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Characterization and prediction of tailpipe ammonia emissions from in-use China 5/6 light-duty gasoline vehicles

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Frontiers of Environmental Science & Engineering 2024年第1期18卷 71-81页

作者： Lewei zeng Fengbin Wang Shupei xiao xuan Zheng Xintong Li Qiyuan Xie xiaoyang Yu Cheng Huang Qingyao Hu Yan You Ye Wu College of Chemistry and Environmental Engineering Shenzhen UniversityShenzhen 518060China State Key Laboratory of Engines Tianjin UniversityTianjin 300072China China Automotive Technology and Research Center Co.Ltd. Tianjin 300300China CATARC Automotive Test Center(Guangzhou)Co.Ltd. Guangzhou 511300China State Environmental Protection Key Laboratory of Cause and Prevention of Urban Air Pollution Complex Shanghai Academy of Environmental SciencesShanghai 200233China National Observation and Research Station of Coastal Ecological Environments in Macao Macao Environmental Research InstituteMacao University of Science and TechnologyMacao SAR 999078China School of Environment State Key Joint Laboratory of Environment Simulation and Pollution ControlTsinghua UniversityBeijing 100084China

On-road tailpipe ammonia (NH3) emissions contribute to urban secondary organic aerosol formation and have direct or indirect adverse impacts on the environment and human health. To understand the tailpipe NH3 emission characteristics, we performed comprehensive chassis dynamometer measurements of NH3 emission from two China 5 and two China 6 light-duty gasoline vehicles (LDGVs) equipped with three-way catalytic converters (TWCs). The results showed that the distance-based emission factors (EFs) were 12.72 ± 2.68 and 3.18 ± 1.37 mg/km for China 5 and China 6 LDGVs, respectively. Upgrades in emission standards were associated with a reduction in tailpipe NH3 emission. In addition, high NH3 EFs were observed during the engine warm-up period in cold-start cases owing to the intensive emissions of incomplete combustion products and suitable catalytic temperature in the TWCs. Notably, based on the instantaneous NH3 emission rate, distinct NH3–emitting events were detected under high/extra high velocity or rapid acceleration. Furthermore, NH3 emission rates correlated well with engine speed, vehicle specific power, and modified combustion efficiency, which were more easily accessible. These strong correlations were applied to reproduce NH3 emissions from China 5/6 LDGVs. The predicted NH3 EFs under different dynamometer and real-world cycles agreed well with existing measurement and prediction results, revealing that the NH3 EFs of LDGVs in urban routes were within 8.55–11.62 mg/km. The results presented here substantially contribute to improving the NH3 emission inventory for LDGVs and predicting on-road NH3 emissions in China.

关键词： NH3 instantaneous emissions Catalytic temperature Vehicle specific power Combustion efficiency Emission prediction

Cigarette Use and Secondhand Smoke Exposure Among Secondary School Students—China,2023

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China CDC weekly 2024年第22期6卷 509-515页

作者： Xinying zeng Shiwei Liu Lin xiao Tobacco Control Office Chinese Center for Disease Control and PreventionBeijingChina

What is already known about this topic?In 2021,the prevalence of experimental and current cigarette use among secondary school students in China stood at 16.7%and 4.7%,***,39.9%of these students were exposed to secondhand smoke at *** is added by this report?In comparison to 2021,the prevalence of current cigarette use remained unchanged at 4.2%in 2023,whereas experimental use declined to 13.7%.Notably,rates were significantly higher among vocational senior high school(VSHS)students relative to their peers in senior high school(SHS)and junior high school(JHS).Furthermore,exposure to secondhand smoke in schools decreased to 35.4%in 2023 from previously recorded levels,with more pronounced reductions observed in JHS and SHS populations and no notable change among VSHS *** are the implications for public health practice?Targeted tobacco control policies are imperative for secondary school students,including the establishment of smoke-free school ***,it is crucial to pay close attention to the needs of VSHS students.

关键词： smoke unchanged senior

mRNA vaccine technology for infectious diseases and beyond

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Science China(Life Sciences) 2024年第10期67卷 2267-2270页

作者： Pei Hao xiao Li xuan Li Wu Zhong Key Laboratory of Molecular Virology and Immunology Shanghai Institute of Immunity and InfectionChinese Academy of SciencesShanghai 200031China Changchun Veterinary Research Institute Chinese Academy of Agricultural SciencesChangchun 130122China Key Laboratory of Synthetic Biology CAS Center for Excellence in Molecular Plant SciencesInstitute of Plant Physiology and EcologyChinese Academy of SciencesShanghai 200032China National Engineering Research Center for the Emergency Drug Beijing Institute of Pharmacology and ToxicologyBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China

The rise of mRNA vaccine technology Vaccines stand as one of the most significant medical advancements,playing a crucial role in the prevention of infectious diseases and the improvement of global *** triumph of smallpox vaccination stands as a towering achievement in the annals of healthcare,leading to the complete elimination of a oncedevastating disease and showcasing the efficacy of vaccination methods.

关键词： methods vaccination prevention

Constructing Built-In Electric Fields with Semiconductor Junctions and Schottky Junctions Based on Mo-MXene/Mo-Metal Sulfides for Electromagnetic Response

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Nano-Micro Letters 2024年第10期16卷 453-473页

作者： xiaojun zeng xiao Jiang Ya Ning Yanfeng Gao Renchao Che School of Materials Science and Engineering Jingdezhen Ceramic UniversityJingdezhen 333403People's Republic of China School of Materials Science and Engineering Shanghai UniversityShanghai 200444People's Republic of China Laboratory of Advanced Materials Shanghai Key Lab of Molecular Catalysis and Innovative MaterialsAcademy for Engineering and TechnologyFudan UniversityShanghai 200438People's Republic of China Zhejiang Laboratory Hangzhou 311100People's Republic of China

The exploration of novel multivariate heterostructures has emerged as a pivotal strategy for developing high-performance electromagnetic wave(EMW)absorption ***,the loss mechanism in traditional heterostructures is relatively simple,guided by empirical observations,and is not *** this work,we presented a novel semiconductor-semiconductor-metal heterostructure sys-tem,Mo-MXene/Mo-metal sulfides(metal=Sn,Fe,Mn,Co,Ni,Zn,and Cu),including semiconductor junctions and Mott-Schottky *** skillfully combining these distinct functional components(Mo-MXene,MoS_(2),metal sulfides),we can engineer a multiple heterogeneous interface with superior absorption capabilities,broad effective absorption bandwidths,and ultrathin matching *** successful establishment of semiconductor-semiconductor-metal heterostructures gives rise to a built-in electric field that intensifies electron transfer,as confirmed by density functional theory,which collaborates with multiple dielectric polarization mechanisms to substantially amplify EMW *** detailed a successful synthesis of a series of Mo-MXene/Mo-metal sulfides featuring both semiconductor-semiconductor and semiconductor-metal *** achievements were most pronounced in Mo-MXene/Mo-Sn sulfide,which achieved remarkable reflection loss values of-70.6 dB at a matching thickness of only 1.885 *** cross-section calculations indicate that these MXene/Mo-metal sulfides have tremendous potential in practical military stealth *** work marks a departure from conventional component design limitations and presents a novel pathway for the creation of advanced MXene-based composites with potent EMW absorption capabilities.

关键词： Semiconductor-semiconductor-metal heterostructure Semiconductor junctions Mott-Schottky junctions Built-in electric field Electromagnetic wave absorption

Dynamic manipulation of multimodal emission in Er^(3+)-activated non-core-shell structure for optical thermometry and information security

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Rare Metals 2024年第4期43卷 1702-1712页

作者： xuan Liu Zi-Xia Lin Yin-Biao Shi xiao-Yan Wang Ming-Ye Ding xiao-Fei Yang College of Science Nanjing Forestry UniversityNanjing210037China Testing Center Yangzhou UniversityYangzhou225009China

Regulating luminescent dynamics of lanthanide-based luminescent materials via external stimuli is of great significance in the fields of optical thermometry and high-level ***,it is still a huge challenge to realize multimodal emissions with tunable color outputs from a single activator in simple structures via smart dynamic control of photon transition ***,we present a mechanistic strategy to achieve multimodal luminescence of Er^(3+)activators with color-switchable outputs in a non-core-shell *** the control of excitation dynamics(λ_(ex)=980,808,1532,377 nm),the population among the intermediate en ergy levels of Er^(3+)and the interaction between Er^(3+)and Yb^(3+)could be precisely modulated through energy transfer and migration processes,leading to the generation of colortunable multimodal luminescence upon diverse excitation modes(non-steady-state,single-/dual-wavelength steady,thermal activation).Inspired by its special luminescent performance,the as-obtained material exhibits great potential in noncontact thermometry,multimodal anticounterfeiting,and high-capacity information encryption by performing a series of proof-of-concept *** findings might provide a conceptual model to modulate the luminescent dynamics in a simple-structured system for the generation of color-adjustable multimodal emissions,which is convenient for the development of advanced luminescent materials toward versatile cuttingedge applications.

关键词： Lanthanide ions Multimodal emission Upconversion Downshifting Anti-counterfeiting Luminescent thermometry

Achieving structurally stable O3-type layered oxide cathodes through site-specific cation-anion co-substitution for sodium-ion batteries

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Journal of Energy Chemistry 2024年第6期93卷 411-418,I0011页

作者： Yihao Shen Chen Cheng xiao Xia Lei Wang Xi Zhou Pan zeng Jianrong zeng Liang Zhang Institute of Functional Nano&Soft Materials(FUNSOM) Soochow UniversitySuzhou 215123JiangsuChina Institute for Advanced Study School of Mechanical EngineeringChengdu UniversityChengdu 610106SichuanChina Shanghai Synchrotron Radiation Facility Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201204China Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China Jiangsu Key Laboratory of Advanced Negative Carbon Technologies Soochow UniversitySuzhou 215123JiangsuChina

O3-type layered oxides have garnered great attention as cathode materials for sodium-ion batteries because of their abundant reserves and high theoretical ***,challenges persist in the form of uncontrollable phase transitions and intricate Na^(+)diffusion pathways during cycling,resulting in compromised structural stability and reduced capacity over *** study introduces a special approach employing site-specific Ca/F co-substitution within the layered structure of O_(3)-NaNi_(0.5)Mn_(0.5)O_(2) to effectively address these ***,the strategically site-specific doping of Ca into Na sites and F into O sites not only expands the Na^(+)diffusion pathways but also orchestrates a mild phase transition by suppressing the Na^(+)/vacancy ordering and providing strong metal-oxygen bonding strength,*** as-synthesized Na_(0.95)Ca_(0.05)Ni_(0.5)Mn_(0.5)O_(1.95)F_(0.05)(NNMO-CaF)exhibits a mild O3→O3+O'3→P3 phase transition with minimized interlayer distance variation,leading to enhanced structural integrity and stability over extended *** a result,NNMO-CaF delivers a high specific capacity of 119.5 mA h g^(-1)at a current density of 120 mA g^(-1)with a capacity retention of 87.1%after 100 *** study presents a promising strategy to mitigate the challenges posed by multiple phase transitions and augment Na^(+)diffusion kinetics,thus paving the way for high-performance layered cathode materials in sodium-ion batteries.

关键词： Sodium-ion batteries O3-type layered oxides Site-specific co-doping Phase transition

Optically levitated micro gyroscopes with an MHz rotational vaterite rotor

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Microsystems & Nanoengineering 2024年第3期10卷 219-227页

作者： Kai zeng Xiangming Xu Yulie Wu Xuezhong Wu Dingbang xiao College of Intelligence Science and Technology National University of Defense TechnologyChangsha 410073China College of Information and Communication National University of Defense TechnologyWuhan 430000China Key Laboratory of Satellite Navigation Technology National University of Defense TechnologyChangsha 410073China

The field of levitated optomechanics has experienced significant advancements in manipulating the translational and rotational dynamics of optically levitated particles and exploring their sensing *** concept of using optically levitated particles as gyroscopes to measure angular motion has long been explored but has not yet been proven either theoretically or *** this study,we present the first rotor gyroscope based on optically levitated high-speed rotating *** gyroscope is composed of a micrometer-size ellipsoidal vaterite particle that is driven to rotate at MHz frequencies in a vacuum *** an external angular velocity is input,the optical axis deviates from its initial position,resulting in changes in the frequency and amplitude of the rotational *** analyzing these changes,the angular velocity of the input can be accurately detected,making it the smallest rotor gyroscope in the *** angular rate bias instability of the gyroscope is measured to be 0.08°/s and can be further improved to as low as 10^(−9)°/h theoretically by cooling the motion and increasing the angular moment of the levitated *** work opens a new application paradigm for levitated optomechanical systems and may pave the way for the development of quantum rotor gyroscopes.

关键词： particles rotational angular

Impact wear properties of dissimilar joints between bainitic frogs and pearlite rails

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Journal of Iron and Steel Research International 2024年第1期31卷 275-287页

作者： Pin-yong zeng Chun-guang Zuo xiao-yu Zhang Wei Li Tribology Research Institute Southwest Jiaotong UniversityChengdu610031SichuanChina

The impact wear behavior and damage mechanism of dissimilar welded joints between U26Mn frog and U75 V rail before and after normalizing treatment were studied by cyclic impact *** experiment indicated that the impact wear volume of the joints increased with the increasing number of impact *** main wear mechanisms include pitting wear,mild fatigue wear,delamination wear,and fatigue wear,and plastic deformation was the primary impact wear *** them,fatigue wear had the greatest influence on wear volume,while other wear mechanisms had limited *** impact wear resistance of the base material was better than that of the heat-affected *** treatment was beneficial to improving the impact wear resistance of welded joints owing to its effect to promote pearlite recovery,grain refinement,and uniform distribution of *** martensite generated in the rail welded joints aggravated the impact wear damage to the materials,which should be avoided.

关键词： Dissimilar welded joint Impact wear Bainitic steel Damage mechanism Wear rate

Observation and analysis of positive leader re-illumination in a 10 m ultra-high voltage transmission line gap under switching impulse voltages

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Plasma Science and Technology 2024年第10期26卷 93-100页

作者： Biao HUANG xuan ZHOU She WANG Chijie ZHUANG Rong zeng Le DENG Eliet Engineering School Changsha University of Science&TechnologyChangsha 410114People’s Republic of China State Key Laboratory of Disaster Prevention&Reduction for Power Grid Changsha University of Science&TechnologyChangsha 410114People’s Republic of China China International Engineering Consulting Co. Ltd.Beijing 100048People’s Republic of China Department of Electrical Engineering Tsinghua UniversityBeijing 100084People’s Republic of China

The leader propagation is one of the most important stages in long air gap *** mechanism behind leader re-illumination remains *** high humidity conditions(20.0–30.1 g/m^(3)),we have conducted experiments of long sparks in a 10 m ultra-high voltage(UHV)transmission line gap under switching impulse *** positive leaders predominantly propagate discontinuously,with almost no significantly continuous propagation *** leader channels are intensely luminous and each elongation segment is straight,with streamers resembling the“branch type”which differs from the“diffuse type”streamers at the front of continuous propagation *** distribution of the propagation velocities is highly random(3.7–18.4 cm/μs),and the average velocity(9.2 cm/μs)significantly exceeds that of continuous propagation(1.5–2.0 cm/μs).Analysis suggests that the current-velocity models suitable for continuous leader propagation do not align well with the experimental data in re-illumination *** on the discharge current waveforms and optical images,it is speculated that the newly elongated leader in re-illumination mode does not evolve gradually from the stem(about 1 cm)but rather evolves overall from a thermal channel much longer than stem.

关键词： long air gap discharge positive leader re-illumination discontinuous leader propagation