基于ADSP-BF533的音频处理系统设计

进行数字信号处理运算的微处理器用于实时快速地实现数字信号处理算法。针对ADSP-BF533的特点介绍了基于该芯片的音频处理系统电路设计,主要包括复位电路、电源单元、存储器单元及模数/数模转换单元等,可作为音频信号处理的通用系统。     

On the complexity of and algorithms for finding the shortest path with a disjoint counterpart

Finding a disjoint path pair is an important component in survivable networks. Since the traffic is carried on the active (working) path most of the time, it is useful to find a disjoint path pair such that the length of the shorter path (to be used as the active path) is minimized. In this paper, we first address such a Min-Min problem. We prove that this problem is NP-complete in either single link cost (e.g., dedicated backup bandwidth) or dual link cost (e.g., shared backup bandwidth) networks. In addition, it is NP-hard to obtain a K-approximation to the optimal solution for any K>1. Our proof is extended to another open question regarding the computational complexity of a restricted version of the Min-Sum problem in an undirected network with ordered dual cost links (called the MSOD problem). To solve the Min-Min problem efficiently, we introduce a novel concept called conflicting link set which provides insights into the so-called trap problem, and develop a divide-and-conquer strategy. The result is an effective heuristic for the Min-Min problem called COnflicting Link Exclusion (COLE), which can outperform other approaches in terms of both the optimality and running time. We also apply COLE to the MSOD problem to efficiently provide shared path protection and conduct comprehensive performance evaluation as well as comparison of various schemes for shared path protection. We show that COLE not only processes connection requests much faster than existing integer linear programming (ILP)-based approaches but also achieves a good balance among the active path length, bandwidth efficiency, and recovery time.     

Carbon Black-Supported Single-Atom Co?N?C as an Efficient Oxygen Reduction Electrocatalyst for H2O2 Production in Acidic Media and Microbial Fuel Cell in Neutral Media

Single metal atom isolated in nitrogen-doped carbon materials (M N C) are effective electrocatalysts for oxygen reduction reaction (ORR), which produces H₂O₂ or H₂O via 2-electron or 4-electron process. However, most of M N C catalysts can only present high selectivity for one product, and the selectivity is usually regulated by complicated structure design. Herein, a carbon black-supported Co N C catalyst (CB@Co N C) is synthesized. Tunable 2-electron/4-electron behavior is realized on CB@Co-N-C by utilizing its H₂O₂ yield dependence on electrolyte pH and catalyst loading. In acidic media with low catalyst loading, CB@Co N C presents excellent mass activity and high selectivity for H₂O₂ production. In flow cell with gas diffusion electrode, a H₂O₂ production rate of 5.04 mol h⁻¹ g⁻¹ is achieved by CB@Co N C on electrolyte circulation mode, and a long-term H₂O₂ production of 200 h is demonstrated on electrolyte non-circulation mode. Meanwhile, CB@Co N C exhibits a dominant 4-electron ORR pathway with high activity and durability in pH neutral media with high catalyst loading. The microbial fuel cell using CB@Co N C as the cathode catalyst shows a peak power density close to that of benchmark Pt/C catalyst.     

Regulating Fe Aggregation State via Unique Fe?N?V Pre-Coordination to Optimize the Adsorption-Catalysis Effect in High-Performance Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) suffer from uncontrollable shuttling behavior of lithium polysulfides (LiPSs: Li₂S_x, 4 ≤ x ≤8) and the sluggish reaction kinetics of bidirectional liquid-solid transformations, which are commonly coped through a comprehensive adsorption-catalysis strategy. Herein, a unique Fe N V pre-coordination is introduced to regulate the content of “dissociative Fe³⁺” in liquid phase, realizing the successful construction of N-doped micro-mesoporous “urchin-like” hollow carbon nanospheres decorated with single atom Fe-N₄ sites and VN nanoparticles (denoted as SA-Fe/VN@NMC). The strong chemisorption ability toward LiPSs and catalyzed Li₂S decomposition behavior on VN, along with the boosted reaction kinetics for sulfur reduction on SA-Fe sites are experimentally and theoretically evidenced. Moreover, the nanoscale-neighborhood distribution of VN and SA-Fe active sites presents synergistic effect for the anchoring-reduction-decomposition process of sulfur species. Thus SA-Fe/VN@NMC presents an optimized adsorption-catalysis effect for the whole sulfur conversion. Therefore, the SA-Fe/VN@NMC based Li-S cells exhibit high cyclic stability (a low decay of 0.024% per cycle over 700 cycles at 1 C, sulfur content: 70 wt%) and considerable rate performance (683.2 mAh g⁻¹ at 4 C). Besides, a high areal capacity of 5.06 mAh cm⁻² is retained after 100 cycles under the high sulfur loading of 5.6 mg cm⁻². This work provides a new perspective to design the integrated electrocatalysts comprising hetero-formed bimetals in LSBs.     

航天级双读数多圈绝对式光电编码器设计

利用多圈光电编码器具有体积小、量程大以及数字量输出等优点,设计了基于双读数系统的航天级多圈绝对式光电编码器。根据航天相机的精度要求,采用精度高、分辨率高的绝对式矩阵玻璃码盘作为一级码盘完成角度测量;根据电机转动的计数要求,采用重量轻,体积小的绝对式矩阵金属码盘作为二级码盘完成对一级码盘的转动圈数计数;其具有的双狭缝及双读数系统可实现信号处理电路冷备份。按照鉴定级航天产品要求,通过热学环境实验和力学环境实验对编码器性能进行了验证。实验结果表明,所设计的编码器精度范围为±100″内、分辨率为80″、测量圈数为16圈、外形尺寸为φ50 mm×50 mm、重量为270 g,稳定性高、可靠性强,且满足高分辨率航天设备设计指标。     

自适应三维分数阶微分增强算法

针对三维数字图像在重构预处理阶段分辨率不高、模糊等影响重构精度的问题,提出了基于自适应三维分数阶微分的增强算法。在将二维分数阶微分推广应用至三维的基础上,尝试性地基于图像自身梯度信息和相邻体素间梯度变化构造了自适应三维分数阶微分阶数,并给出了三维离散滤波模板。利用三维切片图像自身梯度信息解决了不同属性图像及不同图像区域最优的分数阶微分阶数不同的问题,提高了实时处理效率。将自适应增强算法应用至三维边缘曲面追踪算法,可以重构出精度更高的三维数字图像。     

大学计算机专业基于网络的交互式平台设计与实现

文章针对困扰教师的课堂出勤统计、学生知识点掌握程度、学生综合评价和历届学生综合能力比较等难题,通过搭建基于网络的交互式教学辅助平台,从不同角度对数据进行分析统计和可视化展示。该平台对教师及时掌握学生状况,进而进行教学方法的改进和培养学生学习兴趣起到重要的作用,将会成为教师课堂教学的有力助手。     

样本容量对子孔径拼接检测精度影响的分析

应用数理统计理论及线性回归分析方法详细分析了在子孔径拼接检测中样本容量对测量精度的影响,通过计算确定了当子孔径拼接干涉检测中样本容量大于10 4时,即可保证检测精度,又能减小计算的复杂程度。     

Creation of Ghost Illusions Using Wave Dynamics in Metamaterials

The creation of wave‐dynamic illusion functionality is of great interest to various scientific communities because it can potentially transform an actual perception into the pre‐controlled perception, thus empowering unprecedented applications in the advanced‐material science, camouflage, cloaking, optical and/or microwave cognition, and defense security. By using the space transformation theory and engineering capability of metamaterials, a functional “ghost” illusion device, which is capable of creating multiple virtual ghost images of the original object's position under the illumination of electromagnetic waves, is proposed and realized. The scattering signature of the object is thus ghosted and perceived as multiple ghost targets with different geometries and compositions. The ghost‐illusion material, which is being inhomogeneous and anisotropic, is realized using thousands of varying unit cells working at non‐resonance. The experimental demonstration of the ghost illusion validates the theory of scattering metamorphosis and opens a novel avenue to the wave‐dynamic illusion, cognitive deception, manipulate strange light (or matter) behaviors, and design novel optical and microwave devices.     

光纤Bragg光栅地震检波器的研究

由光纤Bragg光栅制成的地震检波器,其采集的传感信息包含在波长上,直接对波长进行调制解调,具有分辨率高、精度高、抗干扰能力强和频带宽等优点.文章研究了光纤Bragg光栅地震检波器,给出其重要参数,并提出了一种新的光纤Bragg光栅地震检波器的解调方案.为光纤Bragg光栅地震检波器的研究以及实际应用提供了依据.