The formation mechanism for the body-centered cubic structure of cluster is proposed and its total energy curve is calculated by the method of a Modified Arrangement Channel Quantum Mechanics. The energy is the funct...The formation mechanism for the body-centered cubic structure of cluster is proposed and its total energy curve is calculated by the method of a Modified Arrangement Channel Quantum Mechanics. The energy is the function of separation R between the nuclei at the center and an apex of the body-centered cubic structure. The result of the calculation shows that the curve has a minimal energy . The binding energy of with respect to was calculated to be 0.8857 a.u. This means that the cluster ofmay be formed in the body-centered cubic structure of .展开更多
The introduction of carbon interstitials into high-entropy alloys(HEAs)provides an effective way to improve their properties.However,all such HEA systems explored so far are limited to those with the face-centered-cub...The introduction of carbon interstitials into high-entropy alloys(HEAs)provides an effective way to improve their properties.However,all such HEA systems explored so far are limited to those with the face-centered-cubic(fcc)structure.Here we report the structural,mechanical and physical properties of the refractory(Nb_(0.375)Ta_(0.25)Mo_(0.125)W_(0.125)Re_(0.125))_(100−x)C_(x) HEAs over a wide x range of 0≤x≤20.It is found that,whereas the starting HEA(x=0)is composed of a major body-centered-cubic(bcc)phase with significant impurities,the bcc phase fraction increases with the C concentration and achieves almost 100%at x=20.Moreover,the increase of C content x results in an expansion of the bcc lattice,an enhancement of the microhardness,an increase in residual resistivity and a small variation of density of states at the Fermi level.All these features are consistent with the expectation that carbon atoms occupy the interstitial site.For x≥11.1,the X-ray photoelectron spectroscopy indicates the bond formation between the carbon and metal atoms,suggesting that some carbon atoms may also reside in the lattice site.In addition,a semiquantitative analysis shows that the enhanced mixing entropy caused by carbon addition plays a key role in stabilizing the(nearly)single solid-solution phase.Our study not only provides the first series of carbon interstitial HEAs with a bcc structure,but also helps to better understand the alloying behavior of carbon in refractory HEAs.展开更多
How to reconstruct a dynamic displacement of slender flexible structures is the key technology to develop smart structures and structural health monitoring(SHM), which are beneficial for controlling the structural vib...How to reconstruct a dynamic displacement of slender flexible structures is the key technology to develop smart structures and structural health monitoring(SHM), which are beneficial for controlling the structural vibration and protecting the structural safety. In this paper, the displacement reconstruction method based on cubic spline fitting is put forward to reconstruct the dynamic displacement of slender flexible structures without the knowledge of modeshapes and applied loading. The obtained strains and displacements are compared with the results calculated by ABAQUS to check the method's validity. It can be found that the proposed method can accurately identify the strains and displacement of slender flexible structures undergoing linear vibrations, nonlinear vibrations, and parametric vibrations. Under the concentrated force, the strains of slender flexible structures will change suddenly along the axial direction. With locally densified measurement points, the present reconstruction method still works well for the strain concentration problem.展开更多
The possibilities of hexagonal boron nitride(hBN) and lithium boron nitride(Li_3BN_2) transition into cubic boron nitride(cBN) under synthetic pressure 5.0 GPa and synthetic temperature 1700 K are analyzed with the us...The possibilities of hexagonal boron nitride(hBN) and lithium boron nitride(Li_3BN_2) transition into cubic boron nitride(cBN) under synthetic pressure 5.0 GPa and synthetic temperature 1700 K are analyzed with the use of the empirical electron theory of solids and molecules. The relative differences in electron density are calculated for dozens of bi-phase interfaces hBN/cBN, Li_3BN_2/cBN. These relative differences of hBN/cBN are in good agreement with the first order of approximation(<10%), while those of Li_3BN_2/cBN are much greater than 10%.This analysis suggests that Li_3BN_2 is impossible to be intermediate phase but is a catalyst and cBN should be directly transformed by hBN.展开更多
The indium tin oxide （ITO） nanoparticles with cubic structure were synthesized by heating a mixture of indium tin hydroxide and sodium chloride at low temper- ature of 300 ℃ for 2 h and washing with water. The effe...The indium tin oxide （ITO） nanoparticles with cubic structure were synthesized by heating a mixture of indium tin hydroxide and sodium chloride at low temper- ature of 300 ℃ for 2 h and washing with water. The effects of sodium chloride addition on the ITO phase and mor- phology were investigated using differential scanning cal- orimetry （DSC）, thermogravimetric analysis （TGA）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. It is found that sodium chloride addition helps the formation of cubic structure of ITO nanoparticles. The particle size of the resulted ITO powder is about 3 nm.展开更多
Mesoporous aluminosilicate with cubic ordered structure was synthesized by two-step crystallization, which showed stronger acid sites and more effective activity for catalytic alkylation of 2, 4-ditert-butylphenol wit...Mesoporous aluminosilicate with cubic ordered structure was synthesized by two-step crystallization, which showed stronger acid sites and more effective activity for catalytic alkylation of 2, 4-ditert-butylphenol with tert-butanol than conventional H-AlMCM-48 materials.展开更多
In this paper we discuss the topological structure near the singular point O (0,0) of the plane cubic system in the undetermined sign case, and give their coefficient conditions.
In order to comprehensively understand the mechanical behavior of biological entities and aerospace applications subjected to hypergravity environments,we delve into the impact of hypergravity on the equivalent compli...In order to comprehensively understand the mechanical behavior of biological entities and aerospace applications subjected to hypergravity environments,we delve into the impact of hypergravity on the equivalent compliance of cubic lattice structures.Capitalizing on the periodic spatial distribution,we employ a unit cell methodology to deduce the homogenized stress-strain relationship for the lattice structures,subsequently obtaining the associated equivalent compliance.The equivalent compliance can be conveniently reduced to instances without hypergravity influence.Furthermore,numerical simulations are executed to validate the derivations and to illustrate that hypergravity indeed affects the mechanical properties of lattice structures.We introduce a non-dimensional hypergravity factor,which quantifies the impact of hypergravity magnitude relative to the Young’s modulus of the base material.Our findings reveal that the hypergravity factor influences perpendicular compliance quadratically and parallel compliance linearly.Simultaneously,the perpendicular shear compliance remains unaffected,whereas the parallel shear compliance experiences an inverse effect.Additionally,the lattice structure transforms into a gradient material oriented in the hypergravity direction,consequently generating a scale effect.展开更多
Cubic boron nitride(CBN)micro powders and mixture of CBN micro powders with Al or Ti powders were fast heated at 1300,1400,1450,1500℃,and then kept for 5 min under spark plasma sintering(SPS).The obtained powders wer...Cubic boron nitride(CBN)micro powders and mixture of CBN micro powders with Al or Ti powders were fast heated at 1300,1400,1450,1500℃,and then kept for 5 min under spark plasma sintering(SPS).The obtained powders were analyzed with XRD.The results show that,simple CBN kept cubic structure after heated at 1300℃;when the temperature rose to 1400℃,some CBN was transformed into hexagonal structured boron nitride(hBN).As for CBN micro powders mixed with aluminum or titanium micro powders,the onset transforming temperature of CBN to hBN get raised.This results indicated that the structural transformation of boron nitride begun from the surface of CBN crystal particle,different coexist elements affect the surface situation of CBN particles.As the stabilities of CBN crystal particle surface improved,the onset structural transform temperature of CBN was also increased.展开更多
Surface structures and properties of Sn islands grown on superconducting substrate 2H-NbSe2（0001）are studied using low temperature scanning tunneling microscopy or spectroscopy.The pure face-centered cubic（fee）str...Surface structures and properties of Sn islands grown on superconducting substrate 2H-NbSe2（0001）are studied using low temperature scanning tunneling microscopy or spectroscopy.The pure face-centered cubic（fee）structure of Sn surface is obtained.Superconductivity is also detected on the fcc-Sn（111）surface,and the size of superconducting gap on the Sn surface is nearly the same as that on the superconducting substrate.Furthermore,phase transition occurs from fcc-Sn（111）toβ-Sn（001）by keeping the sample at room temperature for a certain time.Due to the strain relaxation on theβ-Sn islands,both the in-plane unit cell and out-of-plane structures distort,and the height of surface atoms varies periodically to form a universal ripple structure.展开更多
Gradient cemented carbides with nano-TiN were prepared by the common powder metallurgical procedure. The formation of gradient zone and the microstructure, properties of the alloys were investigated using scanning ele...Gradient cemented carbides with nano-TiN were prepared by the common powder metallurgical procedure. The formation of gradient zone and the microstructure, properties of the alloys were investigated using scanning electron microscope（SEM）, energy dispersive spectroscopy（EDS） and other performance testing apparatus. Moreover, the effect of nano-TiN on the gradient cemented carbide was studied. It is found that gradient zone width increases slightly with nano-TiN introduction. Both cobalt and titanium concentrations reach the maximum near the gradient border. Tungsten concentration shows fluctuation from the surface to the bulk. （Ti ,W）C phase grains are refined for nitrogen introduction. Core-rim structure has been observed under the SEM back-scattered mode. The core appears as dark due to more titanium in it and the rim with more tungsten appears as grey. In addition, the hardness and transverse rupture strength of gradient cemented carbide are enhanced with nano-TiN introduced.展开更多
A structured perturbation analysis of the least squares problem is considered in this paper.The new error bound proves to be sharper than that for general perturbations.We apply the new error bound to study sensitivit...A structured perturbation analysis of the least squares problem is considered in this paper.The new error bound proves to be sharper than that for general perturbations.We apply the new error bound to study sensitivity of changing the knots for curve fitting of interest rate term structure by cubic spline.Numerical experiments are given to illustrate the sharpness of this bound.展开更多
We present an analysis of structural, electronic, and mechanical properties of cubic titanium dioxide （TiO2） using an all electron orthogonalzed linear combinations of atomic orbitals （OLCAO） basis set under the f...We present an analysis of structural, electronic, and mechanical properties of cubic titanium dioxide （TiO2） using an all electron orthogonalzed linear combinations of atomic orbitals （OLCAO） basis set under the framework of density functional theory （DFT）. The structural property, especially the lattice constant a, and the electronic properties such as the band diagram and density of states （DOS） are studied and analyzed. The mechanical properties such as bulk moduli, shear moduli, Young＇s Moduli, and Poison＇s ratio are also investigated thoroughly. The calculations are carried out on shear moduli and anisotropy factor for cubic TiO2. The Vickers hardness is also tested for fluorite and pyrite cubic-structured TiO2. Furthermore, the results are compared with the previous theoretical and experimental results. It is found that DFT- based simulation produces results which are approximation to experimental results, whereas the calculated elastic constants are better than the previous theoretical and experimental values.展开更多
The structure and inagnetostriction of Dy_(0.9-x)Tb_(x)Pr_(0.1)Fe_(1.85) and Dy_(0.9-x)Tb_(x)Pr_(0.1)(Fe_(0.95)Al_(0.05))_(1.8) alloys were investigated.These alloys are substantially single phase with MgCu2-type cubi...The structure and inagnetostriction of Dy_(0.9-x)Tb_(x)Pr_(0.1)Fe_(1.85) and Dy_(0.9-x)Tb_(x)Pr_(0.1)(Fe_(0.95)Al_(0.05))_(1.8) alloys were investigated.These alloys are substantially single phase with MgCu2-type cubic structure.The lattice parameter and Curie temperature of Dy_(0.9-x)Tb_(x)Pr_(0.1)(Fe_(0.95)Al_(0.05))_(1.8) alloys increase steadily with increasing Th content.Tb dependence of magnetostnction in various applied fields for poly crystalline Dy_(0.9-x)Tb_(x)Pr_(0.1)Fe_(1.85) alloys exhibits a peak at x=0.25.The magnetostric-tion of polycrystalline Dy_(0.9-x)Tb_(x)Pr_(0.1)(Fe_(0.95)Al_(0.05))_(1.8) alloys in high applied fields(H>160 kA/m)and in low applied Helds(H≤160 kA/m)exhibits a peak at x=0.3 and x=0.25,respectively.展开更多
Shell-infill structures comprise an exterior solid shell and an interior lattice infill,whose closed features yield superior comprehensive mechanical performance and light weight.Additive manufacturing(AM)can ensure t...Shell-infill structures comprise an exterior solid shell and an interior lattice infill,whose closed features yield superior comprehensive mechanical performance and light weight.Additive manufacturing(AM)can ensure the fabrica-tion of complex structures.Although the mechanical behaviors of lattice structures have been extensively studied,the corresponding mechanical performances of integrated-manufactured shell structures with lattice infills should be systematically investigated due to the coupling effect of the exterior shell and lattice infill.This study investigated the mechanical properties and energy absorption of AlSi10Mg shell structures with a body-centered cubic lattice infill fabricated by AM.Quasi-static compressive experiments and corresponding finite element analysis were conducted to investigate the mechanical behavior.In addition,two different finite element modeling methods were compared to determine the appropriate modeling strategy in terms of deformation behavior.A study of different parameters,including lattice diameters and shell thicknesses,was conducted to identify their effect on mechanical performance.The results demonstrate the mechanical advantages of shell-infill structures,in which the exterior shell strengthens the lattice infill by up to 2.3 times in terms of the effective Young’s modulus.Increasing the infill strut diameter can improve the specific energy absorption by up to 1.6 times.展开更多
1 This paper considers Lagrangian finite elements for structural dynamics constructed with cubic displacement shape functions.The method of templates is used to investigate the construction of accurate mass-stiffness ...1 This paper considers Lagrangian finite elements for structural dynamics constructed with cubic displacement shape functions.The method of templates is used to investigate the construction of accurate mass-stiffness pairs.This method introduces free parameters that can be adjusted to customize elements according to accuracy and rank-sufficiency criteria.One-and two-dimensional Lagrangian cubic elements with only translational degrees of freedom(DOF)carry two additional nodes on each side,herein called side nodes or SN.Although usually placed at the third-points,the SN location may be adjusted within geometric limits.The adjustment effect is studied in detail using symbolic computations for a bar element.The best SN location is taken to be that producing accurate approximation to the lowest natural frequencies of the continuum model.Optimality is investigated through Fourier analysis of the propagation of plane waves over a regular infinite lattice of bar elements.Focus is placed on the acoustic branch of the frequency-vs.-wavenumber dispersion diagram.It is found that dispersion results using the fully integrated consistent mass matrix(CMM)are independent of the SN location whereas its lowfrequency accuracy order is O(κ8),whereκis the dimensionless wave number.For the diagonally lumped mass matrix(DLMM)constructed through the HRZ scheme,two optimal SN locations are identified,both away from third-points and of accuracy order O(κ8).That with the smallest error coefficient corresponds to the Lobatto 4-point integration rule.A special linear combination of CMM and DLMM with nodes at the Lobatto points yields an accuracy of O(κ10)without any increase in the computational effort over CMM.The effect of reduced integration(RI)on both mass and stiffness matrices is also studied.It is shown that singular mass matrices can be constructed with 2-and 3-point RI rules that display the same optimal accuracy of the exactly integrated case,at the cost of introducing spurious modes.The optimal SN location in two-dimensional,bicubic,isoparametric plane stress quadrilateral elements is briefly investigated by numerical experiments.The frequency accuracy of flexural modes is found to be fairly insensitive to that position,whereas for bar-like modes it agrees with the one-dimensional results.展开更多
Herein,we report the synthesis of Zn_(0.7)Mg_(0.3)Nd_(x)Fe_(2-x)O_(4)(where,x=0,0,0,01,0,02)ferrite nanoparticles by employing the sol-gel auto-combustion technique.The X-ray diffraction(XRD)pattern suggests the forma...Herein,we report the synthesis of Zn_(0.7)Mg_(0.3)Nd_(x)Fe_(2-x)O_(4)(where,x=0,0,0,01,0,02)ferrite nanoparticles by employing the sol-gel auto-combustion technique.The X-ray diffraction(XRD)pattern suggests the formation of a pure cubic structure,without any impurity phase,with an Fd3m space group at room temperature.With increasing doping amount,the crystallite size is reported as 35-41 nm,while the lattice parameters rise from 0.8381 to 0.8395 nm.Field emission scanning electron microscopy(FESEM)images show the formation of spherical grains with agglomerated morphology in all the samples,with grain sizes ranging from 49 to 103 nm.Energy dispersive X-ray spectroscopy(EDX)and elemental mapping investigation confirm the chemical purity of all the samples.Fourier transform infrared(FTIR)analysis shows the presence of two prominent peaks around 440 and 560 cm^(-1)that correspond to the octahedral and tetrahedral positions.In addition,the existence of five Raman active vibratio nal modes in all produced specimens again confirms the structural purity of all the samples.The M-H curve shows that saturation magnetization(M_(s))first increases from 14.98 to 28.22 emu/g and then decreases to 18.98emu/g with increasing doping amount.This is due to the A-B type super-exchange interaction for the synthesized samples.The variation in coercivity(H_(c))and magnetic anisotropy(K_(1))suggest the thermal stability of all the samples and can be utilized in transformers and solenoids.展开更多
In this work, ZnSn（OH）6with a cubic structure is successfully synthesized by one-step hydrothermal method without any catalyst. The response and recovery characteristics of gas sensing were investigated against vari...In this work, ZnSn（OH）6with a cubic structure is successfully synthesized by one-step hydrothermal method without any catalyst. The response and recovery characteristics of gas sensing were investigated against various gases via quartz crystal microbalance（QCM） at room temperature. The sensor exhibited high sensitivity and good selectivity toward CO gas. Moreover, a linear dependence of log^（àDelta F）about CO concentration was obtained. It is demonstrated that the QCM sensor coated cubic ZnSn（OH）6could be a suitable candidate for detecting CO.展开更多
1 Introduction Since its first discovery in 1992, ordered mesoporous silica material with large pore size, high surface area, and high pore volume has attracted great attention for the potentially wide application in...1 Introduction Since its first discovery in 1992, ordered mesoporous silica material with large pore size, high surface area, and high pore volume has attracted great attention for the potentially wide application in catalysis, adsorption, separation, and ion exchange, etc. However, the poor hydrothermal stability of mesoporous silica has limited its wide application in industry. Therefore, in the last 10 years, many studies have been dedicated to improving the hydrothermal stability of mesoporous silica. Xiao et al.展开更多
A three-dimensional (3D) dusty plasma crystalline with cubic configurations is considered.We calculate the interaction between particles up to distance (√2)a,implying the second-neighbor interactions for the simple c...A three-dimensional (3D) dusty plasma crystalline with cubic configurations is considered.We calculate the interaction between particles up to distance (√2)a,implying the second-neighbor interactions for the simple cubic structure,the third-neighbor interactions for the body-centered cubic structure,and the forth-neighbor interactions the for face-centered cubic structure.Longitudinal and transverse dispersion relations are derived in arbitrary directions.The dispersion relations are studied in special directions,i.e.(1,0,0),(1,1,0)/(√2),and (1,1,1)/(√3).Study of dispersion relations with more neighbor interactions show that in some cases the results change physically.展开更多
基金The project supported by National Natural Science Foundation of China(Grant No.19974027)the Foundation of Sichuan Provincial Education Committee(Grant No.01LB04)
文摘The formation mechanism for the body-centered cubic structure of cluster is proposed and its total energy curve is calculated by the method of a Modified Arrangement Channel Quantum Mechanics. The energy is the function of separation R between the nuclei at the center and an apex of the body-centered cubic structure. The result of the calculation shows that the curve has a minimal energy . The binding energy of with respect to was calculated to be 0.8857 a.u. This means that the cluster ofmay be formed in the body-centered cubic structure of .
基金the foundation of Westlake University for financial supportThe work at Zhejiang University was supported by the National Key Research and Development Program of China(2017YFA0303002)。
文摘The introduction of carbon interstitials into high-entropy alloys(HEAs)provides an effective way to improve their properties.However,all such HEA systems explored so far are limited to those with the face-centered-cubic(fcc)structure.Here we report the structural,mechanical and physical properties of the refractory(Nb_(0.375)Ta_(0.25)Mo_(0.125)W_(0.125)Re_(0.125))_(100−x)C_(x) HEAs over a wide x range of 0≤x≤20.It is found that,whereas the starting HEA(x=0)is composed of a major body-centered-cubic(bcc)phase with significant impurities,the bcc phase fraction increases with the C concentration and achieves almost 100%at x=20.Moreover,the increase of C content x results in an expansion of the bcc lattice,an enhancement of the microhardness,an increase in residual resistivity and a small variation of density of states at the Fermi level.All these features are consistent with the expectation that carbon atoms occupy the interstitial site.For x≥11.1,the X-ray photoelectron spectroscopy indicates the bond formation between the carbon and metal atoms,suggesting that some carbon atoms may also reside in the lattice site.In addition,a semiquantitative analysis shows that the enhanced mixing entropy caused by carbon addition plays a key role in stabilizing the(nearly)single solid-solution phase.Our study not only provides the first series of carbon interstitial HEAs with a bcc structure,but also helps to better understand the alloying behavior of carbon in refractory HEAs.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51679167 and 51525803)
文摘How to reconstruct a dynamic displacement of slender flexible structures is the key technology to develop smart structures and structural health monitoring(SHM), which are beneficial for controlling the structural vibration and protecting the structural safety. In this paper, the displacement reconstruction method based on cubic spline fitting is put forward to reconstruct the dynamic displacement of slender flexible structures without the knowledge of modeshapes and applied loading. The obtained strains and displacements are compared with the results calculated by ABAQUS to check the method's validity. It can be found that the proposed method can accurately identify the strains and displacement of slender flexible structures undergoing linear vibrations, nonlinear vibrations, and parametric vibrations. Under the concentrated force, the strains of slender flexible structures will change suddenly along the axial direction. With locally densified measurement points, the present reconstruction method still works well for the strain concentration problem.
基金Supported by the National Natural Science Foundation of China under Grant No 51272139
文摘The possibilities of hexagonal boron nitride(hBN) and lithium boron nitride(Li_3BN_2) transition into cubic boron nitride(cBN) under synthetic pressure 5.0 GPa and synthetic temperature 1700 K are analyzed with the use of the empirical electron theory of solids and molecules. The relative differences in electron density are calculated for dozens of bi-phase interfaces hBN/cBN, Li_3BN_2/cBN. These relative differences of hBN/cBN are in good agreement with the first order of approximation(<10%), while those of Li_3BN_2/cBN are much greater than 10%.This analysis suggests that Li_3BN_2 is impossible to be intermediate phase but is a catalyst and cBN should be directly transformed by hBN.
基金supported by the National Natural Science Foundation of China(No.51102022)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20110205120001)the Special Fund for Basic Scientific Research of Central Colleges,Chang'an University(Nos.CHD2012ZD015 and CHD2012JC071)
文摘The indium tin oxide （ITO） nanoparticles with cubic structure were synthesized by heating a mixture of indium tin hydroxide and sodium chloride at low temper- ature of 300 ℃ for 2 h and washing with water. The effects of sodium chloride addition on the ITO phase and mor- phology were investigated using differential scanning cal- orimetry （DSC）, thermogravimetric analysis （TGA）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. It is found that sodium chloride addition helps the formation of cubic structure of ITO nanoparticles. The particle size of the resulted ITO powder is about 3 nm.
基金We thank financial support by the National Natural Science Foundation of China(grant 29973001).
文摘Mesoporous aluminosilicate with cubic ordered structure was synthesized by two-step crystallization, which showed stronger acid sites and more effective activity for catalytic alkylation of 2, 4-ditert-butylphenol with tert-butanol than conventional H-AlMCM-48 materials.
文摘In this paper we discuss the topological structure near the singular point O (0,0) of the plane cubic system in the undetermined sign case, and give their coefficient conditions.
基金supported by the National Natural Science Foundation of China(Grant Nos.11925206,51988101,and 12272340)Zhejiang Provincial Natural Science Foundation of China(Grant No.LD21A020002).
文摘In order to comprehensively understand the mechanical behavior of biological entities and aerospace applications subjected to hypergravity environments,we delve into the impact of hypergravity on the equivalent compliance of cubic lattice structures.Capitalizing on the periodic spatial distribution,we employ a unit cell methodology to deduce the homogenized stress-strain relationship for the lattice structures,subsequently obtaining the associated equivalent compliance.The equivalent compliance can be conveniently reduced to instances without hypergravity influence.Furthermore,numerical simulations are executed to validate the derivations and to illustrate that hypergravity indeed affects the mechanical properties of lattice structures.We introduce a non-dimensional hypergravity factor,which quantifies the impact of hypergravity magnitude relative to the Young’s modulus of the base material.Our findings reveal that the hypergravity factor influences perpendicular compliance quadratically and parallel compliance linearly.Simultaneously,the perpendicular shear compliance remains unaffected,whereas the parallel shear compliance experiences an inverse effect.Additionally,the lattice structure transforms into a gradient material oriented in the hypergravity direction,consequently generating a scale effect.
基金support provided by Natural Science Foundation of Hebei Province(No.E 2006000226)
文摘Cubic boron nitride(CBN)micro powders and mixture of CBN micro powders with Al or Ti powders were fast heated at 1300,1400,1450,1500℃,and then kept for 5 min under spark plasma sintering(SPS).The obtained powders were analyzed with XRD.The results show that,simple CBN kept cubic structure after heated at 1300℃;when the temperature rose to 1400℃,some CBN was transformed into hexagonal structured boron nitride(hBN).As for CBN micro powders mixed with aluminum or titanium micro powders,the onset transforming temperature of CBN to hBN get raised.This results indicated that the structural transformation of boron nitride begun from the surface of CBN crystal particle,different coexist elements affect the surface situation of CBN particles.As the stabilities of CBN crystal particle surface improved,the onset structural transform temperature of CBN was also increased.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0301003 and 2016YFA0300403the National Natural Science Foundation of China under Grant Nos 11521404,11634009,U1632102,11504230,11674222,11574202,11674226,11574201 and U1632272
文摘Surface structures and properties of Sn islands grown on superconducting substrate 2H-NbSe2（0001）are studied using low temperature scanning tunneling microscopy or spectroscopy.The pure face-centered cubic（fee）structure of Sn surface is obtained.Superconductivity is also detected on the fcc-Sn（111）surface,and the size of superconducting gap on the Sn surface is nearly the same as that on the superconducting substrate.Furthermore,phase transition occurs from fcc-Sn（111）toβ-Sn（001）by keeping the sample at room temperature for a certain time.Due to the strain relaxation on theβ-Sn islands,both the in-plane unit cell and out-of-plane structures distort,and the height of surface atoms varies periodically to form a universal ripple structure.
基金Funded by Research Funds for the Central Universities(No.2011SCU11038)Chengdu Science and Technology Project(Nos.10GGZD080GX-268 and 11DXYB096JH-027)
文摘Gradient cemented carbides with nano-TiN were prepared by the common powder metallurgical procedure. The formation of gradient zone and the microstructure, properties of the alloys were investigated using scanning electron microscope（SEM）, energy dispersive spectroscopy（EDS） and other performance testing apparatus. Moreover, the effect of nano-TiN on the gradient cemented carbide was studied. It is found that gradient zone width increases slightly with nano-TiN introduction. Both cobalt and titanium concentrations reach the maximum near the gradient border. Tungsten concentration shows fluctuation from the surface to the bulk. （Ti ,W）C phase grains are refined for nitrogen introduction. Core-rim structure has been observed under the SEM back-scattered mode. The core appears as dark due to more titanium in it and the rim with more tungsten appears as grey. In addition, the hardness and transverse rupture strength of gradient cemented carbide are enhanced with nano-TiN introduced.
基金Funds for Major State The work of the second author is partly supported by the Special Basic Research Projects(2005CB321700)the National Science Foundation of China under grant No.10571031The work of the third author is partly supported by the National Science Foundation of China under grant No.10571031.
文摘A structured perturbation analysis of the least squares problem is considered in this paper.The new error bound proves to be sharper than that for general perturbations.We apply the new error bound to study sensitivity of changing the knots for curve fitting of interest rate term structure by cubic spline.Numerical experiments are given to illustrate the sharpness of this bound.
文摘We present an analysis of structural, electronic, and mechanical properties of cubic titanium dioxide （TiO2） using an all electron orthogonalzed linear combinations of atomic orbitals （OLCAO） basis set under the framework of density functional theory （DFT）. The structural property, especially the lattice constant a, and the electronic properties such as the band diagram and density of states （DOS） are studied and analyzed. The mechanical properties such as bulk moduli, shear moduli, Young＇s Moduli, and Poison＇s ratio are also investigated thoroughly. The calculations are carried out on shear moduli and anisotropy factor for cubic TiO2. The Vickers hardness is also tested for fluorite and pyrite cubic-structured TiO2. Furthermore, the results are compared with the previous theoretical and experimental results. It is found that DFT- based simulation produces results which are approximation to experimental results, whereas the calculated elastic constants are better than the previous theoretical and experimental values.
基金Supported by the National Natural Science Foundation of Cliina.
文摘The structure and inagnetostriction of Dy_(0.9-x)Tb_(x)Pr_(0.1)Fe_(1.85) and Dy_(0.9-x)Tb_(x)Pr_(0.1)(Fe_(0.95)Al_(0.05))_(1.8) alloys were investigated.These alloys are substantially single phase with MgCu2-type cubic structure.The lattice parameter and Curie temperature of Dy_(0.9-x)Tb_(x)Pr_(0.1)(Fe_(0.95)Al_(0.05))_(1.8) alloys increase steadily with increasing Th content.Tb dependence of magnetostnction in various applied fields for poly crystalline Dy_(0.9-x)Tb_(x)Pr_(0.1)Fe_(1.85) alloys exhibits a peak at x=0.25.The magnetostric-tion of polycrystalline Dy_(0.9-x)Tb_(x)Pr_(0.1)(Fe_(0.95)Al_(0.05))_(1.8) alloys in high applied fields(H>160 kA/m)and in low applied Helds(H≤160 kA/m)exhibits a peak at x=0.3 and x=0.25,respectively.
基金Supported by National Natural Science Foundation of China(Grant No.51805032).
文摘Shell-infill structures comprise an exterior solid shell and an interior lattice infill,whose closed features yield superior comprehensive mechanical performance and light weight.Additive manufacturing(AM)can ensure the fabrica-tion of complex structures.Although the mechanical behaviors of lattice structures have been extensively studied,the corresponding mechanical performances of integrated-manufactured shell structures with lattice infills should be systematically investigated due to the coupling effect of the exterior shell and lattice infill.This study investigated the mechanical properties and energy absorption of AlSi10Mg shell structures with a body-centered cubic lattice infill fabricated by AM.Quasi-static compressive experiments and corresponding finite element analysis were conducted to investigate the mechanical behavior.In addition,two different finite element modeling methods were compared to determine the appropriate modeling strategy in terms of deformation behavior.A study of different parameters,including lattice diameters and shell thicknesses,was conducted to identify their effect on mechanical performance.The results demonstrate the mechanical advantages of shell-infill structures,in which the exterior shell strengthens the lattice infill by up to 2.3 times in terms of the effective Young’s modulus.Increasing the infill strut diameter can improve the specific energy absorption by up to 1.6 times.
基金This paper expands on work conducted during the 2005-2006 summer aca-demic recesses while the author was a visitor at CIMNE(Centro Internacional de Métodos Numéricos en Ingenieria)at Barcelona,SpainThe visits were partly supported by fellowships awarded by the Spanish Ministerio de Educación y Cultura during May-June of those years,and partly by the National Science Foundation under grant High-Fidelity Simulations for Heteroge-neous Civil and Mechanical Systems,CMS-0219422。
文摘1 This paper considers Lagrangian finite elements for structural dynamics constructed with cubic displacement shape functions.The method of templates is used to investigate the construction of accurate mass-stiffness pairs.This method introduces free parameters that can be adjusted to customize elements according to accuracy and rank-sufficiency criteria.One-and two-dimensional Lagrangian cubic elements with only translational degrees of freedom(DOF)carry two additional nodes on each side,herein called side nodes or SN.Although usually placed at the third-points,the SN location may be adjusted within geometric limits.The adjustment effect is studied in detail using symbolic computations for a bar element.The best SN location is taken to be that producing accurate approximation to the lowest natural frequencies of the continuum model.Optimality is investigated through Fourier analysis of the propagation of plane waves over a regular infinite lattice of bar elements.Focus is placed on the acoustic branch of the frequency-vs.-wavenumber dispersion diagram.It is found that dispersion results using the fully integrated consistent mass matrix(CMM)are independent of the SN location whereas its lowfrequency accuracy order is O(κ8),whereκis the dimensionless wave number.For the diagonally lumped mass matrix(DLMM)constructed through the HRZ scheme,two optimal SN locations are identified,both away from third-points and of accuracy order O(κ8).That with the smallest error coefficient corresponds to the Lobatto 4-point integration rule.A special linear combination of CMM and DLMM with nodes at the Lobatto points yields an accuracy of O(κ10)without any increase in the computational effort over CMM.The effect of reduced integration(RI)on both mass and stiffness matrices is also studied.It is shown that singular mass matrices can be constructed with 2-and 3-point RI rules that display the same optimal accuracy of the exactly integrated case,at the cost of introducing spurious modes.The optimal SN location in two-dimensional,bicubic,isoparametric plane stress quadrilateral elements is briefly investigated by numerical experiments.The frequency accuracy of flexural modes is found to be fairly insensitive to that position,whereas for bar-like modes it agrees with the one-dimensional results.
基金the Researchers Supporting Project number (RSP-2021/29),King Saud University,Riyadh,Saudi Arabia,for funding this research。
文摘Herein,we report the synthesis of Zn_(0.7)Mg_(0.3)Nd_(x)Fe_(2-x)O_(4)(where,x=0,0,0,01,0,02)ferrite nanoparticles by employing the sol-gel auto-combustion technique.The X-ray diffraction(XRD)pattern suggests the formation of a pure cubic structure,without any impurity phase,with an Fd3m space group at room temperature.With increasing doping amount,the crystallite size is reported as 35-41 nm,while the lattice parameters rise from 0.8381 to 0.8395 nm.Field emission scanning electron microscopy(FESEM)images show the formation of spherical grains with agglomerated morphology in all the samples,with grain sizes ranging from 49 to 103 nm.Energy dispersive X-ray spectroscopy(EDX)and elemental mapping investigation confirm the chemical purity of all the samples.Fourier transform infrared(FTIR)analysis shows the presence of two prominent peaks around 440 and 560 cm^(-1)that correspond to the octahedral and tetrahedral positions.In addition,the existence of five Raman active vibratio nal modes in all produced specimens again confirms the structural purity of all the samples.The M-H curve shows that saturation magnetization(M_(s))first increases from 14.98 to 28.22 emu/g and then decreases to 18.98emu/g with increasing doping amount.This is due to the A-B type super-exchange interaction for the synthesized samples.The variation in coercivity(H_(c))and magnetic anisotropy(K_(1))suggest the thermal stability of all the samples and can be utilized in transformers and solenoids.
基金financially supported by the Key Project of Sichuan provincial Education office(No.13ZA0183)Applied Basic Research Programs of Sichuan Provincial Science and Technology Office(No.2014JY0059)+1 种基金Foundation of Youth Science and Technology Innovation Team of Sichuan Province(No.2015TD0007)Program for New Century Excellent Talents in University of Ministof Education of China(No.NCET-13-0983)
文摘In this work, ZnSn（OH）6with a cubic structure is successfully synthesized by one-step hydrothermal method without any catalyst. The response and recovery characteristics of gas sensing were investigated against various gases via quartz crystal microbalance（QCM） at room temperature. The sensor exhibited high sensitivity and good selectivity toward CO gas. Moreover, a linear dependence of log^（àDelta F）about CO concentration was obtained. It is demonstrated that the QCM sensor coated cubic ZnSn（OH）6could be a suitable candidate for detecting CO.
基金Supported by the National Natural Science Foundation of China(Nos.20401015 and 50574082)Beijing(China) Municipal Natural Science Foundation(No.2082022)the Innovation Project of the Chinese Academy of Sciences(Nos.CXJJ-171 and CXJJ-210)
文摘1 Introduction Since its first discovery in 1992, ordered mesoporous silica material with large pore size, high surface area, and high pore volume has attracted great attention for the potentially wide application in catalysis, adsorption, separation, and ion exchange, etc. However, the poor hydrothermal stability of mesoporous silica has limited its wide application in industry. Therefore, in the last 10 years, many studies have been dedicated to improving the hydrothermal stability of mesoporous silica. Xiao et al.
文摘A three-dimensional (3D) dusty plasma crystalline with cubic configurations is considered.We calculate the interaction between particles up to distance (√2)a,implying the second-neighbor interactions for the simple cubic structure,the third-neighbor interactions for the body-centered cubic structure,and the forth-neighbor interactions the for face-centered cubic structure.Longitudinal and transverse dispersion relations are derived in arbitrary directions.The dispersion relations are studied in special directions,i.e.(1,0,0),(1,1,0)/(√2),and (1,1,1)/(√3).Study of dispersion relations with more neighbor interactions show that in some cases the results change physically.
