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  • modeling  (50)
  • wheat
  • Springer  (79)
  • 2000-2004  (79)
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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
    SHADOC: a multi‐agent model to tackle viability of irrigated systems (2000)
    Springer
    Annals of operations research 94 (2000), S. 139-162 
    Details
    ISSN: 1572-9338
    Keywords: irrigated system ; modeling ; multi‐agent system ; simulation ; social networks ; coordination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract The viability of irrigated systems in the Senegal River Valley is being brought into question today due to their under‐utilization. We assume that their viability depends largely on the way their different components behave and interact. We therefore sought to examine in greater depth today's knowledge of the structure of these systems and activities performed within them. This led to the development of a multi‐agent system model, a kind of virtual irrigated system, with a special focus on rules in use for access to credit, water allocation and cropping season assessment as well as organization and coordination of farmers. The purpose of this paper is to show how this kind of tool is relevant to the study of irrigated systems' viability. As an example it is used to examine the influence of existing social networks on the viability of irrigated systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018908931155
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  • 3
    Electronic Resource
    Electronic Resource
    Product Hardware Complexity and Its Impact on Inventory and Customer On-Time Delivery (2000)
    Springer
    International journal of flexible manufacturing systems 12 (2000), S. 145-163 
    Details
    ISSN: 1572-9370
    Keywords: inventory ; modeling ; postponement ; supply chain management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper studies the impact of a reduction in hardware complexity on the supply-chain inventory against various customer on-time delivery alternatives and manufacturing environments. Different methods of reducing hardware complexity are proposed, and their impact on total supply-chain inventory and customer serviceability quantified. An analytical inventory optimization scheme taking into account multistage supply networks, product structure, forecast accuracy, lead-time variability, and supplier reliability is used to determine optimal inventory levels in a stochastic modeling environment. The analysis is based on a business case for an IBM midrange computer family consisting of more than 200 models and upgrades with hundreds of features. We investigate different hardware complexity reduction strategies, including low-usage feature reduction, low-volume feature reduction, and feature substitution, as well as quick response and postponement mechanisms. Our computational results show that, in a fabrication-fulfillment center environment, reducing hardware complexity results in significantly higher inventory savings than in an integrated manufacturing environment. The results presented in this paper were used to reduce hardware complexity in IBM's midrange computer division.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008191530004
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  • 4
    Electronic Resource
    Electronic Resource
    Theoretical chemistry as a tool for interpreting catalysts selectivities (2000)
    Springer
    Topics in catalysis 13 (2000), S. 213-219 
    Details
    ISSN: 1572-9028
    Keywords: heterogeneous catalysis ; selectivity ; quantum chemistry ; modeling ; butadiene ; α–β unsaturated aldehydes ; enantioselectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Reaching high selectivities is an important concern for heterogeneous catalysis. Insights in the factors which control the reaction selectivity can be obtained from theoretical approaches, also a full computational description of the reaction is not yet possible, due to the great complexity of the molecules generally involved in fine chemical catalysis. Some theoritical works related to the interpretation of chemical selectivity are rewieved in this paper, with a focus on the various types of selectivity: chemoselectivity, regioselectivity and enantioselectivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009002921067
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  • 5
    Electronic Resource
    Electronic Resource
    Simultaneous Records of Methane and Nitrous Oxide Emissions in Rice-Based Cropping Systems under Rainfed Conditions (2000)
    Springer
    Nutrient cycling in agroecosystems 58 (2000), S. 131-139 
    Details
    ISSN: 1573-0867
    Keywords: automated closed chamber method ; wheat ; cowpea ; slow-release nitrogen fertilizer ; residue management ; denitrification ; methane sink ; rainfall
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Rainfed rice (Oryza sativa L.)-based cropping systems are characterized by alternate wetting and drying cycles as monsoonal rains come and go. The potential for accumulation and denitrification of NO3 − is high in these systems as is the production and emission of CH4 during the monsoon rice season. Simultaneous measurements of CH4 and N2O emissions using automated closed chamber methods have been reported in irrigated rice fields but not in rainfed rice systems. In this field study at the International Rice Research Institute, Philippines, simultaneous and continuous measurements of CH4 and N2O were made from the 1994 wet season to the 1996 dry season. During the rice-growing seasons, CH4 fluxes were observed, with the highest emissions being in organic residue-amended plots. Nitrous oxide fluxes, on the other hand, were generally nonexistent, except after fertilization events where low N2O fluxes were observed. Slow-release N fertilizer further reduced the already low N2O emissions compared with prilled urea in the first rice season. During the dry seasons, when the field was planted to the upland crops cowpea [Vigna unguiculata (L.) Walp] and wheat (Triticum aestivum L.), positive CH4 fluxes were low and insignificant except after the imposition of a permanent flood where high CH4 fluxes appeared. Evidences of CH4 uptake were apparent in the first dry season, especially in cowpea plots, indicating that rainfed lowland rice soils can act as sink for CH4 during the upland crop cycle. Large N2O fluxes were observed shortly after rainfall events due to denitrification of accumulated NO3 −. Cumulative CH4 and N2O fluxes observed during this study in rainfed conditions were lower compared with previous studies on irrigated rice fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009842502608
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  • 6
    Electronic Resource
    Electronic Resource
    Issues related to the detection of boundaries (2000)
    Springer
    Landscape ecology 15 (2000), S. 453-466 
    Details
    ISSN: 1572-9761
    Keywords: environmental change ; GIS ; landscape ecology ; modeling ; remote sensing ; riparian ; statistics ; wetland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ecotones are inherent features of landscapes, transitional zones, and play more than one functional role in ecosystem dynamics. The delineation of ecotones and environmental boundaries is therefore an important step in land-use management planning. The delineation of ecotones depends on the phenomenon of interest and the statistical methods used as well as the associated spatial and temporal resolution of the data available. In the context of delineating wetland and riparian ecosystems, various data types (field data, remotely sensed data) can be used to delineate ecotones. Methodological issues related to their detection need to be addressed, however, so that their management and monitoring can yield useful information about their dynamics and functional roles in ecosystems. The aim of this paper is to review boundary detection methods. Because the most appropriate methods to detect and characterize boundaries depend of the spatial resolution and the measurement type of the data, a wide range of approaches are presented: GIS, remote sensing and statistical ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008194205292
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  • 7
    Electronic Resource
    Electronic Resource
    Temperature Modulated DSC. Theoretical interpretation (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 333-343 
    Details
    ISSN: 1572-8943
    Keywords: base line ; DSC ; kinetics ; modeling ; thermodynamics ; TMDSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The application of non-linear heating program to a heat-flux DSC apparatus has attracted much attention. From thermodynamics viewpoint, it is shown that the variation of enthalpy of a sample changing with temperature change is due, to both the true heat capacity of the sample and the enthalpy of some transformations occurring in the sample, characterized by its degree of advance. Using the simple assumption that the rate of the transformation is proportional to the distance from the thermodynamic equilibrium, an electrical model of the thermal event is given. Using the coupled cell model of the DSC apparatus, we show how to obtain the rate of transformation of the sample and heat capacity, which is directly related to the base line of the experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010148200201
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  • 8
    Electronic Resource
    Electronic Resource
    Modeling of the DTG Curves for Oxidation of a Nanosized Molybdenum Ferrite Coupling Mechanics and Diffusion (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 847-858 
    Details
    ISSN: 1572-8943
    Keywords: derivative thermogravimetry ; diffusion-induced stress ; modeling ; molybdenum ferrite ; oxidation kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract From a model for isothermal oxidation kinetics in nanosized ferrite spinels based on a diffusion-induced stress effect, the authors present a modeling of the DTG curves for the oxidation of Fe2+ and Mo3+ cations on octahedral sites of a molybdenum ferrite. This has been made by considering that the chemical diffusion coefficient is given by the relation $$\tilde D = D_o \exp \left( {\frac{{E'_{\text{a}} + pV_{\text{a}} }}{{RT}}} \right)$$ , when D o is a pre-exponential factor, E a ′ an activation energy and V a an activation energy induced by the oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010118207582
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  • 9
    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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  • 10
    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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