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Adaptable Multivariate Calibration Models for Spectral Applications

Description: Multivariate calibration techniques have been used in a wide variety of spectroscopic situations. In many of these situations spectral variation can be partitioned into meaningful classes. For example, suppose that multiple spectra are obtained from each of a number of different objects wherein the level of the analyte of interest varies within each object over time. In such situations the total spectral variation observed across all measurements has two distinct general sources of variation: intra-object and inter-object. One might want to develop a global multivariate calibration model that predicts the analyte of interest accurately both within and across objects, including new objects not involved in developing the calibration model. However, this goal might be hard to realize if the inter-object spectral variation is complex and difficult to model. If the intra-object spectral variation is consistent across objects, an effective alternative approach might be to develop a generic intra-object model that can be adapted to each object separately. This paper contains recommendations for experimental protocols and data analysis in such situations. The approach is illustrated with an example involving the noninvasive measurement of glucose using near-infrared reflectance spectroscopy. Extensions to calibration maintenance and calibration transfer are discussed.
Date: December 20, 1999
Partner: UNT Libraries Government Documents Department

Approximate Public Key Authentication with Information Hiding

Description: This paper describes a solution for the problem of authenticating the shapes of statistically variant gamma spectra while simultaneously concealing the shapes and magnitudes of the sensitive spectra. The shape of a spectrum is given by the relative magnitudes and positions of the individual spectral elements. Class-specific linear orthonormal transformations of the measured spectra are used to produce output that meet both the authentication and concealment requirements. For purposes of concealment, the n-dimensional gamma spectra are transformed into n-dimensional output spectra that are effectively indistinguishable from Gaussian white noise (independent of the class). In addition, the proposed transformations are such that statistical authentication metrics computed on the transformed spectra are identical to those computed on the original spectra.
Date: October 1, 2000
Creator: Thomas, Edward V. & Draelos, Timothy J.
Partner: UNT Libraries Government Documents Department

A study of the stack relaxation in thermal batteries on activation

Description: The stack-relaxation processes occurring in a thermal-battery upon activation and discharge were studied dynamically with a special test fixture that incorporated an internal load cell. The factors which were screened initially included stack diameter and height (number of cells), thickness and binder content of the separator, temperature, and closing pressure. A second series of more-detailed experiments included only those factors that were identified by the screening study as being important (as closing force, number of cells, and separator thickness). The resulting experimental data from this second series of experiments were used to generate a surface-response model based on these three factors. This model accounted for 94% of the variation in the response (final stack-relaxation pressure) over the range of conditions studied.
Date: April 17, 2000
Partner: UNT Libraries Government Documents Department

Advanced Technology Development Program for Lithium-Ion Batteries: Gen 2 Performance Evaluation Final Report

Description: The Advanced Technology Development Program has completed performance testing of the second generation of lithium-ion cells (i.e., Gen 2 cells). The 18650-size Gen 2 cells, with a baseline and variant chemistry, were distributed over a matrix consisting of three states-of-charge (SOCs) (60, 80, and 100% SOC), four temperatures (25, 35, 45, and 55°C), and three life tests (calendar-, cycle-, and accelerated-life). The calendar- and accelerated-life cells were clamped at an open-circuit voltage corresponding to the designated SOC and were subjected to a once-per-day pulse profile. The cycle-life cells were continuously pulsed using a profile that was centered around 60% SOC. Life testing was interrupted every four weeks for reference performance tests (RPTs), which were used to quantify changes in cell degradation as a function of aging. The RPTs generally consisted of C1/1 and C1/25 static capacity tests, a low-current hybrid pulse power characterization test, and electrochemical impedance spectroscopy. The rate of cell degradation generally increased with increasing test temperature, and SOC. It was also usually slowest for the calendar-life cells and fastest for the accelerated-life cells. Detailed capacity-, power-, and impedance-based performance results are reported.
Date: July 1, 2006
Creator: Christophersen, Jon P.; Bloom, Ira; Thomas, Edward V.; Gering, Kevin L.; Henriksen, Gary L.; Battaglia, Vincent S. et al.
Partner: UNT Libraries Government Documents Department

Experiments on Adaptive Techniques for Host-Based Intrusion Detection

Description: This research explores four experiments of adaptive host-based intrusion detection (ID) techniques in an attempt to develop systems that can detect novel exploits. The technique considered to have the most potential is adaptive critic designs (ACDs) because of their utilization of reinforcement learning, which allows learning exploits that are difficult to pinpoint in sensor data. Preliminary results of ID using an ACD, an Elman recurrent neural network, and a statistical anomaly detection technique demonstrate an ability to learn to distinguish between clean and exploit data. We used the Solaris Basic Security Module (BSM) as a data source and performed considerable preprocessing on the raw data. A detection approach called generalized signature-based ID is recommended as a middle ground between signature-based ID, which has an inability to detect novel exploits, and anomaly detection, which detects too many events including events that are not exploits. The primary results of the ID experiments demonstrate the use of custom data for generalized signature-based intrusion detection and the ability of neural network-based systems to learn in this application environment.
Date: September 1, 2001
Partner: UNT Libraries Government Documents Department

Low-Power Public Key Cryptography

Description: This report presents research on public key, digital signature algorithms for cryptographic authentication in low-powered, low-computation environments. We assessed algorithms for suitability based on their signature size, and computation and storage requirements. We evaluated a variety of general purpose and special purpose computing platforms to address issues such as memory, voltage requirements, and special functionality for low-powered applications. In addition, we examined custom design platforms. We found that a custom design offers the most flexibility and can be optimized for specific algorithms. Furthermore, the entire platform can exist on a single Application Specific Integrated Circuit (ASIC) or can be integrated with commercially available components to produce the desired computing platform.
Date: November 1, 2000
Partner: UNT Libraries Government Documents Department

Filling Source Feedthrus with Alumina/Molybdenum CND50 Cermet: Experimental, Theoretical, and Computational Approaches

Description: This report is a summary of the work completed in FY00 for science-based characterization of the processes used to fabricate cermet vias in source feedthrus. In particular, studies were completed to characterize the CND50 cermet slurry, characterize solvent imbibition, and identify critical via filling variables. These three areas of interest are important to several processes pertaining to the production of neutron generator tubes. Rheological characterization of CND50 slurry prepared with 94ND2 and Sandi94 primary powders were also compared. The 94ND2 powder was formerly produced at the GE Pinellas Plant and the Sandi94 is the new replacement powder produced at CeramTec. Processing variables that may effect the via-filling process were also studied and include: the effect of solids loading in the CND50 slurry; the effect of milling time; and the effect of Nuosperse (a slurry ''conditioner''). Imbibition characterization included a combination of experimental, theoretical, and computational strategies to determine solvent migration though complex shapes, specifically vias in the source feedthru component. Critical factors were determined using a controlled set of experiments designed to identify those variables that influence the occurrence of defects within the cermet filled via. These efforts were pursued to increase part production reliability, understand selected fundamental issues that impact the production of slurry-filled parts, and validate the ability of the computational fluid dynamics code, GOMA, to simulate these processes. Suggestions are made for improving the slurry filling of source feedthru vias.
Date: July 1, 2001
Partner: UNT Libraries Government Documents Department