The use of computers in the area of design and manufacturing is commonplace in industry. Many companies are turning to custom designed in-house software to surpass the competition. A growing number are developing knowledge-based expert systems to capture the knowledge of expertise of employees before they retire. The use of traditional artificial intelligence languages can be cumbersome to engineers who are usually familiar with traditional languages such as FORTRAN and C. The use of expert systems shells can often hinder the customization of an expert system due to limitations of the shell. An alternate approach to these methods is the use of an object-oriented framework that facilitates the creation of customized expert systems. This framework, called the Expert Consultation Environment, alleviates the programming problems of expert system development and allows the engineer to concentrate on knowledge acquisition. This thesis describes the design of the rule classes needed by the framework. These are the base Rule class, the Equation Rule class, the Control Rule class, the Constraint Rule class and the Heuristic Rule Class. Also presented, is the development of a methodology used in creating an expert system with the framework. A prototype expert system developed using the framework for parametric, multi-disciplinary, conceptual design of aircraft is described. / Master of Science

Since the availability of the first PHIGS (Programmers Hierarchical Interactive Graphics System) implementation in the mid 1980’s, interest in the use of PHIGS has been steadily growing among the CAD applications developer’s community. Every year, more PHIGS-based CAD applications programs are being created to ensure portability and make use of the high-level support provided by PHIGS [JAYA93b]. One of the common uses of computer graphics in engineering is for the creation of graphs. Commonly used graphs, such as line graphs (two-dimensional or three-dimensional), bar charts, pie charts, surface plots, etc., can be created using PHIGS. This involves the creation of several methods to scale the data, draw the graph, display labels, display axes, display legends and several other programming tasks, which are re-created by each applications program. This thesis describes the creation of an object-oriented class library to facilitate the creation of engineering graphs using PHIGS. This library provides the programmer with a set of tools to create commonly used graphs (line graphs, pie charts, bar charts, polar plots, and 3D plots). The class library will allow PHIGS programmers to quickly and easily create graphs for use with applications programs. This set of classes uses a PHIGS-based, Motif-like interface framework (described by Woyak and Myklebust [WOYA93]). User interface methods to allow the end-user of the graphing program to modify attributes of the graph (e.g. line types, legends, colors, etc.) are encapsulated within this class library and are hidden from the programmer using these classes. The library of classes, the user interface methods, and the use of this system is described in this thesis. / Master of Science

This work is a numerical study of the 2-D heat equation with Dirichlet boundary conditions over a polygonal domain. The motivation for this study is a chemical vapor deposition (CVD) reactor in which a substrate is heated while being exposed to a gas containing precursor molecules. The interaction between the gas and the substrate results in the deposition of a compound thin film on the substrate. Two different numerical approximations are implemented to produce numerical solutions describing the conduction of thermal energy in the reactor. The first method used is a Crank-Nicholson finite difference technique which tranforms the 2-D heat equation into an algebraic system of equations. For the second method, a semi-discrete method is used which transforms the partial differential equation into a system of ordinary differential equations. The goal of this work is to investigate the influence of boundary conditions, domain geometry, and initial condition on thermal conduction throughout the reactor. Once insight is gained with respect to the aforementioned conditions, optimal design and control can be investigated. This work represents a first step in our long term goal of developing optimal design and control of such CVD systems. This work has been funded through Partnerships in Research Excellence and Transition (PRET) grant number F49620-96-1-0329. / Master of Science

Power failure of pumps, sudden valve actions, and the operation of automatic control systems are all capable of generating high pressure waves in domestic water supply systems. These transient conditions resulting in high pressures can cause pipe failures by damaging valves and fittings. In this study, basic equations for solving transient analysis problems are derived using method of characteristics. Two example problems are presented. One, a single pipe system which is solved by developing an excel spreadsheet. Second, a pipe network problem is solved using transient analysis program called TRANSNET. A transient analysis program is developed in Java. This program can handle suddenly-closing valves, gradually-closing valves, pump power failures and sudden demand changes at junctions. A maximum of four pipes can be present at a junction. A pipe network problem is solved using this java program and the results were found to be similar to that obtained from TRANSNET program. The code can be further extended, for example by developing java applets and graphical user interphase to make it more user friendly. A two dimensional (2D) numerical model is developed using MATLAB to analyze gaseous cavitation in a single pipe system. The model is based on mathematical formulations proposed by Cannizzaro and Pezzinga (2005) and Pezzinga (2003). The model considers gaseous cavitation due to both thermic exhange between gas bubbles and surrounding liquid and during the process of gas release. The results from the model show that during transients, there is significant increase in fluid temperature along with high pressures. In literature pipe failures and noise problems in premise plumbing are atributed to gaseous cavitation. / Master of Science

Since the 1960's an overwhelming amount of in-house and custom engineering software has been written. In the effort to reduce the cost of maintaining existing codes and producing new applications, the recent introduction of the object-oriented design approach has proved successful. At the same time graphical user interfaces are gaining in popularity to improve the usability and versatility of an application. This thesis investigates the application of the object-oriented approach to the design of a graphical user interface for an engineering design application. The development of an object-oriented graphical user interface for the NASA Engine Performance Program, a turbine engine design code is presented. The design of the new object-oriented graphical user interface for extensibility and re-usability is discussed. Design considerations for integration of the interface with procedural and object-oriented versions of the conceptual aircraft design program, ACSYNT, are explained. An existing PHIGS-based object-oriented graphical user interfacing framework is extended and built upon to develop the class structure of the interface. The class organization is presented in commonly used notation and described in detail. / Master of Science

No description available.

This dissertation presents a new alternative type of object-oriented load-flow called Segflow. Segment objects are used to support the modeling of individual types of power system equipment. Current and voltage trace techniques are used by Segflow to bind Segment models in support of Kirchoff’s laws. Affiliation objects and the Target Voltage method are used to bring the solution of the Segflow model to the solution of the power system network. An example for modeling a simple transformer is given along with the solution results for a collection of common power system models. ‘ Analysis of the Target Voltage method and simulation results show that Segflow is capable of consistently solving the nonlinear load-flow problem. The object-oriented layout of Segflow provides very distinct modeling advantages. Power system modeling is from the perspective of each equipment’s model. Rather than force all equipment models into large sets of equations to be solved simultaneously by an equation solver, Segflow allows component models to remain intact and independent as Segment objects. Each Segment has a one-to-one correspondence with some piece of equipment in the respective power system which is maintained in the system solution. The behavior of a Segment can be evaluated throughout the load-flow process. An important feature of Segflow is the object-oriented design enabling new equipment models to be added into the Segflow environment as autonomous objects. New models are created from the Segment class and their inputs and outputs are always relative to the same Segment attributes. Because all Segment objects are derived from a Segment modeling class and all Segments are treated the same by Segflow, many types and varieties of power system equipment models can be easily created. A Segflow application is a collection of interacting objects whose interactions lead to a load-flow solution. Segflow is an interesting alternative to classical approaches for solving the load-flow problem with large sets of simultaneous nonlinear equations. It also adds new aspects to the application of object-oriented design in load-flow analysis. / Ph. D.

A prototype of an object-oriented structural analysis program is presented in order to explore object-oriented programming as a viable alternative to procedural programming. Modeling concepts are discussed with respect to procedural programming and object-oriented programming. Through the constructs provided by object-oriented programming, the program's components and component behavior are modeled as one-to-one analogies of their respective real world counterparts. Thus, like a real world structure, a structure in the program is composed of nodes, elements, and loads. The traditional fixed global stiffness matrix is replaced by a dynamic node network allowing the structure to be constructed dynamically. Implementing vector algebra with object-oriented programming removes the need for any explicit global to local or local to global coordinate transformations. These techniques provide a foundation for constructing a visually-oriented analysis and design environment. / M.S.

The object-oriented paradigm is widely advocated and has been used in South African universities since the late 1990s. Object-oriented computer programming is based on the object-oriented paradigm where objects are the building blocks that combine data and methods in the same entity. Students' performance in object-oriented programming (OOP) is a matter of concern. In many cases they lack the ability to apply various supportive techniques in the process of programming. Efficient knowledge, skills and strategies are required during problem solving to enhance the programming process. It is often assumed that students implicitly and independently master these high-level knowledge, skills and strategies, and that teaching should focus on programming content and coding structures only. However, to be successful in the complex domain of OOP, explicit learning of both programming and supportive cognitive techniques is required. The objective of this study was to identify cognitive, metacognitive and problem-solving knowledge, skills and strategies used by successful and unsuccessful programmers in OOP. These activities were identified and evaluated in an empirical research study. A mixed research design was used, where both qualitative and quantitative methods were applied to analyse participants' data. As a qualitative research practice, grounded theory was applied to guide the systematic collection of data and to generate theory. The findings suggest that successful programmers applied significantly more cognitive-, metacognitive- and problem-solving knowledge, skills and strategies, also using a greater variety, than the unsuccessful programmers. Since programming is complex, we propose a learning repertoire based on the approaches of successful programmers, to serve as an integrated framework to support novices in learning OOP. Various techniques should be used during problem solving and programming to meaningfully construct, explicitly reflect on, and critically select appropriate knowledge, skills and strategies so as to better understand, design, code and test programs. Some examples of teaching practices are also outlined as application of the findings of the study. / Mathematical Sciences / PhD. (Nathematics, Science and Tecnical Education)

Approved for public release; distribution is unlimited / Handheld devices have evolved significantly from mere simple organizers to more powerful handheld computers that are capable of network connectivity, giving it the ability to send e-mail, browse the World Wide Web, and query remote databases. However, handheld devices, because of its design philosophy, are limited in terms of size, memory, and processing power compared to desktop computers. This thesis investigates the use of Data Flow Query Language (DFQL) in querying local and remote databases from a handheld device. Creating Standard Query Language (SQL) queries can be a complex undertaking; and trying to create one on a handheld device with a small screen only adds to its complexity. However, by using DFQL, the user can submit queries with an easy to use graphical user interface. Although handheld devices are currently more powerful than earlier PCs, they still require applications with a small footprint, which is a limiting factor for software developed. This thesis will also investigate the best division of labor between handheld device and remote servers. / Sergeant, United States Army