Search

• A portable device was developed to detect moldy cores in apples. • Available spectral shape features are selected through one-way analysis of variance. • A new model was constructed that fused spectral characteristics and shapes. • The device can detect samples with moldy-core degrees less than 6%. Moldy core is a disease that significantly affects apple yield. However, discriminating slightly moldy cores is a substantial challenge in actual production. In this study, a device for detecting moldy cores in apples is developed. The device is supported by a C12880MA sensor and an STM32F103 microcontroller to detect Vis/NIR signals of apples. Experimentally obtained spectral data of Fuji apples were collected to analyze the characteristic wavelengths through different preprocessing methods for the detection of moldy cores. Additionally, multiple spectral shape features were extracted according to peaks and troughs. Significant differences in spectral shape features between healthy and moldy core samples were analyzed via a one-way analysis of variance. Finally, an apple moldy core discrimination model was constructed using an adaptive boosting algorithm that fused spectral characteristics and shapes. The model accuracy of the training set and the test set was 99.1 % and 97.3 %, respectively. Compared with other models, the proposed model effectively improved the accuracy of detecting samples with moldy core degrees less than 6 %. This research provides a novel method for detecting moldy cores, which is of great significance for apple quality management. [ABSTRACT FROM AUTHOR]

Broad-area lasers (BALs) have found applications in a variety of crucial fields on account of their high output power and high energy transfer efficiency. However, they suffer from poor spatial beam quality due to multi-mode behavior along the waveguide transverse direction. In this paper, we propose a novel metasurface waveguide structure acting as a transverse mode selective back-reflector for BALs. In order to effectively inverse design such a structure, a digital adjoint algorithm is introduced to adapt the considerably large design area and the high degree of freedom. As a proof of the concept, a device structure with a design area of 40 × 20 μm2 is investigated. The simulation results exhibit high fundamental mode reflection (above 90%), while higher-order transverse mode reflections are suppressed below 0.2%. This is, to our knowledge, the largest device structure designed based on the inverse method. We exploited such a device and the method and further investigated the device's robustness and feasibility of the inverse method. The results are elaborately discussed. [ABSTRACT FROM AUTHOR]