From a snowflake to the snow cover: processes that shape polar and taiga snowpacks

Thesis (Ph.D.) University of Alaska Fairbanks, 2016Snowpacks found in boreal and polar regions are the most widespread types of snow in the world, covering up to 14% of the globe. In both regions, snow accumulates over a long period (6-7 months), transforming the landscape by the presence of a thin snowpack (≤70 cm), affecting the local climate, ecology, and hydrology. In the case of polar snow, wind plays a crucial role in redistributing snow, and shaping the snow surface. But in the case of the taiga snow found in the forests of the boreal regions, micro-topography and vegetation are stronger drivers of snow distribution than wind. In this dissertation, I explore the mechanisms responsible for shaping the snow surfaces in windy and in calm conditions. Collecting data at the plot scale with a terrestrial lidar, I sought explanations of the features geometry visible on the snow surfaces in grain scale physical processes. Because snow is close to its fusion temperature in this environment, its behavior at the grain scale can greatly influence its bulk properties. So finding linkages between processes occurring at the grain scale and the observable features at the plot scale may be key to furthering our understanding of snow distribution. In the first study, I found that the morphology and the occurrence of the seven known types of snow bedforms are dependent on the ability for wind to erode the surface. Erodibility is directly linked to the sintering of wind-slab grains. For this reason, every snow dune eventually turns into sastrugi. In the second study, I studied the effects of underlying topography on the accumulation of snow in calm conditions. I found that processes such as bouncing, cohesion or interlocking of snowflakes can either enhance or inhibit the smoothing of initial bumps. In the third study, I found that plant canopies affect the deposition of snow in the boreal forest. I could differentiate up to five types of canopies for their effects on snow accumulation. Despite the complexity of the canopy structures we observed, over three years, similar accumulation patterns and reactions of canopies to snow loading were seen. I was surprised to find the presence of subnivean cavities associated to plants with a size equivalent to the average snow depth.Chapter 1 : Introduction -- Chapter 2 : Snow bedforms: a review, new data, and a formation model -- Chapter 3 : How falling and settling of snowflakes smooth a landscape -- Chapter 4 : Snow accumulation in a boreal forest of Interior Alaska recorded with a terrestrial lidar -- Chapter 5 : Conclusions

Juxtaposition as a form feature; syntax captured and explained rather than assumed and modelled

International audienceIn this article, we report on a study conducted to further the design a formal grammar model (AZee), confronting it to the traditional notion of syntax along the way. The model was initiated to work as an unambiguous linguistic input for signing avatars, accounting for all simultaneous articulators while doing away with the generally assumed and separate levels of lexicon, syntax, etc. Specifically, the work presented here focused on juxtaposition in signed streams (a fundamental feature of syntax), which we propose to consider as a mere form feature, and use it as the starting point of data-driven searches for grammatical rules. The result is a tremendous progress in coverage of LSF grammar, and fairly strong evidence that our initial goal is attainable. We give concrete examples of rules, and a clear illustration of the recursive mechanics of the grammar producing LSF forms, and conclude with theoretical remarks on the AZee paradigm in terms of syntax, word/sign order and the like

What constraints for representing multilinearity in Sign language?

International audienceIn this paper, we present our current investigations on one of the main challenges in Sign Language modelling: multilinearity. We explain the way in which we extract grammatical rules from Sign Language corpus, and how we represent them with constraints. Two kinds are needed: time synchronisation and geometric constraints

Elicitation protocol and material for a corpus of long prepared monologues in Sign Language

International audienceIn this paper, we address collection of prepared Sign Language discourse, as opposed to spontaneous signing. Specifically, we aim at collecting long discourse, which creates problems explained in the paper. Being oral and visual languages, they cannot easily be produced while reading notes without distorting the data, and eliciting long discourse without influencing the production order is not trivial. For the moment, corpora contain either short productions, data distortion or disfluencies. We propose a protocol and two tasks with their elicitation material to allow cleaner long-discourse data, and evaluate the result of a recent test with LSF informants

A rule triggering system for automatic text-to-sign translation

International audienceThe topic of this paper is machine translation (MT) from French text to French Sign Language (LSF). After arguing in favour of a rule-based method, it presents the architecture of an original MT system, built on two distinct efforts: formalising LSF production rules and triggering them with text processing. The former is made without any concern for text or translation and involves corpus analysis to link LSF form features to linguistic functions. It produces a set of production rules which may constitute a full LSF production grammar. The latter is an information extraction task from text, broken down in as many subtasks as there are rules in the grammar. After discussing this architecture, comparing it to the traditional methods and presenting the methodology for each task, the paper present the set of production rules found to govern event precedence and duration in LSF, and gives a progress report on the implementation of the rule triggering system. With this proposal, it is also hoped to show how MT can benefit today from Sign Language processing

Non-manual features: the right to indifference

International audienceThis paper discusses the way Sign Language can be described with a global account of the visual channel, not separating manual articulators in any way. In a first section section it shows that non-manuals are often either ignored in favour of manual focus, or included but given roles that are mostly different from the mainly hand-assigned lexical role. A second section describes the AZee model as a tool to describe Sign Language productions without assuming any separation, neither between articulators nor between grammatical roles. We conclude by giving a full AZee description for one of the several examples populating the paper

Modeling French Sign Language: a proposal for a semantically compositional system

International audienceThe recognition of French Sign Language (LSF) as a natural language in 2005 created an important need for the development of tools to make information accessible to the deaf public. With this prospect, the goal of this article is to propose a linguistic approach aimed at modeling the French sign language. We first present the models proposed in computer science to formalize the sign language (SL). We also show the difficulty of applying the grammars originally designed for spoken languages to model SL. In a second step, we propose an approach allowing to take into account the linguistic properties of the SL while respecting the constraints of a modelisation process. By studying the links between semantic functions and their observed forms in Corpus, we have identified several production rules that govern the functioning of the LSF. We finally present the rule functioning as a system capable of modeling an entire utterance in French sign language

La loi de 1912 sur la circulation des « nomades » (Tsiganes) en France

À partir de la fin du XIXe siècle, un ensemble de facteurs d’ordre socio-économique, politique, idéologique concourent à assimiler les Tsiganes à des étrangers et des « asociaux indésirables ». La présente contribution tente d’examiner comment, sous la Présidence de la République d’Armand Fallières, la mobilité tsigane a fait l’objet d’un traitement administratif hostile. L’attitude des pouvoirs publics à l’égard des « nomades » français et étrangers s’est déployée en effet autour d’un dispositif législatif et policier que l’on peut résumer ainsi : surveillance, identification, contrôle. Après le recensement général de 1895 de tous les « nomades, bohémiens et vagabonds », suivi du fichage des « nomades » par les Brigades régionales de police mobile créées en 1907 à l’initiative de Clemenceau, un projet de loi du gouvernement daté du 25 novembre 1908 voit le jour, « relatif à la réglementation de la circulation des nomades ». Le projet, conjugué avec les mesures émises plus tard à la Chambre et au Sénat par les commissions du vagabondage et de la mendicité, donnera lieu à la loi du 16 juillet 1912 sur le port du carnet anthropométrique d’identité. Cette loi discriminatoire et disciplinaire, qui allait durer près de soixante ans, sans susciter aucune critique au sein du discours juridique dominant, constitue l’étape majeure dans le processus de contrôle et d’identification utilisé par la République envers les Tsiganes.The Law of 1912 on the Movement of the «Nomads» (Gypsies) in France. From the end of the nineteenth century onwards, a series of socio-economic, political and ideological factors contribute to consider Gypsies as foreigners and “asocial undesirable people”. The present contribution aims at explaining how, under Armand Fallières’s Presidency, gypsy mobility became the subject of a hostile administrative process. The attitude of the authorities regarding the French and foreign “nomads” was therefore developed through a legal and police device that can be summarized as follows: surveillance, identification, control. After the general census of all the “nomads, Bohemians and vagrants” in 1895, there followed a filing of the “nomads” by the regional Brigades of the mobile police force created in 1907 by Clemenceau, and then a government bill “relating to the regulation of the nomads’movement” emerged on November 25th 1908. This project, combined with the measures later emitted in the Chamber of Deputies and the Senate by the Commissions of vagrancy and begging, will lead to the Law of July 16th on the bearing of the anthropometric identification record. This discriminatory and disciplinary law, which was to last for nearly sixty years, without causing any criticism within the prevailing legal discourse, constitutes the major step in the process of control and identification used by the French Republic towards the Gypsies.La ley de 1912 sobre la circulación de los «nómadas» (gitanos) en Francia. Desde finales del siglo XIX, un conjunto de factores de orden socioeconómico, político e ideológico contribuyeron a asimilar a los gitanos con extranjeros y “asociables indeseables”. Esta contribución trata de examinar cómo, bajo la Presidencia de Armand Fallières, la movilidad gitana fue objeto de un trato administrativo hostil. La actitud de los poderes públicos respecto a los “nómadas” franceses y extranjeros se desplegó en torno a un dispositivo legislativo y policial que puede resumirse de la siguiente manera: vigilancia, identificación y control. Tras el censo general de todos los “nómadas, bohemios y vagabundos” de 1895 y el fichaje de los “nómadas” por las Brigadas regionales de policía creadas en 1907 a iniciativa de Clemenceau, el 25 de noviembre de 1908 vio la luz un proyecto de ley del gobierno relativo a la reglamentación de la circulación de los nómadas. Este proyecto y las medidas que tomaron posteriormente las comisiones de vagabundeo y mendicidad de la Cámara y del Senado darán lugar a la ley del 16 de julio de 1912 relativa al porte del carné de identidad antropométrico. Esta ley discriminatoria y disciplinaria estará en vigor durante cerca de sesenta años sin suscitar crítica alguna en el seno del discurso jurídico dominante. Se trata de la principal etapa en el proceso de control e identificación de gitanos puesto en práctica por la República