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  • Springer  (22)
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  • Technology  (22)
  • 1
    Electronic Resource
    Electronic Resource
    Monitoring and modeling of coastal waters in support of environmental preservation (1996)
    Springer
    Journal of marine science and technology 1 (1996), S. 75-84 
    Details
    ISSN: 1437-8213
    Keywords: monitoring ; modeling ; environmental preservation ; navigation ; nazardous spills ; tidal prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The improved monitoring and modeling capability resulting from recent technological advances in oceanographic sensors, computer processing power, and telecommunications can play a major role in environmental preservation. In particular, this capability can help improve: safe navigation and thus the prevention of maritime accidents that lead to hazardous spills; the effective cleanup of hazardous spills when they do occur; the real-time assessment of water quality problems; the assessment of long-term trends and variability due to both anthropogenic and climate change effects; and the understanding of key physical, chemical, and ecological processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02391163
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  • 2
    Electronic Resource
    Electronic Resource
    Simulation of Nanoparticle Production in Premixed Aerosol Flow Reactors by Interfacing Fluid Mechanics and Particle Dynamics (1999)
    Springer
    Journal of nanoparticle research 1 (1999), S. 305-315 
    Details
    ISSN: 1572-896X
    Keywords: particle population ; fluid mechanics ; flame synthesized aerosols ; CFD ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract The interaction of fluid mechanics and particle dynamics at the very early stages of flame synthesis largely affects the characteristics of the product powder. Detailed simulations provide a better understanding of these processes, which take place in a few milliseconds, and offer the possibility to influence the product characteristics by intelligent selection of the process parameters. The present paper reports on the simulation of titania powder formation by TiCl4 oxidation in an aerosol flow reactor. A commercially available fluid mechanics code is used for the detailed calculation of the fluid flow and the chemical reaction at non-isothermal conditions. This code is then interfaced with a model for aggregate particle dynamics neglecting the spread of the particle size distribution. The simulation shows the onset of the particle formation in the reactor and calculates the dynamic evolution of the aggregate particle size, number of primary particles per aggregate and the specific surface area throughout the reactor. The presented, newly developed calculation technique allows for the first time the simulation of particle formation processes under the authentic, complex conditions as found in actual aerosol reactors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010025121980
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  • 3
    Electronic Resource
    Electronic Resource
    On the plasma chemistry of the C/H system relevant to diamond deposition processes (1996)
    Springer
    Plasma chemistry and plasma processing 16 (1996), S. 173-185 
    Details
    ISSN: 1572-8986
    Keywords: Diamond synthesis ; atomic hydrogen ; modeling ; mass spectrometry ; pulsed rf discharge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The chemistry of hydrogen-rich hydrocarbon-hydrogen mixtures is of primary interest for the understanding of the low-pressure synthesis of diamond. We per formed experiments under well-defined conditions like temperature, pressure, initial gas composition, etc. The gas composition at the end of a flow reactor was analyzed by a calibrated mass spectrometer and compared to results obtained from the Chemkin computer code. Residence thne in the reactor as well as other process parameters were similar to those of diamond-growing PA CVD processes performed earlier with the same experimental set-rip. Modeling and experiment under isothermal conditions show quantitative agreement. We realized time-resolved mass .spectrometry by means of a helium-flushed gas sampling probe. There is evidence that the commonly used reaction kinetic data for the dissociation C2H6 (+ M) ⇔ 2CH,(+M) gives 2 too small C2H4 concentrations for hydrogen-rich conditions. This could be attributed to the poorly known third-body efficiencies of the H2 molecules compared to Ar or C2H6 from which kinetic data are commonly derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01570176
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  • 4
    Electronic Resource
    Electronic Resource
    Modeling of a DC Plasma Torch in Laminar and Turbulent Flow (1997)
    Springer
    Plasma chemistry and plasma processing 17 (1997), S. 409-432 
    Details
    ISSN: 1572-8986
    Keywords: Plasma torch ; modeling ; laminar and turbulent flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A mathematical 2D representation is developed describing the temperature and the velocity profiles in a DC plasma torch and in the resulting plume. It is based on the resolution of conservation equations using the Simple method after Patankar. In the first part, we illustrate the effects of the turbulence, using, on the one hand, two Prandtl's mixing length models and, on the other hand, a standard k – ε model. We also show the influence of physical parameters like the inlet mass flow rate, the current intensity, and the kind of gas (argon or air) on the characteristics of the plasma. The second part of this study presents a comparison of the model with experimental results encountered in the literature. The profiles obtained at the exit of the torch are compared to the mathematical formulation used as boundary condition by the models taking into account only the plasma jet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021847113956
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  • 5
    Electronic Resource
    Electronic Resource
    L.D.A. Simultaneous Measurements of Local Density and Velocity Distribution of Particles in Plasma Fluidized Bed at Atmospheric Pressure (1997)
    Springer
    Plasma chemistry and plasma processing 17 (1997), S. 433-452 
    Details
    ISSN: 1572-8986
    Keywords: Laser Doppler anemometry ; fluidized plasma bed ; particles velocity distribution ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Laser Doppler anemometry (L.D.A.) is an efficient and nonintrusive technique. Today, improved in its configuration, the L.D.A. has been applied even in flowing plasmas. (1,2) In-flight simultaneous measurements were performed for local density and velocity of particle distribution. The measurements provide an insight into thermal and mass transfer, chemical reactivity, and the distribution of residence times of particles in a plasma fluidized bed. The difficulties of L.D.A. in a plasma fludized bed such as high emission intensity of the plasma torch, high temperature, high particle density, and large distribution of particle granulometry were overcomed in the present investigation. The aims achieved were the characterization of the plasma fluidized bed distribution together with accurate measurements of local particle density and velocity as measured by L.D.A.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021899130794
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  • 6
    Electronic Resource
    Electronic Resource
    A Three-Dimensional Two-Phase Model for Thermal Plasma Chemical Vapor Deposition with Liquid Feedstock Injection (1998)
    Springer
    Plasma chemistry and plasma processing 18 (1998), S. 73-89 
    Details
    ISSN: 1572-8986
    Keywords: Thermal plasma ; CVD ; modeling ; liquid precursor ; diamond
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract In this paper, a comprehensive model for thermal plasma chemical vapor deposition (TPCVD) with liquid feedstock injection is documented. The gas flow is assumed to be steady, of a single temperature. Radiation and charged species contributions are excluded, but extensive homogeneous and heterogeneous chemistry is included. The liquid phase is traced by considering individual droplets. Discussion on the model's application to diamond production from acetone in a hydrogen–argon plasma is included. The major conclusions are: (1) Liquid injection possesses a capability to deliver the hydrocarbon precursor directly onto the deposition target. (2) For the case of complete evaporation of the droplet before reaching the substrate, the deposition rate is similar to that obtained with gaseous precursors. (3) The computational results compare well with experimental data. The modeling results can be used to optimize the injection parameters with regard to the deposition rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021741310669
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  • 7
    Electronic Resource
    Electronic Resource
    On the Correlation Between Deposition Rate and Process Parameters in Remote Plasma-Enhanced Chemical Vapor Deposition (1998)
    Springer
    Plasma chemistry and plasma processing 18 (1998), S. 189-214 
    Details
    ISSN: 1572-8986
    Keywords: Remote PECVD ; silicon dioxide ; modeling ; deposition rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Plasma-enhanced chemical vapor deposition has become one of the most important thin film deposition technologies. To avoid direct plasma exposure the substrates may be placed in the remote region. A carrier gas conveys the plasma energy to the deposition area where the reactions with the monomer molecules take place. For the engineering of such a process the modeling of the achievable deposition rate is of great interest. Among different possibilities semiempirical models provide a fast and easily utilizable tool without intensive computer simulations or the necessity of detailed knowledge about the chemistry involved. From deposition experiments with oxygen and an organosilicon monomer (hexamethyldisiloxane, HMDSO) the remote composite parameter is suggested. It combines microwave power, monomer and carrier gas flow rate, and the distance of the substrate from the plasma source. This parameter was derived from the ratio between atomic oxygen and monomer flow rate. In the parameter range considered the deposition rate is described as well ordered and the energy- and monomer-deficient regions are clearly separated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021698331973
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  • 8
    Electronic Resource
    Electronic Resource
    A Mathematical Model of the Carbon Arc Reactor for Fullerene Synthesis (1998)
    Springer
    Plasma chemistry and plasma processing 18 (1998), S. 285-303 
    Details
    ISSN: 1572-8986
    Keywords: Fullerenes ; carbon arc ; plasma process ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A mathematical model of the carbon arc process for the synthesis of fullerenes (C 60 , C 70 ) is developed. The two-dimensional model solves for the velocities, temperature, and total concentration of carbon species. The net emission coefficient method is used for the radiation term. The carbon species conservation equations consider the evaporation of carbon from the anode, cathode surface deposition, and carbon condensation. The thermodynamic and transport properties are calculated as a function of temperature and carbon mass fraction, using the method of Chapman–Enskog. Erosion rates used by the model are determined experimentally. Calculated fields of the velocities, temperatures, carbon mass fraction and current intensity are presented. Comparison is made of the behavior of the arc at 1 and 4 mm interelectrode gaps, and between operation in argon and in helium. The results of simulations provide a justification for the higher yields observed in helium compared to the argon case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021658717860
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  • 9
    Electronic Resource
    Electronic Resource
    Modeling of H2 and H2/CH4 Moderate-Pressure Microwave Plasma Used for Diamond Deposition (1998)
    Springer
    Plasma chemistry and plasma processing 18 (1998), S. 325-362 
    Details
    ISSN: 1572-8986
    Keywords: Microwave plasma ; diamond deposition ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract One-dimensional transport models of moderate-pressure H 2 and H 2 /CH 4 plasmas obtained in a diamond deposition microwave reactor are presented. These models describe the plasma as a thermochemically nonequilibrium flow with three different energy modes. The solution of the one-dimensional plasma transport equations enabled the estimation of plasma species concentrations and temperatures on the axis of the reactor. As far as pure H 2 plasmas are concerned, results showed that the model predictions of gas and vibration temperatures are in good agreement with experimental measurements. The model also yields a relatively good qualitative prediction of the variations of H-atom mole fraction with the power density absorbed by the plasma. The results obtained for H 2 /CH 4 discharges showed that the model prediction on the variations of H-atom mole fraction with methane percentage in the discharge is in good qualitative agreement with experimental results. They also showed that methane is rapidly converted to acetylene before reaching the discharge zone. The concentrations of neutral hydrocarbon species in the reactor are mainly governed by thermal chemistry. The addition of methane strongly affects the ionization kinetics of the plasma. Three major ions are generally obtained in H 2 /CH 4 plasmas: C 2 H 2 + , C 2 H 3 + , and C 2 H 5 + . The relative predominance of these ions depends on the considered plasma region and on the discharge conditions. The ionic species concentrations are also mainly governed by chemistry, except very near the substrate surface. Finally the use of this transport model along with the surface chemistry model of Goodwin (1) enabled us to estimate the diamond growth rate for several discharge conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021845402202
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  • 10
    Electronic Resource
    Electronic Resource
    Experimental and Theoretical Studies of a Pulsed Microwave Excited Ar/CF4 Plasma (1998)
    Springer
    Plasma chemistry and plasma processing 18 (1998), S. 429-446 
    Details
    ISSN: 1572-8986
    Keywords: Pulsed microwave discharge ; plasma ignition ; Ar/CF4 mixture ; plasma processing ; etching ; chemical kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The present work deals with a pulsed microwave discharge in an Ar/CF 4 gas mixture under a low pressure (1–10 mbar). The discharge chamber developed has a cylindrical geometry with a coupling window alternatively made of quartz or alumina. The setup allows one to investigate the plasma–wall interactions (here etching of the quartz window) and the ignition process of the pulsed microwave plasma. Microwave pulses with a duration of 50–200 μs and repetition rate between 1 and 10 kHz are typical for the experiments. The space-time behavior of the fluorine number density in the discharge has been investigated experimentally by optical actinometry. The discharge kinetics is modeled using electron-transport parameters and rate coefficients derived from solutions of the Boltzmann equation. Together with the solution of the continuity and electron balance equations and the rate equations describing the production of CF x (x=2, 3, 4) radicals and F atoms, a good agreement between experimental and theoretical data can be achieved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021803114922
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  • 11
    Electronic Resource
    Electronic Resource
    Modeling and Spectroscopic Investigations on the Evaporation of Zirconia in a Thermal rf Plasma (1999)
    Springer
    Plasma chemistry and plasma processing 19 (1999), S. 341-362 
    Details
    ISSN: 1572-8986
    Keywords: Thermal rf plasma ; modeling ; spectroscopy ; plasma flash evaporation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The evaporation process of zirconia powders injected in a thermal rf plasma is investigated. Both model calculations and optical emission spectroscopy are used to study the evaporation behavior. Gas temperatures and velocity distributions are determined numerically from conservation laws and Maxwell equations. The influence of plasma and particle parameters on the thermal history of entrained particles is discussed. Asymmetric Abel inversion is applied to detect asymmetric emission profiles in the plasma source. Spectroscopic measurements reveal that evaporated zirconium is concentrated near the axis of the plasma. Numerical calculations show that line-integrated emission profiles can be used to distinguish the cases of complete and incomplete evaporation. Axial emission profiles confirm that the evaporation zone is shifted upstream of the plasma when smaller precursor particles are used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021816302453
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  • 12
    Electronic Resource
    Electronic Resource
    Calculated Plasma Parameters and Excitation Spectra of High-Pressure Helium Discharges (1999)
    Springer
    Plasma chemistry and plasma processing 19 (1999), S. 467-486 
    Details
    ISSN: 1572-8986
    Keywords: He-plasma ; excitation spectra ; modeling ; comparison with experiments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A collisional-radiative model was used to study the kinetics of an atmospheric pressure helium discharge. The electron kinetics was obtained from a two-term solution of the Boltzmann equation with electron–electron collisions included. The distribution of the helium electronic excited states was compared to measured values and used to calculate excitation temperatures. The results show that a unique value of the excitation temperature cannot be used to characterize the whole electronic states distribution, because the plasma is not in local thermodynamical equilibrium under the conditions considered. Other calculated discharge parameters, such as the electron temperature, the maintenance electric field, the density of metastable atoms in the 2 3 S state, and the ion densities are presented and compared to experimental data when available.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021878309471
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  • 13
    Electronic Resource
    Electronic Resource
    CARS Diagnostic and Modeling of a Dielectric Barrier Discharge (1999)
    Springer
    Plasma chemistry and plasma processing 19 (1999), S. 445-466 
    Details
    ISSN: 1572-8986
    Keywords: Dielectric barrier discharge ; CARS on N2 and NO ; NO reduction ; chemical and vibrational kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Dielectric barrier discharges (DBD) with planar- and knife-shaped electrodes are operated in N2O2NO mixtures under a pressure of 20 and 98 kPa. They are excited by means of consecutive unipolar or bipolar high-voltage pulse packages of 10 kV at a pulse repetition rate of 1 and 2 kHz. The rotational and vibrational excitation of N 2 molecules and the reduction of nitric oxide (NO) in the discharge have been investigated using coherent anti-Stokes Raman scattering (CARS) technique. Rotational (gas) temperatures near the room temperature and vibrational temperatures of about 800 K at atmospheric pressure and 1400 K at a pressure of 20 kPa are observed. Therefore, chemical reactions of NO with vibrationally excited N 2 are probably insignificant. One-dimensional kinetic models are developed that balance 35 chemical reactions between 10 species and deliver equations for the population density of excited vibrational levels of N 2 together with a solution of the Boltzmann equation for the electrons. A good agreement between measured vibrational temperatures of N 2 , the concentration of NO, and calculated data is achieved. Modeling of the plasma discharge verifies that a DBD operated with a N2NO mixture reduces the NO content, the simultaneous presence of O 2 , already 1%, is enough to prevent the NO reduction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021826325400
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  • 14
    Electronic Resource
    Electronic Resource
    Thinking in Levels: A Dynamic Systems Approach to Making Sense of the World (1999)
    Springer
    Journal of science education and technology 8 (1999), S. 3-19 
    Details
    ISSN: 1573-1839
    Keywords: levels ; complexity ; simulation ; modeling ; science education ; mathematics education ; dynamic systems ; systems thinking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General , Technology
    Notes: Abstract The concept of emergent "levels" (i.e., levels that arise from interactions of objects at lower levels) is fundamental to scientific theory. In this paper, we argue for an expanded role for this concept of levels in science education. We show confusion of levels (and "slippage" between levels) as the source of many of people's deep misunderstandings about patterns and phenomena in the world. These misunderstandings are evidenced not only in students' difficulties in the formal study of science but also in their misconceptions about experiences in their everyday lives. The StarLogo modeling language is designed as a medium for students to build models of multi-leveled phenomena and through these constructions explore the concept of levels. We describe several case studies of students working in StarLogo. The cases illustrate students' difficulties with the concept of levels, and how they can begin to develop richer understandings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009421303064
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  • 15
    Electronic Resource
    Electronic Resource
    Part I: Toward a System of Educational Engineering for Traditional Class Elements: A Case Study in an Introductory Physics Course (1997)
    Springer
    Journal of science education and technology 6 (1997), S. 173-191 
    Details
    ISSN: 1573-1839
    Keywords: Science education ; educational engineering ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General , Technology
    Notes: Abstract In this paper, we present a system for formally characterizing elements of an introductory science class, measuring the performance of a class based on this characterization, and modeling the value of the class based on the measurements. This system allows the iterative improvement of any educational presentation through a model, test, iterate cycle. We propose formal practices involved in iteratively improving an educational experience be called educational engineering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022575606713
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  • 16
    Electronic Resource
    Electronic Resource
    Modeling Microbial Transport and Biodegradation in a Dual-porosity System (1999)
    Springer
    Transport in porous media 35 (1999), S. 49-65 
    Details
    ISSN: 1573-1634
    Keywords: modeling ; biodegradation ; microbial transport ; dual-porosity ; kinetics.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A mathematical model describing microbial transport and growth in a heterogeneous aquifer domain, composed of overlapping subdomains of high-permeability and low-permeability materials, is developed. Each material is conceptually visualized as a continuum which occupies the entire considered spatial aquifer domain. Based on the assumption that advection in the low-permeability domain is negligible, the mathematical model is solved by using a publically available reactive transport code. The importance of modeling microbial transport and growth in such a dual-porosity system is demonstrated through a hypothetical case study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006551627151
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  • 17
    Electronic Resource
    Electronic Resource
    Modeling primary substrate controlled biotransformation and transport of halogenated aliphatics in porous media (1996)
    Springer
    Transport in porous media 24 (1996), S. 203-220 
    Details
    ISSN: 1573-1634
    Keywords: biotransformation ; halogenated solvents ; anaerobic processes ; modeling ; cometabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract In situ biorestoration is a groundwater remediation technique in which the indigenous aquifer bacteria are stimulated by injecting compounds to provide carbon source and energy. Stimulated bacteria may transform the target contaminants such as tetrachloroethylene (PCE) and trichloroethylene (TCE) into intermediate products. In this study, we developed a model to simulate the substrate-limited biotransformation of the halogenated solvents present in anoxic groundwater by sequential reductive dehalogenation under methanogenic conditions. The model consists of conservation of mass equations for the primary substrate, immobile indigenous biomass, organic solvents such as PCE and TCE, and their intermediate products trichloroethylene, dichloroethylene, and vinyl chloride. The utilization of primary substrate and the biotransformation of organic solvents are assumed to follow Monod kinetics. The limiting factor on bacterial growth is assumed to be the primary substrate. The microbial yield coefficient is determined from the stoichiometric equation describing the anaerobic process. The model is solved by using a finite difference technique. Results are presented for three different case studies: continuous injection of primary substrate (acetate), single-pulse injection, and double-pulse injection. The single-pulse or double-pulse injection techniques were found to be more effective than continuous injection of primary substrate. Double-pulse technique reduces the clogging of injection wells caused by excessive microbial growth around boreholes and achieves a more uniform distribution of microbial growth in the subsurface. In all cases target compounds were effectively removed. The results, however, indicate substantial levels of intermediate product accumulation. Numerical results of a simplified model which assumes an abundance of primary substrate and a constant population of biomass, compare favorably with experimental data reported in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00139845
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  • 18
    Electronic Resource
    Electronic Resource
    Some Considerations on Modeling Heat and Mass Transfer in Porous Media (1997)
    Springer
    Transport in porous media 28 (1997), S. 233-251 
    Details
    ISSN: 1573-1634
    Keywords: capillary pressure ; conservation equations ; constitutive equations ; liquid water ; modeling ; thermodynamic equilibrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract In this paper some considerations are presented about the equations needed to set up a model of the process of heat and mass transfer in porous media. A clear classification is made of the various types of equations used and of their physical meaning. Special attention is paid to the thermodynamic equilibrium equations and to their derivation since they are too often taken for granted. The importance of the various transport mechanisms (of mass and energy) is analyzed and the consequences that can arise when some term is neglected are indicated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006525729566
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  • 19
    Electronic Resource
    Electronic Resource
    Single Phase Flow in Partially Fissured Media (1997)
    Springer
    Transport in porous media 28 (1997), S. 285-306 
    Details
    ISSN: 1573-1634
    Keywords: fissured media ; homogenization ; dual porosity ; modeling ; microstructure ; porous media
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Totally fissured media in which the individual cells are isolated by the fissure system are effectively described by double porosity models with microstructure. Such models contain the geometry of the individual cells in the medium and the flux across their interface with the fissure system which surrounds them. We extend these results to a dual-permeability model which accounts for the secondary flux arising from direct cell-to-cell diffusion within the solid matrix. Homogenization techniques are used to construct a new macroscopic model for the flow of a single phase compressible fluid through a partially fissured medium from an exact but highly singular microscopic model, and it is shown that this macroscopic model is mathematically well posed. Preliminary numerical experiments illustrate differences in the behaviour of solutions to the partially fissured from that of the totally fissured case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006562120265
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  • 20
    Electronic Resource
    Electronic Resource
    Part II: A Computationally Based Modeling System for Class Elements Using Formal Observer-Based Experimental Connections (1997)
    Springer
    Journal of science education and technology 6 (1997), S. 193-211 
    Details
    ISSN: 1573-1839
    Keywords: Science education ; educational engineering ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General , Technology
    Notes: Abstract This article extends and refines the modeling system presented previously (Stewart, 1997). The initial system was sufficient for the optimization of delivery of education at a departmental level. This system is greatly more powerful, precise, and scientific, and fulfills the role of a modeling system for the research and development of educational practices. The model is applied to two widely diverse educational processes, Student Actions and Do Homework Problem, establishing the formalism and demonstrating its usefulness. The use of a rigorous computational syntax imposes completeness criteria on the modeling itself and uniformity. Experimental definition of the formation process of the patterns allows anyone to introduce new features of a model. This and the uniformity allows the models to become the property of the education community, not merely a single researcher, in the same way that mathematical models allow scientists to utilize and build upon previous research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022527723551
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  • 21
    Electronic Resource
    Electronic Resource
    Optimally Engineering Traditional Introductory Physics Classes (1997)
    Springer
    Journal of science education and technology 6 (1997), S. 297-314 
    Details
    ISSN: 1573-1839
    Keywords: Science education ; educational engineering ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General , Technology
    Notes: Abstract This paper presents a measurement of the time and resources committed to traditional student actions such as reading and working homework. The perception of the educational value of each basic action for both students and faculty is captured. From this information, basic educational efficiencies are computed for a traditional mechanics course and a non-traditional hands-on Electricity and Magnetism course. The calculations show an allocation of resources in the traditional course which uses the most student time in the least educationally valuable activity. The computed efficiencies also show overseen student note-taking as potentially a very valuable general tool. The techniques presented allow any institution to carry out quantitative educational engineering of their course offerings at the highest level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022502211969
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  • 22
    Electronic Resource
    Electronic Resource
    Pulsing Interial Oscillation, Supercell Storms, and Surface Mesonetwork Data (1998)
    Springer
    Journal of engineering mathematics 34 (1998), S. 277-300 
    Details
    ISSN: 1573-2703
    Keywords: modeling ; supercell storm ; nonlinear ; inertial oscillation ; mesonetwork data.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract The pulsing inertial oscillation (PIO) model is a nonlinear, time-dependent, translating vortex solution of the inviscid, compressible fluid dynamic equations in the middle troposphere. The translation of this vortex during a pulse is strikingly similar to that of a supercell storm – a rotating thunderstorm that can generate tornadoes and hail. Two studies were performed to test the hypothesis that some supercell storms are manifestations of a PIO pulse. The first study applied the model to an intense interior draft whose buoyancy was bounded by a temperature excess of ± 12 K. The peak updraft speed achieved was 41·5 m s−1 and the peak Rossby number was 92·9. The study also pointed to an advanced concept for attaining higher values. The second study applied the PIO model to a supercell storm as a whole and succeeded in replicating its bulk properties, such as mesocylonic circulation, net mass and moisture influxes, and time track. This study also identified a critical feature of the PIO model that could be tested against storm data: The average vertical draft is downward before the turn in the storm track and upward afterwards. In the conventional theory, the average vertical draft is upward from storm inception until dissipation. These differing draft predictions were compared with the best available data, which are surface mesonetwork data. These data were found to support the PIO model. However, surface data alone are not conclusive, and further measurements are warranted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004319330013
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