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  • 1
    Electronic Resource
    Electronic Resource
    Determination of Mechanical Properties for the Hydroforming of Magnesium Sheets at Elevated Temperature (2005)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 6-8 (May 2005), p. 779-786 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Thanks to the low weight, magnesium alloys feature high specific strength and stiffness properties. Thus they prove to be promising materials for todays ambitious automotive light weight construction efforts. Due to their comparative low formability at room temperature the process of magnesium sheet hydroforming can be improved at temperatures higher than 200 °C by the activation of additional sliding planes. This paper illustrates the determination of mechanical properties for the hydroforming of magnesium sheets at elevated temperature. In particular the mechanical behavior at elevated temperature was investigated by means of the tensile test and of the hydraulic bulge test. For the determination of the strains an optical measurement system was introduced into the experimental set-up. The exact knowledge of the strain condition in the area of diffuse necking enabled the determination of the flow curve in the tensile test also beyond the uniform elongation. The influence of temperature and strain rate was analyzed as well as the influence of uni- and biaxial stress state on the flow curve. Using circular and elliptic dies with different aspect ratio the hydraulic bulge test served to determinate the forming limit curves at threedifferent elevated temperatures
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/41/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.6-8.779.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Triangulation Based Digitizing of Tooling and Sheet Metal Part Surfaces - Measuring Technique, Analysis of Deviation to CAD and Remarks on Use of 3D-Coordinate Fields for the Finite Element Analysis (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 344 (July 2007), p. 847-853 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The dynamic development of highly accurate optical measuring machines within the lastyears pushed the introduction of digitizing techniques to many applications in the fields of qualitycontrol, reverse engineering and rapid prototyping. By projecting fringe patterns onto the object'ssurface and recording pictures of the curvature dependant deformation of the pattern, 3Dcoordinates for each camera pixel are calculated on the basis of the principle of triangulation. Thegeneration of a polygon mesh can be used for the analysis of the deviation of a die or a formed partto the initial CAD data, i.e. by means of full field or section based comparison. This paper presentsthe application of the above mentioned techniques on a double sheet hydroforming process. Thegathered 3D data of the clam-shell part as well as of the tooling dies served for the calculation of thedeviation to the respective reference geometry. With respect to the utilization of digitized toolingdata within the finite element analysis, further investigations were performed on the impact of datareduction strategies. Aiming on the minimization of the necessary number of elements, representingthe tooling surface in a discrete state, and on the request for a sufficient degree of accuracy, thesestrategies have to be considered of high priority
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/54/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.344.847.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Improvement of Formability in Tube Hydroforming by Reduction of Friction with a High Viscous Fluid Flow (2005)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 6-8 (May 2005), p. 369-376 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Tube hydroforming is an advanced technology for the manufacturing of lightweightcomponents with complex shape. The forming results can be usually improved if axial feeding at the tube ends is enabled. For very long parts, however, due to the high friction forces acting at high pressure in the feeding zone between tube and die, no material movement towards the expansion area occurs. The tube is only upset in the feeding zone, no compressive stresses take place in the expansion area and the forming results are not satisfactory. This can be avoided by eliminating friction and by inducing additional tangential stresses in axial direction on the tube surface of the feeding area. This paper presents the investigations performed in this direction by using a high viscous fluid flowing along the internal and external surface of the tube. The flow helps to reduce the friction force and allows the sliding between the tube and the tool surface. Experimental tests of tube upsetting under pressure will show the effects of the medium flow on the thickening of the tube wall. Not only increased sliding and homogeneous thickening will be obtained, but even an increaseof the wall thickness in the area close to the expansion zone will be shown. This effect is even stronger when the yield stress in the expansion zone is reduced by means of a previous local heat treatment
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/41/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.6-8.369.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Interstitial nitrogen induced by low-energy ion beam nitridation of AIII–BV semiconductor surfaces (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 6066-6069 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nitridation of GaAs, InAs, and InSb by low-energy N2+ ion bombardment at room temperature was studied by near-edge x-ray absorption fine structure (NEXAFS) and x-ray photoelectron spectroscopy measurements. The formation of thin surface nitride layers, consisting mostly of GaN or InN but also containing minor amounts of mixed nitrides, was observed. Besides the nitride-related features, sharp peaks in the NEXAFS due to π* resonance at 401.0 eV and correlated peaks at 403.8 eV in N 1s core level spectra were detected. Both spectral features could be assigned to the presence of interstitial nitrogen, most likely molecular nitrogen. It was found that the amount of interstitial nitrogen in the surface layer strongly depends on the AIII–BV semiconductor system and may be affected by modification of the conditions during low energy ion bombardment. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1415765
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  • 5
    Electronic Resource
    Electronic Resource
    The cell wall architecture of Candida albicans wild-type cells and cell wall-defective mutants (2000)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 35 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In Candida albicans wild-type cells, the β1,6-glucanase-extractable glycosylphosphatidylinositol (GPI)-dependent cell wall proteins (CWPs) account for about 88% of all covalently linked CWPs. Approximately 90% of these GPI-CWPs, including Als1p and Als3p, are attached via β1,6-glucan to β1,3-glucan. The remaining GPI-CWPs are linked through β1,6-glucan to chitin. The β1,6-glucanase-resistant protein fraction is small and consists of Pir-related CWPs, which are attached to β1,3-glucan through an alkali-labile linkage. Immunogold labelling and Western analysis, using an antiserum directed against Saccharomyces cerevisiae Pir2p/Hsp150, point to the localization of at least two differentially expressed Pir2 homologues in the cell wall of C. albicans. In mnn9Δ and pmt1Δ mutant strains, which are defective in N- and O-glycosylation of proteins respectively, we observed enhanced chitin levels together with an increased coupling of GPI-CWPs through β1,6-glucan to chitin. In these cells, the level of Pir-CWPs was slightly upregulated. A slightly increased incorporation of Pir proteins was also observed in a β1,6-glucan-deficient hemizygous kre6Δ mutant. Taken together, these observations show that C. albicans follows the same basic rules as S. cerevisiae in constructing a cell wall and indicate that a cell wall salvage mechanism is activated when Candida cells are confronted with cell wall weakening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.01729.x
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  • 6
    Electronic Resource
    Electronic Resource
    Photofragmentation of mass-selected (C6H6)+n clusters: Measurement of monomer–cluster binding energy for n=7–15 (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 1975-1981 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Benzene cluster cations up to 15 molecular units in size, produced in the throat of a supersonic nozzle by laser-induced plasma formation, are studied by mass-selected photofragmentation spectroscopy. All of the clusters exhibit a strong, broad absorption which extends at least from 690 to 1064 nm, centered near 900 nm. This absorption is assigned to the dimer based intervalence transition observed in solid state spectra of the dimer ions. Excitation into this band produces prompt ejection of neutral benzene molecules from the cluster ion. At low fragmentation laser intensities, a single daughter ion species is observed. We observe a simple dependence of the number of neutral molecules ejected on the fragmentation laser wavelength, strongly suggesting a sequential evaporation process of neutral benzene molecules. For clusters larger than six, an average bond energy ranges from 0.37–0.34 eV/molecule, quite close to the heat of vaporization for liquid benzene. The 14 molecule cluster is found to have an anomalously high binding energy, providing strong evidence that it forms a stable icosahedral structure. The general trend of the monomer bond energy with cluster size is well accounted for by a simple model based on macroscopic constructs and liquid benzene dielectric constant, surface tension, and heat of vaporization values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462099
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  • 7
    Electronic Resource
    Electronic Resource
    Auroral and airglow Fabry–Perot spectrometer (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 240-247 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A microcomputer-controlled and piezoelectrically scanned Fabry–Perot spectrometer capable of being transported to remote field sites has been constructed. The Fabry–Perot has a 70-mm aperture and has a provision for computer control of the cavity drift. The instrument has been operated at resolutions from 0.06–1.5 A(ring) in making high-speed observations of the aurora from 7500–8500 A(ring). A separate filter-wheel photometer section provides information on other auroral and airglow emissions such as N+2(4278) and OI(6300). The apparatus is portable and has been operated at Poker Flat, Alaska and Churchill, Canada.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138977
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  • 8
    Electronic Resource
    Electronic Resource
    In situ infrared and visible-light ellipsometric investigations of boron nitride thin films at elevated temperatures (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 526-532 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In situ infrared (IR) spectroscopy and visible-light (VIS) spectroscopic ellipsometry over the spectral range from 700 to 2000 cm−1 and 1.5–3.5 eV, respectively, were used to investigate the optical behavior of boron nitride (BN) thin films at temperatures from room temperature (RT) to 600 °C. The polycrystalline hexagonal (h) and mixed-phase h- and cubic (c)-BN thin films were deposited by magnetron sputtering on [001] silicon. We observe a reversible moisture incorporation process in as-grown h-BN samples. When stored in normal ambient, the h-BN thin films absorb water into thin-film micropores. When annealed in ultrahigh vacuum or a dry nitrogen atmosphere, the samples expel moisture but retain their microstructure. This is observable by reduction of the thin-film refractive indices in accordance with changes in the IR lattice resonance behavior. The optical properties of high c-BN content thin films remain unchanged during annealing. And both intrinsic h- and c-BN thin-film VIS refractive indices are nearly temperature independent, at least up to 600 °C. Therefore, RT BN optical constants can be used for feedback loop control in in situ thin-film growth at temperatures up to 600 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368083
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  • 9
    Electronic Resource
    Electronic Resource
    The effect of an oxidant on the production of metal smoke particles
    Amsterdam : Elsevier
    Surface Science Letters 106 (1981), S. A166-A167 
    Details
    ISSN: 0167-2584
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0167-2584(81)90315-7
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  • 10
    Electronic Resource
    Electronic Resource
    The formation of cosmic grains: An experimental and theoretical study
    Amsterdam : Elsevier
    Surface Science Letters 106 (1981), S. A192-A193 
    Details
    ISSN: 0167-2584
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0167-2584(81)90379-0
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