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A methodology was developed in this study for identifying the cognitive, pedagogical, and computational characteristics of computer-based learning environments. The characterization of the cognitive and pedagogical features was achieved by decomposing the learning environments into episodes which were composed of sequences of "views". Each "view" was described in terms of the different types of knowledge presented, the pedagogical strategies used to present the knowledge, and the forms and functions of user-computer interactions elicited. The computational characteristics were described in terms of modularity and other programming properties. The methodology was applied to characterizing the instructional programs produced by student teachers using Logo. / The results showed that this methodology can successfully identify the cognitive, pedagogical and computational characteristics of the learning environments. It can also clarify what can be learned in a microworld, especially the "powerful ideas" in Logo environments. In addition, the usability and constraints of learning environments in meeting the learners' cognitive needs during the learning process can be assessed.

A data structure editor is presented for use in an integrated, fragment-based programming environment. This editor employs high resolution computer graphics to present the user with an iconic representation of the internal storage of a running program. / The editor allows the creation, modification, and deletion of data structures. These abilities allow the user to quickly sketch data structures with which to test incomplete program fragments, alleviating the need for driver routines. / To keep the user cognizant of events inside his program, a technique for automated display management is presented allowing the user to keep the most important objects in the viewport at all times. A history facility permits the user to see the former values of all variables. / Execution controls are provided allowing the user to control the scope and speed of execution, manipulate frames on the run-time stack, set breakpoints, and profile the executing algorithm.

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Better methods for teaching computer science are needed. While no clear winner emerges in studies on the effectiveness of teaching media, the use of several media can be mutually reinforcing. Methods available to computer science teachers include lecturing, giving projector demonstrations, conducting hands-on sessions, monitoring independent study, and making a teaching machine available for group or individual use.A main strength of the teaching machine is its furnishing immediate feedback as students answer its quizzes. Teaching machines can assist in the major components of instruction: presenting information, guiding students, providing practice, and assessing student learning. They may take the form of tutorials, drills, simulations, or games. Good tutorials include directions, presentation frames, quizzes, assessment of student responses (with hints following mistakes), and facility to branch to different parts of the machine. A teaching machine's usefulness may be validated by comparing pre-test and post-test scores, by tracking student performance, and by field observation. Machines may be used solo or as a supplement and used with a whole class or as a means for bright students to forge ahead or slow students to catch up. / Department of Computer Science

Communication and networking are vast areas which are developing rapidly. It is very important to know in detail how the system works, how it can be enhanced to meet today's requirement, how to implement the appropriate techniques to obtain desired results etc. To explain all of the above, simulation techniques were adopted. Simulation plays an important role in developming new designs and modifying existing systems to make them more feasible and efficient.Protocols are the back bones of the communication systems and play a major role in data transfer. The review of literature provides an explanation of ISO/OSI models, layered approach and concepts of simulation. The simulation was carried out to explain the concepts of error detection, error correction and flow control in Data Link layer. Ada was used to develop the software, because of its concurrent processing tools called tasks. Also state-of-the-art utilities like Vax/Vms Screen Management System, File Definition Language, and Debugger were us ed in the program development. / Department of Computer Science

The purpose of this study is to explore the relationship between hit ratio of cache memory and design parameters. Cache memories are widely used in the design of computer system architectures to match relatively slow memories against fast CPUs. Caches hold the active segments of a program which are currently in use. Since instructions and data in cache memories can be referenced much faster than the time required to access main memory, cache memories permit the execution rate of the machine to be substantially increased. In order to function effectively, cache memories must be carefully designed and implemented. In this study, a trace-driven simulation study of direct mapped, associative mapped and set-associative mapped cache memories is made. In the simulation, cache fetch algorithm, placement policy, cache size and various parameters related to cache design and the resulting effect on system performance is investigated. The cache memories are simulated using the C language and the simulation results are analyzed for the design and implementation of cache memories. / Department of Physics and Astronomy

The Monte Carlo-type statistical ray-tracing method was used to investigate the performance of the line-focusing Fresnel mirror solar concentrator. An optical model of the line-focusing Fresnel mirror concentrator using the statistical ray-tracing approach was developed. Many rays of sunlight from the solar disk were selected at random and traced through the concentrator in this model. This optical model permits calculation of the local and geometric concentration ratios. The latter requires an energyloss analysis. Small sun-tracking errors of the diurnal or transverse type were included in the model.Based on the optical model and the Monte Carlo-type statistical ray-tracing method, a computer program was written implementing the model and computations using Pascal. To facilitate performance comparisons, a baseline concentrator design was adopted. To study the effects of imperfect tracking, performance data were generated for small tracking errors up to approximately two and one-half degrees. The selected mirror configuration permitted comparisons between the statistical approach and previous applications of the "extreme ray" analysis for an imperfectly tracking mirror concentrator.Simulation results demonstrated that the concentration characteristics are highly sensitive to the tracking error. The geometric concentration ratio dramatically decreases when the tracking error increases, which is the same as the "extreme ray" analysis. Results of some typical numerical calculations are presented graphically and discussed. / Department of Physics and Astronomy

The G-Net research group at Ball State University previously developed a graph editor, written in Java, with limited algorithm support. This editor was modified until the code had the instability of a legacy system. It was decided that, rather than continue working with the old system, a new version would be created.The enhancements planned for this new version were more efficient data structures, easy addition of new algorithms, and animated algorithm output. Additionally, the new version was to be written in compliance with the latest Java standards. This paper describes the structure of this new program, Jedit3.1. An overview of the structure of the program and detailed descriptions of the material that future programmers will need to understand in order to add new algorithms is included. Appropriate descriptions are included for files that future programmers should understand but not necessarily modify. / Department of Computer Science

The solar concentration performance of a tracking, flat-base, line-focusing Fresnel mirror was investigated in this study. The Fresnel mirror consists of flat mirror strips situated on a base and oriented at appropriate angles to focus incident light to a desired line. Simple optical ray tracing and energy conservation were used to develop a mathematical model of the concentrator assuming small or zero diurnal tracking errors. The model analyzed the concentrator design and provided detailed expressions for the geometric evaluation of the concentrated sunlight rays in the focal plane above the mirror. The local concentration ratio and the geometric concentration ratio were introduced to describe the intensity profile in the focal plane and the average concentration of sunlight on a target absorber. Included in the model were losses of incident sunlight due to imperfect reflection, nonreflecting portions of the base, and blockage by adjacent mirror strips when imperfect tracking occurs.Based on the analytical model and using the Ada high level language, a computer program was written to simulate the concentrator. To facilitate performance comparisons, a baseline concentrator design was adopted. To study the effects of imperfect tracking, performance data were generated for small tracking errors up to approximately two and one-half degrees. The effects of design variations were studied by varying the concentrator focal length, strip width, and base width.Simulation results demonstrated that the concentration characteristics were highly sensitive to tracking error. Intensity profile shifts relative to the target caused the highest losses in intercepted sunlight.Design decisions were found to dramatically affect the concentration character- istics. For the baseline concentrator under perfect tracking conditions, an optimum focal length was identified. Except for the disadvantage of added costs, decreased strip widths was found to be a way to increase both the maximum and average concentration ratio for the absorber. Using smaller strip widths might, however, critically affect the energy intercepted by the target under imperfect tracking. Increasing the concentrator base width increased the total amount of power in the focal plane, with a higher maximum concentration ratio and additional tailing of the intensity profile. / Department of Physics and Astronomy