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Effects of the nozzle structure and fluidized gas composition on the gas-particle two-phase jet characteristic in a powder fuel scramjet

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Particuology 2024年第9期92卷 166-179页

作者： Changfei Zhuo Hongming Ding Xiaobin Ren Hanyu deng Xiong Chen School of Mechanical and Engineering Key Laboratory of Special Engine TechnologyMinistry of EducationNanjing University of Science and TechnologyNanjing210094China Department of Mechanical Engineering National University of Singapore9 Engineering Drive 1Singapore117576 Shanxi North Xing'an Chemical Industry Co. Ltd.Taiyuan030008China

The interaction between nozzle design and fluidization gas composition significantly influences the dynamics within a powder fuel scramjet's combustion *** investigate this relationship,an experimental study utilized high-speed shadow imaging technology to explore the macroscopic aspects of powder fuel *** investigation examined various convergence angles,nozzle throat lengths,and fluidized gas *** findings include:During jet development,powder fuel initially concentrates near the axis,with non-convergence angle nozzles exhibiting longer concentrated distribution periods than convergence angle *** nozzle convergence angles lead to increased penetration distance,frontal velocity,and radial diffusion distance during the initial stages of jet ***,stable jet shapes show larger divergence angles as nozzle convergence angle decreases,with the largest divergence angle observed atα=60°.In the initial 0-7 ms of jet development,the powder fuel jet demonstrates greater penetration distance and frontal velocity under certain ***,penetration distance and frontal velocity increase with throat length from 7 to 20 ms,accompanied by changes in divergence ***,at a throat length(l)of 2 mm,the near-field divergence angle measures 46.50°,and the far-field divergence angle is 22.25°.Conversely,at l=8mm,the near-field divergence angle is 33.49°,and the far-field divergence angle is 23.21°.The fluidization gas composition minimally affects jet penetration distance and frontal velocity during the initial 0-3 ***,due to hydrogen's low density,hydrogen/powder fuel jets exhibit shorter distances and velocities compared to nitrogen/powder fuel *** fluidization also results in larger divergence angles,particularly in the near *** findings underscore the importance of nozzle design and fluidization gas composition in optimizing scramjet performance and efficiency.

关键词： Multiphase flows Gas-particle two-phase jet Nozzle contraction angle Powder fuel scramjet

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Ameliorating the Strength-Modulus Synergy in GNPs Reinforced Mg-Zn-Zr Composites via Multidirectional Forging and Hot Extrusion Deformation

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Acta Metallurgica Sinica(English Letters) 2024年第3期37卷 425-437页

作者： Yuhao Chen Kaibo Nie Kunkun deng Zhilong Liu Quanxin Shi College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan 030024China State Key Laboratory of Compressor Technology(Compressor Technology Laboratory of Anhui Province) Hefei 230031China Instrumental Analysis Center Taiyuan University of TechnologyTaiyuan 030024China

The integration of lightweight and high-modulus magnesium-based materials is becoming increasingly valued as structural materials due to the complexity and intelligence of industrial products like automobiles and *** this study,the graphene nanoplatelets(GNPs)/Mg-Zn-Zr composites with 0.5 wt%GNPs were successfully prepared by the combination of multidirectional forging(MDF)and hot extrusion(Ex).The newly-developed composites after multi-step deformation possessed excellent strength and modulus,with a tensile strength exceeding 375 MPa and an elastic modulus reaching 54 *** results revealed that the stripping and thinning of GNPs bands parallel to the extrusion direction occurred after MDF+Ex,which promoted the dynamic recrystallization and the formation of numerous fine *** significant improvement in comprehensive mechanical performances of the composites could be primarily ascribed to the refinement of grain size caused by the optimized distribution of GNPs,and efficient load transfer facilitated by the tight interface.

关键词： Magnesium matrix composites Graphene nanoplatelets(GNPs) Multi-step deformation Microstructure Strength-modulus

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Visible Light Indoor Positioning System Based on Pisarenko Harmonic Decomposition and Neural Network

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Chinese Journal of Electronics 2024年第1期33卷 195-203页

作者： Li ZHAO Yi REN Qi WANG Lange deng Feng ZHANG School of Electronic Information Engineering Xi’an Technological University

Visible-light indoor positioning is a new generation of positioning technology that can be integrated into smart lighting and optical communications. The current received signal strength(RSS)-based visible-light positioning systems struggle to overcome the interferences of background and indoor-reflected noise. Meanwhile, when ensuring the lighting, it is impossible to use the superposition of each light source to accurately distinguish light source information; furthermore, it is difficult to achieve accurate positioning in complex indoor environments. This study proposes an indoor positioning method based on a combination of power spectral density detection and a neural network. The system integrates the mechanism for visible-light radiation detection with RSS theory, to build a back propagation neural network model fitting for multiple reflection channels. Different frequency signals are loaded to different light sources at the beacon end, and the characteristic frequency and power vectors are obtained at the location end using the Pisarenko harmonic decomposition method. Then, a complete fingerprint database is established to train the neural network model and conduct location tests. Finally, the location effectiveness of the proposed algorithm is verified via actual positioning experiments. The simulation results show that, when four groups of sinusoidal waves with different frequencies are superimposed with white noise, the maximum frequency error is 0.104 Hz and the maximum power error is 0.0362 W. For the measured positioning stage, a 0.8 m × 0.8 m × 0.8 m solid wood stereoscopic positioning model is constructed, and the average error is 4.28 cm. This study provides an effective method for separating multi-source signal energies, overcoming background noise, and improving indoor visible-light positioning accuracies.

关键词： Neural networks Measurement uncertainty Position measurement Harmonic analysis Light emitting diodes Frequency estimation Indoor positioning systems

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Proton‑Prompted Ligand Exchange to Achieve High‑Efficiency CsPbI_(3) Quantum Dot Light‑Emitting Diodes

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Nano-Micro Letters 2024年第6期16卷 53-62页

作者： Yanming Li Ming deng Xuanyu Zhang Lei Qian Chaoyu Xiang Laboratory of Advanced Nano‑Optoelectronic Materials and Devices Qianwan Institute of CNITECHNingbo 315300People’s Republic of China Division of Functional Materials and Nanodevices Ningbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201People’s Republic of China Zhejiang Provincial Engineering Research Center of Energy Optoelectronic Materials and Devices Ningbo Institute of Materials Technology&EngineeringChinese Academy of SciencesNingbo 315201People’s Republic of China Faculty of Electrical Engineering and Computer Science Ningbo UniversityNingbo 315211ZhejiangPeople’s Republic of China University of Nottingham Ningbo China Ningbo 315100People’s Republic of China

CsPbI_(3)perovskite quantum dots(QDs)are ideal materials for the next generation of red light-emitting ***,the low phase stability of CsPbI_(3)QDs and long-chain insulating capping ligands hinder the improvement of device *** in-situ ligand replacement and ligand exchange after synthesis were often difficult to ***,we proposed a new ligand exchange strategy using a proton-prompted insitu exchange of short 5-aminopentanoic acid ligands with long-chain oleic acid and oleylamine ligands to obtain stable small-size CsPbI_(3)*** exchange strategy maintained the size and morphology of CsPbI_(3)QDs and improved the optical properties and the conductivity of CsPbI_(3)QDs *** a result,high-efficiency red QD-based light-emitting diodes with an emission wavelength of 645 nm demonstrated a record maximum external quantum efficiency of 24.45%and an operational half-life of 10.79 h.

关键词： CsPbI_(3) perovskite quantum dots Light-emitting diodes Ligand exchange Proton-prompted in-situ exchange

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Dissolution behavior of Al_(2)O_(3)inclusions into CaO-MgO-SiO_(2)-Al_(2)O_(3)-TiO_(2)system ladle slags

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International Journal of Minerals,Metallurgy and Materials 2024年第5期31卷 977-987页

作者： Zhiyin deng Xiaomeng Zhang Guangyu Hao Chunxin Wei Miaoyong Zhu Key Laboratory for Ecological Metallurgy of Multimetallic Mineral(Ministry of Education) Northeastern UniversityShenyang 110819China School of Metallurgy Northeastern UniversityShenyang 110819China TBEA Shenyang Transformer Group Co. Ltd.Shenyang 110141China Angang Steel Co. Ltd.Anshan 114021China

To investigate the dissolution behaviors of Al_(2)O_(3)inclusions in CaO-5wt%MgO-SiO_(2)-30wt%Al_(2)O_(3)-TiO_(2)system ladle slags,confocal scanning laser microscopy was conducted on the slags with different TiO_(2)contents(0-10wt%),and scanning electron microscopy was performed to study the interfacial reaction between Al_(2)O_(3)and this slag *** results disclose that the dissolution of Al_(2)O_(3)inclusions does not result in the formation of new phases at the boundary between the slag and the *** TiO_(2)-bearing and TiO_(2)-free ladle slags,there is no difference in the dissolution mechanism of Al_(2)O_(3)inclusions at steelmaking *** layer diffusion is found as the controlling step of the dissolution of Al_(2)O_(3),and the diffusion coefficient is in the range of 4.18×10^(-10)to 2.18×10^(-9)m^(2)/s at 1450-1500℃.Compared with the solubility of Al_(2)O_(3)in the slags,slag viscosity and temperature play a more profound role in the dissolution of Al_(2)O_(3)inclusions.A lower viscosity and a lower melting point of the slags are beneficial for the *** addition of TiO_(2)(e.g.,5wt%)in ladle slags can enhance the dissolution of Al_(2)O_(3)inclusions because of the low viscosity and melting point of the slags,while excessive addition of TiO_(2)(e.g.,10wt%)shows the opposite trend.

关键词： inclusions dissolution ladle refining slag titanium dioxide confocal scanning laser microscopy

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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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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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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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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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