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Effects of ignition voltage and electrode structure on electric ignition and combustion characteristics of Ammonium Dinitramide(ADN)-based liquid propellants in electric ignition mode in inert gas environment

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Chinese Journal of Aeronautics 2024年第4期37卷 229-242页

作者： Lei LI Guoxiu LI Hongmeng LI Zhaopu YAO Tao ZHANG Jinze WU Shuo ZHANG School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China beijing Institute of Control Engineering Beijing 100190China

Hydrazine is toxic and carcinogenic, which greatly increases the difficulty of application and no longer meets the needs of green aerospace. As a green propellant, the Ammonium Dinitramide(ADN)-based liquid propellant has the advantages of higher specific impulse, being non-toxic,pollution-free, and easy storage. However, an ADN-based space engine in orbit has exposed the problems of high-temperature deactivation of catalysts and cold-start failure. An active ignition technology—electric ignition technology was explored in this paper to break through the technical bottleneck of catalyst deactivation and the inability to a cold start. An experimental system of a constant-volume combustor for the ADN-based liquid propellant based on the electric ignition method was established. The electric ignition and combustion characteristics of the ADN-based liquid propellant in a volume combustor with an electric ignition method were studied. The influencing mechanisms of the ignition voltage and the electrode structure on the electric ignition characteristics of the ADN-based liquid propellant were investigated. An elevation of the ignition voltage could facilitate the ignition process of the ADN-based liquid propellant, curtail electric energy input and heating effect, while exerting an adverse impact on the combustion process of the *** increase in the ignition voltage enhanced the ignition process of the propellant while simultaneously suppressing its combustion process when utilizing mesh electrodes. Compared to the strip electrodes, the mesh electrodes increased the contact area between the electrodes and the propellant,increased the electric energy input power in the electric ignition process, and reduced the ignition delay time. The mesh electrodes could promote the combustion process of the propellant to a certain extent.

关键词： ADN-based liquid propellant Resistive ignition Electrical ignition characteristic Combustion Inert gas

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Probing the peripheral self-generated magnetic field distribution in laser-plasma magnetic reconnection with Martin-Puplett interferometer polarimeter

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Chinese Physics B 2024年第4期33卷 129-134页

作者：张雅芃姚嘉文刘正东马作霖仲佳勇 Department of Astronomy Beijing Normal UniversityBeijing 100875China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China

Magnetic reconnection of the self-generated magnetic fields in laser-plasma interaction is an important laboratory method for modeling high-energy density astronomical and astrophysical *** use the Martin-Puplett interferometer(MPI)polarimeter to probe the peripheral magnetic fields generated in the common magnetic reconnection configuration,two separated coplanar plane targets,in laser-target *** introduce a new method that can obtain polarization information from the interference pattern instead of the sinusoidal function fitting of the intensity.A bidirectional magnetic field is observed from the side view,which is consistent with the magneto-hydro-dynamical(MHD)simulation results of self-generated magnetic field *** find that the cancellation of reverse magnetic fields after averaging and integration along the observing direction could reduce the magnetic field strength by one to two orders of *** indicates that imaging resolution can significantly affect the accuracy of measured magnetic field strength.

关键词： laser-plasma experiment polarimeter self-generated magnetic field magnetic reconnection

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Sparse convolutional model with semantic expression for waste electrical appliances recognition

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Science China(Technological Sciences) 2024年第9期67卷 2881-2893页

作者： HAN HongGui LIU YiMing LI FangYu DU YongPing Faculty of Information Technology Beijing University of TechnologyBeijing 100124China beijing Key Laboratory of Computational Intelligence and Intelligent System Beijing 100124China Engineering Research Center of Digital Community Ministry of EducationBeijing 100124China beijing Artificial Intelligence Institute and beijing Laboratory for Intelligent Environmental Protection Beijing 100124China

Deep neural networks play an important role in the recognition of waste electrical appliances. However, deep neural network components still lack reliability in decision-making features. To address this problem, a sparse convolutional model with semantic expression(SCMSE) is proposed. First, a low-rank sparse semantic expression component, combining the benefits of residual networks and sparse representation, is adapted to enhance sparse feature extraction and semantic expression. Second, a reliable network architecture is obtained by iterating the optimal sparse solution, enhancing semantic expression. Finally, the results of visualization experiments on the waste electrical appliances dataset demonstrate that the proposed SCMSE can obtain excellent semantic performance.

关键词： sparse convolutional model deep neural network semantic expression visualization computer vision

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Detecting short-term gravitational waves from post-merger hyper-massive neutron stars with a kilohertz detector

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Chinese Physics B 2024年第8期33卷 222-228页

作者：陈奕康朱宗宏 Institute for Frontier in Astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China Department of Astronomy Beijing Normal UniversityBeijing 100875China

Gravitational waves emanating from binary neutron star inspirals,alongside electromagnetic transients resulting from the aftermath of the GW170817 merger,have been successfully ***,the intricate post-merger dynamics that bridge these two sets of observables remain *** includes if,and when,the post-merger remnant star collapses to a black hole,and what are the necessary conditions to power a short gamma-ray burst,and other observed electromagnetic *** focus is on the detection of gravitational wave(GW)emissions from hyper-massive neutron stars(NSs)formed through binary neutron star(BNS)*** several kilohertz GW detectors,we simulate BNS mergers within the detection limits of LIGO-Virgo-KARGA *** objective is to ascertain the fraction of simulated sources that may emit detectable post-merger GW *** kilohertz detectors equipped with a new cavity design,we estimate that approximately 1.1%-32%of sources would emit a detectable post-merger GW *** fraction is contingent on the mass converted into gravitational wave energy,ranging from 0.01M_(sun)to 0.1M_(sun).Furthermore,by evaluating other well-regarded proposed kilohertz GW detectors,we anticipate that the fraction can increase to as much as 2.1%-61%under optimal performance conditions.

关键词： neutron star mergers gravitational waves

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A new fluorocarbon adhesive:Inhibiting agglomeration during combustion of propellant via efficient F-Al_(2)O_(3) preignition reaction

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Carbon Energy 2024年第6期6卷 292-305页

作者： Qifa Yao Min Xia Chao Wang Fanzhi Yang Wei Yang Yunjun Luo School of Materials Science and Engineering Beijing Institute of TechnologyBeijingChina Key Laboratory of High Energy Density Materials Ministry of EducationBeijing Institute of TechnologyBeijingChina School of Aerospace Engineering Beijing Institute of TechnologyBeijingChina Advanced Research Institute of Multidisciplinary Science Beijing Institute of TechnologyBeijingChina

Inhibiting the agglomeration of molten aluminum particles packed in the binder network is a promising scheme to achieve efficient combustion of solid *** this investigation,the hydroxyl-terminated structured fluorinated alcohol compound(PFD)was introduced to modify the traditional polyethylene glycol/polytetrahydrofuran block copolymerization(HTPE)binder;that is,a unique fluorinated polyether(FTPE)binder was synthesized by embedding fluorinated organic segments into the HTPE binder via crosslinking *** FTPE was applied in aluminum-based propellants for the first *** to the complete release of fluorinated organic active segments in the range of 300℃to 400℃,the burning rate of FTPEbased propellant increased from 4.07(0%PFD)to 6.36 mm/s(5%PFD),increased by 56.27%under 1 *** reaction heat of FTPE propellants increased from 5.95(0%PFD)to 7.18 MJ/kg(5%PFD)under 3.0 MPa,indicating that HTPE binder modified with PFD would be conducive to inhibiting the D90 of condensed combustion products(CCPs)dropped by 81.84%from 75.46(0%PFD)to 13.71μm(5%PFD)under 3.0 MPa,in consistent with the significant reduction of aluminum agglomerates observed on the quenched burning surface of the *** results demonstrated that a novel FTPE binder with PFD can release fluorinated organic active segments,which motivate preignition reaction with the alumina shell in the early stage of aluminum combustion,and then enhance the melting diffusion effect of aluminum to inhibit the agglomeration.

关键词： agglomeration characteristics aluminum particles combustion fluorine alcohol compounds HTPE propellants

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Analytical model of vertical load acting on jacked pipe considering soil arching effect in cohesionless soil

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Underground Space 2024年第1期14卷 263-284页

作者： Yu Zhang Lianjin Tao Xu Zhao Jun Liu Weizhang Liao Fei Guo Xiaohui Yang Ruiqin Zhong beijing Advanced Innovation Center for Future Urban Design Beijing University of Civil Engineering and ArchitectureBeijing 102627China The Key Laboratory of Urban Security and Disaster Engineering Ministry of EducationBeijing University of TechnologyBeijing 100024China beijing Municipal Construction Group Co. LtdBeijing 100045China beijing Municipal Engineering Institute Beijing 100037China

For the project of pipe jacking in cohesionless soil,it is key to determine the vertical load on jacked pipe so as to predict the jacking force *** this paper,a new parabolic soil arching model was proposed to calculate the vertical load on jacked *** proposed analytical model was composed of parabolic soil arching zone,parabola-typed collapse zone and friction arch *** with existing literature,the key parameters(i.e.,height of parabolic soil arching,horizontal pressure coefficient and width and height of friction arch)were *** addition,considering that the trajectory of major stress is parabola,the formula of horizontal pressure coefficient was deduced in the friction *** parabolic soil arching zone is assumed as a three-hinged arch with reasonable arch axis,and the formula of load transfer was derived considering the transition effect of parabolic soil *** results of experiment,theoretical models and numerical model were adopted to verify the proposed analytical ***,the influence of the key parameters on the vertical load on jacked pipe were also discussed in *** work provides a meaningful reference for evaluating the vertical load on jacked pipe for design of pipe jacking.

关键词： Jacked pipe Soil arching effect Theoretical model Parabolic soil arching model Vertical load

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Yolk-shell FeCu/NC electrocatalyst boosting high-performance zinc-air battery

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Nano Research 2024年第9期17卷 7918-7925页

作者： Chen Liang Tianyu Zhang Shilun Sun Aijuan Han Zenghui Qiu Haijun Xu Junfeng Liu State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical TechnologyBeijing 100029China College of Mathematics&Physics Beijing University of Chemical TechnologyBeijing 100029China beijing Bioprocess Key Laboratory Beijing University of Chemical TechnologyBeijing 100029China

Iron-nitrogen-carbon single-atom catalysts(Fe-N-C SACs)are widely acknowledged for their effective oxygen reduction activity,however,their activity requires further ***,additional structural optimization is necessary to enhance mass transport and achieve higher power density in practical ***,using ZIF-8 as a template,we synthesized yolk-shell catalysts featuring complex sites of Fe single atoms and Cu nanoclusters(y-FeCu/NC)via partial etching and liquid-phase *** synthesized y-FeCu/NC catalyst exhibits high specific surface area and mesoporous *** with the advantages of highly active sites and yolk-shell structure,the y-FeCu/NC catalyst demonstrated outstanding catalytic performance in the oxygen reduction reaction,achieving a half-wave potential(E_(1/2))of 0.97 V in 0.1 M *** a practical energy device,Zn-air battery(ZAB)assembled with y-FeCu/NC catalyst achieved a remarkable power density of 356.3 mW·cm^(-2),representing an improvement of approximately 28.5%compared to its solid FeCu/NC ***,it showcased impressive stability,surpassing all control samples.

关键词： atomic Fe-N4 sites Cu nanoclusters yolk-shell structure oxygen reduction reaction zinc-air battery

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基于大型无人机航磁全轴梯度测量技术研究与应用

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地球物理学报 2024年第8期67卷 3162-3172页

作者：郭华鞠星韩松王萌王明李冰梁韧中国自然资源航空物探遥感中心北京100086

目前,我国航空物探在远海地区和青藏高原地区的工作程度并不高,这主要是由于我国现有有人机航空物探飞行平台的续航里程不够远或者无法在高海拔地区开展大比例尺、低高度飞行测量工作.由于彩虹4无人机的续航时间达到20余小时,飞行高度可... 详细信息

目前,我国航空物探在远海地区和青藏高原地区的工作程度并不高,这主要是由于我国现有有人机航空物探飞行平台的续航里程不够远或者无法在高海拔地区开展大比例尺、低高度飞行测量工作.由于彩虹4无人机的续航时间达到20余小时,飞行高度可达7300 m,经过项目研制,基于彩虹4无人机航磁全轴梯度测量系统突破了探测装置的集成设计、磁干扰特性的优化提升等一系列关键技术,首次实现了基于无人机的航磁总场、横向梯度、垂直梯度的一站式测量,航磁总场补偿后标准差优于±30 pT,横向梯度补偿后标准差优于±2 pT/m,垂向梯度补偿后标准差优于±6 pT/m,达到同类测量系统的国际领先水平,大大提升了我国在艰难地区和远海地区的勘查能力.

关键词：大型无人机航磁全轴梯度横向梯度垂向梯度

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Improving lipid production by Rhodotorula glutinis for renewable fuel production based on machine learning

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Frontiers of Chemical Science and Engineering 2024年第5期18卷 23-35页

作者： Lihe Zhang Changwei Zhang Xi Zhao Changliu He Xu Zhang National Energy R&D Center for Biorefinery Beijing University of Chemical TechnologyBeijing 100029China Collage of Life Science and Technology Beijing University of Chemical TechnologyBeijing 100029China beijing Key Laboratory of Bioprocess Beijing University of Chemical TechnologyBeijing 10029China

Microbial lipid fermentation encompasses intricate complex cell growth processes and heavily relies on expert experience for optimal *** modeling of the fermentation process assists researchers in making intelligent decisions,employing logical reasoning and strategic planning to optimize lipid *** this study,the effects of medium components and concen-trations on lipid fermentation were investigated,*** then,leveraging the collated data,a variety of machine learning algorithms were used to model and optimize the lipid fermentation *** models,based on artificial neural networks and support vector machines,achieved R?values all higher than 0.93,ensuring accurate predictions of the fermentation *** linear regression was used to evaluate the respective target parameter,which were affected by the medium components of lipid ***,single and multi-objective optimiza-tion were conducted for lipid fermentation using the genetic *** results demonstrated the maximum biomass of 50.3 g·L^(-1) and maximum lipid concentration of 14.1 g:L^(-1) with the error between the experimental and predicted values less than 5%.The results of the multi-objective optimization reveal the synergistic and competitive relationship between biomass,lipid concentration,and conversion rate,which lay a basis for in-depth optimization and amplification.

关键词： microbial lipid machine learning artificial neural network support vector machine genetic algorithm

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Numerical study on ignition start-up process of an underwater solid rocket motor across a wide depth range

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Chinese Journal of Aeronautics 2024年第10期37卷 136-157页

作者： Deyou WANG Shipeng LI Ge JIN Ruyao WANG Dian GUAN Ningfei WANG School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China beijing System Design Institute of Electro-mechanic Engineering Beijing 100854China

Solid rocket motors have important applications in the propulsion of trans-media vehicles and underwater launched *** this paper,the ignition start-up process of an underwater solid rocket motor across a wide depth range has been numerically studied.A novel multi-domain integrated model has been developed by combining the solid propellant ignition and combustion model with the volume of fluid multiphase *** integrated model enables the coupled simulation of the propellant combustion and gas flow inside the motor,along with the gas jet evolution in the external water *** detailed flow field developments in the combustion chamber,nozzle,and wake field are carefully *** variation rules of the internal ballistics and thrust performance are also *** effects of environmental medium and operating depth on the ignition start-up process are systematically *** results show that the influence of the operating environment on the internal ballistic characteristics is primarily reflected in the initial period after the nozzle closure *** development of the gas jet in water lags significantly compared with that in *** the water depth increases,the ignition delay time of the motor is shortened,and the morphology evolution of the gas jet is significantly compressed and ***,the necking and bulging of the jet boundary near the nozzle outlet and the consequent shock oscillations are intensified,resulting in stronger fluctuations in the wake pressure field and motor thrust.

关键词： Underwater propulsion Solid rocket motor Ignition start-up process Underwater gas jet Thrust oscillation

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