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Stability analysis of linear/nonlinear switching active disturbance rejection control based MIMO continuous systems

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Journal of Systems Engineering and Electronics 2021年第4期32卷 956-970页

作者： WAN Hui qi xiaohui LI Jie Department of Unmanned Aerial Vehicle Engineering Army Engineering University of PLAShijiazhuang 050003China The 32nd Research Institute China Electronics Technology Group CorporationShanghai 201800China

In this paper,a linear/nonlinear switching active disturbance rejection control(SADRC)based decoupling control approach is proposed to deal with some difficult control problems in a class of multi-input multi-output(MIMO)systems such as multi-variables,disturbances,and coupling,***,the structure and parameter tuning method of SADRC is introduced into this *** on this,virtual control variables are adopted into the MIMO systems,making the systems *** the SADRC controller is designed for every *** this,a stability analyzed method via the Lyapunov function is proposed for the whole ***,some simulations are presented to demonstrate the anti-disturbance and robustness of SADRC,and results show SADRC has a potential applications in engineering practice.

关键词： linear/nonlinear switching active disturbance rejection control(SADRC) multi-input multi-output(MIMO)continuous system decoupling control stability analysis

Random field characterization of uniaxial compressive strength and elastic modulus for intact rocks

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Geoscience Frontiers 2018年第6期9卷 1609-1618页

作者： Huaxin Liu xiaohui qi School of Civil and Environmental Engineering Nanyang Technological University

Rock properties exhibit spatial variabilities due to complex geological processes such as sedimentation,metamorphism, weathering, and tectogenesis. Although recognized as an important factor controlling the safety of geotechnical structures in rock engineering, the spatial variability of rock properties is rarely quantified. Hence, this study characterizes the autocorrelation structures and scales of fluctuation of two important parameters of intact rocks, i.e. uniaxial compressive strength(UCS) and elastic modulus(EM).UCS and EM data for sedimentary and igneous rocks are collected. The autocorrelation structures are selected using a Bayesian model class selection approach and the scales of fluctuation for these two parameters are estimated using a Bayesian updating method. The results show that the autocorrelation structures for UCS and EM could be best described by a single exponential autocorrelation function. The scales of fluctuation for UCS and EM respectively range from 0.3 m to 8.0 m and from 0.3 m to 8.4 *** results serve as guidelines for selecting proper autocorrelation functions and autocorrelation distances for rock properties in reliability analyses and could also be used as prior information for quantifying the spatial variability of rock properties in a Bayesian framework.

关键词： Uniaxial compressive strength Elastic modulus Scale of fluctuation Autocorrelation function Spatial variability Bayesian approach

Direction navigability analysis of geomagnetic field based on Gabor filter

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Journal of Systems Engineering and Electronics 2018年第2期29卷 378-385页

作者： XIAO Jing DUAN Xiusheng qi xiaohui WANG Jianchen Army Engineering University Shijiazhuang 050003China Government Representative Office Northwestern Polytechnical UniversityXi’an 710065China

Direction navigability analysis is a supplement to the navigability analysis theory, in which extraction of the direction suitable-matching features(DSMFs) determines the evaluation performance. A method based on the Gabor filter is proposed to estimate the direction navigability of the geomagnetic field. First,the DSMFs are extracted based on the Gabor filter’s ***, in the view of pattern recognition, the classification accuracy in fault diagnosis is introduced as the objective function of the hybrid particle swarm optimization(HPSO) algorithm to optimize the Gabor filter’s parameters. With its guidance, the DSMFs are extracted. Finally, a direction navigability analysis model is established with the support vector machine(SVM), and the performances of the models under different objective functions are discussed. Simulation results show the parameters of the Gabor filter have a significant influence on the DSMFs, which, in turn, affects the analysis results of direction navigability. Moreover, the risk of misclassification can be effectively reduced by using the analysis model with optimal Gabor filter parameters. The proposed method is not restricted in geomagnetic navigation, and it also can be used in other fields such as terrain matching and gravity navigation.

关键词： geomagnetic navigation navigability analysis direction navigability Gabor filter direction suitable-matching feature

Physical layer security in multi-antenna cognitive heterogeneous cellular networks: a unified secrecy performance analysis

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Science China(Information Sciences) 2018年第2期61卷 149-163页

作者： xiaohui qi Kaizhi HUANG Bin LI Liang JIN Xinsheng JI National Digital Switching System Engineering & Technological Research Center School of Information and Electronics Beijing Institute of Technology

Cognitive heterogeneous cellular networks(CHCNs) are emerging as a promising approach to next-generation wireless communications owing to their seamless coverage and high network *** this paper, we describe our reliance on multi-antenna technology and a secrecy transmission protocol to ensure the reliability and security of downlink underlay CHCNs. First, we introduce a two-tier CHCN model using a stochastic geometry framework, and derive the probability distribution of the indicator function for a secrecy transmission scheme. We then investigate the connection outage probability, secrecy outage probability(SOP), and transmission SOP of both primary and cognitive users under a secrecy guard scheme and a threshold-based scheme. Furthermore, we reveal some insights into the secrecy performance by properly setting the predetermined access threshold and the radius of detection region for the secrecy transmission scheme. Finally, simulation results are provided to show the influence of the antenna system, eavesdropper density, predetermined access threshold, and radius of the detection region on the reliability and security performance of a CHCN.

关键词： cognitive heterogeneous cellular network physical layer security secrecy guard scheme threshold-based scheme multi-antenna technique

Endoplasmic reticulum stress and cardiovascular diseases

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Journal of Geriatric Cardiology 2009年第1期6卷 49-55页

作者： xiaohui Duan Yongfen qi Chaoshu Tang Institute of Cardiovascular Research Peking University First Hospital Beijing 100034 China Department of Physiology and Pathophysiology Peking University Health Science Center Beijing 100191 China Institute of Cardiovascular Research Peking University First Hospital Beijing 100034 China Department of Physiology and Pathophysiology Peking University Health Science Center Beijing 100191 China

The endoplasmic reticulum (ER) serves several important functions, mainly post-translational modification, folding and assembly of newly synthesized secretary proteins, synthesizing lipids and cellular calcium storage. Various factors can disrupt ER homeostasis and disturb its functions, which leads to the accumulation of unfolded and misfolded proteins and to potential cellular dysfunction and pathological consequences, collectively termed ER stress. Recent progress suggests that ER stress plays a key role in the immune response, diabetes, tumor growth, and some neurodegenerative diseases. In particular, ER stress is involved in several processes of cardiovascular diseases, such as ischemia/reperfusion injury, cardiomyopathy, cardiac hypertrophy, heart failure, and atherosclerosis. Further research on the relation of ER stress to cardiovascular diseases will greatly enhance the understanding of these pathological processes and provide novel avenues to potential therapies.

关键词： endoplasmic reticulum stress cardiovascular diseases

Physical Layer Security of Multi-hop Aided Downlink MIMO heterogeneous Cellular Networks

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China Communications 2016年第S2期13卷 120-130页

作者： xiaohui qi Kaizhi Huang Zhihao Zhong Xiaolei Kang Zhou Zhong National Digital Switching System Engineering & Technological Research Center

This study investigates physical layer security in downlink multipleinput multiple-output(MIMO) multi-hop heterogeneous cellular networks(MHCNs),in which communication between mobile users and base stations(BSs) is established by a single or multiple hops,to address the problem of insufficient security performance of MIMO heterogeneous cellular ***,two-dimensional homogeneous Poisson point processes(HPPPs) are utilized to model the locations of K-tier BSs in MIMO MHCNs and receivers,including those of legitimate users and ***,based on the channel gain distribution and the statistics property of HPPP,the achievable ergodic rates of the main and eavesdropper channels in direct and ad hoc links are derived,***,the secrecy coverage probability and the achievable ergodic secrecy throughput of downlink MIMO MHCNs are explored,and their expressions are ***,the correctness of the theoretical derivation is verified through Monte Carlo simulations.

关键词： multi-hop heterogeneous cellular networks secrecy coverage probability stochastic geometry secrecy throughput

Prediction of interfaces of geological formations using the multivariate adaptive regression spline method

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Underground Space 2021年第3期6卷 252-266页

作者： xiaohui qi Hao Wang Xiaohua Pan Jian Chu Kiefer Chiam School of Civil and Environmental Engineering Nanyang Technological University639798Singapore Building and Construction Authority 200 Braddell Road579700Singapore

The design and construction of underground structures are significantly affected by the distribution of geological *** of the geological interfaces using limited data has been a difficult task.A multivariate adaptive regression spline(MARS)method capable of modeling nonlinearities automatically was used in this study to spatially predict the elevations of geological *** data from two sites in Singapore were used to evaluate the capability of the MARS method for predicting geological *** comparing the predicted values with the borehole data,it is shown that the MARS method has a mean of root mean square error of 4.4 m for the predicted elevations of the Kallang Formation–Old Alluvium *** addition,the MARS method is able to produce reasonable prediction intervals in the sense that the percentage of testing data covered by 95% prediction intervals was close to the associated confidence level,95%.More importantly,the prediction interval evaluated by the MARS method had a non-constant width that appropriately reflected the data density and geological complexity.

关键词： Geological interface Rockhead Multivariate adaptive regression spline Spatial prediction

Assembly and Post-modification of Fe3O4@MIL-100(Fe) for Knoevenagel Condensation

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Chemical Research in Chinese Universities 2018年第4期34卷 655-660页

作者： ZHANG Yanmei ZHANG Fan ZHANG Xiang XU Yingmei qi xiaohui QUAN Chunshan Key Laboratory of Biotechnology and Bioresources Utilization Ministry of Education College of Life Science Dalian Minzu University Dalian 116600 P. R. China

Many efforts have been devoted to the integration of magnetic nanoparticles and metal organic frame- works, which makes it easy and simple to separate the nano-sized metal organic frameworks from liquid phase. Amino-functionalized magnetic metal organic frameworks[Fe3O4@MIL-100（Fe）-NH2] were prepared by a stepwise assembly method followed by post-modification with electron-rich reagent. This magnetic catalyst was characterized by means of X-ray diffraction（XRD）, transmission electron microscopy（TEM）, scanning electron micrnscopy（SEM） and nitrogen adsorption, and tested in Knoevenagel condensation as a base catalyst. The magnetic catalyst exhibits a core-shell structure and can afford a high activity for the Knoevenagel condensation due to its bifunctional property and reduced diffusion limitation. Furthermore, it could be recovered magnetically and recycled three times. Although activity loss was observed in the recycle experiments, it could be reactivated by dispersing in a fresh modifier solution.

关键词： Fe3O4 MIL-100(Fe) Heterogeneous catalyst Knoevenagel condensation Magnetic separation

Chemical Characteristics and Anticoagulant Activities of Two Sulfated Polysaccharides from Enteromorpha linza (Chlorophyta)

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Journal of Ocean University of China 2013年第1期12卷 175-182页

作者： qi xiaohui MAO Wenjun CHEN Yin CHEN Yanli ZHAO Chunqi LI Na WANG Chunyan Key Laboratory of Marine Drugs Ministry of Education Institute of Marine Drug and Food Ocean University of China

Two sulfated polysaccharides, designated MP and SP, were extracted from the marine green alga Enteromorpha linza using hot water and then purified using ion-exchange and size-exclusion chromatography. The anticoagulant activities of MP and SP were examined by determination of their activated partial thromboplastin time （APTT）, thrombin time （TT） and prothrombin time （PT） using human plasma. Results showed that MP and SP were composed of abundant rhamnose with small amounts of xylose and glucuronic acid, whereas SP also contained a small amount of galactose. Approximate molecular weights of MP and SP were 535 and 502 kDa, respectively. As compared with SP, MP had higher contents of sulfate ester （19.0%） and uronic acid （14.9%）. The MP mainly consisted of （1→4）-linked rhamnose residues with partially sulfated groups at the C-3 position, and small amounts of （1→3, 4）-linked rhamnose, （1→2,4）-linked rhamnose, （1→4）-linked glucuronic acid and （1→4）-linked xylose residues. The SP contained abundant （1→4）-linked rhamnose with minor amounts of （1→3）-linked rhanmose, （1→3, 4）-linked rhamnose, （1→2, 4）-linked rhanmose, （1→4）4inked glucuronic acid, （1→4）-linked xylose, and （1→3）-linked galactose residues. The sulfate groups were mainly located at C-3 of （1→4）-linked rhamnose residues. Both MP and SP, in particular the former, effectively prolonged APTT and TT. This work demonstrates that MP and SP have unique structural characteristics distinct from those of other sulfated polysaccharides from Enteromorpha. The MP is a potential source of anticoagulant, and the difference in anticoagulant activities of the two sulfated polysaccharides is directly linked to the discrepancy of their chemical features.

关键词： Marine green alga Enteromorpha linza sulfated polysaccharide chemical characteristic anticoagulant activity