Neighborhood fusion-based hierarchical parallel feature pyramid network for object detection

In order to improve the detection accuracy of small objects,a neighborhood fusion-based hierarchical parallel feature pyramid network(NFPN)is proposed.Unlike the layer-by-layer structure adopted in the feature pyramid network(FPN)and deconvolutional single shot detector(DSSD),where the bottom layer of the feature pyramid network relies on the top layer,NFPN builds the feature pyramid network with no connections between the upper and lower layers.That is,it only fuses shallow features on similar scales.NFPN is highly portable and can be embedded in many models to further boost performance.Extensive experiments on PASCAL VOC 2007,2012,and COCO datasets demonstrate that the NFPN-based SSD without intricate tricks can exceed the DSSD model in terms of detection accuracy and inference speed,especially for small objects,e.g.,4%to 5%higher mAP(mean average precision)than SSD,and 2%to 3%higher mAP than DSSD.On VOC 2007 test set,the NFPN-based SSD with 300×300 input reaches 79.4%mAP at 34.6 frame/s,and the mAP can raise to 82.9%after using the multi-scale testing strategy.

结合空洞卷积与注意力机制的道路提取方法

针对高分辨率影像中道路情况复杂,存在细小道路和被建筑、阴影等隔断道路,导致道路提取精度不高的问题,提出一种结合空洞卷积单元和并行注意力机制模块的改进模型AP-LinkNet。该模型是通过在下采样编码过程中扩大感受野和深层次关注道路特征以达到更高的细节道路提取精度。其中空洞卷积模块在扩大感受野的同时不改变空间上像素之间的关系,并行注意力机制提高输入影像采样过程中对通道和空间信息的关注度,并加权赋值给解码步骤的反卷积特征。结合两种机制的特点,减少复杂道路背景的噪声扰乱性以及提高道路提取模型的整体精度。与DeepLabV3+、U-Net、LinkNet和D-LinkNet模型做对比分析,AP-LinkNet模型在DeepGlobe数据集上道路提取的F_(1)分数和IOU评价指标为80.69%和78.65%,其中F_(1)分数分别高出对比模型11.71%、5.24%、3.97%和3.58%。结果表明模型精确度和鲁棒性更高,对于高分影像狭窄、被遮挡等复杂道路细节提取效果好。

Deep Learning Approach for COVID-19 Detection in Computed Tomography Images

With the rapid spread of the coronavirus disease 2019(COVID-19)worldwide,the establishment of an accurate and fast process to diagnose the disease is important.The routine real-time reverse transcription-polymerase chain reaction(rRT-PCR)test that is currently used does not provide such high accuracy or speed in the screening process.Among the good choices for an accurate and fast test to screen COVID-19 are deep learning techniques.In this study,a new convolutional neural network(CNN)framework for COVID-19 detection using computed tomography(CT)images is proposed.The EfficientNet architecture is applied as the backbone structure of the proposed network,in which feature maps with different scales are extracted from the input CT scan images.In addition,atrous convolution at different rates is applied to these multi-scale feature maps to generate denser features,which facilitates in obtaining COVID-19 findings in CT scan images.The proposed framework is also evaluated in this study using a public CT dataset containing 2482 CT scan images from patients of both classes(i.e.,COVID-19 and non-COVID-19).To augment the dataset using additional training examples,adversarial examples generation is performed.The proposed system validates its superiority over the state-of-the-art methods with values exceeding 99.10%in terms of several metrics,such as accuracy,precision,recall,and F1.The proposed system also exhibits good robustness,when it is trained using a small portion of data(20%),with an accuracy of 96.16%.

坐标并行注意力下密集空洞卷积的脉络膜分割

脉络膜的变化与很多眼科疾病密切相关。医生在诊断过程中常需要手动分割光学断层扫描图像(Optical Coherence Tomography,OCT)中的脉络膜,再定量分析脉络膜健康状况,但人工分割费时费力。脉络膜自动分割难点在于OCT图像中脉络膜下边界模糊,很难捕捉上下文信息,并且脉络膜结构跟视网膜结构比较类似,容易混淆。为了解决该难点,本文提出了融合坐标并行注意力模块和密集空洞卷积模块的残差编解码模型;设计了一种桥结构,包含了注意力机制和空洞卷积,在增加模型感受野的同时抑制浅层噪声;同时为了使模型关注脉络膜结构信息,引入了一种包含结构相似性的混合损失函数来训练模型。实验结果表明,该模型能有效提升对脉络膜的分割精度,在OCT脉络膜数据集上,Dice系数和Jaccard相似度达到了97.63%和95.28%。

融合余弦退火与空洞卷积的遥感影像语义分割

为了捕捉遥感影像中丰富的上下文信息与多尺度的地物信息,改进集成模型的策略,提高语义分割精度,提出一种融合周期递增余弦退火与多尺度空洞卷积的高分辨率遥感影像语义分割方法。方法引入多尺度并行的空洞卷积,有利于捕捉更大范围的上下文信息,在不增加参数的情况下,提高网络对多尺度对象的辨识能力;使用全连接条件随机场引入空间和边缘的上下文信息,提高网络对遥感影像的细节分割能力;引入周期递增的余弦退火策略调整学习率,获得合适数量的局部最优解,集成局部最优解进一步提升网络在像素上的分类能力。在Gaofen Image Dataset数据集上的实验结果表明,多尺度并行空洞卷积可以充分捕捉遥感影像上的多尺度地物信息,能有效辨识复杂对象;空间和边缘上下文信息的引入使语义分割对象的边界辨识更精准;周期递增余弦退火策略能明显减少集成模型的推理时间,模型的总体精度与Kappa系数均优于目前主流的语义分割模型。