A state-space approach to optimum postfiltering of sampled data

In this paper, we apply state-space techniques to the problem of reconstructing a random continuous-time waveform from its discrete-time samples. The optimal zero-lag filter that accomplishes this is well known, but to our knowledge the smoothing problem has not been previously considered in this context. We develop smoothing algorithms in the mixed-time framework appropriate to the interpolation problem, and then compare our results with those obtained previously in discrete time. Our results are related to those previously obtained in a simple and intuitive way, and the required computations are straightforward modifications of those described previously for purely discrete and purely continuous time.     

Simple Plots Improve Software Reliability Prediction Models

Software reliability prediction is accomplished by fitting a nonhomogeneous Poisson process (NHPP) model to data from software testing. The data consist of the cumulative time and the cumulative number of failures found in software testing. The NHPP model can be used to predict the reliability of the software product at the time of release or to determine how much further testing must be done to reach a specified failure rate. Models are normally fitted to software testing data using Poisson regression by the method of maximum likelihood. We encountered difficulties fitting models when numerical algorithms failed to converge or when we were unable to discriminate among several models with the same number of parameters. These difficulties were the result of having no likelihood ratio test to compare models with the same number of parameters and anomalies in the data that caused numerical algorithms to fail. We found that a simple cumulative plot of the data (cumulative failures on the vertical axis vs. cumulative test time on the horizontal axis) helped in spotting anomalies in the data and selecting an appropriate model to fit. A second plot of running products of ratios of the probability densities for the predictions made from competing models, called the prequential likelihood ratio, helped in discriminating between models. Use of these plots helped resolve the difficulties we experienced in fitting models to the software testing data.     

A methodology for the evaluation of research and development projects and associated resource allocation

This paper develops a methodology for the evaluation of research and development projects and the allocation of resources for the development of large scale technologies. The methodology is directed at the problem of selecting a research portfolio when the number of projects is large enough that enumeration of all the possibilities is impractical. In a series of successive screening stages, the number of candidate portfolios is reduced to a practical number. The initial screening stage is based on projected performance of the technology. Successive stages first screen market penetration by ignoring competition from other projects in the portfolio, and then screen by considering project competition. Thus succeeding stages in the methodology are successively finer but more costly to implement. Project screening techniques, which include elimination by aspects, ranking, and stochastic dominance are applied througout the methodology to result in a heuristic and effective approach to evaluation, and associated resource allocation, in very large scale systems.     

Optimal open-loop feedback control for linear systems with unknown parameters

The problem of controlling a class of linear systems with unknown parameters is considered. The optimal open-loop strategies are obtained for linear systems with unknown parameters in the system matrix with a quadratic performance index. The method of solution is based upon the use of the Hamilton-Jacobi theory.     

Vegetation height estimation from Shuttle Radar Topography Mission and National Elevation Datasets

A study was conducted to determine the feasibility of obtaining estimates of vegetation canopy height from digital elevation data collected during the 2000 Shuttle Radar Topography Mission (SRTM). The SRTM sensor mapped 80% of the Earth's land mass with a C-band Interferometric Synthetic Aperture Radar (InSAR) instrument, producing the most complete digital surface map of Earth. Due to the relatively short wavelength (5.6 cm) of the SRTM instrument, the majority of incoming electromagnetic energy is reflected by scatterers located within the vegetation canopy at heights well above the “bald-Earth” surface. Interferometric SAR theory provides a basis for properly identifying and accounting for the dependence of this scattering phase center height on both instrument and target characteristics, including relative and absolute vertical error and vegetation structural attributes.An investigation to quantify the magnitude of the vertical error component was conducted using SRTM data from two vegetation-free areas in Iowa and North Dakota, revealing absolute errors of −4.0 and −1.1 m, respectively. It was also shown that the relative vertical error due to phase noise can be reduced significantly through sample averaging. The relative error range for the Iowa site was reduced from 13 to 4 m and for the North Dakota site from 7 to 3 m after averaging of 50 samples. Following error reduction, it was demonstrated that the SRTM elevation data can be successfully correlated via linear regression models with ground-measured canopy heights acquired during the general mission timeframe from test sites located in Georgia and California. Prior to outlier removal and phase noise reduction, initial adjusted r² values for the Georgia and California sites were 0.15 and 0.20, respectively. Following outlier analysis and averaging of at least 20 SRTM pixels per observation, adjusted r² values for the Georgia and California sites improved to 0.79 (rmse=1.1 m) and 0.75 (rmse=4.5 m), respectively. An independent validation of a novel bin-based modeling strategy designed for reducing phase noise in sample plot data confirmed both the robustness of the California model (adjusted r²=0.74) as well as the capacity of the binning strategy to produce stable models suitable for inversion (validated rmse=4.1 m). The results suggest that a minimum mapping unit of approximately 1.8 ha is appropriate for SRTM-based vegetation canopy height mapping.     

Computation of upper and lower bounds to the frequencies of elastic systems by the method of Lehmann and Maehly

A method, called the Lehmann-Maehly method, for determining upper and lower bounds for eigenvalues, which was introduced by Bazley and Fox⁴ in 1964, is applied to the determination of bounds to the frequencies of elastic systems. In reviewing the fundamental theory involved, the present paper emphasizes the physical significance of the adjoint operators T and T* employed. An error in the paper by Bazley and Fox is noted and it is pointed out that with the corrected theory it is possible to use the Lehmann-Maehly method as a procedure for computing converging sequences of upper and lower bounds merely by varying a constant, the shifting constant. Thus, sequences of bounds are shown to be easily obtainable without prior knowledge of rough bounds, and the procedure for obtaining the bounds is not significantly more difficult to apply than the familiar Rayleigh-Ritz method for upper bounds. Since displacements and stresses are independently varied, the displacement functions used in the approximation procedure are only required to satisfy prescribed displacement boundary conditions while the stress functions only need satisfy the natural (stress) boundary conditions. Operators are derived for a non- uniform beam based on Timoshenko beam theory. Tables of bounds computed by the Lehmann-Maehly method and also the Rayleigh-Ritz method are given as an illustrative example.     

Interpreting top-down mass spectra using spectral alignment

Recent advances in mass spectrometry instrumentation, such as FTICR and OrbiTrap, have made it possible to generate high-resolution spectra of entire proteins. While these methods offer new opportunities for performing "top-down" studies of proteins, the computational tools for analyzing top-down data are still scarce. In this paper we investigate the application of spectral alignment to the problem of identifying protein forms in top-down mass spectra (i.e., identifying the modifications, mutations, insertions, and deletions). We demonstrate how spectral alignment efficiently discovers protein forms even in the presence of numerous modifications and how the algorithm can be extended to discover positional isomers from spectra of mixtures of isobaric protein forms.     

Geological and Physical Factors Affecting the Friction Angle of Compacted Sands

This study evaluated the effects of physical characteristics and geologic factors on the shear strength of compacted sands from Wisconsin that are used as granular backfill for mechanically stabilized earth walls and reinforced soil slopes. Physical properties and shear strength were determined for 30 compacted sands collected from a broad range of geological deposits. Relationships between strength/deformation behavior, geologic origin, and physical properties were used to categorize the sands into four friction angle groups. Sands with the lowest friction angle are derived from weathering of underlying sandstones, and tend to be medium-fine, well-rounded, and poorly graded sands. Sands with the highest friction angle are from recent glacial activity and tend to be coarser grained, well-graded, and/or angular sands. A multivariate regression model was developed that can be used to predict friction angle (?′) of compacted sands from comparable geological origins based on effective particle size (D10), maximum dry unit weight (γdmax), and Krumbein roundness (Rs).     

Treatment of Cr(VI) in COPR Using Ferrous Sulfate–Sulfuric Acid or Cationic Polysulfides

Column tests were conducted to evaluate two treatment strategies for reducing and stabilizing hexavalent chromium, Cr(VI), in chromium ore processing residue (COPR): permeation with a FeSO4–H2SO4 solution and blending with a cationic polysulfide reagent (CaSX). Cr(VI) leached at concentrations exceeding 50?mg/L from untreated COPR permeated with synthetic groundwater for >20 pore volumes of flow (PVF), and concentrations of Cr(VI) in the solid phase remained high (6,600?mg/kg). Permeation with solutions containing FeSO4–H2SO4 eliminated Cr(VI) from the effluent after initial, elevated leaching of Cr(VI) (100–1,500?mg/kg); however, high solid-phase concentrations of Cr(VI) remained in the column residuals (>1,300?mg/kg). COPR treated with CaSX leached Cr at <0.33?mg/L for 23.5 PVF and had solid-phase concentrations of Cr(VI) <10?mg/kg, although mineralogical analyses of treated solids showed potential chromate-containing mineral phases. Mineralogical analyses showed that precipitation and cementation occurred in the pore space of the COPR permeated with FeSO4–H2SO4, initially lowering the hydraulic conductivity > two orders of magnitude. However, acid dissolution channels eventually formed, resulting in preferential flow. COPR permeated with FeSO4–H2SO4 contained less brownmillerite and Cr(VI)-bearing hydrocalumite and hydrogarnet relative to untreated COPR. For COPR treated with CaSx, S encapsulated the subparticles of COPR with some micropore penetration, suggesting permanence of excess reductant after leaching with 23.5 PVF of synthetic rainwater.     

Reestablishing mental health services in St. Bernard Parish, Louisiana, following Hurricane Katrina.

In August 2005, Hurricane Katrina struck the Gulf Coast causing widespread residential displacement, unemployment, and compromised social networks for the residents of St. Bernard Parish, Louisiana. Symptoms of grief, depression, anxiety, posttraumatic stress, adjustment disorders, and psychosis were anecdotally reported among clinic patients during the authors' deployment to the parish in December 2005 (4 months post-Katrina). These anecdotal reports were confirmed through the analysis of survey data that were collected during the authors' follow-up visit in August 2006 (11 months post-Katrina). In collaboration with the United States Public Health Service, the parish has prioritized restoring medical and mental health services to the parish in its efforts to rebuild and repopulate. Implications for mental health practice and public policy are summarized. (PsycINFO Database Record (c) 2010 APA, all rights reserved)