Isothermal hot compression tests of as-cast high-Cr ultra-super-critical（USC） rotor steel with columnar grains perpendicular to the compression direction were carried out in the temperature range from 950 to 1250...Isothermal hot compression tests of as-cast high-Cr ultra-super-critical（USC） rotor steel with columnar grains perpendicular to the compression direction were carried out in the temperature range from 950 to 1250°C at strain rates ranging from 0.001 to 1 s^（-1）. The softening mechanism was dynamic recovery（DRV） at 950°C and the strain rate of 1 s^（-1）, whereas it was dynamic recrystallization（DRX） under the other conditions. A modified constitutive equation based on the Arrhenius model with strain compensation reasonably predicted the flow stress under various deformation conditions, and the activation energy was calculated to be 643.92 kJ ×mol^（-1）. The critical stresses of dynamic recrystallization under different conditions were determined from the work-hardening rate（θ）–flow stress（σ） and-θ/σ–σ curves. The optimum processing parameters via analysis of the processing map and the softening mechanism were determined to be a deformation temperature range from 1100 to 1200°C and a strain-rate range from 0.001 to 0.08 s^（-1）, with a power dissipation efficiency η greater than 31%.展开更多
This paper researches and analyses the critical envirormental situation in the Middle Reaches of the Yellow River and compiles the map of critical environmental situation of this area (1:2,000,000). Five types of envi...This paper researches and analyses the critical envirormental situation in the Middle Reaches of the Yellow River and compiles the map of critical environmental situation of this area (1:2,000,000). Five types of environmental situation (ES) are divided, namely, conflict ES, critical ES, crisis ES, disastrous ES and accidental ES and 7 groups of main factors are used to identify and classify the critical environmental situation after considering the speciality of this region and the law of guiding factors. They are pollution, endemic disease, soil erosion, drought and water-shortage, forest degeration, wind-erosion and desertification, and soil salinization. Based on mapping and analysis, the paper also concludes the regional distribution law of critical environmental situation of this region and divides it into 8 small districts through combining the critical envirormental situation, regional distribution law and guiding factors. This can provide scientific basis and reference for preserving and renovating the environments with different fragile types and fragile levels.展开更多
We examine when a meromorphic quadratic differential φ with prescribed poles is the Schwarzian derivative of a rational map. We give a necessary and sufficient condition: In the Laurent series of φ around each pole ...We examine when a meromorphic quadratic differential φ with prescribed poles is the Schwarzian derivative of a rational map. We give a necessary and sufficient condition: In the Laurent series of φ around each pole c, the most singular term should take the form(1- d2)/(2(z- c)2), where d is an integer, and then a certain determinant in the next d coefficients should vanish. This condition can be optimized by neglecting some information on one of the poles(i.e., by only requiring it to be a double pole). The case d = 2 was treated by Eremenko(2012). We show that a geometric interpretation of our condition is that the complex projective structure induced by φ outside the poles has a trivial holonomy group. This statement was suggested to us by Thurston in a private communication. Our work is related to the problem of finding a rational map f with a prescribed set of critical points, since the critical points of f are precisely the poles of its Schwarzian derivative.Finally, we study the pole-dependency of these Schwarzian derivatives. We show that, in the cubic case with simple critical points, an analytic dependency fails precisely when the poles are displaced at the vertices of a regular ideal tetrahedron of the hyperbolic 3-ball.展开更多
Scar-related ventricular tachycardia(VT)is a malignant arrhythmia with high mortality rates in patients with cardiomyopathies such as ischemic and dilated cardiomyopathy.[1]While implantable cardioverter defibrillator...Scar-related ventricular tachycardia(VT)is a malignant arrhythmia with high mortality rates in patients with cardiomyopathies such as ischemic and dilated cardiomyopathy.[1]While implantable cardioverter defibrillators(ICD)effectively terminate VT episodes and prevent sudden cardiac death,recurrent ICD discharges may precipitate electrical storms and severely impair quality of life.Radiofrequency catheter ablation is another available treatment for VT but faces challenges in rapidly mapping the critical isthmus during hemodynamically unstable VT.Stereotactic arrhythmia radioablation(STAR)has emerged as a novel,non-invasive,and effective approach for refractory VT over the past decade.展开更多
We prove that in dimensions three and higher the Landau-Lifshitz-Gilbert equation with small initial data in the critical Besov space is globally well-posed in a uniform way with respect to the Gilbert damping paramet...We prove that in dimensions three and higher the Landau-Lifshitz-Gilbert equation with small initial data in the critical Besov space is globally well-posed in a uniform way with respect to the Gilbert damping parameter. Then we show that the global solution converges to that of the Schr¨odinger maps in the natural space as the Gilbert damping term vanishes. The proof is based on some studies on the derivative Ginzburg-Landau equations.展开更多
基金supported by the Major State Basic Research Development Program of China (No.2011CB012900)the National Natural Science Foundation of China (No.51374144)the Shanghai Rising-Star Program (No.14QA1402300)
文摘Isothermal hot compression tests of as-cast high-Cr ultra-super-critical（USC） rotor steel with columnar grains perpendicular to the compression direction were carried out in the temperature range from 950 to 1250°C at strain rates ranging from 0.001 to 1 s^（-1）. The softening mechanism was dynamic recovery（DRV） at 950°C and the strain rate of 1 s^（-1）, whereas it was dynamic recrystallization（DRX） under the other conditions. A modified constitutive equation based on the Arrhenius model with strain compensation reasonably predicted the flow stress under various deformation conditions, and the activation energy was calculated to be 643.92 kJ ×mol^（-1）. The critical stresses of dynamic recrystallization under different conditions were determined from the work-hardening rate（θ）–flow stress（σ） and-θ/σ–σ curves. The optimum processing parameters via analysis of the processing map and the softening mechanism were determined to be a deformation temperature range from 1100 to 1200°C and a strain-rate range from 0.001 to 0.08 s^（-1）, with a power dissipation efficiency η greater than 31%.
文摘This paper researches and analyses the critical envirormental situation in the Middle Reaches of the Yellow River and compiles the map of critical environmental situation of this area (1:2,000,000). Five types of environmental situation (ES) are divided, namely, conflict ES, critical ES, crisis ES, disastrous ES and accidental ES and 7 groups of main factors are used to identify and classify the critical environmental situation after considering the speciality of this region and the law of guiding factors. They are pollution, endemic disease, soil erosion, drought and water-shortage, forest degeration, wind-erosion and desertification, and soil salinization. Based on mapping and analysis, the paper also concludes the regional distribution law of critical environmental situation of this region and divides it into 8 small districts through combining the critical envirormental situation, regional distribution law and guiding factors. This can provide scientific basis and reference for preserving and renovating the environments with different fragile types and fragile levels.
基金supported by National Natural Science Foundation of China (Grant Nos. 11125106 and 11501383)Project LAMBDA (Grant No. ANR-13-BS01-0002)
文摘We examine when a meromorphic quadratic differential φ with prescribed poles is the Schwarzian derivative of a rational map. We give a necessary and sufficient condition: In the Laurent series of φ around each pole c, the most singular term should take the form(1- d2)/(2(z- c)2), where d is an integer, and then a certain determinant in the next d coefficients should vanish. This condition can be optimized by neglecting some information on one of the poles(i.e., by only requiring it to be a double pole). The case d = 2 was treated by Eremenko(2012). We show that a geometric interpretation of our condition is that the complex projective structure induced by φ outside the poles has a trivial holonomy group. This statement was suggested to us by Thurston in a private communication. Our work is related to the problem of finding a rational map f with a prescribed set of critical points, since the critical points of f are precisely the poles of its Schwarzian derivative.Finally, we study the pole-dependency of these Schwarzian derivatives. We show that, in the cubic case with simple critical points, an analytic dependency fails precisely when the poles are displaced at the vertices of a regular ideal tetrahedron of the hyperbolic 3-ball.
文摘Scar-related ventricular tachycardia(VT)is a malignant arrhythmia with high mortality rates in patients with cardiomyopathies such as ischemic and dilated cardiomyopathy.[1]While implantable cardioverter defibrillators(ICD)effectively terminate VT episodes and prevent sudden cardiac death,recurrent ICD discharges may precipitate electrical storms and severely impair quality of life.Radiofrequency catheter ablation is another available treatment for VT but faces challenges in rapidly mapping the critical isthmus during hemodynamically unstable VT.Stereotactic arrhythmia radioablation(STAR)has emerged as a novel,non-invasive,and effective approach for refractory VT over the past decade.
基金supported by Australian Research Council Discovery Project (Grant No. DP170101060)National Natural Science Foundation of China (Grant No. 11201498)the China Scholarship Council (Grant No. 201606495010)
文摘We prove that in dimensions three and higher the Landau-Lifshitz-Gilbert equation with small initial data in the critical Besov space is globally well-posed in a uniform way with respect to the Gilbert damping parameter. Then we show that the global solution converges to that of the Schr¨odinger maps in the natural space as the Gilbert damping term vanishes. The proof is based on some studies on the derivative Ginzburg-Landau equations.
