共查询到20条相似文献，搜索用时 31 毫秒
1.
YU Yao-yong YOU Ying 《浙江大学学报(A卷英文版)》2006,7(6):1068-1076
INTRODUCTION One century ago, Hilbert announced his famous 23 problems. The Hilbert’s Fourth Problem is to characterize the (not-necessarily-reversible) distance functions on an open subset in ún such that straight lines are shortest paths. Distance functions induced by a Finsler metric are regarded as smooth ones. Thus Hilbert’s Fourth Problem in the smooth case is to characterize Finsler metric on an open subset in ún whose geodesics are straight lines. Finsler metric on an ope… 相似文献
2.
ZHAO Li-li 《浙江大学学报(A卷英文版)》2007,8(6):957-962
In this paper, we consider some polynomial (α,β)-metrics, and discuss the sufficient and necessary conditions for a Finsler metric in the form F=α a1β a2β2/α a4β4/α3 to be projectively flat, where ai (i=1,2,4) are constants with a1≠0, α is a Riemannian metric and β is a 1-form. By analyzing the geodesic coefficients and the divisibility of certain polynomials, we obtain that there are only five projectively flat cases for metrics of this type. This gives a classification for such kind of Finsler metrics. 相似文献
3.
HAN Jing-wei YU Yao-yong 《浙江大学学报(A卷英文版)》2007,8(6):963-968
In this work, we study the Asanov Finsler metric F=α(β2/α2 gβ/α 1)1/2exp{(G/2)arctan[β/(hα) G/2]}, where α=(αijyiyj)1/2 is a Riemannian metric and β=biyj is a 1-form, g∈(-2,2), h=(1-g2/4)1/2, G=g/h. We give the necessary and sufficient condition for Asanov metric to be locally projectively flat, i.e., α is projectively flat and β is parallel with respect to α. Moreover, we proved that the Douglas tensor of Asanov Finsler metric vanishes if and only if β is parallel with respect to α. 相似文献
4.
Let Γd2nbe the set of trees with a given diameter d having a perfect matching,where 2n is the number of vertex.For a tree T in Γd2n,let Pd+1be a diameter of T and q = d m,where m is the number of the edges of perfect matching inPd+1.It can be found that the trees with minimal energy in Γd2nfor four cases q = d 2,d 3,d 4,[d2],and two remarks aregiven about the trees with minimal energy in Γd2nfor2d 33q d 5 and [d2] + 1 q2d 33 1. 相似文献
5.
1 Introduction We consider the finite digraphs that do not havemultiple arcs or loops , but pairs of opposite arcs areallowed.LetD=(V,A) be a digraph , whereVisthe set of vertices andAis the set of arcs .If there isan arc (x,y) fromxtoy,thenthe vertexxis … 相似文献
6.
Tim Molseed 《The American journal of distance education》2013,27(4):254-267
Abstract The effectiveness of a peer review process for online graduate students is predicated on a balance between social- and task-directed communications. The defining criteria of learning communities are presented to illustrate the operational meaning of social and the criteria for Critical Thinking used to illustrate the operational meaning of task response types. The social responses were further categorized as an opinion/evaluative or anecdotal/reflective comment and task responses subcategorized as either a content or style comment. The hypothesis that a significant difference would be found between the social and task responses was accepted as was the second hypothesis that there would be a significant difference between the content and style responses. 相似文献
7.
WANG Ya-qin 《浙江大学学报(A卷英文版)》2007,8(10):1691-1694
Let K be a closed convex subset of a real reflexive Banach space E, T：K→K be a nonexpansive mapping, and f：K→K be a fixed weakly contractive （may not be contractive） mapping. Then for any t∈（0, 1）, let x1∈K be the unique fixed point of the weak contraction x1→tf（x）＋（1-t）Tx. If T has a fixed point and E admits a weakly sequentially continuous duality mapping from E to E^＊, then it is shown that {xt} converges to a fixed point of T as t→0. The results presented here improve and generalize the corresponding results in （Xu, 2004）. 相似文献
8.
Let R be a ring, a ,b ∈ R, ( D , α ) and (G , β ) be two generalized derivations of R . It is proved that if aD ( x ) = G ( x )b for all x ∈ R, then one of the following possibilities holds: (i) If either a or b is contained in C , then α = β= 0 and there exist p , q ∈ Qr ( RC) such that D ( x )= px and G ( x )= qx for all x ∈ R;(ii) If both a and b are contained in C , then either a = b= 0 or D and G are C-linearly dependent;(iii) If neither a nor b is contained in C , then there exist p , q ∈ Qr ( RC) and w ∈ Qr ( R) such that α ( x ) = [ q ,x] and β ( x ) = [ x ,p] for all x ∈ R, whence D ( x )= wx-xq and G ( x )= xp + avx with v ∈ C and aw-pb= 0. 相似文献
9.
Shailesh A. Shirali 《Resonance》2007,12(7):27-43
For non-negative integers k, n, let P
k
(n) denote the sum {fx27-1}. We show by two different means that if k ≥ 3 and odd, then n
2(n+1)2 iss a factor of the polynomial P
k
(n); and if k ≥ 2 and even, then n (n+1) (2n+1) is a factor of the polynomial P
k
(n). We also derive a relatively unknown result first obtained by Johann Faulhaber in the 17th century.
Shailesh Shirali has been at Rishi Valley School, Andhra Pradesh (Krishnamurti Foundation India) since the 1980’s. He has
a deep interest in teaching and writing about mathematics at the high school/post school levels, with particular emphasis
on problem solving and on historical aspects of the subject. He has been involved in the Mathematics Olympiad movement at
the national and international level for the past two decades. He is the author of several expository books and articles aimed
at interested high school students. 相似文献
10.
Consider the positive d-dimensional lattice d (d≥2) with partial ordering ≤, let {XK; K ∈ d } be i.i.d. random vari- ables taking values in a real separable Hilbert space (H, ||·||) with mean zero and covariance operator ∑, and set partial sums SN =∑K≤NXK, K , N ∈ d . Under some moment conditions, we obtain the precise asymptotics of a kind of weighted infinite series for partial sums SN as ε 0 by using the truncation and approximation methods. The results are related to the convergence rates of the law of the logarithm in Hilbert space, and they also extend the results of (Gut and Spǎtaru, 2003). 相似文献
11.
几乎正则图的全符号控制 总被引：1，自引：2，他引：1
1IntroductionFor notation and graph theory terminology we ingeneral follow[1].LetG=(V,E)be a graph with thevertex setVand the edge setE,andletvbe a vertexinV.The open neighborhood ofvisN(v)={u∈V|uv∈E}and the closed neighborhood ofvisN[v]={v}∪N(v).The d… 相似文献
12.
AtCRE1 is known to be a cytokinin receptor inArabidopsis. TheAtCRE1 protein contains CHASE domain at the N-terminal part, followed by a transmitter (histidine kinase) domain and two receiver
domains. The N-terminal CHASE domain ofAtCRE1 contains putative recognition sites for cytokinin. Five CHASE domains containing proteins were found in rice,osCRL1a,OsCRL1b,OsCRL2,OsCRL3, andOsCRL4.OsCRL1a,OsCRL1b,OsCRL2 andOsCRL3 contain the four domains existing inCRE1, whereasOsCRL4 only contains the CHASE domain and a putative Ser/Thr protein kinase domain. The authors cloned the encoding geneOsCRL4 and found that it represents a new member of the cytokinin receptor protein in rice.
Project supported by the National Natural Science Foundation of China 相似文献
13.
This preliminary study examines the utility of the Community Engagement Commitment Scale and reports on factors that predict student-teachers' commitment to community engagement in their second year of study at a South African university. Independent variables included Dalbert's personal belief in a just world, an adaptation of Rusbult et al.'s original predictors of Commitment level (Satisfaction, Quality of alternatives, Investment size) and a new factor, Meaningfulness. The latter factor is based theoretically on the work of Lieberman and Heine, Proulx and Vohs and was included to study the extent to which identity-expression could be related to Commitment level. We administered the Community Engagement Commitment Scale on a non-random sample of 414 student-teachers in their second year of study, who all participated in compulsory community engagement project. The results support a four-factor model of Commitment with Meaningfulness, Quality of alternatives and Investment as predictors of Commitment level. Surprisingly, all the Satisfaction items loaded with the Commitment level items on one factor. Together, Meaningfulness, Quality of alternatives and Investment accounted for approximately two-thirds of the variance in Commitment level. Significant (p?Meaningfulness and Commitment level. The results of the study suggest the importance of studying meaningfulness as an additional predictor of Commitment level in community engagement contexts. 相似文献
14.
Pinchas Tamir 《International Journal of Science Education》2013,35(3):327-338
Summaries English A special cognitive‐preference inventory dealing with agriculture was developed, validated and administered to 943 middle‐school students and their teachers. This is the first reported study of cognitive preferences of 7th and 8th grade (12 to 13 year‐old) students. The inventory was found to be a valid and reliable measure of cognitive preferences related to agricultural topics studied in Israeli schools. Preference for application (A) was found to be negatively correlated in different students with either recall (R) or principles (P) or critical questioning (Q). Studying the ‘new’ agriculture compared with the ‘old’, resulted in a lower preference for R and a higher preference for A. Female students had, on the average, a higher preference for R and P while males tended to prefer A and Q. Children whose fathers were simple workers had the highest preference for R while children whose fathers were academics had the lowest preference for R. Teachers, when compared with their students, had a much higher preference for P and a much lower preference for R. A close correspondence was found between reported emphasis in classroom tests and the cognitive‐preference modes of teachers. 相似文献
15.
Margareta Maria Thomson 《教育心理学》2016,36(3):502-525
This study focused on investigating the types of schooling beliefs (teaching and learning) expressed through metaphorical images by prospective teachers (PTs) from the United States. Participants (N = 215) rated 10 schooling metaphors illustrating the student–school–teacher relationships (i.e. Passenger–Bus–Driver; Student is a passenger, School is a bus and Teacher is a driver). Two main factors, a student-centred and a teacher-centred approach described the key schooling beliefs of PTs. Additionally, differences in PTs’ schooling beliefs across typologies/clusters of PTs were found. Further, qualitative data from interviews illustrated how each cluster specifically expressed their instructional views. 相似文献
16.
LU Li-gang YAN Li-tan XIANG Li-chi 《浙江大学学报(A卷英文版)》2007,8(1):158-163
INTRODUCTION Throughout this paper, we shall work with a filtered complete probability space (?,F,(Ft),P) sat-isfying the usual conditions. Let B=(Bt)t≥0 be a stan-dard Brownian motion with B0=0. Denote by ú the set of all non-negative real numbers. Recall that a diffusion process X starting at x≥0 is called the square of a Bessel process of dimension δ>0 if d X t = δd t 2 | X t |d Bt , X 0= x, (1) Clearly, this equation has a unique non-negative strong solution X, i.e., … 相似文献
17.
18.
Greer Anne Wenh‐In Ng 《Religious education (Chicago, Ill.)》2013,108(3):308-319
Abstract This article addresses the dilemma faced by religious and theological educators committed to a feminist, liberative pedagogy when teaching learners in the church whose Confucian upbringing has socialized them into different means of instruction. After a brief sketch of the Confucian ethos that permeates the life of such persons and communities in present‐day North America, the article examines the pedagogical practices of Confucius/Kongzi, traces the historical development of Confucianism, and suggests how we might live and teach in the tension of what appears to be two extremes of pedagogical practice. At fifteen 1 set my heart on learning; at thirty I firmly took my stand; ... At seventy 1 followed my heart's desire without overstepping the boundaries of right. —Analects 2:4 Learning something and practicing it often—is this not a delight? —Analects 1:1 Whenever three persons walk together, there is sure to be a teacher for me. —Analects 7:22 I learn without flagging and teach without growing weary. —Analects 7:34 相似文献
19.
The aim of this research is to characterize the development of fatigue damage by means of stress-strain hysteresis. Experiments were conducted on 14 specimens made of cold-finished unannealed AISI 1018 steel. Results demonstrate that the mechanical hysteresis loop areas, when plotted as a function of the number of loading cycles, show significant variations and demonstrate the three principal stages concerning the progress of the fatigue failure--initial accommodation, accretion of damage and terminal failure. These three stages of fatigue are marked by the transitions at cycles N2 and N3. Experimental results show that although fatigue life Nf ranges from 2644 cycles to 108 992 cycles, the ratios of N2/Nf and N3/Nf tend to be stable： N2/Nf=I 0.7%, N3/Nf=91.3%. 相似文献
20.
Zhang Hanlin 《上海大学学报(英文版)》1998,2(3):191-193
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