The transition metal-catalyzed C–H activation have been considered as increasingly useful approach for installing new functional groups onto organic small molecules due to their high step-and atom-economy,the abundan...The transition metal-catalyzed C–H activation have been considered as increasingly useful approach for installing new functional groups onto organic small molecules due to their high step-and atom-economy,the abundance of hydrocarbon compounds,and the potential for late-stage functionalization of complex organic molecules.The ortho-and meta-C-H activation and functionalization of aromatic compounds have been widely explored in recent years,however the distal para-C-H activation and functionalization has remained a significant challenge because of the difficulty in forming energetically favorable metallacyclic transition states.The utilization of appropriate directing groups or templates as well as the meticulous design of catalysts and ligands has proven to be effective in transition-metal-catalyzed remote para-C-H bonds activation and functionalization of aromatic compounds.This review aims to summarize the strategies for controlling para-selective C–H functionalization using the directing group,template engineering,and catalyst/ligand design under transition metals catalysis in recent years.展开更多
The fabrication of Invar/MnCu functionally graded material(FGM)through directed energy deposition(DED)can satisfy the demands for precision devices in aerospace,providing lightweight properties and integrating thermal...The fabrication of Invar/MnCu functionally graded material(FGM)through directed energy deposition(DED)can satisfy the demands for precision devices in aerospace,providing lightweight properties and integrating thermal stability and vibration damping capabilities.However,basic research on Invar/MnCu FGM is still lacking,hindering its potential applications.To address this gap,this study was conducted using mixed powders and consistent process parameters to print experiments for Invar/MnCu FGM and homogeneous samples.Phases,microstructures,compositions,and thermal expansion properties were thoroughly examined.Three types of defects were detected in the Invar/MnCu FGM sample:unmelted Invar 36 powders,cracks,and pores.The mechanism of unmelted powders was deeply discussed,attributing it to material properties influencing laser absorptivity,the required time for melting powder,and effects on solidus temperature.The mechanism of cracks was also discussed,attributing it to theγ-Fe dendritic structure causing low melting point metal to form an intergranular liquid film,harmful secondary phases mismatched with the terminal alloy,and obvious tensile stresses during the DED process.Additionally,an effective strategy was proposed to reduce defects in Invar/MnCu FGM.After optimization,the specimens exhibited excellent tensile properties,with a yield strength of 262±5 MPa,an ultimate tensile strength of 316±7 MPa,and an elongation of 3%±1%.This research provides valuable references and insights for subsequent work,offering robust support for better understanding and designing other FGM.展开更多
The nanofluid-based direct absorption solar collector(NDASC)ensures that solar radiation passing through the tube wall is directly absorbed by the nanofluid,reducing thermal resistance in the energy transfer process.H...The nanofluid-based direct absorption solar collector(NDASC)ensures that solar radiation passing through the tube wall is directly absorbed by the nanofluid,reducing thermal resistance in the energy transfer process.However,further exploration is required to suppress the outward thermal losses from the nanofluid at high temperatures.Herein,this paper proposes a novel NDASC in which the outer surface of the collector tube is covered with functional coatings and a three-dimensional computational fluid dynamics model is established to study the energy flow distributions on the collector within the temperature range of 400-600 K.When the nanofluid’s absorption coefficient reaches 80 m^(-1),the NDASC shows the optimal thermal performance,and the NDASC with local Sn-In_(2)O_(3) coating achieves a 7.8% improvement in thermal efficiency at 400 K compared to the original NDASC.Furthermore,hybrid coatings with Sn In_(2)O_(3)/WTi-Al_(2)O_(3) are explored,and the optimal coverage angles are determined.The NDASC with such coatings shows a 10.22%-17.9% increase in thermal efficiency compared to the original NDASC and a 7.6%-19.5% increase compared to the traditional surface-type solar collectors,demonstrating the effectiveness of the proposed energy flow control strategy for DASCs.展开更多
An unauthorised version of the Chinese MMSE was used in this article by the authors without permission from the copyright owner,PAR.Necessary permission has now been retrospectively obtained from PAR.The MMSE is a cop...An unauthorised version of the Chinese MMSE was used in this article by the authors without permission from the copyright owner,PAR.Necessary permission has now been retrospectively obtained from PAR.The MMSE is a copyrighted instrument and may not be used or reproduced in whole or in part,in any form or language,or by any means without the written permission of PAR(www.parinc.com).展开更多
The rnemmorphic functions of positive order(both finite positive order and infinite order) are discussed.First,the precise order and type function are given by using the characteristic function.Then some singular dire...The rnemmorphic functions of positive order(both finite positive order and infinite order) are discussed.First,the precise order and type function are given by using the characteristic function.Then some singular directions are defined and their existence is proved.展开更多
Aim To study the value distribution of meromorphic functions in angular domains, the deficiency, the deficient value, the Nevanlinna direction and other singular directions. Methods A fundamental inequality of Nevan...Aim To study the value distribution of meromorphic functions in angular domains, the deficiency, the deficient value, the Nevanlinna direction and other singular directions. Methods A fundamental inequality of Nevanlinna characteristic functions in the angular domain was used, which is similar with the Nevanlinna secondary fundamental theorem. Results The deficiency and deficient value of meromorphic functions about an angular domain and a direction were defined. The definition of Nevanlinna direction was improved. Conclusion For a family of meromorphic functions, it is proved that the number of deficient values is at most countable and the sum of deficiencies isnt greater than 2. The existence of the Nevanlinna direction is obtained. The existence of Borel and Julia directions and the relation between them are found.展开更多
In this paper, a notation delta(x)(w) is derived from the counting function N-x(r, w) of branch points of algebriod functions. With this notation, the authors give the definition of the Nevanlinna direction for algebr...In this paper, a notation delta(x)(w) is derived from the counting function N-x(r, w) of branch points of algebriod functions. With this notation, the authors give the definition of the Nevanlinna direction for algebriod functions and discuss its existence in certain condition. By this notation the authors also obtain the numbers of exceptional value of the Julia direction and Borel direction of algebriod functions are not more than 2 + [delta(x) (w)] here [x] implies an maximum integer number which does not exceed x.展开更多
A directional function for frequencies equal to and larger than the peak frequency of a wind-wave frequency spectrum is constructed by fitting the angular spreading based on the analytically derived directional spectr...A directional function for frequencies equal to and larger than the peak frequency of a wind-wave frequency spectrum is constructed by fitting the angular spreading based on the analytically derived directional spectrum of Wen et al. (1993, Journal of Oceanography, 49(2), 131～147, 149～172). For frequencies smaller than the peak frequency, the directional function is obtained by comparing and analyzing existing formulas. The nondimensional wind-wave frequency spectrum of Wen et al. (1994, Progress in Natural Seience, 4(4). 407～427;4 (5), 586～596) has been used together with the directional function just mentioned to obtain the directional spectrum for easier application.展开更多
A brand new direct and adaptive slicing approach is proposed, which canapparently improve the part accuracy and reduce the building time. At least two stages are includedin this operation: getting the crossing contour...A brand new direct and adaptive slicing approach is proposed, which canapparently improve the part accuracy and reduce the building time. At least two stages are includedin this operation: getting the crossing contour of the cutting plane with the solid part anddetermining the layer thickness. Apart from usual SPI algorithm, slicing of the solid model has itsspecial requirements. Enabling the contour line segments of the cross-section as long as possible isone of them, which is for improving manufacturing efficiency and is reached by adaptively adjustingthe step direction and the step size at every crossing point to obtain optimized secant height. Thelayer thickness determination can be divided into two phases: the geometry-based thicknessestimation and the material-based thickness verifying. During the former phase, the geometrytolerance is divided into two parts: a variety of curves are approximated by a circular arc, whichintroduces the first part, and the deviation error between the contour line in LM process and thecircular arc generates the second part. The latter phase is mainly verifying the layer thicknessestimated in the former stage and determining a new one if necessary. In addition, an example usingthis slicing algorithm is also illustrated.展开更多
In this article, the relationship between the Borel direction of algebroidal function and its coefficient functions is studied for the first time. To begin with, several theorems of algebroidal functions in unit disk ...In this article, the relationship between the Borel direction of algebroidal function and its coefficient functions is studied for the first time. To begin with, several theorems of algebroidal functions in unit disk are proved. By these theorems, some interesting conclusions are obtained.展开更多
In this study,the transverse vibration of a traveling beam made of functionally graded material was analyzed.The material gradation was assumed to vary continuously along the thickness direction of the beam in the for...In this study,the transverse vibration of a traveling beam made of functionally graded material was analyzed.The material gradation was assumed to vary continuously along the thickness direction of the beam in the form of power law exponent.The effect of the longitudinally varying tension due to axial acceleration was highlighted,and the dependence of the tension on the finite support rigidity was also considered.A complex governing equation of the functionally graded beam was derived by the Hamilton principle,in which the geometric nonlinearity,material properties and axial load were incorporated.The direct multiscale method was applied to the analysis process of an axially moving functionally graded beam with timedependent velocity,and the natural frequency and solvability conditions were obtained.Based on the conditions,the stability boundaries of subharmonic resonance and combination resonance were obtained.It was found that the dynamic behavior of axial moving beams could be tuned by using the distribution law of the functional gradient parameters.展开更多
Well production optimization is a complex and time-consuming task in the oilfield development.The combination of reservoir numerical simulator with optimization algorithms is usually used to optimize well production.T...Well production optimization is a complex and time-consuming task in the oilfield development.The combination of reservoir numerical simulator with optimization algorithms is usually used to optimize well production.This method spends most of computing time in objective function evaluation by reservoir numerical simulator which limits its optimization efficiency.To improve optimization efficiency,a well production optimization method using streamline features-based objective function and Bayesian adaptive direct search optimization(BADS)algorithm is established.This new objective function,which represents the water flooding potential,is extracted from streamline features.It only needs to call the streamline simulator to run one time step,instead of calling the simulator to calculate the target value at the end of development,which greatly reduces the running time of the simulator.Then the well production optimization model is established and solved by the BADS algorithm.The feasibility of the new objective function and the efficiency of this optimization method are verified by three examples.Results demonstrate that the new objective function is positively correlated with the cumulative oil production.And the BADS algorithm is superior to other common algorithms in convergence speed,solution stability and optimization accuracy.Besides,this method can significantly accelerate the speed of well production optimization process compared with the objective function calculated by other conventional methods.It can provide a more effective basis for determining the optimal well production for actual oilfield development.展开更多
Axon regeneration and remyelination of the damaged region is the most common repair strategy for spinal cord injury.However,achieving good outcome remains difficult.Our previous study showed that porcine decellularize...Axon regeneration and remyelination of the damaged region is the most common repair strategy for spinal cord injury.However,achieving good outcome remains difficult.Our previous study showed that porcine decellularized optic nerve better mimics the extracellular matrix of the embryonic porcine optic nerve and promotes the directional growth of dorsal root ganglion neurites.However,it has not been reported whether this material promotes axonal regeneration in vivo.In the present study,a porcine decellularized optic nerve was seeded with neurotrophin-3-overexpressing Schwann cells.This functional scaffold promoted the directional growth and remyelination of regenerating axons.In vitro,the porcine decellularized optic nerve contained many straight,longitudinal channels with a uniform distribution,and microscopic pores were present in the channel wall.The spatial micro topological structure and extracellular matrix were conducive to the adhesion,survival and migration of neural stem cells.The scaffold promoted the directional growth of dorsal root ganglion neurites,and showed strong potential for myelin regeneration.Furthermore,we transplanted the porcine decellularized optic nerve containing neurotrophin-3-overexpressing Schwann cells in a rat model of T10 spinal cord defect in vivo.Four weeks later,the regenerating axons grew straight,the myelin sheath in the injured/transplanted area recovered its structure,and simultaneously,the number of inflammatory cells and the expression of chondroitin sulfate proteoglycans were reduced.Together,these findings suggest that porcine decellularized optic nerve loaded with Schwann cells overexpressing neurotrophin-3 promotes the directional growth of regenerating spinal cord axons as well as myelin regeneration.All procedures involving animals were conducted in accordance with the ethical standards of the Institutional Animal Care and Use Committee of Sun Yat-sen University(approval No.SYSU-IACUC-2019-B034)on February 28,2019.展开更多
This work presents a novel approach combining radial basis function(RBF)interpolation with Galerkin projection to efficiently solve general optimal control problems.The goal is to develop a highly flexible solution to...This work presents a novel approach combining radial basis function(RBF)interpolation with Galerkin projection to efficiently solve general optimal control problems.The goal is to develop a highly flexible solution to optimal control problems,especially nonsmooth problems involving discontinuities,while accounting for trajectory accuracy and computational efficiency simultaneously.The proposed solution,called the RBF-Galerkin method,offers a highly flexible framework for direct transcription by using any interpolant functions from the broad class of global RBFs and any arbitrary discretization points that do not necessarily need to be on a mesh of points.The RBF-Galerkin costate mapping theorem is developed that describes an exact equivalency between the Karush-Kuhn-Tucker(KKT)conditions of the nonlinear programming problem resulted from the RBF-Galerkin method and the discretized form of the first-order necessary conditions of the optimal control problem,if a set of discrete conditions holds.The efficacy of the proposed method along with the accuracy of the RBF-Galerkin costate mapping theorem is confirmed against an analytical solution for a bang-bang optimal control problem.In addition,the proposed approach is compared against both local and global polynomial methods for a robot motion planning problem to verify its accuracy and computational efficiency.展开更多
The three-dimensional free vibration analysis of a multi-directional func- tionally graded piezoelectric （FGP） annular plate resting on two parameter （Pasternak） elastic foundations is investigated under different...The three-dimensional free vibration analysis of a multi-directional func- tionally graded piezoelectric （FGP） annular plate resting on two parameter （Pasternak） elastic foundations is investigated under different boundary conditions. The material properties are assumed to vary continuously along the radial and thickness directions and have exponent-law distribution. A semi-analytical approach named the state space based differential quadrature method （SSDQM） is used to provide an analytical solution along the thickness using the state space method （SSM） and an approximate solution along the radial direction using the one-dimensional differential quadrature method （DQM）. The influence of the Winkler and shear stiffness of the foundation~ the material property graded variations, and the circumferential wave number on the nomdimensional natural frequency of multi-directional FGP annular plates is studied.展开更多
In this paper, we prove that for an algebroid function w（z）, the singular direction argz = φ0, satisfying that for arbitrary ε（0 〈 ε 〈 2/π） and any given α ∈ C^^,limr→＋∞ log τ/n（τ,φ0-ε,φ0＋ε,w=a...In this paper, we prove that for an algebroid function w（z）, the singular direction argz = φ0, satisfying that for arbitrary ε（0 〈 ε 〈 2/π） and any given α ∈ C^^,limr→＋∞ log τ/n（τ,φ0-ε,φ0＋ε,w=a）=＋∞ holds with at most; 2v possible exceptional values of a, is the Ncvanlinna direction of w（z）.展开更多
We performed functional MRI examinations in six right-handed healthy subjects.During functional MRI scanning,transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cor...We performed functional MRI examinations in six right-handed healthy subjects.During functional MRI scanning,transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cortex and the cathode over the left primary sensorimotor cortex using dual-hemispheric transcranial direct current stimulation.This was compared to a cathode over the left supraorbital area using conventional single-hemispheric transcranial direct current stimulation. Voxel counts and blood oxygenation level-dependent signal intensities in the right primary sensorimotor cortex regions were estimated and compared between the two transcranial direct current stimulation conditions.Our results showed that dual-hemispheric transcranial direct current stimulation induced greater cortical activities than single-hemispheric transcranial direct current stimulation.These findings suggest that dual-hemispheric transcranial direct current stimulation may provide more effective cortical stimulation than single-hemispheric transcranial direct current stimulation.展开更多
Assuming the material properties varying with an exponential law both in the thick- ness and radial directions, axisymmetric bending of two-directional functionally graded circular and annular plates is studied using ...Assuming the material properties varying with an exponential law both in the thick- ness and radial directions, axisymmetric bending of two-directional functionally graded circular and annular plates is studied using the semi-analytical numerical method in this paper. The deflections and stresses of the plates are presented. Numerical results show the well accuracy and convergence of the method. Compared with the finite element method, the semi-analytical nu- merical method is with great advantage in the computational efficiency. Moreover, study on ax- isymmetric bending of two-directional functionally graded annular plate shows that such plates have better performance than those made of isotropic homogeneous materials or one-directional functionally graded materials. Two-directional functionally graded material is a potential alternative to the one-directional functionally graded material. And the integrated design of materials and structures can really be achieved in two-directional functionally graded materials.展开更多
Direct air capture(DAC)of CO_(2)plays an indispensable role in achieving carbon-neutral goals as one of the key negative emission technologies.Since large air flows are required to capture the ultradilute CO_(2)from t...Direct air capture(DAC)of CO_(2)plays an indispensable role in achieving carbon-neutral goals as one of the key negative emission technologies.Since large air flows are required to capture the ultradilute CO_(2)from the air,lab-synthesized adsorbents in powder form may cause unacceptable gas pressure drops and poor heat and mass transfer efficiencies.A structured adsorbent is essential for the implementation of gas-solid contactors for cost-and energy-efficient DAC systems.In this study,efficient adsorbent poly(ethyleneimine)(PEI)-functionalized Mg-Al-CO_(3)layered double hydroxide(LDH)-derived mixed metal oxides(MMOs)are three-dimensional(3D)printed into monoliths for the first time with more than 90%adsorbent loadings.The printing process has been optimized by initially printing the LDH powder into monoliths followed by calcination into MMO monoliths.This structure exhibits a 32.7%higher specific surface area and a 46.1%higher pore volume,as compared to the direct printing of the MMO powder into a monolith.After impregnation of PEI,the monolith demonstrates a large adsorption capacity(1.82 mmol/g)and fast kinetics(0.7 mmol/g/h)using a CO_(2)feed gas at 400 ppm at 25℃,one of the highest values among the shaped DAC adsorbents.Smearing of the amino-polymers during the post-printing process affects the diffusion of CO_(2),resulting in slower adsorption kinetics of pre-impregnation monoliths compared to post-impregnation monoliths.The optimal PEI/MeOH ratio for the post-impregnation solution prevents pores clogging that would affect both adsorption capacity and kinetics.展开更多
基金support from the National Natural Science Foundation of China(No.21901206)Postdoctoral Science Foundation of China(No.2022M712589)+2 种基金General Key R&D Projects in Shaanxi Province(No.2023-YBGY-321)Natural Science Foundation of Chongqing(No.CSTB2022NSCQ-MSX0826)National&Local Joint Engineering Research Center for mineral Salt Deep Utilization,Huaiyin Institute of Technology(No.SF202407)for financial support。
文摘The transition metal-catalyzed C–H activation have been considered as increasingly useful approach for installing new functional groups onto organic small molecules due to their high step-and atom-economy,the abundance of hydrocarbon compounds,and the potential for late-stage functionalization of complex organic molecules.The ortho-and meta-C-H activation and functionalization of aromatic compounds have been widely explored in recent years,however the distal para-C-H activation and functionalization has remained a significant challenge because of the difficulty in forming energetically favorable metallacyclic transition states.The utilization of appropriate directing groups or templates as well as the meticulous design of catalysts and ligands has proven to be effective in transition-metal-catalyzed remote para-C-H bonds activation and functionalization of aromatic compounds.This review aims to summarize the strategies for controlling para-selective C–H functionalization using the directing group,template engineering,and catalyst/ligand design under transition metals catalysis in recent years.
基金supported by the National Key Research and Development Program of China(Nos.2022YFB4600300 and 2022YFB4600301)the National Natural Science Foundation of China(No.52175364)+1 种基金the ND Basic Research Funds of NPU(G2022WD)the Research Fund of the State Key Laboratory of Solidification Processing(NPU),China(No.2023-QZ-04).
文摘The fabrication of Invar/MnCu functionally graded material(FGM)through directed energy deposition(DED)can satisfy the demands for precision devices in aerospace,providing lightweight properties and integrating thermal stability and vibration damping capabilities.However,basic research on Invar/MnCu FGM is still lacking,hindering its potential applications.To address this gap,this study was conducted using mixed powders and consistent process parameters to print experiments for Invar/MnCu FGM and homogeneous samples.Phases,microstructures,compositions,and thermal expansion properties were thoroughly examined.Three types of defects were detected in the Invar/MnCu FGM sample:unmelted Invar 36 powders,cracks,and pores.The mechanism of unmelted powders was deeply discussed,attributing it to material properties influencing laser absorptivity,the required time for melting powder,and effects on solidus temperature.The mechanism of cracks was also discussed,attributing it to theγ-Fe dendritic structure causing low melting point metal to form an intergranular liquid film,harmful secondary phases mismatched with the terminal alloy,and obvious tensile stresses during the DED process.Additionally,an effective strategy was proposed to reduce defects in Invar/MnCu FGM.After optimization,the specimens exhibited excellent tensile properties,with a yield strength of 262±5 MPa,an ultimate tensile strength of 316±7 MPa,and an elongation of 3%±1%.This research provides valuable references and insights for subsequent work,offering robust support for better understanding and designing other FGM.
基金Project(52476095)supported by the National Natural Science Foundation of ChinaProject(kq2506013)supported by Changsha Outstanding Innovative Youth Training Program,China。
文摘The nanofluid-based direct absorption solar collector(NDASC)ensures that solar radiation passing through the tube wall is directly absorbed by the nanofluid,reducing thermal resistance in the energy transfer process.However,further exploration is required to suppress the outward thermal losses from the nanofluid at high temperatures.Herein,this paper proposes a novel NDASC in which the outer surface of the collector tube is covered with functional coatings and a three-dimensional computational fluid dynamics model is established to study the energy flow distributions on the collector within the temperature range of 400-600 K.When the nanofluid’s absorption coefficient reaches 80 m^(-1),the NDASC shows the optimal thermal performance,and the NDASC with local Sn-In_(2)O_(3) coating achieves a 7.8% improvement in thermal efficiency at 400 K compared to the original NDASC.Furthermore,hybrid coatings with Sn In_(2)O_(3)/WTi-Al_(2)O_(3) are explored,and the optimal coverage angles are determined.The NDASC with such coatings shows a 10.22%-17.9% increase in thermal efficiency compared to the original NDASC and a 7.6%-19.5% increase compared to the traditional surface-type solar collectors,demonstrating the effectiveness of the proposed energy flow control strategy for DASCs.
文摘An unauthorised version of the Chinese MMSE was used in this article by the authors without permission from the copyright owner,PAR.Necessary permission has now been retrospectively obtained from PAR.The MMSE is a copyrighted instrument and may not be used or reproduced in whole or in part,in any form or language,or by any means without the written permission of PAR(www.parinc.com).
文摘The rnemmorphic functions of positive order(both finite positive order and infinite order) are discussed.First,the precise order and type function are given by using the characteristic function.Then some singular directions are defined and their existence is proved.
文摘Aim To study the value distribution of meromorphic functions in angular domains, the deficiency, the deficient value, the Nevanlinna direction and other singular directions. Methods A fundamental inequality of Nevanlinna characteristic functions in the angular domain was used, which is similar with the Nevanlinna secondary fundamental theorem. Results The deficiency and deficient value of meromorphic functions about an angular domain and a direction were defined. The definition of Nevanlinna direction was improved. Conclusion For a family of meromorphic functions, it is proved that the number of deficient values is at most countable and the sum of deficiencies isnt greater than 2. The existence of the Nevanlinna direction is obtained. The existence of Borel and Julia directions and the relation between them are found.
基金Supported by the Natioal Natural Science Foundation of China (10271122)
文摘In this paper, a notation delta(x)(w) is derived from the counting function N-x(r, w) of branch points of algebriod functions. With this notation, the authors give the definition of the Nevanlinna direction for algebriod functions and discuss its existence in certain condition. By this notation the authors also obtain the numbers of exceptional value of the Julia direction and Borel direction of algebriod functions are not more than 2 + [delta(x) (w)] here [x] implies an maximum integer number which does not exceed x.
文摘A directional function for frequencies equal to and larger than the peak frequency of a wind-wave frequency spectrum is constructed by fitting the angular spreading based on the analytically derived directional spectrum of Wen et al. (1993, Journal of Oceanography, 49(2), 131～147, 149～172). For frequencies smaller than the peak frequency, the directional function is obtained by comparing and analyzing existing formulas. The nondimensional wind-wave frequency spectrum of Wen et al. (1994, Progress in Natural Seience, 4(4). 407～427;4 (5), 586～596) has been used together with the directional function just mentioned to obtain the directional spectrum for easier application.
基金This project is supported by National Natural Science Foundation of China (No.59975015, No.50275018) Doctoral Foundation of Ministry of Edu-cation of China (No.1999014102).
文摘A brand new direct and adaptive slicing approach is proposed, which canapparently improve the part accuracy and reduce the building time. At least two stages are includedin this operation: getting the crossing contour of the cutting plane with the solid part anddetermining the layer thickness. Apart from usual SPI algorithm, slicing of the solid model has itsspecial requirements. Enabling the contour line segments of the cross-section as long as possible isone of them, which is for improving manufacturing efficiency and is reached by adaptively adjustingthe step direction and the step size at every crossing point to obtain optimized secant height. Thelayer thickness determination can be divided into two phases: the geometry-based thicknessestimation and the material-based thickness verifying. During the former phase, the geometrytolerance is divided into two parts: a variety of curves are approximated by a circular arc, whichintroduces the first part, and the deviation error between the contour line in LM process and thecircular arc generates the second part. The latter phase is mainly verifying the layer thicknessestimated in the former stage and determining a new one if necessary. In addition, an example usingthis slicing algorithm is also illustrated.
文摘In this article, the relationship between the Borel direction of algebroidal function and its coefficient functions is studied for the first time. To begin with, several theorems of algebroidal functions in unit disk are proved. By these theorems, some interesting conclusions are obtained.
基金The authors acknowledge the support of National Natural Science Foundation of China(Nos.11672187,11572182)Natural Science Foundation of Liaoning Province(201602573)+2 种基金the Key Research Projects of Shanghai Science and Technology Commission(No.18010500100)Innovation Program of Shanghai Education Commission(No.2017-01-07-00-09-E00019)Beiyang Young Scholars of Tian jin University(2019XRX-0027).
文摘In this study,the transverse vibration of a traveling beam made of functionally graded material was analyzed.The material gradation was assumed to vary continuously along the thickness direction of the beam in the form of power law exponent.The effect of the longitudinally varying tension due to axial acceleration was highlighted,and the dependence of the tension on the finite support rigidity was also considered.A complex governing equation of the functionally graded beam was derived by the Hamilton principle,in which the geometric nonlinearity,material properties and axial load were incorporated.The direct multiscale method was applied to the analysis process of an axially moving functionally graded beam with timedependent velocity,and the natural frequency and solvability conditions were obtained.Based on the conditions,the stability boundaries of subharmonic resonance and combination resonance were obtained.It was found that the dynamic behavior of axial moving beams could be tuned by using the distribution law of the functional gradient parameters.
基金supported partly by the National Science and Technology Major Project of China(Grant No.2016ZX05025-001006)Major Science and Technology Project of CNPC(Grant No.ZD2019-183-007)
文摘Well production optimization is a complex and time-consuming task in the oilfield development.The combination of reservoir numerical simulator with optimization algorithms is usually used to optimize well production.This method spends most of computing time in objective function evaluation by reservoir numerical simulator which limits its optimization efficiency.To improve optimization efficiency,a well production optimization method using streamline features-based objective function and Bayesian adaptive direct search optimization(BADS)algorithm is established.This new objective function,which represents the water flooding potential,is extracted from streamline features.It only needs to call the streamline simulator to run one time step,instead of calling the simulator to calculate the target value at the end of development,which greatly reduces the running time of the simulator.Then the well production optimization model is established and solved by the BADS algorithm.The feasibility of the new objective function and the efficiency of this optimization method are verified by three examples.Results demonstrate that the new objective function is positively correlated with the cumulative oil production.And the BADS algorithm is superior to other common algorithms in convergence speed,solution stability and optimization accuracy.Besides,this method can significantly accelerate the speed of well production optimization process compared with the objective function calculated by other conventional methods.It can provide a more effective basis for determining the optimal well production for actual oilfield development.
基金supported by grants from the National Key R&D Program of China,No.2017YFA0104704(to BQL)the Young Elite Scientist Sponsorship Program(YESS)by China Association for Science and Technology(CAST),No.2018QNRC001(to BQL)+1 种基金the Fundamental Research Funds for the Central Universities,China,No.18ykpy38(to BQL)the National Natural Science Foundation of China,Nos.81971157(to BQL),81891003(to YSZ).
文摘Axon regeneration and remyelination of the damaged region is the most common repair strategy for spinal cord injury.However,achieving good outcome remains difficult.Our previous study showed that porcine decellularized optic nerve better mimics the extracellular matrix of the embryonic porcine optic nerve and promotes the directional growth of dorsal root ganglion neurites.However,it has not been reported whether this material promotes axonal regeneration in vivo.In the present study,a porcine decellularized optic nerve was seeded with neurotrophin-3-overexpressing Schwann cells.This functional scaffold promoted the directional growth and remyelination of regenerating axons.In vitro,the porcine decellularized optic nerve contained many straight,longitudinal channels with a uniform distribution,and microscopic pores were present in the channel wall.The spatial micro topological structure and extracellular matrix were conducive to the adhesion,survival and migration of neural stem cells.The scaffold promoted the directional growth of dorsal root ganglion neurites,and showed strong potential for myelin regeneration.Furthermore,we transplanted the porcine decellularized optic nerve containing neurotrophin-3-overexpressing Schwann cells in a rat model of T10 spinal cord defect in vivo.Four weeks later,the regenerating axons grew straight,the myelin sheath in the injured/transplanted area recovered its structure,and simultaneously,the number of inflammatory cells and the expression of chondroitin sulfate proteoglycans were reduced.Together,these findings suggest that porcine decellularized optic nerve loaded with Schwann cells overexpressing neurotrophin-3 promotes the directional growth of regenerating spinal cord axons as well as myelin regeneration.All procedures involving animals were conducted in accordance with the ethical standards of the Institutional Animal Care and Use Committee of Sun Yat-sen University(approval No.SYSU-IACUC-2019-B034)on February 28,2019.
文摘This work presents a novel approach combining radial basis function(RBF)interpolation with Galerkin projection to efficiently solve general optimal control problems.The goal is to develop a highly flexible solution to optimal control problems,especially nonsmooth problems involving discontinuities,while accounting for trajectory accuracy and computational efficiency simultaneously.The proposed solution,called the RBF-Galerkin method,offers a highly flexible framework for direct transcription by using any interpolant functions from the broad class of global RBFs and any arbitrary discretization points that do not necessarily need to be on a mesh of points.The RBF-Galerkin costate mapping theorem is developed that describes an exact equivalency between the Karush-Kuhn-Tucker(KKT)conditions of the nonlinear programming problem resulted from the RBF-Galerkin method and the discretized form of the first-order necessary conditions of the optimal control problem,if a set of discrete conditions holds.The efficacy of the proposed method along with the accuracy of the RBF-Galerkin costate mapping theorem is confirmed against an analytical solution for a bang-bang optimal control problem.In addition,the proposed approach is compared against both local and global polynomial methods for a robot motion planning problem to verify its accuracy and computational efficiency.
文摘The three-dimensional free vibration analysis of a multi-directional func- tionally graded piezoelectric （FGP） annular plate resting on two parameter （Pasternak） elastic foundations is investigated under different boundary conditions. The material properties are assumed to vary continuously along the radial and thickness directions and have exponent-law distribution. A semi-analytical approach named the state space based differential quadrature method （SSDQM） is used to provide an analytical solution along the thickness using the state space method （SSM） and an approximate solution along the radial direction using the one-dimensional differential quadrature method （DQM）. The influence of the Winkler and shear stiffness of the foundation~ the material property graded variations, and the circumferential wave number on the nomdimensional natural frequency of multi-directional FGP annular plates is studied.
基金supported by NSFC (10471048)NSF of Henan Province in China (112300410300)
文摘In this paper, we prove that for an algebroid function w（z）, the singular direction argz = φ0, satisfying that for arbitrary ε（0 〈 ε 〈 2/π） and any given α ∈ C^^,limr→＋∞ log τ/n（τ,φ0-ε,φ0＋ε,w=a）=＋∞ holds with at most; 2v possible exceptional values of a, is the Ncvanlinna direction of w（z）.
基金supported by a National Research Foundation of Korea Grant funded by the Korean Government,No.2009-0064682
文摘We performed functional MRI examinations in six right-handed healthy subjects.During functional MRI scanning,transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cortex and the cathode over the left primary sensorimotor cortex using dual-hemispheric transcranial direct current stimulation.This was compared to a cathode over the left supraorbital area using conventional single-hemispheric transcranial direct current stimulation. Voxel counts and blood oxygenation level-dependent signal intensities in the right primary sensorimotor cortex regions were estimated and compared between the two transcranial direct current stimulation conditions.Our results showed that dual-hemispheric transcranial direct current stimulation induced greater cortical activities than single-hemispheric transcranial direct current stimulation.These findings suggest that dual-hemispheric transcranial direct current stimulation may provide more effective cortical stimulation than single-hemispheric transcranial direct current stimulation.
基金Project supported by the National Natural Science Foundation of China (No.10432030).
文摘Assuming the material properties varying with an exponential law both in the thick- ness and radial directions, axisymmetric bending of two-directional functionally graded circular and annular plates is studied using the semi-analytical numerical method in this paper. The deflections and stresses of the plates are presented. Numerical results show the well accuracy and convergence of the method. Compared with the finite element method, the semi-analytical nu- merical method is with great advantage in the computational efficiency. Moreover, study on ax- isymmetric bending of two-directional functionally graded annular plate shows that such plates have better performance than those made of isotropic homogeneous materials or one-directional functionally graded materials. Two-directional functionally graded material is a potential alternative to the one-directional functionally graded material. And the integrated design of materials and structures can really be achieved in two-directional functionally graded materials.
基金supported by the Shanghai Agricultural Science and Technology Program (2022-02-08-00-12-F01176)he National Natural Science Foundation of China (52006135)
文摘Direct air capture(DAC)of CO_(2)plays an indispensable role in achieving carbon-neutral goals as one of the key negative emission technologies.Since large air flows are required to capture the ultradilute CO_(2)from the air,lab-synthesized adsorbents in powder form may cause unacceptable gas pressure drops and poor heat and mass transfer efficiencies.A structured adsorbent is essential for the implementation of gas-solid contactors for cost-and energy-efficient DAC systems.In this study,efficient adsorbent poly(ethyleneimine)(PEI)-functionalized Mg-Al-CO_(3)layered double hydroxide(LDH)-derived mixed metal oxides(MMOs)are three-dimensional(3D)printed into monoliths for the first time with more than 90%adsorbent loadings.The printing process has been optimized by initially printing the LDH powder into monoliths followed by calcination into MMO monoliths.This structure exhibits a 32.7%higher specific surface area and a 46.1%higher pore volume,as compared to the direct printing of the MMO powder into a monolith.After impregnation of PEI,the monolith demonstrates a large adsorption capacity(1.82 mmol/g)and fast kinetics(0.7 mmol/g/h)using a CO_(2)feed gas at 400 ppm at 25℃,one of the highest values among the shaped DAC adsorbents.Smearing of the amino-polymers during the post-printing process affects the diffusion of CO_(2),resulting in slower adsorption kinetics of pre-impregnation monoliths compared to post-impregnation monoliths.The optimal PEI/MeOH ratio for the post-impregnation solution prevents pores clogging that would affect both adsorption capacity and kinetics.
