Showing papers by "Ryerson University published in 2009"

Multilevel Converters: An Enabling Technology for High-Power Applications

Abstract: Multilevel converters are considered today as the state-of-the-art power-conversion systems for high-power and power-quality demanding applications. This paper presents a tutorial on this technology, covering the operating principle and the different power circuit topologies, modulation methods, technical issues and industry applications. Special attention is given to established technology already found in industry with more in-depth and self-contained information, while recent advances and state-of-the-art contributions are addressed with useful references. This paper serves as an introduction to the subject for the not-familiarized reader, as well as an update or reference for academics and practicing engineers working in the field of industrial and power electronics.

Multidimensional Modulation Technique for Cascaded Multilevel Converters

Abstract: Multilevel cascaded H-bridge converters have found industrial application in the medium-voltage high-power range. In this paper, a generalized modulation technique for this type of converter based on a multidimensional control region is presented. Using the multidimensional control region, it is shown that all previous modulation techniques are particularized versions of the proposed method. Several possible solutions to develop a specific implementation of the modulation method are addressed in order to show the potential possibilities and the flexibility of the proposed technique. In addition, a feedforward version of this technique is also introduced to determine the switching sequence and the switching times, avoiding low harmonic distortion with unbalanced dc voltages. Experimental results are shown in order to validate the proposed concepts.

Developments in National Policies for Food and Nutrition Security in Brazil

Abstract: Brazil is on track to achieve many of the Millennium Development Goals, and this is widely credited to bold and innovative government policies backed by new forms of popular participation in social policy. This article examines evaluation evidence on two of the most important recent initiatives in Brazil's policies for food and nutrition security (conditional cash transfers through Bolsa Familia and support for family agriculture through the Programa de Aquisicao de Alimentos). It also considers advances in older policies (such as the School Meals programme) and the work of the National Council for Food and Nutrition Security, which has culminated in national legislation establishing food and nutrition security as a right.

Practical Application of an Indigenous Research Framework and Two Qualitative Indigenous Research Methods: Sharing Circles and Anishnaabe Symbol-Based Reflection

Abstract: Increasingly, research involving Indigenous people is being undertaken by Indigenous researchers, who bring forward world views that shape the approach of the research, the theoretical and conceptual frameworks, as well as the epistemology, methodology, and ethics Many times such research bridges Western practices and Indigenous knowledges; however, bringing together these two world views can also present challenges This paper explores the challenges and lessons learned in the practical application of an Indigenous research framework and qualitative inquiry Two qualitative Indigenous research methods – sharing circles and Anishnaabe Symbol-Based Reflection – will be discussed

Spread of a Novel Influenza A (H1N1) Virus via Global Airline Transportation

Abstract: International air travelers departing from Mexico in March and April 2009 were unknowingly transporting a novel influenza A (H1N1) virus around the world. The purpose of this analysis was to show h...

The Impact of Corporate Social Responsibility on the Cost of Bank Loans

Abstract: This study examines the link between corporate social responsibility and bank debt. Our focus on banks exploits their specialized role as quasi-insider delegated monitors. We find that firms with the worst social responsibility scores pay up to 20 basis points more than the most responsible firms. However, we find that for the majority of firms, the impact of CSR is not economically important. The modest premiums associated with CSR suggest that banks do not regard corporate social responsibility as significantly value enhancing or risk reducing.

Institutionalizing Precarious Immigration Status in Canada

Abstract: This paper analyzes the institutionalized production of precarious migration status in Canada. Building on recent work on the legal production of illegality and non-dichotomous approaches to migratory status, we review Canadian immigration and refugee policy, and analyze pathways to loss of migratory status and the implications of less than full status for access to social services. In Canada, policies provide various avenues of authorized entry, but some entrants lose work and/or residence authorization and end up with variable forms of less-than-full immigration status. We argue that binary conceptions of migration status (legal/illegal) do not reflect this context, and advocate the use of ‘precarious status’ to capture variable forms of irregular status and illegality, including documented illegality. We find that elements of Canadian policy routinely generate pathways to multiple forms of precarious status, which is accompanied by precarious access to public services. Our analysis of the production of...

Entrepreneurship and economic growth: Evidence from emerging and developed countries

Abstract: This paper presents an extension to the economic growth model developed by Wong, Ho, and Autio (2005), to reflect differences in the economic effects of opportunity and necessity-based entrepreneurship in both emerging and developed countries. Data from 44 countries for the years 2004 and 2005, as collected by Global Entrepreneurship Monitor (GEM) research and Global Competitiveness Report (GCR) research, are used to identify predictors of GDP growth for emerging and developed nations. The GEM data are used to determine the effect of different types of entrepreneurship on GDP growth. The GCR data operationalize additional control variables suggested by three economic growth theories: new economic geography, endogenous growth theory and national systems of innovation. This contribution to the literature suggests that, in developed countries, a significant portion of economic growth rates can be attributed to high-expectation entrepreneurs exploiting national investments in knowledge creation and regulatory...

Outbreak of Multidrug-Resistant Pseudomonas aeruginosa Colonization and Infection Secondary to Imperfect Intensive Care Unit Room Design

Abstract: Background. Pseudomonas aeruginosa has been increasingly recognized for its ability to cause significant hospital‐associated outbreaks, particularly since the emergence of multidrug‐resistant strains. Biofilm formation allows the pathogen to persist in environmental reservoirs. Thus, multiple hospital room design elements, including sink placement and design, can impact nosocomial transmission of P. aeruginosa and other pathogens. Methods. From December 2004 through March 2006, 36 patients exposed to the intensive care unit or transplant units of a tertiary care hospital were infected with a multidrug‐resistant strain of P. aeruginosa. All phenotypically similar isolates were examined for genetic relatedness by means of pulsed‐field gel electrophoresis. Clinical characteristics of the affected patients were collected, and a detailed epidemiological and environmental investigation of potential sources was carried out. Results. Seventeen of the infected patients died within 3 months; for 12 (71%) of these p...

The Effect of a Market Orientation, Entrepreneurial Orientation, and Technological Capability on Innovativeness: A Study of Young Biotechnology Ventures in the United States and in Scandinavia

Abstract: Previous research suggests that in order to excel in innovativeness, a firm should simultaneously be market oriented, proactive, and willing to take risks, as well as have access to superior techno...

On vortex shedding from an airfoil in low-Reynolds-number flows

Abstract: Development of coherent structures in the separated shear layer and wake of an airfoil in low-Reynolds-number flows was studied experimentally for a range of airfoil chord Reynolds numbers, 55 × 10 3 ≤ Re c ≤ 210 × 10 3 , and three angles of attack, α = 0°, 5° and 10°. To illustrate the effect of separated shear layer development on the characteristics of coherent structures, experiments were conducted for two flow regimes common to airfoil operation at low Reynolds numbers: (i) boundary layer separation without reattachment and (ii) separation bubble formation. The results demonstrate that roll-up vortices form in the separated shear layer due to the amplification of natural disturbances, and these structures play a key role in flow transition to turbulence. The final stage of transition in the separated shear layer, associated with the growth of a sub-harmonic component of fundamental disturbances, is linked to the merging of the roll-up vortices. Turbulent wake vortex shedding is shown to occur for both flow regimes investigated. Each of the two flow regimes produces distinctly different characteristics of the roll-up and wake vortices. The study focuses on frequency scaling of the investigated coherent structures and the effect of flow regime on the frequency scaling. Analysis of the results and available data from previous experiments shows that the fundamental frequency of the shear layer vortices exhibits a power law dependency on the Reynolds number for both flow regimes. In contrast, the wake vortex shedding frequency is shown to vary linearly with the Reynolds number. An alternative frequency scaling is proposed, which results in a good collapse of experimental data across the investigated range of Reynolds numbers.

Radio Resource Allocation Algorithms for the Downlink of Multiuser OFDM Communication Systems

Abstract: This article surveys different resource allocation algorithms developed for the downlink of multiuser OFDM wireless communication systems. Dynamic resource allocation algorithms are categorized into two major classes: margin adaptive (MA) and rate adaptive (RA). The objective of the first class is to minimize the total transmit power with the constraint on users' data rates whereas in the second class, the objective is to maximize the total throughput with the constraints on the total transmit power as well as users' data rates. The overall performance of the algorithms are evaluated in terms of spectral efficiency and fairness. Considering the trade-off between these two features of the system, some algorithms attempt to reach the highest possible spectral efficiency while maintaining acceptable fairness in the system. Furthermore, a large number of RA algorithms considers rate proportionality among the users and hence, are categorized as RA with constrained-fairness. Following the problem formulation in each category, the discussed algorithms are described along with their simplifying assumptions that attempt to keep the performance close to optimum but significantly reduce the complexity of the problem. It is noted that no matter which optimization method is used, in both classes, the overall performance is improved with the increase in the number of users, due to multiuser diversity. Some on-going research areas are briefly discussed throughout the article.

Cultural Competency as New Racism: An Ontology of Forgetting

Abstract: This article argues that cultural competency promotes an obsolete view of culture and is a form of new racism. Cultural competency resembles new racism both by otherizing non-whites and by deploying modernist and absolutist views of culture while not using racialist language. Drawing on child welfare, cultural competence is shown to repeat what Lowe (1993) calls an ontology of forgetting Canada's history of colonialism and racism. A recommendation is made for jettisoning cultural competency and emphasizing instead a self-reflexive grappling with racism and colonialism.

Virtual team collaboration: building shared meaning, resolving breakdowns and creating translucence

Abstract: Managing international teams with geographically distributed participants is a complex task. The risk of communication breakdowns increases due to cultural and organizational differences grounded in the geographical distribution of the participants. Such breakdowns indicate general misunderstandings and a lack of shared meaning between participants. In this paper, we address the complexity of building shared meaning. We examine the communication breakdowns that occurred in two globally distributed virtual teams by providing an analytical distinction of the organizational context as the foundation for building shared meaning at three levels. Also we investigate communication breakdowns that can be attributed to differences in lifeworld structures, organizational structures, and work process structures within a virtual team. We find that all communication breakdowns are manifested and experienced by the participants at the work process level; however, resolving breakdowns may require critical reflection at other levels. Where previous research argues that face-to-face interaction is an important variable for virtual team performance, our empirical observations reveal that communication breakdowns related to a lack of shared meaning at the lifeworld level often becomes more salient when the participants are co-located than when geographically distributed. Last, we argue that creating translucence in communication structures is essential for building shared meanings at all three levels.

A Novel Three-Phase Three-Leg AC/AC Converter Using Nine IGBTs

Abstract: This paper proposes a novel three-phase nine-switch ac/ac converter topology. This converter features sinusoidal inputs and outputs, unity input power factor, and more importantly, low manufacturing cost due to its reduced number of active switches. The operating principle of the converter is elaborated; its modulation schemes are discussed. Simulated semiconductor loss analysis and comparison with the back-to-back two-level voltage source converter are presented. Finally, experimental results from a 5-kVA prototype system are provided to verify the validity of the proposed topology.

A Novel Control Scheme for Current-Source-Converter-Based PMSG Wind Energy Conversion Systems

Abstract: A novel control scheme for permanent-magnet synchronous generator is proposed in this paper, where a current-source converter is employed as the bridge between the generator and the grid for high-power wind energy conversion systems. In these medium voltage (2.3-13.8 kV) level applications, current-source converters not only have inherent advantages, but also present some challenges for controller design due to the DC link choke and filter capacitors. The control strategy is developed to achieve better performances with improved dynamic response. By maintaining the grid-side converter modulation index at the highest possible level, the proposed control scheme reduces the DC link current to a minimum value to reduce converter conduction loss. The systempsilas dynamic performance is further improved by adopting generator-side power feedforward. Simulation and experimental results are provided to verify the proposed control scheme.

Enhanced Modeling and Solution of Layered Queueing Networks

Abstract: Layered queues are a canonical form of extended queueing network for systems with nested multiple resource possession, in which successive depths of nesting define the layers. The model has been applied to most modern distributed systems, which use different kinds of client-server and master-slave relationships, and scales up well. The layered queueing network (LQN) model is described here in a unified fashion, including its many more extensions to match the semantics of sophisticated practical distributed and parallel systems. These include efficient representation of replicated services, parallel and quorum execution, and dependability analysis under failure and reconfiguration. The full LQN model is defined here and its solver is described. A substantial case study to an air traffic control system shows errors (compared to simulation) of a few percent. The LQN model is compared to other models and solutions, and is shown to cover all their features.

Adaptive Control of an Electrically Driven Nonholonomic Mobile Robot via Backstepping and Fuzzy Approach

Abstract: This paper investigates the tracking control of an electrically driven nonholonomic mobile robot with model uncertainties in the robot kinematics, the robot dynamics, and the wheel actuator dynamics. A robust adaptive controller is proposed with the utilization of adaptive control, backstepping and fuzzy logic techniques. The proposed control scheme employs the adaptive control approach to design an auxiliary wheel velocity controller to make the tracking error as small as possible in consideration of uncertainties in the kinematics of the robot, and makes use of the fuzzy logic systems to learn the behaviors of the unknown dynamics of the robot and the wheel actuators. The approximation errors and external disturbances can be efficiently counteracted by employing smooth robust compensators. A major advantage of the proposed method is that previous knowledge of the robot kinematics and the dynamics of the robot and wheel actuators is no longer necessary. This is because the controller learns both the robot kinematics and the robot and wheel actuator dynamics online. Most importantly, all signals in the closed-loop system can be guaranteed to be uniformly ultimately bounded. For the dynamic uncertainties of robot and actuator, the assumption of ldquolinearity in the unknown parametersrdquo and tedious analysis of determining the ldquoregression matricesrdquo in the standard adaptive robust controllers are no longer necessary. The performance of the proposed approach is demonstrated through a simulation example.

VPR 5.0: FPGA cad and architecture exploration tools with single-driver routing, heterogeneity and process scaling

Abstract: The VPR toolset [6, 7] has been widely used to perform FPGA architecture and CAD research, but has not evolved over the past decade to include many architectural features now present in modern FPGAs. This paper describes a new version of the toolset that includes four significant features: first, it now supports a broad range of single-driver routing architectures [29, 4, 16]. Single-driver routing has significantly different architectural and electrical properties from the multi-driver approach previously modelled, and is now employed in the majority of FPGAs sold. Second, the new release can now model a heterogeneous selection of hard logic blocks, which could include the hard memory and multipliers that are now ubiquitous in FPGAs. Third, we provide optimized electrical models of a wide range of architectures in different process technologies, including a range of area-delay tradeoffs for each single architecture. Prior releases of VPR did not publish even one architecture file with accurate resistance and capacitance parameters. Finally, to maintain robustness and to support future development the release includes a set of regression tests to check functionality and quality of result of the output of the tools.To illustrate the use of the new features, we present a new look at the FPGA area vs. logic block LUT size question that shows that small LUT sizes, with the use of carefully optimized electrical design and single-driver architectures, have better area (relative to 4-LUTs) than previously thought. Another experiment shows that several of the previous architectural results are invariant in moving from multi-driver to single-driver routing architecture and across a range of process technologies.

Community collaboration and climate change research in the Canadian Arctic

Abstract: Research on climate change impacts, vulnerability and adaptation, particularly projects aiming to contribute to practical adaptation initiatives, requires active involvement and collaboration with community members and local, regional and national organizations that use this research for policy-making. Arctic communities are already experiencing and adapting to environmental and socio-cultural changes, and researchers have a practical and ethical responsibility to engage with communities that are the focus of the research. This paper draws on the experiences of researchers working with communities across the Canadian Arctic, together with the expertise of Inuit organizations, Northern research institutes and community partners, to outline key considerations for effectively engaging Arctic communities in collaborative research. These considerations include: initiating early and ongoing communication with communities, and regional and national contacts; involving communities in research design and development; facilitating opportunities for local employment; and disseminating research findings. Examples of each consideration are drawn from climate change research conducted with communities in the Canadian Arctic.

Exploration of the Relationship Between Household Food Insecurity and Diabetes in Canada

Abstract: Objective: To determine the household food insecurity (HFI) prevalence in Canadians with diabetes and its relationship with diabetes management, self-care practices and health status. Research Design and Methods: We analyzed data from Canadians with diabetes aged 12 and older (N=6,237) from cycle 3.1 of the Canadian Community Health Survey, a population-based cross-sectional survey conducted in 2005. The HFI prevalence in Canadians with diabetes was compared to those without diabetes. The relationships between HFI and management services, self-care practices, and health status were examined for Ontarians with diabetes (N=2,523). Results: Household food insecurity was more prevalent amongst people with diabetes [9.3% (8.2-10.4)] than amongst those without [6.8% (6.5-7.0)] and was not associated with diabetes management services, but was associated with physical inactivity [OR,1.54 (1.10-2.17)], lower fruit and vegetable consumption [OR,0.52 (0.33-0.81)], current smoking [OR,1.71 (1.09–2.69)], unmet healthcare needs [OR,2.71 (1.74–4.23)], having been an overnight patient [OR,2.08 (1.43–3.04)], having a mood disorder [OR,2.18 (1.54–3.08)], suffered effects of a stroke [OR,2.39 (1.32–4.32)], lower satisfaction with life [OR,0.28 (0.18–0.43)], self-rated general [OR,0.37 (0.21–0.66)], and mental [OR,0.17 (0.10–0.29)] health, and higher self-perceived stress [OR,2.04 (1.30–3.20)]. The odds of HFI were higher for someone diagnosed with diabetes younger than forty years of age [OR, 3.08 (1.96-4.84)]. Conclusions: Household food insecurity prevalence is higher amongst Canadians with diabetes, and is associated with increased likelihood of unhealthy behaviours, psychological distress, and poorer physical health.

Top management support of enterprise systems implementations

Abstract: Despite the general consensus regarding the critical role of top management in the information systems (ISs) implementation process, the literature has not yet provided a clear and compelling understanding of the top management support (TMS) concept. Applying metastructuring (Orlikowski et al., 1995) as a guiding framework for understanding TMS behaviors, this paper attempts to address the gap by focusing on two key questions: (1) What supportive actions do top managers engage in during IS implementations? (2) How do these actions affect IS implementation outcomes? Analyses of in-depth case studies at two Canadian universities that had implemented a large-scale enterprise system revealed three distinct types of TMS actions: TMS – resource provision (TMSR – actions related to supplying key resources such as funds, technologies, staff, and user training programs); TMS – change management (TMSC – actions related to fostering organizational receptivity of a new IS); and TMS – vision sharing (TMSV – actions related to ensuring that lower-level managers develop a common understanding of the core objectives and ideals for the new system). Results suggest that different support behaviors exercise different influences on implementation outcomes, and that top managers need to adjust their support actions to achieve the desired outcomes. In particular, TMSR affected project completion, TMSC impacted formation of user skills and attitudes, and TMSV influenced middle manager buy-in. Theoretical and practical implications of these findings are discussed.