基于多层次特征融合的口腔粘膜性疾病识别方法北大核心CSCD

口腔粘膜性疾病的识别主要依靠医生肉眼观察并进行主观判断,该方法导致疾病识别的准确率低、医生的工作量大。针对以上问题提出一种基于多层次特征融合的口腔粘膜性疾病识别方法。对口腔疾病图像提取深层次特征和浅层次特征共两种,使用EfficientNet模型做深层特征的提取,使用HSV、方向梯度直方图(histogram of oriented gradient,HOG)和灰度共生矩阵(gray-level co-occurrence matrix,GLCM)分别提取口腔疾病的颜色、形状以及纹理的浅层特征,将特征融合后利用随机森林(random forest,RF)算法进行特征选择,选取特征重要性更大的特征,降低特征的维度。最后结合多种机器学习分类器进行分类识别。使用收集到的口腔粘膜疾病数据集进行实验验证,实验结果表明,该方法能达到准确率(accuracy,Acc)92.89%、灵敏度(sensitivity,Sen)89.91%、特异性(specificity,Spe)96.06%以及AUC(area under the curve)98.09%,有效地解决识别中误判多、准确率低等问题。     

LDPC码译码算法及性能分析

为了进一步降低低密度奇偶校验(LDPC)码译码算法的复杂度,基于经典置信传播(BP)译码算法,给出了对数域迭代后验概率对数似然比(APP LLR)算法。通过概率域的和积算法(SPA)和对数域的迭代APP LLR算法的性能仿真及分析可见,迭代APP LLR算法能以较小的性能损失换取复杂度的大幅降低。进一步选用迭代APP LLR算法,结合不同地形条件下的VHF频段信道模型,仿真了LDPC码编译码系统的性能。理论分析及仿真结果均表明,基于迭代APP LLR算法的LDPC码,实现简单,性能优异,具有良好的工程应用前景。     

城市轨道交通与通信信号系统

微电子技术、信息技术和计算机网络技术彻底改变了轨道交通信号技术的现状,产生了城市轨道交通信号系统。其在轨道交通安全运行和通行能力方面发挥了巨大作用,不但使运行效率大幅提高,而且实现了列车运行的自动化。     

基于激光自混合干涉调频信号的位移测量实验

激光自混合干涉在高精度测量领域发挥着越来越重要的作用,微位移测量已应用于大型土木结构、航空航天、健康监测等。传统测量以调幅信号为主,但随着噪声加强,测量误差越来越大,甚至难以测量。为此,采用马赫-曾德尔干涉仪,实现了调幅/调频信号转换。针对大噪声环境下的调频信号,利用多次希尔伯特变换进行相位解卷,实现了原始信号的重构。数值仿真结果证明了该方法的有效性,在10 dB白噪声环境中,系统的信噪比为10.0614 dB,估计误差为0.0614 dB。实验结果表明,微位移重构的误差在100 nm以内,且调频信号的信噪比远高于调幅信号。该方法适用于超精密测量,且在大噪声环境下仍具有较高的信噪比。     

Bioinspired Supramolecular Slippery Organogels for Controlling Pathogen Spread by Respiratory Droplets

Surface-deposited pathogens are sources for the spread of infectious diseases. Protecting public facilities with a replaceable or recyclable antifouling coating is a promising approach to control pathogen transmission. However, most antifouling coatings are less effective in preventing pathogen-contained respiratory droplets because these tiny droplets are difficult to repel, and the deposited pathogens can remain viable from hours to days. Inspired by mucus, an antimicrobial supramolecular organogel for the control of microdroplet-mediated pathogen spread is developed. The developed organogel coating harvests a couple of unique features including localized molecular control-release, readily damage healing, and persistent fouling-release properties, which are preferential for antifouling coating. Microdroplets deposited on the organogel surfaces will be spontaneously wrapped with a thin liquid layer, and will therefore be disinfected rapidly due to a mechanism of spatially enhanced release of bactericidal molecules. Furthermore, the persistent fouling-release and damage-healing properties will significantly extend the life-span of the coating, making it promising for diverse applications.     

Channel Arrangement for optical communication subsystems with 12 parallel channels

This paper devoted to report the design and the achievement of an optical communication subsystem with 12 parallel channels in one chip. The system is capable of,transmitting 10 Gbps bidirectional date over hundreds of meters. It can provide error detection and correction by using 8B/10B encoding and Cyclical Redundancy Checking （CRC） encoding when only single-channel fails. The design scheme has already passed the simulation in FPGA. This technique is useful to enhance the capability and the reliability of the very short reach （VSR） transmission systems.     

LTCC-Based Highly Integrated Millimeter-Wave Receiver Front-End Module

This paper presents the design and fabrication of a highly integrated Low Temperature Co-fired Ceramic (LTCC) receiver front-end module. This LTCC module is a dual channel receiver module, works at Ka-band, and fabricated including six Ferro A6M dielectric layers and five metal layers, contains eight embedded resistors and eight MMICs. All MMICs are mounted into pre-making cavities on the top surface of the LTCC substrate. Three slot coupled waveguide-to-microstrip transitions are integrated at LTCC substrate to realize RF and LO signal input. The developed module is highly integrated and reliable, which has a compact size of 58 × 50 × 22 mm³ (including the metal cavity). Each channel of the receiver has the noise figure of less than 9 dB and the gain of more than 24 dB at Ka-band.     

EOS中透明传输问题分析及解决方案

在SDH网络上传送以太网业务(EOS,Ethernet over SDH)具有巨大的优势。EOS能利用现有的SDH网络为以太网业务传送提供完善的OAM性能。在EOS系统中,透明传输以太网业务有非常重要的作用。本文详细分析了时钟、故障传递、流量控制和自协商相关的透明传输问题,相应的解决方案也同时提出。     

高分辨率SAR图像目标峰值特征提取

峰值特征是进行SAR图像自动目标识别的重要特征。本文提出了SAR图像目标的通用高斯峰值模型,根据该模型提出了目标峰值提取方法。利用实测数据以及蒙特卡罗仿真结果表明:通用高斯峰值模型是实际峰值的一种精确模型,基于该模型的峰值提取方法具有良好的提取精度。     

UWB技术在有线电视网中的应用

起宽带(Ultra Wideband，UWB)技术是近几年发展起来的一项十分有潜力的无线通信技术，以其高性能、低成本的无线数据通信能力，成为实现无线个人局域网的富有竞争力的技术之一。依据起宽带技术的主要特点，讨论了该技术在有线电视网中应用的优势及其实现，这不仅为解决有线电视网带宽“瓶颈”问题提供了有效的方案，也使UWB技术得到了更广泛的应用。