In a two-dimensional and linear framework, a transformation was developed to derive eigensolutions of internal waves over a subcritical hyperbolic slope and to approximate the continental slope and shelf. The transfor...In a two-dimensional and linear framework, a transformation was developed to derive eigensolutions of internal waves over a subcritical hyperbolic slope and to approximate the continental slope and shelf. The transformation converts a hyperbolic slope in physical space into a flat bottom in transform space while the governing equations of internal waves remain hyperbolic. The eigensolutions are further used to study the evolution of linear internal waves as it propagates to subcritical continental slope and shelf. The stream function, velocity, and vertical shear of velocity induced by internal wave at the hyperbolic slope are analytically expressed by superposition of the obtained eigensolutions. The velocity and velocity shear increase as the internal wave propagates to a hyperbolic slope. They become very large especially when the slope of internal wave rays approaches the topographic slope, which is consistent with the previous studies.展开更多
To revise P-wave velocity and thickness of the hydrate layer in the Shenhu area of the South China Sea, acoustic and resistivity logging curves are reanalyzed. The waterlogging phenomenon is found in the shallow sedim...To revise P-wave velocity and thickness of the hydrate layer in the Shenhu area of the South China Sea, acoustic and resistivity logging curves are reanalyzed. The waterlogging phenomenon is found in the shallow sediments of five drilling wells, which causes P-wave velocity to approximate the propagation velocity of sea water(about 1500 m s-1). This also affects the identification of the hydrate layer and results in the underestimate of its thickness. In addition, because there could be about a 5 m thick velocity ramp above or below the hydrate layer as interpreted by acoustic and resistivity logging curves, the recalibrated thickness of this layer is less than the original estimated thickness. The recalibrated P-wave velocity of the hydrate layer is also higher than the original estimated velocity. For the drilling well with a relatively thin hydrate layer, the velocity ramp plays a more important role in identifying and determining the thickness of the layer.展开更多
In order to study buckling propagation mechanism in deep sea pipelines, the contact between pipeline's inner walls in buckling process was studied. A two-dimensional ring model was used to represent the pipeline a...In order to study buckling propagation mechanism in deep sea pipelines, the contact between pipeline's inner walls in buckling process was studied. A two-dimensional ring model was used to represent the pipeline and a nonlinear spring model was adopted to simulate the contact between inner walls. Based on the elastoplastic constitutive relationship and the principle of virtual work theory, the coupling effect of pipeline's nonlinear large deformation and wall contact was included in the theoretical analysis with the aid of MATLAB, and the application scope of the theoretical model was also discussed. The calculated results show that during the loading process, the change in external pressure is closely related to the distribution of section stress, and once the walls are contacting each other, the external pressure increases and then remains stable after it reaches a specific value. Without fracture, the pipeline section will stop showing deformation. The results of theoretical calculations agree well with those of numerical simulations. Finally, in order to ensure reliability and accuracy of the theoretical results, the collapse pressure and propagation pressure were both verified by numerical simulations and experiments. Therefore, the theoretical model can be used to analyze pipeline's buckling deformation and contact between pipeline's inner walls, which forms the basis for further research on three-dimensional buckling propagation.展开更多
By using function one direction S-rough sets （function one direction singular rough sets）, the concept of one direction rough law is proposed, where one direction rough law is the law pair { w（x）-, w（x） - } comp...By using function one direction S-rough sets （function one direction singular rough sets）, the concept of one direction rough law is proposed, where one direction rough law is the law pair { w（x）-, w（x） - } composed by w（x）- and w（x）-, ffthe attribute set {a_ , a-} of function one direction S-rough sets changes, then one direction rough law { w（x）_, w（x）- } will change, too. By employing ellipse curves, the concept of one direction rough law security is presented, the security theorem of one direction rough law is proposed and the applications are given. One direction rough law security, which is generated by the intersection and penetration between function one direction S-rough sets and ellipse curves, is a new applied research direction of function S-rough sets.展开更多
Phase transition can strongly change the stress wave propagation features. In this paper, the characteristic wave propagation under combined tension and torsion impact loading was studied with a simplified constitutiv...Phase transition can strongly change the stress wave propagation features. In this paper, the characteristic wave propagation under combined tension and torsion impact loading was studied with a simplified constitutive model of phase transition considering both pressure and shear stress. The results showed that for loading from the austenitic phase to the mixed phase, the wave propagation was similar to that in the elasto-plastic materials. However, for an instantaneous loading from the austenitic phase or mixed phase directly to the martensitic phase, a coupling shock wave(CSHW) with phase transition was predicted due to the second phase strengthening effect, which has barely been studied before. Through analysis of the constitutive equations with phase transition and the discontinuity conditions of shock waves, the control equations of the generalized Hugoniot curve was obtained and the CSHW problem with phase transition was solved analytically. An independent numerical simulation of step loading along a NiTi thin walled tube suffering a combined tension-torsion impact loading was given to prove the existence of CSHW. The simulation discloses the formation mechanism of CSHW and the adjusting process of the stress state ahead of CSHW, which reflects the intrinsic characteristic of materials with strong nonlinear constitutive behavior.展开更多
基金Supported by the National Nature Science Foundation of China (No.40406008 and 40876015)the Foundation for Open Projects of the Key Lab of Physical Oceanography,The Ministry of Education,China (No.200309).
文摘In a two-dimensional and linear framework, a transformation was developed to derive eigensolutions of internal waves over a subcritical hyperbolic slope and to approximate the continental slope and shelf. The transformation converts a hyperbolic slope in physical space into a flat bottom in transform space while the governing equations of internal waves remain hyperbolic. The eigensolutions are further used to study the evolution of linear internal waves as it propagates to subcritical continental slope and shelf. The stream function, velocity, and vertical shear of velocity induced by internal wave at the hyperbolic slope are analytically expressed by superposition of the obtained eigensolutions. The velocity and velocity shear increase as the internal wave propagates to a hyperbolic slope. They become very large especially when the slope of internal wave rays approaches the topographic slope, which is consistent with the previous studies.
基金supported by the National Natural Science Foundation of China (Nos. 41273066 and MRE200805)
文摘To revise P-wave velocity and thickness of the hydrate layer in the Shenhu area of the South China Sea, acoustic and resistivity logging curves are reanalyzed. The waterlogging phenomenon is found in the shallow sediments of five drilling wells, which causes P-wave velocity to approximate the propagation velocity of sea water(about 1500 m s-1). This also affects the identification of the hydrate layer and results in the underestimate of its thickness. In addition, because there could be about a 5 m thick velocity ramp above or below the hydrate layer as interpreted by acoustic and resistivity logging curves, the recalibrated thickness of this layer is less than the original estimated thickness. The recalibrated P-wave velocity of the hydrate layer is also higher than the original estimated velocity. For the drilling well with a relatively thin hydrate layer, the velocity ramp plays a more important role in identifying and determining the thickness of the layer.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51239008 and 51179126)the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No. 2011ZX05026-005)
文摘In order to study buckling propagation mechanism in deep sea pipelines, the contact between pipeline's inner walls in buckling process was studied. A two-dimensional ring model was used to represent the pipeline and a nonlinear spring model was adopted to simulate the contact between inner walls. Based on the elastoplastic constitutive relationship and the principle of virtual work theory, the coupling effect of pipeline's nonlinear large deformation and wall contact was included in the theoretical analysis with the aid of MATLAB, and the application scope of the theoretical model was also discussed. The calculated results show that during the loading process, the change in external pressure is closely related to the distribution of section stress, and once the walls are contacting each other, the external pressure increases and then remains stable after it reaches a specific value. Without fracture, the pipeline section will stop showing deformation. The results of theoretical calculations agree well with those of numerical simulations. Finally, in order to ensure reliability and accuracy of the theoretical results, the collapse pressure and propagation pressure were both verified by numerical simulations and experiments. Therefore, the theoretical model can be used to analyze pipeline's buckling deformation and contact between pipeline's inner walls, which forms the basis for further research on three-dimensional buckling propagation.
基金Natural Science Foundation of Fujian Province of China( No.2009J01293)Open Project of Brain-like Key Laboratory Research of Fujian Province of China (No. BLISSOS20101015)
文摘By using function one direction S-rough sets （function one direction singular rough sets）, the concept of one direction rough law is proposed, where one direction rough law is the law pair { w（x）-, w（x） - } composed by w（x）- and w（x）-, ffthe attribute set {a_ , a-} of function one direction S-rough sets changes, then one direction rough law { w（x）_, w（x）- } will change, too. By employing ellipse curves, the concept of one direction rough law security is presented, the security theorem of one direction rough law is proposed and the applications are given. One direction rough law security, which is generated by the intersection and penetration between function one direction S-rough sets and ellipse curves, is a new applied research direction of function S-rough sets.
基金supported by the National Natural Science Foundation of China(Grant No.11072240)
文摘Phase transition can strongly change the stress wave propagation features. In this paper, the characteristic wave propagation under combined tension and torsion impact loading was studied with a simplified constitutive model of phase transition considering both pressure and shear stress. The results showed that for loading from the austenitic phase to the mixed phase, the wave propagation was similar to that in the elasto-plastic materials. However, for an instantaneous loading from the austenitic phase or mixed phase directly to the martensitic phase, a coupling shock wave(CSHW) with phase transition was predicted due to the second phase strengthening effect, which has barely been studied before. Through analysis of the constitutive equations with phase transition and the discontinuity conditions of shock waves, the control equations of the generalized Hugoniot curve was obtained and the CSHW problem with phase transition was solved analytically. An independent numerical simulation of step loading along a NiTi thin walled tube suffering a combined tension-torsion impact loading was given to prove the existence of CSHW. The simulation discloses the formation mechanism of CSHW and the adjusting process of the stress state ahead of CSHW, which reflects the intrinsic characteristic of materials with strong nonlinear constitutive behavior.
