Search results for "Plane"
showing 10 items of 6821 documents
Information nutritionnelle, choix et caractéristiques des consommateurs
2012
Consumers’ food decisions are based on the information they receive and on their own individual characteristics. This paper is based on an experiment using experimental economics and sensory evaluation to measure individual characteristics of participants and to analyze the impact of nutritional information relative to orange juice. The aim is to explore the potential link between specific characteristics (risk aversion, time preference) and the reactions of consumers to nutritional information. The results show that participants react significantly to this information supplied, positively for the pure orange juice and a negatively for orange nectars. In addition, “risk averse” individuals …
Monitoring Cropland Phenology on Google Earth Engine Using Gaussian Process Regression
2021
Monitoring cropland phenology from optical satellite data remains a challenging task due to the influence of clouds and atmospheric artifacts. Therefore, measures need to be taken to overcome these challenges and gain better knowledge of crop dynamics. The arrival of cloud computing platforms such as Google Earth Engine (GEE) has enabled us to propose a Sentinel-2 (S2) phenology end-to-end processing chain. To achieve this, the following pipeline was implemented: (1) the building of hybrid Gaussian Process Regression (GPR) retrieval models of crop traits optimized with active learning, (2) implementation of these models on GEE (3) generation of spatiotemporally continuous maps and time seri…
The effect of climate on the spread of the COVID-19 pandemic: A review of findings, and statistical and modelling techniques
2020
The new SARS-CoV-2 coronavirus has spread rapidly around the world since it was first reported in humans in Wuhan, China, in December 2019 after being contracted from a zoonotic source. This new virus produces the so-called coronavirus 2019 or COVID-19. Although several studies have supported the epidemiological hypothesis that weather patterns may affect the survival and spread of droplet-mediated viral diseases, the most recent have concluded that summer weather may offer partial or no relief of the COVID-19 pandemic to some regions of the world. Some of these studies have considered only meteorological variables, while others have included non-meteorological factors. The statistical and…
Ethically Researching Local Impacts of Environmental Change without Travel
2021
Responses to the COVID-19 pandemic, which began in 2020, included local and international travel restrictions alongside limits on face-to-face gatherings. These measures impinged on participatory research examining local impacts of environmental change. In response, many researchers adopted techniques that could be implemented without travel. This article explores some of the consequent research ethics issues.
$\Omega$-symmetric measures and related singular integrals
2019
Let $\mathbb{S} \subset \mathbb{C}$ be the circle in the plane, and let $\Omega: \mathbb{S} \to \mathbb{S}$ be an odd bi-Lipschitz map with constant $1+\delta_\Omega$, where $\delta_\Omega>0$ is small. Assume also that $\Omega$ is twice continuously differentiable. Motivated by a question raised by Mattila and Preiss in [MP95], we prove the following: if a Radon measure $\mu$ has positive lower density and finte upper density almost everywhere, and the limit $$ \lim_{\epsilon \downarrow 0} \int_{\mathbb{C} \setminus B(x,\epsilon)} \frac{\Omega\left((x-y)/|x-y|\right)}{|x-y|} \, d\mu(y) $$ exists $\mu$-almost everywhere, then $\mu$ is $1$-rectifiable. To achieve this, we prove first that if …
Integrability of orthogonal projections, and applications to Furstenberg sets
2022
Let $\mathcal{G}(d,n)$ be the Grassmannian manifold of $n$-dimensional subspaces of $\mathbb{R}^{d}$, and let $\pi_{V} \colon \mathbb{R}^{d} \to V$ be the orthogonal projection. We prove that if $\mu$ is a compactly supported Radon measure on $\mathbb{R}^{d}$ satisfying the $s$-dimensional Frostman condition $\mu(B(x,r)) \leq Cr^{s}$ for all $x \in \mathbb{R}^{d}$ and $r > 0$, then $$\int_{\mathcal{G}(d,n)} \|\pi_{V}\mu\|_{L^{p}(V)}^{p} \, d\gamma_{d,n}(V) \tfrac{1}{2}$ and $t \geq 1 + \epsilon$ for a small absolute constant $\epsilon > 0$. We also prove a higher dimensional analogue of this estimate for codimension-1 Furstenberg sets in $\mathbb{R}^{d}$. As another corollary of our method,…
Visible parts of fractal percolation
2009
We study dimensional properties of visible parts of fractal percolation in the plane. Provided that the dimension of the fractal percolation is at least 1, we show that, conditioned on non-extinction, almost surely all visible parts from lines are 1-dimensional. Furthermore, almost all of them have positive and finite Hausdorff measure. We also verify analogous results for visible parts from points. These results are motivated by an open problem on the dimensions of visible parts.
The richest superclusters : I Morphology
2007
We study the morphology of the richest superclusters from the catalogues of superclusters of galaxies in the 2dF Galaxy Redshift Survey and compare the morphology of real superclusters with model superclusters in the Millennium Simulation. We use Minkowski functionals and shapefinders to quantify the morphology of superclusters: their sizes, shapes, and clumpiness. We generate empirical models of simple geometry to understand which morphologies correspond to the supercluster shapefinders. We show that rich superclusters have elongated, filamentary shapes with high-density clumps in their core regions. The clumpiness of superclusters is determined using the fourth Minkowski functional $V_3$.…
Multi-scale morphology of the galaxy distribution
2006
Many statistical methods have been proposed in the last years for analyzing the spatial distribution of galaxies. Very few of them, however, can handle properly the border effects of complex observational sample volumes. In this paper, we first show how to calculate the Minkowski Functionals (MF) taking into account these border effects. Then we present a multiscale extension of the MF which gives us more information about how the galaxies are spatially distributed. A range of examples using Gaussian random fields illustrate the results. Finally we have applied the Multiscale Minkowski Functionals (MMF) to the 2dF Galaxy Redshift Survey data. The MMF clearly indicates an evolution of morpho…
Emergencia planetaria : necesidad de un planteamiento global
2007
Las noticias de degradación ambiental han saltado a las primeras páginas y editoriales de los periódicos y las reclamaciones ciudadanas empiezan a multiplicarse. Todo parece indicar que estamos asistiendo a una progresiva toma de conciencia. Sin embargo, las incomprensiones y las reticencias a la modificación de comportamientos siguen siendo graves, con una fuerte tendencia a los planteamientos parciales y al reduccionismo causal, ignorando la estrecha vinculación de los problemas y la necesidad de abordarlos conjuntamente. El objetivo de este trabajo es, precisamente, mostrar la vinculación de los problemas que caracterizan la actual situación de emergencia planetaria, que no se limitan al…