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Influence of bolt dynamic installation on topography characteristics and mechanical behaviors of CFRP interference-fit bolted joints

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Chinese Journal of Aeronautics 2024年第2期37卷 482-500页

作者： Xiaohe WANG Zengqiang cao Yuehaoxuan WANG Yingjiang GUO School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an 710072China NPU Xuhang Electromagnetic Technology Co. Ltd.Xi’an 710100China

As the controlled research of Dynamic Installation(DI)and Static Installation(SI),a new interference installation method was developed based on electromagnetic loading to enhance the mechanical properties of composite structures.Four different interference-fit sizes were considered,ranging from a net fit to 2.0%.The experiments were conducted to evaluate the installation resistance and the mechanical behavior of the joint under external loads.Meanwhile,an FFA model to model the stress distribution and damage behavior of the bolt-hole contact interface was established.The load-displacement curve and damage modes of experiments were used to verify the FEA results.The results show that the installation resistance during DI process was remarkably lower than that of SI process corresponding to all interference-fit sizes,and the stress amplitudes induced by interference were larger and widely distributed.The damage of the hole wall was positively correlated with interference fit size,but DI can significantly reduce the damage compared to SI.In performance tests,DI enhanced the static bearing capacity and extended longer fatigue life of the joints than SI.DI methods can be an effective way to achieve highly reliable interference joints in composite structures.

关键词： Carbon Fiber-Reinforced Polymer(CFRP) Bolted joints Interference-fit Electromagnetic installation Finite Element Analysis(FEA) Damage mechanics Bearing behavior

Experimental and Numerical Investigation of Non-synchronous Blade Vibration Excitation in a Transonic Axial Compressor

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Journal of Thermal Science 2024年第2期33卷 602-610页

作者： WANG Songbai WU Yadong CHEN Yong cao Zhipeng School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai200240China AECC Sichuan Gas Turbine Establishment Chengdu610500China

The complex flow phenomenon of rotating instability(RI) and its induced non-synchronous vibration(NSV) have become a significant challenge as they continuously increase aerodynamic load.This study aims to provide an understanding of the non-synchronous blade vibration phenomenon caused by the rotating instability of a transonic axial compressor rotor.In this case,blade vibrations and non-synchronous excitation are captured by strain gauges and unsteady wall pressure transducer sensors.Unsteady numerical simulations for a full-annulus configuration are used to obtain the non-synchronous flow excitation.The results show that the first-stage rotor blade exhibits an NSV close to the first bending mode;NSV is accompanied by a sharp increase in pressure pulsation;amplitude can reach 20%,and unsteady aerodynamic frequency will lock in a structural mode frequency when the blade vibrates in a large-amplitude motion.The predicted NSV frequency aligns well with the experimental results.The dominant mode of circumferential instability flow structure is approximately 47% of the number blades,and the cell size occupies 2-3 pitches in the circumferential direction.The full-annulus unsteady simulations demonstrate that the streamwise oscillation of the shedding and reattachment vortex structure is the main cause of NSV owing to the strong interaction between the tip leakage and separation vortices near the suction surface.

关键词： non-synchronous vibration transonic axial compressor rotor blade rotating instabilities unsteady flow

Resilience-incorporated seismic risk assessment of precast concrete frames with“dry”connections

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Earthquake Engineering and Engineering Vibration 2024年第2期23卷 403-425页

作者： Wu Chenhao Tang Yuchuan cao Xuyang Wu Gang Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education Nanjing 211102China Department of Civil and Environmental Engineering University of CaliforniaLos AngelesCA 90095USA School of Civil Engineering Southeast UniversityNanjing 211102China College of Civil and Transportation Engineering Hohai UniversityNanjing 210024China

A resilience-incorporated risk assessment framework is proposed and demonstrated in this study to manifest the advantageous seismic resilience of precast concrete frame(PCF)structures with“dry”connections in terms of their low damage and rapid recovery.The framework integrates various uncertainties in the seismic hazard,fragility,capacity,demand,loss functions,and post-earthquake recovery.In this study,the PCF structures are distinguished from ordinary reinforced concrete frame(RCF)structures by characterizing multiple limit states for the PCF based on its unique damage mechanisms.Accordingly,probabilistic story-wise pushover analyses are performed to yield story-wise capacities for the predefined limit states.In the seismic resilience analysis,a step-wise recovery model is proposed to idealize the functionality recovery process,with separate considerations of the repair and non-repair events.The recovery model leverages the economic loss and downtime to delineate the stochastic post-earthquake recovery curves for the resilience loss estimation.As such,contingencies in the probabilistic post-earthquake repairs are incorporated and the empirical judgments on the recovery parameters are largely circumvented.The proposed framework is demonstrated through a comparative study between two“dry”connected PCFs and one RCF designed as alternative structural systems for a prototype building.The results from the risk quantification indicate that the PCFs show reduced loss hazards and lower expected losses relative to the RCF.Particularly,the PCF equipped with energy dissipation devices at the“dry”connections largely reduces the expected economic loss,downtime,and resilience loss by 29%,56%,and 60%,respectively,compared to the RCF.

关键词： precast concrete frame non-emulative precast system seismic resilience seismic risk functional recovery

H∞ Robustness for Distributed Control in Autonomous Microgrids Considering Cyber Disturbances

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 696-706页

作者： Ge cao Guannan Lou Wei Gu Lina Sheng School of Electrical Engineering Southeast UniversityNanjing 210096China

The physical connections and logical relationships between microgrids and communication networks allow microgrids to develop into typical cyber-physical systems(CPSs).With the extensive use of open communication mechanisms,the impact of cyber disturbances in public communication networks cannot be diminshed.In this paper,a parameter optimal method for a distributed secondary controller based on the robust control theory and consensus algorithm is presented to enhance the robustness of a secondary control system under data disturbance,parameter perturbation,and time delay.First,a distributed secondary control strategy of microgrids is demonstrated that coordinates frequency and voltage restoration and power sharing.Then,considering the impact of cyber events on the secondary control,a distributed robust controller gain design method is proposed to satisfy the H∞ performance index.The solution of the distributed robust control is transformed into a linear matrix in equation problem and latency margin is simultaneously obtained.Finally,a test microgrid CPS is simulated with and without time delay to investigate the impact of cyber events on system operational states and the effectiveness and robustness of the proposed method.

关键词： Cyber disturbance cyber-physical lsystem distributed control microgrid robust H∞control

Numerical study of the influence of the atmospheric pressure on the thermal environment in the passenger cabin

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Building Simulation 2024年第2期17卷 253-265页

作者： Xin Su Yu Guo Zhengwei Long Yi cao Tianjin Key Lab.of Indoor Air Environmental Quality Control School of Environmental Science and EngineeringTianjin UniversityTianjin300072China Shanghai Aircraft Design and Research Institute Jinke RoadPudong DistrictShanghai201210China

The cabin air pressure remains lower than the horizontal atmospheric pressure when the airplane is in flight.Air pressure is one of the parameters that must be taken into consideration while studying the thermal environment of an airplane cabin.There are still no reference values for aircraft cabins despite the fact that numerous studies on low pressure heat transfer have demonstrated the connection between convective heat transfer coefficient(CHTC)and air pressure.In this paper,a correction method for CHTC under low pressure conditions was established by using the dummy heat dissipation in the low-pressure cabin experiment.On this basis,a thermal environment simulation model was developed,then was applied to the simulation of a seven-row aircraft cabin containing 42 passengers,and the CHTC and heat loss of dummy surface in the cabin were obtained.Finally,the results of PMV calculated by using heat dissipation and air parameters at sampling points were compared.The results show that the modified CHTC can accurately reflect the cabin thermal environment under low pressure conditions,and the correction of CHTC can be realized by adjusting the turbulent Prandtl number,which is nonlinear correlated with the pressure.The simulation results of the thermal environment in the seven-row cabin show that the CHTC changes by about 42%before and after modification.The air pressure decreases during take-off,which reduces the average CHTC of the crew surface from 5.09 W/(m^(2)·K)to 4.56 W/(m^(2)·K),but the air temperature rises by about 0.2°C as a whole.The deviation of PMV results calculated by using simulated heat loss data and using air parameters of measuring points in space is up to 0.5,but the latter is representative for calculating the thermal comfort level of the whole cabin.

关键词： low pressure aircraft cabin simulation heat dissipation convective heat transfer coefficient

Estimation of Hammerstein nonlinear systems with noises using filtering and recursive approaches for industrial control

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Frontiers of Information Technology & Electronic Engineering 2024年第2期25卷 260-271页

作者： Mingguang ZHANG Feng LI Yang YU Qingfeng cao School of Electrical&Information Engineering Jiangsu University of TechnologyChangzhou213001China College of Electrical Energy and Power EngineeringYangzhou UniversityYangzhou225127China

This paper discusses a strategy for estimating Hammerstein nonlinear systems in the presence of measurement noises for industrial control by applying filtering and recursive approaches.The proposed Hammerstein nonlinear systems are made up of a neural fuzzy network(NFN)and a linear state`-space model.The estimation of parameters for Hammerstein systems can be achieved by employing hybrid signals,which consist of step signals and random signals.First,based on the characteristic that step signals do not excite static nonlinear systems,that is,the intermediate variable of the Hammerstein system is a step signal with different amplitudes from the input,the unknown intermediate variables can be replaced by inputs,solving the problem of unmeasurable intermediate variable information.In the presence of step signals,the parameters of the state-space model are estimated using the recursive extended least squares(RELS)algorithm.Moreover,to effectively deal with the interference of measurement noises,a data filtering technique is introduced,and the filtering-based RELS is formulated for estimating the NFN by employing random signals.Finally,according to the structure of the Hammerstein system,the control system is designed by eliminating the nonlinear block so that the generated system is approximately equivalent to a linear system,and it can then be easily controlled by applying a linear controller.The effectiveness and feasibility of the developed identification and control strategy are demonstrated using two industrial simulation cases.

关键词： Hammerstein nonlinear systems Neural fuzzy network Data filtering Hybrid signals Industrial control

Multi-scenario land use prediction and layout optimization in Nanjing Metropolitan Area based on the PLUS model

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Journal of Geographical Sciences 2024年第7期34卷 1415-1436页

作者： cao Ji cao Weidong cao Yuhong WANG Xuewei ZHANG Yizhen MA Jinji School of Geography and Tourism Anhui Normal UniversityWuhuAnhui241002China School of Ecology and Environment Anhui Normal UniversityWuhuAnhui241002China

The metropolitan area is a crucial spatial element in promoting new urbanization in China.It possesses theoretical and empirical value in the determination of the evolutionary patterns and development trends necessary for regional integration and high-quality development.This study focused on Nanjing Metropolitan Area,the first national metropolitan area in China,and established three development scenarios by combining ecological–economic spatial conflict(EESC)zones and national key ecological functional areas.These scenarios simulate the spatial distribution of future land use and land cover change(LUCC)using the development zone planning function of the patch generation land use simulation(PLUS)model.The results show that:(1)Between 2000 and 2020,the most prominent characteristics of land use change were largely the massive expansion of built-up land and the significant decline of farmland,while changes in the area of ecological land were less evident.(2)EESC areas experienced significant changes over the past 20 years,but the overall level of conflict was low.Ecological land was the main land use type in the lowest-conflict area,while built-up land was the main land use type in the highest-conflict area.(3)From 2030 to 2050,further expansion of built-up areas is expected,with continued decrease of farmland.The regulation of these land use changes can be achieved through different development zone plans.The economic development scenario had the largest built-up land area,while the ecological protection scenario had the largest farmland area.This study simulates the spatial pattern changes in the metropolitan area based on spatial conflict patterns and national main functional area planning process,providing a scientific reference for future spatial planning and management.

关键词： land use change spatial conflict patch-generating simulation land use prediction Nanjing Metropolitan Area

Distributed Heterogeneous Multi-Agent Optimization with Stochastic Sub-Gradient

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Journal of Systems Science & Complexity 2024年第4期37卷 1470-1487页

作者： HU Haokun MO Lipo cao Xianbing School of Mathematics and Statistics Central South University School of Mathematics and Statistics Beijing Technology and Business University Research Centre for Agri-Product Quality Traceability Beijing Technology and Business University School of Computer and Artificial Intelligence Beijing Technology and Business University China Food Flavor and Nutrition Health Innovation Center Beijing Technology and Business University

This paper studies the optimization problem of heterogeneous networks under a timevarying topology. Each agent only accesses to one local objective function, which is nonsmooth. An improved algorithm with noisy measurement of local objective functions' sub-gradients and additive noises among information exchanging between each pair of agents is designed to minimize the sum of objective functions of all agents. To weaken the effect of these noises, two step sizes are introduced in the control protocol. By graph theory, stochastic analysis and martingale convergence theory, it is proved that if the sub-gradients are uniformly bounded, the sequence of digraphs is balanced and the union graph of all digraphs is joint strongly connected, then the designed control protocol can force all agents to find the global optimal point almost surely. At last, the authors give some numerical examples to verify the effectiveness of the stochastic sub-gradient algorithms.

关键词： Communication noises distributed stochastic optimization heterogeneous networks sub-gradient measurement noises

Research on a multi‑dimensional image information fusion algorithm based on NSCT transform

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Frontiers of Optoelectronics 2024年第1期17卷 29-44页

作者： Yuxiang Su Xi Liang Danhua cao Zhenyu Yang Yuanlong Peng Ming Zhao School of Optical and Electronic Information Huazhong University of Science and TechnologyWuhan 430074China State Grid Information and Telecommunication Branch Beijing 100761China

Traditional inspection cameras determine targets and detect defects by capturing images of their light intensity,but in complex environments,the accuracy of inspection may decrease.Information based on polarization of light can characterize various features of a material,such as the roughness,texture,and refractive index,thus improving classification and recognition of targets.This paper uses a method based on noise template threshold matching to denoise and preprocess polarized images.It also reports on design of an image fusion algorithm,based on NSCT transform,to fuse light intensity images and polarized images.The results show that the fused image improves both subjective and objective evaluation indicators,relative to the source image,and can better preserve edge information and help to improve the accuracy of target recognition.This study provides a reference for the comprehensive application of multi-dimensional optical information in power inspection.

关键词： Power inspection Object detection Polarization imaging Image fusion Image denoising