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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 410-416 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper a differential equation is obtained for the variation of the poloidal magnetic field along the cross section of the magnetic field surfaces in a tokamak. Toroidal axisymmetry is assumed. The coefficients of the differential equation depend on the curvature of the family of curves orthogonal to the magnetic field lines. Several shapes of magnetic field surfaces have been analyzed in detail as families of nested curves of circular, elliptic, and triangular elliptic shapes. Closed analytic solutions have been obtained in some cases. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 649-651 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Electron beam ion sources produce very highly charged ions most efficiently in a batch mode as the confinement time can be directly optimized for the production of the desired charge state. If, after confinement, the voltage of the ion-confining downstream dam is lowered rapidly, all ions escape and form an ion beam pulse with a length of a few tens of μs. Raising the main trap voltage while maintaining a constant dam voltage in a "spill-over expulsion" reduces the energy spread of the expelled ions. The longer time periods of "slow-," "leaky batch mode-," and "direct current (dc) batch mode-" expulsions allow for increasing the ion beam duty cycle. Combining the rapid expulsion with one of the latter methods allows for the expulsion of the ions of a single batch in many small microbunches with variable intervals, maintaining the low energy spread and the increased duty cycle of slow expulsions. Combining the "microbunching" with "dc batch mode production" and a multitrap operation will eventually allow for the production of equally intense ion bunches over a wide range of frequencies without any deadtime, and with minimal compromise on the most efficient production parameters. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Oversized dopant ions such as yttrium and lanthanum segregate to grain boundaries and reduce the tensile creep rate of α-Al2 O3 by 2-3 orders of magnitude. One explanation for this behavior is that the oversized segregants give rise to a “site-blocking” effect for grain boundary diffusion. It has also been speculated that the dopant ions modify the grain boundary structure in alumina and reduce the creep rate by promoting the formation of special (e.g., coincidence site lattice (CSL)) grain boundaries. In order to test the latter hypothesis, we have used electron backscattered Kikuchi diffraction to characterize the misorientation and special grain boundary distribution for undoped and 1000-ppm-yttrium-doped alumina. The results show that the grain boundary structure in alumina (as characterized by the frequency of selected CSLs and misorientation distribution) was not significantly changed by the addition of yttrium, indicating that creep retardation results mainly from site-blocking.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective Toobtain a prevalence estimate for chronic pelvic pain in women in the United Kingdom by analysing published data.Design Systematic review of published papers.Setting The general population or hospitals in the United Kingdom.Population Women participating in relevant community surveys or control women participating in hospital-based studies.Methods Papers were retrieved by systematically searching the databases MEDLINE, EMBASE and PsycLit, and by hand searching. Studies were included if they 1. were community-based and reported prevalence rates of chronic pelvic pain, dyspareunia, dysmenorrhoea, or abdominal pain, or 2. referred to a clinical population but reported prevalence rates in a disease-free control group.Main outcome measures Prevalence rates for chronic pelvic pain including any overlap with dyspareunia, dysmenorrhoea and abdominal pain.Results No community-based study has been performed that provides an estimate of the prevalence of chronic pelvic pain in the general UK population. A rate of 39% was reported in women undergoing laparoscopy for sterilisation or investigation of infertility in the single study from the United Kingdom investigating chronic pelvic pain unrelated to menstruation or intercourse. Prevalence rates for dyspareunia, dysmenorrhoea, and abdominal pain found in UK community-based studies were 8%, 45%, to 97%, and 23% to 29%, respectively, but definitions used varied greatly.Conclusions Because chronic pelvic pain can reduce the quality of life and general wellbeing, there is a need for a community-based study into the prevalence of chronic pelvic pain and its effect upon the lives of women in the UK.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The infiltration of glass melts into fully dense Al2O3 and MgO ceramics has been studied with emphasis on elucidating the penetration mechanism and the change in shape and size of the solid grains that accompany the penetration process. For Al2O3, penetrated by a Ca—Al—Si—O glass melt, the grains developed a prismatic shape consistent with interface-reaction-controlled grain growth. For MgO, penetrated by a Ca—Mg—Si—O glass melt, the grains maintained a spherical shape consistent with diffusion-controlled grain growth. When glass penetrated into the dense polycrystalline alumina specimen, it resulted in a homogeneous distribution of liquid phase and a uniform grain size throughout the whole specimen. In contrast, when glass penetrated the magnesia specimen, the volume fraction of liquid phase at the surface region (which was in direct contact with the melt) was higher than that in the center region. Furthermore, the average grain size was larger in the center, where the volume fraction of glass was lower. This microstructural inhomogeneity stayed uncorrected even after prolonged annealing treatments. Reasons for this behavior are discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The crack healing and strength behavior of an alumina-silicon carbide (Al2O3-SiC) nanocomposite (Al2O3+ 5 vol% 0.2 μm SiC particles) has been studied, as a function of the crack size and the annealing environment. Results show that annealing treatments can significantly increase the indentation strength. The annealing atmosphere has a profound influence on the extent of crack healing and the degree of strength recovery. Annealing in argon results in a strength increase of 50%, whereas annealing in air yields a three-fold improvement in the indentation strength. Scanning electron microscopic observation has shown that healing of indentation cracks occurs in both environments, with the greater degree of healing occurring during annealing in air. Implications of the findings to the strengthening mechanism in Al2O3 (SiC) nanocomposites will be discussed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A potentially more cost-efficient method of growing single-crystal relaxor-based ferroelectric materials has been investigated. Seed single crystals of Pb(Mg1/3Nb2/3)O3(PMN)—;35 mol% PbTiO3(PT) were embedded within polycrystalline powders and annealed at temperatures from 900° to 1200°C. The boundary of the single crystal migrated through the polycrystal matrix under the influence of grain boundary curvature; growth distances of several millimeters were observed, verifying the feasibility of the approach. The grown single crystals exhibited macroscopic cubic growth morphologies with (100) faces. Strain levels as high as 0.68% under an electric field of 30 kV/cm were observed in initial measurements.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The reaction-bonded aluminum oxide process begins with aluminum, Al2O3, and usually ZrO2 powders that have been attrition-milled in an organic liquid. The attrition-milled powder is then compacted and heat-treated in air to produce polycrystalline, Al2O3-based ceramics. Safety considerations have made it desirable for the milling liquid to be changed from acetone to a less-flammable solvent. In this paper, mineral spirits, ethanol, and mineral spirits that contains 2 wt% stearic acid are presented as viable alternatives to acetone. The effects of changing the milling liquid on the reaction process and the properties of the final fired ceramic are investigated.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Toughness-curve (T- or R-curve) behavior of a composite of 30 vol%, polycrystalline, coarse-grained, spherical alumina agglomerates dispersed throughout a fine-grained, 50/50 vol% alumina-mullite matrix, and that of its microstructural end-members (100% matrix and 100% alumina), were studied using the indentation-strength-in-bending technique. T-curves were deconvoluted from indentation-strength data using an indentation fracture mechanics model. The monolithic matrix and alumina exhibited an invariant toughness and a moderate T-curve, respectively. In comparison, the composite exhibited a pronounced T-curve. The T-curve of the composite is best explained as deriving from the interaction of a propagating crack with the alumina agglomerates: crack propagation experiments revealing two possible toughening mechanisms-intra-agglomerate frictional grain bridging and elastic bridging ligaments in the matrix that appeared to be associated with alumina agglomerates. Rule-of-mixtures toughness calculations indicated that intra-agglomerate bridges could account for only a fraction of the toughening exhibited by the composite. It is suggested that the extra toughening arises from the elastic bridging ligaments.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 1036-1038 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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