每年初冬时节,国家I级保护植物,被誉为“植物黄金”的南方红豆杉就会果挂满枝,红彤彤、亮晶晶的果实如珠如玉,小巧可人。据《中国植物志》中记载南方红豆杉一般需种植7~8年才能开花结果,珍稀名贵。它四季常青、树形美观、枝条飘逸洒脱,...每年初冬时节,国家I级保护植物,被誉为“植物黄金”的南方红豆杉就会果挂满枝,红彤彤、亮晶晶的果实如珠如玉,小巧可人。据《中国植物志》中记载南方红豆杉一般需种植7~8年才能开花结果,珍稀名贵。它四季常青、树形美观、枝条飘逸洒脱,是深受人们喜爱的观赏树种。南方红豆杉(Taxus wallichiana var. mairei)是红豆杉科红豆杉属常绿乔木,为裸子植物。花期在2~3月,种子11~12月成熟,其树干通直,树皮呈灰褐色或红褐色,常纵裂或剥落。叶呈深绿色,为条形或条状披针形,微弯,背面中脉隆起,腹面中脉两侧,各有一条灰绿色或黄绿色气孔带。展开更多
A new method for shape modification of non-uniform rational B-splines (NURBS) curves was presented, which was based on constrained optimization by means of altering the corresponding weights of their control points. U...A new method for shape modification of non-uniform rational B-splines (NURBS) curves was presented, which was based on constrained optimization by means of altering the corresponding weights of their control points. Using this method, the original NURBS curve was modified to satisfy the specified geometric constraints, including single point and multi-point constraints. With the introduction of free parameters, the shapes of modified NURBS curves could be further controlled by users without destroying geometric constraints and seem more naturally. Since explicit formulae were derived to compute new weights of the modified curve, the method was simple and easy to program. Practical examples showed that the method was applicable for computer aided design (CAD) system.展开更多
This paper describes a new method for simulation of the cross section shape of log. The self-developed MQK3102 log shape recognizing machine was used to acquire the finite discrete sampling points on the cross section...This paper describes a new method for simulation of the cross section shape of log. The self-developed MQK3102 log shape recognizing machine was used to acquire the finite discrete sampling points on the cross section of log and those points were fitted with the quadratic B-spline parametric curve. This method can clearly stimulate the real shape of the log cross section and is characterized by limited sampling points and high speed computing. The computed result of the previous curve does not affect the next one, which may avoid the graphic distortion caused by the accumulative error. The method can be used to simulate the whole body shape of log approximately by sampling the cross sections along the length direction of log, thus providing a reference model for optimum saw cutting of log.展开更多
The discrete element method is used to simulate specimens under three different loading conditions（conventional triaxial compression,plane strain,and direct shear）with different initial conditions to explore the und...The discrete element method is used to simulate specimens under three different loading conditions（conventional triaxial compression,plane strain,and direct shear）with different initial conditions to explore the underlying mechanics of the specimen deformation from a microscale perspective.Deformations of specimens with different initial void ratios at different confining stresses under different loading conditions are studied.Results show that the discrete element models successfully capture the specimen deformation and the strain localization.Particle behaviors including particle rotation and displacement and the mesoscale void ratio distributions are used to explain the strain localization and specimen deformation.It is found that the loading condition is one of the most important factors controlling the specimen deformation mode.Microscale behavior of the granular soil is the driving mechanics of the macroscale deformation of the granular assembly.展开更多
Aluminum and silver strips were cold welded by rolling and a bimetallic strip was produced. To create cold weld between A1 and Ag, mating surfaces were specially prepared and various rolling thickness reductions were ...Aluminum and silver strips were cold welded by rolling and a bimetallic strip was produced. To create cold weld between A1 and Ag, mating surfaces were specially prepared and various rolling thickness reductions were applied. The minimum critical thickness reduction to begin cold weld was specified as 70% which equals 0.1630 critical rolling shape factors. The bimetallic strips were treated by diffusion annealing at 400 ~C and various annealing time. The A1/Ag interface of strips was observed by scanning electron microscope to investigate the formation of hard and brittle probable phases. The effect of anneal time on diffusion distance and phase transformation was also analysed by EDS analysis and line scan. A diffusion region along the interface in the Ag side was observed and its width increased with prolonging annealing time. Some 8 phases were detected close to the interface after anneal treating for 3 h and 8 phase was thicker and more continuous by increasing annealing time. The microhardness measurement showed that in spite of formation of 8 phase due to diffusion annealing, the interface hardness was reduced.展开更多
We investigate experimentally the depositions of two contiguous debris flows flowing into a main river reach.The aim of the present experimental research is to analyze the geometry and the mutual interactions of debri...We investigate experimentally the depositions of two contiguous debris flows flowing into a main river reach.The aim of the present experimental research is to analyze the geometry and the mutual interactions of debris flow deposits conveyed by these tributaries in the main channel.A set of 19 experiments has been conducted considering three values of the confluence angle,two slopes of the tributary,and three different triggering conditions(debris flows occurring simultaneously in the tributaries,or occurring first either in the upstream or in the downstream tributary).The flow rate along the main channel was always kept constant.During each experiment the two tributaries had the same slope and confluence angle.The analysis of the data collected during the experimental tests indicates that the volume of the debris fan is mainly controlled by the slope angle,as expected,while the shape of the debris deposit is strongly influenced by the confluence angle.Moreover,in the case of multiple debris flows,the deposit shape is sensitive to the triggering conditions.Critical index for damming formation available in literature has been considered and applied to the present case,and,on the basis of the collected data,considerations about possible extension of such indexes to the case of multiple confluences are finally proposed.展开更多
文摘每年初冬时节,国家I级保护植物,被誉为“植物黄金”的南方红豆杉就会果挂满枝,红彤彤、亮晶晶的果实如珠如玉,小巧可人。据《中国植物志》中记载南方红豆杉一般需种植7~8年才能开花结果,珍稀名贵。它四季常青、树形美观、枝条飘逸洒脱,是深受人们喜爱的观赏树种。南方红豆杉(Taxus wallichiana var. mairei)是红豆杉科红豆杉属常绿乔木,为裸子植物。花期在2~3月,种子11~12月成熟,其树干通直,树皮呈灰褐色或红褐色,常纵裂或剥落。叶呈深绿色,为条形或条状披针形,微弯,背面中脉隆起,腹面中脉两侧,各有一条灰绿色或黄绿色气孔带。
文摘A new method for shape modification of non-uniform rational B-splines (NURBS) curves was presented, which was based on constrained optimization by means of altering the corresponding weights of their control points. Using this method, the original NURBS curve was modified to satisfy the specified geometric constraints, including single point and multi-point constraints. With the introduction of free parameters, the shapes of modified NURBS curves could be further controlled by users without destroying geometric constraints and seem more naturally. Since explicit formulae were derived to compute new weights of the modified curve, the method was simple and easy to program. Practical examples showed that the method was applicable for computer aided design (CAD) system.
基金The research is supported by Project of National Natural Science Foundation of China(30571455)and National "948" Project(2005-4-62)
文摘This paper describes a new method for simulation of the cross section shape of log. The self-developed MQK3102 log shape recognizing machine was used to acquire the finite discrete sampling points on the cross section of log and those points were fitted with the quadratic B-spline parametric curve. This method can clearly stimulate the real shape of the log cross section and is characterized by limited sampling points and high speed computing. The computed result of the previous curve does not affect the next one, which may avoid the graphic distortion caused by the accumulative error. The method can be used to simulate the whole body shape of log approximately by sampling the cross sections along the length direction of log, thus providing a reference model for optimum saw cutting of log.
基金The National Natural Science Foundation of China(No.51079030)
文摘The discrete element method is used to simulate specimens under three different loading conditions（conventional triaxial compression,plane strain,and direct shear）with different initial conditions to explore the underlying mechanics of the specimen deformation from a microscale perspective.Deformations of specimens with different initial void ratios at different confining stresses under different loading conditions are studied.Results show that the discrete element models successfully capture the specimen deformation and the strain localization.Particle behaviors including particle rotation and displacement and the mesoscale void ratio distributions are used to explain the strain localization and specimen deformation.It is found that the loading condition is one of the most important factors controlling the specimen deformation mode.Microscale behavior of the granular soil is the driving mechanics of the macroscale deformation of the granular assembly.
文摘Aluminum and silver strips were cold welded by rolling and a bimetallic strip was produced. To create cold weld between A1 and Ag, mating surfaces were specially prepared and various rolling thickness reductions were applied. The minimum critical thickness reduction to begin cold weld was specified as 70% which equals 0.1630 critical rolling shape factors. The bimetallic strips were treated by diffusion annealing at 400 ~C and various annealing time. The A1/Ag interface of strips was observed by scanning electron microscope to investigate the formation of hard and brittle probable phases. The effect of anneal time on diffusion distance and phase transformation was also analysed by EDS analysis and line scan. A diffusion region along the interface in the Ag side was observed and its width increased with prolonging annealing time. Some 8 phases were detected close to the interface after anneal treating for 3 h and 8 phase was thicker and more continuous by increasing annealing time. The microhardness measurement showed that in spite of formation of 8 phase due to diffusion annealing, the interface hardness was reduced.
基金supported by the project GAPDEMM – GIS-based integrated platform for Debris Flow Monitoring, Modeling and Hazard Mitigation – founded by Fondazione Cassa di Risparmio di Padova e Rovigo in framework of Progetti di Eccellenza 2011-2012
文摘We investigate experimentally the depositions of two contiguous debris flows flowing into a main river reach.The aim of the present experimental research is to analyze the geometry and the mutual interactions of debris flow deposits conveyed by these tributaries in the main channel.A set of 19 experiments has been conducted considering three values of the confluence angle,two slopes of the tributary,and three different triggering conditions(debris flows occurring simultaneously in the tributaries,or occurring first either in the upstream or in the downstream tributary).The flow rate along the main channel was always kept constant.During each experiment the two tributaries had the same slope and confluence angle.The analysis of the data collected during the experimental tests indicates that the volume of the debris fan is mainly controlled by the slope angle,as expected,while the shape of the debris deposit is strongly influenced by the confluence angle.Moreover,in the case of multiple debris flows,the deposit shape is sensitive to the triggering conditions.Critical index for damming formation available in literature has been considered and applied to the present case,and,on the basis of the collected data,considerations about possible extension of such indexes to the case of multiple confluences are finally proposed.
