Early modern period | EPFL Graph Search

The early modern period of modern history spans the period after the Late Middle Ages of the post-classical era (1400–1500) to the beginning of the Age of Revolutions (1800). Although the chronological limits of this period are open to debate, the timeframe is variously demarcated by historians as beginning with the fall of Constantinople in 1453, the Renaissance period in Europe and Timurid Central Asia, the end of the Crusades, the Age of Discovery (especially the voyages of Christopher Columbus beginning in 1492 but also Vasco da Gama's discovery of the sea route to India in 1498), and ending around the French Revolution in 1789, or Napoleon's rise to power. Historians in recent decades have argued that from a worldwide standpoint, the most important feature of the early modern period was its spreading globalizing character. New economies and institutions emerged, becoming more sophisticated and globally articulated over the course of the period. The early modern period also incl

Improving slash-and-burn agriculture in Central Menabe, Madagascar

Justine Marie Gay des Combes

Slash-and-burn agriculture is considered as an important driver of deforestation in the tropics. In Madagascar, a biodiversity hotspot, this type of agriculture particularly threatens the tropical forest cover. On the south-western coast of the island, in Central Menabe, the dry tropical forest of Kirindy suffers from an annual deforestation of 2.6%. At such alarming rate, the forest will have entirely disappeared by 2050. The attention of past research programs and conservation actions were mainly on studying the forest or the general interactions between local populations and the forest, with little focus on the slash-and-burn agricultural system itself. Hence, understanding the cultivation practices and assessing alternatives to them is crucial to improve the current forest conservation initiatives. The present thesis answers to the need of an in-depth study of the agricultural practices in Central Menabe. The project aims to (1) analyze the practices of slash-and-burn cultivation in Kirindy forest, (2) explore alternative slash-and-burn practices which may be more sustainable for the forest, (3) determine the implementation perspectives of these alternatives. In a first stage, we have characterized soil productivity along repetitive slash-and-burn cultivation cycles and the farmerâs perception of their agricultural system. Then, we experimented a selective slash-and-burn agriculture (where trees are left intentionally within the cultivated fields), coupled with compost amendment. Finally, we have assessed the implementation potential of that technique through interviews and participating workshops with local farmers. Our findings highlighted that soil depletion due to plant uptake and erosion or leaching by heavy rains, as well as weed invasion were important problems of slash-and-burn cultivation in Central Menabe. Farmers perceive weeding as a work overload. Decrease in grain yield due to slash-and-burn agriculture reaches about 40% after three years of cultivation on the same field (from 4 to 2.5 t ha-1), and decreases up to 75% after a single cyclonic rainy season (from 4 to 1 t ha-1). Further, we demonstrated that combining compost and wood ashes (from the burnings) seems a promising solution to sustain cultivation on the fields. Compost, combined with wood ashes, multiplied corn yield by 5 compared to traditional slash-and-burn agriculture. Growth rates were accelerated and phenology stages of maize plants advanced. Furthermore, this combination also increased soil security by improving the remaining stock of nutrients after a rain simulation. On the other hand, a partial remaining tree cover (selective slash-and-burn agriculture) improved corn yields only when the soil was amended with ashes, not with compost, nor the combination of both. Implementing composting in the forest dwelling communities appears to be a challenging task. Several barriers were highlighted, among them the most important was the water constraints during a consequent period of time related to compost maintenance. Alternative slash-and-burn practices have not been much studied so far because the use of fire was always considered as destructive. Thus, our result will contribute to the development of new forest management strategies which would balance conservation of habitats and rural communities agricultural needs, while minimizing the impact on primary forest.

EPFL2017

Autogenous Shrinkage and Hydration Kinetics of SH-UHPFRC under Moderate to Low Temperature Curing Conditions

Mohammadhadi Kazemi Kamyab

Strain Hardening Ultra High Performance Fiber Reinforced Concrete (SH-UHPFRC) were used successfully over the last 8 years in numerous cast in place rehabilitation applications as long lasting waterproofing layers (20 to 30 mm thickness) and, combined with rebar, to increase the structural load bearing capacity of existing bridge decks or building slabs (50 to 70 mm thickness). In composite applications on reinforced concrete substrates, SH-UHPFRC provide a deformation capability (strain hardening) larger than their free shrinkage which makes localized macro cracking at service state very unlikely. On the other hand some specific conditions of microclimatic state of the substrate (moisture and thermal conditions) and climatological (temperature and humidity) of the site such as casting at low temperatures (winter conditions) might increase the autogenous shrinkage and thus eigenstresses of the freshly cast SH-UHPFRC and hinder the development of its tensile strength or/and deformability. Combination of these specific circumstances could compromise the SH-UHPFRC protective functions due to the occurrence of localized macro cracks, making the objective of using SH-UHPFRC as a onetime intervention strategy in rehabilitation application obsolete. Advancement in hydration at early age leads to formation of partially emptied capillary spaces contributing to self-desiccation, decrease of the relative humidity and increase of the capillary depression. Since water is under depression, the solid porous material is under compression forcing the material to shrink. From the aforementioned, it can be deduced that the autogenous shrinkage is a force driven phenomenon: a force is applied on the ageing viscoelastic porous skeleton and the apparent structural response of the bulk cementitious material is the autogenous shrinkage strain. Based on the aforementioned two levels of investigation were considered in this thesis: I. Material level: ageing viscoelastic porous skeleton of hydrating cementitious material II. Structural level: autogenous shrinkage development under the action of its driving forces The objective of this thesis was to study the development of the autogenous shrinkage and its relation with the development of microstructure and mechanical properties in SH-UHPFRC cured at moderate and low temperature conditions (1 to 20°C). Focus was put on: (1) kinetics and magnitude of hydration of silica fume and cement, (2) activation energy of the processes, (3) stiffness (E modulus and Poisson ratio) development, and (4) states of water and pore development. Finally a cross link analysis of information obtained from material and structural level was carried out to better highlight the mechanisms and driving forces of autogenous shrinkage. CM22-TKK, a SH-UHPFRC developed at MCS for rehabilitation applications, on the basis of CEMTECmultiscale® fibrous mixes, was used. Silica fume is one of the major constituents of CM22-TKK (26% by mass of cement). Extent of the silica fume pozzolanic reaction significantly affects the pore size distribution of the UHPFRC matrix which then influences the development of the relative humidity, self-desiccation and finally autogenous deformation. Detailed experimental investigation performed showed that only maximum 8% by mass of cement out of 26% silica fume used in the recipe reacts in moderate and low temperature curing conditions. Finally, a model of silica-fume degree of reaction as a function of curing temperature (5 to 250 °C) was proposed on the basis of a detailed literature survey of existing works with low W/B mixes. The activation energy of the thermo-mechanical properties was evaluated for thermo (cumulative heat of hydration) and mechanical properties development (such as dynamic Elastic modulus, dynamic Poisson’s ratio and compressive strength). A single activation energy Ea of 27.4 KJ/mol could successfully model the activation of all properties. Since maturity was not a proper reference to compare the autogenous deformations at various temperatures, a more fundamental reference such as degree of hydration was used. Experimental investigation was carried out using different techniques such as isothermal calorimetry and 29Si solid NMR to evaluate the development of the degree of hydration of cement and silica fume in UHPFRC at moderate and low temperature curing conditions. The ultimate degree of hydration of cement in CM22-TKK for a closed system was 0.34. There was a close correspondence between the experimental results and the predictions of the volumetric phase distribution models of Waller (0.28) and Jensen (0.32). Finally, the De Schutter et al. 1996 model was used to describe the mechanical properties (Emodulus and Poisson ratio) as function of degree of hydration. Nondestructive and non-invasive 1H-NMR was used to evaluate volumetric phase distribution development at 20°C, especially the classification of the water types (capillary, gel and C-S-H interlayer water) which brought fully new and valuable information about the hydration kinetics and pore size development. The results were also compared with Jensen volumetric phase distribution model to check the advantages and limitation of both approaches. Finally experimental investigation was carried out to follow the development of autogenous shrinkage and eigenstresses (in case of restrained shrinkage) of CM22-TKK cured in isotherm conditions (1 to 20°C). Eigenstresses were obtained and used to highlight the effect of the viscous response of the material at the different temperatures investigated. The previously mentioned results on the kinetics of the silica fume reaction, cement hydration and evolution of states of water and development of stiffness were then put into perspective with the trends observed on the autogenous shrinkage and eigenstresses development.

EPFL2013

The Core Literature of the Historians of Venice

Giovanni Colavizza

Over the past decades, the humanities have been accumulating a growing body of literature at an increasing pace. How does this impact their traditional organization into disciplines and fields of research therein? This article considers history, by examining a citation network among recent monographs on the history of Venice. The resulting network is almost connected, clusters of monographs are identifiable according to specific disciplinary areas (history, history of architecture, and history of arts) or periods of time (middle ages, early modern, and modern history), and a map of the recent trends in the field is sketched. Most notably a set of highly cited works emerges as the core literature of the historians of Venice. This core literature comprises a mix of primary sources, works of reference, and scholarly monographs and is important in keeping the field connected: monographs usually cite a combination of few core and a variety of less well-cited works. Core primary sources and works of reference never age, while core scholarly monographs are replaced at a very slow rate by new ones. The reliance of new publications on the core literature is slowly rising over time, as the field gets increasingly more varied.