Showing papers by "Worcester Polytechnic Institute published in 2010"

Global Positioning System: Signals, Measurements, and Performance

Abstract: The Global Positioning System (GPS) is a satellite-based navigation and time transfer system developed by the U.S. Department of Defense. It serves marine, airborne, and terrestrial users, both military and civilian. Specifically, GPS includes the Standard Positioning Service (SPS) which provides civilian users with 100 meter accuracy, and it serves military users with the Precise Positioning Service (PPS) which provides 20-m accuracy. Both of these services are available worldwide with no requirement for a local reference station. In contrast, differential operation of GPS provides 2- to 10-m accuracy to users within 1000 km of a fixed GPS reference receiver. Finally, carrier phase comparisons can be used to provide centimeter accuracy to users within 10 km and potentially within 100 km of a reference receiver. This advanced tutorial will describe the GPS signals, the various measurements made by the GPS receivers, and estimate the achievable accuracies. It will not dwell on those aspects of GPS which are well known to those skilled in the radio communications art, such as spread-spectrum or code division multiple access. Rather, it will focus on topics which are more unique to radio navigation or GPS. These include code-carrier divergence, codeless tracking, carrier aiding, and narrow correlator spacing.

Achieving Secure, Scalable, and Fine-grained Data Access Control in Cloud Computing

Abstract: Cloud computing is an emerging computing paradigm in which resources of the computing infrastructure are provided as services over the Internet. As promising as it is, this paradigm also brings forth many new challenges for data security and access control when users outsource sensitive data for sharing on cloud servers, which are not within the same trusted domain as data owners. To keep sensitive user data confidential against untrusted servers, existing solutions usually apply cryptographic methods by disclosing data decryption keys only to authorized users. However, in doing so, these solutions inevitably introduce a heavy computation overhead on the data owner for key distribution and data management when fine-grained data access control is desired, and thus do not scale well. The problem of simultaneously achieving fine-grainedness, scalability, and data confidentiality of access control actually still remains unresolved. This paper addresses this challenging open issue by, on one hand, defining and enforcing access policies based on data attributes, and, on the other hand, allowing the data owner to delegate most of the computation tasks involved in fine-grained data access control to untrusted cloud servers without disclosing the underlying data contents. We achieve this goal by exploiting and uniquely combining techniques of attribute-based encryption (ABE), proxy re-encryption, and lazy re-encryption. Our proposed scheme also has salient properties of user access privilege confidentiality and user secret key accountability. Extensive analysis shows that our proposed scheme is highly efficient and provably secure under existing security models.

Privacy-Preserving Public Auditing for Data Storage Security in Cloud Computing

Abstract: Cloud Computing is the long dreamed vision of computing as a utility, where users can remotely store their data into the cloud so as to enjoy the on-demand high quality applications and services from a shared pool of configurable computing resources. By data outsourcing, users can be relieved from the burden of local data storage and maintenance. However, the fact that users no longer have physical possession of the possibly large size of outsourced data makes the data integrity protection in Cloud Computing a very challenging and potentially formidable task, especially for users with constrained computing resources and capabilities. Thus, enabling public auditability for cloud data storage security is of critical importance so that users can resort to an external audit party to check the integrity of outsourced data when needed. To securely introduce an effective third party auditor (TPA), the following two fundamental requirements have to be met: 1) TPA should be able to efficiently audit the cloud data storage without demanding the local copy of data, and introduce no additional on-line burden to the cloud user; 2) The third party auditing process should bring in no new vulnerabilities towards user data privacy. In this paper, we utilize and uniquely combine the public key based homomorphic authenticator with random masking to achieve the privacy-preserving public cloud data auditing system, which meets all above requirements. To support efficient handling of multiple auditing tasks, we further explore the technique of bilinear aggregate signature to extend our main result into a multi-user setting, where TPA can perform multiple auditing tasks simultaneously. Extensive security and performance analysis shows the proposed schemes are provably secure and highly efficient.

Fuzzy Keyword Search over Encrypted Data in Cloud Computing

Abstract: As Cloud Computing becomes prevalent, more and more sensitive information are being centralized into the cloud. For the protection of data privacy, sensitive data usually have to be encrypted before outsourcing, which makes effective data utilization a very challenging task. Although traditional searchable encryption schemes allow a user to securely search over encrypted data through keywords and selectively retrieve files of interest, these techniques support only exact keyword search. That is, there is no tolerance of minor typos and format inconsistencies which, on the other hand, are typical user searching behavior and happen very frequently. This significant drawback makes existing techniques unsuitable in Cloud Computing as it greatly affects system usability, rendering user searching experiences very frustrating and system efficacy very low. In this paper, for the first time we formalize and solve the problem of effective fuzzy keyword search over encrypted cloud data while maintaining keyword privacy. Fuzzy keyword search greatly enhances system usability by returning the matching files when users' searching inputs exactly match the predefined keywords or the closest possible matching files based on keyword similarity semantics, when exact match fails. In our solution, we exploit edit distance to quantify keywords similarity and develop an advanced technique on constructing fuzzy keyword sets, which greatly reduces the storage and representation overheads. Through rigorous security analysis, we show that our proposed solution is secure and privacy-preserving, while correctly realizing the goal of fuzzy keyword search.

Better to be frustrated than bored: The incidence, persistence, and impact of learners' cognitive-affective states during interactions with three different computer-based learning environments

Abstract: We study the incidence (rate of occurrence), persistence (rate of reoccurrence immediately after occurrence), and impact (effect on behavior) of students' cognitive-affective states during their use of three different computer-based learning environments. Students' cognitive-affective states are studied using different populations (Philippines, USA), different methods (quantitative field observation, self-report), and different types of learning environments (dialogue tutor, problem-solving game, and problem-solving-based Intelligent Tutoring System). By varying the studies along these multiple factors, we can have greater confidence that findings which generalize across studies are robust. The incidence, persistence, and impact of boredom, frustration, confusion, engaged concentration, delight, and surprise were compared. We found that boredom was very persistent across learning environments and was associated with poorer learning and problem behaviors, such as gaming the system. Despite prior hypothesis to the contrary, frustration was less persistent, less associated with poorer learning, and did not appear to be an antecedent to gaming the system. Confusion and engaged concentration were the most common states within all three learning environments. Experiences of delight and surprise were rare. These findings suggest that significant effort should be put into detecting and responding to boredom and confusion, with a particular emphasis on developing pedagogical interventions to disrupt the ''vicious cycles'' which occur when a student becomes bored and remains bored for long periods of time.

Attribute based data sharing with attribute revocation

Abstract: Ciphertext-Policy Attribute Based Encryption (CP-ABE) is a promising cryptographic primitive for fine-grained access control of shared data. In CP-ABE, each user is associated with a set of attributes and data are encrypted with access structures on attributes. A user is able to decrypt a ciphertext if and only if his attributes satisfy the ciphertext access structure. Beside this basic property, practical applications usually have other requirements. In this paper we focus on an important issue of attribute revocation which is cumbersome for CP-ABE schemes. In particular, we resolve this challenging issue by considering more practical scenarios in which semi-trustable on-line proxy servers are available. As compared to existing schemes, our proposed solution enables the authority to revoke user attributes with minimal effort. We achieve this by uniquely integrating the technique of proxy re-encryption with CP-ABE, and enable the authority to delegate most of laborious tasks to proxy servers. Formal analysis shows that our proposed scheme is provably secure against chosen ciphertext attacks. In addition, we show that our technique can also be applicable to the Key-Policy Attribute Based Encryption (KP-ABE) counterpart.

Measuring performance of two-stage network structures by DEA: A review and future perspective

Abstract: Data envelopment analysis (DEA) is a method for measuring the efficiency of peer decision making units (DMUs). An important area of development in recent years has been devoted to applications wherein DMUs represent two-stage or network processes. One particular subset of such processes is those in which all the outputs from the first stage are the only inputs to the second stage. The current paper reviews these models and establishes relations among various approaches. We show that all the existing approaches can be categorized as using either Stackelberg (leader-follower), or cooperative game concepts. Future perspectives and challenges are discussed.

Understanding organization-enterprise system fit: a path to theorizing the information technology artifact

Abstract: Packaged software applications such as enterprise systems are designed to support generic rather than specific requirements, and hence are likely to be an imperfect fit in any particular instance. Using critical realism as our philosophical perspective, we conducted a three-year qualitative study of misfits that arose from an enterprise system (ES) implementation. A detailed analysis of the observed misfits resulted in a richer understanding of the concept of fit and of the ES artifact itself. Specifically, we found six misfit domains (functionality, data, usability, role, control and organizational culture) and within each, two types of misfit (deficiencies and impositions). These misfit types correspond to two newly defined types of fit: fit as coverage and fit as enablement. Our analysis of fit also revealed a new conceptualization of the ES artifact, with implications for IT artifacts in general.

Generation Y, web design, and eye tracking

Abstract: Generation Y (age 18-31) is a very large and economically powerful generation, containing eighty-two million people and spending $200 billion annually It is not surprising that companies are interested in gaining the patronage of this group, particularly via the web Surprisingly, very little research into making web pages appealing to this important demographic has been done This paper addresses this need through two separate studies The first, an online survey, provides evidence that our proposed score for predicting the visual appeal of web pages reflects the self report measure of what pages Generation Y likes To refine these findings, an eye tracking study is conducted using the pages that were most and least liked in Study I Participants' eye movement is tracked while browsing these pages, providing evidence of what attracts their attention The results of these two studies suggest that Generation Y may prefer pages that include a main large image, images of celebrities, little text, and a search feature This research has important implications

Securing Personal Health Records in Cloud Computing: Patient-Centric and Fine-Grained Data Access Control in Multi-owner Settings

Abstract: Online personal health record (PHR) enables patients to manage their own medical records in a centralized way, which greatly facilitates the storage, access and sharing of personal health data. With the emergence of cloud computing, it is attractive for the PHR service providers to shift their PHR applications and storage into the cloud, in order to enjoy the elastic resources and reduce the operational cost. However, by storing PHRs in the cloud, the patients lose physical control to their personal health data, which makes it necessary for each patient to encrypt her PHR data before uploading to the cloud servers. Under encryption, it is challenging to achieve fine-grained access control to PHR data in a scalable and efficient way. For each patient, the PHR data should be encrypted so that it is scalable with the number of users having access. Also, since there are multiple owners (patients) in a PHR system and every owner would encrypt her PHR files using a different set of cryptographic keys, it is important to reduce the key distribution complexity in such multi-owner settings. Existing cryptographic enforced access control schemes are mostly designed for the single-owner scenarios.

Modeling individualization in a bayesian networks implementation of knowledge tracing

Abstract: The field of intelligent tutoring systems has been using the well known knowledge tracing model, popularized by Corbett and Anderson (1995), to track student knowledge for over a decade Surprisingly, models currently in use do not allow for individual learning rates nor individualized estimates of student initial knowledge Corbett and Anderson, in their original articles, were interested in trying to add individualization to their model which they accomplished but with mixed results Since their original work, the field has not made significant progress towards individualization of knowledge tracing models in fitting data In this work, we introduce an elegant way of formulating the individualization problem entirely within a Bayesian networks framework that fits individualized as well as skill specific parameters simultaneously, in a single step With this new individualization technique we are able to show a reliable improvement in prediction of real world data by individualizing the initial knowledge parameter We explore three difference strategies for setting the initial individualized knowledge parameters and report that the best strategy is one in which information from multiple skills is used to inform each student's prior Using this strategy we achieved lower prediction error in 33 of the 42 problem sets evaluated The implication of this work is the ability to enhance existing intelligent tutoring systems to more accurately estimate when a student has reached mastery of a skill Adaptation of instruction based on individualized knowledge and learning speed is discussed as well as open research questions facing those that wish to exploit student and skill information in their user models.

Enacting the ‘true self’: Towards a theory of embodied authentic leadership

Abstract: This paper argues that although authentic leadership may be rooted in the notion of a ‘true self’, it is through the embodiment of that ‘true self’ that leaders are perceived as authentic or not. In making this claim, we consider ways in which a somatic sense of self contributes to the felt sense of authenticity, and how through engaging with somatic cues, leadership can be performed in a way which is experienced as authentic, both to the leader and to those he or she seeks to lead. In developing our ideas further, we draw from the acting theory of Stanislavski (1936a, 1936b, 1961) to explore how authentic dramatic performances are created, focusing on the role of emotional memory, the magic ‘if’ and physical action in performances. We propose three key components of a resulting theory of how embodied authentic leadership is created: self exposure, relating, and making leaderly choices.

On the leakage of personally identifiable information via online social networks

Abstract: For purposes of this paper, we define "Personally identifiable information" (PII) as information which can be used to distinguish or trace an individual's identity either alone or when combined with other information that is linkable to a specific individual. The popularity of Online Social Networks (OSN) has accelerated the appearance of vast amounts of personal information on the Internet. Our research shows that it is possible for third-parties to link PII, which is leaked via OSNs, with user actions both within OSN sites and elsewhere on non-OSN sites. We refer to this ability to link PII and combine it with other information as "leakage". We have identified multiple ways by which such leakage occurs and discuss measures to prevent it.

Coordination with a Backup Supplier Through Buy-Back Contract Under Supply Disruption

Abstract: This paper studies a buy-back contract between a buyer and a backup supplier when the buyer’s main supplier experiences disruptions. The expected profit functions and the optimal decisions of the contract players are derived through a sequential optimization process. The common properties of the contract as well as the differences under the demand uncertainty and the main supplier’s recurrent supply uncertainty are explored through comparative studies and numerical examples. The study contributes to the literature by providing a better understanding of the impacts of demand and supply uncertainties and by shedding insights on the value of a backup supply.

Computer aided fixture design: Recent research and trends

Abstract: Widely used in manufacturing, fixtures have a direct impact upon product manufacturing quality, productivity and cost, so much attention has already been paid to the research of computer aided fixture design (CAFD) and many achievements in this field have been reported. In this paper, a literature survey of computer aided fixture design and automation over the past decade is proposed. First, an introduction is given on the fixture applications in industry. Then, significant works done in the CAFD field, including their approaches, requirements and working principles are discussed. Finally, some prospective research trends are also discussed.

Recognizing engagement in human-robot interaction

Abstract: Based on a study of the engagement process between humans, we have developed and implemented an initial computational model for recognizing engagement between a human and a humanoid robot. Our model contains recognizers for four types of connection events involving gesture and speech: directed gaze, mutual facial gaze, conversational adjacency pairs and backchannels. To facilitate integrating and experimenting with our model in a broad range of robot architectures, we have packaged it as a node in the open-source Robot Operating System (ROS) framework. We have conducted a preliminary validation of our computational model and implementation in a simple human-robot pointing game.

Bench to batch: advances in plant cell culture for producing useful products.

Abstract: Despite significant efforts over nearly 30 years, only a few products produced by in vitro plant cultures have been commercialized. Some new advances in culture methods and metabolic biochemistry have improved the useful potential of plant cell cultures. This review will provide references to recent relevant reviews along with a critical analysis of the latest improvements in plant cell culture, co-cultures, and disposable reactors for production of small secondary product molecules, transgenic proteins, and other products. Some case studies for specific products or production systems are used to illustrate principles.

Kinetics of the Hydrogen Electrode Reaction

Abstract: It is well recognized that the standard Butler–Volmer equation is lacking in an adequate description of the kinetics of the hydrogen electrode reaction over the complete range of potentials for the alkaline as well as the acid electrolytes. Further, it is unable to explain the asymmetry in current vs potential observed in the hydrogen evolution reaction HER vs the hydrogen oxidation reaction HOR. In fact, even kinetic descriptions via two-step mechanisms Volmer–Heyrovsky, Volmer–Tafel, or Heyrovsky– Tafel are individually applicable only in limited potential ranges. We present an approach that provides explicit rate expressions involving kinetics of all the three steps Tafel–Volmer–Heyrovsky simultaneously, as well as more limiting rate expressions based on two-step pathways. The analysis is based on our recently developed graph–theoretic approach that provides accurate rate laws by exploiting the electrical analogy of the reaction network. The accuracy of the resulting rate expressions, as well as their asymmetric potential dependence, for both HOR and HER is illustrated here based on step kinetics provided in the literature for Pt catalyst in 0.5 M NaOH solution.

Myosin XI Is Essential for Tip Growth in Physcomitrella patens

Abstract: Class XI myosins are plant specific and responsible for cytoplasmic streaming. Because of the large number of myosin XI genes in angiosperms, it has been difficult to determine their precise role, particularly with respect to tip growth. The moss Physcomitrella patens provides an ideal system to study myosin XI function. P. patens has only two myosin XI genes, and these genes encode proteins that are 94% identical to each other. To determine their role in tip growth, we used RNA interference to specifically silence each myosin XI gene using 5' untranslated region sequences. We discovered that the two myosin XI genes are functionally redundant, since silencing of either gene does not affect growth or polarity. However, simultaneous silencing of both myosin XIs results in severely stunted plants composed of small rounded cells. Although similar to the phenotype resulting from silencing of other actin-associated proteins, we show that this phenotype is not due to altered actin dynamics. Consistent with a role in tip growth, we show that a functional, full-length fusion of monomeric enhanced green fluorescent protein (mEGFP) to myosin XI accumulates at a subcortical, apical region of actively growing protonemal cells.

Bioethanol and biodiesel: alternative liquid fuels for future generations.

Abstract: The global population is expected to increase by approximately 3 billion people by 2050. With this increase in population, industry, transportation the cost of fossil fuels will grow dramatically. New technologies are needed for fuel extraction using feedstocks that do not threaten food security, cause minimal or no loss of natural habitat and soil carbon. At the same time, waste management has to be improved and environmental pollution should be minimized or eliminated. Liquid biofuels such as lignocellulosic-based ethanol from plant biomass and algal-based biodiesel are sustainable, alternative biofuels that could stabilize national security and provide clean energy for future generations. Ideally, the technology should also foster recycling of agricultural feedstocks and improve soil fertility and human health. This article provides updated information on the energy potential and breadth of liquid biofuel biotechnology.

The margrave tool for firewall analysis

Abstract: Writing and maintaining firewall configurations can be challenging, even for experienced system administrators. Tools that uncover the consequences of configurations and edits to them can help sysadmins prevent subtle yet serious errors. Our tool, Margrave, offers powerful features for firewall analysis, including enumerating consequences of configuration edits, detecting overlaps and conflicts among rules, tracing firewall behavior to specific rules, and verification against security goals. Margrave differs from other firewall-analysis tools in supporting queries at multiple levels (rules, filters, firewalls, and networks of firewalls), comparing separate firewalls in a single query, supporting reflexive ACLs, and presenting exhaustive sets of concrete scenarios that embody queries. Margrave supports real-world firewall-configuration languages, decomposing them into multiple policies that capture different aspects of firewall functionality. We present evaluation on networking-forum posts and on an in-use enterprise firewall-configuration.

Latency can kill: precision and deadline in online games

Abstract: The growth in network capacities and availability has been accompanied by a proliferation of online games. While online games perform well under many network conditions, Internet delays can often degrade online game performance. The precise impact that latency has on online gameplay depends upon the game type and the actions within the game. While the effects of latency on specific games has been studied, knowledge about the effects of latency on classes of games and about the effects of latency on different player actions is lacking. This paper presents a broad, perspective-based classification of games based on player control and camera view. The foundation of the game classification are player actions, each of which is defined by its precision and deadline requirements. Experiments with controlled amount of precision, deadline and latency support the classification. This classification of games should prove useful for game designers, network engineers and game players themselves as they build and play on tomorrow's networks.

Distinct functional roles of homologous Cu+ efflux ATPases in Pseudomonas aeruginosa

Abstract: In bacteria, most Cu(+) -ATPases confer tolerance to Cu by driving cytoplasmic metal efflux. However, many bacterial genomes contain several genes coding for these enzymes suggesting alternative roles. Pseudomonas aeruginosa has two structurally similar Cu(+) -ATPases, CopA1 and CopA2. Both proteins are essential for virulence. Expressed in response to high Cu, CopA1 maintains the cellular Cu quota and provides tolerance to this metal. CopA2 belongs to a subgroup of ATPases that are expressed in association with cytochrome oxidase subunits. Mutation of copA2 has no effect on Cu toxicity nor intracellular Cu levels; but it leads to higher H(2) O(2) sensitivity and reduced cytochrome oxidase activity. Mutation of both genes does not exacerbate the phenotypes produced by single-gene mutations. CopA1 does not complement the copA2 mutant strain and vice versa, even when promoter regions are exchanged. CopA1 but not CopA2 complements an Escherichia coli strain lacking the endogenous CopA. Nevertheless, transport assays show that both enzymes catalyse cytoplasmic Cu(+) efflux into the periplasm, albeit CopA2 at a significantly lower rate. We hypothesize that their distinct cellular functions could be based on the intrinsic differences in transport kinetic or the likely requirement of periplasmic partner Cu-chaperone proteins specific for each Cu(+) -ATPase.

Comparing knowledge tracing and performance factor analysis by using multiple model fitting procedures

Abstract: Student modeling is very important for ITS due to its ability to make inferences about latent student attributes. Although knowledge tracing (KT) is a well-established technique, the approach used to fit the model is still a major issue as different model-fitting approaches lead to different parameter estimates. Performance Factor Analysis, a competing approach, predicts student performance based on the item difficulty and student historical performances. In this study, we compared these two models in terms of their predictive accuracy and parameter plausibility. For the knowledge tracing model, we also examined different model fitting algorithms: Expectation Maximization (EM) and Brute Force (BF). Our results showed that KT+EM is better than KT+BF and comparable with PFA in predictive accuracy. We also examined whether the models' estimated parameter values were plausible. We found that by tweaking PFA, we were able to obtain more plausible parameters than with KT.

Magnetic nanoparticle enhanced surface plasmon resonance sensing and its application for the ultrasensitive detection of magnetic nanoparticle-enriched small molecules.

Abstract: Magnetic nanoparticles (MNPs) have been frequently used in bioseparation, but their applicability in bioassays is limited due to their extremely small size so that sensitive detection is difficult to achieve using a general technique. Here, we present an amplification technique using MNPs for an enhanced surface plasmon resonance (SPR) bioassay. The amplification effect of carboxyl group modified Fe3O4 MNPs of two sizes on SPR spectroscopy is first demonstrated by assembling MNPs on amino group modified SPR gold substrate. To further evaluate the feasibility of the use of Fe3O4 MNPs in enhancing a SPR bioassay, a novel SPR sensor based on an indirect competitive inhibition assay (ICIA) is developed for detecting adenosine by employing Fe3O4 MNP−antiadenosine aptamer conjugates as the amplification reagent. The results confirm that Fe3O4 MNPs can be used as a powerful amplification agent to provide a sensitive approach to detect adenosine by SPR within the range of 10−10 000 nM, which is much superior to t...