The pixel purity index (PPI) algorithm proposed by Boardman, et al.1 identifies potential endmember pixels in multispectral imagery. The algorithm generates a large number of skewers (unit vectors in random directions), and then computes the dot product of each skewer with each pixel. The PPI is incremented for those pixels associated with the extreme values of the dot products. A small number of pixels (a subset of those with the largest PPI values) are selected as pure and the rest of the pixels in the image are expressed as linear mixtures of these pure endmembers. This provides a convenient and physically-motivated decomposition of the image in terms of a relatively few components. We report on a variant of the PPI algorithm in which blocks of B skewers are considered at a time. From the computation of B dot products, one can produce a much larger set of derived dot products that are associated with skewers that are linear combinations of the original B skewers. Since the derived dot products involve only scalar operations, instead of full vector dot products, they can be very cheaply computed. We will also discuss a hardware implementation on a field programmable gate array (FPGA) processor …

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Sensitivity and uncertainty methods have been developed to aid in the establishment of areas of applicability and validation of computer codes and nuclear data for nuclear criticality safety studies. A key component in this work is the generation of sensitivity and uncertainty parameters for typically several hundred benchmarks experiments used in validation exercises. Previously, only one-dimensional sensitivity tools were available for this task, which necessitated the remodeling of multidimensional inputs in order for such an analysis to be performed. This paper describes the development of the SEN3 Monte Carlo based sensitivity analysis sequence for SCALE. Two options in the SEN3 package for the reconstruction of angular-dependent forward and adjoint fluxes are described and contrasted. These options are the direct calculation of flux moments versus the calculation of angular fluxes, with subsequent conversion to flux moments prior to sensitivity coefficient generation. The latter technique is found to be significantly more efficient.

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Experimental methods are discussed for studying band structure, effective mass, and other electronic properties relevant to mobility, including scattering mechanisms, relaxation time, and the influence of grain boundaries (GBs) in polycrystalline transparent conducting oxide (TCO) films. Impedance spectroscopy permits evaluation of the GB potential barrier height and density-of-states. These studies enable an estimate of the limiting mobility achievable for practical transparent conducting oxides to be made. The equipment for measurement of the four transport coefficients is discussed, and examples of its application to films of ZnO, SnO2, and Cd2SnO4 are given.

We have clearly shown that the film morphology dictates the anti-stiction properties of FDTS coatings. Release stiction is not observed when ideal monolayer films are present but can be extensive when thicker aggregate structures are present. This finding is significant because it indicates that agglomerate formation during processing is a major source of irreproducible behavior when FDTS coatings are used to release micromachined parts. The results could also help explain why coatings that are aged at high. humidity start to stick to each other. (AFM results show that humid environments promote the formation of aggregates from monolayer films.) The reason why aggregate structures promote stiction is currently unknown. However, it appears that aggregates interfere with the ability of FDTS to form dense, well-ordered coatings under microstructures, leading to surfaces that are sufficiently hydrophilic to allow for release stiction via an attractive Laplace force during drying.

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The A0 photo-injector produces electron bunches of 1--14 nC charge with an energy of 18 MeV. Detailed measurements and optimization of emittance have been carried out for a number of gun and laser operating conditions, beam line optics conditions, and at a number of beam line locations. Results are compared with the predictions of simulations using HOMDYN.

This paper presents the latest results from experiment E787, at Brookhaven National Laboratory, on K{sup +} {r_arrow} {pi}{sup +} {nu}{bar {nu}} and radiative K{sup +} decays. The result for K{sup +} {r_arrow} {pi}{sup +} {nu}{bar {nu}} uses data collected in runs taken during 1995, 1996 and 1997. In addition, they discuss plans for future measurements of K{sup +} {r_arrow} {pi}{sup +} {nu}{bar {nu}}.

A number of laboratories have now demonstrated that catalyst-assisted NaAlH{sub 4} can reversibly absorb and desorb hydrogen in the solid state at moderate temperatures. An understanding of the mechanisms by which bulk decomposition and reformation of the compound can occur in the presence of a surface catalyst is important to improving the kinetic and thermodynamic properties of alanates for use in hydrogen storage applications. Using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), the authors have examined the microstructure and elemental composition of Na alanate samples, doped using a liquid Ti/Zr catalyst precursor, for a number of conditions. First, microscopy and compositional analyses were performed at different stages of the decomposition process within the first desorption cycle. Second, the material was characterized after multiple absorption/desorption cycles (5 cycles). Finally, the effects of the catalyst doping procedure on particle size, surface morphology and surface composition were examined. Significant changes in particle morphology and in elemental distribution were found to be induced by the desorption and cycling processes. Importantly, the measurements indicate that the initial dehydriding reactions were accompanied by significant enhancement of Al concentration toward the surface of particles and that elemental segregation occurred with repeated absorption/desorption cycles.

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The use of Probabilistic Structural Analysis Methods (PSAM) has received much attention over the past several decades due in part to enhanced reliability theories, computational capabilities, and efficient algorithms. The need for this development was already present and waiting at the door step. Automotive design and manufacturing has been greatly enhanced because of PSAM and reliability methods, including reliability-based optimization. This demand was also present in the US Department of Energy (DOE) weapons laboratories in support of the overarching national security responsibility of maintaining the nations nuclear stockpile in a safe and reliable state.

In this paper an optimization-based method of drift prevention is presented for learning control of underdetermined linear and weakly nonlinear time-varying dynamic systems. By defining a fictitious cost function and the associated model-based sub-optimality conditions, a new set of equations results, whose solution is unique, thus preventing large drifts from the initial input. Moreover, in the limiting case where the modeling error approaches zero, the input that the proposed method converges to is the unique feasible (zero error) input that minimizes the fictitious cost function, in the linear case, and locally minimizes it in the (weakly) nonlinear case. Otherwise, under mild restrictions on the modeling error, the method converges to a feasible sub-optimal input.

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Kinetic analysis of dynamic tracer data is performed with the goal of evaluating myocardial radiotracers for cardiac nuclear medicine imaging. Data from experiments utilizing the isolated rabbit heart model are acquired by sampling the venous blood after introduction of a tracer of interest and a reference tracer. We have taken the approach that the kinetics are properly characterized by an impulse response function which describes the difference between the reference molecule (which does not leave the vasculature) and the molecule of interest which is transported across the capillary boundary and is made available to the cell. Using this formalism we can model the appearance of the tracer of interest in the venous output of the heart as a convolution of the appearance of the reference tracer with the impulse response. In this work we parameterize the impulse response function as the sum of a large number of exponential functions whose predetermined decay constants form a spectrum, and each is required only to have a nonnegative coefficient. This approach, called spectral analysis, has the advantage that it allows conventional compartmental analysis without prior knowledge of the number of compartments which the physiology may require or which the data will support.

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The Department of Energy (DOE) has given the Spallation Neutron Source (SNS) project approval to begin Title I design of the proposed facility to be built at Oak Ridge National Laboratory (ORNL) and construction is scheduled to commence in FY01 . The SNS initially will consist of an accelerator system capable of delivering an {approximately}0.5 microsecond pulse of 1 GeV protons, at a 60 Hz frequency, with 1 MW of beam power, into a single target station. The SNS will eventually be upgraded to a 2 MW facility with two target stations (a 60 Hz station and a 10 Hz station). The radiation transport analysis, which includes the neutronic, shielding, activation, and safety analyses, is critical to the design of an intense high-energy accelerator facility like the proposed SNS, and the Monte Carlo method is the cornerstone of the radiation transport analyses.

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