American Civil War | EPFL Graph Search

The American Civil War (April 12, 1861 – May 26, 1865; also known by other names) was a civil war in the United States. It was fought between the Union ("the North") and the Confederacy ("the South"), the latter formed by states that had seceded. The central cause of the war was the dispute over whether slavery would be permitted to expand into the western territories, leading to more slave states, or be prevented from doing so, which many believed would place slavery on a course of ultimate extinction. Decades of political controversy over slavery were brought to a head by the victory in the 1860 U.S. presidential election of Abraham Lincoln, who opposed slavery's expansion into the western territories. An initial seven southern slave states responded to Lincoln's victory by seceding from the United States and, in February 1861, forming the Confederacy. The Confederacy seized U.S. forts and other federal assets within their borders. Four more southern states seceded after the

Civil war hinders crop production and threatens food security in Syria

Xi Li, Li Mi

Assessing the impact of violent conflict on Syrian agriculture is challenging given data limitations and attributability issues. Using satellite data at 30 m spatial resolution, we found that the extent of productive cropland showed greater interannual variability and spatial heterogeneity after the start of the civil war in 2011. Using changes in satellite-based night-time light as a proxy for war impact intensity, we also found that cropland close to severely impacted urban settlements faced greater disruption. Fixed-effects models revealed the relationship between productive cropland and precipitation for the pre-war period, whereas a counterfactual scenario constructed for the period 2012-2019 showed substantial variation at the regional level. While the ongoing conflict promoted cropland cultivation in safer zones, cropland reduction took place in the country's northwest and southeast regions. Our study demonstrated the combined utility of daytime and night-time satellite data to assess food insecurity in extreme environments and can help guide distribution of food and aid in Syria. Conflicts are known to disrupt agriculture, food supply chains and the economy at large. Mapping and quantifying such disruptions, although key for aid planning, remains a challenge in war zones. This study uses daytime and night-time satellite data from Syria over 1998-2019 to assess the link between war-induced impacts on infrastructure and urban areas with cropland dynamics.

NATURE PORTFOLIO2022

Le temple d'Hathor à Dendara

Pierre Zignani

Dendara, July 16, 54 BCE, began the reconstruction of the temple dedicated to the goddess Hathor. Founded under Ptolemy XII, the temple studied here stands at the end of an architectural tradition developed over three millennia. Its state of conservation is exceptional. It is the latest preserved monumental cult building of the pharaonic civilisation. It is a particularly well-suited testimony for an attempt to comprehend the architectural conception of a culture with which no modern society has kept any direct connection. The starting point of this study is a precise survey which constitutes the scientific documentation. The establishment of these data went along with the observation of indications, dimensions, orientations and alterations which allows to identify constant characteristics belonging to the process of designing the structure of the temple. This study uses no technical methodology but rather presents a research of knowledge through observation, hypotheses and verification. There is no pretension to exhaustiveness. This study tries to find, from the territory to the details, breaches, or to give access, into the knowledge belonging to the way of designing. The plans and sections are accompanied by a research which begins with a presentation of the nature of the architectural study of the building belonging to a disappeared culture. Then follows the study of the Egyptian temple and of the technical details of the survey. A building belongs to a territory. The absence of any documentation, the disappearance of vestiges dug out since the end of the 19th century as well as the actual policy of land reclaiming on the site made a cartography of the whole area of the ancient city necessary as a salvage. This led to some thoughts about the urban shape around the temple and about the limits of the space between the divine and the civil world. The reconstruction of a temenos wall brought with it a large reorganisation and renovation of the city and caused an important tabula rasa of civil districts. A global description of the building precedes the chapter concerning the organisation of the space. The world being set up around the god, it progresses from the most holy place towards the civil environment. The system underlying the height of the different spaces can only be determined when taking the heart of the temple as point of origin. Particular attention was devoted to the means which the ancient builders had at their disposal in order to control the precision of their accomplishment. Although rules concerning the outer measurements of the naos and the inner volume of the cella could be determined, it is impossible to reduce the dimensioning of the Egyptian space to a system of constant proportions. The study of the use of the space confirms this statement as it reveals that the functional elements of doors and windows do not follow any ideal formal rules. They are the result of a topological conception where geometric accuracy sacralises different needs; sometimes trivial when one considers light as a physical agent necessary to the daily functioning of human beings in a structure belonging to the divine. The intelligence and the accuracy of these accomplishments clearly required a global and initial conception of the architectural object. The durability of the building was the ultimate reason for the designers' research of technical quality. No single part of the construction, from the foundations to the top of the cornices, escaped this ancient concern. This led to an evolution towards a monolithic character of the masonry and the integration of solutions to contain factors of degradation, such as the rain. This concern also includes a tradition of a seismic culture as well as an execution which optimises the performance of labour and the materials. In parallel to this evolution on can observe the emergence of an ancient analysis of the phenomenon of differential sinking and the development of details which allow a dynamic management of major sources of destruction. Computer modelling helped to check the pertinence of some of these ultimate systems of management of deformation. From the temple of Hathor at Dendara one can conclude that the competence of building has attained a high degree of complexity and of meaning as far as the production of an architectural form is concerned which had to obey to an ideal of perfection and inalterability. Beyond the secular world, the formal conceptualisation of the divine universe also became an intellectual challenge with various referential levels. The architectural composition went along with an active research of technical solutions in order to optimise the art of building.

EPFL2004

Robust system identification and model predictions in the presence of systematic uncertainty

Romain Pasquier, Ian Smith

Model-based data-interpretation techniques are increasingly used to improve the knowledge of complex system behavior. Physics-based models that are identified using measurement data are generally used for extrapolation to predict system behavior under other actions. In order to obtain accurate and reliable extrapolations, model-parameter identification needs to be robust in terms of variations of systematic modeling uncertainty introduced when modeling complex systems. Approaches such as Bayesian inference are widely used for system identification. More recently, error-domain model falsification (EDMF) has been shown to be useful for situations where little information is available to define the probability density function (PDF) of modeling errors. Model falsification is a discrete population methodology that is particularly suited to knowledge intensive tasks in open worlds, where uncertainty cannot be precisely defined. This paper compares conventional uses of approaches such as Bayesian inference and EDMF in terms of parameter-identification robustness and extrapolation accuracy. Using Bayesian inference, three scenarios of conventional assumptions related to inclusion of modeling errors are evaluated for several model classes of a simple beam. These scenarios are compared with results obtained using EDMF. Bayesian model class selection is used to study the benefit of posterior model averaging on the accuracy of extrapolations. Finally, ease of representation and modification of knowledge is illustrated using an example of a full-scale bridge. This study shows that EDMF leads to robust identification and more accurate predictions than conventional applications of Bayesian inference in the presence of systematic uncertainty. These results are illustrated with a full-scale bridge. This example shows that the engineering knowledge necessary to perform parameter identification and remaining-fatigue-life predictions of a complex civil structure is easily represented by the EDMF methodology. Model classes describing complex systems should include two components: (1) unknown physical parameters that are identified using measurements; (2) conservative modeling error estimations that cannot be represented only as uncertainties related to physical parameters. In order to obtain accurate predictions, both components need to be included in the model-class definition. This study indicates that Bayesian model class selection may lead to over-confidence in certain model classes, resulting in biased extrapolation.