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SSRN 2023年

作者： Zhu, Yulong Cao, Yu Ma, Junhao Zhang, Jieke He, Qubo Luo, Rui Jia, Xuhong Liu, Quanyi Xiao, Jun College of Civil Aviation Safety Engineering Civil Aviation Flight University of China Guanghan618307 China College of Materials Science and Engineering Chongqing University Chongqing400044 China Civil Aircraft Fire Science and Safety Engineering Key Laboratory of Sichuan Province China Chongqing Materials Research Institute Co. Ltd Chongqing400707 China School of Materials Science and Engineering Jiangsu University Jiangsu Zhenjiang212013 China State Key Laboratory of Compressor Technology Hefei General Machinery Research Institute Co. Ltd Anhui Hefei230031 China

Cryogenic deformation was introduced in thermomechanical processing to restrict dislocation mobility and tailor the initial dislocation distribution at the deformation stage, subsequently followed by annealing treatment to alter the grain boundary characteristic distribution with a view to the feasibility of grain boundary engineering in Incoloy 925. The microstructural evolution deformed at cryogenic (77K) and room temperature (298K) under various rolling reductions and annealing conditions was systematically studied to optimize the grain boundary network, which is evaluated using multi-source quantitative statistics of the twin related domains. The results showed that cryogenic deformation can adjust the dislocation accumulation mode and plastic deformation mechanism. Geometrically dislocation distributions with fishbone-like, ribbon-like or lamellar distributions can be observed from HR-EBSD-derived geometrically necessary dislocation distribution maps. During the subsequent annealing, the samples with 5% and 15% pre-strain are incapable of producing the ideal twin related domains, while the sample annealed at 1075°C with 10% pre-strain show the optimization of GBCD with the highest Σ3 n (n = 1, 2, and 3) boundary fraction of 69.67%. Compared with room temperature pre-deformation, cryogenic deformation can effectively reduce the critical temperature of GBE, and also leads to the proportion of Σ3 n boundaries increasing from 31.47% to 67.46% in 10%/1050°C sample. Meanwhile, with the appropriate strain, cryogenic deformation is more conducive to optimizing the GBCD than room-temperature deformation. © 2023, The Authors. All rights reserved.

关键词： Room temperature

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Characterizing Burning Behaviour of Convection-Controlled Pool Fires at Sub-Atmospheric Pressure by Stagnation Theory

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SSRN 2023年

作者： Guo, Youwei Xiao, Guoqing Chen, Jian Xiong, XingYu Deng, Hongbo Liu, Xiang Wang, Lingyuan Li, Yuanyuan College of Chemistry and Chemical Engineering Southwest Petroleum University Sichuan Chengdu610500 China Oil & Gas Fire Protection Key Laboratory of Sichuan Province Sichuan Chengdu611731 China Gas Reservoir Geol & Exploita Sichuan Chengdu610500 China College of Safety Science and Engineering Xi’an University of Science and Technology 710054 China College of Civil Aviation Safety Engineering Civil Aviation Flight University of China Sichuan Deyang618307 China Civil Aircraft Fire Science and Safety Engineering Key Laboratory of Sichuan Province Sichuan Deyang618307 China

Pool fires play a critical role in examining the burning behaviour of diffusion flames and are sensitive to changes in scale and environmental conditions. Understanding the evolution of pool fires under low-pressure conditions, common in plateau or flight scenarios, is essential for both fire safety and energy utilization. This study investigates the effects of pressure on pool fires through a series of small-scale experiments carried out in a pressure chamber that provides stable conditions ranging from 95 kPa to 40 kPa. Pool scales between 7 cm and 16 cm were examined, a range dominated by convective heat transfer. Methanol and heptane were chosen to discern fuel-specific variations in burning behaviour under decreased pressure. The findings demonstrate an increase in the axial flame temperature with reducing pressure, while radiative output exhibits an inverse relationship with pressure. Additionally, convective heat transfer toward surroundings appears to rise with decreasing pressure. A modified stagnation theory solution is proposed to model the mass burning rate of convection-controlled pool fires under low pressure, which shows satisfactory agreement with the experimental data. This research could potentially contribute to the comprehension of pool fires and the safety of energy in sub-atmospheric pressure conditions in the future. © 2023, The Authors. All rights reserved.

关键词： Energy utilization

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Failure analysis of sensor diaphragm cracking

Failure analysis of sensor diaphragm cracking

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2021 International Conference on Electronic Materials and Information Engineering, EMIE 2021

作者： Huan-Ping, Kong De-Lin, Liu Chang-Kui, Liu AECC Beijing Institute of Aeronautical Materials Beijing China Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation Beijing China Key Lab. of Sci. and Technol. on Aero. Mat. Test. and Evaluation of Aero Engine Corporation of China Beijing China Aviation Key Laboratory of Science and Technology on Materials Testing and Evaluation Beijing China AECC Failure Analysis Center Beijing China

The sensor diaphragm cracked during the test project. Through macro and micro morphology observation, metallographic examination and hardness test, the diaphragm failure properties and reasons were determined. The results showed that the failure nature of the faulted diaphragm was bidirectional bending fatigue cracking. 1# crack failure was related to the greater bending stress borne at the bottom of the outermost corrugation. 2# crack failure was related to the greater stress borne by the root at the boundary between the outermost corrugation and the outer edge, the appearance of grain boundaries caused by the pickling process promoted the initiation and propagation of 2# crack. © Published under licence by IOP Publishing Ltd.

关键词： Diaphragms

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3 Nm-Sized Porous Graphene-Based Anion Exchange Membranes for Efficient and Stable Water Electrolysis

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SSRN 2024年

作者： Liu, Xiang Zhang, Ai ling Yu, Hao Chen, Liang Zhang, Lei Zhao, Yong Li, Jialu Zhang, Weiqi Zhou, Zhiting Zhou, Yongyan Wang, Yuanyuan Ou, Jian Zhen Civil Aircraft Fire Science and Safety Engineering Key Laboratory of Sichuan Province Guanghan618307 China College of Civil Aviation Safety Engineering Civil Aviation Flight University of China School of Science Sichuan Guanghan618307 China Xihua University Jinzhou Road Sichuan Chengdu610039 China Sichuan Key Technology Engineering Research Center for All-electric Navigable Aircraft Sichuan Guanghan618307 China Key Laboratory of Advanced Technologies of Materials Ministry of Education School of Materials Science and Engineering Southwest Jiaotong University Chengdu610031 China School of Engineering RMIT University MelbourneVIC3000 Australia The 7th Oil Production Plant of Changqing Oilfield Gansu Qingyang745708 China

Alkaline water electrolysis is one of the primary drivers of hydrogen energy development, and anion exchange membranes (AEMs) play a dual role in ensuring both conductivity and safety. However, traditional polymer AEMs have a wide pore size distribution and poor chemical stability, making it difficult to achieve a long-term balance between conductivity and safety of the water electrolysis system. Here, we select inorganic two-dimensional multilayer graphene oxide (GO) membranes as AEMs, using carboxylated wrinkled graphene (WG) and ethylenediamine (EDA) to create a cation-modified porous EDA-GO/WG (E-W/G) composite membrane with a 3 nm pore size. The enlarged channel size and enhanced hydrophilicity improve OH- permeability compared to the pristine GO membrane, while the strengthened hydration layer acts as a barrier to hydrophobic gases for O2/H2 separation. The results show that the prepared E-W/G membrane exhibits superior current density (600 mA cm-2) and gas impermeability (gas purity 99.99%) compared to the commercial Fumasep FAA-3-50 membrane (590 mA cm-2 and 99.81%, respectively). Furthermore, after continuous testing for 168 hours in high-temperature and alkaline environments, the E-W/G membrane maintained conductivity comparable to its initial state and showed enhanced gas impermeability. Our strategy provides new insights into the design of high-performance AEMs and is expected to contribute to the advancement of the hydrogen energy industry. © 2024, The Authors. All rights reserved.

关键词： Graphene

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Sub-Nano Porous Graphene-Based Membranes Enabled by In-Situ-Grown Zif-8 for Enhanced CO2 Capture

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SSRN 2024年

作者： Zhang, Lei Zhao, Yong Yu, Hao Chen, Liang Liu, Xiang Zhang, Ailing Ou, Jian Zhen Civil Aircraft Fire Science and Safety Engineering Key Laboratory of Sichuan Province Guanghan618307 China College of Civil Aviation Safety Engineering Civil Aviation Flight University of China School of Science Sichuan Guanghan618307 China Xihua University Jinzhou Road Sichuan Chengdu610039 China Sichuan Key Technology Engineering Research Center for All-electric Navigable Aircraft Sichuan Guanghan618307 China Key Laboratory of Advanced Technologies of Materials Ministry of Education School of Materials Science and Engineering Southwest Jiaotong University Chengdu610031 China School of Engineering RMIT University MelbourneVIC3000 Australia The 7th Oil Production Plant of Changqing Oilfield Gansu Qingyang745708 China

Graphene oxide (GO) membranes hold promise for selective CO2 adsorption over N2 due to their carboxyl groups, making them attractive for flue gas CO2 capture. However, challenges such as limited carboxyl content, flexible nanosheets, and dense layer stacking hinder their N2/CO2 gas selectivity, pressure resistance, and permeability. In this study, we introduce a specific sub-nanometer framework structure within GO membranes by in-situ growing ZIF-8 nanocrystals. This novel approach, achieved through simultaneous infiltration of zinc nitrate and 2-methylimidazole precursors on both sides of the membrane, enhances CO2 capture and pressure resistance capabilities of resulting ZIF-8@GO composite membranes. Additionally, the incorporation of carboxylated wrinkled graphene (WG) and ethylenediamine (EDA) cross-linking agent molecules improves CO2 capture capability and introduces reinforced porous structures to enhance permeability. Experimental results demonstrate remarkable permeability, selectivity, and pressure resistance of the prepared ZIF-8@EDA-WG/GO composite membranes. Under a gas pressure of 0.2 MPa, permeability reaches 1850 GPU, with theoretical selectivity for N2/CO2 single gas and separation factors for mixed gases of 19 and 32.3, respectively, surpassing conventional GO membranes (200 GPU, 1.4, and 2.1). Even under elevated air pressure conditions (1.2 MPa), the composite membranes maintain a theoretical selectivity of 13.4. Our CO2 capture membrane design strategy not only advances the development of functional membranes but also contributes to mitigating CO2 emissions from flue gas, thereby combating global warming. © 2024, The Authors. All rights reserved.

关键词： Graphene

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Dual-Robust Integrated Sensing and Communication: Beamforming under CSI Imperfection and Location Uncertainty

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arXiv 2024年

作者： Lyu, Wanting Yang, Songjie Xiu, Yue Chen, Xinyi Zhang, Zhongpei Assi, Chadi Yuen, Chau National Key Laboratory of Wireless Communications University of Electronic Science and Technology of China Chengdu611731 China College of Air Traffic Civil Aviation Flight University of China Guanghan618311 China Concordia University MontrealQCH3G 1M8 Canada The School of Electrical and Electronics Engineering Nanyang Technological University 639798 Singapore

A dual-robust design of beamforming is investigated in an integrated sensing and communication (ISAC) system. Existing research on robust ISAC waveform design, while proposing solutions to imperfect channel state information (CSI), generally depends on prior knowledge of the target’s approximate location to design waveforms. This approach, however, limits the precision in sensing the target’s exact location. In this paper, considering both CSI imperfection and target location uncertainty, a novel framework of joint robust optimization is proposed by maximizing the weighted sum of worst-case data rate and beampattern gain. To address this challenging problem, we propose an efficient two-layer iteration algorithm based on S-Procedure and convex hull. Finally, numerical results verify the effectiveness and performance improvement of our dual-robust algorithm, as well as the trade-off between communication and sensing performance. Copyright © 2024, The Authors. All rights reserved.

关键词： Optimization

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Extremely Large-Scale Dynamic Metasurface Antennas (XL-DMAs): Near-Field Modeling and Channel Estimation

arXiv

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arXiv 2024年

作者： Yang, Songjie Lyu, Wanting Ning, Boyu Xiu, Yue Xiong, Youzhi Chen, Hua Assi, Chadi Yuen, Chau The National Key Laboratory of Wireless Communications University of Electronic Science and Technology of China Chengdu611731 China College of Air Traffic Management Civil Aviation Flight University of China Sichuan618311 China College of Physics and Electronic Engineering Sichuan Normal University Chengdu610101 China The Faculty of Electrical Engineering and Computer Science Ningbo University Ningbo315211 China The Zhejiang Key Laboratory of Mobile Network Application Technology Ningbo315211 China Concordia University MontrealQCH3G 1M8 Canada The School of Electrical and Electronics Engineering Nanyang Technological University Singapore

Dynamic metasurface antennas (DMAs) represent a novel transceiver array architecture for extremely large-scale (XL) communications, offering the advantages of reduced power consumption and lower hardware costs compared to conventional arrays. This paper focuses on near-field channel estimation for XL-DMAs. We begin by analyzing the near-field characteristics of uniform planar arrays (UPAs) and introducing the Oblong Approx. model. This model decouples elevation-azimuth (EL-AZ) parameters for XL-DMAs, providing an effective means to characterize the near-field effect. It offers simpler mathematical expressions than the second-order Taylor expansion model, all while maintaining negligible model errors for oblong-shaped arrays. Building on the Oblong Approx. model, we propose an EL-AZ-decoupled estimation framework that involves near- and far-field parameter estimation for AZ/EL and EL/AZ directions, respectively. The former is formulated as a distributed compressive sensing problem, addressed using the proposed off-grid distributed orthogonal least squares algorithm, while the latter involves a straightforward parallelizable search. Crucially, we illustrate the viability of decoupled EL-AZ estimation for near-field UPAs, exhibiting commendable performance and linear complexity correlated with the number of metasurface elements. Moreover, we design an measurement matrix optimization method with the Lorentzian constraint on DMAs and highlight the estimation performance degradation resulting from this constraint. Copyright © 2024, The Authors. All rights reserved.

关键词： Channel estimation

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An Intrusive Gibbs Sampling Method for Implementating the Non-Synchronous Measurements of Microphone Arrays: An Alternative Way for the Expectation Maximization Algorithm of Non-Synchronous Measurements

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SSRN 2024年

作者： Xu, Lingji Zeng, Fanchang Antoni, Jerome Yu, Liang Li, Zhenglin Wang, Ran Jiang, Weikang Southern Marine Science and Engineering Guangdong Laboratory Zhuhai519000 China Ministry of Education Zhuhai519082 China Laboratoire Vibrations Acoustique INSA-Lyon Batiment St. Exupery 25 bis av. Jean Capelle Villeurbanne69621 Cedex France School of Civil Aviation Northwestern Polytechnical University Xi’an710072 China State Key Laboratory of Airliner Integration Technology and Flight Simulation Shanghai200126 China College of Logistics Engineering Shanghai Maritime University Shanghai201306 China State Key Laboratory of Mechanical System Vibration Shanghai Jiao Tong University Shanghai200240 China

The non-synchronous measurements of microphone arrays are a powerful method for achieving large arrays and/or high microphone density by scanning the object of interest from a sequential movement of an arbitrary prototype array. It has attracted great interest recently since it is beyond the fundamental limitation of working frequency that is determined by the aperture and microphone density of an array. A crucial problem of non-synchronous measurements is to recover the missing phase relations information between consecutive positions compared with the synchronous measurements. The problem in the traditional solution is generally attributed to the matrix completion problem of a block diagonal spectral matrix. In the paper, this problem of non-synchronous measurements has been investigated as a problem of solving a system of equations in the Bayesian formalism. The Gibbs sampling method (a probabilistic approach) is proposed in this paper to reconstruct the source field that is encoded by unobservable latent variables. The proposed method can directly sample in the posterior probability density function (PDF) of all random variables. In the numerical simulations, convergence diagnosis of the Markov chain is illustrated through three approaches (i.e. trace plot, ergodic mean plot, and autocorrelation function plot). Acoustical source reconstruction error is also discussed with respect to the frequency range, signal-to-noise ratio (SNR), measurement distances, and shift distance of non-synchronous measurements. The proposed method is shown to return similar results with the Expectation Maximization algorithm of non-synchronous measurements. The effectiveness of the proposed method is also validated by experiments in a semi-anechoic chamber. © 2024, The Authors. All rights reserved.

关键词： Probability density function

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A vision-based navigation method for eVTOL final approach in urban air mobility(UAM) 4

A vision-based navigation method for eVTOL final approach in...

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4th CAA International Conference on Vehicular Control and Intelligence, CVCI 2020

作者： Ye, Siyuan Wan, Zeyu Zeng, Long Li, Chenglong Zhang, Yu College of Aeronautical Engineering Civil Aviation Flight University of China Guanghan618307 China College of Control Science and Engineering Zhejiang University Hangzhou310027 China College of Air Traffic Management Civil Aviation Flight University of China Guanghan618307 China Civil Aviation Flight University of China Department of Navigation Engineering Guanghan618307 China State Key Laboratory of Industrial Control Technology College of Control Science and Engineering Zhejiang University Hangzhou310027 China

ISBN: (纸本)9781728184968

Urban air mobility(UAM) is an emerging way of air transportation by using self-pilot electric vertical takeoff and landing (eVTOL) vehicles to transport people and cargo in an urban area. The final approach is the critical stage in the operation. Accurate location information and vertical height guidance are needed in this stage. In addition to the common GNSS/INS integrated navigation system, this work proposes an independent vision-based method to provide redundant location information in the final approach for eVTOL vehicles. The simulation results show that the positioning accuracy of the visual method is within 1.5 meters when the vehicles are no more than 25 meters away from the reference place. © 2020 IEEE.

关键词： Air mobility

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Research on the design of smart morphing long-endurance UAVs

Research on the design of smart morphing long-endurance UAVs

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作者： Ma, T. Liu, Y. Yang, D. Zhang, Z. Wang, X. Hao, S. Beijing Advanced Subject Center of Advanced Unmanned Aerial Vehicles Key Laboratory of Advanced Technology of Intelligent Unmanned Flight System Ministry of Industry and Information Technology Institute of Unmanned System Beihang University Beijing China School of Aeronautic Science and Engineering Beihang University Beijing China SATM Cranfield University Cranfield United Kingdom School of Aeronautic Science and Engineering Beihang University Beijing China School of Aeronautic Science and Engineering Hiwing General Aviation Equipment Co. LTD Beihang University Beijing China

To improve the endurance performance of long-endurance Unmanned Aerial Vehicles (UAVs), a smart morphing method to adjust the UAV and flight mode continuously during flight is proposed. Using this method as a starting point, a smart morphing long-endurance UAV design is conducted and the resulting improvement in the endurance performance studied. Firstly, the initial overall design of the smart morphing long-endurance UAV is carried out, then the morphing form is designed and various control parameters are selected. Secondly, based on multi-agent theory, an architecture for the smart morphing control system is built and the workflow of the smart morphing control system is planned. The morphing decision method is designed in detail based on the particle swarm optimisation algorithm. Finally, a simulation of the smart morphing approach in the climb and cruise stages is carried out to quantitatively verify the improvement in the endurance performance. The simulation results show that the smart morphing method can improve the cruise time by 4.1% with the same fuel consumption. ©

关键词： Antennas

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