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Fractal autoencoder with redundancy regularization for unsupervised feature selection

Science China(Information Sciences) 2025年第2期68卷 89-102页

作者： Meiting SUN Fangyu LI Honggui HAN School of Information Science and Technology Beijing University of Technology Beijing Key Laboratory of Computational Intelligence and Intelligent System Engineering Research Center of Digital Community Ministry of Education Beijing Institute of Artificial Intelligence

Feature selection is a crucial step in data preprocessing because feature selection reduces the dimensionality of data by eliminating irrelevant and redundant features. Since manual labeling is expensive, unsupervised feature selection has received increasing attention in recent years. However, existing unsupervised feature selection methods tend to prioritize selecting highly correlated features over exploring feature diversity. Thus, a regularized fractal autoencoder(RFAE) method is proposed to select informative features in an unsupervised way. Specifically, the fractal autoencoder network extends autoencoders to construct a correspondence neural network and a selection neural network. The correspondence neural network exploits interfeature correlations and the selection neural network selects the informative features. A redundancy regularization strategy consists of a redundancy elimination regularization term based on the dependency between features and a sparse regularization term based on the group lasso. The redundancy regularization strategy eliminates feature subset redundancy and enhances network generalization ability. Extensive experimental results on six publicly available datasets show that the proposed RFAE outperforms the compared methods regarding clustering accuracy and classification accuracy. Moreover, the proposed RFAE achieves acceptable computation efficiency.

关键词： unsupervised feature selection fractal autoencoder correspondence neural network selection neural network redundancy regularization strategy

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Multi-Targets Visiting Orbit Design Based on Numerical Method

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Guidance,Navigation and Control 2025年第1期05卷 139-148页

作者： Zenan Zhong Zhengxiang Sun Songyan Wang Tao Chao Ming Yang Control and Simulation Center Harbin Institute of Technology National Key Laboratory of Modeling and Simulation for Complex Systems Harbin Institute of Technology Beijing Institute of Space Long March Vehicle

In this paper, for the two/three targets in the circle orbit with the same altitude, a numerical method is presented to design an orbit for a spacecraft to visit multiple targets without maneuvering. First,for the two targets' case, an equation is established by the relationship of the two angles that both are the function of the time, one of the angles is the angle between two targets' geocentric position vectors at two times, and another one is the spacecraft flight angle during the two times. The visit time can be solved by the assumption that one of the visit times is known in the equation, and the orbit element can be transferred from the position and velocity vector determined by the solved visit time. Then, for the three targets' case, the problem is decoupled into two cases of two targets, and there is a public target in each case. Based on the method for two targets, two different orbits can be obtained by determining the visit time of the public target. The difference between two orbits can be expressed by the difference in velocity vectors of the public target at different times. A sampling method is utilized to select two velocity vectors with relatively small differences as initial values, the Newton iteration method is used to obtain visit times with higher accuracy. simulation results illustrate the effectiveness of the orbit design methods.

关键词： Orbit design method multiple targets visit circle orbit non-maneuvering

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Experimental determination of stripping foil thickness on the XiPAF synchrotron

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Nuclear Science and Techniques 2025年第3期36卷 27-37页

作者： Xiao-Yu Liu Hong-Juan Yao Shu-Xin Zheng Ze-Jiang Wang Yang Xiong Pei-Zhi Fang Zhong-Ming Wang Key Laboratory of Particle&Radiation Imaging Tsinghua UniversityBeijing 100084China Laboratory for Advanced Radiation Sources and Application Tsinghua UniversityBeijing 100084China Department of Engineering Physics Tsinghua UniversityBeijing 100084China National Key Laboratory of Intense Pulsed Radiation Simulation and Effect Northwest Institute of Nuclear TechnologyXi’an 710024China

Stripping injection overcomes the limitations of Liouville's theorem and is widely used for beam injection and accumulation in high-intensity *** interaction between the stripping foil and beam is crucial in the study of stripping injection,particularly in low-energy stripping injection synchrotrons,such as the XiPAF *** foil thickness is the main parameter that affects the properties of the beam after *** thin stripping foil is reinforced with collodion during its ***,the collodion on the foil surface makes it difficult to determine its equivalent thickness,because the mechanical measurements are not sufficiently reliable or convenient for continuously determining foil *** propose an online stripping foil thickness measurement method based on the ionization energy loss effect,which is suitable for any foil thickness and does not require additional *** studies were conducted using the XiPAF *** limitation of this method was examined,and the results were verified by comparing the experimentally obtained beam current accumulation curves with the simulation *** confirms the accuracy and reliability of the proposed method for measuring the stripping foil thickness.

关键词： Stripping injection Foil thickness Synchrotron Injection efficiency Experimental study

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Impedance control method of the cylindrical virtual cathode reflex triode based on multi-ring cathode

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Plasma Science and technology 2025年第4期27卷 88-94页

作者： Mengfan ZHANG Dingguo LAI Qifu XU Mengtong QIU National Key Laboratory of Intense Pulsed Radiation Simulation and Effect Northwest Institute of Nuclear TechnologyXi’an 710024People’s Republic of China Department of Engineering Physics Tsinghua UniversityBeijing 100084People’s Republic of China

The cylindrical virtual cathode reflex triode is a new type of pulsed hard X-ray load,which has the advantages of simple structure,high radiation conversion efficiency,and simplicity in seriesparallel *** paper presents a method to reduce the impedance of the triode using a multiring *** average electric field on the ring-cathode emission surface is enhanced due to edge effect,and the beam intensity is greatly increased in proportion to the square of the electric field ***-ring cathode is used to enlarge the emission ***,the reflex triode can work at lower impedance and generate a stronger beam under the same anode-cathode *** addition,the electric field enhancement of the cathode reduces the cathode emission stabilization time and enhances the operation stability of the *** effects of parameters such as ring width and ring gap on the triode impedance are simulated and *** cathode emission stabilization time and the X-ray conversion efficiency are *** design basis of cathode structure parameters and the impedance control method of the cylindrical virtual cathode reflex triode are given according to the simulations.

关键词： pulsed hard X-ray reflex triode high current electron beam bremsstrahlung(Some figures may appear in colour only in the online journal)

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Electrospraying Si/SiO_(x)/C and Sn/C nanosphere arrays on carbon cloth for high-performance flexible lithium-ion batteries

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Journal of Semiconductors 2025年第1期46卷 234-243页

作者： Di Chen Rui Li Chunxue Liu Kai Jiang School of Integrated Circuits and Electronics Beijing Institute of TechnologyBeijing 100081China College of Physics and Mathematics University of Science and TechnologyBeijing 100083China Falculty of Hepato-Pancreato-Biliary Surgery Chinese PLA General HospitalInstitute of Hepatobiliary Surgery of Chinese PLA& Key Laboratory of Digital Hepetobiliary SurgeryChinese PLABeijing 100853China

Exploring electrode materials with larger capacity,higher power density and longer cycle life was critical for developing advanced flexible lithium-ion batteries(LIBs).Herein,we used a controlled two-step method including electrospraying followed with calcination treatment by CVD furnace to design novel electrodes of Si/Si_(x)/C and Sn/C microrods array consisting of nanospheres on flexible carbon cloth substrate(denoted as Si/Si_(x)/C@CC,Sn/C@CC).Microrods composed of cumulated nanospheres(the diameter was approximately 120 nm)had a mean diameter of approximately 1.5μm and a length of around 4.0μm,distributing uniformly along the entire woven carbon *** of Si/Si/Si_(x)/C@CC and Sn/C@CC products were synthesized as binder-free anodes for Li-ion battery with the features of high reversible capacity and excellent *** Si/Six/C electrode exhibited high specific capacity of about 1750 mA∙h∙g^(−1)at 0.5 A∙g^(−1)and excellent cycling ability even after 1050 cycles with a capacity of 1388 mA∙h∙g^(−1).Highly flexible Si/Si_(x)/C@CC//LiCoO_(2)batteries based on liquid and solid electrolytes were also fabricated,exhibiting high flexibility,excellent electrical stability and potential applications in flexible wearable electronics.

关键词： electrospraying Si/SiO_(x)/C Sn/C lithium-ion batteries

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EBSD and Phase-Field Crystal simulation Revealed the Inhibition of Al_(3)Ti on Crack Extention in TC4-2024Al Laminated Composites

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Acta Metallurgica Sinica(English Letters) 2025年第2期38卷 259-275页

作者： Yihong Liu Zhuo Song Muxi Li Kangan Wang Zhiping Xiong Hua Hou Yuhong Zhao School of Materials Science and Engineering Collaborative Innovation Center of Ministry of Education and Shanxi Province for High-Performance Al/Mg Alloy MaterialsNorth University of ChinaTaiyuan 030051China National Key Laboratory of Science and Technology on Materials Under Shock and Impact Beijing Institute of TechnologyBeijing 100081China School of Materials Science and Engineering Taiyuan University of Science and TechnologyTaiyuan 030024China Beijing Advanced Innovation Center for Materials Genome Engineering University of Science and Technology BeijingBeijing 100083China Institute for Materials Intelligent Technology Liaoning Academy of MaterialsShenyang 110004China

In Ti-Al laminated composites,cracks nucleate preferentially at the Al_(3)Ti layer,but the inhibitory effect of Al_(3)Ti on crack extension is ***,by combining experiment and phase-field crystal simulation,we found that the micrometer Al_(3)Ti particles in the diffusion layer play the role of crack deflection and passivation,which is attributed to the lattice distortion induced by Al_(3)Ti consumes the energy of the crack in *** addition,it is found that the growth process of Al_(3)Ti is divided into two stages:nucleation stage and growth *** with the growth stage,the Al_(3)Ti grains in the nucleation stage are finer in the growth *** grains show better crack deflection and avoid stress concentration.

关键词： Ti-Al laminated composites Phase-field crystal simulation Growth kinetics Bending properties Crack extension

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Numerical analysis of hydrogen peroxide injection effect on the combustion characteristics of a staged combustion aft-injected hybrid rocket motor

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Acta Astronautica 2025年 234卷 429-444页

作者： Deng, Luojun Ping, Li Chen, Changrui Wang, Weizong Zhang, Guangchuan Yang, Yuxin School of Astronautics Beihang University Beijing100191 China Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies Beijing100191 China The Institute of Xi'an Aerospace Solid Propulsion Technology Xi'an710025 China National Key Laboratory of Solid Rocket Propulsion Xi'an710025 China

The staged combustion aft-injected hybrid rocket motor is a novel propulsion system that utilizes an independent fuel-rich solid propellant gas generator, with high performance and promising application prospects. However, its performance is significantly influenced by the hydrogen peroxide injection scheme. Therefore, a three-dimensional numerical model based on the Euler-Lagrange framework for multiphase turbulent flow and combustion is established. Based on the validated model, the detailed flow and combustion characteristics are carefully discussed. It is found that the combustion flow field exhibits distinct partition characteristics. And the recirculation zones appearing in the motor head enhance mixing combustion. Then, the effects of axial injection angles and axial/swirl injection ratios on the combustion flow field and motor performance are investigated. The results indicate that the larger the axial injection angle, the deeper and earlier the mixing of hydrogen peroxide and primary combustion gas occurs, thereby enhancing the combustion efficiency and specific impulse. To achieve better motor performance, the axial injection angle should not be less than 30°. Additionally, a smaller axial/swirl injection ratio leads to more droplets accumulating near the wall, resulting in incomplete mixing evaporation and hence motor performance loss. However, this also significantly decreases the temperature near the motor head and wall, which positively impacts the motor's thermal protection. This study suggests that the axial/swirl injection ratio should be controlled around 4:1, as the specific impulse decreases by only 2.3 %. This paper provides valuable guidance for the design of injection schemes for the staged combustion aft-injected hybrid rocket motor. © 2025

关键词： Boosters (rocket)

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Geochemical characteristics and source analysis of rare earth elements in Qinghai Lake sediments

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Acta Geochimica 2025年第2期44卷 231-246页

作者： Guangying Li Yingyi Meng Jinhan Zhou Di Ming Lijun Dai Lingqing Wang Qinghai Ecological Environment Planning and Environmental Protection Technology Center Xining 810007China Key Laboratory of Land Surface Pattern and Simulation Institute of Geographical Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China

This study investigates the distribution,geochemical behavior,and potential anthropogenic influences of rare earth elements(REEs)in the surface sediments of Qinghai Lake,the largest saline lake in China.A total of 36 surface sediment samples were analyzed for REE concentrations with a combination of self-organizing maps(SOM)and positive matrix factorization(PMF).Results indicate distinct enrichment patterns,with light REEs(LREEs)exhibiting higher concentrations than heavy REEs(HREEs),reflecting natural abundances and geochemical *** minimum value was found in Lu as low as 0.091 mg/kg,and the maximum concentration was exhibited in Ce at 78.877 mg/*** index(I_(geo))analysis reveals minor to moderate enrichment of specific REEs of Sm and Nd,suggesting possible localized anthropogenic inputs,particularly near river *** analysis using inverse distance weighting(IDW)and self-organizing maps(SOM)highlights significant correlations between REE distributions and riverine inputs,underscoring fluvial transport's role in sedimentary REE *** identifies mixed natural and anthropogenic sources,with agricultural and industrial activities contributing to elevated REE levels in *** findings provide critical insights into the geochemical behavior of REEs in saline lake systems and off er a foundation for pollution control and sustainable resource management in sensitive environments like Qinghai Lake.

关键词： Rare earth elements Qinghai Lake Sediments Anthropogenic impact Sources

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Research on Advanced Fine Detection technology Based on Complex tectonics of Coal Mine Driving Face

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ce/papers 2025年第2期8卷 590-600页

作者： Ding, Lian Xie, Zhiqing Sun, Jie Wang, Huayao Zhao, Xin Prospecting Institute China National Administration of Geology Key Laboratory of Transparent Mine Geology and Digital Twin Technology National Mine Safety Administration Beijing100039 China

The underground excavation work in coal mines is affected by many factors such as excavation equipment, underground geological conditions, and human operations, resulting in many safety hazards. In the construction process of excavation and mining, it is particularly important to choose scientific and reasonable advanced fine detection methods. Taking the complex geological structure of Tunbao Coal Mine in Xinjiang as an example, in view of the problems such as the inability to effectively advance and accurately detect the faults in front of the head-on and adjust the roadway slope in advance during the tunneling of the coal mine, geophysical advance exploration must be carried out before the tunneling to meet the purpose of reducing the impact of complex geological structures, realizing the fine exploration of the coal mine, and also highly catering to the requirements of intelligent construction of the coal mine. In the specific work process, through the comparative analysis of different detection technology principles and advantages and disadvantages, combined with the coal face structure and geophysical characteristics of Tunbao Coal mine, analysis of the use of trough wave advance detection tunneling scheme, finally summed up the application of three trough wave advance detection methods, to provide a certain reference for similar mines. © 2025 Ernst & Sohn GmbH.

关键词： Coal mines

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New digital drilling process monitoring: Instrumentation, validation and calibration

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Journal of Rock Mechanics and Geotechnical Engineering 2025年第1期17卷 31-54页

作者： Yanpeng Sun Zuyu Chen Fangcai Xu Yufei Zhao Ruilang Cao Dong Li State Key Laboratory of Eco-hydraulics in Northwest Arid Region Xi'an University of TechnologyXi'an710048China State Key Laboratory of Simulation and Regulation of the Water Cycle in River Basins China Institute of Water Resources and Hydropower ResearchBeijing100048China Sinohydro Foundation Engineering Co. Ltd.Tianjin301700China North China Institute of Science&Technology Langfang065201China

This study aims to enhance the digital drilling process monitoring(DPM)or monitoring while drilling(MWD)technique,which is a widely recognized method in geological exploration for evaluating rock mass ***,robust displacement and torque measurement facilities for rotary-core drilling are *** conventional cable encoder for displacement measurement is replaced with a magnetostrictive displacement sensor,which is more reliable in harsh field drilling *** enables the measurement of the bit position with an accuracy of<1 *** importantly,this new instrument is proven to be successful in improving the detection of structural discontinuities with thicknesses>1 *** addition,by measuring the electric current of the driving motor,the torque applied to the bit is conveniently and accurately *** innovations ensure high-quality data collection for DPM ***,two indices derived from DPM are proposed to quantitatively describe rock mass *** specific energy index(SEI)and specific penetration index(SPI)are based on the principles of energy conservation and Mohr-Coulomb failure criterion,*** field tests conducted in a dam grouting area confirm a linear relationship between the thrust force and penetration per rotation,and between the torque and penetration per *** correlation ratios of the related regressions are typically>*** two indices allow for the quantitative interpretation of DPM data into rock mechanics characteristics,such as uniaxial compressive strength,rock quality designation(RQD),and rock mass permeability,eliminating the need for subjective judgment normally involved in the currently used rock mass quality rating approaches.

关键词： Drilling process monitoring Specific penetration index Specific energy index Fracture identification

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