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Nuclear Science, IEEE Transactions on

Issue 6 • Date Dec. 1998

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Displaying Results 1 - 8 of 8
  • 1998 Index IEEE Transactions on Nuclear Science Vol. 45 (Author Index)

    Page(s): 1 - 26
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    Freely Available from IEEE
  • Subject index

    Page(s): 26 - 57
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    Freely Available from IEEE
  • Analytical calculation of photon distributions in SPECT projections

    Page(s): 3202 - 3214
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    In this paper the authors present a method for analytically calculating the distribution of photons detected in single photon emission computed tomography (SPECT) projections. The technique is applicable to sources in homogeneous and nonhomogeneous media. The photon distribution (primary, first-, and second-order Compton scatter) is computed using a precalculated camera-dependent look-up table in conjunction with an attenuation map of the scattering object and a map of the activity distribution. The speed and accuracy of this technique is compared to that of Monte Carlo simulations. The cases considered are a point source in a homogeneous and also in a nonhomogeneous scattering medium, an extended source in a nonhomogeneous medium, and a homogeneous cylinder filled uniformly with activity. The method is quantitatively accurate and faithfully reproduces the spatial distribution of the unscattered and scattered photons. For comparable statistical precision in the peak of the calculated distribution, their approach can result in a gain in calculation time over Monte Carlo simulators. For point sources, the computation times are improved by a factor of 20-150. However, this gain depends on the source configuration, and calculation times become comparable for an 800 voxel source and are five times slower for a 55000 voxel source. The method also offers an increase in the speed of computation of higher order Compton scatter events over a similar analytical technique View full abstract»

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  • Threshold voltage stabilization in radiation environments

    Page(s): 3175 - 3178
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    CMOS circuit hardness to total ionizing dose is improved by a circuit technique that dynamically adjusts well and/or substrate voltages to maintain constant device threshold voltages. Threshold voltage excursions below a reference value activate an oscillator driving a charge pump. Stabilization is demonstrated experimentally. Techniques for optimizing the circuitry for various CMOS technology implementations are provided and supported with simulations View full abstract»

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  • An information theory-based approach for quantitative evaluation of user interface complexity

    Page(s): 3165 - 3174
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    Development of effective measures for the complexity of human-computer interface design based on a proper model is desirable in order to improve the human performance and to facilitate the system development. In this paper, the authors propose the task-to-action (TTA) model which can describe the task-performing procedure of human operators. Quantitative interface design complexity measures using an informational entropy concept are also proposed to determine the user interface complexity, i.e., operation complexity, transition complexity, and screen complexity. Two experiments are performed in this work to show the validity of the proposed model and the measures: one is to test the validity of the TTA model with the case of information-seeking problem and the other for the suggested entropy measures View full abstract»

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  • Electric currents through ion tracks in silicon devices

    Page(s): 3153 - 3164
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    A modified form of Ohm's law, describing electric currents through ion tracks, is presented as a tool for future theoretical modeling efforts related to charge collection from ion tracks in silicon devices. The equation is rigorously derived from the drift/diffusion equations and accounts for all currents (electron and hole, drift, and diffusion). While only one quantitative result is given, a fairly complete description of charge collection from ion tracks in silicon diodes is qualitatively discussed View full abstract»

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  • ROTOR: the VLSI switched current amplifier for high-rate high-resolution spectroscopy with asynchronous event occurrence

    Page(s): 3179 - 3183
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    In this paper the authors present a novel JFET/CMOS signal processor, ROtational TrapezOidal Readout (ROTOR), conceived for high-rate high-resolution X-ray spectroscopy with asynchronous event occurrence. The circuit is of time-variant nature, uses no fast channel as a trigger, and displays a quasitrapezoidal weight function with virtually no exponential tail. Such a finite-width weight function is typically nearly optimal for submicrosecond processing times and is adequate when intense radiation fluxes must be handled. The filter also permits us to suppress possible ballistic deficits View full abstract»

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  • Application of fault detection and identification (FDI) techniques in power regulating systems of nuclear reactors

    Page(s): 3184 - 3201
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    Application of failure detection and identification (FDI) algorithms have essentially been limited to identification of a global fault in the system, and no further attempts have been made to locate subcomponent faults for root cause analysis. This paper presents Kalman filter-based methods for FDI in power regulating systems of nuclear reactors. The attempt here is to explain how the behavior of the states, residues, and covariances can be interpreted to identify subcomponent faults. An alternative to the Kalman filter-the risk-sensitive filter-is also introduced. Comparison of its performance with the Kalman filter-based FDI algorithms is studied. All simulation studies have been carried out on postulated faults in the power regulating system of heavy water moderated, low pressure vertical tank-type research reactors View full abstract»

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Aims & Scope

IEEE Transactions on Nuclear Science focuses on all aspects of the theory and applications of nuclear science and engineering, including instrumentation for the detection and measurement of ionizing radiation; particle accelerators and their controls; nuclear medicine and its application; effects of radiation on materials, components, and systems; reactor instrumentation and controls; and measurement of radiation in space.

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