One of the basic requirements of communication protocols in a heterogeneous computer network is a standard external data-transfer representation. Abstract Syntax Notation One (ASN.1) has been widely used in international standard specifications. Its transfer-syntax of Basic Encoding Rules (BER) is applied as the standard external data representation. This thesis presents an efficient BER implementation, called the ED library. The ED library includes a number of encoding and decoding routines that may be used as primitive functions to compose encoders and decoders for arbitrarily complicated ASN.1 data-types. The Performance of the ED library is measured and discussed. Based on the ED library, an ASN.1-C compiler, called CASN1, is designed and implemented to release communication software programmers from the arduous work of translating protocol-defined data-types and constructing their encoders and decoders. Given an ASN.1 protocol specification, CASN1 automatically translates the input ASN.1 modules into C and generates the BER encoders and decoders for the protocol denned data-types. This thesis discusses the design principles, user interface, internal structures, and the implementation and of CASN1. Example applications are given. Both the ED library and CASN1 are implemented in C on UNIX 4.2 BSD using the YACC and LEX tools. / Science, Faculty of / Computer Science, Department of / Graduate

Considerable work has been recently devoted to the automatic generation of syntax analyzers. This work has been generally concerned with extending the power of the parser generator technigues, rather than improving the syntactic specification mechanism. Se present a new parsing language which attempts to unify syntax and semantics. In addition, the language provides a mechanism by which reasonable error recovery can be naturally included in the syntax specification. / Science, Faculty of / Computer Science, Department of / Graduate

The fact and rule list internal to Prolog is capable of handling as many facts as available memory resources permit. A solution to this limitation is to store facts on disk, retrieving them into a main memory database buffer only as needed. Allocating a fixed portion of main memory to buffer database facts frees up scarce main memory for more frequently accessed rules and data structures internal to Prolog. The Prolog Database System built in connection with this project transparently stores and retrieves facts on disk and evaluates them in the order they were asserted allowing for the transfer of existing small scale prototypes into large scale production systems. <p>Since existing relational database techniques were not designed to function in a Prolog environment where facts are evaluated in database facilities were designed, developed, and integrated into Prolog. These database facilities include a unique page replacement policy designed to minimize expensive page faults during the execution of a Prolog program. The look ahead page replacement policy looks ahead on database pages while they are in main memory in order to determine whether they are likely to be accessed again in the future. In this way, a near optimal working set of database pages is maintained in the database buffer, assisting with minimizing expensive page faults. / Master of Science

<p>Results of stability analyses with the commercial finite element program ABAQUS are presented. Buckling and nonlinear analysis of an Euler column and a Von Mises truss are presented. In addition, linear, buckling and nonlinear analyses are carried out on a Varax dome.</p> / Master of Science

no abstract provided by author / Master of Science

The dissertation presents the computational technique Particle-In-Cell, or PIC for short, and its applications in studying the magnetospheres of neutron stars, modeled as conducting rotators with strong magnetic fields. Pigeon, an open-source PIC simulator written by the author in modern C++, is anatomically examined as an instrument to illustrate the principles, algorithms and engineering difficulties of the PIC technique. Two types of rotators are studied using Pigeon. The monopolar rotator, which has an exact solution in the force free limit, serves as a tester for the code, as well as an example of the PIC's capability. The main application of Pigeon is on the ab initio simulation of an (axisymmetric) dipolar rotator with self-consistent gamma ray photon emission and pair creation, the study of which could reveal valuable information of the mechanism of the pulsars. Thanks to the performance boost brought by Pigeon's dynamic load balancing functionality, we are able to perform the simulation with a 4096x4096 high resolution grid. The high resolution is critical in obtaining a Lorentz factor of 10000 of the polar cap potential drop, which in turn enables good separations of energy levels and hence makes the simulation closer to representing the real-life pulsars. With the high resolution, we are also able to study the Y point more closely, where we find that the angular momentum conservation dictates the process of magnetic flux surface crossing that is responsible for the release of electromagnetic energies into the plasma.

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