This dissertation presents several solutions on the simulation of weakly nonlinear circuits. The work is motivated by the increasing demand on fast yet accurate simulation methods circuits (IC)s, and the current lack of such methods in the electronic design automation (EDA) / computer-aided design (CAD) community. Three types of frequency domain methods are studied to analyze weakly nonlinear circuits. The first method employs numerical multi-dimensional inverse Laplace transform based on Laguerre function expansion. An adaptive mesh refinement (AMR) technique is developed and its parallel implementation is introduced to speed up the computation. The second method applies a Fourier series based algorithm to invert Laplace transform. The algorithm is straightforward to implement, and gives increasing accuracy with increasing number of frequency sampling points. It employs a fast Fourier transform (FFT)-based method to directly invert the frequency domain solution. Its parallel routine is also studied. The third method is based on Gaver functional. It enjoys a high accuracy independent of the number of sampling points, and for multidimensional simulation, only the diagonal points in the matrix are required to be computer, which can be further speeded up by parallel implementation. Numerical results show that the aforementioned three methods enjoy good accuracy as well as high efficiency. A comparative study is carried out to investigate the strengths and drawbacks of each method. / published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

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R1162 is efficiently mobilized during conjugation by IncP-1 plasmids such as RK2 and R751. Transfer is terminated when the transferred strand, linearized at the 38 base-pair origin of transfer (oriT), is recircularized by the plasmid encoded protein MobA. For strand rejoining, MobA covalently linked to the 5' end of the strand rejoins the ends by a reversible transesterification reaction. The minimal oriT fragment of R1162 contains a highly conserved 12 base region (core) including the cleavage site and a ten base imperfect inverted repeat (IR) that is not highly conserved. From those oligonucleotides with a partially degenerate oriT core base sequence, the subpopulations that are bound by MobA, cleaved and rejoined by this protein and support termination of transfer were identified. Both the IR and the adjacent core bases TAA, are needed for tight binding to MobA, whereas the location of the dinucleotide YG determines the site of strand cleavage. At the IR MobA stabilizes duplex DNA during gel electrophoresis and binds weakly to oligonucleotides lacking the outer arm of the inverted repeat, supporting a model where secondary structure at IR provides a duplex region needed for binding during termination (Zhang and Meyer 1995). Significantly altered IR sequences did allow strong binding to MobA yet completely different IR sequences did not, indicating the IR serves a structural role for binding with low base specificity. A 184 residue aminoterminal MobA fragment capable of binding and cleaving oriT was identified by using phage display and partial enzymatic digestion of the protein. No smaller fragments that could bind or cleave oriT were identified. An active nucleoprotein intermediate consisting of MobA covalently linked to the 5' end of the cleaved oriT was used to show that a single molecule of MobA is sufficient to carry out all the DNA processing steps during transfer. / text

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Communication protocols, a class of critical systems, play an important role in industry. These protocols are critical because the tolerance for faults in these systems is low and it is highly desirable that these systems work correctly. Therefore, an effective methodology for describing and verifying that these systems behave according to their specifications is vitally important. Model checking is a verification technique in which a mathematically precise model of the system, either concrete or with abstraction, is built and a specification of how the system should behave is given. Then the system is considered correct if its model satisfies its specification. However, due to their size and complexity, critical systems, such as communication systems, are notoriously resistant to formal modelling and verification. In this thesis, we propose using graph transformation systems (GTSs), a visual semantic modelling approach, to model the behaviour of dynamically evolving communication protocols. Then, we show how a GTS model can facilitate verification of invariant properties of potentially unbounded communication systems. Finally, due to the use of similar isomorphic components in communication systems, we show how to exploit symmetries of these dynamically evolving models described by GTSs, to reduce the size of the model under verification. We use graph transformation systems to provide an expressive and intuitive visual description of the system state as a graph and for the computations of the system as a finite set of rules that transform the state graphs. Our model is well-suited for describing the behaviour of individual components, error-free communication channels amongst the components, and dynamic component creation and elimination. Thus, the structure of the generated model closely resembles the way in which communication protocols are typically separated into three levels: the first describing local features or components, the second characterizing interactions among components, and the third showing the evolution of the component set. The graph transformation semantics follows this scheme, enabling a clean separation of concerns when describing a protocol. This separation of concerns is a necessity for formal analysis of system behaviour. We prove that the finite set of graph transformation rules that describe behaviour of the system can be used to perform verification for invariant properties of the system. We show that if a property is preserved by the finite set of transformation rules describing the system model, and if the initial state satisfies the property, then the property is an invariant of the system model. Therefore, our verification method may avoid the explicit analysis of the potentially enormous state space that the transformation rules encode. In this thesis, we also develop symmetry reduction techniques applicable to dynamically evolving GTS models. The necessity to extend the existing symmetry reduction techniques arises because these techniques are not applicable to dynamic models such as those described by GTSs, and, in addition, these existing techniques may offer only limited reduction to systems that are not fully symmetric. We present an algorithm for generating a symmetry-reduced quotient model directly from a set of graph transformation rules. The generated quotient model is bisimilar to the model under verification and may be exponentially smaller than that model.

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<p>This research is an evaluative case study of transformation in a Historically White University in South Africa. The research occurs within the context of redress against the inequality and exclusion created by the legacy of apartheid. The research is a qualitative and quantinative study. it is based on based on desk research and include a literature review. Internet search as well as an analysis of key organisational and policy context documents such as reports, projects and surveys are used. semi-structured interviews was held with a sample of staff.</p>

This qualitative study of an adult literacy program, Literacy for Liberation, operated by a non-governmental organization and serving a marginalized demographic in Haiti, considered the impact of a literacy program designed to enhance technical and critical literacy skills while promoting communal and individual change. Data, collected in five open-ended interviews and two observations, focused on the contextual, logistical, and beneficial aspects of the program. Results were analyzed using markers from Freire’s framework of critical pedagogy: humanization, situated literacy, dialogue and consciousness-raising, and transformation. Findings revealed limited economic, social, and communal benefits, and that replication of the program may be possible if certain steps are followed. Overall conclusions demonstrated that expanding literacy programs in this setting can facilitate social and economic progress for previously illiterate adults and future generations, particularly where structural inequality is evident. Final recommendations included comparison studies of other programs and longitudinal research of descending generations.

The problem area addressed in this thesis is extraction of a data design from existing data intensive program code. The purpose of this is to help a software maintainer to understand a software system more easily because a view of a software system at a high abstraction level can be obtained. Acquiring a data design from existing data intensive program code is an important part of reverse engineering in software maintenance. A large proportion of software systems currently needing maintenance is data intensive. The research results in this thesis can be directly used in a reverse engineering tool. A method has been developed for acquiring data designs from existing data intensive programs, COBOL programs in particular. Program transformation is used as the main tool. Abstraction techniques and the method of crossing levels of abstraction are also studied for acquiring data designs. A prototype system has been implemented based on the method developed. This involved implementing a number of program transformations for data abstraction, and thus contributing to the production of a tool. Several case studies, including one case study using a real program with 7000 Hues of source code, are presented. The experiment results show that the Entity-Relationship Attribute Diagrams derived from the prototype can represent the data designs of the original data intensive programs. The original contribution of the thesis is that the approach presented in this thesis can identify and extract data relationships from the existing code by combining analysis of data with analysis of code. The approach is believed to be able to provide better capabilities than other work in the field. The method has indicated that acquiring a data design from existing data intensive program code by program transformation with human assistance is an effective method in software maintenance. Future work is suggested at the end of the thesis including extending the method to build an industrial strength tool.