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  • Articles  (16)
  • Polymerization
  • modeling
  • 2000-2004  (16)
  • 1960-1964
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  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (13)
  • Physics  (5)
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  • Articles  (16)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Adsorption 6 (2000), S. 93-104 
    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
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  • 2
    ISSN: 1572-8935
    Keywords: Functional monomers ; Polymerization ; Copolymerization ; Kinetic studies ; Reactivity ratios
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract 1-Cyanoethanoyl-4-acryloylthiosemicarbazide (CEATS) was synthesized for the first time as a new chelating monomer. Its structure was confirmed by both elemental and spectral analyses. Radical polymerization and copolymerization of CEATS was been carried out in dimethylformamide (DMF) in the presence of azobisisobutyronitrile (AIBN) as an initiator. Kinetic studies for the polymerization behavior of CEATS were performed. The complex formation of the CEATS monomer and polymer (PCEATS) with Cu II cation was investigated and its stability constant determined. The rate of copolymerization of CEATS with some conventional monomers, namely vinyl acetate, methyl methacrylate and acrylonitrile, was measured as a function of the mole fraction of the monomers. The reactivity ratios (r1, r2) for the various copolymer systems investigated together with the Q and e values of the CEATS monomer were determined. Moreover, the thermal gravimetric analysis of the prepared polymers and their copolymers with acrylonitrile were also studied.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of flexible manufacturing systems 12 (2000), S. 145-163 
    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.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plasma chemistry and plasma processing 20 (2000), S. 65-86 
    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.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plasma chemistry and plasma processing 20 (2000), S. 521-553 
    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.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials synthesis and processing 8 (2000), S. 139-144 
    ISSN: 1573-4870
    Keywords: TiO2 ; phase transformations ; mechanical alloying ; kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A high-pressure and high-temperature phase of TiO2 : TiO2 II is formed transiently during room-temperature high-energy ball milling of anatase TiO2 : TiO2 anatase → TiO2 II → TiO2 rutile. Rutile is the only phase present after prolonged ball milling. The present paper focuses on the influences of physical and chemical processing conditions on the transformation kinetics. The effects of two milling parameters on the kinetics of phase transformation of anatase TiO2 were investigated: the nature of milling tools and the powder-to-ball weight ratio R. Granulometric characterizations and TEM observations have demonstrated that the transformation of TiO2 anatase into TiO2 II occurs without fracturing of particles and that TiO2 II nanograins form at the surface of anatase particles. The parameter R affects only the transformation rate. For a given R, the transformation rate is the largest with alumina grinding tools, intermediate with zirconia tools, and the smallest with steel tools. The parameters involved in current models of the mechanical alloying process do not suffice to explain the differences in transformation rates observed here. A parameter, which takes into account the influence of the mechanical properties of grinding materials, is considered.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 53 (2000), S. 49-75 
    ISSN: 1573-4889
    Keywords: FeCrAl ; α Al2O3 ; high-temperature resistance ; residual stresses ; thermal stresses ; X-ray diffraction ; relaxation ; modeling ; elasto-viscoplastic model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The stresses generated in alumina scales during different oxidation stepscontrol the protective character of such scales and their lifetime. Laboratoryand industrial Fe–Cr–Al alloys, differing by their impuritycontent and preparation, and for which the oxidation kinetics werepreviously characterized, were studied here to experimentally determine ortheoretically calculate the stress level in the alumina scales. Theexperiments were performed by X-ray diffraction (XRD) at room temperature,using the sin2psi method. The oxide-stress level wascorrelated with many parameters, such as the scale microstructure andmorphology, the nature of the substrate, the substrate and oxide thickness,the oxide grain size, the cooling rate, etc. A numerical elasto-viscoplasticmodel was developed to calculate the thermal stresses and to point out theeffect of the relaxation phenomena either during cooling or duringisothermal treatment after oxidation. The results obtained by theelasto-viscoplastic model are in good agreement with the experimental ones.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials synthesis and processing 8 (2000), S. 73-85 
    ISSN: 1573-4870
    Keywords: Chemical vapor deposition (CVD) ; diamond films ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The evolution of grain size, grain-size distribution, morphological and crystallographic texture, surface roughness, and the contribution of various surface facets to the growth of polycrystalline diamond films is performed by carrying out a series of two-dimensional computer simulations. The films are assumed to grow from a set of randomly oriented, {100}- and {111}-faceted nuclei by the motion of their vertices (the points where the adjoining facets of the same or neighboring grains meet). The vertex velocities are found to be a function of the orientation and the growth rate of the adjoining facets. To quantify the latter, a {100} to {111} growth-rate parameter is used. The results show that the evolution of the grain size and its distribution, surface roughness, morphological and crystallographic texture, and the portion of the film grown from different surface facets are all mutually linked and governed by the magnitude of the growth-rate parameter. The latter can be controlled by the CVD processing conditions, such as the substrate temperature, reactor pressure, mole fraction of carbon-source gas (e.g., CH4, C2H2).
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of wood science 46 (2000), S. 143-148 
    ISSN: 1611-4663
    Keywords: α-Pinene ; Phenol ; Formaldehyde ; Polymerization ; Condensation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Synthesis conditions of terpene-phenol-aldehyde resin with a high softening point were studied based on the reactions amongα-pinene, phenol, and formaldehyde. A suitable catalyst system and the best processing conditions were obtained by laboratory experiments. The influence of the raw materials ratios, reaction temperature, reaction time, and catalyst dose on the softening point, yield, and color of the synthesized resin was examined. The physical and chemical characteristics of the resin were determined: softening point ≥140°C (ball and ring method); color value ≤7 (Gardner); acid value (KOH mg/g) 〈1; bromine value (Br2 mg/100g) 〈64; saponification value (KOH mg/g) 〈1; average molecular weight ∼830. The yield of resin was more than 85% (based on the total raw material).
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Autonomous robots 8 (2000), S. 25-42 
    ISSN: 1573-7527
    Keywords: visual servoing ; robust control ; mobile robot ; vehicles ; modeling ; vision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We have been interested in Automatic Guided Vehicles (AGV) for several years. In this paper, we synthesize controllers for AGV applications using monocular vision. In particular, we are interested in road following and direction change tasks, and in analyzing the influence of extrinsic camera parameter perturbations on vehicle behavior. We use the bicycle as the kinematic vehicle model, and we choose the position of the white band on the road as the sensor signal. We define an interaction between the camera, which is mounted inside the vehicle, and the white band detected in the image space. Using this kind of interaction, we present how to use a pole assignment technique to solve the servoing task. We show the simulation and experimental results (1/10 scale demonstrator) with and without perturbations. We then investigate the use of a robust controller to slow down the effect of perturbations on the behavior of the vehicle.
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