List-mode likelihood: EM algorithm and image quality estimationdemonstrated on 2-D PET

Using a theory of list-mode maximum-likelihood (ML) source reconstruction presented recently by Barrett et al. (1997), this paper formulates a corresponding expectation-maximization (EM) algorithm, as well as a method for estimating noise properties at the ML estimate. List-mode ML is of interest in cases where the dimensionality of the measurement space impedes a binning of the measurement data. It can be advantageous in cases where a better forward model can be obtained by including more measurement coordinates provided by a given detector. Different figures of merit for the detector performance can be computed from the Fisher information matrix (FIM). This paper uses the observed FIM, which requires a single data set, thus, avoiding costly ensemble statistics. The proposed techniques are demonstrated for an idealized two-dimensional (2-D) positron emission tomography (PET) [2-D PET] detector. The authors compute from simulation data the improved image quality obtained by including the time of flight of the coincident quanta     

Kinetics of zones of plastic deformation in fatigue failure

Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 5, pp. 51–56, September–October, 1992.     

Efficient design/simulation algorithms for simultaneous switching noise in leadframe packages

 Two new modeling and simulation approaches for Simultaneous Switching Noise (SSN) are described and compared to “brute force” simulation by SPICE. Both simulation accuracy and simulation run-time are considered. The two new approaches are: 1) the “effective inductance” method, in which an approximate, very efficient method of extracting an SSN L _eff  is utilized; and 2) the “macromodel” method, in which the complex inductance network responsible for SSN is represented by only a few dominant poles in the frequency domain and the time domain response is obtained by an efficient convolution algorithm. Both approaches are shown to be accurate and fast, but only the effective inductance algorithm is robust in numerical convergence. Received: 19 March 1997 / Accepted: 25 March 1997     

Calculation and design of vibrational mills

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 1, pp. 14–15, January, 1992.     

Selection of Protector Parameters for Right Bidirectional Transducers

The paper compares experimental and calculated pulse shapes and spectra of signals for bidirectional right transducers with radically different protectors, namely, those from epoxy glue with a filler and ceramic. The new data support the previously made conclusion (from calculated parameters of emitted pulses) that in protectors from composite materials (with low propagation velocities of longitudinal elastic waves) signal spectra can have several pronounced peaks, and their waveforms can exhibit beats (oscillating amplitude modulation).     

Free spanning ductile vierendeel frame: A system for high-rise buildings in seismic areas

The paper has described the composition and structural behavior of a free spanning ductile frame system to be used in seismic areas. The inelastic performance, ductility, and redundancy of the system is compared with a conventional ductile moment resisting frame. It is shown that the structural performance of the system is equal or better than the conventional system. The paper also describes successful application of the system to commercial high-rise buildings.