Ogden's lemma for random permitting and forbidding context picture languages and table-driven context-free picture languages

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, February 16, 2015.Random context picture grammars are used to generate pictures through successive refinement. There are three important subclasses of random context picture grammars, namely random permitting context picture grammars, random forbidding context picture grammars and table-driven context-free picture grammars. These grammars generate the random permitting context picture languages, random forbidding context picture languages and table-driven context-free picture languages, respectively. Theorems exist which provide necessary conditions that have to be satisfied by a language before it can be classified under a particular subclass. Some of these theorems include the pumping and shrinking lemmas, which have been developed for random permitting context picture languages and random forbidding context picture languages respectively. Two characterization theorems were developed for the table-driven context-free picture languages. This dissertation examines these existing theorems for picture languages, i.e., the pumping and shrinking lemmas and the two characterisation theorems, and attempts to prove theorems, which will provide an alternative to the existing theorems and thus provide new tools for identifying languages that do not belong to the various classes. This will be done by adapting Ogden’s idea of marking parts of a word which was done for the string case. Our theorems essentially involve marking parts of a picture such that the pumping operation increases the number of marked symbols and the shrinking operation reduces it

Generating similar images using bag context picture grammars

A Dissertation submitted to the Faculty of Science in partial fulfilment of the requirements for the degree of Master of Science University of the Witwatersrand, Johannesburg, February 2018Formal language theory was born in the middle of the 20th century as a tool for modeling and investigating syntax of natural languages. It was developed in connection with the handling of programming languages. Bag context grammars are a fairly new grammar class where bag context tree grammars have been defined. Bag context is used to regulate rewriting in tree grammars. In this dissertation we use bag context to regulate rewriting in picture grammars and thus to generate similar pictures. This work is exploratory work since bag context picture grammars have not been defined. We use examples to show how bag context picture grammars can be used to generate pictures. In this work bag context picture grammars are defined and used to generate similar pictures. Pictures generated by random context picture grammars and three of their sub-classes are selected and bag context picture grammars are used to generate the same pictures to those selected. A lemma is defined that is used to convert the class of random context picture grammars and three of their sub-classes into equivalent bag context picture grammars. For each grammar selected, an equivalent bag context picture grammar is created and used to generate several pictures that are similar to each other. Similarity is defined by noting small differences that are seen in pictures that belong to the same gallery. In this work we generate similar pictures with bag context picture grammars and thus make the discovery that bag context gives a certain level of control in terms of rules applied in a grammar.XL201

Facets for Art Gallery Problems

The Art Gallery Problem (AGP) asks for placing a minimum number of stationary guards in a polygonal region P, such that all points in P are guarded. The problem is known to be NP-hard, and its inherent continuous structure (with both the set of points that need to be guarded and the set of points that can be used for guarding being uncountably infinite) makes it difficult to apply a straightforward formulation as an Integer Linear Program. We use an iterative primal-dual relaxation approach for solving AGP instances to optimality. At each stage, a pair of LP relaxations for a finite candidate subset of primal covering and dual packing constraints and variables is considered; these correspond to possible guard positions and points that are to be guarded. Particularly useful are cutting planes for eliminating fractional solutions. We identify two classes of facets, based on Edge Cover and Set Cover (SC) inequalities. Solving the separation problem for the latter is NP-complete, but exploiting the underlying geometric structure, we show that large subclasses of fractional SC solutions cannot occur for the AGP. This allows us to separate the relevant subset of facets in polynomial time. We also characterize all facets for finite AGP relaxations with coefficients in {0, 1, 2}. Finally, we demonstrate the practical usefulness of our approach. Our cutting plane technique yields a significant improvement in terms of speed and solution quality due to considerably reduced integrality gaps as compared to the approach by Kr\"oller et al.Comment: 29 pages, 18 figures, 1 tabl

Influence of climate control strategies and the impact of visitors on the conservation of cultural heritage

Given the current issues surrounding the environmental control in museums, particularly revolving around hygrothermal conditions of the internal microclimate, it is important to gain perspective by looking into the past and asserting how it shaped present circumstances on defining climate control strategies. Developments witnessed in science and technology over the past century attest to new approaches and dynamic methodologies that seek to cut energy costs and move from stringent targets to more flexible specifications, opting for simpler and passive measures that intend to be more sustainable. However, differing views exist on these pertaining issues, which accounts for disparities in operating methods and applied standards all over the world that further amplifies the discussion. Tourism can be seen be seen as one of the foremost agents for cultural exchange as well as a major vehicle in facilitating the preservation of cultural heritage with the allocation of resources for its maintenance. However, this relationship between tourism and Heritage Places can often be seen as conflicting in nature, by the fact that it can both lead to opportunities as well as potential complications. Visitors in museum buildings have therefore an impact in the preservation of cultural heritage, given that they influence the internal climate, particularly in terms of hygrothermal conditions, which could possibly induce new concerns as well as hinder their sustainable management. For the present study, an account on the level of climate control strategies used throughout the past century was performed through an exhaustive literature review along with an evaluation of its impact on the sustainability of cultural heritage as well as an analysis of the influence of tourism on its conservation. Therefore, the current work evaluates the impact that tourism, specifically if practiced in an unsustainable way, may infer to the overall preservation of artefacts, mainly on the prediction of mechanical, biological and chemical damage risks. With the aid of a simulation software – EnergyPlus – a model of a generic room from the National Museum of Ancient Art in Lisbon (Portugal) (NMAA) was generated and virtually placed for each district of Portugal, varying also the number in visitors per hour, aiming to estimate – from a risk-based approach – the influence this concerning topic in today’s society has on the internal climate and ultimately the preservation of the artefacts being displayed. In terms of risk assessment, the results show that each increase in occupancy aggravates the potential for damage in each of the considered cases. A geographical distribution of risk is also evidenced, presented in maps, which indicates certain regions where risk is higher than others

Advanced Decision-Oriented Software for the Management of Hazardous Substances: Part II: A Demonstration Prototype System

This report describes the implementation of a first demonstration prototype of an integrated, interactive, computer-based decision support and information system for the management of hazardous substances. Recognizing the potentially enormous development effort required and the open-ended nature of such a project, we have opted for a strategy that takes advantage of the large volume of scientific software already available. A modular design philosophy enables us to develop individual building blocks, which are valuable products in their own right, in the various phases of the project. This also makes it possible to interface and integrate the modules in a framework which, above all, has to be flexible and easily modifiable with growing experience of use. The demonstration prototype can be constructed at relatively low cost and only incremental effort, by using an open architecture concept for this framework, with a functional and problem-oriented, rather than a structural and methodological design. The system design combines several methods of applied systems analysis and operations research, planning and policy sciences, and artificial intelligence into one fully integrated software system. The basic objective is to provide a broad group of users direct and easy access to these largely formal and complex methods

A novel approach to reduce fire exposure and promote nature conservation in Mediterranean ecosystems: the case study of Reserva Natural da Serra da Malcata, Portugal

Mestrado Mediterranean Forestry and Natural Resources Management - Instituto Superior de Agronomia - ULIn Portugal, wildfires represent a major concern that yearly produces numerous economic and environmental losses. Currently, there is a continuous increase of biomass accumulation which increases wildfire risk into Mediterranean protected areas due to lack of management. An example is the protected area of Serra da Malcata, where prescribed burning has been implemented. However, fuel treatments implementation within preserved areas remains quasi forbidden in the major cases. The main objective is to develop and asses a novel approach to reduce fire exposure and simultaneously promote conservation habitat within Natura 2000 Habitats of Reserva Natural da Serra Malcata. For this aim, fire exposure assessment of three different fuel management scenarios: current situation, planned treatments and low intense treatments within Habitat Natura 2000 promoting conservation goals, were done by using burn probability modelling under extreme conditions for 24h burn period. Results showed similar performance of conservation enhancement scenario if compare with planned treatment scenario. Nevertheless, biggest fire exposure reductions were observed within Natura 2000 network. Limitations and assumptions derived from input parameters, model validation or fire simulator could affect fire exposure results. However, results open the debate to include fuel treatments within protected areas for achieving medium- and long-term fire risk reductio

Užití členů v odborných textech z oblasti teorie a dějin umění

Tato bakalářská práce se zabývá determinací vlastních jmen z oblasti výtvarného umění. Tzv. proper names ("názvy") mohou být popsány jako výrazy, které obsahují jedno nebo více jmen, obecných a/nebo vlastních, která utváří jak řídící člen nominální fráze, tak i členy závislé. Struktura proper names je neměnná, protože proper names vystupují formálně jako jedna gramatická a sémantická jednotka. Reference proper names je omezena na negenerickou určitou situační referenci. Proper names označují jedinečnou, v dané situaci jednoznačně identifikovatelnou osobu nebo věc. Obecně lze říci, že proper names se objevují pouze se členem určitým a nebo bez členu. Bezčlennost je zde odlišena od členu nulového, tzv. zero article. Příklady, které znázorňují užití prostředků determinace proper names z oblasti umění, byly excerpovány ze současných britských časopisů věnujících se výtvarnému umění. Excerpta byla rozdělena do sedmi sémanticky odlišených skupin, z nichž většina nebyla vzhledem k užití členů přesněji popsána žádnou anglickou gramatikou. Příklady byly blíže popsány a z rozboru byly vyvozeny určité závěry, které však nemohou být pokládány za jasně stanovená pravidla, ale spíše jako tendence použití členů v názvech několika významově odlišených skupin proper names.9. Abstract This thesis deals with the use of determiners in proper names concerning visual art. Proper names are expressions that can comprise one or more words, either a common or a proper noun head with common or proper noun dependents. Although they have an internal structure that can be analysed as a structure of a common noun phrase, the structure of proper names is unchangeable since they function as a single grammatical and semantic unit. The reference of proper names is limited to non-generic situational reference. They refer directly to a particular person or object uniquely recoverable in the situation. Generally, the use of articles with proper names is limited to the definite or the null article (which is distinguished from the zero article). Examples demonstrating the use of determiners with proper names concerning art were excerpted from contemporary British art magazines. The excerpts were divided into seven semantic categories, most of which have not been covered, with respect to the use of articles, by any representative English grammar. The examples were analysed and described and conclusions were drawn. However, the results of this thesis cannot be considered as a set of clear-cut rules but rather an outline of tendencies in the use of articles with several semantically distinguished...Department of the English Language and ELT MethodologyÚstav anglického jazyka a didaktikyFaculty of ArtsFilozofická fakult