Showing papers by "Clarkson University published in 2004"
TL;DR: In this paper, the authors examine the links among strategic purchasing, supply management, and firm performance, and empirically test a number of hypothesized relationships based on a sample of 221 United States manufacturing firms.
882 citations
TL;DR: In this article, an overview of the current state of the research field of adaptive and environmentally sensitive polymer surfaces designed to respond to external stimuli in a controlled and predictable manner is presented.
538 citations
TL;DR: The authors discusses the evolution of science and policies to control acid rain in Europe and the United States over the past several decades, and discusses the emergence of acid rain as an environmental concern, scientific evidence about the effects of acidic deposition on natural ecosystems, US and European acid rain control policies, studies of the costs and benefits of reducing acid rain, and different policy contexts in Europe.
336 citations
TL;DR: Swelling (and shrinking) of poly(2-vinylpyridine), P2VP, polymer brushes, caused by pH changes, could be readily monitored by transmission surface plasmon resonance, T-SPR, spectroscopy.
Abstract: Swelling (and shrinking) of poly(2-vinylpyridine), P2VP, polymer brushes, caused by pH changes, could be readily monitored by transmission surface plasmon resonance, T-SPR, spectroscopy. Gold nanoparticles attached to the P2VP polymer brushes dramatically enhanced the pH-induced shift in the T-SPR absorption spectra. (A 50 nm shift of the absorption maximum of the T-SPR spectrum of the supporting gold nanoislands was observed upon changing the pH from 5.0 to 2.0, corresponding to a swelling of the polymer brushes from 8.1 ± 0.7 to 24.0 ± 2.0 nm. Same shift in the opposite direction was observed upon changing the pH from 2.0 to 5.0.)
334 citations
TL;DR: In this paper, fine and coarse fractions of airborne particulate matter (PM) were collected in a semi-residential (AECD) area from June 2001 to June 2002 of Dhaka and in an urban area of Rajshahi, a city in northwestern region of Bangladesh from August 2001 to May 2002.
288 citations
TL;DR: The Susceptible-Infected-Removed (SIR) epidemiological model is studied with various immunization strategies, including random, targeted and acquaintance immunization, and analytical results for the total number of infected individuals are derived.
Abstract: We study the behavior of epidemic spreading in networks, and, in particular, scale free networks. We use the Susceptible-Infected-Removed (SIR) epidemiological model. We give simulation results for the dynamics of epidemic spreading. By mapping the model into a static bond-percolation model we derive analytical results for the total number of infected individuals. We study this model with various immunization strategies, including random, targeted and acquaintance immunization.
264 citations
TL;DR: How did Singapore manage to get most of its public services deliverable online?
Abstract: How did Singapore manage to get most of its public services deliverable online?
236 citations
TL;DR: In this paper, the thermal optical reflectance (TOSR) method was used to divide carbon into four organic carbon, pyrolized organic carbon (OP), and three elemental carbon (EC) fractions.
215 citations
TL;DR: In this article, continuous and semi-continuous measurements of organic carbon (OC), elemental carbon (EC) and PM 2:5 were performed during the summer of 2002 in Rochester, NY and Philadelphia, PA.
203 citations
TL;DR: This study couples Particle Image Velocimetry (PIV) and multipoint wall pressure measurements using POD and LSE to estimate the full velocity field from the wall pressure alone and yields a sufficiently accurate estimate of the velocity field that the incipient condition can be detected.
Abstract: Low-dimensional methods including the Proper Orthogonal Decomposition (POD) and Linear Stochastic Estimation (LSE) have been applied to the flow between a backward facing ramp and an adjustable flap. A range of flap angles provide a flow which is incipiently separated and can be used to flesh out ideas for active feedback separation control strategies. The current study couples Particle Image Velocimetry (PIV) and multipoint wall pressure measurements using POD and LSE to estimate the full velocity field from the wall pressure alone. This technique yields a sufficiently accurate estimate of the velocity field that the incipient condition can be detected. The ability to estimate the state of the flow without inserting probes into the flow is important for the development of practical active feedback flow control strategies
180 citations
TL;DR: It is indicated that the temperature-resolved carbon fraction data can be utilized to enhance source apportionment, especially with respect to the separation of diesel emissions from gasoline vehicle sources.
Abstract: Integrated ambient particulate matter < or =2.5 microm in aerodynamic diameter (PM2.5) samples were collected at a centrally located urban monitoring site in Washington, DC, on Wednesdays and Saturdays using Interagency Monitoring of Protected Visual Environments samplers. Particulate carbon was analyzed using the thermal optical reflectance method that divides carbon into four organic carbon fractions, pyrolyzed organic carbon, and three elemental carbon fractions. A total of 35 variables measured in 718 samples collected between August 1988 and December 1997 were analyzed. The data were analyzed using Positive Matrix Factorization and 10 sources were identified: sulfate (SO4(2-))-rich secondary aerosol I (43%), gasoline vehicle (21%), SO4(2-)-rich secondary aerosol II (11%), nitrate-rich secondary aerosol (9%), SO4(2-)-rich secondary aerosol III (6%), incinerator (4%), aged sea salt (2%), airborne soil (2%), diesel emissions (2%), and oil combustion (2%). In contrast to a previous study that included only total organic carbon and elemental carbon fractions, motor vehicles were separated into fractions identified as gasoline vehicle and diesel emissions containing carbon fractions whose abundances were different between the two sources. This study indicates that the temperature-resolved carbon fraction data can be utilized to enhance source apportionment, especially with respect to the separation of diesel emissions from gasoline vehicle sources. Conditional probability functions using surface wind data and deduced source contributions aid in the identifications of local sources.
Proceedings Article•
27 Jun 2004TL;DR: It is argued that this model of research, which is enabled by open source software, is an important step in transferring the results of computer science research into production environments.
Abstract: Xen is an x86 virtual machine monitor produced by the University of Cambridge Computer Laboratory and released under the GNU General Public License. Performance results comparing XenoLinux (Linux running in a Xen virtual machine) to native Linux as well as to other virtualization tools such as User Mode Linux (UML) were recently published in the paper "Xen and the Art of Virtualization" at the Symposium on Operating Systems Principles (October 2003). In this study, we repeat this performance analysis of Xen. We also extend the analysis in several ways, including comparing XenoLinux on x86 to an IBM zServer. We use this study as an example of repeated research. We argue that this model of research, which is enabled by open source software, is an important step in transferring the results of computer science research into production environments.
TL;DR: Adaptive resource allocation for multimedia quality of service (QoS) support in broadband wireless networks is examined and an effective and efficient measurement-based dynamic resource allocation scheme is proposed to meet the target handoff-dropping probability.
Abstract: Adaptive resource allocation for multimedia quality of service (QoS) support in broadband wireless networks is examined in this work. A service model consisting of three service classes with different handoff-dropping requirements is presented. Appropriate call-admission control and resource-reservation schemes are developed to allocate resources adaptively to the real-time service classes with a stringent delay bound. Moreover, we propose an effective and efficient measurement-based dynamic resource allocation scheme to meet the target handoff-dropping probability. The nonreal-time applications, serviced by the best-effort model, are supported. The system accommodates adaptive multimedia applications to further reduce the blocking and dropping probabilities of real-time applications. Based on a multidimensional model analysis, simulations are conducted to evaluate the system performance. The simulation results show that the proposed system can satisfy the desired QoS of multimedia applications under different traffic loads, while achieving high utilization.
TL;DR: It is demonstrated that a wide variety of indoor human resuspension activities increase human exposure to PM and contribute to the “personal cloud” effect.
Abstract: Continuous laser particle counters collocated with time-integrated filter samplers were used to measure personal, indoor, and outdoor particulate matter (PM) concentrations for a variety of prescribed human activities during a 5-day experimental period in a home in Redwood City, CA, USA. The mean daytime personal exposures to PM(2.5) and PM(5) during prescribed activities were 6 and 17 times, respectively, as high as the pre-activity indoor background concentration. Activities that resulted in the highest exposures of PM(2.5), PM(5), and PM(10) were those that disturbed dust reservoirs on furniture and textiles, such as dry dusting, folding clothes and blankets, and making a bed. The vigor of activity and type of flooring were also important factors for dust resuspension. Personal exposures to PM(2.5) and PM(5) were 1.4 and 1.6 times, respectively, as high as the indoor concentration as measured by a stationary monitor. The ratio of personal exposure to the indoor concentration was a function of both particle size and the distance of the human activity from the stationary indoor monitor. The results demonstrate that a wide variety of indoor human resuspension activities increase human exposure to PM and contribute to the "personal cloud" effect.
TL;DR: In this article, conditional probability function (CPF) and nonparametric regression (NPR) were used to identify directions of PM2.5 sources from cyclohexane data from Houston, TX and correctly showed the direction of the source.
TL;DR: In this article, a stochastic optimal control of a vehicle suspension on a random road is studied, where a sensor is mounted in the front bumper that measures the road irregularity at some distances in front of the vehicle and two other sensors also measure relative velocities of vehicle body with respect to the unsprung masses in the vehicle suspension spaces.
TL;DR: Two case studies are presented to illustrate SDG-based analysis of process flowsheets containing many units and control loops and it is shown that digraph-based steady-state analysis results in good diagnostic resolution.
TL;DR: In this article, the authors analyzed decoherence of an electron in a double dot due to the interaction with acoustic phonons and showed that in common semiconductors, such as Si and GaAs, the latter mechanism determines the upper limit for the double-dot charge qubit performance measure.
Abstract: We analyze decoherence of an electron in a double dot due to the interaction with acoustic phonons. For large tunneling rates between the quantum dots, the main contribution to decoherence comes from the phonon emission relaxation processes, while for small tunneling rates, the virtual-phonon, dephasing processes dominate. Our results show that in common semiconductors, such as Si and GaAs, the latter mechanism determines the upper limit for the double-dot charge qubit performance measure.
TL;DR: This research studies HPB comprised of end-grafted polystyrene (PS) and poly(2-vinyl pyridine) (P2VP), which involves the use of an "intermolecular glue" acting as a binding/anchoring interlayer between the polymer brush and the substrate, a silicon wafer.
Abstract: Smart surfaces can be described as surfaces that have the ability to respond in a controllable fashion to specific environmental stimuli. A heterogeneous (mixed) polymer brush (HPB) can provide a synthetic route to designing smart polymer surfaces. In this research we study HPB comprised of end-grafted polystyrene (PS) and poly(2-vinyl pyridine) (P2VP). The synthesis of the HPB involves the use of an "intermolecular glue" acting as a binding/anchoring interlayer between the polymer brush and the substrate, a silicon wafer. We compare anchoring layers of epoxysilane (GPS), which forms a self-assembled monolayer with epoxy functionality, to poly(glycidyl methacrylate) (PGMA), which forms a macromolecular monolayer with epoxy functionality. The PS and P2VP were deposited onto the wafers in a sequential fashion to chemically graft PS in a first step and subsequently graft P2VP. Rinsing the HPB in selective solvents and observing the change in water contact angle as a function of the HPB composition studied the switching nature of the HPB. Scanning probe microscopy was used to probe the topography and phase imagery of the HPB. The nature of the anchoring layer significantly affected the wettability and morphology of the mixed brushes.
TL;DR: Experiments clearly demonstrate a crossover from IPT to DLA for the injection of a zero-viscosity fluid as the injection velocity was increased from zero and simulations support the predicted IPT-to-DLA crossover, as well as the predicted power-law behavior of the characteristic crossover length.
Abstract: Invasion percolation with trapping (IPT) and diffusion-limited aggregation (DLA) are simple fractal models, which are known to describe two-phase flow in porous media at well defined, but unphysical limits of the fluid properties and flow conditions. A decade ago, Fernandez, Rangel, and Rivero predicted a crossover from IPT (capillary fingering) to DLA (viscous fingering) for the injection of a zero-viscosity fluid as the injection velocity was increased from zero. [Phys. Rev. Lett. 67, 2958 (1991)]]. We have performed experiments in which air is injected into a glass micromodel to displace water. These experiments clearly demonstrate this crossover as the injection velocity of the air is increased. Furthermore, simulations, using our standard pore-level model, also support the predicted IPT-to-DLA crossover, as well as the predicted power-law behavior of the characteristic crossover length.
TL;DR: Results from this study suggest that an aging time of 10 sec and a dilution air ratio of 20 are sufficient to obtain representative primary particle emission samples from stationary combustion sources.
Abstract: Currently, we have limited knowledge of the physical and chemical properties of emitted primary combustion aerosols and the changes in those properties caused by nucleation, condensation growth of volatile species, and particle coagulations under dilution and cooling in the ambient air. A dilution chamber was deployed to sample exhaust from a pilot-scale furnace burning various fuels at a nominal heat input rate of 160 kW/h(-1) and 3% excess oxygen. The formation mechanisms of particles smaller than 420 nm in electrical mobility diameter were experimentally investigated by measurement with a Scanning Mobility Particle Sizer (SMPS) as a function of aging times, dilution air ratios, combustion exhaust temperatures, and fuel types. Particle formation in the dilution process is a complex mixture of nucleation, coagulation, and condensational growth, depending on the concentrations of available condensable species and solid or liquid particles (such as soot, ash) in combustion exhausts. The measured particle size distributions in number concentrations measured show peaks of particle number concentrations for medium sulfur bituminous coal, No. 6 fuel oil, and natural gas at 40-50 nm, 70-100 nm, and 15-25 nm, respectively. For No. 6 fuel oil and coal, the particle number concentration is constant in the range of a dilution air ratio of 50, but the number decreases as the dilution air ratio decreases to 10. However, for natural gas, the particle number concentration is higher at a dilution air ratio of 10 and decreases at dilution air ratios of 20-50. At a dilution air ratio of 10, severe particle coagulation occurs in a relatively short time. Samples taken at different combustion exhaust temperatures for these fuel types show higher particle number concentrations at 645 K than at 450 K. As the aging time of particles increases, the particles increase in size and the number concentrations decrease. The largest gradient of particle number distribution occurs within the first 10 sec after dilution but shows only minor differences between 10 and 80 sec. The lifetimes of the ultrafine particles are relatively short, with a scale on the order of a few seconds. Results from this study suggest that an aging time of 10 sec and a dilution air ratio of 20 are sufficient to obtain representative primary particle emission samples from stationary combustion sources.
TL;DR: In this paper, the relative merits of using polymers over metals are shown through a quantitative comparison, between PVDF and Hastelloy heat exchangers, when incorporating the same tube dimensions, thickness and fluid film coefficients, significant cost savings can be achieved using the PVDF exchanger.
TL;DR: In this article, a one-dimensional model for natural gas production from the dissociation of methane hydrate in a confined reservoir by a depressurizing well is presented. But the model does not consider the effect of temperature and pressure in the hydrate and gas regions.
TL;DR: In this article, the authors used the thermal optical reflectance method, which divides carbon into four organic carbon, pyrolyzed organic carbon (OP), and three elemental carbon (EC) fractions.
Abstract: [i] Integrated, 24-hour, ambient PM 2.5 (particulate matter <2.5 μm in aerodynamic diameter) samples were collected at a rural monitoring site in Brigantine, New Jersey, on Wednesdays and Saturdays using Interagency Monitoring of Protected Visual Environments (IMPROVE) samplers. Particulate carbon was analyzed using the thermal optical reflectance method, which divides carbon into four organic carbon (OC), pyrolyzed organic carbon (OP), and three elemental carbon (EC) fractions. A total of 910 samples and 36 variables collected between March 1992 and May 2001 were analyzed using positive matrix factorization, and 11 sources were identified: sulfate-rich secondary aerosol I (48%), gasoline vehicle (13%), aged sea salt (8%), sulfate-rich secondary aerosol II (7%), nitrate-rich secondary aerosol (6%), sulfate-rich secondary aerosol III (5%), sea salt (4%), airborne soil (4%), diesel emission (3%), incinerator (2%), and oil combustion (1%). Temperature-resolved carbon fractions enhanced source separations including three sulfate-rich secondary aerosols and two traffic-related sources that had different abundances of carbon fractions different between sources. Conditional probability functions using surface wind data and deduced source contributions aid in the identification of local sources. Potential source contribution function (PSCF) analysis shows the regional influence of sulfate-rich secondary aerosols. Backward trajectories indicate that the highly elevated airborne soil impacts at the monitoring site were likely caused by either Asian or Sahara dust storms.
TL;DR: In this paper, the effect of spin-orbit interaction and in-plane effective magnetic field on the conductance of a quasi-one-dimensional ballistic electron system was studied, and the authors generalize the Landauer formula at finite temperatures to incorporate these special features of the dispersion relation.
Abstract: We study the effect of spin-orbit interaction and in-plane effective magnetic field on the conductance of a quasi-one-dimensional ballistic electron system. The effective magnetic field includes the externally applied field, as well as the field due to polarized nuclear spins. The interplay of the spin-orbit interaction with effective magnetic field significantly modifies the band structure, producing additional subband extrema and energy gaps, introducing the dependence of the subband energies on the field direction. We generalize the Landauer formula at finite temperatures to incorporate these special features of the dispersion relation. The obtained formula describes the conductance of a ballistic conductor with an arbitrary dispersion relation.
TL;DR: While overall there was agreement on the importance of a number of sources, R&D professionals in SMEs valued customers, coworkers, marketing, and journals more highly, while professionals in large firms valued suppliers more highly.
Abstract: Prior research studies have concluded that the innovative output of small and medium sized firms (SMEs) exceeds that of larger firms. One of the critical ingredients of innovation is the source of the idea or inspiration for the innovation. The purpose of this study was to compare the relative importance of 14 different sources of product and process innovation as reported by 235 professional R&D workers in large and small technology-based firms. While overall there was agreement on the importance of a number of sources, R&D professionals in SMEs valued customers, coworkers, marketing, and journals more highly, while professionals in large firms valued suppliers more highly. Implications of these results, in light of the previous research studies on innovation, are addressed.
TL;DR: A thin polyelectrolyte film with a gradual change of the composition (ratio between two different oppositely charged surface-grafted weak polyElectrolytes) with a gradient in surface charge density creates a gradient of the wetting behavior.
Abstract: We report on a thin polyelectrolyte film (mixed polyelectrolyte brush) with a gradual change of the composition (ratio between two different oppositely charged surface-grafted weak polyelectrolytes) across the sample. The gradient of surface composition creates a gradient in surface charge density and, consequently, a gradient of the wetting behavior. The gradient film is sensitive to a pH signal and can be reversibly switched via pH change.
TL;DR: In this paper, a positive matrix factorization (PMF) method was used for fine particle composition data from samples collected at Queens College during July 2001 were studied using PMF, which used the estimated errors in the data to provide optimal point-by-point weighting and permits efficient treatment of missing and below detection limit values.
TL;DR: Hourly averaged particle size distributions measured at a centrally located urban site in Seattle were analyzed through the application of bilinear positive matrix factorization (PMF) and Unmix to study underlying size distributions and their daily patterns.
Abstract: Hourly averaged particle size distributions measured at a centrally located urban site in Seattle were analyzed through the application of bilinear positive matrix factorization (PMF) and Unmix to study underlying size distributions and their daily patterns. A total of 1051 samples each with 16 size intervals from 20 to 400 nm were obtained from a differential mobility particle sizer operating between December 2000 and February 2001. Both PMF and Unmix identify four similar underlying factors in the size distributions. Factor 1 is an accumulation mode particle size spectrum that shows a regular nocturnal pattern, and factor 2 is a larger particle distribution. Factor 3 is assigned as a traffic-related particle distribution, based on its correlations with accompanying gas-phase measurements, and has a regular weekday-high rush-hour pattern. Factor 4 is a traffic-related particle size distribution that has a regular rush-hour pattern on weekdays as well as weekends. Conditional probability functions (CPF) were computed using wind profiles and factor contributions. The results of CPF analysis suggest that these factors are correlated with surrounding particle sources of wood burning, secondary aerosol, diesel emissions, and motor vehicle emissions.
TL;DR: The positive matrix factorization (PMF) method was applied to particle size-distribution data acquired during the Pittsburgh Air Quality Study (PAQS) from July 2001 to August 2001.
Abstract: Positive matrix factorization (PMF) method was applied to particle size-distribution data acquired during the Pittsburgh Air Quality Study (PAQS) from July 2001 to August 2001. After removing those days with nucleation events, a total of 1632 samples, each with 165 evenly-sized intervals from 0.003 to 2.5 μm, were obtained from scanning mobility particle spectrometer (SMPS) and aerodynamic particle sampler (APS). The temporal resolution was 15 min. The values for each set of five consecutive-size bins were averaged to produce 33 new size channels. The size distributions of particle number as well as volume were analyzed with a bilinear model. Three kinds of information were used to identify the sources: the number and volume size distributions associated with the factors, the time frequency properties of the contribution of each source (Fourier analysis of source contribution values) and the correlations of the contribution values with the gas-phase data and some composition data. Through these analyses, ...