Saint Mary's University

About: Saint Mary's University is a education organization based out in Halifax, Nova Scotia, Canada. It is known for research contribution in the topics: Population & Stars. The organization has 1931 authors who have published 4993 publications receiving 143226 citations.

Mass accretion rates in self-regulated disks of t tauri stars

Abstract: We have studied numerically the evolution of protostellar disks around intermediate- and upper-mass T Tauri stars (0.25 M☉ < M* < 3.0 M☉) that have formed self-consistently from the collapse of molecular cloud cores. In the T Tauri phase, disks settle into a self-regulated state, with low-amplitude nonaxisymmetric density perturbations persisting for at least several million years. Our main finding is that the global effect of gravitational torques due to these perturbations is to produce disk accretion rates that are of the correct magnitude to explain observed accretion onto T Tauri stars. Our models yield a correlation between accretion rate and stellar mass M* that has a best fit ∝ M*1.7, in good agreement with recent observations. We also predict a near-linear correlation between the disk accretion rate and the disk mass.

A time-use activity-pattern recognition model for activity-based travel demand modeling

Abstract: This study develops a new comprehensive pattern recognition modeling framework that leverages activity data to derive clusters of homogeneous daily activity patterns, for use in activity-based travel demand modeling. The pattern recognition model is applied to time use data from the large Halifax STAR household travel diary survey. Several machine learning techniques not previously employed in travel behavior analysis are used within the pattern recognition modeling framework. Pattern complexity of activity sequences in the dataset was recognized using the FCM algorithm, and resulted in identification of twelve unique clusters of homogeneous daily activity patterns. We then analysed inter-dependencies in each identified cluster and characterized the cluster memberships through their socio-demographic attributes using the CART classifier. Based on the socio-demographic characteristics of individuals we were able to correctly identify which cluster individuals belonged to, and also predict various information related to their activities, such as start time, duration, travel distance, and travel mode, for use in activity-based travel demand modeling. To execute the pattern recognition model, the 24-h activity patterns are split into 288 three dimensional 5 min intervals. Each interval includes information on activity types, duration, start time, location, and travel mode if applicable. Results from aggregated statistical evaluation and Kolmogorov–Smirnov tests indicate that there is heterogeneous diversity among identified clusters in terms of temporal distribution, and substantial differences in a variety of socio-demographic variables. The homogeneous clusters identified in this study may be used to more accurately predict the scheduling behavior of specific population groups in activity-based modeling, and hence to improve prediction of the times and locations of their travel demands. Finally, the results of this study are expected to be implemented within the activity-based travel demand model, Scheduler for Activities, Locations, and Travel (SALT).

The quiet Americans: Formative context, the Academy of Management leadership, and the management textbook, 1936-1960

Abstract: Building on recent interest in formative contexts and management in the USA, this article explores the contribution of the Academy of Management to the development of modern management theory. Drawing on archival research and content analysis of selected management textbooks, we examine the development of the Academy of Management from 1936 to 1960 and the role of its presidents in the dissemination of management theory. We conclude that there is some evidence that the Academy allied itself with dominant Cold War themes that translated into a philosophy of management, which influenced the character of the organization for decades.Though it is unlikely that the Academy per se had much influence on the development of management theory, its early leadership may have had a disproportionate influence through the medium of the business textbook.

Competing dwarf males: sexual selection in an orb-weaving spider

Abstract: Hypotheses for the adaptive significance of extreme female-biased sexual size dimorphism (SSD) generally assume that in dimorphic species males rarely interfere with each other. Here we provide the first multivariate examination of sexual selection because of male-male competition over access to females in a species with 'dwarf' males, the orb-weaving spider Argiope aurantia. Male A. aurantia typically try to mate opportunistically during the female's final moult when she is defenceless. We show that, contrary to previous hypotheses, the local operational sex ratio (males per female on the web) is male-biased most of the season. Both interference and scramble competition occur during opportunistic mating, the former leading to significant selection for large male body size. Male condition and leg length had no effect on mating success independent of size. We discuss these findings in the context of the evolution of extreme female-biased SSD in this clade.