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Friction moment calculation method for tapered roller bearings under combined loads

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Science China(Technological Sciences) 2024年第8期67卷 2565-2578页

作者： LI XinBin LIU Jing HUANG SuHe PAN Guang School of Marine Science and Technology Northwestern Polytechnical UniversityXi’an 710072China Key Laboratory for Unmanned Underwater Vehicle Northwestern Polytechnical UniversityXi’an 710072China System engineering Research institute Beijing 100094China

Tapered roller bearings(TRBs) can withstand axial loads, radial loads, and overturning moments. The performance, safety, and efficiency of rotating machinery are directly influenced by the friction moments within the TRBs. However, most current research has relied on empirical formulas that focus on axial loads. Additionally, the friction coefficient between the rollers and the inner ring rib has been defined using simple empirical methods. In actual applications, the loads on TRBs are not purely axial or radial, and simple empirical friction coefficients do not adequately account for the varying lubrication conditions. To address this challenge, this study proposes an improved method for calculating the friction moments of TRB under combined axial and radial loads. This study employs a calculation method for sliding friction coefficients that can model dry, boundary, elastohydrodynamic, and mixed lubrication conditions. To demonstrate the advantages of the proposed method, the friction moments obtained using the existing and proposed methods are compared. Additionally, the influence of TRB structural parameters on the friction moment is discussed. An experimental study is conducted to validate the effectiveness of the proposed method. The findings provide valuable insights for designing TRB structural parameters to minimize friction moments.

关键词： tapered roller bearing friction moment structural parameters combined loads

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Fe-N-C core-shell catalysts with single low-spin Fe(Ⅱ)-N_(4)species for oxygen reduction reaction and high-performance proton exchange membrane fuel cells

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Journal of Energy Chemistry 2024年第6期93卷 538-546,I0013页

作者： Yan Wan Linhui Yu Bingxin Yang Caihong Li Chen Fang Wei Guo Fang-Xing Xiao Yangming Lin Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials Xiamen Institute of Rare Earth MaterialsHaixi InstituteChinese Academy of SciencesXiamen 361021FujianChina CAS Key Laboratory of Urban Pollutant Conversion Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021FujianChina Fujian institute of Research on the Structure of Matter Chinese Academy of SciencesFuzhou 350002FujianChina College of Materials Science and engineering Fuzhou UniversityNew CampusMinhou 350108FujianChina College of Chemistry and Materials Science Fujian Normal UniversityFuzhou 350117FujianChina

Fe-N-doped carbon materials(Fe-N-C)are promising candidates for oxygen reduction reaction(ORR)relative to Pt-based catalysts in proton exchange membrane fuel cells(PEMFCs).However,the intrinsic contributions of Fe-N_(4)moiety with different chemical/spin states(e.g.D1,D2,D3)to ORR are unclear since various states coexist *** the present work,Fe-N-C core-shell nanocatalyst with single lowspin Fe(Ⅱ)-N_(4)species(D1)is synthesized and identified with ex-situ ultralow temperature Mossbauer spectroscopy(T=1.6 K)that could essentially differentiate various Fe-N_(4)states and invisible Fe-O *** quantifying with CO-pulse chemisorption,site density and turnover frequency of Fe-N-C catalysts reach 2.4×10^(-9)site g^(-1)and 23 e site~(-1)s^(-1)during the ORR,***-wave potential(0.915V_(RHE))of the Fe-N-C catalyst is more positive(approximately 54 mV)than that of Pt/***,we observe that the performance of PEMFCs on Fe-N-C almost achieves the 2025 target of the US Department of Energy by demonstrating a current density of 1.037 A cm^(-2)combined with the peak power density of 0,685 W cm^(-2),suggesting the critical role of Fe(Ⅱ)-N_(4)site(D1).After 500 h of running,PEMFCs still deliver a power density of 1.26 W cm^(-2)at 1.0 bar H_(2)-O_(2),An unexpected rate-determining step is figured out by isotopic labelling experiment and theoretical *** work not only offers valuable insights regarding the intrinsic contribution of Fe-N_(4)with a single spin state to alkaline/acidic ORR,but also provides great opportunities for developing high-performance stable PEMFCs.

关键词： Fuel cells Oxygen reduction reaction Non-platinum group metals(PGMs) Isotopic labelling Active site TOF

A method for support stiffness failure identification in a steel spring floating slab track of urban railway: a case study in China

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Journal of Zhejiang University-Science A(Applied Physics & engineering) 2024年第3期25卷 206-222页

作者： Junyuan ZHENG Caiyou ZHAO Duojia SHI Ping WANG Jian WANG Bolong JIANG Xi SHENG Key Laboratoryof High-speed Railway engineering Ministry of EducationSouthwest Jiaotong UniversityChengdu 60031China School of Civil engineering Southwest Jiaotong UniversityChengdu 610031China 01 DYNA(Qingdao)Test&Data Co. Ltd.Qingdao 266000China Rail Transit Digital Construction and Measurement Technology National engineering Research Center China Railway Design CorporationTianjin300308China institute of Urban Smart Transportation&Safety Maintenance Shenzhen UniversityShenzhen 518060China

The extensive use of steel spring floating slab tracks has effectively addressed the challenge of alleviating the environmental vibrations induced by urban rail transit ***,under the combined action of train dynamic loads and complex environmental factors,problems,such as the fracture of steel spring vibration isolators and suspension vibrations induced by the uneven settlement of the base,often *** failure of isolator support stiffness is often hidden in its early stages and is challenging to identify by conventional detection *** the same time,it will aggravate the wheel-rail interaction,accelerate the deterioration of track structure,and even affect the driving *** study first establishes a detailed coupled train-floating slab track-foundation analytical *** the influence of the vibration isolator support stiffness failure on the dynamic indices of the floating slab track system response is analyzed.A set of defect identification methods that can detect the number of failed steel springs,severity of damage,and their location is ***,an intelligent monitoring system for support stiffness of floating slab track is built by combining the density-based spatial clustering of applications with noise algorithm and statistical data analysis and is applied to a rail line in southern *** a three-year monitoring campaign,a suspension failure and a fracture of a steel spring were each successfully detected and detailed failure information was *** investigation results were consistent with the damage identification *** repair,the track structure dynamic response returned to the average pre-damage level and further deterioration had been *** proposed damage identification methods and monitoring system provide an approach for intelligent identification of track structure support stiffness failures.

关键词： Floating slab track Support stiffness Detailed analytical model Failure identification Monitoring system

Simultaneously achieving high energy density and responsivity in submicron BaTiO_(3) film capacitors integrated on Si

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Journal of Advanced Ceramics 2024年第2期13卷 198-206页

作者： Jun Ouyang Yinxiu Xue Chuanqi Song Meiling Yuan Kun Wang Yuyao Zhao Hongbo Cheng Hanfei Zhu Chao Liu institute of Advanced Energy Materials and Chemistry School of Chemistry and Chemical EngineeringQilu University of Technology(Shandong Academy of Sciences)Jinan 250353China Key Laboratory of Key Film Materials&Application for Equipment School of Material Sciences and EngineeringXiangtan UniversityXiangtan 411105China School of Materials Science and engineering Shandong UniversityJinan 250061China Academic Affairs Office Civil Aviation University of ChinaTianjin 300300China China Tobacco Shandong Industrial Co. Ltd.Jinan 250014China

In the research field of energy storage dielectrics,the“responsivity”parameter,defined as the recyclable/recoverable energy density per unit electric field,has become critically important for a comprehensive evaluation of the energy storage capability of a *** this work,high recyclable energy density and responsivity,i.e.,W_(rec)=161.1 J·cm^(-3) and ξ=373.8 J·(kV·m^(2))^(-1),have been simultaneously achieved in a prototype perovskite dielectric,BaTiO_(3),which is integrated on Si at 500℃ in the form of a submicron thick *** ferroelectric film features a multi-scale polar structure consisting of ferroelectric grains with different orientations and inner-grain ferroelastic domains.A LaNiO_(3) buffer layer is used to induce a{001}textured,columnar nanograin microstructure,while an elevated deposition temperature promotes lateral growth of the nanograins(in-plane diameter increases from~10-20 nm at lower temperatures to~30 nm).These preferably oriented and periodically regulated nanograins have resulted in a small remnant polarization and a delayed polarization saturation in the film’s P-E behavior,leading to a high recyclable energy ***,an improved polarizability/dielectric constant of the BaTiO_(3) film has produced a much larger maximum polarization than those deposited at lower temperatures at the same electric field,leading to a record-breaking responsivity for this simple perovskite.

关键词： energy storage energy density responsivity BaTiO_(3) dielectric capacitor Si

Disentangling the relative contributions of variables determining the divergence of hoarding strategies of rodents

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Current Zoology 2024年第2期70卷 270-272页

作者： Bo Wang School of Resources and environmental engineering Anhui UniversityHefei 230601China Anhui Province Key Laboratory of Wetland Ecosystem Protection and Restoration Anhui UniversityHefei 230601China Anhui Shengjin Lake Wetland Ecology National Long-Term Scientific Research Base DongzhiAnhui 247230China

Understanding the driving mechanism of the divergence of hoarding strategies of animals(i.e.,scatter-hoarding ***-hoarding)is crucial to understand the ecological and evolutionary implications of plant-animal *** et al.(2022)compiled a global-scale dataset from the published literature including 183 species of seed-hoarding rodents,and concluded that phylogenetic conservatism,functional traits,and environmental factors counted for the hoarding behavior divergence of rodents.A more thought-provoking question may be asked:Do these variables contribute equally or not to explain the divergence of hoarding strategies?Here,we re-analyzed Zhang et al's(2022)dataset using partial Ralk calculation(Ives 2019)to parse out the relative contri-lik butions of these variables.

关键词： hoarding strategies rodents

Changes in global land surface frozen ground and freeze-thaw processes during 1950-2020 based on ERA5-Land data

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Advances in Climate Change Research 2024年第2期15卷 265-274页

作者： Yong YANG Ren-Sheng CHEN Yong-Jian DING Hong-Yuan LI Zhang-Wen LIU Qilian Alpine Ecology and Hydrology Research Station Key Laboratory of Ecological Safety and Sustainable Development in Arid LandsNorthwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 73000China State Key Laboratory of Cryospheric Sciences Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 73000China Shandong Provincial Key Laboratory of Water and Soil Conservation and environmental Protection College of Resources and EnvironmentLinyi UniversityLinyi 276000China

Frozen ground(FG)plays an important role in global and regional climates and environments through changes in land freeze-thaw processes,which have been conducted mainly in different ***,the changes in land surface freeze-thaw processes under climate change on a global scale are still *** on ERA5-Land hourly land skin temperature data,this study evaluated changes in the global FG area,global land surface first freeze date(FFD),last freeze date(LFD)and frost-free period(FFP)from 1950 to *** results show that the current FG areas(1991-2020 mean)in the Northern Hemisphere(NH),Southern Hemisphere(SH),and globe are 68.50×10^(6),9.03×10^(6),and 77.53×10^(6)km^(2),which account for 72.4%,26.8%,and 60.4%of the exposed land(excluding glaciers,ice sheets,and water bodies)in the NH,SH and the globe,respectively;further,relative to 1951-1980,the FG area decreased by 1.9%,8.8%,and 2.8%,*** FG at lower latitudes degrades to intermittently FG,and intermittently FG degrades to non-frozen ground,which caused the global FG boundary to retreat to higher latitudes from 1950 to *** annual FG areas in the NH,SH,and globe all show significant decreasing trends(p<0.05)from 1950 to 2020 at-0.32×10^(6),-0.22×10^(6),and-0.54×10^(6)km^(2)per decade,*** FFP prolongation in the NH is mainly influenced by LFD advance,while in the SH it is mainly controlled by FFD *** prolongation trend of FFP in the NH(1.34 d per decade)is larger than that in the SH(1.15 d per decade).

关键词： Frozen ground Freeze-thaw processes Frost-free period First freeze date Global warming

The regulatory role of m^(6)A modification in the maintenance and differentiation of embryonic stem cells

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Genes & Diseases 2024年第5期11卷 126-139页

作者： Jin Zhang Lingling Tong Yuchen Liu Xiang Li Jiayi Wang Ruoxin Lin Ziyu Zhou Yunbing Chen Yanxi Chen Yirong Liu Di Chen Center for Reproductive Medicine of the Second Affiliated Hospital Center for Regeneration and Cell Therapy of Zhejiang University-University of Edinburgh Institute(ZJU-UoE Institute)Zhejiang University School of MedicineZhejiang UniversityHangzhouZhejiang 310003China Zhejiang University-University of Edinburgh institute(ZJU-UoE institute) Zhejiang University School of MedicineZhejiang UniversityHangzhouZhejiang 310003China College of Materials and Chemical engineering Minjiang UniversityFuzhouFujian 350108China National Key Laboratory of Biobased Transportation Fuel Technology HainingZhejiang 314400China

As the most prevalent and reversible internal epigenetic modification in eukaryotic mRNAs,N6-methyladenosine(m^(6)A)post-transcriptionally regulates the processing and metabolism of mRNAs involved in diverse biological processes.m^(6)A modification is regulated by m^(6)A writers,erasers,and *** evidence suggests that m^(6)A modification plays essential roles in modulating the cell-fate transition of embryonic stem *** investigation of embryonic stem cell maintenance and differentiation is critical for understanding early embryonic development,which is also the premise for the application of embryonic stem cells in regenerative *** review highlights the current knowledge of m^(6)A modification and its essential regulatory contribution to the cell fate transition of mouse and human embryonic stem cells.

关键词： Cell-fate transition Embryonic stem cell Epigenetic modification m^(6)A modification Post-transcriptional regulation

Photocatalytic synthesis of small-molecule drugs by porous framework materials

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Chinese Chemical Letters 2024年第3期35卷 52-65页

作者： Yingying Zhao Jiangpei Yuan Lei Zhu Yu Fang State Key Laboratory of Chemo/Bio-Sensing and Chemometrics College of Chemistry and Chemical EngineeringHunan UniversityChangsha 410082China Innovation institute of Industrial Design and Machine Intelligence Quanzhou-Hunan University Quanzhou 362801China

Small-molecule drugs are widely used in daily *** are still issues with the current industrial synthesis techniques for small-molecule drugs,such as the use of expensive metal catalysts,convoluted reaction processes,and non-recyclable *** benefits of photocatalytic organic synthesis over conventional techniques are mild conditions,environmental friendliness,and great *** framework materials can precisely modulate catalytic sites'electronic state and ligand structure to improve photocatalytic *** particular,MOFs,COFs and PCCs based photocatalysts have received extensive research interest due to their unique morphology,structural adjustability,high photocatalytic performance,unique recyclability,excellent chemical stability,easy synthesis and low ***,a key area for future research is the development of porous framework materials as photocatalysts for the synthesis of small-molecule drugs or drug precursors.

关键词： Small-molecule drug Porous framework materials Photocatalysis

Influence of layer thickness on formation quality,microstructure,mechanical properties,and corrosion resistance of WE43 magnesium alloy fabricated by laser powder bed fusion

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Journal of Magnesium and Alloys 2024年第4期12卷 1367-1385页

作者： Bangzhao Yin Jinge Liu Bo Peng Mengran Zhou Bingchuan Liu Xiaolin Ma Caimei Wang Peng Wen Yun Tian Yufeng Zheng State Key Laboratory of Tribology in Advanced Equipment Beijing100084China Department of Mechanical engineering Tsinghua UniversityBeijing 100084China institute for Precision Medicine Tsinghua UniversityBeijing102218China Department of Orthopaedics Peking University Third HospitalBeijing 100191China Beijing AKEC Medical Co. Ltd.Beijing 102200China School of Materials Science and engineering Peking UniversityBeijing 100871China engineering Research Center of Bone and Joint Precision Medicine Ministry of EducationBeijing 100191China

Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical *** thickness(LT)is of great significance to the L-PBF process but has not been studied for Mg *** this study,WE43 Mg alloy bulk cubes,porous scaffolds,and thin walls with layer thicknesses of 10,20,30,and 40μm were *** required laser energy input increased with increasing layer thickness and was different for the bulk cubes and porous *** tended to occur at the connection joints in porous scaffolds for LT40 and could be eliminated by reducing the laser energy *** thin wall parts,a large overhang angle or a small wall thickness resulted in porosity when a large layer thicknesses was used,and the porosity disappeared by reducing the layer thickness or laser energy input.A deeper keyhole penetration was found in all occasions with porosity,explaining the influence of layer thickness,geometrical structure,and laser energy input on the *** the samples achieved a high fusion quality with a relative density of over 99.5%using the optimized laser energy *** increased layer thickness resulted to more precipitation phases,finer grain sizes and decreased grain *** the similar high fusion quality,the tensile strength and elongation of bulk samples were significantly improved from 257 MPa and 1.41%with the 10μm layer to 287 MPa and 15.12%with the 40μm layer,in accordance with the microstructural *** effect of layer thickness on the compressive properties of porous scaffolds was ***,the corrosion rate of bulk samples accelerated with increasing the layer thickness,mainly attributed to the increased number of precipitation phases.

关键词： Magnesium alloy WE43 Laser powder bed fusion Layer thickness Process optimization