Inner and Outer Rounding of Boolean Operations on Lattice Polygonal Regions

Robustness problems due to the substitution of the exact computation on real numbers by the rounded floating point arithmetic are often an obstacle to obtain practical implementation of geometric algorithms. If the adoption of the --exact computation paradigm--[Yap et Dube] gives a satisfactory solution to this kind of problems for purely combinatorial algorithms, this solution does not allow to solve in practice the case of algorithms that cascade the construction of new geometric objects. In this report, we consider the problem of rounding the intersection of two polygonal regions onto the integer lattice with inclusion properties. Namely, given two polygonal regions A and B having their vertices on the integer lattice, the inner and outer rounding modes construct two polygonal regions with integer vertices which respectively is included and contains the true intersection. We also prove interesting results on the Hausdorff distance, the size and the convexity of these polygonal regions

Mediterranean Morphologies in Hot Summer Conditions: Learning from France’s “Glorious Thirty” Holiday Housing:

Climate change and rising temperatures lead to an air-conditioning proliferation in summertime of the Mediterranean regions. This study links urban morphology to the microclimate. It claims that a lesson can be drawn from holiday housing morphologies designed with an additive approach during the “Glorious Thirty” French coastal development (1946-75).  It is based on a morphological analysis of four case studies, with on the one hand re-drawing and site visiting, on the other hand, assessment of environmental performance through key parameters: Absolute Rugosity, Compactness Ratio, Building Density, Mineralization, Sky View Factor (SVF) and Height/Width (H/W) Ratio. Compared to literature reference values of a traditional courtyard morphology, the case studies are less compact and with a lower H/W Ratio (higher SVF), but they are less mineral than a historic medieval city centre. This research contributes to the search for semi-collective alternatives (for example additive morphologies) to individual housing in peri-urban areas, with high environmental performance in the summertime.

Integrating Wind Flow Analysis in Early Urban Design: Guidelines for Practitioners

The research focused on simulating wind patterns in urban planning design offers substantial contributions to both the social and economic aspects of the urban planning and design field. To begin with, it addresses a critical factor in urban development, especially in Mediterranean climates, where natural ventilation significantly influences summer comfort. By incorporating predictive numerical simulations of urban wind patterns, this study provides valuable insights into improving outdoor thermal comfort within urban areas. This holds particular importance in the context of adapting to climate change, as it equips urban planners and architects with informed decision-making tools to create more sustainable and comfortable urban environments. Additionally, this research makes an economic contribution by presenting guidelines for iterative wind simulations in the early stages of designing medium-scale urban projects. Through the validation of a simulation workflow, it streamlines the design process, potentially reducing the time and resources required for urban planning and architectural design. This enhanced efficiency can result in cost savings during project development. Moreover, the study's recommendations concerning simulation parameters, such as wind tunnel cell size and refinement levels, offer practical insights for optimizing simulation processes, potentially lowering computational expenses and improving the overall economic viability of urban design projects. To summarize, this research effectively addresses climate-related challenges, benefiting both social well-being and economic efficiency in the field of urban planning and design, while also providing guidance for more efficient simulation-driven design procedures

On Order Types of Random Point Sets

A simple method to produce a random order type is to take the order type of a random point set. We conjecture that many probability distributions on order types defined in this way are heavily concentrated and therefore sample inefficiently the space of order types. We present two results on this question. First, we study experimentally the bias in the order types of $n$ random points chosen uniformly and independently in a square, for $n$ up to $16$. Second, we study algorithms for determining the order type of a point set in terms of the number of coordinate bits they require to know. We give an algorithm that requires on average $4n \log\_2 n+O(n)$ bits to determine the order type of $P$, and show that any algorithm requires at least $4n \log\_2 n - O(n \log\log n)$ bits. This implies that the concentration conjecture cannot be proven by an "efficient encoding" argument

Sustainable construction for affordable housing program in Kabul

Afghanistan suffers from four decades of war, caused a massive migration of the rural population to the cities. Kabul was originally designed for 1,5 million people, where now 5 million people live. The importation of modern western styles housing for rapid reconstruction reveals apparent cultural conflict and significant environmental footprint. The new constructive cultures for sustainable reconstruction should necessary consider the use of local materials combined with modern technologies. Earthen architecture underlies the embodiment of Afghanistan architecture. The aim of this research is to revisit traditional afghan earthen construction with the tools of industrial modernity. Three soils of the Kabul region were first characterized. Then, sun-dried mud brick and compressive earth block, with and without stabilization have been prepared and tested in the laboratory to develop the most suitable earth construction element which is cost effective and easily available compared to the imported modern products

Le tampon mélangeur

Les méthodes de randomisation ont eu un grand succès en géométrie algorithmique car elles conduisent fréquemment à des algorithmes plus simples à programmer et parfois plus efficaces que leurs équivalents déterministes. Un algorithme est randomisé lorsque celui-ci effectue des choix aléatoires pour parvenir à ses fins, pour la catégorie des algorithmes incrémentaux à laquelle nous nous intéressons, le hasard intervient, par exemple, dans l'ordre d'insertion des données. L'analyse de tels algorithmes est alors faite en moyenne sur les différents ordres possibles. Cependant, choisir un ordre d'insertion aléatoire nécessite d'attendre l'ensemble des données avant de les insérer, ce qui fait que l'algorithme n'est plus en ligne. Une solution possible consiste, cependant, à intercaler un tampon mélangeur de taille $k$ entre le processus qui fournit les données et l'entrée de l'algorithme afin d'effectuer un mélange local de l'ordre initial nous permettant ainsi d'introduire assez de randomisation pour nous garantir une amélioration de la complexité moyenne d'algorithmes en ligne dépendant de l'ordre d'insertion. Ainsi après avoir illustré ce type de technique sur le problème du tri, nous donnons quelques résultats obtenus pour des problèmes plus géométriques tels que la triangulation de Delaunay ou le cloisonnement vertical de segments pour lesquels il existe des algorithmes incrémentaux. Typiquement, pour un algorithme randomisé en $O(n \log n)$ ou $O(n)$, le cas le pire est au moins quadratique et l'utilisation des stratégies proposées permet d'obtenir une complexité O(\fracn^2 \log k{k}).

Effet de l'angle de charge sur les harmoniques d'efforts magnétiques dans les machines synchrones à aimants permanents surfaciques

International audienceCet article étudie l'effet de l'angle de charge sur les efforts harmoniques de Maxwell (tangentiels et radiaux) et les bruits et vibrations d'origine magnétique dans deux machines synchrones à aimants permanents (MSAP) surfaciques d'architectures très différentes : une machine à 6 dents et 2 paires de pôles, à faible couple et très haute vitesse, et une autre à 120 dents et 58 paires de pôles, à fort couple et faible vitesse. Les efforts magnétiques en présence sont d'abord analysés de manière théorique. Des simulations numériques électromagnétiques et vibro-acoustiques sont ensuite réalisées à l'aide du logiciel MANATEE. Il est montré que l'angle du courant optimal permettant de minimiser les efforts et le bruit de « denture » liés à l'interaction entre pôles et encoches n'est pas identique à celui minimisant les couples pulsatoires ; de même l'angle du courant minimisant les efforts harmoniques radiaux n'est pas nécessairement celui minimisant les efforts harmoniques tangentiels. L'angle de courant minimisant le courant consommé (MTPA) n'est pas celui minimisant les vibrations d'origine magnétique : un compromis doit donc être effectué entre performances électromagnétiques et vibro-acoustiques.</div

A generator of random convex polygons in a disc

International audienceWe propose an algorithm that generates a random polygon as a convex hull of n points uniformly and independently distributed in a disc without explicitly generate all the points

Agathe, an ephemeral island of the Languedoc coast? (Agde Hérault, France)

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