Mask(1) disease(1) Hierarchical(1) aggregation(1) IMPROVE(1) NMS(1) virus transmission(1) face mask detection(1) Convolution(1) Improved YoloV3 algorithm(1) MONITOR(1) applied(1) COVID-19(1) Epidemic(1) mechanism(1) Precision(1) detection efficiency(1) performed(1) database(1) information(1) matrix(1) Feature extraction and fusion(1) effective(1) adopted(1) Coronavirus disease 2019(1) Accuracy(1) Face mask(1) Algorithms(1) datasets(1) eight(1)