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  • Springer  (602)
  • Wiley  (15)
  • Oxford University Press  (8)
  • American Institute of Physics (AIP)  (7)
  • 2015-2019  (536)
  • 2005-2009  (21)
  • 1990-1994  (38)
  • 1980-1984  (37)
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  • 1
    Electronic Resource
    Electronic Resource
    Laser drilling into an absorbing liquid (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 551-556 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interaction of continuous CO2 laser radiation with water is described. Tightly focused radiation at powers of up to 120 W is used to generate and maintain a conical depression in the water surface similar to the keyhole created during laser penetration welding. The observed penetration depth of up to 7 mm is explained in terms of a hydrodynamic model and observations on the interaction induced liquid flows are described. The momentum reaction to the flow of steam up out of the keyhole generates a downward flow in the liquid around the keyhole with a velocity of ∼20 cm/s under the conditions of these experiments. The experiment has also been performed under variable gravity conditions provided by the NASA KC-135 Microgravity Aircraft to observe effects associated with changes in hydrostatic pressure and buoyancy on the system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350404
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  • 2
    Electronic Resource
    Electronic Resource
    The Young's modulus of silica beads/epoxy composites: Experiments and simulations (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1442-1455 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of particulate volume fraction vp and diameter dp on the composite Young's modulus Ec is studied both experimentally, using a silica bead/epoxy system, as well as with the help of computer simulations. The experimental and simulation results show that for a given particulate size, the overall Ec vs vp curve displays a concave upward shape and not a linear shape. This superlinear trend of the data implies that the average strain normalized to the applied strain λ=ε¯p/εc transferred to the particulates increases with volume fraction. The above finding is explained in terms of a mean-field picture, where a single particle interacts with an effective medium consisting of the remaining particles embedded in the matrix. As the modulus of the effective medium surrounding a reference particle increases with vp, the modulus mismatch between the reference particulate and the medium is consequently reduced. This leads to an overall increase in the normalized average strain λ transferred to each particulate as vp is increased. The experimental results using silica particulates with various sizes dp, as well as the simulation results, show that smaller particulates provide an increased composite modulus as compared to larger particulates, at constant vp. General equations are developed, which relate the composite modulus to the average particle stress or strain, given only information about the volume fraction and the Young's modulus of each of the phases present.Through the application of these relations, it is found that smaller particulates display a greater amount of normalized average strain λ transferred than larger particulates. The effect of particulate Young's modulus Ep in combination with particulate size on the resulting Ec is also studied using simulations only. It is found that for a low particulate to matrix modulus ratio Ep/Em, the particulate size has very little influence on Ec. Moreover, the shape of the Ec vs vp curve can be well approximated by a straight line up to large values of vp. On the other hand, as the ratio Ep/Em is increased, the superlinear trend of the composite modulus Ec vs vp data is more apparent. This results in a smaller range of the Ec vs vp curve, which can be approximated by a linear function. It is also found that the extent of this linear region also decreases with particle size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356378
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of H concentration in LiNbO3 by photorefractive fixing (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 3212-3214 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new method to determine the proton concentration in LiNbO3 is presented. The method is based on the measurement of the diffraction efficiency of a photorefractive grating in two situations. It is first measured after recording at room temperature, and second after saturation of the fixing process at a given temperature (about 150 °C). From only these two experimental data, the value obtained for the proton concentration in our sample is H0=(4.4±0.7)×1018 cm−3. This value agrees, within the experimental error, with that obtained from the infrared absorption arising from the OH− stretching bond.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106742
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  • 4
    Electronic Resource
    Electronic Resource
    Gigahertz switching behavior of polarization-bistable InGaAsP/InP lasers under high-frequency current modulation (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 830-832 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The switching dynamics between TE- and TM-polarization states is studied in a strained ridge-waveguide InGaAsP/InP laser that exhibits TE/TM bistability. Using current modulation with frequencies between 50 and 500 MHz, three types of emission are distinguished. With increasing modulation amplitude, the laser runs through a region of TE emission, a range of stochastic switching between TE and TM modes, and a third region of regular polarization switching. The minimum modulation amplitude for regular switching rises strongly with frequency while the respective switching times decrease from about 700 ps at 50 MHz down to 250 ps around 500 MHz, corresponding to gigahertz mode switching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111028
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  • 5
    Electronic Resource
    Electronic Resource
    Temperature dependence of the electron energy gap of high TC superconductors studied by work function spectroscopy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1726-1728 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Work function measurements with the so-called onset technique have been used to study the temperature-dependent behavior of the electron energy gap of YBa2Cu3O7−x superconducting films. In the temperature range from TC down to 30 K a BCS-like behavior with gap width 2Δ0 at T=0 between 38 and 62 meV is found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111989
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  • 6
    Electronic Resource
    Electronic Resource
    Accelerator and target studies for heavy ion fusion at the Gesellschaft für Schwerionenforschung (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1313-1317 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The new Schwerionen-Synchrotron (SIS)/Experimenteller Speicher-Ring (ESR) heavy ion accelerator facility [Nucl. Instrum. Methods A 278, 7, 19 (1989)], built for basic atomic and nuclear physics at Darmstadt (Federal Republic of Germany), also provides unique possibilities to study rf accelerator and beam/target interaction physics for inertial confinement fusion driven with heavy ion beams. It is the first machine that offers this opportunity. Beam parameters and experiments planned over the next five years are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859548
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  • 7
    Electronic Resource
    Electronic Resource
    Meander coupler, a novel wavelength division multiplexer/demultiplexer (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2517-2519 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have realized a novel wavelength division multiplexer/demultiplexer based on rib waveguides in GaInAsP/InP. The device is a strongly asymmetric codirectional coupler with periodic variation of the coupling constant and has sinc2-type characteristics. Our devices have center wavelengths around 1.3 μm, filter half-widths 10–15 nm, and far end isolation down to −17 dB. The structure is suited for integration into optoelectronic integrated circuits for applications in bidirectional optical communication systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103841
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  • 8
    Electronic Resource
    Electronic Resource
    α-Vertex separator is NP-hard even for 3-regular graphs (1991)
    Springer
    Computing 46 (1991), S. 343-353 
    Details
    ISSN: 1436-5057
    Keywords: PLA-folding ; vertex separation ; complexity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Zwei diskrete Optimierungsprobleme beim VLSI-Design sind die Fläche eines programmierbaren logischen Arrays (PLA) zu reduzieren und einen Graphen in möglichst gleich große Teilgraphen zu zerlegen. Wir zeigen, daß eine in der Praxis oft benutzte Flächenreduktionstechnik, das Blockfolding, äquivalent ist zu dem Problem, Graphen durch Wegnahme von Knoten zu zerlegen. Es wird gezeigt, daß dieses Problem schon für 3-reguläre GraphenNP-schwer ist.
    Notes: Abstract Two discrete optimization problems arising in VLSI are to reduce the area of a programmable logic array (PLA) and to separate graphs uniformly. We show that a commonly used area reduction technique called blockfolding is equivalent to separating graphs by vertex deletion. The later problem is shown to be NP-complete even for 3-regular-graphs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02257778
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  • 9
    Electronic Resource
    Electronic Resource
    NMR-measurements on polyethyleneoxide samples rotating around the magic axis (1980)
    Springer
    Colloid & polymer science 258 (1980), S. 753-759 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Zusammenfassung Es werden Messungen des Abfalls der transversalen Magnetisierung von geschmolzenem Polyethylenoxid sowohl unter gewöhnlichen Bedingungen als auch bei Rotation der Probe um die magische Achse durchgeführt. Bei Molekulargewichten unterhalb von etwa 6.000 findet man bei den nicht-rotierenden Proben einen exponentiellen Abfall, der auch bei einer Rotation der Probe unverändert bleibt. Bei höherliegenden Molekulargewichten erhält man dagegen für die nicht-rotierenden Proben einen nichtexponentiellen Abfall, der bei einer Rotation mit zwei kHz in einen exponentiellen Abfall übergeht. Die Ergebnisse werden mit Hilfe der Annahme erklärt, daß bei Molekulargewichten über 6.000 Kettenverschlaufungen auftreten, die zu einer anisotropen Bewegung der Moleküle führen. Diese Annahme wird durch Viskositätsmessungen erhärtet. Ähnliche Ergebnisse werden auch für in Chloroform gelöstem Polyethylenoxid erhalten. Oberhalb einer kritischen Konzentration, die um so geringer ist, je höher das Molekulargewicht wird, wird die Bewegung der Moleküle vermutlich als Folge von Kettenverschlaufungen anisotrop. Aus der Rotationsfrequenz, die erforderlich ist, um den Einfluß der anisotropen Bewegung zu beseitigen, werden Rückschlüsse auf die Lebensdauer der Kettenverschlaufungen gezogen.
    Notes: Summary The decay of the transversal magnetization of molten polyethylene oxide is measured not only under usual conditions but also while the sample is rotating around the magic axis. For molecular weights below about 6,000, the decay of the samples not rotating is exponential and the same as that obtained for the rotating samples. For molecular weights above that value, for the samples not rotating, a non exponential decay is obtained which goes over in a decay which is almost exponential if the sample rotates with 2 kHz. The results are explained by the assumption that, for molecular weights above 6,000, chain entanglements 'occur due to which the molecular motion becomes anisotropic. This assumption is in agreement with viscosity measurements. Similar results are obtained for polyethylene oxide solved in chloroform. Above a critical concentration, which decreases with increasing molecular weight, probably due to entanglements, the motion of the molecules becomes anisotropic. From the revolution frequency which is necessary to ommit the influence of anisotropic motion, conclusions concerning the lifetime of an entanglement are drawn.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01384366
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  • 10
    Electronic Resource
    Electronic Resource
    Bistable operation of a GaAs-AlGaAs diode laser coupled to an external resonator of narrow spectral bandwidth (1982)
    Springer
    Optical and quantum electronics 14 (1982), S. 375-389 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The influence of an external dispersive resonator on the emission properties of a double heterostructure semiconductor laser operating at room temperature has been investigated. The proper design of the external resonator (frequency selectivity and efficient back-coupling of the radiation leaving the diode) demonstrates that a laser with optical feedback can show bistability and hysteresis phenomena. The dispersive bistability has its origin in the dependence of the refractive index on carrier density, temperature and optical power. Hysteresis curves have been measured by changing the injection current or by tuning the dispersive element. We have found a threshold in the injection current for the onset of the hysteretic behaviour. Moreover, a theoretical model has been established to explain the essential features of the experimental results. Hysteresis cycles for different experiments have been calculated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00620422
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