Based on the features of the design and assembly of rnodular fixtures, a new design system which combines intelligent selection of elements and interactive assembly is presented.Using the fixture design datum, the sys...Based on the features of the design and assembly of rnodular fixtures, a new design system which combines intelligent selection of elements and interactive assembly is presented.Using the fixture design datum, the system can automatically select elements,and can interactively assemble together these elements based on AutoCAD. An example is given to illustrate it.展开更多
Informatization, intellectualization, standardization and flexibility are the development direction and trend of warehousing technology and management in China. Shelf selection and standardization are of great signifi...Informatization, intellectualization, standardization and flexibility are the development direction and trend of warehousing technology and management in China. Shelf selection and standardization are of great significance for relevant enterprises to reduce management costs, improve production efficiency and improve service level. According to the storage demand, storage conditions, goods status and supporting equipment, the storage system is divided into four categories;Accordingly, the shelf assembly is divided into four levels. The tolerance, deformation and clearance of shelf assembly at all levels have different technical requirements and operation specifications. The problems encountered in the development of shelf selection standards include both technical and methodological problems, as well as social problems such as centralized coordination;It is necessary to further investigate and study, think and explore, coordinate and communicate, find ways and take measures as soon as possible, so as to smoothly promote the development of standards and issue and implement standards as soon as possible.展开更多
Parallel robots with SCARA（selective compliance assembly robot arm） motions are utilized widely in the field of high speed pick-and-place manipulation. Error modeling for these robots generally simplifies the parall...Parallel robots with SCARA（selective compliance assembly robot arm） motions are utilized widely in the field of high speed pick-and-place manipulation. Error modeling for these robots generally simplifies the parallelogram structures included by the robots as a link. As the established error model fails to reflect the error feature of the parallelogram structures, the effect of accuracy design and kinematic calibration based on the error model come to be undermined. An error modeling methodology is proposed to establish an error model of parallel robots with parallelogram structures. The error model can embody the geometric errors of all joints, including the joints of parallelogram structures. Thus it can contain more exhaustively the factors that reduce the accuracy of the robot. Based on the error model and some sensitivity indices defined in the sense of statistics, sensitivity analysis is carried out. Accordingly, some atlases are depicted to express each geometric error’s influence on the moving platform’s pose errors. From these atlases, the geometric errors that have greater impact on the accuracy of the moving platform are identified, and some sensitive areas where the pose errors of the moving platform are extremely sensitive to the geometric errors are also figured out. By taking into account the error factors which are generally neglected in all existing modeling methods, the proposed modeling method can thoroughly disclose the process of error transmission and enhance the efficacy of accuracy design and calibration.展开更多
The solvent selection methodology developed earlier by. Gani （tal. （Comp. Chem. Eng., 2005）has been extended to handle multi-step reaction systems. The solvent selection problem was formulated based on the methodol...The solvent selection methodology developed earlier by. Gani （tal. （Comp. Chem. Eng., 2005）has been extended to handle multi-step reaction systems. The solvent selection problem was formulated based on the methodology guidelines, and solved using ICAS software tool. A list with solvent candidates is generated so that it can be further investigated experimentally. Comments and clarifications from chemists have been incorporated into the problem forrnulations to clarify the role of the solvents in the chemistry and potential reactivity issues. Highly promising results were obtained, in accordance with. industrial process data.展开更多
The transformation of natural habitats into human-modified landscapes has far-reaching consequences for species distribution and abundance.As species adapt to these changing environments,shifts in distribution pattern...The transformation of natural habitats into human-modified landscapes has far-reaching consequences for species distribution and abundance.As species adapt to these changing environments,shifts in distribution patterns,niche dynamics,and interspecies interactions may occur,impacting biodiversity at multiple levels and potentially leading to ecosystem imbalances.This study aims to assess the impact of variations in vegetation composition and human disturbance on the distribution of sympatric breeding birds and to determine the extent of niche overlap or differentiation among these species.We conducted field surveys and collected data on bird distribution,vegetation composition,and level of human disturbance in eastern Inner Mongolian grasslands.We focused on the six most frequently co-occurring breeding birds,representing a mix of sparrows,larks,and corvids.Generalized Additive Models revealed varying responses of species occurrence along habitat gradients.Species like the Eurasian Skylark(Alauda arvensis),Mongolian Lark(Melanocorypha mongolica),and Asian Shorttoed Lark(Calandrella cheleensis),increased in larger and more connected habitats,while others,like the Tree Sparrow(Passer montanus),Eurasian Magpie(Pica pica),and Barn Swallow(Hirundo rustica),adapted to more fragmented habitats.Niche analysis indicated habitat generalists tended to occupy larger niches than grassland specialists.Substantial niche overlap was also found among the six co-occurring bird species.Conservation efforts should consider the specific needs of specialist species and strive to maintain or restore critical grassland habitats.Additionally,promoting sustainable agricultural practices that balance the needs of birds and human activities can contribute to the coexistence of generalist and specialist bird species in modified landscapes.展开更多
This study marks the birth of visible and selective click covalent assembly.It is achieved by amplifying orthogonal alkyne−azide click chemistry through interfacial multisite interactions between azide/alkyne function...This study marks the birth of visible and selective click covalent assembly.It is achieved by amplifying orthogonal alkyne−azide click chemistry through interfacial multisite interactions between azide/alkyne functionalized polymer hydrogels.Macroscopic assembly of hydrogels via host−guest chemistry or noncovalent interactions such as electrostatic interactions has been reported.Unlike macroscopic supramolecular assembly,here we report visible and selective“click”covalent assembly of hydrogels at the macroscale.LEGO-like hydrogels modified with alkyne and azide groups,respectively,can click together via the formation of covalent bonds.Monomer concentration-dependent assembly and selective covalent assembly have been studied.Notably,macroscopic gel assembly clearly elucidates click preferences and component selectivity not observed in the solution reactions of competing monomers.展开更多
The planetary roller screw mechanism(PRSM)is a novel precision transmission mechanism that realizes the conversion between linear and rotary motions.The contact characteristics of helical surfaces directly determine P...The planetary roller screw mechanism(PRSM)is a novel precision transmission mechanism that realizes the conversion between linear and rotary motions.The contact characteristics of helical surfaces directly determine PRSM’s performance in load-carrying capacity and transmission accuracy.Therefore,studying the contact characteristics of PRSM forms the fundamental basis for enhancing its transmission performance.In this study,a three-dimensional parametric analysis method of contact characteristics is proposed based on the PRSM meshing principle and PyVista(a high-level API to the Visualization Toolkit).The proposed method considers the influence of machining errors among various thread teeth.The effects of key machining errors on contact positions and axial clearance,as well as their sensitivities,are analyzed.With excellent solution accuracy,this method exhibits higher calculation efficiency and stronger robustness than the analytical and numerical meshing models.The influence of nominal diameter and pitch errors of the screw,roller,and nut on the axial clearance follows a linear relationship,whereas flank angle errors have negligible effects on the axial clearance.The corresponding influence coefficients for these three machining errors on the axial clearance are 0.623,0.341,and 0.036.The variations in contact positions caused by individual errors are axisymmetric.Flank angle errors and roller diameter errors result in linear displacements of the contact points,whereas pitch errors cause the contact points to move along the arc of the roller diameter.Based on the proposed threedimensional parametric contact characteristics analysis method,the Fuzzy C-Means clustering algorithm considering error sensitivity is utilized to establish a component grouping technique in the selective assembly of critical PRSM components,ensuring the rational and consistent clearances based on the given component’s machining errors.This study provides effective guidance for analyzing contact characteristics and grouping in selective assembly for PRSM components.It also presents the proposed method’s potential applicability to similar calculation problems for contact positions and clearances in other transmission systems.展开更多
The well controllable selective growth of carbon nanotubes (CNTs)on the desired area is an important issue for their future applications. In this study, a novel method for selective growth of CNTs was proposed by usin...The well controllable selective growth of carbon nanotubes (CNTs)on the desired area is an important issue for their future applications. In this study, a novel method for selective growth of CNTs was proposed by using the technology of self-assembly monolayers (SAMs) and the Fe-assisted CNTs growth. The Si wafers with the a : Si/Si3N4 layer patterns were first prepared by low pressure chemical vapor deposition (LPCVD)and lithography techniques to act as the substrates for selective deposition of SAMs. The selectivity of SAMs from APTMS solution (N-(2-aminoethyl)-3-aminopropyltrimethoxsilane) is based on its greater reactivity of head group on a-Si than Si3N4 films. The areas of pattern with SAMs will first chelate the Fe3+ ions by their diamine-terminated group. The Fe3+ ions were then consolidated to become Fe-hydroxides in sodium boron hydride solution to form the Fe-hydroxides pattern. Finally, the Fe-hydroxides pattern was pretreated in H plasma to become a well-distributed Fe nano-particles on the surface, and followed by CNTs deposition using Fe as catalyst in a microwave plasma-chemical vapor deposition (MP-CVD) system to become the CNTs pattern. The products in each processing step, including microstructures and lattice images of CNTs, were characterized by contact angle measurements, scanning electron microscopy (SEM), XPS, Auger spectroscopy, transmission electron microscopy (TEM) and high resolution TEM (HRTEM)deposition. The results show that the main process parameters include the surface activation process and its atmosphere, consolidation time and temperature, H plasma pretreatment. The function of each processing step will be discussed.展开更多
Calixarenes and pillararenes are cyclic oligomers containing repeating units of phenol and methane. The modification of ionized groups bring calixarenes and pillararenes derivates both good water solubility and strong...Calixarenes and pillararenes are cyclic oligomers containing repeating units of phenol and methane. The modification of ionized groups bring calixarenes and pillararenes derivates both good water solubility and strong binding affinities towards various organic/inorganic/biological guest molecules in both water and the solid state. Meanwhile, the pre-organized structures of these compounds are indispensable in constructing of stimuli-responsive supramolecular assembly. With these properties, the supramolecular selective binding and molecular assembly based on calixarene/pillararene are widely used in enzyme tandem assay, stimuli-responsive nanostructure, drug delivery, organelle fluorescent imaging, photo-controlled morphological change, organic and inorganic hybrid material, solid tunable photo-luminescence and so on. This review summarized the recent research progresses on the calixarene/pillararene-based supramolecular systems and discussed the expectation of the future development.展开更多
文摘Based on the features of the design and assembly of rnodular fixtures, a new design system which combines intelligent selection of elements and interactive assembly is presented.Using the fixture design datum, the system can automatically select elements,and can interactively assemble together these elements based on AutoCAD. An example is given to illustrate it.
文摘Informatization, intellectualization, standardization and flexibility are the development direction and trend of warehousing technology and management in China. Shelf selection and standardization are of great significance for relevant enterprises to reduce management costs, improve production efficiency and improve service level. According to the storage demand, storage conditions, goods status and supporting equipment, the storage system is divided into four categories;Accordingly, the shelf assembly is divided into four levels. The tolerance, deformation and clearance of shelf assembly at all levels have different technical requirements and operation specifications. The problems encountered in the development of shelf selection standards include both technical and methodological problems, as well as social problems such as centralized coordination;It is necessary to further investigate and study, think and explore, coordinate and communicate, find ways and take measures as soon as possible, so as to smoothly promote the development of standards and issue and implement standards as soon as possible.
基金Supported by National Natural Science Foundation of China(Grant No.51305222)National Key Scientific and Technological Program of China(Grant No.2013ZX04001-021)
文摘Parallel robots with SCARA（selective compliance assembly robot arm） motions are utilized widely in the field of high speed pick-and-place manipulation. Error modeling for these robots generally simplifies the parallelogram structures included by the robots as a link. As the established error model fails to reflect the error feature of the parallelogram structures, the effect of accuracy design and kinematic calibration based on the error model come to be undermined. An error modeling methodology is proposed to establish an error model of parallel robots with parallelogram structures. The error model can embody the geometric errors of all joints, including the joints of parallelogram structures. Thus it can contain more exhaustively the factors that reduce the accuracy of the robot. Based on the error model and some sensitivity indices defined in the sense of statistics, sensitivity analysis is carried out. Accordingly, some atlases are depicted to express each geometric error’s influence on the moving platform’s pose errors. From these atlases, the geometric errors that have greater impact on the accuracy of the moving platform are identified, and some sensitive areas where the pose errors of the moving platform are extremely sensitive to the geometric errors are also figured out. By taking into account the error factors which are generally neglected in all existing modeling methods, the proposed modeling method can thoroughly disclose the process of error transmission and enhance the efficacy of accuracy design and calibration.
基金PRISM FP6 Marie Curie Research Training Network (MRTN-CT-2004-512233)
文摘The solvent selection methodology developed earlier by. Gani （tal. （Comp. Chem. Eng., 2005）has been extended to handle multi-step reaction systems. The solvent selection problem was formulated based on the methodology guidelines, and solved using ICAS software tool. A list with solvent candidates is generated so that it can be further investigated experimentally. Comments and clarifications from chemists have been incorporated into the problem forrnulations to clarify the role of the solvents in the chemistry and potential reactivity issues. Highly promising results were obtained, in accordance with. industrial process data.
基金supported by the National Natural Science Foundation of China (No.32201304)the Fundamental Research Funds for the Central Universities (No.2412022QD026)。
文摘The transformation of natural habitats into human-modified landscapes has far-reaching consequences for species distribution and abundance.As species adapt to these changing environments,shifts in distribution patterns,niche dynamics,and interspecies interactions may occur,impacting biodiversity at multiple levels and potentially leading to ecosystem imbalances.This study aims to assess the impact of variations in vegetation composition and human disturbance on the distribution of sympatric breeding birds and to determine the extent of niche overlap or differentiation among these species.We conducted field surveys and collected data on bird distribution,vegetation composition,and level of human disturbance in eastern Inner Mongolian grasslands.We focused on the six most frequently co-occurring breeding birds,representing a mix of sparrows,larks,and corvids.Generalized Additive Models revealed varying responses of species occurrence along habitat gradients.Species like the Eurasian Skylark(Alauda arvensis),Mongolian Lark(Melanocorypha mongolica),and Asian Shorttoed Lark(Calandrella cheleensis),increased in larger and more connected habitats,while others,like the Tree Sparrow(Passer montanus),Eurasian Magpie(Pica pica),and Barn Swallow(Hirundo rustica),adapted to more fragmented habitats.Niche analysis indicated habitat generalists tended to occupy larger niches than grassland specialists.Substantial niche overlap was also found among the six co-occurring bird species.Conservation efforts should consider the specific needs of specialist species and strive to maintain or restore critical grassland habitats.Additionally,promoting sustainable agricultural practices that balance the needs of birds and human activities can contribute to the coexistence of generalist and specialist bird species in modified landscapes.
基金Guangdong Provincial Pearl River Talents Program (No.2021ZT090195)Guangdong Basic and Applied Basic Research Foundation (No.2020A1515110777)Shenzhen Science,Technology and Innovation Committee (STIC)Shenzhen Key Laboratory Fund (No.ZDSYS20220507161600001)for the financial support for this work.
文摘This study marks the birth of visible and selective click covalent assembly.It is achieved by amplifying orthogonal alkyne−azide click chemistry through interfacial multisite interactions between azide/alkyne functionalized polymer hydrogels.Macroscopic assembly of hydrogels via host−guest chemistry or noncovalent interactions such as electrostatic interactions has been reported.Unlike macroscopic supramolecular assembly,here we report visible and selective“click”covalent assembly of hydrogels at the macroscale.LEGO-like hydrogels modified with alkyne and azide groups,respectively,can click together via the formation of covalent bonds.Monomer concentration-dependent assembly and selective covalent assembly have been studied.Notably,macroscopic gel assembly clearly elucidates click preferences and component selectivity not observed in the solution reactions of competing monomers.
基金supported by the National Key R&D Program of China(Grant No.2023YFB3406404).
文摘The planetary roller screw mechanism(PRSM)is a novel precision transmission mechanism that realizes the conversion between linear and rotary motions.The contact characteristics of helical surfaces directly determine PRSM’s performance in load-carrying capacity and transmission accuracy.Therefore,studying the contact characteristics of PRSM forms the fundamental basis for enhancing its transmission performance.In this study,a three-dimensional parametric analysis method of contact characteristics is proposed based on the PRSM meshing principle and PyVista(a high-level API to the Visualization Toolkit).The proposed method considers the influence of machining errors among various thread teeth.The effects of key machining errors on contact positions and axial clearance,as well as their sensitivities,are analyzed.With excellent solution accuracy,this method exhibits higher calculation efficiency and stronger robustness than the analytical and numerical meshing models.The influence of nominal diameter and pitch errors of the screw,roller,and nut on the axial clearance follows a linear relationship,whereas flank angle errors have negligible effects on the axial clearance.The corresponding influence coefficients for these three machining errors on the axial clearance are 0.623,0.341,and 0.036.The variations in contact positions caused by individual errors are axisymmetric.Flank angle errors and roller diameter errors result in linear displacements of the contact points,whereas pitch errors cause the contact points to move along the arc of the roller diameter.Based on the proposed threedimensional parametric contact characteristics analysis method,the Fuzzy C-Means clustering algorithm considering error sensitivity is utilized to establish a component grouping technique in the selective assembly of critical PRSM components,ensuring the rational and consistent clearances based on the given component’s machining errors.This study provides effective guidance for analyzing contact characteristics and grouping in selective assembly for PRSM components.It also presents the proposed method’s potential applicability to similar calculation problems for contact positions and clearances in other transmission systems.
文摘The well controllable selective growth of carbon nanotubes (CNTs)on the desired area is an important issue for their future applications. In this study, a novel method for selective growth of CNTs was proposed by using the technology of self-assembly monolayers (SAMs) and the Fe-assisted CNTs growth. The Si wafers with the a : Si/Si3N4 layer patterns were first prepared by low pressure chemical vapor deposition (LPCVD)and lithography techniques to act as the substrates for selective deposition of SAMs. The selectivity of SAMs from APTMS solution (N-(2-aminoethyl)-3-aminopropyltrimethoxsilane) is based on its greater reactivity of head group on a-Si than Si3N4 films. The areas of pattern with SAMs will first chelate the Fe3+ ions by their diamine-terminated group. The Fe3+ ions were then consolidated to become Fe-hydroxides in sodium boron hydride solution to form the Fe-hydroxides pattern. Finally, the Fe-hydroxides pattern was pretreated in H plasma to become a well-distributed Fe nano-particles on the surface, and followed by CNTs deposition using Fe as catalyst in a microwave plasma-chemical vapor deposition (MP-CVD) system to become the CNTs pattern. The products in each processing step, including microstructures and lattice images of CNTs, were characterized by contact angle measurements, scanning electron microscopy (SEM), XPS, Auger spectroscopy, transmission electron microscopy (TEM) and high resolution TEM (HRTEM)deposition. The results show that the main process parameters include the surface activation process and its atmosphere, consolidation time and temperature, H plasma pretreatment. The function of each processing step will be discussed.
基金the National Natural Science Foundation of China (Nos. 21672113, 21432004, 21772099,21861132001)
文摘Calixarenes and pillararenes are cyclic oligomers containing repeating units of phenol and methane. The modification of ionized groups bring calixarenes and pillararenes derivates both good water solubility and strong binding affinities towards various organic/inorganic/biological guest molecules in both water and the solid state. Meanwhile, the pre-organized structures of these compounds are indispensable in constructing of stimuli-responsive supramolecular assembly. With these properties, the supramolecular selective binding and molecular assembly based on calixarene/pillararene are widely used in enzyme tandem assay, stimuli-responsive nanostructure, drug delivery, organelle fluorescent imaging, photo-controlled morphological change, organic and inorganic hybrid material, solid tunable photo-luminescence and so on. This review summarized the recent research progresses on the calixarene/pillararene-based supramolecular systems and discussed the expectation of the future development.
