Papers by Author: Dong Lai Xu

Abstract: Insect infestation is a common problem for stored grain. In this paper, a novel pattern recognition approach combining an olfactory neural network entitled KIII with support vector machine (SVM) is proposed and used in conjunction with an electronic nose to generate recognition models. Using this approach, feature vectors are firstly processed by KIII model which stimulates information processing function of olfactory bulb, and then classified by SVM. Through optimization of SVM model parameters, the data are mapped into high dimension space and the stored wheat samples with different degrees of insect damage are distinguished successfully. The experimental results demonstrate that the proposed method can achieve up to 100% classification rate and significantly outperforms the conventional KIII-Minimum Euclidean Distance Classifier.

Abstract: Electromagnetic wave absorbers can be widely used in Electromagnetic Compatibility (EMC). We proposed a novel multilayer structure of metal alloy-ferrite-plastic composites. A new structure with Frequency Selected Surface (FSS), which has filter characteristic, embedded in the composites was fabricated to improve the absorption performance. In bandwidth of 8.04GHz, the reflectivity was smaller than-8dB and the thickness was only 2.6mm. The reflectivity was measured using a standard NRL Arch technique in a frequency range of 3-18 GHz. The experimental results indicate that it is possible to make a desirable thin, broadband EMW absorber by the incorporation of an FSS into the magnetic absorbing materials.

Abstract: Creep damage is one of the serious problems for the high temperature industries and computational approach (such as continuum damage mechanics) has been developed and used, complementary to the experimental approach, to assist safe operation. However, there are no ready creep damage constitutive equations to be used for predicting the lifetime for this type of alloy, particularly for low stress. This paper presents an analysis of the cavity nucleation, growth and coalescence mechanism of 9Cr-1Mo-VNb steel (P91 type) under high and low stress levels and multi-axial stress state.

Abstract: The preliminary validation of in-house finite element analysis software for creep damage mechanics is reported. The Finite Element Analysis Method and the programme strcuture for creep damage problem were reported elsewhere and the validation conducted so far include plane stress, plane strain, and axisymmetric cases. Furture work is also outlined.

Abstract: There is a need for a computational tool for analyzing creep damage problems for the research community and high temperature industries, and dedicated in-house software still has its merits and advantages. This paper reports the development of such software including the development of finite element algorithms based on CDM for creep damage analysis, and the use of some standard subroutines in programming, and sample of validation.

Abstract: This paper reported a validation of computational software system for creep damage analysis using circular notched bar. The complete computational software system for creep damage analysis consists of pre-and post-processing and the numerical solver and here the validation is primarily for the pre-and post-processing section developed by the authors. The creep damage evolution with time was post-processed interactively via FEMSYS.

Abstract: This paper presents an improved video segmentation scheme, which consists of two stages: initial segmentation and motion estimation. In the initial segmentation, the watershed transformation followed by a region adjacency graph guided region merging process is used to partition the first video frame into spatial homogenous regions. Then the motion of changed region is estimated. Based on the highly efficient quadratic motion model, the motion estimation is undertaken using Gauss-Newton Levenberg-Marquardt method to minimize the least-square error function. Experimental results show the proposed scheme provides high performance in terms of segmentation accuracy and video compression ratio.

Abstract: This paper presents a review of developing of creep damage constitutive equations for high chromium alloy (such as P91 alloy). Firstly, it briefly introduces the background of creep damage for P91 materials. Then, it summarizes the typical creep damage constitutive equations developed and applied for P91 alloy, and the main deficiencies of KRH (Kachanov-Robatnov-Hayhurst) type and Xus type constitutive equations. Finally it suggests the directions for future work. This paper contributes to the knowledge for the developing creep damage constitutive equations for the specific material.

Abstract: This paper reports a review on the computational (finite element) software for creep damage analysis. Firstly, it summarizes the current state of how to obtain such computational capability then it concludes with a preference of in-house software. It further reviews the validation practice. Finally, it completes with an outlines of the approach to be used in the developing in-house FE software.

Abstract: This paper reports a literature review on the development of computational software system for creep damage analysis for weldment. It starts with a brief review on the creep damage problem in weldment and the computational approach; identifies the need for computational approach and the un-availability of such computational system; further details on the preliminary development progress of a transfer programme and constitutive equation subroutines. This paper contributes to knowledge to the development of computational system for creep damage analysis.