Automata and men : the shift towards a human ideal in the fiction of Wyndham Lewis

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Can mean shift trackers perform better?

Many tracking algorithms have difficulties dealing with occlusions and background clutters, and consequently don't converge to an appropriate solution. Tracking based on the mean shift algorithm has shown robust performance in many circumstances but still fails e.g. when encountering dramatic intensity or colour changes in a pre-defined neighbourhood. In this paper, we present a robust tracking algorithm that integrates the advantages of mean shift tracking with those of tracking local invariant features. These features are integrated into the mean shift formulation so that tracking is performed based both on mean shift and feature probability distributions, coupled with an expectation maximisation scheme. Experimental results show robust tracking performance on a series of complicated real image sequences. © 2010 IEEE.

Neural Network Evidence for the Coupling of Presaccadic Visual Remapping to Predictive Eye Position Updating.

As we look around a scene, we perceive it as continuous and stable even though each saccadic eye movement changes the visual input to the retinas. How the brain achieves this perceptual stabilization is unknown, but a major hypothesis is that it relies on presaccadic remapping, a process in which neurons shift their visual sensitivity to a new location in the scene just before each saccade. This hypothesis is difficult to test in vivo because complete, selective inactivation of remapping is currently intractable. We tested it in silico with a hierarchical, sheet-based neural network model of the visual and oculomotor system. The model generated saccadic commands to move a video camera abruptly. Visual input from the camera and internal copies of the saccadic movement commands, or corollary discharge, converged at a map-level simulation of the frontal eye field (FEF), a primate brain area known to receive such inputs. FEF output was combined with eye position signals to yield a suitable coordinate frame for guiding arm movements of a robot. Our operational definition of perceptual stability was "useful stability," quantified as continuously accurate pointing to a visual object despite camera saccades. During training, the emergence of useful stability was correlated tightly with the emergence of presaccadic remapping in the FEF. Remapping depended on corollary discharge but its timing was synchronized to the updating of eye position. When coupled to predictive eye position signals, remapping served to stabilize the target representation for continuously accurate pointing. Graded inactivations of pathways in the model replicated, and helped to interpret, previous in vivo experiments. The results support the hypothesis that visual stability requires presaccadic remapping, provide explanations for the function and timing of remapping, and offer testable hypotheses for in vivo studies. We conclude that remapping allows for seamless coordinate frame transformations and quick actions despite visual afferent lags. With visual remapping in place for behavior, it may be exploited for perceptual continuity.

Circuits for Presaccadic Visual Remapping.

Saccadic eye movements rapidly displace the image of the world that is projected onto the retinas. In anticipation of each saccade, many neurons in the visual system shift their receptive fields. This presaccadic change in visual sensitivity, known as remapping, was first documented in the parietal cortex and has been studied in many other brain regions. Remapping requires information about upcoming saccades via corollary discharge. Analyses of neurons in a corollary discharge pathway that targets the frontal eye field (FEF) suggest that remapping may be assembled in the FEF's local microcircuitry. Complementary data from reversible inactivation, neural recording, and modeling studies provide evidence that remapping contributes to transsaccadic continuity of action and perception. Multiple forms of remapping have been reported in the FEF and other brain areas, however, and questions remain about reasons for these differences. In this review of recent progress, we identify three hypotheses that may help to guide further investigations into the structure and function of circuits for remapping.

Automata and men : the shift towards a human ideal in the fiction of Wyndham Lewis

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

New Narratives of International Security Governance: The Shift from Global Interventionism to Global Self-Policing

This article examines the transformation in the narratives of the international governance of security over the last two decades. It suggests that there has been a major shift from governing interventions designed to address the causes of security problems to the regulation of the effects of these problems. In rearticulating the goals of international actors, the means and mechanisms of security governance have also changed, no longer focused on the universal application of Western knowledge and resources but rather on the unique local and organic processes at work in societies that bear the brunt of these problems. This transformation takes the conceptualisation of security governance out of the traditional terminological lexicon of security expertise and universal solutions and instead articulates the problematic of security and the policing of global risks in terms of local management processes, suggesting that decentralised coping strategies and self-policing are more effective and sustainable solutions.

What is social innovation? The paradigm shift and its relationship with Social Work

Innovation is a fundamental part of social work. In recent years there has been a shift in the innovation paradigm, making it easier to accept this relationship. National and supranational policies aimed at promoting innovation appear to be specifically guided by this idea. To be able to affirm this hypothesis, it is necessary to review the perception that social workers have of their duties. It is also useful to examine particular cases that show how such social innovation arises.

Estudio sobre la contribución de la radio al envejecimiento activo. Fase incial: análisis cuantitativo de la presencia de la vejez en los magazines de radio

Este trabajo aborda la posible contribución de la radio al envejecimiento activo. La ética comunicativa actual debe tener presentes los colectivos más vulnerables de la sociedad y uno de ellos es el de la vejez. Se recogen en el artículo los principales datos demográficos sobre población mayor, cuyo crecimiento es tal que se hace necesario un cambio de paradigma a la hora de abordar estos cambios, lo que se conoce como envejecimiento activo. Se plantea que la radio, por sus peculiares características, puede contribuir a promover dicho paradigma. Pero es necesario partir de datos objetivos y el artículo concluye presentando los datos y gráficos de la investigación realizada sobre la presencia de la vejez en los magazines matinales de las cuatro emisoras más importantes del país.

Climate driven regime shift of a temperate marine ecosystem

Ecosystem reconfigurations arising from climate-driven changes in species distributions are expected to have profound ecological, social, and economic implications. Here we reveal a rapid climate-driven regime shift of Australian temperate reef communities, which lost their defining kelp forests and became dominated by persistent seaweed turfs. After decades of ocean warming, extreme marine heat waves forced a 100-kilometer range contraction of extensive kelp forests and saw temperate species replaced by seaweeds, invertebrates, corals, and fishes characteristic of subtropical and tropical waters. This community-wide tropicalization fundamentally altered key ecological processes, suppressing the recovery of kelp forests.

Climate driven regime shift of a temperate marine ecosystem

Ecosystem reconfigurations arising from climate-driven changes in species distributions are expected to have profound ecological, social, and economic implications. Here we reveal a rapid climate-driven regime shift of Australian temperate reef communities, which lost their defining kelp forests and became dominated by persistent seaweed turfs. After decades of ocean warming, extreme marine heat waves forced a 100-kilometer range contraction of extensive kelp forests and saw temperate species replaced by seaweeds, invertebrates, corals, and fishes characteristic of subtropical and tropical waters. This community-wide tropicalization fundamentally altered key ecological processes, suppressing the recovery of kelp forests.

Global impacts of the 1980s regime shift

Despite evidence from a number of Earth systems that abrupt temporal changes known as regime shifts are important, their nature, scale and mechanisms remain poorly documented and understood. Applying principal component analysis, change-point analysis and a sequential t-test analysis of regime shifts to 72 time series, we confirm that the 1980s regime shift represented a major change in the Earth's biophysical systems from the upper atmosphere to the depths of the ocean and from the Arctic to the Antarctic, and occurred at slightly different times around the world. Using historical climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and statistical modelling of historical temperatures, we then demonstrate that this event was triggered by rapid global warming from anthropogenic plus natural forcing, the latter associated with the recovery from the El Chichón volcanic eruption. The shift in temperature that occurred at this time is hypothesized as the main forcing for a cascade of abrupt environmental changes. Within the context of the last century or more, the 1980s event was unique in terms of its global scope and scale; our observed consequences imply that if unavoidable natural events such as major volcanic eruptions interact with anthropogenic warming unforeseen multiplier effects may occur.

Global impacts of the 1980s regime shift

Despite evidence from a number of Earth systems that abrupt temporal changes known as regime shifts are important, their nature, scale and mechanisms remain poorly documented and understood. Applying principal component analysis, change-point analysis and a sequential t-test analysis of regime shifts to 72 time series, we confirm that the 1980s regime shift represented a major change in the Earth's biophysical systems from the upper atmosphere to the depths of the ocean and from the Arctic to the Antarctic, and occurred at slightly different times around the world. Using historical climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and statistical modelling of historical temperatures, we then demonstrate that this event was triggered by rapid global warming from anthropogenic plus natural forcing, the latter associated with the recovery from the El Chichón volcanic eruption. The shift in temperature that occurred at this time is hypothesized as the main forcing for a cascade of abrupt environmental changes. Within the context of the last century or more, the 1980s event was unique in terms of its global scope and scale; our observed consequences imply that if unavoidable natural events such as major volcanic eruptions interact with anthropogenic warming unforeseen multiplier effects may occur.

Righe spettrali: formazione, shift ed allargamento

In questo breve elaborato si vuole spiegare l’importanza dello studio di un corpo celeste mediante l’osservazione del suo spettro ovvero un grafico del flusso emesso in funzione della frequenza o della lunghezza d’onda nel quale sono presenti righe spettrali, formate dall’interazione tra materia e radiazione, a causa dell’assorbimento od emissione di fotoni a seguito di transizioni elettroniche, ma anche vibrazionali e rotazionali per le molecole. In particolare, dall’analisi delle righe spettrali si traggono diverse informazioni sull’oggetto, quali, la composizione e l’abbondanza delle specie chimiche che lo compongono in base al tipo di righe presenti e alla loro intensità, si deduce la temperatura e la pressione dell’oggetto studiato dalla larghezza di queste, ancora, informazioni sul moto relativo e la distanza dall’osservatore misurando lo shift delle righe; infine densità e campi magnetici del mezzo interstellare. Per molti oggetti astronomici, troppo distanti, lo studio dello spettro è l’unico modo per trarre conclusioni sulla loro natura. Per questo, nel primo capitolo si ricava l’equazione del trasporto radiativo, soffermandosi sui processi che regolano l’assorbimento e l’emissione di energia. Il secondo capitolo invece, tratta il caso particolare delle atmosfere stellari, nel quale si ricava, con una serie di approssimazioni fatte sull’equazione del trasporto radiativo, quale parte osserviamo di una stella e dove si formano le righe spettrali. Successivamente ci si è concentrati sui meccanismi che portano alla formazione delle righe spettrali, analizzando sia le transizioni radiative con i coefficienti di Einstein, sia quelle collisionali, e distinguendo tra transizioni permesse o proibite con le regole di selezione. Infine si sono esaminate le informazioni che si possono ricavare dalle righe spettrali, approfondendo sui fenomeni di shift e modifica di queste, descrivendo più nel dettaglio la riga a 21 cm dell’atomo di idrogeno, fondamentale in astrofisica.

Shift Scheduling in Services When Employees Have Limited Availability: An L. P. Approach

This paper compares two linear programming (LP) models for shift scheduling in services where homogeneously-skilled employees are available at limited times. Although both models are based on set covering approaches, one explicitly matches employees to shifts, while the other imposes this matching implicitly. Each model is used in three forms—one with complete, another with very limited meal break placement flexibility, and a third without meal breaks—to provide initial schedules to a completion/improvement heuristic. The term completion/improvement heuristic is used to describe a construction/ improvement heuristic operating on a starting schedule. On 80 test problems varying widely in scheduling flexibility, employee staffing requirements, and employee availability characteristics, all six LP-based procedures generated lower cost schedules than a comparison from-scratch construction/improvement heuristic. This heuristic, which perpetually maintains an explicit matching of employees to shifts, consists of three phases which add, drop, and modify shifts. In terms of schedule cost, schedule generation time, and model size, the procedures based on the implicit model performed better, as a group, than those based on the explicit model. The LP model with complete break placement flexibility and implicitly matching employees to shifts generated schedules costing 6.7% less than those developed by the from-scratch heuristic.