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  • control theory
  • kinetics
  • Springer  (71)
  • Public Library of Science (PLoS)
  • 1975-1979  (71)
Collection
Publisher
  • Springer  (71)
  • Public Library of Science (PLoS)
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of solution chemistry 6 (1977), S. 203-216 
    ISSN: 1572-8927
    Keywords: Glucose ; kinetics ; mixed solvent ; kinetic isotope effect ; enthalpy of activation ; entropy of activation ; tetrahydrofuran ; tert-butanol ; mutarotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The mutarotation rates of glucose in aqueous mixtures of tetrahydrofuran andtert-butanol in the mole fraction (xi) range 0〈xi〈0.2 have been measured at 5° intervals in the range 5–35°C. The kinetic deuterium isotope effects have been determined for the same solvent compositions at 25 and 35°C. A statistical analysis of the Arrhenius plots indicates that the experimental errors, although small, are too large for the establishment of any compensation behavior between ΔH
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  • 2
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    Journal of solution chemistry 5 (1976), S. 163-169 
    ISSN: 1572-8927
    Keywords: Solvent effects ; tetramethylurea ; hydrolysis ; hydrogen bonding ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Tetramethylurea was hydrolyzed in aqueous hydrochloric acid at temperatures of 80, 90, and 100°C. All reactions were carried out in an excess of both tetramethylurea and water, with first-order dependence on acid concentration being observed. As the concentration of water was increased, the rate of hydrolysis decreased until equimolar amounts of water and tetramethylurea were present. Subsequent addition of water had no effect on the observed rate.
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  • 3
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    European journal of clinical pharmacology 10 (1976), S. 43-48 
    ISSN: 1432-1041
    Keywords: Spironolactone ; acetylsalicylic acid ; fludrocortisone ; kinetics ; pharmacology ; interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of 600 mg acetylsalicylic acid (ASA) on the renal excretion and clearance of canrenone, the principal unconjugated metabolite of spironolactone, was examined in a double-blind crossover study in six healthy subjects. ASA significantly reduced the urinary excretion, and the fractional excretion, of canrenone between 4 — 6 hours after administration of 50 mg spironolactone. The pharmacological activity of spironolactone, assessed simultaneously by alterations in fludrocortisone-induced urinary electrolyte changes, was slightly but not significantly reduced. The reductions in urinary canrenone excretion correlated with changes in the urinary log 10 Na/K ratio. The results suggest that canrenone may be actively secreted at the proximal renal tubule, and that secretion is blocked by ASA or its conjugates. This is a possible mechanism for the pharmacological interaction between ASA and spironolactone which has been described previously.
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  • 4
    ISSN: 1432-1041
    Keywords: Theophylline ; kinetics ; apnea ; premature newborns ; developmental pharmacology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Aminophylline (theophylline-ethylenediamine) was administered to 27 premature newborns to prevent apneic spells. Of the 22 patients monitored for theophylline concentration, a therapeutic blood level was reached in 19 in 1–2 days, and 3 stayed below it. ‘Toxic’ blood levels (≥20 µg/ml) were reached in 3 cases, one of whom showed signs of toxicity. Theophylline treatment was not efficient in the prevention of apnea when a serious underlying disease was present. Theophylline blood half-life (mean : 27.0 h) and clearance (mean 12.9 ml/h/kg) confirmed the slow elimination pattern of the drug in the premature infant.
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  • 5
    ISSN: 1573-4889
    Keywords: tantalum alloy ; oxygen ; dissolution ; kinetics ; oxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Oxygen was added to T-111 (Ta-8W-2Hf, wt.%) at 820 and 990°C at an oxygen pressure of about 3×10−4 Torr (4×10−2N/m2). The technique employed permitted predetermined and reproducible doping of T-111 up to 3.0 at% oxygen. Based on the temperature dependence of the doping reaction, it is concluded that the initial rates of oxygen pickup are probably controlled by solution of oxygen into the T-111 lattice. Although hafnium oxides are more stable than those of tantalum or tungsten, analyses of extracted residues indicate that the latter oxides predominate in the as-doped specimens, presumably because of the higher concentrations of tantalum and tungsten in the alloy. However, high-temperature annealing promotes gettering of dissolved oxygen and of other oxides to form hafnium oxides. Small amounts of tantalum and tungsten oxides were still present after high-temperature annealing. Tungsten oxide (WO3) volatilizes slightly from the surface of T-111 at 990°C. The vaporization of WO3 has no apparent affect on the doping reaction.
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  • 6
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    Oxidation of metals 11 (1977), S. 127-132 
    ISSN: 1573-4889
    Keywords: Duplex oxides ; copper oxidation ; kinetics ; oxygen partitioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The theory for the growth of a double oxide layer proposed by Yurek, Hirth, and Rapp, has been applied to copper using experimental rate-constant data obtained by Valensi. Calculated thicknesses of the layers agree very well with experimentally measured values.
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  • 7
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    Oxidation of metals 9 (1975), S. 459-472 
    ISSN: 1573-4889
    Keywords: Cr ; oxidation ; kinetics ; Cr2O3 grain size ; short-circuit diffusion ; surface ; preparation ; Fe-Cr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Cr was oxidized in 1 aim O2 at 980, 1090, and 1200°C. ElectropolishedCr and some orientations of etched Cr oxidize rapidly and develop compressive stress in the growing Cr2O3; other orientations oxidize slowly, apparently free of stress. SEM examination of fracture sections shows that the thick oxide is polycrystalline whereas the thin oxide on etched Cr is monocrystalline. It is deduced that the monocrystalline oxide grows by lattice diffusion of cations outward, and the polycrystalline layer by the two-way transport of cation diffusion outward and anion diffusion inward along oxide grain boundaries. The consequent formation of oxide within the body of the polycrystalline layer generates compressive stress and leads to wrinkling by plastic deformation. The activation energy for oxidation of Cr by cation lattice transport is 58 kcal/mole. Polycrystalline Cr2O3 forms on Fe-26Cr alloy, whether electropolished or etched; oxidation is accordingly rapid and accompanied by compressive stress.
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  • 8
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    Oxidation of metals 10 (1976), S. 85-95 
    ISSN: 1573-4889
    Keywords: boron carbide ; oxidation ; kinetics ; chromatography method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Thermogravimetry and gas-adsorption chromatography were used to study the kinetics of formation of solid and gaseous products during the hightemperature oxidation of compact boron carbide in oxygen at 740 Torr. Oxidation resistance was observed at temperatures up to 1200°C. The main oxidation products were B2O3 and CO2. Oxidation was paralinear; the carbon consumption exceeded the consumption of boron as compared to the ratio of these elements in the compound B4C. This difference resulted in carbon depletion of the carbide layer in the substrate near the scale〉.
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  • 9
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    Oxidation of metals 10 (1976), S. 361-376 
    ISSN: 1573-4889
    Keywords: metals ; scale structure ; epitaxy ; kinetics ; diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An explanation of the deviation from the parabolic law is the treatment which considers both shortcircuit and lattice diffusion in the oxide scale. In this study we examine how the oxidation kinetics are influenced by changing the structure of the scale of copper oxide in order to confirm the role of short-circuit diffusion in determining the oxidation rate. In addition we explain the oxidation kinetics of copper and nickel by using a model of the scale structure which includes recrystallization and grain growth. Results are as follows: (1) The nucleation and growth behavior of oxide have a direct effect on the structure and in turn the oxidation kinetics due to short-circuit diffusion. (2) A modified treatment is valid in the region where volume diffusion and short-circuit diffusion play an important role in which it is necessary to consider the scale structure such as the grain size distribution and the boundary width. (3) When recrystallization takes place it is necessary to consider the model of a two-layered scale structure which is different in properties and morphology. (4) In this region the rate curves are S-shaped when oxide recrystallization takes place and exhibit a transition from a parabolic to an nth-power relationship (n〉2) when grain growth takes place.
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  • 10
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    Oxidation of metals 11 (1977), S. 225-239 
    ISSN: 1573-4889
    Keywords: tantalum ; oxidation ; high temperature ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of tantalum in oxygen-nitrogen and oxygen-inert gas mixtures at925°C has been studied. The oxygen pressure was close to 0.5 atm in all experiments, and partial pressures of the second component of from 0 to 180 Torr were employed. Spherical specimens were used to provide quantitatively significant kinetic data. A model has been proposed which suggests that the oxygen pressure at the reaction interface close to the metal surface is lower than the external pressure because of the finite permeability of the porous outer oxide layer, and that the inert gas effectively reduces the permeability. The model gives good quantitative agreement with the experimental results.
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  • 11
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    Oxidation of metals 11 (1977), S. 365-381 
    ISSN: 1573-4889
    Keywords: cobalt oxidation ; kinetics ; parabolic rate constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Precise values of parabolic rate constants of cobalt oxidation have been determined over a wide range of temperature (950–1300°C) and oxygen pressure (6.58× 10−4−0.658 atm). The dependence of the calculated values of parabolic rate constants k″p on oxygen pressure and temperature can be described by the following empirical equation: $$k''_p = const. \cdot {\text{p}}_{O_2 }^{{\text{1/n}}} \cdot exp ( - {\text{E}}_{\text{k}} /RT)$$ The exponent 1/n decreases with an increase in temperature from 1/3.40 at 950°C to 1/3.96 at 1300°C, whereas the activation energy Ek decreases with an increase in the oxygen pressure from 41.7 to 38.1 kcal/mole.
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  • 12
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    Oxidation of metals 13 (1979), S. 77-88 
    ISSN: 1573-4889
    Keywords: BaTiO3 ; kinetics ; solid state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The solid-state reaction between barium carbonate and rutile powders to form barium metatitanate BaTiO3 was studied by thermogravimetric analysis, X rays, and microscopy. Phase-stability domains were drawn in a temperature— $${\text{p}}_{CO_2 } $$ , diagram. The dependence of the reaction kinetics on $${\text{p}}_{CO_2 } $$ , $${\text{p}}_{O_2 } $$ or $${\text{p}}_{N_2 } $$ is discussed. In particular, the rate continuously decreases when $${\text{p}}_{CO_2 } $$ , or $${\text{p}}_{N_2 } $$ increases, but it reaches a maximum as a function of $${\text{p}}_{O_2 } $$ .
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  • 13
    ISSN: 1573-4889
    Keywords: Cu-Si alloys ; oxidation ; kinetics ; silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of Cu-Si alloys (containing up to 4.75 wt. % Si) in $${\text{p}}_{O_2 } $$ =0.01 atm from 800 to 1000°C has been investigated using thermogravimetry and other techniques. A 0.04% Si alloy followed a parabolic oxidation law with a rate similar to that of pure Cu. As the Si concentration increased the rate decreased and became irregular owing to SiO2 particles or flakes at the alloy-scale interface. It is considered that sintering of SiO2 particles and rupture of the sinter because of contraction during sintering are responsible for the irregular kinetics. A SiO2 layer forms directly on the 4.75% Si alloy which oxidizes uniformly. The SiO2 was always amorphous. In pure CO2 a similar pattern of amorphous SiO2 particles, flakes, and layers occurs.
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  • 14
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    Oxidation of metals 13 (1979), S. 283-298 
    ISSN: 1573-4889
    Keywords: oxidation ; surface alloys ; Fe-Cr alloys ; iron ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of several surface and bulk Fe-Cr alloys and iron at 300°C and 4×10−6 Torr oxygen was studied. The surface alloys were fabricated by implantation of 25 keV Cr ions into the outermost 300Å of polycrystalline iron samples. The oxide thickness as a function of oxygen exposure was obtained using proton-excited X-ray analysis, and composition profiles of oxide films were obtained using Auger electron spectroscopy and ion sputtering. The addition of Cr to Fe by surface and bulk alloying caused the oxidation rate to decrease and changed the oxidation kinetics from parabolic (for Fe) to logarithmic (for Cr concentrations ≥4.7at.%). Interpretation of the data in terms of simple oxidation theories indicates that the Cr additions may reduce the oxidation rate by altering the electronic properties of the metal-oxide interface.
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  • 15
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    Oxidation of metals 13 (1979), S. 255-272 
    ISSN: 1573-4889
    Keywords: oxidation ; Fe-C ; graphite deposition ; nonadherent oxide ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of Fe-C alloys containing 0.5 and 1.0% C was studied in 1 atm O2 at 700° C. The oxidation rate is considerably slower than for pure Fe. The oxide scale formed is detached, multilayered, and overoxidized, containing little or no FeO. A thin film of graphite was identified at the metal-oxide interface by electron diffraction. It is proposed that the slow oxidation and abnormal scale are caused by a residue of graphite left at the metal surface from the oxidation of Fe3C. This inhibition of the oxidation of Fe by carbon at 700°C is in contrast to the stimulation observed at 500°C.
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  • 16
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    Oxidation of metals 13 (1979), S. 301-309 
    ISSN: 1573-4889
    Keywords: NiO ; Electrical conductivity ; gas-solid equilibria ; kinetics ; equivalent circuit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In a previous work it has been stated that the NiO electrical conductivity changes connected to the oxygen pressure changes may be considered as a transitory phenomenon. A mixed kinetics case controlled by the formation of surface cation vacancies and their diffusion in the bulk is proposed to explain the reaction process. By means of an equivalent electrical circuit in good agreement with the kinetics model it was possible to reproduce the experimental phenomenon.
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  • 17
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    Oxidation of metals 13 (1979), S. 481-504 
    ISSN: 1573-4889
    Keywords: kinetics ; sulfidation ; Fe-Cr-Al alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The influence of aluminium on the kinetics and mechanism of high-temperature sulfidation of Fe-Cr alloys containing 20 at.% chromium has been investigated. It has been found that the addition of aluminum greatly improves the scaling resistance of Fe-Cr alloys against attack by sulfur vapors at high temperatures.
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  • 18
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    Oxidation of metals 9 (1975), S. 357-365 
    ISSN: 1573-4889
    Keywords: kinetics ; zirconia ; defect structure ; ionic conductivity ; yttria dopant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A Zr-0.5 Y alloy was found to oxidize about 6 times faster than pure zirconium over the temperature range of 400 to 565°C. The activation energies were nearly identical (∼32 kcal/mole). The activation energies correspond to grain boundary diffusion of oxygen through the scale. The higher oxidation rate of the alloy was attributed to a higher anion vacancy concentration and the assumption that diffusion sites in the lattice and boundaries were in local equilibrium. Measurements on yttria-doped zirconia showed that ionic conductivity was increased markedly by yttrium and extended over a wide range of oxygen pressure. The defect structure of the doped oxide was changed to one of oxygen vacancies, even at the high end of the oxygen pressure range, 10−8 to 0.2 atm, over which pure ziconia contains oxygen interstitials. The doped oxide was found to be extrinsic over the entire range of oxygen pressure and, although ionic conductivity predominated, electronic conductivity was still appreciable. The electronic conductivity, however, was still sufficiently high so that electron transport was not rate-controlling in the predominantly ionic-conducting scale.
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  • 19
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    Oxidation of metals 10 (1976), S. 97-103 
    ISSN: 1573-4889
    Keywords: silicon carbide ; oxidation ; molecular oxygen ; glow-discharge oxygen plasma ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation kinetics and structure of the oxide scales formed on high-density SiC were studied in molecular oxygen at 740 Torr and in a glow-discharge oxygen plasma at 0.1 Torr at temperatures of 1000, 1100, and 1200°C. The monatomic oxygen formed by the glow discharge markedly increased the reaction rate and the vaporization of some of the oxidation products. The marked differences in kinetics suggest that the rate-controlling step during oxidation in molecular oxygen is the dissociation of adsorbed diatomic oxygen to the monatomic species. Films formed in molecular oxygen were mostly amorphous SiO2 with small inclusions of SiC and graphite, whereas films formed in dissociated oxygen were primarily amorphous SiO2 containing SiO, S2O3, and the coesite form of SiO2.
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  • 20
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    Oxidation of metals 12 (1978), S. 215-225 
    ISSN: 1573-4889
    Keywords: oxidation ; Fe-Ni alloys ; kinetics ; scale morphology ; EPMA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of an Fe—19.34 wt. % Ni alloy in dry CO2 has been studied at 700—1000°C using thermogravimetry, metallography, and EPMA. Weight gains for oxygen consumption followed a linear-parabolic-linear sequence at all temperatures. During the initial linear stage the scale consisted mainly of magnetite and the activation energy of 133±25 kJ · mole−1 is considered to be due to dissociation of CO2 into CO and adsorbed oxygen on the outer magnetite surface. During the parabolic oxidation stage a continuous Ni-rich layer containing ∼ 70% Ni forms a barrier to the diffusion which has an activation energy of 192±79 kJ · mole−1. The breakdown of the barrier layer causes a return to linear kinetics with an activation energy of 138±42 kJ · mole−1 for dissociation of CO2 on the outer surface. During the final linear stage there is pronounced general and intergranular subscale formation. Detailed information is presented of the Ni redistribution and concentrations during oxidation and its correlation with the kinetics and morphology.
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  • 21
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    Oxidation of metals 9 (1975), S. 99-116 
    ISSN: 1573-4889
    Keywords: oxidation ; kinetics ; ilmenite ; rutile ; pseudobrookite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of ilmenite (FeTiO3) in air and dry oxygen was investigated over the temperature interval 600 to 970°C. Dense platelets of ilmenite crystals as well as powder samples of ilmenite were oxidized. The weight data were recorded employing a thermobalance. The oxidation kinetics of ilmenite platelets were parabolic except for the initial stages during which logarithmic kinetics were observed. For powder samples the logarithmic rate law was followed primarily. The logarithmic rate law was attributed to free penetration of oxygen through cracks and short-circuit paths. The activation energies associated with the logarithmic rate law were nearly one-half of those obtained from parabolic oxidation. The growth morphology of the products of oxidation of ilmenite was observed with a scanning electron microscope. The effect of growth morphology on the kinetics is discussed, and a probable reaction mechanism is suggested for the oxidation of ilmenite.
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  • 22
    ISSN: 1573-4889
    Keywords: kinetics ; cobalt and nickel oxidation ; parabolic rate constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new fast method is proposed for the determination of parabolic rate constants of metal oxidation as a function of pressure and temperature. The method consists of determining rate constants by oxidation of a single metal sample in a continuous manner, periodically changing the oxidant pressure or temperature. This method eliminates a number of errors inherent in the classical method which involves the use of a new metal specimen in each experiment and it further shortens the time of evaluating the functions k p '' = f (p, T). The method is particularly suitable for the determination of rate constants of slow processes. To verify the proposed method measurements of the kinetics of oxidation of cobalt and nickel at different oxygen pressures over the temperature range 1000–1300° C were carried out.
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  • 23
    ISSN: 1573-4889
    Keywords: kinetics ; oxidation ; microcalorimetry ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In the kinetic theories of Bodenstein or Semenov the expression for the rate of a chemical reaction with several elementary stages can be expressed by different physical parameters. If two experimental methods are used, one method of necessity being microcalorimetry to measure the thermal flux produced by the reaction, it is possible to distinguish a pure kinetics case from a mixed one. The two-method technique has been verified by a study of the oxidation of niobium.
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  • 24
    ISSN: 1573-4889
    Keywords: titanium ; nitridation ; kinetics ; diffusion ; scaling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The nitridation behavior of titanium has been examined in an atmosphere of nitrogen over the temperature range 900–1000° C. In addition to determining the reaction kinetics, microhardness and metallographic studies have been carried out on the nitrided substrates and nitride scales. Overall parabolic kinetics were exhibited, while a linear scaling reaction (associated principally with Ti2N formation) was observed. Extensive dissolution of nitrogen in the substrate was evident from the microhardness studies, and at 950 and 1000° C the growth of the nitrogen-stabilized αTi phase layer followed a parabolic law. Consideration of all the observed processes and derived data suggested that diffusion of nitrogen in the metal substrate was probably the rate-controlling mechanism.
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  • 25
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    Oxidation of metals 11 (1977), S. 263-276 
    ISSN: 1573-4889
    Keywords: nickel ; sulfidation ; kinetics ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The reaction between pure nickel and H2S-H2 mixtures containing 1–65% H2S has been studied over the temperature range 450–600°C. The sulfidation of nickel in the temperature range 560–600°C has been found to follow a linear rate law at low concentrations of H2S and a parabolic rate law at higher concentrations (10% and 65% H2S); X-ray examination of the scale formed on the metal showed it to be almost entirely β-Ni3S2. On the basis of the kinetics and marker studies it can be concluded that the sulfide scale on nickel is formed by the outward transport of the metal and the inward transport of sulfur. In the temperature range 450–500°C the sulfidation of nickel follows a parabolic rate law. In mixtures containing 10% H2S the scale formed contains voids, the occurrence of which is connected with formation of Ni7S6. It has also been shown that the rate of transport through the Ni3S2 layer has an essential influence on the formation of a continuous layer of Ni7S6. Marker studies have shown that both nickel and sulfur appear to be mobile in β′-Ni3S2.
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  • 26
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    Oxidation of metals 12 (1978), S. 67-82 
    ISSN: 1573-4889
    Keywords: oxidation ; Fe-C ; kinetics ; oxide grain size ; grain-boundary diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Fe-C alloys containing 0.1, 0.5, and 1.0% C were oxidized in 1 atm O2 at 500°C. Two specimen preparations were used: annealed followed by slow cooling to form coarse pearlite plus proeutectoid ferrite or cementite; and cold-worked by abrading after annealing. The cold-worked alloys oxidize more rapidly. Annealed pearlite oxidizes faster than annealed ferrite. The differences in oxidation rate are caused by differences in the Fe3O4 grain size, that is, by the number of oxide grain boundaries available to act as easy diffusion paths for the outward diffusion of Fe through the Fe3O4. The oxidation rate constant is 10 times larger for fine-grained poly crystalline oxide than for oxide in which the Fe3O4 is monocrystalline.
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  • 27
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    Oxidation of metals 13 (1979), S. 437-456 
    ISSN: 1573-4889
    Keywords: Fe-Cr ; oxidation ; kinetics ; oxide morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Ferritic polycrystalline Fe-24 wt.% Cr was oxidized in pure oxygen at 190 ≤ T≤490° C and pressures in the range 5.3×10−2–13.3 Pa for periods of up to 5 hr. The reaction proceeded in three stages. An initial period of accelerating rate was accompanied by oxide island nucleation and growth. Following island coalescence the rate was approximately logarithmic at low temperatures and somewhat slower than parabolic at high temperatures. Rate control during this period was thought to be due to mass transport through the oxide grain boundaries left by the island impingement process. During these first two stages the oxide formed was γ-M2O3 with possibly some spinel. The final stage of reaction involved the appearance of α-M2O3 on the outer oxide surface and a substantial slowing of the oxidation rate due to the low diffusivity in this phase.
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  • 28
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    Oxidation of metals 13 (1979), S. 89-104 
    ISSN: 1573-4889
    Keywords: BaTiO3 ; kinetics ; solid state ; mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The authors propose a mechanism for the solid-solid reaction BaCO3+ TiO2→BaTiO3+CO2. This mechanism is based on the real structure of the present semiconductors. The reactions at different interfaces and the diffusing species are identified. The reaction rates are calculated and the dependence of the reaction rate upon O2, N2, and CO2 gas pressure is interpreted and discussed.
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    Oxidation of metals 13 (1979), S. 119-158 
    ISSN: 1573-4889
    Keywords: nickel-chromium alloys ; oxidation ; high temperature ; kinetics ; mechanisms
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of binary Ni-Cr alloys containing 44 and 50 wt. % Cr has been studied over a range of oxygen partial pressures at temperatures between 800 and 1100°C. The effects of cold work, surface preparation, and distribution of the Cr-rich second phase have been studied. The oxidation behavior is complex and cannot be described by a single model. The oxide grows by short-circuit diffusion as well as bulk transport through Cr 2 O 3 scales. The scale-growth mechanism includes extensive metal-oxide separation requiring Cr vapor transport to the scale, compressive stresses within the oxide which result in scale bulging and cracking, and the formation of a second oxide layer which results in voids being incorporated into the scale. Any factor which reduces the oxide grain size, such as cold work, finer distribution of the Cr-rich α phase or reduced oxygen pressure, results in an increased oxidation rate of binary alloys because of an increased number of grain-boundary short-circuit diffusion paths.
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    Journal of pharmacokinetics and pharmacodynamics 3 (1975), S. 277-290 
    ISSN: 1573-8744
    Keywords: sulfobromophthalein (BSP) ; kinetics ; BSP disposition ; mathematical model ; flow-limited
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A linear, flow-limited mathematical model of drug kinetics was used to simulate total sulfobromophthalein (BSP) kinetics in normal anesthetized rats during intravenous infusions and following rapid intravenous injections. Four parameters were used to characterize the distribution and biliary and urinary excretion of BSP: liver- to- plasma concentration ratio, extrahepatic tissue- to- plasma concentration ratio, liver clearance rate constant, and renal plasma clearance rate constant. The same parameters appear to characterize the kinetics of BSP in man through the successful application of “scale- up” techniques utilizing data from experiments in rats. Plasma levels of BSP corresponding to intravenous infusions and rapid intravenous injections in man are approximated by computer simulation.
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    Journal of pharmacokinetics and pharmacodynamics 5 (1977), S. 183-192 
    ISSN: 1573-8744
    Keywords: propranolol ; kinetics ; volunteers ; bioavailability ; threshold dose
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics of propranolol in blood was studied in healthy volunteers, following intravenous administration of 0.1 mg/kg and increasing oral doses of 10,20, and 40 mg, using a specific and sensitive gas Chromatographie method. The systemic availability of orally administered propranolol varied from 9% to 38% between subjects, but it was constant within each subject. A linear relationship was found between the area under the blood concentration-time curve and the oral dose. At variance with literature data, we could not observe a threshold dose.
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    Journal of pharmacokinetics and pharmacodynamics 6 (1978), S. 389-397 
    ISSN: 1573-8744
    Keywords: probenecid ; methotrexate ; cerebrospinal fluid ; kinetics ; interaction ; dogs ; choroid plexus ; intrathecal
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Probenecid is known to inhibit the renal excretion of methotrexate (MTX) and the transport of organic anions by the choroid plexus of the brain. The effect of probenecid on the CSF clearance of MTX given by the intrathecal route was examined in anesthetized dogs. Plasma and CSF MTX levels were measured following intrathecal injection of 0.4 mg/kg MTX, with and without pretreatment with probenecid. In the absence of probenecid, the peak plasma MTX concentration of 3.18×10−7±1.09×10−7 M (mean±SD) was reached 5 hr after intrathecal injection. With probenecid pretreatment, the mean peak plasma MTX concentration was lower (2.09×10−7+-0.98×10−7 M) and plasma disappearance was prolonged. A biexponential decay of CSF MTX levels was observed over the duration of sampling. The half-life of the second exponential phase was 21 hr without probenecid pretreatment and was longer after probenecid pretreatment. These results provide strong evidence that probenecid inhibits transfer of MTX from CSF to plasma following intrathecal injection.
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    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 557-578 
    ISSN: 1573-8744
    Keywords: kinetics ; enzyme induction ; drug interaction
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Equations were derived to describe the time course of drug levels during auto- and heteroinduction under a variety of input conditions. These equations were based on a pharmacokinetic theory of induction which assumes that metabolic clearance increases exponentially to a maximum value and that the rate of this increase is governed by the degradation rate constant of the induced enzyme (k′). Closed form solutions could be obtained only for intravenous single-dose (case I) and multiple-dose (case IV) administration. For each of the other cases, constant-rate intravenous infusion (case III), oral single-dose administration (case II), and multiple-dose administration (case V), an exact solution (not closed form) and an approximation (closed form) were derived. Two sets of equations were derived for each of the five cases to take into consideration the possibility of a latency term (λ).Plots of drug amount X(or concentration C) vs. time (t) were constructed. In case I, a log Xvs. tplot was convex, the slope increasing with time. In case II, Xincreased,reached a peak, and decayed as in case I. In case III (λ 〉 5In 2V/Q) Creached a preinduction steady state before decreasing to a lower (induced) steady state. When λ=0, Creached a maximum before decreasing to the same induced steady state. The behavior of Cvs. tfor cases IV and V was similar to that for case III. Determination of parameters was attempted in case III. Nonlinear least-square fitting of generated data with 3–9% error yielded reasonable estimates of k′.
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    Journal of optimization theory and applications 15 (1975), S. 393-411 
    ISSN: 1573-2878
    Keywords: Convexity ; control theory ; generalized control theory ; lower closure theorems ; calculus of variations
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    Topics: Mathematics
    Notes: Abstract The theory of measurable set-valued mappings allows us to study some problems of optimal control in the framework of minimization of convex functionals and thus to obtain existence theorems. When the functionals are nonconvex, we obtain the existence theorems for control problems which are weakly perturbed from the initial one. In this regard, we specify some theorems of nonconvex optimization.
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    Journal of optimization theory and applications 15 (1975), S. 413-440 
    ISSN: 1573-2878
    Keywords: Existence theorems ; necessary conditions ; control theory ; linear systems
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    Topics: Mathematics
    Notes: Abstract The basic problem considered may be described briefly as follows. LetX,Y, andZ be normed linear spaces,T:D(T)→Y,S:D(S)→Z linear operators withD(T) $$ \subseteq$$ X andD(S) $$ \subseteq$$ X,Ω $$ \subseteq$$ X a convex set containing the zero elementθ, andJ a real-valued convex function defined onX×Y such that (i) J(x,y)⩾-0 for (x,y)teX×Y, (ii) J(θ,θ)=0, (iii) J(x,y)→+∞, as (∥x∥2+∥y∥2)1/2→+∞. Givenζ∈Y andη∈S[core T Ω∩;D(S)], find an elementx=x 0 which minimizesJ(x,ζ−Tx) on the set {x∈[Ω∩;D(S)∩;D(T)]:Sx=η}. The abovementioned problem, together with certain special cases, is analyzed using the classical techniques of functional analysis. Existence problems are considered for a certain class of closed linear operators. In particular, existence of an optimal solution is determined by evaluating a generalized Minkowski functional at the point (ζ,η) inY×Z. A necessary condition is presented for special cases, and corresponding characterizations of optimal solutions are made in terms of the adjoint operators. These results are applicable to linear minimum effort problems, constrained variational problems, optimal control of distributive systems, and certain ill-posed variational problems.
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    Journal of optimization theory and applications 15 (1975), S. 533-547 
    ISSN: 1573-2878
    Keywords: Decomposition methods ; large-scale systems ; calculus of variations ; control theory ; multidimensional control problems
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    Topics: Mathematics
    Notes: Abstract The search for the optimum control of complex static or dynamic processes according toconventional optimization methods involves many problems due, in particular, to the volume and complexity of calculations. And, as the dimensions of the systems studied increases steadily, even if a theoretical solution is still possible, an acceptable solution from the economic standpoint can no longer be hoped for. To overcome these difficulties, an effective means is certainly the introduction of multilevel optimization methods. The use of such a technique for a static optimization of complex systems has already been discussed, and the problems of dynamic optimization are dealt with here. As for static systems, three decomposition methods can be applied. The different tasks to which they lead are examined for each of the levels, and the stability of coordinators is studied.
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    Journal of optimization theory and applications 17 (1975), S. 273-278 
    ISSN: 1573-2878
    Keywords: Optimal control ; existence theorems ; control theory
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    Topics: Mathematics
    Notes: Abstract Using a recent result due to Berkovitz, we prove the existence of an optimal control in a broad class of problems, under relatively mild conditions.
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    Journal of optimization theory and applications 19 (1976), S. 29-45 
    ISSN: 1573-2878
    Keywords: Existence theorems ; nonlinear Volterra equations ; usual solutions ; lower closure theorems ; control theory ; initial-value problems
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    Topics: Mathematics
    Notes: Abstract Existence theorems are stated and proved for optimal control problems monitored by a nonlinear Volterra-type integral equation. Growth conditions are taken into consideration which ensure the needed compactness on the set of trajectories and entail the existence of the usual optimal solutions for the given problem. Weak or approximate solutions are taken into consideration in a subsequent paper.
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    Journal of optimization theory and applications 21 (1977), S. 199-211 
    ISSN: 1573-2878
    Keywords: Variable-metric methods ; optimization theorems ; Hilbert spaces ; control theory
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    Topics: Mathematics
    Notes: Abstract In this paper, the Hilbert-space analogue of a result of Huang, that all the methods in the Huang class generate the same sequence of points when applied to a quadratic functional with exact linear searches, is established. The convergence of a class of direct prediction methods based on some work of Dixon is then proved, and these methods are then applied to some control problems. Their performance is found to be comparable with methods involving exact linear searches.
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    Journal of optimization theory and applications 26 (1978), S. 117-129 
    ISSN: 1573-2878
    Keywords: Generalized geometric programming ; control theory ; convex analysis ; duality
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    Notes: Abstract The interest in convexity in optimal control and the calculus of variations has gone through a revival in the past decade. In this paper, we extend the theory of generalized geometric programming to infinite dimensions in order to derive a dual problem for the convex optimal control problem. This approach transfers explicit constraints in the primal problem to the dual objective functional.
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    Journal of optimization theory and applications 29 (1979), S. 253-290 
    ISSN: 1573-2878
    Keywords: Sufficient optimality conditions ; indirect control proof ; intermediate constraints ; E-dominance ; control theory
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    Notes: Abstract A sufficient condition is given for an arc to be optimal in a general control problem with intermediate constraints. The method of proof is indirect, a la Hestenes, and requires the functionH of the maximum principle to satisfy a concavity property in the control variable, called localE-dominance.
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    Journal of optimization theory and applications 29 (1979), S. 629-658 
    ISSN: 1573-2878
    Keywords: Differential games ; pursuit-evasion problems ; optimal strategies ; control theory ; duality theory
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    Notes: Abstract We study optimal control problems which are the duals, in a specified sense, to a certain class of linear differential games. Directly verifiable conditions, in terms of the data of the game, for uniqueness of solutions of the dual problem and thus for uniqueness of winning policies for the differential game, are derived. As a byproduct, in the particular context of two-dimensional problems, a strong result concerning normality is obtained. As a second byproduct, several geometrical and topological properties of thestar difference are derived. This set operation is of paramount importance for the study of rich classes of differential and difference games extending far beyond that treated here.
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    Journal of optimization theory and applications 16 (1975), S. 539-548 
    ISSN: 1573-2878
    Keywords: Embedding theorems ; integral equations ; control theory ; state variable constraints
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    Topics: Mathematics
    Notes: Abstract In this paper, an embedding theorem is established for a system of nonlinear integral equations of the Volterra type. The main result is basic in the development of a maximum principle for an optimal control problem in which the state variables are determined as solutions to integral equations.
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    Journal of optimization theory and applications 19 (1976), S. 125-140 
    ISSN: 1573-2878
    Keywords: Lower closure theorems ; upper semicontinuity ; control theory ; existence theorems
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    Topics: Mathematics
    Notes: Abstract In the context of a recent geometric condition of Cesari, used in the reduction of seminormality requirements in lower closure theorems, this paper shows that the existence of a strongly convergent selection from the sequence of orientor fields, under Kuratowski property (K), is adequate to guarantee lower closure theorems. This generalization is justified through examples. Several related remarks are made.
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    Journal of optimization theory and applications 19 (1976), S. 165-183 
    ISSN: 1573-2878
    Keywords: Lower closure theorems ; Nemitsky operators ; upper semicontinuity ; control theory ; existence theorems ; orientor fields ; functional analysis
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    Topics: Mathematics
    Notes: Abstract This paper focuses on certain analytic criteria given by the authors in earlier works, for the geometric property of upper semicontinuity of set-valued functions, used in the proofs of lower closure theorems, and hence in existence theory. In particular, it is observed that, under Filippov-type condition (namely, when the set of controls is bounded in measure or in norm), mere Carathéodory-type continuity of the relevant functionsf is sufficient to guarantee a weak form of property (Q), and in turn the lower closure theorems.
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    Journal of optimization theory and applications 19 (1976), S. 577-585 
    ISSN: 1573-2878
    Keywords: Bounded control problems ; control theory ; controllability ; linear systems
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    Notes: Abstract We study the null controllability with bounded controls of an ordinary control process in ℝ n . To prove controllability conditions for the nonautonomous case, we need to generalize the definition of characteristic exponents of a linear system. Some theorems on characteristic exponents are stated.
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    Journal of optimization theory and applications 20 (1976), S. 245-250 
    ISSN: 1573-2878
    Keywords: Queueing ; control theory ; singular control ; steady state
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    Notes: Abstract The optimal control for the service rate of a single-server queue with limited waiting space is derived. Costs are associated with providing the service and with waiting. A comparison with the traditional steady-state result is made.
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    Journal of optimization theory and applications 20 (1976), S. 439-454 
    ISSN: 1573-2878
    Keywords: Attainable sets ; approximation theory ; control theory ; bang-bang control
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    Notes: Abstract We display a class of control systems in the plane for which it is generically true that the set attainable from any point in the plane is a closed Whitney prestratified set. That is, even if the attainable set of some given system is not closed, we can approximate the system as closely as we wish by another system whose attainable sets are closed.
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    Journal of optimization theory and applications 20 (1976), S. 499-500 
    ISSN: 1573-2878
    Keywords: Retarded control problems ; necessary conditions ; control theory ; time-delay systems
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    Topics: Mathematics
    Notes: Abstract Typographical errors are corrected in Ref. 1.
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    Journal of optimization theory and applications 21 (1977), S. 83-89 
    ISSN: 1573-2878
    Keywords: Augmented penalty functions ; control theory ; delayed control systems ; retarded control problems ; computing methods
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    Notes: Abstract A descent method is given for the numerical solution of delayed optimal control problems with fixed delays by first reducing them to nondelayed problems and then using the technique of augmented penalty functions. The system resulting from the reduction to a nondelayed problem is of higher order than the original system; however, the time is proportionally shorter, and the variational matrices are sparse.
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    Journal of optimization theory and applications 22 (1977), S. 41-49 
    ISSN: 1573-2878
    Keywords: Controllability ; nonlinear systems ; sufficiency theorems ; control theory ; comparison theorems
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    Notes: Abstract Some sufficient conditions are presented for the controllability of general nonlinear systems. First, the controllability problem is transformed into the problem of existence of fixed points for some operator; using Schauder's theorem, it is derived that a sufficient condition for controllability is the existence of a subsetS inC n+m (T) which is invariant for a derived operator. Secondly, with the aid of the notion of comparison principle, the existence of the subsetS is guaranteed by the existence of solutions for some nonlinear integral inequality or equality equations. For example, one solution for such nonlinear integral equations is obtained under the assumption of the uniform boundedness for a nonlinear term of the differential equation.
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    Journal of optimization theory and applications 22 (1977), S. 79-89 
    ISSN: 1573-2878
    Keywords: Management science ; advertising ; control theory ; distributed time lags
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    Notes: Abstract The Nerlove-Arrow model of optimal dynamic advertising policies is generalized by incorporating a continuously distributed lag between advertising expenditures and increases in the stock of goodwill. This leads to a control problem where the equation of motion is given by an integro-differential equation. The transitory and steady-state properties of the optimal policies are examined, both for a general lag function and for a gamma distributed lag. The dependence of the steady-state solution on the parameters of the gamma distribution is also investigated. An example is given using specific demand and cost functions.
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    Journal of optimization theory and applications 22 (1977), S. 399-415 
    ISSN: 1573-2878
    Keywords: Variable-metric methods ; optimization theorems ; Hilbert spaces ; control theory
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    Notes: Abstract In this paper, the convergence of variable-metric methods without line searches (direct prediction methods) applied to quadratic functionals on a Hilbert space is established. The methods are then applied to certain control problems with both free endpoints and fixed endpoints. Computational results are reported and compared with earlier results. The methods discussed here are found to compare favorably with earlier methods involving line searches and with other direct prediction quasi-Newton methods.
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    Journal of optimization theory and applications 23 (1977), S. 465-470 
    ISSN: 1573-2878
    Keywords: Sufficiency theorems ; optimal control theory ; control theory ; optimization theorems
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    Notes: Abstract It is always possible to transform a nonautonomous optimal control problem into an autonomous one. However, the direct sufficient conditions may yield no information when applied to this autonomous problem, even though they do allow one to conclude sufficiency when applied to the original nonautonomous problem.
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    Journal of optimization theory and applications 24 (1978), S. 153-167 
    ISSN: 1573-2878
    Keywords: Fredholm integral operators ; algebraic invariants ; control theory ; Riccati equation ; numerical methods
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    Notes: Abstract Using the well-known and specific connections between Fredholm integral equations, two-point boundary-value problems, and linear dynamics-quadratic cost control processes, we present a complete, independent set of algebraic invariants suitable for classifying a wide range of Fredholm integral operators with respect to a certain group of transformations. The group, termed theRiccati group, is naturally suggested by the control theoretic setting, but seems nonintuitive from a purely integral-equations point of view. Computational considerations resulting from this classification are discussed.
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    Journal of optimization theory and applications 25 (1978), S. 323-323 
    ISSN: 1573-2878
    Keywords: Isoperimetric problems ; control parameters ; maximum principle ; terminal constraints ; control theory
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    Topics: Mathematics
    Notes: Abstract A reply is made to the comment of Forster and Long.
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    Journal of optimization theory and applications 25 (1978), S. 317-322 
    ISSN: 1573-2878
    Keywords: Isoperimetric problems ; control parameters ; maximum principle ; terminal constraints ; control theory
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    Notes: Abstract Schmitendorf's formulation of the terminal conditions is shown to be a special case of Hestenes' formulation, despite his claim to the contrary. Imaginative use of Hestenes' control parameters enables the application of Hestenes' theorem to a wide variety of problems. Schmitendorf's rank condition on the terminal constraints can be dispensed with.
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    Journal of optimization theory and applications 25 (1978), S. 469-473 
    ISSN: 1573-2878
    Keywords: Differential games ; Pareto-optimality ; multicriteria optimization ; control theory
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    Topics: Mathematics
    Notes: Abstract A class of differential games consisting of three players is presented. It is assumed that two of them, forming a coalition and working together, oppose the other. Under some additional assumptions, an optimality criterion for the players who form a coalition is proposed.
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    Journal of optimization theory and applications 16 (1975), S. 119-133 
    ISSN: 1573-2878
    Keywords: Structural optimization ; minimum-weight design ; control theory ; distributed parameter problems ; two-point boundary-value problems
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    Notes: Abstract This paper presents an application of two solution methods to the least-weight optimization of a simple sandwich beam with a frequency constraint. The first method, an adaptation of a numericalshooting technique used in optimal control, is found to give good results if unknown initial conditions can be reasonably approximated. The second method, a perturbation method used widely in theoretical mechanics and aerodynamics, yields approximate analytical expressions. These expressions can be used in turn to estimate starting values for the numerical technique. Converged numerical results are presented for a least-weight cantilever beam with fixed fundamental frequency and for a beam on simple supports with fixed fundamental frequency.
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    Journal of optimization theory and applications 15 (1975), S. 327-339 
    ISSN: 1573-2878
    Keywords: Education planning ; maximum principle ; control theory ; optimum investments
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    Notes: Abstract This paper describes the application of the discrete maximum principle to the problem of the introduction of universal primary education.
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    Journal of optimization theory and applications 15 (1975), S. 347-359 
    ISSN: 1573-2878
    Keywords: Stochastic control theory ; existence of optimal stochastic controls ; stochastic optimization ; control theory ; stochastic differential equations
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    Notes: Abstract The paper treats the problem of existence of optimal controls for a large class of delay-differential Itô equations, where the control is a nonanticipative measurable function of the trajectory (the case of complete information). The technique, which seems simpler than past approaches to the problem, requires the use of results on weak convergence of measures, and gives fairly general results. Control can be either over a fixed-time interval, or it can terminate when a target set is reached, and there can be additional (almost everywhere continuous) side constraints.
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    Journal of optimization theory and applications 17 (1975), S. 93-114 
    ISSN: 1573-2878
    Keywords: Controllability ; maximum principle ; nonlinear systems ; control theory ; bounded-state problems
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    Notes: Abstract A controllability minimum principle and two associated transversality conditions are presented, dealing with the controllability of nonlinear systems. The theorems represent necessary conditions for a control function to generate a system path which lies in the boundary of the set of points that are controllable to a target. The theorems presented here are controllability counterparts to Pontryagin's maximum principle, and undoubtedly these results will seem familiar or may have occurred to other researchers in the area of optimal control. The purpose of this paper is to make the distinction explicit and to establish the validity of these controllability theorems on their own merits. The theorems are demonstrated using a simple example and the principal result (a controllability minimum principle) is shown to be equivalent to the Kalman controllability criterion for linear systems.
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    Journal of optimization theory and applications 17 (1975), S. 523-543 
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    Keywords: Controllability ; playability ; Lyapunov functions ; control theory ; differential games
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    Topics: Mathematics
    Notes: Abstract A dynamical system is assumed to be governed by a set of ordinary differential equations subject to control. The set of points in state space from which there exist permissible controls that can transfer these points to a prescribed target set in a finite time interval is called a capture set. The task of determining the capture set is studied in two contexts. first, in the case of the system subject to a single control vector; and second, in the case of the system subject to two control vectors each operated independently. In the latter case, it is assumed that one controller's aim is to cause the system to attain the target, and the other's is to prevent that from occurring. Sufficient conditions are developed that, when satisfied everywhere on the interior of some subset of the state space, ensure that this subset is truly a capture set. A candidate capture set is assumed to have already been predetermined by independent methods. The sufficient conditions developed herein require the use of an auxiliary scalar function of the state, similar to a Lyapunov function. To ensure capture, five conditions must be satisfied. Four of these constrain the auxiliary state function. Basically, these four conditions require that the boundary of the controllable set be an envelope of the auxiliary state function and that that function be positive inside the capture set, approaching zero value as the target set is approached. The final condition tests the inner product of the gradient of the auxiliary state function with the system state velocity vector. If the sign of that inner product can be made negative everywhere within the test subset, then that subset is a capture set.
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  • 64
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    Journal of optimization theory and applications 18 (1976), S. 73-79 
    ISSN: 1573-2878
    Keywords: Differential games ; pursuit-evasion problems ; optimal strategies ; duality theory ; control theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract It is shown that linear differential pursuit games with linear targets, if player controls are required to be piecewise constant or if player controls areL 1-functions (but pursuer control is bang-bang whenever quarry control is), are equivalent to a linear, autonomous control problem. As a byproduct, a sufficient condition for terminating the game, in Pontryagin's sense, is obtained.
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  • 65
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    Journal of optimization theory and applications 18 (1976), S. 371-377 
    ISSN: 1573-2878
    Keywords: Retarded control problems ; necessary conditions ; control theory ; time-delay systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A method is exhibited which transforms a large class of optimal control problems with fixed delays to nondelayed problems, thus permitting classical results to be used in their analysis.
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  • 66
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    Journal of optimization theory and applications 18 (1976), S. 561-567 
    ISSN: 1573-2878
    Keywords: Isoperimetric problems ; maximum principle ; necessary conditions ; control variable constraints ; control theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Necessary conditions are derived for optimal control problems subject to isoperimetric constraints and for optimal control problems with inequality constraints at the terminal time. The conditions are derived by transforming the problem into the standard form of optimal control problems and then using Pontryagin's principle.
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  • 67
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    Journal of optimization theory and applications 19 (1976), S. 381-400 
    ISSN: 1573-2878
    Keywords: Variable metric methods ; optimization theorems ; Hilbert spaces ; control theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper is concerned with some of the most powerful methods of minimizing functionals on Hilbert space. It is established that certain classes of these methods are equivalent and their convergence is proved for certain nonquadratic functionals on a Hilbert space. A computational study of these methods applied to a control problem is also included with particular reference to the equivalence of methods mentioned above.
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  • 68
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    Journal of optimization theory and applications 27 (1979), S. 135-146 
    ISSN: 1573-2878
    Keywords: Differential games ; Pareto optimality ; multicriteria optimization ; control theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Optimal control problems with a vector performance index and uncertainty in the state equations are investigated. Nature chooses the uncertainty, subject to magnitude bounds. For these problems, a definition of optimality is presented. This definition reduces to that of a minimax control in the case of a scalar cost and to Pareto optimality when there is no uncertainty or disturbance present. Sufficient conditions for a control to satisfy this definition of optimality are derived. These conditions are in terms of a related two-player zero-sum differential game and suggest a technique for determining the optimal control. The results are illustrated with an example.
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  • 69
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    Journal of optimization theory and applications 27 (1979), S. 377-398 
    ISSN: 1573-2878
    Keywords: Stochastic control problems ; existence theorems ; probability theory ; control theory ; stochastic differential equations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We give existence theorems for stochastic control problems with a lower semicontinuous cost functional and governed by Ito equations. We prove that two formulations of the fundamental problem are equivalent, one involving nonanticipative controls and the other involving (measurable) feedback controls. We then use the concept ofconvergence in distribution to prove existence for the first problem, and hence for the second as well. While our work has certain similarities with a paper of Kushner, our techniques are different and lead to more general results.
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  • 70
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    Journal of optimization theory and applications 16 (1975), S. 303-325 
    ISSN: 1573-2878
    Keywords: Computing methods ; algorithms for optimal control ; finite difference methods ; differential equations ; control theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper presents eight algorithms for solving optimal control problems with general constraints on the control and inequality constraints on the terminal state. These algorithms are of the differential dynamic programming type and bear a strong kinship to nonlinear programming algorithms of the feasible direction type.
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  • 71
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    Journal of optimization theory and applications 16 (1975), S. 497-517 
    ISSN: 1573-2878
    Keywords: Bang-bang control ; time-optimal control ; switching surfaces ; multidimensional control problems ; control theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This article deals with bang-bang solutions of linear time-optimal control problems. Linear multivariable systems are considered which have one or more control components. It is shown in which way the control components act together to make the system achieve the ultimate aim (namely, the origin in the state space) as quickly as possible. The theory only applies to initial positions sufficiently near the origin. Criteria are given which give the number of switches per control component. Asymptotic dependences of the switching times and the final time on the distance of the initial position from the origin are established. The theory provides a numerical procedure to calculate the time-optimal control. These calculations are very simple. Basic to the proof of these results is a generalized implicit function theorem due to Artin (Ref. 1).
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