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An automated approach to calculating the maximum diameters of multiple cutters and their paths for sectional milling of centrifugal impellers on a 4_(1/2)-axis cNc machine

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chinese Journal of Aeronautics 2019年第4期32卷 1030-1039页

作者： Baohai WU zezhong c.chen Ming LUO Dinghua ZHANG Feiyan HAN School of Mechanical Engineering Northwestern Polytechnical University Department of Mechanical Industrial and Aerospace EngineeringConcordia University college of Mechanical Engineering Xi'an University of Science and Technology

Power generators and chemical engineering compressors include heavy and large centrifugal impellers. To produce these impellers in high-speed machining, a 4?-axis milling machine(or a 4-axis machine plus an indexing table) is often used in the industry, which is more rigid than a5-axis milling machine. Since impeller blades are designed with complex B-spline surfaces and impeller channels spaces vary significantly, it is more efficient to use multiple cutters as large as possible to cut a channel in sections and a blade surface in patches, instead of only using a small cutter to machine a whole blade and a channel. Unfortunately, no approach has been established to automatically calculate the largest diameters of cutters and their paths, which include the indexing table angles. To address this problem, an automated and optimization approach is proposed. Based on the structure of a 4?-axis machine, a geometric model for a cutter gouging/interfering the impeller is formulated, and an optimization model of the cutter diameter in terms of the indexing table angle is established at a cutter contact(cc) point on a blade surface. Then, the diameters of the tools,their orientations, and the indexing table angles are optimized, and each tool's paths are generated for machining its corresponding impeller section. As a test, an impeller is efficiently machined with these tools section by section; thus, this approach is valid. It can be directly used in the industry to improve efficiency of machining centrifugal impellers.

关键词： Automated path generation 4_(1/2)-Axis cNc machining centrifugal impeller machining cutter diameter optimization Sectional machining

Deflagration and detonation induced by shock wave focusing at different Mach numbers

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chinese Journal of Aeronautics 2024年第2期37卷 249-258页

作者： zezhong YANG Jun chenG Bo ZHANG School of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai 200240China

Shock wave focusing is an effective way to create a hot spot or a high-pressure and hightemperature region at a certain place,showing its unique usage in detonation initiation,which is beneficial for the development of detonation-based engines.The flame propagation behavior after the autoignition induced by shock wave focusing is crucial to the formation and self-sustaining of the detonation wave.In this study,wedge reflectors with two different angles(60°and 90°)and a planar reflector are employed,and the Mach number of incident shock waves ranging from 2.0 to 2.8 is utilized to trigger different flame propagation modes.Dynamic pressure transducers and the high-speed schlieren imaging system are both employed to investigate the shock-shock collision and ignition procedure.The results reveal a total of four flame propagation modes:deflagration,DDT(Deflagration-to-Detonation Transition),unsteady detonation,and direct detonation.The detonation wave formed in the DDT and unsteady detonation mode is only approximately 75%-85%of the chapman-Jouguet(c-J)speed;meanwhile,the directly induced detonation wave speed is close to the c-J speed.Transverse waves,which are strong evidence for the existence of detonation waves,are discovered in experiments.The usage of wedge reflectors significantly reduces the initial pressure difference ratio needed for direct detonation ignition.We also provide a practical method for differentiating between detonation and deflagration modes,which involves contrasting the speed of the reflected shock wave with the speed of the theoretically nonreactive reflected shock wave.These findings should serve as a reference for the detonation initiation technique in advanced detonation propulsion engines.

关键词： Deflagration Detonation Hydrogen Ignition Shock wave focusing

Long-Lasting Filtration of Oily Water by Anti-Fouling Underwater Oleophobic Sand Particles

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Journal of Bionic Engineering 2024年第2期21卷 913-923页

作者： Xingyu Liu Junxu chen Rui Wang Yifan Su Zhangheng Zhou zezhong Hou Zhuoran Li Junhao Zhao Weicai Shi Xinquan Yu Zhaopeng Yu Youfa Zhang State Key Laboratory of Advanced Technology for Float Glass CNBM Research Institute for Advanced Glass Materials Group Co.LtdBengbu233000China Jiangsu Key Laboratory of Advanced Metallic Materials School of Materials Science and EngineeringSoutheast UniversityNanjing211189China Research Institute of Petroleum Engineering Technology of Jiangsu Oilfield Yangzhou225009China Kunshan Industrial Technology Research Institute Kunshan215300SuzhouChina School of Automotive Engineering Changshu Institute of TechnologyChangshu215500SuzhouChina

The produced water from the oilfield was purified with filter material and then injected back into the ground.The serpentine filter material was easy to harden with the increase in filtration amount,which affected the water quality.A superhydrophilic/underwater oleophobic serpentine filter material was successfully prepared by a simple method of coating modification,which exhibited long-lasting filtration of oily water,good filtration and anti-fouling properties,and resistance to harden.The film-forming material of the superhydrophilic/underwater oleophobic coating was composed of SiO_(2) particles with small size,which could completely and evenly cover the filter particle.The weight loss was only 7.6%after mechanical stirring for 90 min.compared with the original filter material,the superhydrophilic/underwater oleophobic serpentine filter material showed a better anti-fouling ability and resistance to harden.The filtration of crude oil emulsion and oil slick sewage showed a better backwashing performance.After 35 cycles of continuous filtration of suspended solids in wastewater,the backwashing rate reached 78.4%.The results provided an effective method for the filtration of oily wastewater in the oilfield.

关键词： Serpentine Underwater oleophobic Water immersion resistance Anti-fouling Hardening resistance

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

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 diseases.The 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 disease.Methods:PubMed,Web of Science,and Embase databases were systematically reviewed for related studies published between January 1,2003,and August 31,2023.All randomized and non-randomized controlled trials of exercise interventions with autoimmune disease study participants that evaluated inflammation-related biomarkers were included.The quality of evidence was assessed using the Tool for the assEssment of Study qualiTy and reporting in EXercise scale and cochrane bias risk tool.Results:A total of 14,565 records were identified.After screening the titles,abstracts,and full texts,87 were eligible for the systematic review.These 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 interventions.Regular exercise interventions combined with multiple exercise modes were associated with greater benefits.conclusion:Regular exercise training by patients with autoimmune disease exerts an anti-inflammatory influence.This systematic review provides support for the promotion and development of clinical exercise intervention programs for patients with autoimmune disease.Most patients with autoimmune disease can safely adopt moderate exercise training protocols,but changes in inflammation biomarkers will be modest at best.Acute exercise interventions are ineffective or even modestly but transiently pro-inflammatory.

关键词： Autoimmune diseases cytokines Inflammation Physical activity Training

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 mobility.Ferrihydrites(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)mixtures.However,the mechanism of cr(Ⅵ)retention by Si-Fh mixtures is poorly understood.In this study,the behaviors and mechanisms of cr(Ⅵ)adsorption onto Si-Fh with different Si/Fe molar ratios was investigated.Transmission 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 Si-Fh.The 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 ratios.This 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)increases.However,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 repulsion.Overall,the increase in the electrostatic repulsion has a greater impact on adsorption than the additional complexation with Si-Fh.Density 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

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 designed.Then,a distributed dynamic ETM which only uses local information is developed for the MASs with large-scale networks.It 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 time.In addition,it is easier to find a trade-off between the convergence rate and the minimum inter-event time by an adjustable parameter.Furthermore,the results are extended to regional consensus of the MASs with the bounded control protocol.Numerical 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

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 performance.First, 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

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 regions.Due 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 communities.This 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 decades.The 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 soils.In 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 characteristics.Insights 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 subjected to cyclic loadings associated with seismic eve

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