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Performance analysis of two-dimensional DOA estimation for uniform circular array
Chen Liupeng,Mou Weihua,Lv Zhicheng,Zhang Yonghu,Hu Lizhi,Ou Gang 한국통신학회 2023 ICT Express Vol.9 No.5
Perturbation analysis of direction of arrival (DOA) estimation has been studied mostly on one-dimensional arrays rather than planar arrays, which remains room for exploration. For uniform circular arrays with various model errors, we establish the corresponding system model. Then a performance analysis of the two-dimensional MUSIC algorithm is proposed by first-order error analysis and verified by simulation. The results show that the root-mean-squared error of DOA estimation is proportional to the standard deviation of the model errors, including gain-phase errors, sensor position errors, and mutual coupling effect.
Infuence of Dynamic Characteristics of Induction Motor on Voltage Sag Caused by Short Circuit Fault
Jiming Chen,Hai Zuo,Qianyu Yu,Lizhi Qi,Mingxiao Zhu 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.4
Voltage sag is a signifcant problem that afects the quality of power, and some researches have been performed on this theme. The characteristic of load is an important factor afecting the voltage sag, which is rarely studied. This paper investigates the infuence of dynamic characteristics of induction motor on voltage sag caused by short circuit fault. The analytic expression of induction electromotive force is derived by space vector method. The mechanism of amplitude and waveform changes caused by dynamic load characteristics of induction motor are analyzed. The results indicate that the voltage at the load terminal of the induction motor is higher than that at the static load during the sag. Besides, the voltage sag waveform is not in rectangular shape. The static load terminal voltage returns to normal value quickly, while the voltage at the load terminal of the induction motor needs about 200 ms after the fault is removed. Induction motors can reduce the magnitude of voltage sags caused by short circuit faults, but will extend the duration. At the same time, the bigger the induction motor capacity is, the longer the voltage recovery time after sag is.
MICROSTRUCTURE AND TRIBOLOGY OF $TiB_2$ AND $TiB_2$-TiN DOUBLE-LAYER COATINGS
Yang, Yunjie,Chen, Lizhi,Zheng, Zhihong,Wang, Xi,Liu, Xianghuai The Korean Vacuum Society 1995 Applied Science and Convergence Technology Vol.4 No.s2
$TiB_2$-TiN double-layer coating have been prepared by ion beam enhanced deposition. AES, XRD, TEM and HRTEM were employed to characterize the $TiB_2$ layer. The microhardness of the coatings was evaluated by an ultra low-load microhardness indenter system, and the tribological behavior was examined by a ball-on-disc tribology wear tester. It was found that in a single titanium diboride layer, the composition is uniform along the depth of the film, and it is mainly composed of nanocrystalline $TiB_2$ with hexagonal structure, which resulted from the ion bombardment during the film growth. The hardness of the $TiB_2$ films increases with increasing ion energy, and approaches a maximum value of the $TiB_2$ films increases with increasing ion energy, and approaches a maximum value of 39 Gpa at ion energy of 85 keV. The tribological property of the TiB2 films is also improved by higher energy of 85keV. The tribological property of the $TiB_2$ films is also improved by higher energy ion beam bombardment. There is no major disparity in the mechanical properties of double-layer $TiB_2$/TiN coatings and TiN/$TiB_2$ coatings. Both show an improved wear resistance compared with single-layer $TiB_2$ films. The adhesion of double-layer coatings is also superior to that of single-layer films.
Image Captioning with Synergy-Gated Attention and Recurrent Fusion LSTM
Yang, You,Chen, Lizhi,Pan, Longyue,Hu, Juntao Korean Society for Internet Information 2022 KSII Transactions on Internet and Information Syst Vol.16 No.10
Long Short-Term Memory (LSTM) combined with attention mechanism is extensively used to generate semantic sentences of images in image captioning models. However, features of salient regions and spatial information are not utilized sufficiently in most related works. Meanwhile, the LSTM also suffers from the problem of underutilized information in a single time step. In the paper, two innovative approaches are proposed to solve these problems. First, the Synergy-Gated Attention (SGA) method is proposed, which can process the spatial features and the salient region features of given images simultaneously. SGA establishes a gated mechanism through the global features to guide the interaction of information between these two features. Then, the Recurrent Fusion LSTM (RF-LSTM) mechanism is proposed, which can predict the next hidden vectors in one time step and improve linguistic coherence by fusing future information. Experimental results on the benchmark dataset of MSCOCO show that compared with the state-of-the-art methods, the proposed method can improve the performance of image captioning model, and achieve competitive performance on multiple evaluation indicators.
Multiple-mode Adaptive State Estimator for Nonlinear Switched Systems
Junqi Yang,Yantao Chen,Lizhi Cui 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.4
This paper deals with the issue of state estimator design for nonlinear switched systems. A multiplemodeadaptive estimator is proposed under mode-dependent average dwell time (MDADT) switching, and theswitching signal with MDADT constraint is also obtained to guarantee the exponential stability of estimation errordynamics, where the Lipschitz constant may be unknown since it is adaptively adjusted by designing an adaptationlaw. Based on both Lyapunov stable theory and the feasible solution of an optimization problem with linear matrixinequality constraint, the gain matrices and switching signals are provided, respectively. The sufficient conditionsof the existence of multiple-mode adaptive switched estimator are also derived. Meanwhile, the above methodsare also extended to the case of the average dwell time (ADT) switching, and an algorithm is given to summarizethe implementation of the proposed estimators. Finally, the effectiveness of the designed methods is illustrated bysimulation examples.
Yongqing Cao,Tao Zeng,Wei Han,Xueying Ma,Tiantian Gu,Li Chen,Yong Tian,Wenwu Xu,Jianmei Yin,Guohui Li,Lizhi Lu,Shuangbao Gun Asian Australasian Association of Animal Productio 2024 Animal Bioscience Vol.37 No.1
Objective: Tibetan chickens, which have unique adaptations to extreme high-altitude environments, exhibit phenotypic and physiological characteristics that are distinct from those of lowland chickens. However, the mechanisms underlying hypoxic adaptation in the liver of chickens remain unknown. Methods: RNA-sequencing (RNA-Seq) technology was used to assess the differentially expressed genes (DEGs) involved in hypoxia adaptation in highland chickens (native Tibetan chicken [HT]) and lowland chickens (Langshan chicken [LS], Beijing You chicken [BJ], Qingyuan Partridge chicken [QY], and Chahua chicken [CH]). Results: A total of 352 co-DEGs were specifically screened between HT and four native lowland chicken breeds. Gene ontology and Kyoto encyclopedia of genes and genomes enrichment analyses indicated that these co-DEGs were widely involved in lipid metabolism processes, such as the peroxisome proliferator-activated receptors (PPAR) signaling pathway, fatty acid degradation, fatty acid metabolism and fatty acid biosynthesis. To further determine the relationship from the 352 co-DEGs, protein-protein interaction network was carried out and identified eight genes (ACSL1, CPT1A, ACOX1, PPARC1A, SCD, ACSBG2, ACACA, and FASN) as the potential regulating genes that are responsible for the altitude difference between the HT and other four lowland chicken breeds. Conclusion: This study provides novel insights into the molecular mechanisms regulating hypoxia adaptation via lipid metabolism in Tibetan chickens and other highland animals.