A numerical study on mechanical metamaterials in classical guitars

LAUREA MAGISTRALETradizionalmente, il legno è sempre stato uno dei materiali più usati nella costruzione degli strumenti musicali, essendo un materiale al contempo molto leggero e molto rigido, proprietà che gli permettono di irradiare suono in maniera molto efficiente. Alcuni tipi di legno sono considerati particolarmente adatti all'uso in strumenti musicali di alta qualità, poichè tendono ad esibire le proprietà meccaniche ideali allo scopo. La disponibilità di questi legni, tuttavia, può spesso essere limitata, a causa della deforestazione o del restringimento degli habitat causato dal cambiamento climatico. Il legno, inoltre, presenta proprietà meccaniche estremamente variabili, anche all'interno della stessa tipologia, per cui solo una frazione del legno disponibile ha le caratteristiche adatte per l'uso in strumenti di pregio. Avere la possibilità di intervenire a piacimento sulle proprietà meccaniche del legno, dunque, renderebbe l'approvvigionamento di materiali molto più semplice ed economico. Con questo scopo in mente, ci rivolgiamo al campo dei metamateriali meccanici in cerca di ispirazione. I metamateriali sono materiali compositi che presentano proprietà meccaniche particolari derivate dalla loro struttura, invece che dalla loro composizione. Il punto di partenza di questa tesi è un recente studio che dimostra che le proprietà meccaniche delle piastre sottili di legno possono essere modificate ad hoc intagliando degli specifici pattern di buchi, creando così un metamateriale 2D su base legnosa. In questa tesi studiamo l'uso di tali metamateriali nelle tavole armoniche delle chitarre classiche. Tramite modellazione a elementi finiti studiamo il loro effetto sui modi di vibrazione e sulla risposta in frequenza dello strumento, nonchè sulla sua capacità di sopportare il carico imposto dalla corde in tensione. I risultati mostrano che è possibile, con questi metamateriali, costruire uno strumento più sonoro senza alterarne radicalmente il timbro caratteristico e senza comprometterne l'integrità strutturale. Ne concludiamo che i metamateriali potrebbero rappresentare uno strumento potente per l'innovazione nella liuteria.Traditionally, wood has been one of the most widely used materials in the construction of musical instruments, as its high stiffness-to-density ratio makes it an excellent sound radiator. Some specific kinds of woods, commonly referred to as tonewoods, are held in high regard, as they tend to exhibit just the right mechanical properties necessary to produce high quality instruments. The supplies of these woods, however, are especially prone to shortages due to deforestation or to climate change-related habitat shrinking. Moreover, even within the same species, wood exhibits high variability in its mechanical properties, so only a fraction of the samples from an available supply will be suitable for use in high-end musical instruments. Having the possibility of deliberately engineering the mechanical behaviour of wood would make sourcing the materials easier and cheaper, and it would allow for greater consistency across similar instruments. Searching for a means to achieve this, we look to the field of mechanical metamaterials for inspiration. Metamaterials are composite materials which exhibit unique mechanical properties derived from their structure rather than their composition and as such, they offer a great deal of control over their properties. The starting point of our work is represented by recent results which show that the mechanical properties of rectangular, thin wooden plates can be purposefully adjusted by carving them with specific patterns of holes, effectively creating a 2D wooden metamaterial. In this thesis we investigate the use of such metamaterials in the soundboards of classical guitars. By way of finite element simulations, we study their effect on the modal behavior and on the mobility frequency response of the instrument, and on its ability to sustain the load exerted by the tension of the strings. Our results show that it is possible, thanks to the metamaterials, to build an instrument which is overall louder than the traditional design without radically altering its timbre, and without compromising its structural integrity. As such, metamaterials have the potential to represent a new and powerful tool in the arsenal of guitar makers

Analysis of three decades of research in marine sciences in Uruguay through mapping of science and bibliometric indexes

Uruguay has recently expanded its Exclusive Economic Zone (EEZ), having more aquatic sovereignty than terrestrial territories. In this country, various State institutions have carried out the study of marine science for several decades, but their academic development has not been analyzed. The formal evaluation of scientific research represents a crucial opportunity to define long-term policies requiring greater knowledge of the territory and its resources. In this context, this work carries out a systematic and quantitative review of Uruguay authors' international publications over three decades. The productivity indicators trend is evaluated concerning context variables, predominant research topics are identified, and collaboration networks are characterized. We collected and analyzed data on marine science articles in which an author or co-author is affiliated to an institution in Uruguay from 1990 to 2018 using the Scopus database. It was found that scientific activity measured by a bibliographic analysis showed an increase in the number of articles, authors, and research topics but nowadays show signs of stagnation. Moreover, specific indicators show a great degree of centralism (institutional and authorial), low dynamism, and decreased international collaboration. The largest academic capacities are focused in specific biological disciplines, with little physics and almost nil in geology and chemistry. Decentralization and strengthening sectorial funding for marine science will boost Uruguay's discipline for facing future challenges

Virtually Rebuilding Çatalhöyük History Houses

A 3D reconstruction of part of the Çatalhöyük ‘Shrine’ 10 sequence has been developed with the aim to analyze, visualize, and interpret a number of buildings rebuilt multiple times in the same place. More than twenty years of excavations on the East Mound at Çatalhöyük have produced comprehensive interpretations of the repetition of architectural elements and buildings over time, providing thorough understanding of social organization, property, power, and religion in early settled life. Current visualization technologies allow us to simulate the tridimensional context, shared material culture, and experiential aspects of the unique urban environment at Çatalhöyük. However, these modern applications require archaeologists to address methodological questions such as: “what is the significance of virtually rebuilding Çatalhöyük history houses?” and “Can a 3D visualization of a sequence of buildings tell us more about the religious rituals, social organization, and history making practices at Çatalhöyük?” This chapter discusses the 3D reconstruction and interactive exploration of three Çatalhöyük history houses (‘Shrine’ VIA.10, VIAB.10, and VII.10) with the objective to define a new approach to digital archaeology and heritage interpretation that integrates a plurality of data in a visual-analytical environment, where advanced interactive techniques simulate the cosmology, building practices, material culture, and history-making aspects of Çatalhöyük

Marine mammal research in South America: 30 years of publication efforts and collaborative networks

A notable diversity of marine mammals inhabits the Atlantic and Pacific waters of South America. For decades, South American countries have been producing scientific research focused on these species. However, still, there is no systematic assessment of the magnitude and main subjects on which this research has been focused. This study analyzes the trends and patterns in scientific research on marine mammals in South America, evaluating a pool of bibliometric indicators and mapping collaborative relationships among countries, authors, and research areas. Academic documents were retrieved from two bibliographic databases: SCOPUS and SciELO, from 1990 to 2020. Results showed a gradual increase in publications along the three study decades. Brazil played a central role in the number of publications in both databases, followed by Argentina and Chile. The South American publications on marine mammals were centralized in a small number of journals, and few authors were responsible for a large proportion of contributions. The authors showed a moderate level of collaboration, mainly reflecting stronger links among neighbor countries, including co-authorships with North American and European countries. The most frequent keywords reflected three clusters centered in taxonomic groups (Cetacea, Odontoceti, and Pinnipedia) and two centered in research subjects (pollution and phylogenetics). The scope of the contributions differed among collections. Nevertheless, both databases were complementary and contributed to show marine mammals' research in South America

Using trophic modeling: evaluating fisheries discard effect on the Río de la Plata estuary and coastal shelf

While fishing discards and bycatch are worrisome for fisheries management, research has been mainly focused on commercial or threatened species, while the ecosystem effects were largely neglected. In this work, the effects of discard and fishing efforts on the structure and the functioning of the food web of the Río de la Plata (RdlP) were analyzed using mass balance and dynamic trophic modeling. Discard is consumed almost entirely by several species with a large preference for it, producing mixed trophic impacts. The role of discard on the global attributes of the RdlP ecosystem does not seem important, resulting in a low incidence in trophic flows, growth, and development of the trophic web. Dynamic simulations showed a mixed response to variations of discards, with some groups responding positively and others negatively. For example, a decrease in discards would produce a slight decrease in the biomass of most functional groups, being more pronounced in the predators of the system. Variations in biomass produced by discards are more sensitive under the assumption of bottom-up ecosystem control than mixed control and to a lesser extent under top-down control. Our work confirms a complex relationship between discards and ecosystem functioning, warning about the beneficial result of discard reduction policies.CSIC: Grupos N°32CSIC: VUSP M

Spatial analysis and heritage conservation. Leveraging 3-D data and GIS for monitoring earthen architecture

This paper discusses new advances in heritage site monitoring using a geo-spatial method for assessing the state of preservation of earthen architecture overtime as a preventive conservation measure. The proposed method leverages a comprehensive (quantitative–qualitative) approach that gathers multi-temporal data including environmental information collected by means of environmental loggers, qualitative vulnerability assessment of mud-brick walls, and surface change detection information obtained by comparing terrestrial laser scanning point cloud capturing the decay of building's wall features over time. Producing a detailed spatial understanding of the conservation issues that affect mud-brick walls in large earthen sites, this method can be used by conservators to rapidly identify which buildings require immediate intervention and lay the basis for future evaluation of the conservation actions undertaken. To test the effectiveness of the proposed geospatial model in producing a comprehensive view of the environmental risk and pattern of decay that affect mudbrick structures, this paper presents analyses and results obtained in a six-year study at Çatalhöyük, Turkey. Our results corroborate the effectiveness of the proposed method and prove that it can be successfully employed to create preventive conservation measures at other earthen sites inside and outside the Near East

Understanding Taphonomy Through 3D and 2D Records: A Case Study from the Tropical Maya Area

Mortuary archaeology in the Maya region is complicated by both cultural and natural factors. Distinctive funerary depositional and post-depositional secondary activities, in addition to tropical climate, contribute to the complexity of pre-Hispanic Maya funerary practices. This paper proposes to merge 2D and 3D recording data to obtain a comprehensive understanding of the taphonomic phenomena that affect heavily altered burials at the site of Palenque, Mexico. Employing an archaeothanatological approach, we argue that careful 3D imaging, integrated with earlier produced legacy data, provides additional insight into the formation processes of funerary contexts compared to previous methods. Digital photogrammetric analyses improve our capacity to reconstruct joint articulations of the body and its original funerary deposition in situ. The results of this research elucidate the intentional activities that led to the archaeological arrangement of the grave assemblage. By noticing the degree of articulation and clarifying the pace at which bodies decomposed, these results showcase the depositional sequence of one collective mixed burial from Group IV, a domestic compound in Palenque. These results suggest the viability of 3D methodologies in assessing post-depositional disturbances and movements of the body, both for illuminating funerary taphonomic practices and serving as important recording procedures for the future

An analysis of meiofauna knowledge generated by Latin American researchers

The study of benthic meiofauna has been undertaken in Latin America since the beginning of the 20th century, recently gaining attention due to its recognized role on the ecological functioning of meiofauna assemblages. Bibliometric data provide information regarding research results, explain the degree to which a subject has advanced, and identify its major strengths and weaknesses. In Latin American countries, this type of review is scarce for meiofauna communities. This study analyzes knowledge of marine meiofauna by focusing on the documents Latin American authors published from 1990 to 2021. Documents from three bibliographic databases were analyzed to obtain the most relevant bibliometric indicators. Moreover, the interrelationships between authors, countries, and concepts were analyzed using science mapping techniques. Latin American research on marine meiofauna has increased since the 1990s, producing a total of 399 documents over three decades by almost 1,000 authors. Brazil produced the majority of these documents (predominantly published by Brazilian authors and institutions). The number of documents by country was associated with five development indicators. Their main sources and keywords indicate that ecology, oceanography, and biogeography were the main addressed topics, especially on deep marine environments. Most productive authors were clustered into main research groups with varying degrees of links. We conclude that research efforts on marine meiofauna are gaining importance despite the small number of documents by a relatively low number of research groups. We found a high centralization of documents by countries and a relation with four indicators, such as country size and research spending. Greater regional collaboration could further expand the knowledge of marine meiofauna in Latin America

¿Regulación sectorial o normas de competencia?: El principio de supletoriedad en el caso Speedy Naked

This paper analyses the supplementary application of competition laws in Peru, and it assesses the criteria established in the procedure initiated against Telefónica del Perú S.A.A. for the alleged abuse of its dominant position in the form of tying. It outlines the scope for the supplementary application of competition laws and provides a definition that intends to preserve the integrity of the legal system when conflicts between regulation and competition arise.Se analizan los alcances del principio de supletoriedad en el Perú y se evalúa la definición de su ámbito de aplicación en el caso iniciado en contra de la empresa Telefónica del Perú S.A.A. por prácticas de abuso de posición de dominio en la modalidad de ventas atadas. Se propone una conceptualización del principio que busca resguardar la integridad del sistema jurídico en los casos de conflictos normativos entre regulaciónsectorial y normas de competencia

The Mausoleum Architectural Project: Reinterpreting Palenque's temple of the inscriptions through 3D data-driven architectural analysis

The Temple of the Inscriptions at Palenque, Mexico, is an outstanding example of Classic Maya architecture erected in the seventh century as the funerary building for ruler K'inich Janab Pakal. For decades, scholars have speculated on its construction sequence and the potential existence of hidden rooms on either side of Pakal's mortuary chamber. This article aims to advance understanding of the Temple's architectural context in light of new 3D data. After reviewing the application of drone-based photogrammetry and terrestrial Light Detection and Ranging in the Maya area, we argue that these techniques are capable of enhancing the architectural analysis of the Temple of the Inscriptions and showing that this structure was part of a larger architectural project, encompassing the adjacent Temple XIII, and the connecting stepped building platform. Our findings demonstrate that the basal platforms for the Temple of the Inscriptions and Temple XIII were erected contemporaneously and that the design of their mortuary chambers follows a tripartite layout we identified in Palenque's elite funerary architecture and associated mortuary practices. We conclude that these three buildings were part of a mausoleum architectural project, the construction of which was initiated by Pakal to reshape Palenque's site-core and enshrine the ruling family's power and ancestors