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Ignition processes and characteristics of charring conductive polymers with a cavity geometry in precombustion chamber for applications in micro/nano satellite hybrid rocket motors

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Defence Technology（防务技术） 2024年第2期32卷 55-66页

作者： Zhiyuan Zhang Hanyu deng Wenhe Liao Bin Yu Zai Yu Nanjing University of Science and Technology Nanjing 210094China

The arc ignition system based on charring polymers has advantages of simple structure,low ignition power consumption and multiple ignitions,which bringing it broadly application prospect in hybrid propulsion system of micro/nano ***,charring polymers alone need a relatively high input voltage to achieve pyrolysis and ignition,which increases the burden and cost of the power system of micro/nano satellite in practical *** conductive substance into charring polymers can effectively decrease the conducting voltage which can realize low voltage and low power consumption repeated ignition of arc ignition *** this paper,a charring conductive polymer ignition grain with a cavity geometry in precombustion chamber,which is composed of PLA and multiwall carbon nanotubes(MWCNT)was *** detailed ignition processes were analyzed and two different ignition mechanisms in the cavity of charring conductive polymers were *** ignition characteristics of charring conductive polymers were also investigated at different input voltages,ignition grain structures,ignition locations and injection schemes in a visual ignition *** results demonstrated that the ignition delay and external energy required for ignition were inversely correlated with the voltages applied to ignition ***,the incremental depth of cavity shortened the ignition delay and external energy required for ignition while accelerated the propagation of *** the depth of cavity increased from 2 to 6 mm(at 50 V),the time of flame propagating out of ignition grain changed from 235.6 to 108 ms,and values of mean ignition delay time and mean external energy required for ignition decreased from 462.8 to 320 ms and 16.2 to 10.75 J,*** rear side of the cavity was the ideal ignition position which had a shorter ignition delay and a faster flame propagation speed in comparison to other ignition *** to direct injection scheme,swirlin

关键词： Micro/nano satellite hybrid propulsion Arc ignition Charring conductive polymer Ignition mechanism Ignition characteristic Repeated ignition

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Absolute pose estimation of UAV based on large-scale satellite image

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Chinese Journal of Aeronautics 2024年第6期37卷 219-231页

作者： Hanyu WANG Qiang SHEN Zilong deng Xinyi CAO Xiaokang Wang School of Mechatronical Engineering Beijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China

Obtaining absolute pose based on pre-loaded satellite images is one of the important means of autonomous navigation for small Unmanned Aerial Vehicles(UAVs)in Global Navigation Satellite System(GNSS)denied *** of the previous works have tended to build Convolutional Neural Networks(CNNs)to extract features and then directly regress the pose,which will fail when solving the challenges caused by the huge viewpoint and size differences between“UAV-satellite”image pairs in real-world ***,this paper proposes a probability distribution/regression integrated deep model with the attention-guided triple fusion mechanism,which estimates discrete distributions in pose space and three-dimensional vectors in translation *** order to overcome the shortage of the relevant dataset,this paper simulates image datasets captured by UAVs with forward-facing cameras during target searching and autonomous *** effectiveness,superiority,and robustness of the proposed method are verified by simulated datasets and flight tests.

关键词： Satellite imagery Unmanned Aerial Vehicle(UAV) Deep neural networks Vision navigation von Mises-Fisher distribution

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Microstructure Regulation and Combustion Performance Optimization of PVDF/Al Composite Powder by Non-covalent Functionalized Graphenes

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Journal of Wuhan University of Technology(Materials Science) 2024年第4期39卷 904-911页

作者：易卓然 deng Haoyuan QIN Mei 孙一 LUO Guoqiang State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070China

Graphene prepared by non-covalent modification of sulfonated poly(ether-ether-ketone)(SPG)was combined with polyvinylidene fluoride(PVDF)/Al to improve the PVDF/Al thermal conductivity while reducing the effect of the thermal resistance at the graphene-polymer *** regulation rule of SPG with different contents on the energy release of fluorine-containing system was *** the content of SPG is 4%,the peak pressure and rise rate of SPG/PVDF/Al composite powder during ignition reach the maximum of 4845.28 kPa and 8683.58 kPa/*** the content of SPG is 5%,the PVDF/Al composite powder is completely coated by SPG,and the calorific value of the material reachs the maximum of 29.094 kJ/*** the design and micro-control of the composite powder,the calorific value of the material can be effectively improved,but the improvement of the mass release rate still depends on the graphene content and surface modification state.

关键词： energetic materials PVDF/Al composites graphene modification energy release combustion

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Effect of streamlined nose length on aerodynamic performance of high-speed train with a speed of 400 km/h

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第7期25卷 525-540页

作者： Nianxun LI Tian LI Zhiyuan DAI deng QIN Jiye ZHANG State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu 610031China

The streamlined nose length(SNL)plays a crucial role in determining the aerodynamic performance of high-speed *** appropriate SNL can not only effectively reduce the magnitude of aerodynamic drag and lift forces,but also improve the performance of the high-speed train in tunnel passing and crosswind *** this study,a numerical simulation of the aerodynamic performance of high-speed trains at a speed of 400 km/h,with varying SNLs,is conducted using the k-ωshear stress transport(SST)turbulence *** different SNLs include 6.0,7.0,8.0,9.0,9.8,12.0,15.0,and 18.0 *** order to validate the accuracy of the numerical simulation,its results are compared with wind tunnel test data obtained from the *** simulation is carried out using compressible and incompressible gases to determine the effect of gas compressibility on *** impact of SNL on the aerodynamic performance of the trains is analyzed in terms of aerodynamic forces,velocity,and pressure *** comparison to the original train,the train with a 6.0 m SNL experienced a 10.8%increase in overall aerodynamic ***,the lift forces on the head and tail cars increased by 35.7%and 75.5%,*** the other hand,the train with an 18.0 m SNL exhibited a 16.5%decrease in aerodynamic ***,the lift forces on the head and tail cars decreased by 21.9%and 49.7%,*** aerodynamic drag force of the entire train varies linearly with the SNL,while the aerodynamic lift of the tail car follows a quadratic function in relation to the SNL.

关键词： Streamlined nose length(SNL) High-speed train Aerodynamic performance Numerical simulation Flow structures

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Performance Improvement of Two-Phase Steam Ejector based on CFD Techniques,Response Surface Methodology and Genetic Algorithm

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Journal of Thermal Science 2024年第2期33卷 675-695页

作者： ZHANG Hao ZHAO Hongxia ZHANG Xiuao ZENG Hongxuan deng Jianqiang School of Energy and Power Engineering Shandong UniversityJi’nan250061China School of Chemical Engineering and Technology Xi’an Jiaotong UniversityXi’an710049China

The steam ejector is a crucial component in the waste heat recovery *** performance determines the amount of recovered heat and system ***,poor ejector performance has always been the main bottleneck for system ***,this study proposes an optimization methodology to improve the steam ejector's performance by utilizing computational fluid dynamics(CFD) techniques,response surface methodology(RSM),and genetic algorithm(GA).Firstly,a homogeneous equilibrium model(HEM) was established to simulate the two-phase flow in the steam ***,the orthogonal test was presented to the screening of the key decision variables that have a significant impact on the entrainment ratio(ER).Next,the RSM was used to fit a response surface regression model(RSRM).Meanwhile,the effect of the interaction of geometric parameters on the performance of the steam ejector was ***,GA was employed to solve the RSRM's global optimal ER *** results show that the RSRM exhibits a good fit for ER(R^(2)=0.997).After RSM and GA optimization,the maximum ejector efficiency is 27.94%,which is 48.38% higher than the initial ejector of 18.83%.Furthermore,the optimized ejector efficiency is increased by 46.4% on average under off-design ***,the results reveal that the combination of CFD,RSM,and GA presents excellent reliability and feasibility in the optimization design of a two-phase steam ejector.

关键词： two-phase steam ejector optimization methodology CFD techniques response surface methodology genetic algorithm homogeneous equilibrium model

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A cumulative damage model for predicting and assessing raveling in asphalt pavement using an energy dissipation approach

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Frontiers of Structural and Civil Engineering 2024年第6期18卷 949-962页

作者： Kailing deng Duanyi WANG Cheng TANG Jianwen SITU Luobin CHEN School of Civil Engineering and Transportation South China University of TechnologyGuangzhou 510640China

Raveling is a common distress of asphalt pavements,defined as the removal of stones from the pavement *** predict and assess raveling quantitatively,a cumulative damage model based on an energy dissipation approach has been developed at the meso *** construct the model,a new test method,the pendulum impact test,was employed to determine the fracture energy of the stone-mastic-stone meso-unit,while digital image analysis and dynamic shear rheometer test were used to acquire the strain rate of specimens and the rheology property of mastic,*** of the model reveals that when the material properties remain constant,the cumulative damage is directly correlated with loading time,loading amplitude,and loading ***,damage increases with superimposed linear and cosine variations over time.A higher stress amplitude results in a more rapidly increasing rate of damage,while a lower load frequency leads to more severe damage within the same loading ***,an example of the application of the model has been presented,showing that the model can be utilized to estimate failure life due to *** model is able to offer a theoretical foundation for the design and maintenance of anti-raveling asphalt pavements.

关键词： asphalt pavement raveling cumulative damage dissipation energy theory

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Attention Guided Food Recognition via Multi-Stage Local Feature Fusion

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Computers, Materials & Continua 2024年第8期80卷 1985-2003页

作者： Gonghui deng Dunzhi Wu Weizhen Chen School of Electrical and Electronic Engineering Wuhan Polytechnic UniversityWuhan430048China

The task of food image recognition,a nuanced subset of fine-grained image recognition,grapples with substantial intra-class variation and minimal inter-class *** challenges are compounded by the irregular and multi-scale nature of food *** these complexities,our study introduces an advanced model that leverages multiple attention mechanisms and multi-stage local fusion,grounded in the ConvNeXt *** model employs hybrid attention(HA)mechanisms to pinpoint critical discriminative regions within images,substantially mitigating the influence of background ***,it introduces a multi-stage local fusion(MSLF)module,fostering long-distance dependencies between feature maps at varying *** approach facilitates the assimilation of complementary features across scales,significantly bolstering the model’s capacity for feature ***,we constructed a dataset named Roushi60,which consists of 60 different categories of common meat *** evaluation of the ETH Food-101,ChineseFoodNet,and Roushi60 datasets reveals that our model achieves recognition accuracies of 91.12%,82.86%,and 92.50%,*** figures not only mark an improvement of 1.04%,3.42%,and 1.36%over the foundational ConvNeXt network but also surpass the performance of most contemporary food image recognition *** advancements underscore the efficacy of our proposed model in navigating the intricate landscape of food image recognition,setting a new benchmark for the field.

关键词： Fine-grained image recognition food image recognition attention mechanism local feature fusion

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Coordination structure regulation in non-flammable electrolyte enabling high voltage lithium electrochemistry

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Journal of Energy Chemistry 2024年第9期96卷 282-290页

作者： Zhiwen deng Ye Jia Yan deng Changhaoyue Xu Xuemei Zhang Qiujie He Jianan Peng Hao Wu Wenlong Cai College of Materials Science and Engineering Sichuan UniversityChengdu 610064SichuanChina Engineering Research Center of Alternative Energy Materials and Devices Sichuan UniversityChengdu 610064SichuanChina

High-voltage battery systems bring significant increases in energy density but are also accompanied by fast degradation of electrochemical performance and serious safety ***,Li^(+)coordination structure regulation was conducted to formulate a non-flammable electrolyte,which consists of 1.5 M lithium bis(fluor sulfonyl)imide(LiFSI)in triethyl phosphate and methyl 2,2,2-trifluoromethyl carbonate(FEMC).The renamed TEP-FEMC-FEC(TFF)electrolyte exhibits an FSI^(−)-dominated solvation structure contributed by the weakly-solvating ability of *** generated inorganic-rich interfacial layers are conducive to stabilizing the phase transition of high-voltage cathodes while suppressing the dendritic growth on lithium metal or co-intercalation behavior in graphite *** TFF electrolyte enables LiCoO_(2)||Li batteries to achieve capacity maintenance over 79%after 400 cycles with high-rate of 5 C at an ultra-high voltage of 4.6 V,and an outstanding capacity exceeding 100 mA h g^(−1)even at a super-high current density of 20 ***,the Ah-level LiCoO_(2)||graphite pouch cells also exhibit high capacity retention and satisfactory safety performance even under fast *** work provides a novel research direction for the pursuit of high energy density non-flammable electrolytes.

关键词： Non-flammable Solvation structure High-voltage Lithium batteries

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Quantitatively Evaluating the Erosion and Preservation of Supergene Oxide Zones:Evidence from the Yulong Porphyry Cu Deposit,Eastern Tibetan Plateau

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Journal of Earth Science 2024年第1期35卷 280-282页

作者： Xiao-Dong deng Jian-Wei Li State Key Laboratory of Geological Processes and Mineral Resources and School of Earth ResourcesChina University of GeosciencesWuhan 430074China

*** and erosion of sulfide ore deposits are important for understanding the post-mineralization processes that have significant effects on the preservation of primary orebodies(Velasco et al.,2013;Braxton et al.,2009;Brimhall et al.,1985).Supergene oxide zones are often developed in sulfide ore deposits,and are mainly composed of iron oxides and hydroxides zones in weathering profile(Andrew,1984;Thornber et al.,1981).

关键词： Eastern Tibetan weathering

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Numerical Study on Reduction in Aerodynamic Drag and Noise of High-Speed Pantograph

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Computer Modeling in Engineering & Sciences 2024年第5期139卷 2155-2173页

作者： deng Qin Xing Du Tian Li Jiye Zhang State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu610031China School of Electrical Engineering Southwest Jiaotong UniversityChengdu610031China

Reducing the aerodynamic drag and noise levels of high-speed pantographs is important for promoting environmentally friendly,energy efficient and rapid advances in train *** computational fluid dynamics theory and the K-FWH acoustic equation,a numerical simulation is conducted to investigate the aerodynamic characteristics of high-speed pantographs.A component optimization method is proposed as a possible solution to the problemof aerodynamic drag and noise in high-speed *** results of the study indicate that the panhead,base and insulator are the main contributors to aerodynamic drag and noise in high-speed ***,a gradual optimization process is implemented to improve the most significant components that cause aerodynamic drag and *** optimizing the cross-sectional shape of the strips and insulators,the drag and noise caused by airflow separation and vortex shedding can be *** aerodynamic drag of insulator with circular cross section and strips with rectangular cross section is the *** insulators and optimizing the chamfer angle and height of the windward surface of the strips can improve the aerodynamic performance of the *** addition,the streamlined fairing attached to the base can eliminate the complex flow and shield the radiated *** contrast to the original pantograph design,the improved pantograph shows a 21.1%reduction in aerodynamic drag and a 1.65 dBA reduction in aerodynamic noise.

关键词： High-speed pantograph aerodynamic drag aerodynamic noise reduction optimizing

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