Assessing the geometry and tuning properties of historical timbilas through non-destructive reverse engineering techniques

Timbilas are xylophones finely manufactured and tuned by the Chopi people from Mozambique. In the context of a research project, we aim at assessing the construction and acoustical features of a set of historical instruments by developing non-destructive characterization techniques based on reverse engineering, with main objectives to assess their original tuning and musical scale. In this thesis, we present the methodology and workflow that have been developed for the study of the collection of historical timbilas of the National Museum of Ethnology of Lisbon, which is the world's largest collection of the Mozambican instrument. In a first stage, contactless geometrical measurements were performed on a ninebar timbila by using 3D scanning Technology, resulting in a detailed geometrical description of the instrument bars. In a second stage, the 3D collected geometrical data was used as input to Finite Element computations in order to calculate the modal frequencies and mode shapes of each bar of the instrument. Results stemming from our modal computations were compared with modal data obtained from vibrational measurements, proving the efficiency of the proposed approach. Final stage was using the data as input for developing a sound synthesis model for recreating the sound of the timbila bars.Timbilas são xilofones cuidadosamente construídos e afinados pelos Chopes, povo de Moçambique que cultiva uma das mais importantes tradições musicais do sul da África. No contexto de um projeto interdisciplinar de investigação, objetivamos avaliar as características geométricas e acústicas de alguns exemplares históricos, desenvolvendo técnicas não-destrutivas de caracterização baseadas num processo de engenharia reversa, com o principal objetivo de avaliar a afinação e a escala musical de um conjunto de instrumentos. A metodologia desenvolvida consiste no levantamento preciso da geometria das barras a partir de tecnologia de imagens scanner 3D, resultando numa descrição detalhada de sua morfologia. Num segundo passo, realizamos cálculos modais a partir de um modelo por Elementos Finitos 3D construido a partir dos dados coletados, a fim de calcular as frequências modais e formas vibratórias das principais ressonâncias de cada barra do instrumento. Os resultados dos cálculos modais foram finalmente comparados com os valores de parâmetros modais identificados a partir de medições vibratórias, demonstrando a utilidade e eficácia da metodologia proposta. O estágio final foi a utilização dos dados para criar um modelo de síntese sonora para as barras da timbila

Derived Algebraic Geometry

This text is a survey of derived algebraic geometry. It covers a variety of general notions and results from the subject with a view on the recent developments at the interface with deformation quantization.Comment: Final version. To appear in EMS Surveys in Mathematical Science

Synchronization in complex networks

Synchronization processes in populations of locally interacting elements are in the focus of intense research in physical, biological, chemical, technological and social systems. The many efforts devoted to understand synchronization phenomena in natural systems take now advantage of the recent theory of complex networks. In this review, we report the advances in the comprehension of synchronization phenomena when oscillating elements are constrained to interact in a complex network topology. We also overview the new emergent features coming out from the interplay between the structure and the function of the underlying pattern of connections. Extensive numerical work as well as analytical approaches to the problem are presented. Finally, we review several applications of synchronization in complex networks to different disciplines: biological systems and neuroscience, engineering and computer science, and economy and social sciences.Comment: Final version published in Physics Reports. More information available at http://synchronets.googlepages.com

Musical Composition in the Context of Globalization: New Perspectives on Music History in the 20th and 21st Century

This book discusses the effects of cultural globalization on processes of composition and distribution of art music in the 20th and 21st century. Christian Utz provides the foundations of a global music historiography, building on new models such as transnationalism, entangled histories, and reflexive globalization. The relationship between music and broader changes in society forms the central focus and is treated as a pivotal music-historical dynamic.Dieses Buch diskutiert die Auswirkungen der kulturellen Globalisierung auf Prozesse der Komposition und Verbreitung von Kunstmusik im 20. und 21. Jahrhundert. Christian Utz liefert die Grundlagen einer globalen Musikhistoriographie, die auf neuen Modellen wie Transnationalismus, Verflechtungsgeschichte und reflexiver Globalisierung aufbaut. Das Verhältnis zwischen Musik und breiteren gesellschaftlichen Veränderungen bildet den zentralen Fokus der Studien und wird als zentrale musikgeschichtliche Dynamik begriffen

Forest cover and its change in Unguja Island, Zanzibar

Tropical forests are sources of many ecosystem services, but these forests are vanishing rapidly. The situation is severe in Sub-Saharan Africa and especially in Tanzania. The causes of change are multidimensional and strongly interdependent, and only understanding them comprehensively helps to change the ongoing unsustainable trends of forest decline. Ongoing forest changes, their spatiality and connection to humans and environment can be studied with the methods of Land Change Science. The knowledge produced with these methods helps to make arguments about the actors, actions and causes that are behind the forest decline. In this study of Unguja Island in Zanzibar the focus is in the current forest cover and its changes between 1996 and 2009. The cover and changes are measured with often used remote sensing methods of automated land cover classification and post-classification comparison from medium resolution satellite images. Kernel Density Estimation is used to determine the clusters of change, sub-area –analysis provides information about the differences between regions, while distance and regression analyses connect changes to environmental factors. These analyses do not only explain the happened changes, but also allow building quantitative and spatial future scenarios. Similar study has not been made for Unguja and therefore it provides new information, which is beneficial for the whole society. The results show that 572 km2 of Unguja is still forested, but 0,82–1,19% of these forests are disappearing annually. Besides deforestation also vertical degradation and spatial changes are significant problems. Deforestation is most severe in the communal indigenous forests, but also agroforests are decreasing. Spatially deforestation concentrates to the areas close to the coastline, population and Zanzibar Town. Biophysical factors on the other hand do not seem to influence the ongoing deforestation process. If the current trend continues there should be approximately 485 km2 of forests remaining in 2025. Solutions to these deforestation problems should be looked from sustainable land use management, surveying and protection of the forests in risk areas and spatially targeted self-sustainable tree planting schemes.Siirretty Doriast