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Engineering Example (engineering + example)

Distribution by Scientific Domains
Engineering62%

Selected Abstracts

Analysis of coupled seepage and temperature fields in concrete dam

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 6 2002
Article first published online: 28 MAR 200, Chai Junrui
Abstract It is very important to investigate the coupled problem and solution of seepage and temperature fields in the concrete dam. Seepage through the concrete dam influences the distribution of the temperature field in the dam by heat exchange. The temperature field in the dam also influences the hydraulic conductivity and seepage through the dam. The mechanism of the action and reaction between the seepage and temperature fields in the concrete dam is analysed according to the seepage characteristics of the concrete dam. The continuum mathematical model for coupled seepage and temperature fields in the concrete dam is presented, and the iterative steps and the finite element numerical solution method for the coupled model are proposed. An engineering example is also given to show the applicability of the proposed model and numerical solution method. It can be shown from the example that the difference between the coupled and uncoupled solution to the two fields in the dam is about 4,5%. Copyright © 2002 John Wiley & Sons, Ltd. [source]

A new formulation of Signorini's type for seepage problems with free surfaces

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2005
H. Zheng
Abstract A new variational inequality formulation for seepage problems with free surfaces is presented, in which a boundary condition of Signorini's type is prescribed over the potential seepage surfaces. This makes the singularity of seepage points eliminated and the location of seepage points determined easily. Compared to other variational formulations, the proposed formulation can effectively overcome the mesh dependency and significantly improve the numerical stability. A very challenging engineering example with complicated geometry and strong inhomogeneity is investigated in detail. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Bayesian meta-modelling of engineering design simulations: a sequential approach with adaptation to irregularities in the response behaviour

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 15 2005
A. Farhang-Mehr
Abstract Among current meta-modelling approaches, Bayesian-based interpolative methods have received significant attention in the literature. These methods are particularly known for their capability to adapt to the response function behaviour in order to generate good meta-models with fewer experiments. Current Bayesian adaptation techniques, however, are mainly based on the assumption that some variables are more important (or sensitive) than others. These less sensitive variables are weighted less or ignored to reduce the dimension of the design space. This assumption limits the scope and applicability of these models since in many practical cases none of the variables can be completely ignored or weighted less than others. This paper proposes a pragmatic approach that identifies regions of the design space where more experiments are needed based on the response function behaviour. The proposed approach adaptively utilizes the information obtained from previous experiments, builds interim meta-models, and identifies ,irregular' regions in which more experiments are needed. The behaviour of the interim meta-model is then quantified as a spatial function and incorporated into the next stage of the design to sequentially improve the accuracy of the obtained meta-model. The performance of the new approach is demonstrated using a numerical and an engineering example. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Wavelet-based adaptive robust M-estimator for nonlinear system identification

AICHE JOURNAL, Issue 8 2000
D. Wang
A wavelet-based robust M-estimation method for the identification of nonlinear systems is proposed. Because it is not based on the assumption that there is the class of error distribution, it takes a flexible, nonparametric approach and has the advantage of directly estimating the error distribution from the data. This M-estimator is optimal over any error distribution in the sense of maximum likelihood estimation. A Monte-Carlo study on a nonlinear chemical engineering example was used to compare the results with various previously utilized methods. [source]

Fuzzy approach to dependability performance evaluation

QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 7 2008
Dejan Ivezi
Abstract This paper presents a model for dependability performance evaluation by fuzzy sets utilization. Basic dependability indicators (reliability, maintainability and maintenance support) are used for the analysis of technical systems' conditions from the aspects of design, construction, maintenance and logistics. These indicators as well as associated dependability expressions itself are described by linguistic variables, which are characterized by a membership function to the defined classes. The proposed model is primarily appropriate for introduction, analysis and synthesis of information related to quality of systems in operation. Such data are often available only as experts' judgment and estimations. A practical engineering example (mechanical system at bucket wheel excavator) has been presented to demonstrate the proposed dependability analysis and synthesis model. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Some peculiarities of load sharing control

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 7 2003
Eduard Eitelberg
In the recently published book, ,Load Sharing Control' (Eitelberg, 1999), a frequency domain, loop-by-loop load sharing control system design methodology was developed and demonstrated with engineering examples. A number of new concepts were introduced in order to characterize some peculiarities that are not relevant in single-loop control systems, or have been overlooked in the general multivariable control system theory. Some of these concepts and peculiarities are introduced and explained in this paper with a minimum of technical detail. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Model-based synthesis of nonlinear PI and PID controllers

AICHE JOURNAL, Issue 8 2001
Raymond A. Wright
PI and PID controllers continue to be popular methods in industrial applications. It is well known that linear PI and PID controllers result from the application of model-based controller design methods to linear first- and second-order systems. It is shown that nonlinear PI and PID controllers result from the application of nonlinear controller design methods to nonlinear first- and second-order systems. As a result, the controllers resulting from nonlinear model-based control theory are put in a convenient form, more amenable to industrial implementation. Additionally, the quantities used in the controller are useful for monitoring the process and quantifying modeling error. Chemical engineering examples are used to illustrate the resulting control laws. A simulation example further demonstrates the performance of the nonlinear controllers, as well as their useful process monitoring quantities. [source]

Understanding the shape of the mixture failure rate (with engineering and demographic applications)

APPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 6 2009
Maxim Finkelstein
Abstract Mixtures of distributions are usually effectively used for modelling heterogeneity. It is well known that mixtures of DFR distributions are always DFR. On the other hand, mixtures of IFR distributions can decrease, at least in some intervals of time. As IFR distributions often model lifetimes governed by ageing processes, the operation of mixing can dramatically change the pattern of ageing. Therefore, the study of the shape of the observed (mixture) failure rate in a heterogeneous setting is important in many applications. We study discrete and continuous mixtures, obtain conditions for the mixture failure rate to tend to the failure rate of the strongest populations and describe asymptotic behaviour as t,,. Some demographic and engineering examples are considered. The corresponding inverse problem is discussed. Copyright © 2009 John Wiley & Sons, Ltd. [source]