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  • American Institute of Physics (AIP)  (3)
  • 1985-1989  (3)
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Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 285-292 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Principles and design details are described for a fully automatic system measuring frequency and temperature spectra of the complex elastic, dielectric, and piezoelectric constants of polymer films. A microcomputer is used to control all processes including wave generation, sampling, and calculations. A sinusoidal excitation wave is written onto a RAM, readout by an external clock, and applied to a sample via a D/A converter. The resulting signals related to force, deformation, charge, and voltage are simultaneously sampled using the same clock and are determined as complex quantities through Fourier transformation. Their ratios give corresponding complex response functions. A multifrequency signal consisting of eight sinusoidal waves with frequencies of common ratio 2 is used to obtain frequency spectra over two decades at a time. This system operates over a frequency range from 0.01 to 100 Hz for elastic and piezoelectric measurements and from 0.01 Hz to 10 kHz for dielectric measurements at temperatures from −160 to 250 °C with an accuracy of 0.1% in tan δ.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 1701-1704 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The piezoelectric strain constant d32 of uniaxially stretched and poled PVDF [poly(vinylidene fluoride)] was found to be a nonlinear function of the applied stress or strain. The nonlinear behavior manifests itself, in good agreement with the predictions of the phenomenological theory of nonlinear piezoelectricity, by a piezoelectric constant d32 which decreases with increasing stress and by the occurrence of the second harmonic component (2f) of the polarization for a sinusoidal stress (frequency f). The nonlinearity has been tentatively attributed to the stress-induced variation of the distance between parallel chains in the PVDF crystals and their interfaces, causing a reduction of the dipolar and nondipolar interchain interactions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3297-3299 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The d=2 random-field Ising system Rb2Co0.85 Mg0.15F4 has been studied using pulsed, high-field magnetization M measurements. A relatively sharp metastability boundary TF(H) has been discovered which separates a frozen region below from an equilibrium one above TF(H). TF(H) scales as does the (destroyed) phase transition "Tc(H)'' as TN −TF(H) ∝H2/φ, with the measured crossover exponent φ=1.8±0.1 in good agreement with the d=2 susceptibility exponent γ=7/4. As measured in the pulsed field experiment, TF(H) lies well below "Tc(H)'' but above the value of TF(H) obtained from recent neutron scattering studies. The difference in the two values of TF(H) is attributed to the log t time dependence of the approach to equilibrium and to magnetocaloric effects.
    Type of Medium: Electronic Resource
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