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首先给出空间简单光滑曲线Γ绕空间直线l旋转所得到的旋转曲面面积以及围成立体的体积求法,作为特例又给出了空间曲线Γ绕坐标轴旋转所得到的旋转曲面面积及围成立体的体积求法,同时也得到了平面曲线Γ绕直线l及坐标轴旋转分别所得到的旋转曲面面积和围成立体的体积求法. 相似文献
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In this paper two nonmonolone curved search (NCS) algorithms fur unconstrained optimization are presented. The NCS algorithms possess both a global convergence properly and a quadratic rale of convergence. Some numerical results are also reported which show that the NCS algorithn is superior to the usual curved search (UCS)aIgorithm for typical lest problems. 相似文献
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高等数学教材中关于二次曲面形状的讨论都采用截痕法.教学中引入直纹面概念,可为建筑施工专业的学生密切联系工程实际提供理论依据,收到较好的教学效果. 相似文献
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Dimitrios E. Kalikakis 《Transactions of the American Mathematical Society》2005,357(7):2829-2841
The notion of a saddle surface is well known in Euclidean space. In this work we extend the idea of a saddle surface to geodesically connected metric spaces. We prove that any solution of the Dirichlet problem for the Sobolev energy in a nonpositively curved space is a saddle surface. Further, we show that the space of saddle surfaces in a nonpositively curved space is a complete space in the Fréchet distance. We also prove a compactness theorem for saddle surfaces in spaces of curvature bounded from above; in spaces of constant curvature we obtain a stronger result based on an isoperimetric inequality for a saddle surface. These results generalize difficult theorems of S.Z. Shefel' on compactness of saddle surfaces in a Euclidean space.
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本文对比研究了关于弹性波模拟中的曲边地表形状处理的两种方法,一种是用给定的实际介质数值划定的地表形状,另一种是用样条插值逼近地表形状.本文采用有限元方法进行弹性波数值模拟,给出了基于这两种方法计算的数值例子,并对结果进行了分析比较.结果表明使用后一种方法对地表进行处理时,地表人工离散产生的干扰明显减少,优于前一种方法. 相似文献
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本文在Finsler曲面上定义了一个新的不变量H。该不变量等于零刻画了Riemann流形。文章给出了H的一个上界并且构造了H为常值的非Riemann的Finsler曲面。此外,本文还推广了Landsberg曲面的Gaus-Bonnet-Chern定理并分类了非正曲率的Finsler曲面。 相似文献
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讨论三元二次曲面是封闭图形的条件及封闭图形所围图形体积的计算,并将结果的形式推广到二元和一元二次方程所围封闭图形的判定上和面积或长度的计算上. 相似文献
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程少华 《数学的实践与认识》2007,37(1):61-65
曲面重构是逆向工程中的关键技术.根据非均匀有理B样条曲面矩阵表达式,对于造型曲面上的(2m+1)×(2n+1)个型值数据点,推导了一个仅利用型值点数据反算二次非均匀有理B样条曲面控制顶点的算法.数值算例表明了该算法的有效性. 相似文献
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赵虹 《数学的实践与认识》2013,43(10)
给出n元二次曲面是椭球面的充要条件和所对应的n维椭球体的体积计算公式,并且条件和体积的计算中只用到曲面中的系数行列式,使判定和体积计算较为方便. 相似文献
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用格子Boltzmann方法,数值研究流过前后排列两旋转圆柱体的二维层流.用二阶精度的速度场和温度场,数值化涉及运动的曲线边界.在Reynolds数为100,Prandtl数为0.71时,研究旋转速度比的变化和不同间距的影响.在4种不同间距(3, 1.5, 0.7, 0.2)下,研究旋转速度比的不同范围.结果表明,当间距取大数值时,第1个圆柱体的升力和阻力系数,与单个圆柱体相类似;对所有间距(除间距3以外),第2个圆柱体的升力系数,随着角速度的增加而减小,而阻力系数反而增加.圆柱体表面平均周期Nusselt数的结果表明,当两圆柱体间距小且角速度又低时,热传导是主要的传热机理,而当间距大且角速度又高时,对流是主要的传热机理. 相似文献
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《Optimization》2012,61(3):235-243
In this paper, we derive an unconstrained convex programming approach to solving convex quadratic programming problems in standard form. Related duality theory is established by using two simple inequalities. An ?-optimal solution is obtained by solving an unconstrained dual convex program. A dual-to-primal conversion formula is also provided. Some preliminary computational results of using a curved search method is included 相似文献
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本文是采用回归旋转设计方法,研究两套种作物农艺优化的数学模型.利用计算机模拟仿真,优化农艺方案.示范验证表明,这种试验方法可行,优化方案应用效果显著. 相似文献
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A second order isoparametric finite element method (IPFEM) is proposed for elliptic interface problems. It yields better accuracy than some existing second-order methods, when the coefficients or the flux across the immersed curved interface is discontinuous. Based on an initial Cartesian mesh, a mesh optimization strategy is presented by employing curved boundary elements at the interface, and an incomplete quadratic finite element space is constructed on the optimized mesh. It turns out that the number of curved boundary elements is far less than that of the straight one, and the total degree of freedom is almost the same as the uniform Cartesian mesh. Numerical examples with simple and complicated geometrical interfaces demonstrate the efficiency of the proposed method. 相似文献
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This study investigated the sound absorption of a nonlinearly vibrating curved panel backed by a cavity. Very few studies on similar nonlinear structural-acoustic problems have been conducted to date, although there have been many on nonlinear plate or linear structural-acoustic problems. A curved panel is considered because the overall absorption bandwidth can be designed by appropriately adjusting the panel curvature, which is a key factor in controlling the structural resonant frequencies and absorption peaks. The theoretical formulation is developed based on the assumptions of quadratic and cubic nonlinear structural vibrations, and the linear acoustic pressure induced within the cavity. An approach based on the numerical integration method is developed to solve the nonlinear governing equation of the structural-acoustic problem. In the parametric study, the panel displacement amplitude converges with an increasing number of modes. The effects of excitation level, cavity depth, and damping factor are also examined. The quadratic and cubic nonlinearities and their effects on the sound absorption are also investigated. An experiment was conducted. The theoretical and experimental observations correspond reasonably with each other. 相似文献
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Monica Roşiu 《复变函数与椭圆型方程》2015,60(2):181-190
We extend the notion and basic properties of quadratic differential divisors to a Klein surface, using the corresponding form’s divisors from the double cover of the Klein surface. 相似文献
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《Journal of Pure and Applied Algebra》2023,227(3):107208
We develop a curved Koszul duality theory for algebras presented by quadratic-linear-constant relations over unital versions of binary quadratic operads. As an application, we study Poisson n-algebras given by polynomial functions on a standard shifted symplectic space. We compute explicit resolutions of these algebras using curved Koszul duality. We use these resolutions to compute derived enveloping algebras and factorization homology on parallelized simply connected closed manifolds with coefficients in these Poisson n-algebras. 相似文献
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R. Delpak 《Applied Mathematical Modelling》1980,4(5):357-368
A curved parametric element, capable of giving the natural unforced and undamped frequencies of thin rotational shells has been developed. The new formulation possesses a number of interesting features including true nodal conformity, genuine curved generator, optional number of degrees of freedom and variable thickness. The nature of the displacements and the generation of the stiffness and the mass matrices are outlined in the text. Finally the accuracy of the present formulation is examined by considering a selection of well known examples. 相似文献