号。测试结果显示,该电路使多环谐振式微机械陀螺幅点信号的频率跟踪精度达到了0.78Hz,频率跟踪时间小于40μs,使控制电路的性能得到了极大提升。     

Additive Manufacturing of Batteries

Additive manufacturing, i.e., 3D printing, is being increasingly utilized to fabricate a variety of complex‐shaped electronics and energy devices (e.g., batteries, supercapacitors, and solar cells) due to its excellent process flexibility, good geometry controllability, as well as cost and material waste reduction. In this review, the recent advances in 3D printing of emerging batteries are emphasized and discussed. The recent progress in fabricating 3D‐printed batteries through the major 3D‐printing methods, including lithography‐based 3D printing, template‐assisted electrodeposition‐based 3D printing, inkjet printing, direct ink writing, fused deposition modeling, and aerosol jet printing, are first summarized. Then, the significant achievements made in the development and printing of battery electrodes and electrolytes are highlighted. Finally, major challenges are discussed and potential research frontiers in developing 3D‐printed batteries are proposed. It is expected that with the continuous development of printing techniques and materials, 3D‐printed batteries with long‐term durability, favorable safety as well as high energy and power density will eventually be widely used in many fields.     

4D Printing at the Microscale

3D printing of adaptive and dynamic structures, also known as 4D printing, is one of the key challenges in contemporary materials science. The additional dimension refers to the ability of 3D printed structures to change their properties—for example, shape—over time in a controlled fashion as the result of external stimulation. Within the last years, significant efforts have been undertaken in the development of new responsive materials for printing at the macroscale. However, 4D printing at the microscale is still in its early stages. Thus, this progress report will focus on emerging materials for 4D printing at the microscale as well as their challenges and potential applications. Hydrogels and liquid crystalline and composite materials have been identified as the main classes of materials representing the state of the art of the growing field. For each type of material, the challenges and critical barriers in the material design and their performance in 4D microprinting are discussed. Importantly, further necessary strategies are proposed to overcome the limitations of the current approaches and move toward their application in fields such as biomedicine, microrobotics, or optics.     

2D/2D 1T‐MoS2/Ti3C2 MXene Heterostructure with Excellent Supercapacitor Performance

2D/2D heterostructures can combine the collective advantages of each 2D material and even show improved properties from synergistic effects. 2D Transition metal carbide Ti₃C₂ MXene and 2D 1T‐MoS₂ have emerged as attractive prototypes in electrochemistry due to their rich properties. Construction of these two 2D materials, as well as investigation about synergistic effects, is absent due to the instability of 1T‐MoS₂. Here, 3D interconnected networks of 1T‐MoS₂/Ti₃C₂ MXene heterostructure are constructed by magneto‐hydrothermal synthesis, and the electrochemical storage mechanisms are investigated. Improved extra capacitance is observed due to enlarged ion storage space from a synergistically interplayed effect in 3D interconnected networks. Outstanding rate performance is realized because of ultrafast electron transport originating from Ti₃C₂ MXene. This work provides an archetype to realize excellent electrochemical properties in 2D/2D heterostructures.     

Phthalocyanine‐Based 2D Conjugated Metal‐Organic Framework Nanosheets for High‐Performance Micro‐Supercapacitors

2D conjugated metal‐organic frameworks (2D c‐MOFs) are emerging as a novel class of conductive redox‐active materials for electrochemical energy storage. However, developing 2D c‐MOFs as flexible thin‐film electrodes have been largely limited, due to the lack of capability of solution‐processing and integration into nanodevices arising from the rigid powder samples by solvothermal synthesis. Here, the synthesis of phthalocyanine‐based 2D c‐MOF (Ni₂[CuPc(NH)₈]) nanosheets through ball milling mechanical exfoliation method are reported. The nanosheets feature with average lateral size of ≈160 nm and mean thickness of ≈7 nm (≈10 layers), and exhibit high crystallinity and chemical stability as well as a p‐type semiconducting behavior with mobility of ≈1.5 cm² V^?1 s^?1 at room temperature. Benefiting from the ultrathin feature, the nanosheets allow high utilization of active sites and facile solution‐processability. Thus, micro‐supercapacitor (MSC) devices are fabricated mixing Ni₂[CuPc(NH)₈] nanosheets with exfoliated graphene, which display outstanding cycling stability and a high areal capacitance up to 18.9 mF cm^?2; the performance surpasses most of the reported conducting polymers‐based and 2D materials‐based MSCs.     

用于数字D类音频功放的伪自然采样算法综述

伪自然采样方法是对数字D类音频功放中均匀采样脉冲宽度调制（Uniform-sampling Pulse Width Modulation,UPWM）失真校正的主流方法。近年来,如何使伪自然采样算法在校正谐波失真的同时降低算法的计算复杂度成为研究重点。首先介绍了伪自然采样方法的谐波失真校正原理,然后从UPWM面临的问题出发分别描述和分析了近年来涌现的各种伪自然采样算法的原理及其存在的问题,最后从谐波失真校正效果和计算复杂度方面比较和综合评价了不同伪自然采样算法,并展望了伪自然采样算法未来需要进一步研究的方向。     

应用纵向分区彩虹全息术合成断层图像的三维消色像

报道了应用纵向分割多狭缝曝光彩虹全息术合成多幅断层图像为三维消色像的方法及其实验结果。通过将主全息图记录狭缝按纵向分割并结合使用循环分割和色散补偿光栅 ,实现了在较高的分辨率和较低色模糊的多幅断层像的白光三维消色像的合成 ,并提高了再现像的视觉亮度、视场和立体感。     

一种用于高速A/D转换器的高精度参考电压电阻网络

提高分压电阻网络输出参考电压的精度对设计高速A/D转换器有重要意义.本文基于对参考电压非线性误差的分析提出一种并联式高精度参考电压电阻网络,给出其输出参考电压在最坏情况下的非线性误差分布形式.详细的讨论以及模拟结果表明勿需补偿电路,并联式电阻网络通过减少支路电阻串上的电阻数目能有效地抑制由于负载效应造成的参考电压非线性误差,使得输出参考电压的精度明显提高,同时稳定速度加快,驱动负载能力强,对温度的灵敏度低,适合于多种结构的高速A/D转换器,如:全并行、分步式、折叠式等.     

回顾我国电信科研历程展望民族信息产业发展

本文回顾了近５０年来我国电信科研和产业的成果,重点介绍了列入国家计划的正在进行的课题,展望电信技术的发展方向和研究开发任务。