Showing papers by "Worcester Polytechnic Institute published in 2006"

Latency and player actions in online games

Abstract: Latency determines not only how players experience online gameplay but also how to design the games to mitigate its effects and meet player expectations.

DEA models for supply chain efficiency evaluation

Abstract: An appropriate performance measurement system is an important requirement for the effective management of a supply chain. Two hurdles are present in measuring the performance of a supply chain and its members. One is the existence of multiple measures that characterize the performance of chain members, and for which data must be acquired; the other is the existence of conflicts between the members of the chain with respect to specific measures. Conventional data envelopment analysis (DEA) cannot be employed directly to measure the performance of supply chain and its members, because of the existence of the intermediate measures connecting the supply chain members. In this paper it is shown that a supply chain can be deemed as efficient while its members may be inefficient in DEA-terms. The current study develops several DEA-based approaches for characterizing and measuring supply chain efficiency when intermediate measures are incorporated into the performance evaluation. The models are illustrated in a seller-buyer supply chain context, when the relationship between the seller and buyer is treated first as one of leader-follower, and second as one that is cooperative. In the leader-follower structure, the leader is first evaluated, and then the follower is evaluated using information related to the leader's efficiency. In the cooperative structure, the joint efficiency which is modelled as the average of the seller's and buyer's efficiency scores is maximized, and both supply chain members are evaluated simultaneously. Non-linear programming problems are developed to solve these new supply chain efficiency models. It is shown that these DEA-based non-linear programs can be treated as parametric linear programming problems, and best solutions can be obtained via a heuristic technique. The approaches are demonstrated with a numerical example.

Location-based compromise-tolerant security mechanisms for wireless sensor networks

Abstract: Node compromise is a serious threat to wireless sensor networks deployed in unattended and hostile environments. To mitigate the impact of compromised nodes, we propose a suite of location-based compromise-tolerant security mechanisms. Based on a new cryptographic concept called pairing, we propose the notion of location-based keys (LBKs) by binding private keys of individual nodes to both their IDs and geographic locations. We then develop an LBK-based neighborhood authentication scheme to localize the impact of compromised nodes to their vicinity. We also present efficient approaches to establish a shared key between any two network nodes. In contrast to previous key establishment solutions, our approaches feature nearly perfect resilience to node compromise, low communication and computation overhead, low memory requirements, and high network scalability. Moreover, we demonstrate the efficacy of LBKs in counteracting several notorious attacks against sensor networks such as the Sybil attack, the identity replication attack, and wormhole and sinkhole attacks. Finally, we propose a location-based threshold-endorsement scheme, called LTE, to thwart the infamous bogus data injection attack, in which adversaries inject lots of bogus data into the network. The utility of LTE in achieving remarkable energy savings is validated by detailed performance evaluation.

Quantification of dental microwear by tandem scanning confocal microscopy and scale-sensitive fractal analyses.

Abstract: Dental microwear analysis is among the most commonly used approaches to reconstructing the diets of extinct animal species and past peoples. The usual procedure involves imaging tooth wear surfaces by scanning electron microscopy (SEM). Surfaces are characterized quantitatively by measurement of individual wear features (pits and scratches) on photomicrographs. Recent studies of living animals have shown associations between diets on one hand and patterns of dental microwear on the other. Furthermore, patterns on fossil teeth have been used to reconstruct diets in extinct forms. However, conventional methods for microwear analysis are limited. Scanning electron microscopy does not provide a true representation of these surfaces in three dimensions, and identification and measurement of individual features is time consuming, subjective, and subject to high interobserver error. This paper describes a new approach to the analysis of dental microwear using tandem scanning confocal microscopy and scale-sensitive fractal analyses. The instrument used in this study provides three-dimensional coordinates representing surfaces at a resolution equivalent to that employed by most SEM microwear studies. Fractal analyses offer objective, repeatable, quantitative characterization of surfaces. This approach eliminates major sources of error and increases power to resolve differences between species. Moreover, rapid surface characterization will allow examination of large samples to assess within species variation and to make finer distinctions between species.

Integrated computational materials engineering: A new paradigm for the global materials profession

Abstract: Integrated computational materials engineering is a field of study whose time has come. It promises to link manufacturing and design via advanced materials models in a seamless, integrated computational environment. The feasibility of ICME and its benefits have been demonstrated by several projects that have developed methods which are in use in the aerospace and automotive industries. To fully realize the potential of ICME, anumber of technical, cultural, and organizational challenges have been identified and must be overcome.

MASK: anonymous on-demand routing in mobile ad hoc networks

Abstract: The shared wireless medium of mobile ad hoc networks facilitates passive, adversarial eavesdropping on data communications whereby adversaries can launch various devastating attacks on the target network. To thwart passive eavesdropping and the resulting attacks, we propose a novel anonymous on-demand routing protocol, termed MASK, which can accomplish both MAC-layer and network-layer communications without disclosing real IDs of the participating nodes under a rather strong adversary model. MASK offers the anonymity of senders, receivers, and sender-receiver relationships in addition to node unlocatability and untrackability and end-to-end flow untraceability. It is also resistant to a wide range of attacks. Moreover, MASK preserves the high routing efficiency as compared to previous proposals. Detailed simulation studies have shown that MASK is highly effective and efficient

Expression profiling of auxin-treated Arabidopsis roots: toward a molecular analysis of lateral root emergence.

Abstract: Treating Arabidopsis roots with exogenous auxin results in dramatic changes in cellular processes including de novo induction of lateral roots which later emerge through the overlying cells. Microarray experiments reveal approximately 80 genes that are substantially up-regulated in the root over the first 12 h following auxin treatment. We hypothesize that the observed increase in expression of pectate lyase family genes leads to degradation of the pectin-rich middle lamellae, allowing cells in the parent root to separate cleanly. Differences in the degree of pectin methylation in lateral and parent roots may explain why lateral roots are not degraded themselves.

Packed Tubular Reactor Modeling and Catalyst Design using Computational Fluid Dynamics

Abstract: Computational fluid dynamics (CFD) is rapidly becoming a standard tool for the analysis of chemically reacting flows. For single-phase reactors, such as stirred tanks and “empty” tubes, it is already well-established. For multiphase reactors such as fixed beds, bubble columns, trickle beds and fluidized beds, its use is relatively new, and methods are still under development. The aim of this chapter is to present the application of CFD to the simulation of three-dimensional interstitial flow in packed tubes, with and without catalytic reaction. Although the use of CFD to simulate such geometrically complex flows is too expensive and impractical currently for routine design and control of fixed-bed reactors, the real contribution of CFD in this area is to provide a more fundamental understanding of the transport and reaction phenomena in such reactors. CFD can supply the detailed three-dimensional velocity, species and temperature fields that are needed to improve engineering approaches. In particular, this chapter considers the development of CFD methods for packed tube simulation by finite element or finite volume solution of the governing partial differential equations. It discusses specific implementation problems of special relevance to packed tubes, presents the validation by experiment of CFD results, and reviews recent advances in the field in transport and reaction. Extended discussion is given of two topics: heat transfer in packed tubes and the design of catalyst particles for steam reforming.

Role of cranberry juice on molecular-scale surface characteristics and adhesion behavior of Escherichia coli.

Abstract: Cranberry juice has long been believed to benefit the prevention and treatment of urinary tract infections (UTIs). As the first step in the development of infection, bacterial adhesion is of great research interest, yet few studies have addressed molecular level adhesion in this context. P-fimbriated Escherichia coli play a major role in the development of a serious type of UTI, acute pyelonephritis. Experiments were conducted to investigate the molecular-scale effects of cranberry juice on two E. coli strains: HB101, which has no fimbriae, and the mutant HB101pDC1 which expresses P-fimbriae. Atomic force microscopy (AFM) was used to investigate both bacterial surface characteristics and adhesion forces between a probe surface (silicon nitride) and the bacteria, providing a direct evaluation of bacterial adhesion and interaction forces. Cranberry juice affected bacterial surface polymer and adhesion behavior after a short exposure period (<3 h). Cranberry juice affected the P-fimbriated bacteria by decreasing the adhesion forces between the bacterium and tip and by altering the conformation of the surface macromolecules on E. coli HB101pDC1. The equilibrium length of polymer (P-fimbriae) on this bacterium decreased from approximately 148 to approximately 48 nm upon being exposed to cranberry juice. Highly acidic conditions were not necessary for the prevention of bacterial adhesion, since neutralization of cranberry juice solutions to pH = 7.0 allowed us to observe differences in adhesion between the E. coli strains. Our results demonstrate molecular-level changes in the surfaces of P-fimbriated E. coli upon exposure to neutralized cranberry juice.

LEDS: Providing Location-Aware End-to-End Data Security in Wireless Sensor Networks

Abstract: Providing desirable data security, that is, confidentiality, authenticity, and availability, in wireless sensor networks (WSNs) is challenging, as a WSN usually consists of a large number of resource constraint sensor nodes that are generally deployed in unattended/hostile environments and, hence, are exposed to many types of severe insider attacks due to node compromise. Existing security designs mostly provide a hop-by-hop security paradigm and thus are vulnerable to such attacks. Furthermore, existing security designs are also vulnerable to many types of Denial of Service (DoS) attacks, such as report disruption attacks and selective forwarding attacks and thus put data availability at stake. In this paper, we seek to overcome these vulnerabilities for large-scale static WSNs. We come up with a location-aware end-to-end security framework in which secret keys are bound to geographic locations and each node stores a few keys based on its own location. This location-aware property effectively limits the impact of compromised nodes only to their vicinity without affecting end-to-end data security. The proposed multifunctional key management framework assures both node-to-sink and node-to-node authentication along the report forwarding routes. Moreover, the proposed data delivery approach guarantees efficient en-route bogus data filtering and is highly robust against DoS attacks. The evaluation demonstrates that the proposed design is highly resilient against an increasing number of compromised nodes and effective in energy savings. Index Terms—Data security, wireless sensor network, end-to-end, DoS attack, false-data injection attack.

Experiential Learning Environments: Do They Prepare Our Students to be Self-Directed, Life-Long Learners?

Abstract: Recent research indicates that traditional academic structures may not effectively promote self-directed learning. We investigated whether an experiential interdisciplinary projects program, called the Global Studies Program, increased readiness for self-directed learning (SDL) and life-long learning (LLL) using three methods: a nationally recognized course evaluation system called the Individual Development and Educational Assessment system (IDEA); an internal student project quality assessment protocol; and the Self-Directed Learning Readiness Scale (SDLRS). Student self-assessments through the IDEA system showed Global Studies Program students reported much greater progress in LLL-related skills than did national and local comparison groups. Similarly, review of student projects by independent faculty teams found Global Studies Program students consistently outscored on-campus project students in LLL-related measures by wide margins. The SDLRS also showed a positive, but less emphatic increase in SDL readiness among a Global Studies Program cohort. The research demonstrates the success of one experiential learning environment in promoting SDL/LLL, while raising interesting issues regarding alternative methods of measuring potential benefits.

A wearable reflectance pulse oximeter for remote physiological monitoring.

Abstract: To save life, casualty care requires that trauma injuries are accurately and expeditiously assessed in the field. This paper describes the initial bench testing of a wireless wearable pulse oximeter developed based on a small forehead mounted sensor. The battery operated device employs a lightweight optical reflectance sensor and incorporates an annular photodetector to reduce power consumption. The system also has short range wireless communication capabilities to transfer arterial oxygen saturation (SpO(2)), heart rate (HR), body acceleration, and posture information to a PDA. It has the potential for use in combat casualty care, such as for remote triage, and by first responders, such as firefighters.

Detection and analysis of off-task gaming behavior in intelligent tutoring systems

Abstract: A major issue in Intelligent Tutoring Systems is off-task student behavior, especially performance-based gaming, where students systematically exploit tutor behavior in order to advance through a curriculum quickly and easily, with as little active thought directed at the educational content as possible. The goal of this research was to explore the phenomena of off-task gaming behavior within the Assistments system. Machine-learned gaming-detection models were developed to investigate underlying factors related to gaming, and an analysis of gaming within the Assistments system was conducted to compare some of the findings of prior studies.

Generating a privacy footprint on the internet

Abstract: As a follow up to characterizing traffic deemed as unwanted by Web clients such as advertisements, we examine how information related to individual users is aggregated as a result of browsing seemingly unrelated Web sites. We examine the privacy diffusion on the Internet, hidden transactions, and the potential for a few sites to be able to construct a profile of individual users. We define and generate a privacy footprint allowing us to assess and compare the diffusion of privacy information across a wide variety of sites. We examine the effectiveness of existing and new techniques to reduce this diffusion. Our results show that the size of the privacy footprint is a legitimate cause for concern across the sets of sites that we study.

Critical Casimir force in 4He films: confirmation of finite-size scaling.

Abstract: We present new capacitance measurements of critical Casimir force-induced thinning of 4He films near the superfluid transition, focused on the region below Tlambda where the effect is the greatest. 4He films of 238, 285, and 340 A thickness are adsorbed on atomically smooth, N-doped silicon substrates. The Casimir force scaling function theta, deduced from the thinning of these three films, collapses onto a single universal curve, attaining a minimum theta=-1.30+/-0.03 at x=td1/nu=-9.7+/-0.8 A1/nu. The collapse confirms the finite-size scaling origin of the dip in the film thickness. Separately, we also confirm the presence down to 2.13 K of the Goldstone or surface fluctuation force, which makes the superfluid film approximately 2 A thinner than the normal film.

Single versus multiple sourcing in the presence of risks

Abstract: This paper relies on a decision-tree approach to aid a buying firm in determining the optimal size of its supply base in the presence of risks. The risk under consideration refers to any unpredictable operations interruptions caused by all suppliers being unavailable to satisfy the buying firm's demand. The relationship between the levels of risk and associated trade-offs is captured by a decision-tree model, from which the expected cost function is formulated. The exact or approximate optimal solutions for various scenarios, as well as their sensitivity, are obtained and examined.

Benchmarking with quality-adjusted DEA (Q-DEA) to seek lower-cost high-quality service: Evidence from a U.S.bank application

Abstract: Benchmarking is a widely cited method to identify and adopt best-practices as a means to improve performance. Data envelopment analysis (DEA) has been demonstrated to be a powerful benchmarking methodology for situations where multiple inputs and outputs need to be assessed to identify best-practices and improve productivity in organizations. Most DEA benchmarking studies have excluded quality, even in service-sector applications such as health care where quality is a key element of performance. This limits the practical value of DEA in organizations where maintaining and improving service quality is critical to achieving performance objectives. In this paper, alternative methods incorporating quality in DEA benchmarking are demonstrated and evaluated. It is shown that simply treating the quality measures as DEA outputs does not help in discriminating the performance. Thus, the current study presents a new, more sensitive, quality-adjusted DEA (Q-DEA), which effectively deals with quality measures in benchmarking. We report the results of applying Q-DEA to a U.S. bank's 200-branch network that required a method for benchmarking to help manage operating costs and service quality. Q-DEA findings helped the bank achieve cost savings and improved operations while preserving service quality, a dimension critical to its mission. New insights about ways to improve branch operations based on the best-practice (high-quality low-cost) benchmarks identified with Q-DEA are also described in the paper. This demonstrates the practical need and potential benefits of Q-DEA and its efficacy in one application, and also suggests the need for further research on measuring and incorporating quality into DEA benchmarking.

Extending task technology fit with computer self-efficacy

Abstract: This study is part of a stream of research that has a goal of understanding software utilization choices of users by extending and testing TTF models in a variety of domains using various methods of model estimation. In particular, this study extends a Task-Technology Fit (TTF) model by including the Computer Self-Efficacy (CSE) construct, a strategy of model extension suggested by Berthon et al. (2002). In this study, the domain is the utilization of modeling tools by business students. The TTF models are estimated using PLS. This study finds that CSE, i.e., users' beliefs in their ability to use a technology, in a TTF model increases the explanatory power of the model over one with only task characteristics, technology functionality, and the fit (interaction) between them. CSE has a direct effect on tool utilization, but no significant interaction, i.e., fit, effects.

Wearable vibrotactile systems for virtual contact and information display

Abstract: This paper presents a development history of a wearable, scalable vibrotactile stimulus delivery system. This history has followed a path from desktop-based, fully wired systems, through hybrid approaches consisting of a wireless connection from the host computer to a body-worn control box and wires to each tactor, to a completely wireless system employing Bluetooth technology to connect directly from the host to each individual tactor unit. Applications for such a system include delivering vibrotactile contact cues to users of virtual environments, providing directional cues in order to increase situational awareness in both real and virtual environments, and for general information display in wearable contexts. Through empirical study, we show that even a simple configuration, such as eight tactors arrayed around the torso, can be effective in increasing situational awareness in a building-clearing task, compared to users who perform the same task without the added cues.

Model reduction and coarse-graining approaches for multiscale phenomena

Abstract: Computation of Invariant Manifolds.- A New Model Reduction Method for Nonlinear Dynamical Systems Using Singular PDE Theory.- A Versatile Algorithm for Computing Invariant Manifolds.- Covering an Invariant Manifold with Fat Trajectories.- "Ghost" ILDM-Manifolds and Their Identification.- Dynamic Decomposition of ODE Systems: Application to Modelling of Diesel Fuel Sprays.- Model Reduction of Multiple Time Scale Processes in Non-standard Singularly Perturbed Form.- Coarse-Graining and Ideas of Statistical Physics.- Basic Types of Coarse-Graining.- Renormalization Group Methods for Coarse-Graining of Evolution Equations.- A Stochastic Process Behind Boltzmann's Kinetic Equation and Issues of Coarse Graining.- Finite Difference Patch Dynamics for Advection Homogenization Problems.- Coarse-Graining the Cyclic Lotka-Volterra Model: SSA and Local Maximum Likelihood Estimation.- Relations Between Information Theory, Robustness and Statistical Mechanics of Stochastic Uncertain Systems via Large Deviation Theory.- Kinetics and Model Reduction.- Exactly Reduced Chemical Master Equations.- Model Reduction in Kinetic Theory.- Novel Trajectory Based Concepts for Model and Complexity Reduction in (Bio)Chemical Kinetics.- Dynamics of the Plasma Sheath.- Mesoscale and Multiscale Modeling.- Construction of Stochastic PDEs and Predictive Control of Surface Roughness in Thin Film Deposition.- Lattice Boltzmann Method and Kinetic Theory.- Numerical and Analytical Spatial Coupling of a Lattice Boltzmann Model and a Partial Differential Equation.- Modelling and Control Considerations for Particle Populations in Particulate Processes Within a Multi-Scale Framework.- Diagnostic Goal-Driven Reduction of Multiscale Process Models.- Understanding Macroscopic Heat/Mass Transfer Using Meso- and Macro-Scale Simulations.- An Efficient Optimization Approach for Computationally Expensive Timesteppers Using Tabulation.- A Reduced Input/Output Dynamic Optimisation Method for Macroscopic and Microscopic Systems.

Energy comparison of AES and SHA-1 for ubiquitous computing

Abstract: Wireless sensor networks and Radio Frequency Identifiers are becoming mainstream applications of ubiquitous computing They are slowly being integrated into our infrastructure and therefore must incorporate a certain level of security However, both applications are severely resource constrained Energy scavenger powered sensor nodes and current RFID tags provide only 20 μ W to 50 μ W of power to the digital component of their circuits This makes complex cryptography a luxury In this paper we present a novel ultra-low power SHA-1 design and an energy efficient ultra-low power AES design Both consume less than 30 μ W of power and can therefore be used to provide the basic security services of encryption and authentication Furthermore, we analyze their energy consumption based on the TinySec protocol and come to the somewhat surprising result, that SHA-1 based authentication and encryption is more energy efficient than using AES for payload sizes of 17 bytes or larger

Bacterial activity, community structure, and centimeter-scale spatial heterogeneity in contaminated soil.

Abstract: In an anthropogenically disturbed soil (88% sand, 8% silt, 4% clay), 150-mg samples were studied to examine the fine-scale relationship of bacterial activity and community structure to heavy metal contaminants. The soils had been contaminated for over 40 years with aromatic solvents, Pb, and Cr. Samples from distances of <1, 5, 15, and 50 cm over a depth range of 40–90 cm underwent a sequential analysis to determine metabolic potential (from 14C glucose mineralization), bacterial community structure [using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE)], and total extractable Pb and Cr levels. Metabolic potential varied by as much as 10,000-fold in samples <1 cm apart; log–log plots of metal concentration and microbial metabolic potential showed no correlation with each other. Overall, metal concentrations ranged from 9 to 29,000 mg kg−1 for Pb and from 3 to 8500 mg kg−1 for Cr with small zones of high contamination present. All regions exhibited variable metal concentrations, with some soil samples having 30-fold differences in metal concentration in sites <1 cm apart. Geostatistical analysis revealed a strong spatial dependence for all three parameters tested (metabolic activity, Pb, and Cr levels) with a range up to 30 cm. Kriging maps showed that in zones of high metal, the corresponding metabolic activity was low suggesting that metals negatively impacted the microbial community. PCR-DGGE analysis revealed that diverse communities were present in the soils with a random distribution of phylotypes throughout the sampling zones. These results suggest the presence of spatially isolated microbial communities within the soil profile.

The effects of frame rate and resolution on users playing first person shooter games

Abstract: The rates and resolutions for frames rendered in a computer game directly impact the player performance, influencing both the overall game playability and the game's enjoyability. Insights into the effects of frame rates and resolutions can guide users in their choice for game settings and new hardware purchases, and inform system designers in their development of new hardware, especially for embedded devices that often must make tradeoffs between resolution and frame rate. While there have been studies detailing the effects of frame rate and resolution on streaming video and other multimedia applications, to the best of our knowledge, there have been no studies quantifying the effects of frame rate and resolution on user performance for computer games. This paper presents results of a carefully designed user study that measures the impact of frame rate and frame resolution on user performance in a first person shooter game. Contrary to previous results for streaming video, frame rate has a marked impact on both player performance and game enjoyment while resolution has little impact on performance and some impact on enjoyment.