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Nano-sized stationary phase packings retained by single-particle frit for microchip liquid chromatography

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Chinese Chemical Letters 2024年第4期35卷 486-489页

作者： Wangyan Hu Ke Li Xiangnan Dou Ning Li Xiayan Wang Center Excellence for Environmental Safety and Biological Effects Beijing Key Laboratory for Green Catalysis and SeparationDepartment of ChemistryBeijing University of TechnologyBeijing 100124China Center for Environmental metrology National Institute of MetrologyBeijing 100029China

Modern chromatography is increasingly focused on miniaturization and integration. Compared to conventional liquid chromatography, microfluidic chip liquid chromatography(microchip-LC) has the potential due to its zero-dead volume connection and ease of integration. Nano-sized packings have the potential to significantly enhance separation performance in microchip-LC. However, their application has been hindered by packing difficulties. This study presents a method for packing nano-sized silica particles into a microchannel as the stationary phase. The microchip-LC packed column was prepared by combining the weir and the porous silica single-particle as frit to retain the packing particles. A surface tensionbased single-particle picking technique was established to insert porous single-particle frit into glass microchannels. Additionally, we developed a slurry packing method that utilizes air pressure to inject nano-sized packing into the microchannel. Pressure-driven chromatographic separation was performed using this nano-packed column integrated into a glass microchip. The mixture of four PAHs was successfully separated within just 8 min using a 5 mm separation channel length, achieving high theoretical plates(10~6plates/m). Overall, these findings demonstrate the potential of utilizing nano-sized packings for enhancing chromatographic performance in microchip systems.

关键词： Nano-size packing Single-particle frit Packed column Microchip LC Chromatographic separation

Dynamic Scene Graph Generation of Point Clouds with Structural Representation Learning

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Tsinghua Science and Technology 2024年第1期29卷 232-243页

作者： Chao Qi Jianqin Yin Zhicheng Zhang Jin Tang School of Artificial Intelligence Beijing University of Posts and TelecommunicationsBeijing 100876China Standard and metrology Research institute China Academy of Railway Sciences Corporation LimitedBeijing 100081China

Scene graphs of point clouds help to understand object-level relationships in the 3D *** graph generation methods work on 2D structured data,which cannot be used for the 3D unstructured point cloud *** point-cloud-based methods generate the scene graph with an additional graph structure that needs labor-intensive manual *** address these problems,we explore a method to convert the point clouds into structured data and generate graphs without given ***,we cluster points with similar augmented features into groups and establish their relationships,resulting in an initial structural representation of the point ***,we propose a Dynamic Graph Generation Network(DGGN)to judge the semantic labels of targets of different *** dynamically splits and merges point groups,resulting in a scene graph with high *** show that our methods outperform other baseline *** output reliable graphs describing the object-level relationships without additional manual labeled data.

关键词： scene graph generation structural representation point cloud

A redundant subspace weighting procedure for clock ensemble

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Chinese Physics B 2024年第4期33卷 435-442页

作者：徐海陈煜刘默驰王玉琢 National institute of metrology Beijing 100029China Key Laboratory of State Administration for Market Regulation Beijing 100029China China National Intellectual Property Administration Beijing 100088China

A redundant-subspace-weighting(RSW)-based approach is proposed to enhance the frequency stability on a time scale of a clock *** this method,multiple overlapping subspaces are constructed in the clock ensemble,and the weight of each clock in this ensemble is defined by using the spatial covariance *** superimposition average of covariances in different subspaces reduces the correlations between clocks in the same laboratory to some *** optimizing the parameters of this weighting procedure,the frequency stabilities of virtual clock ensembles are significantly improved in most cases.

关键词： weighting method redundant subspace clock ensemble time scale

Origin and evolution of false brinelling and fretting corrosion under rolling conditions

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Friction 2024年第4期12卷 618-631页

作者： Xin JIA Lu HUANG Miao SUN Wenbin LI National institute of metrology Beijing 100029China Yantai Tiancheng Machinery Co. Ltd.Yantai 264006China

Rolling bearings working in oscillating applications often suffer from false brinelling and fretting corrosion that limit their service *** present,the study of oscillation-induced failures is primarily dominated by a large number of sliding and bench ***,most of the previous work are not able to fully describe the two closely related but different failure *** this study,the origin and evolution of the two failures are thoroughly investigated under strictly controlled oscillating rolling *** results show that failure evolves from false brinelling to fretting corrosion under dry friction conditions regardless of the oscillation *** process is accompanied by a large area peeling and serious oxidation,and the oxygen content increases from 2.50 wt%to 21.22 wt%.Oxidation is a crucial factor in the evolution of false brinelling into fretting ***,the distribution of microwear and oxygen content depend on the oscillation *** lubrication conditions,the friction coefficient(COF)is smaller in the initial stage and led to local slip or transient instability of rolling ***,the size of the wear marks and COF increased and appeared to be larger than those under a dry friction ***,grease can separate the contact surfaces,only surface deformation owing to false brinelling and slight damage at the roughness level *** evolution of false brinelling and fretting corrosion is also closely related to residual *** brinelling often occurrs with residual stress accomulation,meanwhile,the residual stress increases from 120 to 300 *** peeling occurs,residual stress is *** failure pattern transformed from false brinelling to fretting corrosion and is accompanied by *** far,none of investigation is able to show satisfactory evolution of oscillating-induced failures,this study may contribute to more scientific understanding of rolling bearings against long-

关键词： oscillating false brinelling fretting corrosion wear residual stress

Accurate Quantification of Pure Thiacloprid with Mass Balance and Quantitative H-NMR

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Journal of Analysis and Testing 2024年第1期8卷 1-8页

作者： Mengling Tu Wei Zhang Yunxiao Zhu Wen Ma Xiao Li Shukun Zhou Hongmei Li Xianjiang Li Key Laboratory of Chemical metrology and Applications on Nutrition and Health for State Market Regulation Division of Metrology in ChemistryNational Institute of MetrologyBeijing 100029China State Key Laboratory of Heavy Oil Processing College of Chemical Engineering and EnvironmentChina University of PetroleumBeijing 102249China State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical SciencesPeking UniversityBeijing 100191China

Thiacloprid is the first-generation neonicotinoid insecticide,which is widely used in modern *** materials are essential for sound measurement and traceability of results in chemical *** thiacloprid was comprehensively assessed by two orthonormal methods:mass balance(MB) and quantitative nuclear magnetic resonance spectroscopy(qNMR).From MB,its mass fraction value was 998.4 mg/g with the subtraction of structurally related impurities(99.87%),inorganic impurities(0.006 mg/g),water(0.33 mg/g),and volatile organic solvent(0 mg/g).To guarantee sufficient separation of structurally related purity,peak purity of thiacloprid was evaluated by five points of UV *** the qNMR of hydrogen,its mass fraction value was 995.7 mg/g which was traced to the internal standard(methyl sulfone).Finally,the certified value was assigned to 997 mg/g,together with an expanded uncertainty of 3 mg/g(k=2).This high-purity thiacloprid can be applied to routine monitoring in agriculture and the food fields.

关键词： Mass balance Quantitative nuclear magnetic resonance spectroscopy Reference material Thiacloprid

Research Progress of Agricultural Genetically Modified Crop Safety Evaluation

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Journal of Northeast Agricultural University(English Edition) 2024年第03期 74-84页

作者： Li Ran Liang Liang Zhao Haibo Zhao Yujia Fan Peilei Liu Ran Zhao Yue beijing institute of metrology

The commercial cultivation of genetically modified (GM) crops has eased the global food crisis and brought considerable economic and social benefits to countries. Because of the potential safety problems, it is necessary to make clear the molecular genetic characteristics,edible safety,planting,processing,and other aspects of the safety evaluation of GM crops. The safety problems existing in the cultivation of GM crops, safety evaluation and detection of GM crops were introduced in this paper, which provided the basis for safety evaluation and effective supervision of GM crops and the *** cultivation and reasonable supervision based on safety evaluation have far-reaching significance for ensuring consumer safety, enhancing the credibility of the national political system and enhancing citizens'confidence in the safety of GM crop products for consumption.

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Microwave electrometry with Rydberg atoms in a vapor cell using microwave amplitude modulation

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Chinese Physics B 2024年第5期33卷 65-74页

作者：郝建海贾凤东崔越王昱寒周飞刘修彬张剑谢锋白金海尤建琦王宇钟志萍 School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyKey Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua UniversityBeijing 100084China Science and Technology on metrology and Calibration Laboratory Changcheng Institute of Metrology & MeasurementAviation Industry Corporation of ChinaBeijing 100095China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100190China

We have theoretically and experimentally studied the dispersive signal of the Rydberg atomic electromagneticallyinduced transparency(EIT)Autler–Townes(AT)splitting spectra obtained using amplitude modulation of the microwave(MW)electric *** addition to the two zero-crossing points interval△f_(zeros),the dispersion signal has two positive maxima with an interval defined as the shoulder interval△f_(sho),which is theoretically expected to be used to measure a much weaker MW electric *** relationship of the MW field strength E_(MW)and△f_(sho)is experimentally studied at the MW frequencies of 31.6 GHz and 9.2 GHz *** results show that△f_(sho)can be used to characterize the much weaker E_(MW)than that of△f_(zeros)and the traditional EIT–AT splitting interval△f_(m);the minimum E_(MW)measured by△f_(sho)is about 30 times smaller than that by△f_(m).As an example,the minimum E_(MW)at 9.2 GHz that can be characterized by△f_(sho)is 0.056 mV/cm,which is the minimum value characterized by the frequency interval using a vapor cell without adding any auxiliary *** proposed method can improve the weak limit and sensitivity of E_(MW)measured by the spectral frequency interval,which is important in the direct measurement of weak E_(MW).

关键词： quantum sensor Rydberg atoms electromagnetically induced transparency amplitude modulation

Species profile and reactivity of volatile organic compounds emission in solvent uses,industry activities and from vehicular tunnels

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Journal of Environmental Sciences 2024年第1期135卷 546-559页

作者： Haimei Huang Zhangwei Wang Chunhao Dai Hai Wu Jia Guo Chunjie Wang Xiaoshan Zhang State Key Laboratory of Urban and Regional Ecology Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China Hunan Agricultural University Changsha 430106China National institute of metrology Beijing 100029China

A survey was conducted of the volatile organic compounds(VOCs)released from sources of solvent use,industry activities and vehicle emissions in Guiyang,a capital city of *** were collected by canisters and analyzed by *** species profiles of VOCs emitted from sources were *** showed that xylenes,ethylbenzene,acetone and dichloromethane were the characteristics species for painting,2-propanol and ethyl acetate for printing,α-pinene for solid wood furniture manufacturing,and 2-butanone for biscuit *** characteristics species could be as tracers for the sources *** most of samples from the solvent use,the benzene/toluene(B/T)ratio was less than 0.3,indicating that the ratio could be as the indicator for tracing the solvent use related *** results also suggested that the toluene/xylene(T/X)ratio be as the indicator to distinguish the VOCs sources of painting(2).Aromatics contributed the most to ozone formation potential(OFP)of most painting and non-paper printing sources,and oxygen-containing VOCs(OVOCs)were major species contributing to OFP of the sources from food production and paper *** OFP of the VOCs emissions from vehicle in tunnels and from other manufactures were dominated by both aromatics and ***α-pinene could explain 56.94%and 32.54%of total OFP of the VOCs sources from filing cabinet and solid wood furniture manufacturing,which was rarely been involved in previous studies of VOCs source profiles,indicating that the species of concern for VOCs sources are still insufficient at present.

关键词： Volatile organic compounds(VOCs) Species profile BTEX ratio Source reactivity

Pluggable multitask diffractive neural networks based on cascaded metasurfaces

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Opto-Electronic Advances 2024年第2期7卷 23-31页

作者： Cong He Dan Zhao Fei Fan Hongqiang Zhou Xin Li Yao Li Junjie Li Fei Dong Yin-Xiao Miao Yongtian Wang Lingling Huang beijing Engineering Research Center of Mixed Reality and Advanced Display Key Laboratory of Photoelectronic Imaging Technology and System of Ministry of Education of ChinaSchool of Optics and PhotonicsBeijing Institute of TechnologyBeijing 100081China institute of Modern Optics Tianjin Key Laboratory of Optoelectronic Sensor and Sensing Network TechnologyNankai UniversityTianjin 300350China Department of Physics and Optoelectronics Faculty of ScienceBeijing University of TechnologyBeijing 100124China beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100191China beijing Aerospace institute for metrology and Measurement Technology Beijing 100076China

Optical neural networks have significant advantages in terms of power consumption,parallelism,and high computing speed,which has intrigued extensive attention in both academic and engineering *** has been considered as one of the powerful tools in promoting the fields of imaging processing and object ***,the existing optical system architecture cannot be reconstructed to the realization of multi-functional artificial intelligence systems *** push the development of this issue,we propose the pluggable diffractive neural networks(P-DNN),a general paradigm resorting to the cascaded metasurfaces,which can be applied to recognize various tasks by switching internal *** the proof-of-principle,the recognition functions of six types of handwritten digits and six types of fashions are numerical simulated and experimental demonstrated at near-infrared ***,the proposed paradigm not only improves the flexibility of the optical neural networks but paves the new route for achieving high-speed,low-power and versatile artificial intelligence systems.

关键词： optical neural networks diffractive deep neural networks cascaded metasurfaces