Waverider configurations derived from general conical flowfields

A method based on the computational fluid dynamics (CFD) is presented for a flexible waverider's design. The generating bodies of this method could be any cones. In addition, either the leading edge or the profile of the scramjet's inlet is used as the waverider's definition curve, parameterized by the quadric function, the sigmoid function or the B-spline function. Furthermore, several numerical examples are carried out to validate the method and the relevant codes. The CFD results of the configurations show that all the designs are successful. Moreover, primary suggestions are proposed for practical design by comparing the geometrical and aerodynamic performances of the cone-derived waveriders at Mach 6.

Comparison of wavelet transform methods - The compression of IR spectral data

In this paper, an introduction of wavelet transform and multi-resolution analysis is presented. We describe three data compression methods based on wavelet transform for spectral information,and by using the multi-resolution analysis, we compressed spectral data by Daubechies's compactly supported orthogonal wavelet and orthogonal cubic B-splines wavelet, Using orthogonal cubic B-splines wavelet and coefficients of sharpening signal are set to zero, only very few large coefficients are stored, and a favourable data compression can be achieved.

基于IGES的卷曲类工件结构光测量路径规划研究

本文通过对卷曲类工件IGES文件的分析,本文提出了一种新的基于IGES文件的测量路径规划策略。根据张量积曲面的性质,提出了一种曲面组合算法,运用了张量积曲面的性质,将曲面操作转化为多次曲线操作,将IGES文件中存储的多片曲面片组合为一整片曲面,从而为自由曲面测量路径的提取提供了数学模型。运用二次逼近原理,提出了一种B样条曲线上的等距采样算法。通过在实际系统进行实验,上述策略及算法得到了验证,并在自主开发的智能测量建模加工一体化装备中得到了应用。

监控式水下机械手及相关技术的研究

水下机械手作为水下机器人通用作业工具得到广泛地应用，目前水下机械手的主要操作方式为主从方式。虽然主从方式具有操作直观，灵活的特点，但难于完成需要精确定位，轨迹控制的水下作用，如海洋石油钻井平台导管架的检查作用。为了扩展水下机器人的作业能力，提高水下作业智能化程度，沈阳自动化所承担国家863课题“水下虚拟遥操作与监控机械手系统”关键技术的研究工作。作者参加了此课题的研究工作，以Schilling水下机械手为研究对象，深入研究机械手的作用功能，对机械手的逆运动学，焊缝空间轨迹规划作了深入的研究，形成本文阐述的主要内容。由于Schilling水下机械手各关节之间的连接参数中存在多个偏距，其运动学逆解不能简单由解析方式给出。机械手进行控制与轨迹规划等操作必须找到一种快速求解的方法。本篇文章得出一种基于信赖域法的机械手运动学逆解算法。由于该算法具有收敛速度快的特点，故可以被应用于在线求解机械手运动学逆解；由于没有直接求解二阶导数，故不存在奇异解的问题。经理论分析和实验证明该方法在解决水下监控机械手在线跟踪水下结构物空间轨迹的技术问题具有较好的效果。作为课题的实际应用背景的导管架焊缝曲面为一复杂的空间曲面。为了实现课题的研究目标，本课题不仅要求解焊缝的轨迹，而且要给出其法线方向。对于这样一个问题，用空间解析几何和微分几何方法是很难求解的，本文给出了一种基于B样条参数曲面及曲面求交的方法，具有速度快，通用性强的优点。

Single ionization of helium by antiproton impact

We study the ionization of helium (fie) in collision with antiprotons (p) in the energy range from 10 keV to 1000 keV. We adopt a semiclassical single center close coupling approach in which the wave function for the electron is expanded in a B-spline basis centered on the nucleus of the He atom, The calculations are performed using two different models: the independent particle (IP) model and the one-electron (OE) approximation. The interaction between the active electron and the rest of the atom, i.e. passive electron and nucleus, is represented by a model potential. The results obtained are compared with experimental data as well as with existing theoretical calculations. (c) 2005 Published by Elsevier B.V.

Ionization of atomic hydrogen and He+ by slow antiprotons

We study the ionization of H(1s), He+(1s) and He+(2s) by antiprotons in the energy range from 0.1 to 500 keV. We adopt a semiclassical single centre close-coupling approach in which the wavefunction for the electron is expanded in a B-spline basis centred on the nucleus of the atom/ion. Comparison is made with existing theoretical calculations and available experimental data. The results are encouraging.

Many-body theory of positron-atom interactions

A many-body theory approach is developed for the problem of positron-atom scattering and annihilation. Strong electron- positron correlations are included nonperturbatively through the calculation of the electron-positron vertex function. It corresponds to the sum of an infinite series of ladder diagrams, and describes the physical effect of virtual positronium formation. The vertex function is used to calculate the positron-atom correlation potential and nonlocal corrections to the electron-positron annihilation vertex. Numerically, we make use of B-spline basis sets, which ensures rapid convergence of the sums over intermediate states. We have also devised an extrapolation procedure that allows one to achieve convergence with respect to the number of intermediate- state orbital angular momenta included in the calculations. As a test, the present formalism is applied to positron scattering and annihilation on hydrogen, where it is exact. Our results agree with those of accurate variational calculations. We also examine in detail the properties of the large correlation corrections to the annihilation vertex.

Dynamics of Gompertzian tumour growth under environmental fluctuations

We investigate the effect of correlated additive and multiplicative Gaussian white noise oil the Gompertzian growth of tumours. Our results are obtained by Solving numerically the time-dependent Fokker-Planck equation (FPE) associated with the stochastic dynamics. In Our numerical approach we have adopted B-spline functions as a truncated basis to expand the approximated eigenfunctions. The eigenfunctions and eigenvalues obtained using this method are used to derive approximate solutions of the dynamics under Study. We perform simulations to analyze various aspects, of the probability distribution. of the tumour cell populations in the transient- and steady-state regimes. More precisely, we are concerned mainly with the behaviour of the relaxation time (tau) to the steady-state distribution as a function of (i) of the correlation strength (lambda) between the additive noise and the multiplicative noise and (ii) as a function of the multiplicative noise intensity (D) and additive noise intensity (alpha). It is observed that both the correlation strength and the intensities of additive and multiplicative noise, affect the relaxation time.

3D die shape optimisation for net-shape forging of aerofoil blades

This paper reports on work in developing a finite element (FE) based die shape optimisation for net-shape forging of 3D aerofoil blades for aeroengine applications. Quantitative representations of aerofoil forging tolerances were established to provide a correlation between conventional dimensional and shape specifications in forging production and those quantified in FE simulation. A new direct compensation method was proposed, employing variable weighting factors to minimise the total forging tolerances in forging optimisation computations. A surface approximation using a B-spline surface was also developed to ensure improved die surface quality for die shape representation and design. For a Ni-alloy blade test case, substantial reduction in dimensional and shape tolerances was achieved using the developed die shape optimisation system.

Energy levels, wavefunction compositions and electric dipole transitions in neutral Ca

A configuration-interaction approach, based on the use of B-spline basis sets combined with a model potential including monoelectronic and dielectronic core polarization effects, is employed to calculate term energies and wavefunctions for neutral Ca. Results are reported for singlet and triplet bound states, and some quasi-bound states above the lowest ionization limit, with angular momentum up to L = 4. Comparison with experiment and with other theoretical results shows that this method yields the most accurate energy values for neutral Ca obtained to date. Wavefunction compositions, necessary for labelling the levels, and the effects of semi-empirical polarization potentials on the wavefunctions are discussed, as are some recent identifications of doubly-excited states. It is shown that taking into account dielectronic core polarization changes the energies of the lowest terms in Ca significantly, in general by a few hundred cm(-1), the effect decreasing rapidly for the higher bound states. For Rydberg states with n approximate to 7 the accuracy of the results is often better than a few cm(-1). For series members (or perturbers) with a pronounced 3d character the error can reach 150 cm(-1). The wavefunctions are used to calculate oscillator strengths and lifetimes for a number of terms and these are compared with existing measurements. The agreement is good but points to a need for improved measurements.

Recoil-induced electronic excitation and ionization in one-and two-electron ions

The electronic redistribution of an ion or atom induced by a sudden recoil of the nucleus occurring during the emission or capture of a neutral particle is theoretically investigated. For one-electron systems, analytical expressions are derived for the electronic transition probabilities to bound and continuum states. The quality of a B-spline basis set approach is evaluated from a detailed comparison with the analytical results. This numerical approach is then used Io study the dynamics of two-electron systems (neutral He and Ne ) using correlated wavefunctions for both the target and daughter ions. The total transition probabilities to discrete states, autoionizing states and direct single- and double-ionization probabilities are calculated from the pseudospectra. Sum rules for transition probabilities involving an initial bound state and a complete final series are discussed.

INFLUENCE OF CORE POLARIZATION ON THE ELECTRON-AFFINITY OF CA

We have developed a method, based on the use of B-spline basis sets and model potentials, for determining properties of systems with two or three electrons outside a polarizable closed-shell core. It is applied to the calculation of the electron affinity of Ca and the resulting value of 17.7 meV is in excellent agreement with the most recent experiments. It is found that the dielectronic core-valence interaction reduces the electron affinity by 39.5 meV.

Positron scattering and annihilation in hydrogenlike ions

Diagrammatic many-body theory is used to calculate the scattering phase shifts, normalized annihilation rates Zeff, and annihilation ? spectra for positron collisions with the hydrogenlike ions He+, Li2+, B4+, and F8+. Short-range electron-positron correlations and longer-range positron-ion correlations are accounted for by evaluating nonlocal corrections to the annihilation vertex and the exact positron self-energy. The numerical calculation of the many-body theory diagrams is performed using B-spline basis sets. To elucidate the role of the positron-ion repulsion, the annihilation rate is also estimated analytically in the Coulomb-Born approximation. It is found that the energy dependence and magnitude of Zeff are governed by the Gamow factor that characterizes the suppression of the positron wave function near the ion. For all of the H-like ions, the correlation enhancement of the annihilation rate is found to be predominantly due to corrections to the annihilation vertex, while the corrections to the positron wave function play only a minor role. Results of the calculations for s-, p-, and d-wave incident positrons of energies up to the positronium-formation threshold are presented. Where comparison is possible, our values are in excellent agreement with the results obtained using other, e.g., variational, methods. The annihilation-vertex enhancement factors obtained in the present calculations are found to scale approximately as 1+(1.6+0.46l)/Zi, where Zi is the net charge of the ion and l is the positron orbital angular momentum. Our results for positron annihilation in H-like ions provide insights into the problem of positron annihilation with core electrons in atoms and condensed matter systems, which have similar binding energies.

Time-dependent R-matrix theory applied to two-photon double ionization of He

We introduce a time-dependent R-matrix theory generalized to describe double-ionization processes. The method is used to investigate two-photon double ionization of He by intense XUV laser radiation. We combine a detailed B-spline-based wave-function description in an extended inner region with a single-electron outer region containing channels representing both single ionization and double ionization. A comparison of wave-function densities for different box sizes demonstrates that the flow between the two regions is described with excellent accuracy. The obtained two-photon double-ionization cross sections are in excellent agreement with other cross sections available. Compared to calculations fully contained within a finite inner region, the present calculations can be propagated over the time it takes the slowest electron to reach the boundary.

Genetic programming and bacterial algorithm for neural networks and fuzzy systems design

In the field of control systems it is common to use techniques based on model adaptation to carry out control for plants for which mathematical analysis may be intricate. Increasing interest in biologically inspired learning algorithms for control techniques such as Artificial Neural Networks and Fuzzy Systems is in progress. In this line, this paper gives a perspective on the quality of results given by two different biologically connected learning algorithms for the design of B-spline neural networks (BNN) and fuzzy systems (FS). One approach used is the Genetic Programming (GP) for BNN design and the other is the Bacterial Evolutionary Algorithm (BEA) applied for fuzzy rule extraction. Also, the facility to incorporate a multi-objective approach to the GP algorithm is outlined, enabling the designer to obtain models more adequate for their intended use.