To determine the potential effects of climate change on crop phenological development and productivity, an integrated analysis was conducted based on the observed climatic and phenological records of Northeast China f...To determine the potential effects of climate change on crop phenological development and productivity, an integrated analysis was conducted based on the observed climatic and phenological records of Northeast China from 1992 to 2012. A set of quality assurance procedures, including repeated record checks, agro-meteorological station selection, internal consistency checks, temporal outlier checks, spatial outlier checks, and interpolation of missing data, were designed and applied to the phenology datasets of spring maize and paddy rice. Our results indicated that almost all phenological dates of spring maize and paddy rice became increasingly delayed from 1992 to 2012, The duration of the growing season was prolonged, particularly for the grain-filling stage （GS3）. The prolonged growing season was beneficial to productivity. For spring maize, the average precipitation during GS3 decreased at a rate of 27.46 mm/decade, and the annual accumulated temperature over 10℃ increased at a rate of 31.07℃/ decade. Farmers initiatively adjusted crop cultivars and selected drought-resistant crops to cope with the challenges of drought.展开更多
Some possible alternative solutions of near-tip fields are studied for plane-strain Mode-I qua- si-static steady crack growth in incompressible(v=1/2)elastic perfectly-plastic media.A group of four-sector so- lutions ...Some possible alternative solutions of near-tip fields are studied for plane-strain Mode-I qua- si-static steady crack growth in incompressible(v=1/2)elastic perfectly-plastic media.A group of four-sector so- lutions and a three-sector solution in which the elastic-unloading region vanishes are given.Stress functions,plas- tic flow factors and plastic strains in each region are also given.展开更多
A mechanical model of a fracturing viscoelastic material was developed to investigate viscous effects in a dynamically growing crack-tip field. It was shown that in the stable creep-growing phase, elastic deformation ...A mechanical model of a fracturing viscoelastic material was developed to investigate viscous effects in a dynamically growing crack-tip field. It was shown that in the stable creep-growing phase, elastic deformation and viscous deformation are equally dominant in the near-tip field, and stress and strain have the same singularity, namely, （σ-e）∝r^-1/（n-1）. The asymptotic solution of separating variables of stress, stain and displacement in the crack-tip field was obtained by asymptotic analysis, and the resulting numerical value of stress and strain in the crack-tip field was obtained by the shooting method and the boundary condition of a mode I crack. Through numerical calculation, it was shown that the near-tip fields are mainly governed by the creep exponent n and Mach number M. When n →∞, the asymptotic solution of a viscoelastic material can be degenerated into that of Freund＇s elastic-ideally plastic material by analyzing basic equations.展开更多
Based on the theoretical framework for crack growth analysis provided by Gao and Hwang, the 5-sector soiution of near-tip fields of mode-I cracks growing quasi-statically and steadily in compressible elastic perfectly...Based on the theoretical framework for crack growth analysis provided by Gao and Hwang, the 5-sector soiution of near-tip fields of mode-I cracks growing quasi-statically and steadily in compressible elastic perfectly plastic materials is obtained.As Poisson's ratio v tends to 1/2,the 5-sector solution degener- ates to the 4-sector solution of near-tip fields of crack growth in incompressible elastic perfectly plastic materials.展开更多
A higher order asymptotic solution of near-tip field is studied for plane-atrain Mode-Ⅰ quasi-static steady crack growth in the incompressible (v=1/2) elastic perfectly-plastic media.The results show that the near-ti...A higher order asymptotic solution of near-tip field is studied for plane-atrain Mode-Ⅰ quasi-static steady crack growth in the incompressible (v=1/2) elastic perfectly-plastic media.The results show that the near-tip stress and strain are fully continuous,and the strain possesses In (A/r) singularity at the crack tip.The expressions of the stress,strain and velocity in each region are also given.展开更多
Based on grow tree composite model, Finite Field Wavelet Grow Tree (FW-GT) was proposed in this paper. FW-GT is a novel framework to be used in data encryption enhancing data security. It is implemented by replacement...Based on grow tree composite model, Finite Field Wavelet Grow Tree (FW-GT) was proposed in this paper. FW-GT is a novel framework to be used in data encryption enhancing data security. It is implemented by replacement operator and wavelet operator. Forward integration and inverse decomposition of FW-GT are performed by replacement, inverse wavelets and its corresponding replacement, wavelet transforms. Replacement operator joined nonlinear factor, wavelet operator completed data transformation between lower dimensional space and higher dimensional space. FW-GT security relies on the difficulty of solving nonlinear equations over finite fields. By using FW-GT, high security of data could be obtained at the cost of low computational complexity. It proved FW-GT algorithm’s correctness in this paper. The experimental result and theory analysis shows the excellent performance of the algorithm.展开更多
In creeping solids,plane stress and plane strain solutions for asymptotic singular crack-tip fields have been first put forward by Riedel and Rice with C^(*)as the dominating parameter and developed by Xiang and Guo i...In creeping solids,plane stress and plane strain solutions for asymptotic singular crack-tip fields have been first put forward by Riedel and Rice with C^(*)as the dominating parameter and developed by Xiang and Guo into three-dimensional solution(3D)for stationary cracks under the domination of C^(*)with the constraint factor Tz.However,how to characterize the 3D crack-tip fields under creep damage-induced quasistatic growing conditions remains challenging.In this study,we reveal that,for 3D quasistatic growing cracks,the leading singular solution can effectively characterize the crack-tip stress distributions with relative errors less than 10.8%for relative creep time up to 0.8 in various specimens with finite thickness.For a given relative time,Tz distributions can be unified by the equivalent thickness concept,Beq.The results show that C^(*)-T_(z) can effectively quantify both the load and constraint effects on the crack-tip fields.Such geometry independent dominance can considerably simplify the treatments of load and constraint effects,thereby promoting the application of fracture mechanics in high-temperature damage tolerance designs.展开更多
In the 5-sector solution by Drugan et al. for near-tip field of plane strain crack growing in compressible materials, the plastic flow rule is violated in the plastic zone (called the nonsingular zone by Rice) between...In the 5-sector solution by Drugan et al. for near-tip field of plane strain crack growing in compressible materials, the plastic flow rule is violated in the plastic zone (called the nonsingular zone by Rice) between the central fan sector and the elastic unloading sector. Based on the theoretical framework provided by Rice and supplemented by the "unloading boundary theorem", the correct formulation of the problem is given and the correct asymptotic solution for the near-tip field of the crack growth is obtained.展开更多
基金financially supported by the National Basic Research Program of China(2010CB951501)
文摘To determine the potential effects of climate change on crop phenological development and productivity, an integrated analysis was conducted based on the observed climatic and phenological records of Northeast China from 1992 to 2012. A set of quality assurance procedures, including repeated record checks, agro-meteorological station selection, internal consistency checks, temporal outlier checks, spatial outlier checks, and interpolation of missing data, were designed and applied to the phenology datasets of spring maize and paddy rice. Our results indicated that almost all phenological dates of spring maize and paddy rice became increasingly delayed from 1992 to 2012, The duration of the growing season was prolonged, particularly for the grain-filling stage （GS3）. The prolonged growing season was beneficial to productivity. For spring maize, the average precipitation during GS3 decreased at a rate of 27.46 mm/decade, and the annual accumulated temperature over 10℃ increased at a rate of 31.07℃/ decade. Farmers initiatively adjusted crop cultivars and selected drought-resistant crops to cope with the challenges of drought.
基金Project supported by the State Education Commission under a funding program for Excellent University Young Faculties and National Natural Science Foundation of China.
文摘Some possible alternative solutions of near-tip fields are studied for plane-strain Mode-I qua- si-static steady crack growth in incompressible(v=1/2)elastic perfectly-plastic media.A group of four-sector so- lutions and a three-sector solution in which the elastic-unloading region vanishes are given.Stress functions,plas- tic flow factors and plastic strains in each region are also given.
基金Supported by the Nature foundation of Heilongjiang Province under Grant No. A009 the foundation of Harbin Engineering University under Grant No. HEUF04005.
文摘A mechanical model of a fracturing viscoelastic material was developed to investigate viscous effects in a dynamically growing crack-tip field. It was shown that in the stable creep-growing phase, elastic deformation and viscous deformation are equally dominant in the near-tip field, and stress and strain have the same singularity, namely, （σ-e）∝r^-1/（n-1）. The asymptotic solution of separating variables of stress, stain and displacement in the crack-tip field was obtained by asymptotic analysis, and the resulting numerical value of stress and strain in the crack-tip field was obtained by the shooting method and the boundary condition of a mode I crack. Through numerical calculation, it was shown that the near-tip fields are mainly governed by the creep exponent n and Mach number M. When n →∞, the asymptotic solution of a viscoelastic material can be degenerated into that of Freund＇s elastic-ideally plastic material by analyzing basic equations.
基金The project supported by the National Natural Science Foundation of China.
文摘Based on the theoretical framework for crack growth analysis provided by Gao and Hwang, the 5-sector soiution of near-tip fields of mode-I cracks growing quasi-statically and steadily in compressible elastic perfectly plastic materials is obtained.As Poisson's ratio v tends to 1/2,the 5-sector solution degener- ates to the 4-sector solution of near-tip fields of crack growth in incompressible elastic perfectly plastic materials.
基金The project supported by National Natural Science Foundation of China
文摘A higher order asymptotic solution of near-tip field is studied for plane-atrain Mode-Ⅰ quasi-static steady crack growth in the incompressible (v=1/2) elastic perfectly-plastic media.The results show that the near-tip stress and strain are fully continuous,and the strain possesses In (A/r) singularity at the crack tip.The expressions of the stress,strain and velocity in each region are also given.
文摘Based on grow tree composite model, Finite Field Wavelet Grow Tree (FW-GT) was proposed in this paper. FW-GT is a novel framework to be used in data encryption enhancing data security. It is implemented by replacement operator and wavelet operator. Forward integration and inverse decomposition of FW-GT are performed by replacement, inverse wavelets and its corresponding replacement, wavelet transforms. Replacement operator joined nonlinear factor, wavelet operator completed data transformation between lower dimensional space and higher dimensional space. FW-GT security relies on the difficulty of solving nonlinear equations over finite fields. By using FW-GT, high security of data could be obtained at the cost of low computational complexity. It proved FW-GT algorithm’s correctness in this paper. The experimental result and theory analysis shows the excellent performance of the algorithm.
基金supported by the National Key Research and Development Program of China(Grant No.2019YFA0705400)the Natural Science Foundation of Jiangsu Province(Grant No.BK20212008)+2 种基金the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures(Grant No.MCMS-I-0421K01)the Fundamental Research Funds for the Central Universities(Grant Nos.NJ2020003,and NZ2020001)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘In creeping solids,plane stress and plane strain solutions for asymptotic singular crack-tip fields have been first put forward by Riedel and Rice with C^(*)as the dominating parameter and developed by Xiang and Guo into three-dimensional solution(3D)for stationary cracks under the domination of C^(*)with the constraint factor Tz.However,how to characterize the 3D crack-tip fields under creep damage-induced quasistatic growing conditions remains challenging.In this study,we reveal that,for 3D quasistatic growing cracks,the leading singular solution can effectively characterize the crack-tip stress distributions with relative errors less than 10.8%for relative creep time up to 0.8 in various specimens with finite thickness.For a given relative time,Tz distributions can be unified by the equivalent thickness concept,Beq.The results show that C^(*)-T_(z) can effectively quantify both the load and constraint effects on the crack-tip fields.Such geometry independent dominance can considerably simplify the treatments of load and constraint effects,thereby promoting the application of fracture mechanics in high-temperature damage tolerance designs.
基金Project supported by the National Natural Science Foundation of China
文摘In the 5-sector solution by Drugan et al. for near-tip field of plane strain crack growing in compressible materials, the plastic flow rule is violated in the plastic zone (called the nonsingular zone by Rice) between the central fan sector and the elastic unloading sector. Based on the theoretical framework provided by Rice and supplemented by the "unloading boundary theorem", the correct formulation of the problem is given and the correct asymptotic solution for the near-tip field of the crack growth is obtained.
