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Effects of layer interactions on instantaneous stability of finite Stokes flows

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Applied Mathematics and Mechanics(English Edition) 2024年第1期45卷 69-84页

作者： chen ZHAO Zhenli chen c.T.MUTASA Dong LI School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China

The stability analysis of a finite Stokes layer is of practical importance in flow control. In the present work, the instantaneous stability of a finite Stokes layer with layer interactions is studied via a linear stability analysis of the frozen phases of the base flow. The oscillations of two plates can have different velocity amplitudes, initial phases, and frequencies. The effects of the Stokes-layer interactions on the stability when two plates oscillate synchronously are analyzed. The growth rates of two most unstable modes when δ ckness and the half height of the channel, respectively. However, their vorticities are different. The vorticity of the most unstable mode is symmetric, while the other is asymmetric. The Stokes-layer interactions have a destabilizing effect on the most unstable mode when δ ct when δ > 0.68. However, the interactions always have a stabilizing effect on the other unstable mode. It is explained that one of the two unstable modes has much higher dissipation than the other one when the Stokes-layer interactions are strong. We also find that the stability of the Stokes layer is closely related to the inflectional points of the base-flow velocity profile. The effects of inconsistent velocity-amplitude, initial phase, and frequency of the oscillations on the stability are analyzed. The energy of the most unstable eigenvector is mainly distributed near the plate of higher velocity amplitude or higher oscillation frequency. The effects of the initial phase difference are complicated because the base-flow velocity is extremely sensitive to the initial phase.

关键词： finite Stokes layer instantaneous stability Stokes-layer interaction asynchronous oscillation

Sensitivity and inter-observer variability for capsule endoscopy image analysis in a cohort of novice readers

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World Journal of Gastroenterology 2006年第8期12卷 1249-1254页

作者： gary c chen Pedram Enayati Tam Tran Mary Lee-Henderson clifford Quan Gareth Dulai Ian Arnott James Sul Rome Jutabha UcLA center for Small Bowel Diseases UCLA Medical CenterLos AngelesCAUnited States Cedars-Sinai Medical CenterLos AngelesCAUnited States UcLA center for Small Bowel Diseases UCLA Medical CenterLos AngelesCAUnited States David Geffen School of Medicine at UCLALos AngelesCAUnited States

AIM： To determine the performance of novice readers （4^th year medical students） for detecting capsule endoscopy findings. METHODS： Ten capsule endoscopy cases of small bowel lesions were administered to the readers. Gold standard findings were pre-defined by gastroenterologists. Ten gold standard ＂targets＂ were identified among the 10 cases. Readers were given a 30-min overview of Rapid Reader software and instructed to mark any potential areas of abnormalities. A software program was developed using SAS to analyze the thumbnailed findings. RESULTS： The overall sensitivity for detecting the gold standard findings was 80%. As a group, at least 5 out of 10 readers detected each gold standard finding per recording. All the gold standard targets were identified when the readers＇ results were combined. Incidental finding/false positive rate ranged between 8.2-59.8 per reader. cONcLUSION： A panel of medical students with minimal endoscopic experience can achieve high sensitivity in detecting lesions on capsule endoscopy. A group of novice readers can pre-screen recordings to thumbnail potential areas of small bowel lesions for further review. These thumbnails must be reviewed to determine the clinical relevance. Further studies are ongoing to assess other cohorts.

关键词： capsule endoscopy analysis Small bowel lesions Novice readers Sensitivity

Local MFS Matrix Decomposition Algorithms for Elliptic BVPs in Annuli

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NUMERIcAL MATHEMATIcS-THEORY METHODS AND APPLIcATIONS 2024年第1期17卷 93-120页

作者： chen, c. S. Karageorghis, Andreas Lei, Min Univ Southern Mississippi Sch Math & Nat Sci Hattiesburg MS 39406 USA Univ cyprus Dept Math & Stat POB 20537 CY-1678 Nicosia Cyprus Taiyuan Univ Technol Coll Math Taiyuan 030024 Peoples R China

We apply the local method of fundamental solutions (LMFS) to boundary value problems (BVPs) for the Laplace and homogeneous biharmonic equations in annuli. By appropriately choosing the collocation points, the LMFS discretization yields sparse block circulant system matrices. As a result, matrix decomposition algorithms (MDAs) and fast Fourier transforms (FFTs) can be used for the solution of the systems resulting in considerable savings in both computational time and storage requirements. The accuracy of the method and its ability to solve large scale problems are demonstrated by applying it to several numerical experiments.

关键词： Local method of fundamental solutions Poisson equation biharmonic equation matrix decomposition algorithms fast Fourier transforms BOUNDARY-VALUE-PROBLEMS FUNDAMENTAL-SOLUTIONS RBF ALGORITHMS

Dynamic Event-Triggered consensus control for Input constrained Multi-Agent Systems With a Designable Minimum Inter-Event Time

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IEEE/cAA Journal of Automatica Sinica 2024年第3期11卷 649-660页

作者： Meilin Li Yue Long Tieshan Li Hongjing Liang c.L.Philip chen the School of Automation Engineering University of Electronic Science and Technology of ChinaChengdu 611731China IEEE the Yangtze Delta Region Institute University of Electronic Science and Technology of ChinaHuzhou 313000 the Laboratory of Electromagnetic Space cognition and Intelligent control Beijing 100089China the School of computer Science and Engineering South China University of TechnologyGuangzhou 510006

This paper investigates the consensus control of multi-agent systems(MASs) with constrained input using the dynamic event-triggered mechanism(ETM).consider the MASs with small-scale networks where a centralized dynamic ETM with global information of the MASs is first ***,a distributed dynamic ETM which only uses local information is developed for the MASs with large-scale *** is shown that the semi-global consensus of the MASs can be achieved by the designed bounded control protocol where the Zeno phenomenon is eliminated by a designable minimum inter-event *** addition,it is easier to find a trade-off between the convergence rate and the minimum inter-event time by an adjustable ***,the results are extended to regional consensus of the MASs with the bounded control *** simulations show the effectiveness of the proposed approach.

关键词： constrained input designable minimum inter-event time directed communication topology dynamic event-triggered mechanism MASs consensus control

A Bayesian Mixture Model Approach to Disparity Testing

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Applied Mathematics 2024年第3期15卷 214-234页

作者： gary c. McDonald Department of Mathematics and Statistics Oakland University Rochester USA

The topic of this article is one-sided hypothesis testing for disparity, i.e., the mean of one group is larger than that of another when there is uncertainty as to which group a datum is drawn. For each datum, the uncertainty is captured with a given discrete probability distribution over the groups. Such situations arise, for example, in the use of Bayesian imputation methods to assess race and ethnicity disparities with certain insurance, health, and financial data. A widely used method to implement this assessment is the Bayesian Improved Surname Geocoding (BISG) method which assigns a discrete probability over six race/ethnicity groups to an individual given the individual’s surname and address location. Using a Bayesian framework and Markov chain Monte carlo sampling from the joint posterior distribution of the group means, the probability of a disparity hypothesis is estimated. Four methods are developed and compared with an illustrative data set. Three of these methods are implemented in an R-code and one method in WinBUGS. These methods are programed for any number of groups between two and six inclusive. All the codes are provided in the appendices.

关键词： Bayesian Improved Surname and Geocoding (BISG) Mixture Likelihood Function Posterior Distribution Metropolis-Hastings Algorithms Random Walk chain Independence chain Gibbs Sampling WinBUGS

Adaptive neural network control of a 2-DOF helicopter system considering input constraints and global prescribed performance

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Science china(Information Sciences) 2024年第7期67卷 224-239页

作者： Zhijia ZHAO Jiale WU Zhijie LIU We HE c.L.Philip chen School of Mechanical and Electrical Engineering Guangzhou University School of Intelligence Science and Technology and Key Laboratory of Intelligent Bionic Unmanned Systems of Ministry of Education University of Science and Technology Beijing School of computer Science and Engineering South China University of Technology Pazhou Lab

In this study, an adaptive neural network(NN) control is proposed for nonlinear two-degree-offreedom(2-DOF) helicopter systems considering the input constraints and global prescribed ***, radial basis function NN(RBFNN) is employed to estimate the unknown dynamics of the helicopter system. Second, a smooth nonaffine function is exploited to approximate and address nonlinear constraint functions. Subsequently, a new prescribed function is proposed, and an original constrained error is transformed into an equivalent unconstrained error using the error transformation and barrier function transformation methods. The analysis of the established Lyapunov function proves that the controlled system is globally uniformly bounded. Finally, the simulation and experimental results on a constructed Quanser's test platform verify the rationality and feasibility of the proposed control.

关键词： adaptive NN control 2-DOF helicopter global prescribed performance input constraints

Mechanistic insight into cr(Ⅵ)retention by Si-containing ferrihydrite

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Journal of Environmental Sciences 2024年第5期139卷 217-225页

作者： Ying Hu Qiang Xue Honghan chen Huaming Guo Kenneth c.carroll Song Wang MOE Key Laboratory of Groundwater circulation and Environmental Evolution School of Water Resources and EnvironmentChina University of Geosciences(Beijing)Beijing 100083China Beijing Key Laboratory of Water Resources and Environmental Engineering School of Water Resources and EnvironmentChina University of GeosciencesBeijing 100083China State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesBeijing 100083China Plant&Environmental Science New Mexico State UniversityNM 88003USA Institute of Theoretical chemistry College of ChemistryJilin UniversityChangchun 130023China

Hexavalent chromium[cr(Ⅵ)]causes serious harm to the environment due to its high toxicity,solubility,and ***(Fh)are the main adsorbent and trapping agent of cr(Ⅵ)in soils and aquifers,and they usually coexist with silicate(Si),forming Si-containing ferrihydrite(Si-Fh)***,the mechanism of cr(Ⅵ)retention by Si-Fh mixtures is poorly *** this study,the behaviors and mechanisms of cr(Ⅵ)adsorption onto Si-Fh with different Si/Fe molar ratios was *** electron microscope,Fourier transform infrared spectroscopy,X-ray diffraction,X-ray photoelectron spectroscopy,and other techniques were used to characterize Si-Fh and cr(Ⅵ)-loading of *** results show that specific surface area of Si-Fh increases gradually with increasing Si/Fe ratios,but cr(Ⅵ)adsorption on Si-Fh decreases with increasing Si/Fe *** is because with an increase in Si/Fe molar ratio,the point of zero charge of Si-Fh gradually decreases and electrostatic repulsion between Si-Fh and cr(Ⅵ)***,the complexation of cr(Ⅵ)is enhanced due to the increase in adsorbed hydroxyl(A-OH-)on Si-Fh with increasing Si/Fe molar ratio,which partly counteracts the effect of the electrostatic ***,the increase in the electrostatic repulsion has a greater impact on adsorption than the additional complexation with *** functional theory calculation further supports this observation,showing the increases in electron variation of bonding atoms and reaction energies of inner spherical complexes with the increase in Si/Fe ratio.

关键词： Hexavalent chromium Ferrihydrite Si/Fe ratio cr(Ⅵ)Adsorption

Liquefaction susceptibility and deformation characteristics of saturated coral sandy soils subjected to cyclic loadings-a critical review

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Earthquake Engineering and Engineering Vibration 2024年第1期23卷 261-296页

作者： chen Guoxing Qin You Ma Weijia Liang Ke Wu Qi c.Hsein Juang Institute of Geotechnical Engineering Nanjing Tech UniversityNanjing 210009China civil Engineering and Earthquake Disaster Prevention center of Jiangsu Province Nanjing 210009China School of Mechanical Engineering Nanjing University of Science and TechnologyNanjing 210094China college of civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 210016China Glenn Department of civil Engineering Clemson UniversityClemsonSC 29634USA

coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical *** to the unique marine depositional environment of coral sandy soils,the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering *** paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three *** focus of coverage includes the contractive-dilative behavior,the pattern of excess pore-water pressure(EPWP)generation and the liquefaction mechanism and liquefaction resistance,the small-strain shear modulus and strain-dependent shear modulus and damping,the cyclic softening feature,and the anisotropic characteristics of undrained responses of saturated coral sandy *** particular,the advances made in the past decades are reviewed from the following aspects:(1)the characterization of factors that impact the mechanism and patterns of EPWP build-up;(2)the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient;(3)the establishment of the invariable form of strain-based,stress-based,or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction;(4)the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus;and(5)the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation *** gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjecte

关键词： liquefaction susceptibility dynamic deformation characteristics coral sandy soil cyclic loading review and prospect

The anti-inflammatory effects of exercise on autoimmune diseases:A 20-year systematic review

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Journal of Sport and Health Science 2024年第3期13卷 353-367,I0001页

作者： Beibei Luo Dao Xiang Xiaorong Ji Xuan chen Rui Li Shuxin Zhang Yujun Meng David c.Nieman Peijie chen School of Exercise and Health Shanghai University of SportShanghai 200438China Shanghai Key Laboratory of Human Performance Shanghai University of SportShanghai 200438China Department of Diving and Hyperbaric Medicine Naval Medical CenterShanghai 200433China National Key Laboratory of Immunity and Inflammation Naval Medical UniversityShanghai 200433China Human Performance Laboratory Appalachian State UniversityNorth Carolina Research CampusKannapolisNC 28081USA Research Institute for Doping control Shanghai University of SportShanghai 200438China

Background:The anti-inflammatory effect of exercise may be an underlying factor in improving several autoimmune *** aim of this systematic review was to examine the evidence on the role of exercise training in mitigating inflammation in adolescents and adults with autoimmune ***:PubMed,Web of Science,and Embase databases were systematically reviewed for related studies published between January 1,2003,and August 31,*** randomized and non-randomized controlled trials of exercise interventions with autoimmune disease study participants that evaluated inflammation-related biomarkers were *** quality of evidence was assessed using the Tool for the assEssment of Study qualiTy and reporting in EXercise scale and cochrane bias risk ***:A total of 14,565 records were *** screening the titles,abstracts,and full texts,87 were eligible for the systematic *** studies were conducted in 25 different countries and included a total of 2779 participants(patients with autoimmune disease,in exercise or control groups).Overall,the evidence suggests that inflammation-related markers such as c-reactive protein,interleukin 6,and tumor necrosis factor a were reduced by regular exercise *** exercise interventions combined with multiple exercise modes were associated with greater ***:Regular exercise training by patients with autoimmune disease exerts an anti-inflammatory *** systematic review provides support for the promotion and development of clinical exercise intervention programs for patients with autoimmune *** patients with autoimmune disease can safely adopt moderate exercise training protocols,but changes in inflammation biomarkers will be modest at *** exercise interventions are ineffective or even modestly but transiently pro-inflammatory.

关键词： Autoimmune diseases cytokines Inflammation Physical activity Training