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1.
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
2.
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
3.
1 Introduction Inthepastdecadeorso ,theexistenceofglobalat tractorsandtheestimatesoftheirHausdorffandfractaldimensionshavebeeninvestigatedfornumerousdissipa tivenonlinearpartialdifferentialequationswhichareau tonomous[1~ 4 ].Thenon autonomousinfinite dynami… 相似文献
4.
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
5.
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
6.
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
7.
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
8.
姜海益 《浙江大学学报(A卷英文版)》2004,5(7):754-758
Let k,m,n be positive integers,and k≥2,α∈(0,1],0<r<min {m,n} an integer,d=r (m-r)/(k α),and iff∈ Ck,α(Rm,R″),A =Cr(f)= {x ∈ Rm ,rank(Df(x))≤r},thenf(A)is d-null.Thus the statement posed by Arthur Sard in 1965 can be completely solved when k≥2. 相似文献
9.
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
10.
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
11.
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
12.
Philip A. Trostel 《Research in higher education》2010,51(3):220-247
This study quantifies one part of the return to U.S. public investment in college education, namely, the fiscal benefits associated
with greater college attainment. College graduates pay much more taxes than those not going to college. Government expenditures
are also much less for college graduates than for those without a college education. Indeed, over an average lifetime, total
government spending per college degree is negative. That is, direct savings in post-college government expenditures (conservatively,
about 85,000 per four-year-equivalent degree over an average lifetime) are greater than government expenditures on higher education (generously, about85,000 per four-year-equivalent degree over an average lifetime) are greater than government expenditures on higher
education (generously, about 74,500 per degree). Plus, the direct extra tax revenues from college graduates alone (roughly
$471,000 per degree over a lifetime) are more than six times the gross government cost per college degree. The average real
fiscal internal rate of return on government investment in college students is conservatively estimated to be 10.3%. 相似文献
13.
Kyong Hee Chon Won-Chan Lee Stephen B. Dunbar 《Journal of Educational Measurement》2010,47(3):318-338
In this study we examined procedures for assessing model-data fit of item response theory (IRT) models for mixed format data. The model fit indices used in this study include PARSCALE's G2 , Orlando and Thissen's S − X2 and S − G2 , and Stone's χ2* and G2* . To investigate the relative performance of the fit statistics at the item level, we conducted two simulation studies: Type I error and power studies. We evaluated the performance of the item fit indices for various conditions of test length, sample size, and IRT models. Among the competing measures, the summed score-based indices S − X2 and S − G2 were found to be the sensible and efficient choice for assessing model fit for mixed format data. These indices performed well, particularly with short tests. The pseudo-observed score indices, χ2* and G2* , showed inflated Type I error rates in some simulation conditions. Consistent with the findings of current literature, the PARSCALE's G2 index was rarely useful, although it provided reasonable results for long tests. 相似文献
14.
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
15.
Pigeons were trained in a duration-comparison procedure to peck one key if the comparison duration (c) was 1 sec shorter than a standard duration (s), and another key if c was 1 sec longer than s. During training, the s-c delay was 1 sec, and the total duration of an s-c pair was not predictive of the correct choice. In Experiment 1, during equal-duration pair test trials, pigeons increasingly
responded long (i.e., c τ s) as the s-c delay was lengthened. In Experiment 2, we demonstrated that s affected long responding on equal-duration test trials, even at the 8-sec s-c delay. In Experiment 3, long responding increased as the s-c delay was lengthened, even when stimulus conditions during the s-c delay differed from those during the intertrial interval (ITI). Additional analyses indicated that it was unlikely that the
increase in long responding was due to the pigeons’ adding the s-c delay to c and comparing the total against the duration of s. The increase in long responding with an increase in s-c delay is more consistent with subjective shortening of s than with confusion between the s-c delay and the ITI. 相似文献
16.
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
17.
《Equity & Excellence in Education》2013,46(5):4-11
Following is the text of two letters written by Willie Johnson of Chicago. The first one appeared in the Chicago Sun‐Times near the end of his first year as a student in hitherto all‐white Washington High School; the second, at the completion of his senior year. We ore grateful to Sun‐Times Editor James Hoge for permission to reprint the letters. 相似文献
18.
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
19.
《The International Journal of Art & Design Education》1997,16(1):91-101
McGeoch, B. And Porch, S Looking at Scottish Art Malcolm Dickson (editor) Art with People Hugh Ferguson Glasgow School of Art - The History Alan Crawford Charles Rennie Mackintosh Wendy Kaplan (editor) Charles Rennie Mackintosh Pamela Robertson Charles Rennie Mackintosh: Art is the Flower Janice Helland The Studios of Frances and Margaret Macdonald Architecture on Disc, Glasgow, 1995 Glasgow-on-Disc Prairie Multimedia Inc., Chicago, 1995 Frank Lloyd Wright Companion 相似文献
20.
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