The optimal attitude control of an underactuated spacecraft is investigated in this paper. The flywheels of the spacecraft can somehow only provide control inputs in two independent directions. The dynamic equations a...The optimal attitude control of an underactuated spacecraft is investigated in this paper. The flywheels of the spacecraft can somehow only provide control inputs in two independent directions. The dynamic equations are formulated for the spacecraft under a nonholonomic constraint resulting from the constant time-rate of the total angular momentum of the system. The reorientation of such underactuated spacecraft is transformed into an optimal control problem. A genetic algorithm is proposed to derive the control laws of the two flywheels angle velocity inputs. The control laws are approximated by the discrete orthogonal wavelets. The numerical simulations indicate that the genetic algorithm with the wavelet approximation is an effective approach to deal with the optimal reorientation of underactuated spacecraft.展开更多
The present paper investigates the chaotic attitude dynamics and reorientation maneuver for completely viscous liquid-filled spacecraft with flexible appendage. All of the equations of motion are derived by using Lagr...The present paper investigates the chaotic attitude dynamics and reorientation maneuver for completely viscous liquid-filled spacecraft with flexible appendage. All of the equations of motion are derived by using Lagrangian mechanics and then transformed into a form consisting of an unperturbed part plus perturbed terms so that the system's nonlinear characteristics can be exploited in phase space. Emphases are laid on the chaotic attitude dynamics produced from certain sets of physical parameter values of the spacecraft when energy dissipation acts to derive the body from minor to major axis spin. Numerical solutions of these equations show that the attitude dynamics of liquid-filled flexible spacecraft possesses characteristics common to random, non- periodic solutions and chaos, and it is demonstrated that the desired reorientation maneuver is guaranteed by using a pair of thruster impulses. The control strategy for reorientation maneuver is designed and the numerical simulation results are presented for both the uncontrolled and controlled spins transition.展开更多
Depletion-induced stress change causes the redistribution of stress field in reservoirs,which can lead to the reorientation of principal stresses.Stress reorientation has a direct impact on fracture propagation of inf...Depletion-induced stress change causes the redistribution of stress field in reservoirs,which can lead to the reorientation of principal stresses.Stress reorientation has a direct impact on fracture propagation of infill wells.To understand the effect of stress reorientation on the propagation of infill well’s fractures,an integrated simulation workflow that combines the reservoir flow calculation and the infill well hydraulic fracturing modeling is adopted.The reservoir simulation is computed to examine the relationship between the extent of stress reversal region and reservoir properties.Then,the hydraulic fracturing model considering the altered stress field for production is built to characterize the stress evolution of secondary fracturing.Numerical simulations show that stress reorientation may occur due to the decreasing of the horizontal stresses in an elliptical region around the parent well.Also,the initial stress difference is the driving factor for stress reorientation.However,the bottom hole pressure,permeability and other properties connected with fluid flow control timing of the stress reorientation.The decrease of the horizontal stresses around the parent well lead to asymmetrical propagation of a hydraulic fracture of the infill well.The study provides insights on understanding the influence of stress reorientation to the infill well fracturing treatment and interference between parent and infill wells.展开更多
In this work,we report the reorientation of magnetization by spin-orbit torque(SOT)in YIG/Pt bilayers.The SOT is investigated by measuring the spin Hall magnetoresistance(SMR),which is highly sensitive to the directio...In this work,we report the reorientation of magnetization by spin-orbit torque(SOT)in YIG/Pt bilayers.The SOT is investigated by measuring the spin Hall magnetoresistance(SMR),which is highly sensitive to the direction of magnetic moment of YIG.An external in-plane rotating magnetic field which is applied to the YIG/Pt bilayers,and the evolutions of SMR under different injected currents in the Pt layer,result in deviation of SMR curve from the standard shape.We conclude that the SOT caused by spin accumulation near the interface between YIG and Pt can effectively reorient the inplane magnetic moment of YIG.This discovery provides an effective way to modulate YIG magnetic moments by electrical methods.展开更多
The temperature-driven spin reorientation transition of magnetron sputtered Ni/Si (111) systems has been studied. The relationship between ac initial susceptibility and temperature of nickel films with different thi...The temperature-driven spin reorientation transition of magnetron sputtered Ni/Si (111) systems has been studied. The relationship between ac initial susceptibility and temperature of nickel films with different thicknesses shows that the magnetization orientation changes from in-plane to out-of-plane with the increase of temperature. The temperature dependence of mugnetoelastic, magneto-crystalline, and magnetostatic anisotropies determines the direction of the reorientation transition. The temperature-driven spin reorientation transition is supported by Hall coefficient measurements which show that its temperature dependence is similar to that of susceptibility.展开更多
DyTiFe_(11) compound is a ferromagnetic substance.It has tetragonal body-centered ThMn_(12)-type crystallographic structure.At room temperature,the easy magnetization direction is the c-axis.A spin reorientation begin...DyTiFe_(11) compound is a ferromagnetic substance.It has tetragonal body-centered ThMn_(12)-type crystallographic structure.At room temperature,the easy magnetization direction is the c-axis.A spin reorientation begins to appear at about 175K.The contribution of Fe sublattice to magnetocrystalline anisotropy was determined by experiments and that of Dy sublattice was obtained by using single ion model calculation.Results show that the spin reorientation arises from the competition of anisotropy between Fe and Dy sublattices.展开更多
INTRODUCTION The conformational state transition of polymer chains relates to crystallization processes, migration ofthe chains in solution, fluctuation of the end-to-end distance of random coils, and the relaxation a...INTRODUCTION The conformational state transition of polymer chains relates to crystallization processes, migration ofthe chains in solution, fluctuation of the end-to-end distance of random coils, and the relaxation and phasetransitions of polymers. A description of the conformational state transition requires questions about; 1) howmany stable conformational states for a specific σ bond; 2) the barriers between the states; 3) the mechanismof the conformational transition; 4) any cooperative behavior during the transition. Flory and his coworkers展开更多
The effects of Al substitution for Fe on the structure, magnetics, magnetostriction, anisotropy and spin reorientation of a series of Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 alloys (x=0.05, 0.1, 0.15, 0.2, 0.25, 0.3) at room te...The effects of Al substitution for Fe on the structure, magnetics, magnetostriction, anisotropy and spin reorientation of a series of Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 alloys (x=0.05, 0.1, 0.15, 0.2, 0.25, 0.3) at room temperature have been investigated. The alloys of Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 substantially retain MgCu2-type C-15 cubic Laves phase structure when x<0.2. The mixed phases appear with x = 0.2, and cubic Laves phase decreases with increasing x. The magnetostriction of the Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 alloys decreases drastically with increasing x and the giant magnetostrictive effect disappears for x > 0.15. Fortunately, a small amount of Al substitution is beneficial to a decrease in the magnetocrystalline anisotropy. The spin reorientation temperature decreases with increasing x. The analysis of the Mssbauer spectra indicates that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry with the increase of Al concentration x, namely, spin reorientation, resulting in the change of macroscopical magnetic properties and magnetostriction. The hyperfine field decreases, but the isomer shifts increases with Al concentration increasing and the quadruple splitting QS shows a weak concentration dependence.展开更多
Microtubule reorientation is a long-standing observation that has been implicated in regulating the inhibitory effect of ethylene on axial elongation of plant cells. However, the signaling mechanism underlying ethylen...Microtubule reorientation is a long-standing observation that has been implicated in regulating the inhibitory effect of ethylene on axial elongation of plant cells. However, the signaling mechanism underlying ethylene-induced microtubule reorientation has re- mained elusive. Here, we reveal, by live confocal imaging and kinetic root elongation assays, that the time courses of ethylene-induced microtubule reorientation and root elongation inhibition are highly correlated, and that microtubule reorientation is required for the full responsiveness of root elongation to ethylene treatment. Our genetic analysis demonstrated that the effect of ethylene on microtubule orientation and root elongation is mainly transduced through the canonical linear ethylene signaling pathway. By using pharmacological and genetic analyses, we demonstrate further that the TIR1/AFBs-Aux/IAAs-ARFs auxin signaling pathway, but not the ABP1-ROP6-RlC1 auxin signaling branch, is essential for ethylene-induced microtubule reorientation and root elongation inhibition. Together, these findings offer evidence for the functional significance and elucidate the signaling mechanism for ethylene-induced microtubule reorientation in fast root elongation inhibition in Arabidopsis.展开更多
A constitutive model is developed for the transformation, reorientation and plastic deformation of shape memory alloys (SMAs). It is based on the concept that an SMA is a mixture composed of austenite and martensite...A constitutive model is developed for the transformation, reorientation and plastic deformation of shape memory alloys (SMAs). It is based on the concept that an SMA is a mixture composed of austenite and martensite, the volume fraction of each phase is transformable with the change of applied thermal-mechanical loading, and the constitutive behavior of the SMA is the combination of the individual behavior of its two phases. The deformation of the martensite is separated into elastic, thermal, reorientation and plastic parts, and that of the austenite is separated into elastic, thermal and plastic parts. Making use of the Tanaka's transformation rule modified by taking into account the effect of plastic deformation, the constitutive model of the SMA is obtained. The ferroelasticity, pseudoelastieity and shape memory effect of SMA Au-47.5 at.%Cd, and the pseudoelasticity and shape memory effect as well as plastic deformation and its effect of an NiTi SMA, are analyzed and compared with experimental results.展开更多
We discuss some key aspects of our recent theoretical work on water reorientation dynamics,which is important in a wide range of phenomena,including aqueous phase chemical reactions,protein folding,and drug binding to...We discuss some key aspects of our recent theoretical work on water reorientation dynamics,which is important in a wide range of phenomena,including aqueous phase chemical reactions,protein folding,and drug binding to proteins and DNA. It is shown that,contrary to the standard conception that these dynamics are diffusional,the reorientation of a water molecule occurs by sudden,large amplitude angular jumps. The mechanism involves the exchange of one hydrogen bond for another by the reorienting water,and the process can be fruitfully viewed as a chemical reaction. The results for reorientation times,which can be well described analytically,are discussed in the context of the molecular level interpretation of recent ultrafast infrared spectroscopic results,focusing on the concepts of structure making/breaking and solvent 'icebergs'.展开更多
Nd12.3Fe81.7-xZrxB6.0 (x=0,1.5) and (NdDyTb)12.3(FeZrNbCu)81.7-yCoyB6.0 (y=0,12) ribbons were prepared by melt spinning at 22 m/s and subsequent annealing.The influences of Zr,Dy/Tb and Co substitutions on magnetic pr...Nd12.3Fe81.7-xZrxB6.0 (x=0,1.5) and (NdDyTb)12.3(FeZrNbCu)81.7-yCoyB6.0 (y=0,12) ribbons were prepared by melt spinning at 22 m/s and subsequent annealing.The influences of Zr,Dy/Tb and Co substitutions on magnetic properties and spin reorientation transitions of nanophase Nd2Fe14B have been systematically investigated.Compared with Zr-free sample,the remanence,intrinsic coercivity and maximum energy product for Nd12.3Fe80.2Zr1.5B6.0 ribbon increase by 10.8 %,17.8 % and 60.2 %,respectively.The significant improvement of magnetic properties originates from the finer grains of the sample by introducing Zr,which leads to the stronger exchange coupling between neighboring grains.The intrinsic coercivity for (DyTb)-substituted ribbon is significantly increased although the remanence is reduced,which could be compensated by the substitution of Co for Fe.The spin reorientation temperature Tsr of nanocrystalline Nd2Fe14B alloys was determined by measuring the ac magnetic susceptibility.It was found to be lower than that of bulk Nd2Fe14B.The substitutions of Zr,Dy/Tb and Co result in reduction of Tsr.The smaller the grain size,the lower the Tsr will be.Influence of spin reorientation on magnetization characteristics of nanophase Nd2Fe14B was discussed.展开更多
This study investigated a peculiar phenomenon of self-reorientation of thermally formed R phase in nanocrystalline Ti_(50)Ni_(45.5)Fe_(4.5)by means of in-situ syn-chrotron high energy X-ray diffraction(HE-XRD).Two sam...This study investigated a peculiar phenomenon of self-reorientation of thermally formed R phase in nanocrystalline Ti_(50)Ni_(45.5)Fe_(4.5)by means of in-situ syn-chrotron high energy X-ray diffraction(HE-XRD).Two samples with different average grain sizes of 40 and 90 nm were investigated.R phase in the 40-nm grain size sample was found to self-reorient gradually upon cooling,whereas the same phenomenon did not occur in the 90-nm grain size sample.This self-reorientation process is attributed to the development and evolution of an internal stress anisotropy caused by the second order continuous lattice distortion of R phase upon further cooling in the small nanograined matrix,which lacks the self-accommodation mechanism for internal stress cancellation.展开更多
The effect of Pr substitution for Dy on the magnetic and magnetostrictive properties, anisotropy, spin reorientation and Mssbauer effect of a series of Tb0.3Dy0.7-xPrx(Fe0.9Al0.1)1.95 (x=0,0.1,0.20,0.25,0.30,0.35) a...The effect of Pr substitution for Dy on the magnetic and magnetostrictive properties, anisotropy, spin reorientation and Mssbauer effect of a series of Tb0.3Dy0.7-xPrx(Fe0.9Al0.1)1.95 (x=0,0.1,0.20,0.25,0.30,0.35) alloys at room temperature have been investigated. It was found that a small amount of Pr substitution is beneficial to a decrease in the magnetocrystalline anisotropy for the Tb0.3Dy0.7-xPrx(Fe0.9Al0.1)1.95 alloys. The magnetostriction decreases drastically with increasing x and the magnetostrictive effect disappears for x>0.2. However, the magnetostriction exhibits a slightly bigger value at x=0.1 than the free alloys and is saturated more easily with the magnetic field H. The saturation magnetization and Curie temperature decrease monotonously, but the spontaneous magnetostriction increases linearly with increasing x, whereas the spin reorientation temperature increases first, then decreases rapidly and reaches the maximum at x=0.1. The analysis of Mssbauer spectra indicated that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry with the Pr concentration x, namely spin reorientation. Compared with Al substitution for Fe, the effect of Pr substitution for Dy on spin reorientation is relatively small. The hyperfine field increases with Pr concentration increasing, and the isomer shifts and the quadrupole splitting (QS) show weak concentration dependence.展开更多
Twinning stress is known to be a critical factor for the actuating performance of magnetic shape memory alloys because of the harmful deterioration of their magnetic field-induced strain effect.However,the intrinsic o...Twinning stress is known to be a critical factor for the actuating performance of magnetic shape memory alloys because of the harmful deterioration of their magnetic field-induced strain effect.However,the intrinsic origin of the high twinning stress is still in debate.In this work,we firstly fill this gap by precisely probing the reorientation behaviors of A-C and A-B two common macro-twin interfaces under the stimulus of uniaxial compression in-situ transmission electron microscope.The grain boundary is proved to be the main reason for large twinning stress.The twinning stress of the A-C and A-B type interfaces quantitatively are~0.69 and 1.27 MPa within the plate respectively.The A-C type interface evidently has smaller twinning stress and larger deformation variable than the A-B interface.Under the action of compression,not only the orientations of the crystals have changed,but also the roles of the major and minor lamellae have changed for both interfaces due to the movements of twinning dislocations.Combining insitu and quasi in-situ electron diffraction data,the reorientation process is clearly and intuitively shown by the stereographic projection.Atomic models and the theory of dislocation motion are proposed to phenomenologically clarify the intrinsic mechanism.This work is believed to not only provide a deeper understanding of the deformation mechanism of magnetic shape memory alloys under uniaxial compression testing,but also discover that compression training is not the mechanical training way to decrease the twinning stress of non-modulated martensite in single crystal shape memory alloys.展开更多
Spin reorientation transition (SRT) has attracted substantial attention due to its important role in the ultrafast control of spins. However, the transition temperature is usually too low for its practical application...Spin reorientation transition (SRT) has attracted substantial attention due to its important role in the ultrafast control of spins. However, the transition temperature is usually too low for its practical applications. Here, we demonstrate the ability to modulate the SRT temperature in PrFe_(1−x)Mn_(x)O_(3) single crystals from 196 K to 317 K across the room temperature by varying the Mn concentration. Interestingly, the Γ_(4) to Γ_(1) spin reorientation of the Mn-doped PrFeO_(3) is distinct from the Γ_(4) to Γ_(2) spin reorientation transition as in the parent material. Because of the coupling between rare-earth ions and transition-metal ions in determining the SRT temperature, the demonstrated control scheme of spin reorientation transition temperature by Mn-doping is expected to be used in temperature control magnetic switching devices and applicable to many other rare-earth orthoferrites.展开更多
Upon massive generation of anisotropic grains of azo dye methyl orange in a gelatin film exposed to active polarized light, a cluster of micro crystals with optical axes of similar orientations has been produced. The ...Upon massive generation of anisotropic grains of azo dye methyl orange in a gelatin film exposed to active polarized light, a cluster of micro crystals with optical axes of similar orientations has been produced. The anisotropy observed has been found to disappear under exposure to active natural light.展开更多
Natural fish scales demonstrate outstanding mechanical efficiency owing to their elaborate architectures and thereby may serve as ideal prototypes for the architectural design of man-made materials.Here bioinspired ma...Natural fish scales demonstrate outstanding mechanical efficiency owing to their elaborate architectures and thereby may serve as ideal prototypes for the architectural design of man-made materials.Here bioinspired magnesium composites with fish-scale-like orthogonal plywood and double-Bouligand architectures were developed by pressureless infiltration of a magnesium melt into the woven contextures of continuous titanium fibers.The composites exhibit enhanced strength and work-hardening ability compared to those estimated from a simple mixture of their constituents at ambient to elevated temperatures.In particular,the double-Bouligand architecture can effectively deflect cracking paths,alleviate strain localization,and adaptively reorient titanium fibers within the magnesium matrix during the deformation of the composite,representing a successful implementation of the property-optimizing mechanisms in fish scales.The strength of the composites,specifically the effect of their bioinspired architectures,was interpreted based on the adaptation of classical laminate theory.This study may offer a feasible approach for developing new bioinspired metal-matrix composites with improved performance and provide theoretical guidance for their architectural designs.展开更多
G-quadruplexes(GQs) are guanine-rich, non-canonical nucleic acid structures that play fundamental roles in biological processes. Their structure and function are strongly influenced by their hydration shells. Although...G-quadruplexes(GQs) are guanine-rich, non-canonical nucleic acid structures that play fundamental roles in biological processes. Their structure and function are strongly influenced by their hydration shells. Although extensively studied through various experimental and computational methods, hydration patterns near DNA remain under debate due to the chemically and topologically heterogeneous nature of the exposed surface. In this work, we employed all-atom molecular dynamics(MD) simulation to study the hydration patterns of GQ DNA. The Drude oscillator model was used in MD simulation as a computationally efficient method for modeling electronic polarization in DNA ion solutions. Hydration structure was analyzed in terms of radial distribution functions and high-density three-dimensional hydration sites. Analysis of hydration dynamics focused on self-diffusion rates and orientation time correlation at different structural regions of GQ DNA.The results show highly heterogeneous hydration patterns in both structure and dynamics;for example, there are several insular high-density sites in the inner channel, and ‘spine of water’ in the groove. For water inside the loop, anomalous diffusion is present over a long time scale, but for water around the phosphate group and groove, diffusion becomes normal after ~30 ps. These essentially correspond to deeply buried structural water and strong interaction with DNA, respectively.展开更多
The effects of Nd doping on the microstructures and magnetic properties of Sm_(1-x)Nd_(x)(Co_(0.695)Fe_(0.2)Cu_(0.08)Zr_(0.025))7.2(x = 0, 0.3, 0.5, 0.7, 1.0) permanent magnets are studied. The scanning electron micro...The effects of Nd doping on the microstructures and magnetic properties of Sm_(1-x)Nd_(x)(Co_(0.695)Fe_(0.2)Cu_(0.08)Zr_(0.025))7.2(x = 0, 0.3, 0.5, 0.7, 1.0) permanent magnets are studied. The scanning electron microscope(SEM) analysis of the solid solution states of the magnets shows that with the increase of Nd content, the distribution of elements becomes inhomogeneous and miscellaneous phase will be generated. Positive temperature coefficient of coercivity(β) appears in each of the samples with x = 0.3, 0.5, and 0.7. The corresponding positive β temperatures are in ranges of about 70 K–170 K,60 K–260 K, 182 K–490 K for the samples with x = 0.3, 0.5, and 0.7, respectively. Thermomagnetic analysis shows that spin-reorientation-transition(SRT) of the cell boundary phase is responsible for this phenomenon. On the basis of this discovery, the Sm_(0.7)Nd_(0.3)(Co_(0.695)Fe_(0.2)Cu_(0.08)Zr_(0.025))7.2magnet possessing thermal stability with β ≈-0.002 %/K at the temperature in a range of 150 K–200 K is obtained.展开更多
基金supported by the National Natural Science Foundation of China (10772020)
文摘The optimal attitude control of an underactuated spacecraft is investigated in this paper. The flywheels of the spacecraft can somehow only provide control inputs in two independent directions. The dynamic equations are formulated for the spacecraft under a nonholonomic constraint resulting from the constant time-rate of the total angular momentum of the system. The reorientation of such underactuated spacecraft is transformed into an optimal control problem. A genetic algorithm is proposed to derive the control laws of the two flywheels angle velocity inputs. The control laws are approximated by the discrete orthogonal wavelets. The numerical simulations indicate that the genetic algorithm with the wavelet approximation is an effective approach to deal with the optimal reorientation of underactuated spacecraft.
基金supported by the National Natural Science Foundation of China (10572022, 10772026)
文摘The present paper investigates the chaotic attitude dynamics and reorientation maneuver for completely viscous liquid-filled spacecraft with flexible appendage. All of the equations of motion are derived by using Lagrangian mechanics and then transformed into a form consisting of an unperturbed part plus perturbed terms so that the system's nonlinear characteristics can be exploited in phase space. Emphases are laid on the chaotic attitude dynamics produced from certain sets of physical parameter values of the spacecraft when energy dissipation acts to derive the body from minor to major axis spin. Numerical solutions of these equations show that the attitude dynamics of liquid-filled flexible spacecraft possesses characteristics common to random, non- periodic solutions and chaos, and it is demonstrated that the desired reorientation maneuver is guaranteed by using a pair of thruster impulses. The control strategy for reorientation maneuver is designed and the numerical simulation results are presented for both the uncontrolled and controlled spins transition.
基金the support provided by the Scientific Research and Technology Development Project of CNPC(Grant No.kt2017-19-01-1)the National Natural Science Foundation of China(Grant No.41772286,No.42077247 and No.42002271)+2 种基金Petro China Innovation Foundation(Grant No.2018D-5007-0202)Project funded by China Postdoctoral Science Foundation(Grant No.2021T140514)Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.Z020009)。
文摘Depletion-induced stress change causes the redistribution of stress field in reservoirs,which can lead to the reorientation of principal stresses.Stress reorientation has a direct impact on fracture propagation of infill wells.To understand the effect of stress reorientation on the propagation of infill well’s fractures,an integrated simulation workflow that combines the reservoir flow calculation and the infill well hydraulic fracturing modeling is adopted.The reservoir simulation is computed to examine the relationship between the extent of stress reversal region and reservoir properties.Then,the hydraulic fracturing model considering the altered stress field for production is built to characterize the stress evolution of secondary fracturing.Numerical simulations show that stress reorientation may occur due to the decreasing of the horizontal stresses in an elliptical region around the parent well.Also,the initial stress difference is the driving factor for stress reorientation.However,the bottom hole pressure,permeability and other properties connected with fluid flow control timing of the stress reorientation.The decrease of the horizontal stresses around the parent well lead to asymmetrical propagation of a hydraulic fracture of the infill well.The study provides insights on understanding the influence of stress reorientation to the infill well fracturing treatment and interference between parent and infill wells.
基金Project supported by the Natural Science Foundation of Shaanxi Province,China(Grant No.2020JM-088)the National Natural Science Foundation of China(Grant Nos.51572222,51701158,and 51872241)the Fundamental Research Funds for the Central Universities,China(Grant Nos.3102017jc01001 and 310201911cx044).
文摘In this work,we report the reorientation of magnetization by spin-orbit torque(SOT)in YIG/Pt bilayers.The SOT is investigated by measuring the spin Hall magnetoresistance(SMR),which is highly sensitive to the direction of magnetic moment of YIG.An external in-plane rotating magnetic field which is applied to the YIG/Pt bilayers,and the evolutions of SMR under different injected currents in the Pt layer,result in deviation of SMR curve from the standard shape.We conclude that the SOT caused by spin accumulation near the interface between YIG and Pt can effectively reorient the inplane magnetic moment of YIG.This discovery provides an effective way to modulate YIG magnetic moments by electrical methods.
基金supported by the National Natural Science Foundation of China (Grant No 10334080)
文摘The temperature-driven spin reorientation transition of magnetron sputtered Ni/Si (111) systems has been studied. The relationship between ac initial susceptibility and temperature of nickel films with different thicknesses shows that the magnetization orientation changes from in-plane to out-of-plane with the increase of temperature. The temperature dependence of mugnetoelastic, magneto-crystalline, and magnetostatic anisotropies determines the direction of the reorientation transition. The temperature-driven spin reorientation transition is supported by Hall coefficient measurements which show that its temperature dependence is similar to that of susceptibility.
文摘DyTiFe_(11) compound is a ferromagnetic substance.It has tetragonal body-centered ThMn_(12)-type crystallographic structure.At room temperature,the easy magnetization direction is the c-axis.A spin reorientation begins to appear at about 175K.The contribution of Fe sublattice to magnetocrystalline anisotropy was determined by experiments and that of Dy sublattice was obtained by using single ion model calculation.Results show that the spin reorientation arises from the competition of anisotropy between Fe and Dy sublattices.
文摘INTRODUCTION The conformational state transition of polymer chains relates to crystallization processes, migration ofthe chains in solution, fluctuation of the end-to-end distance of random coils, and the relaxation and phasetransitions of polymers. A description of the conformational state transition requires questions about; 1) howmany stable conformational states for a specific σ bond; 2) the barriers between the states; 3) the mechanismof the conformational transition; 4) any cooperative behavior during the transition. Flory and his coworkers
基金supported by the National Natural Science Foundation of China (Grant No. 10574059)the Natural Science Foundation of Gansu Province (Grant No. 0710RJZA074)+2 种基金the Scientific Research Project of Bureau of Education of Gansu Province (Grant No. 0711B-04)the Key Project of the Science and Technology Research of Ministry of Education (Grant No. 209127)the "Qing Lan" Talent Engineering Funds of Lanzhou Jiaotong University
文摘The effects of Al substitution for Fe on the structure, magnetics, magnetostriction, anisotropy and spin reorientation of a series of Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 alloys (x=0.05, 0.1, 0.15, 0.2, 0.25, 0.3) at room temperature have been investigated. The alloys of Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 substantially retain MgCu2-type C-15 cubic Laves phase structure when x<0.2. The mixed phases appear with x = 0.2, and cubic Laves phase decreases with increasing x. The magnetostriction of the Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 alloys decreases drastically with increasing x and the giant magnetostrictive effect disappears for x > 0.15. Fortunately, a small amount of Al substitution is beneficial to a decrease in the magnetocrystalline anisotropy. The spin reorientation temperature decreases with increasing x. The analysis of the Mssbauer spectra indicates that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry with the increase of Al concentration x, namely, spin reorientation, resulting in the change of macroscopical magnetic properties and magnetostriction. The hyperfine field decreases, but the isomer shifts increases with Al concentration increasing and the quadruple splitting QS shows a weak concentration dependence.
基金supported by grants from the National Natural Science Foundation of China(31700239)to Y.W.and(91740203)to H.G.China Postdoctoral Science Foundation(2012M510263 and 2014M560845)to Y.W
文摘Microtubule reorientation is a long-standing observation that has been implicated in regulating the inhibitory effect of ethylene on axial elongation of plant cells. However, the signaling mechanism underlying ethylene-induced microtubule reorientation has re- mained elusive. Here, we reveal, by live confocal imaging and kinetic root elongation assays, that the time courses of ethylene-induced microtubule reorientation and root elongation inhibition are highly correlated, and that microtubule reorientation is required for the full responsiveness of root elongation to ethylene treatment. Our genetic analysis demonstrated that the effect of ethylene on microtubule orientation and root elongation is mainly transduced through the canonical linear ethylene signaling pathway. By using pharmacological and genetic analyses, we demonstrate further that the TIR1/AFBs-Aux/IAAs-ARFs auxin signaling pathway, but not the ABP1-ROP6-RlC1 auxin signaling branch, is essential for ethylene-induced microtubule reorientation and root elongation inhibition. Together, these findings offer evidence for the functional significance and elucidate the signaling mechanism for ethylene-induced microtubule reorientation in fast root elongation inhibition in Arabidopsis.
基金Project supported by the National Natural Science Foundation of China (No. 10976032)
文摘A constitutive model is developed for the transformation, reorientation and plastic deformation of shape memory alloys (SMAs). It is based on the concept that an SMA is a mixture composed of austenite and martensite, the volume fraction of each phase is transformable with the change of applied thermal-mechanical loading, and the constitutive behavior of the SMA is the combination of the individual behavior of its two phases. The deformation of the martensite is separated into elastic, thermal, reorientation and plastic parts, and that of the austenite is separated into elastic, thermal and plastic parts. Making use of the Tanaka's transformation rule modified by taking into account the effect of plastic deformation, the constitutive model of the SMA is obtained. The ferroelasticity, pseudoelastieity and shape memory effect of SMA Au-47.5 at.%Cd, and the pseudoelasticity and shape memory effect as well as plastic deformation and its effect of an NiTi SMA, are analyzed and compared with experimental results.
基金was supported in part by National Science Foundation (Grant Nos. CHE-0417570 and CHE-0750477)
文摘We discuss some key aspects of our recent theoretical work on water reorientation dynamics,which is important in a wide range of phenomena,including aqueous phase chemical reactions,protein folding,and drug binding to proteins and DNA. It is shown that,contrary to the standard conception that these dynamics are diffusional,the reorientation of a water molecule occurs by sudden,large amplitude angular jumps. The mechanism involves the exchange of one hydrogen bond for another by the reorienting water,and the process can be fruitfully viewed as a chemical reaction. The results for reorientation times,which can be well described analytically,are discussed in the context of the molecular level interpretation of recent ultrafast infrared spectroscopic results,focusing on the concepts of structure making/breaking and solvent 'icebergs'.
文摘Nd12.3Fe81.7-xZrxB6.0 (x=0,1.5) and (NdDyTb)12.3(FeZrNbCu)81.7-yCoyB6.0 (y=0,12) ribbons were prepared by melt spinning at 22 m/s and subsequent annealing.The influences of Zr,Dy/Tb and Co substitutions on magnetic properties and spin reorientation transitions of nanophase Nd2Fe14B have been systematically investigated.Compared with Zr-free sample,the remanence,intrinsic coercivity and maximum energy product for Nd12.3Fe80.2Zr1.5B6.0 ribbon increase by 10.8 %,17.8 % and 60.2 %,respectively.The significant improvement of magnetic properties originates from the finer grains of the sample by introducing Zr,which leads to the stronger exchange coupling between neighboring grains.The intrinsic coercivity for (DyTb)-substituted ribbon is significantly increased although the remanence is reduced,which could be compensated by the substitution of Co for Fe.The spin reorientation temperature Tsr of nanocrystalline Nd2Fe14B alloys was determined by measuring the ac magnetic susceptibility.It was found to be lower than that of bulk Nd2Fe14B.The substitutions of Zr,Dy/Tb and Co result in reduction of Tsr.The smaller the grain size,the lower the Tsr will be.Influence of spin reorientation on magnetization characteristics of nanophase Nd2Fe14B was discussed.
基金financially supported by the National Natural Science Foundation of China (Nos.51731010, 51831006,51871241,51971243 and 91963112)Australian Research Council (No.DP190102990)
文摘This study investigated a peculiar phenomenon of self-reorientation of thermally formed R phase in nanocrystalline Ti_(50)Ni_(45.5)Fe_(4.5)by means of in-situ syn-chrotron high energy X-ray diffraction(HE-XRD).Two samples with different average grain sizes of 40 and 90 nm were investigated.R phase in the 40-nm grain size sample was found to self-reorient gradually upon cooling,whereas the same phenomenon did not occur in the 90-nm grain size sample.This self-reorientation process is attributed to the development and evolution of an internal stress anisotropy caused by the second order continuous lattice distortion of R phase upon further cooling in the small nanograined matrix,which lacks the self-accommodation mechanism for internal stress cancellation.
基金Supported by the National Natural Science Foundation of China (Grant No.10574059)the Natural Science Foundation of Gansu Province (Grant No.0710RJZA074)+1 种基金the Second Scientific Research Project of Bureau of Gansu Education‘Qing Lan’ Talent Engineering Funds of Lanzhou Jiaotong University
文摘The effect of Pr substitution for Dy on the magnetic and magnetostrictive properties, anisotropy, spin reorientation and Mssbauer effect of a series of Tb0.3Dy0.7-xPrx(Fe0.9Al0.1)1.95 (x=0,0.1,0.20,0.25,0.30,0.35) alloys at room temperature have been investigated. It was found that a small amount of Pr substitution is beneficial to a decrease in the magnetocrystalline anisotropy for the Tb0.3Dy0.7-xPrx(Fe0.9Al0.1)1.95 alloys. The magnetostriction decreases drastically with increasing x and the magnetostrictive effect disappears for x>0.2. However, the magnetostriction exhibits a slightly bigger value at x=0.1 than the free alloys and is saturated more easily with the magnetic field H. The saturation magnetization and Curie temperature decrease monotonously, but the spontaneous magnetostriction increases linearly with increasing x, whereas the spin reorientation temperature increases first, then decreases rapidly and reaches the maximum at x=0.1. The analysis of Mssbauer spectra indicated that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry with the Pr concentration x, namely spin reorientation. Compared with Al substitution for Fe, the effect of Pr substitution for Dy on spin reorientation is relatively small. The hyperfine field increases with Pr concentration increasing, and the isomer shifts and the quadrupole splitting (QS) show weak concentration dependence.
基金financially supported by the National Natural Science Foundation of China(Nos.51771085,51571104,51801087,91962212 and 11874189)the Fundamental Research Funds for the Central Universities(No.lzujbky-2020–58)+1 种基金the supports from the National Natural Science Foundation of China(No.91963123)the Ten Thousand Talents Plan of Zhejiang Province of China(No.2018R52003)。
文摘Twinning stress is known to be a critical factor for the actuating performance of magnetic shape memory alloys because of the harmful deterioration of their magnetic field-induced strain effect.However,the intrinsic origin of the high twinning stress is still in debate.In this work,we firstly fill this gap by precisely probing the reorientation behaviors of A-C and A-B two common macro-twin interfaces under the stimulus of uniaxial compression in-situ transmission electron microscope.The grain boundary is proved to be the main reason for large twinning stress.The twinning stress of the A-C and A-B type interfaces quantitatively are~0.69 and 1.27 MPa within the plate respectively.The A-C type interface evidently has smaller twinning stress and larger deformation variable than the A-B interface.Under the action of compression,not only the orientations of the crystals have changed,but also the roles of the major and minor lamellae have changed for both interfaces due to the movements of twinning dislocations.Combining insitu and quasi in-situ electron diffraction data,the reorientation process is clearly and intuitively shown by the stereographic projection.Atomic models and the theory of dislocation motion are proposed to phenomenologically clarify the intrinsic mechanism.This work is believed to not only provide a deeper understanding of the deformation mechanism of magnetic shape memory alloys under uniaxial compression testing,but also discover that compression training is not the mechanical training way to decrease the twinning stress of non-modulated martensite in single crystal shape memory alloys.
基金This work was supported by the Ministry of Science and Technology of the People’s Republic of China(No.2018YFB0704402)the National Natural Science Foundation of China(NSFC,Nos.12074242,11774217,and 12074241)the Science and Technology Commission of Shanghai Municipality(No.21JC1402600).
文摘Spin reorientation transition (SRT) has attracted substantial attention due to its important role in the ultrafast control of spins. However, the transition temperature is usually too low for its practical applications. Here, we demonstrate the ability to modulate the SRT temperature in PrFe_(1−x)Mn_(x)O_(3) single crystals from 196 K to 317 K across the room temperature by varying the Mn concentration. Interestingly, the Γ_(4) to Γ_(1) spin reorientation of the Mn-doped PrFeO_(3) is distinct from the Γ_(4) to Γ_(2) spin reorientation transition as in the parent material. Because of the coupling between rare-earth ions and transition-metal ions in determining the SRT temperature, the demonstrated control scheme of spin reorientation transition temperature by Mn-doping is expected to be used in temperature control magnetic switching devices and applicable to many other rare-earth orthoferrites.
文摘Upon massive generation of anisotropic grains of azo dye methyl orange in a gelatin film exposed to active polarized light, a cluster of micro crystals with optical axes of similar orientations has been produced. The anisotropy observed has been found to disappear under exposure to active natural light.
基金the financial support by the National Key R&D Program of China under grant number 2020YFA0710404the National Natural Science Foundation of China under grant number 51871216+6 种基金the KC Wong Education Foundation(GJTD-2020-09)the Liao Ning Revitalization Talents Programthe State Key Laboratory for Modification of Chemical Fibers and Polymer Materials at Donghua Universitythe Opening Project of Jiangsu Province Key Laboratory of High-End Structural Materials under grant number hsm1801the Opening Project of National Key Laboratory of Shock Wave and Detonation Physics under grant number 6142A03203002the Youth Innovation Promotion Association CASsupported by the Multi-University Research Initiative under grant number AFOSR-FA9550-151-0009 from the Air Force Office of Scientific Research
文摘Natural fish scales demonstrate outstanding mechanical efficiency owing to their elaborate architectures and thereby may serve as ideal prototypes for the architectural design of man-made materials.Here bioinspired magnesium composites with fish-scale-like orthogonal plywood and double-Bouligand architectures were developed by pressureless infiltration of a magnesium melt into the woven contextures of continuous titanium fibers.The composites exhibit enhanced strength and work-hardening ability compared to those estimated from a simple mixture of their constituents at ambient to elevated temperatures.In particular,the double-Bouligand architecture can effectively deflect cracking paths,alleviate strain localization,and adaptively reorient titanium fibers within the magnesium matrix during the deformation of the composite,representing a successful implementation of the property-optimizing mechanisms in fish scales.The strength of the composites,specifically the effect of their bioinspired architectures,was interpreted based on the adaptation of classical laminate theory.This study may offer a feasible approach for developing new bioinspired metal-matrix composites with improved performance and provide theoretical guidance for their architectural designs.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11705160 and 11647074)。
文摘G-quadruplexes(GQs) are guanine-rich, non-canonical nucleic acid structures that play fundamental roles in biological processes. Their structure and function are strongly influenced by their hydration shells. Although extensively studied through various experimental and computational methods, hydration patterns near DNA remain under debate due to the chemically and topologically heterogeneous nature of the exposed surface. In this work, we employed all-atom molecular dynamics(MD) simulation to study the hydration patterns of GQ DNA. The Drude oscillator model was used in MD simulation as a computationally efficient method for modeling electronic polarization in DNA ion solutions. Hydration structure was analyzed in terms of radial distribution functions and high-density three-dimensional hydration sites. Analysis of hydration dynamics focused on self-diffusion rates and orientation time correlation at different structural regions of GQ DNA.The results show highly heterogeneous hydration patterns in both structure and dynamics;for example, there are several insular high-density sites in the inner channel, and ‘spine of water’ in the groove. For water inside the loop, anomalous diffusion is present over a long time scale, but for water around the phosphate group and groove, diffusion becomes normal after ~30 ps. These essentially correspond to deeply buried structural water and strong interaction with DNA, respectively.
基金supported by the National Key Research and Development Program of China (Grant Nos. 2021YFB3803003 and 2021YFB3503101)the Major Project of “Science and Technology Innovation 2025” in Ningbo, China (Grant No. 2020Z044)+1 种基金the Zhejiang Provincial Key Research and Development Program, China (Grant No. 2021C01172)the National Natural Science Funds of China (Grant No. 51601209)。
文摘The effects of Nd doping on the microstructures and magnetic properties of Sm_(1-x)Nd_(x)(Co_(0.695)Fe_(0.2)Cu_(0.08)Zr_(0.025))7.2(x = 0, 0.3, 0.5, 0.7, 1.0) permanent magnets are studied. The scanning electron microscope(SEM) analysis of the solid solution states of the magnets shows that with the increase of Nd content, the distribution of elements becomes inhomogeneous and miscellaneous phase will be generated. Positive temperature coefficient of coercivity(β) appears in each of the samples with x = 0.3, 0.5, and 0.7. The corresponding positive β temperatures are in ranges of about 70 K–170 K,60 K–260 K, 182 K–490 K for the samples with x = 0.3, 0.5, and 0.7, respectively. Thermomagnetic analysis shows that spin-reorientation-transition(SRT) of the cell boundary phase is responsible for this phenomenon. On the basis of this discovery, the Sm_(0.7)Nd_(0.3)(Co_(0.695)Fe_(0.2)Cu_(0.08)Zr_(0.025))7.2magnet possessing thermal stability with β ≈-0.002 %/K at the temperature in a range of 150 K–200 K is obtained.