H.L. Liew

Multifrequency Analysis using Matrix Padé–via–Lanczos

In many problems in acoustics, the frequency response is required over a large range of frequencies in order to characterize the behavior of the system. The simplest approach based on solving the matrix system of equations arising from a finite element discretization of the problem across a frequency range using a direct or iterative solver at each frequency can be prohibitively expensive. However, in modeling a physical problem, the analyst may be interested only in the solution on a subset of the computational domain, called the partial field. This smaller field of interest may be used to form a Pad´e approximation for the matrix equations in the frequency domain, constructing a reduced–order model that can be solved efficiently over multiple frequencies to compute the response of the partial field. In this chapter, the matrix Pad´e–via–Lanczos algorithm is applied to structural acoustics and for problems with non–reflecting boundary conditions. The approach is extended by the introduction of an adaptive scheme which can automatically span a frequency range of interest, producing an efficient and robust algorithm for multifrequency analysis.

Adjoint‐based sensitivity analysis of fluid‐structure interaction vibrations

Adjoint‐based sensitivity analysis for the cavity fluid‐structure interaction vibrations problem, with the inclusion of prestress and internal pressurization, is considered. The formulation employs a continuum approach in which the adjoint model is defined by employing a new duality relation between the sensitivities and the adjoint variables. For complex problems, such as fluid‐structure interaction, the new duality relation provides an unambiguous approach for the construction of the adjoint variational problem in contrast to the standard approach. It also provides useful insight into the interpretation of the adjoint method. The resulting adjoint formulation for sensitivities is based on evaluation of inner products of the adjoint and state variables and is efficient because it requires the calculation of the adjoint field only once, regardless of the number of decision variables. In order to assess the accuracy of the adjoint approach for sensitivities in fluid‐structure interaction problems, a model ...

Statistical analysis of imperfection effect on cylindrical buckling response

It is widely reported that no efficient guidelines for modelling imperfections in composite structures are available. In response, this work evaluates the imperfection factors of axially compressed Carbon Fibre Reinforced Polymer (CFRP) cylinder with different ply angles through finite element (FE) analysis. The sensitivity of imperfection factors were analysed using design of experiment: factorial design approach. From the analysis it identified three critical factors that sensitively reacted towards buckling load. Furthermore empirical equation is proposed according to each type of cylinder. Eventually, critical buckling loads estimated by empirical equation showed good agreements with FE analysis. The design of experiment methodology is useful in identifying parameters that lead to structures imperfection tolerance.

Recent status of the KamLAND experiment

Abstract The KamLAND experiment is a very long baseline reactor ν e oscillation experiment. This experiment has sensitivity to the oscillation parameters Δm2 > 10−5 eV2 and sin2 2θ > 0.2, using reactor ν e which come typically from 170km away. This sensitive region completely covers the currently most favored MSW-LMA solution for the solar neutrino deficit problem. After 5 years of detector construction, the data taking started successfully in Jan. 2002. The detector performance is sufficient to perform reactor ν e physics and we expect the first physics result will come out soon. In this paper, the KamLAND detector, its expected sensitivities, history, and recent progress since the time of the conference, are briefly described.