The Naval Postgraduate School is a fully accredited research university operated by the United States Navy. Located in Monterey, California, it grants master's degrees, engineer's degrees and doctoral degrees. The school also offers research fellowship opportunities at the postdoctoral level through the National Research Council research associateship program. Wikipedia.
Garfinkel S.L.,Naval Postgraduate School, Monterey
Computers and Security | Year: 2013
Bulk data analysis eschews file extraction and analysis, common in forensic practice today, and instead processes data in "bulk," recognizing and extracting salient details ("features") of use in the typical digital forensics investigation. This article presents the requirements, design and implementation of the bulk-extractor, a high-performance carving and feature extraction tool that uses bulk data analysis to allow the triage and rapid exploitation of digital media. Bulk data analysis and the bulk-extractor are designed to complement traditional forensic approaches, not replace them. The approach and implementation offer several important advances over today's forensic tools, including optimistic decompression of compressed data, context-based stop-lists, and the use of a "forensic path" to document both the physical location and forensic transformations necessary to reconstruct extracted evidence. The bulk-extractor is a stream-based forensic tool, meaning that it scans the entire media from beginning to end without seeking the disk head, and is fully parallelized, allowing it to work at the maximum I/O capabilities of the underlying hardware (provided that the system has sufficient CPU resources). Although bulk-extractor was developed as a research prototype, it has proved useful in actual police investigations, two of which this article recounts. © 2012 Elsevier Ltd. All rights reserved.
Radko T.,Naval Postgraduate School, Monterey
Journal of Fluid Mechanics | Year: 2010
An analytical model is developed to explain the equilibration mechanism of the salt finger instability in unbounded temperature and salinity gradients. The theory is based on the weakly nonlinear asymptotic expansion about the point of marginal instability. The proposed solutions attribute equilibration of salt fingers to a combination of two processes: (i) the triad interaction and (ii) spontaneous development of the mean vertical shear. The non-resonant triad interactions control the equilibration of linear growth for moderate and large values of Prandtl number (Pr) and for slightly unstable parameters. For small Pr and/or rigorous instabilities, the mean shear effects become essential. It is shown that, individually, neither the mean field nor the triad interaction models can accurately describe the equilibrium patterns of salt fingers in all regions of the parameter space. Therefore, we propose a new hybrid model, which represents both stabilizing effects in a single framework. The resulting solutions agree with the fully nonlinear numerical simulations over a wide range of governing parameters. Copyright © Cambridge University Press 2010.
Royset J.O.,Naval Postgraduate School, Monterey
Mathematical Programming | Year: 2012
Optimality functions define stationarity in nonlinear programming, semi-infinite optimization, and optimal control in some sense. In this paper, we consider optimality functions for stochastic programs with nonlinear, possibly nonconvex, expected value objective and constraint functions. We show that an optimality function directly relates to the difference in function values at a candidate point and a local minimizer. We construct confidence intervals for the value of the optimality function at a candidate point and, hence, provide a quantitative measure of solution quality. Based on sample average approximations, we develop an algorithm for classes of stochastic programs that include CVaR-problems and utilize optimality functions to select sample sizes. © 2011 Springer and Mathematical Optimization Society(outside the USA).
Arkes J.,Naval Postgraduate School, Monterey
Obesity | Year: 2012
This research examines whether family disruptions (i.e., divorces and separation) contribute to children's weight problems. The sample consists of 7,299 observations for 2,333 children, aged 5-14, over the 1986-2006 period, from a US representative sample from the Child and Young Adult Survey accompanying the National Longitudinal Survey of Youth (NLSY). The study uses individual-fixed-effects models in a longitudinal framework to compare children's BMI and weight problems before and after a disruption. Furthermore, besides doing a before-after comparison for children, the study also estimates the effects at various periods relative to the disruption in order to examine whether children are affected before the disruption and whether any effects change as time passes from the disruption, as some effects may be temporary or slow to develop. Despite having a larger sample than the previous studies, the results provide no evidence that, on average, children's BMI and BMI percentile scores (measured with continuous outcomes) are affected before the disruption, after the disruption, and as time passes from the disruption, relative to a baseline period a few years before the disruption. However, children experiencing a family disruption do have an increased risk of obesity (having a BMI percentile score of 95 or higher) in the two years leading up to the disruption as well as after the disruption, and as time passes from the disruption. © 2011 The Obesity Society.
Fricker R.D.,Naval Postgraduate School, Monterey
Statistics in Medicine | Year: 2011
This paper briefly summarizes a short course I gave at the 12th Biennial Centers for Disease Control and Prevention (CDC) and Agency for Toxic Substances and Disease Registry (ATSDR) Symposium held in Decatur, Georgia on April 6, 2009. The goal of this short course was to discuss various methodological issues of biosurveillance detection algorithms, with a focus on the issues related to developing, evaluating, and implementing such algorithms. The PowerPoint slides from the complete talk can be accessed at. Published in 2011 by John Wiley & Sons, Ltd.