Modelling of shear strength of rockfills used for the construction of rockfill dams

This paper presents the results of examination of shear properties of rockfills used for the construction of rockfill dams. Based on the results of a large number of experiments, mathematical model of the shear strength of the rockfill was derived, as a function of normal stress, initial compaction and uniaxial compressive strength of intact rock material. Using this model it is possible to make a realistic assessment of the shear strength of a rockfill for the Preliminary Design. The experimental data used for modelling were obtained by direct shear tests performed in the majority at the “Jaroslav Cerni” Institute for Development of Water Resources in Belgrade, Serbia.     

Aliasing detection and resolving in the estimation of polynomial-phase signal parameters

A novel method for aliasing detection and resolving in the estimation of polynomial-phase signal (PPS) parameters is presented. Aliasing is detected using two high-order ambiguity functions (HAFs) of a uniformly sampled PPS embedded in noise. If aliasing occurred, we propose a way of recovering the true parameters from their aliased positions. To that end, a closed-form expression for the true parameter value is derived. As opposed to the concurrent methods, the proposed method provides much more robust results with higher order PPSs and does not require nonuniform sampling. In addition, it can be readily extended to the multicomponent PPS case. Simulations support the theoretical results.     

An improvement in the calculation of the magnetic field for an arbitrary geometry coil with rectangular cross section

Hong Lei, Lian‐Ze Wang and Zi‐Niu Wu presented new simple and convenient solutions of the magnetic field for an arbitrary geometry coil with rectangular cross section. They treated two types of basic forms: the trapezoidal prism segment and curved prism segment. The curved prism segment has been divided into a series of small trapezoidal prism segments with the same cross section and its magnetic field is a vector sum of the individual fields created by each small trapezoidal prism conductor. For one trapezoidal prism conductor the magnetic field is obtained by 1‐D integrals using Romberg numerical integration. In this paper, we give a completely analytical solution of these 1‐D integrals that considerably saves the computational time especially in the computation of the magnetic field nearby the conductor surface, at the conductor surface and inside the conductor. From obtained analytical expressions the treatment of singularities can be easily done. Also, we tested four types of numerical integration (Gaussian, Romberg, Simpson and Lobatto) to find the most convenient singularity treatment of 1‐D integrals. These obtained results are compared with those obtained analytically so that one can understand the advantage of the proposed approach. The paper points out on the accuracy and the computational cost. Copyright © 2005 John Wiley & Sons, Ltd.     

Aeroelastic applications of the Connection Machine

This paper describes the implementation of a dynamical systems approach to aeroelastic analysis using the Connection Machine model 2 (CM-2). Through numerical simulation, the regions of harmonic and chaotic behavior in the δ,R_x (velocity, in-plane load) plane have been examined in detail. These regions are of interest in evaluation of the fatigue life of fluttering plates. The CM-2 computer architecture allows the removal of many of the previous simplifying and limiting assumptions regarding the prediction of the stability regions maps. Owing to its high-speed prediction capability, the CM-2, with framebuffer, offers 'real-time' display of the solution as it evolves during the prediction process. This feature gives insight into the fundamental way in which the solution evolves. This is essential in defining the scenarios describing roads to chaotic behavior of the dissipative dynamical systems.