The electronic structure and magnetic properties of Co/Al2O3/Co with O-terminated and Al-terminated interface models of different thicknesses are investigated by first-principles discrete variational ...method with the local-spin-density approximation. Our calculations results show that the magnetic moment of interface Co layer is enhanced for Al-terminated and weakened for O-terminated interface compared with that of bulk Co. For O-terminated interface models, spin polarization at Fermi energy of Co layer at interface exhibits negative and becomes positive for O layer at interface. In contrast, both Co and Al layers at interface possess negative SP for the Al-terminated interface models. We have also found that TMR ratio of Al-terminated interface models is much larger than that of O-terminated interface. In addition, the change of SP with the thickness of insulating layer is in a similar way as that of magnetic moment.
Automatic recognition of marine mammals plays a significant role in the protection of endangered marine species, generally utilizing their vocalizations. In this paper, we propose a novel visual ...feature extraction approach for whale and dolphin signals incorporating variational mode decomposition (VMD) and Hilbert transform (VMD-HT) to construct the high-resolution time-frequency signatures and using gray level co-occurrence matrix (GLCM) to extort image features. Firstly, the objected signals are decomposed by VMD algorithm into multiple intrinsic mode functions (IMFs), which can capture local frequency features precisely. Secondly, the time-frequency signature of the objected signal with high resolution is constructed by linear superposition operation of each IMF time-frequency image depicted through Hilbert transform (HT). Thirdly, the image features are extracted using GLCM. Eventually, support vector machine (SVM) is adopted to validate the classification performance of the proposed method. The experimental results verify that the resolution improvement of time-frequency image attains the correct recognition rate and the proposed method accuracy is higher than the compared method about 11.11%
Insulator fault recognition is a common hidden danger that affects the normal operation of the power system. In recent years, UAV aerial images have been widely used to identify defects in ...insulators. In order to solve the problem of low efficiency caused by manual inspection and traditional image defect detection methods, this paper proposed a modified Faster R-CNN model to improve the accuracy of model detection and reduce the amount of model parameters. Based on the traditional Faster R-CNN detection framework, the proposed method selected ResNet- 50 to replace VGGNet-16 as the feature extraction networks. The database used 781 labeled UAV aerial insulator images, and they are divided into training set, validation set and test set according to the ratio of 6:2:2. The mAP of the modified feature network model reached 62.41%, and the network model parameter size was 25.26M. Compared with the original framework with VGGNet-16 as the feature network, the mAP increased by 3.43% and the parameter amount was compressed by 4.41 times. The results show that the improved algorithm reduces the missed detection rate and false detection rate, and on the basis of improving the recognition accuracy, it can greatly reduce the amount of network parameters. And it can better meet the needs of lightweight network structure in actual scenarios.
The electronic structure and magnetic properties of Co/Al
2O
3/Co with O-terminated and Al-terminated interface models of different thicknesses are investigated by first-principles discrete ...variational method with the local-spin-density approximation. Our calculations results show that the magnetic moment of interface Co layer is enhanced for Al-terminated and weakened for O-terminated interface compared with that of bulk Co. For O-terminated interface models, spin polarization at Fermi energy of Co layer at interface exhibits negative and becomes positive for O layer at interface. In contrast, both Co and Al layers at interface possess negative SP for the Al-terminated interface models. We have also found that TMR ratio of Al-terminated interface models is much larger than that of O-terminated interface. In addition, the change of SP with the thickness of insulating layer is in a similar way as that of magnetic moment.
An efficient intracavity KTA optical parametric oscillator (OPO) driven by diode-end-pumped acousto-optical Q-switched Nd:YVO(4) laser is demonstrated. The mode mismatch between fundamental cavity ...and OPO cavity caused by the thermal lens effect in Nd:YVO(4) crystal as the pump power increased was studied. To lessen mode mismatch, a thermal lens-like cavity mirror made of plane BK7 glass induced by idler absorption was introduced into the OPO cavity. Under a diode pump power of 20 W, a maximum 1535nm light output power of 3.6 W was achieved at the pulse repetition rate of 60 kHz, corresponding to a diode-to-signal conversion efficiency of 18%. This is the highest efficiency reported for eye-safe laser based on intracavity OPO.
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