Generalized Derivations in Prime Rings     

吴伟  宛昭勋 《天津大学学报(英文版)》2011,17(1):75-78

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   

Projectively flat Asanov Finsler metric     

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   

Congruences for finite triple harmonic sums   总被引：1，自引：0，他引：1  

FU Xu-dan ZHOU Xia CAI Tian-xin 《浙江大学学报(A卷英文版)》2007,8(6):946-948

Zhao (2003a) first established a congruence for any odd prime p>3, S(1,1,1;p)≡-2Bp-3 (mod p), which holds when p=3 evidently. In this paper, we consider finite triple harmonic sum S(α,β,γ;p) (mod p) is considered for all positive integers α,β,γ. We refer to w=α β γ as the weight of the sum, and show that if w is even, S(α,β,γ;p)≡0 (mod p) for p≥w 3; if w is odd, S(α,β,γ;p)≡rBp≥w (mod p) for p≥w, here r is an explicit rational number independent of p. A congruence of Catalan number is obtained as a special case.  相似文献   

A CHASE domain containing protein kinaseOsCRL4, represents a newAtCRE1-like gene family in rice     

Qiu-min  Han  Hua-wu  Jiang  Xiao-peng  Qi  Jie  Yu  Ping  Wu 《浙江大学学报(A卷英文版)》2004,5(6):629-633

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   

Results on energies for trees with a given diameter having perfect matching     

王文环  康丽英 《上海大学学报(英文版)》2011,15(6):493-500

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   

有向线图中的(k,l)-核     

鲁勤  单而芳  赵敏 《上海大学学报(英文版)》2006,10(6):484-486

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   

Viscosity approximation methods with weaMy contractive mappings for nonexpansive mappings     

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   

Association between infection of different strains of <Emphasis Type="Italic">Porphyromonas gingivalis</Emphasis> and <Emphasis Type="Italic">Actinobacillus actinomycetemcomitans</Emphasis> in subgingival plaque and clinical parameters in chronic periodontitis   总被引：3，自引：1，他引：2  

Wu YM  Yan J  Chen LL  Gu ZY 《Journal of Zhejiang University. Science. B》2007,8(2):121-131

Objective： The aim of this study was to investigate subgingival infection frequencies ofPorphyromonas gingivalis and Actinobacillus actinomycetemcomitans strains with genetic variation in Chinese chronic periodontitis （CP） patients and to evaluate its correlation with clinical parameters. Methods： Two multiplex polymerase chain reaction （PCR） assays were developed to detect the 16SrDNA, collagenase （prtC） and fimbria （fimA） genes of P. gingivalis and the 16SrDNA, leukotoxin （lktA） and fimbria-associated protein （fap） genes ofA. actinomycetemcomitans in 60 sulcus samples from 30 periodontal healthy subjects and in 122 subgingival plaque samples from 61 patients with CP. The PCR products were further T-A cloned and sent for nucleotide sequence analysis. Results： The 16SrDNA,prtC andfimA genes ofP. gingivalis were detected in 92.6%, 85.2% and 80.3% of the subgingival plaque samples respectively, while the 16SrDNA, lktA andfap genes ofA. actinomycetemcomitans were in 84.4%, 75.4% and 50.0% respectively. Nucleotide sequence analysis showed 98.62%-100% homology of the PCR products in these genes with the reported sequences. P. gingivalis strains with prtC＋/fimA＋ and A. actinomycetemcomitans with lktA＋ were predominant in deep pockets （〉6 mm） or in sites with attachment loss 〉5 mm than in shallow pockets （3-4 mm） or in sites with attachment loss 〈2 mm （P〈0.05）. P. gingivalis strains withprtC＋/fimA＋ also showed higher frequency in gingival index （GI）=3 than in GI=1 group （P〈0.05）. Conclusion： Infection ofP. gingivalis with prtC＋/fimA＋ and A. actinomycetemcomitans with lktA＋ correlates with periodontal destruction of CP in Chinese. Nonetheless P. gingivalis fim4, prtC genes and A. actinomycetem- comitans lktA gene are closely associated with periodontal destruction, while A. actinomycetemcomitansfap gene is not.  相似文献   

Projectively flat exponential Finsler metric     

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   

Precise asymptotics in the law of the logarithm for random fields in Hilbert space     

FU Ke-ang  ZHANG Li-xin 《浙江大学学报(A卷英文版)》2007,8(4):651-659

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   

受外部周期激励的弱阻尼受迫KdV方程的吸引子     

刘玉荣  刘曾荣  郑永爱  Liu Yu-rong  LIU Zeng-rong  ZHENG Yong-ai 《上海大学学报(英文版)》2000,4(3):194-196

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　Ｉｎｔｈｅｐａｓｔｄｅｃａｄｅｏｒｓｏ ,ｔｈｅｅｘｉｓｔｅｎｃｅｏｆｇｌｏｂａｌａｔ ｔｒａｃｔｏｒｓａｎｄｔｈｅｅｓｔｉｍａｔｅｓｏｆｔｈｅｉｒＨａｕｓｄｏｒｆｆａｎｄｆｒａｃｔａｌｄｉｍｅｎｓｉｏｎｓｈａｖｅｂｅｅｎｉｎｖｅｓｔｉｇａｔｅｄｆｏｒｎｕｍｅｒｏｕｓｄｉｓｓｉｐａ ｔｉｖｅｎｏｎｌｉｎｅａｒｐａｒｔｉａｌｄｉｆｆｅｒｅｎｔｉａｌｅｑｕａｔｉｏｎｓｗｈｉｃｈａｒｅａｕ ｔｏｎｏｍｏｕｓ[1～ 4 ].Ｔｈｅｎｏｎ ａｕｔｏｎｏｍｏｕｓｉｎｆｉｎｉｔｅ ｄｙｎａｍｉ…  相似文献   

L^p-estimates on a ratio involving a Bessel process     

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   

Exploring pre-service student-teachers' commitment to community engagement in the second year of training     

Salomé Human-Vogel  Hanlie Dippenaar 《高等教育研究与发展》2013,32(2):188-200

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   

在n维赋范空间中单位球体积及其渐进性质     

黄智悦  何斌吾 《上海大学学报(英文版)》2008,12(2):107-109

Let Bnp={x ∈ Rn‖|x ‖p≤l} be the unit ball ofp norm in the n-dimensional normed space p. The formula for the volume of Bnp was obtained and its asymptotic properties were found out as n→∞and p→∞.  相似文献   

Metaphorical images of schooling: beliefs about teaching and learning among prospective teachers from the United States displaying different motivational profiles     

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   

A new fast algorithm for computing the distance between two disjoint convex polygons based on Voronoi diagram     

YANG Cheng-lei QI Meng MENG Xiang-xu LI Xue-qing WANG Jia-ye 《浙江大学学报(A卷英文版)》2006,7(9):1522-1529

INTRODUCTION To compute the minimum distance between two convex polygons or polyhedrons is often a main step of many applications, such as collision detection (Choi et al., 2006; Li et al., 2003), path planning. In order to reduce the time complexity of the algorithm as much as possible, the convex property must be applied fully. Edelsbrunner (1985) proposed an algorithm for computing the minimum distance between two dis- joint convex polygons. The algorithm takes O(logm logn) time, and …  相似文献   

On sums of powers of integers     

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   

The generative paradigm     

Chris Loynes 《Journal of Adventure Education & Outdoor Learning》2013,13(2):113-125

This research highlights the learning of female offenders on a 20-day tailor-made experiential adventure education course (Women in Action) delivered by Outward Bound New Zealand. The aims of the course were to increase self-awareness, to develop an understanding of the concept of choice and self responsibility, to improve communication skills and to effectively influence others. Twenty-seven women were interviewed immediately after the course and 14 of these, three months post-course. Most women indicated that their self-confidence had increased and they had become more self-aware. Key factors in facilitating learning opportunities for the women were the instructors and the course environment both physical and social. The holistic course approach provided physical, creative, emotional and reflective opportunities, enabling all the women to develop personally. The challenge of applying their learning on return to prison was highlighted by some participants.