Fluctuations of conserved quantities, such as baryon, electric charge, and strangeness number, are sensitive observables in relativistic heavy-ion collisions to probe the QCD phase transition and search for the QCD cr...Fluctuations of conserved quantities, such as baryon, electric charge, and strangeness number, are sensitive observables in relativistic heavy-ion collisions to probe the QCD phase transition and search for the QCD critical point. In this paper, we review the experimental measurements of the cumulants(up to fourth order) of event-byevent net-proton(proxy for net-baryon), net-charge and netkaon(proxy for net-strangeness) multiplicity distributions Au+Au collisions at sNN^(1/2) 7:7; 11:5; 14:5; 19:6; 27;39; 62:4; 200 Ge V from the first phase of beam energy scan program at the relativistic heavy-ion collider(RHIC). We also summarize the data analysis methods of suppressing the volume fluctuations, auto-correlations, and the unified description of efficiency correction and error estimation.Based on theoretical and model calculations, we will discuss the characteristic signatures of critical point as well as backgrounds for the fluctuation observables in heavy-ion collisions. The physics implications and the future secondphase of the beam energy scan(2019–2020) at RHIC will also be discussed.展开更多
Up to now it is known that almost all ultrahigh-pressure (UHP) metamorphism of non-impact origin occurred in continent-continent collisional orogenic belt, as has been evidenced by many outcrops in the eastern hemisph...Up to now it is known that almost all ultrahigh-pressure (UHP) metamorphism of non-impact origin occurred in continent-continent collisional orogenic belt, as has been evidenced by many outcrops in the eastern hemisphere. UHP metamorphic rocks are represented by coesite- and diamond-bearing eclogites and eclogite facies metamorphic rocks formed at 650-800℃ and 2.6-3.5 GPa, and most of the protoliths of UHP rocks are volcanic-sedimentary sequences of continental crust. From these it may be deduced that deep subduction of continental crust may have occurred. However, UHP rocks are exposed on the surface or occur near the surface now, which implies that they have been exhumed from great depths. The mechanism of deep subduction of continental crust and subsequent exhumation has been a hot topic of the research on continental dynamics, but there are divergent views. The focus of the dispute is how deep continental crust is subducted so that UHP rocks can be formed and what mechanism causes it to be subducted to great depths and again exhumed to the shallow surface. Through an analysis of the continental process and mechanical boundary conditions of the Dabie collisional belt-an UHP metamorphic belt where the largest area of UHP rocks in the world is exposed, this paper discusses the variations of viscous stresses and average pressure in the viscous fluid caused by tectonism with rock physical properties and the contribution of the tectonic stresses to production of UHP. Calculation indicates that the anomalous stress state on the irregular boundary of a continental block may give rise to stress concentration and accumulation at local places (where the compressional stress may be 5-9 times higher than those in their surroundings). The tectonic stresses may account for 20-35% of the total UHP. So we may infer that the HP (nigh-pressure)-UHP rocks in the Dabie Mountains were formed at depths of 60-80 km. Thus the authors propose a new genetic model of UHP rocks-the point-collision model. This model conforms to the basic principles of the mechanics and also to the geologic records and process in the Dabie orogenic belt. It can explain why UHP rocks do nol exist along the entire length of the collisional orogen but occur in some particular positions. The authors also propose that the eastern and western corners of the Himalaya collision zone are typical point-collision areas and that almost all UHP metamorphism of continental crustal rocks occurred in the two particular positions.展开更多
Let P=(po, p1,..., pn-1 ) and Q=(qo,q1..., qm-1) be two arbitrary convex polygonsin plane. In this paper, the author studies the problems of how to quickly determine their possiblecollision range and movable range. In...Let P=(po, p1,..., pn-1 ) and Q=(qo,q1..., qm-1) be two arbitrary convex polygonsin plane. In this paper, the author studies the problems of how to quickly determine their possiblecollision range and movable range. In the paper, a new sufficient and necessary condition for decidingpossible collision is proposed,and the basic characters of the oblique supporting lines are investigated,and on these grounds the problem to determine the possible collision range is transformed into thatof searching the supporting points on the sets of convex polygon vertexs. Using the strategy ofsearching simultaneously the sets of vertexes of P and Q, the author constructs the fast algorithmfor finding the supporting points, the time-complexity of which is O(log2(m + n)). Based on theseresults, the algorithms to quickly determine the range are given, which possess the time-complexityof O(log2(m+n)).展开更多
基于MATLAB矢量化的物质点法(material point method,MPM)框架,分析车身前防撞梁的碰撞冲击问题。MPM在每一迭代步将物理参数在物质点和背景网格间相互映射,使用MATLAB矢量化框架可以使用户在快速入门的同时保证求解效率,其应力更新采...基于MATLAB矢量化的物质点法(material point method,MPM)框架,分析车身前防撞梁的碰撞冲击问题。MPM在每一迭代步将物理参数在物质点和背景网格间相互映射,使用MATLAB矢量化框架可以使用户在快速入门的同时保证求解效率,其应力更新采用车身结构材料的弹塑性本构模型。前防撞梁碰撞冲击数值算例结果表明,MPM可以保证求解精度,同时矢量化技术可以大幅提高求解效率。展开更多
基金supported in part by the Mo ST of China 973-Project(No.2015CB856901)the National Natural Science Foundation of China(No.11575069)
文摘Fluctuations of conserved quantities, such as baryon, electric charge, and strangeness number, are sensitive observables in relativistic heavy-ion collisions to probe the QCD phase transition and search for the QCD critical point. In this paper, we review the experimental measurements of the cumulants(up to fourth order) of event-byevent net-proton(proxy for net-baryon), net-charge and netkaon(proxy for net-strangeness) multiplicity distributions Au+Au collisions at sNN^(1/2) 7:7; 11:5; 14:5; 19:6; 27;39; 62:4; 200 Ge V from the first phase of beam energy scan program at the relativistic heavy-ion collider(RHIC). We also summarize the data analysis methods of suppressing the volume fluctuations, auto-correlations, and the unified description of efficiency correction and error estimation.Based on theoretical and model calculations, we will discuss the characteristic signatures of critical point as well as backgrounds for the fluctuation observables in heavy-ion collisions. The physics implications and the future secondphase of the beam energy scan(2019–2020) at RHIC will also be discussed.
基金the keyfundamentalgeologicalresearch project (No.9501102-3) the Ninth Five-Year Plan supported by the Ministry of Land and Resources a projectsupported by National Natural Science Foundation ofChina grant 19972064.
文摘Up to now it is known that almost all ultrahigh-pressure (UHP) metamorphism of non-impact origin occurred in continent-continent collisional orogenic belt, as has been evidenced by many outcrops in the eastern hemisphere. UHP metamorphic rocks are represented by coesite- and diamond-bearing eclogites and eclogite facies metamorphic rocks formed at 650-800℃ and 2.6-3.5 GPa, and most of the protoliths of UHP rocks are volcanic-sedimentary sequences of continental crust. From these it may be deduced that deep subduction of continental crust may have occurred. However, UHP rocks are exposed on the surface or occur near the surface now, which implies that they have been exhumed from great depths. The mechanism of deep subduction of continental crust and subsequent exhumation has been a hot topic of the research on continental dynamics, but there are divergent views. The focus of the dispute is how deep continental crust is subducted so that UHP rocks can be formed and what mechanism causes it to be subducted to great depths and again exhumed to the shallow surface. Through an analysis of the continental process and mechanical boundary conditions of the Dabie collisional belt-an UHP metamorphic belt where the largest area of UHP rocks in the world is exposed, this paper discusses the variations of viscous stresses and average pressure in the viscous fluid caused by tectonism with rock physical properties and the contribution of the tectonic stresses to production of UHP. Calculation indicates that the anomalous stress state on the irregular boundary of a continental block may give rise to stress concentration and accumulation at local places (where the compressional stress may be 5-9 times higher than those in their surroundings). The tectonic stresses may account for 20-35% of the total UHP. So we may infer that the HP (nigh-pressure)-UHP rocks in the Dabie Mountains were formed at depths of 60-80 km. Thus the authors propose a new genetic model of UHP rocks-the point-collision model. This model conforms to the basic principles of the mechanics and also to the geologic records and process in the Dabie orogenic belt. It can explain why UHP rocks do nol exist along the entire length of the collisional orogen but occur in some particular positions. The authors also propose that the eastern and western corners of the Himalaya collision zone are typical point-collision areas and that almost all UHP metamorphism of continental crustal rocks occurred in the two particular positions.
文摘Let P=(po, p1,..., pn-1 ) and Q=(qo,q1..., qm-1) be two arbitrary convex polygonsin plane. In this paper, the author studies the problems of how to quickly determine their possiblecollision range and movable range. In the paper, a new sufficient and necessary condition for decidingpossible collision is proposed,and the basic characters of the oblique supporting lines are investigated,and on these grounds the problem to determine the possible collision range is transformed into thatof searching the supporting points on the sets of convex polygon vertexs. Using the strategy ofsearching simultaneously the sets of vertexes of P and Q, the author constructs the fast algorithmfor finding the supporting points, the time-complexity of which is O(log2(m + n)). Based on theseresults, the algorithms to quickly determine the range are given, which possess the time-complexityof O(log2(m+n)).
文摘基于MATLAB矢量化的物质点法(material point method,MPM)框架,分析车身前防撞梁的碰撞冲击问题。MPM在每一迭代步将物理参数在物质点和背景网格间相互映射,使用MATLAB矢量化框架可以使用户在快速入门的同时保证求解效率,其应力更新采用车身结构材料的弹塑性本构模型。前防撞梁碰撞冲击数值算例结果表明,MPM可以保证求解精度,同时矢量化技术可以大幅提高求解效率。
