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This paper gives an algorithm for computing invariant rings of reductive groups in arbitrary characteristic.


The algorithm presented here computes a geometric characteristic of this action in the case where G is connected and reductive, and $\rho$ is a morphism of algebraic groups: The algorithm takes as input the


We present an algorithm for computing the invariant field k(X)G.


More precisely, we give an algorithm for computing a nonempty open subset of X with a geometric quotient.


We show that the rate of convergence for this reconstruction algorithm is geometric and computable in advance.

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 HAJIFII is a program system developed by Chinese Aeronautical Establishment(CAE). It is able to accomplish the calculation of the modal characteristics of aircraft structures as well as the flutter and gust response analysis with the active control system taken into account. The structural model may be composed of 99 substructures each with 7000 degrees of freedom. 300 panels may be used in the calculation of nonsteady aerodynamic forces and 50 modes in the flutter and gust response analysis. The data generation... HAJIFII is a program system developed by Chinese Aeronautical Establishment(CAE). It is able to accomplish the calculation of the modal characteristics of aircraft structures as well as the flutter and gust response analysis with the active control system taken into account. The structural model may be composed of 99 substructures each with 7000 degrees of freedom. 300 panels may be used in the calculation of nonsteady aerodynamic forces and 50 modes in the flutter and gust response analysis. The data generation system permits the flexible use of numerical data and topological description. 31 prescribed computational flows are supplied and an user can also organize his own computational flows as he needs. A structure can be discretized into finite elements or simulated by single spar. For the management of the stiffness and mass matrix a modified hypermatrix method is employed to omit all of inactive zero elements more effectively. A new algorithm, called a revised simultaneous iteration procedure, has been developed to solve the real eigenvalue problem and is more effective than the current agorithm. Modal synthesis technique with both free and fixed interfaces is adopted. Besides, two new methods of synthesis have been developed from the concept of multilevel substructures. Nonsteady aerodynamic forces are calculated by means of subsonic doublet lattice method for multiwings and aerodynamic forces in Laplace plane can be approximated with a curvefitting procedure based on sinusoidal data. Flutter equations are solved by Vg and pk methods and the continuous atmosphere turbulance are used in the gust response analysis. The system consists of a sequence of functional modules so it can be modified and extended easily. An advanced file management system has also been developed. There are approximately 26000 FORTRAN IV statements in the system. The HAJIFII was applied to analyzing a number of typical aircraft structures and gave good results.  HAJIFⅡ是中国航空研究院领导研制的航空结构动力分析系统。它可以进行结构的固有动力特性计算,以及带主动控制系统的飞机颤振计算和突风响应计算。它具有31条固定流程、2600条FORTRAN语句。允许使用99个原级子结构,每个子结构的自由度数可达7000。颤振计算和突风响应计算中,可以使用50个形态。非定常空气动力计算的分块数可达300个。在刚度矩阵和质量矩阵的管理上,采用超元矩阵方法做“宏观处理”,并用有效列方法做“微观处理”,发展了新的同时迭代算法,以提高实特征值计算的效率。设计了比较完整的形态综合法计算程序,除固定界面法和自由界面法之外,还发展了分级综合和逐步综合的新方法。非定常空气动力计算方面,引入了用曲线拟合方法把谐振荡空气动力转入拉氏平面的技术。用本系统计算了一批典型的结构,取得了良好结果。  Numerical methods for treating body boundary conditions in transonic flow through cascades are discussed in this paper. The purpose is to seek for a better algorithm for calculating boundary flow parameters which matches the internal difference scheme, so as to increase the accuracy of computation.First, characteristic relations on body boundaries arc derived. Second, five algorithms for boundary parameters are described briefly. Numerical tests on these algorithms have been made.The numerical... Numerical methods for treating body boundary conditions in transonic flow through cascades are discussed in this paper. The purpose is to seek for a better algorithm for calculating boundary flow parameters which matches the internal difference scheme, so as to increase the accuracy of computation.First, characteristic relations on body boundaries arc derived. Second, five algorithms for boundary parameters are described briefly. Numerical tests on these algorithms have been made.The numerical experiments show that the computational result of Denton's revised algorithm extrapolating parabolically along the y axis is the best of the five; this algorithm matches our internal difference scheme. Also, it can express more correctly the physical characteristics of transonic flow field with shock in plane cascades.  本文讨论了跨音速叶栅物面边界的数值处理方法,目的是寻求与我们所用内点格式相匹配的边界上流动参数的算法,以提高计算精度。本文首先推导了适合于物面边界计算的特征关系式,其次总结了五种边界处理方法,进行了数值试验。计算结果表明,配合我们的内点计算格式,以y向抛物外推的Denton修正法计算效果较好,能够较精确地反映跨音速叶栅带激波流场的物理特点。  In this paper a method is presented, in which the rotation angle from sunearth midsean λ_(se) in addition to the earth angle θ_e and sun angle θ_s are simultaneously used for determinating spinstabilized geostationary satellite attitude. This method gives uniquely one unambiguous attitude. Solution, simplifies the algorithm, eliminates regions of high correlation and low measurement density occuring when using two attitude measurements, and provides geometric condition where singularity occures only if... In this paper a method is presented, in which the rotation angle from sunearth midsean λ_(se) in addition to the earth angle θ_e and sun angle θ_s are simultaneously used for determinating spinstabilized geostationary satellite attitude. This method gives uniquely one unambiguous attitude. Solution, simplifies the algorithm, eliminates regions of high correlation and low measurement density occuring when using two attitude measurements, and provides geometric condition where singularity occures only if the earth and sun vectors are colinear. By this method, the angle λ_(se) is conveniently incorporated into the kalman or least square filter. Digital simulation showed that better accuracy of attitude determination and filter estimation can be obtained bv this method.  本文提出一种同时利用地球角θ_c、太阳角θ_s和星日星地转动角λ_(sc)三种姿态测量信息,确定卫星姿态的方法。该法算式简易,可唯一地确定卫星姿态。消除了采用两种姿态测量信息的姿态确定方法所引起的高相关和低测量密度的不良区域。本文方法仅有太阳矢量和地球矢量共线的几何限制,能方便地把λ_(sc)引入滤波器。通过数字仿真,表明此法可得到良好的姿态确定精度及滤波估计。   << 更多相关文摘 
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