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1.
Burkardt,J.V,29 O,形ordan,E.,1 76 Chan,L.C.,57 Chen,H.,1 Chen,丫T.,138 Chen,2.,1 13 Cho,D.,44 Qiu,J.,435 Rong,2.,275 Dai,丫一H.,460 de川meida,V,410 Du,K.,357 Sheng,Q.,198 Shishkin,G.1.,150,214 Siebert,K.G.,245 Stylles,J.,  相似文献   

2.
设1,r1,r2,...rm,x,1,r1,r2...,rm,x,y,y∈(a,b),a,b,1,r1,r2,...,rm。  相似文献   

3.
关于方程xy+yz+zx=n的正整数解   总被引:1,自引:1,他引:0  
陈锡庚  乐茂华 《数学学报》1998,41(3):577-582
本文在广义Riemann猜想成立的条件下证明了:当且仅当正整数n=1,2,4,6,10,18,22,30,42,58,70,78,102,130,190,210,330,462时,方程xy+yz+zx=n无正整数解(x,y,z).  相似文献   

4.
乐茂华 《数学进展》1996,25(4):328-333
本文证明了:方程x2+2m=yn,x,y,m,n∈N,gcd(x,y)=1,n>2仅有有限多组解(x,y,m,n),而且当(x,y,m,n)≠(5,3,1,3),(11,5,2,3),(7,3,5,4)时,n是适合n≡7(mod8)以及23≤n<8.5·106的奇素数,max(x,y,m)<C1;方程x2-2m=yn,x,y,m,n∈N,gcd(x,y)=1,y>1;n>2仅有有限多组解(x,y,m,n),而且这些解都满足n<2·109炉以及max(x,y,m)<C2,这里C1,C2是可有效计算的绝对常数.  相似文献   

5.
《高等数学研究》2009,12(2):30-30
数学类:概率论(北京大学,陈大岳),高等数学(北京航空航天大学,郑志明),数值分析(大连理工大学,于波),高等数学(合肥工业大学,朱士信),复变函数(湖州师范学院,刘太顺),泛函分析(内蒙古大学,孙炯),代数与几何(清华大学,张贺春),数学分析与习题课(苏州大学,谢惠民),金融衍生物定价理论(同济大学,姜礼尚),数学建模(厦门大学,谭忠),高等数学(郑州大学,李梦如),数值分析(中南大学,韩旭里).  相似文献   

6.
《上海中学数学》2011,(7):15-16,59-62
一、选择题 I.已知U={1,2,3,4,5,6,7,8},A={1,3,5,7},B={2,4,5},则C0(AUB)=  相似文献   

7.
大家都知道斐波那契(Fibonacci Number)关于兔子繁殖的故事.兔子每月的数量依次为一个数列:1,1,2,3,5,8,13,21,34,55,89,144,233,377…,设这个数列记为{Fn}:F1,F2,F3,F4,…,Fn,…,易知,F1=F2=1,从第3项起每一项都等于它的前两项的和,  相似文献   

8.
群J~(6,k_1,…,k_l)的决定   总被引:1,自引:0,他引:1  
吴振德  刘宗泽 《数学学报》1994,37(3):296-300
设 k1<k2<…< kl, ki;为正整数,我们已决定群J6,k2,…,kl(ki为偶数, k2> 12),本文决定了群J6,10,k3…,kl,J6,8,k3,…,k1(k3> 10),J6,8,10,k4,…,kl(ki为偶数)  相似文献   

9.
文[1]中,王方汉老师有如下猜想:当n为形如4m-1(mEN)的素数时,生成数列凡一l=(1,2,…,牛/,M,…,2,l)所确定的数列B,,具有遍历性.也就是说,设数列凡1=(r,12,…,r。-l),h为正整数,B。=(hi,bZ,…,b。),1=hi<bZ<…<b。且均为整数,设凡;与B。之间有如下映射关系:。。。。,;;=(1,2,…,宁,宁,…,2,1)且n为形如4m-1的素数时,数列B。各项被n除的余数恰是0,1,2,…,n-1的一个全排列.显然,数列B。=(hi,bZ,…,b。)各项被n除的余数恰是0,1,2,…,n一且的一个全排列等价于…  相似文献   

10.
X1,…,Xm;Y1,…,Yn为独立随机样本,X,X1,…,Xm同分布,X-F,F(0)=0,Y,Y1,…,Ynm同分布,Y的分布函数为G(y)=1/μ∫yω(t,β)dF(t),y≥0,其中,β∈R,μ=∫0^∞ω(t,β)dF(t),0〈μ,ω(t,β)〈∞,F,μ和β均未知,ω(t,β)的形式已知,设θ为一待估参数,且存在一已知函数ψ(X,θ)满足EFψ(X,θ)=0,本文利用经验似然法给出  相似文献   

11.
The influence of displacements of tensioned fibers on the impregnation of fibrous layers with a polymer melt and on the final composite structure is studied. Using computer simulation, it is shown that, during impregnation, the structure of tensioned fibrous layers changes considerably depending on the initial arrangement and tensioning of fibers. The consolidated regions formed under the melt front move inside the impregnated layer with the advancing melt front. Displacement of the tensioned fibers as well as the formation of “washouts” favors the impregnation of internal layers, but cause significant inhomogeneity of the polymer structure. The surface (on the side of the melt flow) regions are more saturated with the polymer than the internal ones. A difference in the melt percolation mechanisms at various impregnation regimes is revealed. The effective permeability coefficients of a tensioned fiber layer are not constant but depend on the conditions and regimes of impregnation. Submitted to the 11th Conference on the Mechanics of Composite Materials (Riga, June 11–15, 2000). Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 2, pp. 259–270, March–April, 2000.  相似文献   

12.
Two polyester-based polymer concretes with various volume content of diabase as an extender and aggregate are tested in creep under compression at different stress levels. The phenomenological and structural approaches are both used to analyze the experimental data. Common features of changes in the instantaneous and creep compliances are clarified, and a phenomenological creep model which accounts for the changes in the instantaneous compliance and in the retardation spectrum depending on the stress level is developed. It is shown that the model can be used to describe the experimental results of stress relaxation and creep under repeated loading. Modeling of the composite structure and subsequent solution of the optimization problem confirm the possibility of the existence of an interphase layer more compliant than the binder. A direct correlation between the interphase volume content and the instantaneous compliance of the composite is revealed. It is found that the distinction in nonlinearity of the viscoelastic behavior of the two polymer concretes under investigation can be due to the difference in their porosity. Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000.) Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 2, pp. 147–164, 2000.  相似文献   

13.
The shear failure of reinforced concrete beams needs more attention than the bending failure since no or only small warning precedes the failure. For this reason, it is of utmost importance to understand the shear bearing capacity and also to be able to undertake significant rehabilitation work if necessary. In this paper, a design model for the shear strengthening of concrete beams by using fiber-reinforced polymers (FRP) is presented, and the limitations of the truss model analogy are highlighted. The fracture mechanics approach is used in analyzing the bond behavior between the FRP composites and concrete. The fracture energy of concrete and the axial rigidity of the FRP are considered to be the most important parameters. The effective strain in the FRP when the debonding occurs is determined. The limitations of the anchorage length over the cross section are analyzed. A simple iterative design method for the shear debonding is finally proposed. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 3, pp. 357–372, May–June, 2008.  相似文献   

14.
This paper investigates the exact and approximate spectrum assignment properties associated with realizable output-feedback pole-placement type controllers for single-input single-output linear time-invariant time-delay systems with commensurate point delays. The controller synthesis problem is discussed through the solvability of a set of coupled diophantine equations of polynomials. An extra complexity is incorporated to the above design to cancel extra unsuitable dynamics being generated when solving the above diophantine equations. Thus, the complete controller tracks any arbitrary prefixed (either finite or delaydependent) closed-loop spectrum. However, if the controller is simplified by deleting the above mentioned extra complexity, then the robust stability and approximated spectrum assignment are still achievable for a certain sufficiently small amount of delayed dynamics. Finally, the approximate spectrum assignment and robust stability problems are revisited under plant disturbances if the nominal controller is maintained. In the current approach, the finite spectrum assignment is only considered as a particular case to the designer‘s choice of a (delay-dependent) arbitrary spectrum assignment objective.  相似文献   

15.
We consider error estimates for optimal and Gaussian quadrature formulas if the integrand is analytic and bounded in a certain complex region. First, a simple technique for the derivation of lower bounds for the optimal error constants is presented. This method is applied to Szeg?-type weight functions and ellipses as regions of analyticity. In this situation, the error constants for the Gaussian formulas are close to the obtained lower bounds, which proves the quality of the Gaussian formulas and also of the lower bounds. In the sequel, different regions of analyticity are investigated. It turns out that almost exclusively for ellipses, the Gaussian formulas are near-optimal. For classes of simply connected regions of analyticity, which are additionally symmetric to the real axis, the asymptotic of the worst ratio between the error constants of the Gaussian formulas and the optimal error constants is calculated. As a by-product, we prove explicit lower bounds for the Christoffel-function for the constant weight function and arguments outside the interval of integration. September 7, 1995. Date revised: October 25, 1996.  相似文献   

16.
Dynamical spin susceptibility is calculated for the tJ model in the superconducting phase using the memory function method in terms of the Hubbard operators. The self-consistent system of equations for the memory function is obtained within the mode-coupling approximation. Both itinerant hole excitations and localized spin fluctuations contribute to the memory function. Moreover, the itinerant contribution itself consists of two parts, i.e., the contribution of Bogoliubov quasiparticles and that of Cooper pairs. The spin dynamics is diffusive in the hydrodynamic limit, but the itinerant part does not contribute to the spin diffusion. In the high frequency region, spin–wave-like excitations continue to exist. We discuss our analytic results in the light of neutron scattering experiments performed on the cuprate superconductors.  相似文献   

17.
颤振分析中判断颤振临界速度的重要依据是系统V-g和V-f图,即系统特征值随参数的变化曲线.在几乎所有商用软件及自编程序的输出结果中,有时会出现所谓的"窜支"现象,这给颤振临界速度和颤振穿越分支及耦合形式的判断带来很大不便.通过隐函数定理可以证明,除重特征值点以外,系统特征值连续依赖于系统参数变化.依据多元向量值函数连续性,建立对特征值的排列算法,给出系统特征根轨迹的正确曲线,再输出V-g和V-f图数据,从而避免"窜支"现象.编制应用程序,通过几个典型算例对算法进行了验证.该工作能够有效简化颤振分析的后处理工作,提高分析效率.  相似文献   

18.
It is considered the class of Riemann surfaces with dimT1 = 0, where T1 is a subclass of exact harmonic forms which is one of the factors in the orthogonal decomposition of the spaceΩH of harmonic forms of the surface, namely The surfaces in the class OHD and the class of planar surfaces satisfy dimT1 = 0. A.Pfluger posed the question whether there might exist other surfaces outside those two classes. Here it is shown that in the case of finite genus g, we should look for a surface S with dimT1 = 0 among the surfaces of the form Sg\K , where Sg is a closed surface of genus g and K a compact set of positive harmonic measure with perfect components and very irregular boundary.  相似文献   

19.
This paper demonstrates the application of both numerical simulation and empirical equation in predicting the penetration of a concrete target by an ogive-nosed projectile. The results from the experiment performed by Gran and Frew [In-target radial stress measurements from penetration experiments into concrete by ogive-nose steel projectiles, Int. J. Impact Eng. 19 (8) (1997) 715–726] are used as a benchmark for comparison. In the numerical simulations a 3.0-caliber radius-head steel ogival-nose projectile with a mass of 2.3 kg is fired against cylindrical concrete target with a striking velocity of 315 m/s. The simulation, performed using AUTODYN 2-D, assesses three numerical schemes, namely Langrange, Euler–Lagrange coupling and smooth particles hydrodynamics SPH–Lagrange coupling, in predicting the maximum depth of penetration and the radial stress–time response of the concrete target. When assessing the three solution techniques we hypothesize that the effect of strain rate on strength for the concrete target does not adversely affect the prediction on the maximum depth of penetration and the radial stress–time response of the concrete target. In the empirical approach the penetration equation developed by Forrestal et al. [An empirical equation for penetration depth of ogive-nose projectiles into concrete targets, Int. J. Impact Eng. 15 (4) (1994) 395–405] is used to determine the maximum depth of penetration and the deceleration–time response. The deceleration–time response for the projectile using the empirical approach is compared with those obtained from the numerical simulations. Results from both the numerical and empirical approaches are consistent. The calculated depth of penetration from both approaches yield relatively good agreement with that obtained from the experiment. The numerical simulations using each of the three numerical schemes are also able to reproduce the profiles from the radial stress measurements. Simulations using the SPH numerical scheme give the best overall agreement. The good overall agreement with the experimental radial stress measurements and consistent results between both empirical and numerical approach, enhanced the confidence in engineers and ballisticians when using these two approaches in complementing full-scale testing.  相似文献   

20.
We give a necessary and sufficient condition for the existence of an exponential attractor. The condition is formulated in the context of metric spaces. It also captures the quantitative properties of the attractor, i.e., the dimension and the rate of attraction. As an application, we show that the evolution operator for the wave equation with nonlinear damping has an exponential attractor.  相似文献   

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