Phosphine-sulfonate based palladium is one of the most extensively studied catalyst systems in olefin polymerization.This type of catalyst features six-membered chelate ring size,and can enable the copolymerizations o...Phosphine-sulfonate based palladium is one of the most extensively studied catalyst systems in olefin polymerization.This type of catalyst features six-membered chelate ring size,and can enable the copolymerizations of ethylene with a wide variety of polar monomers.In this contribution,we decide to investigate the influence of chelate ring size on the properties of phosphinesulfonate palladium catalysts.As such,a series of phosphine-sulfonate ligands and the corresponding seven-membered ring Pd(II)complexes[κ~2-(P,O)-2-(CH_2-PR_1R_2)-4-methylphenyl-sulfonato]Pd(Me)(DMSO)(Pd1,R_1=R_2=Cy,Pd2,R_1=R_2=o-Me O-C_6H_4;Pd3,R_1=Ph,R_2=2-[2,6-(Me O)_2C_6H_3]C_6H_4;DMSO=dimethyl sulfoxide)were designed,prepared and characterized.These palladium complexes are moderately active when they were applied in ethylene polymerization and copolymerizations with methyl acrylate and butyl vinyl ether.However,their properties are greatly reduced from those of the classic six-membered ring phosphine-sulfonate palladium complex Pd2′.The experimental results indicate that the bigger chelate ring size can increase the ligand flexibility and damage the catalytic properties for the phosphine-sulfonate type palladium catalysts.展开更多
The de novo design of new peptide assemblies that expands the repertoire of biomaterial nanostructures has been of a tremendous challenge.Hence,it is evident that a successful research achievement in this area would i...The de novo design of new peptide assemblies that expands the repertoire of biomaterial nanostructures has been of a tremendous challenge.Hence,it is evident that a successful research achievement in this area would increase the understanding of molecular interactions in supramolecules and create novel scaffolds exploitable in biotechnology and synthetic biology.The manipulation of cyclic peptide self-assembly is particularly intriguing for this purpose.Herein,we report that a novel type of cyclic peptides,referred to as chiral tether constrained cyclic peptides(CCP),shows promising self-assembly properties.CCPs are the first example of a controllable assembly of all-L-α-cyclic peptides with different ring sizes.A noteworthy feature of the CCP system is good tolerance of different secondary structures,ring size,and peptide sequence.Based on this system,a variety of nanostructures could be constructed,which display different physical properties,rendering it an excellent platform for molecular interaction studies.Further,demonstrate potential applications of these peptide assemblies in bioimaging and energy storage.展开更多
During cold ring rolling process, changing the sizes of forming rolls including driver roll and idle roll will lead to a change of amount of feed Ah and contact areas between ring blank and forming rolls, thus a chang...During cold ring rolling process, changing the sizes of forming rolls including driver roll and idle roll will lead to a change of amount of feed Ah and contact areas between ring blank and forming rolls, thus a change of the shape and dimension of deformation zone located in the gap of forming rolls is found. It has a significant effect on metal flow and the forming quality of deformed ring. So the size effect of forming rolls on cold ring rolling was investigated by three-dimensional dynamic explicit FEM under ABAQUS environment. The obtained results thoroughly reveal the influence laws of the sizes of forming rolls on the average spread, fishtail coefficient, degree of inhomogeneous deformation and force and power parameters etc not only provide an important basis for design of the forming rolls and optimization of cold ring rolling process, but also reveal the plastic deformation mechanism of cold ring rolling.展开更多
The cast preformed forming process(CPFP) is increasingly considered and applied in the metal forming industries due to its short process, low cost, and environmental friendliness, especially in the aerospace field. Ho...The cast preformed forming process(CPFP) is increasingly considered and applied in the metal forming industries due to its short process, low cost, and environmental friendliness, especially in the aerospace field. However, how to establish a unified model of a non-uniform as-cast billet depicting the flow stress and microstructure evolution behaviors during hot working is the key to microstructure prediction and parameter optimization of the CPFP. In this work, hot compression tests are performed using a non-uniform as-cast 42 CrMo billet at 1123–1423 K and 0.01–1sà1. The effect laws of the non-uniform state of the as-cast billet with different initial grain sizes on the flow stress and microstructure are revealed deeply. Based on experimental results, a unified model of flow stress and grain size evolutions is developed by the internal variable modeling method. Verified results show that the model can well describe the responses of the flow stress and microstructure to deformation conditions and initial grain sizes. To further evaluate its reliability, the unified model is applied to FE simulation of the cast preformed ring rolling process.The predictions of the rolling force and grain size indicate that it could well describe the flow stress and microstructure evolutions during the process.展开更多
Study on the grain size distribution characteristics and the frictional strength behavior of the slide deposits are helpful to disclose the landslide runout process and understand the mechanism of a long runout landsl...Study on the grain size distribution characteristics and the frictional strength behavior of the slide deposits are helpful to disclose the landslide runout process and understand the mechanism of a long runout landslide. We performed grain size distribution analysis on samples collected from Chenjiaba landslide induced by Wenchuan earthquake. The grain size distribution of samples from the landslide sections quantitatively depicts a gradual coarsening upward grading from shear zone to the top section. Then a multistage-multiphase ring shearing approach was used to determine a comparative shear strength behavior of samples from each landslide section. In this method, a sample was sheared continuously for large displacement and fast rate on different normal stress conditions. The multiphase shear mode with a maximum of 105 mm/min rate has allowed observing the qualitative change and patterns of the frictional resistance behaviors of soils under different normal stresses. The results of coefficient of friction values under multiphase shear mode have shown substantial post peak shear weakening behaviors after large shear displacement that can be narrated with long runout processes. The shear strength test results indicate that the shear zone samples have developed higher friction angle values compared to overlying section samples, on the last phase of shear process, which may be very important to understand the braking mechanism of a long runout landslide.展开更多
动力集中动车组司机室侧墙的加强肋结构具有提高强度和减缓振动的优点,对确保司机室人员的安全起重要作用。在确保结构安全的基础上,根据合理的传力路径进行结构加固,可以实现司机室侧墙加强肋及相关结构的轻量化,对动力集中动车组司机...动力集中动车组司机室侧墙的加强肋结构具有提高强度和减缓振动的优点,对确保司机室人员的安全起重要作用。在确保结构安全的基础上,根据合理的传力路径进行结构加固,可以实现司机室侧墙加强肋及相关结构的轻量化,对动力集中动车组司机室的设计有重要意义。文中采用拓扑优化方法对某型动力集中动车组车体司机室侧墙结构进行拓扑优化设计,寻求加强肋结构和与其连接的柱体结构的最优布局,以此为基础,重构侧墙加强肋及司机室结构,并对重构的加强肋结构、柱体结构和司机室圈梁结构进行尺寸优化。计算结果表明:在满足BS EN 12663-1:2010静强度条件和TB/T 3548—2019标准下,经过优化设计,司机室圈梁结构、加强肋结构及与加强肋连接柱体结构的总质量相对于初始设计减小32%,轻量化效果显著。针对优化后的车体司机室结构进行有限元强度计算和疲劳校核,满足静强度和疲劳强度要求。展开更多
基金supported by the National Natural Science Foundation of China (21690071, 51522306)
文摘Phosphine-sulfonate based palladium is one of the most extensively studied catalyst systems in olefin polymerization.This type of catalyst features six-membered chelate ring size,and can enable the copolymerizations of ethylene with a wide variety of polar monomers.In this contribution,we decide to investigate the influence of chelate ring size on the properties of phosphinesulfonate palladium catalysts.As such,a series of phosphine-sulfonate ligands and the corresponding seven-membered ring Pd(II)complexes[κ~2-(P,O)-2-(CH_2-PR_1R_2)-4-methylphenyl-sulfonato]Pd(Me)(DMSO)(Pd1,R_1=R_2=Cy,Pd2,R_1=R_2=o-Me O-C_6H_4;Pd3,R_1=Ph,R_2=2-[2,6-(Me O)_2C_6H_3]C_6H_4;DMSO=dimethyl sulfoxide)were designed,prepared and characterized.These palladium complexes are moderately active when they were applied in ethylene polymerization and copolymerizations with methyl acrylate and butyl vinyl ether.However,their properties are greatly reduced from those of the classic six-membered ring phosphine-sulfonate palladium complex Pd2′.The experimental results indicate that the bigger chelate ring size can increase the ligand flexibility and damage the catalytic properties for the phosphine-sulfonate type palladium catalysts.
基金We acknowledge financial support from the Natural Science Foundation of China(grant nos.21778009,21801019,21977010,81701818,and 51803006)the Shenzhen Science and Technology Innovation Committee(nos.JCYJ20170817172023838 and JCYJ20180507181527112).
文摘The de novo design of new peptide assemblies that expands the repertoire of biomaterial nanostructures has been of a tremendous challenge.Hence,it is evident that a successful research achievement in this area would increase the understanding of molecular interactions in supramolecules and create novel scaffolds exploitable in biotechnology and synthetic biology.The manipulation of cyclic peptide self-assembly is particularly intriguing for this purpose.Herein,we report that a novel type of cyclic peptides,referred to as chiral tether constrained cyclic peptides(CCP),shows promising self-assembly properties.CCPs are the first example of a controllable assembly of all-L-α-cyclic peptides with different ring sizes.A noteworthy feature of the CCP system is good tolerance of different secondary structures,ring size,and peptide sequence.Based on this system,a variety of nanostructures could be constructed,which display different physical properties,rendering it an excellent platform for molecular interaction studies.Further,demonstrate potential applications of these peptide assemblies in bioimaging and energy storage.
基金Prqject(50335060) supported by the National Natural Science Foundation for Key Program of China Project (50225518) supported by the National Science Found of China for Distinguished Young Scholars
文摘During cold ring rolling process, changing the sizes of forming rolls including driver roll and idle roll will lead to a change of amount of feed Ah and contact areas between ring blank and forming rolls, thus a change of the shape and dimension of deformation zone located in the gap of forming rolls is found. It has a significant effect on metal flow and the forming quality of deformed ring. So the size effect of forming rolls on cold ring rolling was investigated by three-dimensional dynamic explicit FEM under ABAQUS environment. The obtained results thoroughly reveal the influence laws of the sizes of forming rolls on the average spread, fishtail coefficient, degree of inhomogeneous deformation and force and power parameters etc not only provide an important basis for design of the forming rolls and optimization of cold ring rolling process, but also reveal the plastic deformation mechanism of cold ring rolling.
基金supported by the National Natural Science Foundation of China (No’s. 51575448 and 51135007)
文摘The cast preformed forming process(CPFP) is increasingly considered and applied in the metal forming industries due to its short process, low cost, and environmental friendliness, especially in the aerospace field. However, how to establish a unified model of a non-uniform as-cast billet depicting the flow stress and microstructure evolution behaviors during hot working is the key to microstructure prediction and parameter optimization of the CPFP. In this work, hot compression tests are performed using a non-uniform as-cast 42 CrMo billet at 1123–1423 K and 0.01–1sà1. The effect laws of the non-uniform state of the as-cast billet with different initial grain sizes on the flow stress and microstructure are revealed deeply. Based on experimental results, a unified model of flow stress and grain size evolutions is developed by the internal variable modeling method. Verified results show that the model can well describe the responses of the flow stress and microstructure to deformation conditions and initial grain sizes. To further evaluate its reliability, the unified model is applied to FE simulation of the cast preformed ring rolling process.The predictions of the rolling force and grain size indicate that it could well describe the flow stress and microstructure evolutions during the process.
基金supported by funds from the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No.XDA23090402the National Science Foundation of China under the Grants Nos. 41672307, 41790442 and 41702345CAS-TWAS presidential fellowship program for funding his Doctoral study (Ph.D)
文摘Study on the grain size distribution characteristics and the frictional strength behavior of the slide deposits are helpful to disclose the landslide runout process and understand the mechanism of a long runout landslide. We performed grain size distribution analysis on samples collected from Chenjiaba landslide induced by Wenchuan earthquake. The grain size distribution of samples from the landslide sections quantitatively depicts a gradual coarsening upward grading from shear zone to the top section. Then a multistage-multiphase ring shearing approach was used to determine a comparative shear strength behavior of samples from each landslide section. In this method, a sample was sheared continuously for large displacement and fast rate on different normal stress conditions. The multiphase shear mode with a maximum of 105 mm/min rate has allowed observing the qualitative change and patterns of the frictional resistance behaviors of soils under different normal stresses. The results of coefficient of friction values under multiphase shear mode have shown substantial post peak shear weakening behaviors after large shear displacement that can be narrated with long runout processes. The shear strength test results indicate that the shear zone samples have developed higher friction angle values compared to overlying section samples, on the last phase of shear process, which may be very important to understand the braking mechanism of a long runout landslide.
文摘动力集中动车组司机室侧墙的加强肋结构具有提高强度和减缓振动的优点,对确保司机室人员的安全起重要作用。在确保结构安全的基础上,根据合理的传力路径进行结构加固,可以实现司机室侧墙加强肋及相关结构的轻量化,对动力集中动车组司机室的设计有重要意义。文中采用拓扑优化方法对某型动力集中动车组车体司机室侧墙结构进行拓扑优化设计,寻求加强肋结构和与其连接的柱体结构的最优布局,以此为基础,重构侧墙加强肋及司机室结构,并对重构的加强肋结构、柱体结构和司机室圈梁结构进行尺寸优化。计算结果表明:在满足BS EN 12663-1:2010静强度条件和TB/T 3548—2019标准下,经过优化设计,司机室圈梁结构、加强肋结构及与加强肋连接柱体结构的总质量相对于初始设计减小32%,轻量化效果显著。针对优化后的车体司机室结构进行有限元强度计算和疲劳校核,满足静强度和疲劳强度要求。
