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  • 1
    Digitale Medien
    Digitale Medien
    Quantitative nondestructive evaluation with ultrasonic method using neural networks and computational mechanics (1995)
    Springer
    Computational mechanics 15 (1995), S. 521-533 
    Details
    ISSN: 1432-0924
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract  This paper describes an inverse analysis method using hierarchical neural networks and computational mechanics, and its application to the quantitative nondestructive evaluation with the ultrasonic method. The present method consists of three subprocesses. First, by parametrically changing the location and size of a defect hidden in solid, elastic wave propagation in the solid is calculated with the dynamic finite element method. Second, the back-propagation neural network is trained using the calculated relationships between the defect parameters and the dynamic responses of solid surface. Finally, the trained network is utilized to determine appropriate defect parameters from some measured dynamic responses of solid surface. The accuracy and efficiency of the present method are discussed in detail through the identification of size and location of a defect hidden in solid.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00350265
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  • 2
    Digitale Medien
    Digitale Medien
    Spin fluctuations of La2−xSrxCu1−yZnyO4−δ (x=0.14, y=0.012) (abstract) : 37th annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6333-6333 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Magnetism of high-Tc superconductors is still the subject of intensive investigation. Zn substitution for Cu together with removal of oxygen suppresses the superconductivity quickly. We prepared two crystals to perform a neutron scattering study of the spin fluctuations of La2−xSrxCu1−yZnyO4−δ. One is a Zn-doped and deoxygenated crystal La1.86Sr0.14Cu0.988Zn0.012O4−δ (#1) which does not show superconductivity above 1.5 K. The other is a Zn-doped crystal La1.86Sr0.14Cu0.988Zn0.012O4 (#2) which shows superconductivity below 16 K. The incommensurate spin excitations observed previously in superconducting samples1,2 containing no Zn remain in both samples. However, there is significant difference in the spectral weight χ‘(q,ω) at low temperatures between the non-superconducting and superconducting Zn-doped crystals. In crystal #1 the spectral weight at low temperatures is qualitatively similar to that of Zn-undoped non-superconducting samples.3 In crystal #2 the spectral weight at low temperatures is qualitatively similar to that of Zn-undoped superconducting samples.1,2 These results demonstrate that there is an intimate relationship between the magnetism and the superconductivity. We are in the process of further measurements.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.352638
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  • 3
    Digitale Medien
    Digitale Medien
    Shielded MR head for high-density magnetic recording (invited) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4847-4850 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A narrow-gap shielded magnetoresistive (MR) head with a 8-μm track width has been constructed for high-density magnetic recording. The head consists of a pair of NiFe shields and a trilayered MR element between the shields. In the MR element NiFe, Ti, and amorphous CoZrMo films are used. The thickness of the three layers and the shields, as well as the shield gap length, are optimized with a one-dimensional self-consistent calculation. The shielded MR head has been fabricated using calculated thickness parameters for individual layers: 60 nm for CoZrMo with 40 nm NiFe and 20 nm Ti, 1-μm shields, and 0.5 μm for the total shield gap. The reproduced characteristics from the MR head are evaluated with a plated disk. Neither Barkhausen noise nor distortion is observed in the output waveform. The output voltage is 600 μVpp at a 4 mA/μm sense current with 30 kFCI transition density. The D50 transition density is 40 kFCI. These values are in good agreement with the calculated values. Assuming a 12-μm track pitch, crosstalk is −29 dB from off-track crosstalk characteristics. This shielded MR head has a potential to achieve high recording density with 40 kBPI and 2000 TPI for small-size disk drives.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.344756
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  • 4
    Digitale Medien
    Digitale Medien
    Inverse magnetostriction effect on magnetoresistive response for evaporated NiFe and NiFeCo films : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4671-4673 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The relations between inverse magnetostriction energy ε and magnetoresistive (MR) response have been investigated for Ni82Fe18 films and Ni82Fe12Co6 films that have about twice the uniaxial anisotropy energy as the NiFe films. To obtain films with various ε values (50–800 J/m3), internal stress σ for the films is changed by the deposition conditions and film thickness control. The σ is measured by the bending method. The σ changes for both films are related to microstructure differences. Hysteresis or Barkhausen jump is observed for the NiFe films with absolute ε value ||ε|| more than 120–130 J/m3, and for the NiFeCo films with ||ε|| more than 300–330 J/m3. The threshold ||ε|| values are on the same order of magnitude as the calculated uniaxial anisotropy for each film. To obtain smooth MR response, it is very important to reduce the ||ε|| to less than the uniaxial anisotropy energy value, by deposition conditions and film thickness control.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.348293
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  • 5
    Digitale Medien
    Digitale Medien
    Ab initio determination of mode coupling in HSSH: The torsional splitting in the first excited S–S stretching state (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5905-5909 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A mechanism for the enhanced splitting detected in the millimeter-wave rotational spectra of the first excited S–S stretching state of HSSH (disulfane) has been studied. The mechanism, which involves a potential coupling between the first excited S–S stretching state and excited torsional states, has been investigated in part by the use of ab initio theory. Based on an ab initio potential surface, coupling matrix elements have been calculated, and the amount of splitting has then been estimated by second-order perturbation theory. The result, while not in quantitative agreement with the measured splitting, lends plausibility to the assumed mechanism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457459
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  • 6
    Digitale Medien
    Digitale Medien
    Design and manufacture of a 10-T superconducting wiggler magnet at TERAS : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1960-1963 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The 10-T wiggler is an iron-cored superconducting wiggler destined for Electrotechnical Laboratory's 800-MeV electron storage ring to enhance the available radiation. The design and manufacturing contract for this magnet was started in April 1990 and was preceded by a feasibility study. The major features of the magnet are described in the article. Also, the effect of the superconducting wiggler with high magnetic field on the stored electron beam has been simulated. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1145770
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  • 7
    Digitale Medien
    Digitale Medien
    Single bunch injection system of the storage ring NIJI-IV for free electron laser use (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2796-2800 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The system of single bunch injection (SBI) for the storage ring NIJI-IV was completed. The system was used for the injection of the short pulse beams from an electron gun into only one of the 16 rf buckets in the ring. On a compact storage ring, the multipulse beams in one pulse train can be stored into only one of many bunches by one injection. The optimum number of the grid pulse in one pulse train was determined to improve the storage efficiency and the storage current by one injection. The keeping time of the bump orbit was calculated by using the transfer matrices. The optimum pulse number obtained by the calculation is 2. In the SBI system, the number of grid pulses in one pulse train can be selected by the gate circuit. A snap off diode and a clip line are used to generate 2 ns grid pulses. The measured grid pulse was shorter than the longitudinal space 5.5 ns of the rf bucket with voltage of −80 V. The EIMAC Y-646B cathode-grid assembly is used as the electron source. It is expected that the injection system provides a higher peak current and easier free electron laser use operation in comparison with the rf-knockout system. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1145557
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  • 8
    Digitale Medien
    Digitale Medien
    Photovoltage generation of Si/C60 heterojunction (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2798-2800 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Photovoltage generation was observed for C60/Si heterojunction fabricated by the deposition of C60 thin film on Si substrate. Four types of Si substrates (two for p-type and two for n-type) were used. All junctions showed rectifying behaviors and photovoltage generation under illumination of Ar-ion laser. The highest value of the photovoltage was 0.40 V. From the saturated photovoltage values for four junctions, the Fermi level of C60 thin film was estimated to be located about 4.7 eV below the vacuum level. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.361114
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  • 9
    Digitale Medien
    Digitale Medien
    Estimation of the interface states density of a Si/C60 heterojunction by frequency-dependent capacitance–voltage characteristics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 6246-6251 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Capacitance–voltage (C–V) characteristics of a Si/C60 heterojunction, i.e., a HF solution (7.3% HF+30% NH4F) treated Si surface interfaced solid crystal of C60 molecules, were measured while applying various ac frequencies. The entire C60 thin film and near-interface region of the Si wafer behaved as a depletion region, with the C–V curve showing two distinct regions: one above and one below a threshold bias voltage. Below the threshold, C–V characteristics were dependent on applied frequency, which suggests the presence of interface states that only affect capacitance at lower frequencies. This frequency dependence was analyzed by assuming a suitable equivalent circuit, and based on derived curve-fitting circuit parameters the interface states density was accordingly estimated to have a value as low as ∼1011/cm2 eV. Such a small density indicates that only a few lattice defects occur within the interface of the HF-treated Si surface and C60 crystal. Although no frequency dependence was observed above the threshold, the C–V characteristics were found to be dependent on the width of the depletion region in Si. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.364438
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  • 10
    Digitale Medien
    Digitale Medien
    In situ observation of molecular beam epitaxy of GaAs and AlGaAs under deficient As4 flux by scanning reflection electron microscopy (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 622-624 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The initial stages of molecular beam epitaxial (MBE) growth of GaAs and AlGaAs are directly observed by scanning reflection electron microscopy. Under deficient As4 flux, it is shown that dark areas appear within several layers of growth, but disappear within several seconds of growth interruption, indicating that they are droplets of Ga and Al. The distance between the droplets is approximately 1 μm, which is identical in GaAs and AlGaAs growth. Thus, the diffusion length of Ga and Al on a group III-rich surface at around 600 °C is estimated to be about 5000 A(ring), which is the largest among previous reports. The role of droplet disappearance in interface flattening in alternating supply MBE is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.101829
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