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Research is presented concerning the use of a noninvasive electro-optical technique for the measurement of a 45 MeV picosecond electron beam bunch's temporal duration. The amplitude of the electro-optical modulation is discussed.

Technical barriers in the analysis of motion and disorder in crystal structures are evaluated. Recent advances point out that determination of the crystal structures over a range of temperatures and measuring temperature dependence of the amplitudes of the microscopic oscillators in quantum and classical regimes can now be determined.

The problem of estimating the amplitude of a signal is addressed using higher-order statistics. The probability distribution of the noise is assumed to be unknown so that the maximum likelihood estimator cannot be calculated. The estimator is taken as a polynomial of the observation, the coefficients of which are determined so that the estimate is unbiased with minimum variance. This method generalizes the linear approach, and the estimate variance is reduced. The case of linear-quadratic estimation is detailed, and numerical examples are presented.

A digital sampling technique is proposed which reduces the sampling rate required to measure amplitude and PW50 of playback waveforms relative to full bandwidth sampling in magnetic head testing. Simulations and experiments are presented using the technique. The implementation of the digital sampling technique is straightforward and can be applied to very narrow PW50s over a wide range of testing frequencies. Index Terms - Amplitude, digital sampling, pulse width, magnetic recording.

In this paper, we present an accurate measurement method for acquiring the two-tone transfer characteristics of high-power amplifiers. The measurement setup and sequence are described. The measured amplitude and phase data of the two-tone fundamental, third-order intermodulation, and fifth-order intermodulation components versus input power level are also presented. The measured two-tone transfer characteristics are very useful for the design of a predistortion linearizer or for nonlinear model extraction for high-power amplifiers. Index Terms--AM-AM, AM-PM, high-power amplifier, memory effect, two-tone transfer characteristics.

A blind algorithm for the estimation of amplitude, phase, and relative time delay of each user in multiple-access communication systems is proposed. This algorithm is based on the cyclostationarity features of the received signals and provides estimates of the unknown parameters that are intrinsically immune to the effects of noise and interference, provided that a cycle frequency of the user signals exists, which is not shared with the disturbance terms. The proposed estimators are, under milder assumptions, asymptotically unbiased and consistent. Moreover, the proposed algorithm is asymptotically near-far resistant and is not based on the usual assumption of white and/or Gaussian noise.

Whether electromagnetic precursors to earthquakes (EQs) exist is an important question not only for EQ prediction but also for understanding the physical processes of EQ generation. Slow transient geoelectric potential changes have been observed before several recent EQs in Japan. In most cases, they appeared 1-19 days before the EQs, and their duration and intensity were several minutes to 1 h and 1-2 mV/100 m. The changes appeared before five of all six EQs with magnitude [is greater than or equal to] 5 that occurred within 20 km of our stations during the observation period. Changes were also detected at greater epicentral distances (up to 75 km) before two other EQs, including one EQ of magnitude 4.7, which was preceded by a signal simultaneously recorded at three widely separated stations. These geoelectric potential changes have been distinguished through the following criteria from a multitude of other changes, which were noise of various origins. (i) The selected changes were proportional in amplitude to the length of the recording station's short ([approximately equals] 100 m) dipoles and were simultaneously detected also on long (1-10 km) dipoles when the latter were in operation. (ii) No such changes occurred during the observation period that were not followed by EQs. Although the EQ precursory nature of these geoelectric potential changes is admittedly unproven, it seems that the present results warrant continued serious research into the occurrence, generation, and transmission of these signals and their possible causal relationship to EQs.

The exact nature of the polarization processes in low-loss materials is not sufficiently understood and good experimental material is relatively scarce. Dielectric response of [Alpha]-PVDF covering 8.5 decades of frequency between [10.sup.2] and 3x[10.sup.6] Hz and a range of temperatures between 103 and 138 K were analyzed to reveal the nature of the dominant polarization process. Correcting for a series resistance and a Debye-like loss process at 50 kHz, the 'universal' fractional power law of dielectric response is well maintained, the residual tan [Delta] falls between 0.002 and 0.02 depending on temperature and frequency, with the residual loss process presumed to be due to hopping charge carriers having an activation energy of 0.035 eV. The universal process itself has a relatively high loss but its amplitude is low and this accounts for the low tan [Delta].

General equations are derived for computing the amplitude matrix for a nonspherical particle in an arbitrary orientation and for arbitrary illumination and scattering directions with respect to the laboratory reference frame, provided that the scattering problem can be solved with respect to the particle reference frame. These equations are used along with the T-matrix method to provide benchmark results for homogeneous, dielectric, rotationally symmetric particles. The computer code is publicly available on the World-Wide Web at http://www.giss.nasa.gov/~crmim. OCIS codes: 010.1310, 290.0290, 290.1310, 290.4210, 290.5850.