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Robustness of ventilation systems in the control of walking-induced indoor fluctuations: Method development and case study

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Building Simulation 2022年第9期15卷 1645-1660页

作者： Jianlin Ren Junjie he Xiangfei Kong Hongwan Li School of Energy and Environmental Engineering Hebei University of TechnologyTianjin300401China Department of Environmental Engineering Sciences University of FloridaUSA

Walking-induced fluctuations have a significant influence on indoor airflow and pollutant dispersion.This study developed a method to quantify the robustness of ventilation systems in the control of walking-induced fluctuation control.Experiments were conducted in a full-scale chamber with four different kinds of ventilation systems:ceiling supply and side return(CS),ceiling supply and ceiling return(CC),side supply and ceiling return(SC),and side supply and side return(SS).The measured temperature,flow and pollutant field data was(1)denoised by FFT filtering or wavelet transform;(2)fitted by a Gaussian function;(3)feature-extracted for the range and time scale disturbance;and then(4)used to calculate the range scale and time scale robustness for different ventilation systems with dimensionless equations developed in this study.The selection processes for FFT filtering and wavelet transform,FFT filter cut-off frequency,wavelet function,and decomposition layers are also discussed,as well as the threshold for wavelet denoising,which can be adjusted accordingly if the walking frequency or sampling frequency differs from that in other studies.The results show that for the flow and pollutant fields,the use of a ventilation system can increase the range scale robustness by 19.7%-39.4% and 10.0%-38.8%,respectively;and the SS system was 7.0%-25.7% more robust than the other three ventilation systems.However,all four kinds of ventilation systems had a very limited effect in controlling the time scale disturbance.

关键词： FFT filtering wavelet denoising Gaussian fitting feature extraction robust

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Enhanced mechanical properties of Mg-3Al-1Zn alloy sheets through slope extrusion

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International Journal of Minerals,Metallurgy and Materials 2022年第7期29卷 1343-1350页

作者： Huabao Yang Yanfu Chai Bin Jiang Chao he Junjie he Qingshan Yang Ming Yuan School of Mechanical and Electrical Engineering Shaoxing UniversityShaoxing 312000China Tianjin Key Laboratory of Composite&Functional Materials School of Materials Science and EngineeringTianjin UniversityTianjin 300072China State Key Laboratory of Mechanical Transmissions College of Materials Science and EngineeringChongqing UniversityChongqing 400044China College of Materials Science and Engineering Yunnan UniversityKunming 650091China School of Metallurgy and Material Engineering Chongqing University of Science and TechnologyChongqing 401331China

A novel extrusion approach,entitled slope extrusion(SE),was employed to manufacture AZ31(Mg-3Al-1 Zn,wt%)alloy sheets.The microstructures,textures,and mechanical properties were investigated,compared with those of the AZ31 sheet fabricated by conventional extrusion(CE).Through the combination of finite element simulation and actual experiment,the ultimate results indicated that significant grain refinement(from 9.1 to 7.7 and 5.6μm)and strong basal texture(from 12.6 to 17.6 and 19.5 mrd)were achieved by the SE process.The essence was associated with the additional introduced inclined interface in the process of SE,which could bring about more asymmetric deformation and stronger accumulated strain along the ND when compared with the process of CE.As a consequence,the SE sheets exhibited a higher yield strength(YS)and ultimate tensile strength(UTS)than the counterparts of the CE sheet,which was mainly assigned to the synergistic effects from grain refining and texture strengthening.

关键词： AZ31 Mg alloy sheets slope extrusion microstructure texture strength

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An experimental study on metal precipitation driven by fluid mixing: implications for genesis of carbonate-hosted lead–zinc ore deposits

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Acta Geochimica 2019年第2期38卷 202-215页

作者： Yan Zhang Runsheng Han Xing Ding Junjie he Yurong Wang Geological Survey Center for Non-ferrous Mineral Resources Kunming University of Science and Technology State Key Laboratory of Isotope Geochemistry Guangzhou Institute of Geochemistry Chinese Academy of Sciences CAS Center for Excellence in Tibetan Plateau Earth Sciences Key Laboratory of Mineralogy and Metallogenic Guangzhou Institute of Geochemistry Chinese Academy of Sciences University of Chinese Academy of Sciences

A type of carbonate-hosted lead–zinc(Pb–Zn)ore deposits, known as Mississippi Valley Type(MVT)deposits, constitutes an important category of lead–zinc ore deposits. Previous studies proposed a fluid-mixing model to account for metal precipitation mechanism of the MVT ore deposits, in which fluids with metal-chloride complexes happen to mix with fluids with reduced sulfur, producing metal sulfide deposition. In this hypothesis, however, the detailed chemical kinetic process of mixing reactions, and especially the controlling factors on the metal precipitation are not yet clearly stated. In this paper, a series of mixing experiments under ambient temperature and pressure conditions were conducted to simulate the fluid mixing process, by titrating the metal-chloride solutions, doping withor without dolomite, and using NaHS solution. Experimental results, combined with the thermodynamic calculations, suggest that H_2S, rather than HS^-or S^(2-),dominated the reactions of Pb and/or Zn precipitation during the fluid mixing process, in which metal precipitation was influenced by the stability of metal complexes and the pH. Given the constant concentrations of metal and total S in fluids, the pH was a primary factor controlling the Pb and/or Zn metal precipitation. This is because neutralizing or neutralized processes for the ore-forming fluids can cause instabilities of Pb and/or Zn chloride complexes and re-distribution of sulfur species, and thus can facilitate the hydrolysis of Pb and Zn ions and precipitation of sulfides. Therefore, a weakly acidic to neutral fluid environment is most favorable for the precipitation of Pb and Zn sulfides associated with the carbonate-hosted Pb–Zn deposits.

关键词： Metal precipitation Fluid mixing Sulfur species MVT lead-zinc ore deposits Carbonate-hosted lead-zinc deposits

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Relating Initial Texture to Deformation Behavior During Cold Rolling and Static Recrystallization Upon Subsequent Annealing of an Extruded WE43 Alloy

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Acta Metallurgica Sinica(English Letters) 2022年第11期35卷 1793-1811页

作者： Qinghang Wang Haowei Zhai Hongbo Xia Lintao Liu Junjie he Dabiao Xia Hong Yang Bin Jiang School of Mechanical Engineering Yangzhou UniversityYangzhou 225127China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing 400044China School of Materials and Energy Yunnan UniversityKunming 650599China The Center of New Energy Materials and Manufacturing Jihua LaboratoryFoshan 528000China

Deformation behaviors during cold rolling and static recrystallization behaviors upon subsequent annealing of an extruded WE43 alloys with different initial textures were investigated in this study.Three types of differently textured WE43 initial alloys were labeled as samplesⅠ,ⅡandⅢ.The results showed that multiple twinning modes and basal slip dominated the deformation of samples during cold rolling.Cold-rolled sampleⅠactivated the larger number of double twins with high strain energy,accompanied by the more uniform strain distribution,than cold-rolled samplesⅡandⅢ.During subsequent annealing,recrystallized grains preferentially occurred in double twins,twin-twin intersections and grain boundaries,thereby making cold-rolled sampleⅠhave the more rapid recrystallization rate.Similar recrystallization textures formed in three types of cold-rolled samples at the recrystallization nucleation stage,and they never largely changed with the annealing time due to the uniform grain growth induced by the solute drag and the precipitation pinning at grain boundaries.After full recrystallization,the grain growth was controlled by the solute drag,instead of precipitates which were re-dissolved into the matrix.Finally,the nucleation and growth kinetics of static recrystallization were calculated,and the effects of initial texture on activation energies of recrystallization nucleation and growth were discussed.

关键词： WE43 alloy Texture Cold rolling Annealing Static recrystallization

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Coastal bathymetry inversion using SAR-based altimetric gravity data:A case study over the South Sandwich Island

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Geodesy and Geodynamics 2023年第3期14卷 212-222页

作者： Yihao Wu junjie Wang Xiufeng he Yunlong Wu Dongzhen Jia Yueqian Shen School of Earth Sciences and Engineering Hohai UniversityNanjing 211100China Key Laboratory of Geological Survey and Evaluation of Ministry of Education China University of GeosciencesWuhan 430079China

The global bathymetry models are usually of low accuracy over the coastline of polar areas due to the harsh climatic environment and the complex topography.Satellite altimetric gravity data can be a supplement and plays a key role in bathymetry modeling over these regions.The Synthetic Aperture Radar(SAR)altimeters in the missions like CryoSat-2 and Sentinel-3A/3B can relieve waveform contamination that existed in conventional altimeters and provide data with improved accuracy and spatial resolution.In this study,we investigate the potential application of SAR altimetric gravity data in enhancing coastal bathymetry,where the effects on local bathymetry modeling introduced from SAR altimetry data are quantified and evaluated.Furthermore,we study the effects on bathymetry modeling by using different scale factor calculation approaches,where a partition-wise scheme is implemented.The numerical experiment over the South Sandwich Islands near Antarctica suggests that using SARbased altimetric gravity data improves local coastal bathymetry modeling,compared with the model calculated without SAR altimetry data by a magnitude of 3:55 m within 10 km of offshore areas.Moreover,by using the partition-wise scheme for scale factor calculation,the quality of the coastal bathymetry model is improved by 7.34 m compared with the result derived from the traditional method.These results indicate the superiority of using SAR altimetry data in coastal bathymetry inversion.

关键词： Coastal bathymetry inversion Synthetic aperture radar altimeter Sentinel-3A/3B CryoSat-2 Altimetric gravity data Scale factor

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Synthesis and electrochemical properties of Zn_3V_3O_8 as novel anode material

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Chinese Chemical Letters 2019年第3期30卷 806-808页

作者： Yunxia Jin Junjie he Zaihua Ou Chuanqi Feng Guangxue Zhang Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials & Ministry of Education Key Laboratory for Synthesis and Applications of Organic Functional Molecules Hubei University Nanxian Fanggu Middle School School of Nuclear Technology and Chemistry & Biology Hubei University of Science and Technology

Zn_3V_3O_8 two-dimensional micro sheets are successfully synthesized by combination of solvothermal method and heat treatment. The X-ray diffraction(XRD) and field emission scanning electron microscopy(SEM) are used to characterize the structure and morphology of the samples, and the battery testing system is used to investigate its electrochemical performance. The results show that the Zn_3V_3O_8 is successfully obtained using mix solvent(water:ethylene glycol =1:1), and the sample takes on morphology of two-dimensional sheets. The initial discharge capacity for Zn_3V_3O_8 two-dimensional micro sheets is 752.0 mAh/g at 100 mA/g in the voltage range of 0.01-3 V. After heat treatment in a tube furnace at 550 ℃, the sample had the initial discharge capacity as 1152.0 mAh/g and maintained it at 901.4 mAh/g after 100 cycles. The good electrochemical performance for Zn_3V_3O_8 two-dimensional micro sheets make it possible to be used as novel anode for lithium ion battery application.

关键词： Inorganic compound Inorganic synthesis Electronic materials Anode material Zn3V3O8

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Endless recrystallization of high-entropy alloys at high temperature

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Journal of Materials Science & Technology 2022年第33期128卷 71-81页

作者： Qingfeng Wu Zhijun Wang Feng he Zhongsheng Yang junjie Li Jincheng Wang State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China

In traditional physical metallurgy,once recrystallization occurs,it will proceed to 100%along with time even at relatively low temperatures,resulting in the limited thermal stability of partially recrystallized alloys.here,we proposed the strategy of achieving the endless recrystallization state at high temperature(~0.6T_(m))in high entropy alloys for the first time.The partially recrystallized microstructures remained stable after annealing at 700℃ for 1440 h toward endless recrystallization with kinetics analysis.Benefiting from the ultra-thermostable heterostructures,the alloy exhibited excellent mechanical properties of~1.6 GPa tensile strength at room temperature and~1.1 GPa tensile strength at 600°C even after exposure at 700℃ for 720 h.The kinetics of recovery,recrystallization,grain growth,and precipitate coarsening were quantitatively analyzed to uncover the mechanisms of endless recrystallization.The results revealed that the stable state of 50%recrystallization at 700℃ can be attributed to the precipitates inhibited recrystallization and the continued recovery decreased stored energy in the non-recrystallized regions.Furthermore,the grain size was stable in the recrystallized regions due to the strong pinning effect of the intergranular precipitates with slow coarsening rates.These findings created a brand-new state of endless recrystallization with the combination of recovery and recrystallization,which can significantly broaden the service temperature range of heterogeneous materials.

关键词： Endless recrystallization High-entropy alloy Partial recrystallization Thermal stability High-temperature mechanical properties

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Grain size dependence of annealing strengthening of an extruded Mg-Gd-Zn alloy subjected to pre-compression deformation

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Journal of Magnesium and Alloys 2022年第12期10卷 3576-3588页

作者： Qinghang Wang Siyuan Chen Bin Jiang Zhaoyang Jin Lingyu Zhao Junjie he Dingfei Zhang Guangsheng Huang Fusheng Pan School of Mechanical Engineering Yangzhou UniversityYangzhou225127China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing400044China School of Materials and Energy Yunnan UniversityKunming650599China

In this work, pre-strain annealing strengthening(PSAS) effect was investigated in an extruded Mg-1.0Gd-1.5 Zn(wt.%) alloy with respect to different grain sizes. The evolution of microstructures was provided by scanning electron microscopy(SEM), electron backscattered diffraction(EBSD), transmission electron microscopy(TEM) and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM) under the initial state, pre-compression, intermediate annealing and re-compression conditions. The obtained results showed a grain size-dependent PSAS effect in the alloy. The sample with larger grain sizes corresponded to a higher strengthening effect, which mainly resulted from a more remarkable hindrance for the growth of existing twins and a larger proportion of activation for the nucleation of new twins. This was closely associated with the increase of back stress and friction stress for twin boundary motion impeded by the larger restraint of dislocations, the higher stress field surrounding solutes and the more Zn segregation. In addition to twinning behavior, Guinier Preston(G.P.) zones on basaldislocations were found after intermediate annealing and provided an extra strengthening by inhibiting the motions of gilding pre-existing dislocations and newly formed ones, but it was independent on the grain size.

关键词： Mg-Gd-Zn alloy Grain size Pre-compression Annealing strengthening Twinning

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Molecular behavior and interactions with microbes during anaerobic degradation of bio-derived DOM in waste leachate

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Journal of Environmental Sciences 2023年第4期126卷 174-183页

作者： junjie Qiu Tianqi Li Fan Lü Yulong Huang Chao Li Hua Zhang Liming Shao Pinjing he Institute of Waste Treatment and Reclamation Tongji UniversityShanghai 200092China Shanghai Institute of Pollution Control and Ecological Security Shanghai 200092China Shanghai Engineering Research Center of Multi-source Solid Wastes Co-Processing and Energy Utilization Shanghai 200092China

It is the key to control bio-derived dissolved organic matters (DOM) in order to reduce the effluent concentration of wastewater treatment, especially for waste leachate with high organic contaminants. In the present study, the anaerobic degradation of aerobically stabilized DOM was investigated with DOM substrate isolated through electrodialysis. The degradation of bio-derived DOM was confirmed by reduction of 15%of total organic carbon in 100 days.We characterized the molecular behavior of bio-derived DOM by coupling molecular and biological information analysis. Venn based Sankey diagram of mass features showed the transformation of bio-derived DOM mass features. Occurrence frequency analysis divided mass features into six categories so as to distinguish the fates of intermediate metabolites and persistent compounds. Reactivity continuum model and machine learning technologies realized the semi-quantitative determination on the kinetics of DOM mass features in the form of pseudo-first order, and confirmed the reduction of inert mass features. Furthermore, network analysis statistically establish relationship between DOM mass features and microbes to identify the active microbes that are able to utilize bio-derived DOM. This work confirmed the biological technology is still effective in controlling recalcitrant bio-derived DOM during wastewater treatment.

关键词： Soluble microbial products Data mining Machine learning Solid waste Orbitrap

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Synchrophasor-based Online State Estimated in Large-scale Power Grid

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CSEE Journal of Power and Energy Systems 2023年第5期9卷 1613-1622页

作者： junjie Lin Chao Lu Wenchao Song Yingduo Han Yinsheng Su he Huang Licheng Li the College of Electrical Engineering and Automation Fuzhou UniversityFuzhouChina the Department of Electrical Engineering Tsinghua UniversityBeijingChina the State Key Lab of Power systems Department of Electrical EngineeringTsinghua UniversityBeijingChina China Southern Power Grid GuangzhouChina

With integration of a larger amount of clean power sources and power electronic equipment,operation and dynamic characteristics of the power grid are becoming more and more complicated and stochastic.Therefore,it is necessary and urgent to obtain accurate real-time states,which is difficult from traditional state estimation.This paper systematically develops a phasor measurement unit(PMU)based real-time state estimator for a realistic large-scale power grid for the first time.The estimator mainly relies on three refined algorithms,i.e.,an improved linear state estimation algorithm,a practical bad data identification method and a distributed topology check technique.Furthermore,a novel system architecture is designed and implemented for the China Southern Power Grid.Numerical simulations and extensive field operation results of the state estimator recorded under both normal and abnormal situations are presented.All the tests and field results demonstrate the advantages of the proposed algorithms in terms of online system monitoring and feasibility of refreshing the states of the whole system at intervals of tens of milliseconds.

关键词： PMU-based state estimation design and implementation bad data identification topology analysis

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