Based on new high-resolution seismic profiles and existing structural and sedimentary results, a superposition deformation model for Cenozoic Bachu Uplift of northwestern Tarim Basin, northwestern China is proposed. T...Based on new high-resolution seismic profiles and existing structural and sedimentary results, a superposition deformation model for Cenozoic Bachu Uplift of northwestern Tarim Basin, northwestern China is proposed. The model presents the idea that the Bachu Uplift suffered structure superposition deformation under the dual influences of the Cenozoic uplifting of Southern Tianshan and Western Kunlun orogen, northwestern China. In the end of the Eocene (early Himalayan movement), Bachu Uplift started to be formed with the uplifting of Western Kunlun, and extended NNW into the interior of Kalpin Uplift. In the end of the Miocene (middle Himalayan movement), Bachu Uplift suffered not only the NNW structure deformation caused by the Western Kunlun uplifting, but also the NE structure deformation caused by the Southern Tianshan uplifting, and the thrust front fault of Kalpin thrust system related to the Southern Tianshan orogen intrudes southeastward into the hinterland of Bachu Uplift and extends NNE from well Pil to Xiaohaizi reservoir and Gudongshan mountain, which resulted in the strata folded and denuded strongly. In the end of the Pliocene (late Himalayan movement), the impact of Southern Yianshan orogen decreased because of the stress released with the breakthrough upward of Kalpin fault extending NE, and Bachu Uplift suffered mainly the structure deformation extending NW-NNW caused by the uplifting of Western Kunlun orogen.展开更多
The structure of a Hamiltonian matrix for a quantum chaotic system, the nuclear octupole deformation model, has been discussed in detail. The distribution of the eigenfunctions of this system expanded by the eigenstat...The structure of a Hamiltonian matrix for a quantum chaotic system, the nuclear octupole deformation model, has been discussed in detail. The distribution of the eigenfunctions of this system expanded by the eigenstates of a quantum integrable system is studied with the help of generalized Brillouin?Wigner perturbation theory. The results show that a significant randomness in this distribution can be observed when its classical counterpart is under the strong chaotic condition. The averaged shape of the eigenfunctions fits with the Gaussian distribution only when the effects of the symmetry have been removed.展开更多
In this research,mechanical stress,static strain and deformation analyses of a cylindrical pressure vessel subjected to mechanical loads are presented.The kinematic relations are developed based on higherorder sinusoi...In this research,mechanical stress,static strain and deformation analyses of a cylindrical pressure vessel subjected to mechanical loads are presented.The kinematic relations are developed based on higherorder sinusoidal shear deformation theory.Thickness stretching formulation is accounted for more accurate analysis.The total transverse deflection is divided into bending,shear and thickness stretching parts in which the third term is responsible for change of deflection along the thickness direction.The axisymmetric formulations are derived through principle of virtual work.A parametric study is presented to investigate variation of stress and strain components along the thickness and longitudinal directions.To explore effect of thickness stretching model on the static results,a comparison between the present results with the available results of literature is presented.As an important output,effect of micro-scale parameter is studied on the static stress and strain distribution.展开更多
In this study, the effect of extreme laser fields on the α decay process of ground-state even–even nuclei was investigated.Using the deformed Gamow-like model, we found that state-of-the-art lasers can cause a sligh...In this study, the effect of extreme laser fields on the α decay process of ground-state even–even nuclei was investigated.Using the deformed Gamow-like model, we found that state-of-the-art lasers can cause a slight change in the α decay penetration probability of most nuclei. In addition, we studied the correlation between the rate of change of the α decay penetration probability and angle between the directions of the laser electric field and α particle emission for different nuclei. Based on this correlation, the average effect of extreme laser fields on the half-life of many nuclei with arbitrary α particle emission angles was calculated. The calculations show that the laser suppression and promotion effects on the α decay penetration probability of the nuclei population with completely random α particle-emission directions are not completely canceled.The remainder led to a change in the average penetration probability of the nuclei. Furthermore, the possibility of achieving a higher average rate of change by altering the spatial shape of the laser is explored. We conclude that circularly polarized lasers may be helpful in future experiments to achieve a more significant average rate of change of the α decay half-life of the nuclei population.展开更多
The North China block,the western portion of the Sino- Korean Craton,is rounded byYanshanian in the north and Qinling- Dabie orogenic belts in the south.The widespread de-velopment of extensional basins in thisblock i...The North China block,the western portion of the Sino- Korean Craton,is rounded byYanshanian in the north and Qinling- Dabie orogenic belts in the south.The widespread de-velopment of extensional basins in thisblock indicates horizontal extension or continued thin-ning of a previousely thickened,unstable lithosphere throughout the Mesozoic.In this pa-per,we attempt to simulate numerically the geodynamical process of the basin formation byusing the mountain- basin evolution system.We assume thatthe formation of numeroussedi-mentary basins in the North China block is the resultofthe crustal extension,which destruc-ts rapidly the previously thickened crust.The gravitational collapse of the thickened crust ispossibly triggered by the re- orientation of the far- field stress regime,or the relaxation of theboundary resistantstress.展开更多
Compaction processes are one the most important par ts of powder forming technology. The main applications are focused on pieces for a utomotive, aeronautic, electric and electronic industries. The main goals of the c...Compaction processes are one the most important par ts of powder forming technology. The main applications are focused on pieces for a utomotive, aeronautic, electric and electronic industries. The main goals of the compaction processes are to obtain a compact with the geometrical requirements, without cracks, and with a uniform distribution of density. Design of such proc esses consist, essentially, in determine the sequence and relative displacements of die and punches in order to achieve such goals. A.B. Khoei presented a gener al framework for the finite element simulation of powder forming processes based on the following aspects; a large displacement formulation, centred on a total and updated Lagrangian formulation; an adaptive finite element strategy based on error estimates and automatic remeshing techniques; a cap model based on a hard ening rule in modelling of the highly non-linear behaviour of material; and the use of an efficient contact algorithm in the context of an interface element fo rmulation. In these references, the non-linear behaviour of powder was adequately desc ribed by the cap plasticity model. However, it suffers from a serious deficiency when the stress-point reaches a yield surface. In the flow theory of plasticit y, the transition from an elastic state to an elasto-plastic state appears more or less abruptly. For powder material it is very difficult to define the locati on of yield surface, because there is no distinct transition from elastic to ela stic-plastic behaviour. Results of experimental test on some hard met al powder show that the plastic effects were begun immediately upon loading. In such mater ials the domain of the yield surface would collapse to a point, so making the di rection of plastic increment indeterminate, because all directions are normal to a point. Thus, the classical plasticity theory cannot deal with such materials and an advanced constitutive theory is necessary. In the present paper, the constitutive equations of powder materials will be discussed via an endochronic theory of plasticity. This theory provides a unifi ed point of view to describe the elastic-plastic behaviour of material since it places no requirement for a yield surface and a ’loading function’ to disting uish between loading an unloading. Endochronic theory of plasticity has been app lied to a number of metallic materials, concrete and sand, but to the knowledge of authors, no numerical scheme of the model has been applied to powder material . In the present paper, a new approach is developed based on an endochronic rate independent, density-dependent plasticity model for describing the isothermal deformation behavior of metal powder at low homologous temperature. Although the concept of yield surface has not been explicitly assumed in endochronic theory, it is shown that the cone-cap plasticity yield surface (Fig.1), which is the m ost commonly used plasticity models for describing the behavior of powder materi al can be easily derived as a special case of the proposed endochronic theory. Fig.1 Trace of cone-cap yield function on the meridian pl ane for different relative density As large deformation is observed in powder compaction process, a hypoelastic-pl astic formulation is developed in the context of finite deformation plasticity. Constitutive equations are stated in unrotated frame of reference that greatly s implifies endochronic constitutive relation in finite plasticity. Constitutive e quations of the endochronic theory and their numerical integration are establish ed and procedures for determining material parameters of the model are demonstra ted. Finally, the numerical schemes are examined for efficiency in the model ling of a tip shaped component, as shown in Fig.2. Fig.2 A shaped tip component. a) Geometry, boundary conditio n and finite element mesh; b) density distribution at final stage of展开更多
In the process of thin-wall parts assembly for an antenna,the parts assembly deformation deviation is occurring due to the riveting assembly.In view of the riveting assembly deformation problems,it can be analyzed thr...In the process of thin-wall parts assembly for an antenna,the parts assembly deformation deviation is occurring due to the riveting assembly.In view of the riveting assembly deformation problems,it can be analyzed through transient and static simulation.In this work,the theoretical deformation model for riveting assembly is established with round head rivet.The simulation analysis for riveting deformation is carried out with the riveting assembly piece including four rivets,which comparing with the measuring points experiment results of riveting test piece through dealing with the experimental data using the point coordinate transform method and the space line fitting method.Simultaneously,the deformation deviation of the overall thin-wall parts assembly structure is analyzed through finite element simulation;and its results are verified by the measuring experiment for riveting assembly with the deformation deviation of some key points on the thin-wall parts.Through the comparison analysis,it is shown that the simulation results agree well with the experimental results,which proves the correctness and effectiveness of the theoretical analysis,simulation results and the given experiment data processing method.Through the study on the riveting assembly for thin-wall parts,it will provide a theoretical foundation for improving thin-wall parts assembly quality of large antenna in future.展开更多
The permafrost development in the Qinghai-Tibet Engineering Corridor(QTEC)is affected by natural environment changes and human engineering activities.Human engineering activities may damage the permafrost growing envi...The permafrost development in the Qinghai-Tibet Engineering Corridor(QTEC)is affected by natural environment changes and human engineering activities.Human engineering activities may damage the permafrost growing environment,which in turn impact these engineering activities.Thus high spatial-temporal resolution monitoring over the QTEC in the permafrost region is very necessary.This paper presents a method for monitoring the frozen soil area using the intermittent coherencebased small baseline subset(ICSBAS).The method can improve the point density of the results and enhance the interpretability of deformation results by identifying the discontinuous coherent points according to the coherent value of time series.Using the periodic function that models the seasonal variation of permafrost,we separate the long wavelength atmospheric delay and establish an estimation model for the frozen soil deformation.Doing this can raise the monitoring accuracy and improve the understanding of the surface deformation of the frozen soil.In this study,we process 21 PALSAR data acquired by the Alos satellite with the proposed ICSBAS technique.The results show that the frozen soil far from the QTR in the study area experiences frost heave and thaw settlement(4.7 cm to8.4 cm)alternatively,while the maximum settlement along the QTR reaches 12 cm.The interferomatric syntnetic aperture radar(InSAR)-derived results are validated using the ground leveling data nearby the Beiluhe basin.The validation results show the InSAR results have good consistency with the leveling data in displacement rates as well as time series.We also find that the deformation in the permafrost area is correlated with temperature,human activities and topography.Based on the interfering degree of human engineering activities on the permafrost environment,we divide the QTEC along the Qinghai-Tibet Railway into engineering damage zone,transition zone and natural permafrost.展开更多
Interferometric synthetic aperture radar (InSAR) images reveal deformation around northern Hejin, Shanxi Province. The small baseline subset (SBAS) approach for InSAR-derived deformation indicates that the observe...Interferometric synthetic aperture radar (InSAR) images reveal deformation around northern Hejin, Shanxi Province. The small baseline subset (SBAS) approach for InSAR-derived deformation indicates that the observed deformation pattern can be characterized by the sum of two phenomena: background subsidence from December 2003 to February 2009 with a cumulative displacement of approximately 5 cm and uplift from Febru- ary 2009 to November 2010 with a cumulative displacement of approximately 2.5 cm. Deformation modeling indicates that the local deformation was caused by the closing and opening of a sill beneath northern Hejin. The modeled sill which is approximately 5 km long, 2 km wide, is centered at 1.5 km depth. The deformation was caused by the withdrawal and influx of subsurface water.展开更多
A model suitable for describing the mechanical response of thin elastic objects is proposed to simulate the deformation of guide wires in minimally invasive interventions. The main objective of this simulation is to p...A model suitable for describing the mechanical response of thin elastic objects is proposed to simulate the deformation of guide wires in minimally invasive interventions. The main objective of this simulation is to provide doctors an opportunity to rehearse the surgery and select an optimal operation plan before the real surgery. In this model the guide wire is discretized with the multi-body representation and its elastic energy derivate from elastic theory is a polynomial function of the nodal displacements. The vascular structure is represented by a tetrahedron mesh extended from the triangular mesh of the artery, which can be extracted from the patient's CT image data. The model applies the energy decline process of the conjugate gradient method to the deformation simulation of the guide wire. Experimental results show that the polynomial relationship between elastic energy and nodal displacements tremendously simplifies the evaluation of the conjugate gradient method and significantly improves the model's efficiency. Compared with models depending on an explicit scheme for evaluation, the new model is not only non-conditionally stable but also more efficient. The model can be applied to the real-time simulation of guide wire in a vascular structure.展开更多
A new method for iris recognition using a multi-matching system based on a simplified deformable model of the human iris was proposed. The method defined iris feature points and formed the feature space based on a wa...A new method for iris recognition using a multi-matching system based on a simplified deformable model of the human iris was proposed. The method defined iris feature points and formed the feature space based on a wavelet transform. In the matching stage it worked in a crude manner. Driven by a simplified deformable iris model, the crude matching was refined. By means of such multi-matching system, the task of iris recognition was accomplished. This process can preserve the elastic deformation between an input iris image and a template and improve precision for iris recognition. The experimental results indicate the va- lidity of this method.展开更多
In this paper, we present a new deformable model for shape segmentation, which makes two modifications to the original level set implementation of deformable models.The modifications are motivated by difficulties that...In this paper, we present a new deformable model for shape segmentation, which makes two modifications to the original level set implementation of deformable models.The modifications are motivated by difficulties that we have encountered in applying deformable models to segmentation of medical images.The level set algorithm has some advantages over the classical snake deformable models.However, it could develop large gaps in the boundary and holes within the objects.Such boundary gaps and holes of objects can cause inaccurate segmentation that requires manual correction.The proposed method in this paper possesses an inherent property to detect gaps and holes within the object with a single initial contour and also does not require specific initialization.The first modification is to replace the edge detector by some area constraint, and the second modification utilizes weighted length constraint to regularize the curve under evolution.The proposed method has been applied to both synthetic and real images with promising results.展开更多
We prepared concretes(RC0, RC30, and RC100) with three different mixes. The poresize distribution parameters of RAC were examined by high-precision mercury intrusion method(MIM) and nuclear magnetic resonance(NMR...We prepared concretes(RC0, RC30, and RC100) with three different mixes. The poresize distribution parameters of RAC were examined by high-precision mercury intrusion method(MIM) and nuclear magnetic resonance(NMR) imaging. A capillary-bundle physical model with random-distribution pores(improved model, IM) was established according to the parameters, and dry-shrinkage strain values were calculated and verified. Results show that in all pore types, capillary pores, and gel pores have the greatest impacts on concrete shrinkage, especially for pores 2.5-50 and 50-100 nm in size. The median radii are 34.2, 31, and 34 nm for RC0, RC30, and RC100, respectively. Moreover, the internal micropore size distribution of RC0 differs from that of RC30 and RC100, and the pore descriptions of MIM and NMR are consistent both in theory and in practice. Compared with the traditional capillary-bundle model, the calculated results of IM have higher accuracy as demonstrated by experimental verifi cation.展开更多
A new type of deformed XXZ model was constructed and diagonalized by the coordinate Bethe ansatz method. We obtained the energy and the Bethe ansatz equations of the model and also discussed some thermodynamics of the...A new type of deformed XXZ model was constructed and diagonalized by the coordinate Bethe ansatz method. We obtained the energy and the Bethe ansatz equations of the model and also discussed some thermodynamics of the model.展开更多
Located at the forefront of the collision between the Indian and Eurasian Plates,the Tibetan Plateau experiences intense crustal movement.Traditional ground-based geodetic monitoring,such as GNSS and leveling,is chall...Located at the forefront of the collision between the Indian and Eurasian Plates,the Tibetan Plateau experiences intense crustal movement.Traditional ground-based geodetic monitoring,such as GNSS and leveling,is challenging,due to factors such as high altitude and harsh climate,making it difficult to accurately determine a high-resolution crustal deformation field of the plateau.Unaffected by ground observation conditions,InSAR technique has key advantages for obtaining extensive and high-resolution crustal deformation fields.This makes it indispensable for crustal deformation monitoring on the Tibetan Plateau.This study used Sentinel-1 data from 2014 to 2020 to compute the ascending and descending InSAR deformation fields for the Tibetan Plateau.This was conducted with a measurement accuracy of approximately 3 mm/yr.Building upon this,we integrated InSAR and GNSS data to yield kilometer-resolution three-dimensional(3D)crustal deformation and strain rate fields for the Tibetan Plateau.A spherical wavelet analysis was used to decompose the 3D deformation field and separate the nontectonic crustal deformation to increase the strength of the tectonic deformation signal.Short-wavelength(<110 km)deformations match the distribution of fault movement,post-seismic deformations,and other non-tectonic factors.Long wavelength(>110 km)deformation mainly results from subsidence in the central plateau and uplifts along the Himalayan Arc.This indicates that the Tibetan Plateau may have stopped the entire uplift and entered a local collapse stage.Furthermore,the deformation fields at different spatial scales reveal that the plateau exhibits discontinuous deformation in short wavelengths and continuous deformation in long wavelengths.The findings of this study contribute to resolving the controversy between the Block and Continuum Deformation models of the Tibetan Plateau.展开更多
Minimization of energy functional of shape deformation under given constraints is used to generate fair curves and surfaces. This approach allows the user to design the shape interactively by applying different geomet...Minimization of energy functional of shape deformation under given constraints is used to generate fair curves and surfaces. This approach allows the user to design the shape interactively by applying different geometric constraints, external loads and physical parameters. Testing this way in a prototype system shows that the operators offer an intuitive way of shape modeling.展开更多
The mechanical and microstructural properties as well as crystallographic textures of asymmetrically rolled low carbon steel were studied.The modelling of plastic deformation was carried out in two scales:in the macro...The mechanical and microstructural properties as well as crystallographic textures of asymmetrically rolled low carbon steel were studied.The modelling of plastic deformation was carried out in two scales:in the macro-scale,using the finite elements method,and in the crystallographic scale,using the polycrystalline deformation model.The internal stress distribution in the rolling gap was calculated using the finite elements method and these stresses were then applied to the polycrystalline elasto-plastic deformation model.Selected mechanical properties,namely residual stress distribution,deformation work,applied force and torques,and bend amplitude,were calculated.The diffraction measurements,X-ray and electron backscatter diffraction,enabled the examination of texture heterogeneity and selected microstructure characteristics.The predicted textures agree well with those determined experimentally.The plastic anisotropy of cold rolled ferritic steel samples,connected with texture,was expressed by Lankford coefficient.展开更多
The plane-strain compression test for three kinds of materials was carried out in a temperature range between room temperature and 400℃.Theσ-εcurves and strain-hardening rate at different temperatures were simulate...The plane-strain compression test for three kinds of materials was carried out in a temperature range between room temperature and 400℃.Theσ-εcurves and strain-hardening rate at different temperatures were simulated and a reasonable fit to the experimental data was obtained.A modified model created by data inference and computer simulation was developed to describe the strain hardening at a large deformation,and the predicted strain hardening are in a good agreement with that observed in a large range of stress.The influences of different parameters on strain hardening behaviour under large deformation were analysed.The temperature increase within the test temperatures for stainless steel 18/8 Ti results in dropping of flow stress and strain-hardening rate.For favourableγ-fibre texture to obtain high r,the cold rolling was applied at large reduction.In the experimental procedure,the X-ray diffraction test was carried out to compare the strain hardening and microstructure under large deformation for a bcc steel(low carbon steel SS-1142).The results indicate that the high strain-hardening rate possibly occurs when the primary slip plane{110}is parallel to the rolling plane and the strainhardening rate decreases when lots of{110}plane rotate out from the orientation{110}∥RP.展开更多
On the basis of the assumption that the human face belongs to a linear class, a multiple-deformation model is proposed to recover face shape from a few points on a single 2D image. Compared to the conventional methods...On the basis of the assumption that the human face belongs to a linear class, a multiple-deformation model is proposed to recover face shape from a few points on a single 2D image. Compared to the conventional methods, this study has the following advantages. First, the proposed modified 3D sparse deforming model is a noniterative approach that can compute global translation efficiently and accurately. Subsequently, the overfitting problem can be alleviated based on the proposed multiple deformation model. Finally, by keeping the main features, the texture generated is realistic. The comparison results show that this novel method outperforms the existing methods by using ground truth data and that realistic 3D faces can be recovered efficiently from a single photograph.展开更多
In this paper, a finite element method (FEM)-based multi-phase problem based on a newly proposed thermal elastoplastic constitutive model for saturated/unsaturated geomaterial is discussed. A program of FEM named as...In this paper, a finite element method (FEM)-based multi-phase problem based on a newly proposed thermal elastoplastic constitutive model for saturated/unsaturated geomaterial is discussed. A program of FEM named as SOFT, adopting unified field equations for thermo-hydro-mechanical-air (THMA) behavior of geomaterial and using finite element-finite difference (FE-FD) scheme for so/l-water-air three-phase coupling problem, is used in the numerical simulation. As an application of the newly proposed numerical method, two engineering problems, one for slope failure in unsaturated model ground and another for in situ heating test related to deep geological repository of high-level radioactive waste (HLRW), are simulated. The model tests on slope failure in unsaturated Shirasu ground, carried out by Kitamura et al. (2007), is simulated in the framework of soil-water-air three-phase coupling under the condition of constant temperature. While the in situ heating test reported by Munoz (2006) is simulated in the same framework under the conditions of variable temperature hut constant air pressure.展开更多
基金Project supported by the National Science and Technology Project of Tenth Five Years (No.2001BA605A06A)Science and Tech-nology Cooperation Program of SINOPEC (No.FYWX04-06),China
文摘Based on new high-resolution seismic profiles and existing structural and sedimentary results, a superposition deformation model for Cenozoic Bachu Uplift of northwestern Tarim Basin, northwestern China is proposed. The model presents the idea that the Bachu Uplift suffered structure superposition deformation under the dual influences of the Cenozoic uplifting of Southern Tianshan and Western Kunlun orogen, northwestern China. In the end of the Eocene (early Himalayan movement), Bachu Uplift started to be formed with the uplifting of Western Kunlun, and extended NNW into the interior of Kalpin Uplift. In the end of the Miocene (middle Himalayan movement), Bachu Uplift suffered not only the NNW structure deformation caused by the Western Kunlun uplifting, but also the NE structure deformation caused by the Southern Tianshan uplifting, and the thrust front fault of Kalpin thrust system related to the Southern Tianshan orogen intrudes southeastward into the hinterland of Bachu Uplift and extends NNE from well Pil to Xiaohaizi reservoir and Gudongshan mountain, which resulted in the strata folded and denuded strongly. In the end of the Pliocene (late Himalayan movement), the impact of Southern Yianshan orogen decreased because of the stress released with the breakthrough upward of Kalpin fault extending NE, and Bachu Uplift suffered mainly the structure deformation extending NW-NNW caused by the uplifting of Western Kunlun orogen.
文摘The structure of a Hamiltonian matrix for a quantum chaotic system, the nuclear octupole deformation model, has been discussed in detail. The distribution of the eigenfunctions of this system expanded by the eigenstates of a quantum integrable system is studied with the help of generalized Brillouin?Wigner perturbation theory. The results show that a significant randomness in this distribution can be observed when its classical counterpart is under the strong chaotic condition. The averaged shape of the eigenfunctions fits with the Gaussian distribution only when the effects of the symmetry have been removed.
文摘In this research,mechanical stress,static strain and deformation analyses of a cylindrical pressure vessel subjected to mechanical loads are presented.The kinematic relations are developed based on higherorder sinusoidal shear deformation theory.Thickness stretching formulation is accounted for more accurate analysis.The total transverse deflection is divided into bending,shear and thickness stretching parts in which the third term is responsible for change of deflection along the thickness direction.The axisymmetric formulations are derived through principle of virtual work.A parametric study is presented to investigate variation of stress and strain components along the thickness and longitudinal directions.To explore effect of thickness stretching model on the static results,a comparison between the present results with the available results of literature is presented.As an important output,effect of micro-scale parameter is studied on the static stress and strain distribution.
基金This work was supported by the National Nature Science Foundation of China(Nos.12375244,12135009)the Science and Technology Innovation Program of Hunan Province(No.2020RC4020)+1 种基金the Hunan Provincial Innovation Foundation for Postgraduate(No.CX20210007)Natural Science Research Project of Yichang City(No.A23-2-028).
文摘In this study, the effect of extreme laser fields on the α decay process of ground-state even–even nuclei was investigated.Using the deformed Gamow-like model, we found that state-of-the-art lasers can cause a slight change in the α decay penetration probability of most nuclei. In addition, we studied the correlation between the rate of change of the α decay penetration probability and angle between the directions of the laser electric field and α particle emission for different nuclei. Based on this correlation, the average effect of extreme laser fields on the half-life of many nuclei with arbitrary α particle emission angles was calculated. The calculations show that the laser suppression and promotion effects on the α decay penetration probability of the nuclei population with completely random α particle-emission directions are not completely canceled.The remainder led to a change in the average penetration probability of the nuclei. Furthermore, the possibility of achieving a higher average rate of change by altering the spatial shape of the laser is explored. We conclude that circularly polarized lasers may be helpful in future experiments to achieve a more significant average rate of change of the α decay half-life of the nuclei population.
文摘The North China block,the western portion of the Sino- Korean Craton,is rounded byYanshanian in the north and Qinling- Dabie orogenic belts in the south.The widespread de-velopment of extensional basins in thisblock indicates horizontal extension or continued thin-ning of a previousely thickened,unstable lithosphere throughout the Mesozoic.In this pa-per,we attempt to simulate numerically the geodynamical process of the basin formation byusing the mountain- basin evolution system.We assume thatthe formation of numeroussedi-mentary basins in the North China block is the resultofthe crustal extension,which destruc-ts rapidly the previously thickened crust.The gravitational collapse of the thickened crust ispossibly triggered by the re- orientation of the far- field stress regime,or the relaxation of theboundary resistantstress.
文摘Compaction processes are one the most important par ts of powder forming technology. The main applications are focused on pieces for a utomotive, aeronautic, electric and electronic industries. The main goals of the compaction processes are to obtain a compact with the geometrical requirements, without cracks, and with a uniform distribution of density. Design of such proc esses consist, essentially, in determine the sequence and relative displacements of die and punches in order to achieve such goals. A.B. Khoei presented a gener al framework for the finite element simulation of powder forming processes based on the following aspects; a large displacement formulation, centred on a total and updated Lagrangian formulation; an adaptive finite element strategy based on error estimates and automatic remeshing techniques; a cap model based on a hard ening rule in modelling of the highly non-linear behaviour of material; and the use of an efficient contact algorithm in the context of an interface element fo rmulation. In these references, the non-linear behaviour of powder was adequately desc ribed by the cap plasticity model. However, it suffers from a serious deficiency when the stress-point reaches a yield surface. In the flow theory of plasticit y, the transition from an elastic state to an elasto-plastic state appears more or less abruptly. For powder material it is very difficult to define the locati on of yield surface, because there is no distinct transition from elastic to ela stic-plastic behaviour. Results of experimental test on some hard met al powder show that the plastic effects were begun immediately upon loading. In such mater ials the domain of the yield surface would collapse to a point, so making the di rection of plastic increment indeterminate, because all directions are normal to a point. Thus, the classical plasticity theory cannot deal with such materials and an advanced constitutive theory is necessary. In the present paper, the constitutive equations of powder materials will be discussed via an endochronic theory of plasticity. This theory provides a unifi ed point of view to describe the elastic-plastic behaviour of material since it places no requirement for a yield surface and a ’loading function’ to disting uish between loading an unloading. Endochronic theory of plasticity has been app lied to a number of metallic materials, concrete and sand, but to the knowledge of authors, no numerical scheme of the model has been applied to powder material . In the present paper, a new approach is developed based on an endochronic rate independent, density-dependent plasticity model for describing the isothermal deformation behavior of metal powder at low homologous temperature. Although the concept of yield surface has not been explicitly assumed in endochronic theory, it is shown that the cone-cap plasticity yield surface (Fig.1), which is the m ost commonly used plasticity models for describing the behavior of powder materi al can be easily derived as a special case of the proposed endochronic theory. Fig.1 Trace of cone-cap yield function on the meridian pl ane for different relative density As large deformation is observed in powder compaction process, a hypoelastic-pl astic formulation is developed in the context of finite deformation plasticity. Constitutive equations are stated in unrotated frame of reference that greatly s implifies endochronic constitutive relation in finite plasticity. Constitutive e quations of the endochronic theory and their numerical integration are establish ed and procedures for determining material parameters of the model are demonstra ted. Finally, the numerical schemes are examined for efficiency in the model ling of a tip shaped component, as shown in Fig.2. Fig.2 A shaped tip component. a) Geometry, boundary conditio n and finite element mesh; b) density distribution at final stage of
基金Project(51675100)supported by the National Natural Science Foundation of ChinaProject(2016ZX04004008)supported by the National Numerical Control Equipment Major Project of ChinaProject(6902002116)supported by the Foundation of Certain Ministry of China
文摘In the process of thin-wall parts assembly for an antenna,the parts assembly deformation deviation is occurring due to the riveting assembly.In view of the riveting assembly deformation problems,it can be analyzed through transient and static simulation.In this work,the theoretical deformation model for riveting assembly is established with round head rivet.The simulation analysis for riveting deformation is carried out with the riveting assembly piece including four rivets,which comparing with the measuring points experiment results of riveting test piece through dealing with the experimental data using the point coordinate transform method and the space line fitting method.Simultaneously,the deformation deviation of the overall thin-wall parts assembly structure is analyzed through finite element simulation;and its results are verified by the measuring experiment for riveting assembly with the deformation deviation of some key points on the thin-wall parts.Through the comparison analysis,it is shown that the simulation results agree well with the experimental results,which proves the correctness and effectiveness of the theoretical analysis,simulation results and the given experiment data processing method.Through the study on the riveting assembly for thin-wall parts,it will provide a theoretical foundation for improving thin-wall parts assembly quality of large antenna in future.
基金supported by the National Natural Science Foundation of China(42174026)the National Key Research and Development Program of China(2021YFE011004)。
文摘The permafrost development in the Qinghai-Tibet Engineering Corridor(QTEC)is affected by natural environment changes and human engineering activities.Human engineering activities may damage the permafrost growing environment,which in turn impact these engineering activities.Thus high spatial-temporal resolution monitoring over the QTEC in the permafrost region is very necessary.This paper presents a method for monitoring the frozen soil area using the intermittent coherencebased small baseline subset(ICSBAS).The method can improve the point density of the results and enhance the interpretability of deformation results by identifying the discontinuous coherent points according to the coherent value of time series.Using the periodic function that models the seasonal variation of permafrost,we separate the long wavelength atmospheric delay and establish an estimation model for the frozen soil deformation.Doing this can raise the monitoring accuracy and improve the understanding of the surface deformation of the frozen soil.In this study,we process 21 PALSAR data acquired by the Alos satellite with the proposed ICSBAS technique.The results show that the frozen soil far from the QTR in the study area experiences frost heave and thaw settlement(4.7 cm to8.4 cm)alternatively,while the maximum settlement along the QTR reaches 12 cm.The interferomatric syntnetic aperture radar(InSAR)-derived results are validated using the ground leveling data nearby the Beiluhe basin.The validation results show the InSAR results have good consistency with the leveling data in displacement rates as well as time series.We also find that the deformation in the permafrost area is correlated with temperature,human activities and topography.Based on the interfering degree of human engineering activities on the permafrost environment,we divide the QTEC along the Qinghai-Tibet Railway into engineering damage zone,transition zone and natural permafrost.
基金supported by the Special Earthquake Research Project of the China Earthquake Administration(201208009)
文摘Interferometric synthetic aperture radar (InSAR) images reveal deformation around northern Hejin, Shanxi Province. The small baseline subset (SBAS) approach for InSAR-derived deformation indicates that the observed deformation pattern can be characterized by the sum of two phenomena: background subsidence from December 2003 to February 2009 with a cumulative displacement of approximately 5 cm and uplift from Febru- ary 2009 to November 2010 with a cumulative displacement of approximately 2.5 cm. Deformation modeling indicates that the local deformation was caused by the closing and opening of a sill beneath northern Hejin. The modeled sill which is approximately 5 km long, 2 km wide, is centered at 1.5 km depth. The deformation was caused by the withdrawal and influx of subsurface water.
文摘A model suitable for describing the mechanical response of thin elastic objects is proposed to simulate the deformation of guide wires in minimally invasive interventions. The main objective of this simulation is to provide doctors an opportunity to rehearse the surgery and select an optimal operation plan before the real surgery. In this model the guide wire is discretized with the multi-body representation and its elastic energy derivate from elastic theory is a polynomial function of the nodal displacements. The vascular structure is represented by a tetrahedron mesh extended from the triangular mesh of the artery, which can be extracted from the patient's CT image data. The model applies the energy decline process of the conjugate gradient method to the deformation simulation of the guide wire. Experimental results show that the polynomial relationship between elastic energy and nodal displacements tremendously simplifies the evaluation of the conjugate gradient method and significantly improves the model's efficiency. Compared with models depending on an explicit scheme for evaluation, the new model is not only non-conditionally stable but also more efficient. The model can be applied to the real-time simulation of guide wire in a vascular structure.
文摘A new method for iris recognition using a multi-matching system based on a simplified deformable model of the human iris was proposed. The method defined iris feature points and formed the feature space based on a wavelet transform. In the matching stage it worked in a crude manner. Driven by a simplified deformable iris model, the crude matching was refined. By means of such multi-matching system, the task of iris recognition was accomplished. This process can preserve the elastic deformation between an input iris image and a template and improve precision for iris recognition. The experimental results indicate the va- lidity of this method.
基金Supported by the National Natural Science Foundation of China (No.60472071, 60532080, 60602062)the Natural Science Foundation of Beijing (No.4051002)
文摘In this paper, we present a new deformable model for shape segmentation, which makes two modifications to the original level set implementation of deformable models.The modifications are motivated by difficulties that we have encountered in applying deformable models to segmentation of medical images.The level set algorithm has some advantages over the classical snake deformable models.However, it could develop large gaps in the boundary and holes within the objects.Such boundary gaps and holes of objects can cause inaccurate segmentation that requires manual correction.The proposed method in this paper possesses an inherent property to detect gaps and holes within the object with a single initial contour and also does not require specific initialization.The first modification is to replace the edge detector by some area constraint, and the second modification utilizes weighted length constraint to regularize the curve under evolution.The proposed method has been applied to both synthetic and real images with promising results.
基金Funded by the National Natural Science Foundation of China(51202304)the China Postdoctoral Science Foundation(2014M552320)+1 种基金Scientific,the Technological Talents’Special Funds of Wanzhou District and Scientific and Technological Research Program of Chongqing Municipal Education Commission(KJ1401016)the Youth Project of Chongqing Three Gorges College(13QN-20)
文摘We prepared concretes(RC0, RC30, and RC100) with three different mixes. The poresize distribution parameters of RAC were examined by high-precision mercury intrusion method(MIM) and nuclear magnetic resonance(NMR) imaging. A capillary-bundle physical model with random-distribution pores(improved model, IM) was established according to the parameters, and dry-shrinkage strain values were calculated and verified. Results show that in all pore types, capillary pores, and gel pores have the greatest impacts on concrete shrinkage, especially for pores 2.5-50 and 50-100 nm in size. The median radii are 34.2, 31, and 34 nm for RC0, RC30, and RC100, respectively. Moreover, the internal micropore size distribution of RC0 differs from that of RC30 and RC100, and the pore descriptions of MIM and NMR are consistent both in theory and in practice. Compared with the traditional capillary-bundle model, the calculated results of IM have higher accuracy as demonstrated by experimental verifi cation.
基金The project supported by National Natural Science Foundation of China under Grant No. 90403019
文摘A new type of deformed XXZ model was constructed and diagonalized by the coordinate Bethe ansatz method. We obtained the energy and the Bethe ansatz equations of the model and also discussed some thermodynamics of the model.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(SETP)(Grant No.2019QZKK0901)the National Natural Science Foundation of China(Grant Nos.42130101,42074007,and 42104061)+1 种基金the National Key Research and Development Program of China(Grant No.2017YFC1500501)the Natural Science Basic Research Program of Shaanxi(Grant No.2023-JC-QN-0292)。
文摘Located at the forefront of the collision between the Indian and Eurasian Plates,the Tibetan Plateau experiences intense crustal movement.Traditional ground-based geodetic monitoring,such as GNSS and leveling,is challenging,due to factors such as high altitude and harsh climate,making it difficult to accurately determine a high-resolution crustal deformation field of the plateau.Unaffected by ground observation conditions,InSAR technique has key advantages for obtaining extensive and high-resolution crustal deformation fields.This makes it indispensable for crustal deformation monitoring on the Tibetan Plateau.This study used Sentinel-1 data from 2014 to 2020 to compute the ascending and descending InSAR deformation fields for the Tibetan Plateau.This was conducted with a measurement accuracy of approximately 3 mm/yr.Building upon this,we integrated InSAR and GNSS data to yield kilometer-resolution three-dimensional(3D)crustal deformation and strain rate fields for the Tibetan Plateau.A spherical wavelet analysis was used to decompose the 3D deformation field and separate the nontectonic crustal deformation to increase the strength of the tectonic deformation signal.Short-wavelength(<110 km)deformations match the distribution of fault movement,post-seismic deformations,and other non-tectonic factors.Long wavelength(>110 km)deformation mainly results from subsidence in the central plateau and uplifts along the Himalayan Arc.This indicates that the Tibetan Plateau may have stopped the entire uplift and entered a local collapse stage.Furthermore,the deformation fields at different spatial scales reveal that the plateau exhibits discontinuous deformation in short wavelengths and continuous deformation in long wavelengths.The findings of this study contribute to resolving the controversy between the Block and Continuum Deformation models of the Tibetan Plateau.
文摘Minimization of energy functional of shape deformation under given constraints is used to generate fair curves and surfaces. This approach allows the user to design the shape interactively by applying different geometric constraints, external loads and physical parameters. Testing this way in a prototype system shows that the operators offer an intuitive way of shape modeling.
基金Projects(DEC-2011/01/B/ST8/07394,DEC-2011/01/D/ST8/07399)supported by the Polish National Centre for Science(NCN)The support of the Polish Ministry of Science and Higher Education and of the French ANR 05-BLAN-0383 project
文摘The mechanical and microstructural properties as well as crystallographic textures of asymmetrically rolled low carbon steel were studied.The modelling of plastic deformation was carried out in two scales:in the macro-scale,using the finite elements method,and in the crystallographic scale,using the polycrystalline deformation model.The internal stress distribution in the rolling gap was calculated using the finite elements method and these stresses were then applied to the polycrystalline elasto-plastic deformation model.Selected mechanical properties,namely residual stress distribution,deformation work,applied force and torques,and bend amplitude,were calculated.The diffraction measurements,X-ray and electron backscatter diffraction,enabled the examination of texture heterogeneity and selected microstructure characteristics.The predicted textures agree well with those determined experimentally.The plastic anisotropy of cold rolled ferritic steel samples,connected with texture,was expressed by Lankford coefficient.
文摘The plane-strain compression test for three kinds of materials was carried out in a temperature range between room temperature and 400℃.Theσ-εcurves and strain-hardening rate at different temperatures were simulated and a reasonable fit to the experimental data was obtained.A modified model created by data inference and computer simulation was developed to describe the strain hardening at a large deformation,and the predicted strain hardening are in a good agreement with that observed in a large range of stress.The influences of different parameters on strain hardening behaviour under large deformation were analysed.The temperature increase within the test temperatures for stainless steel 18/8 Ti results in dropping of flow stress and strain-hardening rate.For favourableγ-fibre texture to obtain high r,the cold rolling was applied at large reduction.In the experimental procedure,the X-ray diffraction test was carried out to compare the strain hardening and microstructure under large deformation for a bcc steel(low carbon steel SS-1142).The results indicate that the high strain-hardening rate possibly occurs when the primary slip plane{110}is parallel to the rolling plane and the strainhardening rate decreases when lots of{110}plane rotate out from the orientation{110}∥RP.
基金the Program for New Century Excellent Talents in University(NCET) The National Natural Science Foundation of China+1 种基金Beijing Natural Science Foundation ProgramBeijing Science and Educational Committee Program.
文摘On the basis of the assumption that the human face belongs to a linear class, a multiple-deformation model is proposed to recover face shape from a few points on a single 2D image. Compared to the conventional methods, this study has the following advantages. First, the proposed modified 3D sparse deforming model is a noniterative approach that can compute global translation efficiently and accurately. Subsequently, the overfitting problem can be alleviated based on the proposed multiple deformation model. Finally, by keeping the main features, the texture generated is realistic. The comparison results show that this novel method outperforms the existing methods by using ground truth data and that realistic 3D faces can be recovered efficiently from a single photograph.
文摘In this paper, a finite element method (FEM)-based multi-phase problem based on a newly proposed thermal elastoplastic constitutive model for saturated/unsaturated geomaterial is discussed. A program of FEM named as SOFT, adopting unified field equations for thermo-hydro-mechanical-air (THMA) behavior of geomaterial and using finite element-finite difference (FE-FD) scheme for so/l-water-air three-phase coupling problem, is used in the numerical simulation. As an application of the newly proposed numerical method, two engineering problems, one for slope failure in unsaturated model ground and another for in situ heating test related to deep geological repository of high-level radioactive waste (HLRW), are simulated. The model tests on slope failure in unsaturated Shirasu ground, carried out by Kitamura et al. (2007), is simulated in the framework of soil-water-air three-phase coupling under the condition of constant temperature. While the in situ heating test reported by Munoz (2006) is simulated in the same framework under the conditions of variable temperature hut constant air pressure.