The impedance matching of absorbers is a vital factor affecting their microwave absorption(MA)properties.In this work,we controllably synthesized Material of Institute Lavoisier 88C(MIL-88C)with varying aspect ratios(...The impedance matching of absorbers is a vital factor affecting their microwave absorption(MA)properties.In this work,we controllably synthesized Material of Institute Lavoisier 88C(MIL-88C)with varying aspect ratios(AR)as a precursor by regulating oil bath conditions,followed by one-step thermal decomposition to obtain carbon-coated iron-based composites.Modifying the precursor MIL-88C(Fe)preparation conditions,such as the molar ratio between metal ions and organic ligands(M/O),oil bath temperature,and oil bath time,influenced the phases,graphitization degree,and AR of the derivatives,enabling low filler loading,achieving well-matched impedance,and ensuring outstanding MA properties.The MOF-derivatives 2(MD_(2))/polyvinylidene Difluoride(PVDF),MD_(3)/PVDF,and MD4/PVDF absorbers all exhibited excellent MA properties with optimal filler loadings below 20 wt%and as low as 5 wt%.The MD_(2)/PVDF(5 wt%)achieved a maximum effective absorption bandwidth(EAB)of 5.52 GHz(1.90 mm).The MD_(3)/PVDF(10 wt%)possessed a minimum reflection loss(RL_(min))value of−67.4 at 12.56 GHz(2.13 mm).A symmetric gradient honeycomb structure(SGHS)was constructed utilizing the high-frequency structure simulator(HFSS)to further extend the EAB,achieving an EAB of 14.6 GHz and a RL_(min) of−59.0 dB.This research offers a viable inspiration to creating structures or materials with high-efficiency MA properties.展开更多
Studies showed that complexation of polyphenols with milk allergens reduced their immunogenic potential.However,the relationship between structures of polyphenols and their hypoallergenic effects on milk allergens in ...Studies showed that complexation of polyphenols with milk allergens reduced their immunogenic potential.However,the relationship between structures of polyphenols and their hypoallergenic effects on milk allergens in association with physiological and conformational changes of the complexes remain unclear.In this study,polyphenols from eight botanical sources were extracted to prepare non-covalent complexes withβ-lactoglobulin(β-LG),a major allergen in milk.The dominant phenolic compounds bound toβ-LG with a diminished allergenicity were identified to investigate their respective role on the structural and allergenic properties ofβ-LG.Extracts from Vaccinium fruits and black soybeans were found to have great inhibitory effects on the IgE-and IgG-binding abilities ofβ-LG.Among the fourteen structure-related phenolic compounds,flavonoids and tannins with larger MWs and multi-hydroxyl substituents,notably rutin,EGCG,and ellagitannins were more potent to elicit changes on the conformational structures ofβ-LG to decrease the allergenicity of complexedβ-LG.Correlation analysis further demonstrated that a destabilized secondary structure and protein depolymerization caused by polyphenol-binding were closely related to the allergenicity property of formed complexes.This study provides insights into the understanding of structure-allergenicity relationship ofβ-LG-polyphenol interactions and would benefit the development of polyphenol-fortified matrices with hypoallergenic potential.展开更多
The trace identity is extended to the quadratic-form identity. The Hamiltonian structures of the multi-component Guo hierarchy, integrable coupling of Guo hierarchy and （2＋l）-dimensional Guo hierarchy are obtained ...The trace identity is extended to the quadratic-form identity. The Hamiltonian structures of the multi-component Guo hierarchy, integrable coupling of Guo hierarchy and （2＋l）-dimensional Guo hierarchy are obtained by the quadraticform identity. The method can be used to produce the Hamiltonian structures of the other integrable couplings or multi-component hierarchies.展开更多
We study structural,mechanical,and electronic properties of C_（20）,Si_（20） and their alloys（C_（16）Si_4,C_（12）Si_8,C_8Si_（12）,and C_4Si_（16）） in C2/m structure by using density functional theory（DFT） ba...We study structural,mechanical,and electronic properties of C_（20）,Si_（20） and their alloys（C_（16）Si_4,C_（12）Si_8,C_8Si_（12）,and C_4Si_（16）） in C2/m structure by using density functional theory（DFT） based on first-principles calculations.The obtained elastic constants and the phonon spectra reveal mechanical and dynamic stability.The calculated formation enthalpy shows that the C-Si alloys might exist at a specified high temperature scale.The ratio of BIG and Poisson＇s ratio indicate that these C-Si alloys in C2/m-20 structure are all brittle.The elastic anisotropic properties derived by bulk modulus and shear modulus show slight anisotropy.In addition,the band structures and density of states are also depicted,which reveal that C_（20）,C_（16）Si_4,and Si_（20） are indirect band gap semiconductors,while C_8Si_（12） and C_4Si_（16） are semi-metallic alloys.Notably,a direct band gap semiconductor（C_（12）Si_8） is obtained by doping two indirect band gap semiconductors（C_（20） and Si_（20））.展开更多
The structure of any a.s. self-similar set K(w) generated by a class of random elements {gn,wσ} taking values in the space of contractive operators is given and the approximation of K(w) by the fixed points {Pn,wσ} ...The structure of any a.s. self-similar set K(w) generated by a class of random elements {gn,wσ} taking values in the space of contractive operators is given and the approximation of K(w) by the fixed points {Pn,wσ} of {gn,ow} is obtained. It is useful to generate the fractal in computer.展开更多
Designing low-cost,easy-fabricated,highly stable and active electrocatalysts for oxygen evolution reaction(OER) is crucial for electrochemical(EC) and solar-driven photoelectrochemical(PEC) water splitting.By using a ...Designing low-cost,easy-fabricated,highly stable and active electrocatalysts for oxygen evolution reaction(OER) is crucial for electrochemical(EC) and solar-driven photoelectrochemical(PEC) water splitting.By using a facile heating-electrodeposition method,here we fabricated a porous but crystalline Fe-doped Ni3 S2.A thin porous surface NiFe hydroxide layer(~10 nm) is then formed through OER-running.By virtue of the core Fe-doped Ni3 S2 with good conductivity and the shell NiFe hydroxide surface with good electrocatalytic activity,the core-shell nanostructure on Ni foam exhibits excellent OER activity in 1 M NaOH,needing only 195 and 230 mV to deliver 10 and 100 mA/cm^(2),respectively,much more superior to those of 216 and 259 mV for the sample deposited under normal temperature.The enhanced photo-response of the sulfide@hydroxide core-shell structure was also demonstrated,due to the efficient transfer of photo-generated carriers on the core/shell interface.More interestingly,it shows a good compatibility with Si based photoanode,which exhibits an excellent PEC performance with an onset potential of 0.86 V vs.reversible hydrogen electrode,an applied bias photon-to-current efficiency of 5.5% and a durability for over 120 h under AM 1.5 G 1 sun illumination,outperforming the state-of-the-art Si based photoanodes.展开更多
Understanding the interaction between canopy structure and the parameters of interception loss is essential in predicting the variations in partitioning rainfall and water resources as affected by changes in canopy st...Understanding the interaction between canopy structure and the parameters of interception loss is essential in predicting the variations in partitioning rainfall and water resources as affected by changes in canopy structure and in implementing water-based management in semiarid forest plantations.In this study,seasonal variations in rainfall interception loss and canopy storage capacity as driven by canopy structure were predicted and the linkages were tested using seasonal filed measurements.The study was conducted in nine 50 m×50 m Robinia pseudoacacia plots in the semiarid region of China’s Loess Plateau.Gross rain-fall,throughfall and stemflow were measured in seasons with and without leaves in 2015 and 2016.Results show that measured average interception loss for the nine plots were 17.9% and 9.4% of gross rainfall during periods with leaves (the growing season) and without leaves, respectively. Average canopy storage capacity estimated using an indirect method was 1.3 mm in the growing season and 0.2 mm in the leafless season. Correlations of relative interception loss and canopy storage capacity to canopy variables were highest for leaf/wood area index (LAI/WAI) and canopy cover, fol-lowed by bark area, basal area, tree height and stand density. Combined canopy cover, leaf/wood area index and bark area multiple regression models of interception loss and canopy storage capacity were established for the growing season and in the leafless season in 2015. It explained 97% and 96% of the variations in relative interception loss during seasons with and without leaves, respectively. It also explained 98% and 99% of the variations in canopy storage capacity during seasons with and without leaves, respectively. The empiri-cal regression models were validated using field data col-lected in 2016. The models satisfactorily predicted relative interception loss and canopy storage capacity during seasons with and without leaves. This study provides greater under-standing about the effects of changes in tree canopy structure (e.g., dieback or mortality) on hydrological processes.展开更多
A theoretical study of resonant tunneling is carried out for an inverse parabolic double-barrier structure subjected to an external electric field. Tunneling transmission coefficient and density of states are analyzed...A theoretical study of resonant tunneling is carried out for an inverse parabolic double-barrier structure subjected to an external electric field. Tunneling transmission coefficient and density of states are analyzed by using the non-equilibrium Green＇s function approach based on the finite difference method. It is found that the resonant peak of the transmission coefficient, being unity for a symmetrical case, reduces under the applied electric field and depends strongly on the variation of the structure parameters.展开更多
An Mg-Zn-Mn-Ca alloy with high Zn content was fabricated by vacuum melting. The as-cast microstructure was investigated using XRD, SEM and EDS. It was shown that the alloy was composed of α-Mg, strip-like Ca2Mg6Zn3 a...An Mg-Zn-Mn-Ca alloy with high Zn content was fabricated by vacuum melting. The as-cast microstructure was investigated using XRD, SEM and EDS. It was shown that the alloy was composed of α-Mg, strip-like Ca2Mg6Zn3 and a few Mn- containing phases. Most of the Ca2Mg6Zn3 phase was distributed at grain boundaries while Mn-containing particles were deposited within grains. The as-cast samples were immersed in a Hank＇s balanced salt solution （HBSS） up to 24 h. The corroded surface morphology and cross-section microstructure were analyzed after different time of immersion so as to understand the corrosion behavior of the alloy. During immersion in the HBSS, the alloy corroded homogeneously at the very beginning and then localized corrosion occurred. The secondary phases protruded on the surface due to the dissolution of α-Mg, suggesting micro- galvanic corrosion occurred with secondary phases acting as the cathode and ct-Mg as the anode. Micro-cracks were formed at the interfaces between Ca2Mg6Zn3 and α-Mg, indicating an undermining tendency of the secondary phases.展开更多
Micro-nano structured Li Fe（1-x）MnxPO4/C（0≤x≤0.05）cathodes were prepared by spray drying,followed by calcination at 700°C.The spherical Li Fe（1-x）MnxPO4/C（0≤x≤0.05）particles with the size of 0.5 to5.0...Micro-nano structured Li Fe（1-x）MnxPO4/C（0≤x≤0.05）cathodes were prepared by spray drying,followed by calcination at 700°C.The spherical Li Fe（1-x）MnxPO4/C（0≤x≤0.05）particles with the size of 0.5 to5.0μm are composed of lots of nanoparticles of 20 to 30 nm,and have the well-developed interconnected pore structure.In contrast,when Mn doping content is 3 mol%（x=0.03）,the Li Fe（0.97）Mn（0.03）PO4/C demonstrates maximum specific surface area of 31.30 m^2/g,more uniform pore size and relatively better electrochemical performance.The initial discharge capacities are 161.59,157.04 and 153.13 m Ah/g at a discharge rate of 0.2,0.5 and 1 C,respectively.Meanwhile,the discharge capacity retentions are～100%after 120 cycles.The improved electrochemical performance should be attributed to higher specific surface,smaller polarization voltage,and a high Li~＋diffusion rate due to the micro-nano porous structure and lattice expansion produced by Mn doping.展开更多
Based on the multiplicity results of Benci and Fortunato [4], we consider some elliptic systems with strongly indefinite quadratic part, and establish the existence of infinitely many nontrivial solutions in a suitabl...Based on the multiplicity results of Benci and Fortunato [4], we consider some elliptic systems with strongly indefinite quadratic part, and establish the existence of infinitely many nontrivial solutions in a suitable family of products of fractional Sobolev spaces.展开更多
This paper calculated load-carrying of isogrid and orthogrid of carbon-epoxy composite trellis wound structure(C/E CTWS) using non-linear finite element method.Based on the analysis,test cases were designed and tests ...This paper calculated load-carrying of isogrid and orthogrid of carbon-epoxy composite trellis wound structure(C/E CTWS) using non-linear finite element method.Based on the analysis,test cases were designed and tests of axial compression were carried.Analysis result and test result fit well.In order to be used in the project,this kind of structure cut-out repairing was calculated.The method presented in this paper has been proved and can be used to solve complicated engineering problems.According to calculations and experimental results combined with application,a principle of choosing wound structure is obtained and principle could be applied to engineering.展开更多
In the teaching of translation and grammar,it is essential that the English sentence structure is analyzed and transformation of sentence structures both in English and Chinese in class and after class. However,many k...In the teaching of translation and grammar,it is essential that the English sentence structure is analyzed and transformation of sentence structures both in English and Chinese in class and after class. However,many kinds of English sentences structures prevent the students who study English from getting the basic idea and concept of a sentence in translation or grammatical analysis. In this paper,the author submitted the basic mould of simplification of English sentence structure,and the students can learn and master the translating technique through the simplified English sentence structure. Thus it helps to improve students' competence of translation.展开更多
In this paper, the equilibrium geometry, harmonic frequency and dissociation energy of S2^- and S3^- have been calculated at QCISD/6-311＋＋G（3d2f） and B3P86/6-311＋＋G（3d2f） level. The S2^- ground state is of 2II...In this paper, the equilibrium geometry, harmonic frequency and dissociation energy of S2^- and S3^- have been calculated at QCISD/6-311＋＋G（3d2f） and B3P86/6-311＋＋G（3d2f） level. The S2^- ground state is of 2IIg, the S3^- ground state is of 2B1 and S3^- has a bent （C2v） structure with an angle of 115.65° The results are in good agreement with these reported in other literature. For S3^- ion, the vibration frequencies and the force constants have also been calculated. Base on the general principles of microscopic reversibility, the dissociation limits has been deduced. The Murrell-Sorbie potential energy function for S2^- has been derived according to the ab initio data through the least- squares fitting. The force constants and spectroscopic data for S2^- have been calculated, then compared with other theoretical data. The analytical potential energy function of S3^- have been obtained based on the many-body expansion theory. The structure and energy can correctly reappear on the potential surface.展开更多
Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the ac...Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the active site hosts, its hostility to electron/mass transfer could lead to the incomplete fulfillment of the catalytic activity. Besides, the formation of inactive metallic Fe particles during the conventional catalyst synthesis could also decrease the active site density and complicate the identification of real active site. Herein, we developed a facial hydrogen etching methodology to yield single site Fe-N-C catalysts featured with micro/mesoporous hierarchical structure. The hydrogen concentration in pyrolysis process was designated to effectively regulate the pore structure and active site density of the resulted catalysts.The optimized sample achieves excellent ORR catalytic performance with an ultralow H2O2 yield(1%)and superb stability over 10,000 cycles. Our finding provides new thoughts for the rational design of hierarchically porous carbon-based materials and highly promising non-precious metal ORR catalysts.展开更多
Intelligent structures like zero Poisson’s ratio(ZPR)cellular structures have been widely applied to the engineering fields such as morphing wings in recent decades,owing to their outstanding characteristics includin...Intelligent structures like zero Poisson’s ratio(ZPR)cellular structures have been widely applied to the engineering fields such as morphing wings in recent decades,owing to their outstanding characteristics including light weight and low effective modulus. In-plane and out-of-plane mechanical properties of ZPR cellular structures are investigated in this paper. A theoretical method for calculating in-plane tensile modulus,in-plane shear modulus and out-of-plane bending modulus of ZPR cellular structures is proposed,and the impacts of the unit cell geometrical configurations on in-plane tensile modulus,in-plane shear modulus and out-of-plane bending modulus are studied systematically based on finite element(FE)simulation. Experimental tests validate the feasibility and effectiveness of the theoretical and FE analysis. And the results show that the in-plane and out-of-plane mechanical properties of ZPR cellular structures can be manipulated by designing cell geometrical parameters.展开更多
基金financially supported by the National Natural Science Foundation of China(51972049,52073010,and 52373259)the Projects of the Science and Technology Department of Jilin Province(20230201132GX)the Projects of the Education Department of Jilin Province(JJKH20220123KJ)。
文摘The impedance matching of absorbers is a vital factor affecting their microwave absorption(MA)properties.In this work,we controllably synthesized Material of Institute Lavoisier 88C(MIL-88C)with varying aspect ratios(AR)as a precursor by regulating oil bath conditions,followed by one-step thermal decomposition to obtain carbon-coated iron-based composites.Modifying the precursor MIL-88C(Fe)preparation conditions,such as the molar ratio between metal ions and organic ligands(M/O),oil bath temperature,and oil bath time,influenced the phases,graphitization degree,and AR of the derivatives,enabling low filler loading,achieving well-matched impedance,and ensuring outstanding MA properties.The MOF-derivatives 2(MD_(2))/polyvinylidene Difluoride(PVDF),MD_(3)/PVDF,and MD4/PVDF absorbers all exhibited excellent MA properties with optimal filler loadings below 20 wt%and as low as 5 wt%.The MD_(2)/PVDF(5 wt%)achieved a maximum effective absorption bandwidth(EAB)of 5.52 GHz(1.90 mm).The MD_(3)/PVDF(10 wt%)possessed a minimum reflection loss(RL_(min))value of−67.4 at 12.56 GHz(2.13 mm).A symmetric gradient honeycomb structure(SGHS)was constructed utilizing the high-frequency structure simulator(HFSS)to further extend the EAB,achieving an EAB of 14.6 GHz and a RL_(min) of−59.0 dB.This research offers a viable inspiration to creating structures or materials with high-efficiency MA properties.
基金supported by the Zhejiang Provincial Natural Science Foundation of China(LGN22C200027 and LZ23C200001).
文摘Studies showed that complexation of polyphenols with milk allergens reduced their immunogenic potential.However,the relationship between structures of polyphenols and their hypoallergenic effects on milk allergens in association with physiological and conformational changes of the complexes remain unclear.In this study,polyphenols from eight botanical sources were extracted to prepare non-covalent complexes withβ-lactoglobulin(β-LG),a major allergen in milk.The dominant phenolic compounds bound toβ-LG with a diminished allergenicity were identified to investigate their respective role on the structural and allergenic properties ofβ-LG.Extracts from Vaccinium fruits and black soybeans were found to have great inhibitory effects on the IgE-and IgG-binding abilities ofβ-LG.Among the fourteen structure-related phenolic compounds,flavonoids and tannins with larger MWs and multi-hydroxyl substituents,notably rutin,EGCG,and ellagitannins were more potent to elicit changes on the conformational structures ofβ-LG to decrease the allergenicity of complexedβ-LG.Correlation analysis further demonstrated that a destabilized secondary structure and protein depolymerization caused by polyphenol-binding were closely related to the allergenicity property of formed complexes.This study provides insights into the understanding of structure-allergenicity relationship ofβ-LG-polyphenol interactions and would benefit the development of polyphenol-fortified matrices with hypoallergenic potential.
文摘The trace identity is extended to the quadratic-form identity. The Hamiltonian structures of the multi-component Guo hierarchy, integrable coupling of Guo hierarchy and （2＋l）-dimensional Guo hierarchy are obtained by the quadraticform identity. The method can be used to produce the Hamiltonian structures of the other integrable couplings or multi-component hierarchies.
基金Project supported by the National Natural Science Foundation of China(Grant No.61474089)the Open Fund of Key Laboratory of Complex Electromagnetic Environment Science and Technology,China Academy of Engineering Physics(Grant No.2015-0214.XY.K)
文摘We study structural,mechanical,and electronic properties of C_（20）,Si_（20） and their alloys（C_（16）Si_4,C_（12）Si_8,C_8Si_（12）,and C_4Si_（16）） in C2/m structure by using density functional theory（DFT） based on first-principles calculations.The obtained elastic constants and the phonon spectra reveal mechanical and dynamic stability.The calculated formation enthalpy shows that the C-Si alloys might exist at a specified high temperature scale.The ratio of BIG and Poisson＇s ratio indicate that these C-Si alloys in C2/m-20 structure are all brittle.The elastic anisotropic properties derived by bulk modulus and shear modulus show slight anisotropy.In addition,the band structures and density of states are also depicted,which reveal that C_（20）,C_（16）Si_4,and Si_（20） are indirect band gap semiconductors,while C_8Si_（12） and C_4Si_（16） are semi-metallic alloys.Notably,a direct band gap semiconductor（C_（12）Si_8） is obtained by doping two indirect band gap semiconductors（C_（20） and Si_（20））.
基金Supported by NNSF of China and the Foundation of Wuhan University
文摘The structure of any a.s. self-similar set K(w) generated by a class of random elements {gn,wσ} taking values in the space of contractive operators is given and the approximation of K(w) by the fixed points {Pn,wσ} of {gn,ow} is obtained. It is useful to generate the fractal in computer.
基金supported by the National Natural Science Foundation of China(Grant No.51672183)a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)。
文摘Designing low-cost,easy-fabricated,highly stable and active electrocatalysts for oxygen evolution reaction(OER) is crucial for electrochemical(EC) and solar-driven photoelectrochemical(PEC) water splitting.By using a facile heating-electrodeposition method,here we fabricated a porous but crystalline Fe-doped Ni3 S2.A thin porous surface NiFe hydroxide layer(~10 nm) is then formed through OER-running.By virtue of the core Fe-doped Ni3 S2 with good conductivity and the shell NiFe hydroxide surface with good electrocatalytic activity,the core-shell nanostructure on Ni foam exhibits excellent OER activity in 1 M NaOH,needing only 195 and 230 mV to deliver 10 and 100 mA/cm^(2),respectively,much more superior to those of 216 and 259 mV for the sample deposited under normal temperature.The enhanced photo-response of the sulfide@hydroxide core-shell structure was also demonstrated,due to the efficient transfer of photo-generated carriers on the core/shell interface.More interestingly,it shows a good compatibility with Si based photoanode,which exhibits an excellent PEC performance with an onset potential of 0.86 V vs.reversible hydrogen electrode,an applied bias photon-to-current efficiency of 5.5% and a durability for over 120 h under AM 1.5 G 1 sun illumination,outperforming the state-of-the-art Si based photoanodes.
基金This study is supported by National Key Research and Development Program(2016YFC0501603).
文摘Understanding the interaction between canopy structure and the parameters of interception loss is essential in predicting the variations in partitioning rainfall and water resources as affected by changes in canopy structure and in implementing water-based management in semiarid forest plantations.In this study,seasonal variations in rainfall interception loss and canopy storage capacity as driven by canopy structure were predicted and the linkages were tested using seasonal filed measurements.The study was conducted in nine 50 m×50 m Robinia pseudoacacia plots in the semiarid region of China’s Loess Plateau.Gross rain-fall,throughfall and stemflow were measured in seasons with and without leaves in 2015 and 2016.Results show that measured average interception loss for the nine plots were 17.9% and 9.4% of gross rainfall during periods with leaves (the growing season) and without leaves, respectively. Average canopy storage capacity estimated using an indirect method was 1.3 mm in the growing season and 0.2 mm in the leafless season. Correlations of relative interception loss and canopy storage capacity to canopy variables were highest for leaf/wood area index (LAI/WAI) and canopy cover, fol-lowed by bark area, basal area, tree height and stand density. Combined canopy cover, leaf/wood area index and bark area multiple regression models of interception loss and canopy storage capacity were established for the growing season and in the leafless season in 2015. It explained 97% and 96% of the variations in relative interception loss during seasons with and without leaves, respectively. It also explained 98% and 99% of the variations in canopy storage capacity during seasons with and without leaves, respectively. The empiri-cal regression models were validated using field data col-lected in 2016. The models satisfactorily predicted relative interception loss and canopy storage capacity during seasons with and without leaves. This study provides greater under-standing about the effects of changes in tree canopy structure (e.g., dieback or mortality) on hydrological processes.
文摘A theoretical study of resonant tunneling is carried out for an inverse parabolic double-barrier structure subjected to an external electric field. Tunneling transmission coefficient and density of states are analyzed by using the non-equilibrium Green＇s function approach based on the finite difference method. It is found that the resonant peak of the transmission coefficient, being unity for a symmetrical case, reduces under the applied electric field and depends strongly on the variation of the structure parameters.
文摘An Mg-Zn-Mn-Ca alloy with high Zn content was fabricated by vacuum melting. The as-cast microstructure was investigated using XRD, SEM and EDS. It was shown that the alloy was composed of α-Mg, strip-like Ca2Mg6Zn3 and a few Mn- containing phases. Most of the Ca2Mg6Zn3 phase was distributed at grain boundaries while Mn-containing particles were deposited within grains. The as-cast samples were immersed in a Hank＇s balanced salt solution （HBSS） up to 24 h. The corroded surface morphology and cross-section microstructure were analyzed after different time of immersion so as to understand the corrosion behavior of the alloy. During immersion in the HBSS, the alloy corroded homogeneously at the very beginning and then localized corrosion occurred. The secondary phases protruded on the surface due to the dissolution of α-Mg, suggesting micro- galvanic corrosion occurred with secondary phases acting as the cathode and ct-Mg as the anode. Micro-cracks were formed at the interfaces between Ca2Mg6Zn3 and α-Mg, indicating an undermining tendency of the secondary phases.
基金financially supported by the Department of Education of Liaoning Province of China
文摘Micro-nano structured Li Fe（1-x）MnxPO4/C（0≤x≤0.05）cathodes were prepared by spray drying,followed by calcination at 700°C.The spherical Li Fe（1-x）MnxPO4/C（0≤x≤0.05）particles with the size of 0.5 to5.0μm are composed of lots of nanoparticles of 20 to 30 nm,and have the well-developed interconnected pore structure.In contrast,when Mn doping content is 3 mol%（x=0.03）,the Li Fe（0.97）Mn（0.03）PO4/C demonstrates maximum specific surface area of 31.30 m^2/g,more uniform pore size and relatively better electrochemical performance.The initial discharge capacities are 161.59,157.04 and 153.13 m Ah/g at a discharge rate of 0.2,0.5 and 1 C,respectively.Meanwhile,the discharge capacity retentions are～100%after 120 cycles.The improved electrochemical performance should be attributed to higher specific surface,smaller polarization voltage,and a high Li~＋diffusion rate due to the micro-nano porous structure and lattice expansion produced by Mn doping.
文摘Based on the multiplicity results of Benci and Fortunato [4], we consider some elliptic systems with strongly indefinite quadratic part, and establish the existence of infinitely many nontrivial solutions in a suitable family of products of fractional Sobolev spaces.
文摘This paper calculated load-carrying of isogrid and orthogrid of carbon-epoxy composite trellis wound structure(C/E CTWS) using non-linear finite element method.Based on the analysis,test cases were designed and tests of axial compression were carried.Analysis result and test result fit well.In order to be used in the project,this kind of structure cut-out repairing was calculated.The method presented in this paper has been proved and can be used to solve complicated engineering problems.According to calculations and experimental results combined with application,a principle of choosing wound structure is obtained and principle could be applied to engineering.
文摘In the teaching of translation and grammar,it is essential that the English sentence structure is analyzed and transformation of sentence structures both in English and Chinese in class and after class. However,many kinds of English sentences structures prevent the students who study English from getting the basic idea and concept of a sentence in translation or grammatical analysis. In this paper,the author submitted the basic mould of simplification of English sentence structure,and the students can learn and master the translating technique through the simplified English sentence structure. Thus it helps to improve students' competence of translation.
基金Project supported by the National Natural Science Foundation of China （Grant No 10574039）,the Key Program of Science and Technology Research of Education Ministry, China （Grant No 206084）, Innovation Talents of Institution of Higher Education of Henan Province, China （Grant No 2006KYCX002）, the Natural Science Foundation of Education Bureau of Henan Province, China （Grant No 200510476004）.
文摘In this paper, the equilibrium geometry, harmonic frequency and dissociation energy of S2^- and S3^- have been calculated at QCISD/6-311＋＋G（3d2f） and B3P86/6-311＋＋G（3d2f） level. The S2^- ground state is of 2IIg, the S3^- ground state is of 2B1 and S3^- has a bent （C2v） structure with an angle of 115.65° The results are in good agreement with these reported in other literature. For S3^- ion, the vibration frequencies and the force constants have also been calculated. Base on the general principles of microscopic reversibility, the dissociation limits has been deduced. The Murrell-Sorbie potential energy function for S2^- has been derived according to the ab initio data through the least- squares fitting. The force constants and spectroscopic data for S2^- have been calculated, then compared with other theoretical data. The analytical potential energy function of S3^- have been obtained based on the many-body expansion theory. The structure and energy can correctly reappear on the potential surface.
基金supported by the National Natural Science Foundation of China(21633008,21433003,U1601211,21733004)National Science and Technology Major Project(2016YFB0101202)+1 种基金Jilin Province Science and Technology Development Program(20150101066JC,20160622037JC,20170203003SF,20170520150JH)Hundred Talents Program of Chinese Academy of Sciences and the Recruitment Program of Foreign Experts(WQ20122200077)
文摘Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the active site hosts, its hostility to electron/mass transfer could lead to the incomplete fulfillment of the catalytic activity. Besides, the formation of inactive metallic Fe particles during the conventional catalyst synthesis could also decrease the active site density and complicate the identification of real active site. Herein, we developed a facial hydrogen etching methodology to yield single site Fe-N-C catalysts featured with micro/mesoporous hierarchical structure. The hydrogen concentration in pyrolysis process was designated to effectively regulate the pore structure and active site density of the resulted catalysts.The optimized sample achieves excellent ORR catalytic performance with an ultralow H2O2 yield(1%)and superb stability over 10,000 cycles. Our finding provides new thoughts for the rational design of hierarchically porous carbon-based materials and highly promising non-precious metal ORR catalysts.
基金supported by the National Natural Science Foundation of China(No.11872207)the Aeronautical Science Foundation of China (No. 20180952007)+1 种基金the Foundation of National Key Laboratory on Ship Vibration and Noise(No.614220400307)the National Key Research and Development Program of China (No.2019YFA708904)。
文摘Intelligent structures like zero Poisson’s ratio(ZPR)cellular structures have been widely applied to the engineering fields such as morphing wings in recent decades,owing to their outstanding characteristics including light weight and low effective modulus. In-plane and out-of-plane mechanical properties of ZPR cellular structures are investigated in this paper. A theoretical method for calculating in-plane tensile modulus,in-plane shear modulus and out-of-plane bending modulus of ZPR cellular structures is proposed,and the impacts of the unit cell geometrical configurations on in-plane tensile modulus,in-plane shear modulus and out-of-plane bending modulus are studied systematically based on finite element(FE)simulation. Experimental tests validate the feasibility and effectiveness of the theoretical and FE analysis. And the results show that the in-plane and out-of-plane mechanical properties of ZPR cellular structures can be manipulated by designing cell geometrical parameters.
