Two new Mn(Ⅱ)coordination polymers,namely{[Mn_(2)(HL)(phen)_(3)(H_(2)O)_(2)]·7.5H_(2)O}_n(1)and[Mn_(4)(HL)_(2)(1,4-bib)_(3)(H_(2)O)_(2)]_n(2),were synthesized under hydrothermal conditions by using Mn(Ⅱ)ions an...Two new Mn(Ⅱ)coordination polymers,namely{[Mn_(2)(HL)(phen)_(3)(H_(2)O)_(2)]·7.5H_(2)O}_n(1)and[Mn_(4)(HL)_(2)(1,4-bib)_(3)(H_(2)O)_(2)]_n(2),were synthesized under hydrothermal conditions by using Mn(Ⅱ)ions and 6-(3',4'-dicarboxylphenoxy)-1,2,4-benzenetricarboxylic acid(H_(5)L)in the presence of N-auxiliary ligands 1,10-phenanthroline(phen)and1,4-bis(1H-imidazol-1-yl)benzene(1,4-bib).The structures of coordination polymers 1 and 2 were characterized by infrared spectroscopy,single-crystal X-ray diffraction,thermogravimetric analysis,and powder X-ray diffraction.Single-crystal X-ray diffraction reveals that 1 has a 1D chain structure based on binuclear Mn(Ⅱ)units,while 2 features a(3,8)-connected 3D network structure based on tetranuclear Mn(Ⅱ)units.Magnetic studies show that 1 and 2exhibit antiferromagnetic interactions between manganese ions.2 shows stronger antiferromagnetic interactions due to the shorter Mn…Mn distances within the tetranuclear manganese units.CCDC:2357601,1;2357602,2.展开更多
Different solvothermal reactions of ZnC2O_(4)with oxalic acid(H_(2)ox)and 1,2,4-triazole(Htrz)successfully gave a new quaternary(NJTU-Bai83,NJTU-Bai=Nanjing Tech University Bai's group)and a new quinary(NJTU-Bai84...Different solvothermal reactions of ZnC2O_(4)with oxalic acid(H_(2)ox)and 1,2,4-triazole(Htrz)successfully gave a new quaternary(NJTU-Bai83,NJTU-Bai=Nanjing Tech University Bai's group)and a new quinary(NJTU-Bai84)anionic metal-organic frameworks(MOFs),where NJTU-Bai83=(Me_(2)NH_(2))2[Zn_(3)(trz)_(2)(ox)_(3)]·2H_(2)O and NJTU-Bai84=(Me_(2)NH_(2))[Zn_(3)(trz)_(3)(ox)_(2)]·H_(2)O,respectively.With the[Zn_(2)(ox)4(trz)_(2)]secondary building unit(SBU)in NJTU-Bai83 replaced by the[Zn_(3)(ox)_(2)(trz)_(6)]and planar[Zn(ox)_(2)(trz)_(2)]ones in NJTU-Bai84,2D supramolecular building layers(SBLs)are changed from the A-layer and B-layer to another A-layer,while pillars are transformed from the tetrahedral[Zn(ox)_(2)(trz)_(2)]SBU to the irregular tetrahedral[Zn(ox)_(2)(trz)_(2)]and planar[Zn(ox)_(2)(trz)_(2)]SBUs.Thus,cdq-topological quaternary NJTU-Bai83 is tuned to(4,4,8)-c new topological quinary NJTU-Bai84.Two MOFs were well characterized by powder X-ray diffraction,thermogravimetric analysis,elemental analysis,etc.CCDC:2351819,NJTU-Bai83;2351820,NJTU-Bai84.展开更多
The irreversible phase transition and interface side reactions during the cycling process severely limit the large scale application of nickel-rich layered oxides Li[Ni_(x)Co_(y)Mn_(1−x−y)]O_(2)(NCM,x>0.8).Herein,w...The irreversible phase transition and interface side reactions during the cycling process severely limit the large scale application of nickel-rich layered oxides Li[Ni_(x)Co_(y)Mn_(1−x−y)]O_(2)(NCM,x>0.8).Herein,we have designed LiNi_(0.8)Co_(0.1)Mn 0.1 O_(2)cathodes modified by Nb/Al co-doping and LiNbO_(3)/LiAlO_(2)composite coating.Detailed characterization reveals that Nb/Al co-doping can stabilize the crystal structure of the cathodes and expand the layer spacing of the layered lattice,thereby increasing the diffusion rate and reversibility of Li^(+).And the composite coatings can improve the electrochemical kinetic and inhibit the erosion of acidic substances by hindering direct contact between the cathodes and electrolyte.As a result,the Ni-rich cathodes with dual modification can still exhibit a higher capacity of 184.02 mA·h/g after 100 cycles with a capacity retention of up to 98.1%,and can still release a capacity of 161.6 mA·h/g at a high rate of 7 C,meanwhile,it shows excellent thermal stability compared to bare NCM.This work provides a new perspective for enhancing electrochemical properties of cathodes through integrated strategies.展开更多
Seeking for innovative structures with higher mechanical performance is a continuous target in railway vehicle crashworthiness design.In the present study,three types of hexagonal reinforced honeycomb-like structures ...Seeking for innovative structures with higher mechanical performance is a continuous target in railway vehicle crashworthiness design.In the present study,three types of hexagonal reinforced honeycomb-like structures were developed and analyzed subjected to out-of-plane compression,namely triangular honeycomb(TH),double honeycomb(DH)and full inside honeycomb(FH).Theoretical formulas of average force and specific energy absorption(SEA)were constructed based on the energy minimization principle.To validate,corresponding numerical simulations were carried out by explicit finite element method.Good agreement has been observed between them.The results show that all these honeycomb-like structures maintain the same collapsed stages as conventional honeycomb;cell reinforcement can significantly promote the performance,both in the average force and SEA;full inside honeycomb performs better than the general,triangular and double schemes in average force;meanwhile,its SEA is close to that of double scheme;toroidal surface can dissipate higher plastic energy,so more toroidal surfaces should be considered in design of thin-walled structure.These achievements pave a way for designing high-performance cellular energy absorption devices.展开更多
Fuzzy entropy was designed for non convex fuzzy membership function using well known Hamming distance measure.The proposed fuzzy entropy had the same structure as that of convex fuzzy membership case.Design procedure ...Fuzzy entropy was designed for non convex fuzzy membership function using well known Hamming distance measure.The proposed fuzzy entropy had the same structure as that of convex fuzzy membership case.Design procedure of fuzzy entropy was proposed by considering fuzzy membership through distance measure,and the obtained results contained more flexibility than the general fuzzy membership function.Furthermore,characteristic analyses for non convex function were also illustrated.Analyses on the mutual information were carried out through the proposed fuzzy entropy and similarity measure,which was also dual structure of fuzzy entropy.By the illustrative example,mutual information was discussed.展开更多
Based on the physical meaning of sensitivity,a new finite element(FE) model updating method was proposed. In this method,a three-dimensional FE model of the Nanjing Yangtze River Bridge(NYRB) with ANSYS program was es...Based on the physical meaning of sensitivity,a new finite element(FE) model updating method was proposed. In this method,a three-dimensional FE model of the Nanjing Yangtze River Bridge(NYRB) with ANSYS program was established and updated by modifying some design parameters. To further validate the updated FE model,the analytical stress-time histories responses of main members induced by a moving train were compared with the measured ones. The results show that the relative error of maximum stress is 2.49% and the minimum relative coefficient of analytical stress-time histories responses is 0.793. The updated model has a good agreement between the calculated data and the tested data,and provides a current baseline FE model for long-term health monitoring and condition assessment of the NYRB. At the same time,the model is validated by stress-time histories responses to be feasible and practical for railway steel bridge model updating.展开更多
In the present work, scandium elements with a series of contents(0.06 wt.%, 0.10 wt.%, 0.14 wt.%,0.17 wt.%, 0.20 wt.% and 0.25 wt.%) were added in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and the corresponding as-cas...In the present work, scandium elements with a series of contents(0.06 wt.%, 0.10 wt.%, 0.14 wt.%,0.17 wt.%, 0.20 wt.% and 0.25 wt.%) were added in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and the corresponding as-cast microstructure characteristics including grains and phases were thoroughly investigated. The results indicated that fine grain boundaries existed in these alloys and fine MgZn2phases discontinuously distributed on them. Besides,AlZnMgCu eutectic phases and Sc, Zr-containing phases with flocculent morphology were observed. As scandium contents vary from 0.06 wt.% to 0.17 wt.%, the average grain size continuously decreased and its equiaxial characteristics were strengthened. Meanwhile, the content of AlZnMgCu eutectic phase showed a decrease trend. When scandium contents were 0.20 wt.% and 0.25 wt.%, no further enhancement on grain refinement was observed, so as to the reduction of AlZnMgCu eutectic phase content. Besides, Sc, Zr-containing phases with blocky morphology were observed and the alloy with a scandium content of 0.25 wt.% possessed a larger amount of blocky Sc, Zr-containing phase than the alloy with a scandium content of 0.20 wt.%. Grain refinement and reduction of AlZnMgCu eutectic phase content associated with scandium addition were discussed.展开更多
Ultrafine tungsten carbide and fine cobalt as well as nano yttrium oxide powders were used as the raw materials. The effects of hot-press below the eutectic temperature and conventional liquid phase sintering on the s...Ultrafine tungsten carbide and fine cobalt as well as nano yttrium oxide powders were used as the raw materials. The effects of hot-press below the eutectic temperature and conventional liquid phase sintering on the structures and properties of WC-20Co-1Y2O3 cemented carbide were studied. It is shown that hot-pressed alloy has the character of isotropic properties and microstructure with homogeneous and ultrafine WC grains. However, the ultrafine and fully-densified structure is developed at the cost of the presence of large amount of cobalt-lake （unevenly distributed binder phase）, and thus lower strength. Yttrium oxide in the alloy cannot play the role of grain growth inhibitor fully when cemented carbide with high content of cobalt and ultrafine raw materials is sintered at high liquid phase sintering temperature. Peculiar platelet-enhanced bi-model structure is formed in WC-20Co-1Y2O3 cemented carbide by conventional liquid phase sintering, which points out that yttrium oxide in the alloy facilitates the formation of plate-like WC grain.展开更多
The constitutive model of rock can be built by mechanics elements because there are many kinds of damages in rock under varied loads.It is resumed that rock contains many microstructures and a structure of Bingham.The...The constitutive model of rock can be built by mechanics elements because there are many kinds of damages in rock under varied loads.It is resumed that rock contains many microstructures and a structure of Bingham.The microstructure consists of two embranchments that are the unit of a spring and a gliding slice in series and the unit of a spring and a cementation bar in series,the two units connect each other in parallel.These microstructures are arranged disorderly or in the order of a certain state.A certain distribution of microstructures represents one type of rock.Two kinds of rock's constitutive relationship were deduced by using the model.One is the model in which many parallel microstructures and a structure of Bingham connect in series.And it is used to homogeneous rock.The other is the model in which many microstructures and a structure of Bingham connect in series.And it is used to the rock with much crack or microcrack in a certain direction.The two kinds of constitutive relationship were verified by the studied cases.The constitutive model of rock built by using mechanics elements is verified to be reasonable.Moreover,different types of rocks may be described with mechanics elements with different distributions.展开更多
A new type of pit supporting structure, which was tested and verified using the sensor monitoring technology, was presented. The new supporting structure is assembled by prefabricated steel structural units. The adjac...A new type of pit supporting structure, which was tested and verified using the sensor monitoring technology, was presented. The new supporting structure is assembled by prefabricated steel structural units. The adjacent steel structural units are jointed with fasteners, and each steel structural unit has a certain radian and is welded by two steel tubes and one piece of steel disc. In order to test and verify the reliability of the new supporting structure, the field tests are designed. The main monitoring programs include the hoop stress of supporting structure, lateral earth pressure, and soil deformation. The monitoring data of the field tests show that the new supporting structure is convenient, reliable and safe.展开更多
The finite element model is established according to the experimental results,and then the experimental results are verified by simulation calculation.In terms of the combination of finite element analysis and experim...The finite element model is established according to the experimental results,and then the experimental results are verified by simulation calculation.In terms of the combination of finite element analysis and experiment,the effect of particle size of CuO and SnO_(2) on the stress,strain and microstructure of AgCuOSnO_(2) composite during hot extrusion was studied.The results illustrate that with the decrease of particle size,the dispersion of the second phase increases gradually,while the possibility of“tail shrinkage”of the billet decreases continuously;cubic CuO will evolve to fibrosis,and the degree of fibrosis will increase with the decrease of the particle size and ring clusters.Specifically,the degree of fibrosis at the middle end of the billet is higher than that at the front end,the degree of fibrosis at the front end is higher than that at the back end,and the degree of fibrosis on the surface is higher than that in the core;part of CuO fibers will bend,and the degree of buckling strength is positively correlated with the size of particles and their annular clusters.Additionally,there is fiber CuO in the front and back end of the billet that are inconsistent with the extrusion direction,and the degree of difference was negatively correlated with the particle size.展开更多
The finite element analysis （FEA） software Ansys was employed to study the stress state of the dies of both plane and non-plane parting face structures with uniform interference and the die of plane parting face str...The finite element analysis （FEA） software Ansys was employed to study the stress state of the dies of both plane and non-plane parting face structures with uniform interference and the die of plane parting face structure with non-uniform interference. Considering the symmetry of the die, a half gear tooth model of the two-ring assembled die with 2.5 GPa inner pressure was constructed. Four paths were defined to investigate the stress state at the bottom comer of the die where stress concentration was serious. FEA results show that the change of parting face from non-plane to plane can greatly reduce the stress at the teeth tips of the die so that the tip fracture is avoided. The interference structure of the die is the most important influencing factor for the stress concentration at the bottom comer. When non-uniform interference is adopted the first principal stress at the comer on the defined paths of the die is much lower than that with uniform interference. The bottom hole radius is another important influencing factor for the comer stress concentration. The first principal stress at the comer of the plane parting face die with non-uniform interference is reduced from 2.3 to 1.9 GPa when the hole radius increases from 12.5 to 16.0 mm. The optimization of the die structure increases the life of the die from 100 to 6 000 hits.展开更多
The conventional linear quadratic regulator(LQR) control algorithm is one of the most popular active control algorithms.One important issue for LQR control algorithm is the reduction of structure's degrees of free...The conventional linear quadratic regulator(LQR) control algorithm is one of the most popular active control algorithms.One important issue for LQR control algorithm is the reduction of structure's degrees of freedom(DOF). In this work, an LQR control algorithm with superelement model is intended to solve this issue leading to the fact that LQR control algorithm can be used in large finite element(FE) model for structure. In proposed model, the Craig-Bampton(C-B) method, which is one of the component mode syntheses(CMS), is used to establish superelement modeling to reduce structure's DOF and applied to LQR control algorithm to calculate Kalman gain matrix and obtain control forces. And then, the control forces are applied to original structure to simulate the responses of structure by vibration control. And some examples are given. The results show the computational efficiency of proposed model using synthesized models is higher than that of the classical method of LQR control when the DOF of structure is large. And the accuracy of proposed model is well. Meanwhile, the results show that the proposed control has more effects of vibration absorption on the ground structures than underground structures.展开更多
Based on the biological prototype characteristics of shark’s gill jet orifice,the flexible driving characteristics of ionic exchange polymer metal composites(IPMC)artificial muscle materials and the use of sleeve fle...Based on the biological prototype characteristics of shark’s gill jet orifice,the flexible driving characteristics of ionic exchange polymer metal composites(IPMC)artificial muscle materials and the use of sleeve flexible connector,the IPMC linear driving unit simulation model is built and the IPMC material-driving dynamic control structure of bionic gill unit is developed.Meanwhile,through the stress analysis of bionic gill plate and the motion simulation of bionic gill unit,it is verified that various dynamic control and active control of the jet orifice under the condition of different mainstream field velocities will be taken by using IPMC material-driving.Moreover,the large-deflection deformation of bionic gill plate under dynamic pressure and the comparative analysis with that of a rigid gill plate is studied,leading to the achievement of approximate revised modifier from real value to theoretical value of the displacement control of IPMC.展开更多
An element coupling model (ECM) method was proposed to simulate the global behavior and local damage of a structure.In order to reflect the local damage and improve the computational efficiency,three-dimensional (3D) ...An element coupling model (ECM) method was proposed to simulate the global behavior and local damage of a structure.In order to reflect the local damage and improve the computational efficiency,three-dimensional (3D) solid elements and one-dimensional (1D) beam element were coupled by the multi-point constraint equations.A reduced scale 1?8 model test was simulated by the ECM and a full three dimensional model (3DM) contrastively.The results show that the global behavior and local damages of ECM agree well with the test and 3DM.It is indicated that the proposed method can be used in the structural nonlinear analysis accurately and efficiently.展开更多
Due to outstanding ductility and high strength,the steel plate shear wall(SPSW)is recognized as a good lateral system for building structures; particularly as it interacts with earthquake resistant design.This study a...Due to outstanding ductility and high strength,the steel plate shear wall(SPSW)is recognized as a good lateral system for building structures; particularly as it interacts with earthquake resistant design.This study aims to reveal the dynamic and cyclic behavior of steel plated shear wall.Finite element method of analysis was implemented in order to simulate the behavior of such a wall structure.To determine the dynamic behavior of un-stiffened plate shear wall,two different analytical models were implemented.The post buckling strength of steel plate subjected to lateral loading was also employed.The story shear-drift diagrams of steel shear wall system were presented.The strength and ductility of the system obtained from the analysis were compared with those of steel shear wall tests reported before.The pertinent parameters of the steel shear wall system such as plate thickness,column and beam stiffness and the plate aspect ratio were recognized and their effects were recorded.The effect of stiffeners on the behavior of the SPSW was also investigated.展开更多
Alumina ceramics are widely used in many fields such as cutting tools,laser shock materials,roadbed board and refractory.Herein,Al_(2)O_(3)ceramics are prepared by a low-cost pressureless sintering technology,using th...Alumina ceramics are widely used in many fields such as cutting tools,laser shock materials,roadbed board and refractory.Herein,Al_(2)O_(3)ceramics are prepared by a low-cost pressureless sintering technology,using the binary sintering aids of MgO and SiO_(2).The effects of sintering temperature and the ratio of binary sintering aids on the mechanical properties and microstructure of Al_(2)O_(3)ceramics are investigated.A spinel second phase(MgAl_(2)O_(4))is found out by the analysis of the results of XRD and EDS when MgO and SiO_(2)are introduced in the samples.The optimum properties are found when MgO content is 20 wt.%based on the total sintering aids and the sintering temperature is 1550℃.The bending strength and the bulk density reach a maximum value of 314 MPa and 3.73 g/cm^(3),respectively.The addition of appropriate amount of SiO_(2)makes the formation of liquid phase sintering and the removal of large pores.Meanwhile,a small amount of magnesium oxide doping has an effect on the grain refinement from the microstructure of the sample.Therefore,it is believed that MgO and SiO_(2)are the ideal sintering aids for promoting the densification and property of alumina ceramics.展开更多
Effect of element cerium （Ce） on microstructure and mechanical properties of A1-Zn-Mg-Cu alloys has been investigated by transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, differential s...Effect of element cerium （Ce） on microstructure and mechanical properties of A1-Zn-Mg-Cu alloys has been investigated by transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, differential scanning calorimetry （DSC） and hardness test. The results show that addition of Ce can remarkably refine the as-cast grains and eutectic microstructure. A transformation from Mg（Zn,Cu,A1）2 phase to A12CuMg phase is observed during homogenization. Furthermore, the Ce addition introduces changes in the precipitation process and consequently in the age-hardening behavior of the alloy. Microstructural measurements reveal that the addition of Ce promotes the precipitation of η＇ phase, but it also partly retards the precipitation of GP zones. The density of precipitates decreases in a certain degree and rod-like η＇ precipitates increase when Ce content is from 0.2% to 0.4% （mass fraction）.展开更多
The structural system failure probability(SFP) is a valuable tool for evaluating the global safety level of concrete gravity dams.Traditional methods for estimating the failure probabilities are based on defined mathe...The structural system failure probability(SFP) is a valuable tool for evaluating the global safety level of concrete gravity dams.Traditional methods for estimating the failure probabilities are based on defined mathematical descriptions,namely,limit state functions of failure modes.Several problems are to be solved in the use of traditional methods for gravity dams.One is how to define the limit state function really reflecting the mechanical mechanism of the failure mode;another is how to understand the relationship among failure modes and enable the probability of the whole structure to be determined.Performing SFP analysis for a gravity dam system is a challenging task.This work proposes a novel nonlinear finite-element-based SFP analysis method for gravity dams.Firstly,reasonable nonlinear constitutive modes for dam concrete,concrete/rock interface and rock foundation are respectively introduced according to corresponding mechanical mechanisms.Meanwhile the response surface(RS) method is used to model limit state functions of main failure modes through the Monte Carlo(MC) simulation results of the dam-interface-foundation interaction finite element(FE) analysis.Secondly,a numerical SFP method is studied to compute the probabilities of several failure modes efficiently by simple matrix integration operations.Then,the nonlinear FE-based SFP analysis methodology for gravity dams considering correlated failure modes with the additional sensitivity analysis is proposed.Finally,a comprehensive computational platform for interfacing the proposed method with the open source FE code Code Aster is developed via a freely available MATLAB software tool(FERUM).This methodology is demonstrated by a case study of an existing gravity dam analysis,in which the dominant failure modes are identified,and the corresponding performance functions are established.Then,the dam failure probability of the structural system is obtained by the proposed method considering the correlation relationship of main failure modes on the basis of the mechanical mechanism analysis with the MC-FE simulations.展开更多
文摘Two new Mn(Ⅱ)coordination polymers,namely{[Mn_(2)(HL)(phen)_(3)(H_(2)O)_(2)]·7.5H_(2)O}_n(1)and[Mn_(4)(HL)_(2)(1,4-bib)_(3)(H_(2)O)_(2)]_n(2),were synthesized under hydrothermal conditions by using Mn(Ⅱ)ions and 6-(3',4'-dicarboxylphenoxy)-1,2,4-benzenetricarboxylic acid(H_(5)L)in the presence of N-auxiliary ligands 1,10-phenanthroline(phen)and1,4-bis(1H-imidazol-1-yl)benzene(1,4-bib).The structures of coordination polymers 1 and 2 were characterized by infrared spectroscopy,single-crystal X-ray diffraction,thermogravimetric analysis,and powder X-ray diffraction.Single-crystal X-ray diffraction reveals that 1 has a 1D chain structure based on binuclear Mn(Ⅱ)units,while 2 features a(3,8)-connected 3D network structure based on tetranuclear Mn(Ⅱ)units.Magnetic studies show that 1 and 2exhibit antiferromagnetic interactions between manganese ions.2 shows stronger antiferromagnetic interactions due to the shorter Mn…Mn distances within the tetranuclear manganese units.CCDC:2357601,1;2357602,2.
文摘Different solvothermal reactions of ZnC2O_(4)with oxalic acid(H_(2)ox)and 1,2,4-triazole(Htrz)successfully gave a new quaternary(NJTU-Bai83,NJTU-Bai=Nanjing Tech University Bai's group)and a new quinary(NJTU-Bai84)anionic metal-organic frameworks(MOFs),where NJTU-Bai83=(Me_(2)NH_(2))2[Zn_(3)(trz)_(2)(ox)_(3)]·2H_(2)O and NJTU-Bai84=(Me_(2)NH_(2))[Zn_(3)(trz)_(3)(ox)_(2)]·H_(2)O,respectively.With the[Zn_(2)(ox)4(trz)_(2)]secondary building unit(SBU)in NJTU-Bai83 replaced by the[Zn_(3)(ox)_(2)(trz)_(6)]and planar[Zn(ox)_(2)(trz)_(2)]ones in NJTU-Bai84,2D supramolecular building layers(SBLs)are changed from the A-layer and B-layer to another A-layer,while pillars are transformed from the tetrahedral[Zn(ox)_(2)(trz)_(2)]SBU to the irregular tetrahedral[Zn(ox)_(2)(trz)_(2)]and planar[Zn(ox)_(2)(trz)_(2)]SBUs.Thus,cdq-topological quaternary NJTU-Bai83 is tuned to(4,4,8)-c new topological quinary NJTU-Bai84.Two MOFs were well characterized by powder X-ray diffraction,thermogravimetric analysis,elemental analysis,etc.CCDC:2351819,NJTU-Bai83;2351820,NJTU-Bai84.
基金Project(2023JJ40759)supported by the Natural Science Foundation of Hunan Province,China。
文摘The irreversible phase transition and interface side reactions during the cycling process severely limit the large scale application of nickel-rich layered oxides Li[Ni_(x)Co_(y)Mn_(1−x−y)]O_(2)(NCM,x>0.8).Herein,we have designed LiNi_(0.8)Co_(0.1)Mn 0.1 O_(2)cathodes modified by Nb/Al co-doping and LiNbO_(3)/LiAlO_(2)composite coating.Detailed characterization reveals that Nb/Al co-doping can stabilize the crystal structure of the cathodes and expand the layer spacing of the layered lattice,thereby increasing the diffusion rate and reversibility of Li^(+).And the composite coatings can improve the electrochemical kinetic and inhibit the erosion of acidic substances by hindering direct contact between the cathodes and electrolyte.As a result,the Ni-rich cathodes with dual modification can still exhibit a higher capacity of 184.02 mA·h/g after 100 cycles with a capacity retention of up to 98.1%,and can still release a capacity of 161.6 mA·h/g at a high rate of 7 C,meanwhile,it shows excellent thermal stability compared to bare NCM.This work provides a new perspective for enhancing electrochemical properties of cathodes through integrated strategies.
基金Projects(51875581,51505502)supported by the National Natural Science Foundation of ChinaProjects(2017M620358,2018T110707)supported by China Postdoctoral Science FoundationProject(kq1905057)supported by the Training Program for Excellent Young Innovators of Changsha,China
文摘Seeking for innovative structures with higher mechanical performance is a continuous target in railway vehicle crashworthiness design.In the present study,three types of hexagonal reinforced honeycomb-like structures were developed and analyzed subjected to out-of-plane compression,namely triangular honeycomb(TH),double honeycomb(DH)and full inside honeycomb(FH).Theoretical formulas of average force and specific energy absorption(SEA)were constructed based on the energy minimization principle.To validate,corresponding numerical simulations were carried out by explicit finite element method.Good agreement has been observed between them.The results show that all these honeycomb-like structures maintain the same collapsed stages as conventional honeycomb;cell reinforcement can significantly promote the performance,both in the average force and SEA;full inside honeycomb performs better than the general,triangular and double schemes in average force;meanwhile,its SEA is close to that of double scheme;toroidal surface can dissipate higher plastic energy,so more toroidal surfaces should be considered in design of thin-walled structure.These achievements pave a way for designing high-performance cellular energy absorption devices.
基金Work supported by the Second Stage of Brain Korea 21 Projects Work(2010-0020163) supported by the Priority Research Centers Program through the National Research Foundation (NRF) funded by the Ministry of Education,Science and Technology of Korea
文摘Fuzzy entropy was designed for non convex fuzzy membership function using well known Hamming distance measure.The proposed fuzzy entropy had the same structure as that of convex fuzzy membership case.Design procedure of fuzzy entropy was proposed by considering fuzzy membership through distance measure,and the obtained results contained more flexibility than the general fuzzy membership function.Furthermore,characteristic analyses for non convex function were also illustrated.Analyses on the mutual information were carried out through the proposed fuzzy entropy and similarity measure,which was also dual structure of fuzzy entropy.By the illustrative example,mutual information was discussed.
基金Project(2001G025) supported by the Foundation of the Science and Technology Section of Ministry of Railway of ChinaProject(2006FJ4233) supported by Hunan Postdoctoral Scientific Program of ChinaProject(2006) supported by the Postdoctoral Foundation of Central South University,China
文摘Based on the physical meaning of sensitivity,a new finite element(FE) model updating method was proposed. In this method,a three-dimensional FE model of the Nanjing Yangtze River Bridge(NYRB) with ANSYS program was established and updated by modifying some design parameters. To further validate the updated FE model,the analytical stress-time histories responses of main members induced by a moving train were compared with the measured ones. The results show that the relative error of maximum stress is 2.49% and the minimum relative coefficient of analytical stress-time histories responses is 0.793. The updated model has a good agreement between the calculated data and the tested data,and provides a current baseline FE model for long-term health monitoring and condition assessment of the NYRB. At the same time,the model is validated by stress-time histories responses to be feasible and practical for railway steel bridge model updating.
基金Projects(2020YFB0311400ZL, 2020YFF0218202) supported by the National Key R&D Program of ChinaProject supported by Youth Fund Project of GRINM Group Co.,Ltd.,China。
文摘In the present work, scandium elements with a series of contents(0.06 wt.%, 0.10 wt.%, 0.14 wt.%,0.17 wt.%, 0.20 wt.% and 0.25 wt.%) were added in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and the corresponding as-cast microstructure characteristics including grains and phases were thoroughly investigated. The results indicated that fine grain boundaries existed in these alloys and fine MgZn2phases discontinuously distributed on them. Besides,AlZnMgCu eutectic phases and Sc, Zr-containing phases with flocculent morphology were observed. As scandium contents vary from 0.06 wt.% to 0.17 wt.%, the average grain size continuously decreased and its equiaxial characteristics were strengthened. Meanwhile, the content of AlZnMgCu eutectic phase showed a decrease trend. When scandium contents were 0.20 wt.% and 0.25 wt.%, no further enhancement on grain refinement was observed, so as to the reduction of AlZnMgCu eutectic phase content. Besides, Sc, Zr-containing phases with blocky morphology were observed and the alloy with a scandium content of 0.25 wt.% possessed a larger amount of blocky Sc, Zr-containing phase than the alloy with a scandium content of 0.20 wt.%. Grain refinement and reduction of AlZnMgCu eutectic phase content associated with scandium addition were discussed.
文摘Ultrafine tungsten carbide and fine cobalt as well as nano yttrium oxide powders were used as the raw materials. The effects of hot-press below the eutectic temperature and conventional liquid phase sintering on the structures and properties of WC-20Co-1Y2O3 cemented carbide were studied. It is shown that hot-pressed alloy has the character of isotropic properties and microstructure with homogeneous and ultrafine WC grains. However, the ultrafine and fully-densified structure is developed at the cost of the presence of large amount of cobalt-lake （unevenly distributed binder phase）, and thus lower strength. Yttrium oxide in the alloy cannot play the role of grain growth inhibitor fully when cemented carbide with high content of cobalt and ultrafine raw materials is sintered at high liquid phase sintering temperature. Peculiar platelet-enhanced bi-model structure is formed in WC-20Co-1Y2O3 cemented carbide by conventional liquid phase sintering, which points out that yttrium oxide in the alloy facilitates the formation of plate-like WC grain.
基金Projects(10472134,50490274) supported by the National Natural Science Foundation of China
文摘The constitutive model of rock can be built by mechanics elements because there are many kinds of damages in rock under varied loads.It is resumed that rock contains many microstructures and a structure of Bingham.The microstructure consists of two embranchments that are the unit of a spring and a gliding slice in series and the unit of a spring and a cementation bar in series,the two units connect each other in parallel.These microstructures are arranged disorderly or in the order of a certain state.A certain distribution of microstructures represents one type of rock.Two kinds of rock's constitutive relationship were deduced by using the model.One is the model in which many parallel microstructures and a structure of Bingham connect in series.And it is used to homogeneous rock.The other is the model in which many microstructures and a structure of Bingham connect in series.And it is used to the rock with much crack or microcrack in a certain direction.The two kinds of constitutive relationship were verified by the studied cases.The constitutive model of rock built by using mechanics elements is verified to be reasonable.Moreover,different types of rocks may be described with mechanics elements with different distributions.
基金Project(41202220) supported by the National Natural Science Foundation of ChinaProject(20120022120003) supported by the Research Fund for the Doctoral Program of Higher Education, China+1 种基金Project(2-9-2012-65) supported by the Fundamental Research Funds for the Central Universities, ChinaProject(2013006) supported by the Research Fund for Key Laboratory on Deep GeoDrilling Technology, Ministry of Land and Resources, China
文摘A new type of pit supporting structure, which was tested and verified using the sensor monitoring technology, was presented. The new supporting structure is assembled by prefabricated steel structural units. The adjacent steel structural units are jointed with fasteners, and each steel structural unit has a certain radian and is welded by two steel tubes and one piece of steel disc. In order to test and verify the reliability of the new supporting structure, the field tests are designed. The main monitoring programs include the hoop stress of supporting structure, lateral earth pressure, and soil deformation. The monitoring data of the field tests show that the new supporting structure is convenient, reliable and safe.
基金Project(2017FA027)supported by the Key Project of Science and Technology of Yunnan Province,China。
文摘The finite element model is established according to the experimental results,and then the experimental results are verified by simulation calculation.In terms of the combination of finite element analysis and experiment,the effect of particle size of CuO and SnO_(2) on the stress,strain and microstructure of AgCuOSnO_(2) composite during hot extrusion was studied.The results illustrate that with the decrease of particle size,the dispersion of the second phase increases gradually,while the possibility of“tail shrinkage”of the billet decreases continuously;cubic CuO will evolve to fibrosis,and the degree of fibrosis will increase with the decrease of the particle size and ring clusters.Specifically,the degree of fibrosis at the middle end of the billet is higher than that at the front end,the degree of fibrosis at the front end is higher than that at the back end,and the degree of fibrosis on the surface is higher than that in the core;part of CuO fibers will bend,and the degree of buckling strength is positively correlated with the size of particles and their annular clusters.Additionally,there is fiber CuO in the front and back end of the billet that are inconsistent with the extrusion direction,and the degree of difference was negatively correlated with the particle size.
基金Project(2006BAF04B06) supported by the National Key Technology R & D Program of ChinaProject(2005AA101B19) supported by the Key Technology R & D Program of Hubei Province, China
文摘The finite element analysis （FEA） software Ansys was employed to study the stress state of the dies of both plane and non-plane parting face structures with uniform interference and the die of plane parting face structure with non-uniform interference. Considering the symmetry of the die, a half gear tooth model of the two-ring assembled die with 2.5 GPa inner pressure was constructed. Four paths were defined to investigate the stress state at the bottom comer of the die where stress concentration was serious. FEA results show that the change of parting face from non-plane to plane can greatly reduce the stress at the teeth tips of the die so that the tip fracture is avoided. The interference structure of the die is the most important influencing factor for the stress concentration at the bottom comer. When non-uniform interference is adopted the first principal stress at the comer on the defined paths of the die is much lower than that with uniform interference. The bottom hole radius is another important influencing factor for the comer stress concentration. The first principal stress at the comer of the plane parting face die with non-uniform interference is reduced from 2.3 to 1.9 GPa when the hole radius increases from 12.5 to 16.0 mm. The optimization of the die structure increases the life of the die from 100 to 6 000 hits.
基金Project(LZ2015022)supported by Educational Commission of Liaoning Province of ChinaProjects(51138001,51178081)supported by the National Natural Science Foundation of China+1 种基金Project(2013CB035905)supported by the Basic Research Program of ChinaProjects(DUT15LK34,DUT14QY10)supported by Fundamental Research Funds for the Central Universities,China
文摘The conventional linear quadratic regulator(LQR) control algorithm is one of the most popular active control algorithms.One important issue for LQR control algorithm is the reduction of structure's degrees of freedom(DOF). In this work, an LQR control algorithm with superelement model is intended to solve this issue leading to the fact that LQR control algorithm can be used in large finite element(FE) model for structure. In proposed model, the Craig-Bampton(C-B) method, which is one of the component mode syntheses(CMS), is used to establish superelement modeling to reduce structure's DOF and applied to LQR control algorithm to calculate Kalman gain matrix and obtain control forces. And then, the control forces are applied to original structure to simulate the responses of structure by vibration control. And some examples are given. The results show the computational efficiency of proposed model using synthesized models is higher than that of the classical method of LQR control when the DOF of structure is large. And the accuracy of proposed model is well. Meanwhile, the results show that the proposed control has more effects of vibration absorption on the ground structures than underground structures.
基金Project(51275102)supported by the National Natural Science Foundation of ChinaProject(HEUCF140713)supported by the Fundamental Research Funds for the Central Universities,China
文摘Based on the biological prototype characteristics of shark’s gill jet orifice,the flexible driving characteristics of ionic exchange polymer metal composites(IPMC)artificial muscle materials and the use of sleeve flexible connector,the IPMC linear driving unit simulation model is built and the IPMC material-driving dynamic control structure of bionic gill unit is developed.Meanwhile,through the stress analysis of bionic gill plate and the motion simulation of bionic gill unit,it is verified that various dynamic control and active control of the jet orifice under the condition of different mainstream field velocities will be taken by using IPMC material-driving.Moreover,the large-deflection deformation of bionic gill plate under dynamic pressure and the comparative analysis with that of a rigid gill plate is studied,leading to the achievement of approximate revised modifier from real value to theoretical value of the displacement control of IPMC.
基金Project(2007CB714202) supported by the National Key Basic Research Program of ChinaProject(SLDRCE10-B-07) supported by theMinistry of Science and Technology of China
文摘An element coupling model (ECM) method was proposed to simulate the global behavior and local damage of a structure.In order to reflect the local damage and improve the computational efficiency,three-dimensional (3D) solid elements and one-dimensional (1D) beam element were coupled by the multi-point constraint equations.A reduced scale 1?8 model test was simulated by the ECM and a full three dimensional model (3DM) contrastively.The results show that the global behavior and local damages of ECM agree well with the test and 3DM.It is indicated that the proposed method can be used in the structural nonlinear analysis accurately and efficiently.
文摘Due to outstanding ductility and high strength,the steel plate shear wall(SPSW)is recognized as a good lateral system for building structures; particularly as it interacts with earthquake resistant design.This study aims to reveal the dynamic and cyclic behavior of steel plated shear wall.Finite element method of analysis was implemented in order to simulate the behavior of such a wall structure.To determine the dynamic behavior of un-stiffened plate shear wall,two different analytical models were implemented.The post buckling strength of steel plate subjected to lateral loading was also employed.The story shear-drift diagrams of steel shear wall system were presented.The strength and ductility of the system obtained from the analysis were compared with those of steel shear wall tests reported before.The pertinent parameters of the steel shear wall system such as plate thickness,column and beam stiffness and the plate aspect ratio were recognized and their effects were recorded.The effect of stiffeners on the behavior of the SPSW was also investigated.
基金Projects(11772207,U2130128)supported by the National Natural Science Foundation of ChinaProjects(E2019210042,E2017210065)supported by the Natural Science Foundation of Hebei Province,China+3 种基金Project(QN2019137)supported by the Natural Science Foundation of the Hebei Education Department,ChinaProject(A2019210204)supported by the Natural Science Foundation of Hebei Province for Distinguished Young Scholars,ChinaProject(216Z4302G)supported by Central Government Guiding Local Science and Technology Development,ChinaProject supported by Youth Top-notch Talents Supporting Plan of Hebei Province,China。
文摘Alumina ceramics are widely used in many fields such as cutting tools,laser shock materials,roadbed board and refractory.Herein,Al_(2)O_(3)ceramics are prepared by a low-cost pressureless sintering technology,using the binary sintering aids of MgO and SiO_(2).The effects of sintering temperature and the ratio of binary sintering aids on the mechanical properties and microstructure of Al_(2)O_(3)ceramics are investigated.A spinel second phase(MgAl_(2)O_(4))is found out by the analysis of the results of XRD and EDS when MgO and SiO_(2)are introduced in the samples.The optimum properties are found when MgO content is 20 wt.%based on the total sintering aids and the sintering temperature is 1550℃.The bending strength and the bulk density reach a maximum value of 314 MPa and 3.73 g/cm^(3),respectively.The addition of appropriate amount of SiO_(2)makes the formation of liquid phase sintering and the removal of large pores.Meanwhile,a small amount of magnesium oxide doping has an effect on the grain refinement from the microstructure of the sample.Therefore,it is believed that MgO and SiO_(2)are the ideal sintering aids for promoting the densification and property of alumina ceramics.
基金Project(2010CB731706) supported by the National Basic Research Program of China
文摘Effect of element cerium （Ce） on microstructure and mechanical properties of A1-Zn-Mg-Cu alloys has been investigated by transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, differential scanning calorimetry （DSC） and hardness test. The results show that addition of Ce can remarkably refine the as-cast grains and eutectic microstructure. A transformation from Mg（Zn,Cu,A1）2 phase to A12CuMg phase is observed during homogenization. Furthermore, the Ce addition introduces changes in the precipitation process and consequently in the age-hardening behavior of the alloy. Microstructural measurements reveal that the addition of Ce promotes the precipitation of η＇ phase, but it also partly retards the precipitation of GP zones. The density of precipitates decreases in a certain degree and rod-like η＇ precipitates increase when Ce content is from 0.2% to 0.4% （mass fraction）.
基金Projects(51409167,51139001,51179066)supported by the National Natural Science Foundation of ChinaProjects(201401022,201501036)supported by the Ministry of Water Resources Public Welfare Industry Research Special Fund,ChinaProjects(GG201532,GG201546)supported by the Scientific and Technological Research for Water Conservancy,Henan Province,China
文摘The structural system failure probability(SFP) is a valuable tool for evaluating the global safety level of concrete gravity dams.Traditional methods for estimating the failure probabilities are based on defined mathematical descriptions,namely,limit state functions of failure modes.Several problems are to be solved in the use of traditional methods for gravity dams.One is how to define the limit state function really reflecting the mechanical mechanism of the failure mode;another is how to understand the relationship among failure modes and enable the probability of the whole structure to be determined.Performing SFP analysis for a gravity dam system is a challenging task.This work proposes a novel nonlinear finite-element-based SFP analysis method for gravity dams.Firstly,reasonable nonlinear constitutive modes for dam concrete,concrete/rock interface and rock foundation are respectively introduced according to corresponding mechanical mechanisms.Meanwhile the response surface(RS) method is used to model limit state functions of main failure modes through the Monte Carlo(MC) simulation results of the dam-interface-foundation interaction finite element(FE) analysis.Secondly,a numerical SFP method is studied to compute the probabilities of several failure modes efficiently by simple matrix integration operations.Then,the nonlinear FE-based SFP analysis methodology for gravity dams considering correlated failure modes with the additional sensitivity analysis is proposed.Finally,a comprehensive computational platform for interfacing the proposed method with the open source FE code Code Aster is developed via a freely available MATLAB software tool(FERUM).This methodology is demonstrated by a case study of an existing gravity dam analysis,in which the dominant failure modes are identified,and the corresponding performance functions are established.Then,the dam failure probability of the structural system is obtained by the proposed method considering the correlation relationship of main failure modes on the basis of the mechanical mechanism analysis with the MC-FE simulations.
