Showing papers by "Worcester Polytechnic Institute published in 2009"
01 Oct 2009
TL;DR: This paper reviewed the history and current trends in the field of EDM and discussed trends and shifts in the research conducted by this community, and discussed the increased emphasis on prediction, the emergence of work using existing models to make scientific discoveries, and the reduction in the frequency of relationship mining within the EDM community.
Abstract: We review the history and current trends in the field of Educational Data Mining (EDM). We consider the methodological profile of research in the early years of EDM, compared to in 2008 and 2009, and discuss trends and shifts in the research conducted by this community. In particular, we discuss the increased emphasis on prediction, the emergence of work using existing models to make scientific discoveries ("discovery with models"), and the reduction in the frequency of relationship mining within the EDM community. We discuss two ways that researchers have attempted to categorize the diversity of research in educational data mining research, and review the types of research problems that these methods have been used to address. The most cited papers in EDM between 1995 and 2005 are listed, and their influence on the EDM community (and beyond the EDM community) is discussed.
1,217 citations
13 Jul 2009
TL;DR: Wang et al. as discussed by the authors proposed an effective and flexible distributed scheme with two salient features, opposing to its predecessors, by utilizing the homomorphic token with distributed verification of erasure-coded data, achieving the integration of storage correctness insurance and data error localization, i.e., the identification of misbehaving server(s).
Abstract: Cloud Computing has been envisioned as the next-generation architecture of IT Enterprise. In contrast to traditional solutions, where the IT services are under proper physical, logical and personnel controls, Cloud Computing moves the application software and databases to the large data centers, where the management of the data and services may not be fully trustworthy. This unique attribute, however, poses many new security challenges which have not been well understood. In this article, we focus on cloud data storage security, which has always been an important aspect of quality of service. To ensure the correctness of users' data in the cloud, we propose an effective and flexible distributed scheme with two salient features, opposing to its predecessors. By utilizing the homomorphic token with distributed verification of erasure-coded data, our scheme achieves the integration of storage correctness insurance and data error localization, i.e., the identification of misbehaving server(s). Unlike most prior works, the new scheme further supports secure and efficient dynamic operations on data blocks, including: data update, delete and append. Extensive security and performance analysis shows that the proposed scheme is highly efficient and resilient against Byzantine failure, malicious data modification attack, and even server colluding attacks.
799 citations
21 Sep 2009
TL;DR: Wang et al. as discussed by the authors considered the task of allowing a third party auditor (TPA), on behalf of the cloud client, to verify the integrity of the dynamic data stored in the cloud.
Abstract: Cloud Computing has been envisioned as the next-generation architecture of IT Enterprise. It moves the application software and databases to the centralized large data centers, where the management of the data and services may not be fully trustworthy. This unique paradigm brings about many new security challenges, which have not been well understood. This work studies the problem of ensuring the integrity of data storage in Cloud Computing. In particular, we consider the task of allowing a third party auditor (TPA), on behalf of the cloud client, to verify the integrity of the dynamic data stored in the cloud. The introduction of TPA eliminates the involvement of client through the auditing of whether his data stored in the cloud is indeed intact, which can be important in achieving economies of scale for Cloud Computing. The support for data dynamics via the most general forms of data operation, such as block modification, insertion and deletion, is also a significant step toward practicality, since services in Cloud Computing are not limited to archive or backup data only. While prior works on ensuring remote data integrity often lacks the support of either public verifiability or dynamic data operations, this paper achieves both. We first identify the difficulties and potential security problems of direct extensions with fully dynamic data updates from prior works and then show how to construct an elegant verification scheme for seamless integration of these two salient features in our protocol design. In particular, to achieve efficient data dynamics, we improve the Proof of Retrievability model [1] by manipulating the classic Merkle Hash Tree (MHT) construction for block tag authentication. Extensive security and performance analysis show that the proposed scheme is highly efficient and provably secure.
769 citations
TL;DR: The current paper develops an additive efficiency decomposition approach wherein the overall efficiency is expressed as a (weighted) sum of the efficiencies of the individual stages and can be applied under both CRS and variable returns to scale (VRS) assumptions.
563 citations
17 Aug 2009
TL;DR: This 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 else-where on non-OSN sites.
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 else-where 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.
389 citations
TL;DR: In this paper, the impact of supply disruption risks on the choice between the famous single and dual sourcing methods in a two-stage supply chain with a non-stationary and price-sensitive demand is evaluated.
Abstract: The focus of this paper is placed on evaluating the impacts of supply disruption risks on the choice between the famous single and dual sourcing methods in a two-stage supply chain with a non-stationary and price-sensitive demand. The expected profit functions of the two sourcing modes in the presence of supply chain disruption risks are first obtained, and then compared so that the critical values of the key factors affecting the final choice are identified. Finally, the sensitivity of the buyer's expected profit to various input factors is examined through numerical examples, which provide guidelines for how to use each sourcing method.
369 citations
TL;DR: In this article, the authors identify four processes that are part of arts-based methods in organizational development and change and identify four steps that are involved in each of these four processes.
Abstract: With the rising use of arts-based methods in organizational development and change, scholars have started to inquire into how and why these methods work. We identify four processes that are particu...
337 citations
20 Apr 2009
TL;DR: This paper reports on a longitudinal study consisting of multiple snapshots of an examination of the diffusion of private information for users as they visit various Web sites triggering data gathering aggregation by third parties.
Abstract: For the last few years we have been studying the diffusion of private information for users as they visit various Web sites triggering data gathering aggregation by third parties. This paper reports on our longitudinal study consisting of multiple snapshots of our examination of such diffusion over four years. We examine the various technical ways by which third-party aggregators acquire data and the depth of user-related information acquired. We study techniques for protecting privacy diffusion as well as limitations of such techniques. We introduce the concept of secondary privacy damage. Our results show increasing aggregation of user-related data by a steadily decreasing number of entities. A handful of companies are able to track users' movement across almost all of the popular Web sites. Virtually all the protection techniques have significant limitations highlighting the seriousness of the problem and the need for alternate solutions.
308 citations
TL;DR: There are distinct advantages to using closed systems, but technical challenges still remain, and development of a more controllable, economical, and efficient closed culturing system is needed.
Abstract: Cultivating and harvesting of products from microalgae has led to increasing commercial interest in their use for producing valuable substances for food, feed, cosmetics, pharmaceuticals, and biodiesel, as well as for mitigation of pollution and rising CO2 in the environment This review outlines different bioreactors and their current status, and points out their advantages and disadvantages Compared with open-air systems, there are distinct advantages to using closed systems, but technical challenges still remain In view of potential applications, development of a more controllable, economical, and efficient closed culturing system is needed Further developments still depend on continued research in the design of photobioreactors and break-throughs in microalgal culturing technologies
305 citations
TL;DR: With increasing research on system integration for image‐guided therapy (IGT), there has been a strong demand for standardized communication among devices and software to share data such as target positions, images and device status.
Abstract: Background With increasing research on system integration for imageguided therapy (IGT), there has been a strong demand for standardized communication among devices and software to share data such as target positions, images and device status.
301 citations
TL;DR: The results show that the ASSISTment system can do a reliably better job predicting student end-of-year exam scores by leveraging the interaction data, and the model based on only the interaction information makes better predictions than the traditional assessment model that uses only information about correctness on the test items.
Abstract: Secondary teachers across the United States are being asked to use formative assessment data (Black and Wiliam 1998a,b; Roediger and Karpicke 2006) to inform their classroom instruction. At the same time, critics of US government's No Child Left Behind legislation are calling the bill "No Child Left Untested". Among other things, critics point out that every hour spent assessing students is an hour lost from instruction. But, does it have to be? What if we better integrated assessment into classroom instruction and allowed students to learn during the test? We developed an approach that provides immediate tutoring on practice assessment items that students cannot solve on their own. Our hypothesis is that we can achieve more accurate assessment by not only using data on whether students get test items right or wrong, but by also using data on the effort required for students to solve a test item with instructional assistance. We have integrated assistance and assessment in the ASSISTment system. The system helps teachers make better use of their time by offering instruction to students while providing a more detailed evaluation of student abilities to the teachers, which is impossible under current approaches. Our approach for assessing student math proficiency is to use data that our system collects through its interactions with students to estimate their performance on an end-of-year high stakes state test. Our results show that we can do a reliably better job predicting student end-of-year exam scores by leveraging the interaction data, and the model based on only the interaction information makes better predictions than the traditional assessment model that uses only information about correctness on the test items.
TL;DR: Results for compressible gas-water systems show that the new method can simulate interface dynamics accurately, including the effect of surface tension, and can be used for simulations of fluid interface with large density differences.
TL;DR: A new computational approach was proposed to calculate the total number of Pb and Se atoms in different sized particles, which played a key role on the accurate determination of the strongly size-dependent extinction coefficient.
Abstract: Atomic compositions and molar extinction coefficients of PbSe semiconductor nanocrystals were determined by atomic absorption spectrometry, UV−vis−NIR spectrophotometry, and transmission electron microscopy. The Pb/Se atomic ratio was found to be size-dependent with a systematic excess of Pb atoms in the PbSe nanocrystal system. Experimental results indicated that the individual PbSe nanocrystal was nonstoichiometric, consisting of a PbSe core and an extra layer of Pb atoms. For these nonstoichiometric PbSe semiconductor nanocrystals, we proposed a new computational approach to calculate the total number of Pb and Se atoms in different sized particles. This calculation played a key role on the accurate determination of the strongly size-dependent extinction coefficient, which followed a power law with an exponent of ∼2.5.
TL;DR: Plaques with prior ruptures are associated with higher critical stress conditions, both at ulcer sites and when compared with nonruptured plaques, and plaque stress analysis may provide additional stress indicators helpful for image-based plaque vulnerability assessment.
Abstract: Background and Purpose— It has been hypothesized that high structural stress in atherosclerotic plaques at critical sites may contribute to plaque disruption. To test that hypothesis, 3D fluid-structure interaction models were constructed based on in vivo MRI data of human atherosclerotic carotid plaques to assess structural stress behaviors of plaques with and without rupture. Methods— In vivo MRI data of carotid plaques from 12 patients scheduled for endarterectomy were acquired for model reconstruction. Histology confirmed that 5 of the 12 plaques had rupture. Plaque wall stress (PWS) and flow maximum shear stress were extracted from all nodal points on the lumen surface of each plaque for analysis. A critical PWS (maximum of PWS values from all possible vulnerable sites) was determined for each plaque. Results— Mean PWS from all ulcer nodes in ruptured plaques was 86% higher than that from all nonulcer nodes (123.0 versus 66.3 kPa, P<0.0001). Mean flow maximum shear stress from all ulcer nodes in rupt...
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Abstract: While the use of internal, external, and both types of environmental audits are becoming more pervasive in society, little is known about the stakeholder influences associated with their use, in large part because previous research has viewed them as a uniform type of management practice. This study draws on stakeholder theory to explore organizations' use of different types of environmental audits. It uses international manufacturing data to show that significant variations in the use of environmental audits are associated with differences in stakeholder influences, and that a more nuanced treatment is needed when evaluating these audits.
TL;DR: In this paper, a liquid piston is proposed to improve the efficiency of gas compression and expansion, which can also be used as a medium to carry heat into and out of the compression chamber.
TL;DR: The effective thermal conductivity of the anisotropic MWCNTs increased smoothly with increasing temperature and is indicative of the one-dimensional nature of the heat flow.
Abstract: We present a study of the specific heat and effective thermal conductivity in anisotropic and randomly oriented multi-wall carbon nanotube (MWCNT) and randomly oriented single-wall carbon nanotube (SWCNT) composites from 300 to 400 K Measurements on randomly oriented MWCNTs and SWCNTs were made by depositing a thin film of CNTs within a calorimetric cell Anisotropic measurements were made on MWCNTs grown inside the highly ordered, densely packed nanochannels of anodic aluminum oxide The specific heat of randomly oriented MWCNTs and SWCNTs showed similar behavior to the specific heat of bulk graphite powder However, the specific heat of aligned MWCNTs is smaller and has weaker temperature dependence than that of the bulk above room temperature The effective thermal conductivity of randomly oriented MWCNTs and SWCNTs is similar to that of powder graphite, exhibiting a maximum value near 364 K indicating the onset of phonon-phonon scattering The effective thermal conductivity of the anisotropic MWCNTs increased smoothly with increasing temperature and is indicative of the one-dimensional nature of the heat flow
TL;DR: Relations and equivalence between two existing DEA approaches that address measuring the performance of two-stage processes are examined.
TL;DR: Exocytosis emerges as a prime candidate for the initiation and regulation of oscillatory pollen tube growth and the anticipatory increase in wall material predicts, to a high degree, the rate and extent of the subsequent growth surge.
Abstract: We examined exocytosis during oscillatory growth in lily (Lilium formosanum and Lilium longiflorum) and tobacco (Nicotiana tabacum) pollen tubes using three markers: (1) changes in cell wall thickness by Nomarski differential interference contrast (DIC), (2) changes in apical cell wall fluorescence in cells stained with propidium iodide (PI), and (3) changes in apical wall fluorescence in cells expressing tobacco pectin methyl esterase fused to green fluorescent protein (PME-GFP). Using PI fluorescence, we quantified oscillatory changes in the amount of wall material from both lily and tobacco pollen tubes. Measurement of wall thickness by DIC was only possible with lily due to limitations of microscope resolution. PME-GFP, a direct marker for exocytosis, only provides information in tobacco because its expression in lily causes growth inhibition and cell death. We show that exocytosis in pollen tubes oscillates and leads the increase in growth rate; the mean phase difference between exocytosis and growth is –98° ± 3° in lily and –124° ± 4° in tobacco. Statistical analyses reveal that the anticipatory increase in wall material predicts, to a high degree, the rate and extent of the subsequent growth surge. Exocytosis emerges as a prime candidate for the initiation and regulation of oscillatory pollen tube growth.
TL;DR: In this article, the authors proposed a heat-mining method for asphalt pavements, using an appropriate fluid flowing in pipes installed within the pavement, to reduce pavement and near-surface air temperature.
Abstract: A rise in temperature of asphalt pavements contributes towards the urban heat island effect, causes problems with air quality and increases the power requirement for cooling buildings. A high temperature would also lead to the potential of rutting failure in asphalt pavements. The concept of mining heat from asphalt pavements, utilising an appropriate fluid flowing in pipes installed within the pavement, has been proposed. Theoretical considerations and results of laboratory testing and modelling simulation have been presented. The results indicate that the concept is feasible, and that the efficiency of heat mining can be improved by selecting appropriate surface layer and aggregates for pavement materials. The use of this proposed method would lead to a significant reduction in pavement and near-surface air temperature, and extension of asphalt pavement life.
TL;DR: It is shown that when the model is feasible, the approach yields super-efficiency scores that are equivalent to those arising from the original model, and the newly developed approach is illustrated with two real world data sets.
Abstract: The super-efficiency data envelopment analysis (DEA) model is obtained when a decision making unit (DMU) under evaluation is excluded from the reference set. This model provides for a measure of stability of the “efficient” status for frontier DMUs. Under the assumption of variable returns to scale (VRS), the super efficiency model can be infeasible for some efficient DMUs, specifically those at the extremities of the frontier. The current study develops an approach to overcome infeasibility issues. It is shown that when the model is feasible, our approach yields super-efficiency scores that are equivalent to those arising from the original model. For efficient DMUs that are infeasible under the super-efficiency model, our approach yields optimal solutions and scores that characterize the extent of super-efficiency in both inputs and outputs. The newly developed approach is illustrated with two real world data sets.
TL;DR: In this article, the feasibility of using 100% RAP HMA as a base course with warm-mix asphalt (WMA) additives (Sasobit H8 or Advera zeolite) at a lower temperature (125°C) was investigated.
Abstract: The soaring cost of liquid asphalt binder and anticipated stricter environmental regulations have driven highway agencies to maximize the amount of reclaimed asphalt pavement (RAP) used for pavement construction. However, because of already aged and stiffened asphalt binder in RAP, the use of high percentages of RAP in hot-mix asphalt (HMA) presents many challenges. Problems with workability and compactability during construction need to be resolved first. This study investigated the feasibility of using 100% RAP HMA as a base course with warm-mix asphalt (WMA) additives (Sasobit H8 or Advera zeolite) at a lower temperature (125°C). Mix samples (control set with 100% RAP; a set with 100% RAP plus Sasobit H8 at 1.5%, 2.0%, and 5.0%; and a set with 100% RAP plus Advera zeolite at 0.3%, 0.5%, and 0.7%) were compacted with 50 gyrations. Their workability, bulk specific gravity, indirect tensile strength at 0°C, and moduli at 0°C, 26.7°C, and 50°C were determined. The effects of different amounts of WMA additi...
TL;DR: The implications of this study are that it may be worth the cost and effort to give Web-based homework when students have access to the needed equipment, such as in schools that have implemented one-to-one computing programs.
Abstract: This study compared learning for fifth grade students in two math homework conditions. The paper-and-pencil condition represented traditional homework, with review of problems in class the following day. The Web-based homework condition provided immediate feedback in the form of hints on demand and step-by-step scaffolding. We analyzed the results for students who completed both the paper-and-pencil and the Web-based conditions. In this group of 28 students, students learned significantly more when given computer feedback than when doing traditional paper-and-pencil homework, with an effect size of .61. The implications of this study are that, given the large effect size, it may be worth the cost and effort to give Web-based homework when students have access to the needed equipment, such as in schools that have implemented one-to-one computing programs.
TL;DR: A moment closure method for stochastically modeled chemical or biochemical reaction networks that derives the dynamics of means and all central moments from a chemical master equation and estimates the errors in the means and central moments generated by the approximation method.
Abstract: In this paper we present a moment closure method for stochastically modeled chemical or biochemical reaction networks. We derive a system of differential equations which describes the dynamics of means and all central moments from a chemical master equation. Truncating the system for the central moments at a certain moment term and using Taylor approximation, we obtain explicit representations of means and covariances and even higher central moments in recursive forms. This enables us to deal with the moments in successive differential equations and use conventional numerical methods for their approximations. Furthermore, we estimate the errors in the means and central moments generated by the approximation method. We also find the moments at equilibrium by solving truncated algebraic equations. We show in examples that numerical solutions based on the moment closure method are accurate and efficient by comparing the results to those of stochastic simulation algorithms.
TL;DR: This paper proposes two protocols, GREES-L andGREES-M, which combine geographic routing and energy efficient routing techniques and take into account the realistic lossy wireless channel condition and the renewal capability of environmental energy supply when making routing decisions.
Abstract: Wireless sensor networks are characterized by multihop wireless lossy links and resource constrained nodes. Energy efficiency is a major concern in such networks. In this paper, we study Geographic Routing with Environmental Energy Supply (GREES) and propose two protocols, GREES-L and GREES-M, which combine geographic routing and energy efficient routing techniques and take into account the realistic lossy wireless channel condition and the renewal capability of environmental energy supply when making routing decisions. Simulation results show that GREESs are more energy efficient than the corresponding residual energy based protocols and geographic routing protocols without energy awareness. GREESs can maintain higher mean residual energy on nodes, and achieve better load balancing in terms of having smaller standard deviation of residual energy on nodes. Both GREES-L and GREES-M exhibit graceful degradation on end-to-end delay, but do not compromise the end-to-end throughput performance.
24 Mar 2009
TL;DR: This work develops the first solution for incremental detection of neighbor-based patterns specific to sliding window scenarios, exploiting the "predictability" property of sliding windows to elegantly discount the effect of expiring objects on the remaining pattern structures.
Abstract: The discovery of complex patterns such as clusters, outliers, and associations from huge volumes of streaming data has been recognized as critical for many domains. However, pattern detection with sliding window semantics, as required by applications ranging from stock market analysis to moving object tracking remains largely unexplored. Applying static pattern detection algorithms from scratch to every window is prohibitively expensive due to their high algorithmic complexity. This work tackles this problem by developing the first solution for incremental detection of neighbor-based patterns specific to sliding window scenarios. The specific pattern types covered in this work include density-based clusters and distance-based outliers. Incremental pattern computation in highly dynamic streaming environments is challenging, because purging a large amount of to-be-expired data from previously formed patterns may cause complex pattern changes including migration, splitting, merging and termination of these patterns. Previous incremental neighbor-based pattern detection algorithms, which were typically not designed to handle sliding windows, such as incremental DBSCAN, are not able to solve this problem efficiently in terms of both CPU and memory consumption. To overcome this, we exploit the "predictability" property of sliding windows to elegantly discount the effect of expiring objects on the remaining pattern structures. Our solution achieves minimal CPU utilization, while still keeping the memory utilization linear in the number of objects in the window. Our comprehensive experimental study, using both synthetic as well as real data from domains of stock trades and moving object monitoring, demonstrates superiority of our proposed strategies over alternate methods in both CPU and memory utilization.
TL;DR: Results confirm that aptamer-Au NPs conjugates is a powerful sandwich element and an excellent amplification reagent for SPR-based sandwich immunoassay.
TL;DR: A detailed study of a pentylcyanobiphenyl liquid crystal and a CdS QD colloidal dispersion by probing the dielectric property epsilon and relaxation as a function of an applied ac electric field Eac suggests that the arrangement of the QDs is mediated by the LC.
Abstract: Assembling quantum dots (QDs) into nanoscale configurations over macroscopic dimensions is an important goal to realizing their electro-optical potential. In this Rapid Communication, we present a detailed study of a pentylcyanobiphenyl liquid crystal (LC) and a CdS QD colloidal dispersion by probing the dielectric property epsilon and relaxation as a function of an applied ac electric field Eac. In principle, dispersing QDs in a nematic LC medium can direct the dots to align in nearly one-dimensional chainlike structures along the nematic director and these assemblies of QDs can be directed by external electric fields. In a uniform planar aligned cell, the Freedericksz switching of the LC+QDs appears as a two-step process with the same initial switching field as the bulk but with the final epsilon value larger than that for an aligned bulk LC. The relaxation of epsilon immediately following the removal of Eac follows a single-exponential decay to its original value that is slower than the bulk but becomes progressively faster with increasing Eac, eventually saturating. These results suggest that the arrangement of the QDs is mediated by the LC.
TL;DR: It was demonstrated that the as-prepared SnO nanoflowers could be utilized as good anode materials for lithium ion rechargeable batteries with a high capacity of around 800 mA h g(-1), close to the theoretical value.
Abstract: A facile and reproducible approach was reported to synthesize nanoparticle-attached SnO nanoflowers via decomposition of an intermediate product Sn6O4(OH)4. Sn6O4(OH)4 formed after introducing water into the traditional nonaqueous reaction, and then decomposed to SnO nanoflowers with the help of free metal cations, such as Sn2+, Fe2+, and Mn2+. This free cation-induced formation process was found independent of the nature of the surface ligand. It was demonstrated further that the as-prepared SnO nanoflowers could be utilized as good anode materials for lithium ion rechargeable batteries with a high capacity of around 800 mA h g−1, close to the theoretical value (875 mA h g−1).
TL;DR: Measurements of the material strength limits for human atherosclerotic carotid artery sections containing type II and III lesions could be useful in improving computational models that assess plaque vulnerability.