Topological correction of hypertextured implicit surfaces for ray casting

Hypertextures are a useful modelling tool in that they can add three-dimensional detail to the surface of otherwise smooth objects. Hypertextures can be rendered as implicit surfaces, resulting in objects with a complex but well defined boundary. However, representing a hypertexture as an implicit surface often results in many small parts being detached from the main surface, turning an object into a disconnected set. Depending on the context, this can detract from the realism in a scene where one usually does not expect a solid object to have clouds of smaller objects floating around it. We present a topology correction technique, integrated in a ray casting algorithm for hypertextured implicit surfaces, that detects and removes all the surface components that have become disconnected from the main surface. Our method works with implicit surfaces that are C2 continuous and uses Morse theory to find the critical points of the surface. The method follows the separatrix lines joining the critical points to isolate disconnected components

Ray casting implicit fractal surfaces with reduced affine arithmetic

A method is presented for ray casting implicit surfaces defined by fractal combinations of procedural noise functions. The method is robust and uses affine arithmetic to bound the variation of the implicit function along a ray. The method is also efficient due to a modification in the affine arithmetic representation that introduces a condensation step at the end of every non-affine operation. We show that our method is able to retain the tight estimation capabilities of affine arithmetic for ray casting implicit surfaces made from procedural noise functions while being faster to compute and more efficient to store

Caution is needed when applying Margalef diversity index

The use of diversity indices has increased due to the necessity of testing different methodologies to develop the ecological status classification of water bodies within the water framework directive implementation. The Margalef diversity index is one of the indices applied within these aims. Several software packages calculate various diversity indices. However, these packages do not give any warning that for the Margalef index the data must be organized as absolute numbers and not as a density data matrix. In data expressed as number of individuals per square meter, if the sample size is lower than a square meter this index is sub estimated. With other diversity indices commonly used in ecological evaluation it is indifferent to use density data or absolute numbers since these indices only consider relative proportions in their calculus

Desenvolvimento da economia do mar : turismo marítimo

O Turismo Marítimo está muito pouco dinamizado e estruturado em Portugal, prevendo-se que, perante a situação nacional ainda bastante precária e a grande atractividade e forte competitividade do país nesta área, poderão registar-se, nos próximos 10 anos, crescimentos anuais superiores a 10%. A dinamização de desportos como o surf, o kitesurf e o mergulho e ainda a vela, remo e canoagem, que podem ser praticados em qualquer altura do ano, em todo o país, e a criação de infraestruturas de apoio à navegação de recreio, adaptando e recuperando áreas estuarinas desqualifi cadas e infraestruturas portuárias desaproveitadas e promovendo o emprego ligado a actividades económicas complementares, são algumas das formas que permitirão aumentar a captação de procura turística internacional ligada às actividades náuticas e ao turismo dinâmico em busca de “experiências” ligadas ao mar, trazendo novas receitas para Portugal e contribuindo para consolidar a atractividade do nosso país como destino turístico

Ultra short laser pulse characterization device based on disordered nonlinear crystals

In this project we build and test a compact and portable optical device for ultrashort pulse characterization. This setup allows the measurement of the pulse duration as well as its chirp parameter by using the so called transverse single-shot auto-correlation scheme, using, as novelty, a random nonlinear crystal. A companion software has been developed to automatize the device and process the acquired data by following a preprogrammed algorithms and showing the results in easy and understandable manner

Scientific Networks and the diplomatic colonization of Africa in the late nineteenth century

Science diplomacy is usually discussed as a post-Second World War phenomenon. However, the links between science and diplomacy can be traced to earlier periods. This case analyzes one example related to the European colonization of Africa in the late nineteenth century, known as the "Scramble for Africa". Scientists usually perform only advisory roles in politics. In this case, a scientist attained important political responsibilities, ultimately becoming Minister of Foreign Affairs and conducting formal diplomatic negotiations. This scientist was José Vicente Barbosa du Bocage (1823-1907), a nineteenth-century Portuguese zoologist. Bocage's knowledge of African geography acquired via his scientific studies and at the head of the Lisbon Geographical Society, as well as the scientific, colonial, and political networks he joined or formed, allowed for his political rise. Once in a position of power, he placed knowledgeable Portuguese personalities at the center of colonial discussions with powerful rival countries, such as France and Germany, ultimately seizing some colonial victories for Portugal in Africa. This case shows that while science diplomacy can be a tool for cooperation, it can also be used to gain competitive advantage over rivals.publishersversionpublishe

Ethnohistory: The ancient authors’ reports on Southwest Iberia – an example

Calouste Gulbenkian Foundation and University of Algarv