CRITICAL EXTINCTION EXPONENTS FOR POLYTROPIC FILTRATION EQUATIONS WITH NONLOCAL SOURCE AND ABSORPTION

In this article, by applying the super-solution and sub-solution methods, instead of energy estimate methods, the authors investigate the critical extinction exponents for a polytropic filtration equation with a nonlocal source and an absorption term, and give a classification of the exponents and coefficients for the solutions to vanish in finite time or not, which improve one of our results （Applicable Analysis, 92（2013）, 636-650） and the results of Zheng et al （Math. Meth. Appl. Sci., 36（2013）, 730-743）.

Hyperspectral Image Super-Resolution Network Based on Reinforcing Inter-Spectral Incremental Information

Hyperspectral images typically have high spectral resolution but low spatial resolution,which impacts the reliability and accuracy of subsequent applications,for example,remote sensingclassification and mineral identification.But in traditional methods via deep convolution neural net-works,indiscriminately extracting and fusing spectral and spatial features makes it challenging toutilize the differentiated information across adjacent spectral channels.Thus,we proposed a multi-branch interleaved iterative upsampling hyperspectral image super-resolution reconstruction net-work(MIIUSR)to address the above problems.We reinforce spatial feature extraction by integrat-ing detailed features from different receptive fields across adjacent channels.Furthermore,we pro-pose an interleaved iterative upsampling process during the reconstruction stage,which progres-sively fuses incremental information among adjacent frequency bands.Additionally,we add twoparallel three dimensional(3D)feature extraction branches to the backbone network to extractspectral and spatial features of varying granularity.We further enhance the backbone network’sconstruction results by leveraging the difference between two dimensional(2D)channel-groupingspatial features and 3D multi-granularity features.The results obtained by applying the proposednetwork model to the CAVE test set show that,at a scaling factor of×4,the peak signal to noiseratio,spectral angle mapping,and structural similarity are 37.310 dB,3.525 and 0.9438,respec-tively.Besides,extensive experiments conducted on the Harvard and Foster datasets demonstratethe superior potential of the proposed model in hyperspectral super-resolution reconstruction.

Linear Active Disturbance Rejection Control and Stability Analysis for Modular Multilevel Converters Under Weak Grid

The modular multilevel converters(MMCs) are popularly used in high-voltage direct current(HVDC) transmission systems. However, for the direct modulation based MMC, its complex internal dynamics and the interaction with the grid impedance would induce the frequency coupling effect, which may lead to instability issues, especially in the case of weak grid. To effectively suppress the sub-and super-synchronous oscillations, this paper proposes a linear active disturbance rejection control(LADRC) based MMC control strategy. The LADRC mainly consists of the linear extended state observer(LESO) and the linear state error feedback(LSEF). And it is a potential method to enhance the system stability margin, attributing to its high anti-interference capability and good tracking performance. Thereupon, the system small-signal impedance model considering frequency coupling is established. And the effect of the introduction of the LADRC on the system stability is further investigated using the Nyquist criterion. Particularly, the influences of key control parameters on the stability are discussed in detail. Meanwhile, the impact of LADRC on the transient performance is explored through closed-loop zero poles. Finally, the correctness of the theoretical analysis and the effectiveness of the proposed control strategy are verified via electromagnetic simulations.

Expression patterns and functional divergence of homologous genes accompanied by polyploidization in cotton(Gossypium hirsutum L.)

Naturally allotetraploid cotton has been widely used as an ideal model to investigate gene expression remodeling as a consequence of polyploidization.However,the global gene pattern variation during early fiber development was unknown.In this study,through RNA-seq technology,we comprehensively investigated the expression patterns of homologous genes between allotetraploid cotton(G.hirsutum)and its diploid progenitors(G.arboreum and G.raimondii)at the fiber early development stage.In tetraploid cotton,genes showed expression level dominance(ELD)bias toward the A genome.This phenomenon was explained by the up-/downregulation of the homologs from the nondominant progenitor(D genome).Gene ontology(GO)enrichment results indicated that the ELD-A genes might be a prominent cause responsible for fiber property change through regulating the fatty acid biosynthesis/metabolism and microtubule procession,and the ELD-D genes might be involved in transcription regulation and stress inducement.In addition,the number and proportion of completely A-and D-subfunctionalized gene were similar at different fiber development stages.However,for neofunctionalization,the number and proportion of reactivated D-derived genes were greater than those of A at 3 and 5 DPA.Eventually,we found that some homologous genes belonging to several specific pathways might create novel asymmetric transcripts between two subgenomes during polyploidization and domestication process,further making the fiber property meet the human demands.Our study identified determinate pathways and their involved genes between allotetraploid cotton and their progenitors at early fiber development stages,providing new insights into the mechanism of cotton fiber evolution.

Impedance Modeling and Stability Factor Assessment of Grid-connected Converters Based on Linear Active Disturbance Rejection Control

—With the increase of converter-based renewable energy generation connected into the power grid, the interaction between renewable energy and grid impedance has introduced lots of new issues, among which the sub-and super-synchronous oscillation phenomenon makes a big concern. The linear active disturbance rejection control(LADRC) is a potential way to improve the damping characteristics of the grid-connected system, but the key factors and influencing mechanism on system stability are unknown. This paper establishes the equivalent impedance and coupling admittance models of a typical three-phase grid-connected converter. Then, the influence of the key factors such as the bandwidth of the LADRC and grid impedance on the stability and frequency coupling effect is assessed in detail. Finally, the theoretical analysis results are verified by simulations and experiments.