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Chinese Journal of Aeronautics 2020年第7期33卷 1867-1876页

作者： Yong WANG qian’gang ZHENG Zhigui XU Haibo ZHANG College of Energy and Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China AECC Aero Engine Control System Institute Wuxi 214063China

In order to compensate for the disturbance of wide variation in rotor demanded torque on power turbine speed and realize the fast response control of turboshaft engine during variable rotor speed,a cascade PID control method based on the acceleration estimator of gas turbine speed(Ngdot)and rotor predicted torque feedforward is ***,a two-speed Dual Clutch Transmission(DCT)model is applied in the integrated rotor/turboshaft engine system to achieve variable rotor ***,an online estimation method of Ngdot based on the Linear Quadratic Gaussian with Loop Transfer Recovery(LQG/LTR)is proposed for power turbine speed cascade ***,according to the cascade PID controller based on Ngdot estimator,a rotor demanded torque predicted method based on the Min-batch Gradient Descent-Neural Network(MGD-NN)is put forward to compromise the influence of rotor torque *** simulation results show that compared with cascade PID controller based on Ngdot estimator and the one combined with collective pitch feedforward control,the novel control method proposed can reduce the overshoot of power turbine speed by more than 20%,which possesses faster response,superior dynamic effect and satisfactory robustness *** control method proposed can realize the fast response control of turboshaft engine with variable rotor speed better.

关键词： LQG/LTR Ngdot estimator Rotor predicted torque feedforward Turboshaft engine Variable rotor speed

Research on nonlinear model predictive control for turboshaft engines based on double engines torques matching

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Chinese Journal of Aeronautics 2020年第2期33卷 561-571页

作者： Yong WANG qian’gang ZHENG Ziyan DU Haibo ZHANG College of Energy and Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

In order to reach a compromise between fast response control and torques matching control in double turboshaft engines,research on nonlinear model predictive control for turboshaft engines based on double engines torques matching is ***,a Nonlinear Model Predictive Control(NMPC)method is proposed,which combines the control index of the power turbine speed with torques matching of double engines *** addition to the control index,the difference of output torques between each engine is also incorporated in the objective function as a penalty term to ensure constant speed control and short torques matching *** results demonstrate that relative to unilateral torques matching,the settling time of the bidirectional matching method can be reduced by nearly 30.8%.Nevertheless,compared with the bidirectional torques matching method under the cascade PID controller,the NMPC method can decrease the overshoot of the power turbine speed by 65%and reduce the matching time by 15.5%*** fast response control of turboshaft engines,fast torques matching control of double engines is accomplished as well.

关键词： Double turboshaft engines Fast response control Helicopter Nonlinear model predictive control Torques matching method

Microstructure, thermophysical property and ablation behavior of high thermal conductivity carbon/carbon composites after heat-treatment

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Chinese Journal of Aeronautics 2020年第5期33卷 1541-1548页

作者： Xue-Song LIU qian-gang FU Hui WANG qiang SONG State Key Laboratory of Solidification Processing Shannxi Province Key Laboratory of Fiber Reinforced Light Composite MaterialsNorthwestern Polytechnical UniversityXi'an 710072PR China

Uni-directional carbon/carbon composites with high thermal conductivity are suitable to supply continuous thermal protection for future reentry vehicles since they could reduce surface temperature and ablation rates simultaneously in harsh *** this work,the high thermal conductivity carbon/carbon composites were prepared by chemical vapor *** heat-treatment,both their open porosity and internal friction increase due to the fiber/matrix thermal expansion mismatch;while their thermal conductive performance become better due to more complete carbon *** raising heat-treatment temperature from 1800℃to 2450℃,the mass and linear ablation rates of C/C composites with fibers vertical to the oxyacetylene torch for 60 s decrease from 0.66 mg/s and 2.95μm/s to 0.51 mg/s and 2.05μm/s *** improved ablation resistance is resulted from the increased thermal conductivity from 282 to 508 W/(m·K)and more carbon fibers exposed to the flame during ablation,which have better oxidation resistance than those of carbon *** such ablation rates become larger for composites with fibers parallel to the flame,from 1.02 mg/s and 3.73μm/s to 1.28 mg/s and 5.0μm/s respectively since the ablation occurred more easily through gaps at the fiber/matrix interfaces,which become larger and are always exposed to the flame for this case.

关键词： Ablation Carbon/carbon composites Fiber orientation Heat treatment Thermal conductivity

Information Flow Security Models for Cloud Computing

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Computers, Materials & Continua 2020年第12期65卷 2687-2705页

作者： Congdong Lv Ji Zhang Zhoubao Sun gang qian Nanjing Audit University Nanjing211815China Center for Data Science Courant Institute of Mathematical SciencesNew York UniversityNew York10011-8868USA

Cloud computing provides services to users through *** open mode not only facilitates the access by users,but also brings potential security *** cloud computing,the risk of data leakage exists between users and virtual *** direct or indirect data leakage,it can be regarded as illegal information ***,such as access control models can control the information flow,but not the covert information ***,it needs to use the noninterference models to detect the existence of illegal information flow in cloud computing *** noninterference models are not suitable to certificate information flow in cloud computing *** this paper,we propose several information flow models for cloud *** model is for transitive cloud computing *** others are for intransitive cloud computing *** concurrent access actions execute in the cloud architecture,we want that security domain and security domain do not affect each other,that there is no information flow between security *** in fact,there will be more or less indirect information flow between security *** models are concerned with how much information is allowed to *** example,in the CIP model,the other domain can learn the sequence of *** in the CTA model,the other domain can’t learn the *** security model will be used in an architecture depends on the security requirements for that architecture.

关键词： Cloud computing security information flow security noninterference noninterference models

A Cloud Computing Security Model Based on Noninterference

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Wuhan University Journal of Natural Sciences 2019年第3期24卷 194-200页

作者： Lü Congdong qian gang CHEN Tao School of Information Engineering Nanjing Audit University People's Court Judicial Big Data Research Base Southeast University

In cloud computing, the risk of data leakage exists between users and virtual machines. Whether it is direct or indirect data leakage, it can be regarded as illegal information flow. Methods such as access control models can control the information flow rather than the covert information flow. Therefore, it needs to use the noninterference models to detect the existence of illegal information flow in cloud computing. Typical noninterference models are not suitable to verificate information flow in cloud computing. When concurrent access actions execute in the cloud architecture, security domains do not affect each other, because there is no information flow between security domains. Based on this, we propose noninterference for cloud architecture in which concurrent access and sequential access coexist. When the sequential actions execute, the information flow between security domains can flow in accordance with established rules. When concurrent access actions execute, there should not be the information flow between security domains.

关键词： cloud computing security information flow security noninterference noninterference models

Friction and wear properties of Cu-based self-lubricating composites in air and vacuum conditions

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Acta Metallurgica Sinica(English Letters) 2012年第5期25卷 391-400页

作者： Shiyin HUANG Yi FENG Kewang DING gang qian Hongjuan LIU Yang WANG Department of Material Science and Engineering Hefei University of Technology Hefei 230009 China

Cu-based self-lubricating materials containing two different solid lubricants （graphite and MoSs） were fabricated by P/M hot pressing techniques. Physical and mechan- ical properties of the samples were examined. The effects of graphite and MoSs contents on friction coefficient and wear rate were investigated by a ring-on-disc wear machine in air and vacuum conditions, respectively. Tribo-films formed on the worn surfaces were characterized by scanning electron microscopy （SEM） and X-ray photo- electron spectroscopy （XPS）. The results indicated that density, hardness and bending strength all increased with the increasing content of MoS2, while the relative density was opposite. Sample B containing 15 vol. pct graphite and 15 vol. pct MoS2 pos- sessed superior tribological properties both in air and vacuum conditions. However, the tribo-films formed on the worn surfaces of the sample B were greatly discrepant in composition at different testing conditions. In air, the volume ratio of MoS2 and graphite in the tribo-films is 0.31：1 whereas the ratio in vacuum is 1.07：1.

关键词： Self-lubricating composite Air and vacuum conditions Frictioncoefficient Wear rate Synergistic effect

Effect of Electrical Current on the Tribological Behavior of the Cu-WS_2-G Composites in Air and Vacuum

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Chinese Journal of Mechanical Engineering 2013年第2期26卷 384-392页

作者： qian gang FENG Yi LI Bin HUANG Shiyin LIU Hongjuan DING Kewang School of Materials Science and Engineering Hefei University of Technology

As the traditional graphite-based composites cannot meet the requirement of rapid developing modern industry, novel sliding electrical contact materials with high self-lubricating performance in multiple environments are eagerly required. Herein a copper-based composite with WS2 and graphite as solid lubricant are fabricated by powder metallurgy hot-pressed method. The friction and wear behaviors of the composites with and without current are investigated under the condition with sliding velocity of 10 m/s and normal load of 2.5N/cm 2 in both air and vacuum. Morphologies of the worn surfaces are observed by optical microscope and compositions of the lubricating films are analyzed by XPS. Surface profile curves and roughness of the worn surfaces are obtained by 2205 surface profiler. The results of wear tests show that the friction coefficient and wear volume loss of the composites with current are greater than that without current in both air and vacuum due to the adverse effects of electrical current which damaged the lubricating film partially and roughed the worn surfaces. XPS results demonstrate that the lubricating film formed in air is composed of oxides of Cu, WS2 , elemental S and graphite, while the lubricating film formed in vacuum is composed of Cu, WS2 and graphite. Because of the synergetic lubricating action of oxides of Cu, WS2 and graphite, the composites show low friction coefficient and wear volume loss in air condition. Owing to the fact that graphite loses its lubricity which makes WS2 become the only lubricant, severe adhesive and abrasive wear occur and result in a high value of wear rate in vacuum condition. The formation of the lubricating film on the contact interface between the brush and ring is one of the factors which can greatly affect the wear performance of the brushes. The low contact voltage drop of the composites in vacuum condition is attributed to the high content of Cu in the surface film. This study fabricated a kind of new sli

关键词： Cu-WS2-G composites electrical current air and vacuum environments friction and wear contact voltage drop

Effective Response of Nonlinear Spherical Coated Composites Under External AC and DC Electric Field

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Communications in Theoretical Physics 2009年第4期51卷 743-747页

作者： SHEN Yu-Yan CHEN Xiao-gang LI qian-qian CUI Wei HAO Yan-Hua College of Science Inner Mongolia University of Technology Hohhot 010051 China

Under the external AC and DC electric field, the effective response of nonlinear spherical coated composites, which obey the constitutive relation of electric displaeement and electric field, is investigated in the dilute limit by using the perturbation method. The local potentials in inclusion and host regions are derived at all harmonics. Moreover, the formulae of the effective linear and nonlinear responses are given in the dilute limit.

关键词： nonlinear composites effective response AC electric field

Constant current electrodeposition preparation of nickel layer and its mechanical properties in ionic liquid

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Rare Metals 2023年第5期42卷 1752-1759页

作者： Jian-gang qian Tie-Jun Li Xin Li Xiao-Tian Hu Jing Li School of Chemistry and Environment Beihang UniversityBeijing100191China

Smooth and compact nickel layers were successfully prepared in the ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate(BMIMBF4)by constant current electrodeposition *** effects of temperature,additive content,current density,and deposition time on the performance of the nickel layers were systematically *** electron microscopy(SEM)and X-ray diffraction(XRD)were used to analyze the surface morphology and composition of the nickel ***,the tensile strengths of the nickel layers were tested by universal tensile testing *** results show that different process conditions have a great effect on morphology and performance of the electrodeposited nickel *** optimization of process parameters is as follows:BMIMBF4 to ethylene glycol(EG)volume ratio of 2:1,deposition temperature of 120℃,and current density of 1.2 mA·cm^(-2).Current density has a greater influence on the tensile strength of the nickel layer,and the maximum value of tensile strength is 1275 MPa.

关键词： Nickel layer Ionic liquid Electrodeposition Tensile strength

Production of biomass-derived monomers through catalytic conversion of furfural and hydroxymethylfurfural

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Green Chemical Engineering 2021年第2期2卷 158-173页

作者： hirong Yang Jing Zhang gang qian Xuezhi Duan Xinggui Zhou State Key Laboratory of Chemical Engineering East China University of Science and TechnologyShanghai200237China

The synthesis of biomass-derived monomers has received great attention in recent years,motivated by the depletion of fossil fuels and environmental ***,the intrinsic functionality within the biomass or biomass-derived chemicals has great potential to produce new types of monomers containing multiple acid or alcohol groups,thereby leading to materials with novel *** their versatile functional groups and easy production from cellulose/hemicellulose,furfural and hydroxymethylfurfural were regarded as very important biomass-derived platform chemicals through which multiple monomers can be produced via heterogeneous *** the current review,recent development in heterogeneous catalysis for the production of 6 bio-based monomers,furfuryl alcohol,2,5-bis(hydroxymethyl)furan,2,5-bis-(hydroxymethyl)tetrahydrofuran,1,5-pentanediol,1,6-hexanediol,and 2,5-furandicarboxylic acid,from furfural and hydroxymethylfurfural is reviewed and *** major challenge is how to efficiently and selectively convert specific functional group(s)in furfural and hydroxymethylfurfural during the production of these ***,catalyst stability issues need to be addressed due to necessity of using hot water as reaction medium and high tendency of carbonaceous deposit formation on catalyst *** current review mainly focuses on efforts of catalytic site design and modification,including selection of metal/support,use of synergy between metal and support,tuning metal size,use of inverse catalysts,adding catalytic promoters,constructing bimetallic sites,etc.,to realize efficient,selective and stable production of bio-based monomers from furfural and hydroxymethylfurfural.

关键词： Biomass-derived monomers Catalyst design Furfural Hydroxymethylfurfural Heterogeneous catalysis