Showing papers by "Rensselaer Polytechnic Institute published in 2001"

Industrial biocatalysis today and tomorrow

Abstract: The use of biocatalysis for industrial synthetic chemistry is on the verge of significant growth. Biocatalytic processes can now be carried out in organic solvents as well as aqueous environments, so that apolar organic compounds as well as water-soluble compounds can be modified selectively and efficiently with enzymes and biocatalytically active cells. As the use of biocatalysis for industrial chemical synthesis becomes easier, several chemical companies have begun to increase significantly the number and sophistication of the biocatalytic processes used in their synthesis operations.

SPADE: An Efficient Algorithm for Mining Frequent Sequences

Abstract: In this paper we present SPADE, a new algorithm for fast discovery of Sequential Patterns. The existing solutions to this problem make repeated database scans, and use complex hash structures which have poor locality. SPADE utilizes combinatorial properties to decompose the original problem into smaller sub-problems, that can be independently solved in main-memory using efficient lattice search techniques, and using simple join operations. All sequences are discovered in only three database scans. Experiments show that SPADE outperforms the best previous algorithm by a factor of two, and by an order of magnitude with some pre-processed data. It also has linear scalability with respect to the number of input-sequences, and a number of other database parameters. Finally, we discuss how the results of sequence mining can be applied in a real application domain.

Composite Quasar Spectra from the Sloan Digital Sky Survey

Abstract: We have created a variety of composite quasar spectra using a homogeneous data set of over 2200 spectra from the Sloan Digital Sky Survey (SDSS). The quasar sample spans a redshift range of 0.044 ≤ z ≤ 4.789 and an absolute r' magnitude range of -18.0 to -26.5. The input spectra cover an observed wavelength range of 3800–9200 A at a resolution of 1800. The median composite covers a rest-wavelength range from 800 to 8555 A and reaches a peak signal-to-noise ratio of over 300 per 1 A resolution element in the rest frame. We have identified over 80 emission-line features in the spectrum. Emission-line shifts relative to nominal laboratory wavelengths are seen for many of the ionic species. Peak shifts of the broad permitted and semiforbidden lines are strongly correlated with ionization energy, as previously suggested, but we find that the narrow forbidden lines are also shifted by amounts that are strongly correlated with ionization energy. The magnitude of the forbidden line shifts is 100 km s-1, compared with shifts of up to 550 km s-1 for some of the permitted and semiforbidden lines. At wavelengths longer than the Lyα emission, the continuum of the geometric mean composite is well fitted by two power laws, with a break at ≈5000 A. The frequency power-law index, αν, is -0.44 from ≈1300 to 5000 A and -2.45 redward of ≈5000 A. The abrupt change in slope can be accounted for partly by host-galaxy contamination at low redshift. Stellar absorption lines, including higher order Balmer lines, seen in the composites suggest that young or intermediate-age stars make a significant contribution to the light of the host galaxies. Most of the spectrum is populated by blended emission lines, especially in the range 1500–3500 A, which can make the estimation of quasar continua highly uncertain unless large ranges in wavelength are observed. An electronic table of the median quasar template is available.

Applications of Carbon Nanotubes

Abstract: Carbon nanotubes have attracted the fancy of many scientists worldwide. The small dimensions, strength and the remarkable physical properties of these structures make them a very unique material with a whole range of promising applications. In this review we describe some of the important materials science applications of carbon nanotubes. Specifically we discuss the electronic and electrochemical applications of nanotubes, nanotubes as mechanical reinforcements in high performance composites, nanotube-based field emitters, and their use as nanoprobes in metrology and biological and chemical investigations, and as templates for the creation of other nanostructures. Electronic properties and device applications of nanotubes are treated elsewhere in the book. The challenges that ensue in realizing some of these applications are also discussed from the point of view of manufacturing, processing, and cost considerations.

The Impacts of Emoticons on Message Interpretation in Computer-Mediated Communication:

Abstract: Emoticons are graphic representations of facial expressions that many e-mail users embed in their messages. These symbols are widely known and commonly recognized among computer-mediated communication (CMC) users, and they are described by most observers as substituting for the nonverbal cues that are missing from CMC in comparison to face-to-face communication. Their empirical impacts, however, are undocumented. An experiment sought to determine the effects of three common emoticons on message interpretations. Hypotheses drawn from literature on nonverbal communication reflect several plausible relationships between emoticons and verbal messages. The results indicate that emoticons’ contributions were outweighed by verbal content, but a negativity effect appeared such that any negative message aspect—verbal or graphic—shifts message interpretation in the direction of the negative element.

Cellular automata microsimulation for modeling bi-directional pedestrian walkways

Abstract: Pedestrian flow is inherently complex, more so than vehicular flow, and development of microscopic models of pedestrian flow has been a daunting task for researchers. This paper presents the use of Cellular automata (CA) microsimulation for modeling bi-directional pedestrian walkways. It is shown that a small rule set is capable of effectively capturing the behaviors of pedestrians at the micro-level while attaining realistic macro-level activity. The model provides for simulating three modes of bi-directional pedestrian flow: (a) flows in directionally separated lanes, (b) interspersed flow, and (c) dynamic multi-lane (DML) flow. The emergent behavior that arises from the model, termed CA-Ped, is consistent with well-established fundamental properties.

Two-phase modeling of deflagration-to-detonation transition in granular materials: Reduced equations

Abstract: Of the two-phase mixture models used to study deflagration-to-detonation transition in granular explosives, the Baer–Nunziato model is the most highly developed. It allows for unequal phase velocities and phase pressures, and includes source terms for drag and compaction that strive to erase velocity and pressure disequilibria. Since typical time scales associated with the equilibrating processes are small, source terms are stiff. This stiffness motivates the present work where we derive two reduced models in sequence, one with a single velocity and the other with both a single velocity and a single pressure. These reductions constitute outer solutions in the sense of matched asymptotic expansions, with the corresponding inner layers being just the partly dispersed shocks of the full model. The reduced models are hyperbolic and are mechanically as well as thermodynamically consistent with the parent model. However, they cannot be expressed in conservation form and hence require a regularization in order to fully specify the jump conditions across shock waves. Analysis of the inner layers of the full model provides one such regularization [Kapila et al., Phys. Fluids 9, 3885 (1997)], although other choices are also possible. Dissipation associated with degrees of freedom that have been eliminated is restricted to the thin layers and is accounted for by the jump conditions.

Mechanisms of Enhanced Osteoblast Adhesion on Nanophase Alumina Involve Vitronectin

Abstract: The role, including concentration, conformation, and bioactivity, of adsorbed vitronectin in enhancing osteoblast adhesion on nanophase alumina was investigated in the present study. Vitronectin adsorbed in a competitive environment in the highest concentration on nanophase alumina compared to conventional alumina. Enhanced adsorption of vitronectin on nanophase alumina was possibly due to decreased adsorption of apolipoprotein A-I and/or increased adsorption of calcium on nanophase alumina. In a novel manner, the present study utilized surface-enhanced Raman scattering (SERS) to determine the conformation of vitronectin adsorbed on nanophase alumina. These results provided the first evidence of increased unfolding of vitronectin adsorbed on nanophase alumina. Increased adsorption of calcium on nanophase alumina may affect the conformation of adsorbed vitronectin specifically to promote unfolding of the macromolecule to expose cell-adhesive epitopes recognized by specific cell-membrane receptors. Results ...

Efficiently mining maximal frequent itemsets

Abstract: We present GenMax, a backtracking search based algorithm for mining maximal frequent itemsets. GenMax uses a number of optimizations to prune the search space. It uses a novel technique called progressive focusing to perform maximality checking, and diffset propagation to perform fast frequency computation. Systematic experimental comparison with previous work indicates that different methods have varying strengths and weaknesses based on dataset characteristics. We found GenMax to be a highly efficient method to mine the exact set of maximal patterns.

Internet Use Among College Students: An Exploratory Study

Abstract: The author and associates surveyed 1,300 college students in classrooms at eight academic institutions to identify how the students' use of the Internet has affected their social or academic lives. Although the typical Internet-using student uses the Internet for 100 minutes per day, a small group of students use the Internet to a degree that interferes with other aspects of their lives. Most of them are men and are found among the hard science academic majors. Some ideas for dealing with this problem are suggested.

Is a Picture Worth a Thousand Words?: Photographic Images in Long-Term and Short-Term Computer-Mediated Communication

Abstract: This article asks whether, and when, participants benefit from seeing each other's faces in computer-mediated communication. Although new technologies make it relatively easy to exchange images over the Internet, our formal understanding of their impacts is not clear. Some theories suggest that the more one can see of one's partners, the better one will like them. Others suggest that long-term virtual team members may like each other better than would those who use face-to-face interaction. The dynamic underlying this latter effect may also pertain to the presentation of realistic images compared with idealized virtual perceptions. A field experiment evaluated the timing of physical image presentations for members of short-term and long-term virtual, international groups. Results indicate that in new, unacquainted teams, seeing one's partner promotes affection and social attraction, but in long-term online groups, the same type of photograph dampens affinity.

Monazite–Xenotime–Garnet Equilibrium in Metapelites and a New Monazite–Garnet Thermometer

Abstract: Prograde suites of pelitic rocks were examined with electron microprobe INTRODUCTION and laser ablation inductively coupled plasma mass spectrometry to Monazite [(Ce,La,Th)PO4] plays an important role in determine the systematics of element partitioning between coexisting studies of igneous and metamorphic petrogenesis. Foremonazite, xenotime, and garnet. Monazite grains that grew in most, monazite is used to date specific events in a equilibrium with xenotime are enriched in Y and Dy compared with petrogenetic sequence (e.g. Parrish, 1990; Harrison et al., monazite that grew in xenotime-absent assemblages. Y and heavy 1997; Hawkins & Bowring, 1999; Foster et al., 2000). rare earth element contents of monazite coexisting with xenotime Monazite may contain a large percentage of the sample increase with rising temperature. Monazite–xenotime Y–Gd and rare earth element (REE) budget and, thus, exert an Y–Dy partitioning is systematic within a metamorphic grade, and important influence on the evolution of melt composition increases slightly with increasing metamorphic grade, suggesting (Wark & Miller, 1993; Bea, 1996). The thermobarometric that monazite–xenotime pairs approached partitioning equilibrium. potential of monazite (coexisting with xenotime) has been Garnet and monazite in both xenotime-bearing and xenotime-absent recognized, leading to calibration of monazite geoassemblages show a strong ( R = 0·94) systematic relationship thermometers (Gratz & Heinrich, 1997, 1998; Heinrich between inverse temperature and ln( KEq ) for the net-transfer equiet al., 1997; Andrehs & Heinrich, 1998). In addition, the librium YAG+OH-Ap+ (25/4)Qtz= (5/4)Grs+ (5/4)An recognition that nearly all lead in monazite is radiogenic + 3YPO4-Mnz + 1/2H2O, suggesting that garnet and monazite (Parrish, 1990; Montel et al., 1994) has led to development crystallized in compositional equilibrium. The following temand application of electron microprobe monazite dating perature–KEq relationship for the equilibrium above has been derived: techniques (Suzuki & Adachi, 1991; Montel et al., 1996; Williams et al., 1999). T(°C)= −1·45P(bars)+447772(±32052) 567(±40)−Rln( KEq ) −273·15 Full realization of monazite as a thermochronometer requires detailed understanding of the specific reactions responsible for its formation. Previous studies of monazite with a precision of some ±30°C for temperature estimates. Our petrogenesis have focused on monazite compositional observations suggest that major and accessory phases interact in a zonation (Zhu & O’Nions, 1999a, 1999b), monazite coupled fashion during metamorphism, and also approach a state growth kinetics (Ayers et al., 1999), behavior of monazite of compositional equilibrium as reactions proceed. during hydrothermal alteration (Poitrasson et al., 1996; Crowley & Ghent, 1999) and melting events (Watt, 1995), or, to a limited extent, the influence of major-phase mineral assemblage in monazite reactivity (Zhu &

Fundamentals of thermal-fluid sciences

Abstract: 1 Introduction and Overview PART I Thermodynamics 2 Basic Concepts of Thermodynamics 3 Properties of Pure Substances 4 Energy Transfer by Heat, Work, and Mass 5 The First Law of Thermodynamics 6 The Second Law of Thermodynamics 7 Entropy 8 Power and Refrigeration Cycles PART II Fluid Mechanics 9 Gas Mixtures and Psychrometrics 10 Properties of Fluids 11 Fluid Statics 12 Momentum Analysis of Flow Structures 13 Bernoulli and Energy Equations 14 Flow in Pipes 15 Flow Over Bodies: Drag and Lift Part III Heat Transfer 16 Mechanisms of Heat Transfer 17 Steady Heat Conduction 18 Transient Heat Conduction 19 Forced Convection 20 Natural Convection 21 Fundamentals of Thermal Radiation 22 Radiation Heat Transfer 23 Heat Exchanges PART IIII Appendices Appendix 1 Property Tables and Charts (SI Units) Appendix 1 Property Tables and Charts (English Units) Appendix 3 Introduction to EES

The Effect of Reward Structures on the Performance of Cross-Functional Product Development Teams

Abstract: This study examines the effect of reward structures on the performance of cross-functional product development teams. Results suggest that when it is easy to evaluate individual performances, position-based differential rewards lead to greater satisfaction. For long and complex projects, process-based rewards have a negative effect and outcome-based rewards have a positive effect on performance. For risky projects and highly competitive or relatively stable industries, a nonlinear and monotonically decreasing relationship exists between outcome-based rewards and product quality.

Interstellar Extinction and Polarization in the Taurus Dark Clouds: The Optical Properties of Dust near the Diffuse/Dense Cloud Interface

Abstract: Observations of interstellar linear polarization in the spectral range 0.35-2.2??m are presented for several stars reddened by dust in the Taurus region. Combined with a previously published study by Whittet et al., these results represent the most comprehensive data set available on the spectral dependence of interstellar polarization in this nearby dark cloud (a total of 27 sight lines). Extinction data for these and other reddened stars in Taurus are assembled for the same spectral range, combining published photometry and spectral classifications with photometry from the Two Micron All Sky Survey. The polarization and extinction curves are characterized in terms of the parameters ?max (the wavelength of maximum polarization) and RV (the ratio of total to selective extinction), respectively. The data are used to investigate in detail the question of whether the optical properties of the dust change systematically as a function of environment, considering stars observed through progressively more opaque (and thus progressively denser) regions of the cloud. At low visual extinctions (0 3, real changes in grain properties occur, characterized by observed RV values in the range 3.5-4.0. A simple model for the development of RV with AV suggests that RV may approach values of 4.5 or more in the densest regions of the cloud. The transition between normal extinction and dense cloud extinction occurs at AV ~ 3.2, a value coincident with the threshold extinction above which H2O-ice is detected on grains within the cloud. Changes in RV are thus either a direct consequence of mantle growth or occur under closely similar physical conditions. Dust in Taurus appears to be in a different evolutionary state compared with other nearby dark clouds, such as ? Oph, in which coagulation is the dominant physical process.

A stabilized finite element method for the incompressible Navier-Stokes equations using a hierarchical basis

Abstract: Stabilized finite element methods have been shown to yield robust, accurate numerical solutions to both the compressible and incompressible Navier-Stokes equations for laminar and turbulent flows. The present work focuses on the application of higher-order, hierarchical basis functions to the incompressible Navier-Stokes equations using a stabilized finite element method. It is shown on a variety of problems that the most cost-effective simulations (in terms of CPU time, memory, and disk storage) can be obtained using higher-order basis functions when compared with the traditional linear basis. In addition, algorithms will be presented for the efficient implementation of these methods within the traditional finite element data structures

Optimal line-sweep-based decompositions for coverage algorithms

Abstract: Robotic coverage is the problem of moving a sensor or actuator over all points in given region. Ultimately, we want a coverage path that minimizes some cost such as time. We take the approach of decomposing the coverage region into subregions, selecting a sequence of those subregions, and then generating a path that covers each subregion in turn. We focus on generating decompositions based upon the planar line sweep. After a general overview of the coverage problem, we describe how our assumptions lead to the optimality criterion of minimizing the sum of subregion altitudes (which are measured relative to the sweep direction assigned to that subregion). For a line-sweep decomposition, the sweep direction is the same for all subregions. We describe how to find the optimal sweep direction for convex polygonal worlds. We then introduce the minimal sum of altitudes (MSA) decomposition in which we may assign a different sweep direction to each subregion. This decomposition is better for generating an optimal coverage path. We describe a method based on multiple line sweeps and dynamic programming to generate the MSA decomposition.

Observer-based control of systems with slope-restricted nonlinearities

Abstract: An observer design is presented which makes use of bounds on the slope of system nonlinearities. Necessary and sufficient conditions are derived for the feasibility of the design. A class of state feedback control laws are characterized which, when implemented with the observer states, ensure global asymptotic stability. One such certainty-equivalence design is illustrated on an active magnetic bearing example.

Comparative Localization of Academic and Industrial Spillovers

Abstract: This paper studies localization of academic and industrial knowledge spillovers. Using data on U.S. Research and Development laboratories, that quantify spatial aspects of learning about universities and firms as well as their locations, I find that academic spillovers are more localized than industrial spillovers. I also find that localization is increased by nearby stocks of R&D, but reduced by laboratory and firm size. These results on localized academic spillovers reflect open science and the industry-university cooperative movement, which encourage firms to work with local universities, so that localization coincides with the public goods nature of science. This situation contrasts with relations to other firms, where contractual arrangements are needed to access proprietary information, often at a considerable distance.

A direct comparison between terahertz time-domain spectroscopy and far-infrared Fourier transform spectroscopy

Abstract: We perform a comprehensive comparison between terahertz (THz) time-domain spectroscopy and conventional far-infrared Fourier transform spectroscopy, including radiation source, detector, signal to noise ratio, bandwidth, availability, applications, and their own uniqueness. In terms of signal to noise ratio, THz time-domain spectroscopy is advantageous at low frequencies under 3 THz, while Fourier transform spectroscopy works better at frequencies above 5 THz. In addition, we provide a detailed discussion of the unique features of THz time-domain spectroscopy and its application to dynamic and time-resolved processes.

Natural language interface using constrained intermediate dictionary of results

Abstract: A method for processing a natural language input provided by a user includes: providing a natural language query input to the user; performing, based on the input, a search of one or more language-based databases; providing, through a user interface, a result of the search to the user; identifying, for the one or more language-based databases, a finite number of database objects; and determining a plurality of combinations of the finite number of database objects. The one or more language-based databases include at least one metadata database including at least one of a group of information types including case information, keywords, information models, and database values.

Observation of exclusive deeply virtual Compton scattering in polarized electron beam asymmetry measurements

Abstract: We report the first results of the beam spin asymmetry measured in the reaction e + p -> e + p + gamma at a beam energy of 4.25 GeV. A large asymmetry with a sin(phi) modulation is observed, as predicted for the interference term of Deeply Virtual Compton Scattering and the Bethe-Heitler process. The amplitude of this modulation is alpha = 0.202 +/- 0.028. In leading-order and leading-twist pQCD, the alpha is directly proportional to the imaginary part of the DVCS amplitude.

Light in the built environment: potential role of circadian disruption in endocrine disruption and breast cancer

Abstract: Life in industrialized societies is primarily life inside buildings. Illumination from electric lighting in the built environment is quite different from solar radiation in intensity, spectral content, and timing during the 24-hour daily period. Humans evolved over millions of years with the day-night pattern of solar radiation as the primary circadian cue. This pattern maintained a 24-hour rhythm of melatonin release, as well as a host of other physiological rhythms including the sleep-wake cycle. Electric lighting in the built environment is generally more than sufficient for visual performance, but may be inappropriate for the maintenance of normal neuroendocrine rhythms in humans; e.g., insufficient during the day and too much at night. Lighting standards and engineering stress visual performance, whereas circadian function is not currently emphasized. The molecular biological research on the circadian clock and on mechanisms of phototransduction makes it clear that light for vision and light for circadian function are not identical systems. In particular, if electric lighting as currently employed contributes to 'circadian disruption' it may be an important cause of 'endocrine disruption' and thereby contribute to a high risk of breast cancer in industrialized societies.