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

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

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

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

LUNEX5 : A FEL PROJECT TOWARDS THE FIFTH GENERATION IN FRANCE

ISBN978-3-95450-117-5 - http://accelconf.web.cern.ch/AccelConf/FEL2011/papers/tupa09.pdfInternational audienc

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