Systematic comparison of trip distribution laws and models

Trip distribution laws are basic for the travel demand characterization needed in transport and urban planning. Several approaches have been considered in the last years. One of them is the so-called gravity law, in which the number of trips is assumed to be related to the population at origin and destination and to decrease with the distance. The mathematical expression of this law resembles Newton's law of gravity, which explains its name. Another popular approach is inspired by the theory of intervening opportunities which argues that the distance has no effect on the destination choice, playing only the role of a surrogate for the number of intervening opportunities between them. In this paper, we perform a thorough comparison between these two approaches in their ability at estimating commuting flows by testing them against empirical trip data at different scales and coming from different countries. Different versions of the gravity and the intervening opportunities laws, including the recently proposed radiation law, are used to estimate the probability that an individual has to commute from one unit to another, called trip distribution law. Based on these probability distribution laws, the commuting networks are simulated with different trip distribution models. We show that the gravity law performs better than the intervening opportunities laws to estimate the commuting flows, to preserve the structure of the network and to fit the commuting distance distribution although it fails at predicting commuting flows at large distances. Finally, we show that the different approaches can be used in the absence of detailed data for calibration since their only parameter depends only on the scale of the geographic unit.Comment: 15 pages, 10 figure

X-ray reflectivity, diffraction and grazing incidence small angle X-ray scattering as complementary methods in the microstructural study of sol–gel zirconia thin films

X-ray reflectometry, X-ray diffraction and grazing incidence small angle X-ray scattering have been complementary used to fully characterize zirconia (ZrO2) thin films obtained by the sol–gel route. The films were synthesized on various sapphire (Al2O3), silicon (Si) and glass mirrorpolished wafers by a dip-coating process in a zirconia precursor sol. Versus the synthesis parameters as alkoxide sol concentration, withdrawal speed and annealing temperature, the microstructure of the layer is managed and its different microstructural parameters such as thickness, mass density, crystalline phase, grain size and spatial arrangement have been determined. The as prepared layers are amorphous. During a thermal treatment at low temperature (<1000 -C), the layers thickness decreases while their mass density increases. Simultaneously the zirconia precursor crystallises in the zirconia tetragonal form and the coating is made of randomly oriented nanocrystals which self organise in a dense close-packed microstructure. At low temperature, this microstructural evolution is similar whatever the substrate. Moreover, the layer evolves as the corresponding bulk xerogel showing that the presence of the interface does not modify the thermal microstructure evolution of the layer which is controlled by a normal grain growth leading to relatively dense nanocrystalline thin films

Phénoménologie et psychanalyse, une problématique "parenté"?

International audienceIl s'agira de faire état, en amont de la question d’un dialogue possible, de ce qui a été jusqu’à maintenant peu évoqué dans les divers articles de cet ouvrage, à savoir de ce qui sépare ces deux champs théoriques : la phénoménologie et la psychanalyse. Non pas dans le but de réfuter la possibilité de tout dialogue entre ces deux discours (l’altérité n’a jamais rendu impossible le dialogue puisque celui-ci naît d’un écart). Mais dans le but de mettre en question la « parenté » de l’une avec l’autre. C’est en effet par ce terme que Merleau-Ponty désignait le rapport de la phénoménologie et de la psychanalyse, souhaitant même, disait-il, « aggraver » cette parenté. Dans sa Préface à Hesnard de 1961 , il affirme à cet égard qu’elles « se dirigent toutes deux vers la même latence », soutenant par là que la quête de l’une et de l’autre à défaut d’adopter une méthode semblable comportent un même horizon. On ne s’étonne pas assez de ce rapprochement qu’opère Merleau-Ponty entre ce que la phénoménologie a nommé le pré-réflexif et la psychanalyse l’inconscient. Aussi s’agira-t-il premièrement de faire entendre l’originalité d’une telle affirmation dans le contexte phénoménologico-psychanalytique. Puis d’ouvrir des pistes pour envisager les difficultés qui demeurent à supposer une telle parenté si l’on souhaite conserver son tranchant à l’invention freudienne

Le jeu comme trompe-l'oeil et la dénégation

International audienceContrarily to M. Klein and D.W. Winnicott, who, generally speaking, look favorably on play in the cure, for us it appears impossible to talk about play in general without considering that there exist several types of play. Also, following the examples of J. Piaget for developmental psychology and R. Caillois for sociology, we propose a Freudian “structural classification of play,” and we distinguish three types of plays: play based on the mechanism of negation (Verneinung), play based on the mechanism of disavowal (Verleugnung), and play based on the mechanism of foreclosure (Verwerfung). This article develops the first type of play based on the mechanism of negation – which is what studies of play typically allude to – that we will call “trompe-l’œil” play. In order to illustrate this category, we will study the horse game played by “Little Hans” in Freud's famous analysis, which immediately follows the young patient's phobia. We maintain that the transition from phobic symptom to play is the result of an intervention of the Law. Play based on the mechanism of negation veils the reality of castration, and succeeds the child to move beyond merely being played upon by his fantasy – as in the case of the phobic symptom – allowing him instead to play with his fantasy. Here, the “trompe-l’œil” game can be considered therapeutic, or, at least, its emergence can be considered the effect of the analyst's therapeutic intervention.Contrairement à M. Klein et D.W. Winnicott qui envisagent, de manière générale, le jeu de manière favorable à la cure, il nous apparaît comme impossible de parler du jeu en général sans considérer qu’il existe plusieurs types de jeux. Aussi, comme J. Piaget l’avait proposé pour la psychologie développementale et R. Caillois pour la sociologie, proposons-nous une « classification structurale des jeux » qui épouse le champ freudien et repérons-nous trois types de jeux : les jeux fondés sur le mécanisme de la dénégation (Verneinung), les jeux fondés sur le mécanisme du déni (Verleugnung) et les jeux fondés sur le mécanisme de la forclusion (Verwerfung). Dans cet article est développé le premier type de jeu fondé sur le mécanisme de la dénégation – celui auquel les études sur « le » jeu font en général allusion – que nous appellerons un jeu « trompe-l’œil ». Afin d’illustrer cette catégorie, c’est le jeu du cheval du « petit Hans », célèbre psychanalyse de Freud, qui succède immédiatement à la phobie, qui est étudié. Nous soutenons que le passage du symptôme phobique au jeu résulte d’un rappel de la loi. Le jeu fondé sur le mécanisme de la dénégation, en tant que permettant de voiler la castration, permet à l’enfant de ne plus être totalement joué par son fantasme – comme dans le symptôme phobique – mais de jouer de son fantasme. En cela, le jeu « trompe-l’œil » peut être considéré comme thérapeutique ou, au moins, son émergence comme l’effet d’une intervention thérapeutique de l’analyste

A commuting network model: going to the bulk

The influence of commuting in socio-economic dynamics increases constantly. Analysing and modelling the networks formed by commuters to help decision-making regarding the land-use has become crucial. This paper presents a simple spatial interaction simulated model with only one parameter. The proposed algorithm considers each individual who wants to commute, starting from their living place to all their workplaces. It decides where the location of the workplace following the classical rule inspired from the gravity law consisting in a compromise between the job offers and the distance to the jobs. The further away the job offer is, the more important it must be in order to be considered. Inversely, only the quantity of offers is important for the decision when these offers are close. The paper also presents a comparative analysis of the structure of the commuting networks of the four European regions to which we apply our model. The model is calibrated and validated on these regions. Results from the analysis shows that the model is very efficient in reproducing most of the statistical properties of the network given by the data sources.Comment: submitted to JASS

Is spatial information in ICT data reliable?

An increasing number of human activities are studied using data produced by individuals' ICT devices. In particular, when ICT data contain spatial information, they represent an invaluable source for analyzing urban dynamics. However, there have been relatively few contributions investigating the robustness of this type of results against fluctuations of data characteristics. Here, we present a stability analysis of higher-level information extracted from mobile phone data passively produced during an entire year by 9 million individuals in Senegal. We focus on two information-retrieval tasks: (a) the identification of land use in the region of Dakar from the temporal rhythms of the communication activity; (b) the identification of home and work locations of anonymized individuals, which enable to construct Origin-Destination (OD) matrices of commuting flows. Our analysis reveal that the uncertainty of results highly depends on the sample size, the scale and the period of the year at which the data were gathered. Nevertheless, the spatial distributions of land use computed for different samples are remarkably robust: on average, we observe more than 75% of shared surface area between the different spatial partitions when considering activity of at least 100,000 users whatever the scale. The OD matrix is less stable and depends on the scale with a share of at least 75% of commuters in common when considering all types of flows constructed from the home-work locations of 100,000 users. For both tasks, better results can be obtained at larger levels of aggregation or by considering more users. These results confirm that ICT data are very useful sources for the spatial analysis of urban systems, but that their reliability should in general be tested more thoroughly.Comment: 11 pages, 9 figures + Appendix, Extended version of the conference paper published in the proceedings of the 2016 Spatial Accuracy Conference, p 9-17, Montpellier, Franc

Molecular Dynamics approach of sol–gel transition: Comparison with experiments

A new aggregation model by a Molecular Dynamics approach at constant temperature was compared with experimental results on a zirconia precursor gelling process. The evolution of the distribution of the experimental scattered intensities (small angle X-ray scattering curves), during gelling, was compared with the results of our Molecular Dynamics method, via the computation of structure factors of the numerical structure for different times:a very good agreement was found. Our numerical model allows one to understand the evolution as a function of time of the size and quantity of matter corresponding to the upper limit of the fractal domain

Using neutral cline decay to estimate contemporary dispersal: a generic tool and its application to a major crop pathogen

Dispersal is a key parameter of adaptation, invasion and persistence. Yet standard population genetics inference methods hardly distinguish it from drift and many species cannot be studied by direct mark-recapture methods. Here, we introduce a method using rates of change in cline shapes for neutral markers to estimate contemporary dispersal. We apply it to the devastating banana pest Mycosphaerella fijiensis, a wind-dispersed fungus for which a secondary contact zone had previously been detected using landscape genetics tools. By tracking the spatio-temporal frequency change of 15 microsatellite markers, we find that σ, the standard deviation of parent–offspring dispersal distances, is 1.2 km/generation1/2. The analysis is further shown robust to a large range of dispersal kernels. We conclude that combining landscape genetics approaches to detect breaks in allelic frequencies with analyses of changes in neutral genetic clines offers a powerful way to obtain ecologically relevant estimates of dispersal in many species

Fluctuations in fluid invasion into disordered media

Interfaces moving in a disordered medium exhibit stochastic velocity fluctuations obeying universal scaling relations related to the presence or absence of conservation laws. For fluid invasion of porous media, we show that the fluctuations of the velocity are governed by a geometry-dependent length scale arising from fluid conservation. This result is compared to the statistics resulting from a non-equilibrium (depinning) transition between a moving interface and a stationary, pinned one.Comment: 4 pages, 4 figure

Sol–gel synthesis and characterization of barium (magnesium) aluminosilicate glass sealants for solid oxide fuel cells

Solid oxide fuel cells (SOFC) correspond to efficient energy conversion systems coupled with low emissions of pollutants. In the aim to fabricate high temperature planar SOFC, glass and glass-ceramic sealants are developed to associate several criteria and properties : high thermal expansion (11.0 to 12.0 ⋅ 10− 6 K− 1), high electrical resistance > 2 kΩ/cm2, good thermochemical compatibility with the other active materials of the fuel cell, and stability under H2 and H2O atmospheres at an operation temperature of 800 °C for a long time. According to these requirements, new BAS (BaO–Al2O3–SiO2) and BMAS (BaO–MgO–Al2O3–SiO2) glass-ceramic sealants have been developed by sol–gel route which is a non-conventional process for such applications. By this soft chemistry process, we anticipate a decrease in the glasses processing temperature due to a better homogeneity between cationic precursors in the mixture and a more important reactivity of materials. Experimental results in terms of thermomechanical properties, thermal expansion coefficient, crystalline phase content, and microstructure were discussed. In particular, the influence of the %BaO on the thermomechanical properties of glass-ceramics was described. Changes in properties of glass-ceramics were closely related to the microstructure. The influence of MgO on glass processing temperatures, on the structure and on the microstructure is evaluated in order to confirm that these glass-ceramics are promising candidates to SOFC applications. So, after performing a systematic investigation to the various systems, the properties of suitable glass were proposed