检索结果-南通市图书馆

Semi-supervised remote sensing image scene classification with prototype-based consistency

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第2期37卷 459-470页

作者： Yang LI Zhang LI Zi WANG Kun WANG Qifeng YU college of aerospace Science and engineering National University of Defense TechnologyChangsha 410073China

Deep learning significantly improves the accuracy of remote sensing image scene classification,benefiting from the large-scale ***,annotating the remote sensing images is time-consuming and even tough for *** neural networks trained using a few labeled samples usually generalize less to new unseen *** this paper,we propose a semi-supervised approach for remote sensing image scene classification based on the prototype-based consistency,by exploring massive unlabeled *** this end,we,first,propose a feature enhancement module to extract discriminative *** is achieved by focusing the model on the foreground ***,the prototype-based classifier is introduced to the framework,which is used to acquire consistent feature *** conduct a series of experiments on NWPU-RESISC45 and Aerial Image Dataset(AID).Our method improves the State-Of-The-Art(SOTA)method on NWPU-RESISC45 from 92.03%to 93.08%and on AID from 94.25%to 95.24%in terms of accuracy.

关键词： Semi-supervised learning Remote sensing Scene classification Prototype network Deep learning

Accurately tracking hypersonic gliding vehicles via an LEO mega-constellation in relay tracking mode

在线全文

学校读者我要写书评

暂无评论

Journal of Systems engineering and Electronics 2024年第1期35卷 211-221页

作者： LI Zhao WANG Yidi ZHENG Wei college of aerospace Science and engineering National University of Defense TechnologyChangsha 410073China

In order to effectively defend against the threats of the hypersonic gliding vehicles(HGVs),HGVs should be tracked as early as possible,which is beyond the capability of the ground-based *** benefited by the developing megaconstellations in low-Earth orbit,this paper proposes a relay tracking mode to track HGVs to overcome the above *** whole tracking mission is composed of several tracking intervals with the same *** each tracking interval,several appropriate satellites are dispatched to track the *** that are planned to take part in the tracking mission are selected by a new derived observability *** tracking performances of the proposed tracking mode and the other two traditional tracking modes,including the stare and track-rate modes,are compared by *** results show that the relay tracking mode can track the whole trajectory of a HGV,while the stare mode can only provide a very short tracking ***,the relay tracking mode achieve higher tracking accuracy with fewer attitude controls than the track-rate mode.

关键词： target tracking mega-constellation hypersonic gliding vehicle(HGV) sensor selection observability analysis

Reliability analysis of carbon fiber rod-reinforced umbilical cable under tension using an improved sampling method

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2024年第4期21卷 2769-2778页

作者： Yu Zhang Hong-Yu Zhang Ran Xia Si-Ao Jiang Fang Wang college of Safety and Ocean engineering China University of Petroleum China Academy of aerospace Aerodynamics China Aerospace Science and Technology Group college of engineering Science and Technology Shanghai Ocean University

The umbilical cable is a vital component of subsea production systems that provide power, chemical agents, control signals et al., and its requirement for reliability is exceedingly high. However, as the umbilical cable is a composite structure comprising multiple functional units, the reliability analysis of such cables involves numerous parameters that can impact calculation efficiency. In this paper, the reliability analysis of a new kind of umbilical cable with carbon fiber rod under tension is analyzed. The global dynamic analytical model is first established to determine the maximum tension load, then the local analytical model of umbilical cable including each unit are constructed by finite element method(FEM). Based on the mechanical analytical model, the reliability of umbilical cable under tension load is studied using response surface method(RSM) and Monte Carlo method. During the calculation process, a new tangent plane sampling method to calculate the response surface function(RSF) is proposed in this paper, which could make sampling points faster come close to the RSF curve, and it is proved that the calculation efficiency increases about 33% comparing with traditional method.

关键词： Umbilical cable Carbon fiber rod Failure analysis Response surface method Reliability

A unified intelligent control strategy synthesizing multi-constrained guidance and avoidance penetration

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China(Information sciences) 2024年第7期67卷 329-330页

作者： Sibo ZHAO Jianwen ZHU Weimin BAO Xiaoping LI School of aerospace Science and Technology Xidian University college of Missile engineering Rocket Force University of Engineering China aerospace Science and Technology Corporation

Satisfying various terminal constraints and achieving evasive flight in no-flying-zones (NFZs) are two important flight missions undertaken by high velocity vehicles. We studied an intelligent maneuvering guidance strategy using deep reinforcement learning (DRL) methods to achieve the coordination and unification of evasive flight and multi-constrained guidance with minimal energy loss.

关键词： Energy dissipation

An Aerial–Wall Robotic Insect That Can Land, Climb, and Take Off from Vertical Surfaces

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Research 2024年第1期2023卷 149-163页

作者： Qian Li Haoze Li Huan Shen Yangguang Yu Haoran He Xincheng Feng Yi Sun Zhiyuan Mao Guangming Chen Zongjun Tian Lida Shen Xiangming Zheng Aihong Ji college of Mechanical and Electrical engineering Nanjing University of Aeronautics and AstronauticsNanjingChina college of aerospace engineering Nanjing University of Aeronautics and AstronauticsNanjingChina State Key Laboratory of Mechanics and Control for aerospace Structures Nanjing University of Aeronautics and AstronauticsNanjingChina

Insects that can perform flapping-wing flight,climb on a wall,and switch smoothly between the 2 locomotion regimes provide us with excellent biomimetic ***,very few biomimetic robots can perform complex locomotion tasks that combine the 2 abilities of climbing and ***,we describe an aerial–wall amphibious robot that is self-contained for flying and climbing,and that can seamlessly move between the air and *** adopts a flapping/rotor hybrid power layout,which realizes not only efficient and controllable flight in the air but also attachment to,and climbing on,the vertical wall through a synergistic combination of the aerodynamic negative pressure adsorption of the rotor power and a climbing mechanism with bionic adhesion *** the basis of the attachment mechanism of insect foot pads,the prepared biomimetic adhesive materials of the robot can be applied to various types of wall surfaces to achieve stable *** longitudinal axis layout design of the rotor dynamics and control strategy realize a unique cross-domain movement during the flying–climbing transition,which has important implications in understanding the takeoff and landing of ***,it enables the robot to cross the air–wall boundary in 0.4 s(landing),and cross the wall–air boundary in 0.7 s(taking off).The aerial–wall amphibious robot expands the working space of traditional flying and climbing robots,which can pave the way for future robots that can perform autonomous visual monitoring,human search and rescue,and tracking tasks in complex air–wall environments.

关键词： robot smoothly Vertical

A novel seal-flow multi-vortex friction stir lap welding of metal to polymer matrix composites

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第1期37卷 451-462页

作者： Shuaiqiang NIAN Mingshen LI Shude JI Wei HU Zhiqing ZHANG Zelin SUN college of aerospace engineering Shenyang Aerospace UniversityShenyang 110136China State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China

The friction stir lap welding(FSLW)of metal to polymer is a challenging work due to the unavoidable polymer *** this problem,a novel seal-flow multi-vortex friction stir lap welding(SM-FSLW)technology based on the subversively-designed multi-step pin was put *** 7075 aluminum alloy and short glass fiber-reinforced polyether ether ketone(PEEK)as research subjects,the welding temperature,material flow,formation and tensile shear strength of dissimilar materials lap joint under the SM-FSLW were studied and compared with those under traditional FSLW based on the conical *** multi-step pin rather than the conical pin effectively hindered the polymer overflowing due to the formation of vortexes by the step,thereby attaining a joint with a smooth *** with traditional FSLW,the SMFSLW obtained the higher welding temperature,the more violent material flow and the larger area with high flow velocity,thereby producing the macro-mechanical and micro-mechanical interlockings and then heightening the joint loading *** tensile shear strength of lap joint under SM-FSLW was 27.8% higher than that under traditional *** SM-FSLW technology using the multi-step pin provides an effective way on obtaining a heterogeneous lap joint of metal to polymer with the excellent formation and high strength.

关键词： Friction stir lap welding Metal to polymer Multi-step pin Material flow Tensile shear strength

Effect of kerosene injection states on mixing and combustion characteristics in a cavity-based supersonic combustor

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第4期37卷 308-320页

作者： Xu LIU Peibo LI Fei LI Hongbo WANG Mingbo SUN Chao WANG Yixin YANG Dapeng XIONG Yanan WANG Science and Technology on Scramjet Laboratory College of Aerospace Science and EngineeringNational University of Defense TechnologyChangsha 410073China

It has been found that the static pressure distribution along the axial direction of liquid kerosene is lower than that of the gaseous kerosene under the same flow condition and overall equivalent ratio from previous *** further investigate this phenomenon,a compressible two-phase parallel simulation method is utilized to analyze the mixing and combustion characteristics of gaseous and liquid kerosene jets in a cavity-based supersonic *** numerical results are consistent with the experiments and demonstrate that gaseous injection leads to a cavity shear layer that dives deeper into the cavity,forming two recirculation zones in the front and rear of the *** contrast,the cavity shear layer is closer to the mainstream during liquid injection,and only a large recirculation zone is formed in the rear of the *** a result of the cavity shear layer and the recirculating flow,the fuel vapor of gaseous injection accumulates in the front of the cavity,while for the liquid injection,the fuel vapor disperses in the cavity,cavity shear layer,and the region above,and the rear of the cavity has a higher fuel vapor concentration than the *** unique fuel distribution causes the combustion area to be concentrated in the cavity during the gaseous injection but dispersed inside and downstream of the cavity during the liquid *** a result,forming a thermal throat under the same conditions is more challenging during liquid injection,and the generated static pressure distribution is lower than that during the gaseous injection.

关键词： Gaseous injection Liquid injection Mixing process Combustion Supersonic flow

Tuning heterogeneous microstructures to enhance mechanical properties of nano-TiN particle reinforced Haynes 230 composites by laser powder bed fusion

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2024年第9期43卷 4548-4565页

作者： Wen-Jie Liu Hui Li Qian-Xing Yin He-Jun Du School of Power and Mechanical engineering Wuhan University The Institute of Technological sciences Wuhan University School of Mechanical&aerospace engineering Nanyang Technological University

Laser powder bed fusion(LPBF) is considered to be one of the most promising additive manufacturing technologies for producing components with geometries and high geometrical precision that are unattainable by traditional technologies. The superalloy exhibits exceptional mechanical and high-temperature performances,rendering it a prime candidate for advanced aero-engine applications. Despite the high demand for LPBF-manufactured superalloys, the superalloy is one of the materials manufactured difficultly by LPBF due to their large laser absorptivity fluctuation, poor molten pool stability and sharp temperature gradient. Hence, superalloys are characterized by severe pores, undesirable coarse columnar grains and poor mechanical properties. In this work, the effect of nano-Ti N particles on defects, molten pool characteristics and microstructure and performance of the composites were investigated. The 4.5 wt% Ti N/Haynes230 samples exhibited exceptional nanohardness and elastic modulus with maximum values reaching 5.53 GPa and 240.03 GPa, respectively. These superior mechanical properties were attributed to the combined effects of spatter and gas pore inhibition, grain refinement and duplex nanophases strengthening. Moreover, the stability of molten pool was enhanced, and spatter was effectively suppressed by adding nano-Ti N particles, while grain refinement and columnar to equiaxed transitions were promoted. Furthermore, the matrix exhibited a high dislocation density due to a significant hindrance of dislocation movement caused by massive nano-phases(e.g., Ti N and M23C6), resulting in the formation of extensive dislocation tangles and *** work offers novel insights into the role of nanoparticles reinforced superalloy composites by LPBF.

关键词： Composites Laser powder bed fusion Mechanical properties Microstructure Molten pool characteristics

Gas film/regenerative composite cooling characteristics of the liquid oxygen/liquid methane (LOX/LCH4) rocket engine

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & engineering) 2024年第8期25卷 631-649页

作者： Xinlin LIU Jun SUN Zhuohang JIANG Qinglian LI Peng CHENG Jie SONG Science and Technology on Scramjet Laboratory College of Aerospace Science and EngineeringNational University of Defense TechnologyChangsha 410073China

The thermal protection of rocket engines is a crucial aspect of rocket engine *** this paper,the gas film/regenerative composite cooling of the liquid oxygen/liquid methane(LOX/LCH4)rocket engine thrust chamber was investigated.A gas film/regenerative composite cooling model was developed based on the Grisson gas film cooling efficiency formula and the one-dimensional regenerative cooling *** accuracy of the model was validated through experiments conducted on a 6 kg/s level gas film/regenerative composite cooling thrust ***,key parameters related to heat transfer performance were *** results demonstrate that the model is sufficiently accurate to be used as a preliminary design *** temperature rise error of the coolant,when compared with the experimental results,was found to be less than 10%.Although the pressure drop error is relatively large,the calculated results still provide valuable guidance for heat transfer *** addition,the performance of composite cooling is observed to be superior to regenerative *** the gas film flow rate results in higher cooling efficiency and a lower gas-side wall ***,the position at which the gas film is introduced greatly impacts the cooling *** optimal introduction position for the gas film is determined when the film is introduced from a single row of *** optimal introduction position results in a more uniform wall temperature distribution and reduces the peak ***,it is observed that a double row of holes,when compared to a single row of holes,enhances the cooling effect in the superposition area of the gas film and further lowers the gas-side wall *** results provide a basis for the design of gas film/regenerative composite cooling systems.

关键词： Liquid oxygen/liquid methane(LOX/LCH4)rocket engine Gas film cooling Regenerative cooling Heat transfer characteristics