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Dissertations and Theses Collection (Open Access)

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Articles 91 - 106 of 106

Full-Text Articles in Physical Sciences and Mathematics

Dynamic Queue Management For Hospital Emergency Room Services, Kar Way Tan Dec 2013

Dynamic Queue Management For Hospital Emergency Room Services, Kar Way Tan

Dissertations and Theses Collection (Open Access)

The emergency room (ER) – or emergency department (ED) – is often seen as a place with long waiting times and a lack of doctors to serve the patients. However, it is one of the most important departments in a hospital, and must efficiently serve patients with critical medical needs. In the existing literature, addressing the issue of long waiting times in an ED often takes the form of single-faceted queue-management strategies that are either from a demand perspective or from a supply perspective. From the demand perspective, there is work on queue design such as priority queues, or queue …


Anomaly Detection On Social Data, Hanbo Dai Jun 2013

Anomaly Detection On Social Data, Hanbo Dai

Dissertations and Theses Collection (Open Access)

The advent of online social media including Facebook, Twitter, Flickr and Youtube has drawn massive attention in recent years. These online platforms generate massive data capturing the behavior of multiple types of human actors as they interact with one another and with resources such as pictures, books and videos. Unfortunately, the openness of these platforms often leaves them highly susceptible to abuse by suspicious entities such as spammers. It therefore becomes increasingly important to automatically identify these suspicious entities and eliminate their threats. We call these suspicious entities anomalies in social data, as they often hold different agenda comparing to …


Fair Cost Sharing Auction Mechanisms In Last Mile Ridesharing, Duc Thien Nguyen Jan 2013

Fair Cost Sharing Auction Mechanisms In Last Mile Ridesharing, Duc Thien Nguyen

Dissertations and Theses Collection (Open Access)

With rapid growth of transportation demands in urban cities, one major challenge is to provide efficient and effective door-to-door service to passengers using the public transportation system. This is commonly known as the Last Mile problem. In this thesis, we consider a dynamic and demand responsive mechanism for Ridesharing on a non-dedicated commercial fleet (such as taxis). This problem is addressed as two sub-problems, the first of which is a special type of vehicle routing problems (VRP). The second sub-problem, which is more challenging, is to allocate the cost (i.e. total fare) fairly among passengers. We propose auction mechanisms where …


The Informavore Shopper: Analysis Of Information Foraging, System Design, And Purchasing Behavior In Online Retail Stores, Jeff Min Teck Hong Jan 2013

The Informavore Shopper: Analysis Of Information Foraging, System Design, And Purchasing Behavior In Online Retail Stores, Jeff Min Teck Hong

Dissertations and Theses Collection (Open Access)

Global online retail sales are on the rise and are predicted to experience a double digit growth annually over the next three years. Given little marginal cost involved in adding new products and brands to their catalogues, online retailers tend to increase product and brand offerings to increase sales by selling products that could not have been sold due to space constraints in physical stores. Frank Urbanowski, Director of MIT Press, attributed the 12% increase in sales of backlist titles directly to increased accessibility to these titles through the Internet. For consumers, the ability to buy products that they would …


Towards Secure And Usable Leakage-Resilient Password Entry, Qiang Yan Jan 2013

Towards Secure And Usable Leakage-Resilient Password Entry, Qiang Yan

Dissertations and Theses Collection (Open Access)

Password leakage is one of the most common security threats for pervasive password based user authentication. The design of a secure and usable password entry against password leakage remains a challenge since twenty year ago when the first academic proposal attempted to address it. This dissertation focuses on investigating the difficulty in designing leakage-resilient password entry (LRPE) schemes and exploring the feasibility of constructing secure and usable LRPE schemes with the assistance of state-of-the-art technology. The first work in this dissertation reveals the infeasibility of designing practical LRPE schemes in the absence of trusted devices by investigating the inherent tradeoff …


Exploiting Human Factors In User Authentication, Payas Gupta Jan 2013

Exploiting Human Factors In User Authentication, Payas Gupta

Dissertations and Theses Collection (Open Access)

Our overarching issue in security is the human factor – and dealing with it is perhaps one of the biggest challenges we face today. Human factor is often described as the weakest part of a security system and users are often described as the weakest link in the security chain. In this thesis, we focus on two problems which are caused by human factors in user authentication and propose respective solutions. a) Secrecy information inference attack – publicly available information can be used to infer some secrecy information about the user. b) Coercion attack – where an attacker forces a …


Impact Of Multimedia In Sina Weibo, Xun Zhao Jan 2013

Impact Of Multimedia In Sina Weibo, Xun Zhao

Dissertations and Theses Collection (Open Access)

Multimedia contents such as images and videos are widely used in social network sites nowadays. Sina Weibo, a Chinese microblogging service, is one of the first microblog platforms to incorporate multimedia content sharing features. This thesis provides statistical analysis on how multimedia contents are produced, consumed, and propagated in Sina Weibo. Based on 230 million tweets and 1.8 million user profiles in Sina Weibo, we study the impact of multimedia contents on the popularity of both users and tweets as well as tweet life span. In addition to consider the multimedia impact on popularity, we also compare the user influence …


Understanding And Rejecting Errant Touches On Multi-Touch Tablets, Ke Shu Jan 2013

Understanding And Rejecting Errant Touches On Multi-Touch Tablets, Ke Shu

Dissertations and Theses Collection (Open Access)

Given the pervasion of multi-touch tablet, pen-based applications have rapidly moved onto this new platform. Users draw both with bare fingers and using capacitive pens as they would do on paper in the past. Unlike paper, these tablets cannot distinguish legitimate finger/pen input from accidental touches by other parts of the user’s hand. In this thesis, we refer it to as errant touch rejection problem since users may unintentionally touch the screen with other parts of their hand. In this thesis, I design, implement and evaluate new approaches, bezel-focus rejection, of preventing errant touches on multi-touch tablets. I began the …


A Study Of The Imitation, Collection And Usability Issues Of Keystroke Biometrics, Chee Meng Tey Jan 2013

A Study Of The Imitation, Collection And Usability Issues Of Keystroke Biometrics, Chee Meng Tey

Dissertations and Theses Collection (Open Access)

The majority of authentication systems used today involves passwords, where a user is required to remember and key in the correct password to login. Keystroke biometrics is an alternative approach whereby users are identified by one or more features such as (a) the timing between keystrokes, (b) how long users hold each key and (c) how hard users press each key. It is being assumed in prior research that the way one user types a password/word is different from the way another user types the same password and this characteristic remains stable over time. Existing literature however left open three …


Predictive Modeling For Navigating Social Media, Meiqun Hu Jan 2012

Predictive Modeling For Navigating Social Media, Meiqun Hu

Dissertations and Theses Collection (Open Access)

Social media changes the way people use the Web. It has transformed ordinary Web users from information consumers to content contributors. One popular form of content contribution is social tagging, in which users assign tags to Web resources. By the collective efforts of the social tagging community, a new information space has been created for information navigation. Navigation allows serendipitous discovery of information by examining the information objects linked to one another in the social tagging space. In this dissertation, we study prediction tasks that facilitate navigation in social tagging systems. For social tagging systems to meet complex navigation needs …


Go Niche Or Go Home: Influence Maximization In The Presence Of Strong Opponent, Long Foong Liow Jan 2012

Go Niche Or Go Home: Influence Maximization In The Presence Of Strong Opponent, Long Foong Liow

Dissertations and Theses Collection (Open Access)

In hotly contested product categories dominated by a few powerful firms, it is quite common for weaker or late entrants to focus only on particular segments of the whole market. The rationale for such strategy is intuitive: to avoid direct confrontation with heavy-weight firms, and to concentrate in segments where these weaker firms have comparative advantages. In marketing, this is what people called “go niche or go home”. The niche-building strategy may rely on “homophily”, which implies that consumers in a particular market segment might possess certain set of attributes that cause them to appreciate certain products better (in other …


Robust Execution Strategy For Scheduling Under Uncertainity, Na Fu Jan 2012

Robust Execution Strategy For Scheduling Under Uncertainity, Na Fu

Dissertations and Theses Collection (Open Access)

Resource Constrained Project Scheduling Problems with minimum and maximum time lags (RCPSP/max) provides a general model for resource scheduling in many real-world problems (such as manufacturing and construction engineering). Due to its practical importance and generality, providing effective algorithms and scalable solutions for RCPSP/max is a topic of growing research. Traditional methods have addressed deterministic models with all parameters known with certainty. In this thesis, we are concerned with RCPSP/max problems in an uncertain environment where durations of activities are stochastic and resource availabilities are subject to unforeseen breakdowns. We propose methods for generating robust execution strategy to protect against …


Novel Techniques Of Using Diversity In Software Security And Information Hiding, Jin Han Jan 2012

Novel Techniques Of Using Diversity In Software Security And Information Hiding, Jin Han

Dissertations and Theses Collection (Open Access)

Diversity is an important and valuable concept that has been adopted in many fields to reduce correlated risks and to increase survivability. In information security, diversity also helps to increase both defense capability and fault tolerance for information systems and communication networks, where diversity can be adopted from many different perspectives. This dissertation, in particular, focuses mainly on two aspects of diversity – the application software diversity and the diversity in data interpretation. Software diversity has many advantages over mono-culture in improving system security. A number of previous researches focused on utilizing existing off-theshelf diverse software for network protection and …


The Valuation Of User-Generated Content: A Structural, Stylistic And Semantic Analysis Of Online Reviews, Noi Sian Koh Dec 2011

The Valuation Of User-Generated Content: A Structural, Stylistic And Semantic Analysis Of Online Reviews, Noi Sian Koh

Dissertations and Theses Collection (Open Access)

The ability and ease for users to create and publish content has provided vast amount of online product reviews. However, the amount of data is overwhelmingly large and unstructured, making information difficult to quantify. This creates challenge in understanding how online reviews affect consumers’ purchase decisions. In my dissertation, I explore the structural, stylistic and semantic content of online reviews. Firstly, I present a measurement that quantifies sentiments with respect to a multi-point scale and conduct a systematic study on the impact of online reviews on product sales. Using the sentiment metrics generated, I estimate the weight that customers place …


Mining Antagonistic Communities From Social Networks, Kuan Zhang Jan 2010

Mining Antagonistic Communities From Social Networks, Kuan Zhang

Dissertations and Theses Collection (Open Access)

In this thesis, we examine the problem of mining antagonistic communities from social networks. In social networks, people with opposite opinions normally behave differently and form sub-communities each of which containing people sharing some common behaviors. In one scenario, people with opposite opinions show differences in their views on a set of items. Another scenario is people explicitly expressing whom they agree with, like or trust as well as whom they disagree with, dislike or distrust. We defined the indirect and direct antagonistic groups based on the two scenarios. We have developed algorithms to mine the two types of antagonistic …


Security And Performance Analysis For Rfid Protocols, Bing Liang Jan 2010

Security And Performance Analysis For Rfid Protocols, Bing Liang

Dissertations and Theses Collection (Open Access)

Radio Frequency Identification (RFID) is an advanced object identification technology that has already been applied in various industries. However, the insecure nature of the communication channel between readers and tags makes RFID systems vulnerable to various kinds of attacks. In recent years, many new methods have been proposed to improve the security of RFID systems, such as disabling tags, agent management and establishing cryptographic protocols. Among them, we focus on the last approach, which is more economic and convenient in certain cases. The first part of our work is to categorize typical existing RFID protocols according to their security levels. …