A HYBRID STRESS QUADRILATERAL SHELL ELEMENT WITH FULL ROTATIONAL D.O.F.S

A 4-node hybrid stress quadrilateral shell element with 3 rotational d.o.f.s per node is presented. The mid-surface displacement of the element is founded on Allman's rotation. The equal-rotation mode intrinsic to the rotation is suppressed by a stabilization vector. The assumed stress field and the stabilization scalar is chosen such that membrane locking can be avoided. Computational efficiency of the element is improved by employing orthogonal stress modes and admissible matrix formulation. Popular benchmark tests are attempted and the results are found to be satisfactory. © 1997 by John Wiley & Sons, Ltd.     

SOLID ELEMENTS WITH ROTATIONAL DOFs BY EXPLICIT HYBRID STABILIZATION

Two brick elements equipped with Allman's rotation are presented. Strain energy of both elements is sub-integrated by the second order quadrature which gives rise to the hourglass mechanisms. Inasmuch as Allman's rotation is employed, the elements are also plagued by the equal-rotation mechanisms. Variational functional containing independently assumed stress, displacement and rotation is employed to formulate the stabilization devices for the elements. Computational cost of the elements is reduced by incorporating the explicit hybrid stabilization technique. Popular numerical benchmarks are studied and the present elements are found to be competitive to other state-of-the-art elements.     

Effect of magnetostriction on fracture of a soft ferromagnetic medium with a crack-like flaw

The magnetic‐induction field in the vicinity of an elliptical inclusion embedded in an infinite soft ferromagnetic medium is determined based on complex potential theory. By using a constitutive relation of magnetostriction for isotropic materials, the stress field in the vicinity of an elliptical flaw is obtained. Furthermore, the stress field at the tip of a slender elliptical crack is determined for the case in which only an external magnetic field perpendicular to the major axis of the ellipse is applied at infinity. The results indicate that the stress field in the neighbourhood of the tip is governed by the magnetostriction and permeability of the soft ferromagnetic material. The induction magnetostrictive modulus is a key parameter in determining which of the two mechanisms, i.e., magnetostriction and magnetic‐force‐induced deformation, is dominant in determining the stress field in the neighbourhood of the tip of a crack‐like flaw. With regard to the influence of the magnetic field on the apparent toughness of a soft ferromagnetic body with a crack‐like flaw, soft ferromagnetic materials can be roughly divided into two categories: one possesses a large induction magnetostrictive modulus and the other has a small modulus. An approximate criterion for categorizing the materials is presented. For the benefit of engineering design, the expressions of the stress‐intensity factor for these two categories of soft ferromagnetic materials are presented. The results show that the stress‐intensity factor is affected not only by the flaw geometry, but also by the permeability of the medium inside the flaw.     

Comments on ‘Convergence property of interval matrices and interval polynomials’

This note shows that the discrete linear interval system result of Mori and Kokame (1987) is also applicable to linear discrete time systems with linearly dependent perturbations.     

Robust H_2 estimation and control

This paper is concerned with the H2 estimation and control problems for uncertain discretetime systems with norm-bounded parameter uncertainty. We first present an analysis result on H2 norm bound for a stable uncertain system in terms of linear matrix inequalities (LMIs). A solution to the robust H2 estimation problem is then derived in terms of two LMIs. As compared to the existing results, our result on robust H2 estimation is more general. In addition, explicit search of appropriate scaling parameters is not needed as the optimization is convex in the scaling parameters. The LMI approach is also extended to solve the robust H2 control problem which has been difficult for the traditional Riccati equation approach since no separation principle has been known for uncertain systems. The design approach is demonstrated through a simple example.     

Second International Conference on Production Research

A mathematical model that predicts the dynamic flows in cellular mobile networks with handoff procedures is described in this paper. Two types of handoff procedures considered in the model are the non-prioritized and the prioritized or reserved channel schemes. The dynamic behaviour of this model makes it suitable to analyse dynamic channel allocation methods as well as to analyse the robustness of the system under perturbation. The basic concept of our model is based on the fluid flow theory and the queueing theory. Discrete event simulations were performed and the results were found to be comparable to the results obtained using the mathematical model.     

A systematic approach to ON-OFF event detection and clustering analysis of non-intrusive appliance load monitoring

The aim of non-intrusive appliance load monitoring (NIALM) is to disaggregate the energy consumption of individual electrical appliances from total power consumption utilizing non-intrusive methods. In this paper, a systematic approach to ON-OFF event detection and clustering analysis for NIALM were presented. From the aggregate power consumption data set, the data are passed through median filtering to reduce noise and prepared for the event detection algorithm. The event detection algorithm is to determine the switching of ON and OFF status of electrical appliances. The goodness-of-fit (GOF) methodology is the event detection algorithm implemented. After event detection, the events detected were paired into ON-OFF pairing appliances. The results from the ON-OFF pairing algorithm were further clustered in groups utilizing the K-means clustering analysis. The K-means clustering were implemented as an unsupervised learning methodology for the clustering analysis. The novelty of this paper is the determination of the time duration an electrical appliance is turned ON through combination of event detection, ON-OFF pairing and K-means clustering. The results of the algorithm implementation were discussed and ideas on future work were also proposed.     

ADAPTIVE EQUALIZATION WITH RLS-MLSE ASSISTED BY FEC BLOCK CODING FOR FADING MOBILE RADIO CHANNELS

In this paper, we propose an adaptive maximum-likelihood (ML) sequence estimator with RLS channel estimation, which is assisted by forward error control (FEC) coding. The reliable symbols reconstructed in the FEC decoder are used as the feedback signal to the RLS channel estimator. The scheme is compared with decision feedback equalization (DFE) with RLS algorithm, which is assisted by FEC coding. Computer simulations show that in frequency-selective fast fading mobile radio channels, the proposed scheme performs better at moderate Doppler frequencies. It is suitable for four-phase modulation data transmission at the rate of several 10 kb/s in 900 MHz band or in the 1800 MHz band.     

Some properties of the canonical parameter space

The canonical parameter space is symmetric. This simple result is used to extend several theorems on root location involving polynomials where only one class of polynomials is given. The smallest region containing polynomials with largest absolute-value zero of unity or less is derived. This leads to a simple proof for the strongest sufficient condition for the stability of linear discrete-time systems using absolute norms.     

Correcting Argoun's approach for the stability of interval matrices

Recently Xu and Shao (1989) pointed out that the approach of Argoun (1986) for the stability of interval matrices is incorrect. This note corrects his approach so that it can be used to check the stability of linear continuous-time systems with perturbations.