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Microcrack-and microvoid-related impact damage and ignition responses for HMX-based polymer-bonded explosives at high temperature

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Defence Technology（防务技术） 2022年第9期18卷 1602-1621页

作者： Hai-jiao xue yan-qing wu Kun yang Yi wu State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China School of Aerospace Engineering Beijing Institute of TechnologyBeijing100081China

Investigating the damage and ignition behaviors of polymer-bonded explosive(PBX) under a coupled impact and high-temperature loading condition is required for the safe use of charged PBXs. An improved combined microcrack and microvoid model(CMM) was developed for better describing the thermal effects of deformation, damage, and ignition responses of PBXs. The main features of the model under typical dynamic loadings(i.e. uniaxial tension and compression, and lateral confinement) at different initial temperature were first studied. And then the effects of temperature on impact-shear sensitivity of HMX-based PBXs were investigated. The results showed that the ignition threshold velocity of shear-crack hotspots exhibits an increase from 260 to 270 to 315-325 m/s when initial temperature increases from 301 to 348 K;and then the threshold velocity decreases to 290-300 m/s with the initial temperature continually increasing to 378 K. The predicted ignition threshold velocity level of the explosives under coupled impact and high temperature loading conditions were consistent with the experimental data.

关键词： PBX Thermal-mechanical coupling Numerical simulation Impact Sensitivity

Characteristics of SEN clogging and adhesive behavior of oxide inclusion during continuous casting of Ti-stabilized ultra-pure ferritic stainless steels

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Journal of Iron and Steel Research(International) 2023年第10期30卷 1939-1951页

作者： xue-feng Bai yan-hui Sun Hui-bin wu Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing100083China

Submerged entry nozzle(SEN)clogging during continuous casting of Ti-stabilized ultra-pure ferritic stainless(Ti-UPFS)steels was systematically investigated via cross-sectional analysis and acid dissolution treatment.The SEN deposit profile was characterized as occurring in three major layers:(1)an eroded refractory layer;(2)an initial adhesive layer comprised an Al_(2)O_(3)-ZrO_(2) composite sub-layer and a dense Al_(2)O_(3)-based deposit sub-layer;and(3)a porous multiphase deposit layer mainly consisting of MgO·Al_(2)O_(3),CaO-Al_(2)O_(3),and CaO-TiOx.The MgO·Al_(2)O_(3)-rich inclusions did not adhere directly to the eroded refractory but were entrapped during the deposit growth.Results of inclusion characterization in the tundish revealed that the MgO·Al2O3-rich particles present in the tundish served as the primary source of clogging deposits.Furthermore,a novel cavity-induced adhesion model by circular approximation was established to explain the effects of complex inclusion characteristics and refractory material type on adhesion force.A high number of small MgO·Al_(2)O_(3) inclusions were expected to accelerate the buildup of clogging deposits.Improving the modification of MgO·Al_(2)O_(3)-rich inclusions in the size range of 2-4μm by Ca treatment was crucial to minimizing the risk of SEN clogging during the continuous casting of Ti-UPFS steels.

关键词： Ti-stabilized ultra-pure ferritic stainless steel Submerged entry nozzle clogging MgO·Al_(2)O_(3)-rich inclusion Adhesion Continuous casting

Advances in Noble Metal-Decorated Metal Oxide Nanomaterials for Chemiresistive Gas Sensors:Overview

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纳微快报：英文版 2023年第6期15卷 353-427页

作者： Li‑Yuan Zhu Lang‑Xi Ou Li‑Wen Mao xue‑Yan Wu Yi‑Ping Liu Hong‑Liang Lu State Key Laboratory of ASIC and System Shanghai Institute of Intelligent Electronics and SystemsSchool of MicroelectronicsFudan UniversityShanghai 200433People’s Republic of China School of Opto‑Electronic Information and Computer Engineering University of Shanghai for Science and TechnologyShanghai 200093People’s Republic of China State Key Laboratory of Metal Matrix Composites School of Material Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240People’s Republic of China

Highly sensitive gas sensors with remarkably low detection limits are attractive for diverse practical application fields including real-time environmental monitoring,exhaled breath diagnosis,and food freshness analysis.Among various chemiresistive sensing materials,noble metal-decorated semiconducting metal oxides(SMOs)have currently aroused extensive attention by virtue of the unique electronic and catalytic properties of noble metals.This review highlights the research progress on the designs and applications of different noble metal-decorated SMOs with diverse nanostructures(e.g.,nanoparticles,nanowires,nanorods,nanosheets,nanoflowers,and microspheres)for high-performance gas sensors with higher response,faster response/recovery speed,lower operating temperature,and ultra-low detection limits.The key topics include Pt,Pd,Au,other noble metals(e.g.,Ag,Ru,and Rh.),and bimetals-decorated SMOs containing ZnO,SnO_(2),WO_(3),other SMOs(e.g.,In_(2)O_(3),Fe_(2)O_(3),and CuO),and heterostructured SMOs.In addition to conventional devices,the innovative applications like photo-assisted room temperature gas sensors and mechanically flexible smart wearable devices are also discussed.Moreover,the relevant mechanisms for the sensing performance improvement caused by noble metal decoration,including the electronic sensitization effect and the chemical sensitization effect,have also been summarized in detail.Finally,major challenges and future perspectives towards noble metal-decorated SMOs-based chemiresistive gas sensors are proposed.

关键词： Noble metal Bimetal Semiconducting metal oxide Chemiresistive gas sensor Electronic sensitization Chemical sensitization

Spatiotemporal variation and correlation of soil enzyme activities and soil physicochemical properties in canopy gaps of the Tianshan Mountains,Northwest China

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Journal of Arid Land 2022年第7期14卷 824-836页

作者： ABAY Peryzat GONG Lu CHEN Xin LUO yan wu xue College of Ecology and Environment Xinjiang UniversityUrumqi 830017China Key Laboratory of Oasis Ecology Ministry of EducationUrumqi 830017China College of Resources and Environmental China Agricultural UniversityBeijing 100083China

The study of the heterogeneity of soil enzyme activities at different sampling locations in canopy gaps will help understand the influence mechanism of canopy gaps on soil ecological processes.In this paper,we analyzed the spatiotemporal variation of soil enzyme activities and soil physicochemical properties at different sampling locations(closed canopy,expanded edge,canopy edge,gap center)in different sampling time(December,February,April,June,August,and October)on the northern slope of the Tianshan Mountains,Northwest China.The results showed that soil catalase,cellulase,sucrase,and acid phosphatase activities were relatively high from June to October and low from December to April,and most of soil enzyme activities were higher at closed canopy than at gap center.Soil urease activity was high during December-February.The soil temperature reached the highest value during June-August and was relatively high at gap center in October,December,and February.Soil water content was significantly higher in December and April than in other months.Soil bulk density was higher at gap center than at closed canopy in December.Soil pH and soil electrical conductivity in most months were higher at closed canopy than at gap center.Soil organic carbon,soil total nitrogen,and soil total phosphorus were generally higher at gap center than at closed canopy.Furthermore,sampling time played a leading role in the dynamic change of soil enzyme activity.The key factors affecting soil enzyme activity were soil temperature and soil water content,which were governed by canopy gaps.These results provide important support for further understanding the influence mechanism of forest ecosystem management and conservation on the Tianshan Mountains.

关键词： soil enzyme activity soil physicochemical property spatiotemporal variation canopy gap Tianshan Mountains

Dynamic emission characteristics and control strategies of air pollutants from motor vehicles in downtown Beijing,China

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Journal of Environmental Sciences 2024年第2期136卷 637-646页

作者： yan Shen Tongran wu Aiping Lian Jie Gao Fei Peng Guohua Song xuefang wu yangyang Cui Xinyu Liu Yunfei Wan Jing yan Yifeng xue National Engineering Research Center of Urban Environmental Pollution Control Beijing Municipal Research Institute of Eco-Environmental ProtectionBeijing 100037China Beijing Municipal Ecology and Environment Bureau Beijing 100048China Beijing Jiaotong University Beijing 100091China

This study combined the real-time monitoring and investigation of traffic flows to comprehensively analyze the road traffic flow and vehicle structure in downtown Beijing.A dynamic emission inventory of motor vehicle air pollutants in downtown Beijing in 2021 was established,and the impact of these emissions on air quality was simulated and quantified,and different emission reduction control scenarios were proposed to evaluate their environmental improvement effects and explore measures to mitigate the impact of pollution emissions.The results show that the high traffic flow and the structure of the motor vehicle emissions in downtown Beijing are the main causes of severe motor vehicle pollution.Monitoring data shows that traffic flow in central Beijing is dominated by small passenger vehicles,while the vehicle mix is better than in other regions,with 72.0%of vehicles meeting"National V"or higher emission standards.However,to achieve higher air quality goals,further reducing vehicle emissions is necessary.Based on dynamic traffic flow,the average daily emissions of nitrogen oxides(NOX),particulate matters(PM_(2.5))and volatile organic compounds(VOC)from motor vehicles in central Beijing are 17.7 tons,0.6 tons and 14.0 tons,respectively,accounting for 23.0%of the city’s average daily motor vehicle emissions.If a zero-emission zone for motor vehicles were implemented in central Beijing,the annual average emission level of pollutants will be reduced by 10.4%to 21.0%.The designation of ultra-low emission zones for motor vehicles could be effective in improving the air quality in the center of Beijing.

关键词： Motor vehicle Air pollutant Emission characteristics Control strategy Beijing

On Degenerate Array Type Polynomials

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Computer Modeling in Engineering & Sciences 2022年第4期130卷 295-305页

作者： Lan wu xue-yan Chen Muhammet Cihat Dagli Feng Qi Key Laboratory of Intelligent Manufacturing Technology Inner Mongolia Minzu UniversityTongliao028000Inner MongoliaChina Department of Mathematics Akdeniz UniversityAntalya07058Turkey Institute of Mathematics Henan Polytechnic UniversityJiaozuo454010China School of Mathematical Sciences Tiangong UniversityTianjin300387China

In the paper,with the help of the Fa′a di Bruno formula and an identity of the Bell polynomials of the second kind,the authors define degenerateλ-array type polynomials,establish two explicit formulas,and present se... 详细信息

关键词： Degenerate array polynomial Stirling number of the second kind generating function explicit formula recurrence relation

Ten-year emission characteristics of atmospheric pollutants from incineration of sacrificial offerings in China

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Journal of Environmental Sciences 2022年第4期34卷 391-400页

作者： yangyang Cui Gen Zhang Wei Wang yan Shen Xiaoman Zhai xuefang wu Renfei Li Bobo wu Yifeng xue National Engineering Research Center of Urban Environmental Pollution Control Beijing Municipal Research Institute of Environmental ProtectionBeijing 100037China State Key Laboratory of Severe Weather&Key Laboratory for Atmospheric Chemistry of CMA Institute of Atmospheric CompositionChinese Academy of Meteorological SciencesBeijing 100081China Key Laboratory of Pollution Control of Ministry of Civil Affairs 101 Institute of Ministry of Civil AffairsBeijing 100070China Beijing Technology and Business University Beijing 100048China

The incineration of sacrificial offerings is a significant widely practiced custom that is also a kind of neglected air pollution source in China.Our results showed that the emission factors of particulate matter,SO_(2),CO,NO_(x),and VOCs emitted from the incineration of sacrificial offerings with purification systems were reduced by 95%,19%,9%,82%,and 42%,respectively,compared with those without a purification system,revealing a significant effect of the flue gas purification system on reducing particulate matter and gaseous pollutants.The emission level of air pollutants from the incineration of sacrificial offerings remained stable before 2013 and then showed a remarkable decrease after the implementation of China′s Air Pollution Prevention Action Plan in 2013.The emissions of TSP(total suspended particulate),PM_(10),PM_(2.5),and NO_(x)in 2009 were 8222,6106,5656 and 15,878 ton,respectively,obviously higher than 3434,2551,2305 and 8579 ton in 2019.Such trend was affected by both the quantity of incineration and the installation rate of purification systems after the Emission Standard of Air Pollutants for Crematory(GB 13801-2015)issued in China.Distinct spatial distribution of atmospheric pollutants from incineration of sacrificial offerings was found with higher in the east and south of China than the west and north of China,which is proportional to the regional economy and population.The maximum ground-level concentration typically occurred at 0.12-0.2 km from the pollution source,posing potential health risks to people entering and exiting funeral and burial sites and nearby residents.

关键词： Incineration of sacrificial offerings Atmospheric pollutants Purification system Emission inventory

Photonuclear production of nuclear isomers using bremsstrahlung induced by laser-wakefield electrons

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Nuclear Science and Techniques 2023年第5期34卷 112-124页

作者： Hao-yang Lan Di wu Jia-Xin Liu Jian-Yao Zhang Huan-Gang Lu Jian-Feng Lv xue-Zhi wu Wen Luo xue-Qing yan State Key Laboratory of Nuclear Physics and Technology and Key Laboratory of HEDP of the Ministry of EducationCAPTPeking UniversityBeijing 100871China School of Nuclear Science and Technology University of South ChinaHengyang 421001China

In this study,we theoretically investigate the feasibility of using laser-wakefield accelerated(LWFA)electrons for the photonuclear measurement of nuclear isomers according to the characteristics of the electrons obtained from LWFA experiments conducted at the Compact Laser-Plasma Accelerator(CLAPA)laboratory.The experiments at the CLAPA show that a stable electron beam with an energy of 78-135 MeV and a charge of 300-600 pC can be obtained.The bremsstrahlung spectra were simulated using Geant4,which suggests that a bremsstrahlung source with a peak intensity of 10^(19) photons/s can be generated.Theoretical calculations of isomer production cross sections from the photonuclear reactions on six target nuclei,^(197)Au,^(180)Hf,^(159)Tb,^(115)In,^(103)Rh,and ^(90)Zr,were performed and compared with the available experimental data in EXFOR,which suggest that further experiments are required for a series of photonuclear reaction channels.Flux-averaged cross sections and isomer ratios(IR)resulting from such bremsstrahlung sources are theoretically deduced.The results suggest that IR measurements can be used to constrain nuclear components,such asγstrength function and optical model potential.In addition,the detection of the decay characteristics was evaluated with Geant4 simulations.The use of the LWFA electron beam and its bremsstrahlung for photonuclear studies involving nuclear isomers is anticipated.

关键词： Photonuclear reactions Laser–plasma acceleration Flux-averaged isomer ratio

Vehicle emissions of primary air pollutants from 2009 to 2019 and projection for the 14th Five-Year Plan period in Beijing, China

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Journal of Environmental Sciences 2023年第2期124卷 513-521页

作者： Tongran wu yangyang Cui Aiping Lian Ye Tian Renfei Li Xinyu Liu Jing yan Yifeng xue Huan Liu Bobo wu National Engineering Research Center of Urban Environmental Pollution Control Beijing Municipal Research Institute of Environmental ProtectionBeijing 100037China Beijing Municipal Ecology and Environment Bureau Beijing 100048China State Key Joint Laboratory of ESPC School of EnvironmentTsinghua UniversityBeijing 100084China School of Ecology and Environment Beijing Technology and Business UniversityBeijing 100048China

Over the past decade,the emission standards and fuel standards in Beijing have been upgraded twice,and the vehicle structure has been improved by accelerating the elimination of 2.95 million old vehicles.Through the formulation and implementation of these policies,the emissions of carbon monoxide(CO),volatile organic compounds(VOCs),nitrogen oxides(NO_(x)),and fine particulate matter(PM_(2.5))in 2019 were 147.9,25.3,43.4,and 0.91 kton in Beijing,respectively.The emission factor method was adopted to better understand the emissions characteristics of primary air pollutants from combustion engine vehicles and to improve pollution control.In combination with the air quality improvement goals and the status of social and economic development during the 14th Five-Year Plan period in Beijing,different vehicle pollution control scenarios were established,and emissions reductions were projected.The results show that the emissions of four air pollutants(CO,VOCs,NO_(x),and PM_(2.5))fromvehicles in Beijing decreased by an average of 68% in 2019,compared to their levels in 2009.The contribution of NOx emissions from diesel vehicles increased from 35% in 2009 to 56% in 2019,which indicated that clean and energy-saving diesel vehicle fleets should be further improved.Electric vehicle adoption could be an important measure to reduce pollutant emissions.With the further upgrading of vehicle structure and the adoption of electric vehicles,it is expected that the total emissions of the four vehicle pollutants can be reduced by 20%-41% by the end of the 14th Five-Year Plan period.

关键词： Emission variations Vehicle structure Electric vehicle 14th Five-Year Plan Air pollution