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Superior compound coatings prepared by low-temperature vanadium-nitrocarburizing duplex treatment

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Rare Metals 2024年第4期43卷 1828-1835页

作者： Gen Jin Fang-Fang Xu Xun-Xun hu yue Xu School of Chemistry Beihang UniversityBeijing100191China Guobiao(Beijing)Testing and Certification Co. LtdBeijing100088China School of Materials Science and Engineering Beihang UniversityBeijing100191China

Superior compound coatings were prepared on CK45 steel surface by vanadium-nitrocarburizing duplex treatment in low-temperature salt *** this study,the microhardness,the phase constitution and the compositional distribution in the coatings prepared under different conditions were systematically *** results indicated that the reactions among activated vanadium,carbon and nitrogen atoms occurred on the steel surface,leading to the formation of compound coatings composed of outermost and compound *** mechanism for the formation of compound layer as well as the growth kinetics of the layer was also *** the duplex treatment,the wear and corrosion resistances of steel surface were significantly *** was found that the growth kinetics of compound layer obeyed the parabolic law,with the activation energy of 122.82 kJ·moL^(-1).

关键词： Vanadium-nitrocarburizing duplex treatment Compound coatings Microstructure Formation mechanism Growth kinetics

Ramsey Numbers of Trees Versus Multiple Copies of Books

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Acta Mathematicae Applicatae Sinica 2024年第3期40卷 600-612页

作者： Xiao-bing GUO Si-nan hu yue-jian PENG School of Mathematical Sciences Luoyang Normal UniversityLuoyang 471934China School of Mathematics Hunan UniversityChangsha 410082China

Given two graphs G and H,the Ramsey number R(G,H) is the minimum integer N such that any two-coloring of the edges of K_(N) in red or blue yields a red G or a blue *** v(G) be the number of vertices of G and χ(G) be the chromatic number of *** s(G) denote the chromatic surplus of G,the number of vertices in a minimum color class among all proper χ(G)-colorings of *** showed that R(G,H)≥(v(G)-1)(χ(H)-1)+s(H) if G is connected and v(G)≥s(H).A connected graph G is H-good if R(G,H)=(v(G)-1)(χ(H)-1)+s(H).Let tH denote the disjoint union of t copies of graph H,and let G∨H denote the join of G and *** a complete graph on n vertices by K_(n),and a tree on n vertices by T_(n).Denote a book with n pages by B_(n),i.e.,the join K_(2) ∨■.Erd?s,Faudree,Rousseau and Schelp proved that T_(n) is B_(m)-good if n≥*** this paper,we obtain the exact Ramsey number of T_(n) versus 2B_(2).Our result implies that T_(n) is 2B_(2)-good if n≥5.

关键词： ramsey number ramsey goodness tree book

Climatic drivers of the Canadian wildfire episode in 2023

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Atmospheric and Oceanic Science Letters 2024年第4期17卷 23-28页

作者： Yihan hu Xu yue Chenguang Tian Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control Collaborative Innovation Center of Atmospheric Environment and Equipment TechnologySchool of Environmental Science and EngineeringNanjing University of Information Science&Technology(NUIST)NanjingChina

2023年5月加拿大发生极端野火事件并持续4个月时间.野火污染物排放对当地和下风向的空气质量造成了严重影响.本文对驱动此次野火事件的气象因子和相关大尺度环流进行了探究.研究表明,此次极端野火排放的二氧化碳相较往年同期增长了0.37G... 详细信息

2023年5月加拿大发生极端野火事件并持续4个月时间.野火污染物排放对当地和下风向的空气质量造成了严重影响.本文对驱动此次野火事件的气象因子和相关大尺度环流进行了探究.研究表明,此次极端野火排放的二氧化碳相较往年同期增长了0.37Gt (527.1%).受罗斯贝波频散影响,同期加拿大中西部区域出现持续的位势高度正异常,促进气流下沉并引发局地高温,中西部区域5-6月最高温平均上升8.11℃,部分区域甚至超过10℃,导致野火排放的显著增长.受有利地形和泛北极地区快速增暖的影响,预期未来加拿大中西部发生极端野火的概率可能会显著上升.

关键词：野火气候变化遥相关极端天气碳排放

Slippery hydrogel with desiccation-tolerant‘skin’for high-precision additive manufacturing

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International Journal of Extreme Manufacturing 2024年第2期6卷 486-500页

作者： Desheng Liu Pan Jiang yue hu Yaozhong Lu Yixian Wang Jiayu Wu Danli hu Tao Wu Xiaolong Wang State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000People’s Republic of China CAS Key Laboratory of Chemistry of Northwestern Plant Resources Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000People’s Republic of China Shandong Laboratory of Advanced Materials and Green Manufacturing at Yantai Yantai Zhongke Research Institute of Advanced Materials and Green Chemical EngineeringYantai 264006People’s Republic of China Key Laboratory of Materials-Oriented Chemical Engineering of Xinjiang Uygur Autonomous Region School of Chemistry and Chemical EngineeringShihezi UniversityShihezi 832003People’s Republic of China

Hydrogels inevitably undergo dehydration,structural collapse,and shrinkage deformation due to the uninterrupted evaporation in the atmosphere,thereby losing their flexibility,slipperiness,and manufacturing ***,we propose a novel bioinspired strategy to construct a spontaneously formed‘skin’on the slippery hydrogels by incorporating biological stress metabolites trehalose into the hydrogel network,which can generate robust hydrogen bonding interactions to restrain water *** contents of trehalose in hydrogel matrix can also regulate the desiccation-tolerance,mechanical properties,and lubricating performance of slippery hydrogels in a wide *** vat photopolymerization three-dimensional printing and trehalose-modified slippery hydrogels enables to achieve the structural hydrogels with high resolution,shape fidelity,and sophisticated architectures,instead of structural collapse and shrinkage deformation caused by *** thus,this proposed functional hydrogel adapts to manufacture large-scale hydrogels with sophisticated architectures in a long-term *** a proof-of-concept demonstration,a high-precision and sophisticated slippery hydrogel vascular phantom was easily fabricated to imitate guidewire ***,the proposed protocol is universally applicable to diverse types of hydrogel *** strategy opens up a versatile methodology to fabricate dry-resistant slippery hydrogel for functional structures and devices,expanding their high-precision processing and broad applications in the atmosphere.

关键词： slippery hydrogel trehalose desiccation tolerance vat photopolymerization 3D printing hydrogen bonding

Low-latitude hydroclimate changes related to paleomagnetic variations during the Holocene in coastal southern China

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高等学校学术文摘·地球科学前沿 2024年第2期18卷 324-335页

作者： Tingwei ZHANG Xiaoqiang YANG Jian YIN qiong CHEN Jianfang hu Lu WANG Mengshan JU Qiangqiang WANG School of Earth Science and Engineering/Guangdong Provincial Key Laboratory of Geodynamics and Geohazards/Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)Sun Yat-sen UniversityGuangzhou 510275China Institute of Cultural Heritage Shandong UniversityQingdao 266237China State Key Laboratory of Organic Geochemistry Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou 510640China College of Urban and Environmental Sciences Peking UniversityBeijing 100871China Institute of Oceanology Chinese Academy of SciencesQingdao 266071China

The variations in precipitation have displayed a complex pattern in different regions since the *** formation processes may have a significant impact on precipitation,especially during the tropical marine processes and summer monsoon which convey abundant water vapor to coastal southern China and inland ***,we use two 7500 year sedimentary records from the Pearl River Delta and the closed Maar Lake,respectively,in coastal southern China to reconstruct the mid-to-late-Holocene humidity variability and explore its possible relationship with cloud cover modulated by the Earth's magnetic fields(EMF).Our proxy records document an apparent increase in wetness in coastal southern China between 3.0 and 1.8 kyr *** apparent increase in humidity appears to be consistent with the lower virtual axial dipole moments and,in turn,with a lower *** correlation suggests that the EMF might have been superimposed on the weakened monsoon to regulate the mid-to-late-Holocene hydroclimate in coastal southern China through the medium of galactic cosmic rays,aerosols,and cloud ***,further investigations are needed to verify this interaction.

关键词： hydroclimate variations Earth’s magnetic field coastal southern China the Holocene epoch

A small organic molecule strategy for remedying oxygen vacancies by bismuth defects in BiOBr nanosheet with excellent photocatalytic CO_(2)reduction

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Nano Research 2024年第1期17卷 297-306页

作者： Jing Xie Zhenjiang Lu yue Feng Jianguo huang Jindou hu Aize Hao Yali Cao State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources College of ChemistryXinjiang UniversityUrumqi 830046China

Defect modulation currently plays a decisive role in addressing the poor photoabsorption,sluggish electron hole separation,and high CO_(2)activation barrier in photocatalytic CO_(2)***,hunting for a straightforward strategy to balance the concentration of oxygen vacancy and metal cation defect in one photocatalyst is still a great ***,a bismuth vacancies BiOBr nanosheets(BiOBr-1)on the exposed[001]facets were constructed via an acetic acid molecule modification strategy,which can repair oxygen defect by bismuth vacancy in low-temperature solid-state chemical *** from the formed bismuth defects that can not only broaden light absorption and elevate charge separation efficiency,but also enhance adsorption and activation of CO_(2)molecules,the evolution rates of photocatalytic CO_(2)conversion into CO(71.23μmol·g^(-1)·h^(-1))and CH4(8.90μmol·g^(-1)·h^(-1))attained by BiOBr-1 are superior 7.1 and 11 times to that of plate-like *** photocatalytic mechanisms including adsorption concentration and activation process of CO_(2)are further revealed by the in situ diffuse reflectance infrared flourier transform spectra(DRIFTS).This finding of the existence of distinct defects in ultrathin nanosheets undoubtedly leads to new possibilities for photocatalyst design using two-dimensional materials with high solar-driven photocatalytic activity.

关键词： solid-state synthesis BiOBr metal vacancies photocatalysis carbon dioxide reduction

Contact detumbling toward a nutating target through deformable effectors and prescribed performance controller

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Journal of Systems Engineering and Electronics 2024年第3期35卷 753-768页

作者： ZANG yue ZHANG Yao hu Quan LI Mou CHEN Yujun School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China China Academy of Space Technology Beijing 100029China

Detumbling operation toward a rotating target with nutation is meaningful for debris removal but challenging. In this study, a deformable end-effector is first designed based on the requirements for contacting the nutating target. A dual-arm robotic system installed with the deformable end-effectors is modeled and the movement of the end-tips is analyzed. The complex operation of the contact toward a nutating target places strict requirements on control accuracy and controller robustness. Thus, an improvement of the tracking error transformation is proposed and an adaptive sliding mode controller with prescribed performance is designed to guarantee the fast and precise motion of the effector during the contact ***, by employing the proposed effector and the controller,numerical simulations are carried out to verify the effectiveness and efficiency of the contact detumbling toward a nutating target.

关键词： nutating target contact detumbling dual-arm space robot deformable end-effector prescribed performance controller

Complete kinetic model for esterification reaction of lauric acid with glycerol to synthesize glycerol monolaurate

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中国化学工程学报（英文版） 2024年第6期70卷 211-221页

作者： Han-Qiao hu yue Zhang Ming Fan Yong Cai Guang-Wen Chu Liang-Liang Zhang Research Center of the Ministry of Education for High Gravity Engineering and Technology Beijing University of Chemical Technology Beijing 100029 China Petrochemical Research Institute China National Petroleum Corporation Beijing 102206 China Research Center of the Ministry of Education for High Gravity Engineering and Technology Beijing University of Chemical Technology Beijing 100029 China State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical Technology Beijing 100029 China

Glycerol monolaurate (GML) is a widely used industrial chemical with excellent emulsification and antibacterial effect. The direct esterification of glycerol with lauric acid is the main method to synthesize GML. In this work, the kinetic process of direct esterification was systematically studied using p-tolue-nesulfonic acid as catalyst. A complete kinetic model of consecutive esterification reaction has been established, and the kinetic equation of acid catalysis was deduced. The isomerization reactions of GML and glycerol dilaurate were investigated. It was found that the reaction was an equilibrium reaction and the reaction rate was faster than the esterification reaction. The kinetic equations of the consecutive esterification reaction were obtained by experiments as k1 =(276+92261Xcat)exp(-37720/RT) and k2 =(80+4413Xcat)exp(-32240/RT). The kinetic results are beneficial to the optimization of operating conditions and reactor design in GML production process.

关键词： Esterification Glycerol monolaurate Kinetics Mass transfer p-toluenesulfonic acid

How aging affects bone health via the intestinal micro-environment

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BIOCELL 2024年第3期48卷 353-362页

作者： huAN hu yue huANG FANGZHOU LIU QIAN WANG YANZI YAO School of Stomatology Zunyi Medical UniversityZunyiChina Microbial Resources and Drug Development Key Laboratory of Guizhou Tertiary Institution Zunyi Medical UniversityZunyiChina Department of Stomatology Luoyang Maternal and Child Health HospitalLuoyangChina

Increasing life expectancy and an aging population lead to age-related bone diseases like osteoporosis and low bone mass more *** conditions represent a common,costly and chronic burden,not only for elderly but also to society at ***,elucidating the pathophysiology and developing effective therapies for these diseases is of paramount *** advances in research have identiﬁed the gut as a novel and promising target for addressing bone disorders,giving rise to the concept of the“gut-bone axis”.An in-depth review of the latest insights into the effects of age-related physiological changes in the gastrointestinal tract on bone health is presented in this *** examines how the“gut-bone”axis interacts with bone aging across various domains,including metabolism,nutrition,intestinal permeability,immunity,and oxidative stress.

关键词： Gut barrier Skeletal system Senescent Gut-bone axis Gut microbiota