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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 23 (1987), S. 0 
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : This paper describes the formulation and application of a ground-water hydraulic management model to determine the optimal development and operating policies of a regional aquifer in the Eastern Province of Saudi Arabia. The hydraulic response of the aquifer system is represented by a simulation model that is linked to an optimization management model using response functions. Yearly optimal ground-water extraction rates over a planning horizon of 15 years are determined for four scenarios, each reflecting alternative ground-water development policies. The results are presented in the form of tradeoff curves, relating drawdowns to optimal pumpage, which may enhance the decisionmaker's ability to select the best development policy from a set of alternatives. The results illustrate how various optimal management schemes can be devised to increase the total withdrawal from the aquifer while preventing excessive de-watering.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 14 (1991), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The thermal-mechanical fatigue behaviour of a cast cobalt based superalloy, MAR-M 509 was investigated. Hollow smooth specimens were submitted to temperature cycling between 600 and 1050°C. The mechanical strain vs temperature cycle shows a diamond shape with peak strains at intermediate temperatures. The stress-strain behaviour as well as fatigue life curves are reported. A significant part of total life is spent in crack initiation. Comparison with isothermal low cycle fatigue was made at the temperature where peak strains occurred. Isothermal low cycle fatigue life to crack initiation was shown to give a conservative estimate of thermal mechanical fatigue life provided extra strains due to differences in thermal expansion coefficients of the oxide scale and base alloy were taken into account.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 2 (1979), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The initiation and the propagation of fatigue cracks and the low cycle fatigue life of a cast cobalt base superalloy was studied at 293K, 973K and 1173K by optical and scanning electron microscopy. A substantial decrease in fatigue life occurred at 973 and 1173K when compared to room temperature life. A time-dependent bulk damage was evidenced at 1173K which was determined by quantitative microscopy for two plastic strain levels. High strain fatigue crack propagation experiments were carried out at room temperature and at 1173K. From these experiments the decrease of the overall fatigue life at high temperature was shown to result from a considerable reduction of the initiation period due to oxidation and also from a significant acceleration of the crack propagation rate in the presence of oxidation and bulk damage.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 11 (1988), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The thermal fatigue behaviour of a cast cobalt superalloy was investigated. Wedge type specimens were tested on a rig using flame heating. A standard cycle from 200 to 1100°C was used for most tests and the specimen geometry was changed to investigate a broad range of thermal fatigue lives. The maximum temperature was also varied for a single specimen geometry. The thermal fatigue life to create a 1 mm deep crack ranges from a few tens to one thousand cycles. Crack initiation occurs early in life at oxidised interdendritic carbides as in high-temperature, low-cycle fatigue. Precipitation of small chromium-rich carbides was found to occur in the dendrites during thermal fatigue cycling. An identical precipitate distribution could be induced by a two stage thermal treatment as shown by quantitative metallography. The isothermal stress-strain behaviour at high temperature was so shown to be almost insensitive to the microstructure changes induced by thermal fatigue.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 11 (1988), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Thermal fatigue data on MAR-M509 reported in a companion paper were used to evaluate four life prediction models. The temperature-stress-strain history of the critical element at the thin edge of wedge specimens was computed for this purpose. The analysis method uses a finite element computation of the temperature field and a uniaxial calculation of the stress-strain cycle using a cyclic viscoplastic constitutive equation. The influence of specimen geometry and of maximum temperature on the thermal fatigue life to initiate a macroscopic crack was accounted for by variations in stress and mechanical strain ranges at the thin edge. The accumulated and cyclic creep damage models were found to overestimate thermal fatigue life in all the cases. Models which describe oxidation fatigue crack growth interactions, and which are borne out by metallographic observations on wedge specimens, were found to give reliable predictions of thermal fatigue life.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Ultrasructure Research 61 (1977), S. 243-253 
    ISSN: 0022-5320
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Ultrasructure Research 82 (1983), S. 283-295 
    ISSN: 0022-5320
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0248-4900
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0248-4900
    Keywords: adenocarcinoma cells ; confocal laser scanning microscopy ; intercellular cysts ; intracellular lumens
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-6903
    Keywords: Microglia ; brain ; prostaglandin ; indomethacin ; complement receptor ; Mac-1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The current study was undertaken to study the role of prostaglandins in regulating microglial activation. Mice were treated with indomethacin (2 μg/ml) in their drinking water to selectively inhibit cyclooxygenase activity. After 4–8 days, the effect of inhibiting prostaglandin synthesis on microglial activity was evaluated. This was accomplished by analyzing microglial expression of Mac-1 (C3 complement receptor) as an indicator of activation. Mac-1 expression was assessed by immunohistochemistry of fixed brain cryosections, and by flow cytometric analysis of immunostained single cell suspensions. Both methods demonstrated that compared to age-matched, untreated controls, brains of indomethacin-treated mice had increased levels of Mac-1 expression, suggesting an increase in the state of microglial activation. These results demonstrate the importance of prostaglandins in down regulating microglial activity, and that inhibition of prostaglandin synthesis with indomethacin may act to increase the reactivity of the brain's immune system.
    Type of Medium: Electronic Resource
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