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Al-Li alloy has been widely used in aerospace field attribute to the advantages of lower density, higher strength, damage tolerance and corrosion resistance. Dynamic recrystallization phenomena exist in Al-Li alloy during hot deformation. This paper overviews the dynamic recrystallization behavior occurring in hot processing of Al-Li alloy. The research history of dynamic recrystallization is summarized, together with the key factors that influencing the dynamic recrystallization processes including stacking fault energy, grain size, hot processing conditions and secondary particles. The nucleation mechanisms and conditions of discontinuous dynamic recrystallization, continuous dynamic recrystallization and geometric dynamic recrystallization are depicted and analyzed respectively, followed by a discussion on the effects of the forward three dynamic recrystallization mechanisms regarding the mechanical properties and microstructure. Ultimately, the unsolved and challenging scientific and technological issues are highlighted with some aspects desiring further exploration. It is feasible to provide ideas and inspiration for scholars to better comprehend dynamic recrystallization mechanisms during the hot deformation of Al-Li alloy with the assistance of electron backscatter diffraction and transmission electron microscopy characterization methods.

To address the technical problems of target detection and identification of missile-borne radar in the background of strong ground clutter, we propose to combine the high resolution range profile (HRRP) technology and Doppler beam sharpening (DBS) technology to carry out two-dimensional high-resolution imaging of the ground to improve the performance of radar target detection and identification in the presence of clutter. The method uses the linear frequency modulation stepped frequency (LFM-SF) signal as the basic waveform. Firstly, the Doppler effect caused by the platform speed is discussed in detail and corrected. Then, HRRP sequences corresponding to each frame are obtained through distance profile extraction, and aiimuth high resolution is achieved using fast Fourier transform (FFT). Finally, motion compensation is applied to the errors caused by the platform in actual light conditions, completing the two-dimensional resolution of the area within the beam. The processing of measured data has verified the effectiveness and practicality of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Taking plant indigo extract as the research object, the research progress and trend of the detection methods for the main effective components at home and abroad were reviewed. The main components and their functions of plant indigo extract such as indigo and indirubin were summarized. The analytical examination methods of indigo extract were reviewed, mainly including high performance liquid chromatography, thin layer chromatography, thin layer scanning, dual wavelength spectrophotometry, titration analysis, gas chromatography-mass spectrometry and the combination of multiple detection methods. The application of high performance liquid chromatography ( selection of chromatographic column, mobile phase, detection wavelength and evaluation parameters) was emphatically analyzed. At the same time, the problems existed in the present analysis methods were analyzed, and the future development trends of the indigo extract analysis and detection were predicted. [ABSTRACT FROM AUTHOR]

Shandong tobacco leaves were fermented by Enterobacter cloacae F8-2 and Acinetobacter nosocomialis 7S-2 mixed bacteria. The sensory quality, chemical composition and chemical composition of tobacco smoke and microbial community on tobacco leaf surface before and after fermentation were studied. The results showed that when Enterobacter and Acinetobacter were mixed in 1:1 fermentation for 24 h, the aroma of the tobacco leaf increased and the impurity of the tobacco leaf decreased most significantly. After fermentation, methylheptenone, dihydrotomarone and 5-methylfurfural increased by 89.22%, 35.67% and 33.93%, respectively. Nerolol, solanone and acyl alcohol in tobacco smoke increased by 78.01%, 46.83% and 45.95%, respectively. Mixed fermentation had a great impact on the bacterial community on the surface of tobacco leaves, and the microorganisms cooperated with each other in fermentation and symbiosis. At the same time, Enterobacter and Acinetobacter may be related to the production of aromatic substances such as benzaldehyde and methyl heptene ketone. [ABSTRACT FROM AUTHOR]

This paper analyzed literatures on the specificity study of electroencephalogram (EEG) in the diagnosis of depression since 2010 to 2020, summarized the recent research directions in this field and prospected the future research hotspots at home and abroad. Based on databases of China National Knowledge Infrastructure (CNKI) and the core collection of Web of Science (WOS), CiteSpace software was used to analyze the relevant literatures in this research field. The number of relevant literatures, countries, authors, research institutions, key words, cited literatures and periodicals related to this research were analyzed, respectively, to explore research hotspots and development trends in this field. A total of 2 155 articles were included in the WOS database. The most published institution was the University of Toronto, the most published country was the United States, China occupied the third place, and the hot keywords were anxiety, disorder, brain and so on. A total of 529 literatures were included and analyzed in CNKI database. The institution with the most publications was the Mental Health Center of West China Hospital of Sichuan University, and the hot keywords were EEG signal, event-related potential, convolutional neural network, schizophrenia, etc . This study finds that EEG study of depression is developing rapidly at home and abroad. Research directions in the world mainly focus on exploring the characteristics of spontaneous EEG rhythm and nonlinear dynamic parameters during sleep in depressed patients. In addition, synchronous transcranial magnetic stimulation (TMS) and EEG technologies also attract much attention abroad, and the future research hotspot will be on the mechanism of EEG on patients with major depression. Domestic research directions mainly focus on the classification of resting EEG and the control study of resting EEG power spectrum entropy in patients with schizophrenia and depression, and future research hotspot is the basic and clinical EEG study of depressed patients complicated with anxiety.

As the main structural components of cellular and sub-cellular membranes, lipids are a major source of energy and play an important role in various biological processes such as cellular signaling. Lipid profiling has attracted increasing attention in recent years, and chromatography-mass spectrometry techniques for lipid profiling occupy a dominant position in this regard. Sample preparation, which aims at enriching trace substances and reducing matrix interferences, is a crucial step in the analysis of lipids for the intricacy of sample matrices. Here, we review recent developments in sample preparation techniques based on chromatography-mass spectrometry and their application to lipid profiling. Various sample preparation techniques are described and summarized. The extraction methods based on liquid phase included liquid-liquid extraction and single organic solvent extraction. The extraction methods based on solid phase involved solid-phase extraction and solid-phase microextraction. The field-assisted extraction methods cover supercritical fluid extraction, pressurized liquid extraction, microwave-assisted extraction, and ultrasound-assisted extraction. Moreover, online coupling sample preparation methods and sample preparation methods for in vivo lipid analysis are presented. Finally, the problems and trends in sample preparation techniques for lipid profiling based on chromatography-mass spectrometry are discussed. It is believed that efficient development of sample preparation techniques would help improve the sensitivity and selectivity of lipid profiling as well as the analysis speed.