Showing papers by "Florida Atlantic University published in 2009"

A survey of collaborative filtering techniques

Abstract: As one of the most successful approaches to building recommender systems, collaborative filtering (CF) uses the known preferences of a group of users to make recommendations or predictions of the unknown preferences for other users. In this paper, we first introduce CF tasks and their main challenges, such as data sparsity, scalability, synonymy, gray sheep, shilling attacks, privacy protection, etc., and their possible solutions. We then present three main categories of CF techniques: memory-based, modelbased, and hybrid CF algorithms (that combine CF with other recommendation techniques), with examples for representative algorithms of each category, and analysis of their predictive performance and their ability to address the challenges. From basic techniques to the state-of-the-art, we attempt to present a comprehensive survey for CF techniques, which can be served as a roadmap for research and practice in this area.

The role of service level agreements in relational management of information technology outsourcing: an empirical study

Abstract: This study extends the view that formal contracts and relational governance function as complements rather than as substitutes. We investigate how specific characteristics of service level agreements (SLAs) impact relational governance in information technology outsourcing relationships. Eleven contractual elements (categorized into three SLA characteristics: foundation, change, and governance characteristics) are hypothesized to act as complements of three relational governance attributes: relational norms, harmonious conflict resolution, and mutual dependence. Data for the study were collected through a survey of South Korean IT executives. Results of the study support the fundamental proposition of complementarity between formal contracts and relational governance, and indicate that well-structured SLAs have significant positive influence on the various aspects of relational governance in IT outsourcing relationships. However, the study also reveals that change characteristics of SLAs may act as a substitute for relational governance as these characteristics were found to dampen the level of trust and commitment through moderation effects. Overall, the findings support the proposition that well-developed SLAs not only provide a way to measure the service provider's performance, but also enable effective management of outsourcing engagements through the development of partnership-style relationships with high levels of trust and commitment.

An unequal cluster-based routing protocol in wireless sensor networks

Abstract: Clustering provides an effective method for prolonging the lifetime of a wireless sensor network. Current clustering algorithms usually utilize two techniques; selecting cluster heads with more residual energy, and rotating cluster heads periodically to distribute the energy consumption among nodes in each cluster and extend the network lifetime. However, they rarely consider the hot spot problem in multihop sensor networks. When cluster heads cooperate with each other to forward their data to the base station, the cluster heads closer to the base station are burdened with heavier relay traffic and tend to die much faster, leaving areas of the network uncovered and causing network partitions. To mitigate the hot spot problem, we propose an Unequal Cluster-based Routing (UCR) protocol. It groups the nodes into clusters of unequal sizes. Cluster heads closer to the base station have smaller cluster sizes than those farther from the base station, thus they can preserve some energy for the inter-cluster data forwarding. A greedy geographic and energy-aware routing protocol is designed for the inter-cluster communication, which considers the tradeoff between the energy cost of relay paths and the residual energy of relay nodes. Simulation results show that UCR mitigates the hot spot problem and achieves an obvious improvement on the network lifetime.

Parent—Child Relationships During Adolescence

Abstract: Theories of Parent–Adolescent Relationships and Their Influence Interpersonal Processes And Relationship Perceptions The Role of Parent–Child Relationships in Adolescent Adjustment The Interplay of Context and Relationship Processes and Outcomes Conclusion Keywords: parenting; support; conflict; influence; family

The first year of practice: new graduate nurses' transition and learning needs.

Abstract: Although the phenomenon of reality shock has been acknowledged as part of the new graduate nurse transition for decades, there is evidence to suggest that the problems with the transition into practice are more serious today. This article presents findings about the new graduate nurse transition and learning needs from qualitative research conducted in a community-based novice nurse transition program. The new graduate nurse transition and learning needs are examined through the eyes of new graduates and the nursing leaders and preceptors who work with them. Recommendations are offered for continuing education initiatives that can be designed to meet these needs.

Local Bias in Venture Capital Investments

Abstract: This paper examines local bias in the context of venture capital (VC) investments. Based on a sample of US VC investments between 1980 and June 2009, we find more reputable VCs (older, larger, more experienced, and with stronger IPO track record) and VCs with broader networks exhibit less local bias. Staging and preference for technology ventures increases VCs’ local bias. We also find that the VC exhibits stronger local bias when it acts as the lead VC and when it is investing alone. Finally, we show that distance matters for the eventual performance of VC investments.

Interfirm Knowledge Exchanges and the Knowledge Creation Capability of Clusters

Abstract: I build on the literature that views clusters as venues of enhanced knowledge creation and introduce the concept of a cluster's knowledge creation capability. I then develop a model that outlines the antecedents of this concept. The model concentrates on factors that create opportunities for, enable, and increase the effectiveness of interfirm knowledge exchanges among cluster firms. These three sets of factors point to three types of knowledge creation failures within clusters.

An optimal probabilistic forwarding protocolin delay tolerant networks

Abstract: Due to uncertainty in nodal mobility, DTN routing usually employs multi-copy forwarding schemes. To avoid the cost associated with flooding, much effort has been focused on probabilistic forwarding, which aims to reduce the cost of forwarding while retaining a high performance rate by forwarding messages only to nodes that have high delivery probabilities. This paper aims to provide an optimal forwarding protocol which maximizes the expected delivery rate while satisfying a certain constant on the number of forwardings per message. In our proposed optimal probabilistic forwarding (OPF) protocol, we use an optimal probabilistic forwarding metric derived by modeling each forwarding as an optimal stopping rule problem. We also present several extensions to allow OPF to use only partial routing information and work with other probabilistic forwarding schemes such as ticket-based forwarding. We implement OPF and several other protocols and perform trace-driven simulations. Simulation results show that the delivery rate of OPF is only 5% lower than epidemic, and 20% greater than the state-of-the-art delegation forwarding while generating 5% more copies and 5% longer delay.

Beta and gamma rhythms in human auditory cortex during musical beat processing.

Abstract: We examined beta- (approximately 20 Hz) and gamma- (approximately 40 Hz) band activity in auditory cortices by means of magnetoencephalography (MEG) during passive listening to a regular musical beat with occasional omission of single tones. The beta activity decreased after each tone, followed by an increase, thus forming a periodic modulation synchronized with the stimulus. The beta decrease was absent after omissions. In contrast, gamma-band activity showed a peak after tone and omission, suggesting underlying endogenous anticipatory processes. We propose that auditory beta and gamma oscillations have different roles in musical beat encoding and auditory-motor interaction.

Predict and relay: an efficient routing in disruption-tolerant networks

Abstract: Routing is one of the most challenging open problems in disruption-tolerant networks (DTNs) because of the short-lived wireless connectivity environment. To deal with this issue, researchers have investigated routing based on the prediction of future contacts, taking advantage of nodes' mobility history. However, most of the previous work focused on the prediction of whether two nodes would have a contact, without considering the time of the contact. This paper proposes predict and relay (PER), an efficient routing algorithm for DTNs, where nodes determine the probability distribution of future contact times and choose a proper next hop in order to improve the end-to-end delivery probability. The algorithm is based on two observations: one is that nodes usually move around a set of well-visited landmark points instead of moving randomly; the other is that node mobility behavior is semi-deterministic and could be predicted once there is sufficient mobility history information. Specifically, our approach employs a time-homogeneous semi-markov process model that describes node mobility as transitions between landmarks. Landmark transition and sojourn time probability distributions are determined from nodes' mobility history. A simulation study shows that this approach improves the delivery ratio and also reduces the delivery latency compared to traditional DTN routing schemes.

User behaviour towards protective information technologies: the role of national cultural differences

Abstract: Computer technologies that protect data and systems from viruses, unauthorized access, disruptions, spyware and other threats have become increasingly important in the globally networked economy and society. Yet little is known about user attitudes and behaviour towards this category of information technologies. Comparative studies across different cultures in this context are even rarer. In this study, we examine the cross-cultural differences between South Korea and the United States in user behaviour towards protective information technologies. We develop a theoretical model of user behaviour based on the framework of the theory of planned behaviour and national cultural dimensions and indices. We posit that cultural factors moderate the strength of the relationships in the behavioural model in the context of protective information technologies. The model was then empirically tested using structural equation modelling techniques in conjunction with multi-group analysis. Most of the hypothesized moderating effects of national cultural factors were found to be statistically significant. Our findings suggest that cultural factors should be considered in order to design effective information security policies, practices and technologies in global networks where multiple cultures coexist. Theoretical and practical implications of the study are discussed.

Not with a Ten-Foot Pole: Core Stigma, Stigma Transfer, and Improbable Persistence of Men's Bathhouses

Abstract: We examine how organizations that suffer core stigma---disapproval for their core attributes---survive. We explain how men's bathhouses avoid negative attention and minimize the transfer of stigma to their network partners, including customers, suppliers, and regulators, through careful management of their business activities. Using observational, archival, and interview data across different institutional environments, we find that, in response to suffering core stigma, men's bathhouses use a variety of strategies to shield their partners depending, in part, on the level of hostility that they face in their environment. Our work contributes to the emerging literature on organization-level stigma, especially by focusing on how core-stigmatized organizations are able to survive and by drawing attention to the special problem of stigma transfer. Our findings also focus attention on the use of legitimacy in organization studies and call for further examinations of core-stigmatized and other illegitimate organizations to expand our theoretical domain to the fullest range of organizational processes and outcomes.

The Effects of Confidence in Government and Information on Perceived and Actual Preparedness for Disasters

Abstract: This research examines perceived and actual preparedness for two types of natural hazard risks: earthquakes in the Los Angeles County area and hurricanes within the New Orleans metropolitan area. Using data collected from a sample of households in these regions, the influence of individuals' confidence in local government to manage a disaster and exposure to disaster preparedness information sources were tested as explanations for levels of perceived and actual preparedness. Regression analyses show that a high level of confidence in local government to manage a disaster and exposure to more preparedness information sources were associated with a higher level of perceived preparedness. No support for a potential dampening effect of confidence in local government on household preparedness actions was found. The results also reveal only limited support for the impact of information exposure on actual preparedness. The results for actual preparedness vary between the study areas; therefore, we follow the ana...

The effects of procedural and informational justice in the integration of related acquisitions

Abstract: This study explores the independent and interactive effects of procedural justice and informational justice on post-deal value creation in large, related acquisitions. Our results show that informational justice and procedural justice affect different components of value creation. Procedural justice is critical in realizing market position improvements following the integration process, while informational justice is essential in achieving market position gains during integration and financial return gains both during and post-integration. Indicating that the interrelationships between different justice dimensions may be more complex than previously thought, we find that procedural justice reduces the positive effects of informational justice on financial return during the integration process, while it magnifies the effects of informational justice on the combined firms' market position during integration efforts. We explore the implications of these results for future research on the acquisition integration process and for practicing managers engaging in large, related acquisitions. Copyright © 2008 John Wiley & Sons, Ltd.

Knowledge discovery from imbalanced and noisy data

Abstract: Class imbalance and labeling errors present significant challenges to data mining and knowledge discovery applications. Some previous work has discussed these important topics, however the relationship between these two issues has not received enough attention. Further, much of the previous work in this domain is fragmented and contradictory, leading to serious questions regarding the reliability and validity of the empirical conclusions. In response to these issues, we present a comprehensive suite of experiments carefully designed to provide conclusive, reliable, and significant results on the problem of learning from noisy and imbalanced data. Noise is shown to significantly impact all of the learners considered in this work, and a particularly important factor is the class in which the noise is located (which, as discussed throughout this work, has very important implications to noise handling). The impacts of noise, however, vary dramatically depending on the learning algorithm and simple algorithms such as naive Bayes and nearest neighbor learners are often more robust than more complex learners such as support vector machines or random forests. Sampling techniques, which are often used to alleviate the adverse impacts of imbalanced data, are shown to improve the performance of learners built from noisy and imbalanced data. In particular, simple sampling techniques such as random undersampling are generally the most effective.

An overview of IT service management

Abstract: “To the majority of computer scientists, whether in academia or industry, the term “services” is associated with Web services and service-oriented architectures. However, there is a broader story to be told of the remarkable growth of the service sector, which has come to dominate economic activity in most advanced economies over the last 50 years. ... The opportunity to innovate in services, to realize business and societal value from knowledge about service, to research, develop, and deliver new information services and business services, has never been greater.”

Building Administrative Capacity for the Age of Rapid Globalization: A Modest Prescription for the Twenty-First Century

Abstract: The twenty-first century is characterized by rapid change, globalization, hyper-competition, and hyper-uncertainty. Traditional models of governance and public administration are no match for the challenges of this chaotic environment. This essay argues for building new administrative capacity in response to these serious governance dilemmas. Offered as a modest prescription, this new administrative capacity is proposed to cope more effectively with an increasingly unknowable world. The article opens with an overview of key issues, then focuses directly on the nature and trends of global public sector changes, and concludes by elaborating on the building of such administrative capacity. The author's proposals are presented from a macro perspective: first, suggestions for revitalizing public service and administration given the current crisis; second, macro strategies for enhancing capacity design; and third, specific reforms for strengthening governance, instrumental and administrative capacities, along with concrete recommendations for public administration.

A Study on the Relationships of Classifier Performance Metrics

Abstract: There is no general consensus on which classifier performance metrics are better to use as compared to others. While some studies investigate a handful of such metrics in a comparative fashion, an evaluation of specific relationships among a large set of commonly-used performance metrics is much needed in the data mining and machine learning community. This study provides a unique insight into the underlying relationships among classifier performance metrics. We do so with a large case study involving 35 datasets from various domains and the C4.5 decision tree algorithm. A common property of the 35 datasets is that they suffer from the class imbalance problem. Our approach is based on applying factor analysis to the classifier performance space which is characterized by 22 performance metrics. It is shown that such a large number of performance metrics can be grouped into two-to-four relationship-based groups extracted by factor analysis. This work is a step in the direction of providing the analyst with an improved understanding about the different relationships and groupings among the performance metrics, thus facilitating the selection of performance metrics that capture relatively independent aspects of a classifier’s performance.

LocalCom: A Community-based Epidemic Forwarding Scheme in Disruption-tolerant Networks

Abstract: In disruption-tolerant networks (DTNs), network topology constantly changes and end-to-end paths can hardly be sustained. However, social network properties are observed in many DTNs and tend to be stable over time. To utilize the social network properties to facilitate packet forwarding, we present LocalCom, a community-based epidemic forwarding scheme that efficiently detects the community structure using limited local information and improves the forwarding efficiency based on the community structure. We define similarity metrics according to nodes' encounter history to depict the neighboring relationship between each pair of nodes. A distributed algorithm, which only utilizes local information, is then applied to detect communities and the formed communities have strong intra-community connections. We also present two schemes to first select and then prune gateways that connect communities to control redundancy and facilitate efficient intercommunity packet forwarding. Extensive real-trace-driven simulation results are presented to support the effectiveness of our scheme.

Methionine oxidation contributes to bacterial killing by the myeloperoxidase system of neutrophils

Abstract: Reactive oxygen intermediates generated by neutrophils kill bacteria and are implicated in inflammatory tissue injury, but precise molecular targets are undefined. We demonstrate that neutrophils use myeloperoxidase (MPO) to convert methionine residues of ingested Escherichia coli to methionine sulfoxide in high yield. Neutrophils deficient in individual components of the MPO system (MPO, H2O2, chloride) exhibited impaired bactericidal activity and impaired capacity to oxidize methionine. HOCl, the principal physiologic product of the MPO system, is a highly efficient oxidant for methionine, and its microbicidal effects were found to correspond linearly with oxidation of methionine residues in bacterial cytosolic and inner membrane proteins. In contrast, outer envelope proteins were initially oxidized without associated microbicidal effect. Disruption of bacterial methionine sulfoxide repair systems rendered E. coli more susceptible to killing by HOCl, whereas over-expression of a repair enzyme, methionine sulfoxide reductase A, rendered them resistant, suggesting a direct role for methionine oxidation in bactericidal activity. Prominent among oxidized bacterial proteins were those engaged in synthesis and translocation of peptides to the cell envelope, an essential physiological function. Moreover, HOCl impaired protein translocation early in the course of bacterial killing. Together, our findings indicate that MPO-mediated methionine oxidation contributes to bacterial killing by neutrophils. The findings further suggest that protein translocation to the cell envelope is one important pathway targeted for damage.

Thwarting Blackhole Attacks in Disruption-Tolerant Networks using Encounter Tickets

Abstract: Nodes in disruption-tolerant networks (DTNs) usually exhibit repetitive motions. Several recently proposed DTN routing algorithms have utilized the DTNs' cyclic properties for predicting future forwarding. The prediction is based on metrics abstracted from nodes' contact history. However, the robustness of the encounter prediction becomes vital for DTN routing since malicious nodes can provide forged metrics or follow sophisticated mobility patterns to attract packets and gain a significant advantage in encounter prediction. In this paper, we examine the impact of the blackhole attack and its variations in DTN routing. We introduce the concept of encounter tickets to secure the evidence of each contact. In our scheme, nodes adopt a unique way of interpreting the contact history by making observations based on the collected encounter tickets. Then, following the Dempster-Shafer theory, nodes form trust and confidence opinions towards the competency of each encountered forwarding node. Extensive real-trace-driven simulation results are presented to support the effectiveness of our system.

Conventional Mutual Index Funds Versus Exchange Traded Funds

Abstract: This paper examines implications of substitutability of two similar investment vehicles: conventional index mutual funds and exchange traded funds (ETFs). It seeks to explain the coexistence of these vehicle types, which offer a claim on the same underlying index return process, but have distinct organizational structures. This study compares aggregate flows into conventional open-end index funds to those into ETFs for various underlying indexes. The study shows that conventional funds and ETFs are substitutes, but not perfect substitutes. Their coexistence can be explained by a clientele effect that segregates the two vehicles into different market niches.

Feature Selection with High-Dimensional Imbalanced Data

Abstract: Feature selection is an important topic in data mining, especially for high dimensional datasets. Filtering techniques in particular have received much attention, but detailed comparisons of their performance is lacking. This work considers three filters using classifier performance metrics and six commonly-used filters. All nine filtering techniques are compared and contrasted using five different microarray expression datasets. In addition, given that these datasets exhibit an imbalance between the number of positive and negative examples, the utilization of sampling techniques in the context of feature selection is examined.