Scout motor performance analysis and prediction study /PAPS/

Scout motor performance analysis and predictio

On the Origin of Recursive Procedures

We investigate the origin of recursive procedures in imperative programming languages. We attempt to set the record straight, and to identify the trend that led to recursive procedures, by means of an analysis of the related concepts and of the most reliable available documents, as far as known to us. We show that not all of those who were involved in defining these concepts in these documents were fully aware of the implications of their proposals. Our aim is not primarily historical, but to contribute to a clarification of some of the concepts related to recursion. In particular, we demonstrate that recursive procedure declarations and recursive procedure activations are logically disjoint concepts

Dissolving a half century old problem about the implementation of procedures

We investigate the semantics of the procedure concept, and of one of the main techniques introduced by E. W. Dijkstra in his article Recursive Programming to implement it, namely the "static link," sometimes also called "access link" or "lexical link." We show that a confusion about that technique persists, even in recent textbooks. Our analysis is meant to clarify the meaning of that technique, and of the procedure concept. Our main contribution is to propose a better characterization of the "static link."

Effects of radiation environment on reusable nuclear shuttle system

Parametric tradeoff analyses of a wide spectrum of alternate tank configurations to minimize both primary and secondary, direct and scattered radiation sources emanating from the NERVA are reported. The analytical approach utilizing point kernel techniques is described and detailed data are presented on the magnitude of neutron/gamma doses for different locations. Single-tank configurations utilizing smaller cone angles and end cap radii were found to minimize integral radiation levels, hence, stage shielding-weight penalties for shuttle missions. Hybrid configurations employing an upper tank with a reduced cone angle and end cap radius result in low integral payload doses primarily due to the increased separation distance caused by the elongation of the larger capacity upper tank. A preliminary radiation damage assessment is discussed of possible reusable nuclear shuttle materials, components, and subsystems, and the possible effects of the radiation environment on various phases of RNS mission operations

Modules and Dialects as Objects in Grace

Grace is a gradually typed, object-oriented language for use in education; consonant with that use, we have tried to keep Grace as simple and straightforward as possible. Grace needs a module system for several reasons: to teach students about modular program design, to organise large programs, especially its self-hosted implementation, to provide access to resources defined in other languages, and to support different “dialects”—language subsets, or domain specific languages, for particular parts of the curriculum. Grace already has several organising constructs; this paper describes how Grace uses two of them, objects and lexical scope, to provide modules and dialects

Feasibility, parametric design, and comparative analysis of an unguided solid fuel rocket vehicle with solar orbit, earth probe, and re-entry mission capabilities

Feasibility, parametric design, and comparative analysis of unguided solid fuel rocket vehicle with solar orbit, earth probe, and reentry mission capabilitie

Software maintenance: generating front ends for cross referencer tools

This thesis surveys the activities performed in software maintenance and identifies some of the software tools which can be utilised by the maintenance programmer. The most expensive phase of software maintenance is surveyed in more detail and tools to support this activity are identified. A new class of cross referencer tool was designed and investigated. The novel aspect of the cross referencer is that it can be used on more than one language, by utihzing grammar driven generators to customize and make maximum re-use of the language independent components, allowing language specific implementations to be generated with minimal effort. The cross referencer also extends an idea of having different levels of detail in cross reference listings by allowing the tool implementor to specify the contents of each level of detail. A proposed experimental toolkit for the automatic construction of these cross referencer front end tools, from non procedural specifications, is designed and investigated

Phase-Only Digital Encryption

Abstract—We study then-dimensional deconvolution prob-lem associated with an impulse response function and an(additive) noise function that are both characterised by thesame phase-only stochastic spectrum. In this case, it is shownthat the deconvolution problem becomes well-posed and has ageneral solution that is both exact and unique, subject to are-normalisation condition relating to the scale of the solution.While the phase-only spectral model considered is of limitedvalue in general (in particular, problems arising in the fieldsof digital signal processing and communications engineering,specifically with regard to the retrieval of information fromnoise), its application to digital cryptography has potential.One of the reasons for this (as discussed in this paper),is that it provides a method of encrypting data where thediffused plaintext can be effectively embedded in a (phase-only)cipher (subject to the floating point precision used for dataprocessing), thereby fully dissipating the statistical signatureof the plaintext in the distribution of the cipher. Further,a decrypt can be generated that is computationally efficientsubject to the usual cases of sender and receiver havingaccess to identical algorithm(s) and key(s), deconvolution beingequivalent to decryption in the context of the (phase-only)encryption model that is considered. For the two-dimensionalcase, this approach has a potential weakness in terms of a‘correlation attack’ using phase retrieval algorithms and asolution to this problem is provided by introducing a (stochastic)amplitude weighting function. Prototype MATLAB functionsare provided in the Appendices that accompany this paper togive readers the opportunity to repeat the computational resultspresented and extend them further. The functions constitute asymmetric algorithm for encrypting and decrypting full colourimages in which the key(s) have been exchangeda priori. In thiscontext, the final part of the paper considers the applicationof phase-only encryption for key exchange using a Three-way Pass Protocol for which a further prototype MATLABfunction is provided for validation and further development ofthe approach by interested readers