A stratified method to transient stability assessment in large-scale power systems based on mutual information theory and artificial intelligence algorithm is proposed in this paper. A set of inter-complementary dynamic stability features are picked up one by one through the maximum-relevance minimum-redundancy (MRMR) algorithm. Besides, multiple extreme learning machines (ELMs) are trained based on the generated feature datasets. Because of the high requirement of evaluation speed in practical application, in order to balance the contradiction between assessment speed and accuracy, a hierarchical assessment structure is adopted in the final assessment process. Different ensemble classifiers with different response times are trained to construct different layers. The performance of the proposed technique is tested in the IEEE-39 bus system and a practical 1648 bus system provided by PSS/E. The experimental results indicate that, compared to other traditional methods, the proposed hierarchical method can give a more accurate result in a shorter period of time. As an efficient method, it is suitable for on-line transient stability assessment.
Based on serial channelization and coherent detection, a radio-frequency (RF) measurement scheme with a Nyquist-bandwidth detector is proposed and experimentally demonstrated. With a wavelength scanning structure, multiple RF channels serial in the time domain are implemented. A coherent receiving module based on an optical hybrid and balanced photodetectors (BPDs) is constructed to reduce the receiver bandwidth and the bandwidth of the follow-up electronic devices. In this paper, a six-channel 3-GHz-spacing channelizer, with 18-GHz receiving bandwidth and 1.5-GHz BPD, is demonstrated. In addition, multifrequency signals and a linear frequency modulation signal with the slope of 4.53 MHz/s are tested.
A serial photonic channelized radio frequency (RF) measurement scheme is proposed and experimentally demonstrated. This scheme can be used for instantaneous multiple-frequency measurement and capturing key parameters of linear frequency modulation signals. Based on high-speed wavelength scanning, this photonic RF channelizer works serially in time domain, and each wavelength labels a certain RF channel. With only one low-bandwidth photodetector (PD), we can implement multiple channel RF frequency measurements, which have a much simpler structure compared with parallel channelized schemes using broadband filter-bank and multiple PDs.
Ligusticum chuanxiong (LC) is a Chinese materia medica which is widely used in clinical settings to treat headaches, blood extravasation, and arthritis. Recent studies demonstrate that LC possesses versatile pharmacological functions, including antiatherosclerosis, antimigraine, antiaging, and anticancer properties. Moreover, LC also shows protective effects in the progression of different diseases that damage somatic cells. Oxidative stress and inflammation, which can induce somatic cell apoptosis, are the main factors associated with an abundance of diseases, whose progresses can be reversed by LC. In order to comprehensively review the molecular mechanisms associated with the protective effects of LC, we collected and integrated all its related studies on the anti-inflammatory, antioxidant, and antiapoptotic effects. The results show that LC could exhibit the mentioned biological activities by modulating several signaling pathways, specifically the NF-κB, Nrf2, protein kinase, and caspase-3 pathways. In future investigations, the pharmacokinetic properties of bioactive compounds in LC and the signaling pathway modulation of LC could be focused.
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