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Finite element methods for stochastic structures and conditional simulation
Title
Finite element methods for stochastic structures and conditional simulation.
Creator
Ren, Yongjian., Florida Atlantic University, Elishakoff, Isaac, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
This dissertation deals with the non-perturbative finite element methods for stochastic structures and conditional simulation techniques for random fields. Three different non-perturbative finite element schemes have been proposed to compute the first and second moments of displacement responses of stochastic structures. These three methods are based, respectively, on (i) the exact inverse of the global stiffness matrix for simple stochastic structures; (ii) the variational principles for...
Show moreThis dissertation deals with the non-perturbative finite element methods for stochastic structures and conditional simulation techniques for random fields. Three different non-perturbative finite element schemes have been proposed to compute the first and second moments of displacement responses of stochastic structures. These three methods are based, respectively, on (i) the exact inverse of the global stiffness matrix for simple stochastic structures; (ii) the variational principles for statically-determinate beams; and (iii) the element-level flexibility for general stochastic statically indeterminate structures. The non-perturbative finite element method for stochastic structures possesses several advantages over the conventional perturbation-based finite element method for stochastic structures, including (i) applicability to large values of the coefficient of variation of random parameters; (ii) convergence to exact solutions when the finite element mesh is refined; (iii) requirement of less statistical information than that demanded by the high-order perturbation methods. Conditional simulation of random fields has been an extremely important research field in most recent years due to its application in urban earthquake monitoring systems. This study generalizes the available simulation technique for one-variate Gaussian random fields, conditioned by realizations of the fields, to multi-variate vector random field, conditioned by the realizations of the fields themselves as well as the realizations of the fields derivatives. Furthermore, a conditional simulation for non-Gaussian random fields is also proposed in this study by combining the unconditional simulation technique of non-Gaussian fields and the conditional simulation technique of Gaussian fields. Finally, the dissertation incorporates the simulation technique of random field into the non-perturbation finite element method for stochastic structures, to handle the cases where only one-dimensional probability density function and the correlation function of the random parameters are available, the demanded two-dimensional probability density function is unavailable. Simulation technique is applied to generate the samples of random fields which are used to estimate the correlation between flexibilities over elements. The estimated correlation of flexibility is then used in finite element analysis for stochastic structures. For each proposed approach, numerous examples and numerical results have been implemented.
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Date Issued
1998
PURL
http://purl.flvc.org/fcla/dt/12580
Subject Headings
Finite element method, Stochastic processes, Random fields--Mathematical models
Format
Document (PDF)
Remote database access over Internet in Windows environment
Title
Remote database access over Internet in Windows environment.
Creator
Ren, Yongjian., Florida Atlantic University, Hsu, Sam, Solomon, Martin K., College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
Abstract/Description
This thesis deals with remote database access over the Internet. Three different approaches to remote database access, the CGI-based approach, the Oracle Webserver-based approach and the CORBA-based approach, are discussed. Experiments are conducted to compare the pros and cons of each approach. The Oracle database and Microsoft Access database are utilized as the target database systems. For the CGI-based approach, the CGI programs are coded with ProC, Oracle's SQL-embedded C language, in...
Show moreThis thesis deals with remote database access over the Internet. Three different approaches to remote database access, the CGI-based approach, the Oracle Webserver-based approach and the CORBA-based approach, are discussed. Experiments are conducted to compare the pros and cons of each approach. The Oracle database and Microsoft Access database are utilized as the target database systems. For the CGI-based approach, the CGI programs are coded with ProC, Oracle's SQL-embedded C language, in Microsoft Visual C++ developer's studio, and a Student Record example is demonstrated. For the Oracle Webserver-based approach, the Oracle Webserver 1.1 has been setup and an Online Shopping Club example is demonstrated. For the CORBA-based approach, Orbix Web 2.0.1 and JDK 1.1.1 are utilized as the CORBA system and the development language, respectively, and several examples including single server, multiple servers and multiple databases are presented. An extended SQL syntax is proposed to manipulate data from multiple database systems residing on different hosts in one SQL statement. The implementation of extended SQL statements in CORBA's server/client application is also suggested. With the help of extended SQL syntax and CORBA's multiple server access feature, an example of the client application accessing two databases at a time is illustrated. The pros and cons are discussed of the three remote database access approaches studied in the thesis: (I) The CGI-based approach, which is the most generic and widely used approach. (II) The Oracle Webserver approach, which is a relatively simplified way of the CGI approach, easy to apply but limited in applications. (III) The CORBA-based approach, which is the most powerful and sophisticated approach for remote database access.
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Date Issued
1998
PURL
http://purl.flvc.org/fcla/dt/15590
Subject Headings
Database management, World Wide Web, Microsoft network (Online service)
Format
Document (PDF)