In order to meet the forming demands for low plasticity materials and large height-diameter ratio parts, a new process of hydrodynamic deep drawing （HDD） with independent radial hydraulic pressure is proposed. To in...In order to meet the forming demands for low plasticity materials and large height-diameter ratio parts, a new process of hydrodynamic deep drawing （HDD） with independent radial hydraulic pressure is proposed. To investigate the effects of loading paths on the HDD with independent radial hydraulic pressure, the forming process of 5A06 aluminum alloy cylindrical cup with a hemispherical bottom was studied by numerical simulation. By employing the dynamic explicit analytical software ETA/Dynaform based on LS-DYNA3D, the effects of loading paths on the sheet-thickness distribution and surface quality were analyzed. The corresponding relations of the radial hydraulic pressure loading paths and the part＇s strain status on the forming limit diagram （FLD） were also discussed. The results indicated that a sound match between liquid chamber pressure and independent radial hydraulic pressure could restrain the serious thinning at the hemisphere bottom and that through adjusting radial hydraulic pressure could reduce the radial tensile strain and change the strain paths. Therefore, the drawing limit of the aluminum cylindrical cup with a hemispherical bottom could be increased significantly.展开更多
Wild animals and plants have developed a variety of adaptive traits driven by adaptive evolution,an important strategy for species survival and persistence.Uncovering the molecular mechanisms of adaptive evolution is ...Wild animals and plants have developed a variety of adaptive traits driven by adaptive evolution,an important strategy for species survival and persistence.Uncovering the molecular mechanisms of adaptive evolution is the key to understanding species diversification,phenotypic convergence,and inter-species interaction.As the genome sequences of more and more non-model organisms are becoming available,the focus of studies on molecular mechanisms of adaptive evolution has shifted from the candidate gene method to genetic mapping based on genome-wide scanning.In this study,we reviewed the latest research advances in wild animals and plants,focusing on adaptive traits,convergent evolution,and coevolution.Firstly,we focused on the adaptive evolution of morphological,behavioral,and physiological traits.Secondly,we reviewed the phenotypic convergences of life history traits and responding to environmental pressures,and the underlying molecular convergence mechanisms.Thirdly,we summarized the advances of coevolution,including the four main types:mutualism,parasitism,predation and competition.Overall,these latest advances greatly increase our understanding of the underlying molecular mechanisms for diverse adaptive traits and species interaction,demonstrating that the development of evolutionary biology has been greatly accelerated by multi-omics technologies.Finally,we highlighted the emerging trends and future prospects around the above three aspects of adaptive evolution.展开更多
Let F be a field,and let e,k be integers such that 1≤e≤|F\{0}|and k≥0.We show that for any subset{a1,……,ae}■F\{0},the curious identity∑(i1+……ie)∈Z^(e)≥0,i1+……+ie=k a_(1)^(i1)…a_(e)^(ie)=∑i=1 e a_(i)^(k+...Let F be a field,and let e,k be integers such that 1≤e≤|F\{0}|and k≥0.We show that for any subset{a1,……,ae}■F\{0},the curious identity∑(i1+……ie)∈Z^(e)≥0,i1+……+ie=k a_(1)^(i1)…a_(e)^(ie)=∑i=1 e a_(i)^(k+e-1)/∏i≠j=1 e(a_(i)-a_(j))holds with Z≥0 being the set of nonnegative integers.As an application,we prove that for any subset{a_(1)…,a_(e)}■F_(q)\{0}with F_(q)being the finite field of q elements and e,l being integers such that 2≤e≤q-1 and 0≤l≤e-2,∑(i_(1),…,i_(e))∈Z^(e)≥0,i_(1)+…i_(e)=q-e+l a_(1)^(i1)…a_(e)^(ie)=0 Using this identity and providing an extension of the principle of cross-classification that slightly generalizes the one obtained by Hong in 1996,we show that if r is an integer with 1≤r≤q-2,then for any subset{a_(1),…a_(r)}■F_(q)^(*)we have x^(q-1)-1/∏i=1 r(x-a_(i))-∑i=1 q-1-r(∑i_(1)+…+i_(r)=q-1-r-i^(a_(1)^(i1)…a_(r)^(ir)))x^(i).This implies#{x∈Fq*|∑i=0 q-1-4(∑_(i1)+…+ir=q-1-r-i^(a_(1)^(i1)…a_(r)^(ir)))x^(i)=0}=q-1-r.展开更多
文摘In order to meet the forming demands for low plasticity materials and large height-diameter ratio parts, a new process of hydrodynamic deep drawing （HDD） with independent radial hydraulic pressure is proposed. To investigate the effects of loading paths on the HDD with independent radial hydraulic pressure, the forming process of 5A06 aluminum alloy cylindrical cup with a hemispherical bottom was studied by numerical simulation. By employing the dynamic explicit analytical software ETA/Dynaform based on LS-DYNA3D, the effects of loading paths on the sheet-thickness distribution and surface quality were analyzed. The corresponding relations of the radial hydraulic pressure loading paths and the part＇s strain status on the forming limit diagram （FLD） were also discussed. The results indicated that a sound match between liquid chamber pressure and independent radial hydraulic pressure could restrain the serious thinning at the hemisphere bottom and that through adjusting radial hydraulic pressure could reduce the radial tensile strain and change the strain paths. Therefore, the drawing limit of the aluminum cylindrical cup with a hemispherical bottom could be increased significantly.
基金supported by the National Natural Science Foundation of China (31821001)the Strategic Priority Research Program of Chinese Academy of Sciences (XDB31000000)。
文摘Wild animals and plants have developed a variety of adaptive traits driven by adaptive evolution,an important strategy for species survival and persistence.Uncovering the molecular mechanisms of adaptive evolution is the key to understanding species diversification,phenotypic convergence,and inter-species interaction.As the genome sequences of more and more non-model organisms are becoming available,the focus of studies on molecular mechanisms of adaptive evolution has shifted from the candidate gene method to genetic mapping based on genome-wide scanning.In this study,we reviewed the latest research advances in wild animals and plants,focusing on adaptive traits,convergent evolution,and coevolution.Firstly,we focused on the adaptive evolution of morphological,behavioral,and physiological traits.Secondly,we reviewed the phenotypic convergences of life history traits and responding to environmental pressures,and the underlying molecular convergence mechanisms.Thirdly,we summarized the advances of coevolution,including the four main types:mutualism,parasitism,predation and competition.Overall,these latest advances greatly increase our understanding of the underlying molecular mechanisms for diverse adaptive traits and species interaction,demonstrating that the development of evolutionary biology has been greatly accelerated by multi-omics technologies.Finally,we highlighted the emerging trends and future prospects around the above three aspects of adaptive evolution.
基金supported partially by the National Science Foundation of China(Grant#11771304)the Fundamental Research Funds for the Central Universities.
文摘Let F be a field,and let e,k be integers such that 1≤e≤|F\{0}|and k≥0.We show that for any subset{a1,……,ae}■F\{0},the curious identity∑(i1+……ie)∈Z^(e)≥0,i1+……+ie=k a_(1)^(i1)…a_(e)^(ie)=∑i=1 e a_(i)^(k+e-1)/∏i≠j=1 e(a_(i)-a_(j))holds with Z≥0 being the set of nonnegative integers.As an application,we prove that for any subset{a_(1)…,a_(e)}■F_(q)\{0}with F_(q)being the finite field of q elements and e,l being integers such that 2≤e≤q-1 and 0≤l≤e-2,∑(i_(1),…,i_(e))∈Z^(e)≥0,i_(1)+…i_(e)=q-e+l a_(1)^(i1)…a_(e)^(ie)=0 Using this identity and providing an extension of the principle of cross-classification that slightly generalizes the one obtained by Hong in 1996,we show that if r is an integer with 1≤r≤q-2,then for any subset{a_(1),…a_(r)}■F_(q)^(*)we have x^(q-1)-1/∏i=1 r(x-a_(i))-∑i=1 q-1-r(∑i_(1)+…+i_(r)=q-1-r-i^(a_(1)^(i1)…a_(r)^(ir)))x^(i).This implies#{x∈Fq*|∑i=0 q-1-4(∑_(i1)+…+ir=q-1-r-i^(a_(1)^(i1)…a_(r)^(ir)))x^(i)=0}=q-1-r.
