Concordia University

About: Concordia University is a education organization based out in Montreal, Quebec, Canada. It is known for research contribution in the topics: Context (language use) & Control theory. The organization has 13565 authors who have published 31084 publications receiving 783525 citations. The organization is also known as: Sir George Williams University & Loyola College, Montreal.

A Recurrent Neural-Network-Based Sensor and Actuator Fault Detection and Isolation for Nonlinear Systems With Application to the Satellite's Attitude Control Subsystem

Abstract: This paper presents a robust fault detection and isolation (FDI) scheme for a general class of nonlinear systems using a neural-network-based observer strategy. Both actuator and sensor faults are considered. The nonlinear system considered is subject to both state and sensor uncertainties and disturbances. Two recurrent neural networks are employed to identify general unknown actuator and sensor faults, respectively. The neural network weights are updated according to a modified backpropagation scheme. Unlike many previous methods developed in the literature, our proposed FDI scheme does not rely on availability of full state measurements. The stability of the overall FDI scheme in presence of unknown sensor and actuator faults as well as plant and sensor noise and uncertainties is shown by using the Lyapunov's direct method. The stability analysis developed requires no restrictive assumptions on the system and/or the FDI algorithm. Magnetorquer-type actuators and magnetometer-type sensors that are commonly employed in the attitude control subsystem (ACS) of low-Earth orbit (LEO) satellites for attitude determination and control are considered in our case studies. The effectiveness and capabilities of our proposed fault diagnosis strategy are demonstrated and validated through extensive simulation studies.

Entrepreneurship education and training in Canada: a critical assessment

Abstract: Management training is constantly seen as an effective way of providing small‐medium size enterprises with the management expertise they require in order to develop and grow. The SME sector in Canada plays a prominent and essential role in the growth and expansion of the domestic economy through its contribution to the domestic output and job creation. However, this sector suffers from a considerably high failure rate that is largely attributed to the lack of management skills and planning, which can potentially be improved by providing training and education in different business areas. This paper assesses the entrepreneurship education and training efforts in Canada and identifies the common challenges that face this process.

The ‘romance of teams’: Toward an understanding of its psychological underpinnings and implications

Abstract: Although advocates of teamwork suggest that teams enhance performance, empirical evidence does not consistently, or robustly, support these claims. Still, a belief in the effectiveness of teams—among managers, employees, and the general lay population—seems very strong. What accounts for this ‘romance of teams’? In this paper, we offer a psychological answer to this question. We review evidence regarding the actual effectiveness of teams, in order to show that teams are not as effective as many believe them to be, and we argue that the romance of teams stems from the psychological benefits of group-based activity. Specifically, we propose that team members experience both social-emotional, and competence-related, benefits, and we review an eclectic mix of research in support of this claim. We argue that these psychological benefits of teams lead people to assume that teams are ‘high performance’, thus, causing the romance of teams. Finally, we discuss potential implications of the romance for organizations, researchers, and employees.

Clonidine blocks stress-induced reinstatement of heroin seeking in rats: an effect independent of locus coeruleus noradrenergic neurons.

Abstract: Using a reinstatement procedure, it has been shown that intermittent footshock stress reliably reinstates extinguished drug-taking behaviour in rats. Here we studied the role of noradrenaline (NE), one of the main brain neurotransmitters involved in responses to stress, in reinstatement of heroin seeking. We first determined the effect of clonidine, an alpha-2 adrenergic receptor agonist that decreases NE cell firing and release, on stress-induced reinstatement of heroin seeking. Rats were trained to self-administer heroin (0.1 mg/kg per infusion, IV, three 3-h sessions per day) for 9-10 days. Extinction sessions were given for up to 11 days during which saline was substituted for the drug. Tests for reinstatement were then conducted after exposure to intermittent footshock (5, 15 and 30 min, 0.5 mA). During testing, clonidine was injected systemically (10-40 microgram/kg, i.p.) or directly into the lateral or fourth ventricles (1-3 microram). Clonidine (1-2 microgram per site) or its charged analogue, 2-[2, 6-diethylphenylamino]-2-imidazole (ST-91, 0.5-1 microgram per site), was also injected bilaterally into the locus coeruleus (LC), the main noradrenergic cell group in the brain. Clonidine blocked stress-induced reinstatement of drug seeking when injected systemically or into the cerebral ventricles. In contrast, neither clonidine nor ST-91 consistently altered stress-induced reinstatement when injected into the locus coeruleus. We therefore studied the effect of lesions of the lateral tegmental NE neurons on stress-induced reinstatement. 6-Hydroxydopamine (6-OHDA) lesions performed after training for heroin self-administration had no effect on extinction of heroin-taking behaviour, but significantly attenuated reinstatement induced by intermittent footshock. These data suggest that: (i) clonidine prevents stress-induced relapse to heroin seeking by its action on neurons other than those of the locus coeruleus; and (ii) activation of the lateral tegmental NE neurons contributes to stress-induced reinstatement of heroin seeking.