In this article,we conduct a study on mixed quasi-martingale Hardy spaces that are defined by means of the mixed L_(p)-norm.By utilizing Doob’s inequalities,we explore the atomic decomposition and quasi-martingale in...In this article,we conduct a study on mixed quasi-martingale Hardy spaces that are defined by means of the mixed L_(p)-norm.By utilizing Doob’s inequalities,we explore the atomic decomposition and quasi-martingale inequalities of mixed quasi-martingale Hardy spaces.Moreover,we furnish sufficient conditions for the boundedness ofσ-sublinear operators in these spaces.These findings extend the existing conclusions regarding mixed quasi-martingale Hardy spaces defined with the help of the mixed L_(p)-norm.展开更多
Space exploration is significant for scientific innovation,resource utilization,and planetary security.Space exploration involves several systems including satellites,space suits,communication systems,and robotics,whi...Space exploration is significant for scientific innovation,resource utilization,and planetary security.Space exploration involves several systems including satellites,space suits,communication systems,and robotics,which have to function under harsh space conditions such as extreme temperatures(−270 to 1650℃),microgravity(10^(-6)g),unhealthy humidity(<20%RH or>60%RH),high atmospheric pressure(~1450 psi),and radiation(4000–5000 mSv).Conventional energy-harvesting technologies(solar cells,fuel cells,and nuclear energy),that are normally used to power these space systems have certain limitations(e.g.,sunlight dependence,weight,degradation,big size,high cost,low capacity,radioactivity,complexity,and low efficiency).The constraints in conventional energy resources have made it imperative to look for non-conventional yet efficient alternatives.A great potential for enhancing efficiency,sustainability,and mission duration in space exploration can be offered by integrating triboelectric nanogenerators(TENGs)with existing energy sources.Recently,the potential of TENG including energy harvesting(from vibrations/movements in satellites and spacecraft),self-powered sensing,and microgravity,for multiple applications in different space missions has been discussed.This review comprehensively covers the use of TENGs for various space applications,such as planetary exploration missions(Mars environment monitoring),manned space equipment,In-orbit robotic operations/collision monitoring,spacecraft’s design and structural health monitoring,Aeronautical systems,and conventional energy harvesting(solar and nuclear).This review also discusses the use of self-powered TENG sensors for deep space object perception.At the same time,this review compares TENGs with conventional energy harvesting technologies for space systems.Lastly,this review talks about energy harvesting in satellites,TENG-based satellite communication systems,and future practical implementation challenges(with possible solutions).展开更多
In this paper,we studyλ-biharmonic hypersurfaces M_(r)^(5) of 6-dimensional pseudo Riemannian space form N_(p)^(6)(c)with the indexs 0≤p≤6,r=p−1 or p,and constant curvature c.It was proved that if the shape operato...In this paper,we studyλ-biharmonic hypersurfaces M_(r)^(5) of 6-dimensional pseudo Riemannian space form N_(p)^(6)(c)with the indexs 0≤p≤6,r=p−1 or p,and constant curvature c.It was proved that if the shape operator of M_(r)^(5) is diagonalizable,then the mean curvature is a constant.As an application,we find some types of biharmonic hypersurfaces of N_(p)^(6)(c)are minimal.展开更多
Strategically coupling nanoparticle hybrids and internal thermosensitive molecular switches establishes an innovative paradigm for constructing micro/nanoscale-reconfigurable robots,facilitating energyefficient CO_(2)...Strategically coupling nanoparticle hybrids and internal thermosensitive molecular switches establishes an innovative paradigm for constructing micro/nanoscale-reconfigurable robots,facilitating energyefficient CO_(2) management in life-support systems of confined space.Here,a micro/nano-reconfigurable robot is constructed from the CO_(2) molecular hunters,temperature-sensitive molecular switch,solar photothermal conversion,and magnetically-driven function engines.The molecular hunters within the molecular extension state can capture 6.19 mmol g^(−1) of CO_(2) to form carbamic acid and ammonium bicarbonate.Interestingly,the molecular switch of the robot activates a molecular curling state that facilitates CO_(2) release through nano-reconfiguration,which is mediated by the temperature-sensitive curling of Pluronic F127 molecular chains during the photothermal desorption.Nano-reconfiguration of robot alters the amino microenvironment,including increasing surface electrostatic potential of the amino group and decreasing overall lowest unoccupied molecular orbital energy level.This weakened the nucleophilic attack ability of the amino group toward the adsorption product derivatives,thereby inhibiting the side reactions that generate hard-to-decompose urea structures,achieving the lowest regeneration temperature of 55℃ reported to date.The engine of the robot possesses non-contact magnetically-driven micro-reconfiguration capability to achieve efficient photothermal regeneration while avoiding local overheating.Notably,the robot successfully prolonged the survival time of mice in the sealed container by up to 54.61%,effectively addressing the issue of carbon suffocation in confined spaces.This work significantly enhances life-support systems for deep-space exploration,while stimulating innovations in sustainable carbon management technologies for terrestrial extreme environments.展开更多
作为人们日常生活和休闲娱乐活动的重要场所,城市公园绿地活力的提升对优化公共空间布局、提高居民生活质量及推动城市可持续发展具有重要意义。当前,其已成为城市空间研究的热点议题,研究成果数量和社会关注度持续增长。本研究首先,基...作为人们日常生活和休闲娱乐活动的重要场所,城市公园绿地活力的提升对优化公共空间布局、提高居民生活质量及推动城市可持续发展具有重要意义。当前,其已成为城市空间研究的热点议题,研究成果数量和社会关注度持续增长。本研究首先,基于CNKI(中国知网)和WOS(Web of Science)数据库,使用CiteSpace知识图谱工具,系统分析了城市公园绿地活力研究的演进脉络;其次,根据国家政策导向和文献计量法分析了突变节点,并将其分为3个阶段:初步理论探索阶段(2012年以前)、中期实证阶段(2012—2019年)和信息深化阶段(2019年至今);再次,总结了各阶段的研究重点与发展方向,并识别了当前研究中存在的不足;最后,提出了未来深化路径。展开更多
随着全球供应链的日益复杂化和不确定性增加,提升供应链韧性成为我国面临的重要挑战。本文基于Web of Science数据库和知网数据库,结合可视化分析方法,对2013—2024年国内外供应链韧性领域相关文献进行对比分析,研究结果表明:(1)国内研...随着全球供应链的日益复杂化和不确定性增加,提升供应链韧性成为我国面临的重要挑战。本文基于Web of Science数据库和知网数据库,结合可视化分析方法,对2013—2024年国内外供应链韧性领域相关文献进行对比分析,研究结果表明:(1)国内研究起步晚于国外,且发文量少于国外。国外整体合作密切程度强于国内,国内、国外均未形成核心作者群。(2)国内相关研究主要集中在技术创新对供应链韧性的影响、供应链韧性战略以及供应链韧性评价等方面;国外相关研究主要集中在供应链韧性内涵、供应链韧性作用机制、供应链韧性评估模型等方面。(3)国内研究演进脉络分为两个阶段,国外研究演进脉络分为三个阶段。(4)在研究前沿方面,国内现阶段聚焦数字化方面,反映了产业升级需求;国外现阶段侧重于数字化与地缘政治方面。展开更多
In order to simultaneously take the advantages of magnesium and aluminum alloys, AZ80/A1 composite rods were produced using non-equal channel lateral extrusion （NECLE） process at different temperatures. Scanning ele...In order to simultaneously take the advantages of magnesium and aluminum alloys, AZ80/A1 composite rods were produced using non-equal channel lateral extrusion （NECLE） process at different temperatures. Scanning electron microscope （SEM） and energy dispersive spectrometer （EDS） tests as well as the shear punch test were employed to study the quality and strength of the bond between the two alloys. It was found that the process temperature was an important factor affecting the level of interfacial bonding, such that increasing the temperature from 250 to 300℃ has improved the strength by 37% and the thickness of the bond between the layers by 4.5%. Moreover, this temperature rise reduced the maximum required forming load by 13%. However, the hardness tests showed that this increase in the process temperature resulted in 4% decrease in the hardness of the composite bar.展开更多
Non-equal channel lateral extrusion（NECLE） is a new process that can be used to attain higher grain refinement in comparison with equal channel lateral extrusion（ECLE）. The die design for this process was numerica...Non-equal channel lateral extrusion（NECLE） is a new process that can be used to attain higher grain refinement in comparison with equal channel lateral extrusion（ECLE）. The die design for this process was numerically and experimentally studied. After finding a good correlation between the numerical and experimental results, more comprehensive FE analyses were carried out. Different die geometrical parameters were considered and their effects on the induced plastic strain, stress distribution, velocity field and forming load of the process were investigated. It was found that by this process with a suitable set of die geometrical parameters, higher induced effective strain and more homogeneous strain distribution could be achieved in comparison with ECLE operation.展开更多
To overcome the deficiencies of the existing Verhulst GM(1,1) model, based on the existing grey theory, a non-equal-interval direct optimum Verhulst GM(1,1) model is built which chooses a modified n-th component x(n) ...To overcome the deficiencies of the existing Verhulst GM(1,1) model, based on the existing grey theory, a non-equal-interval direct optimum Verhulst GM(1,1) model is built which chooses a modified n-th component x(n) of X(0) as the starting condition of the grey differential model. It optimizes a modified β value and the background value, and takes two times fitting optimization. The new model extends equal intervals to non-equal-intervals and is suitable for general data modelling and estimating parameters of the direct Verhulst GM(1,1). The new model does not need to pre-process the primitive data, nor accumulate generating operation (AGO) and inverse accumulated generating operation (IAGO). It is not only suitable for equal interval data modelling, but also for non-equal interval data modelling. As the new information is fully used and two times fitting optimization is taken, the fitting accuracy is the highest in all existing models. The example shows that the new model is simple and practical. The new model is worth expanding on and applying in data processing or on-line monitoring for tests, social sciences and other engineering sciences.展开更多
The transit time difference of fluid particles moving along the upper and lower surfaces of a lift-producing airfoil is studied here both theoretically and numerically.We show that,under thin airfoil assumption and fo...The transit time difference of fluid particles moving along the upper and lower surfaces of a lift-producing airfoil is studied here both theoretically and numerically.We show that,under thin airfoil assumption and for potential flow,the transit time difference is equal to the circulation divided by the square of the inflow velocity and the lift coefficient is equal to half of the number of chords travelled by the airfoil during the transit time difference.An analysis of transit time difference for very thick airfoil(c.f.very large angle of attack)suggests the transit time may change sign beyond thin airfoil assumption,a conclusion supported by an example of flow with an attached vortex.Thus,fluid particles may transit the upper surface with less,equal and more time than those transiting the lower surface for lift producing airfoils,depending on the configuration of flow structure and geometry.展开更多
本文基于知识图谱理论,选取1986—2024年中国知网(CNKI)收录的1072篇中文文献为样本,并辅以Web of Science核心合集中的英文文献,运用CiteSpace和VOSviewer软件,从发文数量、研究机构、载文期刊、关键词突现、时间演进与聚类等维度,对...本文基于知识图谱理论,选取1986—2024年中国知网(CNKI)收录的1072篇中文文献为样本,并辅以Web of Science核心合集中的英文文献,运用CiteSpace和VOSviewer软件,从发文数量、研究机构、载文期刊、关键词突现、时间演进与聚类等维度,对制造业转型研究的演化脉络和热点主题进行系统梳理。研究发现:制造业转型相关文献数量持续增长,呈现出显著的多学科交叉特征;研究主题经历了从早期的价值链优化,逐步拓展至数字化、绿色化、智能化与服务化等多个路径;近年来,研究重点进一步聚焦于企业绩效、人才培养与国际竞争力等议题。整体来看,制造业转型正由要素驱动向数字技术主导、多路径融合演进。本文研究成果可为理论拓展与政策制定提供系统参考。展开更多
基金Supported by the National Natural Science Foundation of China(11871195)。
文摘In this article,we conduct a study on mixed quasi-martingale Hardy spaces that are defined by means of the mixed L_(p)-norm.By utilizing Doob’s inequalities,we explore the atomic decomposition and quasi-martingale inequalities of mixed quasi-martingale Hardy spaces.Moreover,we furnish sufficient conditions for the boundedness ofσ-sublinear operators in these spaces.These findings extend the existing conclusions regarding mixed quasi-martingale Hardy spaces defined with the help of the mixed L_(p)-norm.
基金supported by Swedish Research Council(Vetenskapsradet,2023-04962).
文摘Space exploration is significant for scientific innovation,resource utilization,and planetary security.Space exploration involves several systems including satellites,space suits,communication systems,and robotics,which have to function under harsh space conditions such as extreme temperatures(−270 to 1650℃),microgravity(10^(-6)g),unhealthy humidity(<20%RH or>60%RH),high atmospheric pressure(~1450 psi),and radiation(4000–5000 mSv).Conventional energy-harvesting technologies(solar cells,fuel cells,and nuclear energy),that are normally used to power these space systems have certain limitations(e.g.,sunlight dependence,weight,degradation,big size,high cost,low capacity,radioactivity,complexity,and low efficiency).The constraints in conventional energy resources have made it imperative to look for non-conventional yet efficient alternatives.A great potential for enhancing efficiency,sustainability,and mission duration in space exploration can be offered by integrating triboelectric nanogenerators(TENGs)with existing energy sources.Recently,the potential of TENG including energy harvesting(from vibrations/movements in satellites and spacecraft),self-powered sensing,and microgravity,for multiple applications in different space missions has been discussed.This review comprehensively covers the use of TENGs for various space applications,such as planetary exploration missions(Mars environment monitoring),manned space equipment,In-orbit robotic operations/collision monitoring,spacecraft’s design and structural health monitoring,Aeronautical systems,and conventional energy harvesting(solar and nuclear).This review also discusses the use of self-powered TENG sensors for deep space object perception.At the same time,this review compares TENGs with conventional energy harvesting technologies for space systems.Lastly,this review talks about energy harvesting in satellites,TENG-based satellite communication systems,and future practical implementation challenges(with possible solutions).
基金Supported by National Natural Science Foundation of China(12161078)Foundation for Innovative Fundamental Research Group Project of Gansu Province(24JRRA778)Project of Northwest Normal University(20240010)。
文摘In this paper,we studyλ-biharmonic hypersurfaces M_(r)^(5) of 6-dimensional pseudo Riemannian space form N_(p)^(6)(c)with the indexs 0≤p≤6,r=p−1 or p,and constant curvature c.It was proved that if the shape operator of M_(r)^(5) is diagonalizable,then the mean curvature is a constant.As an application,we find some types of biharmonic hypersurfaces of N_(p)^(6)(c)are minimal.
基金supported by the National Natural Science Foundation of China(22168008,22378085)the Guangxi Natural Science Foundation(2024GXNSFDA010053)+1 种基金the Technology Development Project of Guangxi Bossco Environmental Protection Technology Co.,Ltd(202100039)Innovation Project of Guangxi Graduate Education(YCBZ2024065).
文摘Strategically coupling nanoparticle hybrids and internal thermosensitive molecular switches establishes an innovative paradigm for constructing micro/nanoscale-reconfigurable robots,facilitating energyefficient CO_(2) management in life-support systems of confined space.Here,a micro/nano-reconfigurable robot is constructed from the CO_(2) molecular hunters,temperature-sensitive molecular switch,solar photothermal conversion,and magnetically-driven function engines.The molecular hunters within the molecular extension state can capture 6.19 mmol g^(−1) of CO_(2) to form carbamic acid and ammonium bicarbonate.Interestingly,the molecular switch of the robot activates a molecular curling state that facilitates CO_(2) release through nano-reconfiguration,which is mediated by the temperature-sensitive curling of Pluronic F127 molecular chains during the photothermal desorption.Nano-reconfiguration of robot alters the amino microenvironment,including increasing surface electrostatic potential of the amino group and decreasing overall lowest unoccupied molecular orbital energy level.This weakened the nucleophilic attack ability of the amino group toward the adsorption product derivatives,thereby inhibiting the side reactions that generate hard-to-decompose urea structures,achieving the lowest regeneration temperature of 55℃ reported to date.The engine of the robot possesses non-contact magnetically-driven micro-reconfiguration capability to achieve efficient photothermal regeneration while avoiding local overheating.Notably,the robot successfully prolonged the survival time of mice in the sealed container by up to 54.61%,effectively addressing the issue of carbon suffocation in confined spaces.This work significantly enhances life-support systems for deep-space exploration,while stimulating innovations in sustainable carbon management technologies for terrestrial extreme environments.
文摘作为人们日常生活和休闲娱乐活动的重要场所,城市公园绿地活力的提升对优化公共空间布局、提高居民生活质量及推动城市可持续发展具有重要意义。当前,其已成为城市空间研究的热点议题,研究成果数量和社会关注度持续增长。本研究首先,基于CNKI(中国知网)和WOS(Web of Science)数据库,使用CiteSpace知识图谱工具,系统分析了城市公园绿地活力研究的演进脉络;其次,根据国家政策导向和文献计量法分析了突变节点,并将其分为3个阶段:初步理论探索阶段(2012年以前)、中期实证阶段(2012—2019年)和信息深化阶段(2019年至今);再次,总结了各阶段的研究重点与发展方向,并识别了当前研究中存在的不足;最后,提出了未来深化路径。
文摘随着全球供应链的日益复杂化和不确定性增加,提升供应链韧性成为我国面临的重要挑战。本文基于Web of Science数据库和知网数据库,结合可视化分析方法,对2013—2024年国内外供应链韧性领域相关文献进行对比分析,研究结果表明:(1)国内研究起步晚于国外,且发文量少于国外。国外整体合作密切程度强于国内,国内、国外均未形成核心作者群。(2)国内相关研究主要集中在技术创新对供应链韧性的影响、供应链韧性战略以及供应链韧性评价等方面;国外相关研究主要集中在供应链韧性内涵、供应链韧性作用机制、供应链韧性评估模型等方面。(3)国内研究演进脉络分为两个阶段,国外研究演进脉络分为三个阶段。(4)在研究前沿方面,国内现阶段聚焦数字化方面,反映了产业升级需求;国外现阶段侧重于数字化与地缘政治方面。
文摘In order to simultaneously take the advantages of magnesium and aluminum alloys, AZ80/A1 composite rods were produced using non-equal channel lateral extrusion （NECLE） process at different temperatures. Scanning electron microscope （SEM） and energy dispersive spectrometer （EDS） tests as well as the shear punch test were employed to study the quality and strength of the bond between the two alloys. It was found that the process temperature was an important factor affecting the level of interfacial bonding, such that increasing the temperature from 250 to 300℃ has improved the strength by 37% and the thickness of the bond between the layers by 4.5%. Moreover, this temperature rise reduced the maximum required forming load by 13%. However, the hardness tests showed that this increase in the process temperature resulted in 4% decrease in the hardness of the composite bar.
文摘Non-equal channel lateral extrusion（NECLE） is a new process that can be used to attain higher grain refinement in comparison with equal channel lateral extrusion（ECLE）. The die design for this process was numerically and experimentally studied. After finding a good correlation between the numerical and experimental results, more comprehensive FE analyses were carried out. Different die geometrical parameters were considered and their effects on the induced plastic strain, stress distribution, velocity field and forming load of the process were investigated. It was found that by this process with a suitable set of die geometrical parameters, higher induced effective strain and more homogeneous strain distribution could be achieved in comparison with ECLE operation.
基金The 11th Five-Year Plan for Key Constructing Academic Subject of Hunan Province(No.XJT2006180)Natural Science Foundation of Hunan Province (No.07JJ3093)Hunan Province Foundation Research Program (No.2007FJ3030,2007GK3058)
文摘To overcome the deficiencies of the existing Verhulst GM(1,1) model, based on the existing grey theory, a non-equal-interval direct optimum Verhulst GM(1,1) model is built which chooses a modified n-th component x(n) of X(0) as the starting condition of the grey differential model. It optimizes a modified β value and the background value, and takes two times fitting optimization. The new model extends equal intervals to non-equal-intervals and is suitable for general data modelling and estimating parameters of the direct Verhulst GM(1,1). The new model does not need to pre-process the primitive data, nor accumulate generating operation (AGO) and inverse accumulated generating operation (IAGO). It is not only suitable for equal interval data modelling, but also for non-equal interval data modelling. As the new information is fully used and two times fitting optimization is taken, the fitting accuracy is the highest in all existing models. The example shows that the new model is simple and practical. The new model is worth expanding on and applying in data processing or on-line monitoring for tests, social sciences and other engineering sciences.
基金supported partly by the National Key Project of China(No.GJXM92579)the National Science and Technology Major Project of China(No.2017-II-003-0015)the National Natural Science Foundation of China(No.11721202)。
文摘The transit time difference of fluid particles moving along the upper and lower surfaces of a lift-producing airfoil is studied here both theoretically and numerically.We show that,under thin airfoil assumption and for potential flow,the transit time difference is equal to the circulation divided by the square of the inflow velocity and the lift coefficient is equal to half of the number of chords travelled by the airfoil during the transit time difference.An analysis of transit time difference for very thick airfoil(c.f.very large angle of attack)suggests the transit time may change sign beyond thin airfoil assumption,a conclusion supported by an example of flow with an attached vortex.Thus,fluid particles may transit the upper surface with less,equal and more time than those transiting the lower surface for lift producing airfoils,depending on the configuration of flow structure and geometry.
文摘本文基于知识图谱理论,选取1986—2024年中国知网(CNKI)收录的1072篇中文文献为样本,并辅以Web of Science核心合集中的英文文献,运用CiteSpace和VOSviewer软件,从发文数量、研究机构、载文期刊、关键词突现、时间演进与聚类等维度,对制造业转型研究的演化脉络和热点主题进行系统梳理。研究发现:制造业转型相关文献数量持续增长,呈现出显著的多学科交叉特征;研究主题经历了从早期的价值链优化,逐步拓展至数字化、绿色化、智能化与服务化等多个路径;近年来,研究重点进一步聚焦于企业绩效、人才培养与国际竞争力等议题。整体来看,制造业转型正由要素驱动向数字技术主导、多路径融合演进。本文研究成果可为理论拓展与政策制定提供系统参考。
