Showing papers by "Worcester Polytechnic Institute published in 2004"

Measuring Information Technology's Indirect Impact on Firm Performance

Abstract: It has been recognized that the link between information technology (IT) investment and firm performance is indirect due to the effect of mediating and moderating variables. For example, in the banking industry, the IT-value added activity helps to effectively generate funds from the customer in the forms of deposits. Profits then are generated by using deposits as a source of investment funds. Traditional efficiency models, such as data envelopment analysis (DEA), can only measure the efficiency of one specific stage when a two-stage production process is present. We develop an efficiency model that identifies the efficient frontier of a two-stage production process linked by intermediate measures. A set of firms in the banking industry is used to illustrate how the new model can be utilized to (i) characterize the indirect impact of IT on firm performance, (ii) identify the efficient frontier of two principal value-added stages related to IT investment and profit generation, and (iii) highlight those firms that can be further analyzed for best practice benchmarking.

The effects of loss and latency on user performance in unreal tournament 2003

Abstract: The growth in the popularity of interactive network games has increased the importance of a better understanding of the effects of packet loss and latency on user performance. While previous work on network games has studied user tolerance for high latencies and has studied the effects of latency on user performance in real-time strategy games, to the best of our knowledge, there has been no systematic study of the effects of loss and latency on user performance. In this paper we study user performance for Unreal Tournament 2003 (UT2003), a popular first person shooter game, under varying amounts of packet loss and latency. First, we deduced typical real world values of packet loss and latency experienced on the Internet by monitoring numerous operational UT2003 game servers. We then used these deduced values of loss and latency in a controlled networked environment that emulated various conditions of loss and latency, allowing us to monitor UT2003 at the network, application and user levels. We designed maps that isolated the fundamental first person shooter interaction components of movement and shooting, and conducted numerous user studies under controlled network conditions. We find that typical ranges of packet loss have no impact on user performance or on the quality of game play. The levels of latency typical for most UT2003 Internet servers, while sometimes unpleasant, do not significantly affect the outcome of the game. Since most first person shooter games typically consist of generic player actions similar to those that we tested, we believe that these results have broader implications.

Public key cryptography in sensor networks—revisited

Abstract: The common perception of public key cryptography is that it is complex, slow and power hungry, and as such not at all suitable for use in ultra-low power environments like wireless sensor networks. It is therefore common practice to emulate the asymmetry of traditional public key based cryptographic services through a set of protocols [1] using symmetric key based message authentication codes (MACs). Although the low computational complexity of MACs is advantageous, the protocol layer requires time synchronization between devices on the network and a significant amount of overhead for communication and temporary storage. The requirement for a general purpose CPU to implement these protocols as well as their complexity makes them prone to vulnerabilities and practically eliminates all the advantages of using symmetric key techniques in the first place. In this paper we challenge the basic assumptions about public key cryptography in sensor networks which are based on a traditional software based approach. We propose a custom hardware assisted approach for which we claim that it makes public key cryptography feasible in such environments, provided we use the right selection of algorithms and associated parameters, careful optimization, and low-power design techniques. In order to validate our claim we present proof of concept implementations of two different algorithms—Rabin’s Scheme and NtruEncrypt—and analyze their architecture and performance according to various established metrics like power consumption, area, delay, throughput, level of security and energy per bit. Our implementation of NtruEncrypt in ASIC standard cell logic uses no more than 3,000 gates with an average power consumption of less than 20 μW. We envision that our public key core would be embedded into a light-weight sensor node architecture.

How many suppliers are best? A decision-analysis approach

Abstract: As more supply chains are becoming dependent upon suppliers, an interruption of supply networks can obstruct the functionality of the entire supply chain. The purpose of this paper is to present what we believe is a useful way to think about the number of suppliers needed in the presence of risks. We model the decision-making process using a decision tree approach. We consider catastrophic, “super-events,” which affect many/all suppliers, as well as “unique events” that affect only a single supplier. The probabilities of these events, the financial loss caused by disasters, and the operating cost of working with multiple suppliers are captured by decision trees, from which the expected cost function is obtained and the optimal number of suppliers is determined. Our methodology will help purchasing managers, materials management, as well as academics that are considering such issues.

A framework for evaluating ERP implementation choices

Abstract: A key issue in enterprise resource planning (ERP) implementation is how to find a match between the ERP system and an organization's business processes by appropriately customizing both the system and the organization. In this paper, we advance a framework for supporting management decision-making about customization choices and the capabilities required to accomplish them. In this framework, we identify various customization possibilities for business processes as well as ERP systems. We also identify technical and process change capabilities required for system and process customization. Combining customization options with change capabilities, we present a useful way for managers to identify feasible customization options for their particular organization. Such a framework also helps managers to recognize the gap between desired customization options and change capabilities. A case study is used to illustrate the application of the framework.

3D MRI-based multicomponent FSI models for atherosclerotic plaques

Abstract: A three-dimensional (3D) MRI-based computational model with multicomponent plaque structure and fluid–structure interactions (FSI) is introduced to perform mechanical analysis for human atherosclerotic plaques and identify critical flow and stress/strain conditions which may be related to plaque rupture. Three-dimensional geometry of a human carotid plaque was reconstructed from 3D MR images and computational mesh was generated using Visualization Toolkit. Both the artery wall and the plaque components were assumed to be hyperelastic, isotropic, incompressible, and homogeneous. The flow was assumed to be laminar, Newtonian, viscous, and incompressible. The fully coupled fluid and structure models were solved by ADINA, a well-tested finite element package. Results from two-dimensional (2D) and 3D models, based on ex vivo MRI and histological images (HI), with different component sizes and plaque cap thickness, under different pressure and axial stretch conditions, were obtained and compared. Our results indicate that large lipid pools and thin plaque caps are associated with both extreme maximum (stretch) and minimum (compression when negative) stress/strain levels. Large cyclic stress/strain variations in the plaque under pulsating pressure were observed which may lead to artery fatigue and possible plaque rupture. Large-scale patient studies are needed to validate the computational findings for possible plaque vulnerability assessment and rupture predictions.

CFD study of fluid flow and wall heat transfer in a fixed bed of spheres

Abstract: A study is presented of the relationship between the local flow field and the local wall heat flux in a packed bed of spheres. Computational fluid dynamics is used as a tool for obtaining the detailed velocity and temperature fields, for gas flowing through a periodic wall segment test cell. Results from the wall segment are demonstrated to reproduce those obtained from a full bed of spheres with tube-to-particle diameter ratio of N = 4. Attempts to correlate the local wall heat flux with local properties of the flow field, such as velocity components, velocity gradients, and components of vorticity, led to the conclusion that local heat transfer rates do not correlate statistically with the local flow field. Instead, a conceptual analysis was used to suggest that local patterns of wall heat flux are related to larger-scale flow structures in the bed. © 2004 American Institute of Chemical Engineers AIChE J, 50: 906–921, 2004

Arabidopsis HMA2, a Divalent Heavy Metal-Transporting PIB-Type ATPase, Is Involved in Cytoplasmic Zn2+ Homeostasis

Abstract: PIB-type ATPases transport heavy metal ions (Cu+, Cu2+, Zn2+, Cd2+, Co2+, etc.) across biological membranes. Several members of this subfamily are present in plants. Higher plants are the only eukaryotes where putative Zn(2+)-ATPases have been identified. We have cloned HMA2, a PIB-ATPase present in Arabidopsis (Arabidopsis thaliana), and functionally characterized this enzyme after heterologous expression in yeast (Saccharomyces cerevisiae). HMA2 is a Zn(2+)-dependent ATPase that is also activated by Cd2+ and, to a lesser extent, by other divalent heavy metals (Pb2+, Ni2+, Cu2+, and Co2+). The enzyme forms an acid-stable phosphorylated intermediate and is inhibited by vanadate. HMA2 interacts with Zn2+ and Cd2+ with high affinity (Zn2+ K(1/2) = 0.11 +/- 0.03 microm and Cd2+ K(1/2) = 0.031 +/- 0.007 microm). However, its activity is dependent on millimolar concentrations of Cys in the assay media. Zn2+ transport determinations indicate that the enzyme drives the outward transport of metals from the cell cytoplasm. Analysis of HMA2 mRNA suggests that the enzyme is present in all plant organs and transcript levels do not change in plants exposed to various metals. Removal of HMA2 full-length transcript results in Zn2+ accumulation in plant tissues. hma2 mutant plants also accumulate Cd2+ when exposed to this metal. These results suggest that HMA2 is responsible for Zn2+ efflux from the cells and therefore is required for maintaining low cytoplasmic Zn2+ levels and normal Zn2+ homeostasis.

Opening the Door to Non-Programmers: Authoring Intelligent Tutor Behavior by Demonstration

Abstract: Intelligent tutoring systems are quite difficult and time inten- sive to develop. In this paper, we describe a method and set of software tools that ease the process of cognitive task analysis and tutor development by allowing the author to demonstrate, instead of programming, the behav- ior of an intelligent tutor. We focus on the subset of our tools that allow authors to create "Pseudo Tutors" that exhibit the behavior of intelligent tu- tors without requiring AI programming. Authors build user interfaces by di- rect manipulation and then use a Behavior Recorder tool to demonstrate al- ternative correct and incorrect actions. The resulting behavior graph is an- notated with instructional messages and knowledge labels. We present some preliminary evidence of the effectiveness of this approach, both in terms of reduced development time and learning outcome. Pseudo Tutors have now been built for economics, analytic logic, mathematics, and language learn- ing. Our data supports an estimate of about 25:1 ratio of development time to instruction time for Pseudo Tutors, which compares favorably to the 200:1 estimate for Intelligent Tutors, though we acknowledge and discuss limitations of such estimates.

Application of Wavelet Approach for ASCE Structural Health Monitoring Benchmark Studies

Abstract: This paper presents an application of wavelet analysis for damage detection and locating damage region(s) for the ASCE structural health monitoring benchmark data The response simulation data were generated basically by a FEM program provided by the ASCE Task Group on Health Monitoring for a four-story prototype building structure subjected to simulated stochastic wind loading Damage was introduced in the middle of response by breaking one or more structure elements such as interstory braces Wavelets were used to analyze the simulation data It was found that structural damage due to sudden breakage of structural elements and the time when it occurred can be clearly detected by spikes in the wavelet details The damaged region can be determined by the spatial distribution pattern of the observed spikes The effects of measurement noise and the severity of damage were investigated The results in this paper illustrate a great promise of wavelet analysis for structural health monitoring, especially for an on-line application

Dynamic plan migration for continuous queries over data streams

Abstract: Dynamic plan migration is concerned with the on-the-fly transition from one continuous query plan to a semantically equivalent yet more efficient plan. Migration is important for stream monitoring systems where long-running queries may have to withstand fluctuations in stream workloads and data characteristics. Existing migration methods generally adopt a pause-drain-resume strategy that pauses the processing of new data, purges all old data in the existing plan, until finally the new plan can be plugged into the system. However, these existing strategies do not address the problem of migrating query plans that contain stateful operators, such as joins. We now develop solutions for online plan migration for continuous stateful plans. In particular, in this paper, we propose two alternative strategies, called the moving state strategy and the parallel track strategy, one exploiting reusability and the second employs parallelism to seamlessly migrate between continuous join plans without affecting the results of the query. We develop cost models for both migration strategies to analytically compare them. We embed these migration strategies into the CAPE [7], a prototype system of a stream query engine, and conduct a comparative experimental study to evaluate these two strategies for window-based join plans. Our experimental results illustrate that the two strategies can vary significantly in terms of output rates and intermediate storage spaces given distinct system configurations and stream workloads.

Random Vibrations with Impacts: A Review

Abstract: Analytical methods and specific results are presented for random vibrations of systems with lumped parameters and “classical” impacts whereby finite relations between impact/rebound velocities are imposed at the impact instants that are not known in advance but rather governed by the equations of motion. Emphasis is placed on the procedures using special piecewise-linear transformation of state variables that exclude the velocity jumps at impacts or makes them small if impact losses are present. In the former case, exact analyses for stationary probability densities of the response to white-noise excitation are possible, whereas the stochastic averaging method is applied in the latter case. Furthermore, the special case of an isochronous system permits a more profound response analysis, such as predicting the spectral density of the response or subharmonic response to narrow-band excitation. The method of direct energy balance is also illustrated, based on direct application of the stochastic differential equation calculus between impacts. Certain two-degree-of-freedom impacting systems are considered, with application to moored systems, as used in ocean engineering.

Characterizing the diffusion/perfusion mismatch in experimental focal cerebral ischemia

Abstract: Diffusion-weighted imaging (DWI) is widely used to investigate hyperacute cerebral ischemia both in experimental stroke models and in patients with ischemic stroke, detecting early ischemic abnormalities related to reduction of the apparent diffusion coefficient (ADC) of brain water.1–8 Perfusion-weighted imaging (PWI) provides information about the hemodynamic status of brain tissue and detects regions with impaired cerebral perfusion.9,10 Clinical reports have demonstrated that the impaired perfusion region is typically larger than the lesion detected by DWI early after stroke onset.11–13 The difference between the PWI and DWI abnormalities was termed the diffusion/perfusion mismatch, and the DWI lesion usually enlarges over time until it coincides with the perfusion deficit.11–13 The mismatch region may represent potentially salvageable brain tissue with timely and appropriate therapy.14 The diffusion/perfusion mismatch evolution has not been well characterized during the first few hours in individual patients, nor in animal models. The aims of this study were to delineate the temporal evolution of the diffusion/perfusion mismatch volume in a rat permanent and temporary focal ischemia model and to confirm that the mismatch region identifies salvageable tissue if subjected to early reperfusion.

Nanoscale Investigation of Pathogenic Microbial Adhesion to a Biomaterial

Abstract: Microbial infections of medical implants occur in more than 2 million surgical cases each year in the United States alone. These increase patient morbidity and mortality, as well as patient cost and recovery time. Many treatments are available, but none are guaranteed to remove the infection. In many cases, the device infections are caused by the adhesion of microbes to the implant, ensuing growth, pathogenesis, and dissemination. The purpose of this work is to examine the initial events in microbial adhesion by simulating the approach and contact between a planktonic cell, immobilized on an atomic force microscope (AFM) cantilever, and a biomaterial or biofilm substrate. The two model microbes used in this study, Candida parapsilosis (ATCC 90018) and Pseudomonas aeruginosa (ATCC 10145), were chosen for both their clinical relevance and their ease of acquisition and handling in the laboratory setting. Attractive interactions exist between C. parapsilosis and both unmodified silicone rubber and P. aeruginosa biofilms. Using C. parapsilosis cells immobilized on AFM cantilevers with a silicone substrate, we have measured attractive forces of 4.3 ± 0.25 nN in the approach portion of the force cycle. On P. aeruginosa biofilms, the magnitude of the attractive force decreases to 2.0 ± 0.40 nN and is preceded by a 2.0-nN repulsion at approximately 75 nm from the cell surface. These data suggest that C. parapsilosis may adhere to both silicone rubber and P. aeruginosa biofilms, possibly contributing to patient morbidity and mortality. Characterization of cell-biomaterial and cell-cell interactions allows for a quantitative link between the physicomechanical and physicochemical properties of implant materials and the nanoscale interactions leading to microbial colonization and infection.

Effect of a Lipid Pool on Stress/Strain Distributions in Stenotic Arteries: 3-D Fluid-Structure Interactions (FSI) Models

Abstract: Nonlinear 3-D models with fluid-structure interactions (FSI) based on in vitro experiments are introduced and solved by ADINA to perform flow and stress/strain analysis for stenotic arteries with lipid cores. Navier-Stokes equations are used as the governing equations for the fluid. Hyperelastic Mooney-Rivlin models are used for both the arteries and lipid cores. Our results indicate that critical plaque stress/strain conditions are affected considerably by stenosis severity, eccentricity, lipid pool size, shape and position, plaque cap thickness, axial stretch, pressure, and fluid-structure interactions, and may be used for possible plaque rupture predictions.

N,N-Dimethylformamide Additions to the Solution for the Electrospinning of Poly(ε-caprolactone) Nanofibers

Abstract: Additives taht exhibit polyelectrolyte behavior such as N,N-dimethylformamide (DMF) may improve the electrospinning characteristics of viscoelastic polymer solutions. DMF additions to the solution lead to extensive jet splaying, thereby reducing the fiber diameter significantly. Nanofibrous structures with diameters of the order of 150 nm can be produced by the addition of about 10 vol.-% DMF to the solvent (chloroform). DMF additions also yield a narrow, unimodal distribution of fibers, compared to the bimodal distribution typically detected in electrospun polymers.

A study of coarsening, recrystallization, and morphology of microstructure in Al-Sc-(Zr)-(Mg) alloys

Abstract: Minor additions of Sc are effective in controlling the recrystallization resistance of 5xxx, 2xxx, and 7xxx aluminum. The addition of Sc to aluminum results in the rapid precipitation of homogeneously distributed Al3Sc dispersoids, which are coherent with the matrix and have the L12 structure. The presence of Al3Sc dispersoids increases the recrystallization resistance of wrought alloys. The higher coarsening rate of Al3Sc compared to that of Al3Zr may limit its applications as a single ancillary addition. When both scandium and zirconium are used in the same alloy, Al3(Sc1-x , Zr x ) dispersoids form. These dispersoids are more effective recrystallization inhibitors than either Al3Sc or Al3Zr. The Al3(Sc1-x , Zr x ) dispersoids precipitate more rapidly than Al3Zr but have a slower coarsening rate than Al3Sc. Furthermore, the distribution of Al3(Sc1-x , Zr x ) is significantly more homogeneous than Al3Zr. It was also established that alloys containing up to 3.5Mg showed improvement in recrystallization resistance when both Sc and Zr were present. Several morphologies of Al3Sc and Al3(Sc1-x , Zr x ) were also observed.

Characterization of Intermetallic Diffusion Barrier and Alloy Formation for Pd/Cu and Pd/Ag Porous Stainless Steel Composite Membranes

Abstract: The formation of the intermetallic diffusion barrier layer by the controlled in-situ oxidation method for Pd and Pd/alloy porous stainless steel composite membranes was investigated. SEM and EDS results showed the existence of an oxide layer as the intermetallic diffusion barrier for oxidation temperatures higher than 600 °C. At oxidation temperatures lower than 600 °C, there might still be an oxide layer at the membrane-substrate interface although it was too thin to be detected by SEM and EDS. The alloy formation study showed that annealing at 500 °C under helium atmosphere did not produce alloys with uniform compositions either for Pd/Ag or Pd/Cu membranes. However, annealing at 600 °C gave a uniform Pd/Cu-porous stainless steel (PSS) composite membrane, with no detectable presence of elements from the PSS substrate, further demonstrating the oxide layer as an effective intermetallic diffusion barrier.

Models for performance benchmarking: Measuring the effect of e-business activities on banking performance

Abstract: The current paper presents mathematical programming models for use in benchmarking where multiple performance measures are needed to examine the performance and productivity changes. The standard data envelopment analysis method is extended to incorporate benchmarks through (i) a variable-benchmark model where a unit under benchmarking selects a portion of benchmarksuch that the performance is characterized in the most favorable light, and (ii) a 4xed-benchmarkmodel where a unit is benchmarked against a 4xed set of benchmarks. The models are applied to a large Canadian bank where some branches’ services are automated to reduce costs and increase the service speed, and ultimately to improve productivity. The empirical investigation indicates that although the performance appears to be improved at the beginning, productivity gain has not been discovered. Our 4nding can facilitate the bankin examining its business options and further point to weaknesses and strengths in branch operations. ? 2004 Elsevier Ltd. All rights reserved.

Enterprise systems, knowledge transfer and power users

Abstract: There are few studies of knowledge transfer (KT) between groups with dissimilar purposes and dissimilar practices, which is the situation when transferring knowledge from an enterprise systems (ES) developer team to the users of the new ES. To support such KT, organizations identify a group of power users to work with the ES team and then to help other users integrate the new system into their operations. That KT process still encounters barriers. In a comparative case study of four such KT situations at two different companies we identify the critical barriers, and empirically uncover two new KT mechanisms that are effective for addressing the KT barriers in the ES context.

Activation of neural pathways associated with sexual arousal in non‐human primates

Abstract: ODORS ARE IMPORTANT in modulating sexual behavior in a variety of species. However, few studies have connected the behavioral response and the brain activation to the odor stimulation. Attractiveness of a female can be transmitted by chemosensory, visual, and auditory cues; ensuring an increase in male sexual behaviors at a time when females are most fertile (1). Chemical or olfactory cues derived from female scent secretions are known to provide cues of the female’s reproductive status and are important in mediating male sexual behavior in marmosets and tamarins (family Callitrichidae) (2). In response, males have increased sexual behaviors such as tongue-flicks, mounts, and ejaculation (3). While male common marmosets respond with sexual behavior to other sensory cues from female marmosets, such as visual, olfactory cues are important for coordinating male sexual activity with female endocrine status (1). Additionally, scent odors from periovulatory marmoset females are preferred over luteal phase scents from the same female (4). Lesions of the medial preoptic area/anterior hypothalamic continuum (MPOA/AH) have been shown to produce deficiencies in male sexual behavior (5) with decreases in precopulatory and copulatory behaviors, mounting, and anogenital investigation of females. The preoptic area of the hypothalamus has input from the olfactory and vomeronasal systems as well as other sensory systems and induces the release of hormones. Using functional magnetic resonance imaging (fMRI), we corroborated the work of Lloyd and Dixson (5) in demonstrating activation of the MPOA/AH (6). Awake male marmosets presented with the scent marks of unfamiliar females showed enhanced signal intensity in the MPOA/AH to the ovulatory scent versus the ovariectomized (OVX) scent. Although both odors elicited activation versus vehicle control, there was greater activation for the ovulatory scent in the awake males. This imaging study provided evidence that olfactory signals activate the MPOA/AH sexual arousal system in the male common marmoset. Brain imaging has many advantages over lesion studies. Awake male marmosets can be imaged repeatedly and remain intact. In addition to examining functionality of specific brain areas, the entire brain can be imaged to provide information on the integration of arousal and inhibitory processes of the brain in responding to sexually relevant cues. Other neural systems interacting with sexual behavior can be imaged to examine positive affect areas of the brain as well as inhibitory processes. Scent detection is a good starting point for examining brain activity since odor cues elicit distinct behavioral actions. Marmosets, as in all callitrichidae species, show distinct hormonal and behavioral responses to relevant chemical sensory cues, and are therefore a good model for examining behavior responses and brain activation. The present study extends our previous analysis to other brain areas. We imaged four male marmosets while presenting periovulatory, ovariectomized female scents and vehicle controls to assess key neural structures involved in stimulus processing for positive affective (reward) sexual chemosensory signals.

Nano-sized beads and porous fiber constructs of Poly(ε-caprolactone) produced by electrospinning

Abstract: Nano-sized beads and non-woven porous fiber constructs of poly(e-caprolactone) were produced by electrospinning. Nearly spherical beads with diameters between 900 nm and 5 μm were produced with dilute solutions with less than 3 wt% PCL. In this case, the initial jet of solution may split into many mini jets almost at the end of the needle and each minijet gradually disintegrates into small droplets. Beyond a critical solution concentration of about 4 wt% PCL, the jet may undergo extensional flow, splitting and splaying to produce a web of interconnected fibers with mean diameters on the order of 300 to 900 nm. Intermolecular entanglements play a dominant role in stabilizing the fibrous structure. A uniform fibrous structure was obtained at 40 kV while at 20 kV a large fraction of beads were present in the electrospun polymer. The fiber diameter in the PCL deposited on the collector typically exhibits a bimodal distribution. Electrospinning lowers the degree of crystallinity in the polymer.