Showing papers by "Concordia University published in 2012"

Signaling in Equity Crowdfunding

Abstract: This paper presents an initial empirical examination of which start-up signals will induce small investors to commit financial resources in an equity crowdfunding context. We examine the impact of firms’ financial roadmaps (e.g., preplanned exit strategies such as IPOs or acquisitions), external certification (awards, government grants and patents), internal governance (such as board structure), and risk factors (such as amount of equity offered and the presence of disclaimers) on fundraising success. Our data highlight the importance of financial roadmaps and risk factors, as well as internal governance, for successful equity crowdfunding. External certification, by contrast, has little or no impact on success. We also discuss the implications for successful policy design.

Corporate governance and environmental performance: is there really a link?

Abstract: Corporate governance scholars are increasingly interested in firms' social and environmental performance. Empirical research in this area, however, has moved forward in an uncoordinated fashion, producing fragmented and contradictory results. Our paper seeks to address this situation by adopting a fact-based research approach that comprehensively explores the link between corporate governance and environmental performance. Specifically, we aim to understand how the relationships between and among the firms' owners, managers, and boards of directors influence environmental performance. We are particularly interested in understanding the interactions among these three key sets of actors. In the end, we offer some observations about governance practices and discuss the implications for theory. Copyright © 2012 John Wiley & Sons, Ltd.

Adaptive Sliding Mode Fault Tolerant Attitude Tracking Control for Flexible Spacecraft Under Actuator Saturation

Abstract: A novel fault tolerant attitude tracking control scheme is developed for flexible spacecraft with partial loss of actuator effectiveness fault. Neural networks are first introduced to account for system uncertainties, and an adaptive sliding mode controller is derived by using on-line updating law to estimate the bound of actuator fault such that any information of the fault is not required. To further address actuator saturation problem, a modified fault tolerant control law is then presented to ensure that the resulting control signal will never incur saturation. It is shown that the roll, pitch and yaw angle trajectories can globally asymptotically track the desired attitude in the face of faulty actuator, system uncertainties, external disturbances and even actuator saturation. A simulation example of a flexible spacecraft is given to illustrate the effectiveness of the proposed controller.

Disruption-Tolerant Networking: A Comprehensive Survey on Recent Developments and Persisting Challenges

Abstract: Nowadays, wireless networks are witnessing several deployments in various extreme environments where they suffer from different levels of link disruptions depending on the severity of the operating conditions. In all cases, their operation requirements are differently altered and their performance is negatively affected rendering them heterogeneous by nature. In the open literature, these networks are known as Intermittently Connected Networks (ICNs). The existing Internet protocols fail to operate properly in the context of ICNs, thus raising a variety of new challenging problems that are attracting the attention of the networking research community. Delay-/Disruption-Tolerant Networking emerged as a highly active area of research where networking experts compete in addressing the various ICN problems. Over time, unicast routing, one of the architectural key components common to all ICNs, became an almost independent field of research in which significant efforts continue to be invested. In contrast, network architectural designs, scheduling and forwarding issues dating from the early days of Inter-Planetary Networks (IPNs) have received relatively little attention and accumulate numerous pending challenges. Moreover, the gap caused by the lack of accurate ICN mathematical models is still large irrespective of some of the appreciated seminal works in this direction. This paper sheds the light over the latest advancements in each of the above-mentioned research sectors and highlight pending open issues in each of them.

Back to the future: revisiting Kotter's 1996 change model

Abstract: Purpose – The purpose of this paper is to gather current (2011) arguments and counterarguments in support of the classic change management model proposed by John P. Kotter in his 1996 book Leading Change. His work was based on his personal business and research experience, and did not reference any outside sources that has questioned its value. A current perspective on a limited tested model aims to be a focus of this paper. Design/methodology/approach – The literature on change management was reviewed for each of the eight steps defined in Kotter's model, to review how much support each of these steps had, individually and collectively, in 15 years of literature. Findings – The review found support for most of the steps, although no formal studies were found covering the entire spectrum and structure of the model. Kotter's change management model appears to derive its popularity more from its direct and usable format than from any scientific consensus on the results. However the model has several limitations, that are identified, impacting upon its universal acceptance and popularity. Research limitations/implications – Further studies should examine the validity of Kotter's model as a whole. More importantly, change management research should form a greater link with stakeholders in order to translate current research into a format usable by practitioners. Practical implications – No evidence was found against Kotter's change management model and it remains a recommendable reference. This paper attempts to “test” the “how‐to‐do‐change management” with empirical and practitioner literature that was not evident in the original text. The model would be most useful as an implementation planning tool, but complementary tools should also be used during the implementation process to adapt to contextual factors or obstacles. Originality/value – Based upon a thorough review, this is the first formal review of Kotter's change management model, 15 years after its introduction.

An artificial neural network method for remaining useful life prediction of equipment subject to condition monitoring

Abstract: Accurate equipment remaining useful life prediction is critical to effective condition based maintenance for improving reliability and reducing overall maintenance cost. In this paper, an artificial neural network (ANN) based method is developed for achieving more accurate remaining useful life prediction of equipment subject to condition monitoring. The ANN model takes the age and multiple condition monitoring measurement values at the present and previous inspection points as the inputs, and the life percentage as the output. A function generalized from the Weibull failure rate function is used to fit each condition monitoring measurement series for a failure history, and the fitted measurement values are used to form the ANN training set so as to reduce the effects of the noise factors that are irrelevant to the equipment degradation. A validation mechanism is introduced in the ANN training process to improve the prediction performance of the ANN model. The proposed ANN method is validated using real-world vibration monitoring data collected from pump bearings in the field. A comparative study is performed between the proposed ANN method and an adapted version of a reported method, and the results demonstrate the advantage of the proposed method in achieving more accurate remaining useful life prediction.

A Survey on Service-Oriented Network Virtualization Toward Convergence of Networking and Cloud Computing

Abstract: The crucial role that networking plays in Cloud computing calls for a holistic vision that allows combined control, management, and optimization of both networking and computing resources in a Cloud environment, which leads to a convergence of networking and Cloud computing. Network virtualization is being adopted in both telecommunications and the Internet as a key attribute for the next generation networking. Virtualization, as a potential enabler of profound changes in both communications and computing domains, is expected to bridge the gap between these two fields. Service-Oriented Architecture (SOA), when applied in network virtualization, enables a Network-as-a-Service (NaaS) paradigm that may greatly facilitate the convergence of networking and Cloud computing. Recently the application of SOA in network virtualization has attracted extensive interest from both academia and industry. Although numerous relevant research works have been published, they are currently scattered across multiple fields in the literature, including telecommunications, computer networking, Web services, and Cloud computing. In this article we present a comprehensive survey on the latest developments in service-oriented network virtualization for supporting Cloud computing, particularly from a perspective of network and Cloud convergence through NaaS. Specifically, we first introduce the SOA principle and review recent research progress on applying SOA to support network virtualization in both telecommunications and the Internet. Then we present a framework of network-Cloud convergence based on service-oriented network virtualization and give a survey on key technologies for realizing NaaS, mainly focusing on state of the art of network service description, discovery, and composition. We also discuss the challenges brought in by network-Cloud convergence to these technologies and research opportunities available in these areas, with a hope to arouse the research community's interest in this emerging interdisciplinary field.

Differentially private sequential data publication via variable-length n-grams

Abstract: Sequential data is being increasingly used in a variety of applications. Publishing sequential data is of vital importance to the advancement of these applications. However, as shown by the re-identification attacks on the AOL and Netflix datasets, releasing sequential data may pose considerable threats to individual privacy. Recent research has indicated the failure of existing sanitization techniques to provide claimed privacy guarantees. It is therefore urgent to respond to this failure by developing new schemes with provable privacy guarantees. Differential privacy is one of the only models that can be used to provide such guarantees. Due to the inherent sequentiality and high-dimensionality, it is challenging to apply differential privacy to sequential data. In this paper, we address this challenge by employing a variable-length n-gram model, which extracts the essential information of a sequential database in terms of a set of variable-length n-grams. Our approach makes use of a carefully designed exploration tree structure and a set of novel techniques based on the Markov assumption in order to lower the magnitude of added noise. The published n-grams are useful for many purposes. Furthermore, we develop a solution for generating a synthetic database, which enables a wider spectrum of data analysis tasks. Extensive experiments on real-life datasets demonstrate that our approach substantially outperforms the state-of-the-art techniques.

Differentially private transit data publication: a case study on the montreal transportation system

Abstract: With the wide deployment of smart card automated fare collection (SCAFC) systems, public transit agencies have been benefiting from huge volume of transit data, a kind of sequential data, collected every day. Yet, improper publishing and use of transit data could jeopardize passengers' privacy. In this paper, we present our solution to transit data publication under the rigorous differential privacy model for the Societe de transport de Montreal (STM). We propose an efficient data-dependent yet differentially private transit data sanitization approach based on a hybrid-granularity prefix tree structure. Moreover, as a post-processing step, we make use of the inherent consistency constraints of a prefix tree to conduct constrained inferences, which lead to better utility. Our solution not only applies to general sequential data, but also can be seamlessly extended to trajectory data. To our best knowledge, this is the first paper to introduce a practical solution for publishing large volume of sequential data under differential privacy. We examine data utility in terms of two popular data analysis tasks conducted at the STM, namely count queries and frequent sequential pattern mining. Extensive experiments on real-life STM datasets confirm that our approach maintains high utility and is scalable to large datasets.

Political Feasibility: A Conceptual Exploration

Abstract: To date there is no systematic exploration of the concept of ‘political feasibility’. We believe that feasibility is a central issue for political philosophy, conceptually as well as practically, a...

The long-term effect of increasing the albedo of urban areas

Abstract: Solar reflective urban surfaces (white rooftops and light-colored pavements) can increase the albedo of an urban area by about 0.1. Increasing the albedo of urban and human settlement areas can in turn decrease atmospheric temperature and could potentially offset some of the anticipated temperature increase caused by global warming. We have simulated the long-term (decadal to centennial) effect of increasing urban surface albedos using a spatially explicit global climate model of intermediate complexity. We first carried out two sets of simulations in which we increased the albedo of all land areas between 20 and 45 latitude respectively. The results of these simulations indicate a long-term global cooling effect of 3 10 15 K for each 1 m 2 of a surface with an albedo increase of 0.01. This temperature reduction corresponds to an equivalent CO2 emission reduction of about 7 kg, based on recent estimates of the amount of global warming per unit CO2 emission. In a series of additional simulations, we increased the albedo of urban locations only, on the basis of two independent estimates of the spatial extent of urban areas. In these simulations, global cooling ranged from 0.01 to 0.07 K, which corresponds to a CO2 equivalent emission reduction of 25‐150 billion tonnes of CO2.

The impact of physical activity on mortality in patients with high blood pressure: a systematic review.

Abstract: Background:Physical activity has been shown to be beneficial for the prevention and management of hypertension. In the general population, physical activity has been shown to decrease mortality.Purpose:The purpose of this systematic review was to identify and synthesize the literature examining the

Who, What, Where, When (and Maybe Even Why)? How the Experience of Sexual Reward Connects Sexual Desire, Preference, and Performance

Abstract: Although sexual behavior is controlled by hormonal and neurochemical actions in the brain, sexual experience induces a degree of plasticity that allows animals to form instrumental and Pavlovian associations that predict sexual outcomes, thereby directing the strength of sexual responding. This review describes how experience with sexual reward strengthens the development of sexual behavior and induces sexually-conditioned place and partner preferences in rats. In both male and female rats, early sexual experience with partners scented with a neutral or even noxious odor induces a preference for scented partners in subsequent choice tests. Those preferences can also be induced by injections of morphine or oxytocin paired with a male rat’s first exposure to scented females, indicating that pharmacological activation of opioid or oxytocin receptors can “stand in” for the sexual reward-related neurochemical processes normally activated by sexual stimulation. Conversely, conditioned place or partner preferences can be blocked by the opioid receptor antagonist naloxone. A somatosensory cue (a rodent jacket) paired with sexual reward comes to elicit sexual arousal in male rats, such that paired rats with the jacket off show dramatic copulatory deficits. We propose that endogenous opioid activation forms the basis of sexual reward, which also sensitizes hypothalamic and mesolimbic dopamine systems in the presence of cues that predict sexual reward. Those systems act to focus attention on, and activate goal-directed behavior toward, reward-related stimuli. Thus, a critical period exists during an individual’s early sexual experience that creates a “love map” or Gestalt of features, movements, feelings, and interpersonal interactions associated with sexual reward.

Flatness-Based Trajectory Planning/Replanning for a Quadrotor Unmanned Aerial Vehicle

Abstract: A flatness-based flight trajectory planning/replanning strategy is proposed for a quadrotor unmanned aerial vehicle (UAV). In the nominal situation (fault-free case), the objective is to drive the system from an initial position to a final one without hitting the actuator constraints while minimizing the total time of the mission or minimizing the total energy spent. When actuator faults occur, fault-tolerant control (FTC) is combined with trajectory replanning to change the reference trajectory in function of the remaining resources in the system. The approach employs differential flatness to express the control inputs to be applied in the function of the desired trajectories and formulates the trajectory planning/replanning problem as a constrained optimization problem.

Note on 'A One-Vendor Multi-Buyer Integrated Production-Inventory Model: The ‘Consignment Stock’ Case'

Abstract: In Zavanella and Zanoni (2009) 'A one-vendor multi-buyer integrated production- inventory model: The ‘Consignment Stock’ Case,' a one-vendor multi-buyer model was established, based on which the cost of the vendor and buyers are derived. However, buyer’s total cost in Equation (2) does not conform with Figure 1 in their paper. To illustrate this point, we provide the exact total cost presentation for a one-vendor two-buyer model, and revisit the numerical studies accordingly.

Direct Discovery of High Utility Itemsets without Candidate Generation

Abstract: Utility mining emerged recently to address the limitation of frequent itemset mining by introducing interestingness measures that reflect both the statistical significance and the user's expectation. Among utility mining problems, utility mining with the itemset share framework is a hard one as no anti-monotone property holds with the interestingness measure. The state-of-the-art works on this problem all employ a two-phase, candidate generation approach, which suffers from the scalability issue due to the huge number of candidates. This paper proposes a high utility itemset growth approach that works in a single phase without generating candidates. Our basic approach is to enumerate itemsets by prefix extensions, to prune search space by utility upper bounding, and to maintain original utility information in the mining process by a novel data structure. Such a data structure enables us to compute a tight bound for powerful pruning and to directly identify high utility itemsets in an efficient and scalable way. We further enhance the efficiency significantly by introducing recursive irrelevant item filtering with sparse data, and a lookahead strategy with dense data. Extensive experiments on sparse and dense, synthetic and real data suggest that our algorithm outperforms the state-of-the-art algorithms over one order of magnitude.

The Evolution of Facilitated Industrial Symbiosis

Abstract: While much work has been done on the conditions surrounding the emergence and establishment of industrial symbiosis, new attention is being paid to understanding the evolution of industrial symbiosis over time. We demonstrate empirically how a new facilitated industrial symbiosis initiative developed and evolved over an eight‐year period. We explore its network evolution by considering how the facilitator’s actions enabled and precluded two fundamental network processes – serendipitous and goal‐directed processes. We discuss implications for a more generalized theory of industrial symbiosis development by exploring why and how different evolutionary trajectories may unfold.