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Experimental studies of explosion energy output with different igniter mass

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Defence Technology（防务技术） 2019年第5期15卷 808-814页

作者： Heyang Xu Weibing Li Wenbin Li yajun Wang Nanjing University of Science and Technology

For study the energy output law of cylindrical charge with shell induced by different input energies,four different black powder masses were selected to ignite the main *** degree of the shell was qualitatively analyzed by the area of holes on the witness plate and the recovered fragments *** theoretical analysis,established the functional relationship between the average mass of fragments and the relative energy output of warhead,obtained how the relative energy output of charge changed with different initial energy *** results showed that the change of input energy could lead to obvious variation in fragment characteristics,and could also control the output of *** the igniter mass increases from 1.55 g to 5.00 g,the relative energy output of the charge increases by 26.28%.Excessive initial input energy will destroy the shell confine in advance,resulting in a decrease in the relative energy output of charge.

关键词： analysis, energy mass

Toward a non-invasive cleaning of the wall painting using polyelectrolyte hydrogel

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Science China(Technological Sciences) 2023年第8期66卷 2213-2224页

作者： LI Qiang WU Chao PENG yajun ZHANG BingJian School of Art and Archaeology Zhejiang UniversityHangzhou 310028China Zhejiang University Press Hangzhou 310028China Zhejiang Museum of Natural History Hangzhou 310000China Department of Chemistry Zhejiang UniversityHangzhou 310027China

Developing advanced cleaning systems for the removal of unwanted layers from painted surfaces is still a challenging issue that needs to be addressed in the field of cultural *** this work,we proposed the use of novel polyelectrolyte hydrogels prepared via free radical polymerization and freeze-thaw *** sulfobetaine methacrylate(SBMA)was crosslinked with methylacryloyloxyethyl trimethylammonium(DMC)through covalent bonding to yield zwitterionic polyelectrolyte poly(SBMA-co-DMC)(PSD).Introducing PSD into the polyvinyl alcohol/carboxymethyl chitosan(PVA/CMC)hydrogel network enhanced the intermolecular electrostatic interactions and changed the porous structure and swelling behaviors,thus leading to improved mechanical *** adsorption ability of the PVA/CMC/PSD polyelectrolyte hydrogels toward dyes(rhodamine B and congo red)and metal ions(Cu^(2+)and K^(+))varied with increasing amounts of PSD,which could be attributed to cationic PSD tuning the net charges in the *** cleaning effectiveness of the PVA/CMC/PSD polyelectrolyte hydrogels was assessed on wall painting mock-ups coated with soil,red paint,and soluble salts,using microscopic and spectroscopic *** results showed that the hydrogel adhered to rough surfaces and removed unwanted substances effectively without leaving determinable residues,providing a possible safe and efficient method for the cleaning of important artifacts.

关键词： polyelectrolyte hydrogel SBMA adsorption cleaning effectiveness

Curvature-Driven Forces Based on Natural Exponential Pair Potential at Micro/Nanoscales

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Acta Mechanica Solida Sinica 2019年第2期32卷 133-147页

作者： Dan Wang yajun Yin Zheng Zhong Zhili Hu State Key Laboratory of Mechanics and Control of Mechanical Structures College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics Nanjing 211100 China Department of Engineering Mechanics School of Aerospace Tsinghua University Beijing 100084 China School of Aerospace Engineering and Applied Mechanics Tongji University Shanghai 200092 China

The natural exponential potential (Ce^R/λ0) widely exists at micro/nanoscales;this paper studies the interaction potential between a curved-surface body and an outside particle base on the natural exponential potential. Mat hematical derivation proves t hat the int er act ion potential can be expressed as a function of curvatures. Then, idealized numerical experiments are designed to verify the accuracy of the curvature-based potential. The driving forces exerted on the particle are discussed and confirmed to be a function of curvatures and the gradient of curvatures, which may explain some abnormal movements at micro/nanoscales.

关键词： Micro/nanoscales Curvature-driven forces Natural exponential pair potential Curvature-based potential

Duality in interaction potentials for curved surface bodies and inside particles

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Applied Mathematics and Mechanics(English Edition) 2017年第8期38卷 1071-1090页

作者： Dan WANG yajun YIN Jiye WU Zheng ZHONG Department of Engineering Mechanics Tsinghua University Department of Civil Engineering Nanjing Tech University Department of Engineering Mechanics Tongji University

Based on the viewpoint of duality, this paper studies the interaction between a curved surface body and an inside particle. By convex/concave bodies with geometric duality, interaction potentials of particles located outside and inside the curved surface bodies are shown to have duality. With duality, the curvature-based potential between a curved surface body and an inside particle is derived. Furthermore, the normal and tangential driving forces exerted on the particle are studied and expressed as a function of curvatures and curvature gradients. Numerical experiments are designed to test accuracy of the curvature-based potential.

关键词： curved duality curvature concave tangential viewpoint convex intersection body radius

Occurrence characteristics of branching structures in equatorial plasma bubbles:a statistical study based on all-sky imagers in China

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Earth and Planetary Physics 2021年第5期5卷 407-415页

作者： Kun Wu JiYao Xu yajun Zhu Wei Yuan State Key Laboratory of Space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China

Branching structure(BS)is a very important phenomenon in the evolution of equatorial plasma bubbles(EPBs),the mechanism of which is widely studied from observation and from ***,occurrence characteristics of branching structure of equatorial plasma bubbles(BSEPBs)have not been well *** this work,we used seven-years(2012-2018)of observations from two all-sky imagers to study occurrence of BSEPBs in *** data reveal a high incidence of BS in EPB cases;in particular,most EPBs occurring on days with geomagnetic disturbances exhibited *** when all EPBs exhibited BS increased significantly in the 2014 solar *** times of BSEPBs varied with local time;most of the BSEPBs began to appear between 21:00 and 22:00 *** the solar maximum,some BSEPBs were observed after *** data also reveal that BSEPBs are characterized primarily by two branches or three ***-branching appeared only in the solar *** events with different coexisting branching structures increased from 2012 to 2014 and decreased from 2014 to *** results strongly suggest that BSEPB occurrence is related to solar activity and geomagnetic activity,and thus provide a new perspective for future studies of EPBs as well as enriching our understanding of ionospheric irregularity.

关键词： branching structure of equatorial plasma bubble equatorial plasma bubble ionospheric irregularity all-sky imager

Synthesis of defect-rich hierarchical sponge-like TiO2 nanoparticles and their improved photocatalytic and photoelectrochemical performance

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Frontiers of Materials Science 2020年第3期14卷 286-295页

作者： Qizhi Tian yajun Ji Yiyi Ojan Abulikemu Abulizi College of Science University of Shanghai for Science and TechnologyShanghai200093China College of Chemistry and Chemical Engineering Xinjiang UniversityUrumqi830046China

Defect-rich hierarchical sponge-like TiO2 nanoparticles were successfully synthesized via the combined one-step hydrothermal method and chemical reduction *** and TEM images showed their porous structure densely packed with even smaller TiO2 particles,while photocatalytic results manifested their superior photocatalytic performance and high *** RhB solution(10 ppm)could be absolutely degraded in 60 min,and the degradation rate was twice that of the sample without the treatment by ***,the TC solution(10 ppm)could be removed by 74.3%in 20 *** measurements also displayed that the photoelectrode based on such defectrich TiO2 nanoparticles had small resistance and improved charge transfer *** improved performance can be assigned to rich defects and phase junctions,which was supported by characterization *** presence of rich defects and phase junctions could not only promote the separation of photogenerated charge carriers,but also accelerate the electron transfer,beneficial for both the photocatalytic and the PEC *** is expected that the obtained hierarchical sponge-like TiO2 nanoparticles with rich defects have great potential for photocatalytic applications.

关键词： TiO2 hydrothermal method nanoparticles photocatalytic performance photoelectrochemical performance defects

Extraction of scandium from red mud by modified activated carbon and kinetics study

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Rare Metals 2008年第3期27卷 223-227页

作者： ZHOU Hualei LI Dongyan TIan yajun CHEN Yunfa State Key Laboratory of Multi-phase Complex System lnstituteqfProcess Engineering Chinese Academy of Sciences Beijing 100080 China School of Applied Sciences University of Science and Technology Beo＇ing Beijing 100083 China

Activated carbon （AC） was modified by tri-butyl phosphate （TBP） for selectively extracting scandium from red mud and characterized by BET （Brunauer-Emmett-Teller） surface area. The modified AC had a preferential adsorption to scandium. The influences of adsorbent dos- age, adsorption temperature, and time on adsorption capacity and selectivity to scandium were examined. An optimum adsorbent dosage （-6.25 g/L）, adsorption temperature （308 K）, and adsorption time （40 min） were figured out. A pseudo-second-order kinetics model was employed for describing the adsorption process of scandium.

关键词： modified activated carbon adsorption red mud scandium

Cooperative control and communication of intelligent swarms:a survey

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Control Theory and Technology 2020年第2期18卷 114-134页

作者： Kun HOU yajun YANG Xuerong YANG Jiazhe LAI Department of Aerospace Science and Technology University o f Aerospace EngineeringBeijing 101416China ZSchool of Aeronautics and Astronautics Sun Yat-Sen UniversityGuangzhou Guangdong 510275China

Individuals exchange information,experience and strategy based on *** is the basis for individuals to form swarms and the bridge of swarms to realize cooperative *** this paper,the multirobot swarm and its cooperative control and communication methods are reviewed,and we summarize these methods from the task,control,and perception *** on the research,the cooperative control and communication methods of intelligent swarms are divided into the following four categories:task assignment based methods(divided into market-based methods and alliance based methods),bio-inspired methods(divided into biochemical information inspired methods,vision based methods and self-organization based methods),distributed sensor fusion and reinforcement learning based methods,and we briefly define each method and introduce its basic *** on WOS database,we divide the development of each method into several stages according to the time distribution of the literature,and outline the main research content of each ***,we discuss the communication problems of intelligent swarms and the key issues,challenges and future work of each method.

关键词： Intelligent swarm cooperative control communication task assignment bio-inspired methods distributed sensor fusion reinforcement learning

Analysis of stability of support and surrounding rock in mining top coa of inclined coal seam

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International Journal of Mining Science and Technology 2014年第1期24卷 63-68页

作者： Xin yajun Gou Panfeng Ge Fudong School of Energy Science and Engineering Henan Polytechnic University Product Department Hebi Coal Co.Ltd.Henan Coal Industry and Chemical Group Co.Ltd.

The study analyzes the characteristics of roof movement in mining top coal of inclined coal seam,and establishes the mechanical model of support and surrounding-rock stability in inclined coal ***,this study carries out the numerical calculation and field observation of roof movement and support stability,and provides the critical control *** results show that the fracture firstly appears in middle-upper roof and extends upwards in top coal caving in inclined coal seam;regular and irregular caving zones appear in middle-upper stress concentration region,and the asymmetric caving arch is finally *** load of middle-upper working face is larger than that of the middle-lower face;dynamic load coefficient of upper support is large,and the load on the front of support is larger than that on the rear of it,which leads to poor support *** of support and surrounding-rock system depends mainly on upper-support stability.

关键词： Inclined coal seamRoof movement Mechanical modelStability