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Characteristics of bioaerosols under high-ozone periods,haze episodes,dust storms,and normal days in xi'an,China

Particuology 2024年第7期90卷 140-148页

作者： Yiming Yang Liu Yang xiaoyan Hu Zhenxing Shen Department of Environmental Science and Engineering Xi’an Jiaotong UniversityXi’an710049China Key Lab of Aerosol Chemistry&Physics SKLLQGInstitute of Earth EnvironmentChinese Academy of SciencesXi’an710049China

The characteristics of bioaerosols and their effects on human beings'health have become a major public concern in the recent *** study compared the characteristics of bioaerosols under different types of pollution(high-ozone[HO]episodes,haze episodes,and dust storms[DSs]),with those of bioaerosols on normal days(NDs)in xi'an,*** concentrations,diurnal variations,and size distribution of bacteria,fungi,and total airborne microbes(TAMs)were *** results showed that the bacterial and fungal concentrations were the highest during DSs and on NDs,reaching 425.2 and 956.9 colony-forming units/m^(3),*** concentration of TAMs was the highest during HO episodes,reaching 10.7×10^(6)cells/m^(3),which was significantly higher than that during the other *** maximum concentrations of bacteria and fungi during HO episodes were observed in the morning,while they appeared separately in the morning and evening during haze *** and TAMs during DSs reached peak concentrations in the morning and evening,which is opposite to the particulate matter(PM)distribution *** NDs,temperature and relative humidity had significant effects on *** size distributions of airborne bacteria exhibited bimodal patterns,whereas unimodal distributions were observed for *** mainly attached in fine particles(<2.1μm)with proportions of 67.4%and 60.5%during haze episodes and DSs,respectively,which means that fungi were easily penetrated into the human respiratory *** evaluation of influence factors revealed that PM_(2.5) and PM10 had negative effects on fungal concentration during DSs,and ozone concentration and temperature were inversely correlated with fungal concentration during HO *** results provide valuable reference data for elucidating the formation and evolution of bioaerosols under different types of pollution.

关键词： Bacteria Fungi Total airborne microbe Different air pollution types Influence factors

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Influence of misting system on the thermal environment and thermal comfort of seated people in semi-outdoor space in xi’an,China

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Frontiers of Architectural Research 2024年第3期13卷 668-681页

作者： Xu xie Zhen Sun xi Zhu Shengkai Zhao Zun Wang Yongchao Zhai College of Architecture Xi’an University of Architecture and TechnologyXi’an 710055China State Key Laboratory of Green Building Xi’an University of Architecture and TechnologyXi’an 710055China

In summer,factors such as solar radiation could make semi-outdoor spaces uncomfortable,and the use of misting systems for evaporative cooling is a low-energy improvement *** investigate the impact of misting system on the thermal environment and thermal comfort of seated people improvement,a field study was conducted at a semi-outdoor cafeteria in xi’*** results indicated that the misting system was capable of reducing the ambient air temperature by 2.4-4.9℃and increasing the relative humidity by 17.1%-17.8%.Participants in misting condition reported lower thermal sensation and higher thermal acceptability,thermal preference,humidity sensation,humidity preference and humidity *** no misting condition,the upper SET*limit acceptable to 80%of the population was 28.5℃.However,in the misting condition,the acceptable percentage of participants in each SET)interval was more than 90%.When SET)was 22.1-23.7℃,the improvement in human thermal comfort through misting system was not *** SET)was 23.7-28.5℃,the misting system significantly improve human thermal ***,two control temperature thresholds of the misting system were provided according to the relationship between 80%,the maximum(89.3%)acceptable percentage and the air temperature,which were 30.1℃and 26.5℃,respectively.

关键词： Misting system Thermal environment Thermal response Acceptable temperature Control strategy

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Water-soluble organic matter with various polarities in PM_(2.5) over xi'an,China:Abundance,functional groups,and light absorption

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Particuology 2024年第1期84卷 281-289页

作者： Xueting Yang Shasha Huang Dan Li Hongmei Xu Yaling Zeng Liu Yang Diwei Wang Ningning Zhang Junji Cao Zhenxing Shen Department of Environmental Science and Engineering Xi'an Jiaotong UniversityXi'an710049China School of Environmental Science and Engineering Southern University of Science and TechnologyShenzhen518055China State Key Laboratory of Loess and Quaternary Geology Institute of Earth EnvironmentChinese Academy of SciencesXi'an710049China

Humic-like substances(HULIS)are a major component of brown carbon and consequently play a major role in climate *** this study,70 PM_(2.5) samples were collected from xi'an in winter 2019 and summer *** HULIS(HULIS-n),acidic HULIS(HULIS-a),and high-polarity water-soluble organic compounds(HP-WSOC)were analyzed to determine their carbon concentrations and measure their ultraviolet-visible absorption and infrared *** the three components,HULIS-n had the highest carbon content in both winter(3.29±1.45μg m^(-3))and in summer(1.38±1.10μg m^(-3)).The semi-quantitative results for the functional groups revealed that HP-WSOC was rich in carboxylic acids and had high aromaticity in winter,whereas HULIS-n was rich in carboxylic acids in ***,HULJS-a was richer in nitrate esters and saturated aliphatic hydrocarbons in summer than in *** results for specific ultraviolet absorbance(SUVA)and E_(250)/E_(365) revealed that HULIS had higher molecular weight and aromaticity in winter than in ***-n dominated in the total light absorption of HULIS+HP-WSOC in both winter(73.08%)and summer(48.57%).Overall,the results on the carbon content,optical properties,and functional groups of WSOCs with differing polarity can improve un-derstanding of environmental and climatic effects.

关键词： Humic-like substances(HULIS) Aromaticity Fourier-transform infrared(FTIR) spectroscopy Light absorbance

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Acoustic carrier signal transmission technology and its potential for in-site monitoring of sliding electrical contact used in gas-insulated switchgear/gas-insulated transmission line

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High Voltage 2024年第2期9卷 287-295页

作者： Chen Chen Yutong Zhang Huijun Zhao Zongren Peng Qingyu Wang xi'an Jiaotong University Xi'anChina

A wireless signal transmission technology based on acoustic carrier is proposed,which overcomes the limitation of electromagnetic signal shielding and shows great potential for in-site monitoring of sliding electrical contact used in gas-insulated switchgear(GIS)/gasinsulated transmission line(GIL).Here,the state parameter of the sliding electrical contact is modulated onto the frequency domain of an ultrasound *** a mechanical wave,the ultrasonic wave is immune to electromagnetic shielding,so that it could carry the sensing signal to penetrate the metal shielding layer and transmit to the external terminals of GIS/*** principle and signal modulation process of the acoustic carrier based transmission system have been demonstrated in *** simulation and experiment have been conducted to analyse the system characteristics as well as optimise the system *** a proof-of-concept application,the in situ and on-line monitoring of the thermal rise of a slide electrical contact both in a current loading equivalent model and a prototype of GIS is *** results fit well with the physical process,and show a good measurement accuracy of 0.6%and tem-perature sensitivity of 400 Hz/℃.

关键词： electrical potential Acoustic

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A low-frequency pure metal metamaterial absorber with continuously tunable stiffness

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Applied Mathematics and Mechanics(English Edition) 2024年第7期45卷 1209-1224页

作者： xingzhong WANG Shiteng RUI Shaokun YANG Weiquan ZHANG Fuyin MA School of Mechanical Engineering Xi’an Jiaotong UniversityXi’an710049China xi’an Precision Machinery Research Institute Xi’an710077China

To address the incompatibility between high environmental adaptability and deep subwavelength characteristics in conventional local resonance metamaterials,and overcome the deficiencies in the stability of existing active control techniques for band gaps,this paper proposes a design method of pure metal vibration damping metamaterial with continuously tunable stiffness for wideband elastic wave *** design a dual-helix narrow-slit pure metal metamaterial unit,which possesses the triple advantage of high spatial compactness,low stiffness characteristics,and high structural stability,enabling the opening of elastic flexural band gaps in the low-frequency *** to the principle of a sliding rheostat,the introduction of continuously sliding plug-ins into the helical slits enables the continuous variation of the stiffness of the metamaterial unit,achieving a continuously tunable band gap *** successfully extends the effective band gap by more than ten *** experimental results indicate that this metamaterial unit can be used as an additional vibration absorber to absorb the low-frequency vibration energy ***,it advances the metamaterial absorbers from a purely passive narrowband design to a wideband tunable *** pure metal double-helix metamaterials retain the subwavelength properties of metamaterials and are suitable for deployment in harsh ***,by adjusting its stiffness,it substantially broadens the effective band gap range,presenting promising potential applications in various mechanical equipment operating under adverse conditions.

关键词： elastic metamaterial absorber continuously tunable stiffness low-frequency vibration damping variable stiffness design pure metal structure

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Heat management technology for solid-state high voltage and high repetitive pulse generators:Towards better effects and reliability

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High Voltage 2024年第1期9卷 2-21页

作者： Yanan Wang Linyuan Ren Zihao Yang Saikang Shen Zichen Deng Qi Yuan Weidong Ding Zhenjie Ding School of Electrical Engineering Xi'an Jiaotong UniversityXi'anChina School of Electronic and Information Engineering Xi'an Jiaotong UniversityXi'anChina

Solid-state high voltage high repetitive pulse generators have a broad prospect in various *** high power and high-frequency operation of the pulse generator suffer from the massive heat dissipation problem,which limits the improvement of the output parameters and even affects the *** article focuses on heat management technology for high voltage high repetitive pulse ***,the typical circuit topology of the high repetitive pulse generators was *** the perspective of different application requirements,the demands of the heat management design were ***,the heat generation characteristics and difficulties of solid-state high voltage high repetitive pulse generators were ***,the different stateof-art cooling techniques were reviewed,and their applicability and limitations for the high voltage high repetitive generators were ***,a flow chart for heat management design was given.

关键词： pulse state high

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Numerical study on the blocking effect of skin on Flash-Ball Impact and damage assessment

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Defence Technology（防务技术） 2024年第3期33卷 532-545页

作者： Dihua Ouyang Chunwei Qin xiaowen Qin Qiantao Zhang xingyu Liu xi'an University of Architecture and Technology Xi'an 710055China Analysis and Testing Center Xi'an University of Architecture and TechnologyXi'an 710055China Engineering University of PAP Xi'an 710086China

To explore the response law of non-lethal large-size kinetic energy projectiles to blunt attack on skin tissue,and to evaluate the skin injury characteristics of the attacked personnel and the use safety of kinetic energy *** on the LS-DYNA simulation software,a three-layer skin simulation model and a Flash-Ball rubber bullet model are established,and the force-time and deformation-time biomechanical corridors of the Flash-Ball rubber bullet impacting human skin tissue are *** corridor curve and the energy transfer and diffusion are analyzed and *** safety evaluation of the damage caused by the rubber bullet shooting a human body at different distances is carried out using the empirical formula of the penetration ***,the safe shooting distance is *** results show that the model used in the simulation has a good correlation with the experimental data,its biomechanical corridor characteristics are different from those of conventional vehicle impact and smallsize projectile response *** energy transfer and action time of medium and low-speed impact may cause greater *** fat layer is the largest energy absorption *** minimum safe shooting distance to ensure skin tissue from penetrating damage is 15.8 m,and the limit specific kinetic energy of skin damage is 7.88 J/cm^(2).This study can be extended to the study of biomechanical response law and safety evaluation under the impact of the same type of large kinetic energy projectile,which provides an important theoretical reference for the police to use large kinetic energy projectiles to conduct safe shooting in peacekeeping operations.

关键词： KIPs Blunt strike Biomechanical response Damage analysis

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Warhead fragments motion trajectories tracking and spatio-temporal distribution reconstruction method based on high-speed stereo photography

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Defence Technology（防务技术） 2024年第7期37卷 162-172页

作者： Pengyu Hu Jiangpeng Wu Zhengang Yan Meng He Chao Liang Hao Bai xi'an Modern Control Technology Research Institute Xi'an710065China xi'an OET Science and Technology Co. LtdXi'an710076China

High speed photography technique is potentially the most effective way to measure the motion parameter of warhead fragment benefiting from its advantages of high accuracy,high resolution and high ***,it faces challenge in dense objects tracking and 3D trajectories reconstruction due to the characteristics of small size and dense distribution of fragment *** address these challenges,this work presents a warhead fragments motion trajectories tracking and spatio-temporal distribution reconstruction method based on high-speed stereo ***,background difference algorithm is utilized to extract the center and area of each fragment in the image ***,a multi-object tracking(MOT)algorithm using Kalman filtering and Hungarian optimal assignment is developed to realize real-time and robust trajectories tracking of fragment *** reconstruct 3D motion trajectories,a global stereo trajectories matching strategy is presented,which takes advantages of epipolar constraint and continuity constraint to correctly retrieve stereo correspondence followed by 3D trajectories refinement using polynomial ***,the simulation and experimental results demonstrate that the proposed method can accurately track the motion trajectories and reconstruct the spatio-temporal distribution of 1.0×10^(3)fragments in a field of view(FOV)of 3.2 m×2.5 m,and the accuracy of the velocity estimation can achieve 98.6%.

关键词： Warhead fragment measurement High speed photography Stereo vision Multi-object tracking Spatio-temporal reconstruction

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Optical Nonlinearity of Violet Phosphorus and Applications in Fiber Lasers

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Chinese Physics Letters 2024年第1期41卷 16-20页

作者：杨慧苒齐梦婷李旭鹏薛泽鲁晨浩成嘉伟韩冬冬李璐 School of Science Xi’an University of Posts and TelecommunicationsXi’an 710121China China Academy of Space Technology(xi’an) Xi’an 710100China School of Electronic Engineering Xi’an University of Posts and TelecommunicationsXi’an 710121China

A D-shaped fiber is coated with a new two-dimensional nanomaterial,violet phosphorus(VP),to create a saturable absorber(SA)with a modulation depth of 3.68%.Subsequently,the SA is inserted into a fiber laser,enabling successful generation of dark solitons and bright–dark soliton pairs through adjustment of the polarization state within the *** further study,mode-locked pulses are achieved,proving the existence of polarization-locked vector *** results indicate that VP can be used as a polarization-independent SA.

关键词： polarization fiber absorber

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Room-temperature Self-healing and Recyclable PDMS Elastomers with Superior Mechanical Properties for Triboelectric Nanogenerators

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Chinese Journal of Polymer Science 2024年第10期42卷 1566-1577,I0014页

作者： Shu-Juan Wang Lu Wang Hong-Zhe Su Zhi-Cheng Wu Qiao-Gen Zhang Wei Fan xin-Li Jing School of Chemistry Joint Innovation Center of Thermal Protection MaterialsXi’an Jiaotong UniversityXi’an710049China School of Electrical Engineering Xi’an Jiaotong UniversityXi’an710049China School of Textile Science and Engineering Xi’an Polytechnic UniversityXi’an710048China

Polydimethylsiloxane(PDMS)is an electron-withdrawing material that is widely used in triboelectric nanogenerators(TENGs).However,PDMS has poor mechanical properties after curing and is easily damaged when subjected to long-term ***,the long-term stable operation of TENGs under mechanical deformation cannot be *** this work,multiple hydrogen bonds and aromatic disulfide bonds were introduced into PDMS *** elastomers exhibited high toughness(a tensile strength of 1.91 MPa and an elongation at break of 340%),good recyclability,and room-temperature self-healing properties(healing efficiency of 96.4%in 24 h).Recyclable sandwich-like triboelectric nanogenerators with excellent electrical output performance(13.5 V)and room-temperature self-healing performance(24 h,98%recovery of self-generating performance)were prepared by utilizing the hydrogen bonding between the PDMS elastomer and *** work reported herein offers theoretical guidance and a compelling strategy for developing high-performance TENG negative friction layers.

关键词： Polydimethylsiloxane Aromatic disulfide bonds Hydrogen bonds Room temperature self-healing Triboelectric nanogenerator

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