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  • Articles  (36)
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  • Springer  (36)
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  • American Geophysical Union
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  • 1
    Electronic Resource
    Electronic Resource
    Transient Thermal Study of an Adsorption Refrigerating Machine (2000)
    Springer
    Adsorption 6 (2000), S. 93-104 
    Details
    ISSN: 1572-8757
    Keywords: adsorption refrigerator ; transient operation ; activated carbon ; methanol ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Adsorption refrigerators are a particular type of refrigerator in which compression is avoided, and in a sense replaced by adsorption. No mobile parts are needed; the energy input, instead of being mechanical, is thermal and is used to achieve desorption. Such machines have a cyclic operation, made of successive adsorption/evaporation and of desorption/condensation steps. The transient operation of adsorption refrigerators is a relatively recent subject of research. The modeling of the adsorber is the key point of such studies, because of the complex coupled heat and mass transfer phenomena that occur during the cycle. The present work therefore presents a study of an annular type adsorber which is intended to account for transient temperatures observed experimentally. The equipment in which the experiments were performed and which uses alcohol adsorption on activated carbon is briefly described, and its operating cycle described, along with typical experimental observations of pressure and temperature transients. A model of the adsorber unit is proposed which accounts for the coupling of adsorption and heat transfer, and describes mass-transfer in the annular adsorbent layer as a global diffusional mechanism with temperature dependent parameters. This model correctly predicts, qualitatively and semi-quantitatively, the observed trends of the temperature changes. Finally, various aspects of the performances are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008907518073
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Electromagnetic Subsurface Imaging. A Case for an Adaptive Born Approximation (1997)
    Springer
    Surveys in geophysics 18 (1997), S. 477-510 
    Details
    ISSN: 1573-0956
    Keywords: electromagnetic ; modeling ; inversion ; imaging ; transient electromagnetic method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The process of interpretation of electromagnetic data has many facets of which fast approximate interpretation techniques is an intriguing one. A new variant of the Born approximation – the Adaptive Born approximation – is presented and exemplified through 1D and 2D imaging techniques for transient electromagnetic data. The Adaptive Born approximation is generally applicable in approximate inversion schemes for inductive electromagnetic data as a one-pass imaging algorithm. Though it is as simple to use as the ordinary Born approximation, it offers a more accurate inverse mapping. In the first part of this paper an attempt will be made to give an overview of fundamental concepts in electromagnetic subsurface imaging relevant for approximate inverse mappings and to outline major trends in present day modeling and inversion of electromagnetic data. This is of course an impossible task – certainly for this author – and much important work will not be mentioned in the limited space of the following. My apologies to the people who are not mentioned and whose research is not given credit here though it should have been. Naturally, my choice of references reflects the “schools” and circles I have been subjected to, but I hope that the list of references to developments in electromagnetic methods will point to papers of importance and thereby to other references for the interested reader.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006593408478
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  • 4
    Electronic Resource
    Electronic Resource
    A Model for diffusion controlled bioavailability of crude oil components (1997)
    Springer
    Biodegradation 8 (1997), S. 287-296 
    Details
    ISSN: 1572-9729
    Keywords: asphaltene ; bioavailability ; biodegradation ; crude oil ; diffusivity ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Crude oil is a complex mixture ofseveral different structural classes of compoundsincluding alkanes, aromatics, heterocyclic polarcompounds, and asphaltenes. The rate and extent ofmicrobial degradation of crude oil depends on theinteraction between the physical and biochemicalproperties of the biodegradable compounds and theirinteractions with the non-biodegradable fraction. Inthis study we have systematically altered theconcentration of non-biodegradable material in thecrude oil and analyzed its impact on transport of thebiodegradable components of crude oil to themicroorganisms. We have also developed a mathematicalmodel that explains and accounts for the dependence ofbiodegradation of crude oil through a putativebioavailability parameter. Experimental resultsindicate that as the asphaltene concentration in oilincreases, the maximum oxygen uptake in respirometersdecreases. The mathematically fitted bioavailabilityparameter of degradable components of oil alsodecreases as the asphaltene concentration increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008293024768
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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    OES Use and Vaporization Modeling for Fly-Ash Plasma Vitrification (2000)
    Springer
    Plasma chemistry and plasma processing 20 (2000), S. 65-86 
    Details
    ISSN: 1572-8986
    Keywords: thermal plasma ; waste processing ; fly-ash vitrification ; optical emission spectroscopy ; volatilization ; lead ; 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 Results are presented of optical emission spectroscopy (OES) application asa control tool to improve fly-ash plasma vitrification. A twin-torch plasmasystem has been used for the fly-ash processing, and a new OES method hasexamined metallic vapors above the melt. The method allows the study ofnonhomogeneous optically thin plasmas exhibiting a symmetry plane withoutsophisticated tomographic systems. The dc arc torches are mounted above acold crucible filled with a synthetic glass. The arc intensity is from200 to 400 Å. Argon is introduced into the torches along the cathodeand the anode, while argon, oxygen or hydrogen are injected through thelance between the torches. Local plasma temperatures above the melt havebeen evaluated using measured relative intensities of spectral lines ofthe plasma-forming gas. Metallic vapor concentration in the plasma isdeduced from the intensity ratio of the metal–gas spectral lines. Leadoxide has been used to study heavy-metal behavior at the fly-ash plasmavitrification. Distribution of the lead along the crucible surface,depending on the plasma-forming gas composition as well as the concentrationevolution with time, have been examined. The elemental analysis of theresultant glass has been measured by scanning electron microscopy (SEM)with energy-dispersive spectrometry (EDS). A predictive model has beenadapted to simulate the noncongruent vaporization of heavy metals from themelt. According to the data obtained, steep variations of the volatility ofthe elements depend strongly on reducing properties of gases controllingthe plasma composition near the melted surface. In addition, the melttemperature and the redox potential of the gas phase are found to be themost critical parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006921927249
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  • 9
    Electronic Resource
    Electronic Resource
    Mathematical Modeling of Silica Anode Decomposition (2000)
    Springer
    Plasma chemistry and plasma processing 20 (2000), S. 521-553 
    Details
    ISSN: 1572-8986
    Keywords: thermal plasma ; transferred arc ; fumed silica ; 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 volatilization of quartz in a transferred arc plasma followed byquench and recondensation is a promising route to the production offumed silica. In this work, an existing model of a transferred arcwas modified and combined with a newly developed model of a moltensilica anode to predict the behavior of a transferred arc evaporatoras a function of current and plasma gas flow rate. The model predictstemperature, current, and flow fields in both the plasma and anode aswell as evaporation rates. Although quantitative agreement withexperimental results was not possible because of insufficient propertydata for silica at high temperature, the results were within an orderof magnitude of those measured experimentally. The model developed isuseful for the design and scaleup of this type of reactor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007083923427
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  • 10
    Electronic Resource
    Electronic Resource
    VOC emissions from primary clarifier weirs (1996)
    Springer
    Water, air & soil pollution 92 (1996), S. 409-419 
    Details
    ISSN: 1573-2932
    Keywords: Volatile organic compounds ; emissions ; wastewater treatment ; weirs ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Volatile organic compounds (VOCs) are emitted from wastewater treatment processes via stripping and volatilization. Significant progress has been made in modeling these emissions, but questions remain regarding operative mass transfer mechanisms in certain processes. In the case of flow over weirs and drop structures, two approaches have been presented: mass transfer is modeled as taking place either (1) entirely in the nappe, or (2) entirely in air bubbles entrained by falling water in the tailwater pool. In the present work, these two very different modeling approaches are evaluated using experimental results on liquid-side concentrations of chlorinated solvents above and below a primary clarifier weir. The model locating the primary emission mechanism within entrained air bubbles in the tailwater pool is found to predict observed liquid-side VOC concentrations better than the model which considers only emissions from the weir nappe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00283570
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  • 11
    Electronic Resource
    Electronic Resource
    Modeling of population dynamics of interacting species: effect of exploitation (1997)
    Springer
    Environmental modeling and assessment 2 (1997), S. 55-63 
    Details
    ISSN: 1573-2967
    Keywords: modeling ; life cycle ; interaction ; copepods ; human exploitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A model representing the predator‐prey interactions between two copepod species, Euterpina acutifrons and Temora stylifera, with unlimited resources was used to study effects of exploitation. Exploitation is modeled by harvesting strategies characterized through three parameters: the selectivity of gear, the frequency of harvest, and the intensity of harvest effort. Simulations of different harvesting strategies suggest that interactions between species influence the dynamic behaviors of the populations as well as harvesting yields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019080420852
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  • 12
    Electronic Resource
    Electronic Resource
    Hybridomas in a bioreactor cascade: modeling and determination of growth and death kinetics (1996)
    Springer
    Cytotechnology 21 (1996), S. 263-277 
    Details
    ISSN: 1573-0778
    Keywords: hybridomas ; serum-free medium ; monoclonal antibodies ; reactor series ; kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Hybridomas were cultured under steady-state conditions in a series of two continuous stirred-tank reactors (CSTRs), using a serum-free medium. The substrate not completely converted in the first CSTR, was transported with the cells to the second one and very low growth rates, high death rates, and lysis of viable cells were observed in this second CSTR. These conditions are hardly accessible in a single vessel, because such experiments would be extremely time-consuming and unstable due to a low viability. In contrast to what is often observed in literature, kinetic parameters could thus be derived without the neccessity for extrapolation to lower growth rates. Good agreement with literature averages for other hybridomas was found. Furthermore, showing that the reactor series is a valuable research tool for kinetic studies under extreme conditions, the possibility to observe cell death under stable and defined steady-state conditions offers interesting opportunities to investigate apoptosis and necrosis. Additionally, a model was developed that describes hybridoma growth and monoclonal antibody production in the bioreactor cascade on the basis of glutamine metabolism. Good agreement between the model and the experiments was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365349
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  • 13
    Electronic Resource
    Electronic Resource
    Principles of Integrated Flow Modeling (2000)
    Springer
    Transport in porous media 41 (2000), S. 105-116 
    Details
    ISSN: 1573-1634
    Keywords: flow ; integration ; Gassmann ; acoustics ; reservoir ; characterization ; modeling ; simulation ; Newton–Raphson
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Integrated flow modeling is the combination of a traditional flow simulator with a petrophysical model. By combining a petrophysical model with a traditional flow model, it is possible to perform calculations that improve our ability to monitor fluid movement in porous media. This paper outlines the formulation of an integrated flow model IFLO and its multi-variable, Newton–Raphson IMPES solution procedure. The benefits of integrated flow modeling and the underlying principles involved in the integration of a flow model with a petrophysical model are presented. Results from the IFLO model are used to illustrate the principles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006658900240
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  • 14
    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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  • 15
    Electronic Resource
    Electronic Resource
    Laboratory, Field and Modeling Studies of Radon‐222 as a Natural Tracer for Monitoring NAPL Contamination (2000)
    Springer
    Transport in porous media 38 (2000), S. 223-240 
    Details
    ISSN: 1573-1634
    Keywords: NAPLs ; radon ; modeling ; monitoring ; partitioning ; tracer ; emanation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The recently developed natural radon tracer method has potential as a rapid, low‐cost, nondestructive, and noninvasive method for quantifying NAPL contamination. In the subsurface, radon‐222 (radon) is produced by the decay of naturally occurring radium‐226 contained in the mineral fraction of aquifer solids. In groundwater radon occurs as a dissolved gas, with a half‐life of 3.83 days. In the absence of NAPL, the radon concentration in groundwater quickly reaches a maximum value that is determined by the mineral composition of the aquifer solids, which controls the rate of radon emanation. In the presence of NAPL, however, the radon concentration in the groundwater is substantially reduced due to the preferential partitioning of radon into the organic NAPL phase. A simple equilibrium model and supporting laboratory studies show the reduction in radon concentration can be quantitatively correlated with residual NAPL saturation. Thus, by measuring the spatial distribution in radon it may be possible to identify locations where residual NAPL is present and to quantify the NAPL saturation. When the basic processes of partitioning, radon emanation from the aquifer solids, and first‐order decay are incorporated into an advective/dispersive transport model, good agreement is obtained with the results of laboratory and field experiments. Model sensitivity analyses shows many factors can contribute to the radon concentration response, including the length of the NAPL zone, NAPL saturation, groundwater velocity, porosity, and radon emanation. Thus, care must be taken when applying the radon method to locate and quantify NAPL contamination in the subsurface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006671519143
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  • 16
    Electronic Resource
    Electronic Resource
    Hydraulics of Peat Filters Treating Septic Tank Effluent (2000)
    Springer
    Transport in porous media 41 (2000), S. 47-60 
    Details
    ISSN: 1573-1634
    Keywords: unsaturated flow ; peat ; filters ; septic ; modeling ; hydraulics ; soil moisture retention curve
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Peat is an alternative filter medium for the treatment of various waste streams including septic tank effluent. The water holding capacity and adsorption capacity of peat make it a favorable filter medium over sand or gravel which are commonly used as the filter medium for the drainage field of septic systems. This paper presents the results of a field study to evaluate the hydraulics of a peat filter used to treat the septic tank effluent from a public school west of Ottawa, Canada. An experimental box was placed within the filter during its construction to provide access to the vertical profile of the peat layer. The filter is periodically pulsed with septic tank effluent, which is distributed over the top of the filter and flows vertically through the peat. The filter was instrumented with tensiometers and transducers to monitor the pore water pressures in response to a pulse of septic tank effluent. An in-depth study of the hydraulics of the system was completed. The soil moisture retention curve and the hydraulic conductivity as a function of density were determined in laboratory experiments. A one-dimensional unsaturated flow model was used to predict the pressure response due to a pulse. A comparison of the field and model results illustrates the impact of the density variations, and the corresponding hydraulic conductivity variations, on the model predictions. The compaction of the peat is an important design consideration for the filter since it directly impacts the flow characteristics and the hydraulic retention time within the filter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006796827147
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  • 17
    Electronic Resource
    Electronic Resource
    Modeling Sediment Transport Dynamics in Thompson Island Pool, Upper Hudson River (2000)
    Springer
    Water quality and ecosystem modeling 1 (2000), S. 193-222 
    Details
    ISSN: 1573-1669
    Keywords: Sediment transport ; modeling ; Upper Hudson River
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Two-dimensional, vertically-averaged hydrodynamic and sediment transport models were developed and applied as part of a PCB fate and transport modeling study of Thompson Island Pool (TIP), Upper Hudson River. Mechanistic formulations were used to simulate cohesive and non-cohesive suspended load transport; site-specific data were extensively used to determine model inputs. This modeling approach is compared and contrasted to non-mechanistic solids transport sub-models used in other contaminant fate studies. A minimum number of model parameters were adjusted to calibrate the sediment transport model using data collected during the 1994 spring flood. The model was validated during the 1997 spring flood and for a 22-year (1977–1998) period. Successful calibration and validation of the model showed that: (1) deposition and resuspension processes were realistically and accurately formulated in the model; (2) the model is an effective diagnostic tool for quantitatively evaluating net deposition and erosion from various areas of TIP; and (3) sediment transport results can be coupled with a PCB fate model with a high degree of confidence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013942801354
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  • 18
    Electronic Resource
    Electronic Resource
    A River Water Quality Model for Chlorophyll and Dissolved Oxygen that Accommodates Zebra Mussel Metabolism (2000)
    Springer
    Water quality and ecosystem modeling 1 (2000), S. 271-309 
    Details
    ISSN: 1573-1669
    Keywords: zebra mussels ; modeling ; water quality ; Seneca River ; dissolved oxygen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The development, testing and application of a dynamic two-dimensional (longitudinal-vertical) mass balance model for dissolved oxygen (DO) and chlorophyll (Chl) for rivers is documented that for the first time accommodates both the oxygen demand and filtering effects of zebra mussels. The test system is a phytoplankton-rich section (∼ 15 km long) of the Seneca River, NY, that is believed to represent an upper bound of the impact of this exotic invader. Changes in common measures of water quality of the river brought about by the zebra mussel invasion are reviewed and related longitudinal patterns in DO, Chl, and Secchi disc transparency are documented. Model testing is supported by comprehensive measurements of DO, Chl, and various forcing conditions over a three-month period, and independent determinations of several model coefficients. Wide variations in the areal consumption rate of DO (ZOD; g·m−2·d−1) and filtering rate (m3·m−2·d−1) of zebra mussels, as determined through model calibration, occurred over the study period. Values of ZOD in areas with dense zebra mussel populations at times (e.g., 〉 50 g·m−2·d−1) were an order of magnitude greater than the sediment oxygen demand associated with organically enriched deposits. The value of determinations of these fluxes from model calibration procedures is evaluated within the context of the limitations of protocols presently available to support independent specification of these rates. Model analyses are conducted to evaluate the relative magnitude of source and sink processes for DO and Chl, the potential operation and implications of feedback from low DO levels on oxygen consumption by zebra mussels, and the sensitivity of model simulations to selected sources of uncertainty and variability. Model projections of oxygen resources of the river are presented in a probabilistic format in evaluating reductions in zebra mussel biomass that would be necessary to eliminate violations of standards and regain assimilative capacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013951003172
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  • 19
    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.
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    URL: http://dx.doi.org/10.1007/BF00139845
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    A Population Density Approach That Facilitates Large-Scale Modeling of Neural Networks: Analysis and an Application to Orientation Tuning (2000)
    Springer
    Journal of computational neuroscience 8 (2000), S. 19-50 
    Details
    ISSN: 1573-6873
    Keywords: neural networks ; modeling ; population density ; orientation tuning ; visual cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine , Physics
    Notes: Abstract We explore a computationally efficient method of simulating realistic networks of neurons introduced by Knight, Manin, and Sirovich (1996) in which integrate-and-fire neurons are grouped into large populations of similar neurons. For each population, we form a probability density that represents the distribution of neurons over all possible states. The populations are coupled via stochastic synapses in which the conductance of a neuron is modulated according to the firing rates of its presynaptic populations. The evolution equation for each of these probability densities is a partial differential-integral equation, which we solve numerically. Results obtained for several example networks are tested against conventional computations for groups of individual neurons. We apply this approach to modeling orientation tuning in the visual cortex. Our population density model is based on the recurrent feedback model of a hypercolumn in cat visual cortex of Somers et al. (1995). We simulate the response to oriented flashed bars. As in the Somers model, a weak orientation bias provided by feed-forward lateral geniculate input is transformed by intracortical circuitry into sharper orientation tuning that is independent of stimulus contrast. The population density approach appears to be a viable method for simulating large neural networks. Its computational efficiency overcomes some of the restrictions imposed by computation time in individual neuron simulations, allowing one to build more complex networks and to explore parameter space more easily. The method produces smooth rate functions with one pass of the stimulus and does not require signal averaging. At the same time, this model captures the dynamics of single-neuron activity that are missed in simple firing-rate models.
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    URL: http://dx.doi.org/10.1023/A:1008912914816
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    The use of system identification techniques in the analysis of oculomotor burst neuron spike train dynamics (1996)
    Springer
    Journal of computational neuroscience 3 (1996), S. 347-368 
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    ISSN: 1573-6873
    Keywords: oculomotor ; burst neurons ; system identification ; saccade ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine , Physics
    Notes: Abstract The objective of system identification methods is to construct a mathematical model of a dynamical system in order to describe adequately the input-output relationship observed in that system. Over the past several decades, mathematical models have been employed frequently in the oculomotor field, and their use has contributed greatly to our understanding of how information flows through the implicated brain regions. However, the existing analyses of oculomotor neural discharges have not taken advantage of the power of optimization algorithms that have been developed for system identification purposes. In this article, we employ these techniques to specifically investigate the “burst generator” in the brainstem that drives saccadic eye movements. The discharge characteristics of a specific class of neurons, inhibitory burst neurons (IBNs) that project monosynaptically to ocular motoneurons, are examined. The discharges of IBNs are analyzed using different linear and nonlinear equations that express a neuron's firing frequency and history (i.e., the derivative of frequency), in terms of quantities that describe a saccade trajectory, such as eye position, velocity, and acceleration. The variance accounted for by each equation can be compared to choose the optimal model. The methods we present allow optimization across multiple saccade trajectories simultaneously. We are able to investigate objectively how well a specific equation predicts a neuron's discharge pattern as well as whether increasing the complexity of a model is justifiable. In addition, we demonstrate that these techniques can be used both to provide an objective estimate of a neuron's dynamic latency and to test whether a neuron's initial firing rate (expressed as an initial condition) is a function of a quantity describing a saccade trajectory (such as initial eye position).
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    URL: http://dx.doi.org/10.1007/BF00161093
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    Achieving the Kyoto Protocol in the U.S.: How Great are the Needed Changes? (2000)
    Springer
    Mitigation and adaptation strategies for global change 5 (2000), S. 123-142 
    Details
    ISSN: 1573-1596
    Keywords: Kyoto Protocol ; GHG ; mitigation strategies ; economiccosts ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Abstract The Kyoto Protocol requires the U.S.to reduce the rate of emissions of six greenhousegases (GHG) to 93% of their 1990 rate and to achievethis target by the 2008 to 2012 commitment period. This study assesses the magnitude of change needed inthe U.S. economy and, specifically, in the U.S. energysector, to achieve and maintain the target establishedby the Kyoto Protocol. A simple carbon (C)emissions-energy model is explained in this analysisusing four key variables. Current and future trendsin C emissions are explained by: the carbon/energy(C/E) ratio, Gross Domestic Product growth, energyprices and an energy trend variable. Potential GHGmitigation policy actions affect C emissionsindirectly by affecting at least one of these keyvariables. The analysis concludes that reducingfossil energy use in the U.S. to meet the Kyoto GHGemissions reduction target would be very costly. Technological progress that reduces C emissions wouldnot be fully sufficient without prematurely abandoningproductive capital equipment. Energy price increasesof about 14% per year, or declines in economic growthof almost 5% per year, could reduce energy demand andassociated C emissions enough to achieve the terms ofthe Kyoto Protocol.
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    URL: http://dx.doi.org/10.1023/A:1009697416321
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    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.
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    URL: http://dx.doi.org/10.1023/A:1006525729566
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    Single Phase Flow in Partially Fissured Media (1997)
    Springer
    Transport in porous media 28 (1997), S. 285-306 
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    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.
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    URL: http://dx.doi.org/10.1023/A:1006562120265
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    Rotational Properties of Cometary Nuclei (2000)
    Springer
    Earth, moon and planets 89 (2000), S. 135-160 
    Details
    ISSN: 1573-0794
    Keywords: C/1995 O1 (Hale-Bopp) ; 19P/Borrelly ; 46P/Wirtanen ; comets ; modeling ; nucleus ; observations ; rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We review several techniques used to retrieve rotational parameters from observations. The spin period of a dozen of comets retrieved with these techniques are summarized. We describe how the spin period of comet Hale-Bopp (C/1995 O1) has been calculated with a high accuracy (11.30–11.34 h). Although several authors converged to a spin axis orientation at (α,δ) = (275 ± 15°, -55 ± 5°), detailed studies indicate that the dust jets morphology in 1996–1997 may be incompatible with this orientation. Comet 19P/Borrelly has been recently observed by the Deep Space 1 spacecraft. At the same time, its spin axis orientation and period have been determined by several authors to be respectively (α,δ) = (225 ± 15°, -10 ± 10°)and 26h. These two comets are likely to be in (or close to) a principal axis spin state. We discuss new modeling of the spin state of comet 46P/Wirtanen, the target of the Rosetta mission. The model involves a three-dimensional shape and thermal model, from which the torque of the non gravitational force is calculated at each time step. The moments of inertia are computed for each irregular shape. The results from numerical integrations show that this comet can remain in a principal axis spin state during more than 10 orbits if the spin period does not get above∼6 h. If the spin period increases, its nucleus gets rapidly into excited spin states. It shows that even small and very active short-period comets are not necessarily in non principal axis spin states. In the last section, the consequences of recent observations and modeling of the rotational parameters of comet nuclei are discussed, and unsolved problems are presented.
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    URL: http://dx.doi.org/10.1023/A:1021598404115
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    Virtual Solar System Project: Learning Through a Technology-Rich, Inquiry-Based, Participatory Learning Environment (2000)
    Springer
    Journal of science education and technology 9 (2000), S. 7-25 
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    ISSN: 1573-1839
    Keywords: virtual reality ; modeling ; constructionism ; astronomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General , Technology
    Notes: Abstract In this manuscript we describe an introductory astronomy course for undergraduate students in which we moved from the large-lecture format to one in which students were immersed in a technologically-rich, inquiry-based, participatory learning environment. Specifically, undergraduate students used 3-D modeling tools to construct virtual reality models of the solar system, and in the process, build rich understandings of various astronomical phenomena. For this study, primarily naturalistic inquiry was used to gain a holistic view of this semester-long course. These data are presented as two case studies focusing on: (1) the role of the teacher in this participatory learning environment; (2) the particular dynamics that formed in each group; (3) the modeling process; (4) the resources used, specifically student-developed inscriptions; and (5) the role of technology and whether learning the technology interfered with learning astronomy. Results indicated that VR can be used effectively in regular undergraduate university courses as a tool through which students can develop rich understandings of various astronomical phenomena.
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    URL: http://dx.doi.org/10.1023/A:1009416822783
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    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.
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    URL: http://dx.doi.org/10.1023/A:1022527723551
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    Optimally Engineering Traditional Introductory Physics Classes (1997)
    Springer
    Journal of science education and technology 6 (1997), S. 297-314 
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    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.
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    URL: http://dx.doi.org/10.1023/A:1022502211969
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    Validation and sensitivity of a convective precipitation model for mountainous areas (1996)
    Springer
    Water, air & soil pollution 90 (1996), S. 313-320 
    Details
    ISSN: 1573-2932
    Keywords: Colorado ; convection ; downscaling ; modeling ; orographic ; precipitation ; summer ; sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A convective precipitation model for use in regions of complex terrain has been developed and applied to the Gunnison River Basin in southwestern Colorado. Spring snowfall in the Rocky Mountain region often has a significant convective component which orographic precipitation models are unable to simulate. Additionally, summertime precipitation is predominately convective in this area and is responsible for a large portion of summer streamflow variability. Streamflow typically increases by 50 to 100 percent of baseflow for moderate rainfall events for periods of up to one week. Larger precipitation episodes can produce peak discharges that exceed the spring snowmelt peaks. Convective precipitation also is important for plant growth, minimum streamflows and fire hazard conditions. In addition, an accurate assessment of the response of hydrologic systems to climate variability and change requires an accurate estimate of convective precipitation in mountainous areas. The convective model accurately reproduced the trend and amount of observed precipitation for the test period August 14–20, 1989. The convective model has applicability for downscaling large-scale model precipitation to smaller scales for use in water quality and quantity assessments.
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    URL: http://dx.doi.org/10.1007/BF00619291
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    Soil Gas Volatile Organic Compound Concentration Contours for Locating Vadose Zone Nonaqueous Phase Liquid Contamination (1997)
    Springer
    Environmental monitoring and assessment 48 (1997), S. 73-100 
    Details
    ISSN: 1573-2959
    Keywords: modeling ; soil gas surveys ; vadose zone ; volatile organic compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Diffusion of VOC from cylindrical vadose zone domains contaminatedwith distributed nonaqueous phase liquid is examined in the steadystate approximation. The effects of first-order biodegradation and ofan extended underlying pool of LNAPL floating on the water table belowthe cylindrical domain are explored by means of an orthogonal functionsapproach. The distribution of VOC in the vadose zone above a floatingcircular LNAPL pool of finite size is explored by a numerical method.The results provide information useful in estimating the spacing anddepth at which soil gas samples should be taken in order to detect thepresence of such source areas. Comparison of model results with soilgas VOC measurements at various depths also provides insight into theextent to which natural biodegradation of the VOCs is taking place.
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    URL: http://dx.doi.org/10.1023/A:1005787129436
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    A Framework for Comprehensive, Integrated, Watershed Monitoring in New York City (2000)
    Springer
    Environmental monitoring and assessment 62 (2000), S. 147-167 
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    ISSN: 1573-2959
    Keywords: modeling ; New York City ; risk assessment ; watershed monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The International Life SciencesInstitute (ILSI) Risk Science Institute (RSI) convenedan expert panel of scientists to developrecommendations for a comprehensive monitoring programfor the Croton and Catskill/Delaware watersheds, whichprovide drinking water to New York City's residents. This effort was conducted as part of efforts topreserve and enhance the quality of New York City'sreservoir system through a watershed protectionprogram. The panel developed recommendations for astrategic framework on which to construct a monitoringprogram. As part of this activity, the paneldetermined whether existing monitoring activities weredeficient and, where activities were deficient, thepanel developed recommendations for additionalinformation that should be collected.The panel recommended the development and use of anintegrated approach to watershed monitoring, whichdraws on modeling, risk-based planning and analysis,statistical sampling and design, and basic compliancemonitoring. The approach should be designed toprovide an assessment of natural and anthropogenicsources of stress to the system as well as anassessment of water quality trends in response tostresses acting in concert, both over the long termand over the five-year New York City Memorandum ofAgreement (MOA) assessment time frame. It should alsoprovide an assessment of the human health andenvironmental risks posed by a variety of stressors,and the impact of management actions implemented toameliorate stressors.
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    URL: http://dx.doi.org/10.1023/A:1006266325869
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    Soil Acidification in Loess and Clay Soils in The Netherlands (2000)
    Springer
    Water, air & soil pollution 120 (2000), S. 139-167 
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    ISSN: 1573-2932
    Keywords: base saturation ; clay soils ; loess soils ; modeling ; nutrient uptake ; soil acidification ; weathering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract To assess the impact of acid deposition on forestedloess and clay soils in the Netherlands, changes inbase saturation and soil solution concentrations weresimulated with the dynamic soil acidification modelReSAM for 38 loess soils and 16 clay soils. Theselected locations represent the range in geographicalposition and diversity in parent material occurring inforested loess and clay soils in the Netherlands. Twodeposition scenarios were used for the period1992–2050: a business as usual scenario (BAU) and ascenario in which deposition was reduced according topresent Dutch policy plans (MV-3). A comparison ofsimulated and measured soil solution concentrationsand base saturation in 1992/1993 showed that the modelsimulated concentrations and base saturation in theloess soils quite good. However, the model tended tooverestimate acidification in the top (0–10 cm) of theclay soils. Despite the reasonable agreement betweenmeasured and simulated data some uncertainty in thevalidity of the model predictions remains because timetrends to validate the model were not available. Themodel predicted a small but ongoing acidificationduring the BAU scenario in the loess soils asindicated by a decline in median base saturation andpH in the topsoil in 2050. Present policy plans (MV-3)lead to a slight recovery of the base saturation in2050 and a decline in Al concentrations. In the claysoils a strong decline in base saturation is simulatedin the topsoil, whereas an increase in base saturationis predicted for the subsoil.
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    Clean water: Factors that influence Its availability, quality and its use: Summary of the International Water Conference (1996)
    Springer
    Water, air & soil pollution 90 (1996), S. 3-7 
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    ISSN: 1573-2932
    Keywords: Clean water ; fresh water ; water resources ; ecological risks ; health risks ; control strategies ; measurement quality ; modeling ; electric utilities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The International Water Conference held in La Jolla, California during 28–30 November 1995, had an objective to provide an opportunity for international information exchange on new research applications and timely policy issues effecting the availability, use and quality of water for power generation. This Conference included the topical areas, the use of water and the management of chemical quality in process wastewaters; physical and biological transformation due to discharges in open surface waters, watersheds and wetlands; the role of risk and cost-benefit assessments; and discussion of the Clean Water Act containments. This Conference Summary contains an overview of the present state of the knowledge regarding the use of water by the electric utility industry and potential future issues as discussed in papers presented at the Conference and a summary of the most important findings and conclusions.
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    Transient modeling of trickling filters for biological ammonia removal (1997)
    Springer
    Environmental modeling and assessment 2 (1997), S. 221-226 
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    ISSN: 1573-2967
    Keywords: ammonia ; biofilm ; modeling ; potable water ; trickling filter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A dynamic model for nitrifying trickling filters is developed, based on material balances in the biofilm and the bulk liquid. The model predicts the profile of ammonia as a function of the operating parameters (volumetric flow rate and feed ammonia concentration) and the biofilm thickness as a function of filter depth and time.
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    URL: http://dx.doi.org/10.1023/A:1019053109465
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    Topology optimization design of continuum structures under stress and displacement constraints (2000)
    Springer
    Applied mathematics and mechanics 21 (2000), S. 19-26 
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    ISSN: 1573-2754
    Keywords: structure ; optimization ; topology optimization ; modeling ; dual programming ; O223 ; TU323
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract Topology optimization design of continuum structures that can take account of stress and displacement constraints simultaneously is difficult to solve at present. The main obstacle lies in that, the explicit function expressions between topological variables and stress or displacement constraints can not be obtained using homogenization method or variable density method. Furthermore, large quantities of design variables in the problem make it hard to deal with by the formal mathematical programming approach. In this paper, a smooth model of topology optimization for continuum structures is established which has weight objective considering stress and displacement constraints based on the independent-continuous topological variable concept and mapping transformation method proposed by Sui Yunkang and Yang Deqing. Moreover, the approximate, explicit expressions are given between topological variables and stress or displacement constraints. The problem is well solved by using dual programming approach, and the proposed element deletion criterion implements the inversion of topology variables from the discrete to the continuous. Numerical examples verify the validity of proposed method.
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    Copper, Chromium, and Arsenic Adsorption and Equilibrium Modeling in An Iron-Oxide-Coated Sand, Background Electrolyte System (2000)
    Springer
    Water, air & soil pollution 119 (2000), S. 105-120 
    Details
    ISSN: 1573-2932
    Keywords: adsorption ; arsenic ; chromium ; copper ; iron-oxide-coated sand ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The adsorption of copper, chromate, and arsenate (CCA)onto iron-oxide-coated sand (IOCS) was examined insingle-metal and mixed-metal systems. Copper andarsenate were strongly adsorbed or formed inner-spheresurface complexes with the IOCS surface while chromatewas weakly adsorbed or formed an outer-sphere surfacecomplex with the IOCS surface. Copper adsorption byIOCS slightly increased in the presence of arsenatebut was not affected by the presence of chromate. Arsenate adsorption was not affected by the presenceof copper and/or chromate. Chromate adsorptionincreased in the presence of copper by the combinationof electrostatic effects and possiblesurface-copper-chromate ternary complex formation. The presence of arsenate significantly decreasedchromate adsorption due to competition for adsorptionsites and electrostatic effects. Using inner-spheresurface complexation constants for copper and arsenateand outer-sphere surface complexation constants forchromate, the triple-layer model (TLM) was successfulin describing adsorption of copper, chromate, andarsenate in single-solute systems. The modelindicated that each metal uses a different number ofadsorption sites. For CCA metals-IOCS systems, theequilibrium constants determined from single-solutesystems were not able to predict adsorption frommulti-solute systems. The TLM does not currentlyaccount for the heterogeneity of oxide surface sitesand the formation of ternary complexes and/or solidphases that do not exist in single-solute systems.
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    URL: http://dx.doi.org/10.1023/A:1005109325539
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