期刊文献+
共找到9篇文章
< 1 >
每页显示 20 50 100
Effect of melt convection on primary dendrite arm spacing in directionally solidified Pb-26%Bi hypo-peritectic alloys 被引量:4
1
作者 胡小武 李双明 +2 位作者 高思峰 刘林 傅恒志 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2011年第1期65-71,共7页
Primary dendrite arm spacing(PDAS) of α phase in directionally solidified Pb-26%Bi(mass fraction) hypo-peritectic alloys was measured by considering the effect of melt convection in cylindrical samples with diffe... Primary dendrite arm spacing(PDAS) of α phase in directionally solidified Pb-26%Bi(mass fraction) hypo-peritectic alloys was measured by considering the effect of melt convection in cylindrical samples with different diameters.The experimental results show the measured PDAS increases with increasing diameter of the sample.At the growth velocity of 5 μm/s,its value changes from 161.5 μm for the sample with 1.8 mm in diameter to 240.4 μm for the sample with 7 mm in diameter.The strong melt convection in large diameter samples causes a high bulk alloy composition and a high concentration gradient in peritectic β phase,resulting in a larger PDAS.Simultaneously,the high concentration gradient could effectively promote the peritectic transformation,enhancing the dissolution of the thin α dendrite. 展开更多
关键词 Pb-26%Bi hypo-peritectic alloy primary dendrite arm spacing melt convection directional solidification
下载PDF
教师“该出手时再出手”
2
作者 郭晓莉 《教育家》 2016年第39期84-85,共2页
随着新课改的不断深入,学生动手实践、自主探索、合作交流等学习方式常常体现在教学过程中,课堂气氛活跃了,学生的学习热情也提高了……师生角色初步实现了比较理想的转换。但一种奇怪的现象也随之出现了:教师在课堂上一味追求自主、合... 随着新课改的不断深入,学生动手实践、自主探索、合作交流等学习方式常常体现在教学过程中,课堂气氛活跃了,学生的学习热情也提高了……师生角色初步实现了比较理想的转换。但一种奇怪的现象也随之出现了:教师在课堂上一味追求自主、合作、探究的学习方式,以至于有时放任自流,任凭学生自主而不去适时指导; 展开更多
关键词 数学学习 新课程理念 自主探索 引导者 四舍五入 人教版 对一对 组织者
下载PDF
Quantum Dialogue by Using Non-Symmetric Quantum Channel 被引量:1
3
作者 詹佑邦 张伶伶 +1 位作者 王郁武 张群永 《Communications in Theoretical Physics》 SCIE CAS CSCD 2010年第4期648-652,共5页
A protocol for quantum dialogue is proposed to exchange directly the communicator's secret messages by using a three-dimensional Bell state and a two-dimensional Bell state as quantum channel with quantum superdence ... A protocol for quantum dialogue is proposed to exchange directly the communicator's secret messages by using a three-dimensional Bell state and a two-dimensional Bell state as quantum channel with quantum superdence coding, local collective unitary operations, and entanglement swapping. In this protocol, during the process of trans- mission of particles, the transmitted particles do not carry any secret messages and are transmitted only one time. The protocol has higher source capacity than protocols using symmetric two-dimensional states. The security is ensured by the unitary operations randomly performed on all checking groups before the particle sequence is transmitted and the application of entanglement swapping. 展开更多
关键词 quantum dialogue non-symmetric quantum channel local collective unitary operation entanglement swapping
下载PDF
The Coupling Constants for.an Electroweak Model with an SU(4)PS ×SU(4)EW Unification Symmetry
4
作者 A.E. Bernardini 《Communications in Theoretical Physics》 SCIE CAS CSCD 2007年第5期879-882,共4页
We introduce the sequence of spontaneous symmetry breaking of a coupling between Pati-Salam and electroweak symmetries SU( 4 )PS × SU( 4 )EW in order to establish a mathematically consistent relation among th... We introduce the sequence of spontaneous symmetry breaking of a coupling between Pati-Salam and electroweak symmetries SU( 4 )PS × SU( 4 )EW in order to establish a mathematically consistent relation among the coupling constants at grand unification energy scale. With the values of baryon minus lepton quantum numbers of known quarks and leptons, by including right-handed neutrinos, we can lind the mixing angle relations at different energy levels up to the electromagnetic U(1)EM scale. 展开更多
关键词 electroweak unification gauge symmetry coupling constants
下载PDF
《一对老熊》阅读
5
作者 薛吉辰 《中学生阅读(高中版)》 2004年第2期46-47,50,共3页
关键词 熊的故事 对一对
原文传递
REAL TOMITA-TAKESAKI THEORY
6
作者 LI BINGREN(Institute of Mathematics, Academia Sinica, Beijing 100080, China) 《Chinese Annals of Mathematics,Series B》 SCIE CSCD 1999年第4期401-406,共6页
Tomita-Takesaki theory in the real case is considered. The author introduces the conception of a nondegenerate pair of closed subspaces in a real Hilbert space. Then a satisfactory real Tomita-Taksaki theory is obtain... Tomita-Takesaki theory in the real case is considered. The author introduces the conception of a nondegenerate pair of closed subspaces in a real Hilbert space. Then a satisfactory real Tomita-Taksaki theory is obtained, and it seems to be a special result of the complex case. 展开更多
关键词 Tomita-Takesaki theory Non-degenerate pair Unitary involution Modular operator
原文传递
Variable sets method for urban flood vulnerability assessment 被引量:11
7
作者 CHEN ShouYu XUE ZhiChun +1 位作者 LI Min ZHU XuePing 《Science China(Technological Sciences)》 SCIE EI CAS 2013年第12期3129-3136,共8页
On the basis of dialectics basic laws and mathematical theorems of variable sets,this paper proposes a variable sets method for urban flood vulnerability assessment.In this method,the comprehensive relative membership... On the basis of dialectics basic laws and mathematical theorems of variable sets,this paper proposes a variable sets method for urban flood vulnerability assessment.In this method,the comprehensive relative membership degree of multi-indices is represented by an index relative difference degree,which follows the characteristics of dialectical philosophy and mathematics.According to the quality-quantity exchange theorem,the relative difference degree of two adjacent levels(h and h+1),whose index standard interval values cross the boundaries,equals 0 in the urban flood vulnerability assessment.On the basis of the opposite unity theorem,the sum of relative membership degrees should be equal to 1 when indices lie in the adjacent degrees h and h+1.The variable sets method is proved to be theoretically rigorous and computationally simple.This paper takes 29 cities of Hunan province as an example to assess the urban flood vulnerability,and then compares the results from this newly developed method with the assessment results obtained from the fuzzy comprehensive evaluation and fuzzy set pair analysis methods. 展开更多
关键词 variable sets urban flood VULNERABILITY ASSESSMENT
原文传递
Nonlocal Symmetries and Exact Solutions for PIB Equation 被引量:2
8
作者 辛祥鹏 苗倩 陈勇 《Communications in Theoretical Physics》 SCIE CAS CSCD 2012年第9期331-337,共7页
In this paper, the symmetry group of the is studied by means of the classical symmetry method (2+l)-dimensionM Painlevd integrable Burgers (PIB) equations Ignoring the discussion of the infinite-dimensional subal... In this paper, the symmetry group of the is studied by means of the classical symmetry method (2+l)-dimensionM Painlevd integrable Burgers (PIB) equations Ignoring the discussion of the infinite-dimensional subalgebra, we construct an optimal system of one-dimensional group invariant solutions. Furthermore, by using the conservation laws of the reduced equations, we obtain nonlocal symmetries and exact solutions of the PIB equations. 展开更多
关键词 classical Lie symmetry method optimal system nonlocal symmetry explicit solution
原文传递
Invariant Functions, Symmetries and Primary Branch Solutions of First Order Autonomous Systems
9
作者 Sen-Yue Lou Ruo-Xia Yao 《Communications in Theoretical Physics》 SCIE CAS CSCD 2017年第7期21-28,共8页
An invariant function (IF) is defined as a multiplier of a symmetry that means a symmetry multiplied by an IF is still a symmetry. Primary branch solutions of arbitrary first order scalar systems can be obtained by ... An invariant function (IF) is defined as a multiplier of a symmetry that means a symmetry multiplied by an IF is still a symmetry. Primary branch solutions of arbitrary first order scalar systems can be obtained by means of the IF and its related symmetry approach. Especially, one recursion operator and some sets of infinitely many high order symmetries are also explicitly given for arbitrary (l q-1)-dimensional first order autonomous systems. Because of the intrusion of the arbitrary function, various implicit special exact solutions can be found by fixing the arbitrary functions and selecting different seed solutions. 展开更多
关键词 invariant functions SYMMETRIES exact solutions invariant operators recursion Operators
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部