Development of an interactive computer graphics system with application to data fitting

The work reported in this thesis is organized into two parts. Part I presents a review study of the existing graphics facilities in terms of hardware and software (Chapter 2), interactive input techniques (Chapter 3) and the organization of graphics output processes and application data structures (Chapter 4). Finally, in Part I, a full account is presented concerning the development and implementation of the basic graphics software package LIGHT. Part II contains a detailed discussion of the implementation of several application programs which employ the basic graphics software developed in Part I. The applications cover the following problem areas: (1) Interpolatory Data Fitting (IDF); (2) Interactive Contour Tracing (ICT); (3) Triangular Mesh Generation (TMG). Finally, full program listings of the basic software and the application modules are given in the Appendices accompanying this thesis

Reliability Abstracts and Technical Reviews January-December 1968

No abstract availabl

Protecting Systems From Exploits Using Language-Theoretic Security

Any computer program processing input from the user or network must validate the input. Input-handling vulnerabilities occur in programs when the software component responsible for filtering malicious input---the parser---does not perform validation adequately. Consequently, parsers are among the most targeted components since they defend the rest of the program from malicious input. This thesis adopts the Language-Theoretic Security (LangSec) principle to understand what tools and research are needed to prevent exploits that target parsers. LangSec proposes specifying the syntactic structure of the input format as a formal grammar. We then build a recognizer for this formal grammar to validate any input before the rest of the program acts on it. To ensure that these recognizers represent the data format, programmers often rely on parser generators or parser combinators tools to build the parsers. This thesis propels several sub-fields in LangSec by proposing new techniques to find bugs in implementations, novel categorizations of vulnerabilities, and new parsing algorithms and tools to handle practical data formats. To this end, this thesis comprises five parts that tackle various tenets of LangSec. First, I categorize various input-handling vulnerabilities and exploits using two frameworks. First, I use the mismorphisms framework to reason about vulnerabilities. This framework helps us reason about the root causes leading to various vulnerabilities. Next, we built a categorization framework using various LangSec anti-patterns, such as parser differentials and insufficient input validation. Finally, we built a catalog of more than 30 popular vulnerabilities to demonstrate the categorization frameworks. Second, I built parsers for various Internet of Things and power grid network protocols and the iccMAX file format using parser combinator libraries. The parsers I built for power grid protocols were deployed and tested on power grid substation networks as an intrusion detection tool. The parser I built for the iccMAX file format led to several corrections and modifications to the iccMAX specifications and reference implementations. Third, I present SPARTA, a novel tool I built that generates Rust code that type checks Portable Data Format (PDF) files. The type checker I helped build strictly enforces the constraints in the PDF specification to find deviations. Our checker has contributed to at least four significant clarifications and corrections to the PDF 2.0 specification and various open-source PDF tools. In addition to our checker, we also built a practical tool, PDFFixer, to dynamically patch type errors in PDF files. Fourth, I present ParseSmith, a tool to build verified parsers for real-world data formats. Most parsing tools available for data formats are insufficient to handle practical formats or have not been verified for their correctness. I built a verified parsing tool in Dafny that builds on ideas from attribute grammars, data-dependent grammars, and parsing expression grammars to tackle various constructs commonly seen in network formats. I prove that our parsers run in linear time and always terminate for well-formed grammars. Finally, I provide the earliest systematic comparison of various data description languages (DDLs) and their parser generation tools. DDLs are used to describe and parse commonly used data formats, such as image formats. Next, I conducted an expert elicitation qualitative study to derive various metrics that I use to compare the DDLs. I also systematically compare these DDLs based on sample data descriptions available with the DDLs---checking for correctness and resilience

Reliability Abstracts and Technical Reviews January-December 1969

No abstract availabl

The New Hampshire, Vol. 76, No. 11 (Oct. 11, 1985)

The student publication of the University of New Hampshire

Interactive airline fleet assignment model

Cover titleSeries statement hand-written on coverMay 1981Includes bibliographical references (p. 105-108)This thesis investigates the Airline Fleet Assignment models which have been designed during the past 10 years within MIT's Flight Transportation Laboratory. Emphasis is placed on developing an interactive computer system, called IFA/1, which simplifies the use of fleet assignment models and improves the insertion or modification of necessary data. The first section gives a general review of the mathematical models used for vehicle planning in air transportation, with special attention given to the Airline Fleet Assignment and Fleet Planning problem. The techniques used to solve these problems are discussed, and one model of particular interest, the FA4 model, is introduced. The second part describes how FA4 is used in practice and points out some of its major deficiencies. An improvement is proposed through the means of an interactive computer package available at the Flight Transportation Laboratory. Future modifications to this interactive system are also discussed. Finally, an alternative solution is suggested to one of the theoretical problems which underlies the Fleet Assignment model: the "phantom frequency problem". This issue is discussed and a new set of equations is proposed which improves the efficiency of the model

Air transportation schedule planning

Cover titleJune 1972Includes bibliographical referencesOne of the routing and scheduling problems faced by an airline is to configure a route network. It seeks to answer the following two questions: First, should scheduled service be provided for a city pair market? Second, if market entry is warranted, should the city pair be served by a non-stop, multi-stop, or connect routing? A profit maximizing airline, in trying to answer these questions, has to abide by the route regulations imposed by the Civil Aeronautics Board. The airline has to take into account the inter carrier route competition. It has to recognize that its share of the passenger demand is a function of the level of service offered, and that passengers usually want to reach their destination in the most convenient routing for themselves. An optimization model is formulated for the route network configuration problem. Because of the huge combinatorial dimensionality inherent in the problem, a special solution method has to be devised. Only a handful of the most promising, feasible route candidates are identified at a time. An optimal choice is immediately made out of the few candidates. These route candidates are generated "as needed" by graph theoretic schemes, while route selection is performed by solving an integer program characterized by an ill-behaved objective function. At each generation/selection step, route network improvement is made by the optimal selection of the route candidate (i) to add to an existing network, (ii) to replace an unprofitable route, or simply (iii) to be deleted from the route network. The solution algorithm is based on the method of successive approximation in dynamic programming. Primal feasibility is maintained at all times. If the algorithm is stopped prematurely, due to limited computational resources, an improved (but not necessarily optimal) solution is always available. A 40-routine computer software package for the algorithm has been developed. It was successfully used to analyze a case study from American Airlines. Our limited computational experience showed that execution time is at least seven times faster than a comparable algorithm.Sponsored in part by Slater Funds for Flight Transportation and the NASA research grant -- Joint University Research Program for Air Transportation Needs, and a fellowship from the M.I.T.-Harvard Joint Center for Urban Studies

Home As A Place Of Work

The focus of this dissertation is essentially theoretical, and to do with concepts, assumptions and dualisms relating to 'home'- and 'work'. These are seen as socially constructed concepts in a dialectical relationship with one another; to understand one it is necessary to understand the other. It is argued that the meaning of 'home', in particular, has been largely taken for granted and unquestioned. A method of interpretation, combining hermeneutics with a critical edge, was roughly followed; incorporated within this were the principles of grounded theory that would permit concepts to be developed from data. A theoretical sample that clearly crossed the boundary between home and work - self-employed independents who worked from home - was targeted, resulting in twenty in-depth interviews. The contrasts between (a) an apparent sense of autonomy but lack of legitimacy, and (b) a relatively good work situation but poor market situation were related to the distinction between being in one's own house -and being self-employed - but being seen as 'at home'. There was found to be a contradiction between what were believed to be the generally accepted meanings of 'home' and 'work' and those of the group; whereas the former were not compatible with using home as a place of work, being a contradiction of one another, the latter were. In this situation, strategies such as avoidance of the term 'at home' and a tendency to use 'professional' were evident. A postal survey provided verification and some clarification of these findings. The theoretical analysis draws on the way in which the separation of 'home' from 'work' resulted from a restricted and simplified model of the Industrial Revolution and the Enlightenment emphasis on rationality. Whereas work was associated with rational liberal economic and scientific values which expressed the legitimate Modern paradigm, home remained associated with conservative values and nature - the non-rational

An investigation into the viability of deploying thin client technology to support effective learning in a disadvantaged, rural high school setting

Computer Based Training offers many attractive learning opportunities for high school pupils. Its deployment in economically depressed and educationally marginalized rural schools is extremely uncommon due to the high technology skills and costs involved in its deployment and ongoing maintenance. This thesis puts forward thin client technology as a potential solution to the needs of education environments of this kind. A functional business case is developed and evaluated in this thesis, based upon a requirements analysis of media delivery in learning, and upon formal cost/performance models and a deployment field trial. Because of the economic constraints of the envisaged deployment area in rural education, an industrial field trial is used, and the aspects of this trial that can be carried over to the rural school situation have been used to assess performance and cost indicators. Our study finds that thin client technology could be deployed and maintained more cost effectively than conventional fat client solutions in rural schools, that it is capable of supporting the learning elements needed in this deployment area, and that it is able to deliver the predominantly text based applications currently being used in schools. However, we find that technological improvements are needed before future multimediaintensive applications can be adequately supported